Channel Estimate

IOSR Journal of Electronics and Communication Engineering (IOSRJECE)

ISSN : 2278-2834 Volume 2, Issue 2 (July-Aug 2012), PP 01-06

www.iosrjournals.org

www.iosrjournals.org 1 | Page

Channel Estimation Algorithm Using an Improved Dft for Mimo-

Ofdm Systems

1Deepthi Harika J,

2Ramana Reddy M

1M.Tech [DSCE], RGMCET

2Associate prof., ECE, RGMCET

Abstract: The Improved DFT-based Channel Estimation Algorithm for MIMO-OFDM System uses the

symmetric property to extend the LS estimate in frequency domain, and calculates the changing rate of the

leakage energy, and selects useful paths by the changing rate.

The Discrete Fourier Transform (DFT) is used for spectral analysis, the sequence usually

represents a finite set of uniformly-spaced time-samples of some signal , where t represents time. The

conversion from a very long (or infinite) sequence to a manageable size entails a type of distortion called

leakage, which is manifested as a loss of detail in the DTFT. Choice of an appropriate sub-sequence length is

the primary key to minimizing that effect. When the available data (and time to process it) is more than the

amount needed to attain the desired frequency resolution, a standard technique is to perform multiple DFTs.

Multiple Input Multiple Output (MIMO) - Orthogonal Frequency Division Multiplexing (OFDM) can not only

effectively enhance the transmission rate and capacity of the wireless communication system but also effectively

combat multipath fading and inter-symbol interference (ISI). MIMO-OFDM technology has become one of the

most promising solutions in the high data rate wireless channel transmission. In the OFDM system with

transmit diversity, when the receiver knows the channel information better, the space-time codes can be decoded

effectively. In order to enhance frequency efficiency, the receiver also needs to know the channel information for

coherent demodulation. So channel estimation is directly related to the system performance.

Least squares (LS) approach is the simplest channel estimation. This algorithm has lower complexity.

However, it has larger mean square error (MSE) and easily influenced by noise and intercarrier interference.

Another approach is also proposed by extending the LS estimate with a symmetric signal of its own. Based on

these two methods, we propose a new method to solve the problem of energy leakage.

Keywords: Channel Estimation, Energy Leakage, DFT- Discrete Fourier transform, MIMO- Multiple Input

Multiple Output, OFDM-Orthogonal Frequency Division Multiplexing.

I. Introduction

Existing Method:

The conventional discrete Fourier transform (DFT) is a specific kind of discrete transform, used in

Fourier analysis. It transforms one function into another, which is called the frequency domain representation, or

simply the DFT, of the original function (which is often a function in the time domain). But the DFT requires an

input function that is discrete and whose non-zero values have a limited (finite) duration. Such inputs are often

created by sampling a continuous function, like a person's voice. Unlike the discrete-time Fourier transform

(DTFT), it only evaluates enough frequency components to reconstruct the finite segment that was analyzed.

Using the DFT implies that the finite segment that is analyzed is one period of an infinitely extended periodic

signal; if this is not actually true, a window function has to be used to reduce the artifacts in the spectrum. For

the same reason, the inverse DFT cannot reproduce the entire time domain, unless the input happens to be

periodic (forever). Therefore it is often said that the DFT is a transform for Fourier analysis of finite-domain

discrete-time functions. The sinusoidal basis functions of the decomposition have the same properties. The

conventional discrete Fourier transforms (DFT)-based approach will cause energy leakage in multipath channel

with non-sample-spaced time delays.

Proposed Method:

DFT contains periodicity. If the original data sequence is not continuous, it will generate additional

high-order component. In order to reduce this high-order component, we can use symmetry principle before

IFFT. With this understanding, we will select paths effectively in order to reduce leakage power by calculating

the changing rate of the leakage energy. The main advantage of this proposed method is that this improved

method uses symmetric property to extend the LS estimate in frequency domain, and calculates the changing

rate of the leakage energy, and selects useful paths by the changing rate.

MIMO-OFDM technology has become one of the most promising solutions in the high data rate

http://en.wikipedia.org/wiki/Frequency_spectrum#Spectrum_analysis

http://en.wikipedia.org/wiki/Spectral_leakage

http://en.wikipedia.org/wiki/Discrete_transform

http://en.wikipedia.org/wiki/Fourier_analysis

http://en.wikipedia.org/wiki/Function_%28mathematics%29

http://en.wikipedia.org/wiki/Frequency_domain

http://en.wikipedia.org/wiki/Time_domain

http://en.wikipedia.org/wiki/Discrete-time_signal

http://en.wikipedia.org/wiki/Sampling_%28signal_processing%29

http://en.wikipedia.org/wiki/Discrete-time_Fourier_transform

http://en.wikipedia.org/wiki/Window_function

Channel Estimation Algorithm using an improved DFT for MIMO-OFDM Systems


wireless channel transmission. This technology can not only effectively enhance the transmission rate and

capacity of the wireless communication system but also effectively combat multipath fading and inter-

symbol interference (ISI)[1]. In the OFDM system with transmit diversity, when the receiver knows the channel

information better, the space-time codes can be decoded effectively. In order to enhance frequency efficiency,

the receiver also needs to know the channel information for coherent demodulation[2]. So channel estimation

is directly related to the system performance.

By now, many channel estimation algorithms have been presented. Least squares (LS) approach

is introduced in [3]. The LS estimation is the simplest channel estimation. This algorithm has lower

complexity. However, it has larger mean square error (MSE) and easily influenced by noise and intercarrier

interference. Linear minimum mean square error (LMMSE) algorithm is introduced in [4]. LMMSE

algorithm is a simplified algorithm of Minimum Mean Square Error (MMSE). Although they can achieve

better performance than LS, they have higher computational-complexity and need to know the channel statistics

which are usually unknown in real system. In [5] and [6], the algorithms of reducing the complexity of the

LMMSE are proposed. But these two modified methods still require exact channel covariance matrices.

In this paper, we focus on DFT-based channel estimation method. This algorithm can make good

compromise between performance and computational complexity[7]. Most of the published work on DFT-

based channel estimation assumes each path delay is an integer multiple of the sampling interval in multipath

channel. However, it is difficult to ensure this condition in real system because of the complexity and

incomprehensibility of the transmission channel. In non- sample-spaced multipath channels, the channel impulse

response will leak to all taps in the time domain. Reference[8] propose a method to reduce leakage power by

calculating energy increasing rate. Another approach is also proposed by extending the LS estimate with a

symmetric signal of its own in [9]. Based on these two methods, we propose a new method to solve the problem

of energy leakage.

Software Required: MATLAB 7.4:

MATLAB is a high-level technical computing language and interactive environment for algorithm

development, data visualization, data analysis, and numeric computation. Using the MATLAB product, you can

solve technical computing problems faster than with traditional programming languages, such as C, C++, and

FORTRAN.

MATLAB in a wide range of applications, including signal and image processing, communications,

control design, test and measurement, financial modeling and analysis, and computational biology. Add-on

toolboxes (collections of special-purpose MATLAB functions, available separately) extend the MATLAB

environment to solve particular classes of problems in these application areas.

MATLAB provides a number of features for documenting and sharing your work. We can integrate your

MATLAB code with other languages and applications, and distribute your MATLAB algorithms and

applications.

The outline of the paper is as follows. In Section II, the MIMO-OFDM system model is described.

In Section III, we introduce LS and conventional DFT-based algorithms. The new method is explained in

Section IV. Simulation results are presented in Section V. Finally Section VI provides our conclusions.

II. Mimo-Ofdm System Model A. Multipath Channel Model

In multipath fading channel, the channel impulse response in time domain could be expressed as:

L-1

h(t ) = ∑ al δ (t − τ l Ts ) (1) l =0

Where L is the number of multipath, al is the complex time varying channel coefficient of

the l -th path, Ts is sampling interval, and τ l Ts is the delay of the l –th path. When τ l is a n i n t e g e r ,

t h e mu l t i p a t h c h a n n e l i s s a m p l e -spaced channel. Or t h e m u l t i p a t h c h a n n e l i s n o n -

sample-spaced channels. From (1) the channel impulse response after

sampling the frequency response of h(t ) is expressed as:

L

hn = ∑ a1 e-jπ/N (n+(N-1)τ

1) sin(πτ1) (2)

i=1 sin π

N

The corresponding frequency response is expressed as:

L

H(k) = ∑ hne(-j2πkl/N)

(3)

i=1

1

N (τ1-n)

http://www.mathworks.com/applications/t_m

http://www.mathworks.com/computational-biology.html



Figure 1. The channel impulse response in non-sample-spaced channel

From Figure 1 it can be seen that the energy leaks to all carriers at the condition of the channel is non-

sampled-spaced channel.

B. MIMO-OFDM Model:

It is assumed that the system has N T transmitter antennas and N R receiver antennas. The total

number of the subcarriers is N . At the sending end, the data stream is modulated by inverse fast Fourier

transform (IFFT) and a guard interval is added for every OFDM symbol to eliminate ISI caused by multi-path

fading channel. The receiver performs opposite operations.

The received signal can be expressed:

NT

Y j (k ) = ∑X i (k )H i, j (k ) + W j (k ) 0 ≤ k ≤ N – 1 (4)

i = 1

Where j = (1,2,…, N R ) , k is the k -th subcarrier, Y j (k ) is the signal of the j -th receive antenna in

frequency domain, X i (k ) is the signal of the i -th transmitter antenna, H i, j (k ) is the discrete response of the

channel on subcarrier k between the i -th transmitter antenna and the j -th receive antenna, and W j (k ) is the

complex Gaussian noise with zero-mean and variance n0 2

III. Channel Estimation Algorithm

A. LS Channel Estimation

LS algorithm is the simplest channel estimation. It is assumed that H LS is the estimate of the

channel impulse response H .The LS estimate of the channel in frequency domain on subcarrier k can be

obtained as:

^

HLS(k)= = H(k)+ 0 < k < N-1 (5)

B. Conventional DFT-based Channel Estimation

In OFDM system, the length of the channel impulse response L is usually less than the length of the

cyclic prefix Lg . Conventional DFT-based algorithm just takes advantage of this feature. It transforms

the in-frequency channel estimation into in-time channel estimation , considers the part which is larger than

Lg as noise, and then treats that part as zero in order to eliminate the impact of the noise. The

algorithm can be summarized as follows:

Step 1: Calculate the LS estimate H LS (k ) in the usual LS manner.

∧

Step 2: Covert H LS (k ) to time domain:

∧ ∧

h LS (n ) = IFFT [H LS (k )» ]= h(n )+ w~(n ) 0 ≤ n ≤ N −1 (6)

where

w~(n) = IFFT [W (k ) X (k )] (7)

Y(k)

X(k)

W(k)

X(k)



• Step 3: Eliminate the impact of the noise in time domain:

∧ ∧

hDFT (n ) = h LS (n) 0 ≤ n ≤ Lg − 1

0 Lg ≤ n ≤ N – 1 (8)

• Step 4: Covert time-domain response to frequency response by fast Fourier transform (FFT): ∧ ∧

H DFT (k) = FFT [h DFT (n)] 0 ≤ k ≤ N – 1 (9)

IV. An Improved Channel Estimation Method DFT contains periodicity. If the original data sequence is not continuous, it will generate additional

high-order component. In order to reduce these high-order component, we can use symmetry principle before

IFFT. With this understanding, we will select paths effectively in order to reduce leakage power by calculating

the changing rate of the leakage energy. The improved algorithm can be summarized as follows:

• Step 1: Calculate the LS estimate H LS (k ) .

• Step 2: Extend H LS (k ) with a symmetric signal of its own:

∧ ∧

H symmetric (k ) = H LS (k ) 0 ≤ k ≤ N −1

∧

H LS (2 N – 1-K) N≤ k ≤ 2N −1 (10)

• Step 3: Covert H symmetric (k ) to time domain by IFFT:

∧

h symmetric (n ) = IFFT [H symmetric (k )] = h(n) + w~(n) 0 ≤ n ≤ 2 N −1 (11)

• Step 4: The energy of the channel impulse response can be expressed as:

2 N −1 ∧

E = ∑ h symmetric (n) (12)

n=0 From Figure 1, we can see the energy concentrates at the ends of the sequences after the energy leakage.

That means the leakage energy concentrates in the middle of the sequences. So (9) can be written as:

N-1 ∧ 2 2 N-1 ∧ 2

E = ∑ h symmetric (n) + ∑ h symmetric (2N −1 − n) (13)

n =0 n=0

N-1

E = ∑ E (n )

n=0

Where ∧ 2 ∧ 2

E (n) = h symmetric (n) + h symmetric (2 N − 1 − n) (14)

E (n ) is the energy of the n -th sampling point. lleakage is defined as the first path number of starting

leaking energy, and E (lleakage ) is defined as the leakage energy between the lleakage -th path and the

(2 N −1 − lleakage ) -th path. E (lleakage ) can be expressed as:

N −1

E (lleakage ) = ∑ E (n ) 0 ≤ lleakage ≤ N −1 (15)

n=lleakage

The changing rate of the leakage energy P(lleakage ) can be defined as:

P(lleakage) = E (lleakage ) − E (lleakage + 1) (16)

E (lleakage )



If P(lleakage ) is large, it shows that it is not the concentrated area of the leakage energy between

the lleakage -th path and the (2 N −1 − lleakage ) -th path. If P(lleakage ) is small, it shows that the change

of the power leakage is not obvious. That means the energy of the lleakage -th path is small compared with

the total leakage energy. We can treat it as zero. Then the channel response can be expressed as:

~

hDFT (n) = 0 lleakage ≤ n ≤ 2 N −1 − lleakage

∧

h symmetric(n) other (17)

∧ ~

In (12), h symmetric (n)contains w (n)except for h(n) . From (7), we can see that w~(n) is determined

by W (k ) and X (k ) . W (k ) is white noise, and its amplitude of the spectrum is constant. So the system uses

the training sequences which have equal amplitude. Then the the changing rate of the leakage energy will

not be affected by the change of the amplitude of X (k ) .

• Step 5: After padding with zeros, convert hDFT (n) frequency domain by FFT:

~ ~

H DFT (k ) = FFT [ hDFT (n)] 0 ≤ k ≤ 2 N – 1 (18)

• Step 6: According to the symmetric property, the corresponding frequency response is expressed as:

∧ ~ ~

HDFT (k) = H DFT(k )+ H DFT (2 N −1 − k ) 0 ≤ k ≤ N −1 (19)

2

V. Simulation Results In the simulations, we assume a MIMO-OFDM system with two transmitter antennas and two

receiver antennas. The multi-path channel consists of 5 independent Rayleigh fading paths and the total

number of sub-carriers is N = 128 . The guard time interval is 16 sample periods. The symbols are

modulated by 16QAM. The delay of the antenna 1 is delay1= 0ˆ0.4ˆ1.2ˆ2.1ˆ3.4˅ μs , and the delay of the

antenna 2is delay2=˄0ˆ0.5ˆ1.5ˆ2.7ˆ4.3˅ μs . Table 1 shows the system introduction.

Table I. System Introduction

Fig.2, 3 respectively shows the MSE and BER performance of the improved DFT-based channel estimation is

better than

the LS estimate and the conventional DFT estimate method. From Fig.2, we can see that the MSE

of the conventional DFT method appears error floor earlier than the improved method with P(lleakage )=4.95

and lleakage =32. And the performance of improved method are both better than LS estimation and

conventional DFT-based channel estimation method. The improved method becomes better when

P(lleakage ) =0.38 and improved method achieves a satisfying tradeoff between lleakage =50. However,

when P(lleakage )=0.19 and lleakage =100, the performance of the improved method degrades. From Fig.3, we

also see it. This is because more noise exists with decrease of P(lleakage ) . So wo should select proper

P(lleakage ) considering the existence of noise in order to achieve better performance.

