Many-user MAC is an important model for understanding energy efficiency of massive random access in 5G and beyond. Introduced in Polyanskiy'2017 for the AWGN channel, subsequent works have provided improved bounds on the asymptotic minimum energy-per-bit required to achieve a target per-user error at a given user density and payload, going beyond the AWGN setting. The best known rigorous bounds use spatially coupled codes along with the optimal AMP algorithm. But these bounds are infeasible to compute beyond a few (around 10) bits of payload. In this paper, we provide new achievability bounds for the many-user AWGN and quasi-static Rayleigh fading MACs using the spatially coupled codebook design along with a scalar AMP algorithm. The obtained bounds are computable even up to 100 bits and outperform the previous ones at this payload.
Fundamental Limits of Coded Caching: Improved Delivery Rate-Cache Capacity Trade-off
一个集中式编码缓存系统,包括一个服务器提供N个流行的文件,每个大小F位,K个用户通过一个无错误的共享链接,被认为是。假设每个用户都配备有具有容量MF位的本地高速缓存存储器,并且内容可以在低流量时段内主动地高速缓存到这些高速缓存中;然而,无需了解用户需求。在流量高峰期,每个用户从服务器请求单个文件。目标是在所有用户需求组合中,最小化服务器在共享链路上传输的比特数(称为传输速率)。提出了一种新的缓存容量为M=(N-1)/K的编码缓存方案。当K > N >= 3时,该方案比文献中已有的编码缓存方案具有更小的传输速率。此外,我们认为,所提出的方案的交付率是在一个常数乘法因子2的最佳交付率的缓存容量1/K <= M <=(N-1)/K,当K > N >= 3。
A Unified Theory of Multiple-Access and Interference Channels via Approximate Capacity Regions for the MAC-IC-MAC
为一类干扰多址接入信道建立近似容量区域,所述干扰多址接入信道由两个多址接入信道(MAC)组成,每个多址接入信道具有任意数量的发射机,每个MAC中的一个发射机对另一MAC的接收机造成干扰,该信道此后称为MAC-IC-MAC。对于离散无记忆(DM)MAC-IC-MAC,得到了两个内界,它们是Chong { \em et al}关于两用户DM干扰信道(IC)的先验内界的推广.对于半确定性的MAC-IC-MAC,它示出,在非干扰发射机的单用户编码和在每个MAC的干扰发射机的叠加编码实现了一个速率区域内的容量区域的可量化的间隙,从而扩展这样的结果为两个用户的半确定性IC由Telatar和Tse。对于高斯MAC-IC-MAC,获得了在容量区域的恒定间隙内的近似容量区域,推广了Etkin { \em et al}针对两用户高斯IC的这样的结果。与上述近似容量结果的两个用户IC的可扩展性需要工会的所有可接受的输入分布,我们的差距结果的半确定性和高斯的MAC-IC-MAC是可以实现的,只有一个子集和所有可接受的编码分布之一,分别。每个小区具有多于一个用户的对称高斯MAC-IC-MAC的对称广义自由度(GDoF)是具有平坦肩部的V形,其是干扰强度(在高SNR下的INR与SNR的比率,两者都以dB表示)和每个小区中的用户数量的函数。...
Improved Characterization of the Memory-Rate Tradeoff for Demand-Private Coded Caching With Multiple Demands
School of Information Science and Engineering, Southeast University(东南大学信息科学与工程学院);National Mobile Communications Research Laboratory, Southeast University(东南大学移动通信国家重点实验室)