An Optimal CDMA Channel Access Protocol

摘要

In CDMA packet radio networks the simultaneous reception of several packets is possible through the use of orthogonal codes. While this provides an opportunity for significantly mcreasmg system throughput there is no known solution for an optimal use of the multiple reception capacity. We approach this challenging problem by proposing a general multiple access packet communication model where N users have access to p common channels(codes),on which they can receive packets in parallel from any other user.For transmission a node can use one of the P channels at a time,and can use difierent channels at difierent times.If more than one user is transmitting simultaneously on the same channel.all transmissions on this channel are considered unsuccessful.We present a new multiple channel access protocol called Gap-Free Fit(GAFF)which.under heavy homogeneous load provably guarantees the mazimum achievable throughput among all possible protocols,including all possible random or deterministic protocols with slotted or unslotted time.The general model can be specialized to difierent systems,according to various realizations of the logical channels.For example.in packet radio networks the channels can be realized by different carrier frequencies(FDMA)or by different codes (CDMA)etc.The simplicRy and optimality of our protocol make it attractive for practical applications.