System lleakage

P(lleakage ) (%)

LS-DFT1 32 4.95

LS-DFT2 50 0.38

LS-DFT3 100 0.19



Figure 2. MSE performance of the improved method.

Figure 3. BER performance of the improved method

VI. Conclusion

In this paper, an improved DFT-based channel estimation method in non-sample-spaced multipath

channel for MIMO- OFDM system is proposed. The improved method uses the symmetric property and

calculates the changing rate of the leakage energy in order to select useful paths. Simulation results show

that the improved method can reduce the leakage energy efficiently. And the MSE and BER performance of the

improved method are both better than LS estimation and conventional DFT-based channel estimation method.

The improved method achieves a satisfying tradeoff between complexity and performance.

VII. Acknowledgment

This w o r k was supported by the Scientific Research Program from the Education

Department of Hebei Province (No. z2005323).

References [1] G.L. Stuber, J.R. Barry, S.W. McLaughlin, Ye Li, M.A. Ingram and T.G. Pratt, “Broadband MIMO-OFDM wireless

communications,” Proceedings of the IEEE, vol. 92, No. 2, pp. 271-294, February. 2004.

[2] Jan-Jaap van de Beek, O.Edfors, and M.Sandell, “On channel estimation in OFDM systems,” Presented at in proceedings of Vehicular Technology, Chicago, pp. 815-819, 1995.

[3] B.Song, L.Gui, and W.Zhang, “Comb type pilot aided channel estimation in OFDM systems with transmit diversity,”

IEEE Trans. Broadcast., vol. 52, pp. 50-57, March. 2006. [4] Noh. M., Lee. Y. , and Park. H. “A low complexity LMMSE channel estimation for OFDM,” IEE Proc. Commum., vol. 153,

No. 5, pp. 645-650, 2006. [5] M. K. Özdemir, H. Arslan, E. Arvas. “Towards Real–Time Adaptive Low–Rank Lmmse Channel Estimation of MIMO–

OFDM Systems,” IEEE Trans. Wireless Commun., vol. 5, no. 10, pp. 2675–2678, October.2006.

[6] I. Tolochko, M. Faulkner. “Real Time Lmmse Channel Estimation for Wireless OFDM Systems with Transmitter Diversity,”

Proc. IEEE Vehic. Tech. Conf. vol. 3, Vancouver, Canada, pp. 1555-1559. September.2002.

[7] O. Edfors, M. Sandell, J.-J. van de Beek, S. K. Wilson, and P. O.Börjesson, “Analysis of DFT-based channel estimators for OFDM,” Wireless Personal Commun, vol. 12, pp. 55-70, January. 2000.

[8] Li Li, Wang ke, and Han li. “Channel Estimation Based on DFT for OFDM Systems on Non-sample Spaced Channel,”

Journal of Wuhan University of Technology, vol. 33, No. 6, pp. 1195-1198, December.2009. [9] Y. Wang, L. Li, P. Zhang and Z. Liu, “Channel estimation for OFDM systems in non-sample-spaced multipath channels,”

Electronics Letters, vol. 45, January. 2009.


ISSN: 2278-2834 Volume 2, Issue 2 (July-Aug 2012), PP 07-10



Design and Verification of Five Port Router for Network on Chip

Using VERILOG

K. Satya1, G. Leenendra Chowdary

2, N. V. G. Prasd

3

1(Student M.Tech (VLSI DESIGN), Department of Electronics & Communication Engg, Sasi Inst. of Technology

& Engg. (SITE), Andhra Pradesh, India) 2(Asst. Professor, Department of Electronics & Communication Engg, Sasi Inst. of Technology & Engg

(SITE) , Andhra Pradesh, India) 3(Head of the Department (ECE), Sasi Inst. of Technology & Engg (SITE), Andhra Pradesh, India)

Abstract: The focus of this Paper is the actual implementation of Network Router and verifies the functionality

of the five port router for network on chip using the latest verification methodologies, Hardware Verification

Languages and EDA tools and qualifies the Design for Synthesis and implementation. This Router design

contains Four output ports and one input port, it is packet based Protocol. This Design consists of Registers,

FSM and FIFO’s. For larger networks, where a direct-mapped approach is not feasible due to FPGA resource

limitations, a virtualized time multiplexed approach was used. Compared to the provided software reference

implementation, our direct-mapped approach achieves three orders of magnitude speedup, while our virtualized

time multiplexed approach achieves one to two orders of magnitude speedup, depending on the network and

router configuration.

Keywords: FIFO, FSM, Network-On-Chip, Register blocks, and Router Simulation.

I. Introduction 90% of ASIC re-spins are due to Functional bugs. As the functional verification decides the quality of

the silicon, we spend 60% of the design cycle time only for the verification/simulation. In order to avoid the

delay and meet the TTM, we use the latest verification methodologies and technologies and accelerate the

verification process.

This project helps one to understand the complete functional verification process of complex ASICs

and SOC’s and it gives opportunity to try the latest verification methodologies, programming concepts like

Object Oriented Programming of Hardware Verification Languages and sophisticated EDA tools, for the high

quality verification.

1.1 Why Would I Need a Router?

For most home users, they may want to set-up a LAN (local Area Network) or WLAN (wireless LAN)

and connect all computers to the Internet without having to pay a full broadband subscription service to their

ISP for each computer on the network. In many instances, an ISP will allow you to use a router and connect

multiple computers to a single Internet connection and pay a nominal fee for each additional computer sharing

the connection. This is when home users will want to look at smaller routers, often called broadband routers that

enable two or more computers to share an Internet connection. Within a business or organization, you may need

to connect multiple computers to the Internet, but also want to connect multiple private networks not all routers

are created equal since their job will differ slightly from network to network. Additionally, you may look at a

piece of hardware and not even realize it is a router.

What defines a router is not its shape, color, size or manufacturer, but its job function of routing data

packets between computers. A cable modem, which routes data between your PC and your ISP can be

considered as a router. In its most basic form, a router could simply be one of two computers running the

Windows 98 (or higher) operating system connected together using ICS (Internet Connection Sharing). In this

scenario, the computer that is connected to the Internet is acting as the router for the second computer to obtain

its Internet connection. Going a step up from ICS, we have a category of hardware routers that are used to

perform the same basic task as ICS, albeit with more features and functions often called broadband or Internet

connection sharing routers, these routers allow you to share one Internet connection with multiple computers.

Broadband or ICS routers will look a bit different depending on the manufacturer or brand, but wired routers are

generally a small box-shaped hardware device with ports on the front or back into which you will plug each

computer along with a port to plug in your broadband modem. These connection ports allow the router to do its

job of routing the data packets between each of the computers and the data going to and from the Internet.

Depending on the type of modem and Internet connection you have, you could also choose a router with phone

or fax machine ports. A wired Ethernet broadband router will typically have a built-in Ethernet switch to allow

Design and Verification of Five Port Router for Network on Chip Using VERILOG


for expansion. These routers also support NAT (network address translation), which allows all of your

computers to share a single IP address on the Internet. Internet connection sharing routers will also provide users

with much needed features such as an SPI firewall or serve as a DHCP Server.

1.1.1. Router Design Principles

Given the strict contest deadline and the short implementation window we adopted a set of design

principles to spend the available time as efficiently as possible. This document provides specifications for the

Router is a packet based protocol. Router drives the incoming packet which comes from the input port to output

ports based on the address contained in the packet. The router is a” Network Router” has a one input port from

which the packet enters. It has four output ports where the packet is driven out. Packet contains 3 parts. They are

Header, data and frame check sequence. Packet width is 8 bits and the length of the packet can be between 1

byte to 63 bytes. Packet header contains three fields DA and length. Destination address (DA) of the packet is of

8 bits. The switch drives the packet to respective ports based on this destination address of the packets. Each

output port has 8- bit unique port address. If the destination address of the packet matches the port address, then

switch drives the packet to the output port, Length of the data is of 8 bits and from 0 to 63. Length is measured

in terms of bytes. Data should be in terms of bytes and can take anything. Frame check sequence contains the

security check of the packet. It is calculated over the header and data. The communication on network on chip is

carried out by means of router, so for implementing better NOC, the router should be efficiently design. This

router supports four parallel connections at the same time. It uses store and forward type of flow control and

FSM Controller deterministic routing which improves the performance of router. The switching mechanism

used here is packet switching which is generally used on network on chip. In packet switching the data the data

transfers in the form of packets between co-operating routers and Independent routing decision is taken. The

store and forward flow mechanism is best because it does not reserve channels and thus does not lead to idle

physical channels. The arbiter is of rotating priority scheme so that every channel once get chance to transfer its

data. In this router both input and output buffering is used so that congestion can be avoided at both sides.

Features

Full duplex synchronous serial data transfer

Variable length of transfer word up to 64 bytes.

HEADER is the first data transfer.

Rx and Tx on both rising or falling

edge of serial clock independently

4 receivers select lines

Fully static synchronous design with

one clock domain

Technology independent VERILOG

Fully synthesizable.

ROUTER is a Synchronous protocol. The clock signal is provided by the master to provide

synchronization. The clock signal controls when data can change and when it is valid for reading. Since

ROUTER is synchronous, it has a clock pulse along with the data. RS-232 and other asynchronous protocols do

not use a clock pulse, but the data must be timed very accurately. Since ROUTER has a clock signal, the clock

can vary without disrupting the data. The data rate will simply change along with the changes in the clock rate.

As compared with its counterpart I2C, ROUTER is more suited for data stream applications. Communication

between IP’s

II. Operation

The Five Port Router Design is done by using of the three blocks. The blocks are 8-Bit Register, Router

Controller and output block. The router controller is design by using FSM design and the output block consists

of four FIFO’s combined together. The FIFO’s store data packets and when you want to send data that time the

data will read from the FIFO’s. In this router design has four outputs i.e. 8-Bit size and one 8-bit data port. It is

used to drive the data into router. we are using the global clock, reset signals, error signal and suspended data

signals are the output’s of the router. The FSM controller gives the error and SUSPENDED_DATA_IN signals.

These functions are discussed clearly in below FSM description. The ROUTER can operate with a single master

device and with one or more slave devices. If a single slave device is used, the RE (read enable) pin may be

fixed to logic low if the slave permits it. Some slaves require the falling edge (HIGH→LOW transition) of the

slave select to initiate an action such as the mobile operators, which starts conversion on said transition. With

multiple slave devices, an independent RE signal is required from the master for each slave device.



III. Figures

Figure 1: Block Diagram of Five Port Route

Figure 2: Internal Structure of Five Port Router

Figure 3: Simulation of FSM Controller

Figure 4: Simulation of Router



IV. Applications When multiple routers are used in interconnected networks, the routers exchange information about

destination addresses, using a dynamic routing protocol. Each router builds up a table listing the preferred routes

between any two systems on the interconnected networks. A router has interfaces for different physical types of

network connections, (such as copper cables, fiber optic, or wireless transmission). It also contains firmware for

different networking protocol standards. Each network interface uses this specialized computer software to

enable data packets to be forwarded from one protocol transmission system to another. Routers may also be

used to connect two or more logical groups of computer devices known as subnets, each with a different sub-

network address. The subnet addresses recorded in the router do not necessarily to map directly to the physical

interface connections.

V. Eda Tools And Methodologies HVL: System VERILOG.

Verification Methodology: Constrained Random Coverage Driven verification Assertion Based Verification.

EDA Tools: Questa - A verification Platform from Mentor Graphics.

VI. Conclusion In this project I have verified the functionality of the ROUTER with the latest Verification

methodology i.e. System VERILOG and observed the code coverage and functional coverage of ROUTER by

using cover points and different test cases (like constrained, weighted and directed test cases). By using these

test cases I had improved the functional coverage of the ROUTER. In this project I used one master and four

slaves to monitor the ROUTER. Thus the functional coverage of the ROUTER was improved.

References [1] D.Chiou,“MEMOCODE2011Hardware/SoftwareCoDesignContest”,https://ramp.ece.utexas.edu/redmine/

Attachments/ DesignContest.pdf

[2] Blue spec Inc, http://www.bluespec.com

[3] Xilinx,“ML605HardwareUserGuide”,http://www.xilinx.com/support/documentation/boardsand

its/ug534.pdf

[4] Xilinx,“LogiCOREIPProcessor Local Bus (PLB) v4.6”, http://www.xilinx.com/support/documentation/ip

documentation/plb v46.pdf

[5] “Application Note: Using the Router Interface to Communicate Motorola, ANN91/D Rev. 1, 01/2001.

[6] Cisco Router OSPF: Design& Implementation Guide, Publisher: McGraw-Hill

[7] “Nortel Secure Router 4134”, Nortel Networks Pvt. Ltd.

[8] “LRM”, IEEE Standard Hardware Description Language Based on the Verilog Hardware Description

Language – IEEE STD 1364-1995.

Books:

[9]. Chris Spears SYSTEMVERILOG FOR VERIFICATION, Publisher: Springer.

[10]. Bhaskar. J, A Verilog HDL Primer, Publisher: Syndicate Publications.

https://ramp.ece.utexas.edu/redmine/

http://www.bluespec.com/

http://www.xilinx.com/support/documentation

http://www.xilinx.com/support/documentation/ip%20documentation/plb%20v46.pdf




ISSN : 2278-2834 Volume 2, Issue 2 (July-Aug 2012), PP 11-13 www.iosrjournals.org


A Dielectric Resonator Antenna Array for Wideband

Applications

Sagar Erande1, Syed Amir Ali

2

1, 2(Amity School of Engineering and Technology, Amity University Uttar Pradesh, India)

Abstract: This paper presents a new approach to design the dielectric resonator antenna (DRA) for wideband

applications, which has a stepped construction the hexagon shaped upper resonator and triangle shaped lower

resonator. The DRA is excited by a conformal inverted-trapezoidal patch connected to a microstrip line. The

wider bandwidth is achieved, because of three factors: compact honeycomb and triangle shaped dielectric

resonator, a conformal inverted-trapezoid patch as a feed mechanism, and a copper-clad substrate as a

baseboard. A 76.25% matching bandwidth (S11<10 dB) is achieved with broadside radiation patterns where the

impedance bandwidth covers a frequency range from 5.1 to 11.1 GHz. Based on the proposed structure, a four-

element array is designed, and the degree of the directivity increases largely.

Keywords: dielectric resonator antenna, hexagonal upper resonator, triangle shaped lower resonator ,

inverted trapezoidal patch, DRA

I. INTRODUCTION A resonant antenna was proposed by Professor S. A. Long in 1983. The dielectric resonator antennas

(DRAs) offer several advantages, such as small size, low dissipation loss. Since the DRA has negligible

metallic loss, it is highly efficient when operated at millimeter wave frequencies. The shapes of DRAs are

various-simple ones, such as a hemispherical DRA [1], a cylindrical DRA [2] and a rectangular DRA [3], and

improved ones, such as truncated tetrahedron shape, split cone shape and half-hemispherical shape DRAs.

