Reserch On Channel Estimation In Lte System

In recent years, with the rapid development of the mobile communication systems, increasing application requirements lead to more and more pressing need for the spectrum resource, which raise higher request for the mobile telecommunication techniques, and then as the transition from the3G mobile communication criteria (e.g. TD-SCDMA, WCDMA) to the4G criteria, the LTE (Long Term Evolution) came into being. In order to promote the system capacity and increase the spectrum usage ratio, the MIMO and OFDM are adopted as the key techniques solution for the physical layer of the LTE system. However, how well these techniques perform largely depend on the performance of the channel estimation. For the channel interference exist, correct signal demodulation requires channel compensation at the receiver.The paper derived from the cooperation project between laboratory and some company, and the author joined in part of the research work, mainly responsible for research and simulation implementation for channel estimation in LTE PUCCH. In this paper, we pursue an effective and feasible channel estimation scenario for the LTE PUCCH. At the beginning of this paper, network architecture and knowledge of the physical layer in the LTE system were introduced, including frame structure, pilot pattern, slot structure and basic physical resource etc., and then we analyzed the theory of the OFDM and SC-FDMA technique. Understanding the wireless channel’s mechanism and setting up effective channel model are very vital for the evaluation of the channel estimation technique. In order to go for the wideband mobile communication system, we adopted the Extended Vehicular A (EVA) channel model, which is suitable to evaluate harsh environment of LTE performance. Then we did theoretical analysis on LS、 MMSE、 DFT algorithm.We also research on detection algorithm.Finally,improved channel estimation and detection methods for PUCCH are exploited.As the PUCCH(the physical uplink control channel) of LTE(Long Term Evolution), PUCCH plays an important role to carry vital information to the evolved-Node-B(eNB).For example the Hybrid-ARQ(HARQ) ACK/NACK,which are corresponding to the downlink assignment and CQI(channel quality information) for resource allocation.But the PUCCH is a narrow-band channel,which is easily to be influenced by inter-user interference especially when timing errors and near-far problem is severe.The improved receiver use the complex exponential functions for channel estimation and MMSE data detection.Therefore it is robust to timing errors and near-far problem.The pilot structure is also changed to reduce the complexity of joint channel estimation.Simulation results illustrates that the improved receiver breaks the error floor encounted in the single user receiver.