An adaptive patterned-subcarrier allocation algorithm for low-complexity multiuser OFDM system

In this paper, an adaptive patterned-subcarrier allocation algorithm is proposed for the enhancement of system capacity and low-complexity implementation of subcarrier identification and selection (SIS) process of multiuser OFDM systems. Although an adaptive multiuser subcarrier allocation algorithm can increase the overall system capacity, there is computational inefficiency in the SIS process of conventional receiver because a N-point FFT (N-FFT) is used even for a user who uses only K subcarriers, where K < N. By providing patterns in the adaptive subcarrier allocation algorithm, however, the computationally efficient implementation of SIS process is achieved by a selected-subcarrier FFT (SSFFT) method that decomposes the sub-matrix consisting of the allocated subcarriers into the multiplication of smaller-point FFTs and the linear transition matrixes. Therefore, high system capacity and low-complexity implementation of SIS can be achieved simultaneously by the proposed algorithm. Simulation results demonstrate that the overall system capacity of the proposed algorithm is much larger than that of a fixed subcarrier allocation algorithm and closes to that of adaptive subcarrier allocation algorithm.