DRAs can be excited with different feeding mechanism, such as coaxial feed, aperture, microstrip line and co-

planar lines [4]. As the present and future communication systems have imposed strict requirements on the

bandwidth of antennas, a lot of bandwidth enhancement techniques are used in designing the dielectric

resonator antenna (DRA), mainly at lowering the inherent Q-factor of the resonator; using external matching

networks; and combining multiple resonators. A much wider bandwidth was achieved by stacking two different DRAs [5, 6], loading a high permittivity, low-profile dielectric disc on top of a conventional homogeneous

DRA in and plugging an inner core into the lower stacked part [7]. In addition, multi-segment DRAs are

developed to enhance its coupling to a microstrip line by inserting one or more thin segments of different

permittivity substrates under a DRA of low permittivity [8].

In this paper, we present a new design in which the homogenous resonator structure is consisted of two

parts: the upper part has a hexagon -liked shape and the lower part has a triangle shape and the feeding

mechanism is a conformal inverted-trapezoidal patch connected to a microstrip line with an intermediate

substrate (low permittivity) inserting technique. The DRA has an obvious advantage of small size, and the

simulated results demonstrate that the proposed DRA achieves a wider impedance bandwidth as much as 78%

with a broadside radiation pattern. In order to increase the degree of directivity, the array composed of 14

elements are designed. In Section 2, antenna geometry is introduced clearly and the simulated results are given in detail. In

Section 3, an array is designed by using the proposed novel DRA elements, and the characteristics of DRA array

will be described. In the last section, conclusions are concluded.

II. ANTENNA CONFIGURATION

Fig. 1 shows the schematic of the proposed DRA and Fig. 2 shows the top view, where a stepped

dielectric resonator is centrally placed on a square substrate with a size of 30mm × 30mm.

Figure 1: Schematic of DRA

A Dielectric Resonator Antenna Array for Wideband Applications


Figure 2: Top View of DRA

with respect to the central frequency at 7 GHz. The upper part of DR is a hexagon -shaped DR with

equal six-side length L1= 6 mm, and height H1=6.35 mm. The lower part is an equiangular-triangle across

section with the height H2=6.5 mm, and length L2=10.4mm. The DR is fabricated on Arlon 600 (tm) microwave dielectric material with a permittivity of ε r =6. The excitation mechanism adopts a conformal

inverted-trapezoid patch attached on one side of the lower layer DR in the x-axis direction and connected to a 50

microstrip feed line. The impedance bandwidth can be enhanced by using a single-sided copper-clad substrate

corresponding to the ground plane .

Using a single-sided copper-clad substrate means inserting a dielectric material between the DR and the

ground plane, where the inserted substrate dielectric constant is much lower than the DR one that enables

correct excitation of the fundamental mode. An appropriate wideband design of the proposed DRA adopts two

methods. The numerical analysis was performed using the commercial full-wave analysis tool Ansoft HFSS

employing the finite element method (FEM). Fig. 3 shows the return loss (s11) of the depicted DRA.

Figure 3. Return loss (S11) of DRA

The matching frequency range of the simulated homogeneous DRA is from 5 .1GHz to 11.1 GHz (S11<10), corresponding to a bandwidth of 76.25%.

Fig. 4 shows the radiation pattern at a resonance frequency of 6 Ghz. It can be seen that the radiation

pattern is symmetrical in the y-z plane (pi=90deg), and in the x-z plane (pi=0deg) mainly due to the asymmetry

of the structure in the x-z plane.

Figure 4: Simulated radiation pattern (db)

III. DESIGN OF AN ARRAY To increase the degree of the directivity, an array is designed with four proposed DRAs. Fig. 5 shows the

geometry of the array, and the microstrip corporate feed is used for feed arrangement. The first balanced line along a distance of quarter wavelength has a characteristic impedance of 70.7, and the second balanced line

along a distance of 5/4 wavelength distance has a characteristic impedance of 50. The formation of a

directional DRA array requires that the DRA elements be positioned with a close spacing between elements.

However, the proximity of the elements results in mutual coupling between elements due to the electromagnetic

A Dielectric Resonator Antenna Array for Wideband Applications


interaction between elements. The mutual coupling may be significant so that it substantially affects the

performance of the array including radiation pattern, directivity, operating frequency and bandwidth. Hence, the

spacing between elements is 0.7λ0.

Figure 5. Geometry of the proposed antenna array

With the following DRA element and array parameters: DRA: H1 =6.35mm, L1=6mm, H2 =6.5mm,

L2=10.4mm, Fig. 6 plots the simulated return loss (S11).

Figure 6. Simulated return loss (S11) of the array

IV. CONCLUSION A hexagonal DRA with advantages of compact structure which the area is 30mm X 30 mm is presented

and a larger bandwidth of 76.25% range from 5GHz to 11.1GHz is obtained. An inverted-trapezoidal patch

excitation has a better impedance matching obviously. The array consisted of the proposed DRA has an

increasing of the degree of the directivity and the impedance bandwidth curves is more smooth in the pass band,

which can be used in wide band communication.

REFERENCES [1] Kishk A.A., Zhou G., and Glisson A.W., “Analysis of dielectric-resonator antennas with emphasis on hemispherical structures,”

IEEE Antennas Propagation Magazine, 36(2), 1994, 20–31.

[2] Kishk A.A., “Wide-band truncated tetrahedron dielectric resonator antenna excited by a coaxial probe,” IEEE Trans. Antennas

Propagation, 51(10), 2003, 2913–2917.

[3] Kishk A.A., Yan Y., and Glisson A.W., “Conical dielectric resonator antennas for wide-band applications,” IEEE Trans. Antennas

Propagation, 2002, 50(4), 469–474.

[4] Junker G.P., Kishk A.A., and Glisson A.W., “Input impedance of dielectric resonator antennas excited by coaxial probe,” IEEE

Trans. Antennas Propagation, 1994, 42, 960–966.

[5] Leung K.W., and Ng H.K., “The slot-coupled hemispherical dielectric resonator antenna with a parasitic patch: Applications to the

circularly polarized antenna and wideband antenna,” IEEE Trans. Antennas Propagation, 2005, 53(5), 1762–1769.

[6] Al Salameh M.S., Antar Y.M.M., and Seguin G.,“Coplanar-waveguide-fed slot-coupled rectangular dielectric resonator antenna,”

IEEE Trans. Antennas Propagation, 2002, 50(10), 1415–1419.

[7] Kishk A.A., Ahn B., and Kajfez D., “Broadband stacked dielectric resonator antennas,” IEEE Electron. Lett., 1989, 25(18), 1231–

1233.

[8] Petosa A., Simons N., Siushansian R., Ittipiboon A., and Cuhaci,M., “Design and analysis of multisegment dielectric resonator

antennas,” IEEE Trans. Antennas Propagation, 2000, 48(5), 738–742.




Dynamic Spectrum Sensing By Channel Information Table in

Cognitive Radios

M.K.Kaushik, Y. Yoganandam (Department Of Electrical Engineering, BITS-Pilani, Hyderabad Campus, Hyderabad, India)

Abstract:The spectrum sensing problem has gained new aspects with cognitive radio and opportunistic

spectrum access concepts. It is one of the most challenging issues in cognitive radio systems. In cognitive radio

networks, the secondary (unlicensed) users need to find idle channels via spectrum sensing for their

transmission. Adaptive spectrum sensing (ASS) is a promising technology in spectrum sensing with an

admirable performance. In ASS, multiple secondary users individually sense the idle channels and send their

decisions to the network center, and then the center will do a final decision. Spectrum sensing, which aims at

detecting spectrum holes, is the precondition for the implementation of cognitive radio (CR). In this work we

formed an information table at MSC (main switching center) which consists of channel information and

according to the requirement any primary or secondary user can fetch that channel and utilize without any

interference. The experiment is conducted on static as well as adaptive environment to check the throughput,

route delay of the conventional as well as proposed method.

Keywords: cognitive radio, cognitive radio network, MANets, spectrum sensing, wireless sensor networks

I. Introduction

RADIO spectrum is usually considered as a scarce resource while measurements show that the

allocated spectrums are vastly under-utilized. The cognitive radio (CR), which has received a considerable

attention, is designed for the secondary users to opportunistically access to the unused primary (licensed)

spectrums without causing interference to the primary users. Ever since the 1920s, every wireless system has

been required to have an exclusive license from the government in order not to interfere with other users of the

radio spectrum. Today, with the emergence of new technologies which enable new wireless services, virtually

all usable radio frequencies are already licensed to commercial operators and government entities. According to

former U.S. Federal Communications Commission (FCC), spectrum is not utilized according to the data rates. On the other hand, not every channel in every band is in use all the time; even for premium frequencies

below 3 GHz in dense, most bands are quiet most of the time.

The FCC in the United States and the Ofcom in the United Kingdom, as well as regulatory bodies in

other countries, have found that most of the precious, licensed radio frequency spectrum resources are

inefficiently utilized. Cognitive radios will help commercial as well as military communication systems, by

eliminating the need for comprehensive frequency planning. They will be capable of sensing the environment,

making decisions on the types of signals present, learning patterns, and choosing the best method of

transmitting the information either on their own or in a network- centric environment. They will be situation-

aware and capable of making decisions to ensure error-free and smooth transfer of bits between the users.

Cognitive radios will be based on software defined radio (SDR) platforms and will try to understand not only

what users want but also what the surrounding environment can provide. Hence spectrum sensing and utilization will be done according to the limits and channel requirements. Through the detection and utilization of the

spectra that are assigned to the licensed users but standing idle at certain times, cognitive radio acts as a key

enabler for spectrum sharing. Spectrum sensing, aiming at detecting spectrum holes (i.e., channels not used by

any primary users), is the precondition for the implementation of cognitive radio. The Cognitive Radio (CR)

nodes must constantly sense the spectrum in order to detect the presence of the Primary Radio (PR) nodes and

use the spectrum holes without causing harmful interference to the PRs. Hence, sensing the spectrum in a

reliable manner is of vital importance and constitutes a major challenge in CR networks. However, detection is

compromised when a user experiences shadowing or fading effects or fails in an unknown way.

Lot of research is happening on spectrum sharing and utilization. In this work the focus is towards

maintaining a spectrum information table at the main switching center and allocates the frequencies accordingly

without any interference among the primary user and secondary user. As the motivation is towards combining

computer networks and communications at one platform and looking for quality of service, applicationof routing protocol also plays main role. Once the optimized routing protocol is applied and spectrum information table is

maintained properly the idle spectrums are assigned to secondary users without any interference.

Dynamic Spectrum Sensing By Channel Information Table in Cognitive Radios


II. Literature Survey Spectrum sensing is a key issue in cognitive radio systems. Single-user spectrum sensing may not be

reliable due to many uncertainties such as fast fading or shadowing.Cognitive radio has received a lot of interest

over the past few years as a promising technology that aims to alleviate the spectrum scarcity problem by allowing unlicensed (secondary) users to access spectrum that is allocated to licensed (primary) users under the

condition of preserving the quality-of-service (QoS) of the licensed networks. In order to locate the nodes which

are in seek of communication is first explored by routing protocol and then the information is sent to the

information table and the communication happens in reliable fashion. Some of the optimized routing protocols

which are in current research are mentioned.

Routing Protocols in Ad-Hoc networks have been classified in many ways [3], based on routing

strategy and network structure. According to routing strategy, the routing protocols can be categorized as table-

driven and source initiated, while depending on the network structure these are classified as flat routing,

hierarchical routing and geographic position assisted routing. It should be mentioned at this point that owing to

the dynamic link topology, there are both unipath and multipath routing protocols. Most multipath routing

protocols are built upon unipath routing protocols, hence we restrict our discussion to mostly unipath routing protocols.

A lot of the routing protocols mainly make use of the flooding technique for route discovery which we

briefly mention as follows: A sender S broadcasts data packet P to all its neighbors and each node receiving P

forwards P to its neighbors - In this way, packet P reaches the destination D provided a path from S to D exists.

Node D does not forward the packet. We describe two routing protocols that make use of this technique, namely

Dynamic Source Routing (DSR)[4] and Ad-hoc On-Demand Distance Vector Routing (AODV)[5]. DSR uses

source routing instead of relying on the routing table at each intermediate device. DSR uses a combination of

Route Request (RREQ), Route Reply (RREP) and Route Error (RERR) messages to establish a route from

source to destination. In addition DSR also uses route caching to speed up route discovery. The main advantage

of DSR is that a route to a destination is established only when it is required to, and a single route discovery

often discovers routes to other destinations in the process. However, the main drawbacks of DSR are increased

size of packet header with the length of the route, stale caches, etc. AODV is a reactive (on-demand) protocol which borrows the advantageous concepts from DSR and DSDV (Destination Sequenced Distance Vector

Routing)(We mention this later) like on-demand route discovery and route maintenance, and the usage of node

sequence numbers from DDSV. The actual working of AODV is beyond our scope. Reference [5] gives a good

description. AODV is one of the most successful routing protocols in MANETs mainly because of its desirable

features like Minimal Space Complexity and Maximum Bandwidth Utilization.

We now look at another widely deployed protocol called Destination Sequenced Distance Vector

Routing Protocol (DSDV) [6]. DSDV is a proactive (means routes are independent of traffic pattern) protocol

which is a modification of the conventional Bellman-Ford algorithm. The important feature of DSDV is the use

of sequence numbers for the routing table entries. These sequence numbers are generated by the destination

stations and routing tables at each node are synchronized by each node advertising its routing table information

to its neighbors frequently. Forwarding decisions are made based on the sequence numbers. The main advantages of DSDV are that it guarantees loop-free paths and always maintains the best path to destination

rather than multiple paths. However, routing table updates are costly, and there is no support for multi-path

routing.

More recently, because of the rapid advances in Global Positioning Systems (GPS), Geographic

Routing Protocols are becoming popular. One such protocol is the Geographic Distance Routing (GEDIR) [7].

In GEDIR, location of the destination node is assumed to be known, and each node knows the locations of its

neighbors and forwards a packet to the neighbor closest to the destination. Many interesting advances have been

made in Geographic Routing like Routing based on Virtual Co-ordinates [9], Routing without Location

Information [8], etc.

In addition to Reactive and Proactive routing protocols, we also have Hybrid schemes like the Zone

Routing Protocol (ZRP) [10] which proactively maintain state information for links within a short distance, say

d, from any given node (Intra-Zone Routing) and uses a route discovery protocol for determining routes to a nodes at a distance greater than d (Inter-Zone Routing).

Most protocols we have seen so far use some kind of flooding. There are few protocols like the Link

Reversal Algorithm and Temporally-Ordered Routing Algorithm (TORA) which try to avoid/reduce flooding

behavior. See [11] and [12] respectively for discussions. Routing Protocols which define the optimization

criteria as a function of the energy consumption are called Power-Aware Routing Protocols [13]. The idea is to

assign each link a weight which is a function of energy consumed when transmitting a packet on that link. The

goal is to route through paths with minimum weight. Such protocols are usually built on top of existing

protocols like DSR.



III. Design Approach: Since the mobile terminals are free to move, it is not guaranteed that any MT involved in a

communication session will remain in the cell it once was during the lifetime of the session. When an MT goes

over to another cell while a call proceeds, the call is passed to the new base station. This procedure is called handoff. The average number of handoffs during a session depends in the cell radii, mobility pattern of the

mobile terminals and call duration.

Two thresholds are set for the handoff procedure. When the power level drops below the first threshold,

the handoff procedure is triggered. As long as the power level remains above the second threshold, which is

lower than the first one, the perception of the signal is enough for proper communication. In order to provide

seamless communication, the received signal powers are monitored. The handoff must be completed before the

signal level drops below the second threshold.

