基于宽带信号的Walsh码扩频通信

沃尔什（Ｗａｌｓｈ）码又称为沃尔什函数，它是一种正交码（序列）。作者通过在多径信道中采用宽带扩频信号舆的理论分析，说明基于宽带信号的正交Ｗａｌｓｈ码的形式及在ＣＤＭＡ系统正、反向信道中进行我直到原理及应用。     

一种灵活的DS-CDMA系统多速率支持方案

本文研究了ＤＳ－ＣＤＭＡ前向链路的可变处理增益多速率传输问题。文中首先指明了现有ＩＳ－９５系统多速率传输的局限性，然后通过分析不同周期离散Ｗａｌｓｈ函数的正交特性，指出如何通过适当分配各个用户信道的Ｗａｌｓｈ码，达到支持多速率业务的目的。分析结果表明，这一改进的多速率传输方案为ＤＳ－ＣＤＭＡ系统应用于第三代移动通信提供了足够的灵活性。     

ADSL的线路调制技术

ＡＤＳＬ在线路调制无后采用过正交幅度调制，无载波幅度相位调制和离散多频调制。ＱＡＭ和ＣＡＰ在６Ｍｂ／ｓ以下的速率和中工作得很好，ＤＭＴ则在更高速率上表现出明显的优势。传统的ＤＭＴ系统采用ＩＤＦＴ和ＤＦＴ实现调制和解调，用散小波变换代替ＤＦＴ的ＤＷＭＴ系统可以获得更好的传输性能。     

正交序列扩频多码CDMA系统在AWGN信道的性能分析

在直接序列扩频通信（ＤＳ－ＣＤＭＡ）系统中，为了有效地实现用户高数据率的传输，本文提出了一种正交扩频多码ＣＤＭＡ系统（称为ＯＭＣ－ＣＤＭＡ）。相似于多载波调制，传输的高数据率首先进行串－并转换，然后对转换后的低数据流用正交序列进行扩频调制。不同于多载波调制，各支路扩频信号用同一载波进行调制。这里，我们对此系统在ＡＷＧＮ信道的性能进行了计算，并对数值结果进行了分析。     

DS—CDMA移动通信系统地址码的正交性

根据直接序列扩频码分多址（ＤＳ－ＣＤＭＡ）系统多址于干扰形成原理，着重分析了ｍ序列，Ｇｏｌｄ序列，Ｗａｌｓｈ序列及其正交性，计算机模拟结果表明，同步状态下Ｗａｌｓｈ序列有理想的正交性，但在非同上状态下正交性不很理想。     

在多径衰落信道下FD/SSMA系统的性能分析

多载波频率分集扩展频谱码分多址系统（ＦＤ／ＳＳＭＡ）是一种基于多载波传输,与直接序列扩展频谱码分多址系统（ＤＳ／ＳＳＭＡ）存在时间－频率对偶关系的扩频多址通信方案。在多径传输信道下,基于ＦＤ／ＳＳＭＡ信号的锐自相关和低互相关特性,本文提出ＦＤ／ＳＳＭＡ系统可以采用路径分集接收的方案。分析和模拟计算表明,在多径衰落信道下,采用路径分集方案时ＦＤ／ＳＳＭＡ系统的性能将得到明显的改善。     

双正交多码CDMA系统在衰落信道的性能分析

在直接序列扩频通信（ＤＳ／ＣＤＭＡ）系统中,为了有效地实现用户高数据率的传输,以适应宽带ＣＤＭＡ技术发展的要求,本文提出了一种双正交多码ＣＤＭＡ系统（称为ＢＭＣ－ＣＤＭＡ）。相似于多载波调制,传输的高数据泫首先进行串－并转换,然后对变换后的低数据流用双正交码进行扩频调制。不同于多载波调制,各支路扩频信号用同一载波进行调制。并对此系统在衰落信道性能进行了计算,还对数值结果进行了分析。     

在多径衰落信道上FD／SSMA系统的性能分析

多载波频率分集扩展频谱码分多址系统是一种基于多载波传播,与直接序列扩展频谱码分多址系统存在时间－频率对偶关系的扩频多址通信方案。在多径传输信道下,基于ＦＤ／ＳＳＭＡ信号的锐自相关和低互相关特性,本文提出了ＦＤ／ＳＳＭＡ系统可以采用路径分集接收的方案。分析和模拟计算表明,在多径衰落信道下,采用路径分集方案时ＦＤ／ＳＳＭＡ系统的性能将得到明显的改善。     

