| Single-Carrier Frequency Division Multiple Access(SC-FDMA)has a low Peak-to-Average Power Ratio(PAPR)compared to Orthogonal Frequency-Division Multiple Access(OFDMA),which is suitable for mobile communication uplink.When the traditional SCFDMA system realizes the channel estimation based on pilot assisted,additional spectrum resources are allocated to the pilot to realize the multiplexing of pilot and data,which reduces the spectrum efficiency and transmission rate.In order to improve the spectral efficiency of SC-FDMA system,the research on the pilot configuration under the system and the corresponding channel estimation method has been widely concerned.There have been certain research results on the pilot configuration method to improve the spectrum efficiency in the SC-FDMA system.According to the current pilot configuration method based on SCFDMA system,further research is carried out in this thesis.The specific research contents include:In view of the problem of poor channel estimation performance caused by the traditional pilot position selection scheme when the SC-FDMA system uses Frequency Domain Pilot Multiplexing Technique(FDPMT)to improve the spectrum efficiency,this thesis proposes an improved Pilot Position Selection(PPS)scheme,the corresponding pilot frequency selection scheme,and a corresponding pilot detection scheme combined with the existing Pilot Position Detection(PPD)method.The improved PPS scheme at the transmitting end selects the initial pilot position of each transmission block based on the original PPS scheme,and reorders the transmission block positions according to the initial pilot position to obtain relatively uniformly distributed interpolation frequency points,which achieves the purpose of improving the channel estimation performance.Then the ZC root sequence with small cross-correlation is selected as the pilot sequence,which carries the index position information of the sorted transmission block.The receiving end first uses the good autocorrelation characteristics of the ZC sequence to perform pilot detection on the current transmission block and obtain the position information of the transmission block,and then performs channel estimation and links the initial channel estimation results of multiple transmission blocks in the coherent time for interpolation.Finally,the transmission block is placed in the initial position and then equalized.The simulation shows that when the pilot overhead is small and the pilot interval does not satisfy the Nyquist sampling theorem,the improved PPS scheme can reduce the Normalized Mean Square Error(NMSE)of channel estimation in frequency selective fading channels and improve the Bit Error Rate(BER)performance of the system.Aiming at the problem of frequency domain data distortion when using FDPMT in SCFDMA system,and the limited ability of frequency domain distortion data recovery when signal reconstruction adopts hard decision in coding system,this paper proposes an improved signal reconstruction algorithm.The improved signal reconstruction algorithm first performs a soft decision on the equalized time domain signal,and then improves the accuracy of the time domain signal through decoding,coding and symbol modulation,thereby improving the problem of frequency domain data distortion,and finally enhances the performance of signal reconstruction through iteration.The simulation results show that the improved signal reconstruction algorithm can improve the BER performance of the coded FDPMT system. |
