Robust Proportional Fair Scheduling with Imperfect CSI and Fixed Outage Probability

Proportional fair (PF) scheduling is known to provide a balance between overall throughput maximization and fairness, by ensuring that users are served at one point in time, even if they experience poor channel conditions. In this regard, the PF scheduler accounts for the current channel state as well as for the throughput a user previously obtained. However, in slow fading scenarios with feedback delays the channel state information (CSI) known to the transmitter is outdated. Consequently, the transmission rates supported by the actual channel are only known imperfectly, which affects the scheduling as well as the rate adaptation, resulting in potential outages. While current schedulers typically ignore the CSI impairment, this work proposes a scheme which accounts for the variance of the CSI impairment and targets to achieve a fixed outage probability, referring to average delay constraints. Simulation results validate the advantages of the robust PF scheduling scheme when it is compared to non-robust solutions.