DS/CDMA系统中的一种自适应单用户接收机

本文提出了一种在异步多径DS/CDMA系统中基于独立分量分析算法的单用户接收机,这种接收机仅需要已知期望用户的定时和特征波形,计算量小、结构简单.它不但能用于在基站进行多用户信号的上行接收,而且适合于用在移动台进行下行接收.其性能较之匹配滤波器和盲MMSE多用户检测器有很大提高.     

MDPSK信号的一种盲接收机

随着通信技术和数字信号处理技术的发展,通信接收机应具有越来越强的参数识别能力。该文提出一种适用于任意进制的差分相移键控信号(MDPSK)的盲接收机结构,在未知信号制式的条件下,该接收机可以取信号的最佳定时同步、自动识别信号的调制制式,实现信号的盲接收。     

多发射与多接收天线系统盲自适应算法研究

提出了一种用于正交空时分组码(OSTBC:Orthogonal Space-Time Block Code)多发射天线多接收天线系统的盲自适应接收机.该方法主要利用了正交空时分组码的内在特性,给出了一个针对正交空时分组码多发射天线多接收天线系统的无约束代价函数,分析了该函数的全局最小值点.利用该无约束代价函数,通过投影逼近方法给出了递推最小二乘(RLS)自适应算法实现.仿真结果表明:该接收机可以很好的跟踪衰落信道的变化,在不利用导频信号的情况下很好的还原出原始的传输信号.     

数字化频率分集的脉冲雷达补盲方法研究与实现

针对某型脉冲雷达对最小探测距离的要求，本文介绍了一种利用双频双脉冲形式进行近区补盲的方法，并且针对该方法设计了在接收机的单通道内实现数字化频率分集的工作方式。 首先，为解决脉冲雷达探测距离存在近区盲区的问题，给出了宽、窄相结合的双频双脉冲的补盲方法，以达到雷达最小探测距离的要求。然后，利用数字化频率分集的思想在接收机单通道内完成双频双脉冲的频率分离，既实现了补盲效果，也突破了传统补盲方法下接收机通道必须完全或部分复制的固有方式，减小了接收系统的体积和复杂度，从而促进脉冲雷达系统实现小型化、轻量化。最后，在某型雷达接收系统中进行了性能测试，验证了本文方法的有效性和实用性。并且该型雷达已经完成了外场试验，最小探测距离符合要求，表明利用数字化频率分集的方式实现脉冲雷达接收机单通道的双频双脉冲补盲方法应用可行。     

多径超宽带接收机的研究和仿真

对多径IR-UWB信号的Rake接收技术原理和结构进行了详细分析。在此基础上仿真了不同Rake接收机的性能,包括部分Rake和选择性Rake,以及具有不同叉指的Rake接收机的性能。仿真结果表明在具有相同叉指条件下,选择性Rake接收机比部分Rake接收机的性能高出3dB。而在相同接收原理下,叉指越多,接收机的性能越好。而2路选择性Rake接收机和5路部分Rake接收机在较低信噪比的情况下,性能并无很大差别。     

一种频率选择性衰落信道下的盲自适应去相关Rake接收机

多用户检测是DS－CDMA系统中的一项关键技术,而Rake接收是解决多径效应的一种有效方法,本文将基于Kalman滤波的多用户检测器与Rake接收相结合,提出了一种频率选择性衰落信道下的盲自适应去相关Rake接收机,研究结果表明,这种接收机具有较强的抑制多址干扰和克服“远－近”效应能力,并且能快速收敛。     

盲扫攻略--以同洲CDVB-3188C为代表的

具有自动搜索功能的盲扫数字接收机自2002年一经推出，就受到了广大用户的一致推崇和肯定。盲扫机的面市彻底结束了以往接收卫星数字信号时，必须知道准确参数的历史，从此可以不必再去搜集和查询各种资料．就能掌握卫星上节目参数的变化情况。到今天，无论何种品牌，何种价位的接收机，几乎全部具有盲扫功能，并且历经创新和改进，其性能更加优异。     

浅谈“盲扫”

"盲扫"是近2年新出现的名词, 所谓"盲扫"是指用户在不知道卫星参数的情况下搜索节目,用户可以对参数了解甚少或者完全不知道,只要天线对正了,就没有问题。操作简便易懂,不需要有专业知识,任何人都很容易操作,这个功能现在已经广泛应用于数字机领域。对于早期接收机设计而言,卫星数字接收机增加盲扫功能是较为困难的,数字信号在接收之前要知道许多参数,例如下行频率,符号率2M-45M,FEC(前向纠错可分为1/2,2/3,3/4,5/6,7/8),极化(水平/ 垂直)等等,缺一不可。这麽多的变量加在一起,而且要同时从950MHz-2150 MHz(接收机可以接收的信号)这麽宽的范围进行搜索,所     