In case of a handoff, the call is transferred to the base station of which the received power level is

highest. Therefore an MT, the initial and a final BS is involved in a handoff procedure. The transfer of pre-

established communication links from one base station to another one takes time. It is possible that new

resources are not available on the way to the new base station. Especially when the carried data rate cannot be determined beforehand, it may be difficult to allocate necessary resources on time. Hence, the gap between two

threshold values should be chosen very carefully to allow the procedure enough time to be completed. Details

and an overview of handoff strategies can be found in [14].

Another important issue is that the data should not be lost during the handoff. According to the

properties and aims of the application and network, deployment of buffers may be necessary. If only multimedia

content is transferred, the buffering may not be necessary. On the other hand, deployment of buffers is

inevitable for handoffs for data transfer. The buffer deployment strategies and how the buffered data can be

transferred to the MT is discussed in [13].

When the scope of the cellular networks is extended to include also multicasting, different

considerations are necessary [14]. Buffering is also deployed in cases of multicasting data to many mobile

terminals over heterogeneous data rates. The synchronization of data during handoffs is a very challenging

problem. A possible solution to this problem is presented in [15].

IV. Mobility Management It is not enough to provide access to the mobile terminals or keep the communication alive despite the

mobility. It is also of vital importance to keep track of the locations of the mobile terminals. Again no

assumption about the location of the mobile terminal is logical. Hence, there should be a way of finding the

mobile terminal in a reasonable time and at a reasonable cost. The efforts to locate the mobile terminals in the

entire network and update of the location information are called Mobility Management.

There are mainly two fundamental operations in location management [16]. The first one is location

update. Location update corresponds to reporting the location of the mobile terminal to its home location register, a database at the home of the mobile terminal. The second operation is paging. This operation

corresponds to broadcasting the identity of a mobile terminal over a certain area. These two operations are

inevitable for locating the mobile terminal. When a call is directed to a mobile terminal, the home location

register is checked to find out the location of the mobile terminal. Then, the call is redirected to the actual

location of the mobile terminal. When the call reaches the designated location, the mobile terminal is paged.

The location data stands most of the time for a group of cells, which is called a location area [17]. The

location update is performed when a mobile terminal enters the location area. If the location area consists of

only one single cell, the exact location is retrieved from the home location register and the paging cost is

minimized. But this would lead to high location update costs and create lots of signaling traffic significantly. On

the other hand, if the size of the location area is increased, the frequency of location updates decreases.

However, paging has to be performed in more than one cell. Note that even if the location area consists of only one cell, paging should be performed.

There are three major different location update strategies. The update may be based on the time

elapsed, the number of movements [16] or the distance traveled [17]. In any case, the location uncertainty

introduced with location areas persists. Therefore, for each approach, the trade-off between the traffic generated

and paging cost has different levels. It is also possible to optimize the location update procedure. In order to

achieve this, a hierarchical structure is proposed in [18]. Here the information dissemination follows a

hierarchical structure. So the amount of data flowing in the network is lowered.

Different ideas and approaches are proposed in the literature to optimize the mobility management.

These considerations also take different levels of constraints and mobility models into account. The common

aims, though, are minimizing the paging and communication load while keeping the location delay in acceptable

amounts. Some related approaches can be found in [16-19].



V. Channel Allocation Schemes The total amount of channels available for the cellular network can be assigned to cells in different

ways. The process of assigning channels either to cells or to calls is called channel allocation. The schemes used

differ in performance, flexibility and complexity. However, there is a tradeoff among these qualities, hence each scheme has advantages and disadvantages.

Channels can be distributed to cells statically, dynamically or in hybrid ways. The most commonly

used scheme is to assign the channel sets statically to the cells. The cells may use the channels from the

available set without any other constraint. This scheme performs well under the uniform traffic load over the

cells. Its performance is also high in cases where the total traffic load is high.

In order to cope with situations where the traffic load differs from one cell to the other and where

traffic load ratios do not change very much over the time, the cells may be borrowed to heavily loaded cells. If

the channel set sizes are not equal, this corresponds to static borrowing. If the system has hot spots where the

traffic intensity increases for short periods of time, then the channels may be lent by the lightly loaded

neighboring cells to the temporarily highly loaded cell. Then the problem is solved at the cost of not being able

to use the borrowed cells in a larger area than before. It is also possible to set limits on the number of cells that can be borrowed in order to prevent

starvation. In any case, a certain borrowing algorithm has to be deployed. The algorithm may choose channels

from the richest cell. Another choice would be to borrow the first available channel in the neighborhood. It is

also possible to return the used channels back to the donor as soon as a channel from the set of channels that

belong to the cell that borrowed becomes available.

It is possible to assign the channels to the cells according to their needs. The channels are kept in a

common set. The cells do not have their own channels. The assignment is done in call basis. In order to stick to

the rules of frequency reuse, the determination of channels to be assigned has to be made carefully. The schemes

that are based on the dynamic channel allocation are examined according to the way the assignment decision is

performed.

The first scheme has a central decision element which decides on the channels that has to be assigned

to calls. As it is the case for all centralized systems, the main drawback of this approach is that the central authority becomes the bottleneck of the system. So it is possible to distribute the decision to the base stations.

The base stations collect local data from their vicinity and make their allocation decisions according to this. The

resulting assignment is not optimal due to local character of the collected data. The results can be specialized

and optimized for the one dimensional movement case.

Another possibility is to combine both approaches into one hybrid system. The entire channel spectrum

is divided into two subsets. The first set is distributed to the cells statically. The remaining channels are assigned

to cells according to the traffic load and call requests. Since the two systems are combined, any choice of the

sub-strategies can be applied to the respective part of the scheme.

VI. System Architecture: To develop a simulation model and generalized architecture is designed as shown below,

Figure1: System Architecture

The first group of experiments deals with the effect of the isolated parameters on the objective

function. For all of these parameters, the relationship between the parameters supplied to the algorithm and the

cost of the system is compared. Furthermore the effects of the design decisions are questioned. Their effect on

the cost is compared with the cost of the system in hand. The comparison is made by comparing the costs under

different arrival rates.

User interface with number

of Nodes in the network

Create

Network

Route discovery

(DSR)

Communicate

Channel

information

table llelele

Forwarding

Destination

Created Network

Discovered Route

Link Req.

Req.

Response Status

Destination status



The aim of the experiments in the second group was to observe the solutions of the adaptive algorithm

in a large part of the parameter space. By doing so, the behavior of the spectrum sensing systems is presented.

The performance of the system under some unexpected increases in the call arrival rates is examined.

The increase in the call arrival rates include calls generated by both mobility class users. The obtained results

are presented graphically.

Lastly, the time complexity of the algorithm is estimated partially by experimental measurements and partially by analysis of the algorithms used in the solution technique. The results of this analysis are also

presented in this section.

For the realization and evaluation of the suggested approach following matlab coding were developed,

1) Msc_mont.m: This function is developed for central monitoring of the channel allocation happening in the

cells by the base stations for the generated request.

2) Data_ex.m: This function is developed for the data exchange between two nodes during uplink and

downlink operation.

3) Comm.m: This function is developed for the selection of the communication process from given source to

destination based on one-hop or two hop communication

4) Creat_ntw.m: This function is developed for the creation of random nodes and the network during the

network creation.

5) Route.m: this function implements the routing protocol in route establishment in the cellular adhoc network. This function estimates the neighbor node, broadcast the packet from a source to destination and predict all

possible paths for creation of possible routes for a given source to destination.

6) Main.m: this is the main unit of the implementation and integratesthe entire sub module for the realization

of the functionality.

7) Node: this function realizes the node unit where the address matching is performed and if the destination

match with the current node address then acknowledgment packet is generated else the packet is forwarded

to the next neighbor cell.

8) Path23.m: this function realizes the path creation from a source to destination. it buffers the one hop

neighbor until the destination is reached in uplink operation.

9) Sel_channel.m: This function selects the channel to be allocated from the IIT list based on the given source

and destination in a cell. The operational flow chart is as presented below

Start

Check for one Hop or 2-Hop call

Check the channel allocation status from MSC

Calculate the probability of allocation

If request is true

If channel is free or probability of allocation is maximum

Allocate the channel

Send the allocation status to MSC

Update the IIT entry in MSC

Update the IIT entry in MSC

If communication is over

Check for a new request from the node

No

No

NoYes

Yes

Yes

Figure 2: Operational flow chart



VII. Results The algorithm is simulated by two case studies viz., static and dynamic topology which is shown in

figures 3 and 4 respectively. From the figures it’s been observed that with the help of channel information table

at main station the primary user and secondary users are allocated without any interference. Some of the parameters like route delay, throughput, route overhead are tested on two kind of topologies with and without

table information at main station. It’s clearly observed that a reliable path is obtained by dynamic routing

protocol and throughput of the system is also maintained properly between licensed and unlicensed users

Case Study 1:Spectrum Sensing when Nodes in the Base Station Area are Static

Figure 3Developed cellular architecture and node distribution for the simulation

(a) (b)

(c) (d)

(e) (f)

Figure 4Static topology (a) Nodes in topology (b) Reliable Route (c) Delay Performance (d) Route Delay Plot

(e) Route overhead (f) Throughput

0 20 40 60 80 100 120 140 160 180 2000

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NODES IN STATIC TOPLOGY FORMATION

0 20 40 60 80 100 120 140 160 180 2000

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No. of data Packets

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Queue

Proposed

conventional

5 6 7 8 9 10 11 12 13 14 150.5

1

1.5

2

2.5

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4

4.5

Offered Load

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Dela

y

Route Delay Plot

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coventional

2 4 6 8 10 12 14 16 18 200

0.2

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e O

verH

ead

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ugpu

t plo

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Proposed

Convnentional



Case Study 2:Dynamic Spectrum Sensing

(a) (b)

(c) (d)

(e) (f)

Figure 7Random topology (a) Nodes in topology (b) Reliable Route (c) Delay Performance (d) Route Delay Plot

(e) Route overhead (f) Throughput

VIII. Conclusion

Spectrum is a very valuable resource in wireless communication systems. Cognitive radio, which is one

of the efforts to utilize the available spectrum more efficiently through opportunistic spectrum usage, has

become an exciting and promising concept. One of the important elements of cognitive radio is sensing the available spectrum opportunities. In this paper by forming an information centric table at the main switching

center the idle spectrum of primary users is been allocated to unlicensed users without any interference and

throughput is also improvised. This is done by considering two case studies viz., static and adaptive allocation

strategies.

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0 20 40 60 80 100 120 140 160 180 2000

20

40

60

80

100

120

140

160

180

200

12

3

45

6

78

9

10

11

12

13

14

15

16

17

18

19

20

NODES IN TOPLOGY FORMATION

0 20 40 60 80 100 120 140 160 180 2000

20

40

60

80

100

120

140

160

180

200

12

3

45

6

78

9

10

11

12

13

14

15

16

17

18

19

20

1 2 3 4 5 6 7 8 9 10

50

100

150

200

250

Delay Performance

No. of data Packets

Data

Que

ue

Proposed

conventional

5 6 7 8 9 10 11 12 13 14 150.5

1

1.5

2

2.5

3

3.5

4

4.5

Offered Load

Rou

te D

elay

Route Delay Plot

Proposed

coventional

2 4 6 8 10 12 14 16 18 200

0.2

0.4

0.6

0.8

1

1.2

1.4

Communication Time

Rou

te O

verH

ead

Conventional

Proposed

1 2 3 4 5 6 7 8 9 10 110

1

2

3

4

5

6

Cycles

Thro

ugpu

t plo

t

Throughput

Proposed

Convnentional



[9] Ivan Stojmenovic, and Xu Lin, “Loop-Free Hybrid Single-Path/Flooding Routing Algorithms with Guaranteed Delivery for

Wireless Networks”, IEEE Transactions on Parallel and Distributed Systems, Vol. 12, Nr. 10 (2001), p. 1023-1032.

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Wireless Communication and Security in Wimax

Fazil Sarfaraz, Tarranum Parveen (Department of Electronics and Communication, LNCTS/RGPV, India)

Abstarct: Wireless communication deals with data transmission over air as interfacing medium between the

transmitting and receiving stations posing data security as biggest challenge. Although, technologies other than

wireless introduced earlier pay significant service to users, the broadband wireless, with mobility is the first

choice of people all over. In this, WiMAX 802.16e is one possibly technology supporting data security. It uses

different authentication and authorization protocols between the client and agent. This paper describes strategy

of WiMAX and security mechanisms used in it.

Keywords: WiMAX, DSN, AAA, WWAN, WBA

I. Introduction In this era of scientific and technical growth, effective communication is a major concerned issue.

Therefore it is mandatory to discuss about the latest communication technology. Wireless technology has taken

vast coverage over wired communication technology. Wireless means transmitting signals using radio waves as

the medium instead of wires. Wireless technologies are used for tasks as simple as switching off the television

or as complex as supplying the sales force with information from an automated enterprise application. Examples

today include cordless keyboards and mice, PDAs, pagers and digital and cellular phones and many more.

Wireless technology provides numerous advantages which make it attractive for the users which include

mobility, reachability, simplicity, maintainability, roaming services, new smart services such as SMS and MMS

and many more.

Wireless technologies are classified depending on their ranges and are designed to serve a specific

usage segment that includesa variety of variables including bandwidth requirements, distance needs and power.

The classifications include Wireless Wide Area Network (WWAN), Wireless Personal Area Network (WPAN),

Wireless Local Area Network (WLAN), Wireless Metropolitan Area Network (WMAN), etc. all these networks

are region specific and differ in terms of speed and range.

However, though comprising of proliferate inherent features and advantages, wireless networks suffer

three major issues i.e. Quality of Service (QoS), Security risk and reachable range. QoS involve interference to

service due to atmospheric imbalance and lost packets of data during transfer. Security risks involve security to

data transfer over wide area. Security mechanisms like the Service Set Identifier (SSID) and Wireless

Equivalency Privacy (WEP) may be adequate for residences and small businesses but they are inadequate for

entities that require stronger security. Reachable range is not so a major issue as it is extended to tens of miles

today.

Wireless Broadband Access (WBA) is a technology that ensures high speed connection over the air. It

uses radio waves to transmit and receive data directly to and from the potential users. This technology includes

3G, Wi-Fi, WiMAX.WBA is a point to multipoint system in which the base station uses an outdoor antenna to

send and receive high-speed data.

