Wireless Communications

Dr. R P. Yadav Professor,

Electronics and Communication Department

MNIT, Jaipur

Former Vice Chancellor

Rajasthan Technical University Kota

Former Chairman

North Western Regional Council Chandigarh

AICTE

Outline

� Communication Systems

� Wireless Communications

� Current Wireless Systems

� Deteriorating factors

� Advantages/Drawbacks� Advantages/Drawbacks

� Design challenges

� Future of Wireless

2

Communication Systems

Transmitter

Carrier

Transmitted

signal

Channel

Received

signal

Receiver

Information to be transmitted

(Baseband signal)

Recovery of information

3

Wireless Communications� Transfer of information without electrical conductor/optical fiber

� Radio

� Free space optical

� Sonic

� Electromagnetic induction

� There are many devices used for wireless communication� There are many devices used for wireless communication

� mobiles.

� Cordless telephones,

� satellite television

� wireless computer parts.

� Current wireless phones include

� 3G and 4G networks

� Bluetooth

� Wi-Fi technologies.4

Wireless Comes of Age

� Guglielmo Marconi invented the wireless telegraph in 1896

� Communication by encoding alphanumeric characters in analog signal

� Sent telegraphic signals across the Atlantic Ocean

� Communications satellites launched in 1960s� Communications satellites launched in 1960s

� Advances in wireless technology

� Radio, television, mobile telephone, communication satellites

� More recently

� Satellite communications, wireless networking, cellular technology

5

Current Wireless Systems

� Cellular systems

� Wireless LANs

� Satellite Systems

� Paging Systems

� Bluetooth� Bluetooth

� Infrared Communication

� Ultra wideband Radios

� Zigbee Radios

6

Wireless Systems: Range Comparison

SatelliteSWMWFMMobile

1,000 Km100 Km10 Km1 Km100 m10 m1 m

SatelliteLinksRadioRadio

FMRadioTelephonyWLANsBlueooth

7

Cellular Systems:Reuse channels to maximize capacity

• Geographic region divided into cells• Frequencies/timeslots/codes reused at spatially-separated

locations.

• Co-channel interference between same color cells.

• Base stations/MTSOs coordinate handoff and control functions

• Shrinking cell size increases capacity, as well as networking • Shrinking cell size increases capacity, as well as networking burden

BASE

STATIO

N MTSO

8

Type of Cells

Satellite

UrbanIn-Building

Global

Suburban

MacrocellMicrocell

Picocell

Basic Terminal

PDA Terminal

Audio/Visual Terminal

9

Contd..

• Cell radii can vary from 10s of meters in buildings to 100s of meters in the cities, up to several kms in the countryside.

• Macrocells, provide overall area coverage.

• Microcells focuses on slow moving subscribers moving • Microcells focuses on slow moving subscribers moving between buildings.

• Picocells focuses on the foyer of a theater, or exhibition centre.

10

Cellular Phone Networks

BSBS

Jaipur

MTSOPSTN

MTSO

BS

MumbaiInternet

11

The Wireless Revolution

Cellular is the fastest growing sector of communication industry (exponential growth since 1982, with over 2 billion users worldwide today)

• Three generations of wireless

– First Generation (1G): Analog 25 or 30 KHz FM, voice only, mostly vehicular communication

– Second Generation (2G): Narrowband TDMA and CDMA, voice and low bit-rate – Second Generation (2G): Narrowband TDMA and CDMA, voice and low bit-rate data, portable units.

2.5G increased data transmission capabilities

– Third Generation (3G): Wideband TDMA and CDMA, voice and high bit-rate data, portable units

– Fourth Generation (4G): Broadband, all-IP packet switched network , dynamic sharing of resourcing, IEEE 802.6m standard plus LTE Advanced.

12

Migration from 2G to 3G Continues to Accelerate

13

Global Handset Demand Remains Strong Across Multiple Segments

14

How Did We Get This Far in Just 25 Years?

