TY - GEN
T1 - Role of Feedback in Modulo-Sum Computation over Erasure Multiple-Access Channels
AU - Wang, I-Hsiang
AU - Lin, Shih-Chun
AU - Huang, Yu-Chih
PY - 2017/6
Y1 - 2017/6
N2 - The problem of computing the modulo-sum of messages over a finite-field erasure multiple access channel (MAC) is studied, and the role of feedback for function computation is explored. Our main contribution is two-fold. First, a new outer hound on the non-feedback computation capacity is proved, which strictly improves the state of the art [1]. The new outer bound answers a previously unsettled question in the affirmative: delayed state feedback strictly increases computation capacity for the two-user erasure MAC universally. The proof leverages the subset entropy inequality by Madiman and Tetali Pl. Second, focusing on the family of linear coding schemes with hybrid-ARQ-type retransmissions, we develop the optimal computation rate with delayed state feedback. For the considered family of schemes, it is always sub-optimal to compute modulo-sum by decoding all messages first. This is in contrast to the non feedback case where sometimes the aforementioned "decode-all" strategy can reach the best known achievable rates.
AB - The problem of computing the modulo-sum of messages over a finite-field erasure multiple access channel (MAC) is studied, and the role of feedback for function computation is explored. Our main contribution is two-fold. First, a new outer hound on the non-feedback computation capacity is proved, which strictly improves the state of the art [1]. The new outer bound answers a previously unsettled question in the affirmative: delayed state feedback strictly increases computation capacity for the two-user erasure MAC universally. The proof leverages the subset entropy inequality by Madiman and Tetali Pl. Second, focusing on the family of linear coding schemes with hybrid-ARQ-type retransmissions, we develop the optimal computation rate with delayed state feedback. For the considered family of schemes, it is always sub-optimal to compute modulo-sum by decoding all messages first. This is in contrast to the non feedback case where sometimes the aforementioned "decode-all" strategy can reach the best known achievable rates.
U2 - 10.1109/ISIT.2017.8006938
DO - 10.1109/ISIT.2017.8006938
M3 - Conference contribution
T3 - IEEE International Symposium on Information Theory
SP - 2293
EP - 2297
BT - 2017 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY (ISIT)
PB - IEEE
T2 - IEEE International Symposium on Information Theory (ISIT)
Y2 - 25 June 2017 through 30 June 2017
ER -