VISHNU VASANT PAVAN

ABHILASH

Contents• Introduction

• What is WiMAX?

• IEEE 802.16 Extensions

• Architecture

• Functionality

• WiMAX Protocol

• Scenario

• Features

• Security Issues

• Benefits

• WiFi vs WiMAX

• WiMAX Applications

• Future of WiMAX

• Conclusion

• References

Introduction

• Broadband accessBroadband access - In your home, you have either a DSL or - In your home, you have either a DSL or cable modem At the office, your company may be using a T1 cable modem At the office, your company may be using a T1 or T3 line.or T3 line.

• WiFi accessWiFi access - In your home, you may have set up a WiFi router that lets you surf the Web while you lounge with your laptop on the road, you can find WiFi hot spots in restaurants, hotels, coffee shops and libraries.

• Dial-up access - If you are still using dial-up, chances are that either broadband access is not available, or you think that broadband access is too expensive

Contd..

• The main problems with broadband access are that it is pretty expensive and it doesn't reach all areas.

• The main problem with WiFi access is that hot spots are very small, so coverage is sparse.

• There is a need for a system which provides high speed of Broadband and is wireless instead of wired.

• WiMAX(Worldwide Interoperability Microwave Access) provides these features .Its also known as IEEE 802.16

What is WiMAX?

• WiMAX (Worldwide Interoperability for microwave access)• A technology based on an evolving standard for point-to-

multi point wireless networking• The commercialization of IEEE 802.16 standard• Solution for Wireless Metropolitan Area Network • BWA (Broadband Wireless Access) Solution• Comply with European BWA standard

• European Telecommunications Standards Institutes's High-performance radio metropolitan area network (HiperMAN)

Wireless MAN (Metropolitan Area Network)

Contd..

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

Operation of WiMAX

• WiMAX consists of two parts

• A WiMAX tower, similar in concept to a cell-phone tower - A single WiMAX tower can provide coverage to a very large area -- as big as 3,000 square miles

• A WiMAX Receiver The receiver and antenna could be a small box or PCMCIA card, or they could be built into a laptop the way WiFi access is today

Service Types

• Non-Line-Of-Sight • A Service where a small antenna on your computer

connects to the tower. In this mode, WiMAX uses a lower frequency range -- 2 GHz to 11 GHz (similar to WiFi)

• Line-Of-Sight• A Service where a fixed dish antenna points straight at the

WiMAX tower from a rooftop or pole. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz

IEEE 802.16

• IEEE 802.16 was completed on Oct, 2004

• Range - 30-mile (50-km) radius from base station

• Speed - 70 megabits per second

• Line-of-sight not needed between user and base station

• Frequency bands - 2 to 11 GHz and 10 to 66 GHz (licensed and unlicensed bands)

• Defines both the MAC and PHY layers and allows multiple PHY-layer specifications

IEEE Extensions

• 802.16a – use the licensed and license-exempt frequencies from 2 to 11Ghz– Support Mesh-Network

• 802.16b– Increase spectrum to 5 and 6GHz– Provide QoS (for real-time voice and video service)

• 802.16c– Represents a 10 to 66GHz system profile

• 802.16d– Improvement and fixes for 802.16a

• 802.16e– Addresses on Mobile– Enable high-speed signal handoffs necessary for communications with

users moving at vehicular speeds

Architecture● P2MP(Point to Multi point)

– Wireless MAN– BS connected to Public Networks– BS serves Subscriber Stations(SS)– Provides SS with first mile access to Public Networks

● Mesh Architecture– Optional architecture for WiMAX

P2MP Architecture

WiMAX Mesh Architecture

WiMAX FUNCTIONALITY

WiMAX Protocol

• Covers MAC layer and PHY layer– PHY layer– Transmission Convergence sublayer– MAC layer

Reference Model

PHY Layer

• In the design of the PHY specification for 10–66 GHz, line-of-sight propagation was deemed a practical necessity.

