A CDMA based MAC protocol for ad hoc networks with directional antennas

One of the traditional MAC protocols used in wireless ad hoc networks is Distributed Coordination Function IEEE 802.11 (DCF). In such protocols, nodes are allowed to access the channel without any base station and omni-directional antennas are used for packet transmission. The main problem in IEEE 802.11 DCF is the existence of silent area which leads to channel spatial reuse reduction and using directional antennas at the nodes can battle this problem. However, using directional antennas itself leads to other problems such as new hidden terminal and deafness problems. In this paper, we propose a new multichannel MAC protocol based on CDMA technique in which directional antennas and CDMA codes are used to specify the channels for different users. In the proposed protocol, a common control channel is used for RTS/CTS handshaking, and other channels are used for data transmission. Simulation results show that the proposed protocol, by using even lower number of codes, improves the network throughput and achieves higher spatial reuse of wireless channel compared with 802.11 DCF, or other traditional protocols such as DMAC (basic Directional MAC) and CDMA based MAC protocols.