双层异构网络中基于有限反馈的空时干扰对齐研究

本文针对双层异构网络，提出一种利用当前和过期发射端信道状态信息（Channel State Information at the Transmitters,CSIT）的异构空时干扰对齐（Heterogeneous Space-Time Interference Alignment,HSTIA）方案.该方案将空时干扰对齐拓展至双层异构网络MISO(Multiple Input Single Output)混合信道，研究可达自由度关于CSI(Channel State Information)反馈时延的折中域.结果表明，增加发射端天线数能有效提高可达自由度.基于该结论，将空时干扰对齐技术扩展至双层异构网络MIMO(Multiple Input Multiple Output)混合信道，分析MIMO系统发射端与接收端天线数比对系统自由度的影响，并进一步研究系统达到该自由度时CSI反馈时延的取值范围.结果表明，当发射端与接收端天线数比足够多时，系统自由度的稳健性随接收端天线数的增加而加强.通过仿真分析验证，HSTIA方案利用本地当前和过期CSIT执行发射预编码，实现不同时隙的干扰信号相互消除，...     

双基地多输入多输出雷达距离欺骗干扰识别技术

针对双基地多输入多输出(Multiple Input Multiple Output,MIMO)雷达面临的距离欺骗干扰问题,提出了一种基于角度定位的距离欺骗干扰识别方法.该方法利用双基地MIMO雷达能够同时测量目标相对于收发阵列的角度、存在信息盈余这一特点,将通过收发角度估算得到的目标距离和与实测距离和相减并与理论的测量极限误差进行比对,最终实现对距离欺骗干扰与真实目标信号的判定识别.理论分析以及仿真结果验证了所提方法的有效性和可行性.     

基于自能量回收的全双工用户协作NOMA系统性能分析

自干扰的存在是全双工(Full Duplex,FD)用户协作中继系统中的不利因素,本文研究了基于自能量回收(Self-Energy Recycling,SER)的FD用户协作非正交多址(Non-Orthogonal Multiple Access,NOMA)中继系统,在FD用户中继处考虑了不同的转发协议以及同时的信息和...     

二维定向瑞克接收机实现方案比较研究

为了充分利用瑞克(RAKE)接收机的多径能量利用效果和智能天线(SA)的定向收发作用,研究了RAKE接收机和智能天线的联合使用,提出了基于智能天线的定向二维(2D)RAKE接收机模型,给出了定向2D-RAKE接收机分别在射频、中频和基带的实现框图、工作原理和输出信号表达式,并对它们的性能以及工程实现做了分析讨论。指出基带定向二维RAKE接收机由于可以在基带上通过幅度加权来实现信号的定向收发,其优点是可以利用目前比较成熟的基带信号处理技术,但是由于不能利用相干解调作用来抑制多径干扰(MPI)和多用户干扰(MAI),存在噪声放大问题;射频定向二维RAKE接收机的信噪比增益最大,但工程实现难度较大;中频定向二维RAKE接收机则具有较高的性价比。     

非理想干扰消除全双工协作NOMA系统性能分析及功率分配

随着非正交多址接入（Non-Orthogonal Multiple Access, NOMA）技术的不断发展,协作NOMA (Cooperative Non-Orthogonal Multiple Access, CNOMA)也受到广泛关注.该文研究了由一个基站（Base Station, BS）、一个远端用户和一个近端用户组成的全双工（Full-Duplex, FD）协作NOMA (FD-CNOMA)系统,其中近端用户作为一个FD解码转发中继以传输远端用户的信号.考虑实际情况中存在基站与远端用户有无直接链路两种情况,以及非理想连续干扰消除（Successive Interference Cancellation, SIC）对系统带来的残留干扰问题,该文提出并解决了在该模型下用户的功率分配问题.最后,该文基于此模型给出了中继用户和远端用户的中断概率闭式表达式和遍历速率的近似闭式表达式.理论分析与仿真结果表明,即便存在非理想SIC和自干扰,相对于半双工（Half-Duplex, HD）协作NOMA(HDCNOMA)和NOMA系统而言,FD-CNOMA系统表现出更好的系统性能.同时,非理想...     