II. Competing Technologies Within the marketplace, WiMAX’s main competition came from widely deployed wireless systems

such as Universal Mobile Telecommunications System (UMTS), CDMA2000, existing Wi-Fi and mesh

networking. In the future, competition will be from the evolution of the major cellular standards to so-called 4G,

high-bandwidth, low-latency, all-IP networks with voice services built on top. The worldwide move to 4G for

GSM/UMTS and AMPS/TIA (including CDMA2000) is the 3GPP Long Term Evolution (LTE) effort.

http://en.wikipedia.org/wiki/File:Wimax.svg

Wireless Communication And Security In Wimax


Speed vs. mobility of wireless systems: Wi-Fi, High Speed Packet Access (HSPA), Universal Mobile

Telecommunications System (UMTS), and GSM

III. Comparison between WiMAX and Wi-Fi Refer to the following TABLE that gives a brief comparison between WiMAX and Wi-Fi

PARAMETERS Wi-Fi WAVE

(802.11p)

Wi-Fi (802.11) WiMAX

(802.16d)

WiMAX ODFMA

(802.16e)

Frequency Band

5.9 GHz 5/2.4 GHz 2-11 GHz 2.3-3.5 GHz

Channel

Bandwidth

10 20 10 5/10/20

Supported Data

rate

3 to 7 Mbps 6 to 54 Mbps 54 Mbps 54 Mbps

Modulation BPSK, QPSK,

16 QAM, 64

QAM

BPSK, QPSK,

16 QAM, 64

QAM

QPSK, 16

QAM, 64

QAM

QPSK, 16 QAM, 64

QAM

Channel Coding

CC 1/2,

2/3,3/4

CC 1/2,

2/3,3/4

CC 1/2,

2/3,3/4

CC 1/2, 2/3,3/4

No. of data

subscribers

48 48 192 360/720/1440

No. of pilot

Carriers

4 4 8 60/120/240

Guard

subcarriers

12 12 56 92/184/368

FFT/IFFT

64 64 256 512/1024/2048

FFT/IFFT

interval

6.4 3.2 22.22 91.43

Subcarrier

spacing

15625 MHz 0.3125 MHz 0.045 MHz 0.0109 MHz

Preamble

Duration

32 us 16 us 55.56 us 102.9 us

Cyclic prefix 1.6 us 0.8 us [5.56](1/4-

1/16)Tb us

11.43 us

OFDMA symbol

duration

8 us 4 us 27.78 us 102.9 us

Layer

CSMA MAC CSMA MAC TDMA OFDMA

Multipath PHY tolerates

only low

multipath

PHY tolerates

only low

multipath

PHY tolerates

only medium

multipath

PHY can tolerate

high multipath (10

us)

IV. WiMAX Theory WiMAX (Worldwide Interoperability for Microwave Access) was formed in April 2001, in

anticipation of the publication of the original 10-66 GHz IEEE 802.16 specifications. WiMAX is a high

throughput packet data transfer technology that supports both delay tolerant, burst-based services like web

browsing, messaging and delay-intolerant services like audio/video calls. These services are provided to the

end-user even while the user is mobile. WiMAX is a wireless communication standard designed to provide 30 to

40 mbps data rates. It is a part of a ‘fourth generation’ or 4G of wireless communication technology. More

strictly WiMAX is an industry trade organization formed by leading communications component and equipment

companies to promote and certify compatibility and interoperability of broadband wireless access equipment

that confirms to the IEEE 802.16 and ETSI HIPERMAN standards.WiMAX is to 802.16 as the Wi-Fi is to

802.11.



V. Features of WiMAX Technology The following potential applications are supported by WiMAX:

Provides portable mobile broadband connectivity across cities and countries through a variety of devices.

Provides a wireless alternative to cable and digital subscriber line (DSL) for large mile broadband access.

Provides data, telecommunications (VoIP) and IPTV services (triple play).

Provides a source of internet connectivity as part of a business continuity plan.

Smart grids and metering.

Can support very high bandwidth solutions where large spectrum deployments (i.e. >10 MHz) are desired

using existing infrastructure keeping costs down.

Can provide wide area coverage and quality of service capabilities.

5.1 Internet Access

WiMAX can provide home or mobile internet access across whole cities or countries. Given the

relatively low costs associated with the deployment of a WiMAX network, it is now economically viable to

provide last-mile broadband Internet access in remote locations.

5.2 BAckhaul

Mobile WiMAX was a replacement entity for cellular phone technologies such as GSM and CDMA or

can be used as an overlay to increase capacity. Fixed WiMAX is also considered as a wireless backhaul

technology for 2G, 3G and 4G networks in both developed and developing nations.

5.3 Triple-A

Wimax supports the technologies that make triple-play service offerings possible (such as Quality of

Service and Multicasting). As wireless progresses to higher bandwidth, it inevitably competes more directly

with cable and DSL, inspiring competitors into collaboration. Also, as wireless broadband networks grow denser

and usage habits shift, the need for increased backhaul and media service will accelerate, therefore the

opportunity to leverage cable assets is expected to increase.

5.4 Deployment

Wimax access was used t assist with communications in Indonesia, after the tsunami in December 2004. It

provided broadband access that helped regenerate communication to and from Indonesia.

WiMAX hardware was donated to FCC (Federal Communications Commission) an FEMA in their

communications efforts in the areas affected by Hurricane Katrina. Volunteers used mainly self-healing

mesh, Voice over Internet Protocol (VoIP), and a satellite uplink combined with Wi-Fi on the local link.

VI. The IEEE 802.16 Standard WiMAX is based upon IEEE Std 802.16e-2005, approved in December 2005. It is a supplement to the

IEEE std 802.16-2004. Thus, these specifications need to be considered.

IEEE 802.16e-2005 has following merits:

Adding support for mobility (soft and hard handover between base stations)

Scaling of the Fast Fourier Transform (FFT) to the channel bandwidth in order to keep the carrier spacing

constant across different channel bandwidths

Advanced antenna diversity schemes, and hybrid automatic repeat request (HARQ)

Adaptive Antenna Systems (AAS) and MIMO technology

Denser sub-channelization, thereby improving indoor penetration

Introducing Turbo-Coding and Low Density Parity Check (LDPC)

Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice-

versa

Adding an extra QoS class for VoIP applications.

VII. WiMAX Physical Layer The updated IEEE 802.16e-2005 uses scalable orthogonal frequency division multiple access. OFDM

(Orthogonal Frequency Division Multiplexing) is a method of encoding digital data on multiple carrier

frequencies. OFDM has developed into a popular scheme for wideband digital communication, whether wireless

or over copper wires, used in applications such as television and audio broadcasting. OFDM is an elegant and

efficient scheme for high data rate transmission in o non-line-of-sight or multipath radio environment.



7.1 PHY-Layer Data Rates Because of the flexible nature of physical layer of WiMAX, data rates performance varies based on the

operating parameters. These include channel bandwidth and the modulation and coding scheme used. Other

parameters, such as number of subchannels, OFDM guard time, and oversampling rate, also have an impact.

7.2 WiMAX OFDM

OFDM belongs to a family of transmission schemes called multicarrier modulation, which is based on

the idea of dividing a give high-bit-rate data stream into several parallel lower bit-rate streams and modulating

each stream on separate carriers, often called subcarriers or tones.

Multicarrier modulation schemes eliminate or minimize intersymbol interference (ISI) by making the

symbol time large enough so that the channel-induced delays. Delay spread being a good measure of this in

wireless channels, are an insignificant (typically, <10%) fraction of the symbol duration. OFDM is spectrally

efficient versions of multicarrier modulation, where the subcarriers are selected such that they are all orthogonal

to one another over the symbol duration, thereby avoiding the need to have non overlapping subcarrier channels

to eliminate inter carrier interference.

In order to completely eliminate ISI, guard intervals are used between OFDM symbols. By making the

guard interval larger than the expected multipath delay spread, ISI can be completely eliminated. Adding guard

interval, however, implies power wastage and a decrease in bandwidth efficiency.

VIII. Adaptive Modulation andCoding in WiMAX WiMAX supports a variety of modulation and coding schemes and allows for the schemes to change

on a burst-by-burst basis per link, depending on channel conditions. Using the channel quality feedback

indicator, the mobile can provide the base station with feedback on the downlink channel quality. For the uplink,

the base station can estimate the channel quality, based on the received signal quality.

Downlink Uplink

Modulati

on

BPSK, QPSK, 16 QAM, 64 QAM;

BPSK optional for OFDMA-PHY

BPSK, QPSK, 16 QAM; 64

QAM optional

Coding

Mandatory: convolutional codes at

rate 1/2, 2/3, 3/4, 5/6

Mandatory: convolutional

codes at rate 1/2, 2/3, 3/4, 5/6

IX. WiMAX MAC (Medium Access Control) Layer (data link layer) The IEEE 802.16 MAC was designed for point-to-multipoint broadband wireless access applications.

The primary task of the WiMAX MAC layer is to provide an interface between the higher transport layers and

the physical layer. The MAC layer takes packets from the upper layer. These packets are called MAC service

data units (MSDUs) and organize them into MAC protocol data units (MPDUs) for transmission over the air.

For received transmissions, the MAC layer does the reverse. The 802.16 MAC is designed for point-to-

multipoint (PMP) applications and is based on collision sense multiple access with collision avoidance

(CSMA/CA).

The MAC incorporates several features that include the following:

Privacy key management (PKM) for MAC layer security.

Broadcast and multicast support.

Manageability primitives.

High-speed handover and mobility management primitives.

Three power management levels, normal operation, sleep and idle.

Five service classes, unsolicited grant service (UGS), real-time polling service (RTPS), non-real-time

polling service (NRTPS), best effort (BE) and extended real-time variable rate (ERT-VR) service.

Support for QoS is a fundamental part of the WiMAX MAC-layer design. WiMAX borrows some of

the basic ideas behind its QoS design for the DOCSIS cable modem standard. Strong QoS control is achieved by

using a connection-oriented MAC architecture, where all downlink and uplink connections are controlled by the

serving BS.



X. WiMAX Quality of Service (QoS) WiMAX Quality of Service or WiMAX QoS is a key element in the delivery of service over the

WiMAX medium. With techniques such as Internet Protocol being used, delays or latency and jitter can be

introduced into the data transmission arena. To overcome the effects of latency and jitter, the concept of quality

of service is used. For WiMAX Qos several techniques and definitions are at the core of implementation.

In order to categorize the different types of quality of service, there are five WiMAX QoS classes that have been

defined.

10.1 Unsolicited Grant Service

The Unsolicited Grant Service, UGS is used for real-time services such as Voice over IP, VoIP for

applications where Wimax is used to replace fixed lines such as E1/T1.

10.2 Real-time Packet Services This WiMAX QoS class is used for real-time services including video streaming. It is also used for

enterprise access services where guaranteed E1/T1 rates are needed but with the possibility of higher bursts if

network capacity is available. This WiMAX QoS class offers a variable bit rate but with guaranteed minimums

for data rate and delay.

10.3 Extended Real Time Packet Services

This WiMAX QoS class is referred to as the Enhanced Rea Time Variable Rate, or Extended Real

Time Packet Services. This WiMAX QoS class is used for applications where variable packet sizes are used –

often where silence suppression is implemented in VoIP. One typical system is Skype.

10.4 Non-real time Packet Services

This WiMAX QoS class is used for services where a guaranteed bit rate is required but the latency is

not critical. It might be used for various forms of file transfer.

10.5 Best Effort

This WiMAX QoS is that used for Internet services such as email and browsing. Data packets are

carried as space becomes available. Delays may be incurred and jitter is not a problem.

XI. WiMAX Security Security in WiMAX is handled by a privacy sublayer within the WiMAX MAC. The key aspects of

WiMAX security are as follows:

11.1 Support for Privacy

User data using cryptographic schemes of proven robustness to provide privacy. Both AES (Advanced

Encryption Standard) and 3DES (Triple Data Encryption Standard) are supported.

11.1.1 Encryption in WiMAX

When transmitting a MAC PDU on a connection that is mapped to a SA, the sender should perform

encryption and data authentication of the MAC PDU payload as specified by that SA. When receiving a

MAC PDU on a connection mapped to an SA, the receiver shall perform decryption and data authentication

of the MAC PDU payload, as specified by that SA.

Two bits of a MAC header contain a key sequence number. The keying material associated with an SA has

a limited lifetime, and the BS periodically refreshes an SA’s keying material. The BS manages a 2-bit key

sequence number independently for each SA and distributes this key sequence number along with the SA’s

keying material to the client SS. The BS increments the key sequence number with each new generation of

keying material. The MAC header includes this sequence number to identify the specific generation of that

SA keying material being used to encrypt the attached payload. Being a 2-bit quantity, the sequence number

wraps around to 0 when it reaches 3.



Security Associations (SA)

A security association is a set of security information a BS and one or more of its client SSs share in

order to support secure communications across the IEEE 802.16 network. Three types of SAs are defined:

Primary, Static and Dynamic. Each SS establishes a primary security association during the SS initializing

process. Static SAs are provisioned by the BS. Dynamic SAs are established and eliminated, on the fly, in

response to the initiation and termination of specific service flows. Both static and dynamic SAs may be shared

by multiple SSs. Each SS shall establish an exclusively Primary SA with its BS. The SAID of any SA’s Primary

SA shall be equal to the basic CID of that SS.

11.2 Device/User authentication WiMAX provides a flexible means for authenticating subscriber stations and users to prevent

unauthorized use. The authentication framework is based on the Internet Engineering Task Force (IETF) EAP,

which supports a variety of credentials, such as username/password, digital certificates, and smart cards.

WiMAX operators can use the certificates for device authentication and use a username/password or smart card

authentication on top of it for user authentication.

11.2.1 EAP Protocol

The Extensible Authentication Protocol (EAP)is a protocol for wireless networks that expands on

authentication methods used by the Point-to-Point Protocol (PPP), a protocol often used when connecting a

computer to the Internet. EAP can support multiple authentication mechanisms, such as token cards, smart

cards, certificates, one-time password and public key authentication.

11.2.1.1 EAP-TLS

EAP-TLS is an extension to the Extensible Authentication Protocol and provides Transport Level

Security (TLS). EAP-TLS provides for mutual authentication ciphersuite negotiation and key exchange between

two endpoints. In WiMAX, EAP-TLS is used in cases where no user authentication is being done and instead

just server and device authentication is done.

11.2.1.2 EAP-TTLS

EAP TTLS is an extension to EAP-TLS. It allows the server to authenticate the client within a secure

connection established during the TLS handshake. Within the secure connection, a number of protocols may be

used to authenticate the client. The CHAP authentication method and MS-CHAPv2 uses a secret only known by

the server and the client. Tunneled CHAP and MS-CHAPv2 authentication shall be supported by the MS and its

AAA server.

11.2.1.3 AAA (AUTHENTICATION, AUTHORIZATION, ACCOUNTING) Server

AAA monitors user access in the network. In AUTHENTICATION, the identity of the user is verified,

using a password etc. During AUTHORIZATION, a check on what services a user is allowed to access and how

much Quality of Service (QoS) the user can get etc. is done. In ACCOUNTING, billing for all services availed

are done, based on the IP flow, duration of access etc.

Fig. 1 WiMAX echo system

WAC: WAC provides/participates in authentication and authorization of MS, MS IP establishment ( by

the DHCP relay/proxy function), MP procedures, idle mode and Paging procedures, QoS management, BS

management etc.

BS

BS

R1 / Ww

R8

R6

R6

BS

BS

WAC R8

R6

R6

R4

WiMAX Network

R3

WAC (FA)

AAA Server OCS

CGw

DNS Server

HA*

R3

R3 MSS DHCP Server

NAT / Firewall

R3



Omc-R (Operation & Maintainance Controller-Radio)

OMC-R is used as the management platform of the WiMAX Radio Access Network (RAN), provisioning

and providing template-based radio configuration.

Performs network surveillance, quality o service monitoring and radio network planning/optimization for

the WiMAX Access Network.

Ntp (Network Time Protocol) Server

It is used toensure time synchronization between every entity that provides timestamps, in order to have a

unique time in the network.

Csn (Core Service Network)

This represents a set of network elements between every entity that provides timestamps, in order to

have a unique time in the network.

Dns (Domain Name Server)

Used to allocate IP address to all RAN NEs, MSs (in the subnet associated to the HA)

Update DNS dynamically (DDNS)

Session Border Controllers (Sbc)

Present at the border of the core network

Acts signaling Application Layer Gateway (ALG) and media gateway for VoIP service.

Handles QoS and acts as the SIP proxy (P-CSCF) between MS and Softswitch.

