Under The Conditions Of Limited Feedback Miso / Mimo-ofdm System Beamforming

The beam-forming technology of signal processing in MIMO system is different from it in the smart antenna system. The beam-forming in MIMO system refers to the transmitters use beam-forming vectors to weight the launching signal to achieve the system diversity gains and some antenna array gains, and receivers estimate channels and at the same time, receivers transmit the channel information in codes with limited feedback bits, the codes which they all know before communication. The beam-forming technology of signal processing in smart antenna system is that receivers enhance the beam waves from a given direction, while suppressing the other no use interference waves.This paper established a MISO/MIMO-OFDM system model and then analyzed the channel capacity, system bit error rate and discussed the relationship of the number of antennas, the number of bits, the outage probability and the distortion. Analysis showed that the increase in the number of transmit antennas could reduce the outage rate, the increase the number of feedback bits could effectively reduce the system's distortion. But the fewer numbers of transmit antennas, the lower distortion of this system at the same conditions of feedback bits. This paper got the basic development of channel modeling ideas under the analysis of the existing wireless channel model and the simulated calculating parameters, namely:to increase the statistical dimension of random process and to increase the degrees of freedom of the function. This paper also made a variety of improvements to the channel models and gave a channel model simulation with a block diagram.This paper provided servial beam-forming algorithms which were given in combination with quantitative conceptions based on the channel capacity and the system bit error rate in accordance with the system model of this paper. The numerical simulation showed that the best choice for the number of feedback bits within the scope of the 8 bits in the case of reducing the computational complexity in this paper. The simulation showed that system used beam-forming algorithm to improve the capacity of the channel, but also reduced the system bit error rate based on the varies of beam-forming algorithms of this paper proposed. In addition, the performance improvement used the adaptive clustering beam-forming algorithm was lower than used the clustering beam-forming algorithm, but it gave a large extent in terms of reduced receivers'feedback bits which was to be send to transmitters. However, the adaptive clustering beam-forming algorithm significantly showed higher computational complexity than the clustering beam-forming algorithm. Thus, to design and choose a more practical beam-forming algorithm is still a topic worthy of further study.