Slotted ALOHA and CSMA Protocols for FMCW Radar Networks

Abstract: We study medium access in FMCW radar networks. We assume that all the radars use same parameters, e.g., chirp duration, chirp slope, cutoff frequency, number of chirps per packet, etc, and propose and analyze slotted ALOHA and CSMA protocols to mitigate narrowband interference. We define a notion of throughput to quantify the performance of the proposed protocols. In the case of ALOHA, we analyze interference probability and throughput as functions of the system parameters. We observe that interference probability and throughput may behave differently than in wireless communication networks. For instance, if the number of chirps per packet is larger than one, the interference probabilities may be smaller for higher transmission rates. We define a medium sensing procedure, referred to as clear channel assessment (CCA), as a part of the proposed CSMA, and also define CCA success and failure events. In CSMA, the radars transmit only after a successful CCA. We study, CCA success probability, interference probability and throughput as functions of the system parameters. We observe that, unlike wireless communication networks, using the highest possible attempt rates may maximize throughput in few network scenarios. We perform an extensive simulation to verify our analytical results and to compare slotted ALOHA and CSMA. We observe that CSMA outperforms ALOHA in all realistic scenarios.