Opportunistic cluster heads for heterogeneous networks combining LoRa and wake-up radio

Connected devices using LoRaWAN standard achieve low energy consumption by leaving their sleep state only to send their data. However, this technique induces a high downlink latency that is not compatible with applications that require a low latency such as remote control or actuatortype applications. To overcome this trade-off between power consumption and latency, we propose in this paper a MAC protocol design leveraging a heterogeneous network architecture composed of both long-range and ultra low power short-range wake-up radios. The proposed protocol does not change the LoRaWAN standard but at each uplink, a node operating in LoRa class A becomes an opportunistic cluster head and thus the gateway takes the opportunity of its receive windows to send commands intended to other nodes. Thanks to this novel network architecture and appropriate MAC protocol, the latency can be reduced while maintaining or even increasing the energy efficiency. Considering clusters of ten nodes, gains of 3.33 and 2.11 can be achieved in latency and power consumption, respectively.