A new generation of 90 Mb/s systems: bandwidth efficient, fieldtested 16-QAM

16-QAM (quadrature amplitude modulation) digital satellite broadcast equipment and satellite communications (SATCOM) systems that double the spectral efficiency of currently operational satellite links is described. It is shown that with this field-proven system, data transmission at a rate of 90 Mb/s (two multiplexed DS-3 signals) is feasible in a transmission bandwidth of 30 MHz. Extensive operational satellite tests performed over the T-303 satellite of AT&T demonstrated a BER <10^-10 and no errors for several days. The practical bandwidth efficiency of these SATCOM systems is 3 b/s/Hz, i.e. double the currently used 1.5 b/s/Hz QPSK (quadrature phase-shift keyed) systems. The doubling of the spectral efficiency is attained with advance modem (modulation-demodulation), adaptive equalization robust synchronization, high-power amplifier (HPA) linearization (predistortion), and low redundancy powerful forward-error-correction (FEC) subsystems. The systems may make possible the conversion of currently operational analog FM links into bandwidth efficient digital systems. In one 30 MHz satellite transponder three to four digitized high quality TV signals could be broadcast, or two standard rate DS-3 signals time-division multiplexed with a DS-1 rate signal and additional auxiliary data streams     

2.5Gb/s SDH/SONET通路终结芯片设计

设计了一种2.5Gb/s同步光纤网络SDH/SONET中通路终结处理器芯片.采用双向4路总线流水线结构,77.76MHz的系统时钟,可实时处理2.5Gb/s的SDH/SONET数据,终结处理后输出TUG-3/VTG信号.包括通道告警、信号失效检测、性能监测和通道跟踪等.支持STS-48/STM-16、4路STS-12/STM-4和4路STS-3/STM-1的处理.     

SDH网络分析测试仪发送模块的设计

提出了一个SDH网络分析仪发送模块的设计方案,可以实现SDH网络分析测试仪发送模块所需的功能--能够产生符合ITU-T G.707标准STM-I、STM-4、STM-16、STM-64帧结构的光信号以及符合ITU-T G.704标准的E1、E3、E4、DS1、DS3各种PDH电信号,同时还能插入各种相关的报警和误码,并提供指针调整功能.所设计的发送模块不仅可以作为SDH网络分析仪中重要的组成部分,也可以作为信号源为各种SDH设备的研发和调试提供标准的SDH信号.     

卫星带宽压缩技术在应急通信中的测试与应用

为有效提高卫星带宽使用效率,在1MHz的卫星转发器带宽上有效传输实际使用带宽为2MHz的CDMA信号,中国电信在多地开展现场验证测试,分别在现有设备上实地验证时隙插入取出、载波叠加和高阶调制三种技术在CDMA应急通信车上的使用,测试CDMA语音业务的主观语音质量、呼叫时延和数据业务的实际吞吐率。测试结果发现三种技术均能满足压缩率预期要求,中国电信可在CDMA应急通信车上应用卫星带宽压缩技术,以满足现网需求。     

Triangular Quadrature Amplitude Modulation

The square quadrature amplitude modulation (QAM) has been widely used for decades. Though it is not optimum in the sense of power efficiency, simple detection makes it in use for numerous digital communication systems deploying high-order modulation. In this paper, we propose new signal sets which make an effective use of limited power resource. We also suggest simple detection methods for the proposed signal sets to be meaningful from a point of view of implementation. The newly proposed constellations can provide advantages of 0.46 dB and 0.55 dB in signal-to-noise ratio over the square QAM in 16-ary and 64-ary signal sets while keeping low complexity for detection     

Carriage of SDH over satellite systems

This paper examines the potential of satellite systems to carry synchronous digital hierarchy (SDH) transmissions and proposes a possible earth-station architecture capitalizing on the benefits that SDH equipment offers. It is shown that a range of SDH multiplexing rates are viable over satellite and that multi-destination operation of satellite systems is facilitated by using the inherent features of the SDH. The use of STM-1 (155 Mbit/s) and sub-STM-1 transmission rates as transmission sections along with appropriate integration of the multiplexing and modem equipment would:. (a) enable SDH path continuity between earth-stations, allowing the satellite network to be integrated with managed terrestrial networks to form global managed transmission platforms. (b) provide bandwidth and equipment savings at earth-stations. Several technical issues relating to SDH operation over satellite systems are considered and SDH pointer corruption is examined in some detail.     

