Sensitivity of random phase error and frequency offset on uplink performance of MC-CDMA
조동균, 김남수, 박윤옥 · 한국통신학회논문지 · 2002
Performance degradation of MC-CDMA with frequency offsed and random phase error is analyzed for the uplink in frequency selective slowly Rayleigh fading channel. The frequency offset denotes the frequency difference between oscillator of transmitter and oscillator of receiver, and random phase error means the phase difference between received carrier and carrier estimated by PLL loop of receiver. In this research, the good approximation methods(LLN, CLT) are adopted to derive the optimum average BER of system by means of analytic approach, and linear approximation is also applied to estimate the statistic of random phase error. From the analysis results, it is concluded that firstly, the smaller frequency offset, the greater degradation effect due to random phase error. Secondly, if the average loop SNR of PLL system is much larger that Ｅ_b/Ｎ_o, the effect of random phase error can be neglected regardless of combining techniques(EGC, MRC) and approximation methods as well as frequency offset. Specially, it is shown that when an average loop SNR is 20dB larger than Ｅ_b/Ｎ_o ,the performance difference compared with case of perfect phase estimation is within 1dB. Thirdly, MRC method outperforms EGC method in uplink.