跳频/多载波频率分集/扩频多址无线通信系统的研究

本文提出了一种跳频／多载波频率分集／扩频多址（ＦＨ／ＭＣＦＤ／ＳＳＭＡ）无线通信系统,给出了ＦＨ／ＭＣＦＤ／ＳＳＭＡ系统的发送和接收模型,对判惟变量统计特性进行了分析,然后对峰窝系统反向链路在理想定时和信道估计条件下用户平均接收误码率进行了仿真。结果表明,ＦＨ／ＭＣＦＤ／ＳＳＭＡ蜂窝通信系统具有较好的抗多径衰落能力,同单载波ＦＨ／ＳＳＭＡ系统相比其误码性能和频谱效率有显著改善。     

扩频多址系统

介绍多载波频率分集扩频多址系统（ＦＤ／ＳＳＭＡ）及其主要特点：ＦＤ／ＳＳＭＡ系统具有低功率谱密度、多址、抗干扰及抗多径能力，ＦＤ／ＳＳＭＡ系统的发送均可用离散傅立叶变换实现，ＦＤ／ＳＳＭＡ系统具有灵活性；ＦＤ／ＳＳＭＡ系统的同步不用考虑伪码的同步。     

OFDM水声通信的水池试验验证

影响高速水声通信的2个主要因素是多径引起的码间干扰和有限带宽。正交频分复用技术（OFDM）是一种多载波传输方案,具有良好的抗多途特性和带宽利用率高的特点,因此,在水下通信中具有很好的应用前景。给出了基于OFDM的水声通信系统方案,该方案通过IFFT/FFT来实现编译码,利用循环前缀来克服ISI。消声水池开展的实验验证了给出方案的有效性。     

FFT算法在OFDM中的应用研究与设计

针对当前高速数据传输技术中多径效应,符号间干扰的缺陷,提出了正交频分复用（OFDM）系统的设计方案。该方案利用快速傅里叶变换FFT实现调制和解调。这里以Quartus Ⅱ为平台用VHDL语言编程实现各模块,设计了FFT处理器。通过综合仿真和时序分析与MATLAB仿真结果比较验证其正确可行。该系统可以解决高速信息流在信道中的传输问题,可以有效地对抗多径效应,消除符号间干扰,实现数据的高速传输。     

Digital transmission of high bit rate signals using 16DAPSK-OFDMmodulation scheme

Radio transmission signals are distorted by multipath propagation and signal level fading in the channel. In the case of digital transmission systems, the distortion of signals causes a degradation of bit error performance. It is an especially severe problem with digital outside-broadcasting-link (OBL) which has to transmit, for example, digital HDTV signals at more than about 45 Mbps. The OFDM modulation scheme can mitigate the adverse effects of multipath fading. An experimental OFDM modem has been developed to enable stable transmission of digital HDTV sources in an OBL. The experimental modem distributes transmitting digital data to 688 carriers in a bandwidth of about 13.5 MHz using the 16DAPSK for each OFDM carrier. A combination of 8DPSK and 2DASK is adopted as the 16DAPSK and another combination of 8DPSK and coherent 2ASK instead of 2DASK is also considered. Indoor transmission experiments confirmed that the 16DAPSK-OFDM is feasible for transmitting high bit rate signals, even under severe propagation conditions     

关于利用FFT的OFDM的实时同步方式的研究

提出了OFDM（正交频分复用）利用FFT（傅里叶变换）实时同步方式的方案,在多径环境下具有有良好的特性。研究了OFDM的原理后,采用防卫间隙相关处理等技术对接收信号进行FFT、检波,进而求得传递函数,并对此传递函数进行IFFT（快速傅里叶逆变换）,求得时间轴延迟信号,实现高精度实时处理。     

