Superposition encoding A distorted version of is is encoded into the inner codebook

1. Interference Channels with Receiver Side Information Nan Liu, Deniz Gunduz, Andrea Goldsmith and H. Vincent Poor Desired Source: Results Desired Source: Channel Model Introduction Interference Channels with Correlated Receiver Side Information ACHIEVEMENT DESCRIPTION MAIN RESULT: When receiver side information is about the desired source, separation is optimal. When receiver side information is about the interfering source, a general joint source-channel coding strategy is proposed. The optimality of separation as well as necessary and sufficient conditions for reliable transmission is characterized for certain special cases. HOW IT WORKS: The main aim of the network is still to reduce interference caused to the other transmitter-receiver pair. Hence, it is best to transmit only what the receiver doesn’t know. When the other receiver has some side information, since this part of the knowledge does not cause interference, include it in the part of interference the other receiver decodes. ASSUMPTIONS AND LIMITATIONS: Due to the difficulty of finding capacity results for the interference channel, tight results are only possible in special cases. • Expand the definition of separation and re-explore the optimality of separation • Generalize our tight results to include all ICs where superposition encoding is optimal Provides several new results regarding the joint source-channel coding of interference channel with receiver side information. While the achievable strategy is general, sufficient and necessary conditions exist only in special cases. • Multiple communication systems operating simultaneously causes interference • In applications such as sensor networks, it is reasonable to assume that the receivers have access to their own correlated observations about the underlying source sequences as well • Traditional interference channel (IC) excludes this possibility, and hence, we study interference channel with receiver side information • Receiver side information about desired source • Receiver side information about interfering source • The goal: understanding how to fully take advantage of side information at the receiver to reduce interference Theorem 1: Separation is optimal, i.e., necessary and sufficient condition for reliable transmission is END-OF-PHASE GOAL where is the capacity region of the interference channel. STATUS QUO • Separation is optimal • Transmitters first apply Slepian-Wolf source coding • Then use optimal IC code to transmit compressed bits • No single-letter characterization for capacity region of IC • Still can prove optimality of separation using n-letter forms It is best to transmit only what the receiver doesn’t know, and also include as much as possible the side information the other receiver knows. • Two source-side information pairs are independent • Side information is about the desired source • How to utilize the side information to reduce the interference to the other transmitter-receiver pair COMMUNITY CHALLENGE The impact of receiver side information on larger networks NEW INSIGHTS The result provides intuition as to how to utilize side information at the receiver to reduce interference Deterministic Side Information IC with Message Side Information Joint Source-Channel Coding Strategy Interfering Source: Channel Model Theorem 2: Separation is optimal, i.e., necessary and sufficient condition for reliable transmission is • Separation is optimal • Encode side information into one message • Encode remaining information into another message • Transmit the two messages using an optimal code for IC with message side information • is the capacity region of IC with message side info • Superposition encoding • A distorted version of is • is encoded into the inner codebook • Receiver 2 decodes using received signal and its side information • Decoding part of the interference helps decoding the desired source • More general than classical IC • In general, no single-letter expression for capacity region • We provide an n-letter form of the capacity region • We prove the optimality of separation using n-letter forms • Two source-side information pairs are independent • Side information is about the interfering source • How the side information about the interference helps in decoding the desired information Insights and Future Work Conclusions Z-channel with Degraded Message Sets Necessary and Sufficient Conditions • Study the problem of joint source-channel coding in transmitting independent sources over IC with receiver side info • Side information about desired source: • Separation is optimal • Transmit only bits the receiver does not know to reduce interference to the other transmitter-receiver pair • Side information about interfering source • Proposed joint source-channel coding strategy • Separation is optimal with deterministic side information • Complete solution for a special case • As a byproduct, capacity region for a class of Z-channels with degraded message sets • Insights • Transmit only the bits the receiver does not know • Include the side information of the interfering receiver as much as possible into the message intended for both receivers • Future work • Expand the definition of separation to include disjoint source- channel distribution • Re-explore optimality of separation under these new definitions • Explore the possibility that the joint source-channel coding strategy is tight for all ICs where superposition encoding is optimal • Apply the insights of using side information to reduce interference to larger wireless networks • For special cases, single-letter expression of can be found • Necessary and sufficient condition described in single-letter form, yielding a complete solution • Superposition encoding is optimal for the underlying IC • Superposition encoding is shown to be still optimal with message side information • Joint source-channel coding strategy is optimal • Z-interference channel with message side information is very much related to Z-channel with degraded message sets, Kramer/Shamai 07 • Characterize the capacity region for a class of Z-channels with degraded message sets