瑞利衰落信道下差分跳频通信系统抗部分频带噪声干扰的性能分析

在瑞利衰落信道和部分频带噪声干扰共存的环境下,针对逐符号检测和按序列检测两种信号检测方法,分别就差分跳频通信系统的误符号性能进行了理论分析,同时做出相应的计算机仿真.结果证实,差分跳频通信技术和按序列检测方法的结合,使通信系统的抗部分频带噪声干扰的性能得到了比较显著的提升.     

一种新的SEC/MRC混合合并技术的研究

针对分集合并通信系统在复杂度与性能之间一直存在矛盾的问题,提出了一种将切换检测合并(SEC)与最大比合并(MRC)相结合的新的混合合并方式,并对各分支为独立同分布(i.i.d.)的瑞利衰落情况进行了研究,给出了中断概率(OP)、平均输出信噪比(SNR)的闭合表达式,以及误码率(BER)的有限区间积分形式表达式。最后将这种SEC/MRC合并方式与MRC及广义选择合并(GSC)进行了比较,结果表明,SEC/MRC合并方式在减少信道接收机数量、降低系统复杂度的情况下,仍能达到很好的性能,具有良好的实际应用价值。     

OFDM系统在时变信道下的迭代干扰抵消算法

为克服正交频分复用(OFDM)系统中因时变多径衰落信道破坏子载波的正交性引起载波间干扰(ICI),从而导致系统性能下降的问题,提出了一种基于最小均方误差(MMSE)估计和迭代算法相结合的迭代干扰抵消算法.为了消除一般MMSE均衡方法将载波间干扰当作加性高斯白噪声(AWGN)所带来的误差,该算法先使用MMSE方法对传输信号进行初值估计,再通过迭代干扰抵消和MMSE均衡相结合,来消除由时变信道所带来的载波间干扰.多次仿真表明,在时变多径衰落信道中使用本算法能够有效地消除载波间干扰,使系统性能得到很好的改善.     

MISO有限反馈误符号率下边界分析

采用矩母函数(MGF)方法进行了多输入单输出(MISO)有限反馈系统误符号率(SER)分析研究。研究表明,有限反馈性能分析对码本设计有指导意义,由于受多方面因素的影响,很难得到误符号率表达式的闭式解,因此进行误符号率下边界的分析是有价值的。本文利用接收信噪比矩母函数和误符号率之间的关系,并且对复球体的球帽表面积做近似处理,得到了误符号率的下边界。该下边界反映了系统的性能受码本大小、发射天线数、调制方式影响,在实际系统的设计中,可以根据误符号率要求得到码本大小。仿真结果验证了理论下边界和实际仿真误符号率的误差小于0.1dB。     

一种应用于FM IBOC DAB系统的比特交织编码调制方案

提出了一种适用于FM IBOC广播系统的比特交织编码调制方案。此方案结合互补增信删余卷积码(CPPC)和基于迭代译码的比特交织编码调制(BICM-ID)算法。互补增信删余卷积码能有效抵抗FM IBOC系统中面对的第一邻频干扰和无线信道噪声、衰落等干扰。同时,运用基于软判决反馈迭代译码的比特交织编码调制算法,可以不通过扩展频带来提高FM IBOC广播系统在瑞利信道中的编码增益。仿真结果表明,本方案能有效提高FM IBOC广播系统的接收性能。     

基于符号调整的OFDM系统载波间干扰抑制方法

基于组合优化理论,提出了一种通过调整子载波调制符号的正负来抑制正交频分复用(OFDM)系统载波间干扰(ICI)的方法.首先推导出了加性高斯白噪声(AWGN)信道下的最优符号选择算法,并给出了降低其复杂度的简化算法;然后给出了二进制相移键控(BPSK)调制下减少算法码率损失的改进算法,而且在频率选择性衰落信道下对以上算法进行了推广.仿真结果证实,提出方法的误码率低于基于选择映射的载波间干扰抑制方法.     

多径信道下基于频域均衡的超奈奎斯特传输

针对在多径信道下进行超奈奎斯特(FTN)传输时,同时存在由FTN与多径信道引入的双重符号间干扰(ISI)的问题,提出了应用频域均衡与低密度奇偶校验(LDPC)编码相结合的接收机结构来提高系统传输性能。该接收机构在接收端利用频域均衡器对由FTN与多径信道引入的符号间干扰进行频域均衡,均衡后的信号再通过LDPC信道译码器,利用最大后验概率准则(MAP)进行判决,最终恢复出原始信息。仿真实验显示,基于频域均衡的FTN传输系统可改善系统传输的误码性能。     

