Channel Estimation Technology Study Based On LTE Wireless Communication System

With the rapid development of mobile communication technology, a new technology named long term evolution (LTE) was proposed, which was used to satisfy the requirement of high quality for a mobile communication system in the future. The advantages of LTE system are high data rates, high spectral efficiency and large cell coverage and so on. At the same time, because the channel estimation is a key technology for realizing the reliability of wireless communication systems, so researching on the channel estimation technique in LTE system is a very great significance job.In this paper, we were mainly research on the channel estimation algorithms for the uplink and downlink of the LTE system. First, make a brief introduction for the background of the LTE project why it’s proposed, and the characteristics of the LTE system, then discussed significance of this paper and current academic research. As followed, we discussed the radio channel which is a very important factor in wireless communication systems, including the propagation characteristics of radio channel, two common fading distributions and two common radio channel models (Clarke and Jakes channel model).After that, introduced the channel estimation technology in OFDM (Orthogonal Frequency Division Multiplexing) system, analyzed the classifications of the pilot patterns, then we mainly discussed four different channel estimation algorithms, which are LS algorithm,MMSE algorithm,LMMSE algorithm and SVD-LMMSE algorithm. And three common interpolation algorithms which are linear interpolation algorithm, Gaussian interpolation algorithm and DFT interpolation algorithm are also introduced.As the most important part of this paper, in chapter 4 and 5 we mainly focus on the channel estimation algorithms design for the uplink and downlink of the LTE system. First we introduced the basic parameters in LTE physical layer, the key technologies (OFDM, OFDMA, MIMO, and so on) in the uplink and downlink and the inserted modes of the pilot signals. Then we designed the transmitting and receiving progresses of the uplink and downlink in physical layer based on the 3GPP TS 32.211-32.213.In the uplink of LTE system, the author proposed a modified channel estimation algorithm based on LS algorithm, which the main ideal is controlling the noise power where is in the length of CP or out of the CP.At the same time the author also consider two window functions to see whether they can influence the performance of algorithms; for the downlink, because the pilots are different, so we main consider the performance of interpolation algorithms, then the author also proposed a new algorithm based on DFT.At the end of the two chapters, we did the simulations for some traditional algorithms and the new proposed algorithms, and analyzed the performance of these algorithms. For the uplink we compared with LS, DFT, DFT+Oversampling and the proposed algorithm, and also compared these two window functions; while for the downlink we compared with LS, DFT and linear interpolation. Because the LS algorithms didn’t consider the influence of noise, from the results we can see that the performance of these modified algorithms is better than LS algorithm. At the same time, these two algorithms have lower complications, so we can use them in the real communication systems.Finally, the author summarized the paper, and forecasted the prospects of further study in the future.