Weighted Least Square Based Iterative Channel Estimation for Uplink NOMA-OFDM Systems

Non-orthogonal multiple access (NOMA) scheme has been recognized as a promising candidate for future generation networks. In order to achieve a superior spectral efficiency, the orthogonal frequency division multiplexing (OFDM) technique can be combined with the NOMA scheme. The hybrid OFDM based NOMA system, however, needs accurate information of the channel for optimum performance. In this paper, an efficient weighted least square based iterative algorithm is developed for channel estimation in NOMA-OFDM systems. The channel estimation is achieved by deriving an iterative linear minimum mean-square-error (LMMSE) algorithm, with a weighted least square algorithm as the initialization point. The proposed channel estimation for NOMA-OFDM systems is developed while considering an imperfect successive interference cancellation (SIC) scenario. Simulation results are presented to show the effect of the proposed channel estimation scheme on the NOMA-OFDM system. The performance of the iterative channel estimation algorithm is analyzed in both fast fading and slow fading multipath channels.