Equalization for OFDMA Systems Exploiting Unused Subchannels

In orthogonal frequency division multiple access (OFDMA) systems, the cyclic prefix (CP) length needs to be no less than the longest channel delay spread of many users, reducing bandwidth efficiency more significantly than in single user OFDM systems. We propose a novel receiver for OFDMA systems with an insufficient CP, exploiting the unused subchannels for a user. With the aid of computer simulations, we demonstrate that the proposed equalization method is superior to the conventional equalization method using a time domain channel shortening filter in terms of the achievable SNR and the error performance