IEEE 802.16 Presented By Saba Arif GCUF

Topics:Introduction Overview of the IEEE 802.16 standard. What is WiMAX WiMAX Services Burst Profile Reference Model MAC PDU format MAC PDU Transmission Fragmentation/Packing Classes of Uplink service Power Management Handoff

Introduction:Wireless Networks are generally less efficient as

compared to wired network.Wireless medium has limited bandwidth Higher packet error rate In response to increase the QOS challenge , the IEEE

802.16 standard known as Worldwide Interoperability for Microwave Access (WiMAX) , has emerged as the strongest competitor for Broadband wireless technology.

Promise to offer guaranteed QOS for wireless users Aimed to provide last-mile wireless broadband

access. Ref:

1009.6091pdf

Overview of the IEEE 802.16 Standard Designed for point-to-point (PTP) and point-to-

multipoint (PTM) topologies but mainly deployed for point to multipoint topologies.

It also support mesh topologies. In PTM a base station (BS) services many subscriber stations (SS) which are mounted outdoors.

IEEE 802.16 has three major versions; 802.16-2001, 802.16-2004 and IEEE 802.16-2005.

ref: http://www.slideshare.net/sajidmarwatt/wimax-ieee-

80216-33468312

What is WiMAX: Today world moves to wireless network.There are two reasons for this: i) People want to have access to the Internet,

home or office (fixed) where the wired access to the Internet is either not available expensive.

ii) They want to access the Internet when they are using their cell phones.

The worldwide interoperability for microwave access(WiMAX) has been designed for these type of applications.

It provide last-mile broadband wireless access. Ref: Data Communication and Networking By Behrouz-

A.Forouzan(p#467)

WiMAX Services:

It’s provide two types of services

i) Fixed WiMAX Optimized for Home/Offices ii) Mobile WiMAX Optimized for Mobiles

Fixed WiMAX

Mobile WiMAX

Burst ProfileThe burst profile is a basic tool in the 802.16

standardMAC Layer. The burst profile allocation, which

changesdynamically and possibly very fast, is aboutphysical transmission.

The burst profiles are used for the link adaptation

procedure.

Reference Model:

Reference Model:

Service Specific Convergence sublayer(CS)

It is used for the transport of all packet based protocols

Such as internet protocol(IP)802.3 Ethernet protocolConnection benefits from a specific Qos.

Reference Model

MAC LayerSub-layer of Data-Link LayerDefine access method and frame formatBandwidth request\AllocationConnection Establishment \ MaintainanceAvoid collisions.

Reference Model:

Security SubLayerProvide authenticationEncryption b/t SS & BS

Reference Model:

Physical Layer An interface between the MAC and the

wireless media where the frames are transmitted and received .

Encoding and Decoding of signals.Convert MAC layer frames into signals

MAC PDU FormatEach MAC PDU consists of three components i) A fixed-length Generic MAC Header ii) A variable length Payload iii) A CRC ( Cyclic Redundancy Check )

6 byte Variable 4 byte

MAC Header Payload Management Message

Types of MAC header

HT EC TYPE BR CID HCS

Header Payload Management Message

HT EC TYPE

RSV CI EKS LEN CID HCS

Bandwidth request MAC header

Generic MAC header

Specification of MAC layerThe first bit in a frame is frame identifier.EC. The encryption control field use one bit

to define weather the frame should be encrypted for security purpose.

Type. Type field use 6 bits to define the type of the frame.

CI. The checksum ID is used 1 bit to define weather the field should be present or not.

Length . Length bit use 11 bits to define the total length of the frame.This field is present in generic frame. Header + Payload + CRC ID (Connection Identifier)

Specification of Mac layerByte needed . use 16 bits to define the

number of bytes needed for allocated slots in physical layer

Connection Identifier . use 16 bits to define connection identifier for the current connection

Header CRC. Both type of frame need to be have 8-bt header CRC field.

Payload . The variable length define the payload

CRC. The last field if present used for error detection over the whole frame

MAC PDU TransmissionThe application first establishes the

connection with the BS as well as the associated service flow (UGS, rtPS, nrtPS or BE).

BS will assign the connection with a unique connection ID (CID).

All packets from the application layer in the SS are classified by the connection classifier based on CID and are forwarded to the appropriate queue. So, the scheduler inside the BS has outdated information about the current state of each uplink connection due to the large Round Trip Delay (RTD) and possible collision occurred in the uplink channel transmission .

MAC PDU Transmission

Multiple MAC PDUs may be concatenated into a single transmission in either the uplink or downlink directions.

Fragmentation is the process in which a MAC SDU isdivided into one or more MAC PDU fragments.

Ref: 1009.6091 pdf

Fragmentation/Packing

It may be interesting to fragment a MAC SDU in many

MAC PDUs or, inversely, to pack more than one MSDU in

Single MAC PDUs.The advantage of fragmentation is to lower

the risk oflosing a whole MSDU to the risk of losing part

of it.

Classes Of Uplink Services:The WiMAX Standard specifies the different

service classes. Classes are Set by Priority wise UGS > rtPS > nrtPS > BE.

UGSUnsolicited Grant Service (UGS): No need to request bandwidth for each

packetThe BS periodically assigns slotsScheduling for DL UGS traffic is not required

Uplink Services

Real-time Polling Service (rtPS): Packets are not fixed in size BS polls the connection of this class

periodically to ask how much bandwidth is needed.The packet with smaller deadline will be

transmitted earlier.

Uplink Classes

Non real-time Polling Service (nrtPS): Used to support traffic with no QoS. May have additional bandwidth allocated throughnon periodic polling.

Best Effort (BE): Used to support traffic with no QoS.There is possibility that BE traffic is starved by thelack of bandwidth.

Model Of Uplink Classes.

Power Management HandoffA telecommunication system (e.g., cable, radio,

satellite), as opposed to sensory aspects of communication(e.g., audio, video).

The standard addresses the support of handovers for both mobile and stationary users.

For mobile users, handovers can occur when wireless link conditions change due to the users’ movement.

For the stationary user, handovers become imminent when the surrounding network environment changes, making one network more attractive than another.

Power Management Handoff

As an example, whenMaking a network transition during a

phone call, the handover procedures should be executed in such a way that any perceptible interruption to the conversation will be minimized.

Thank You