• Because of the point-to-multipoint architecture, the BS basically transmits a TDM signal, with individual subscriber stations allocated time slots serially.

• The PHY specification defined for 10–66 GHz uses burst single-carrier modulation with adaptive burst profiling in  which transmission parameters, including the modulation and coding schemes, may be adjusted individually to each subscriber station (SS) on a frame-by-frame basis. Both TDD and burst FDD variants are defined.

• Channel bandwidths of 20 or 25 MHz (typical U.S. allocation) or 28 MHz (typical European allocation) are specified, along with Nyquist square-root raised-cosine pulse shaping with a roll off factor of 0.25.

Contd..● Adaptive Burst Profiles

– On DL, multiple SS's can associate the same DL burst– On UL, SS transmits in an given time slot with a

specific burst

● Allows use of directional antennas– Improves range

● Allows use of two different duplexing schemes:– Frequency Division Duplexing (FDD)– Time Division Duplexing (TDD)

● Support for both full and half duplex stations

Adaptive PHY

FDD (Frequency Division Duplexing)

● In case of FDD both uplink and downlink channels are on separate frequencies

● The capability of downlink to be transmitted in bursts

simultaneously supports two different modulation types

– Full Duplex SS's( which can transmit and receive simultaneously)

– Half Duplex SS's( which cannot)

FDD Frame bursting

TDD (Time Division Duplexing)

● In case of TDD both uplink and downlink transmissions share the same frequency but are separated on time

● A TDD frame has a fixed duration and also consists of one uplink and one downlink frame

● TDD framing is Adaptive

Time Division Duplexing

Data Rates

ChannelRate (Mhz)

SymbolRate

(Mbd)

BitRate(Mb/s)

BitRate(Mb/s)

BitRate(Mb/s)

20 16 32 64 96

25 20 40 80 120

28 22.4 44.8 89.6 134.4

● Data rates determined by exact modulation and encoding schemes

● TDD and FDD supported in 802.16 to accommodate burst profiling

● 802.16a adds OFDM and OFDMA to support NLOS multipath propagation

Medium Access Control(MAC)

● WirelessMAN: Point-to-Multipoint and optional mesh topology

● Connection-Oriented – Connection ID(CID),Service Flows(FS)

● MAC layer is further subdivided into three layers – Convergence sub-layer (CS)– Common part sub-layer (CPS)– Privacy sub-layer

MAC Addressing

● SS has 48-bit 802.3 MAC address

● BS has 48-bit base station ID – Not a MAC address

● Connection ID (CID) – 16 bit– Used in MAC PDU – Connection Oriented Service

Frame Structure and PDU

• Each MAC packet consists of the three components, – A MAC header, which contains frame control

information.– A variable length frame body, which contains

information specific to the frame type.– A frame check sequence (FCS), which contains an

IEEE 32-bit cyclic redundancy code (CRC).

MAC PDU

CRC(optional)MAC PDU payload (optional)

Generic MACHeader

(6 bytes)

LENmsb(3)

HT

CID msb (8)LEN lsb (8)

Generic MAC Header Format(Header Type (HT) = 0)

BW Req. Header Format(Header Type (HT) =1)

msb lsb

EC

Type (6 bits)rsv

CI

EKS(2)

rsv

HCS (8)CID lsb (8)

BW Req.msb (8)

HT

CID msb (8)BWS Req. lsb (8)

EC

Type (6 bits)

HCS (8)CID lsb (8)

MAC CS Sub Layer

● Interoperability requires convergence sub-layer to be service specific

● Separate CS layers for ATM & packet protocols

● CS Layer:– Receives data from higher layers– Classifies data as ATM cell or packet– Forwards frames to CPS layer

Contd..● Packet Convergence Sub-Layer

– Initial support for Ethernet, VLAN, IPv4, and IPv6– Payload header suppression – Full QoS support

