Achievable Rates of Asymmetrical Multiple Access in Block-Fading Channels

Based on the specification of a high-throughput wireless local area network system we consider the achievable rate regions of time, frequency and code division multiple accessing schemes. We are especially interested in how the schemes compare in a two user scenario with one high-rate and one lowrate user. The channel is modeled as block-fading and frequency selective. We focus on the case in which the transmitters do not know the channel but the receiver does. The transmitters are subject to individual peak or average power constraints. In the context of code division multiple access we also look at successive decoding and interference cancellation (SIC) in addition to optimum joint decoding. We argue that CDMA-like superimposed transmission of a high rate user and low rate users with a SIC receiver is suboptimal yet appropriate to improve the throughput in scenarios similar to our application.