Research On Key Modem Technologies Of Single Carrier FTN Systems

The amount of data transmitted by communication systems increases sharply as the rapid development of wireless communications,and it's extremely urgent to increase the information transmission rate of traditional communication systems and obtain higher spectral efficiency within limited spectrum resources.Faster than Nyquist(FTN)transmission technology provides a non-orthogonal modulation scheme that allows signals to be transmitted at rates higher than the Nyquist rates and allows more symbols to be transmitted in the same bandwidth.FTN technology breaks through the limit of orthogonal modulation and achieves higher system capacity and band utilization than traditonal Nyquist system.As more and more researchers are attracted by FTN technology,the realization of FTN technology has become possible.However,FTN technology brings serious Inter Symbol Interference(ISI),and the synchronization at the receiver are also affected by the acceleration introduced by FTN technology.This thesis focuses on the signal detection technology and carrier recovery technology for FTN systems.The main research results are listed as follows:1)The low-complexity and anti-severe ISI receiver detection technology are studied for single-carrier FTN systems.a)Traditional signal detection algorithms are introduced.By analyzing the existing algorithms,we show the advantages and disadvantages of these algorithms.b)Based on a successive symbol-by-symbol with go-back-K sequence estimator,a successive symbol interference cancellation algorithm based on multi-layer iteration is proposed.The proposed algorithm eliminates ISI by using the continuous received symbol sequence.And the proposed algorithm greatly reduces the complexity of calculation and avoids error propagation.Moreover,the idea of multi-layer iteration is used to improve the performance of the algorithm further.c)Simulations show that the proposed algorithm can approximate the theoretical limit and exceed the performance of traditional FTN detection algorithms considered under the acceleration factors of 0.8 and 0.9 for all the modulation modes of Digital Video Broadcasting-Satellite-Second Generation(DVB-S2).2)Carrier recovery technologies for single-carrier FTN systems are studied.a)The mathematic model of FTN systems is analyzed in the presence of carrier frequency error.There are ISIs in received symbols because of trasmitters' packing,which leads to the performance degradation of the carrier recovery algorithms.b)Classical carrier recovery algorithms are introduced when DVB-S2 frame structue is considered.Mathematical expressions of each algorithm for FTN systems are derivated.c)The performance of DVBS2 carrier recovery algorithms for FTN systems is analyzed.Fitz algorithm and L&R algorithm are hardly affected by FTN packing.When packing ratio are 0.8 and 0.9,Kay algorithm and M&M algorithm will reduce the estimation range slightly,but it will not affect the practical application when the frequency error is not large.