Performance Improvement of LoRa Modulation with Signal Combining

Low-power long-range (LoRa) modulation has been used to satisfy the low power and large coverage requirements of Internet of Things (IoT) networks. In this paper, we investigate performance improvements of LoRa modulation when a gateway is equipped with multiple antennas. We derive the optimal decision rules for both coherent and non-coherent detections when combining signals received from multiple antennas. We present expressions of the symbol/bit error probabilities of both the coherent and non-coherent detections in AWGN and Rayleigh fading channels, respectively. Moreover, we also propose an iterative semi-coherent detection that does not require any overhead to estimate the channel-state-information (CSI) while its performance can approach that of the coherent detection. Simulation and analytical results show very large power gains provided by the use of multiple antennas for all the detection schemes considered.