Improved achievable rates for user cooperation and relay channels

In this paper a new achievable rate region for the user cooperation channel is derived which exceeds the best-known result for this channel. Since the user cooperation channel includes many other known channels as a special case, the new rate region provides improved achievable rates for these cases. The most notable example is that of the Gaussian relay channel, for which we present a new closed form inner bound higher than the only known result for many channel conditions.