Channel Estimation Algorithm For Mimo Systems

During the past twenty years, in the whole world, mobile communication has been developed rapidly and undergone three generations—the first generation based on analog communication, the second generation based on digital communication, and the upcoming third generation based on multimedia communication. The development of each generation is determined by the breakthrough of technology and the innovation of concept.The 2rd generation mobile communication system (2G) was mainly designed for voice and low speed data service. With the demand of good QoS and high data rates, people have focus on 3G and B3G systems. By Orthogonal Frequency Division Multiplexing (OFDM), the channel can be divided into a number of orthogonal sub- channels on which data can be transmitted with low rates simultaneously, thus it can overcome the frequency selective fading effectively.Multiple-Input Multiple-Output (MIMO) is the great breakthrough of smart antennas in wireless communication area, which can make use of the increased spatial channels to improve the system capacity. In MIMO systems, the signal can be sent and received through multiple antennas or antenna arrays. The combination of OFDM and MIMO can effectively alleviate the problem of multi-path propagation, increase system capacity, and obtain more robust system capability, so they are considered as the main stream techniques of the future wireless communication system.As we all know, the capability of wireless communication system is constrained by radio propagation channel, especially for future wideband communication system. So it needs more signal processing techniques to withstand bad radio propagation environment, such as diversity combination, coherent detection and channel encoding and decoding etc. For MIMO physical layer approaches, channel state information is a prerequisite, thus comes many channel estimation approaches and algorithms. The work in this paper includes research on traditional 2-Dimension Pilot Symbol Assisted Modulation(2D-PSAM) and its improved algorithms, a simple channel estimation algorithm for MIMO-OFDM system on Correlation of Pilot Sequences and MIMO channel estimation using Superimposed Training.In chapter 3, a novel channel estimation algorithm for MIMO-OFDM system has been proposed. Two-Dimension Pilot Symbol Assisted Modulation (2D-PSAM) is employed in MIMO-OFDM system for channel estimation. That is by inserting known symbols or pilots in time and frequency domain to estimate the channel frequency response. The proposed method employs iterative low-pass filtering in transform domain which can reduce additive white Gaussian noise and inter-carrier interference effectively.