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26 April 2006 1

Broadband Wireless Access:A Brief Introduction to

IEEE 802.16 and WiMAXProf. Dave Michelson

davem@ece.ubc.caUBC Radio Science Lab

26 April 2006 2

Introduction• The IEEE 802.16/WiMAX standard promises to

revolutionize wireless delivery of broadband services:– an alternative to DSL and cable modems– backhaul for access points and base stations – long-range connections for private networks

• With standards, development, and certification well-advanced, the next major challenge is deployment.

• Now is a good time for wireless professionals to become familiar with WiMAX wireless technology

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Introduction - 2

• What is IEEE 802.16/WiMAX?– a wide area alternative to IEEE 802.11/WiFi?– a threat to cellular telephony (voice and data)?– a method for breaking wireline monopolies?– a method for providing backhaul to IEEE

802.11/WiFi access points?– a single standard or a family of standards?– a universal solution for broadband wireless access?

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Introduction - 3

• How is IEEE 802.16/WiMAX different from (or better than) other wide area wireless standards?– use of OFDM with provision for OFDMA and

MIMO?– support for a wide range of channel bandwidths

(and, as a result, performance levels)?– implementation of differentiated QoS?– support for multiple usage models?– use of system profiles to manage design options?

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ObjectiveThis presentation introduces IEEE 802.16/WiMAX by:

1. Briefly reviewing its history2. Summarizing its key features (and the key

players)3. Reviewing alternative use cases and deployment

scenarios4. Suggesting sources of additional information

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1. A Brief History of IEEE 802.16/WiMAX• In the mid-1990’s, various groups began to promote

“last-mile” fixed wireless access solutions.• Multiple goals:

– Provide the capacity and reliability of wirelinebut with the flexibility and ease of deployment of wireless

– Provide a versatile system for corporate or institutional backhaul/distribution networks

– Break the monopolies of incumbent carriers

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A Brief History of IEEE 802.16/WiMAX - 2

Interest soon focused in two approaches.• LMDS (in Canada, LMCS)

– operates in mm-wave spectrum under LoS conditions– uses conventional QAM modulation with ATM-

derived upper layers to provide high speed service• MMDS (and other nearby bands)

– operates near 2 GHz, usually under LoS conditions– may use any of various PHY, MAC, and NET layers

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A Brief History of IEEE 802.16 and WiMAX - 3

• High costs, lack of standards and fear of vendor lock-in drove off potential LMDS customers.

• In 1999, IEEE 802.16 was formed to address these issues by developing open standards for LMDS.

• In 2001, the IEEE 802.16 standard for BWA systems operating in the 10-66 GHz range was released!

• Since then, however, interest has shifted to a new version of the IEEE 802.16 standard for BWA systems operating in the range 2-11 GHz

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A Brief History of IEEE 802.16 and WiMAX - 4

• Early BWA concepts were based on early WLAN technology and had limited capability.

• In the mid-1990’s, AT&T developed a proprietary “last-mile” access solution (Project Angel) that:– operated near 2 GHz under either LoS or NLoS

conditions– used OFDM and other advanced concepts– delivered high capacity, throughput, and QoS.

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A Brief History of IEEE 802.16 and WiMAX - 5

• By the late 1990’s, many other manufacturers began to pursue development of similar products.

• In response, IEEE 802.16 formed a subgroup to extend the LMDS standard to the range 2-11 GHz.

• Our work at AT&T led to the propagation and channel models adopted by IEEE 802.16.

• IEEE 802.16a was published in 2003.• IEEE 802.16a/b/c and various updates were

incorporated into IEEE 802.16-2004.

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A Brief History of IEEE 802.16 and WiMAX - 6

• IEEE 802.16e seeks to provide the additional features required to serve mobility users.

• Use of Scalable OFDMA, MIMO, etc. permits 63 Mbps DL and 28 Mbps UL in a 10 MHz channel.

• Optimized handover ensures latency < 50 ms.• Flexible key management ensures security.• South Korea’s WiBro is based upon IEEE 802.16e.• IEEE 802.16e was ratified in December 2005

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A Brief History of IEEE 802.16 and WiMAX - 7

• IEEE 802.16’s approach is being used by many other groups including IEEE 802.20, 802.22, 3GPP - LT

• For example, IEEE 802.20 (Mobile Broadband Wireless Access) was established on 11 Dec 2002.

• Aim – specify an air interface designed for IP-based services operating in bands below 3.5 GHz with peak data rates of over 1 Mbit/s.

• A draft IEEE 802.20 specification was balloted and approved on 18 Jan 2006.

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A Brief History of IEEE 802.16 and WiMAX - 8

• In 2001, the WiMAX Forum was formed to address issues beyond standards development, e.g.,– marketing and promotion – development of system profiles– development of certification procedures– government lobbying

• In January 2005, the WiMAX Forum selected Cetecom Spain as its official certification laboratory.

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A Brief History of IEEE 802.16 and WiMAX - 9

• Many pre-WiMAX and WiMAX networks have been trialed and deployed in recent months.

• Pre-WiMAX has several meanings:– compliant but not yet certified– compliance is possible after a firmware upgrade– mostly compliant, but not completely

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The WiMAX Value Chain• IEEE 802.16 – Standards Working Group• WiMAX forum – Industry Advocacy Group• Chip Vendors• Equipment Vendors• System Integrators/VARs• Carriers/Service Providers• End Users

• Certification Labs• Consultants• Information Providers

A Brief History of IEEE 802.16 and WiMAX - 10

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2. Key Features of WiMAX• Major goal of IEEE 802.16 (2-11 GHz): provide a

“universal” solution for broadband wireless access– point-to-multipoint, LoS or NLoS– ranges of “several” km; urban, suburban, rural

• Problem: Can one size really fit all? Different applications have different requirements and constraints for spectrum and performance!

