Effective channel utilization using the RI-BTMA protocol

This paper examines the use of the Receiver Initiated Busy Tone Medium Access (RI-BTMA) protocol in a dense ad hoc network. The RI-BTMA protocol is known to eliminate the hidden and exposed node problems in sparse networks where a transceiver will see one active link or none at all. When multiple links are active, their busy tone signals will interfere. This paper addresses the phase synchronization problem by using the residual frequency offset and a longer sampling time for an incoming transceiver. The problem of choosing a carrier sensing threshold is discussed. In this paper we show that in an ad hoc network nodes which are clustered together have a higher probability of being interrupted. This enforces a spreading or regularization of any randomly generated topology. It is shown through simulations that the effect of the regularization for the RI-BTMA protocol is that the choice of carrier sensing threshold which eliminates the hidden node problem does not vary significantly with link density.