Wi-MAX A EVOLVING 4G TECHNOLOGY4.1 Introduction

The Internet made its debut in India in 1998. The deployment at that time was made

through Circuit Switch technology. The real Internet experience could not be achieved as it

had limited speed besides erratic performance due to high loading of the Telecom

Switches. To overcome these drawbacks, Digital Subscriber Line technology (DSL)

technology was deployed. This could achieve partial improvement due to limited

availability of Copper loops and distance limitations of 2 to 3 Kilometers. In early 2007,

based on WiMAX 802.16.d, ten BTSs were installed in different cities of the country as a

pilot project. The effective use of this technology could not be achieved as WiMAX

802.16.d was on Fixed application and did not support mobility.The real use of Internet

began only in 2008 with the deployment of Mobile Wireless Broadband in BSNL. Detailed

specifications were prepared based on 802.16.e standards with specific nation-wide

deployment strategy.

4.2 What is WiMAX

WiMAX (Worldwide Interoperability for Microwave Access) is a wireless digital

communications system, defined by the IEEE as the 802.16e standard. WiMAX, was

developed to provide a common framework for wireless connectivity in fixed, portable, and

mobile environments. It offers the high-speed connection of broadband and provides

wireless access, significantly reducing deployment costs associated with laying fiber and

extending it to buildings. With its range and open standards design, it will enable wireless

access nearly anywhere, simply by turning on a laptop, PC, or other WiMAX enabled

device. It also has the potential to bring high-speed access to areas that have, thus far, been

uncovered due to a lack of Copper/Fibre. WiMAX can provide Broadband Wireless Access

(BWA) up to 15 Km for fixed stations, 3 to 5 Kms for indoor applications and upto 1 Km

for Mobile stations from BTS location. In contrast, the WiFi/802.11 wireless local area

network standard is limited in most of the cases to only 100 - 300 feet(30-100m). Along

with increased and scalable data capacity, these new networks will be capable of

supporting new, open Internet models and new device distribution & subsidy models for

flexibly accommodating operators business needs. With WiMAX, WiFi-like data rates are

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easily supported, but the issue of interference is lessened. WiMAX operates on licensed

frequencies, providing a regulated environment and viable economic model for wireless

carriers. This unique technology is being deployed for the first time in India. Through this

BSNL will usher in a new era of growth in rural areas. This technology offers broadband

speeds upto 7 Mbps at a distance of 15 Kms. Mobility and

roaming is also provided to WiMAX subscribers through this latest technology.

4.3 Applications of WiMAX technology

WiMAX technology is the solution for many types of high-bandwidth applications at the

same time across long distances and will enable service carriers to converge the all-IP-

based network for triple-play services data, voice, and video. WiMAX with its QoS

support, longer reach, and high data capacity is positioned for fixed broadband access

applications in rural areas, particularly when distance is too large for DSL and cable, as

well as in urban/suburban areas of developing countries. Among applications for residential

are high speed Internet, Voice Over IP telephony and streaming video / online gaming with

additional applications for enterprise such as Video conferencing and 4 Video surveillance,

secured Virtual Private Network (with need for high security). WiMAX technology allows

covering applications with media content requesting more bandwidth. WiMAX allows

portable access applications, with incorporation in notebook computers and PDAs,

allowing for urban areas and cities to become metro zones for portable outdoor

broadband wireless access. As such WiMAX is the natural complement to mobile networks

by offering higher bandwidth and to Wi-Fi networks by offering broadband connectivity in

larger areas At the very basic level, WiMAX will offer the capacity for service providers to

deploy next generation broadband services cost effectively than today, to a wider customer

base, while adding a mobility aspect to those

services. More specifically, however, WiMAX will provide a means for service providers

to offer Quadruple Play services (voice, video, data, mobile), or Triple Play plus Mobile.

Service providers that are able to, on their own, deliver all these services, will have a

distinct advantage. So, with WiMAX, providers have the bandwidth and speed to provide

VoIP, IPTV (including video on demand), and Internet access. The key, then, lies in its

wireless access means, which allows to provide each of these services on a fixed and

mobile basis thus turning it into Quad Play. The benefits of fixed WiMAX are evident

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enough as they are based upon potential cost savings & service efficiency. To enable to

provide mobile voice, video, and data, with the speed to allow VoIP calling, video on

mobile devices and high-speed data transfers brings a new element to todays growing

mobile community.

