The Research Of Channel Estimation In LTE Uplink

The performance of the system is mainly affected by the wireless channel in theWireless Communication System. The signals are transmitted from the transmitting end toreceiving end and the amplitude and phase of the received signals are susceptible to haveserious distortion. It is hard to recover the transmitted signals from the received signalsaccurately. So the receiving end usually adopts channel frequency domain equalization(coherent demodulation) to resist the effects of fading channel. Practical frequency domainequalization systems generally require knowledge of the channel. The research of channelestimation is necessary.This paper mainly studies the channel estimation of LTE (Long Term Evolution) uplink.Because of the development of Broadband wireless system,3GPP (the Third GenerationPartnership Project) proposed an new communication technology—LTE which is an attractivealternative for the4G (4rd Generation) mobile communication system.3GPP prescribesOFDMA for downlink transmission and SC-FDMA for uplink transmission in the LTEcellular system in order to obtain low PAPR (Peak to Average Power Ratio). There are twokinds of LTE system，this paper is based on FDD-LTE.The main contents of this paper are arranged as follows:(1) Firstly, it introduces the principle of SC-FDMA system from the signal processingand the time domain representations of signal under different subcarrier mapping nodes. Italso makes comparisons in terms of SER (Symbol error rate) and PAPR under differentsubcarrier mapping nodes.(2) This paper presents three basic fading nodes in wireless channel: the large scalefading thanks to path loss and the middle scale fading for shadowing and the small scalefading because of the multipath effect and Doppler frequency shift. It also studies thecharacteristics of the small scale fading in detail and gives the channel description parametersso as to eduction classification index.(3) The pilot and the pilot pattern in LTE uplink is discussed in this section. On this basisthe traditional channel estimation techniques such as LS and LMMSE and the commonchannel estimation methods of the data are also told. The section discusses the channelestimation algorithm of the frenquency domain in LTE uplink completely. (4) In the end, it researchs the channel estimation of LTE uplink in transform domain.For the sake of the property of DFT channel estimation in low SNR (Signal to Noise Ratio),this paper proposes a modified channel estimation of DFT. The channel estimation based onDWT is also discussed in this paper, a regulation parameter is introduced to soft thresholdfunction. The property of the modified soft threshold function is improved in contrast to theconventional soft threshold function.