Energy Efficient Coded Random Access for the Wireless Uplink
Energy Efficient Coded Random Access for the Wireless Uplink
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DOI：
10.1109/tcomm.2020.3000635
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发表时间：
2019-07
影响因子：
8.3
通讯作者：
S. Kowshik;K. Andreev;A. Frolov;Yury Polyanskiy
中科院分区：
文献类型：
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作者：
S. Kowshik;K. Andreev;A. Frolov;Yury Polyanskiy
我们讨论了设计通道访问架构的问题，以便为密集的无线节点实现快速、低延迟、无授权和不协调的上行链路。具体来说，我们研究了随机访问码，之前为AWGN MAC引入的随机访问码，在实际更相关的瑞利衰落情况下，当信道增益对解码器未知时。提出了一个随机编码可达性界，并对其进行了非渐近和渐近分析。作为一种候选的实用解决方案，我们提出了一种显式迭代编码方案。这种解决方案的性能惊人地接近有限块长度边界。我们的主要发现有两个方面。首先，就像在AWGN MAC中一样，我们看到联合解码大量用户会导致令人惊讶的相变效应，其中，在低于临界阈值的频谱效率下，完美的多用户干扰抵消是可能的。其次，虽然瑞利衰落的存在显著增加了每比特所需的最小能量，但信道引入的固有随机化使得通过迭代方案更容易获得最佳性能。我们希望随机接入模型的原则性定义，以及他们的信息论分析，将为5G/6G各种随机接入解决方案的统一基准测试和性能比较开辟道路。
We discuss the problem of designing channel access architectures for enabling fast, low-latency, grant-free, and uncoordinated uplink for densely packed wireless nodes. Specifically, we study random-access codes, previously introduced for the AWGN MAC, in the practically more relevant case of Rayleigh fading, when channel gains are unknown to the decoder. We propose a random coding achievability bound, which we analyze both non-asymptotically and asymptotically. As a candidate practical solution, we propose an explicit iterative coding scheme. The performance of such a solution is surprisingly close to the finite blocklength bounds. Our main findings are twofold. First, just like in the AWGN MAC, we see that jointly decoding a large number of users leads to a surprising phase transition effect, where, at spectral efficiencies below a critical threshold, a perfect multi-user interference cancellation is possible. Second, while the presence of Rayleigh fading significantly increases the minimal required energy-per-bit, the inherent randomization introduced by the channel makes it much easier to attain the optimal performance via iterative schemes. We hope that a principled definition of the random-access model, together with their information-theoretic analysis, will open the road towards unified benchmarking and performance comparison of various random-access solutions for the 5G/6G.