● 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

MAC CPS Layer

● Performs typical MAC functions such as addressing– Each SS assigned 48-bit MAC address– Connection Identifiers used as primary address after

initialization

● MAC policy determined by direction of transmission – Uplink is DAMA-TDM– Downlink is TDM

● Data encapsulated in a common format facilitating interoperability– Fragment or pack frames as needed– Changes transparent to receiver

MAC PDU Types

● Data MAC PDUs – HT = 0– Payloads are MAC SDUs/segments, i.e., data from

upper layer (CS PDUs)– Transmitted on data connections

● Management MAC PDUs– HT =0– Payloads are MAC management messages or IP packets

encapsulated in MAC CS PDUs– Transmitted on management connections

● BW Req. MAC PDUs– HT =1; and no payload, i.e., just a Header

MAC PDU Transmission● MAC PDU’s are transmitted on PHY bursts

● The PHY burst can contain multiple FEC blocks

● Concatenation– Multiple MAC PDU's can be concatenated into a single

transmission in either uplink or downlink direction

● Fragmentation– Each MAC SDU can be divided into one or more MAC

PDU's

● Packing– Packs multiple MAC SDU's into a single MAC PDU

MAC Privacy Sub Layer

● Provides secure communication– Data encrypted with cipher clock chaining mode of DES

● Prevents theft of service– SSs authenticated by BS using key management protocol

Transmission Convergence Sublayer

• This layer performs the transformation of variable length MAC protocol data units (PDUs) into the fixed length FEC blocks (plus possibly a shortened block at the end) of each burst.

• The TC layer has a PDU sized to fit in the FEC block currently being filled. It starts with a pointer indicating where the next MAC PDU header starts within the FEC block. The TC PDU format allows resynchronization to the next MAC PDU in the event that the previous FEC block had irrecoverable errors.

WiMAX Scenario

•Consider a scenario where a wimax-enabled computer is 10 miles away from the wimax base station.

•A special encryption code is given to computer to gain access to base station.

•The base station would beam data from the Internet required for computer (at speeds potentially higher than today's cable modems)

Contd..

•The user would pay the provider monthly fee for using the service. The cost for this service could be much lower than current high-speed Internet-subscription fees because the provider never had to run cables.

•The WiMAX protocol is designed to accommodate several different methods of data transmission, one of which is Voice Over Internet Protocol (VoIP).

• If WiMAX-compatible computers become very common, the use of VoIP could increase dramatically. Almost anyone with a laptop could make VoIP calls.

WiMAX Features

•Scalability

•Quality of service

•Range

•Coverage

Scalability

•The 802.16 standard supports flexible radio frequency (RF) channel bandwidths.

•The standard supports hundreds or even thousands of users within one RF channel.

•As the number of subscribers grow the spectrum can be reallocated with process of sectoring.

Quality Of Service

•Primary purpose of QoS feature is to define transmission ordering and scheduling on the air interface. •These features often need to work in conjunction with mechanisms beyond the air interface in order to provide end to end QoS or to police the behaviour or SS.

•Standard defines several QoS related concepts. - Service flow Qos scheduling. - Dynamic service Establishment. -Two Phase Activation Model.

Theory Of Operation•All protocol mechanisms support Qos for both uplink and downlink traffic through the SS and BS. •Requirements for QoS : - A configuration and registration function to pre configure SS based QoS service flows and traffic parameters. - A signalling function for dynamically establishing Qos enabled service flows and traffic parameters. - Utilization of MAC scheduling and QoS traffic parameters for uplink service flows. - Utilization of QoS traffic parameters for downlink service flows.

Service flows•A service flow is a MAC transport service that provides unidirectional transport of packets either to uplink packets transmitted by the SS or to downlink packets transmitted by the BS.

•A service flow is characterized by a set of QoS parameters such as latency,jitter and throughput assurances.

•In order to standardize operations between SS and BS these attributes include details of how the SS requests uplink bandwidth allocations and the expected behaviour of the BS uplink scheduler.

