The broadcast approach in communications systems

Traditional coded communication schemes for block fading channels, with channel state information (CSI) available at the receiving end only are based on fixed rate single level coding. The maximal average achievable throughput is known as the outage capacity. However, a more general approach is known as the multi-layered coded communications, termed the broadcast approach. This strategy facilitates to adapt the reliably decoded rate to the actual channel state without having any feedback link to the transmitter. Several communication settings incorporating the broadcast strategy are discussed. Among these are broadcasting over multiple-input multiple-output (MIMO) fading channels, broadcasting for minimization of expected delay, and broadcasting for minimization of expected distortion for transmission of a Gaussian source over a block fading channel. An outlook of related open problems, where an analytic formulation of a broadcast approach is yet elusive or incomplete are shortly described, followed by a general perspective of layered communications in multi-terminal communication systems.