Research On Differential Space Time Decoding Algorithm For Multi-User MIMO System

MIMO technique, which has been applied to various kinds of communication systems, not only increases the channel capacity of the wireless communication systems but strengthens the system’s decoding reliability. Alamouti code, one of the classical space time block codes, cannot decode when the receivers haven’t got any channel state information. Based on existing differential space time encoding and decoding schemes, more attention is focused on multi-user MIMO system, proposing several differential decoding algorithms and corresponding optimization algorithms.Firstly, a partial differential decoding algorithm based on orthogonal space time block code is proposed, by which we can use only one user’s channel state information to decode two-user’s transmitted sequences. The receiver can decode a weak signal user’s code-words relying on other users’strong signals. Secondly, a partial differential decoding algorithm based differential decoding algorithm is presented which can decode without any channel state information. Rotated constellation encoding is taken to ensure that two users’ code-words are different. Some special circumstances are discussed and effective solutions are introduced. With low decoding complexity, the performance of the differential decoding algorithm cannot compare with existing algorithms. So an optimization algorithm is described based on accumulation joint decoding of several transmitted blocks, which improves the decoding under reasonable decoding complexity. The decoding performance can be further improved by adding delay, however receiver must receive a certain number of transmitted blocks before decoding. Finally, a DSP and FPGA based hardware platform is designed to verify the practicability of the proposed algorithms, in the aspects of memory capacity, operating rate, computational complexity etc. The platform evaluates and optimizes the algorithms, ensuring the algorithms comprise between performance and complexity.Simulations and experiments demonstrate that the proposed algorithms of multi-user MIMO system improve the probability of error, with better performance in memory capacity and computational complexity.