WiMAX

Haiqing Li

Content List

• What is WiMAX?• IEEE 802.16• Design Architecture and Key technologies• Recent Researches• WiMAX vs. 3G• OPNET for WiMax Study• Industry Trends• Reference

What is WiMax

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

to-multipoint 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 Institute's High-performance radio metropolitan area network (HiperMAN) standard

IEEE 802.16

• IEEE 802.16 was completed on Oct, 2004

• Point-to-Multipoint (PMP) broadband wireless access standard for systems in the frequency ranges 10 – 66 GHz and sub 11 GHz.

IEEE 802.16 Extension• 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

The family of 802.16 standard

The family of 802.16 standard

IEEE 802.16

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

Architecture

Physical 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.

Medium Access Control

• The 802.16 medium access control (MAC) layer supports many different physical layer specifications, both licensed and unlicensed.

Frame Structure and PDU

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

control information.– b) A variable length frame body, which

contains information specific to the frame type.

– c) A frame check sequence (FCS), which contains an IEEE 32-bit cyclic redundancy code (CRC).

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 Certification

Security

• Authentication and registration are part of the 802.16 MAC common part sub-layer. Authentication is based on the use of PKI technology-based X.509 digital certificates.

• Each Subscriber Station contains both a manufacturer-issued factory-installed X.509 digital certificate and the certificate of the manufacuturer.

• Privacy Sublayer uses privacy protocol that is based on the privacy key exchange management protocol of the DOCSIS BPI+ specification.

• PKM protocol uses X.509 digital certificates with RSA public key encryption for SS authentication and authorization key exchange.

• Traffic encryption uses DEC.

Mobile

• 802.16e

WiMax Forum

• 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, France Telecom, Qwest, ……

• Comply with the WiMax standard and focus on the interoperability

• WiMax Forum certified product

WiMax Forum Organization and Key Persons

• President and Chairman– Ron Resnick (Intel Corp.)

• Technical Working Group– Gordon Antonello (OFDM Forum)

• Marketing Working Group– Dr. Mo Shakouri (Alvarion)

• Service Provider Working Group– Dean Chang (Aperto Networks)

Recent Researches

• Scalability of Fixed Broadband Wireless Access (BWD) Network

• Bernard Fong, et al. (IEEE Radio Communication, September 2004)

• “Overview of various features of BWA system toward realizing a high level of scalability to support a potentially fast expending network”

• Analysis of provisioning a scalable fixed BWA network by local multipoint distribution service (LMDS) based on various implementation scenarios– Cell Planning– Modulation scheme– Multiple Access– Frequency Reuse

Recent Researches

• QoS– “IEEE 802.16 Based Last Mile Broadband

wireless military networks with Quality of Service support” by Wongthavarawat and Ganz, IEEE 2003

WiMAX vs. 3G

• Comparison of OFDMA and CDMA based technologies

• WiMax systems for portable/nomadic use will have better performance– Interference rejection– Spectral efficiency– Multipath tolerance

• High Data QoS support• Lower future equipment cost• WCDMA has advantage for voice

communication

OPNET Simulation Study for WiMax

• PHY Layer – Virginia Tech, CWT (Center for Wireless Telecommunication)– This research focuses on evaluating the performance of IEEE

802.16’s adaptive PHY capabilities. – A model for IEEE 802.16 using OPNET Modeler and OPNET's

DOCSIS models was developed.– “We wish to study the performance of the various PHY options

provided by IEEE 802.16 under various channel conditions. We intend to propose an algorithm to implement adaptive modulation and coding in such systems.”

–   S. Ramachandran, C. W. Bostian and S. F. Midkiff, “Performance Evaluation of IEEE 802.16 for Broadband Wireless Access,” proc. of OPNETWORK 2002, Aug 2002

– http://www.ee.vt.edu/~shyamal/opnet.htm

• MAC Layer– Norfolk State University– Multimedia performance of IEEE 802.16 MAC– Analyze IEEE 802.16 medium access control (MAC)

sublayer for multimedia– “We will consider two kinds of traffic type to simulate

how to allocate bandwidth efficiently with various traffic combinations to maximize the link utilization.”

– http://www.cs.nsu.edu/research/OPNET/IEEE_802.16.html

OPNET Simulation Study for WiMax

• Resource Allocation in Fixed Broadband Wireless Access (FBWA) Networks – Carleton University – OPNET Modeler and Wireless Module– Incorporating IEEE 802.16a large-scale path-loss model in

OPNET– Simulation of Flat Raleigh Fading in OPNET– Simulating wrap-around interference model in OPNET

• Qos management for two coexisting systems– University of Canterbury– IEEE802.16/3G and IEEE802.16/IEEE802.11e– explore the role of all of these techniques on QoS solutions

taking both implementations and performance into consideration– http://

www.elec.canterbury.ac.nz/research/Networking/opnet.shtml

OPNET Simulation Study for WiMax

Industry News & Trends• THE Wimax Anticlimax -- The first WiMAX products and services will be

available in early 2005. Are they the seeds of 4G mobile networks, or just a cynical attempt to ride the Wi-Fi wave? Andy Dornan, Network Magazine Dec 1, 2004 p38

• Cingular Tips Hand On Wireless Broadband, 3G Plans; Wireless operator indicates it intends to both roll out UMTS 3G service and faster service that will compete with wireless broadband technologies like WiMAX. (Universal Mobile Telecommunications System) InternetWeek Dec 1, 2004

• New Mexico City Launches Largest Municipal Wi-Fi Network; A 103 square mile area is now covered with Wi-Fi and pre-WiMAX access with voice-over-WLAN coming soon. InternetWeek Jan 20, 2005

• Airspan Buys VoIP Equipment Developer; Broadband wireless equipment developer Airspan Networks has purchased Israel-based ArelNet for $8.7 million, a move that will allow the WiMAX equipment developer to increase its support for voice-over-IP (VoIP) services. (Airspan Networks)InformationWeek Dec 29, 2004