UMTS FDD frequency domain equalization based on self cyclic reconstruction

In this paper, a new chip-level MMSE frequency domain equalizer (FDE) is investigated for the downlink frequency division duplex (FDD) mode in UMTS (Universal Mobile Telephone System). The multiple access interference (MAI) and inter chip interference (ICI) can be reduced at the chip level before despreading. For frequency domain equalization, the cyclicity of the received block signal needs to be reconstructed if neither cyclic prefix nor zero-padding are used at the transmitter. We exploit the relationship between the reconstructed part and the equalized signal itself and derive a self cyclic reconstruction scheme. Performance of the proposed MMSE-FDE is shown by computer simulations, compared with performance of FDE with perfect reconstructions. It is shown that the conventional time domain equalization can be implemented in the frequency domain, thus a multimode receiver that can handle both UMTS and OFDM systems in one equalization structure is feasible.