On The Study Of MIMO Communication System

Modern communication system is now developing very fast and has get great success in both technology and commercial field. But there are still many technical problems to be solved for the dream of real time transmitting of multimedia service composed of texts, voice and video. One of these technical problems is high speed wireless access. Many wireless technologies has been proposed, the most attracting one is MIMO technology, which use array antenna at both the transmitting and receiving end.This dissertation focuses on algorithms for a base band processor of MIMO system. The base band processor includes three parts as MIMO equalization, MIMO modulation and de-modulation , and error correcting codes for MIMO system. The optimal design goal of the MIMO base band processor is the ability to provide high rate and low latent wireless transmitting .This global optimal goal rules the optimal design of the three parts of the base band processor.The transmitting environment of MIMO system is always a mobile and multi path environment, so the receiver must get rid of the inter symbol interference and the inter channel interference. There are many equalization method has the ability to cope with this problem. Most of them use training sequence, this leads to a large portion of band width waste. There are also some blind methods for MIMO equalization, but most of them has special requirement on signal structure or noise characteristics. This limits the application of these blind methods. This dissertation proposes MIMO blind equalization with subspace tracking and general Gaussian approximated minimum mutual information blind equalization method. MIMO blind equalization with subspace tracking use subspace tracking technology to modify the subspace method to be a adaptive one so as to be used real timely. Based on the observation that the output of MIMO equalizer has probability distribution very near to high order general Gaussian distribution, this dissertation proposes general Gaussian approximated minimum mutual information MIMO blind equalization. This method needs no restriction on the structure of the transmitting signal, so has wider application field than Constant Modulus algorithm.For the joint diversity and multiplexing optimal MIMO transmitting, this dissertation proposes orthogonal linear dispersive space time code. Orthogonal linear dispersive space time code constructs orthogonal base vector set of base matrix setwith orthogonal column vectors of a orthogonal matrix. This method is very simple in design, modulation and demodulation. The coherent detection of orthogonal linear dispersive space time code based on orthogonal base vectors also improves its BER performance. Orthogonal linear dispersive space time code can also be used as an adaptive one for different application requirement.Another challenge for MIMO base band processor design comes from error correcting codes. In many communication systems , the error correcting codes is concatenation of RS code and convolution code or Turbo code. But convolution code and Turbo code are very difficult to provide high speed transmitting. This dissertation proposes the approach of concatenation of RS code and low density convolution code.Low density convolution code combines the characteristics of convolution code with generating matrix in band form and characteristics of low density parity code with good performance and simple decoding. Low density convolution code has performance optimal to general convolution code and its decoding is very easy to be implemented in pipelined forms. This successfully avoids the decoding delay of low density parity check code.At last the dissertation investigates a MIMO base band processor solution with blind equalization, orthogonal linear dispersive space time code and low density convolution code for optimal design goals of high transmitting rate and low transmitting delay.Simulation result shows that the proposed MIMO system solution has transmitting through put and transmitting delay superior to that of the MIM...