Study On Fast Implementation And Synchronization Techniques In Filter Bank Multicarrier Systems

Filter Bank based Multicarrier (FBMC) technology has a strong ability of anti-multipath interference,and can be a better solution for the contradiction between the high-speed wireless data transmission and sophisticated equalization processing technology,which is one of the core technology of next-generation broadband wireless communications system. OFDM is a special case of FBMC and chose a rectangular pulse as the send and receive filter, which greatly reduced the inter-symbol interference (ISI), however bought at the price of inter-carrier interference (ICI), In order to achieve the right balance between ISI and ICI interference suppression,Need to consider the the FBMC technique that has overall performance with the utilization of non-rectangular pulse.In this paper, a comprehensive introduction to FBMC study status and key technology research, and lists some of the problems in these field remained to be resolved, points out the main contents of this article.Then based on the anslysis of basic characteristics of fading channels in mobile communication,gives comparative analysis of OFDM and FBMC with the areas of the basic principles, baseband equivalent model and spectral characteristics, etc. Special focused on analyzing the links and differences between the two, and gives their corresponding implementation framework. From the baseband implementation point of view, due to the time-domain non-rectangular pulse selected by FBMC,it can improve system performance, but also bring a higher degree of difficulty to the system fast algorithm for modulation and demodulation, synchronization, channel estimation and equalization technology .In order to reduce the implementation complexity of FBMC system,an efficient fast algorithm was presented. The transceiver's baseband system models are presented first based on time-frequency and multicarrier communication theory.Then,a discrete causal model was obtained due to digitized and delayed treatment.Finally,through the utilization of limited pulse truncation length and cyclical nature of complex exponential function, the fast algorithm was developed. Simulation results shows that the accuracy and effectiveness of the method.Multi-carrier technology are more vulnerable to the impact of synchronization error than the single-carrier technology.To solve the influence, we first need to obtain the quantitative interference analysis caused by the synchronization error. An analysis method of effects of synchronization offset on the property of FBMC system is presented. The method first divide demodulator output into signals and interference ,and then based on the the cross-ambiguity function of transmit pulse and receive pulse, get the quantitative analysis of interference and signal,finally calculate the SIR with the utilization of statistical properties of the transmit data.Simulation results show that BER caused by synchronization error is consistent with theoretical calculation of the SIR.Therefore,The reliability of the method is verified.Theoretical analysis and experimental results show that, FBMC as one of multi-carrier technology is also influenced by the synchronization bias like the OFDM. In order to improve the performance of FBMC systems, it is necessary to address the technology. Synchronization problems, due to the synchronization algorithm based on the OFDM system is already very mature, and in a variety of literature and documents related to wireless communication standards are more discussions on both,So in this paper, a synchronization implementation was proposed based on the OFDM symbol structure, including those based on 4 repeat delay-related synchronization and cross-correlation synchronization with ZC sequence. Through analysis, because the advantages and disadvantages of the two kinds of algorithms complement each other exactly, so the proposed system frame structure, containing both the training symbols, such can be integrated both synchronous implementation and with the advantages of better synchronization performance.Using some of very mature synchronization technology of OFDM system and direct application to the FBMC system, although in practice it is feasible, but this method has the following needs for improvement: 1 transmitter and receiver side must have two kinds of carrier modulation and demodulation devices, resulting in increased system complexity; 2 training symbols add inconvenience, in order to prevent other FBMC symbolic impact on the training symbols, it only suitable for emergency communication systems added to the header; 3 for non-emergency communications,OFDM training symbols and the symbols FBMC to add time-domain between the need for additional transitional protection, reducing the spectrum efficiency; 4 due to synchronization symbols and data symbols are not based on the same multi-carrier modulation demodulation techniques, it is difficult to present a joint algorithm to estimate channel and synchronization bias.In order to overcome the above shortcomings, To better enhance system performance, In the final, paper presents a synchronization solution based on training sequence with a frame structure of FBMC.First, By using the transmission of the sequence of same training symbols and which length is greater than the overlap factor,that makes the system time-domain synthetic signal with multiple delayed redundancy features, and then an adaptive frequency offset estimation method and a high precision symbol timing estimation method for FBMC systems are proposed. Theoretical analysis shows that the estimation method are unbiased and gives the estimated variance, Simulation results show that the algorithms are correct and effective.