M-ary Aggregate Spread Pulse Modulation in LPWANs for IoT applications
In low-power wide-area networks (LPWANs), various trade-offs among the bandwidth, data rates, and energy per bit have different effects on the quality of service under different propagation conditions (e.g. various types of fading), interference scenarios, multi-user requirements, and design constraints. Such compromises, and the manner in which they are implemented, fur- ther affect other technical aspects, such as system’s computational complexity and power efficiency. At the same time, this difference in trade-offs also adds to the technical flexibility in addressing a broader range of the Internet of Things (IoT) applications. This paper addresses a physical layer LPWAN approach based on the Aggregate Spread Pulse Modulation (ASPM) and provides a brief assessment of its properties in an additive white Gaussian noise (AWGN) channel. In the binary ASPM, the control of the quality of service is performed through the change in the spectral efficiency, i.e., the data rate at a given bandwidth. Implementing M-ary encoding in ASPM further enables controlling service quality through changing the energy per bit (in about an order of magnitude range) as an additional trade-off parameter. Such encoding is especially useful for improving the ASPM’s energy per bit performance, thus increasing its range and overall energy efficiency, and making it more attractive for use in LPWANs.