A new adaptive MAC layer protocol for wireless ATM networks in harsh fading and interference environments

A new media access protocol is proposed for sharing a high speed radio channel among a number of small wireless packet access units, some of which may be stationary and some of which may be within moving vehicles. Such a system could provide fixed point, pedestrian and remote users with wireless access to CPU and database resources of an underlying ATM wireline network, essentially extending the ATM bandwidth-upon-demand interface directly to the wireless units and enabling delivery of multimedia services (albeit at the lower peak rate afforded by the radio channel). A primary goal of the proposed media access protocol is the pre-delivery of a signal from each packet access unit as needed to enable the deployment of a rapidly adaptive array antenna at the base station, thereby protecting the packet flow in each direction from the effects of both multipath propagation and adjacent channel interference arising in neighboring radio cells. An impairment-robust direct sequence spread spectrum-based polling signal is invoked to stimulate a pilot tone from a given remote immediately prior to packet transfer in either direction, thereby permitting the base station to determine a good set of antenna element combining or power splitting weights to be used for that packet. Reasonable approximations are invoked to study the performance of the proposed protocol, and link utilization efficiency and average message delay are found. By proper choice of protocol parameters, a radio resource utilization efficiency of about 95% is readily achieved. The accuracy of the approximations is confirmed by extensive computer simulations.