Energy-Efficient and Reliable IoT Access Without Radio Resource Reservation

One of the major challenges for Internet-of-Things applications is that existing cellular technologies do not support uplink IoT traffic in an energy-efficient manner. There are two principal ways serving traffic: grant-based (i.e., scheduled) and grant-free random access). Grant-based access provides fine-grained control reliability latency at cost energy consumption required signaling. Grant-free removes signaling overhead looser performance terms latency. However, a precise analysis reliability, (GFA) largely missing. This article focuses on GFA-type protocol, which device transmits several packet replicas, asynchronously with respect to other devices. Using stochastic geometry, we derive closed-form expressions delay, consumption, can be used identify tradeoffs among these parameters. In order improve develop receiver leverages timing frequency offsets devices facilitate resolution collisions. complemented by per-device adaptive scheme controls number transmitted replicas. The evaluation confirms validity potential proposed solution, identifying operating regions GFA outperforms access.