A Novel Efficient Resource Allocation Algorithm for Multiuser OFDM Systems

The key issues in the design of a multiuser orthogonal frequency division multiplexing (MU-OFDM)-based systems are the subcarrier, power, and the bit allocation. Conventionally, the sum capacity of MU-OFDM is maximized when each subchannel is assigned to the user with the best channel-to-noise ratio for that subchannel, with power subsequently distributed by water-filling algorithm. In this paper, several adaptive resource allocation techniques for multiuser OFDM system under various constraints are analyzed. During the analysis, certain techniques strictly maintain proportional rate among users to achieve high quality-of-service (QoS). Few other techniques maximize the sum capacity by efficiently utilizing the unused subchannels, but it fails to maintain the proportional rate among users and thus poor QoS. To maintain target bit error rate (BER), bit allocation algorithms are also analyzed in this paper. In the proposed algorithm, however, the water-filling power allocation is not fully performed; instead, by adjusting only the water-filling level, the transmit power and number of bits are allocated with low computational complexity. Assuming knowledge of the instantaneous channel gains for all users, a resource allocation scheme for a MU-OFDM-based system to simultaneously provide dual services with different QoS is proposed. The proposed algorithm yields less signal to noise ratio (SNR) to achieve same sum capacity of the existing algorithms.