Coding Schemes Incorporating Soft-Decision DPSK over HF Rayleigh Fading Channels

A soft-decision 8-DPSK modulation format is introducedin a concatenated coding scheme and the performance of the resultingsystem is evaluated over a slow Rayleigh fading HF ionospheric link inthe presence of Additive White Gaussian noise (AWGN). Well-known UngerboeckTCM techniques are used as inner codes and a Reed–Solomon blockcode as outer code. The coded/modulated signal is differentially encodedbefore transmission to combat random phase changes caused by the channel.Soft-decision demodulator's output is used as an input to a modifiedViterbi decoder that calculates the Euclidean distances of the receivedsignal from an 8-PSK constellation adapted to the signal's amplitudevariations. Block interleaving techniques are necessary to randomise longbursts of errors caused by the fading channel. Simulation results showthat significant coding gains are achieved with a minor bandwidth expansionover uncoded, diversity or other coded systems. Finally, theinteresting effects of interleaving on the performance of the proposedsystems are analysed.     

The Effect of Metric Modification on the Performance of TCM and Concatenated Systems Over Rayleigh Fading Channels

The performance improvement of conventional TCM schemes over frequency nonselective slow Rayleigh fading channels, caused by a slight modification on the metric calculation of the Viterbi decoder, is investigated in this paper. A statistical analysis of the Euclidean distances at the input of the Viterbi decoder is carried out to explain this improvement. Furthermore, the performance improvement of two concatenated coding systems incorporating the above modification, under the same conditions, is studied. The performance of the TCM and the concatenated systems is evaluated by Monte Carlo simulation. The results show that the examined systems, using the proposed modification on the metric calculation, achieve BER performances comparable to other codes and systems, especially designed for fading channels.     

交织的空时分组码级联不对称网格编码调制方法

根据交织的空时分组码级联TCM编码设计标准,提出了一种空时分组码级联不对称网格编码调制(A-TCM)的优化设计方案,并得到了在空时分组码级联不对称8PSK调制的TCM情况下最优的星座图旋转角度.仿真和分析结果表明,在相同的频谱效益和译码复杂度的情况下,相比传统空时分组码级联TCM的方法,新方法可进一步提高系统性能.     

Improved optical coding method for orthogonal ASK/DPSK modulation format

Orthogonal ASK/DPSK labeling, which encodes label information on optical carriers in a modulation format, is regarded as a competing scheme to subcarrier multiplexed optical labeling. However, the inherent cross-talk limits the extinction ratio (ER) of the payload and label sensitivity. In this paper, two optical coding methods-Manchester coding and 8B10B coding-which can remarkably improve the system quality to obtain acceptable ER are discussed. A novel optical packet encoding methodmark-insertion coding-is demonstrated to significantly reduce cross-talk between the amplitude shift keying ASK) payload and the differential phase shift keying (DPSK) label through spectrum shaping. The performance of mark-insertion coding depends on the number of inserted 'marks'. Finally, the transmission over a 40 km single mode fiber (SMF) is compared with optical label swapping for a. 40 Gbit/s ASK payload and 2.5 Gbit/s DPSK label under these coding schemes. The experimental result is consistent with the theoretical analysis.     

卫星信道中高阶APSK调制的非线性失真补偿算法

针对高阶APSK调制在卫星信道中存在有记忆非线性失真的现象,提出一种联合补偿算法,该算法充分利用APSK调制信号星座图的特点,在大幅度减小无记忆数据预失真计算量的基础上,联合非线性均衡实现对有记忆非线性卫星信道的自适应补偿.其优点是存储量和计算复杂度随调制阶数的增加变化很小.仿真结果表明,该算法能够达到有记忆数据预失真的补偿性能,且最佳工作点提高0.2 dB.     