A 1-GS/s FFT/IFFT processor for UWB applications

In this paper, we present a novel 128-point FFT/IFFT processor for ultrawideband (UWB) systems. The proposed pipelined FFT architecture, called mixed-radix multipath delay feedback (MRMDF), can provide a higher throughput rate by using the multidata-path scheme. Furthermore, the hardware costs of memory and complex multipliers in MRMDF are only 38.9% and 44.8% of those in the known FFT processor by means of the delay feedback and the data scheduling approaches. The high-radix FFT algorithm is also realized in our processor to reduce the number of complex multiplications. A test chip for the UWB system has been designed and fabricated using 0.18-/spl mu/m single-poly and six-metal CMOS process with a core area of 1.76/spl times/1.76 mm/sup 2/, including an FFT/IFFT processor and a test module. The throughput rate of this fabricated FFT processor is up to 1 Gsample/s while it consumes 175 mW. Power dissipation is 77.6 mW when its throughput rate meets UWB standard in which the FFT throughput rate is 409.6 Msample/s.     

面向OFDM的同时同频全双工双向高谱效中继方案

针对同时同频全双工双向中继网络,该文提出一种对中继剩余自干扰信号具有鲁棒性的双向中继传输方案。该文首先对中继剩余自干扰信号进行分析,将无限迭代的剩余自干扰信号建模成等效多径信号,并利用OFDM的循环前缀对抗等效多径现象,以降低中继剩余自干扰信号对系统传输性能的影响。在等效多径方案的基础上,以系统信干噪比最大化为目标,推导出全双工双向中继传输的最佳放大因子求解方法。最后,通过仿真验证所提出的双向中继传输方案的有效性。     

An active tagging system using circular-polarization modulation

An active read/write microwave tagging system using circular-polarization modulation as a novel modulation scheme for radio-frequency identification systems is presented. The proposed modulation scheme reduces demodulation complexity and power consumption on the battery-powered tag. Additional coding of the circular-polarization modulated data reduces transmission errors due to polarization inversion at multipath propagation. In multiple-reader environments, the main jamming threat occurs from power carriers of different interrogators. A combination of circular-polarization modulation and frequency hopping is presented that shows an increased immunity against multipath phenomena for multiple-tag and multiple-reader environments     

无人机地空链路信道特性与宽带数据传输

无人机地空链路数据传输存在多径衰落的影响。详细分析了无人机在滑行、起降和巡航3种状态下地空信道的传输特性。针对滑行、起降阶段多径时延大、存在频率选择性衰落的问题,提出了宽带数据传输技术——单载波频域均衡(SC-FDE)和正交频分复用(OFDM),并对SC-FDE进行了性能仿真。仿真结果表明,SC-FDE可以有效解决无人机滑行、起降阶段的多径衰落影响,提高宽带数据传输质量。     

基于相位补偿的非理想无线轨道角动量复用通信系统研究

电磁波轨道角动量各模态间满足严格正交性,为无线通信系统提供了一个新的复用维度。当前无线轨道角动量通信的研究仍集中于理想视距(LoS)场景,在实际通信场景中,多径效应和非对齐效应等非理想传输情况通常是无法避免的,这会使得无线轨道角动量多入多出(OAM-MIMO)通信系统的性能遭受较大损失。为提升非理想无线OAM-MIMO通信系统性能,该文建模了一种更加符合实际传输场景的毫米波OAM-MIMO 10射线信道模型;然后评估了多径效应和非对齐效应带来的性能损失问题;最后,提出了一种低复杂度的平均相位补偿与迭代功率分配(APC-IPA)联合优化方案来消除非对齐和多径效应造成的相位偏差,提升系统信道容量。仿真结果表明：在同时遭受非对齐和多径效应时,所提APC-IPA联合方案能够有效地提升系统信道容量。     

Design of high-speed digital filters suitable for multi-DSP implementation

A multipath signal processing scheme is proposed to overcome the limitation on throughput rate of present-day LSI devices using a number of digital signal processors. Two methods are proposed to realize a given transfer function H(z) for a digital filter with a throughput rate speed that is N times higher than in conventional methods. The first method, the delayed multipath approach, uses an N-path structure as a building element. These N elements are connected successively with increasing delay units to realize a given transfer function. The second method preprocesses the input signal sequence with an FFT processor and follows it up by N of constituent transfer functions derived from H(z) having real coefficients. The output of these N constituent transfer functions is finally post processed by an inverse FFT processor to obtain the desired output signal. The number of the constituent transfer functions is double for a special case when the transfer function to be implemented has complex valued coefficients.