A cross-layer approach to increase spatial reuse and throughput for ad hoc networks
Three simple, robust distributed channel-access protocols are presented that result in efficient spatial reuse of traffic channels in a direct-sequence spread-spectrum packet radio network consisting of an arbitrary mix of nodes with directional antennas and nodes with omnidirectional antennas. Each protocol uses an RTS/CTS channelaccess control-packet exchange to negotiate the transmission of a data packet from a source node to its link-level destination on a traffic channel. In addition, each protocol includes a mechanism by which a negotiating node pair dynamically determines which in-use traffic channels in the local area should be treated as reserved and which should be treated as available for concurrent use. The performance of each of the three new protocols is compared with two existing implementations of the RTS/CTS channel-access protocol, both of which take a static approach to reuse of traffic channels. The performance of two of the new protocols is examined in detail. It is shown that both yield significantly better performance than either of the two static approaches and that the superior performance is achieved over a wide range of network conditions that include different network densities and different spread-spectrum processing gains.