Rate-Splitting Multiple Access for URLLC Uplink in Physical Layer Network Slicing With eMBB

In this paper, we investigate the problem of heterogeneous service coexistence in the scope of 5G and beyond (B5G) networks, where multiple ultra-reliable low-latency communication (URLLC) and enhanced mobile broadband (eMBB) users are connected to a common base station (BS), sharing physical network resources. In contrast to the orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA) usually adopted in literature, in this work we employ rate splitting multiple access (RSMA) for URLLC transmission, where a URLLC device splits its message into two sub-messages with partial transmission power, which are potentially recovered at the BS by means of successive interference cancellation (SIC). To study the performance of such methods in the presence of eMBB users, we consider both orthogonal and non-orthogonal network slicing approaches to share the network resources between heterogeneous user profiles with diverse requirements. As a result, we show that, in general, RSMA presents an improved performance in terms of sum-rate and reliability, even when transmitting concurrently with eMBB users. Finally, our results also show that the URLLC sum-rate can be increased by properly adjusting the rate splitting factor based on the average signal-to-noise ratio (SNR), not being necessary instantaneous channel state information (CSI).