In addition to simple business and consumer connectivity and backhaul applications,

WiMAX also brings real enhancements to communications capabilities available to

emergency personnel and first responders, which will be able to benefit from not only

voice communications, but also video and data transmissions to more effectively respond

to situations and coordinate responses. WiMAX also speeds deployment of temporary

communications facilities, for international & sporting events and other occasions, for

instance, which require temporary access for visitors, media, and personnel. With WiMAX

towers already in range, all that needs to be added are the appropriate on-premises

equipment to create easy access for such events. In rural areas, where broadband service

has until now been limited or impossible, WiMAX makes high-speed access a reality.

Eliminating the need for running fiber across rough terrain, or through sparsely populated

areas which are both costly endeavors, WiMAX base stations can be built to service the

local areas wirelessly, creating a new revenue source with a considerably lower investment.

In a fixed environment, WiMAX has the ability to provide similar services to what are

already enjoyed by the customers today with the exception that it makes possible the

inclusion of a new set of potential subscribers that have relied on PSTN and dial-up

service. Add to that the mobile aspect of WiMAX, and consumers, businesses, and

government agencies alike will discover a whole new broadband paradigm, which will

significantly enhance their ability to conduct their business simply by not being tied down

by wires.

4.4 WiMAX- A important Technology for fixed and for mobile wireless broadband.

WiMAX is needed as a single technology able to provide fixed and mobile broadband

access. The WiMAX standard was needed to reach the lower cost target that proprietary

wireless solutions were not able due to volume limitations. WiMAX interoperable solutions

enable economies of scale through integration of standard chipsets, making WiMAX

Forum Certified products cost-effective at delivering high-capacity broadband services at

large

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coverage distances in Line of Sight and Non Line of Sight conditions. This is possible with

WiMAX, thanks to the strong industry support through the WiMAX Forum with more than

350 members including equipment vendors, leading chipmakers and service providers.

WiMAX is important for fixed broadband wireless to provide broadband access needed to

enterprises and residential users as an alternative for cable and DSL services, particularly

when access to copper plant is difficult. WiMAX is important for mobile broadband

wireless, as it completes 3G by providing higher performance for

data with more than 1 Mbps downstream to allow connection of laptops and PDAs, and

complete Wi-Fi by providing much wider coverage.

4.5 Key elements of WiMAX Technology

The main element of WiMAX technology is the interoperability of WiMAX equipment,

certified by the WiMAX Forum, resulting in mass volume and confidence for service

provider to buy equipment from more than one company and that everything works

together. The WiMAX Forum put for the first time together leaders in the communications

and computing industries to drive a common platform for the global deployment of IP-

based broadband wireless services. The key driver of WiMAX technology is OFDM

technique and Sub-Channelization which mitigates the problem of interference resulting

from NLOS conditions. These are explained as under: Other key elements are cost,

coverage, capacity and standard for both fixed and mobile wireless access.

4.6 Wi-MAX network architecture

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The WiMAX system broadly consists of a base station and remote stations called CPEs.

The Base Station communicates with one or more CPEs. The Base station and the CPE

provide RF Air Interface compliant with IEEE 802.16e-2005 standards. The Base station

and CPE supports scalable OFDMA with upto 1024 FFT technology. Future expansion to

2048 FFT/20 MHz channel is also possible. The BS & CPE will dynamically select

modulation rates for downlink and uplink transmissions based on previous RF link quality

measurements and available transmit power. The CPE & Base Station System supports

four different uplink Ranging channels as defined in IEEE 802.16e-2005 standards. These

are initial ranging, periodic ranging, bandwidth request and handover. The Base Station

System and CPE supports packet header compression and/or suppression on the BS to CPE

link in both downlink and uplink directions to reduce IP overheads. Base Station is of split

configuration type with RF modules alongwith integrated antenna in a single Box (called

RF Unit) which is pole or wall mountable. The RF Unit is connected to another unit (called

Base Control Unit) through fiber cables carrying IF Tx and Rx signals. The Base Control

Unit is having baseband functionalities and common control functionalities for all sectors.