2.5Gb/s SDH/SONET传送开销处理器芯片实现

设计了一种2.5Gb/s同步光纤网络SDH/SONET中传送开销处理器芯片.采用双向4路总线流水线结构,77.76MHz的系统时钟,即可实时处理2.5Gb/s的SDH/SONET数据.支持STM-16、4路STM-4和STM-1的再生段开销和复用段开销处理以及STS-48、4路STS-12和STS-3的段开销和线路开销处理.采用TSMC 0.13μm工艺流片,电路规模约48万门,技术指标符合ITU-T标准.     

Analysis of different sub-carrier allocation of M-ary QAM-OFDM downlink in RoF system

In this paper, the performance of a 60 GHz radio over fiber (RoF) system with 4/16/64 quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) downstream signals is studied. Delivery of 10 Gbit/s M-ary QAM (MQAM) OFDM signals through the 20-km-long single-mode fiber (SMF) is complicated in terms of intensity modulation and direct detection (IM/DD). Using self-homodyne method, the beating of two independent light waves generating the millimeter-wave at the photodetector can be down-converted to baseband in the electrical domain. Meanwhile, three kinds of sub-carrier arrangement schemes are compared and discussed, and the simulation results show that lower peak-to-average power ratio (PAPR) can be obtained adopting the adjacent scheme. At bit error rate (BER) of 10-3, the receiver sensitivity using 4QAM-OFDM sub-carrier signal is almost enhanced by 4 dB and 9 dB compared with those of 16QAM-OFDM signal and 64QAM-OFDM signal.     

光接入网络中的数字信号处理技术

采用先进的数字信号处理(DSP)技术,在发射机和接收机分别引入预处理和后处理,以提高光接入网络的频谱效率并延长传输距离。研究了一种基于光超奈奎斯特(Super-Nyquist)滤波的类9状态正交振幅调制(9QAM)信号多模均衡(MMEQ)后端DSP算法,使用这种方案,能够有效提高频谱效率,实现了频谱效率高达4 bps/Hz的正交移相键控(QPSK)信号传输;还研究了一种基于数字SuperNyquist信号前端预处理的方案,此方案的优点是不需要光预滤波即可达到相同的频谱效率。使用一个采用直接调制激光器(DML)、直接探测和数字均衡技术的高速无载波幅度相位-64状态正交振幅调制(CAP-64QAM)系统,在20 km标准单模光纤(SSMF)上实现了创纪录的60 Gbit/s CAP-64QAM信号传输;使用相干探测,实现了速率高达100 Gbit/s的64状态正交振幅调制-正交频分复用(16QAM-OFDM)实时传输系统,解决了实时OFDM信号处理中的关键问题。     

Coded QAM using a binary convolutional code

As an alternative to trellis coding, a binary convolutional code is considered for use with such nonbinary modulation schemes as quadrature amplitude modulation (QAM). A Gray code is used to map the encoder output to the M-ary QAM constellation. The focus is on the design of 16-ary coded QAM with a rate 3/4 punctured convolutional code of a constraint length 7. A quantized binary metric generation method is proposed and shown to be suboptimum as compared to the direct use of a M-ary unquantized metric. Impressive coding gains and bandwidth efficiency are shown in comparison with uncoded systems     

卫星通信中的高阶调制技术研究

总结了卫星通信协议GMR-1、DVB中的高阶调制技术,研究了16QAM、16APSK、32APSK调制原理,分析了卫星信道模型,利用Matlab分别搭建AWGN信道和Rician-K信道下各高阶调制信号的收发,得到不同的调制方式在不同信道或在不同衰落因子同一信道下的误码性能。本文的仿真结果对实际卫星通信系统采用高阶调制技术有着一定的借鉴意义。     

