Blind Channel Estimation In Wireless Communication

There are noise， interferences and multipath fading and other elements in wirelesschannels. The capacity and reliability of wireless communications are affected greatly.Since channel estimation plays an important role in wireless communications, it isessential to estimate the channel accurately in real time.Conventional channel estimation dose require the transmission of a trainingsequence which occupies bandwidth and transmitters and receivers need to workcooperatively. Blind channel estimation can retrieve CSI from its output only which ispotential to improve the capacity and reliability of wireless communications. Thistechnology is particularly suitable for special applications. For example, electroniccountermeasure warfare, suddenly break off in multipoint network and transmissionfault monitoring.There are two kinds of algorithms in blind channel estimation. The conventionalalgorithms are based on channel outputs and knowledge of probabilistic model ofchannel input. The other considers the system input to be an unknown deterministicsignal. The thesis first briefly introduces the characteristics of wireless channel and onthat basis chapter three analyses the representative algorithms of the first kind ofmethods mentioned above. In chapter four, one of the second kind of methodscross-relation method is studied deeply which combined with OFDM in frequency andit achieves a good performance. Moreover, a minimum cross-relation algorithm isanalysed which can lower computational complexity. Finally, a detailed analysis of theidentification conditions and how noise impacts the performance of blind channelidentification are given. The simulation illustrates that cross-relation method canaccomplish blind channel estimation based solely on a small number of the outputswhich demonstrates the potential of the algorithm.