Multiple Base Control units can be connected to an indoor unit through Ethernet interfaces.

The indoor unit is called System Controller Unit Or Access Service Network- Gateway

(ASN-GW) Unit having Access Service Network functionalities. As the result of any

successful registration, a CPE will be informed of the unique identity of the BS it is

currently registered with. The OCLAN switch is deployed as Tier-2/Tier-1 Network Device

in the BSNL Multi Play connecting the Tier-1 RPR to DSLAM in other cities. It supports a

wide variety of interfaces, such as 10GE, GE, FE, and POS and can provide multiple

service functions such as MPLS, NAT, QoS, and multicast and bandwidth control.

The Converters (external) for Base Station Data Interface (Ethernet port) is of two types:

(i) Electrical to Optical Converter

(ii) Ethernet to STM-1 Converter

The CPE has a Visual/ audio indication on the unit indicating receive signal strength for

facilitating proper orientation and quick alignment and easy installation. The CPE supports

configuration update overthe- air, software upgrade over-the-air and service provisioning

over-the-air. CPEs are of the following types and categories:

Type I : Indoor Type

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Type II : Outdoor Type

Type III: PCMCIA Type which is a 802.16e-2005 standards based PCMCIA card for

laptops and portable applications.

The System Controller or ASN G/W, Access Service Network Gateway is responsible for

the handovers for portable and mobility applications. Besides, Authentication liaison

between the user/device and the AAA server, Security functions such as Local Key

Distribution Function (LKDF) for delivering Authentication Keys, Paging Controller (PC),

Radio Resource Management and Mobility and connection Management are supported.

The ASN interfaces with Connectivity Service Network (CSN) through GE interface. The

CSN consists of Home Agent Router (HA), Element Management System (EMS) and

AAA server functionality. Each mobile node is assigned to a Home Agent and each mobile

will be assigned a static or dynamic IP address belonging to its home IP network Home

Agent. When a mobile station moves to another network called a foreign network, the

mobile station will register with a Foreign Agent (FA) and the mobile station will be

authenticated and authorized by FA alongwith Visited AAA in consultation with Home

AAA. The FA assigns a care of address to the mobile station. The mobile station registers

the care of address with the Home Agent through the FA which forwards the registration to

the Home Agent. The DHCP (Dual Host Control Protocol) Server of OSS/BSS facilitates

IP address allocation. The system

supports DHCPv4 as a means of providing IP address assignments to the CPEs and any

attached host(s). The simple IP Service will allocate dynamic IP or static IP address to the

mobile station and provides routing service to the mobile station. The network allows

Mobile computing platforms that have had their IP address assigned via DHCP to route

outside of their subnet (via a default gateway) without having to manually configure their

default gateway setting and also to use domain name services without having to manually

configure their DNS server setting. The system securely configures AAA shared secrets to

authenticators within the network and supports a mechanism by which the shared secret

can be modified. The authenticator within the WiMAX infrastructure will support being

configured and utilizes both a primary and secondary next hop AAA server. The EMS

(Element Management System) is GUI based and supports Alarms display in different

colours, all managed base stations display on the topology map and by clicking the object

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of the base station on the screen, the detailed information of the base station will be

displayed. The EMS system provide alarm management features such as, Current alarm

list, Historical alarm list, Pseudo-events notification, Real-time alarm viewer and alarm

management, Alarm filtering & thresholding, Event logging, Real-time map viewer with

topological associations and NE status, Management link monitoring and NE availability

reporting. The Element management also provides Configuration Management functions

such as, Configuration & Parameter of the network elements, Auto-discovery & IP address

tracking and Software configuration.

4.7 Mobile Wireless Broadband deployment in India

India is deploying WAVE-2 Certified IEEE 802.16e-2005 Complaint WiMAX Network

through BSNL. 20 MHZ spectrum has already been allocated to BSNL in frequency band

of 2635 to 2655 MHZ. BSNL has decided broadly that WiMAX will be deployed using

separate Rural and Urban business models. The roll-out of broadband wireless access

services in the country with present status is as detailed below:

4.7.1 The WiMAX Rural Project

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India has 6000 Rural blocks with approx. 650000 villages. BSNL is providing widespread

WiMAX coverage in rural areas using support by various Government schemes (like e-

governance and USO) for making broadband available. BSNL has taken up the task of

providing connectivity to all such initiatives through its WiMAX Rural Projects under two

phases. These projects are being supported by Department of Information Technology.