Charging Gateway

The user’s usage duration, quantity etc. are sent to the charging gateway. It calculates the charges based

on the usage.

HOME AGENT (HA)

It is a router responsible for routing packets from the MS subnet to ASP/ISP and vice-versa.

It makes a match between the CoA (care-of-address) and the HoA (Home address=IP address of the MS in

the network).

Foreign Agent (Fa)

The WAC acts as the FA. It has the CoA of the MS. Any packet meant for the MS is redirected from HA to

FA, which in turn sends to the corresponding MS.

It is router responsible for routing packets from the MS subnet to ASP/ISP and vice-versa. It makes a

match between the CoA (care-or-address) and the HoA (Home address=IP address of the MS in the

network).

Authentication And Encryption

The authentication of the MS is done by means o a signaling exchange using EAP (Extensible

authentication protocol).

EAP allows for a variety of user credentials, including username/password, digital certificates and smart

cards.

The authentication during INE is always started by WAC.

NAI (network access identifier) is given by MS during authentication. It is used for identifying the MS, as

well as routing messages.

MSS BS

PKM-RSP (PKMv2 SA-TEK-

Challenge) 1

PKM-REQ (PKMv2 SA-TEK-Request) 2

PKM-RSP (PKMv2 SA-TEK-

Response) 3

R1



PKM Key exchange

SA-TEK3-way handshake is performed to validate the ASK.

All three messages in the handshake are integrity protected using the new PMK/AK context.

The challenge message maps the AK Sequence number (assigned to PMK) and AKID.

Security parameters negotiation is done in the Request response messages.

11.3 Flexible Key-management protocol The Privacy and Key-management Protocol Version 2 (PKMv2) is used for securely transferring

keying material from the base station to the mobile station, periodically reauthorizing and refreshing the keys.

11.4 Protection of control messages

he integrity of over-the-air control messages is protected by using message digest schemes, such as

AES-based CMAC or MDS-based HMAC.

11.5 Support for fast handover

To support fast handovers, WiMAX allows the MS to use preauthentication with a particular target BS

to facilitate accelerated reentry.

XII. Conclusion The spread of different broadband wireless technologies all over has led to increased dependency and

concern regarding the drawbacks it suffers. Of all drawbacks, security has always been the biggest threat and is

covering broader areas of research. Albeit, with the help of WiMAX technology 802.16e that offers security

relief to a greater extent. The different versions of WiMAX, as defined by IEEE protocols introduced till today

compete in different features. Earlier use of landline and other wired equipments has been replaced by the use of

smart cards, cellular wireless devices and many more and hence, this dependency graph on wireless

communication will also extend to higher limits. Hence, continuous research in this field is always expected.

References [1]. Thesis on WiMAX.

[2]. WiMAX Forum technology (retrieved 2008).

[3]. Roger Marks- IEEE 802.16 WirelessMANStandard:myths and facts. [4]. Carl Weinschenk : Speeding up WiMAX.

[5]. IEEE 802.16e Task Group (Mobile WiMAX). [6]. HIPERMAN/WiMAX testing (retrieved 2008).

[7]. K. Fazel and S. Kaiser, Multi-Carrier and Spread Spectrum Systems: From OFDM and MC-CDMA to LTE and WiMAX. 2nd

edition, John Wiley $ Sons,2008. [8]. M. Ergen, Mobile Broadband-including WiMAX and LTE, Springer, NY, 2009.

[9]. Prashant Sharma (2009), Facts about WiMAX.





Effect of Traffic Pattern on Packet Delivery Ratio in Reactive

Routing Protocol of Manet

Patil V.P. Smt. Indira Gandhi College of Engineering, New Mumbai, India.

Abstract: An ad hoc network is a collection of mobile nodes that dynamically form a temporary network.

Routing in a MANET is challenging because of the dynamic topology and the lack of an existing fixed

infrastructure. In such a scenario a mobile host can act as both a host and a router forwarding packets for other

mobile nodes in the network. Routing protocols used in mobile ad hoc networks (MANET) must adapt to

frequent or continual changes of topology, while simultaneously limiting the impact of tracking these changes

on wireless resources. In his paper investigation has been done on the effect of change in number of nodes, node

speed and pause time on packet delivery ratio (PDR) of MANET reactive routing protocols. Here, it has been

analyzed and compared the performance of MANET routing protocols AODV and DSR based on both CBR and

TCP based traffic patterns. The NS-2 simulator is used for performing various simulations and used awk scripts

for analyzing the results. AODV in the simulation experiment shows the overall best performance. It has an

improvement over DSR.

Keywords: Aodv, Cbr , Dsr, Manet, Ns2, Tcp,

I. Introduction A MANET [1,2] consists of a number of mobile devices that come together to form a network as

needed, without any support from any existing Internet infrastructure or any other kind of fixed stations.

Formally, a MANET can be defined as an autonomous system of nodes or MSs also serving as routers

connected by wireless links, the union of which forms a communication network modeled in the form of an

arbitrary communication graph. In such environment, Neighbor nodes communicate directly with each other‟s

while communication between non-neighbor nodes performed via the intermediate nodes which act as routers.

As the network topology changes frequently because of node mobility and power limitations, efficient routing

protocols are necessary to organize and maintain communication between the nodes.

MANETs have several salient characteristics: i) Dynamic topologies ii) Bandwidth constrained,

variable capacity links, iii) Energy-constrained operation and limited physical security etc. Therefore the routing

protocols used in ordinary wired networks are not well suited for this kind of dynamic environment. In this

paper an effort has been done to evaluate the routing performance of AODV and DSR using Network Simulator

NS2 and results have been analyzed.

The rest of the paper is organized as follows: Section II presents the mobile ad hoc routing protocols.

Section III provides an overview and general comparison of the routing protocols used in the study. The related

work is described in section IV. The simulation environment and performance metrics are described in Section

V and then the results are presented in Section VI. Section VII concludes the paper.

II. Routing Protocols Routing protocols for Mobile ad hoc networks can be broadly classified into two main categories:

Ø Proactive or table-driven routing protocols

Ø Reactive or on-demand routing protocols.

2.1 On-Demand Routing Protocols (Reactive)

Reactive routing protocols [3], [4] try to utilize network bandwidth by creating routes only when

desired by the source node. Once a route has been established, it is maintained by some route maintenance

mechanism as long as it is needed by the source node. When a source node needs to send data packets to some

destination, it checks its route table to determine whether it has a valid route. If no route exists, it performs a

route discovery procedure to find a path to the destination. Hence, route discovery becomes on-demand. These

routing approaches are well known as Reactive routing. Examples of reactive (also called on-demand) ad hoc

network routing protocols include ad hoc on-demand distance vector (AODV), temporally ordered routing

algorithm (TORA), dynamic source routing (DSR)[5].

Effect of Traffic Pattern on Packet Delivery Ratio in Reactive Routing Protocol of MANET


2.2. Table Driven Routing Protocols (Proactive)

In proactive or table-driven routing protocols, each node continuously maintains up-to-date routes to

every other node in the network. Routing information is periodically transmitted throughout the network in

order to maintain routing table consistency. Thus, if a route has already existed before traffic arrives,

transmission occurs without delay. Otherwise, traffic packets should wait in queue until the node receives

routing information corresponding to its destination. However, for highly dynamic network topology, the

proactive schemes require a significant amount of resources to keep routing information up-to-date and reliable.

Certain proactive routing protocols are Destination-Sequenced Distance Vector (DSDV) [9], Wireless Routing

Protocol (WRP) [10, 11], Global State Routing (GSR) [11] and Cluster head Gateway

Switch Routing (CGSR) [11].

III. Overview Of Aodv, Dsr Routing Protocols And Traffic Pattern Types Every routing protocol has its own merits and demerits, none of them can be claimed as absolutely

better than others. In this paper the two reactive routing protocols – AODV, DSDV has been selected for

evaluation.

3.1. Ad hoc On-demand Distance Vector Routing (AODV)

Ad-hoc On-demand distance vector (AODV) [12, 13] is another variant of classical distance vector

routing algorithm, a confluence of both DSDV [9] and DSR [14]. It shares DSR‟s on-demand characteristics

hence discovers routes whenever it is needed via a similar route discovery process. However, AODV adopts

traditional routing tables; one entry per destination which is in contrast to DSR that maintains multiple route

cache entries for each destination. The initial design of AODV is undertaken after the experience with DSDV

routing algorithm. Like DSDV, AODV provides loop free routes while repairing link breakages but unlike

DSDV, it doesn‟t require global periodic routing advertisements. AODV also has other significant features.

Whenever a route is available from source to destination, it does not add any overhead to the packets. However,

route discovery process is only initiated when routes are not used and/or they expired and consequently

discarded. This strategy reduces the effects of stale routes as well as the need for route maintenance for unused

routes. Another distinguishing feature of AODV is the ability to provide unicast, multicast and broadcast

communication. AODV uses a broadcast route discovery algorithm and then the unicast route reply massage.

3.2 Dynamic source routing (DSR)

Dynamic source routing (DSR) [5] is based on source routing where the source specifies the complete

path to the destination in the packet header. All intermediary nodes along the path simply forwards the packet to

the next node as specified in the packet header [5, 6]. This means that intermediate nodes only need to keep

track of their neighboring nodes to forward data packets. The source on the other hand, needs to know the

complete hop sequence to the destination. This eliminates the need for maintaining latest routing information by

the intermediate nodes as in DSDV. In DSR, all nodes in a network cache the latest routing information. When

more than one route to the destination is found, the nodes cache all the route information so that in case of a

route failure, the source node can look up their cache for other possible routes to the destination. If an alternative

route is found, the source node uses that route; else the source node will initiate route discovery operations to

determine possible routes to the destination. During route discovery operation, the source node floods the

network with query packets. Only the destination or a node which already knows the route to destination can

reply to it, hence avoiding the further propagation of query packets from it. If a broken link is detected by a

node, it sends route error messages to the source node. The source node on receiving error messages will initiate

route discovery operations. Unlike DSDV, there are no periodically triggered route updates.

3.3 Traffic type:

There are two types of traffic patterns used in this paper a) TCP and b) UDP (CBR)

a)Transmission Control Protocol (TCP)

It is often referred to as TCP/IP due to the importance of this protocol in the Internet Protocol Suite.

TCP operates at a higher level, concerned only with the two end systems, (e.g. between web browser and a web

server). TCP provides reliable, sequential delivery of a stream of data from one program on one computer to

another program on another computer. Common uses of TCP are e-mailing support, file transfer, Web

applications. Among its features, TCP controls message size, the rate at which messages are exchanged, and

network traffic congestion. As for IP, it handles lower-level transmissions from computer to computer as a

message transferred across the Internet.

b)User Datagram Protocol (UDP)

It is part of the base protocols of the Internet Protocol Suite. Programs on networked computers can

send short messages sometimes called datagrams. UDP does not guarantee any reliability (it happens that

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datagram may be out of order, duplicated, or goes missing without any notice). The fact that no checking

whether all packets are actually delivered is made, UDP proves to be faster and more efficient, for applications

that do not need guaranteed delivery. UDP find its uses in situations like Time-sensitive applications where the

problems due to delayed packets are avoided and It is also useful for servers that answer small queries from

huge numbers of clients. UDP supports packet broadcast (conveys to all on local network) and multicasting

(conveys to all subscribers).

IV. Related Work Several researchers have done the qualitative and quantitative analysis of Ad-hoc Routing Protocols by

means of different performance metrics. They have used different simulators for this purpose. Broch et al. [19],

conducted experiments with DSDV, TORA, DSR and AODV. They used a constant network size of 50 nodes,

10 to 30 traffic sources, seven different pause times and various movement patterns. Packet delivery fraction

(PDF), number of routing packets and distribution of path lengths were used as performance metrics. They

extended ns-2 discrete event simulator [20], developed by the University of California at Berkeley and the VINT

project [21], to correctly model the MAC and physical-layer behavior of the IEEE 802.11 wireless LAN

standard. Ehsan and Uzmi [22], presented the performance comparison of DSDV, AODV, DSR and TORA

based on simulations performed using network simulator-2. Three metrics: normalized routing overhead, packet

delivery fraction and average end to end delay, were used to measure performance. Karthikeyan et al. [23]

studied the Reactive protocols, DSR and AODV as well as a Proactive Protocol, DSDV and their characteristics

with respect to different mobility were analyzed based on packet delivery fraction, routing load, end to-end

delay, number of packets dropped, throughput and jitter using Network Simulator (ns-2). However, in all the

cases, only CBR sources were used for generating traffic.

V. Proposed Methodology And Performance Metrics 5.1 Problem formulation:

The research in this MANET area has continued with prominent studies on routing protocols such as

Ad hoc On-demand Distance Vector (AODV), Destination-Sequenced Distance-Vector Routing protocol,

(DSDV) and Dynamic Source Routing Protocol (DSR). Several studies have been done on the performance

evaluation of routing protocols based on CBR traffic pattern using different evaluation methods. Different

methods and simulation environments give different results and consequently, there is need to broaden the

spectrum to account for effects not taken into consideration in a particular environment. It is observed that most

of the research work is based on CBR traffic pattern whereas most of the traffic approximately 95% on the

Internet carries TCP. It is desirable to study and investigate the Performance of different MANET routing

protocols under both CBR and TCP traffic patterns. In this paper, evaluation has been done for the

performance of Reactive protocols i.e Ad hoc on demand distance vector routing (AODV) and dynamic source

routing (DSR) of mobile ad-hoc network routing protocols for both CBR and TCP traffic patterns. The

performance of these routing protocols is evaluated with respect to effect on packet delivery ratio due to

variation in node density, pause time and node speed.

5.2 Performance metrics:

Design and performance analysis of routing protocols used for mobile ad hoc network (MANET) is

currently an active area of research. To judge the merit of a routing protocol, one needs metrics both- qualitative

and quantitative- with which to measure its suitability and performance. Specifically, this paper evaluates the

performance comparison of AODV and DSR reactive routing protocols .The Packet Delivery Ratio (PDR)

performance metrics is used to compare the performance of these routing protocols in the simulation by varying

node density, pause time ,node speed and for he two traffic patterns TCP and UDP(CBR).

Packet delivery ratio is calculated by dividing the number of packets received by the destination through the

number of packets originated by the application layer of the source. It specifies the Packet loss rate, which limits

the maximum throughput of the network. The better the delivery ratio, the more complete and correct is the

routing protocol.

VI. Simulation, Results And Performance Analysis 6.1 simulations

In this paper, two different scenarios have been taken. In the first scenario, traffic pattern is taken as

TCP and no. of nodes, pause time and node speed have been varied and performance comparison has been made

between AODV and DSR protocols. In the second scenario, traffic pattern is taken as UDP (CBR) and no. of

nodes, pause time and node speed have been varied and a performance comparison has been made between

AODV and DSR protocols. Identical mobility pattern are used across protocols to gather fair results.

The source destination pairs are spread randomly over the network. The mobility model uses „random

waypoint model‟ [24] in a rectangular filed of 1000m x 700m with 25 nodes. During the simulation, each node

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starts its journey from a random spot to a random chosen destination. Once the destination is reached, the node

takes a rest period of time in second and another random destination is chosen after that pause time. This

process repeats throughout the simulation, causing continuous changes in the topology of the underlying

network. Different network scenario for different number of nodes and pause times are generated. The model

parameters that have been used in the following experiments are summarized in Table 1and 2.

6.1.1 Test Scenario 1

In the first scenario, the simulation based on TCP traffic pattern is selected. Parameters of this

scenario are summarized in table 1. Here, TCP sources are used which use flow control and retransmission

feature.

