WiMAX+Evolution


 * 3.0 EVOLUTION OF WIRELESS BROADBAND**

The history of broadband wireless as it relates to WiMAX can be traced back to the desire to find a competitive alternative to traditional wireline-access technologies. Spurred by the deregulation of the telecom industry and the rapid growth of the Internet, several competitive carriers were motivated to find a wireless solution to bypass incumbent service providers. During the past decade or so, a number of wireless access systems have been developed, mostly by start-up companies motivated by the disruptive potential of wireless. These systems varied widely in their performance capabilities, protocols, frequency spectrum used, applications supported and a host of other parameters. Some systems were commercially deployed only to be decommissioned later. Successful deployments have so far been limited to a few niche applications and markets. Clearly, broadband wireless has until now had a checkered record, in part because of the fragmentation of the industry due to the lack of a common standard. The emergence of WiMAX as an industry standard is expected to change this situation. Given the wide variety of solutions developed and deployed for broadband wireless in the past, a full historical survey of these is beyond the scope of this section. Instead, we provide a brief review of some of the broader patterns in this development.

WiMAX technology has evolved through four stages, albeit not fully distinct or clearly sequential:

i. Narrowband wireless local-loop systems - develop and deployed as a voice telephony called wireless local-loop (WLL). - use digital-enhanced cordless telephony (DECT) and code division multiple access (CDMA) standards.

ii. First-generation line-of-sight (LOS) broadband systems (1G) - use as DSL and cable modem with 2.5GHz – 3.5GHz frequencies are called multichannel multipoint distribution services (MMDS). - use same tower with wireless cable subscriber up to 35 miles. - use outsider antenna for a clear LOS transmission path.

iii. Second-generation non-line-of-sight (NLOS) broadband systems (2G) - use newer technology which are orthogonal frequency division multiplexing (OFDM), code division multiple access (CDMA) and multiantenna processing to overcome the LOS issues.

iv. Standards-based broadband wireless systems. - IEEE develop a standard for what was called a wireless metropolitan area network, or wireless MAN.

- work on extending and modifying it to work in both licensed and license-exempt frequencies in the 2GHz to 11GHz range, which would enable NLOS deployments.

- This revised standard, IEEE 802.16-2004, replaces 802.16, 802.16a, and 802.16c with a single standard, which has also been adopted as the basis for HIPERMAN (high-performance metropolitan area network) by ETSI (European Telecommunications Standards Institute).  __**WiMAX Technology** __ **WiMAX** 