Dynamic resource management in the fourth generation wireless systems

In this text, we consider the problem of fair scheduling in the downlink of orthogonal frequency division (OFDM) systems. Based on the proportional fair scheduling algorithm proposed in the CDMA/HDR, we present three schemes to manage the parallel subscribers in the OFDM system to utilize the time selectivity and frequency selectivity. Subcarriers in a slot are divided into several nonoverlapped subbands, which are the scheduling objects. The first scheme is that every subband is placed with a scheduler and the average rates are updated independently; the second scheme transfers the two-dimensional channel resource into one-dimension equivalent channel, and then schedule the resource like in HDR systems; for the third scheme, the users contend every subband in a same slot using one scheduler without updating the average rates, after finishing the slot, the average rates are updated together. Compared to the first scheme, the third one has the least complexity and its performance degrades a bit. It is shown that system throughput is improved by 40%∼100%, the appropriate number of subbands is 16∼32 and scheme 3 is an appropriate choice for practice systems.