Performance Evaluation of Bit Loading, Subcarrier Allocation, and Power Control Algorithms for Cellular OFDMA Systems

We consider the problem of radio resource allocation for QoS support in the downlink of a cellular OFDMA system. The major impairments present are co-channel interference (CCI) and frequency selective fading. The allocation problem involves assignment of base stations, subcarriers and bits, as well as power control, for multiple users. We evaluate the performance of a three-stage, low-complexity, heuristic algorithm, which allows to distribute radio resources among multiple users according to theirs individual QoS requirements, while at the same time maintaining the QoS of already established links in all co-channel cells. The evaluation includes checking system operation for various conditions described by different: a) delay spread, b) data rate required by a single user and c) path loss. It is shown that the proposed method is superior in terms of offered traffic and blocking probability to classical method based on FDMA with power control. Also, the performance of our scheme increases in highly frequency selective environment, disastrous for classical fixed schemes, since our method benefits from multiuser diversity.