Collision-resistant multi-channel M-ASPM configurations with shared single detection channel

Alexei V. Nikitin, Ruslan L. Davidchack

M-ary Aggregate Spread Pulse Modulation (M-ASPM) is a physical layer (PHY) modulation technique that offers several advantages for low-power wide-area networks (LPWANs). For instance, in conventional LPWAN modulations increasing receiver sensitivity by extending symbol duration - thereby proportionally increasing the time-on-air (ToA) - exacerbates collision exposure. In contrast, M-ASPM payload processing gain can vary over a wide range without impacting the effective packet collision rate. In particular, in this work we demonstrate how short front portions of M-ASPM packets can serve as a separate collision-resistant detection channel that, in addition to performing asynchronous packet detection and synchronization, obtains the carrier frequency offset (CFO) for each packet within a desired range and with the required precision. Then, while raising processing gain, the subsequent payload information can be extracted without expanding the sample window per symbol. Consequently, the receiver sensitivity can be significantly increased without exacerbating packet collisions and thus without reducing network throughput under collision-limited operation. We further establish a multi-channel configuration in which numerous quasi-orthogonal payload channels share a single detection channel that additionally performs payload channel identification and selection. Such sharing is especially useful for scaling and economizing LPWAN deployments under diverse technical requirements and constraints. The presented analysis is validated via extensive simulations under high packet collision rates in wide ranges of payload sizes and processing gains, and for varying noise and interference power levels. The results signify that M-ASPM provides a structurally distinct scaling behavior compared to conventional LPWAN modulations, decoupling range extension from collision-induced throughput degradation.