Table 1: Simulation parameters for test case of TCP

PARAMETERS VALUES

No. Of Nodes 10,20,30,40,50

Simulation Time 500 Seconds

Environment Size 1000x700

Simulation Speed 2,5,8,10,12 m/sec

Pause Time 0,50,100,150,200

Packet Size 512 bytes

Routing protocols AODV,DSR

Traffic Type TCP

Simulator type NS2 -2.34

Mobility model Random way point

6.1.2 Test case Scenario 2

In the second scenario, the simulation based on CBR traffic pattern has been chosen. Parameters of this

scenario are summarized in table 2. CBR sources are used that started at different times to get a general view of

how routing protocol behaves.

Table 2: Simulation parameters for test case of UDP(CBR)

PARAMETERS VALUES

No. Of Nodes 10,20,30,40,50

Simulation Time 500 Seconds

Environment Size 1000x700

Simulation Speed 2,5,8,10,12 m/sec

Pause Time 0,50,100,150,200

Packet Size 512 bytes

Routing protocols AODV,DSR

Traffic Type CBR

Simulator type NS2 -2.34

Mobility model Random way point

6.2 Results and performance comparison

Performance of AODV and DSR protocols is evaluated under both CBR and TCP traffic pattern.

Extensive Simulation is done by using NS-2.

The simulation results are shown in the form of line graphs. Graphs show comparison between the two

protocols by varying different numbers of sources on the basis of the Packet delivery ratio as metrics and by

varying node density, node speed, and pause time.

Figure 1 : PDR v/s Pause time using CBR(UDP) Traffic Figure 2 : PDR v/s Pause time using TCP Traffic



Figure 3 : PDR v/s Speed using CBR(UDP) Traffic Figure 4 : PDR v/s Speed using TCP Traffic

Figure -5: PDR v/s No. of Nodes for TCP Traffic Figure- 6:PDR v/s No. of Nodes for CBR

Traffic

Figure-1 shows a comparison between the routing protocols on the basis of packet delivery ratio as a

function of pause time and using CBR (UDP) traffic source with both routing protocols AODV and DSR. It

reflects the completeness and accuracy of the routing protocols. It shows very clear that the performance of

AODV and DSR almost same. Pause time of 0 denotes maximum movement and 200 denote least movement. It

shows at the 0 pause time PDR is very less, its around 94% in both protocols. When pause time is increased the

PDR will be increased but after a particular pause time the PDR will be almost stable.

Figure-2 shows the comparison between AODV and DSR using on the basis of PDR as a function basic

of pause time using TCP traffic source. In this scenario all the PDR outputs above 99% , But it shows DSR‟s

PDR is little bit high compared to AODV.


of Speed using CBR (UDP) traffic source. In this scenario all the PDR outputs above 99%, but it shows

AODV‟s PDR better compare to DSR at all the speed points.


of Speed using TCP traffic source. In this scenario all the PDR outputs above 98%, but it shows DSR‟s PDR

better compare to AODV at all the speed points.

Figure -5 Packet Delivery Ratio v/s No. of Nodes for TCP Traffic: A simulation result of Figure-5

shows that varying no. of nodes: i) Packet delivery ratio for both protocols with varying no. of nodes is stable.

ii) DSR has slightly more packet delivery ratio than AODV.

Figure- 6 Packet Delivery Ratio v/s No. of Nodes for CBR Traffic: For scenario-2 graph generated in

Fig. 6 shows that Packet Delivery ratio of two protocols DSR, AODV is similar.

VII. Conclusion This study was conducted to evaluate the performance of two MANET protocols i.e. AODV, and

DSR based on CMU‟s generated TCP & CBR traffic. These routing protocols were compared in terms of Packet

delivery ratio, when subjected to change in no. of nodes & traffic type, Pause time and node speed. In this paper,

evaluation of the routing protocols, unlike previous works of similar nature, brings out the effect of routing

protocols on the TCP performance. Through experiments, first the essential differences between TCP and UDP

traffic and therefore need to consider TCP traffic for routing protocol performance evaluation. Based on these

experiments performance metrics i.e. Packet delivery ratio was measured for quantifying the performance of the

protocols.

AODV in the simulation experiment shows the overall best performance. It has an improvement over

DSR. It has been further observed that due to the dynamically changing topology and infrastructure less,

decentralized characteristics, security and power awareness is hard to achieve in mobile ad hoc networks.

Hence, security and power awareness mechanisms should be built-in features for all sorts of applications based

on ad hoc network. Performance can also be analyzed for other parameters like Jitter, Routing Overhead,

throughput and average end to end delay. By evaluating the performance of these protocols new protocols can

be implemented or changes can be suggested in the earlier protocols to improve the performance.



References [1] C. E. Perkins and E. M. Royer. “The ad hoc on-demand distance vector protocol,” Ad Hoc Networking, Addison-Wesley, pp. 173-

219, 2001.

[2] D. B. Johnson, D. A. Maltz, and J. Broch, “DSR: the dynamic source routing protocol for multi-hop wireless ad hoc networks,” in

Ad Hoc Networking, Addison-Wesley, 2001, pp. 139-172. [3] Johnson, D. B., Maltz, D. A., Hu, Y. C. and Jetcheva, J. G. 2002. “The dynamic source routing protocol for mobile ad hoc networks

(DSR)”. Draft-ietf-manet-dsr-07.txt.

[4] Perkins, C. E., Royer, E. M. and Das, S. R. 1999. “Ad Hoc On-Demand Distance Vector Routing”. IETF Internet Draft. http://www.ietf.org/internet-drafts/draft-ietf-manetaodv-03.txt.

[5] Anuj K. Gupta, Dr. Harsh Sadawarti, Dr. Anil K. Verma, “Performance analysis of AODV, DSR and TORA Routing Protocols”,

International Journal of Engineering & Technology (IJET), ISSN: 1793-8236, Article No. 125, Vol.2 No.2, April 2010, pp. – 226-231.

[6] Narendran Sivakumar, Satish Kumar Jaiswal, “Comparison of DYMO protocol with respect to various quantitative performance metrics”, ircse 2009.

[7] NS-2, The ns Manual (formally known as NS Documentation) available at http://www.isi.edu/nsnam/ns/doc.NAM

[8] http://www.isi.edu/nsnam/nam/ [9] C. E. Perkins and P. Bhagwat, “Highly Dynamic Destination- Sequenced Distance-Vector Routing (DSDV) for Mobile Computers,”

SIGCOMM, London, UK, August 1994, pp. 234-244.

[10] Vincent D. Park and M.Scott Corson. “A highly adaptive distributed routing algorithm for mobile wireless networks”.In Proceedings of INFOCOM 1997, 1997.

[11] Saleh Ali K.AI-Omari & Putra Sumari “An overview of mobile adhoc networks for the existing protocols and

applications”Internattional Journal on Applications of Graph theory in wireless adhoc networks and sensor networks (Graph-Hoc) , Vol2 No1 March 2010.

[12] C. E. Perkins and E. M. Royer, “Ad Hoc On-demand Distance Vector Routing,” In Proceedings of the 2nd IEEE Workshop on

Mobile Computing Systems and Applications, New Orleans, LA, February 1999, pp. 90-100. [13] C. Perkins, “Ad hoc On demand Distance Vector (AODV) routing”, IETF Internet draft (1997),http://www.ietf.org/internet-

drafts/draftietf- manet-aodv-00.txt.

[14] D. B. Johnson and D. A. Maltz, “Dynamic Source Routing in Ad-Hoc Ad hoc Networks," Mobile Computing, ed. T. Imielinski and H. Korth, Kluwer Academic Publishers, 1996, pp. 153-181.

[15] Dyer T. D., Boppana R. V., “ A Comparison of TCP performance over three routing protocols for mobile adhoc networks “, ACM

Symposium on Mobile Adhoc Networking & Computing (Mobihoc) , October 2001. [16] Suresh Kumar, R K Rathy and Diwakar Pandey, “Traffic pattern based performance comparison of two reactive routing protocols

for ad hoc networks using NS2”, © 2009 IEEE.

[17] Vikas Singla, Rakesh Singla and Ajay Kumar,”Performance Evaluation and Simulation of Mobile Ad-hoc Network Routing Protocols”, International Journal of Engineering and Information Technology, Volume 1 No. 1 October 2009.

[18] Yogesh Chaba, Yudhvir Singh, Manish Joon, "Simulation Based Performance Analysis of On-Demand Routing Protocols in

MANETs," Second International Conference on Computer Modeling and Simulation, 2010. [19] J. Broch, D. A. Maltz, D. B. Johnson, Y. C. Hu and J. Jetcheva, “A Performance Comparison of Multi-Hop Wireless Ad-hoc

Network Routing Protocols,” in Proceedings of the 4th Annual ACM/IEEE International Conference on Mobile Computing and

Networking (MOBICOM’98), October 1998, pp. 85–97. [20] Information Sciences Institute, “ns-2 network simulator,” Software Package, 2003. [Online]. Available:

http://www.isi.edu/nsnam/ns/

[21] “The VINT Project,” USC/ISI, Xerox PARC, LBNL and UC Berkeley,1997. [Online].Available: http://www.isi.edu/nsnam/vint/ [22] Humaira Ehsan and Zartash Afzal Uzmi, “Performance Comparison of Ad-hoc Wireless Network Routing Protocols”, IEEE

Transactions, 2004.

[23] N. Karthikeyan, V. Palanisamy and K. Duraiswamy, “A Performance Evaluation Of Proactive And Reactive Protocols Using ns-2 Simulation”, International J. of Engg. Research & Indu. Appls. (IJERIA).ISSN 0974-1518, Vol.2, No.II (2009), pp 309-326.

[24] Mohd Izuan Mohd Saad “Performance Analysis of Random-Based Mobility Models in MANET Routing Protocol” European

Journal of Scientific Research ISSN 1450-216X Vol.32 No.4 (2009), pp.444-454 © EuroJournals Publishing, Inc. 2009.





Broadband Cpw Fed Slotted Ground Antenna

Ramanjit Singh1, Geetanjali Singla

2, Rajesh Khanna

3

1(Department of electronics and communication, LCET/PTU, India)

2, 3(Department of electronics and communication, Thaper University, India)

Abstract: In this paper, a broadband rectangular microstrip patch antenna fed by coplanar waveguide feed

with two slots in the ground plane is proposed. Investigations are carried out using coplanar waveguide feed

with slotting in the ground plane to optimize the broadband operation. A sensitivity analysis shows the variation

of return loss with different antenna parameters. This design of broadband antenna is obtained by properly

choosing the suitable shape of slots in ground plane and selecting proper shape and size of the radiating patch.

The designed antenna gives a return loss of -61dB and impedance bandwidth of 1.02GHz. The simulated results

for return loss, bandwidth, VSWR and radiation pattern are studied.

Keywords: Broadband, bandwidth, CPW-feed, microstrip patch antenna, return loss,

I. Introduction

The broadband antennas arouse much interest in recent years for different wireless communication

applications such as wireless local area network (WLAN), Wi-MAX and Bluetooth personal network. Therefore

different designs have been proposed to enhance the bandwidth of the antenna. Microstrip patch antennas have

attracted much attention due to their low profile, light weight, ease of fabrication and compatibility with printed

circuits in wireless communication applications. However, they also have a major drawback of narrow

bandwidth [1-5].

To enhance the bandwidth of microstrip patch antenna different techniques have been used. The factors

affecting the bandwidth of microstrip patch antenna are primarily the shape of the radiator, the feeding scheme,

the substrate and the arrangement of radiating and parasitic elements.

Height and dielectric constant of the substrate material affects the antenna impedance bandwidth.

However, the improvement in the bandwidth is quite limited. By varying the shape of the radiating patch the

impedance bandwidth can be improved but this may effect the other performance parameters.

The different feeding techniques are also used for enhancing the bandwidth of microstrip patch

antenna, coplanar waveguide feeding is one of them. It has several advantages on any other feeding method such

as low radiation loss, less dispersion, uniplanar configuration and easy mounting of shunt lumped elements or

active devices without via hole as for the microstrip line. Coplanar waveguide (CPW) fed antennas have been

increasingly studied in recent years. The antenna fed by a microstrip line may result in misalignment because of

the required etching on both sides of the dielectric substrate. The alignment error can be eliminated if a CPW

feed is used to excite the slot, since etching of the slot and feeding line is one sided [6].

Various shapes of CPW-fed slot antennas are proposed for bandwidth enhancement such as triangle-

shaped, square slot antenna, circular slot, bow-tie slot, and hybrid slot. In [1], a large bandwidth CPW-fed wide

slot antenna is proposed. By choosing a suitable combination of feed patch and slot shape, and also tuning their

sizes, an optimum operating bandwidth of 131% is obtained. In [2], novel broadband design of a coplanar

waveguide (CPW)-fed planar monopole antenna with double plus shape slots is proposed. The simulated result

shows a broad impedance bandwidth of 30%, ranging from 4.789 GHz to 6.318 GHz. In [3], a CPW-fed loop

slot antenna with a tuning stub to enhance the bandwidth is presented, where by properly adjusting the location

of a widened tuning stub, wide bandwidth was obtained. Recently a [5] new broadband printed microstrip

Antenna is proposed for UWB application and a impedance bandwidth of approximately 9GHz is obtained.

II. Antenna Design

Fig. 1.1 shows the geometry of the proposed antenna.

Fig. 1.1 Geometry of proposed antenna



The three essential parameters for designing the proposed antenna are

Resonate Frequency (fr) = 2.45 GHz

Dielectric Constant ( r) = 2.2

Substrate Height (h) = 1.6 mm

The dimensions of the proposed antenna substrate are L,W, h that is 59.15mm, 98.15mm, 1.6mm. The

proposed antenna has only a one layer of metallic structure on one side of the substrate because in coplanar

waveguide feeding technique etching is one sided as the radiating patch and ground plane are on the same side

of the substrate.

The length and width of the radiating patch is Lp and Wp, where Lp and Wp has a value of 39.95mm and

78.95mm. The other geometrical parameters of the proposed antenna are width of CPW feed line (W f) 2.47mm,

gap between the feed and the ground plane (S) 0.4mm, length of ground 8.575mm, gap between the patch and

the ground (G) 0.55mm, length of the ground slot (Sl) 9.825mm, width of the ground slot (Sw) 5.2mm. The

proposed CPW fed antenna is simulated with CST microwave studio version 10.

III. Results and Discussion CST microwave studio is a specialized tool for the fast and accurate 3D EM simulation of high

frequency problems. First the simulation was started with a simple coplanar waveguide fed microstrip patch

antenna. Then in order to achieve broader bandwidth slots were added in the ground plane. The optimum

performance results were obtained after a large number of iterations. The slot length and width were varied to

achieve maximum bandwidth and return loss. The simulated and measured return loss and bandwidth of the

above designed broadband microstrip patch antenna fed with coplanar waveguide feeding line is shown in figure

2. From simulation results it is seen that the proposed antenna has a good bandwidth of 1.02GHz ranging from

2.26GHz to 3.29GHz for S11 < −10 dB.

Fig. 2 return loss plot of proposed antenna

As seen the measured return loss is -61dB at the resonating frequency of 2.45GHz. The proposed

antenna has a broader bandwidth covering the require bandwidths of IMT standard for 2300-2400MHz, 2700-

2900MHz, WLAN standard for 2400-2484MHz, Bluetooth standard for 2400-2500MHz and Wi-MAX standard

for 2500-2690MHz.

