(A) new MAC protocol based on the control of maximum transmission power level in wireless ad hoc networks

Abstract

An ad hoc network is a distributed network with no centralized arbitration. Ad hoc nodes contend to get access to the channel in a distributed manner. The DCF of IEEE 802.11 is the basic MAC protocol for wireless ad hoc networks. All the packets in 802.11 DCF are transmitted at fixed maximum power. When a node hears control message, it is enforced to defer the channel access. If a node transmits data after hearing a channel reservation, the transmitted packet could be interfere the on-going transmission and channel utilization could be decreased. It is easily founded that fixed maximum power for any transmission induces low channel utilization. Moreover, it makes communication nodes consume high energy even in the case they are close each other. Power controlled MAC protocol draws attraction to solve the problems of power consumption and channel utilization. However, in a single channel, a node is still demanded to transmit control packets at maximum transmit power to avoid asymmetric link problem. Most researches are focused on power control to reduce node’s consumption. We propose a new MAC protocol to support parallel data transmission in a single channel. In the proposed scheme, when a node sends control packet to reserve the channel, neighbor nodes creates virtual cluster. The virtual cluster gives another chance of channel access to neighbors, while 802.11 DCF makes neighbors defer. Thus, we improve the network throughput by about 40% in a high node density, and about 10% when node density is low. In addition, we observe the average service delay becomes lower and energy efficiency is improved.