Low-Complexity Demodulation for Interleaved OFDMA Downlink System Using   Circular Convolution
  In this paper, a new low-complexity demodulation scheme is proposed for interleaved orthogonal frequency division multiple access (OFDMA) downlink system with N subcarriers and M users using circular convolution. In the proposed scheme, each user's signal is extracted from the received interleaved OFDMA signal of M users by using circular convolution in the time domain and then fast Fourier transformed in the reduced size N over M. It is shown that the computational complexity of the proposed scheme for the interleaved OFDMA downlink system is much less than that of the conventional one. 
Hyun-Seung Joo, Kee-Hoon Kim, Jong-Seon No, and Dong-Joon Shin
cs.IT math.IT