Research Of MAC Power Control In Wireless Ad Hoc Network Based On IEEE802.11

The traditional wireless networks with centralized network topology (such as cellular systems and WLAN with AP) have been challenged to certain extent by the novel ad hoc network topology (such as Ad Hoc networks, wireless sensor networks, and wireless mesh networks). The centralized network topology is characterized by the advantage of its large coverage, centralized network management and unlimited energy supply (from fixed power supply), which can be taken advantage for long-range wireless communications. On the other hand, the ad hoc network has the advantage of flexible topology, requiring no infrastructure, and easy deployment temporarily, and it has attracted much attention and intensive research, especially in some special middle- or short-range application scenarios, such as disaster relief efforts, exhibition, and battlefield.With the development of technologies, the wideband wireless transmission is not so far away. The peak rate of 802.11a with OFDM technology reaches 54Mbps. The newly formed 802.11n group plans to increase the rate further to 108Mbps (with the maximum rate of 320Mbps), using MIMO-OFDM technology. Ultra Wide Band, a candidate for 4G technology, can even raise the rate up to 500Mbps. Though, the battery technology lags through several decades, and may hinder the development of wideband wireless networks. As a result, how to save the battery energy of the wireless nodes is the very important issue, especially in the wireless Ad Hoc networks, where the wireless nodes generally are supplied by battery.At present, the energy saving schemes mainly fall in two categories. The first is dynamically shutting down the wireless network interface card, i.e., forcing the node into sleep mode periodically to save the unnecessary energy consumption. The other is power control by adjusting the transmission power. Power control scheme not only reduces the energy cost of the wireless nodes effectually, but also improves the overall throughput of the network by increasing space reuse of the wireless channel, and reducing co-channel interference among nodes as well. However, the power control in the wireless Ad Hoc network will obviously cause different power levels between different nodes, resulting in the so-called Asymmetric Link Problem. This problem may lead to more collisions, and causes a lot of retransmissions thus consume more...