机载定向红外干扰系统

20 0 2年 1 1月 2 8日 ,一架编号为IZ5 82的以色列航空公司波音 75 7客机 ,刚从肯尼亚蒙巴萨机场起飞 ,两枚“萨姆 - 7”便携式红外制导导弹追踪而来 ,所幸与客机擦身而过 ,这缘于飞机上安装了定向红外干扰系统。为此 ,2 0 0 3年 1月海湾局势紧张时 ,美国空军紧急决定为 1 2架C - 1 7军用运输机配备定向红外干扰系统设备。2 0世纪 90年代初 ,美国特种作战司令部与英国国防部委托诺思罗普·格鲁曼公司牵头研制AN/AAQ - 2 4 (V)定向红外干扰系统。几乎同时 ,美国陆军指定桑德斯公司开始研制AN/ALQ - 2 1 2 (V)定向红外干扰系统。AN/AA…     

基于球形译码的联合多用户检测

针对采用码分多址接入（CDMA,Code Division Multiple Access）的多输入多输出系统（MIMO,Multiple Input Multiple Output）,建立多个用户同步上行接入基站的信道模型,收发端都采用2根天线。在基站端,由于扩频码非完全正交产生多个用户之间干扰和信道干扰影响信号检测的问题,分析并给出了多用户信号的最大似然函数,利用球形译码算法实现多用户的联合检测（Joint MUD,Joint Multiple User Detection）,并行处理信道干扰和多址干扰。仿真结果表明,提出的接收机有较好性能,同时降低了运算的复杂度。     

LSTBC+OFDM分层方法的一种改进

基于OFDMA(Orthogonal Frequency-Division Multiple Access)中不同用户的子载波选择矩阵相互正交,提出了频率选择性衰落信道下分层结构的空时分组编码LSTBC(Layered Space-Time Block Code)的一种改进的分层方法.发射端采用分层结构的空时分组编码结合OFDM技术,在接收端提出了利用OFDM中子载波选择矩阵进行分组干扰抑制,然后对LSTBC的每层进行空时分组码的传统解码.相对于基于奇异值分解的分组干扰抑制方法,该方法只需要一根接收天线,降低了系统接收机设计的复杂度.仿真结果验证该方法的有效性.     

一种结合雾计算的车辆通信网络碰撞避免TDMA MAC协议

智能交通系统的产生和发展对车辆通信的介质访问控制(Medium Access Control,MAC)协议提出了更高的要求.被广泛使用的基于信道竞争的载波侦听多路访问(Carrier Sense Multiple Access,CSMA)协议存在不确定时延问题,基于时分多址(Time Division Multiple...     

基于VLC的测距算法研究

码分多址(Code Division Multiple Access,CDMA)技术的飞行时间(Time-of-Flight,TOF)测距算法可有效克服光干扰。通过模型和算法,把伪噪声序列加入到测距信号中,并在接收机接收到信号时根据伪噪声序列对信号进行检测,以分辨出所需的测距信号。仿真表明,运用了CDMA技术的飞行时间测距系统相对于不运用CDMA的测距系统在性能上有很大优势。在同一光亮度和误码率的情况下,运用CDMA技术使得测距距离有了显著提高,相邻干扰车辆引起的误码率大大降低。     

DS MIMO系统中叠加扩频及SP联合抗干扰

针对将直扩（direct spread, DS）与收发多天线（multiple input multiple output, MIMO）空时分组编码相结合存在多址干扰,且受到宽带干扰尤其强干扰时性能会恶化,提出一种叠加扩频的方法来消除多址干扰,并利用子空间分解（subspace projection, SP）的方法实现对宽带干扰的抑制,即将信道和接收矩阵投影到干噪子空间中构建等效矩阵进行译码,其中通过简化的最大比合并译码降低了空时分组译码复杂度。理论分析及仿真表明该抗干扰方案能够提高DS抗窄带干扰能力,并实现抗宽带干扰和对多址干扰的完全抑制。      

Cooperative power allocation with partial channel information in multi‐cell multi‐user dual‐hop MIMO relay systems

This paper considers cooperative power allocation with the use of partial channel state information (CSI) in a multi‐user dual‐hop relay system with multiple antennas. The end‐to‐end capacity can be improved by dynamically allocating the transmit power of the base station and relay according to co‐channel interference caused by the adjacent relays. The proposed scheme allocates the transmit power in association with the eigenvalues and angle difference between the eigenvectors of transmit correlation matrices of the desired and interference channel. It is shown by means of upper‐bound analysis that the end‐to‐end capacity of the proposed scheme can be maximized in highly correlated channel environments when the principal eigenvectors of transmit correlation matrices of the desired and interference channel are orthogonal to each other. It is also shown that the proposed scheme is robust to the channel estimation error. Finally, the performance of the proposed scheme is verified by the computer simulation. Copyright © 2010 John Wiley & Sons, Ltd.     

