Abstract
A recursive maximum-likelihood (RML) algorithm for channel estimation under rapidly fading channel and colored noise in a multicarrier code-division multiple-access (MC-CDMA) system is proposed in this paper. A moving-average model with exogenous input (MAX) is given to describe the transmission channel and colored noise. Based on the pseudoregression method, the proposed RML algorithm can simultaneously estimate the parameters of channel and colored noise. Following the estimation results, these parameters can be used to enhance the minimum mean-square error (MMSE) equalizer. Considering high-speed mobile stations, a one-step linear trend predictor is added to improve symbol detection. Simulation results indicate that the proposed RML estimator can track the channel more precisely than the conventional estimator. Meanwhile, the performance of the proposed enhanced MMSE equalizer is robust to the rapidly Rayleigh fading channel under colored noise in the MC-CDMA systems.
Highlights
The direct-sequence code-division multiple-access (DSCDMA) technique has already been successfully implemented for third generation (3G) mobile communication systems [1,2,3]
The most important contribution of the proposed method is that the channel impulse response (CIR), the parameters of colored noise, and the power of the driving noise in the MC-CDMA systems can be simultaneously estimated in real time
In the 2D pilot-symbol-aided channel estimation [12], the spaces between pilots in the time domain are chosen according to coherence time Tc ≈ 9/16π fd [32] if the coherent time is defined as the time over which the correlation function is above 0.5
Summary
The direct-sequence code-division multiple-access (DSCDMA) technique has already been successfully implemented for third generation (3G) mobile communication systems [1,2,3]. The frequency-domain channel-estimation methods in the MC-CDMA systems will fail if the channel contains colored noise It is because the colored noise can be considered as a white noise in each subchannel but with different power. A channel-estimation algorithm for MC-CDMA systems under colored noise is proposed in this paper. It is derived based on the recursive maximum likelihood (RML) algorithm. It can jointly estimate the parameters of channel and colored noise in the time domain. The most important contribution of the proposed method is that the channel impulse response (CIR), the parameters of colored noise, and the power of the driving noise in the MC-CDMA systems can be simultaneously estimated in real time. AT denotes the transpose of A, and AH denotes the Hermitian of A. denotes the circular convolution
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