• Solution: Allow choice of options within a consistent framework. Offer a limited set of standard profiles.

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Key Features of WiMAX - 2

• Operating Frequency: 2 – 11 GHz*** • Allocations: Licenced and Unlicenced**• Channel Bandwidth: 1.25 – 20 MHz• Modulation: Single carrier*, 256 OFDM, 2048 OFDMA

– BPSK*, QPSK, 16-QAM, 64-QAM, 256-QAM*

• Antenna system support: Diversity, MIMO, SDMA• Duplexing: FDD, H-FDD, TDD**• Data Rates: From T1 (1.5 MB/s) to over 70 Mb/s

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Key Features of WiMAX - 3

• WiMAX supports flexible frequency allocation and use of system profiles

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26 April 2006 19

Key Features of WiMAX - 4

52 carriers,312.5 kHzspacing

200 carriers,90 kHz

spacing

.

.

.200 carriers,

6.7 kHzspacing

802.11a (18 MHz)

4 BPSK Pilots

8 BPSK Pilots

802.16 (20 MHz)

BPSK, QPSK, 16QAM, 64QAM

BPSK, QPSK, 16QAM, 64QAM

.

.

.

:10 MHz7.0 MHz3.5 MHz

:1.5 MHz

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Key Features of WiMAX - 5

• An estimate of the maximum data rate of a WiMAXsystem operating in the 5 GHz band using OFDM

• System parameters– BW = 20 MHz– SCM = 64-QAM (1 symbol = 6 bits)– No. of data subcarriers = 192– Raw data rate = 100 Mb/s– After accounting for coding/MAC/TDD overhead,

the effective data rate is closer to 70 Mb/s

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Key Features of WiMAX - 6

The IEEE 802.16 MAC layer supports• OFDM and OFDMA• ARQ (Automatic Repeat Request)• Dynamic Frequency Selection• Mesh Networking• Advanced Antenna Systems• Differentiated Quality of Service• Enhanced Security

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3. Key Deployment Scenarios• Links from carriers to major customers• Backhaul for access points and cellular base stations• Long-range connections for private networks• Supervisory control and data acquisition• An alternative to DSL and cable modems• An alternative to cellular data services

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4. Our Research Interest in Fixed Wireless• As systems move to higher frequencies, are deployed in

more challenging environments, or become more complex, models must be updated and extended

• Past work has shown that the fixed wireless channel can range be extremely harsh.

Transmitted Signal

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Our Research Interest in Fixed Wireless - 2

• Existing channel models do not completely capture the dynamics of fixed wireless channels

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Our Research Interest in Fixed Wireless - 3

• Fixed wireless channel dynamics is concerned with the measurement and simulation of the time-varying properties of the channel over the long and short-term.

• Issues include:– physical-statistical description of the channel, – effect of alternative antenna configurations, – development of impairment mitigation strategies, – development of more effective radio resource

management schemes.

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Our Research Interest in Fixed Wireless - 3

• Current Sponsors

• Graduate Students:– Joy Zhang, Jin Ng, Howard Huang, Anthony Liou

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5. Probing Further• IEEE 802.16 - www.ieee802.org/16/

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Probing Further - 2

• WiMAX Forum - www.wimaxforum.org

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Probing Further - 3

• WiMAX @ Intel - www.intel.com/go/wimax

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Probing Further - 4

• Other industry portals, e.g.,– www.wimaxpro.com– www.wimax-industry.com– www.wimax.com

• Booksellers, e.g.,– www.chaptersindigo.ca– www.amazon.ca

• WiMAX conferences• Vendors (white papers, etc.)

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26 April 2006 31

Summary• IEEE 802.16/WiMAX broadband wireless access

supports: – channel bandwidths between 1.5 and 20MHz– data rates ranging from 1.5Mbps to over 70Mbps– the available spectrum and channel widths in

different countries or licensed to different providers– advanced quality-of-service features that ensure

high performance for data, voice and video– system profiles that permit a certain degree of

customization within the IEEE 802.16 framework

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Summary - 2

• The IEEE 802.16/WiMAX community has already achieved several significant milestones:– the IEEE 802.16 standard has been released and

refined.– the WiMAX forum is addressing the needs of

industry for promotion, certification, etc.– vendors have developed silicon and equipment.

• As rollout begins, operators will begin addressing issues that arise during deployment and operation.

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Summary - 3

What will it take for WiMAX to be successful?• Equipment must perform as advertised:

– Coverage, reliability, and interoperability– Quality of service, throughput and capacity

• Deployment must be straightforward; design rules should reduce the need for network tuning

• WiMAX must return value (e.g., performance/cost) that is an order of magnitude higher than existing technology can.

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Next….• Andrew Tsui (Bell Canada) will describe one of the

largest pre-WiMAX rollouts to date• Angela Choi (Industry Canada) will summarize

spectrum allocation and regulatory issuesAfter a break…

• Ben Zarlingo (Agilent Technologies) will describe WiMAX test and measurement solutions

• Angela Ikemoto and Michael Fite (Agilent) will demonstrate measurement of actual WiMAX signals