Overlay transmission of sporadic random access and broadband traffic for 5G networks

Providing services to devices with varied rate, latency and energy consumption requirements is a major challenge for 5th Generation (5G) radio access technology. Overlay transmission or non-orthogonal multiple access, wherein multiple devices with same or different service requirements use the same time-frequency resources, may overcome the poor trunking efficiency of dedicated resource allocation. In this paper, we study the overlay of continuous packet transmission representative of broadband traffic and sporadic random access transmission representative of Internet of Things (IoT) traffic using basic information theoretical tools, and compare the resulting performance with that of dedicated resource assignment. Our analysis shows that overlay transmission can lead to improved data rate for the broadband traffic when the concurrent random access traffic is characterized by sporadic packet arrivals, tight timing constraints and low received Signal-to-Noise ratio (SNR). Significant performance gain is obtained in case the random access user is aware of the broadband user receive power at the base station; however, such gain can only be achieved in a limited SNR region. When such information is not available at the random access user, the achievable rate of the broadband user may be affected by the retransmissions due to packet failures; however, gains with respect to dedicated resource assignment still persist in case of sporadic packet arrival rate and tight timing constraint for the random access user.