Broadcast Strategies for MISO and Multiple Access Channels

This paper studies the use of layered coding in fading multiple- input single-output (MISO) and multiple access channels (MAC). In this setting, the transmitter(s) have no knowledge of the channel state while the receiver has accurate knowledge of it. The channel is assumed to be slowly fading in amplitude with a rapid change in phase. This is used to model a system with low mobility where the surrounding scattering environment is rich and changing quickly. In this setting, codebooks with rates greater than that supported by the channel undergo an outage. Our goal is to layer multiple codebooks at different rates such that the overall average throughput of the channel is maximized. The inherent difficulty in studying such channels is in determining an absolute decoding order at the receiver. In this paper, we focus on a class of strategies based on channel norm that has a natural decoding ordering. We use existing results for single antenna systems to obtain a "good" resource allocation policy for these channels.