Range

•Optimized for up to 50 Km.

•Designed to handle many users spread out over kilometres.

•Designed to tolerate greater multi-path delay spread (signal reflections) up to 10.0μ seconds.

•PHY and MAC designed with multi-mile range in mind.

Coverage •Standard supports mesh network topology.

• Optimized for outdoor NLOS performance.

•Standard supports advanced antenna techniques.

Security Issues

•Security provides subscribers with privacy across the fixes broadband wireless network.

•Security is implemented by encrypting connections between SS and BS.

•Protection against unauthorized access to the data transport services is done by enforcing encryption of the associated service flows across the network.

Security Architecture

•Two component protocols:

- An encapsulation protocol for encrypting packet data across fixed network.

- A key management protocol (PKM) providing the secure distribution of keying data from BS to SS.

Packet Data Encryption

•Encryption services are defined as set of capabilities within the MAC security sub layer.

•MAC Header information specific to encryption is allocated in the generic MAC header format.

•Encryption is always applied to the MACPDU payload, generic MAC is no encrypted.

•All MAC management messages shall be sent in clear to facilitate registration,ranging and normal operation of the MAC.

Key Management Protocol

•An SS uses the PKM protocol to obtain authorization and traffic keying material from the BS.

•PKM protocol is also used for periodic reauthorization and key refresh.

•PKM uses X.509 certificates and the RSA pubic -key encryption algorithm to perform key exchanges between SS and BS.

Contd..

•PKM protocol adheres to a client/server model.

•SS acts like PKM client and requests for keying material and BS acts like PKM server and responds to the requests ensuring that individual SS clients receive only keying material for which they are authorized.

•PKM protocol uses MAC management messaging PKM-RSP messages.

•PKM protocol uses public-key cryptography to establish a shared secret between the SS and the BS.

Security Association•A security Association is the set of security information a BS and one or more of its clients SS s share in order to support secure communication across the IEEE std 802.16 network. •Three types of SA are defined: Primary: SS establishes a primary security association during the SS initialization process. Static: Static SA are provisioned within the BS. Dynamic: Dynamic SA are established and eliminated on fly in response to the initiation and termination of specific service flows.

•Static and Dynamic SA can be shared by multiple SS.

a

Contd..

• Figure conceptually depicts end-to-end Authentication, Authorization, and Accounting (AAA) on 802.16 networks supporting portability and fully mobile operations.

• Encryption (security association) is established using the PKM-EAP protocol.

•Extensible Authentication Protocol (EAP) is carried over RADIUS or DIAMETER to the AAA back end.

• Intel recommends using an end-to-end tunnelling protocol such as Protected EAP (PEAP) or Tunnelled TLS (TTLS) to afford mutual authentication.

• It also recommends 128-bit or better Transport Layer Security (TLS) encryption to further enhance end-to-end security (especially in situations where cryptographically weaker EAP methods may be deployed).

Contd..

Benefits of WiMAX

● Speed– Faster than broadband service

● Wireless– Not having to lay cables reduces cost– Easier to extend to suburban and rural areas

● Broad coverage– Much wider coverage than WiFi hotspots

Benefits for Network Service Providers

•Allow service providers to deliver high throughput broadband based services like VoIP, high-speed Internet and Video

•Facilitate equipment compatibility

•Reduce the capital expenditures required for network expansion

•Provide improved performance and extended range

•Allow service providers to achieve rapid ROI and maximize revenues

Benefits for consumers

● Range of technology and service level choices from both fixed and wireless broadband operators

● DSL-like services at DSL prices but with portability

● Rapidly declining fixed broadband prices

● No more DSL “installation” fees from incumbent

WiFi Vs WiMAX

• Scalability• Relative Performance• Quality of Service• Range• Coverage• Security

Scalability

• Channel bandwidths can be chosen by operator (e.g. for sectorization)

• 1.5 MHz to 20 MHz width channels. MAC designed for scalability. independent of channel bandwidth

• MAC designed to support thousands of users.

