Resource allocation in OFDMA downlink system for QoS requirement of real time service

This paper investigates the resource allocation problem under time-variant channel. The assumption is that the base station has the perfect channel information. In former researches, resource allocation is done under the consideration of static channel and can hardly deal with time-variant channel. So the allocation algorithm performs badly in fading channels (especially in fast fading channels). To solve this problem, allocation must be updated frequently, which is very CPU consuming. So we derive the Power Redundancy method that affords more power than needed to each subcarrier and combats more fade. Computer simulation shows that by using such Power Redundancy method, the Unsatisfied Probability can be improved and the spectrum efficiency degrade little while the update interval becomes longer. By using 2dB power redundancy in fast fading surroundings, the update interval could be 5 times longer than without power redundancy to achieve 5 % Unsatisfied Probability. And in slow-fading channel, the frequency efficiency is improved under the same Update Interval.