Channel Estimation Technology Research In Ofdm Systems

The task of Orthogonal frequency division multiplexing channel estimationtechnology is to estimate the frequency response of wireless channel from transmittingantenna to receiving antenna, and a good techonology of channel estimation is whatmakes some kind of estimated error minimized. Channel estimation is the foundation ofcoherent detection, demodulation, and equalization, and it is one of the key technology inorthogonal frequency division multiplexing systems. In the paper, the researches of theorthogonal frequency division multiplexing channel estimation mainly focuse on resistingsymbol timing offset, interplating, and reducing the complexity of the system, and thedetailed contents are as follows.First of all, in the paper, it will study a kind of channel estimation technology againstsymbol timing errors that interplats to the amplitude and phase respectively to the channelresponse basing on linear interplation. Then a kind of channel estimation technologyagainst symbol timing errors that interplats to the amplitude and phase respectively to thechannel response basing on quadratic interplation is further researched, and it alsocompaired the channel estimation with the linear interplation with the channel estimationwith the quadratic interplation.Secondly, in the presence of the symbol timing errors,the paper will combine theDFT channel estimation algorithm and MMSE channel estimation algorithm respectivelywith the linear interplation method that interpolates to amplitude and phase of the channelfrequency response respectively together, and compaire them with the linear interplationmethod that interpolates to the complex channel frequency response directly.Last of all, the paper will research the time domain channel estimation algorithmbasing on the m sequence, then the time domain channel estimation algorithm basing onthe generalized Chu sequence is designed. In time domain, apart a certain number oforthogonal frequency division multiplexing symbols, the generalized Chu sequence withthe cycle prefix is inserted to the orthogonal frequency division multiplexing symbols asthe training sequence. Then, making full use of the correlation characteristics of the general Chu sequence, the channel impulse response will be estimated and the frequencyresponse of the channel will be getted.