Reliability and Latency Performance of Multi-Connectivity Scheduling Schemes in Multi-User Scenarios

Industrial applications such as closed-loop control require communication systems which provide low latency and high reliability. Current wireless communication systems are not able to fulfill all strict requirements posed by industrial applications. Multi-Connectivity (MC), i.e. using multiple communication paths at the same time, is a promising measure to enhance latency and reliability of wireless communication systems. Different scheduling schemes, i.e. Load Balancing (LB), Packet Duplication (PD) and Packet Splitting (PS), can be utilized to distribute packets over multiple paths. After having identified the impact of link homo- and heterogeneity, SNR regime and link correlation in previous work, the impact of network load and capacity on the different MC scheduling schemes is evaluated in this paper. Measurements in private LTE and WiFi 802.11ac networks are performed for different number of users. Our evaluations support that network load and capacity have a strong impact on latency and reliability performance of MC scheduling schemes. In low load scenarios, PD or PS achieve the best performance, for scenarios with low link correlation and high link correlation, respectively. In scenarios where the network load is close to the capacity limit on the other hand, LB provides the lowest latency and highest reliability. The capacity limit in the multiple user scenario strongly depends on the channel access scheme and its ability to deal with increasing number of users. The insights gained in this work can be used to develop dynamic MC schedulers that adapt the MC scheduling scheme based on SNR regime, link correlation and network load in order to achieve low latency and high reliability in scenarios with varying radio and network conditions.