Rate regions for multiple access relay channels with relay-source feedback

For the multiple-access relay channel with relay-source feedback, we derive an outer bound on the capacity region C_MARC. We also derive an achievable rate region R_FB which is in general larger than the capacity region without feedback. The presence of the feedback enables the sources to understand each other´s messages, which in turn allows the sources to cooperate to resolve the residual uncertainty at the receiver in an efficient way. At the same time, independent fresh information from the sources is superimposed upon the resolution information.