Low-complexity Equalization of OFDM systems using Krylov subspace methods over Doubly Selective Channels

Low complexity equalization with LSRQ and GMRES algorithm is compared with traditional equalization methods. As the next generation technologies like LTE and WiMax have a large number of subcarriers the traditional equalization methods like MF, ZF, MMSE, VBLAST, and SAGE which require matrix inversion become highly complex in time and consume a lot of time to equalize the received signal. An alternative approach that involves solving the system of linear equations using Krylov subspace based methods like LSQR and GMRES is hence employed to equalize the signal in Doubly Selective channels and their performance is compared to the traditional methods. It is found that LSQR algorithm gives performance comparable to MMSE equalization but not as well as VBLAST and SAGE which give a performance gain of about 4.0477 dB and 4.5593 dB at 30dB SNR; trading accuracy for speed. Keywords— Doubly Selective Channel, OFDM, Krylov Subspace methods, Equalization, VBLAST, SAGE, GMRES, LSQR