On the impact of multi-user traffic dynamics on low latency communications

In this paper we study the downlink latency performance in a multi-user cellular network. We use a flexible 5G radio frame structure, where the TTI size is configurable on a peruser basis according to their specific service requirements. Results show that at low system loads using a short TTI (e.g. 0.25 ms) is an attractive solution to achieve low latency communications (LLC). The main benefits come from the low transmission delay required to transmit the payloads. However, as the load increases, longer TTI configurations with lower relative control overhead (and therefore higher spectral efficiency) provide better performance as these better cope with the non-negligible queuing delay. The presented results allow to conclude that support for scheduling with different TTI sizes is important for LLC and should be included in the future 5G.