【作者】 张强；

【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）， 2021， 硕士

【摘要】 近年来,随着无线通信技术的发展,散射通信因其具有通信距离远、抗干扰能力强、可靠性高的优点,在军事通信、灾害应急中被广泛应用。由于其利用大气中散射体的散射效应进行通信,信道传输损耗较大,并且由于存在多径效应和多普勒效应,散射信道具有严重的时间选择性衰落和频率选择性衰落特性。因此,针对散射信道特性设计合理的通信系统显得尤为重要。本文针对散射信道的特性设计实现了单载波频分多址(Single-carrier FrequencyDivision Multiple Access,SC-FDMA)基带系统。论文首先介绍了研究的背景和意义,介绍散射通信的特点以及SC-FDMA技术和现场可编程门阵列(Field Programmable Gate Array,FPGA)技术,并阐述了论文的主要工作和结构安排。然后根据当前散射信道设计了系统的基本参数,包括系统带宽、工作方式、信道划分等。设计基带系统采用数字信号处理器(Digital Signal Processor,DSP)+FPGA实现架构,DSP负责比特级数据处理,包括编码解码、交织解交织等,FPGA则完成调制解调等处理。然后以下行链路接收机和发射机为例,设计并验证了其中FPGA部分算法功能模块。系统采用变换域分集、等增益合并技术来抵抗信道衰落,调制方式有BPSK、QPSK和8PSK;采用适用于频选信道的块状导频;根据散射信道的最大时延扩展设计长度合理的循环前缀;选用具有良好的自相关和互相关特性的恒幅零自相关波形作为同步头序列;采用成型匹配滤波处理使信号适合信道传输。在接收端,首先通过定时同步完成位同步和帧同步;通过频偏估计和补偿完成频率同步;基于导频进行信噪比估计;采用最小二乘(Least Square,LS)法进行信道估计;结合信噪比采用最小均方误差法来进行均衡;最后将数据解调得到的软信息传给DSP。其次,根据系统需求设计DSP与FPGA的交互接口采用串行Rapid IO(Serial Rapid IO,SRIO)接口,并设计了相关的传递参数。同时根据基站和用户的工作状态分别设计了基站端和用户端的工作时序。最后将系统进行上板测试和与射频联调测试,并对测试结果中的资源消耗和处理时延进行了分析。实现结果表明,当前所设计的SC-FDMA基带系统可以很好地应用于当前散射信道下,并且在低信噪比环境下依然保持良好的通信性能。更多还原

【Abstract】 In recent years,with the development of wireless communication technology,scattering communication has been widely used in military communication and disaster emergency because of its advantages of long communication distance,strong anti-interference ability,and high reliability.Because it uses the scattering effect of the scatterers in the atmosphere to communicate,the channel transmission loss is relatively large.Due to the multipath effect and the Doppler effect,the scattering channel has serious time-selective fading and frequency-selective fading characteristics.A communication system with reasonable channel characteristics is particularly important.In this thesis,the SC-FDMA baseband system is designed and implemented according to the characteristics of the scattering channel.The thesis first introduces the background and significance of the research,introduces the characteristics of scatter communication,SCFDMA technology and FPGA technology,and expounds the main work and structural arrangement of the thesis.Then the basic parameters of the system are designed according to the current scattering channel,including system bandwidth,working mode,channel division and so on.The design of the baseband system adopts DSP+FPGA to realize the architecture.DSP is responsible for bit-level data processing,including encoding and decoding,interleaving and de-interleaving,etc.,while FPGA completes modulation and demodulation.Then take the downlink receiver and transmitter as examples,design and verify some of the FPGA algorithm function modules.The system uses transform domain diversity and equal gain combining technology to resist channel fading.Modulation methods include BPSK,QPSK and 8PSK;block pilots suitable for frequency-selected channels are used;cyclic prefixes with reasonable lengths are designed according to the maximum delay of scattering channels;Select a constant amplitude and zero autocorrelation waveform with good autocorrelation and cross-correlation characteristics as the synchronization header sequence;adopt shaping matched filter processing to make the signal suitable for channel transmission.At the receiving end,firstly complete bit synchronization and frame synchronization through timing synchronization;complete frequency synchronization through frequency offset estimation and compensation;estimate signal-to-noise ratio based on pilot;use least-squares method for channel estimation;use least mean square in combination with signal-to-noise ratio The error method is used for equalization;finally,the soft information obtained by data demodulation is transmitted to the DSP.Secondly,the interactive interface between DSP and FPGA is designed according to the system requirements using SRIO interface,and related transfer parameters are designed.At the same time,according to the working status of the base station and the user,the working timings of the base station and the user are designed respectively.Finally,the system was tested on the board and tested with the radio frequency,and the resource consumption and processing delay in the test results were analyzed.The implementation results show that the currently designed SC-FDMA baseband system can be well applied to the current scattering channel,and it still maintains good communication performance in a low signal-to-noise ratio environment.更多还原