WiMAX Protocol

CSCE 4520/5520 Fall 2006

Shori Fukatsu

2

Contents List WiMAX Protocol

About WiMAXPhysical layerMAC layer

Fixed / Mobile WiMAX WiMAX vs Wi-Fi WiMAX applications Reference Quiz

3

WiMAX

Worldwide Interoperability for Microwave Access

“a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL”

Metropolitan Area Network (MAN) Based on IEEE 802.16

4

Purpose of WiMAX

To provide point-to-multipoint wireless access to Internet and other networks

To provide high data rates over 10-40km

5

6

WiMAX Architecture

MIB – Management Information Base

7

802.16 protocol

8

802.16 protocol stack

802.16 covers data link and physical layer

9

IEEE 802.16 Standards

802.16.1 (10-66 GHz, line-of-sight, up to 134Mbit/s) 802.16.2 (minimizing interference between coexisting

WMANs.) 802.16a (2-11 Ghz, Mesh, non-line-of-sight) 802.16b (5-6 Ghz) 802.16c (detailed system profiles) 802.16e (Mobile Wireless MAN) – called MobileWiMAX

10

11

Physical layer (PHY)

12

PHY cont. QPSK: 2 bits/baud (< 10km) QAM-16: 4 bits/baud (6-10km) QAM-64: 6 bits/baud (>6km)

Example: a 25 MHz bandwidth, QPSK can deliver 50 Mbps, QAM-16 100 Mbps, QAM-64 150 Mbps

Baud (Bd): measure of the symbol rate; the number of distinct symbolic changes (signalling event) made to the transmission medium per second in a digitally modulated signal

25 Bd means that 25 symbols are transmitted per second.

13

PHY cont. TDD (time-division duplex)

- use same bandwidth for uplink and downlink

- controlled by timing

FDD (frequency-division duplex)

- use different frequency for uplink and downlink

OFDM (orthogonal frequency-division multiplexing)- enhancement of frequency division multiplexing (FDM)

- maximize use of bandwidth

14

TDD and FDD

15

OFDM

FDM OFDM

OFDM uses bandwidth which is not available for use in FDM

16

MAC layer

Protocol-Independent core (IP, ATM, etc) Support multiple 802.16 PHYs

17

MAC cont.

Each MAC packet contains three components

1. MAC header; contains frame control information

2. variable length frame body; contains information specific to the frame type

3. frame check sequence (FCS); contains an IEEE 32-bit cyclic redundancy code (CRC).

18

MAC cont.

Generic Uplink/Downlink header

19

Downlink Header

20

Downlink Header

Encryption Control (EC): Indicates whether the payload is encrypted

Encryption Key Sequence (EKS): An index into a vector of encryption key information

Length: Length in bytes of the entire MAC frame Connection Identifier: A unidirectional, MAClayer address that ide

ntifies a connection to equivalent peers Header Type: Indicates whether this is a generic or bandwidth requ

est header ARQ Indicator: Indicates whether the frame belongs to an ARQ en

abled connection Fragment Control: Used in fragmentation and reassembly Fragment Sequence Number: Sequence number of the current fra

gment Header Check Sequence: 8-bit CRC to detect errors in the header

21

Uplink Header

22

Uplink Header Slip indicator: indicate a slip of uplink grants relative to

the uplink queue depth Poll-me: request a poll by the base station Grants per interval: the number of bandwidth grants

required in the next time interval Piggyback request: the number of bytes of uplink

capacity requested

23

Bandwidth request and allocation

SSs may request bandwidth in 3 ways:Use the ”contention request opportunities”

interval upon being polled by the BS (multicast or broadcast poll).

Send a standalone MAC message called ”BW request” in an allready granted slot.

Piggyback a BW request message on a data packet.

24

Bandwidth request and allocation cont. BS grants/allocates bandwidth in one of two

modes: Grant Per Subscriber Station (GPSS) Grant Per Connection (GPC)

Decision based on requested bandwidth and QoS requirements vs available resources.

