Research On MAC Protocol For Ad Hoc Networks Based On Smart Antennas And Power Control

A wireless Ad Hoc network is a multi-hop and temporary autonomous system, consisting of a collection of mobile devices or nodes. Due to the sharing characteristics of the wireless medium, Medium Access control (MAC) protocol, which efficiently and reasonably manages the multi-user sharing of limited radio channel resources, becomes the key technology for the development of Ad Hoc networks. In Ad Hoc networks, using smart antennas to transmit directional frames can increase special reuse, reduce interference between simultaneous communications, and hence increase network capacity. Therefore, MAC protocols exploiting smart antennas in Ad Hoc networks attract more and more attention. Besides, the nodes in Ad Hoc networks are battery-powered devices. Power supply is a key constraint in Ad Hoc networks. Therefore, energy-saving mechanism is necessary to extend the network life cycle. An integrated application of smart antenna technology and power control scheme in the design of MAC protocol in Ad Hoc networks can further reduce the network power consumption, decrease interference between simultaneous communications and increase the network throughput. Therefore, relevant researches in this area will have far-reaching significance.This paper introduces both of smart antenna technology and power control scheme to the design of MAC protocol in Ad Hoc networks, and proposes a new PC-DMAC (Power-controlled Directional Medium Access Control Protocol). It uses the standard RTS-CTS-DATA-ACK exchange procedure. Through omni-directional RTS-directional CTS interaction, the nodes in Ad Hoc networks can directionally transmit data frames at the minimal calculated power in order to save power consumption. In addition, busy-tone scheme is adopted to tackle the special hidden terminal problem resulting from using smart antennas in Ad Hoc network. Detailed description of the system model, mechanism used and concrete implementation for PC-DMAC protocol is discussed.Finally, this paper simulates an Ad Hoc communication network using OPNET simulation tool and compares the network performance of Ad Hoc networks adopting IEEE802.11, PCM, DMAC and PC-DMAC protocols respectively under different simulation scenarios. Simulation results validate that PC-DMAC protocol can effectively support the use of smart antenna technology and power control scheme in Ad Hoc networks. It can greatly improve the performance of Ad Hoc networks in terms of network power consumption, throughput and channel utilization.