Instituto de Telecomunicações, 3810-193 Aveiro, Portugal.
ISEL-Instituto Superior de Engenharia Lisboa, Instituto Politécnico de Lisboa, 1959-001 Lisbon, Portugal.
Sensors (Basel). 2022 Jul 14;22(14):5260. doi: 10.3390/s22145260.
LoRa is one of the most prominent LPWAN technologies due to its suitable characteristics for supporting large-scale IoT networks, as it offers long-range communications at low power consumption. The latter is granted mainly because end-nodes transmit directly to the gateways and no energy is spent in multi-hop transmissions. LoRaWAN gateways can successfully receive simultaneous transmissions on multiple channels. However, such gateways can be costly when compared to simpler single-channel LoRa transceivers, and at the same time they are configured to operate with pure-ALOHA, the well-known and fragile channel access scheme used in LoRaWAN. This work presents a fair, control-based channel hopping-based medium access scheme for LoRa networks with multiple single-channel gateways. Compared with the pure-ALOHA used in LoRaWAN, the protocol proposed here achieves higher goodput and fairness levels because each device can choose its most appropriate channel to transmit at a higher rate and spending less energy. Several simulation results considering different network densities and different numbers of single-channel LoRa gateways show that our proposal is able to achieve a packet delivery ratio (PDR) of around 18% for a network size of 2000 end-nodes and one gateway, and a PDR of almost 50% when four LoRa gateways are considered, compared to 2% and 6%, respectively, achieved by the pure-ALOHA approach.
LoRa 是最突出的 LPWAN 技术之一，因为它具有支持大规模物联网网络的合适特性，因为它可以在低功耗下提供远程通信。后者主要是因为终端节点直接向网关发送信号，而在多跳传输中不会消耗能量。LoRaWAN 网关可以成功地在多个频道上同时接收传输。然而，与更简单的单通道 LoRa 收发器相比，这样的网关可能会比较昂贵，同时它们被配置为使用纯 ALOHA 操作，这是 LoRaWAN 中使用的著名且脆弱的信道接入方案。这项工作提出了一种公平的、基于控制的信道跳频的多单通道网关 LoRa 网络介质访问方案。与 LoRaWAN 中使用的纯 ALOHA 相比，这里提出的协议可以实现更高的吞吐量和公平性水平，因为每个设备都可以选择最适合的信道以更高的速率传输，并且消耗更少的能量。考虑到不同的网络密度和不同数量的单通道 LoRa 网关的几个仿真结果表明，与纯 ALOHA 方法相比，我们的方案能够在 2000 个终端节点和一个网关的网络规模下实现约 18%的分组投递率 (PDR)，而当考虑四个 LoRa 网关时，PDR 几乎达到 50%，而纯 ALOHA 方法分别为 2%和 6%。
