Based On The Busy Signal Of The Wireless Network Mac Protocol

Wireless Ad Hoc Networks are characterized by randomly moving nodes, rapidly changing topologies, lack of central nodes, and limited bandwidth. Wireless Ad Hoc Networks have broad application prospects, and therefore, academies and information industy have paid extensive attention in this area recently. Distributed random-access MAC protocols are usually employed in Ad Hoc networks. Most existing MAC protocols for Ad Hoc networks are based on the assumption that the interference range is equal to the transmission range. If the transmitter-receiver distance exceeds the threshold, the interference range of the receiver may be larger than the transmission range, which makes traditional RTS/CTS handshake function inefficiently and results in the problem of large interference range. Consequently, many schemes have been proposed to combat this problem. Nevertheless, most of these schemes assume that there is only a single interfering source when computing SIR (Signal to Interference Ratio), which make it impossible to prohibit the transmissions of all hidden nodes.Based on the analysis of the exposed terminal problem and the interference accumulation phenomenon, this paper has proposed a new busy tone aided MAC protocol with adjustable power, i.e., ADBT (Asymmetrical Dual Busy Tone). The ADBT protocol consists of both unicast protocol and broadcast protocol.With the aid of the busy tone BT-CTS/BT-ACK mechanism, ADBT unicast protocol is able to solve the exposed terminal problem effectively due to the improvement of spatial reuse in the Ad Hoc networks. Moreover, by adjusting the power of busy tone according to the number of interfering sources, ADBT unicast protocol is able to combat the interference accumulation phenomenon successfully, and therefore it can prevent most packet collisions caused by the hidden terminal problem.Moeover, ADBT broadcast protocol is able to improve the reliability and efficiency of the broadcast using the following approach. Firstly, each receiving nodes queries its neighboring nodes with BC-RTS and decide whether it will forward the broadcast packet. As a consequence, the redundancy of data packes can be reduced. Secondly, the pruning criteria is adopted to reduce the redundancy of BC-RTS, which prevents the BC-RTS broadcast storm. Thirdly, a neighboring node replies with BTr instead of CTS, which avoids the collisions of packets. Finally, the power of BTr is changed according to the power of BC-RTS and the packet collision rate, which is able to solve the problem of large interference range and the interference accumulation phenomenon.In addition, the simulation models of the ADBT unicast and broadcast protocol are implemented by OPNET. The results of simulation experiments verify that ADBT unicast protocol can improve the transmission performance and increase the network throughput. On the other hand, ADBT broadcast protocol can improve the broadcast rate.