Research And Implementation Of LTE-A System Downlink MIMO Detection

As MIMO-OFDM technology is widely used in modern wireless communication systems, MIMO detection algorithms and FPGA implementation applied in the LTE/LTE-A system downlink physical layer are mainly studied in this paper.In the beginning, the development of mobile communications and overview of the technical background of the LTE/LTE-A system are introduced. For LTE/LTE-A system MIMO detection, its significance and research status is illustrated.Then some basic principles and key technologies of the LTE-A system downlink physical layer are introduced, including the FDD downlink physical layer frame format and resource mapping principle, modulation and demodulation algorithm of soft information, principles and mapping rules to generate cell-specific reference signal,principle of OFDM and MIMO technology, especially layer mapping and precoding,and the extended ITU channel model, etc.Then MIMO-OFDM system model and multipath fading channel model are applied in LTE-A system to study the MIMO detection algorithms which contain pilot channel estimation algorithms, data interpolation algorithm and signal detection algorithm respectively. The pilot channel estimation includes LS estimation algorithm,MMSE estimation algorithm and LMMSE estimation algorithm. Data channel interpolation algorithm includes constant interpolation algorithm, linear interpolation algorithm and Lagrange interpolation algorithm. Signal detection includes ML detection algorithm, ZF detection algorithms, MMSE detection algorithm, OSIC detection algorithm and SD detection algorithm. Simulation platform of LTE-A downlink physical layer link for MIMO detection is set up based on Matlab, on the condition of the EPA and EVA channel model, the three channel estimation algorithm, three channel interpolation algorithms and five signal detection algorithm are simulated with QPSK,16 QAM and 64 QAM modulation modes respectively. Their results are compared to analyse their performance.Finally, considering performance and implementation complexity as a trade-off, LS estimation algorithm, linear interpolation algorithm and ZF detection algorithm are selected as hardware implementation scheme of MIMO detection in the LTE-Adownlink physical layer program. MIMO detection is devided into four sub-modules:local reference signal generation module, LS estimation module, linear interpolation module and ZF equalization module, whose implementation structures are proposed in details. MIMO detection module is implemented on Xilinx’s Kintex-7 series FPGA chip XC7K325 T with high-performance, and its functional correctness is also verified by comparing the simulation results of floating point of Matlab and Modelsim fixed point.In the end, synthesis report indicates that the resource consumption is within 20%, and the maximum frequency is 273.148 MHz. The throughput reaches 100.91 Mbps under the condition of 64 QAM modulation with 20 MHz system bandwidth and 245.76 MHz system clock, which shows that the implementation of MIMO detection module meet the needs of the project.