Asynchronous Massive Access and Neighbor Discovery Using OFDMA
Asynchronous Massive Access and Neighbor Discovery Using OFDMA
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DOI：
10.1109/tit.2022.3224951
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发表时间：
2017-06
影响因子：
2.5
通讯作者：
Xu Chen;Lina Liu;Dongning Guo;G. Wornell
中科院分区：
文献类型：
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作者：
Xu Chen;Lina Liu;Dongning Guo;G. Wornell
无线物联网（IoT）的基本通信问题是发现大量设备并为它们提供对共享信道的可靠访问。这些设备通常是随机和零星地发送短消息。本文提出了一种新的免授权大规模访问信令方案，其中每个设备以稀疏的音调集编码其身份和/或信息。这种传输以正交频分多址（OFDMA）的形式实现。在一些温和的条件下，假设设备延迟是采样间隔的有界未知倍数，稀疏OFDMA被证明可以实现任意可靠的异步设备识别和消息解码，其码长为$O(K(\log K+\log S +\log N))$，其中$N$表示设备总体，$K$表示活动设备的实际数量，$\log S$本质上等于每个设备可以发送的信息位数。发现和解码的计算复杂度可以为$O(K(\log K)(\log K+\log S+\log N)+K^{2}\log K)$。作为概念验证，提出了一种特定的设计，可以从$N=2^{96}$可能的设备中识别多达200个有源设备，具有多达20个延迟样本，中等信噪比和衰落。如果设备数量为$N=2^{48}$，则每个活动设备也可以同时向接入点传输48位。与标准的开槽ALOHA和载波感知多址（CSMA）方案相比，该方案的码长更有利。
The fundamental communication problem in the wireless Internet-of-Things (IoT) is to discover a massive number of devices and to provide them with reliable access to shared channels. Oftentimes these devices transmit short messages randomly and sporadically. This paper proposes a novel signaling scheme for grant-free massive access, where each device encodes its identity and/or information in a sparse set of tones. Such transmissions are implemented in the form of orthogonal frequency-division multiple access (OFDMA). Under some mild conditions and assuming device delays to be bounded unknown multiples of sampling intervals, sparse OFDMA is proved to enable arbitrarily reliable asynchronous device identification and message decoding with a codelength that is $O(K(\log K+\log S + \log N))$ , where $N$ denotes the device population, $K$ denotes the actual number of active devices, and $\log S$ is essentially equal to the number of information bits each device can send. The computational complexity for discovery and decoding can be made to be $O(K(\log K)(\log K+\log S+\log N)+K^{2}\log K)$ . As a proof of concept, a specific design is proposed to identify up to 200 active devices out of $N=2^{96}$ possible devices with up to 20 samples of delay, moderate signal-to-noise ratios, and fading. If the device population is $N=2^{48}$ instead, each active device can also transmit 48 bits to the access point at the same time. The codelength compares much more favorably with those of standard slotted ALOHA and carrier-sensing multiple access (CSMA) schemes.