Research on the Performance for Chase Combining HARQ Scheme in TD-SCDMA

The rapid relative displacement between mobile terminal and base station will bring big frequency offset value, as a result, the receiver can not achieve the correct signal demodulation. Therefore, an accurate frequency offset estimation can increase the reliability sensibly during the transmission service. Based on TD-SCDMA uplink, this paper elaborates the principle of doppler frequency offset estimation, and a "dual rectification" scheme is proposed, in which the midamble sequence is firstly used to estimate frequency offset, the rectified user data is subsequently demodulated and used to estimate frequency offset. It is found from the emulation that under the same condition of SNR, lower bit error rate is achieved at receiving end by using the algorithm and so the communication quality of system is well improved.