Efficient Subcarrier Allocation for Multiple Access in OFDM Systems

In this paper we propose a computationally effi- cient subcarrier allocation algorithm for a multiuser OFDM system suited for downlink and uplink transmission. The al- gorithm considers user-individual bitrate and power con- straints and allocates to each user the most appropriate subcarriers in a way that the total transmit power is mini- mized. The bit and power allocation for each user is done by a single-user bitloading algorithm on the base of this subcar- rier allocation. The performance of the proposed algorithm is compared to a near-optimum algorithm which is based on Lagrange optimization. It is found that the proposed algo- rithm is computationally much more efficient while is has very little performance degradation, in some situations it even achieves better performance. The execution time for the pro- posed algorithm is compared for different numbers of users and OFDM sizes with the near-optimum algorithm and is found to offer advantages of various orders of magnitudes.

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