Successive Interference Cancellation for Signal Demodulation of Multiple LPWA Systems

With the development of the Internet of Things, the number of low power wide area (LPWA) terminals and LPWA systems has been increasing in unlicensed Sub-GHz bands. Accordingly, it is expected that radio frequency resources will be depleted remarkably, which may cause frequent intra-system and inter-system interferences at gateway (GW) of each system. Thus, we propose power-domain successive interference cancellation (SIC) among multiple LPWA systems. In our method, it is assumed that the GW has modulators and demodulators of multiple systems and can accumulate superposed and received signals. In the SIC algorithm, first, the GW modulates demodulated binary sequence as a replica signal with the modulator of the same system as the demodulator. Then, the GW subtracts the replica signal from the accumulated signals so that the GW can attempt to demodulate the subtracted signals iteratively. Because of the aforementioned assumptions, the subtracted signals can be shared among the demodulators of multiple systems. Simulation results show that our proposed method can significantly reduce packet error rate for the whole system compared to the conventional demodulation without the SIC at the GW of each system.