This paper studies the performance of a transmission and reception scheme for massive access under some practical challenges. One challenge is the near-far problem, i.e., an access point often receives signals from different transmitting devices at vastly different signal strengths. Another challenge is that the signals from different devices may be subject to arbitrary, analog, and heterogeneous delays. This paper considers a fully asynchronous model which is more realistic than the frame or symbol level synchrony needed in most existing work. A main theorem characterizes the asymptotic scaling of the codelength with the number of devices, a device delay upper bound, and the dynamic range of received signal strengths across devices. The scaling result suggests potential advantages of grouping devices with similar received signal strengths and letting the groups use time sharing. The performance of the proposed scheme is evaluated using simulations with and without grouping.

翻译：本文研究了在若干实际挑战下用于大规模接入的传输与接收方案的性能。其中一个挑战是远近效应问题，即接入点接收到的来自不同发射设备的信号强度往往相差悬殊。另一个挑战是不同设备的信号可能遭受任意、模拟且异构的延迟。本文考虑了一种完全非同步模型，该模型比现有大多数工作所需的帧级或符号级同步更为现实。一个主要定理表征了码长随设备数量、设备延迟上限及设备间接收信号强度动态范围渐近缩放的关系。该缩放结果提示了将具有相似接收信号强度的设备分组并采用时分复用的潜在优势。通过有无分组的仿真对所提方案的性能进行了评估。