e use of a wide range of frequencies (frequency diversity) makes the link less susceptible to the rapidly varying fading that is characteristic of mobile applications. Subchannelization is also an option in fixed WiMax, where a subchannelized uplink can be used to trade-off throughput for range, achieving a higher range or increased building penetration for a given CPE transmitter power. Wireless MAN Standards IEEE 802.16 in Practice The familiar model of an IEEE standard being taken up by a trade organisation to drive product and market development is also applicable for 802.16. The WiMAX (Worldwide Interoperability for Microwave Access) Forum aims to fulfil a similar role to that of the Wi-Fi Alliance in relation to the 802.11 suite of standards, namely conformance and interoperability testing and certification. The WiMAX Forum is marketing 802.16d networks under the WiMAX brand as providing fixed, portable and ultimately mobile wireless broadband access without requiring direct line-of-sight to a base station. Data capacities of up to 40 Mbps per channel are headlined, sufficient to support thousands of residential subscribers at DSL connection speeds, while mobile networks are expected to reach 15 Mbps. Initial certification work by the WiMAX Forum members will focus on equipment operating in the 3.5 GHz frequency band with 3.5 MHz channel width, and based on both TDD and FDD. Extensions beyond this initial scope will be dependent on further market demand and product submissions by vendors. Future Developments Further developments of the 802.16 standards suite are currently being progressed by the TGf and TGg Task Groups. 802.16f aims to improve the multi-hop capabilities, as SSs move between BSs in a fixed wireless network, while 802.16g will deliver faster and more efficient handover and improved QoS for mobile connections. Other WMAN Standards ETSI HIPERMAN HIPERMAN, which stands for high performance radio metropolitan area networks, is a proposal from the European Telecommunications Standards Institute (E