IEEE Communications Magazine • October 2008 41 0163-6804/08/$25.00 © 2008 IEEE MOBILE WIMAX AND IEEE 802.16 STANDARDS The WiMAX Forum is an industry consortium promoting the IEEE 802.16 family of standards for broadband wireless access systems. Historical- ly, the first IEEE 802.16 standard (and associated 802.16c profile definitions) addressed primarily line-of-sight (LOS) environments at high fre- quency bands (10–66 GHz) via conventional quadrature amplitude modulation (QAM) single- carrier techniques. The limited market potential for millimeter-wave LOS systems resulted in the development of the IEEE 802.16a amendment to support non-LOS (NLOS) modes in radio bands between 2–11 GHz. The 802.16-2004 standard [1] (also known as 802.16d) made further, more rad- ical changes to 802.16 physical (PHY) layer oper- ation for low frequency (2–11 GHz) bands by adding two additional PHY modes: • A 256-point fast Fourier transform (FFT) orthogonal frequency-division multiplexing (OFDM) PHY mode • A 2048-point FFT orthogonal frequency- division multiple access (OFDMA) PHY mode The well understood goal of these develop- ments was to use OFDM for both downlink (DL) and uplink (UL) to enable relatively sim- ple high-performance receiver structures in the presence of frequency-selective fading channels. This new PHY capability was augmented by addition of several features: • Frequency-diverse and frequency-specific subchannelization schemes where respec- tive groups of physically distributed and physically adjacent subcarriers are used to construct subchannels. These schemes enable both frequency-diverse and frequen- cy-selective scheduling and resource alloca- tion methods. • Adaptive modulation and coding based on hybrid automatic repeat request (HARQ) techniques (previously used in Third Gen- eration Partnership Project [3GPP]/3GPP2 systems such as Enhanced Data Rates for GSM Evolution [EDGE], High-Speed Downlink/Uplink Packet Access [HSDPA/ HSUPA], Evolution Data Optimized [EVDO], etc.) along with support for chase combining (CC) and incremental redundan- cy (IR). • Fast scheduling based on flexible channel quality indication (CQI) • New forward error correction schemes including convolution turbo code (CTC) and low density parity check (LDPC) codes • Support for multi-antenna operation including optional advanced antenna subsystem (AAS) modes, open-loop space time coding (STC) modes (supporting two–four transmit anten- nas), closed-loop multiple-input multiple out- put (MIMO) modes, and uplink coordinated space-division multiple access (SDMA). • Efficient multicast-broadcast transmission schemes using single frequency network (SFN) concepts • Variable frame sizes (e.g., 2 ms, 2.5 ms, 5 ms) The mobility enhancements provided by the later 802.16e amendment [2] further enhanced operation of nomadic, portable, and mobile wireless access, and was published by IEEE at the beginning of 2006. The 802.16e specification (aka 802.16-2005) provides improved support for intercell handoff, directed adjacent-cell measure- ment, and sleep modes to support low-power ABSTRACT Mobile WiMAX was successfully adopted by ITU as one of the IMT-2000 technologies in November 2007. Since then mobile WiMAX (a.k.a. IP-OFDMA) has officially become a major global cellular wireless standard along with 3GPP UMTS/HSPA and 3GPP2 CDMA/ EVDO. Mobile WiMAX is an OFDM-based technology available for deployment today, and new WIMAX devices come to market at much reduced cost than that of current 3G solutions. Currently over 260 service providers are deploy- ing fixed, portable and mobile WiMAX networks in 110 countries. This article provides an overview of the mobile WiMAX system and its performance under various configurations, chan- nel conditions, and types of data traffic. Further- more, the article provides an overview of mobile WiMAX evolution. WIMAX: A TECHNOLOGY UPDATE Fan Wang, Amitava Ghosh, Chandy Sankaran, Philip J. Fleming, Frank Hsieh, and Stanley J. Benes, Networks Advanced Technologies, Motorola Inc. Mobile WiMAX Systems: Performance and Evolution Authorized licensed use limited to: University of Patras. Downloaded on January 20, 2009 at 07:29 from IEEE Xplore. Restrictions apply.