Key Technology Research On Next Generation Digital Television Terrestrial Broadcasting Based On Nx SC-FDMA In Hign Speed Railway

Hybrid broadcasting and wireless communication network is a new generation of wireless communication technology for high speed railway. Combining with the advantages of both the digital television broadcasting and wireless communication systems, the hybrid network sends the hot information to the passengers or the terminals through the broadcasting mode, and provides individual service through traditional cellular networks. However, with the continuous development of high-speed railway in our country, the wireless train-ground communications’ demand for high quality, big bandwidth and high energy efficiency becomes increasingly larger. To meet the above needs, researches on performance boosting technologies of the broadcasting systems in hybrid network are urgency.This dissertation first of all summarizes and describes the demand characteristics of the next generation terrestrial digital television broadcasting for high-speed railway, namely: broadband, green, sparse users, etc. Next, the dissertation introduces a hybrid broadcasting and wireless communication network suitable for high-speed railway solution, which is based on the first generation of traditional terrestrial digital television broadcasting and LTE-R transmission scheme, and focus on how to improve the utilization efficiency of existing wireless communication technology and the passengers’ average throughput. Research results show that improving the capacity of the broadcasting network is one of the most effective ways to increase the users’ average throughput.With the purpose of improving the transmission bandwidth and energy efficiency of traditional terrestrial digital television broadcasting, this paper proposes a next generation broadcasting communication solution based on Nx SC-FDMA for high speed railway. This broadcasting technology utilizes the latest multiple access technology in LTE-Advance system, which not only has the advantages of single carrier transmission technology with low PAPR, but also the ability of aggregating discontinuous sub-carriers. Thus the new broadcasting scheme can achieve the goal of green, broadband communications. The fundamental principle of the proposed broadcasting system and its link structure were researched in this paper, and also with the discussion and simulation of performance comparison between the old and new broadcasting systems. From the simulation results we can see that: the next generation broadcasting transmission scheme does have the characteristics of low PAPR.Then, for the purpose of the Nx SC-FDMA system’s high quality communication, the next generation broadcasting systems’ varying channel estimation based on frequency pilots was researched. Impulse response of dynamic channel cannot be accurately estimated even with pilot signals, the total number of unknown parameters is larger than that of equations. In this dissertation a time-varying channel estimation method based on base extension is applied to accomplish channel estimation under high-speed mobile environment. Through estimating the channel frequency-domain transfer function by the quick time-variation in a symbol period, finally the channel frequency response matrix is calculated, this method increases the accuracy of traditional channel estimation methods.Finally, in order to enhance the performance of the traditional frequency-domain iterative ICI cancellation methods in the next generation broadcasting systems under high-speed mobile scenario, this paper researches the traditional iterative ICI cancellation algorithm with low complexity at first: ICI cancellation algorithm based on simplified matrix inversion and ICI cancellation algorithm based on decision feedback, and found their performance is poor in high-speed mobile environment. Therefore, this dissertation provides an improved iterative ICI elimination algorithm, which reduces the decision error rate by considering the primary ICI’ influence at the beginning of iteration. The simulation shows that the performance of the modified iterative algorithm is slightly poorer than the direct frequency domain equalization algorithm, but achieves a big improvement than traditional algorithm; its computational complexity is significantly decreased because of no matrix inversion through the iterative interference cancellation.