Subspace Decomposition for Channel Estimation in SC-FDE Systems

Single carrier frequency division multiple access (SC-FDMA), a multiple user access scheme based on the single carrier frequency domain equalization (SC-FDE) technique, has been proposed for the uplink in fourth generation (4G) mobile communications. SC- FDE requires reliable channel estimates to maintain an acceptable bit error rate (BER) performance. Much research focuses on the use of pilot symbols which reduces the spectral efficiency of SC-FDE systems. In this paper, we propose a subspace decomposition approach for semi-blind channel estimation in SC-FDE systems as a means to reduce or eliminate the need for pilot symbols and increase their overall spectral efficiency. Simulation results show that, under the conditions presented in this paper, a BER of 10^-3 can be achieved with a power loss of roughly 1 dB compared to a system with perfect channel estimates. This result is achieved with channel estimates that have a normalized mean square error (NMSE) less than 1%.