Research On The Technology Of Single Carrier Frequency Domain Nonlinear Equalization

The rapid development of wideband wireless communication to some large extent enriched people's life. As the wireless channel is not fixed as cable channel when information is transformed in wireless channel, it is inevitable to suffer from the interference of multipath. How to eliminate the interference and guarantee the communication quality is question that people have been constantly discussed.In recent years single carrier modulation (SCM) has again become an interesting and complementary alternative to multicarrier modulations such as orthogonal frequency division multiplexing (OFDM). This has been largely due to the use of nonlinear equalizer structures implemented in part in the frequency domain by means of fast Fourier transform, bring the complexity close to OFDM. Here the nonlinear equalizer is formed with a linear filter to remove part of inter symbol interference, followed by a canceller of remaining interference by using the previous detected data. Indeed, the study of efficient nonlinear frequency domain equalization techniques has further pushed the adaption of SCM in various standards.Firstly, this article elaborates the basic characteristics of the wireless channels, the basic parameters of small scale fading and classification; Established the SUI wireless channel model which was regulated by IEEE802.16.3.Secondly, single carrier transmission system is introduced. Elaborate the key technology in the single carrier transmission system. Demonstrated the conditions of cyclic convolution instead of linear convolution and the frame format in single carrier frequency domain equalization transmission system. Researched the generation of UW sequences and evaluated its properties.After introduced the classification of equalization and its'principle, the detailed deduction of frequency domain linear equalization and decision feedback equalization are given. What's more, the performance of these two kinds of equalizations is given under SUI-5 wireless channel. To analysis the performance of SC-FDE, three aspects are considered: the compute complexity of time domain equalization and frequency domain equalization, compares of channel capacity and Peak-to-Average Power Rate between SC-FDE and OFDM.Finally, some improving algorithm of FD-DFE are studied, mainly including frequency domain iterative block decision feedback equalization (FD-IBDFE), frequency domain equalization noise prediction (FDE-NP), frequency domain bidirectional decision feedback equalization (FD-BiDFE). The average bit error rate curves of these equalizations are given to analysis these performances. Based on these algorithms, a novel frequency domain equalization bidirectional noise prediction (FDE-BiNP) is proposed. Through the simulation, it is easy to find that the proposed algorithm can achieve the same performance with FD-BiDFE, better than FD-DFE and FDE-NP. From the point of compute complexity, the proposed structure has lower complexity than FD-BiDFE. What's more, the coefficients of feed-forward and feedback filter are dependent which is more flexible for design.