标题： 异步mMTC系统的延迟校准联合用户活动检测、信道估计和数据检测研究 显示英文标题

标题： Study of Delay-Calibrated Joint User Activity Detection, Channel Estimation and Data Detection for Asynchronous mMTC Systems

摘要： 这项工作考虑了上行异步的大规模机器类型通信，其中大量低功耗和低成本的设备异步地将短数据包发送到配备多个接收天线的接入点。 如果使用正交前导序列，由于给定的前导序列长度限制，将会发生大规模碰撞。 为了解决这个问题，我们提出了一种延迟校准的联合用户活动检测、信道估计和数据检测算法，并研究了在接收端估计连续值时延时过采样的优势。 所提出的算法基于期望最大化方法，通过注意到碰撞的用户具有不同的时延，交替估计时延并检测活跃用户及其信道和数据。 在贝叶斯推理框架下，我们利用近似消息传递原理开发了一种计算高效的迭代算法，以解决联合用户活动检测、信道估计和数据检测问题。 数值结果表明，所提出的算法在信道和数据符号的归一化均方误差以及误检概率方面是有效的。 显示英文摘要

摘要： This work considers uplink asynchronous massive machine-type communications, where a large number of low-power and low-cost devices asynchronously transmit short packets to an access point equipped with multiple receive antennas. If orthogonal preambles are employed, massive collisions will occur due to the limited number of orthogonal preambles given the preamble sequence length. To address this problem, we propose a delay-calibrated joint user activity detection, channel estimation, and data detection algorithm, and investigate the benefits of oversampling in estimating continuous-valued time delays at the receiver. The proposed algorithm is based on the expectation-maximization method, which alternately estimates the delays and detects active users and their channels and data by noting that the collided users have different delays. Under the Bayesian inference framework, we develop a computationally efficient iterative algorithm using the approximate message passing principle to resolve the joint user activity detection, channel estimation, and data detection problem. Numerical results demonstrate the effectiveness of the proposed algorithm in terms of the normalized mean-squared errors of channel and data symbols, and the probability of misdetection.