An Experimental End-to-End Delay Study of a Sub-1GHz Wireless Sensor Network with LTE Backhaul.

This paper describes an experimental study of network access delay from the end device to the cloud over a network based on Sub 1GHz and LTE based network which may find many practical Internet of Things (IoT) applications when network response time is key and must be closely assessed. For this reason, the authors have built a test-bed using a low cost and ease of deployment wireless sensor network (WSN) based on the IEEE802.15.4g standard that is connected to an LTE modem, providing connectivity to a server in the cloud. The test-bed is used to measure end-to-end packet transfer time from the wireless IoT device to the cloud server, also providing a delay breakdown for every segment of the network. The presented results show the delay performance of the IoT network architecture under varying values of the IoT device periodic reporting time. While the operation modes of the WSN do not significantly affect the network latency, the LTE backhaul connectivity introduces some delay variability, which depends on the IoT device periodic reporting time and other factors. By making use of these results the application designer can estimate the achievable network latency and make sure that the IoT application requirements are met.