# LMAC: Efficient Carrier-Sense Multiple Access for LoRa

Published in MobiCom'20, 2020

Recommended citation: Amalinda Gamage, Jansen Christian Liando, Chaojie Gu, Rui Tan, and Mo Li. "LMAC: Efficient Carrier-Sense Multiple Access for LoRa." In Proceedings of the 26th Annual International Conference on Mobile Computing and Networking, pp. 1-13. 2020. https://wands.sg/publications/full_list/papers/MobiCom_20_1.pdf

Current LoRa networks including those following the LoRaWAN specification use the primitive ALOHA mechanism for media access control due to LoRa’s lack of carrier sense capability. From our extensive measurements, the Channel Activity Detection (CAD) feature that is recently introduced to LoRa for energy-efficiently detecting preamble chirps, can also detect payload chirps reliably. This sheds light on an efficient carrier-sense multiple access (CSMA) protocol that we call LMAC for LoRa networks. This paper presents the designs of three advancing versions of LMAC that respectively implements CSMA, balances the communication loads among the channels defined by frequencies and spreading factors based on the end nodes’ local information and then additionally the gateway’s global information. Experiments on a 50-node lab testbed and a 16-node university deployment show that, compared with ALOHA, LMAC brings up to 2.2× goodput improvement and 2.4× reduction of radio energy per successfully delivered frame. Thus, should the LoRaWAN’s ALOHA be replaced with LMAC, network performance boosts can be realized.

@inproceedings{gamage2020lmac,