A semi-blind time domain equalization of SCFDMA signal

This paper proposes a new semi blind equalizer structure for Single Carrier FDMA (SC-FDMA)[1][2]. SC-FDMA is currently adopted for mobile radio uplink communications in 3G Long Term Evolution (3G LTE). In this system, a Zero-Forcing(ZF) equalization is performed thanks to the addition of a Cyclic Prefix (CP), as in OFDM system, and pilots regularly inserted for channel estimation which lead to the useful throughput degradation. To reduce this degradation we propose in this paper a new structure of semi blind equalizer in time domain based on [3]. A ZF criterion and a simple Minimum Mean Square Error (MMSE) are combined to reduce the number of pilots inserted and to outperform the ZF optimum mean square error. This equalizer is shared in two parts: The filtering itself which is a linear time domain filtering performed before any demodulation device in the receiver side, and the criterion algorithm performed in the time domain after user selection and demodulation which is sometimes a ZF criterion and sometimes MMSE criterion. The results are very convincing both in terms of Mean Square Error and in throughput gain compared to the performances of Zero-Forcing technique used in literature.