Research Of Improved On Sphere Decoding Detection Algorithm For MIMO System

Multiple-Input Multiple-Output (MIMO) makes a significant breakthrough in the field of wireless mobile communication in recent years. MIMO system sets up multiple antennas at the transmitting and receiving terminals respectively and makes full use of the space characteristic of the channel, and realizes the transmission and reception of the multiple data streams in the same frequency band and the same time. MIMO system not only improves the transmission rate and the transmission quality of the communication system, and it does not increase additional bandwidth consumption as well. MIMO is one of the key technologies in the new generation wireless mobile communication system.Firstly, this thesis introduces the basic knowledge of wireless communication channel and the MIMO wireless channel, and analyzes the principle of multiple antenna wireless communication and the current research progress, and mainly researches the traditional signal detection algorithms for MIMO system including ML detection algorithm、ZF detection algorithm、MMSE detection algorithm and IC detection algorithm. Then it compares the simulation experiments and analyzes the detection performance of the traditional detection algorithms.Secondly, this thesis analyzes the sphere decoding algorithm which is widely studied in the MIMO system signal detection algorithms in recent years, and mainly researches two traditional algorithm of the sphere decoding algorithm, namely the VB algorithm and CL algorithm. And this thesis proposes an improved sphere decoding algorithm based on the CL algorithm. The improved sphere decoding algorithm firstly rearranges the channel matrix, and then leads in the idea of radius iteration, establishes a new radius updating formula in order to reduce the computing complexity of the algorithm. The simulation experiments show that compared with the traditional sphere decoding algorithm, the improved sphere decoding algorithm reduces the complexity without causing significant performance losses.Finally, this thesis introduces the generalized sphere decoding algorithm which solves the systems where there are more transmit antennas than the receive antennas, and puts forward a new fast generalized sphere decoding algorithm, namely the double layer sphere decoding algorithm. Because the initial search radius is very important in the whole detection of the double layer sphere decoding algorithm, and the determination of the ideal radius is essentially a process of optimization, so this thesis proposes an improved double layer sphere decoding algorithm based on the ant colony algorithm. It uses the ant colony algorithm to optimize the inside and outside layer inttial search radius in order to reduce the computing complexity of the algorithm. The simulation experiments show that the improved double layer sphere decoding algorithm determines the initial radius of high quality and optimizes the search of the algorithm itself at the same time. In a wide range of SNR, it effectively reduces the computing complexity of double layer sphere decoding algorithm.