Design of Amplitude and Phase Modulated Signals for Differential Space-Time Block Codes

A differential space-time block code (DSTBC) provides full diversity advantage and does not require any radio channel estimation in the receiver, which makes it an attractive alternative to the well-known coherent space-time block code (STBC). However the original design of DSTBC allows only pure phase shift keying (M-PSK) modulation scheme, which are not optimal for M > 4. In this paper a simultaneous amplitude and phase modulation scheme for DSTBC with 2 transmit and several receive antennas is introduced. The performance of the proposed scheme is investigated and compared with DSTBC techniques using pure M-PSK modulation. Alexandre Vanaev received B.Eng. degree in Electrical and Electronic engineering from the St. Petersburg State Polytechnic University, Russia in 1998, and M.Sc. degree in “Information and communication systems” from Technical University Hamburg-Harburg in 2002. He is currently pursuing his Ph.D. in the Technical University Hamburg-Harburg, Department of Telecommunications. His research interests include prospective OFDM-based wireless communication systems and MIMO technology. Prof. Hermann Rohling is with the Technical University Hamburg-Harburg, Germany where he has developed an international reputation for Mobile Communication (4G) and automotive radar systems. Previously Prof. Rohling was with the AEG Research Institute, Ulm as a researcher working in the area of digital signal processing for radar and communications applications. His research interests have includedWideband Mobile Communications especially based on Multicarrier Transmission Techniques (OFDM) for future broadband systems (4G), signal theory, digital radar signal processing, detection, estimation and differential GPS for high precision navigation. Prof. Rohling is a member of Informationstechnische Gesellschaft (ITG), German Institute of Navigation (DGON) and a Fellow of IEEE. He is a chairman of the September 2006 International OFDM Workshop (InOWo 2006) and the International Radar Symposium (IRS 2006) in Krakow, Poland. Prof. Rohling is theVice President of the Technical University Hamburg-Harburg.     

基于正交频分复用的频域差分幅度相位调制

该文提出一种基于频域的幅度两电平的DAPSK+OFDM,并讨论该调制方式在频域的差分调制和解调,然后给出它在白高斯信道的误比特性能公式。最后在典型的调幅(AM)波段信道对它和基于时域的DAPSK+OFDM的误比特性能进行了仿真。结果表明:在短波信道,频域的DAPSK+OFDM比时域的DAPSK+OFDM性能好;在中波信道,时域的DAPSK+OFDM比频域的DAPSK+OFDM性能好。因此,数字调幅广播系统在短波信道可采用频域DAPSK+OFDM,在中长波信道可采用时域DAPSK+OFDM     

相位噪声对PSK系统性能的影响

在介绍相位噪声定义的基础上,分析了相移键控(PSK)接收系统的本振信号源相位噪声对误码率的影响.以QPSK调制方式为例,仿真了相位噪声对系统误码率影响,结果证明了接收系统中本振信号源相位噪声的重要性.以实际工程中使用的本振信号源为例,推导了相位噪声和信号抖动所导致的BPSK和QPSK接收系统信噪比的限制.理论分析与工程...     

宽带无线网络中的自适应编码调制技术研究

由于自适应编码调制技术在宽带无线网络中对于改善频谱利用率和增加数据速率来说是一项能力很强的技术,因此本文针对刚提出的CT-TCM技术,将其与RCPT和ARQ技术结合起来,讨论了一种新的自适应编码调制方案.并对实现该方案的一些具体细节进行了详细的阐述.     

一种高速差分混沌移位键控系统

差分混沌键控(DCSK)系统的最大缺点是参考信号和数据信号消耗了相同比例的比特能量和数据传输速率.为了克服这一缺点,提出了一种高速差分混沌键控系统(HR-DCSK).该系统缩短了原来DCSK参考信号的长度,同时数据信号携带2 bit数据,并将数据信号重复发送,提高了数据传输速率和能量效率.推导出在高斯信道中的比特误码率公式并进行仿真,理论分析和仿真表明,在相同信噪比下,HR-DCSK比调频差分混沌键控系统(FM-DCSK)误码率降低了10％.     

