Improving downlink performance in cellular radio communications

In this work we consider a multiuser coding technique applied to the downlink in cellular radio communications. This technique uses channel knowledge at the transmitter to take advantage of inevitable differences in channel attenuations due to path loss. We restrict ourselves to the simplest channel model, namely a non-fading discrete-time Gaussian channel without inter-cell interference. Using the Broadcast Channel model for the downlink of a two-user system, we show that significant improvement in terms of capacity can be obtained using such techniques in comparison to Orthogonal Multiplexing(OM). We then consider the coding gain of this system compared to uncoded OM. Finally, we describe how this technique can be extended to many users without a significant increase in complexity.