3,867 research outputs found
Multiple Access Channels with States Causally Known at Transmitters
It has been recently shown by Lapidoth and Steinberg that strictly causal
state information can be beneficial in multiple access channels (MACs).
Specifically, it was proved that the capacity region of a two-user MAC with
independent states, each known strictly causally to one encoder, can be
enlarged by letting the encoders send compressed past state information to the
decoder. In this work, a generalization of the said strategy is proposed
whereby the encoders compress also the past transmitted codewords along with
the past state sequences. The proposed scheme uses a combination of
long-message encoding, compression of the past state sequences and codewords
without binning, and joint decoding over all transmission blocks. The proposed
strategy has been recently shown by Lapidoth and Steinberg to strictly improve
upon the original one. Capacity results are then derived for a class of
channels that include two-user modulo-additive state-dependent MACs. Moreover,
the proposed scheme is extended to state-dependent MACs with an arbitrary
number of users. Finally, output feedback is introduced and an example is
provided to illustrate the interplay between feedback and availability of
strictly causal state information in enlarging the capacity region.Comment: Accepted by IEEE Transactions on Information Theory, November 201
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