未知相位信道下 Turbo码编码DPSK信号的联合迭代解调解码

本文提出了未知相位信道下Turbo码编码DPSK信号的联合迭代解调解码算法 .推导了未知相位信道的最大后验概率 (MAP)算法 ,推导表明该MAP算法同样可用前向、后向递推方程来有效实现 .其次 ,采用等效信道的方法将未知相位信道的Turbo码解码问题化为AWGN信道下Turbo码的解码问题 .最后 ,引进了联合迭代解调解码算法 ,可用于Turbo码的解调解码 .模拟表明本文算法可有效用于未知相位信道Turbo码的解码     

差分相移键控的非归零到归零格式转换研究

提出了一种全新的基于相位-强度混合调制和色散补偿的光差分相移键控(DPSK)信号的非归零(NRZ)到归零(RZ)格式转换器,理论分析了转换器参数对转换的影响,数值研究了恶化条件下的10 Gb/s的NRZ-DPSK到RZ-DPSK的格式转换。实验展示了10 Gb/s的DPSK信号格式转换及解调后的误码性能。计算结果表明,通过设计转换器参数可获得低占空比RZ-DPSK信号,且转换后信号质量较高。实验结果表明格式转换功率代价较低,转换后RZ-DPSK信号时间抖动较原NRZ-DPSK信号减小。该格式转换器还适合光四相差分相移键控(DQPSK)的非归零到归零格式转换及多波长操作。     

ASK／FSK光标记交换系统中的OBPF谱均衡法

基于幅移键控／频移键控（ASK／FSK）正交调制光标记交换（0LS）系统工作原理,提出了一种利用光带通滤波器（OBPF）对FSK标记进行谱均衡的方法,从而有效改善ASK净荷接收灵敏度。利用仿真,对40Gb／sASK／FSK正交调制OLS系统,在使用3种不同类型OBPF进行谱均衡时的传输性能进行了验证与比较分析。结果表明...     

符号内连续相位差分相移键控调制方法

提出了一种幅度准恒包络、相位连续的差分相移键控调制与解调方法.该方法设计了一组基带信号集合,根据输入的信息值和状态值选择基带信号来实现信号调制.在信号解调中,通过计算接收信号在一个符号持续时间内的相位变化累积量来判决发送信息.仿真结果表明,该调制方法具有良好的频谱特性和准恒包络特性,并且避免了本振偏离、多普勒频移等引起的符号间相位变化对信号解调的影响.     

光域OOK到电域QPSK直接转换方法

基于光子矢量调制技术,首次提出了光域OOK到电域QPSK的直接转换方法.在提出的方案中,传送到宽带无线接入网中心站的光OOK信号无需光电转换成二进制基带信号,而是在光域直接进行转换,这样就避免了光-电-光转换,降低了系统的复杂性,并且克服了电子瓶颈问题.另外,使用了低硬件要求的PVM方案,降低了系统成本.理论与仿真分析...     

圆偏振移位键控的星地激光通信误码率研究

光束的偏振特性在大气传输中变化比较小,因而偏振移位键控调制具有较高的可靠性。以星地激光通信为背景,研究星地激光通信链路的圆偏振移位键控调制的误码率性能。考虑到大气湍流的影响,采用Hufnagle-Valley大气折射结构常数模型,在Rytov方差分别为0.082,1.11这两种弱、强湍流起伏条件下,通过对比圆偏振移位键控调制和直接检测开-关键控调制的误码率,得到了同等湍流起伏条件下前者误码率性能比后者突出的结论。特别是Rytov方差为0.082时,要达到10-7的误码率,它们对信噪比的要求分别是21.65dB和30dB,圆偏振移位键控调制对信噪比的要求降低了8.35dB。此外,还分析了近地面折射结构常数、天顶角和地面风速这3个因素对误码率的影响,仿真结果表明圆偏振移位键控调制的误码率比直接检测开-关键控调制最少降低2个数量级。因此,圆偏振移位键控调制在未来星地激光通信中有着广阔的发展前景。