What is WiMAX 802.16 Introduction 802.16 MAC Highlights MAC Convergence Sub-Layer (CS) MAC Common Part Sub-Layer (CPS) Advantages/disadvantages Future of WiMAX Questions

Worldwide Interoperability for Microwave Access (WiMAX) is the common name associated to the IEEE 802.16a/REVd/e standards.

These standards are issued by the IEEE 802.16 subgroup that originally covered the Wireless Local Loop technologies with radio spectrum from 10 to 66 GHz.

Coverage range up to 50km and speeds up to 70Mbps(shared among users).

Sridhar IyerIIT Bombay 5

Goal: Provide high-speed Internet access to home and business subscribers, without wires.

Base stations (BS) and subscriber stations (SS)

Centralized access control to prevents collisions

Supports applications with different QoS requirements

WiMAX is a subset of IEEE 802.16 standard

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Provide efficient transport of heterogeneous traffic supporting QoS

Capable of broadband transmissions (2-75 Mbps)◦ Accommodate both continuous and bursty

traffic

Mobile extensions: 802.16e

Wireless Networks Spring 2007

SS has 48-bit IEEE MAC address BS has 48-bit base station ID

◦ Not a MAC address◦ 24-bit operator indicator

16-bit connection ID (CID) 32-bit service flow ID (SFID) 16-bit security association ID (SAID)

ATM Convergence Sub-Layer:

◦ Support for VP/VC switched connections◦ Support for end-to-end signaling of dynamically

created connections ◦ ATM header suppression◦ Full QoS support

Packet Convergence Sub-Layer:

◦ Initial support for Ethernet, VLAN, IPv4, and IPv6◦ Full QoS support

Functions:

◦ Classification: mapping the higher layer PDUs (Protocol Data Units) into appropriate MAC connections.

◦ Payload header suppression (optional)◦ MAC SDU (Service Data Unit), i.e, CS PDU,

formattingPacket PDU

(e.g., IP packet, Ethernet Packet)PHSI

MAC SDU = CS PDU

Payload Header Suppression IndexOptional, Depending on upper layerprotocol

Each SS has 3 management connections in each direction:

◦ Basic Connection:

short and time-urgent MAC management messages MAC mgmt messages as MAC PDU payloads

◦ Primary Management connection:

longer and more delay tolerant MAC mgmt messages MAC mgmt messages as MAC PDU payloads

◦ Secondary Management Connection:

Standard based mgmt messages, e.g., DHCP, SNMP, …etc IP packets based CS PDU as MAC PDU payload

Three components of 802.16 QoS

◦ Service flow QoS scheduling◦ Dynamic service establishment◦ Two-phase activation model (admit first, then activate)

Service Flow

◦ A unidirectional MAC-layer transport service characterized by a set of QoS parameters, e.g., latency, jitter, and throughput assurances

◦ Identified by a 32-bit SFID (Service Flow ID)

Three types of service flows

◦ Provisioned: controlled by network management system ◦ Admitted: the required resources reserved by BS, but not active◦ Active: the required resources committed by the BS

UGS: Unsolicited Grant Services rtPS: Real-time Polling Services nrtPS: Non-real-time Polling Services

BE: Best Effort

UGS: Unsolicited Grant Services◦For CBR or CBR-like services, e.g., T1/E1.◦The BS scheduler offers fixed size UL BW grants on a real-time periodic basis.

◦The SS does not need to send any explicit UL BW req.

rtPS: Real-time Polling Services◦ For rt-VBR-like services, e.g., MPEG video.◦ The BS scheduler offers real-time, periodic, UL BW

request opportunities.◦ The SS uses the offered UL BW req. opportunity to

specify the desired UL BW grant.◦ The SS cannot use contention-based BW req.

nrtPS: non-real-time polling services◦ For nrt-VBR-like services, such as, bandwidth-

intensive file transfer.◦ The BS scheduler shall provide timely (on a order

of a second or less) UL BW request opportunities.◦ The SS can use contention-based BW req.

opportunities to send BW req.

BE: Best Effort◦For best-effort traffic, e.g., HTTP, SMTP.◦The SS uses the contention-based BW request opportunities.

Two types of Contention based UL slots Initial Ranging

Used for new SS to join the system Requires a long preamble

BW Request Used for sending BW req Short preamble

Collision Detection and Resolution Detection: SS does not get the expected response in

a given time Resolution: a truncated binary exponential backoff

window

A Layer-2 sliding-window based flow control mechanism.

Per connection basis. Only effective to non-real-time applications. Uses a 11-bit sequence number field. Uses CRC-32 checksum of MAC PDU to check data

errors. Maintain the same fragmentation structure for

Retransmission. Optional.

Two Major Functions:◦ Secures over-the-air transmissions◦ Protects from theft of service

Two component protocols:◦ Data encryption protocol ◦ A client/server model based Key management

protocol (Privacy Key Management, or PKM)

Wimax Coverage Wimax High Speed Multi-functionality within Wimax Technology Wimax, cheap network  Wimax Rich Features Smart antenna and Mesh Topology Ultra wide Band 

Lack of Quality Wimax range Wimax Bandwidth Expensive network  Bad Weather Power consuming Data Rate

Connectivity for SMBs Wimax Backhaul Nomadic Broadband Broadband for Developing Countries Private Networks

Future of WiMAX !!

Questions ??

IEEE802.16-2004 Alcatel White Paper: WiMAX, making ubiquitous

high-speed data services a reality Intel White Paper: Understanding WiMAX and

3G for Portable/Mobile Broadband Wireless WiMAX Forum: www.wimaxforum.com http://en.wikipedia.org/wiki/WiMax

BS – Base Station SS – Subscriber Station, (i.e., CPE) DL – Downlink, i.e. from BS to SS UL – Uplink, i.e. from SS to BS FDD – Frequency Division Duplex TDD – Time Division Duplex TDMA – Time Division Multiple Access TDM – Time Division Multiplexing OFDM – Orthogonal Frequency Division Multiplexing OFDMA - Orthogonal Frequency Division Multiple Access QoS – Quality of Service

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