Estimate Based On The LTE OFDMA Downlink Channel

As a standard of next generation wireless communication system, proposed by3GPP organization LTE, has begun to receive increasing attention at present. There are two key technologies of the LTE system:OFDM and MIMO, among them, the OFDM technique is the technical foundation and main features of LTE system. Study of channel estimation is the difficulty and hotspot in the research of the mobile communication system. Channel estimation, is to provide conditions for signal detection at the receiving end, the data at the receiving end has important effects on the recovery. At the receiving end, therefore, the study of channel estimation technology has very important significance.Due to multipath fading of wireless channel and the influence of the Doppler frequency shift, this paper used the MATLAB simulation results to analyze its effect on the performance of wireless broadband communication systems; And then combined with OFDM orthogonal frequency division multiplexing technology, using OFDM technique characteristics, can effectively resist multipath fading, raise the utilization rate of spectrum, and the fast Fourier transform technique make the system easy to implement on the hardware; Then, this paper focuses on OFDM systems channel estimation technology in broadband wireless communication systems, with3GPP long term evolution of LTE downlink OFDMA link the air interface technology, combined with the development of the OFDM technology, the advantages and disadvantages of the traditional channel estimation algorithm is studied, on the basis of two kinds of improved channel estimation algorithm is proposed:(1) People draw a channel estimation algorithm based on DFT noise reduction by classical LS channel estimation algorithm, but there are two defects. One is the only cyclic prefix eliminates the noise outside, but there is no cyclic prefix in the noise suppressed; Second, when non-integer sampling, there is energy loss. Improved algorithm by adding window function and setting threshold method to improve the two shortcomings;(2) Wiener filtering algorithm is a kind of algorithm based on MMSE algorithm with better effect, but its complexity is too high. In LTE downlink OFDMA technology is adopted in the link, the multipath fading channel can be seen as the two-dimensional frequency domain and time domain signal. To reduce complexity, respectively in the frequency domain and time domain one-dimension wiener filtering, the channel estimation method can greatly reduce the complexity of the algorithm, and optimize the performance of the estimator. In addition, after the time-frequency two-dimensional channel estimation, no longer need to interpolation calculation;After theory analysis of the two kinds of improved algorithm, design the algorithm process, and according to the flow chart of the MATLAB simulation. Improved algorithm in the second experiment, according to the LTE downlink link protocol standards set by the scene, the algorithm simulation analysis, the simulation results show that the improved algorithm in the base under the premise of without increasing complexity, improves the accuracy of data transmission system, more adapted to the LTE system, which improves the performance of the whole system.Finally, summarizes the work with this article, and puts forward some ideas for future research and ideas.