Study Of OFDM Channel Estimation Method Based On PN Sequence

Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique. Currently, because of nice ability against multipath interference and high bandwidth efficiency, OFDM gets more and more attention especially in a communication system which has a high data rate. OFDM has already been one of key techniques in 4G system. If want to improve system performance by using OFDM, some concerned key-techniques are must be studied. Channel estimation technique is one of such techniques. Only estimate channel first, signal detecting would be completed so that achieve communications.In this thesis, we review the development of OFDM first. Then introduce essential wireless channel knowledge, OFDM principles, OFDM advantages and disadvantages. After these, some OFDM channel estimation algorithms based frequency-domain pilot are introduced, such as Winer filtering algorithm, singular value decomposition algorithm, transform-domain filtering algorithm and time-domain filtering algorithm.Based on these algorithms, a time-domain OFDM channel estimation algorithm using PN sequence is proposed. It detects channel parameters by the favorable autocorrelation property of PN sequence. Simulation result shows that, with the same signal-to-noise ratio (SNR) and channel using rate, the proposed algorithm can implement a much accurate estimation than the conventional frequency-domain channel estimation algorithm based on comb pilots. In addition, an OFDM channel estimation algorithm using PN sequence as cyclic prefix is also be proposed. Simulation result shows that, with the same signal-to-noise ratio (SNR) and channel using rate, this algorithm not only has higher estimation accuracy but also save system resources compared to the conventional frequency-domain channel estimation algorithm based on comb pilots.