• Wide (20MHz) frequency channels

• MAC designed to support 10’s of users

802.16a802.11

Relative Performance

5.0 bps/Hz100 Mbps1.5 – 20 MHz802.16a

2.7 bps/Hz54 Mbps20 MHz802.11

Maximum bps/Hz

Maximum Data Rate

Channel Bandwidth

Quality Of Service (QoS)

• Grant-request MAC

• Designed to support Voice and Video from ground up

• Supports differentiated service levels: e.g. T1 for business customers; best effort for residential.

• Centrally-enforced QoS

• Contention-based MAC (CSMA/CA) => no guaranteed QoS

• Standard cannot currently guarantee latency for Voice, Video

• Standard does not allow for differentiated levels of service on a per-user basis

• 802.11e (proposed) QoS is prioritization only

802.16a802.11

Range

• Optimized for up to 50 Km

• Designed to handle many users spread out over kilometers

• Designed to tolerate greater multi-path delay spread (signal reflections) up to 10.0μ seconds

• PHY and MAC designed with multi-mile range in mind

• Optimized for ~100 meters

• No “near-far” compensation

• Designed to handle indoor multi-path delay spread of 0.8μ seconds

• Optimization centers around PHY and MAC layer for 100m range

802.16a802.11

Coverage

• Optimized for outdoor NLOS performance

• Standard supports mesh network topology

• Standard supports advanced antenna techniques

• Optimized for indoor performance

• No mesh topology support within ratified standards

802.16a802.11

Security

• Existing standard is PKM - EAP• Existing standard is WPA + WEP

• 802.11i in process of addressing security

802.16a802.11

Applications

● Fixed last-mile broadband access as a replacement or substitute for wired DSL, cable, or T1 connections

● Inexpensive backhaul for cell sites and WiFi hotspots

● High speed enterprise connectivity for businesses

● Voice Over Internet Protocol (VOIP)

Future of WiMAX

• WiMAX will be deployed in three phases

• In the first phase WiMAX technology (based on IEEE 802.16-2004) provides fixed wireless connections

• In the second phase WiMAX will be available as a cheap

and self-installing Subscriber Terminal (ST), linked to PC and to antenna

• The third phase enables portability, thus WiMAX (based on IEEE 802.16e) will be integrated into commercial laptops.

WiMAX Technology

WiMAX Forum

● Worldwide Interoperability for Microwave Access

● WiMAX was Founded in April 01’

● No Profit organization comprised of wireless access system manufacturers, component suppliers, software developers and carriers

● A wireless industry consortium that supports and promotes WiMAX’s commercial usage

● Members include Intel, AT&T, Siemens Mobile, British Telecommunications, etc..

● Comply with the WiMAX standard and focus on the interoperability

Conclusion

● WiMAX is poised to be the next Big Thing

● WiMAX will connect you to the internet at faster speeds and from much longer ranges

● WiMAX can handle last-mile access in remote areas

● Mobility can be achieved with design into computer chips

References

● http://www.ceenet.org/workshops/lectures2004/Richard_Perlman/additional_materials_(wimax)/

● www.ewh.ieee.org/r4/chicago/Yu-WiMAX.pdf

● www.WIMAXFORUM.org

● http://computer.howstuffworks.com/wimax.htm

● http://standards.ieee.org/catalog/olis/lanman.html

● http://netgroup.polito.it/Corsi/ISRG/Lucidi/Nicoletti_WiMAX.pdf

● http://www.gartner.com/teleconferences/attributes/attr_133634_115.pdf

Questions

● What are different kinds of service WIMAX offers and what is difference between them?

● How is interoperability achieved in WIMAX?

● How is QOS implemented in WIMAX?

● What is difference between P2MP and Mesh architectures?

● List out three differences between WIMAX and WIFI?

QUESTIONS ?

THANK YOU!