Outage behavior with delay and CSIT

In this paper, we demonstrate that the packet outage probability for fading channels can be significantly reduced by exploiting queuing delay and transmitter channel information. Queuing delay gain is conceptually similar to delay diversity, but at a packet time-scale instead of symbol time-scale. First, we compute a lower bound on outage probability assuming full channel state information at the transmitter (CSIT). We then construct simple outage minimizing transmission policies which adapt the rate and power of the transmitted signal based jointly on buffer occupancy and channel conditions. We demonstrate that the rate of decrease of outage with increasing transmitter channel information is higher for larger delays. We also address the closely coupled problem of designing a practical feedback channel which supplies the CSIT.