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Random Access Channel Coding in the Finite Blocklength Regime

Yavas, Recep Can and Kostina, Victoria and Effros, Michelle (2021) Random Access Channel Coding in the Finite Blocklength Regime. IEEE Transactions on Information Theory, 67 (4). pp. 2115-2140. ISSN 0018-9448. doi:10.1109/tit.2020.3047630.

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Consider a random access communication scenario over a channel whose operation is defined for any number of possible transmitters. As in the model recently introduced by Polyanskiy for the Multiple Access Channel (MAC) with a fixed, known number of transmitters, the channel is assumed to be invariant to permutations on its inputs, and all active transmitters employ identical encoders. Unlike the Polyanskiy model, in the proposed scenario, neither the transmitters nor the receiver knows which transmitters are active. We refer to this agnostic communication setup as the Random Access Channel (RAC). Scheduled feedback of a finite number of bits is used to synchronize the transmitters. The decoder is tasked with determining from the channel output the number of active transmitters, k, and their messages but not which transmitter sent which message. The decoding procedure occurs at a time n_t depending on the decoder’s estimate, t, of the number of active transmitters, k, thereby achieving a rate that varies with the number of active transmitters. Single-bit feedback at each time n_(i,i) ≤ t , enables all transmitters to determine the end of one coding epoch and the start of the next. The central result of this work demonstrates the achievability on a RAC of performance that is first-order optimal for the MAC in operation during each coding epoch. While prior multiple access schemes for a fixed number of transmitters require 2^k−1 simultaneous threshold rules, the proposed scheme uses a single threshold rule and achieves the same dispersion.

Item Type:Article
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URLURL TypeDescription ItemConference Paper
Yavas, Recep Can0000-0002-5640-515X
Kostina, Victoria0000-0002-2406-7440
Effros, Michelle0000-0003-3757-0675
Additional Information:© 2020 IEEE. Manuscript received July 23, 2019; revised August 21, 2020; accepted December 9, 2020. Date of publication December 28, 2020; date of current version March 18, 2021. This work was supported in part by the National Science Foundation (NSF) under Grant CCF-1817241. This article was presented in part at the 2018 IEEE International Symposium on Information Theory (ISIT’18). The authors are grateful to the reviewers—Prof. Jonathan Scarlett and two anonymous reviewers—for their thorough, careful, and insightful feedback, which is reflected in the article.
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Subject Keywords:Channel coding, random access channel, finite blocklength regime, achievability, second-order asymptotics, rateless codes
Issue or Number:4
Record Number:CaltechAUTHORS:20210113-163504947
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Official Citation:R. C. Yavas, V. Kostina and M. Effros, "Random Access Channel Coding in the Finite Blocklength Regime," in IEEE Transactions on Information Theory, vol. 67, no. 4, pp. 2115-2140, April 2021, doi: 10.1109/TIT.2020.3047630
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107464
Deposited By: George Porter
Deposited On:14 Jan 2021 15:01
Last Modified:31 Mar 2021 22:52

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