2.5 Gb/s Optical Transponder技术与设计

网络容量增长的同时也促进了光纤通信技术的发展,使得宽带传输和接入方式处于越来越重要的地位,如何有效地解决光纤干线上和大部分基于电缆局域网的信号转换成为亟待解决的问题,光收发器(opticaltransponder)很好地解决了宽带传输和接入的这一“瓶颈”问题。2.5 Gb/s是目前最流行的传输速率,其相应transponder用于SDH/Sonet OC-48/STM-16的光/电接口。文章介绍了2.5 Gb/s optical transponder的功能、结构等技术和相应的设计方案。     

Performance of a CE16QAM modem in a regenerative satellite system

This paper studies a digital modem for use over a regenerative satellite link. The modem transmits a convolutionally encoded 16-ary quadrature-amplitude-modulated (CE16QAM) signal. The convolutional code has a three-bit constraint length and a coding rate of 3/4. The high power amplifier (HPA) on board the satellite transmitter and at each station may introduce non-linear distortion into the CE16QAM signal, but only a single-link transmission is considered. Several different earth-stations are assumed to be used in an arrangement of frequency division multiple access. Thus adjacent-channel interference (ACI) can be introduced into the signal by the signals that occupy the immediately adjacent frequency bands. Extensive computer-simulation tests have been carried out to determine the effects of bandlimiting, non-linear distortion and ACI, on the tolerance to additive white Gaussian noise of the modem, using an equivalent baseband model of the transmission system. The results are used to select the preferred system arrangement. It has been shown that, with 4 dB output back-off (OBO) in the HPA, a bandwidth efficiency of 2·4 b/s Hz can be achieved, with an improvement in perforamnce of 2·5 dB, relative to that of an ideal uncoded eight-phase-shift keyed (8PSK) signal, at a bit-error rate of 10^·4.     

Influence of coding and hardware imperfections on the bit errorstructure of multilevel QAM systems

When putting together 140-Mb/s 16-ary quadrature amplitude modulation (16-QAM) modems, radio-relay sets, and the appertaining total multiplex/demultiplex equipment, different and even higher bit error rates (BERs) have been measured at the primary low-level 64-kb/s outputs as compared to that at 140 Mb/s. The authors show that this error multiplex effect is mainly caused by the coding of signal points and by hardware imperfections such as carrier and clock phase jitter, nonideal regenerator threshold voltages, etc. They derive the mathematical tools necessary for calculation of the bit error structure at the modem output under optimum and nonoptimum receiver conditions. It is shown how the errors are distributed among the demultiplexer channels. QAM space diagrams of distorted signals are used for calculation of the BERs in the subsystems. Some experimental results emphasize the fact that the multiplex equipment must not be excluded from design considerations for QAM modems. The 16- and 64-QAM systems are compared with respect to their susceptibility to the error multiplex effect, and a scrambling technique is proposed as a possible means to reduce the BER differences     

Comparison of advanced coding and modulation schemes for multicarrier satellite communication systems

Digital satellite communication systems use coherent quaternary PSK (QPSK) as the preferred modulation scheme. In recent years, however, the search for bandwidth and power-efficient digital modulation methods has become an active research area. In this paper the performances of combined coding and modulation schemes employing multilevel signal alphabets are considered, in the framework of a system model which reasonably approximates the INTELSAT SCPC system. The main goal of the research was to investigate whether the efficiency of coded modulation schemes and their savings in transmitted power could be maintained in a system environment dominated by interference more than by the additive white Gaussian noise. A second goal was to compare the performance of signals with constant envelope, such as multilevel PSK, with that of signals allowing variations in amplitude, such as multilevel PSK, with that of signals allowing variations in amplitude, such as multilevel QAM. In the paper, we propose a channel model which is reasonably close to the real system, and a method for performance evaluation leading to an estimate of the asymptotic power gain of the modulation systems. The channel model and the method are applied to the analysis of coded 16- and 32- PSK and QAM.     