多径CDMA信道下基于指数加权最小二乘盲空时多用户检测

本文首先在码片匹配滤波的基础上为多径CDMA信道下的接收机提出四种数据选择方案，分析了各种数据方案对多址干扰与码间干扰的影响；接着提出了基于Rosen梯度投影实现的指数加权最小二乘盲空时多用户检测方法并分析了四种数据选择方案对其运算复杂度的影响；最后通过仿真实验结果表明：本文所提出盲空时多用户检测方法在运算量、收敛速度以及接收性能具有一定的优势。     

非线性盲辨识补偿处理的宽带超外差接收机

提出了一种基于非线性盲辨识补偿处理的新型宽带超外差接收机。在时域,分别提取接收前端输出信号的大信号成分（大功率频率分量）和小信号成分（主要包含非线性失真分量）,并以大信号的非线性模型与小信号的残差平方和最小作为其非线性行为模型参数的辨识准则,利用加权迭代改善算法实现模型参数的自适应提取和更新,最后在线实时地对接收机输出信号进行数字域后补偿处理。实测结果表明,在同时多信号接收的情况下,该非线性盲辨识补偿处理可将整机的无杂散失真动态范围(SFDR)提高超过20dB,极大地提高了在强干扰存在时对微弱信号接收与检测的能力。      

MUI-free receiver for a synchronous DS-CDMA system based on blockspreading in the presence of frequency-selective fading

We discuss a synchronous direct-sequence code division multiple-access (DS-CDMA) system based on block spreading in the presence of frequency-selective fading. Note that block spreading, which is also known as chip interleaving, refers to a spreading of a data block sequence, which is obtained by dividing a data symbol sequence into consecutive blocks. For such a system, we develop a simple new receiver that completely removes the multiuser interference (MUI) without using any channel information. The MUI-free operation is obtained by the use of a shift-orthogonal set of code sequences on which this receiver is based. Within the framework of the MUI-free receiver, we further present a subspace deterministic blind single-user channel estimation algorithm. As a benchmark for the MUI-free receiver and the corresponding subspace deterministic blind single-user channel estimation algorithm, we consider the linear multiuser equalizer and the corresponding subspace deterministic blind multiuser channel estimation algorithm developed by Liu and Xu (1996) for a standard synchronous DS-CDMA system in the presence of frequency-selective fading. We show that the complexity of the MUI-free receiver using the corresponding subspace deterministic blind single-user channel estimation algorithm is much smaller than the complexity of the linear multiuser equalizer using the corresponding subspace deterministic blind multiuser channel estimation algorithm. We further show that the performance of the MUI-free receiver is comparable with the performance of the linear multiuser equalizer. This is for the case in which the channels are known as well as for the case in which the channels are estimated with the corresponding subspace deterministic blind channel estimation algorithm     

Capon multiuser receiver for CDMA systems with space-time coding

We present in this paper a linear blind multiuser receiver, referred to as the Capon receiver, for code-division multiple-access (CDMA) systems utilizing multiple transmit antennas and space-time (ST) block coding. The Capon receiver is designed by exploiting signal structures imposed by both spreading and ST coding. We highlight the unique ST coding induced structure, which is shown to be critical in establishing several analytical results, including self-interference (i.e., spatially mixed signals of the same user) cancellation, receiver output signal-to-interference-and-noise ratio (SINR), and blind channel estimation of the Capon receiver. To resolve the scalar ambiguity intrinsic to all blind schemes, we propose a semi-blind implementation of the Capon receiver, which capitalizes on periodically inserted pilots and the interference suppression ability of the Capon filters, for (slowly) time-varying channels. Numerical examples are presented to compare the Capon receiver with several other training-assisted and (semi-)blind receivers and to illustrate the performance gain of ST-coded CDMA systems over those without ST coding     

An Optimum Blind Receiver for Correlated Rician Fading MIMO Channels

A blind receiver scheme for narrowband separately- correlated Rician block fading coded MIMO systems is described. It is shown that this receiver (which can be interpreted as a limiting case of the optimum pilot-aided receiver) attains the maximum achievable throughput at sufficiently high E_b/N₀ ratio. The influence of the E_b/N₀ ratio and of the channel Rice factor on the receiver performance are studied and it is shown that, as either of these parameters increases, the advantage of the blind versus the pilot-aided receiver becomes more sensible. The results obtained support the intuition that, if the line-of-sight component is sufficiently strong, a blind scheme using only the knowledge of the fading statistics parameters matches or outperforms pilot- aided detection.     

