Research On Key Technologies For Multicarrier Communications Under Wireless Mobile Environments

Orthogonal Frequency Division Multiplexing(OFDM)has been extensively used in the wireless communication systems. It is paid more and more attention to, because of its performance for resisting multipath interference and high efficiency of system bandwidth. Thus a MIMO wireless communication system is produced. MIMO-OFDM system which combines the two technologies to get higher data transfer rates and stronger reliability is becoming the core of next generation of mobile and wireless communication systems.This dissertation discusses some methods of OFDM and MIMO-OFDM system channel estimation. Firstly, studies the wireless channel transmission characteristic, give the mathematic model of common wireless channel. Secondly, introduce the basic principle and implementation of OFDM system, give the OFDM system model, and discuss the key technology of the OFDM system.Thirdly, studies channel estimation of the OFDM system based on pilot frequence and blind channel estimation.Finally, studies channel estimation of the MIMO-OFDM system based on pilot frequence.There are two channel estimation methods based on pilot frequence: pilot frequence channel estimation based on block and pilot frequence channel estimation based on comb. Block plot frequence channel estimation introduces the LS method, MMSE method, LMMSE method and SVD decomposition method. Comb pilot frequence channel estimation studies interpolation estimation on data sub-carrier. And also discusses linear interpolation method, Second polynomial interpolation method and interpolation based on transform domain. Then channel estimation algorithms of MIMO-OFDM system are studied, among which pilot assisted channel estimation is described in detail. And pilot symbols were discussed at the channel estimation criteria and the complete channel response interpolation algorithm.