On the Coexistence of LoRa- and Interleaved Chirp Spreading LoRa-Based Modulations

Abstract

LoRa has recently established itself as one of the leading low power wide area networks (LP-WAN) technologies. LoRa modulation is a chirp spread spectrum-based modulation. Cyclic shifts of a linearly increasing chirp signal constitute a multi-dimensional space for nominal LoRa communication. LoRa networks are typically capacity-limited due to the adopted ALOHA-based medium access scheme. One approach to enhance the network capacity could be by introducing new LoRa-based communication channels that exhibit good cross-correlation properties with respect to the nominal LoRa chirp signals. In our recent work, Interleaved Chirp Spreading LoRa (ICS-LoRa) has been introduced as a new multi-dimensional space generated from interleaved versions of the nominal LoRa chirp signals. ICS-LoRa capable transmitters have used the extended multi-dimensional space to introduce one additional bit within each transmitted chirp signal. In this paper, we investigate the possibility of deploying ICS-LoRa to rather create a new overlapping logical network that co-exists with the nominal LoRa network. This would have the potential of increasing the overall system capacity by up to 100%. Accordingly, we specifically focus on studying the inter-network interference between the nominal LoRa and the ICS-LoRa logical networks at different Signal to Interference Ratio (SIR) and at different Signal to Noise Ratio (SNR) scenarios. Simulation results indicate that ICS-LoRa interference has mild effects on the BER performance of nominal LoRa demodulation and vice versa. Moreover, we demonstrate that the favorable cross-correlation characteristics create a better chance for successful interference cancellation of inter-network interfering signals. This opens further room for enhancing the overall system capacity.