The Research On The Digital Terrestrial Television Broadcasting System Diversity Technology

At present, more than300cities and areas have been covered with Chinese digital terrestrial television broadcasting. Based on the project (The Research on the Digital Terrestrial Television Broadcasting System Diversity Technology) undertaken by the Academy of Broadcasting Planning, SARFT, this thesis conducts research on single-carrier mode in DTMB system in order to guarantee the quality of the DTTB Network and further improve the performance of anti-fading of the broadcasting signal to expand the cover area of the DTTB Network. This thesis proposed three diversity reception schemes which combined with time-domain equalizers. These schemes are verified by theoretical analysis, computer simulations and the physical environment tests.This thesis first studies the features of the equalizer. After that, the analysis of the adopted equalization technology is made from several aspects:the structure of the equalizer, the sampling rate, the convergence rule and the special decision-feedback overlapping of structure. Technically, in condition of dynamic frequency selective channel the deeply fading of channels would result in remarkable decrease of the input SNR of equalizer and lead to severe error propagation, consequently restrict the improvement of the performance of the equalizer. Simulation demonstrates that the equalizer of the existing terrestrial digital television broadcasting single carrier system is unable to cope with the error propagation, and the average error rate is relatively high.Then this thesis has put the emphasis on how to bring diversity reception technology into the existing system, according to the characteristics of the diversity technology and time-domain equalization, this thesis proposed three diversity reception schemes which are Dual Equalizers Selection Combining scheme, Single Equalizer Equal-gain Combining scheme and Dual Feedforward Filters MMSE Combining scheme. Detailed theoretical analysises and simulations results of them are stated in this thesis. It is shown that compared with receiver without using diversity, all these three schemes have reduced the error rate of time-domain equalizer, among which the dual Feedforward Filters MMSE Combining scheme is the optimal one in that the error rate of it is lower than the other two schemes by more than3magnitudes because of its excellent tap update algorithm.In order to verify the correctness of the algorithm proposed in this paper, this article carry out simulation tests in the laboratory under various channel environments, as well as in the actual environment of the Sanhuan Road, Beijing the mobile test and specific locations test is also carried out. The test results show that after using diversity technology, the system’s carrier-to-noise ratio threshold can be increased to nearly3dB. Both theories and simulation experiments prove that with the diversity technology which is helpful to solve the problem that the error rate cannot keep reducing with the increase of SNR in the condition of high input SNR due to the channel fading effect and sequentially tremendously improves the sensitivity of receiver.