General features of IEEE 802.16a , b , d , e
General features of IEEE 802.16a
It was approved in January 2003.
n It covers frequency band between 2GHz and11GHz (licensed and unlicensed).
n Its lower frequencies make non-line of sight a possibility; hence, it makes the IEEE 802.16a standard the appropriate technology for last-mile application where obstacles like trees and buildings are often present and where base stations may need to be roofs of homes or buildings rather than towers on mountains.
- Total data rate can be up to 75 Mb/s in each 20MHz channel.
- It has up to 30 miles of range with a typical cell radius of 4-6 miles.
- It provides an ideal wireless backhaul technology to connect 802.11 wireless LANs and commercial hotspots with the Internet.
n It enables business to flexibly deploy new 802.11 hotspots in locations where traditional wired connection may be unavailable or time consuming to provide and offers service providers around the globe with a flexible new way to stimulate growth of the residential broadband access market segment.
n It will be mostly used for small businesses, residential users and for backhaul or hotspot.
n The most common 802.16 configurations consist of base station mounted on building or tower that communicates on a point to multi-point basis with subscriber station located in businesses and homes.
General features of IEEE 802.16b
IEEE 802.16b aims at the needs of license-exempt (unlicensed) applications around 5-6 GHz.
General features of IEEE 802.16c
The IEEE Standards Board approved IEEE 802.16c in December 2002. The aim was to develop 10- 66 GHz system profiles to aid interoperability specifications for Line-of-Sight broadband wireless access. Its peak (shared) data rate 70Mbits/s, with range up to 50km.
General features of IEEE 802.16d-2004 Fixed WiMAX
IEEE 802.16a has all but been forgotten as the focus recently has been on IEEE 802.16- 2004, which is also known as 802.16REVd .802.16-2004 is an improvement to the 802.16a Standard separately, 802.16-2004, was ratified in July 2004. 802.16-2004 is a wide-ranging standard that includes previous versions and covers both LOS and NLOS applications in the 2-66 GHz frequencies. The changes introduced in 802.16-2004 were focused on fixed and nomadic applications in the 2-11 GHz frequencies. Two multi-carrier modulation techniques are supported in 802.16-2004: OFDM with 256 carriers and OFDMA with 2048 carriers. IEEE 802.16-2004 is a fixed wireless access technology, meaning that it is designed to serve as a wireless DSL replacement technology, to compete with the incumbent DSL or broadband cable providers or to provide basic voice and broadband access in underserved areas where no other access technology exists; examples include developing countries and rural areas in developed countries where running copper wire or cable does not make economic sense.
802.16-2004 is also a viable solution for wireless backhaul for Wi-Fi access points or potentially for cellular networks, in particular if licensed spectrum is used. Finally, in certain configurations, WiMAX Fixed can be used to provide much higher data rates and therefore be used as a T1 replacement option for high-value corporate subscribers. 802.16-2004 can also support VoIP (Voice over Internet Protocol), and assuming that the G.729 (8kbps) codec is used, it reportedly supports up to 96 simultaneous voice calls in a 3.5MHz radio channel. The trade-off is increased path losses at frequencies such as 5.8GHz. It is unlikely that an operator would use 2.4GHz to offer voice services due to the higher probability that interference could develop (simple microwave ovens radiate RF in the 2.4GHz band).
General features of IEEE 802.16e Mobile WiMAX
IEEE 802.16e is the portable or mobile version of WiMAX, which promises to support voice and data sessions at vehicular speeds of up to 120 kilo-meters per hour. The current strategy within the WiMAX Forum is to launch 802.16e with portable features in order to achieve rapid time to market. As the technology and market opportunity matures, the forum intends to introduce full-scale mobility. The main features of mobile WiMAX are:
- Approved on the 23th of September 2004.
- Covers "Physical and Medium Access Control Layers for Combined Fixed and
- Mobile Operation in Licensed Bands.
- Optimized for and backwards compatible with fixed stations.
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