一种基于高阶累积量的复杂调制样式识别方法

针对卫星数字化视频广播第二代标准（Digital Video Broadcasting-Satellite-Second Generation,DVB-S2）中多进制幅度移相键控（Multiple Amplitude and Phase-Shift Keying,MAPSK）和多进制正交幅度调制（Multiple Quadrature Amplitude Modulation,MQAM）信号的调制识别,提出了基于高阶累积量的识别方法。首先对16QAM、32QAM、16APSK、32APSK信号的高阶累积量及其特征进行分析,进而利用其高阶累积量的不同提取用于信号分类的特征参量进行调制识别。给出了算法的详细流程,并对算法进行了仿真分析,结果表明,当样本数越多时,算法信噪比适应能力越好,而与相位偏差无关;在信号样点数为2 048点且信噪比为10 dB时,算法可实现96%的正确识别率,完全满足实际系统对信号分类的需要。     

Automatic modulation recognition algorithm for MQAM signal

An automatic modulation recognition algorithm for MQAM signal was proposed.Firstly,the feature parameter F based on the fourth order cumulants was constructed to classify the square QAM and the cross QAM.Secondly,the compactness of zero center normalized instantaneous amplitude was calculated to identify the 16QAM from the square QAM.Thirdly,the baud rate was estimated by frequency spectrum of amplitude square,and timing was synchronized to delete the ISI and resume the relatively ideal constellations.And aiming at the 32QAM and the 128QAM,two different clustering radii were set,and clustering point density was got respectively by the subtractive clustering algorithm,and then the 32QAM and the 128QAM was classified depending on the difference of density value.In the same way,the 64QAM and the 256QAM were classified.The proposed algorithm can recognize five kinds of QAM signals,including 16QAM signals,32QAM signals,64QAM signals,128QAM signal and 256QAM signal without prior knowledge of frequency and baud rate.Furthermore,the proposed algorithm does not need complex iterative process,which can be applied in practical signal recognition.     

Flexible high-order QAM transmitters for elastic optical networks

In order to adapt to the dynamics in the future optical networks, we propose and experimentally demonstrate two flexible high-order quadrature amplitude modulation (QAM) transmitter schemes: (a) a flexible transmitter using a tandem in-phase/quadrature modulators for generating 16QAM, 32QAM, 64QAM signals; and (b) a scheme based on monolithically integrated quad-Mach–Zehnder in-phase/quadrature with binary driving electronics for synthesizing minimum phase-shift keying (MSK), quadrature phase-shift-keying (QPSK), 8-ary phase-shift keying (8PSK), and 16QAM. These schemes provide different approaches to configure a flexible high-order QAM transmitter, either using cascaded off-the-shelf modulators or via highly integrated monolithic modulator. These flexible and reconfigurable transmitter schemes exhibit different characteristics in terms of system performance, which provides the network operators different flexible transmitter solutions suitable for different application scenarios in elastic optical networks.     

突发自适应调制信号的调制识别算法研究

针对突发自适应调制信号中的PSK和QAM调制方式识别问题,本文提出了一种能够识别BPSK、QPSK、8PSK以及16QAM、32QAM、64QAM、128QAM、256QAM八种信号类型的盲识别算法。该算法首先对信号的循环平稳性进行了分析和讨论,给出了利用循环高阶累积量的特征实现信号识别分类的理论依据。然后,提出了三种基于循环累积量的特征分别实现了QAM和PSK类间识别、MPSK类内识别以及方形QAM与十字形QAM的识别。最后通过对MQAM信号的瞬时幅度分布特性的深入研究和分析,提出了一种基于瞬时包络平方的方差的特征实现了QAM的类内识别。该算法选择了二叉树支持向量机作为识别分类器,并设计了一种新的识别流程完成了对上述信号调制方式的识别。该算法无需精确同步,对载波相位具有较好的鲁棒性,并能够对中频信号进行识别。仿真实验表明,该算法能够实现在较低信噪比条件下突发信号的识别。      

有线数字电视射频信号调制识别研究

从有线数字电视射频信号特征参数提取着手,建立了一套识别16QAM和64QAM射频信号调制方式的数学算法。试验仿真和实际信号验证表明,该算法计算量小,识别率高,易于实现。本项研究为广播电视安全播出和数字电视终端整合提供有益的技术实践。