• Relentless progress in silicon technology� Higher integration, lower costs ($20 phones readily

available in emerging markets), more capabilities.

• Technical advances in air interfaces• Technical advances in air interfaces� Higher efficiency for voice and data services, lower

infrastructure capital costs.

15

An Example: CDMA Network Modems

16

Mobile Processing Power –Changing the Mobile Device

17

Challenge: Battery Technology is Falling Behind

18

Spectral Efficiency: Significant gains so far, but reaching theoretical Limits

19

Interference Cancellation in Action

20

Asynchronous Transmissions & Frame Staggering

21

SIC Had Been Sitting on the Bookshelf…

• Until the perfect storm arrived about 3 years ago…

• Realization that sum rate capacity could be achieved without the need of synchronous transmissions and exponential power distribution

• Process technology node transitions• Process technology node transitions

• Development of embedded memory technology allowed large amounts of on-chip memory

• Thus we had the ingredients and the recipe, all that was left was a lot of hard work…

22

Two Directions

• A. Continue improvements in spectral efficiency with tighter coordination amongst base stations

• B. Change the metrics: Focus on increasing density of deployment to optimize spectral density of deployment to optimize spectral efficiency/area.

23

Summary

• Continued growth in cell-phone penetration.

• Emergence of new class of ‘data-centric’ wireless devices.

• Battery technology not keeping pace, but • Battery technology not keeping pace, but innovative solutions are emerging.

• Traditional optimization in wireless technology reaching its theoretical limits.

• Topology, not technology, will provide the next leap in air interface capacity.

24

Wireless Local Area Networks (WLANs)

01011011

Internet

Access

Point

0101 1011

� WLANs connect “local” computers (100m range)

� Breaks data into packets

� Channel access is shared (random access)

� Backbone Internet provides best-effort service

� Poor performance in some apps (e.g. video)

25

Wireless LAN Standards

• 802.11b (Current Generation)

– Standard for 2.4GHz ISM band (80 MHz)– Frequency hopped spread spectrum– 1.6-10 Mbps, 500 ft range

• 802.11a (Emerging Generation)

– Standard for 5GHz NII band (300 MHz)– OFDM with time division– OFDM with time division– 20-70 Mbps, variable range– Similar to HiperLAN in Europe

• 802.11g (New Standard)

– Standard in 2.4 GHz and 5 GHz bands– OFDM – Speeds up to 54 Mbps

26

Satellite Systems

� Cover very large areas

� Different orbit heights

� GEOs (39000 Km) versus LEOs (2000 Km)

� Optimized for one-way transmission

� Radio (XM, DAB) and movie (SatTV) broadcasting

� Most two-way systems are struggling or bankrupt

� Expensive alternative to terrestrial system

� A few ambitious systems on the horizon

27

Ad-hoc Networks

• Ad Hoc Network is a multi-hop relaying network

• In 1994, Bluetooth proposed by Ericsson to develop a short-range, low-power, low complexity, and inexpensive radio interface

• WLAN 802.11 spec. is proposed in 1997• WLAN 802.11 spec. is proposed in 1997

28

Difference Between Cellular and Ad-hoc Networks

29

Cont…

30

Applications of Ad-hoc Networks

• Military Applications

� Establishing communication among a group of soldiers for tactical operations

� Coordination of military object moving at high speeds such as fleets of airplanes or ships

� Requirements: reliability, efficiency, secure communication, –Requirements: reliability, efficiency, secure communication, and multicasting routing,

• Collaborative and Distributed Computing

� Conference, distributed files sharing

• Emergency Operations

� Search, rescue, crowd control, and commando operations

� Support real-time and fault-tolerant communication paths31

Issues in Ad Hoc Wireless Networks

• Medium access scheme

• Routing, Multicasting, TPC protocol

• Pricing scheme, QoS, Self-organization

• Security, Energy management • Security, • Security, Energy management • Security, Energy management

