# Communication Protocol Design for IoT-Enabled Energy Management in a Smart Microgrid
The existing research papers have mostly investigated IoT-enabled smart energy systems at a conceptual level or from an application perspective. However, the effectiveness of IoT technology will also depend on the reliability and security features of other aspects in the communication model, e.g., the network and physical properties. From a communication technology perspective, different wired and wireless communication schemes have been adopted in smart grid applications. Though wired communication can offer stronger reliability and robustness, wireless communication technologies have more flexibility and less dependence on infrastructure [25]. As a result, wireless technologies are emerging as a popular solution in smart energy applications in the residential context. For example, ZigBee has been deployed for appliance monitoring and sensing applications due to its low power requirement as well as low cost. They can allow for a transmission range of less than 100 m, which is suitable for residential energy applications [26]. Wireless mesh networks have also been a popular choice for smart meter deployment, where each meter has the ability to route the energy consumption data to the nearby smart meters and form a mesh [27]. Though such technologies can enhance coverage, the implementation cost and complexity can be higher. More critical energy applications such as transmission and distribution network monitoring commonly rely on cellular infrastructure, such as LTE, 4G and 5G networks [28; 29]. Though they have a well-developed infrastructure that can be useful in accommodating energy applications, the infrastructure is shared with cellular applications involving voice and data usage. Another emerging technology for smart grid communications includes WiMax, which offers the appropriate designed security and backhaul connectivity mechanisms for critical applications [30]. However, the technology could not progress as expected due to a more widespread infrastructure provided by LTE and 5G networks. Though the aforementioned technologies have been widely used for smart grid applications, they need to be adapted to meet the requirements for IoT-enabled smart grid components. IoT applications heavily rely on low power wide area network (LPWAN) technologies, as it allows IoT devices to operate at a lower power (thus improving the battery life) and communicate over a wider area. It should be noted that in the context of local energy trading, the energy supply/demand balance is achieved within nearby households alone, which are usually within a few kilometres from each other. In this regard, the range offered by LPWAN technologies is appropriate for local energy trading applications. There are a number of LPWAN technologies that are currently being deployed in IoT applications. Some of these protocols operate over an unlicensed spectrum (e.g., LoRa and Sigfox), while others operate over the licensed band (e.g., Long-Term Evolution for Machine type communication (LTE-M) and Narrow Band IoT (NB-IoT)) [31]. Existing research in this domain has focussed on bit error rate (BER) analysis of LoRa technology [32], as well as latency, collision rate and throughput analysis [33]. Though LoRa and Sigfox protocols are widely used by IoT devices, the protocols suffer from efficiency issues due to collisions with interference signals and the resulting packet losses [34]. The authors in [35] have demonstrated that the coverage probability for LoRa networks decreases exponentially with an increase in the number of end devices due to the interference issue. Similar outcomes have also been presented in [36] for LoRa and Sigfox protocols through experimental setups in northern Denmark, where the authors reported a significant increase in failure rate due to external interference. To counter the interference problem, retransmissions for multiple times are usually adopted as a solution [37], which is often not suitable for smart energy applications that require low latency and high reliability.