4.7.2 Rural Project Phase-I (1000 BTS)

BSNL has decided to provide Wireless Broadband connectivity to 1000 Rural Block

Headquarters across the country through WiMAX under Phase-I Project. As of date, 750

BTSs are radiating throughout the country and remaining 250 BTSs are being

commissioned progressively. These 1000 Base stations will provide broadband coverage to

about 11500 Rural Common Service Centers for e-governance.

4.7.3 Rural Project Phase-II (6863 BTS)

In Phase II, it is proposed to provide Wireless Broadband Access connectivity through

6863 BTSs

spread throughout the country. These Base stations will provide Broadband connectivity to

approximately 41000 Rural Common Service centers of e-governance project. This project

is also being supported by Department of Information Technology. The BTSs under this

project will be installed by march 2011. Together these two projects will have foot print in

more than 50 % of Rural areas and shall cover 60 % of population in Rural areas. This will

provide high speed wireless broadband connectivity to these Rural villages. The Rural

Common Service Centers are a part of the Bharat Nirman Programme initiated by the

Honble Prime Minister of India and will help in bridging the digital divide between urban

and rural areas.

4.7.4 The WiMAX Urban Projects

For providing mobile wireless broadband access in Urban areas, BSNL has decided that the

deployment will be made through two routes, i.e., the deployment through own resources

and through franchises.

a) Through own deployment

Two Circles i.e. Kerala and Punjab were selected for BSNLs own deployment to have

firsthand knowledge and experience of WiMAX deployment in Urban areas. BSNL

finalized procurement for 1600 BTSs, i.e., 900 for Kerala and 700 for Punjab to be

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deployed in two years time. The broadband wireless access services in Kerala and Punjab

have since been launched and about 700 BTSs are radiating in these two areas. There is

good response and customers are being provided WiMAX services in these areas.

b) Through franchises

A built & operate model, where a franchisee will make Capital investment and operate the

network on Revenue share basis. BSNL has made the following arrangements:

(i) BSNL has entered into an agreement with a franchisee to provide wireless broadband

access services in Andhra Pradesh, Gujarat and Maharashtra circles on revenue sharing

basis. There are about 3000 customers at present. As per target set in the agreement 50,000

customers in each of the three circles need to be enrolled by the franchisee by the year

2011.

(ii) BSNL has finalized on franchisee basis, the deployment of BWA services through an

expression of interest (EOI) for eleven telecom circles, i.e., Karnataka, Rajasthan, Bihar,

Tamilnadu, UP West, Orissa, Kolkota, Madhya Pradesh, Himachal Pradesh, Haryana and

Chennai. Shortly BSNL will be entering into agreement with the selected franchisees for

deployment of BWA services in these areas. (iii) BSNL is in the process of floating an EOI

for selection of franchisees for five circles, i.e., West Bengal, UP East, J&K, Assam and

North East.

4.7.5 Service Offerings

BSNL is offering this service at a very low cost with starting tariff of Rs.220 per month in

rural areas for speed upto 7 MB. Unlimited download plan is available at the rate of Rs.

999 per month. To kick-start the off-take of WiMAX, BSNL is buying CPEs and will

provide to Customers on Rental basis. Meanwhile BSNL is also working on various models

of bundling to enable different device manufacturers to provide WiMAX enabled device as

a bundled package. BSNL has signed MAP (Market Acceleration Program) with Intel to

ensure availability of Embedded devices at affordable cost. This milestone will also help in

increase the rural tele- density and also will bring rural areas to the broadband map of the

world.

The common service centres (CSCs) which are being set up by Department of

Information Technology in the rural areas of the country will offer the following services:

High speed internet browsing.

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Video conferencing enabling Tele-medicine and Tele-education.

Connectivity for Bank ATMs, Railway Reservation Centers etc.

All applications associated with e-Governance projects of the State Governments.

Connectivity to Village Panchayats through high speed broadband.

Payment of utility bills.

Issue of birth certificates.

