On the Effect of Feedback Delay in the Downlink of Multiuser OFDM Systems

Allocating wireless resources often relies on the accurate feedback of channel state information (CSI). In this paper, we study how strongly a multiuser OFDM downlink with single-cell scheduling and channel estimation suffers from feedback delay. Unlike previous work, we study this degradation for optimal joint power and rate allocation under fairness constraints. After providing an optimal, gradient-based scheduling algorithm we compare the perfect case to the performance with delayed CSI. We find that adjusting the scheduler's fairness cannot mitigate the strong performance loss due to feedback delay while simple linear channel prediction is a powerful tool to do so.