基于列正交变换实现串行干扰消除的MIMO检测算法

针对用于多输入多输出（MIMO）通信系统检测的按序QR分解（SQRD）算法在多径瑞利慢衰落信道中检测误码率较高的不足,提出了一种基于列正交（CO）变换的串行干扰消除（SIC）算法——COSIC。该算法对信道矩阵按列正交变换,避免了求上三角矩阵的运算,并且在判决信号过程中,将先判决出的信号通过信道后的输出向量作为干扰进行消除,在略微增加系统时间复杂度的基础上,使系统检测性能得到了明显改善。在多散射物的无线通信环境下进行的仿真实验证实,与传统的SQRD算法相比,所提算法误码率显著下降．系统检测性能明显改善。     

符号检测辅助的最大信干噪比干扰对齐算法研究

在K×K用户多输入多输出(MIMO)通信系统中,提出了一种符号检测辅助的最大信干噪比(SDA-MAX-SINR)干扰对齐(IA)算法。首先利用传统最大信干噪比(MAX-SINR)干扰对齐算法检测接收信号,其次直接利用检测的接收信号,基于最大信干噪比准则迭代计算接收端干扰抑制矩阵和发射端预编码矩阵。仿真结果表明,与传统的最大信干噪比干扰对齐算法相比,文中所提出的符号检测辅助的最大信干噪比干扰对齐算法在系统的均方误差(MSE)和误码率(BER)上的性能均有明显的改善。     

FQPSK调制在双波散射功率衰落信道下的性能

研究了深空通信系统的性能计算。系统采用Feher正交相移键控(FQPSK)调制和双波散射功率(TWDP)衰落信道,因为TWDP信道模型的散射传输波中含有两个镜面反射多径分量,可依据不同参数表达不同的衰落,因此适合描述复杂的电磁深空通信环境;FQPSK调制与标准QPSK相比具有频谱主瓣窄和滚降快的优势,因此更适合应用于深空通信系统中。为简化系统性能计算,推导了FQPSK调制在TWDP衰落下的误码率闭式解,并验证了推导的正确性。基于深空通信系统仿真平台,分析了不同种类QPSK调制及各种TWDP衰落参数下的误码率性能。结果表明,FQPSK与QPSK相比,结合卷积编码后可实现性能提升。     

A Link-Level Simulator of the cdma2000 Reverse-Link Physical Layer

The cdma2000 system is an evolutionary enhancement of the IS-95 standards which support 3G services defined by the International Telecommunications Union (ITU). cdma2000 comes in two phases: 1XRTT and 3XRTT (1X and 3X indicates the number of 1.25 MHz wide radio carrier channels used and RTT stands for Radio Transmission Technology). The cdma2000 1XRTT, which operates within a 1.25 MHz bandwidth, can be utilized in existing IS-95 CDMA channels as it uses the same bandwidth, while 3XRTT requires the commitment of 5 MHz bandwidth to support higher data rates. This paper describes a software model implementation of the cdma2000 reverse link and its application for evaluating the effect of rake receiver design parameters on the system performance under various multipath fading conditions. The cdma2000 models were developed at the National Institute of Standards and Technology (NIST), using SPW (Signal Processing Worksystem) commercial software tools. The model has been developed in a generic manner that includes all the reverse link six radio configurations and their corresponding data rates, according to cdma2000 specifications. After briefly reviewing the traffic channel characteristics of the cdma2000 reverse link (subscriber to base station), the paper discusses the rake receiver implementation including an ideal rake receiver. It then evaluates the performance of each receiver for a Spreading Rate 3 (3XRTT) operation, which is considered as a true “3G” cdma2000 technology. These evaluations are based on the vehicular IMT-2000 (International Mobile Telecommunication 2000) channel model using the link budget defined in cdma2000 specifications for the reverse link.     

钟差辅助故障卫星检测算法研究

为了提高钟差预测模型辅助故障卫星检测的效果,论文从非线性时间序列的角度对钟差序列进行探讨,提出了基于灰色理论和马尔可夫链的钟差组合预测模型。文章给出了新模型的基本思想和具体实现步骤,然后将基于该模型的钟差预测值引入到接收机中辅助进行检测故障卫星。文末,应用实测数据,验证了新方法的可行性与有效性。本文对故障卫星检测问题的解决提供了新的思路,可以作为提高GPS接收机定位精度以及可靠性等工程应用的参考     

一种基于PFA的多子阵聚束合成孔径声呐成像方法

文章提出了一种基于极坐标格式算法（Polar Format Algorithm,PFA）进行聚束多子阵合成孔径声呐成像的改进方法,建立了非“停-走-停”条件下的斜视成像模型,推导了信号由时域到波数域的解析表达式,给出了信号处理流程。该方法首先使用场景中心点的精确距离史对平台运动误差进行补偿,并通过极坐标算法处理得到粗聚焦的图像。其次,为了解决非场景中心点的残余空变相位误差的补偿问题,对粗聚焦图像进行分块自聚焦处理,使场景边缘点的聚焦效果得到改善。最后,经过子图拼接及几何校正后得到完整的精聚焦图像。仿真及分析结果表明,该方法提高了方位向性能指标,同时也能准确补偿平台运动误差,可以很好地应用于多子阵声呐成像。该方法在大运动误差、大斜视情况下仍具有较好的鲁棒性。     