Land records.

Vehicle registration etc.

4.7.6 The WiMAX Network Architecture

A WiMAX deployment will essentially have two hardware components a WiMAX

tower and a WiMAX receiver. The tower is like a cell tower, which can provide coverage

within a radius of 15 Kms. The tower connects to the Network using a high-bandwidth

connection, i.e., STM-1. The receiver can be an outdoor CPE, indoor CPE or a USB

Dongle. Embedded PCs with built-in WiMAX chips can also be utilized as end devices.

Future projections

Sl Estimates for conditions BSNL Projections Year 2020 Remarks

1 Population 1374 Million As per Census and Growth

2 PC Price 150 USD Price is based on input from Intel *

3 Addressable Market (Income Based) 181 Million Analysis is based on expected

penetration 15 %.

4 Technology Share HSPA-60% EVDO- 5% WiMAX- 35%

3G will saturate because of spectrum and also usage for Voice calls.

5 BSNL Market Share in WiMAX 35 To 40 % Expected number of WIMAX operators to

be 3 nationally. Approx 20 Million WiMAX connections by 2020

4.7.7 Impediments in deployment of WiMAX technology

To the service provider, the benefits of WiMAX as clear, assuming subscribers. But, to win

subscribers will take some education. After all, most people only have a bare bones

understanding of WiFi, if they have broadband at all. So then, being able to address

questions and concerns about WiMAX becomes a key to its successful deployment. The

main concerns that WiMAX still faces are::

1. Technology is still evolving

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Mobile WiMAX is a globally defined standard currently undergoing trial and

interoperability.. At this decade Wimax Technology is not full fledged deployed in most of

the areas of the world with very limited users. Security will grow to be a major issue with

Wimax Technology. Access and authentication remains the essential wireless concern for

enterprise buyers and consumers. There is, however, an increasing alertness that wireless's

fragile link may not be in the security mechanism used to protect it, but rather in the

insecure coding at the software driver level, which can be broken by intellectual hackers.

The prerequisites for a complete Wimax Technology security system are not even covered

by the basic specification. The IEEE 802.16 standard and WiMAX only defines the air

interface and the physical (PHY) layer and Media Access Control (MAC) layers. This still

leaves work to be done on safety and privacy between different communication networks.

The risk is significant and that it might be sensible to employ a second line of defence

against such an attack. Several weaknesses in privacy and key management (PKM) have

also been discovered. PKM prevents eavesdropping and passive attacks by using hashed-

message-authentication code and traffic-encryption keys (TEK). All key negotiation and

data-encryption-key generation rely on the authorization key's (AK) secret. The AK is

generated by the base station, and the TEK is generated from the AK but only has a 2-bit

identifier space, which is insufficient during the AK lifetime. According to experts Wimax

technology is still facing problems in security and also vulnerable to Denial-of-Service

attacks (DOS), because there is no mechanism in place to specifically detect and discard

repeated packets in the message. An attacker could repeat many messages, valid or not, in

an attempt to interfere with the operation of the network. The impact of this type of attack

can be very high, because it might affect the operation of the communication system within

WiMAX Technology. The real test of WiMAX security will come when service providers

begin wide-scale network deployments, and researchers and attackers have access to

service CPE equipment. Other attacks including WiMAX protocol blurring may enable

attackers to further manipulate Base Stations (BS's) or Subscriber Stations (SS's). Until

then, the security of WiMAX technology is limited to forecast. Algorithms of power

control are applied to enhance the general performance of the system, it is deployed by the

base station sending power control information to every Wimax Customer Premise

Equipments (CPEs) to control the transmit power level so that the level inward bound at

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the base station is at a fixed level. In a dynamical changing fading environment this pre-

determined performance level indicates that the Customer Premise Equipment (CPE) only

broadcasts sufficient power to meet this constraint. The communication would be that the

CPE broadcast level is supported on worst case circumstances. The power control

decreases the general power consumption of the Wimax Customer Premise Equipments

(CPE) and the possible interference with other base stations. For Line-of-Sight (LOS) the

transmission power of the Wimax Customer Premise Equipments (CPE) is approximately

comparative to its distance from the base station and for Non-Line-Of-Sight (NLOS) it is

also closely dependant on the clearance and barriers

2. High Cost of Spectrum

In the recent concluded auction of BWA spectrum by DOT, the Service operator has to pay

for one block of 20 MHz, an upfront license fee of 12,776 crores for all the 22 service

Areas of the country. With such a high spectrum cost, it will take many years before the

operators are able to break even. Such a situation is likely to create impediments in smooth

roll out of BWA services in the country.

