Research On Technology Of Equalization And Cooperation In Mobile Communication

The rapid development of automobile industry,high-speed rail and the aviation industry,puts forward some new requirement for the high data rate,large capacity in the fast moving terminals,and reducing the complexity of the communication terminal without degrading the performance has became the target of the communications industry.Because the point-to-point communication can not meet the needs of improving the efficiency of communication transmission,the multiple-input multiple-output transmission system has been invented,but it significantly increased the complexity of system.In order to reduce complexity of system and resist channel fading,the cooperative communication has been used in the mobile communication and the self-organized wireless network.It is very important to research on equalization and cooperation in Mobile Communication.The specific contents of this paper include the following aspects:Firstly,considering fast moving transceivers,we use the basis expansion model(BEM)to model time-varying OFDM channels.Using different BEM's,we investigate various architectures to implement the least-squares(LS)channel estimation(CE)and its corresponding zero-forcing(ZF)channel equalization(EQ).The experimental results show that our implementation for mobile OFDM systems is capable of combatting the time variation of mobile OFDM channels,and more hardware resource utilization is necessary compared with a traditional OFDM design which fails in a time-varying scenario.Secondly,considering the cooperative networking with the presence of multiple carrier frequency offsets(CFOs)at different relays,we researched the theory and method for the extra diversity gain afforded by the distributed nature of the relay system and the diverse CFOs.The full cooperative diversity is normlly only enjoyed by a non-linear equalizers like Maximum-Likelihood Equalizer(MLE),but it's huge complexity is however usually unacceptable in the engineering.We propose a multi-band scheme for cooperative communications and provide theoretical analysis of the proposed cooperative networking based on the analytical upper bound of the channel orthogonality deficiency.Theoretical analysis and simulation results show that the proposed scheme achieves the full cooperative diversity and improves the system capacity,only adopting linear equalizers such as zero-forcing(ZF)and minimum mean square error(MMSE)equalizers.Thirdly,considering the realistic UWB channel,we researched the cooperative communication with a zero-padding Multi-band OFDM.Without extra coding,Zero-padding MB-OFDM has an equivalent property as the distributed codes like frequency-domain linear convolutive codes to achieve the full cooperative diversity with linear receivers like MMSE receiver.Finally,we researched the cooperative localization algorithms technology in the wireless environment,and improved the algorithm performance using the received-signal-strength and the time-difference of arrival.As for the localization based on the RSS,the shadowing effect was introduced,thus the nolinear optimization problem was translated into the non-convexity optimization problem.As for the localization using the TDOA,we considered to use Chan algorithm and Taylor expansion to iteratively achieve an effective result when an initial localization was not good.