Communication Energy and Protocol Considerations in IoT Deployments

In this paper, we experimentally evaluate the impact of protocol features at the transport and application layers on the energy consumed in IoT devices. Our transport layer experiments with TCP and UDP over WiFi indicate that at distances less than 15m between the IoT device and gateway, the difference in energy used by the different transport protocols is not too significant, as long as the number of messages exchanged does not grow significantly. However, adding application layer features through additional message exchanges comes with a significant energy cost. For example, adding DTLS to CoAP is 4x more expensive than using AES with CoAP. In addition, if services at one layer impose a burden on other layers, it may result in significant increase in energy use. We conclude that in an IoT environment, it may be preferable to increase packet sizes rather than number of messages when feasible. Additionally, careful consideration should be given to adding features at a layer if it results in increased energy consumption at another layer.