3. Less-availability of A.C. power in rural areas

The Power outages in Rural areas in India is extremely high and the alternate arrangements

of Battery and Alternators do not prove sufficient to provide continuous service to the

customers. As such, disconnection in services for a considerable period of time cannot be

ruled out at present. Under these circumstances, the success of WiMAX deployment is

fully dependent on regular availability of AC supply. Therefore, success of WiMAX will

depend upon how fast the infrastructure is improved by the Government in the country

resulting in popularity of WBA services to the

satisfaction of customers in rural areas.

4. High WiMAX CPE cost

Another major hurdle that broadband operators would face is that of the cost of WiMax

Customer Premises Equipment (CPEs) that would account for around 50-60 percent of an

operator's capex. The cost of WiMax CPEs is likely to remain on the higher side for

another 2-3 years. As such, operators would find it difficult to roll out WiMax on a mass

scale. Compared to a DSL modem that costs less, the first set of WiMax CPE would cost

nearly two-tothree times more (Rs.5000). According to WiMax Forum, the first generation

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of WiMax Forum Certified CPEs are outdoor-installable subscriber stations. The second

generation of CPEs are indoor self-installable modems similar to a cable or DSL modem,

which are priced approximately half the price of out-door CPEs

(Rs.2500 Rs.3000). Third-generation CPEs are integrated into laptops and other portable

devices. Their cost will be considerably less than the price of indoor CPEs (Rs.1500

2000). In the existing scenario, with the high cost of CPE, it is unlikely that India would

see a dramatic breakthrough in WiMax deployment. Though WiMax Forum has certified a

number of CPEs by different manufacturers, with each one either doing trials or planning,

it is unlikely to gain any precedence over DSL or other initiatives immediately because of

the high cost of CPE.

5. Low PC Penetration

The internet boom has created a volcanic demand for PCs in India, but the low PC

penetration (about 30~35 million) is way far less. There is a dearth of availability of PCs as

well as their awareness in rural areas and for the WiMAX roll-out to be a success, this

aspect assumes significant importance. Under such circumstances, to win the customers in

reural areas, the operators will have to introduce attractive bundled schemes for the PCs

which will put additional strain on the operator cost.

6. Local applications and content in vernacular

Although the Central Government and State Governments have made ambitious plans to

promote computerization in every aspect of day-to-day applications, i.e., Tele-medicine

projects, Payment of utility bills, Land records, Registration/Issue of Birth/Death

Certificates, Driving Licenses, Ration card issue, Mobile Banking, etc., but, their utilization

in the Rural populace of the country is limited in view of constraints noted

in the above paras. Though our country has different regions having multitude of languages

and cultures, we still depend upon applications for WiMAX technology developed in

foreign shores. There is enormous potential in our country to develop the WiMAX

applications in various dialects suitable for different States/ Regions, but as of

today, no local content is visible. The rapid growth of WiMAX in India and its desirable

innovations are not possible in the near future as development of local applications and

content in different languages is in the

nascent stages.

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4.7.8 Important aspects of WiMAX deployment

a) Quality of Service

QoS is ultimately the determining factor in a technologys ability to deliver todays high-

bandwidth services, like VoIP and IP video services, as well as other collaboration-

enhancing applications. In order to provide QoS, WiMAX providers must be able to ensure

low latency. The simple fact is that WiMAX service suffers from nearly no latency across

its wireless connections i.e., less than 10 milliseconds from tower to receiver. The majority

of any latency occurs from the receiver onward, to servers and end users. Thus, as with any

broadband service, it is incumbent upon the business to ensure its network equipment is

properly set up to handle these services, and upon service providers to provide the

appropriate technology to residential subscribers .

b) Security

Considerable attention has been given to network security of late, and WiFi deployments,

in particular, have come under heavy scrutiny for their lack of appropriate security.

