Study on MAC Protocol of LoRa Network Hidden Terminal Based on BTMA

The emergence of low power wide area network(LPWAN) technology allows for longer-distance communication while minimizing power consumption and reducing transmission costs.LoRa(long range) technology,as a standout in this field,is highlyfavored in both industrial and academic circles due to its long-range capabilities,low power consumption,high capacity,strong anti-interference,and high reception sensitivity.However,the widely used ALOHA-based LoRaWAN protocol in the industry struggles to effectively address severe data packet collisions resulting from the massive access of terminal devices to the LoRa network,as well as the hidden terminal problem caused by the LoRa CAD(channel activity detection) feature.This paper proposes a BTMA(busy tone multiple access)-based MAC protocol for LoRa networks,known as the BT-MAC protocol.This protocol leverages LoRa’s high reception sensitivity,with the gateway using “busy tone” beacons to inform each node of the gateway’s operational status,thereby reducing the transmission of invalid packets.Simultaneously,nodes maintain a logical channel matrix with “busy tone” information and local information.By employing an optimal channel selection algorithm,nodes select the best logical channel for transmission,reducing collisions among uplink data packets from end nodes.This effectively mitigates the hidden terminal problem and congestion in LoRa networks.A LoRa network MAC protocol testing platform is built to test the effectiveness of BT-MAC.Extensive concurrent experiments and energy consumption tests are conducted in both indoor and outdoor environments.The experimental results show that the throughput of the BT-MAC protocol is 1.6 times that of the LMAC-2 protocol and 5.1 times that of the ALOHA protocol.Additionally,its packet reception rate is 1.53 times that of the LMAC-2 protocol and 17.2 times that of the ALOHA protocol..The average energy consumption per packet is approximately 64.1% of that of the LMAC-2 protocol and 14.2% of that of the ALOHA protocol.