Performance of Spatially Diverse URLLC and eMBB Traffic in Cell Free Massive MIMO Environments

5G networks are designed to support both high data rate eMBB services, and low-latency high-reliability URLLC services. Multiplexing these two services on the same wireless frequency band leads to a challenging radio resource allocation problem due to their heterogeneous requirements. Usually, multiplexing is based on the puncturing mechanism by URLLC traffic at the expense of the eMBB throughput's reduction. In this paper, we investigate the potential of cell-free massive MIMO to multiplex URLLC and eMBB traffic by exploiting the sole spatial diversity through network slicing. We define a theoretical framework to evaluate the system's performance, based on closed-form expressions for the spectral efficiency and the throughput of eMBB and URLLC services in this new asset. We show that by design the cell-free massive MIMO architecture can support such heterogeneous services without relying on sophisticated interference management techniques or pilot assignment schemes, while guaranteeing their specific QoS requirements.