Research On The Key Issues Of Generalized Multi-Carrier Communication

As the booming development of data communication and multimedia business, the requirement forhigh-speed mobile communications improves unceasingly. In order to provide users excellent experiencesimilar as the traditional Internet in the wireless environment, many problems need to be solved in differentaspects, such as the spectrum resource allocation and the channel fading influence. Therefore the multi-carriertechnology has attracted the extensive attention due to its natural advantages at improving spectrum efficiency,resisting frequency selective fading, and supporting for different business. This thesis focuses on the key issuesin the general multi-carrier (GMC) transmission system.First, with the the traditional digital filter theory, the thesis analyzed the GMC parallel transmission model,that is, model the signal transmission process as a convolution in time domain, then the precision analysis isdone separately for the interference in time domain and frequency domain, where three kinds of prototypefilter are included and compared.This thesis also studies the Doppler shift estimation, which is also an important issue of the GMCtechnology. In order to account for the influence of additive white gaussian noise (AWGN), we compareestimates with and without AWGN, and found that the product of Doppler shift&the time interval will affectthe effect of AWGN, i.e., a certain product may lead to the same noise influence irrespective of the value ofAWGN. Accordingly, we derive the SNR-insenseitive condition and propose an iterative process to refine theDoppler shift estimation. Moreover, a polynomial fitting method is put forward to further improve theestimation accuracy. The simulation showes the forward algorithm performs well in a wide range of SNR andDoppler shifts.The GMC structure causes long subcarrier channel, thus, the thesis first analyzes the equivalent channel,and then studies the design of maximizing shortening SNR shortening impulse response filter, where the filterparameter optimization is investigated in depth. Moreover, since the traditional SIRF aims at the quasi-staticchannel, the thesis analys the SIRF’s mismatch problem in the time-varying channel in terms of the averaged compressing ratio and the mismatched ratio. The results shows that the product of the Doppler Shift and thetime interval should be treated as a key parameter, the ratios will decrease with the product increasing.