Grants are realized through the UL-MAP (Uplink message).

25

Bandwidth request and allocation cont.

26

Fixed and Mobile WiMAX

Fixed WiMAX is optimized for home/office networks

Mobile WiMAX is optimized for mobiles

27

Fixed WiMAX

IEEE 802.16d T1/E1 substitute 1BS – thousands of user < 50km coverage < 75Mbps

28

Fixed WiMAX Architecture

29

Mobile WiMAX

IEEE 802.16e 2-3km coverage (optimal) High speed hand over

(< 50ms latencies) Ensures performance at

vehicular speeds greater than 120km/h

< 30Mbps for downlink < 15Mbps for uplink

30

WiMAX vs Wi-Fi

31

WiMAX vs Wi-Fi cont.

WiMAX is designed to cover large area (multiple homes/buildings), while Wi-Fi is to cover small area (a home/building)

32Comparison of WiMAX, WiFi and 3G technology

33

WiMAX vs Wi-Fi cont.

34

WiMAX applications

Broadband Internet Multimedia IP multimedia subsystem (IMS) Cellular Alternative

35

Broadband Internet

• Fixed WiMAX is substitute for T1

• Mobile WiMAX has larger coverage than WiFi

36

Multimedia

Mobile TV IPTV (TV broadcasting via IP network)

37

Traditional networks

Different device, different network

For example: TV is only for

watching TV Phone is only for call

38

IMS network

One network provides multiple things

For example: Watch TV and use

Internet via cell phone

39

WiMAX as cellular alternative

Support IP by default VoIP

40

41

Reference Frank Ohrtman: “Wimax overview”: http://

www.wimax.com/education/wimax/wimax_overview “The 802.16 WirelessMAN™ MAC: It’s Done, but What Is It?” (2001-

11-12) Zheng Yu Huang (2006-10-25):”Considerations for Next Generation

Telecommunications Deployments in China”, Intel Corporation Michael Richardson and Patrick Ryan (2006-3-19): “WiMAX: Opport

unity or Hype?” “Adaptive Modulation” (2004), Intel Corporation Tim Sanders (2005-9-21): ”WiMax/802.16 Revealed”,

http://www.wi-fiplanet.com/tutorials/article.php/3550476 Michael F. Finneran (2004-6-1) “WiMAX versus Wi-Fi”, dBrn Associa

tes, Inc.

42

Israel Koffman and Vincentzio Roman (2002): “Broadband Wireless Access Solutions Based on OFDM Access in IEEE 802.16”, IEEE Communications Magazine April 2002

WiMAX Forum (2006-8): “Mobile WiMAX – Part I: A Technical Overview and Performance Evaluation”

dailywireless.org (2005-7-8): “Mobile WiMAX Chips”, http://www.dailywireless.org/2005/07/08/mobile-wimax-chips/

Carl Eklund, Roger B. Marks, Kenneth L. Stanwood and Stanley Wang (2002-6): “IEEE Standard 802.16: A Technical Overview of the WirelessMAN™ Air Interface for Broadband Wireless Access”, IEEE Communications Magazine June 2002

Robert Healey (2003):“Network Architecture for WiMAX applications”, Juniper Networks, Inc.

Kuo-Hui Li (2006-6-5): “WiMAX Network Architecture”, Intel Mobility Group

“Technology Primer WiMAX”, http://www.tektronix.com/wimax

43

Quiz

1. How much bps can QPSK (2bits/Bd), QAM-16 (4bits/Bd) and QAM-64 (6bits/Bd) can deliver if a bandwidth is 20MHz?

2. What is the difference between OFDM and FDM?

3. What are the differences between WiMAX and Wi-Fi?

44

Answer

1. QPSK - 40Mbps, QAM-16 - 80Mbps, QAM-64 -120Mbps (slide #11)

2. See slide #14

3. The main difference is that WiMAX is focused on MAN, while Wi-Fi is LAN technology. (slide #30-33)