The Impact of Channel State Information Processing Delay in Optimally Scheduled OFDMA Networks

Dynamically assigning sub-carriers in the downlink of an OFDMA based cellular system has been shown to exhibit a high potential to combat co-channel interference in according systems. So far, related investigations have assumed up-to-date channel state information as input for the sub-carrier assignment mechanisms, omitting the fact that in most cases there is a significant delay between the time of channel state information acquisition and its usage for scheduling purposes. In this paper, we explore the cochannel mitigation performance of optimal sub-carrier allocation subject to the channel state information processing delay. We show that, compared to the random assignment case, large gains can be expected if sub-carriers are assigned dynamically, as long as the delay stays in reasonable bounds. Moreover, we investigate the additional usage of power masks on top of the optimized sub-carrier assignments and show that in this combination, there is hardly a chance for improvement due to power masking1.