is subject to the Terms of Use as given at the website. Access Technologies Chapter 6 including 10.5 GHz, 25 GHz, 26 GHz, 31 GHz, 38 GHz, and 39 GHz. It also supports device interoperability so that carriers can use multiple vendors' products. Furthermore, the standard for the 2 GHz to 11 GHz spectrum supports both unlicensed and licensed bands, a real boon for the entrepreneurial set that does SO much to push the limits of any new innovation. Over the last few years 802.16 has undergone a series of modifica- tions, resulting in the existence of various flavors of the original stan- dard including 802.16a and 802.16e. They are discussed in the sections that follow and shown in Table 6-2. 802.16a IEEE 802.16a was ratified as an extension to the original 802.16 stan- dard in January 2003. It enhances 802.16 and addresses radio systems that operate in the 2 GHz to 11 GHz frequency ranges. It addresses the requirements of both licensed and unlicensed implementations, and sup- Table 6-2 WiMAX Evolution Characteristic 802.16 802.16a 802.16e Standard Date December 2001 January 2003 EOY 2004 Frequency Range 10-66 GHz Less than 11 GHz Less than 6 GHz Transmission Limits Line of Sight Non-Line of Sight Non-Line of Sight Bandwidth 32 to 134 Mbps in Up to 75 Mbps in Up to 15 Mbps in 28 MHz channels 20 MHz channels 5 MHz channels Modulation Scheme QPSK, 16 QAM, OFDM (256 OFDM (256 64QAM subcarriers), subcarriers), QPSK, 16 QAM, QPSK, 16 QAM, 64QAM 64QAM Mobility Options Fixed Fixed and "Portable" Fixed and Mobile Channel Bandwidth 20, 25, 28 MHz Scalable from 1.5 Scalable from 1.5 to 20 MHz to 20 MHz Operating Radius 2-5 Km 7-10 Km 2-5 Km Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Access Technologies Access Technologies ports point-to-multipoint networks as well as mesh topologies within the unlicensed region. IEEE 802.16e 802.16e is an extension of