Relaying Solutions For 5G-IoT Applications: A 3GPP Perspective

In the 5G and beyond era, the Internet of things (IoT) requires widespread coverage in highly dense and hard-to-reach areas. To achieve this, the use of relaying as an energy-efficient mechanism to assist mobile networks in serving the ubiquity and scale of IoT is being studied. While various relaying architectures and technologies have emerged in research and standardization, it is not yet clear which is best suited for IoT applications. In this article, we examine fundamental relay architectures and evaluate the suitability of user equipment (UE)-based relaying solutions and network-based relaying solutions for IoT applications. We analyze the relaying solutions in terms of radio aspects, such as connection establishment, protocol architecture, and resource allocation. Our findings suggest that even though the standardized layer-2-network-based relaying solution (e.g., integrated access and backhaul networks) may be better suited to handle large numbers of low-complexity, low energy-consuming devices with better interference management, any optimizations aimed at supporting IoT traffic will directly affect existing networks, such as the introduction of new control plane signaling over the Uu interface. Conversely, the standardized layer-3-UE-based relaying solution can be optimized for handling massive IoT relaying with minimal impact on existing networks, since the optimizations can be made on the PC-5 interface with a subdued effect on the Uu interface.