Research On Equalization In FMT System

With the improving requirement of the communication system, the performance of single carrier modulation sustains more and more constrains because of channel's time-delay spread, bandwidth limitation and inter-symbol interference(ISI), etc. Multi-carrier modulation has recently evoked considerable interests because of its qualities in resisting multi-path effects and mitigating ISI. Multi-carrier modulation technologies can be divided into two categories. The first one has overlapping sub-channel spectrum, such as the Orthogonal Frequency Division Multiplexing (OFDM). The other one has high-spectral constrains with non overlapping subchannel spectrum, for example the Flitered Multi-tone Modulation (FMT). OFDM is known as a high spectral efficiency multi-carrier modulation technology and has been widely used in practical systems. It combines the technologies of digital modulation, digital signal processing with multi-carrier transmission. However, the orthogonality of OFDM is susceptible to be destroyed in practical transmission and thus produce inter-symbol interference and inter-channel interference. In FMT system, the totally non overlapping spectrum guarantees it's non-sensitivity to frequency offset and thus keeping the orthogonality in transmission.In this thesis, based on the fundamental principle for FMT system, we first introduce the efficient realization of FMT modulation. Then, we study how to remove, the inter-symbol interference of FMT system, which caused by the non perfect reconstruction prototype filter. We first introduce per sub-channel equalizers at the FMT receiver to overcome ISI. There are three traditional equalizers which are the maximum likelihood sequence estimation (MLSE), linear equalization (LE) and decision feedback equalization (DFE). We focus on DFE which could balance the performance with the compute complexity. Then, on the basic of DFE, we develop the data-aided equalizer (DAE) as our second equalization scheme to avoid the performance reduction of DFE and present a two decision algorithm. Moreover, we study the THP pre-coding scheme at the FMT transmitter to solve the ISI problem. At last, we study the trellis code modulation (TCM), and combine it with trellis shaping and THP pre-coding in FMT system. Simulation results shown this scheme can achieve better performance.