Preamble-based improved channel estimation for multiband UWB system in presence of interferences

Interferences reduce the performance of a correct data signal detection and decoding. This problem becomes severe when interferences exist during the period of channel estimation. This will destroy the accuracy of channel estimation and will eventually result severe degradation in the performance of signal detection and decoding in the entire data packet/frame. In this article, we propose an improved channel estimation technique for multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system in presence of interferences. In particular, we work towards a preamble-based channel estimation technique in multi-access and narrowband interfering environments. We construct two preamble symbols with opposite, both in amplitude and phase, sequences in frequency-domain. Time-domain redundancy (TR) is introduced into these preamble symbols before transmission. Based on this time-domain redundancy property, we eliminate multi-access interference (MAI) through an adaptive select and replace (ASR) scheme. We show that the use of opposite sequences in preambles leads a simple addition, subtraction and compare (ASC) scheme to cancel narrowband interference (NBI). In addition, we apply a frequency-domain filter, driven by channel’s power delay profile (PDP), to get a further enhancement in the estimation accuracy. Simulation results urge that our proposed technique outperforms the conventional channel estimation methods.     

机载双基地极化敏感阵列多干扰抑制

为了破解雷达主瓣干扰尤其是多个主副瓣干扰同时抑制的难题,该文利用目标极化散射特性在不同入射角存在差异而干扰近似相同的特点,将极化信息应用到机载双基地雷达,通过构建机载双基地极化敏感阵列来实现主副瓣干扰抑制。该方法主要通过双基地-极化分级抑制来实现。首先重构协方差矩阵遮蔽主瓣干扰来分别抑制双基地主辅雷达副瓣干扰,然后将辅雷达接收数据时域对齐后送主雷达,最后修正主辅雷达主瓣干扰导向矢量,并利用极化对消实现主瓣干扰抑制。仿真结果表明:利用双基地-极化分级抑制方法可实现多个主副瓣干扰同时抑制,大幅提升雷达系统抗干扰能力。      

基于二阶锥规划的相干信号深零陷自适应波束形成

针对常规自适应波束形成算法在强相干干扰情况下零陷深度不够、甚至干扰抑制失效的问题,提出了一种基于二阶锥规划的相干信号深零陷自适应波束形成算法。该算法首先对接收数据协方差矩阵进行Toeplitz重构,使其包含信号和干扰的所有方位信息。然后重构了干扰加噪声协方差矩阵。接着在保证期望方向波束无失真前提下,约束主瓣宽度和旁瓣电平,使得波束形成器干扰和噪声的输出功率最小。最后将该问题转化为凸优化中的二阶锥规划问题,并使用凸优化工具箱进行快速求解。仿真结果验证了该算法的有效性。     

Multiuser receiver scheme for full‐rate space–time coded CDMA system with imperfect estimation

By introducing a full‐rate space–time coding (STC) scheme, a synchronous CDMA (code division multiple access) system with full‐rate STC is given, and the corresponding uplink performance is investigated in Rayleigh fading channel with imperfect estimation. Considering that existing STC‐CDMA system has high decoding complexity, low‐complexity multiuser receiver schemes are developed for perfect and imperfect estimations, respectively. The schemes can make full use of the complex orthogonality of STC to reduce the high decoding complexity of the existing scheme, and have linear decoding complexity compared with the existing scheme with exponential decoding complexity. Moreover, the proposed schemes can achieve almost the same performance as the existing scheme. Compared with full‐diversity STC‐CDMA, the given full‐rate STC‐CDMA can achieve full data rate, low complexity, and partial diversity, and form efficient spatial interleaving. Thus, the concatenation of channel coding can effectively compensate for the performance loss due to partial diversity. Simulation results show that the full‐rate STC‐CDMA has lower bit error rate (BER) than full‐diversity STC‐CDMA systems under the same system throughput and concatenation of channel code. Moreover, the system BER with imperfect estimation are worse than that with perfect estimation due to the estimation error, which implies that the developed multiuser receiver schemes are valid and reasonable. Copyright © 2010 John Wiley & Sons, Ltd.     

