【作者】 张建；

【导师】 栾英姿； 唐斌；

【作者基本信息】 西安电子科技大学 ， 工程硕士（专业学位）， 2020， 硕士

【摘要】 散射通信因为其传播距离远、可靠性高、通信方式灵活以及抗干扰能力强等优点,目前已成为现代无线通信中一种重要的通信方式。但是,由于散射信道中存在多径效应和多普勒频移,相应地也会产生频选衰落和时选衰落,因此本文选择具有时频联合特性的单载波频分多址（Single Carrier Frequency Division Multiple Access,SC-FDMA）技术作为散射通信系统设计方案。作为长期演进计划（Long Term Evolution,LTE）上行链路的调制方案,SC-FDMA技术具有低峰均比和频域均衡等优点,并且可以通过分配子载波实现多用户通信场景。与此同时,在多用户通信系统中,随机接入前导检测是必不可少的部分。在具有低信噪比特点的散射通信场景中,为了保证良好的检测性能,传统的直接相关检测算法需要消耗大量的硬件资源,可能会造成工程中的芯片资源溢出。所以研究一种低复杂度的低信噪比前导检测算法非常有必要。因此,本文针对散射信道特性设计并实现了SC-FDMA基带系统,并在此基础上对低信噪比场景下的前导检测算法进行了研究与实现。本文的主要研究内容包括:（1）针对当前散射信道设计了系统物理层基带部分的参数,包括系统的带宽、通信方式、物理信道划分和帧结构等。在此基础上设计了系统上下行链路基带部分的处理流程。并且对基带算法模块的设计原理进行了推导分析,包括星座映射、分集与合并、子载波映射、添加循环前缀（Cyclic Prefix,CP）、频偏估计与补偿、信噪比估计、信道估计与均衡等。重点介绍了本文针对低信噪比情景下设计的前导序列设计方法和相应的前导检测算法。仿真结果表明,在信噪比为-17d B时,本文所提的前导检测算法的虚警概率和漏检概率都达到了10^-4以下。（2）在MATLAB中设计了基带算法的定点仿真方案,仿真结果表明在硬件设计时选择9位量化位宽,此时的系统性能与全精度情况下基本一致,信噪比损失可以忽略不计。在基带算法的理论基础上,结合定点仿真方案,设计了部分模块的硬件实现架构,包括星座映射、分集、快速傅里叶变换（Fast Fourier Transformation,FFT）/逆快速傅里叶变换（Inverse Fast Fourier Transformation,IFFT）、添加导频、交织式子载波映射、添加CP、前导检测、频偏估计与补偿、信噪比估计、信道估计与补偿等。通过将算法模块的硬件仿真结果与MATLAB中的定点仿真结果对比,验证了各算法硬件模块设计的正确性。（3）结合当前散射信道实测数据,设计并利用MATLAB和现场可编程逻辑门阵列（Field Programmable Gate Array,FPGA）仿真工具实现了系统单链路回环仿真测试方案。仿真结果表明,在信噪比为0d B时,当前所设计的SC-FDMA散射通信系统的误码率为0。针对数字信号处理器（Digital Signal Processor,DSP）+FPGA的系统实现架构,设计了用于FPGA与DSP之间数据传输的接口协议,包括高速串行输入输出（Serial Rapid Input Output,SRIO）接口的工作模式以及FPGA与DSP之间的交互信息。与此同时,设计了硬件系统的工作时序,方便了DSP与FPGA之间的协调工作。最后,利用硬件实现了SC-FDMA散射通信系统基带部分。实现结果表明,当前所设计的系统可以应用于实际的散射通信工程中,并且在低信噪比下仍然具有良好的通信性能。更多还原

【Abstract】 Scattering communication has become an important communication mode in modern wireless communication because of its advantages of long distance of transmission,high reliability,flexible communication mode and strong anti-interference ability.However,due to the existence of multipath effect and Doppler frequency shift in the scattering channel,frequency selective fading and time selective fading will be generated accordingly,so SC-FDMA technology is selected as the design scheme of scattering communication system in this paper.As a modulation scheme of LTE Uplink,SC-FDMA technology has the advantages of low PAPR and frequency domain equalization,and can realize multi-user communication scenarios by assigning subcarriers.At the same time,in multi-user communication system,preamble detection is an essential part.In the scattering communication scene with low SNR,in order to ensure good detection performance,the traditional direct correlation detection algorithm needs to consume a lot of hardware resources,which may cause chip resource overflow in the project.So it is necessary to study a low complexity and low SNR preamble detection algorithm.Therefore,the SC-FDMA baseband system is designed and implemented according to the characteristics of the scattering channel in this paper.On this basis,the preamble detection algorithm in the low SNR scene is studied and implemented.The main contents of this paper include:（1）For the current scattering channel,this paper designs the baseband parameters of the physical layer of the system,including the system bandwidth,communication mode,physical channel division and frame structure.On this basis,the processing flow of the baseband part of the uplink and downlink of the system is designed.The design principle of baseband algorithm module is analyzed,including constellation mapping,diversity and combination,subcarrier mapping,frequency offset estimation and compensation,SNR estimation,channel estimation and equalization.This paper focuses on the design method of the preamble sequence and the corresponding preamble detection algorithm.The simulation results show that when the SNR is-17d B,the false alarm probability and missed detection probability of the algorithm proposed in this paper are all below 10^-4.（2）The fixed-point simulation scheme of baseband algorithm is designed in MATLAB.The simulation results show that the 9-bit quantization bit width is selected in the hardware design.At this time,the system performance is basically the same as that in the case of full precision,and the loss of signal-to-noise ratio can be ignored.Based on the theory of baseband algorithm,combined with the fixed-point simulation scheme,the hardware architecture of some modules is designed,including constellation mapping,diversity,FFT/IFFT,adding pilot,interleaving subcarrier mapping,adding CP,preamble detection,frequency offset estimation and compensation,SNR estimation,channel estimation and compensation,etc.By comparing the hardware simulation results of the algorithm module with the fixed-point simulation results in MATLAB,the correctness of the design of each algorithm hardware module is shown.（3）Combined with the current measured data of scattering channel,a single link loop simulation test scheme is designed and implemented by MATLAB and FPGA simulation tools.The simulation results show that the current SC-FDMA scattering communication system has a bit error rate of 0 when the SNR is 0 d B.According to the system architecture of DSP+FPGA,the interface protocol for data transmission between FPGA and DSP is designed,including the working mode of SRIO interface and the interaction information between FPGA and DSP.At the same time,the timing of hardware system is designed to facilitate the coordination between DSP and FPGA.Finally,the baseband part of SC-FDMA scattering communication system is realized by hardware.The results show that the current system can be used in the actual scattering communication engineering,and still has good communication performance in low SNR.更多还原