Massive Machine-Type Communications (mMTC) is a key service category in the current generation of wireless networks featuring an extremely high density of energy and resource-limited devices with sparse and sporadic activity patterns. In order to enable random access in such mMTC networks, base station needs to identify the active devices while operating within stringent access delay constraints. In this paper, an energy efficient active device identification protocol is proposed in which active devices transmit On-Off Keying (OOK) modulated preambles jointly and base station employs non-coherent energy detection avoiding channel estimation overheads. The minimum number of channel-uses required by the active user identification protocol is characterized in the asymptotic regime of total number of devices $\ell$ when the number of active devices $k$ scales as $k=\Theta(1)$ along with an achievability scheme relying on the equivalence of activity detection to a group testing problem. Several practical schemes based on Belief Propagation (BP) and Combinatorial Orthogonal Matching Pursuit (COMP) are also proposed. Simulation results show that BP strategies outperform COMP significantly and can operate close to the theoretical achievability bounds. In a partial-recovery setting where few misdetections are allowed, BP continues to perform well.

翻译：大规模机器类通信（mMTC）是当前无线网络中的关键业务类别，其特点在于具有极高密度的能量与资源受限设备，且这些设备的活动模式稀疏且偶发。为在此类mMTC网络中实现随机接入，基站需在严格的接入延迟约束下识别活动设备。本文提出了一种能量高效的活动设备识别协议，其中活动设备联合传输采用开关键控（OOK）调制的前导码，基站则通过非相干能量检测避免信道估计开销。当活动设备数量$k$按$k=\Theta(1)$缩放时，在总设备数$\ell$的渐近框架下，刻画了活动用户识别协议所需的最小信道使用次数，并基于活动检测与群组测试问题的等价性提出了一种可实现方案。此外，还提出了基于置信传播（BP）和组合正交匹配追踪（COMP）的多种实用方案。仿真结果表明，BP策略显著优于COMP，且其性能可接近理论可达界。在允许少量漏检的部分恢复场景中，BP仍能保持良好性能。