A New Optimized Algorithm with Nonlinear Filter for Ultra-Tightly Coupled Integrated Navigation System of Land Vehicle

The extended particle filter (EPF) assisted by the Takagi-Sugeno (T-S) fuzzy logic adaptive system (FLAS) is used to design the ultra-tightly coupled GPS/INS (inertial navigation system) integrated navigation, which can maneuver the vehicle environment and the GPS outages scenario. The traditional integrated navigation designs adopt a loosely or tightly coupled architecture, for which the GPS receiver may lose the lock due to the interference/jamming scenarios, high dynamic environments, and the periods of partial GPS shading. An ultra-tight GPS/INS architecture involves the integration of I (in-phase) and Q (quadrature) components from the correlator of a GPS receiver with the INS data. The EPF is a particle filter (PF) which uses the extended Kalman filter (EKF) to generate the proposal distribution. The PF depends mostly on the number of particles in order to achieve a better performance during the high dynamic environments and GPS outages. The T-S FLAS is one of these approaches that can prevent the divergence problem of the filter when the precise knowledge on the system models is not available. The results show that the proposed fuzzy adaptive EPF (FAEPF) can effectively improve the navigation estimation accuracy and reduce the computational load as compared with the EPF and the unscented Kalman filter (UKF).     

Average BER performance of FSO SIM-QAM systems in the presence of atmospheric turbulence and pointing errors

This paper presents the exact average bit error rate (BER) analysis of the free-space optical system employing subcarrier intensity modulation (SIM) with Gray-coded quadrature amplitude modulation (QAM). The intensity fluctuations of the received optical signal are caused by the path loss, atmospheric turbulence and pointing errors. The exact closed-form analytical expressions for the average BER are derived assuming the SIM-QAM with arbitrary constellation size in the presence of the Gamma–Gamma scintillation. The simple approximate average BER expressions are also provided, considering only the dominant term in the finite summations of obtained expressions. Derived expressions are reduced to the special case when optical signal transmission is affected only by the atmospheric turbulence. Numerical results are presented in order to illustrate usefulness of the derived expressions and also to give insights into the effects of different modulation, channel and receiver parameters on the average BER performance. The results show that the misalignment between the transmitter laser and receiver detector has the strong effect on the average BER value, especially in the range of the high values of the average electrical signal-to-noise ratio.     

基于深度神经网络的水声FBMC通信信号检测方法

针对传统水声滤波器组多载波(Filter Bank Multi-Carrier,FBMC)通信接收端需经过信道估计和均衡才可恢复出发送符号,系统复杂度高且信道估计精度不佳等问题.文章将深度神经网络融入到水声多载波通信当中,提出一种基于深度神经网络的水声FBMC信号检测方法.在训练阶段通过大量的数据迭代、调试超参数和优化...     

带有高压贮液器的热泵系统不同充灌量下的实验研究

高压贮液器是制冷、空调、热泵系统中的常用部件,但其对系统性能的影响在相关系统性能分析时却常被忽视。通过实验讨论了在充灌量过少、适量、过量的情况下,高压贮液器对系统工况和性能的影响与制约,并给出了充灌量过少、适量、过量的简易判别标准。     

相位均衡器技术在水声接收机的应用

滤波器相位的非线性引起的信号失真是超短基线接收机系统中必须要解决的问题之一。采用常规滤波器与全通网络级联的方法设计了一种相位均衡器,解决了仅使用常规滤波器带来的非线性相位问题,使超短基线接收机在带宽内保持线性相位。给出了全通网络的原理、电路结构推导,分析了该网络中各参量对相位的影响。在设计实例中,相位均衡技术应用到实际硬件电路中进行测试,并结合试验数据及仿真结果对系统的性能进行评估。测试结果证明了相位均衡器可以实现相位的均衡校正功能,在水声接收机领域中有良好的应用前景。     

Design and comparative performance analysis of different chirping profiles of tanh apodized fiber Bragg grating and comparison with the dispersion compensation fiber for long-haul transmission system

Various dispersion compensation units are presented and evaluated in this paper. These dispersion compensation units include dispersion compensation fiber (DCF), DCF merged with fiber Bragg grating (FBG) (joint technique), and linear, square root, and cube root chirped tanh apodized FBG. For the performance evaluation 10 Gb/s NRZ transmission system over 100-km-long single-mode fiber is used. The three chirped FBGs are optimized individually to yield pulse width reduction percentage (PWRP) of 86.66, 79.96, 62.42% for linear, square root, and cube root, respectively. The DCF and Joint technique both provide a remarkable PWRP of 94.45 and 96.96%, respectively. The performance of optimized linear chirped tanh apodized FBG and DCF is compared for long-haul transmission system on the basis of quality factor of received signal. For both the systems maximum transmission distance is calculated such that quality factor is ≥ 6 at the receiver and result shows that performance of FBG is comparable to that of DCF with advantages of very low cost, small size and reduced nonlinear effects.