WiMAX, on the other hand, has been designed to provide effective security in order to

prevent network intrusion and access violations. WiMAX security is defined in the Privacy

Sub-layer in the MAC Layer, as specified by WiMAX standards. Fixed WiMAX (802.16-

2004) typically uses X.509 certificates for authentication and 56-bit Digital

Encryption System (DES), while Mobile WiMAX (802.16e-2005) uses EAP for

authentication and Advanced Encryption System (AES) for encryption. Both employ

Privacy Key Management (PKM) for authentication between base station and subscriber

station.

c) Reliability

The Five 9s scenario for network uptime has become the dominant standard for providers

when describing their network availability and uptime. However, while landline providers

networks may, in fact, be capable of such reliability, which equates to something like five

minutes of downtime per year and other factors can cause substantial service outages.

Specifically, landline service relies on wires running to the home or business, which

represent a single point of failure, barring several incoming lines, which is a costly

proposition. Because it provides wireless connections to customer premises, WiMAX

eliminates the potential for fibre and cable failures, which, technically, are not a result of a

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providers network failure. Instead, by deploying redundant transmitters to cover an area,

WiMAX providers can easily provide network redundancy, while, at the same time,

expanding their service area with the same equipment. By using only licensed spectrum,

service providers can be assured they are not competing with other carriers for network

resources. Also, since WiMAX radios are predicted to have a lifespan of more than four

decades.

d) Interference

Its no secret that wireless signals are susceptible to interference, i.e., its the nature of the

beast, and its a factor that has required attention from providers since the first wireless

devices. Even now, older, 2.4GHz cordless phones and other home appliances have the

potential to disrupt WiFi signals. Employing counter-interference measures is something

providers need to manage, and it really means nothing more than understanding the

potential sources of interference within the electromagnetic spectrum, and engineering

solutions to work around those obstacles.

There are two general types of interference: Out-of-channel interference is a result of other

transmitters that are not on the same frequency as the primary radio; and co-channel

interference results on the same frequency as the original signal. To eliminate co-channel

interference, precautions must me taken to plan frequency use appropriately, use only

licensed spectrum, and provide dynamic frequency selection. Out-of-channel interference

can largely be avoided through the use of OFDM and OFDMA technologies, as well as any

of a variety of antenna designs specifically developed to avoid interference from other

devices.

4.8 Comparison of Wi-MAX with LTE

Both the technologies are expected to dominate the 4G cellular market. LTE is Long term

Employment, Oh&Long Term Evolution, and WiMAX stands for Worldwide

Interoperability for Microwave Access. LTE and WiMAX are two major 4G cellular

technologies. The LTE vs. WiMAX debate is reminiscent of the erstwhile GSM vs. CDMA

battle. We'll compare LTE and WiMAX from the perspectives of air interface features,

network architecture, and industry trends. In general, they share more similarities than

differences. WiMAX in this article refers to IEEE 802.16e-2005-based mobile WiMAX.

a) Air Interface Features.

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Both LTE and WiMAX aim for superior packet data performance with the peak user data

rates in excess of 100 Mbps (e.g., 300 Mbps) and latency less than 10 ms. Achieving such

data rates is no small task, and, technologies such as OFDMA and advanced antenna

systems are called upon by LTE and WiMAX. While WiMAX uses scalable OFDMA for

both downlink and uplink, LTE uses scalable OFDMA in the downlink and a variation of

OFDMA called SC-FDMA (Single Carrier- Frequency Division Multiple Access) in the

uplink. The use of SC-FDMA results in reduced PAPR (peak-to-average power ratio) for

the mobile device at the expense of increased complexity in both the device and the base

station. In practice, such PAPR reduction could be reflected in a somewhat larger cell

radius or better cell-edge performance in the uplink. The typical subcarrier spacing is 10.94

kHz in WiMAX and 15 kHz in LTE. Such spacing makes the job of the WiMAX receiver a

little easier due to flat fading and allows LTE to support faster moving vehicles due to

additional resistance to Doppler shift. While STC (Space Time Coding) is a more common

transmit diversity for WiMAX, a variation of STC called SFBC (Space Frequency Block

