Researches On Channel Estimation And Schedule Algorithm In Mimo Communication System

Future broadband wireless communication system needs higher spectral efficiency and higher data rate. MIMO-OFDM technique can improve the tolerance limit to noise, interference and multipath effect by introducing array antennas to OFDM communication system and utilizing space-time-frequency three dimensional signal processing tequniche. MIMO-OFDM is an important developing direction of future broadband wireless communication system.In this thesis, the history of mobile communication system is introduced. And the channel characterizes, channel capacity of MIMO system and channel estimation techniques are introduced. Then it mainly studies the PSAM algorithm. Firstly, it introduces the fundamental theory of MIMO system, and compares a series of channel estimation methods. It considers the classical LS and MMSE method, and then proposes the scaled LS and relaxed MMSE methods, which need less channel statistical information and have better performance. In the end, it proposes a linear combine MMSE algorithm for channel estimation. This algorithm improves performance of channel estimation in MIMO system. Compared with classic MMSE algorithm, this algorithm has an improvement of 4dB when the combine factor is 4. Then it mainly studies the frequency-domain and time-domain channel estimation algorithms in MIMO-OFDM system based on PSAM method. Frequency-domain method firstly estimates the channel frequency response (CFR) in pilot position and then estimates CFR in data position by filter processing. Filter processing can be based on interpolation method, transform domain method and wiener filtering. Different interpolation methods are proposed to implement the channel estimation, after which their performance is studied. Time-domain method mainly estimates the channel impulse response (CIR). According to OFDMA cell system, it studies the classical schedule algorithm. Besides, according to the features of user'subchannel and random beamforming, it combines the PF and random beamforming algorithm into downlink OFDMA system. Then it proposes a method to mitigate uplink interference between UEs. This method enables edge-user to be capable to use all the resource, and increase the edge-user's throughput by inter-cell communication.Wireless Broadband technology has been an important direction of future wireless communication. As a high data-rate, high efficiency and high reliability wireless transmition technique, MIMO-OFDM must be developed fastly and the channel estimation technique must be futher studied.