Random Access Channel Coding in the Finite Blocklength Regime
Random Access Channel Coding in the Finite Blocklength Regime
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DOI：
10.1109/tit.2020.3047630
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发表时间：
2021-04
影响因子：
2.5
通讯作者：
Recep Can Yavas;V. Kostina;M. Effros
中科院分区：
文献类型：
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作者：
Recep Can Yavas;V. Kostina;M. Effros
考虑在信道上的随机接入通信场景，该信道的操作被定义用于任何数量的可能发射机。正如Polyanskiy最近为具有固定的已知数量的发射机的多址信道（MAC）引入的模型中那样，假设信道对于其输入上的排列是不变的，并且所有活动的发射机都采用相同的编码器。与Polyanskiy模型不同，在所提出的场景中，发射器和接收器都不知道哪些发射器是活动的。我们将这种不可知的通信设置称为随机接入信道（RAC）。有限比特数的预定反馈用于同步发射机。解码器的任务是从信道输出中确定活动发射机的数量，$k$，以及它们的消息，但不是哪个发射机发送了哪个消息。解码过程发生在时间${n}_{t}$，这取决于解码器对活动发射机的数量$k$的估计$t$，从而实现随活动发射机的数量变化的速率。在每个时间${n}_{i}，{i} \leq {t}$的单比特反馈使所有发射机能够确定一个编码时期的结束和下一个编码时期的开始。这项工作的中心结果表明，RAC的性能是一阶最优的MAC在每个编码时期的操作中的可扩展性。虽然现有的多址接入方案的固定数量的发射机需要2 ^{k}-1 $同时阈值规则，所提出的方案使用一个单一的阈值规则，并实现相同的分散。
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 ${n}_{i}, {i} \leq {t}$ , 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.