The simulation result of voltage standing wave ratio for proposed antenna is shown in figure 3. The

VSWR for proposed antenna is very close to one over the entire operating band which means that antenna is

perfectly matched and there is no mismatch loss.

Fig. 3 VSWR plot for proposed antenna

The radiation pattern plot shows that how antenna radiates in different directions. The maximum gain is

obtained in the broadside direction and this is measured to be 5.00 dB for φ = 90 degrees as shown in figure 4.



Fig.4 Radiation pattern plot for proposed antenna

IV. Sensitivity Analysis

A numerical sensitivity analysis is done to demonstrate the effect of different parameters such as G, S,

and SW on the performance of the designed CPW-fed patch antenna. These parameters are set as variable and

their effects on impedance bandwidth and return loss are investigated.

The first parameter under study is the gap between the ground plane and radiating patch donated as G.

Figure 5 shows the simulated return loss of the proposed antenna with varying feed gap (G) from 40mm to

42mm. The results show that the frequency corresponding to the upper edge of the bandwidth is clearly

independent of the feed gap G, but the frequency corresponding to the lower edge is heavily dependent on this

parameter. It is clear that G is an important parameter that influences the return loss.

Fig. 5 Return loss plot for various values of G

The simulated return loss plot for various values of feed gaps S, the gap between the feed and the

ground plane is shown in figure 6. The result shows that the frequency corresponding to the lower edge of the

bandwidth is independent of the feed gap S, but the frequency corresponding to the upper edge is dependent on

this parameter. The optimum value of S is 2.63 as shown in figure 6.

Fig. 6 return loss plot for various values of S

The simulated return loss plot of proposed antenna for various value of (Sw) width of slot in ground

plane is shown in figure 7. This parameter mainly effect the high frequency performance , the low frequency

performance is clearly independent of Sw. based on these results the optimum value of Sw is 45.7.



Fig. 7 Return loss plot for various values of Sw.

V. Conclusion

The proposed broadband CPW fed antenna with two slots in the ground plane has been simulated. It is

observed that broadband behavior of the designed antenna is mainly because of slotted ground plane. The

proposed antenna has a impedance bandwidth of 42% ranging from 2.26GHz to 3.29GHz with a return loss

value of -61dB and VSWR value 1.0017. The designed antenna can be used for WLAN, Wi-MAX and

Bluetooth applications.

References [1]. A. Dastranj, M. Biguesh, Broadband coplanar waveguide fed wide-slot antenna, Progress in lectromagnetics Research C, 2010, 89-

101.

[2]. D. Parkash, R. Khanna, Design of a broadband CPW-Fed monopole antenna for WLAN operations, MIT International journal of electronics and communication engineering, 2011, 5-7.

[3]. P. Jearapraditkul, W. Kueathaweekun, N. Anantrasirichai, O Sangaroon and T. Wakabayashit, Bandwidth Enhancement of CPW-

Fed Slot Antenna with Inset Tuning Stub,International Symposium on Communications and Information Technologies, 2008. [4]. D. Mitra, D. Das and S. R. Bhadra Chaudhuri, Bandwidth enhancement of microstrip line and CPW-fed asymmetrical slot

antennas, Progress In Electromagnetics Research Letters, 2012, 69–79.

[5]. L. Varshney, V. R. Gupta, H. Kumar, P. Suraj, CPW-Fed Broadband Microstrip Patch Antenna, International journal of advanced engineering and application, 2011

[6]. C.A. Balanis, Antenna Theory Analysis and Design (John Wiley & Sons, Inc., 1997).




Effect of Electrostatic Discharge on Digital and Analog Circuits

1Rajashree Narendra,

2M.L.Sudheer,

3D.C. Pande

1(Department of of Telecommunication / BNMIT, Bangalore) 2(Department of ECE / UVCE, Bangalore) & 3(EMI/EMC Group, LRDE, Bangalore)

Abstract:A comparative study of the effects of electrostatic discharge (ESD) on digital and analog circuits is

carried out. Direct and Indirect discharge is performed on the circuit having both analog and digital circuitry.

First the Indirect discharge on the ground plane is done for different voltages and distances. Then the direct air

discharge is performed near the digital and discreet analog circuitry. These results are compared and the effect of electrostatic discharge over digital and analog circuits is summarized from the experimental results.

Keywords:- Electrostatic Discharge; Indirect discharge; Direct air discharge; Analog circuit; Digital circuit;

ESD simulator; Electromagnetic Interference

I. INTRODUCTION Digital circuits are more susceptible to electrostatic discharge (ESD) than analog circuits. Most of the

electronic components that are considered fairly rugged can be damaged by ESD. Bipolar transistors, the

earliest of the solid state amplifiers, are not immune to ESD, though less susceptible. There are components that

might not be considered at risk, such as some specialized resistors and capacitors. Devices manufactured using MOS (Metal Oxide Semiconductor) technology is more susceptible to ESD [1-4] but some of the newer high

speed components can be ruined with low voltages.

Damage to components can, and usually do, occur when the part is in the ESD path. Many components

in the circuits are very robust, can handle the discharge and undergo upsets. But if a part has a small or thin

geometry as part of their physical structure then the voltage can break down that part of the semiconductor [5-

8]. Currents during the ESD events become quite high, but are in the nanosecond to microsecond time frame.

Part of the component is left permanently damaged by this, which can cause two types of failure modes.

Catastrophic is the easy one, leaving the part completely nonfunctional. The other can be much more serious.

Latent damage may allow the problem component to work for hours, days or even months after the initial

damage before catastrophic failure. Many times these parts are referred to as "walking wounded", since they are

working but bad. If these components end up in a life support role, such as medical or military use, then the

consequences can be grim. Indirect discharge on the horizontal coupling plane (HCP) and direct air discharge is performed [9,10].

The ESD indirect discharge test was carried out to verify the ESD immunities of the analog and digital

components in the circuit.

II. CIRCUIT DIAGRAM AND ITS OPERATION The RC Phase Shift Oscillator produces a sine wave output signal using regenerative feedback from

the resistor-capacitor combination. This resistor-capacitor feedback network is connected as shown in the Fig. 1

as a phase advance network to produce a sine wave oscillation at a frequency of 912Hz with a overall phase-

shift of 360 degrees. By varying one or more of the resistors or capacitors in the phase-shift network, the

frequency can be varied and generally this is done using a 3-ganged variable capacitor. As the resistor-

capacitor combination in the RC Oscillator circuit also acts as an attenuator producing an attenuation of -

1/29th (Vo/Vi = β) per stage, the gain of the amplifier is adjusted sufficiently large to overcome the losses in the

three mesh network.

Zero-crossing detector using inverting op-amp (IC µA741) comparator is depicted in Fig. 1. The circuit produces a change in the output state whenever the input crosses the reference. In this case the reference input is

ground, hence every time the sine wave output crosses the 0V level there will be a shift in the output voltage

level.

Fig. 1 Circuit diagram of RC phase-shift oscillator followed by zero crossing detector.



The initial output of the circuit is shown in Fig. 2. The sine wave is the output of the oscillator, the two square

waves are the output of the zero crossing detector.

Fig. 2 Initial output of the circuit.

III. INDIRECT ESD DISCHARGE Indirect discharge was done on the horizontal plane for different voltages and different distances.

Some of them are presented and discussed. When a discharge of 4kV was given on the horizontal plane at a

distance of 0.9m there was a change in the ZCD output for 6.67µs indicating shift of the oscillator output below

0V for that period of time as shown in Fig. 3.

Fig. 3 Effect of ESD at 4kV and at a distance of 0.9m

The oscillator output goes below the reference voltage of 0V twice when discharged at 8kV at a

distance of about 0.9 m as shown in the Fig. 4. At the first instance it is for a period of about 2µs and second

instance for a period of 1µs which is indicated by the shift of the ZCD output.


A small phase shift and a transient of about 13V is observed at the trigger point in the oscillator output

when discharged at 15kV at a distance of 0.9m as shown in Fig. 5. But a very small transient of about 1V is

observed in the ZCD output because of the data being low at the point of trigger.




The results tabulated are for different voltages at a constant distance of 0.9m from the circuit.

4kV discharge at

0.9m

8kV discharge at

0.9m

15kV discharge at 0.9m

Change in ZCD

output and shift in

oscillator output for 6.67µs

Oscillator output

went below 0V twice

and shift in ZCD output for 2µs

1V transient for ZCD

output and 13V

transient in oscillator output

Now the results for a constant voltage of 8kV at different distances are discussed. The effect of ESD

for 8kV at a distance of 0.9 m is already mentioned in Fig. 4. When 8kV is discharged at a distance 0.7m, a

transient of about 9V and a very small phase shift at the point of trigger is seen and the data goes below 0V for

3 µs as shown in Fig. 6. The data also goes beyond the maximum reference level at the instance of trigger which

is seen by the shift in the ZCD output.


When discharged at a distance of 0.5m as shown in Fig. 7, there is a data shift for 5 µs in the ZCD output

showing the transient going below 0V at that moment, followed by a small phase shift at the point of trigger.




The results tabulated are for different distances at a constant voltage of 8kV from the circuit.

8kV discharge at 0.9 m 8kV discharge at 0.7 m 8kV discharge at 0.5 m

Oscillator output went

below 0V twice and shift

in ZCD output for 2µs and

1 µs

a very small phase shift at

the point of trigger and

shift in ZCD output for 3µs

a very small phase shift

at the point of trigger and

shift in ZCD output for

5µs

IV. DIRECT AIR DISCHARGE Discharge at the ZCD output

The following results are observed when air discharge is conducted near the ZCD output of the circuit.

There is a transient greater than the reference voltage at the oscillator output for 20 µs which is indicated by the

shift at the ZCD output. A phase shift and an increase in the amplitude of the next peak by 1V are observed in

the oscillator output when discharged at 2kV. This is shown in Fig. 8.

Fig. 8 Effect of ESD at ZCD output for 2kV

When discharged at 4kV the oscillator output has a large transient and a 180 degree phase shift

indicated by the ZCD output shift. Also a decrease in the negative peak amplitude and an increase in the peak

amplitude of the next cycle are observed as shown in Fig. 9.

After a discharge of 15kV at the ZCD output, the digital circuit initially works fine indicating the

transition of the oscillator output below the reference voltage. But eventually only the oscillator output recovers

and remains intact but both the square wave output and the ZCD output goes to negative saturation around -10V and the IC µA741 is spoilt. This is depicted in the Fig. 10.





The results are tabulated for air discharge at ZCD output.

2kV discharge 4kV discharge 15kV discharge

ZCD output shift for 20µs,

oscillator suffers a phase

shift and increase in

amplitude there after

Shift in ZCD output and

1800 phase shift and

amplitude change for

oscillator output

Phase shift in oscillator

output and then recovers,

ZCD output goes to

negative saturation

Discharge at the Oscillator output When a 2kV air discharge is given to the pickup point at oscillator output the sine wave had a large

transient which is indicated by the shift in the ZCD and there is an increase in the amplitude by 2V in the next

peak of the sine wave. This is shown in Fig. 11.

A discharge of 4kV at the oscillator output results in a transient greater than 60V at the oscillator

output followed by an increase in the negative peak voltage greater than 0V, also observed is the shift in the

ZCD output for 60 µs and an increase in the peak voltage of the next peak by 2V. This is shown in Fig. 12.

Fig. 11 Effect of ESD at oscillator output for 2kV

Fig. 12 Effect of ESD at oscillator output for 4kV.

A discharge of 8kV at the oscillator output results in a transient which goes below the reference

voltage for 40 µs and then the oscillator output remains above the reference voltage for 750 µs. Also the ZCD

output remains high for entire period of 750 µs as shown in Fig. 13.

When discharged for 15kV the oscillator output goes below 0V for 40 µs. A large transient at the ZCD

after 40 µs shows that the oscillator output goes below and beyond the reference after which the oscillator output remains above 0V for 1.7 ms after which it regains its original functionality. Meanwhile the ZCD output

remains at high till analog output recovers. This is shown in Fig. 14. The analog circuit output recovered earlier

compared to the digital output.

Fig. 13 Effect of ESD at oscillator output for 8kV.



Fig. 14 Effect of ESD at oscillator output for 15kV

The results are tabulated for air discharge at oscillator output.

V. CONCLUSIONS The effect of ESD on the digital data is more pronounced when compared to the analog data. From the

above experimental results it can be definitely said that the digital data is more susceptible to ESD due to its

smaller size and larger complexity when compared to the analog circuits. It can be seen that the analog circuit

can come back to its initial working condition (even sometimes after certain latency period due to the slow

discharge of charges accumulation) even after the ESD affecting it, but a digital circuit gets damaged quickly to

electrostatic discharge.

In the indirect discharge it is seen that the ESD effect depends on both the distance and the discharge

voltage. Higher discharge voltage and shorter distance produces larger data losses and larger transients. The

digital circuit gets damaged at higher discharge voltage. The analog circuit with discreet components is affected

by ESD but it recovers back quickly.

REFERENCES [1] James E. Vinson And Juin J. Liou, “Electrostatic Discharge In Semiconductor Devices: An Overview’, Proceedings of the IEEE,

Vol. 86, No. 2, February 1998, Pp 399-418.

[2] B. Greason, “Dynamics of the basic ESD event,” 1993, EOS/ESD Tutorial Notes, pp. E-1–E-21, Sept. 1993.

[3] C. Diaz, S. M. Kang, and C. Duvvury, “Tutorial electrical overstress and electrostatic discharge,” IEEE Trans. Reliability, vol. 44,

pp. 2–5, Mar. 1995.

[4] W. D. Greason and G. S. P. Castle, “The effects of ESD on microelectronic devices–A review,” IEEE Trans. Industrial

Applications, vol. IA-20, pp. 247–252, Mar./Apr. 1984.

[5] C. Duvvury and A. Amerasekera, “ESD: A pervasive reliability concern for IC technologies,” Proc. IEEE, vol. 81, pp. 690–702,

May 1993.

[6] Hongxia Wanga, Samuel V. Rodrigueza, Cagdas Dirika & Bruce Jacoba, “Electromagnetic Interference and Digital Circuits: An

Initial Study of Clock Networks”, Electromagnetics, Volume 26, Issue 1, 2006, pp 73-86.

[7] Ming-Douker, Jeng-Jie Peng and Hsin-Chin Jiang, “Failure Analysis of ESD damage in a high-voltage driver IC and the effective

ESD protection solution”, Proceedings of 9th IPFA 2002, Singapore, pp 84-89.

[8] C. Duvvury, R.N.Rountree and O. Adams, “ Internal chip ESD phenomena beyond the protection circuit”, IEEE Transactions on

Electron Devices, Vol. 35, No. 12, 1988, pp 2133-2139.

[9] Robert Ashton, ON Semiconductor “Reliability of IEC 61000-4-2 testing on components”, EE Times Design article, 8/10/2008.

[10] Robert Ashton, “System level ESD Testing-The Test setup”, Challenges in testing, Conformity, December 2007, pp 34-40.

2kV discharge at

0.9m

4kV discharge at

0.9m

8kv discharge at

0.9m

15kV discharge at

0.9m

2V increase in amplitude and shift

in ZCD output

Oscillator output has 60V transient,

2V increase in

amplitude and ZCD

output change for

60 µs

Oscillator output goes below reference

for 40 µs, oscillator

and ZCD output

remain high for

750µs

Oscillator output below 0V for 40 µs

and ZCD has huge

transient and remains

high till analog

recovers

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