FSO中分层空时编码的误码性能

分层空时编码(BLAST)虽然具有极高的频谱效率,能成倍提高光通信系统的信息传输速率,但BLAST系统的误码率较大,严重影响了光通信系统的可靠性。在描述了湍流信道中多输入多输出(MIMO)系统的信道模型后,针对多进制脉冲位置调制(Q-PPM)技术,推导出了采用线性译码算法时分层空时码的极大似然判决准则及其误码率公式,并比较了最大似然译码算法、线性译码算法、串行干扰消除译码算法的误码性能。最后,利用仿真实验进行了验证。结果表明:在自由空间光通信(FSO)中,串行干扰消除译码算法的误码性能更接近最大似然译码算法的性能,明显优于线性译码算法。在4×4系统中,当误比特率为2×10-2时,相对于最小均方误差(MMSE)译码算法,最大似然译码算法和MMSE-SIC译码算法的信噪比分别改善了约14.5 dB和7 dB。理论分析与实验结果相一致。     

ICI problem and compensation in MIMO SC‐FDMA system with SC‐SFBC scheme

In this paper, we address the ICI (intercarrier interference) problem and compensation in MIMO (multiple input multiple output) SC‐FDMA (single carrier frequency division multiple access) system that exploits SC‐SFBC (single carrier‐space frequency block coding) scheme. Recently, SC‐FDMA technique has received more attention due to the low PAPR (peak to average power ratio) property. However, SC‐FDMA system is sensitive to phase noise and CFO (carrier frequency offset) which is unavoidable in wireless communication systems. Phase noise and CFO introduce CPE (common phase error) as well as ICI into the received signal and seriously degrade the system performance. Therefore, analysis and suppression of these interferences are of great importance. In this paper, we analyze the interferences in MIMO SC‐FDMA system with SC‐SFBC. Then a new ICI estimation and suppression method is proposed to suppress the interferences. Instead of directly estimating the CFO and phase noise, which is pretty difficult and complex, this algorithm exploits block‐type pilots, which is a common pilot pattern in wireless communication systems, such as LTE standard, to estimate the interferences. After that the interferences are suppressed by the inverse matrix method. Simulation results show that the system performance is significantly improved. Copyright © 2010 John Wiley & Sons, Ltd.     

基于压缩感知的同频干扰下LTE系统信道估计算法

本文提出一种基于压缩感知的同频干扰下长期演进系统信道估计方法。与现有方法不同,本文将干扰和噪声区别对待,利用干扰信号结构建立该系统下多小区信道估计模型(MCCE)。由于无线信道在宽带系统下表现出较为明显的稀疏特性,本文将压缩感知技术应用于上述模型,通过求解新的感知矩阵,并利用多输入多输出信道共有非零支撑集的特性,提出了适用于长期演进系统的联合改进子空间追踪算法(J-MSP),解决了上述模型下字典矩阵列相关度较高的问题;由于所提模型中含有未知的干扰符号,因此还需解决信道和干扰符号的联合估计。仿真结果和分析表明,本文方法在干扰与本小区同步时相比单小区信道估计方法性能显著提升,异步时与最大似然算法性能相当,同时也适用于无干扰场景。      

多小区多用户TDD MIMO下行链路干扰抑制预编码算法

针对多小区多用户TDD MIMO下行链路,提出了一种基于预编码的联合干扰抑制算法。首先,利用广义MMSE信道逆的QR分解设计预编码矩阵抑制下行链路的多用户干扰(MUI)。然后,从信号能量泄露的角度设计第二个预编码矩阵抑制小区间干扰(ICI)和残留的多用户干扰。该算法能够利用TDD MIMO信道的互易性,不需要用户端的反馈。在市区微小区组成的多用户TDD MIMO系统中的仿真结果表明,该算法能有效地提高系统容量和用户端平均信干噪比(SINR)。