Multiple Access Channels with State Information Known at Some Encoders

A multiple access channel (MAC) with channel state information (CSI) non-causally known at some encoders is considered. For simplicity of exposition, a two-encoder model in which one of the encoders is non-causally informed of the CSI is focused. The results can in principle be extended to any number of encoders with a subset of them being informed. Inner and outer bounds for the capacity region in the general discrete memoryless case are derived and specialized to a binary noiseless case. Inner and outer bounds for the capacity region of an additive white Gaussian MAC with one encoder being informed of the CSI are also derived. For both the binary and the Gaussian inner bounds, the informed encoder uses generalized dirty paper coding (DPC) that allows arbitrary correlation between the codeword and the known CSI, with negative correlation being viewed as partial state cancellation. It appears that the generalized DPC can not completely eliminate the effect of the CSI, in contrast to the case of all encoders being informed.