| Multiple input multiple output (MIMO) technology can use a space gain to increase channel capacity in the premise of no increase in system bandwidth and transmission power, that is, utilizing space diversity gain to improve channel reliability and reduce the bit error rate. Therefore, MIMO system has become the key technology of modern wireless communication system. Multiple antenna transmission, however, inevitably increase the interference between the users, which also became the main factor in influencing the channel capacity of MIMO system. Pre-coding technology has become the research hotspot in the MIMO technology since it can effectively eliminate the interference between users. This article simply introduces the model of the MIMO system, the principle of MIMO spatial multiplexing technology and wireless transmission channel characteristics. Then we do research against the pre-coding scheme for MIMO system in depth, and bring in the popular assisted reduction algorithm at present on the basis of the traditional pre-coding scheme, this paper concentrates on as follows:First, we analysis the MIMO system pre-coding algorithm improvement program in depth combining with the lattice reduction auxiliary algorithm on the basis of the traditional pre-coding scheme on transmitter signal. The traditional pre-coding scheme mainly includes dirty paper coding, linear pre-coding scheme and nonlinear pre-coding scheme. Dirty paper coding is a pre-coding scheme in ideal condition, so there is no analysis done in the article for it’s unable to achieve under current conditions. And linear pre-coding scheme includes zero-forcing (ZF) and minimum mean square error (MMSE) with the characteristics of low complexity, while the performance is not ideal. Nonlinear pre-coding scheme is of high practical value, among which the commonly used scheme named THP includes scheme based on ZF criterion and scheme based on MMSE criterion and so on. Compared with the linear pre-coding scheme, the performance of the non-linear pre-coding scheme is better while the computational complexity of the non-linear pre-coding scheme has increased. According to the current popular LLL algorithm, we obtain a new lattice reduction auxiliary (LRA) pre-coding scheme by improving the traditional pre-coding scheme. Theoretical analysis and simulation analysis verified the lattice reduction auxiliary pre-coding scheme has huge performance advantage and practical value.Second, introduce the concept of lattice, obtain an improved GE-LLL algorithm from optimizing LLL algorithm by combining with the genetic strategy, analysis the performance and complexity of the improved algorithm in detail and do verification with the specific data. Then, we analysis the feasibility of the improved algorithm when applied to the pre-coding scheme, and To what extent the improved algorithm when applied to the pre-coding scheme can lead to performance improvement from the perspective of theory analysis.Third, simulation comparison has done between a variety of pre-coding scheme in detail. First, we give and do theoretical analysis on bit error rate (BER) and signal to noise ratio (SNR) simulation curve of a variety of typical linear and nonlinear prediction coding scheme in MIMO system under different conditions according to the traditional pre-coding scheme. And then we do performance simulation on lattice reduction auxiliary pre-coding scheme based on the LLL algorithm and the improved GE-LLL algorithm respectively, it verified that the lattice reduction auxiliary algorithm significantly improve the performance of pre-coding scheme, at the same time proved that the improved algorithm in the application value of pre-coding algorithm. |
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