• Addressing and service discovery

• Deployment considerations

32

Medium Access Scheme

• Distributed operation• fully distributed involving minimum control overhead

• • Synchronization• Mandatory for TDMA-based systems

• Hidden terminals• Hidden terminals• Can significantly reduce the throughput of a MAC protocol

• Exposed terminals

• To improve the efficiency of the MAC protocol, the exposed nodes should be allowed to transmit in a controlled fashion without causing collision to the on-going data transfer

• • Access delay

33

The Major Issues of MAC Scheme

• Throughput and access delay• To minimize the occurrence of collision, maximize channel

utilization, and minimize control overhead

• Fairness

• Equal share or weighted share of the bandwidth to all • Equal share or weighted share of the bandwidth to all competing nodes

• Real-time traffic support

• Resource reservation• Such as BW, buffer space, and processing power

• Capability for power control

• Adaptive rate control

• Use of directional antennas34

The Major Challenge of Routing Protocol

• Mobility result in frequent path break, packet collision, and difficulty in resource reservation

• Bandwidth constraint: BW is shared by every node

• Error-prone and share channel: high bit error rate

• Location-dependent contention: distributing the network • Location-dependent contention: distributing the network load uniformly across the network

• Other resource constraint: computing power, battery power, and buffer storage

35

The Major Requirement of Routing Protocol

• Minimum route acquisition delay

• Quick route reconfiguration: to handle path breaks

• Loop-free routing

• Distributed routing approach

• Minimum control overhead • Minimum control overhead• Minimum control overhead • Minimum control overhead

• Scalability

• Provisioning of QoS: • supporting differentiated classes of services

• Support for time-sensitive traffic

• Security and privacy

36

Quality of Service Provisioning

• QoS often requires negotiation between the host and the network, resource reservation schemes, priority scheduling and call admission control

• QoS in Ad hoc wireless networks can be on a per flow, per link, or per nodeper link, or per node

• Qos Parameters: different applications have different requirements

• Multimedia: bandwidth and delay are the key parameters

• Military: BW, delay, security and reliability

• Emergency search –and-rescue: availability is the key parameters, multiple link disjoint paths

• WSN: battery life, minimum energy consumption

37

Self-Organization

• An important property that an ad hoc wireless network should exhibit is organizing and maintaining the network by itself

• Major activities: neighbour discovery, topology organization, and topology reorganizationorganization, and topology reorganization

• Ad hoc wireless networks should be able to perform self-organization quickly and efficiently

38

Scalability

• The latency of path-finding involved with an on-demand routing protocol in a large ad hoc wireless network may be unacceptably high

• A hierarchical topology-based system and addressing may be more suitable for large ad-hoc wireless networksmay be more suitable for large ad-hoc wireless networks

39

Deteriorating factors

Channel_

Medium through which communication is being held and as we are talking about wireless this is the radio propagation channel

40

Channel provides the connectivity between transmitter and receiver but the same time it exhibits many different forms of channel impairment

Deteriorating factors

Additive Channel Impairment

o Thermal Noiseo AWGNo Reduces signal detect ability at the receiver sideo Can be compensated with high SNR

41

o Can be compensated with high SNR

Multiplicative Channel Impairment

o Multipath propagation o Reduction in usable frequency spectrum

Multiplicative impairment

Frequency dispersion• Fading

• Received signal strength fluctuations

• Long term Fading

� Shadowing and variation in the distances

� Slow rate and can be compensated with Power � Slow rate and can be compensated with Power control

• Short term fading

� Multipath propogation

� Diversity and Error correction coding are used to compensate

Multiplicative impairment

Time dispersion• Inter Symbol Interference (ISI)

• Overlapping in adjacent symbol time

• Can be compensated with use of Equalisers in case of

43

• Can be compensated with use of Equalisers in case of FDMA/TDMA systems and Rake receivers in case of CDMA systems

Types of Small-Scale Fading

44

Physical Factors Influencing Fading in Mobile Radio

Channel

(MRC) � 1) Multipath Propagation

– And strength of multipath signals

– time delay of signal arrival

• large path length differences → large differences in delay between signals

– urban area with many buildings distributed over large spatial scale

45

– urban area with many buildings distributed over large spatial scale

• large # of strong multipath signals with only a few having a large time delay

– suburb with nearby office park or shopping mall

• moderate # of strong multipath signals with small to moderate delay times

– rural → few multipath signals (LOS + ground reflection)

Physical Factors Influencing Fading in Mobile Radio

Channel

(MRC) � 2) Speed of Mobile

– relative motion between base station & mobile causes

random frequency modulation due to Doppler shift (fd)

– Different multipath components may have different

frequency shifts.