一种用于CDMA下行链路的空时编码盲多用户检测

提出了一种适用于下行链路的盲多用户检测器,在下行链路的接收方只需进行简单解码和盲多用户检测就可以获得同采用多天线接收相同的效果。仿真结果表明当加入空时编码和盲多用户检测后对移动接收方南误码率有提高。     

Closed-form blind MIMO channel estimation for orthogonal space-time block codes

In this paper, a new computationally simple approach to blind decoding of orthogonal space-time block codes (OSTBCs) is proposed. Using specific properties of OSTBCs, the authors' approach estimates the channel matrix in a closed form and in a fully blind fashion. This channel estimate is then used in the maximum-likelihood (ML) receiver to decode the information symbols. The proposed estimation technique provides consistent channel estimates, and, as a result, the performance of the authors' blind ML receiver approaches that of the coherent ML receiver, which exploits the exact channel state information (CSI). Simulation results demonstrate the performance improvements achieved by the proposed blind decoding algorithm relative to the popular differential space-time modulation scheme.     

盲速率判决技术在OFDM系统中的应用

该文借助CDMA系统中的盲速率判决技术解决交织与相位旋转(IPR-OFDM)( IPR:Interleaving and Phase Rotation),系统中接收端恢复交织序号,对接收信号进行检测的问题。IPR-OFDM系统在发送端使用了V 个交织器,接收端为了恢复数据需要知道发送端使用的交织器序号进行解交织。一种解决方法是发送辅助信息(SI:Side Information),这需要占用信道容量;该文借助于CDMA系统中速率判决的思想提出一种在接收端进行盲判的方法,它通过检测CRC(循环冗余校验码)和反转误码率(SER)信息等来获得所需要的交织序号,这种方法相对于前者提高了信道利用率。     

Performance Analysis of Partial Relay Selection in Cooperative Spectrum Sharing Systems

Quadrature Phase Shift Keying (QPSK) is one of the important and commonly used modulation formats. Phase precoding was recently proposed as a new approach to achieve blind recovery of co-channel QPSK signals in the CDMA context. In this paper, we propose a new blind receiver for phase precoded QPSK signals, whose performance is significantly better, and close to that of an MMSE receiver. The receiver is derived by exploiting the phase-precoding knowledge, as well as the special structure of the QPSK constellation. Obtained in a closed-form manner, the proposed receiver avoids convergence and initialization problems associated with some of the earlier blind co-channel receivers that were based on the constant modulus (CM) property or finite alphabet (FA) property or Higher Order Statistics (HOS) based receivers. Considering the good performance achieved and the closed-form nature of the detector, phase precoding may be seen as an attractive candidate for co-channel systems employing QPSK signaling to enable efficient blind detection while saving significant data throughput.     

Blind recognition of STBC-OFDM signals based on modified K-S test

Aiming at the problem that existed blind classification of STBC-OFDM in multiple input single output (MISO) communication system,an efficient method for blind classification of space-time block coded orthogonal frequency-division multiplexing (STBC-OFDM) signals based on modified Kolmogorov-Smirnov (K-S) test was proposed,when a single receiver antenna was employed at the receiver.Firstly,the model of received STBC-OFDM signals in MISO systems was given.Secondly,with the correlation of the coding matrix of STBC-OFDM signals,and the discrimination features function provided by the empirical cumulative distribution (CDFs) of the received OFDM blocks was constructed.Finally,the distance between CDFs was tested by the two-sample K-S test,which could blindly classify the STBC-OFDM signals.The proposed algorithm didn't need the estimation of channel,noise statistics and modulation type,and consequently,was well suited for non-cooperative communication context.Theoretical analysis and experimental verify its validity.     

CDMA发射分集系统的多用户检测常模算法分析

空时分集技术的最大优点在于在不增加带宽的情况下可以提高系统的可靠性,是目前移动通信的研究热点.常模算法是一种性能优良的码分多址(CDMA)盲多用户检测技术,能确保判决信号与实际传送信号之间的差错较小,误码率性能良好.文中提出将标准线性受限常模算法(LCCMA)与空时分组码(STBC)相结合,设计出一种收敛快、能够改善系统性能的基于2-空时分组码的多用户接收机.