Non-coherent Space Time Coding And Modulation Design In MIMO System

In recent years, multiple input multiple output(MIMO) technology has been widely adopted, and already entered into wireless communication standards such as the 4G and WIFI because of its great potential to increase transmmistion rate and enhance transmmistion reliability, and it will also be one of future key technologies of the next generation communications system. Presently, most adopted MIMO coding and modulation technologies are coherent space-time codes which need channel estimation. However, in the high-speed mobile environment, channel changes rapidly, the accuracy of channel state information estimation decreases and resource consumption increases, so the non-coherent unitary space-time codes which can get rid of the channel estimation suit this case, and in order to improve the non-coherent system, we construct coded modulation system by cascading LDPC codes with the unitary space-times codes. The main contents of this article has the following two aspects.First, inspired by the structure of space-time block codes,we propose a new unitary space-time code design method, by using the maximum rate orthogonal design as the unitary space-time matrix structure, and traditional high order QAM modulation can be ultilized to construct the uitary space-time signal. The unitary space-time constellation generated by this design performs better than both the famous systematically designed and orthogonally designed code when the code rate is high. And by introducing one-dimensional degree of freedom to orthogonal design unitary space-time code, we can improve the codeword design flexibility, thus obtain a wider range of choice.Second, construct coded MIMO system by casade LDPC code with unitary spacetime code and spatial multipexing code. The designed system can get a well comprehensive performance of transmition rate, error rate and complexity. And, we design an iterative detection and decoding method which detect transmitted signal matrix to enhance channel estimation accuracy thus to improve the decoding performance.