46

frequency shifts.

� 3) Speed of Surrounding Objects

– also influence Doppler shifts on multipath signals

– dominates small-scale fading if speed of objects > mobile

speed

• otherwise ignored

Physical Factors Influencing Fading in Mobile Radio

Channel

(MRC)

� 4)Tx signal bandwidth (Bs)

– The mobile radio channel (MRC) is modeled as filter with

specific bandwidth (BW)

– The relationship between the signal BW & the MRC BW

will affect fading rates and distortion, and so will determine:

47

will affect fading rates and distortion, and so will determine:

a) if small-scale fading is significant

b) if time distortion of signal leads to inter-symbol

interference (ISI)

– An MRC can cause distortion/ISI or small-scale fading, or

both.

• But typically one or the other

48

Path Loss

49

Channel Fading

50

Short term fading Solutions DIVERSITY-

• More than one independently faded version of the transmitted

signal so that if one multipath undergoes a deep fade another

path signal may provide a strong input

� Frequency Diversity

� Time Diversity� Time Diversity

� Space Diversity

• These independently faded signal components at the output of

demodulator are combined with techniques

� Maximal Ratio Combining

� Equal gain combining

� Selective combining

Short term fading Solutions

ERROR CORRECTION CODE

� For independent symbol error

• Block length codes

• Get the coding gain with Controlled redundancy

� For Bursty error enviornment

• Correlated (Fading) channel

• Negative effect over coding gain

• Coding scheme with interleaving

• Delay

• Hardware memory units

Advantages of Wireless Communication

� Any data or information can be transmitted faster and with a high

speed

� Maintenance and installation is less cost for these networks.

� The internet can be accessed from anywhere wirelessly

� It is very helpful for workers, doctors working in remote areas as � It is very helpful for workers, doctors working in remote areas as

they can be in touch with medical centers.

53

Disadvantages of Wireless Communication

� An unauthorized person can easily capture the wireless signals

which spread through the air.

� It is very important to secure the wireless network so that the

information cannot be misused by unauthorized usersinformation cannot be misused by unauthorized users

� Lack of compatibility makes it cumbersome to design and upgrade

the existing systems.

54

Design Challenges

� Hardware Design

� Precise components

� Small, lightweight, low power

� Cheap

� High frequency operations

� System Design

� Converting and transferring information

� High data rates

� Robust to noise and interference

� Supports many users

� Network Design

� Connectivity and high speed

� Energy and delay constrains

55

Future of wireless

� Satellite and Space communication

� Internet of things

� Communication for the smart grid

� Access system and netwok

� Wireless sensor network� Wireless sensor network

� Green Wireless Communication Design

� Wireless optical broadband access network (WOBAN)

� Next Generation Mobile Networks

� In Medical

� Implanted devices

� Remote surgery

56

Top Technology Trends in 2015

1. 5G

2. FIBER EVERYWHERE

3. VIRTUALIZATION, SDN & NFV

4. EVERYWHERE CONNECTIVITY FOR IoT & IoE4. EVERYWHERE CONNECTIVITY FOR IoT & IoE

5. COGNITIVE NETWORKS, BIG DATA

6. CYBERSECURITY

7. GREEN COMMUNICATIONS

8. SMARTER SMARTPHONES, CONNECTED SENSORS

9. NETWORK NEUTRALITY, INTERNET GOVERNANCE

10.MOLECULAR COMMUNICATIONS

Thank YouThank You

58