wimax and ieee 802

8/8/2019 Wimax and Ieee 802

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WIMAX and IEEE 802.16


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Requirement Considerations for

WiMax Wireless links with microwave ormillimeterwaveradios.

uselicensed spectrum (typically).

Aremetropolitan in scale. Provide public network service to fee-payingcutomers (typically)

Use point to multi-point architecture with stationaryrooftop or tower-mounted antennas.

Provideefficient transport of heterogeneous trafficsupporting QoS.

Arecapable ofbroadband transmissions (>2Mbps)


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802.16 wireless service provides acommunication path between a subscribersite(single subscriberdevice ora network

at subscriberpremises) and a corenetwork.

802.16 standards areconcerned with the

airinterfacebetween the subscriberstransreceiverand thebase transreceiverstation.


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Theother two interfaces i.ebetween the

subscriberand the Subscriber transreceiver

Station (SNI) and base transreceiverstation and

core network (BNI) arebeyond the scope of802.16 standards.

Thereason of showing SNI and BNI is that the

subscriberand core technologies have an

impact on the technologies used in the air

interface and the service provided by the

transreceivers stations over the airinterface.


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Protocol Architecture

The 802.16 protocolis concerned with the

lowest two layers of the OSI model.

The 802.16 has a fourlayerarchitecture: Physical

Transmission

Medium Access Control

Convergence

Physical Layerof the OSI Model

Data Link Layer of OSI Model


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IEEE 802.16 Protocol

Architecture


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Functions of Physical Layer

The Physical Layerof 802.16 addresses

themedium-dependent issues, since

the

se

are

cri

tic

alin w

ireless

link d

esign

It specifies the transmission medium and

the frequency band.


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Functions ofTransmission Layer

Encoding / decoding of signals

Preamble generation and removal (for

synchronization). Bit transmission / reception.


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Functions of MAC Layer

On transmission, assemble data into a

frame with address and errordetection

fields.

On reception, disassemble frame, and

perform address recognition and error

detection.

Govern the access to the wireless

transmission medium.


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Functions of MAC Layer

Responsible forsharing access to radio channelbetween thebase station and the subscriberstation.

It defines when and how a base station orsubscriberstation may initiatetransmission onthechannel.

The protocolmust be able to allocate theradiochannelcapacity so as to satisfy QoS demands.

In downstream only one transmitterandtherefore MAC protocolis relatively simpler.However for theupstream there aremultipletransmitterand therefore MAC protocolis morecomplex.


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Functions of Convergence Layer

Encapsulate PDU ofupperlayers in the802.16 MAC/PHY frames.

Map an upperlayeraddress into 802.16addresses.

TranslateupperlayerQoS parameters intonative 802.16 MAC format.

Adapt the time dependencies of theupperlayer trafficinto theequivalent MACservice.


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Services

802.16 is designed to support followingbearerservices

Digital Audio / Video multicast.

DigitalTelephony.

ATM.

IP .

Bridged LAN. Back Haul

FrameRelay


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IEEE 802.16 MAC Layer

Data transmission overairinterface from or to a

given subscriberare structured as sequence of

MAC frames.

MAC protocolis a connection oriented protocoland each MAC frameincludes a connection ID

which is used to deliverincoming data to correct

MAC user.

Thereis also a one-to-onecorrespondence

between connection ID and service flow.


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The service flow defines the QoS parameters forthe PDU that areexchanged on theconnection.

Service flow providemechanism forQoS

management. They areintegral to thebandwidth allocation

process foreach activeconnection.

Service flow parameters arelatency( max

acceptable delay), jitter(Max acceptable delayvariation) and throughput (Min acceptablebitrate).


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IEEE 802.16.1 Frame Format

Header - protocol control information

Downlink header used by thebase station

Uplink header used by the subscriber to convey

bandwidth management needs to base station

Bandwidth request header used by subscriber to request

additional bandwidth

Payload either higher-level data or a MAC control

message

CRC error-detecting code


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IEEE 802.16.1 Frame Format


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Generic Downlink Header

ARQ : Automatic Repeat Request HCS : Header check Sequence.

EC : Encryption Control HT ; Header Type EKS : Encryption Key Sequence PM : Poll me Bit

FC : Fragmentation control SI : Slip Indicator

FSN : Fragment Sequence Number

EC EKS 4bits Length 11 bits

Connection Identifier16 Bits

HT

=0

AR

Q

FC 2

bits

FSN 4 bits HCS 8 bits


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Generic Uplink Header

ARQ : Automatic Repeat Request HCS : Header check Sequence. EC : Encryption Control HT ; Header Type

EKS : Encryption Key Sequence PM : Poll me Bit



EC EKS 4bits Length 11 bits


HT

=0

AR

Q

FC 2

bits

FSN 4 bits Grant Mangement

HCS 8 bits


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Bandwidth Request Header

ARQ : Automatic Repeat Request HCS : Header check Sequence. EC : Encryption Control HT ; Header Type

EKS : Encryption Key Sequence PM : Poll me Bit



1 0 0 0 0 O 0 0 0 0 0 1 1 1 1


HT

=1

Bandwidth Requested

HCS 8 bits


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MAC Management Messages

IEEE 802.16 defines a numberofcontrol

messages that areused by thebase station

and the subscriberto manage the air

interface and manage theexchange of data

overthe various connections. Messages

areused to exchangeoperating

parameters and status and encryption-related information and forcapacity

management.


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Physical Layer Upstream

Transmission Uses a DAMA-TDMA technique

Error correction uses Reed-Solomon code

Modulation scheme based on QPSK


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Physical Layer Downstream

Transmission Continuous downstream mode For continuous transmission stream (audio, video)

Simple TDM scheme is used for channel access

Duplexing technique is frequency division duplex (FDD) Burst downstream mode

Targets burst transmission stream (IP-based traffic)

DAMA-TDMA scheme is used for channel access

Duplexing techniques are FDD with adaptive modulation,frequency shift division duplexing (FSDD), time divisionduplexing (TDD)


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IEEE 802.16a

operates in the 10-to-66-GHz frequency

band

Requires line-of sight antennas.

Frequency Range: 2 to 11 GHz,

Rangeupto 50 km

Data Rates of over70 Mbps.


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802.16 Standards Development

Use wireless links with microwave or millimeter

wave radios

Use licensed spectrum

Are metropolitan in scale

Provide public network service to fee-paying

customers

Use point-to-multipoint architecture with stationaryrooftop or tower-mounted antennas


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802.16 Standards Development

Provide efficient transport of heterogeneous traffic

supporting quality of service (QoS)

Use wireless links with microwave or millimeter

wave radios

Are capable of broadband transmissions (>2 Mbps)


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Physical and transmission layer functions:

Encoding/decoding of signals

Preamble generation/removal

Bit transmission/reception Medium access control layer functions:

On transmission, assemble data into a frame with addressand error detection fields

On reception, disassemble frame, and perform addressrecognition and error detection

Govern access to the wireless transmission medium


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Convergence layer functions:

Encapsulate PDU framing of upper layers intonative 802.16 MAC/PHY frames

Map upper layers addresses into 802.16 addresses Translate upper layer QoS parameters into native

802.16 MAC format

Adapt time dependencies of upper layer traffic into

equivalent MAC service


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IEEE 802.16.1 Services

Digital audio/video multicast

Digital telephony

ATM Internet protocol

Bridged LAN

Back-haul Frame relay


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IEEE 802.16.3 Services

Voice transport

Data transport

Bridged LAN


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wimax and ieee 802

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