The most noticeable technological development in wireless MANs and wireless WANs are embodied by the IEEE 802.16, 802.20, and ETSI HIPERMAN standards. Based on the open IEEE 802.16 and HIPERMAN, a commercialized technology called WiMax has been devised. The WiMax Forum, an industry consortium of over 100 companies, has been formed to promote the technology and provide certified, interoperable WiMax products. IEEE 802.16 specifies the PHY and MAC layers. It will support higher network layers and transport layer protocols such as ATM, Ethernet, and IP.
It is noteworthy that the frequency band of 10 to 66 GHz specified by the initial 802.16 standard requires LOS transmission. Some other frequency bands are also specified in later versions of the standard in order to provide indoor wireless access. The MAC layer portion of 802.16 addresses QoS by introducing a bandwidth request and grant scheme. Terminals can be polled or actively signal the required bandwidth, which is based on traffic QoS parameters. 802.16 employs a public-key infrastructure in conjunction with a digital certificate for authentication.
Extensions of IEEE 802.16 include:
• 802.16a, which specifies a data rate up to 280 Kbps per base station over the 2- to 11-GHz frequency band reaching a maximum of 50 km and mesh deployment.
• 802.16b, which addresses QoS issues surrounding real-time multimedia traffic.
• 802.16c, which defines system profiles that operate at 10 – 66 GHz for interoperability.
• 802.16d, which represents system profile for 802.16a devices.
• 802.16e, which standardizes handoff across base stations for mobile data access.
The ETSI HIPERMAN standard is similar to 802.16a. It has been developed in very close cooperation with IEEE 802.16, such that the HIPERMAN standard and IEEE 802.16a standard can work together seamlessly. As a result, many of the characteristics of 802.16 are available in HIPERMAN, such as QoS support, adaptive modulation, and strong security. HIPERMAN supports both PTM and mesh network configurations. The differences between HIPERMAN and 802.16 are primarily on the PHY layer. In order to create a single interoperable standard for commercialization, as well as product testing and certification, several leaders in the wireless industry formed the WiMax Forum. Another IEEE working group, called IEEE 802.20 Mobile Broadband Wireless Access (MBWA), uses the 500-MHz to 3.5-GHz frequency band for mobile data access, an application also targeted by 802.16e; however, 802.20 does not have as strong industry support as 802.16 does.
Source of Information : Elsevier Wireless Networking Complete 2010