Analogy ofmisi5relesses on Different FreGHz licensed and 5.8GHz unlicensed bands, Radio interface: OFDM, using256 tones, Access Protocols: Downstream - TDMSpectrally agile systems may be required asnew spectrum becomes available in regionsaround the world (e.g. 700 MHz, 1700 MHz).The 2nd International Conference on WirelessBroadband and Ultra Wideband Communications (AusWireless 2007)0-7695-2842-2/07 $25.00 c 2007(Broadcast), Upstream TDMA with access contention,Security via station authentication and encryption, Datarates variable with channel bandwidth 3.5 MHz in 3.5GHz band, 20 MHz in 5.8 GHz band, Actual realizabledata rates are ~ 2b/Hz, and Maximum range ~ 2Km forindoor Non-LOS cellular service at 3.5 GHz. The802.16-2005 standard will introduce the OFDMA(Orthogonal Frequency Division Multiplex Access)method and MIMO (Multiple Input Multiple Output)antenna technology [4] [5]. One of the majoradvantages of OFDM is its extreme robustness inmulti-path environments. The basic operating principlefor OFDM is as follows: (a) A transmit channel isdivided into a large number of parallel sub-channels(N>>1), (b) The data stream from the source is splitinto each sub-channel, (c) Consequently, the data rateof each sub-channel becomes 1/N of the main stringand the symbol duration becomes N times longer, and(d) Each sub-channel is transmitted via a very narrowbandwidth so the signal fading is basically flat withinthe sub-channel. As a result, the longer symbol durationand flat fading make OFDM robust under multi-pathfading with no inter-symbol interference. Combiningadvanced MIMO antenna technology for datatransmission with OFDM enables a number of keyoperational benefits that can translate into significantcost savings and advantages, namely: powerful spectralefficiency and throughput, gains, More efficientutilization of power- for the same power output persector, MIMO provides greater capacity with the samecoverage as single output systems, higher reliabilityand throughput. The system supports adaptivemodulation in the downlink and uplink. Modulationsranging from BPSK 1/2 to 64QAM 3/4 may beemployed. Adaptive modulation techniques, such asmonitoring link quality between the transmitter andreceiver and selecting the highest usable data rate, areused throughout the product range [9] [10] [11].Path loss, dBFig. 4 Cell radius vs. path loss. -- http://www.wretch.cc/blog/chenkobe --

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