Group Members:

1.Maidha Shoukat

2.Asia Aman

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Background

Introduction

Why IEEE 802.22

Concept Of cognitive Radio

Basics Of IEEE 802.22 WRAN

Air Interface

Advantages and Disadvantages

Conclusion

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The IEEE 802.22 standard for a Wireless Regional Area

Network was formally approved on July 2011

In recent years there is a rapid growth in the field of wireless

services

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One particular technology that may bring better spectrum

utilization is that of cognitive radios technology

By using CR technique the radios can sense their

environment and adapt accordingly. The use of cognitive

radio technology is therefore key to the new IEEE 802.22

WRAN standard

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The IEEE 802.22 standard defines a system for a Wireless

Regional Area Network, WRAN that uses unused or white

spaces within the television bands

It utilizes cognitive radio technology to ensure that no

interference is caused to television services by using the

television bands

In this way 802.22 is the first standard to fully incorporate

the concept of cognitive radio

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This standard provides an efficient utilization of UHF and

VHF TV bands between 54 and 862 MHz

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Spectrum scarcity

Demand for higher data rates and coverage

It utilizes TV white spaces

IEEE 802.22 share the geographically unused TV spectrum

in a rural environment to provide broadband access

Use cognitive radio capabilities to avoid interference to

broadcast incumbents and other WRAN systems

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Vacant frequencies made available for unlicensed use at

locations where spectrum is not being used by licensed

services

This spectrum is located in the VHF(54-216 MHz) and UHF

(470-698MHz) frequency bands

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Cognitive radio (CR) is a form of wireless communication in

which a transceiver can intelligently detect which

communication channels are in use and which are not and

instantly move into vacant channels while avoiding occupied

ones

This optimizes the use of available radio-frequency (RF)

spectrum while minimizing interference to other users

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Cognitive radio uses a number of technologies including

Adaptive Radio and Software Defined Radio

In Adaptive Radio the communication system monitors and

modifies its own performance

Software Defined Radio (SDR) where traditional hardware

components including mixers, modulators and

amplifiers have been replaced with intelligent software

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Sensing

CR enables customer premises equipment to sense available channel

Selecting

Select best available channel

coordination

Coordinate spectrum access with other customer premises equipment

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Spectrum Sensing

Spectrum Sharing

Location Identification

Network/System Discovery

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Resource utilization

QoS (Quality of Service)

Incumbent monitoring

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The 802.22 standard includes the following parameters as the

basics of the system

System topology

Coverage area

System capacity

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The 802.22 system is intended

to be a fixed point-to-

multipoint wireless air

interface

In this topology base station

(BS) manages its own cell and

all associated Consumer

Premise Equipments (CPEs),

as shown in Figure

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BS also manages a unique feature of distributed sensing

This is needed to ensure proper incumbent protection and is

managed by the BS, which instructs the various CPEs to

perform distributed measurement of different TV channels

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The coverage area for the

IEEE 802.22 standard is much

greater than many other IEEE

802 standards

The BS coverage range is up

to 100km

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The system has been defined

to enable users to achieve a

level of performance similar

to that of DSL services

available

The downlink or download

speed is around 1.5 Mbps

and an uplink or upstream

speed of 384 kbps

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Base Station

Fixed Station

Decides Channel Availability

Makes Final decision if there is availability of TV channels

Client Station

Customer premises equipment

Fixed location

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The basic specification parameters of the IEEE 802.22

standard can be seen in the table below

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IEEE 802.22 WRAN is established to provide fixed wireless

broadband services using vacant TV channels without causing

harmful interference to incumbent TV broadcast signals

IEEE 802.22 is a standard for Wireless Regional Area

Network using white spaces in the TV frequency spectrum on

a non-interfering basis

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Tolerable level of interference is needed

Reason: In many countries not all available TV channels are

used as it is necessary to allow guard channels between

active high power transmitters to prevent mutual interference

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PHY layer is designed

To support a system that uses vacant TV channels

To provide wireless communication access over distances

of up to 100 km

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PHY specification is based on orthogonal frequency

division multiple access (OFDMA) for both

Upstream (US) access: from CPE to BS with rate 384 kb/s

Downstream (DS) access: from BS to CPE with rate 1.5 Mb/s

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MAC is one of two sub layers that make up the Data Link

Layer of the OSI model

It is responsible for moving data packets to and from one

NIC to another across a shared channel

It determines where one frame starts and other ends

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Frames are grouped into a super frame structure

Super frame allow for better incumbent protection and self-

coexistence

Super frame structure consists of 16 frames

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Each frame consists of:

Super frame preamble used for time synchronization

Frame preamble used for channel estimation

Super frame Control Header (SCH) which carries BS MAC

address along with the schedule of quiet periods for sensing,

as well as other information about the cell. Support the intra-

frame and inter-frame quiet periods management

mechanisms for sensing

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802.22 supports Time Division Duplex (TDD) frame structure

Each frame consists of downlink (DL) sub-frame, uplink (UL)

sub-frame, and the Co-existence Beacon Protocol (CBP)

burst

The UCS window can be used by CPEs to transmit an

indication that an incumbent has been detected on the channel

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A transmit-receive turnaround (TTG) gap is inserted between

the DS and US to allow the CPE to switch between the

receive mode and transmit mode

A receive-transmit turnaround (RTG) gap is inserted at the

end of each frame to allow the BS to switch between its

receiving mode and transmit mode

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The DS/US MAPs are broadcast messages that specify the

resource allocation in the DS and US sub frames, respectively

The SCW is used for execution of the coexistence beacon

protocol (CBP), which involves transmission of coexistence

beacons (or CBP packets) carrying information about the cell

and specific coexistence mechanisms

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Both the BS and CPE have the capability to detect the

presence of an incumbent user on a channel, but the channel

management decisions are made only by the BS

Different techniques used for it are:

Geo-allocation

Global Positioning System (GPS)

Spectrum sensing

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IEEE 802.22 uses lower frequencies

The coverage area for WRAN is much larger than that of other

IEEE 802 standards PAN, LAN & MAN

It provides various type of services like data, voice, audio &

video with appropriate (QOS) support

IEEE 802.22 users are unlicensed users in TV bands and this

decreases the cost of this standard in comparison to some other

standards

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Because the geographical coverage of this standard is in the

range up to 100 Km the propagation delay is more

considerable in this standard in comparison to the others.

Another disadvantage of this standard is the self-

coexistence and hidden incumbent problem.

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IEEE 802.22 is required to reuse the fallow TV spectrum without causing any harmful interference to incumbents (i.e., the TV receivers)

Cognitive radio techniques are of primary importance in order to sense and measure the spectrum and detect the presence/absence of incumbent signals

Base Station and Customer Premise Equipment has Master Slave N/w Architecture

Spectrum sensing is periodically done by BS and CPE CPE Reports spectrum sensing to Base Station (BS) BS makes the final decision

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