28-05-2013, 03:30 PM
BroadbandWireless Access
Broadband wireless access provides high-rate wireless communications between a fixed access point and multiple terminals. These systems were initially proposed to support interactive video service to the home, but the application
emphasis then shifted to providing high speed data access (tens of Mbps) to the Internet, the WWW, and to high speed data networks for both homes and businesses. In the U.S. two frequency bands were set aside for these systems: part of the 28 GHz spectrum for local distribution systems (local multipoint distribution systems or LMDS) and a band in the 2 GHz spectrum for metropolitan distribution systems (multichannel multipoint distribution
services or MMDS). LMDS represents a quick means for new service providers to enter the already stiff competition among wireless and wireline broadband service providers [1, Chapter 2.3]. MMDS is a television and telecommunication delivery system with transmission ranges of 30-50 Km [1, Chapter 11.11]. MMDS has the capability to deliver over one hundred digital video TV channels along with telephony and access to emerging
interactive services such as the Internet. MMDS will mainly compete with existing cable and satellite systems. Europe is developing a standard similar to MMDS called Hiperaccess.
WiMAX is an emerging broadband wireless technology based on the IEEE 802.16 standard [20, 21]. The core 802.16 specification is a standard for broadband wireless access systems operating at radio frequencies between 10 GHz and 66 GHz. Data rates of around 40 Mbps will be available for fixed users and 15 Mbps for mobile users, with a range of several kilometers. Many laptop and PDA manufacturers are planning to incorporateWiMAX once
it becomes available to satisfy demand for constant Internet access and email exchange from any location. WiMax will compete with wireless LANs, 3G cellular services, and possibly wireline services like cable and DSL. The ability of WiMax to challenge or supplant these systems will depend on its relative performance and cost, which
remain to be seen.