Coding) is used in LTE. Both WiMAX and LTE support MIMO (Multiple Input and

Multiple Output) and SDMA (Space/Spatial Division Multiple Access) in the downlink and

SDMA in the uplink. SDMA is referred to as MU (Multi User)- MIMO in LTE and

Collaborative Spatial Multiplexing in WiMAX. In terms of performance, peak user data

rates are approximately 75 Mbps and 63 Mbps in the downlink of LTE and WiMAX,

respectively, and 37.5 Mbps and 28.8 Mbps and in the uplink of LTE and WiMAX,

respectively. These performance estimates assume (10 MHz x 10 MHz) FDD and the use

of 2x2 MIMO in the downlink. The performance gap between LTE and WiMAX from the

perspectives of average sector throughput and user perceived throughput would be

narrower than that for peak performance. The VoIP capacity of LTE can be expected to be

somewhat higher than WiMAX due to more efficient resource allocation techniques. While

both technologies will eventually support TDD and FDD, early WiMAX deployments use

TDD and initial LTE deployments are expected to use FDD.

b) Network Architecture.

The LTE radio network consists of eNode Bs, while the WiMAX radio network consists of

BSs and ASNGWs (Access Services Network- Gateway). The WiMAX core network uses

typical IP network nodes such as AAA Server, Home Agent, DHCP Server, and DNS

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Server and can connect to a Services Network such as IMS. LTE defines a comprehensive

core network called EPC (Evolved Packet Core). This includes special

entities such as MME (Mobility Management Entity), HSS (Home Subscriber System), S-

GW (Serving Gateway), PCRF (Policy & Charging Rules Function), and PDN-GW (Packet

Data Network Gateway) in addition to the nodes mentioned for WiMAX. It is conceivable

that EPC may be used by a WiMAX radio network. EPC can also connect to IMS.

c) Industry Trends.

WiMAX enjoys a broad ecosystem with competition among numerous vendors, many of

them small companies, potentially resulting in a lower cost BS and MS. Most big

manufacturers have WiMAX offerings, Motorola, Samsung, Nokia, Alcatel-Lucent, Nortel,

Intel, and Cisco. Intel and Cisco are new entrants to the mobile cellular world. Notably

absent from the WiMAX list are Qualcomm and Ericsson. LTE has backing

from traditional cellular companies including major 3G operators covering more than 90%

of the cellular market. LTE is offered by the WiMAX companies mentioned earlier except

Cisco and Intel. Assuming (!) that some 1xEV-DO and UMTS systems see LTE overlays,

there could be huge economies of scale benefit due to the large number of subscribers,

leading to low cost user devices. The cost per eNode B may be somewhat higher than a

WiMAX BS due to relatively less intense competition as the typical LTE vendors are likely

to be major vendors who may not face serious threats from small companies. In summary,

Both LTE and WiMAX have a solid backing from industry heavyweights, which provides

adequate ammunition in the fight for dominance.

4.10 Conclusion

WiMAX technology holds great promise for delivering new, high-bandwidth

communications and information services to both geographically remote areas and large

urban populations. From mobile VoIP to social networking, WiMAX is taking off in a big

way. 2.5 and 3G networks have enabled users around the world to access data on their

handsets and laptops. However, as mobile data services increase and more PC users start

using the same broadband Internet applications on the go as they do at home, the

expectation is for mobile data traffic to grow by a factor of enormous proportion. And this

requirement could easily exceed expectations with a surge in applications like rich social

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networking which combine Internet multimedia and mobility. Although 2.5 and 3G

networks will continue to serve up voice and mobile data for the foreseeable future, these

networks will become capacity constrained as mobile broadband data use increases. Hence,

the deployment of WiMAX to offload data-intensive mobile broadband applications is

inevitable and apt.

A quick return of investment(ROI) and the ability to drive profitable services across a

diverse customer base are critical to the success of WiMAX deployment. WiMAX adopted

advanced technologies such as MIMO and Smart Antennae systems increasing over-all

system link-budget during dynamic RF conditions. These enhancements produce higher

capabilities over more expansive coverage areas, reducing the number of cells required and

lowering infrastructure costs normally associated with indoor usage. With centralized

provisioning and simple & rapid installation, WiMAX provides hands-off, error-free

networking for a single home or an entire office.

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