双向HFC网的上下通道异同点

双向HFC网络具有上下两个通道,它们的信号传输方式既有相同点也有不同点,具体说明信号流方向、信号类型、传输方式、光缆拓扑结构、信号测量方法、衰减器与均衡器位置、增益点选择等方面的不同,并说明它们在网络调试中的作用.     

数字电视在网络中的传输

面对各种网络传输技术，采用何种传输方式来传输数字电视信号仍然是行业中有争议的话题。探讨了数字电视在3种网络即SDH网络、ATM网络和IP／以太网中的传输技术，比较了它们的优缺点，指出了基于IP／以太网传输数字电视是未来的发展趋势。     

新型的CATV系统

文章介绍了新型ＣＡＴＶ系统的前端、发射传输方式、光缆干线网络、信号的双向传输，以及网络的综合利用。     

有线与无线信号传输方式特性比较与应用选择

本文讲述了有线和无线信号传输方式的工作原理、优劣比较和应用特性分析，同时通过两种信号传输方式的多个应用实例来探讨不同场合下的最佳信号传输方式。最后，本文基于两种信号传输方式不同特性，对不同信号传输领域中如何选择一个合理的信号传输方式提出了一些有益的建议。     

现代CATV系统

介绍了现代ＣＡＴＶ系统的前端，发射传输方式，光缆干线网络，信号的双向传输，以及ＣＡＴＶ网络的综合利用。     

TD-SCDMA Iub接口的传输方式

首先介绍三种TD-SCDMA Iub接口传输方式的具体实施方案,即基于同步数字体系(SDH)传输网的透明传输方式、基于SDH+ATM交换机的传输方式以及基于MSTP传输网的传输方式,详细分析它们各自的优缺点;然后介绍如何根据实际网络合理地选择适合本地的传输方式;最后对TD-SCDMA无线接入网传输方案进行了展望。     

多制式电视信号测试利器——德力S7000

目前我国电视信号传输方式是多元化的,可分为卫星传输、地面传输、有线传输三大类,各传输方式应用了不同的传输标准(DVB-S、DTMB、DVB-C)。对各种制式信号进行测试时都需要专业的测试仪器,在实际网络测试时,往往需要同时对多种标准的信号测     

利用因特网传输新闻素材

利用传统的微波、光纤、卫星等传输方式来传输视、音频信号 ,这在需要传输素材长度长、传输量大的视、音频信号的时候无疑是首选。由于采用这些传统的传输方式需要事先与当地有关部门联系沟通 ,且必须在约定时间传输。所以在外地向电视台内传输一些传输量小、素材长度较短的视、音频信号 ,特别是一些短而精的新闻报道时 ,如果能利用当地现有的Ｉｎｔｅｒｎｅｔ网络进行新闻事件的稿件以及视、音频信号的传输 ,无疑能避免利用传统传输方式须事先联系、定时传输等烦琐的环节。近年来 ,数据通信的发展使Ｉｎｔｅｒｎｅｔ网络普遍存在于我们的身…     

第三代移动通讯技术在电视直播中的应用

目前电视节目现场直播的信号主要通过卫星、光缆、微波、网络等技术手段进行传输。下面简要介绍下这几种传输方式。     

名词解释

名词解释（续上期）２２波分复用（ＷａｖｅｌｅｎｇｔｈＤｉｖｉｓｉｏｎＭｕｌｔｉｐｌｅｘｉｎｇ，ＷＤＭ）是利用一根光纤同时传送两种以上信号的一种通信方式，与微波通信中的频率分割多路传输方式相对应。在不同波长的光上载不同的信号，并用一根光纤传输它们，故能...     

M－DQCA：可调信道访问光波网介质访问控制协议

本文提出了一种可调信道访问光波网以及适合于该网的介质访问控制协议Ｍ－ＤＱＣＡ，利用波分复用技术将双总线光波网分成多个并行信道，用一个信道专门传输等时业务和请求信息，使网络管理得到简化；利用时隙重用技术，提高了网络的吞吐量；拥塞控制方法与多跳网相比简单得多，各用户只需根据本站缓存的情况来控制输入业务的流量。计算机仿真表明，Ｍ－ＤＱＣＡ光波网具有很好的性能。     

一种融合流形学习和深度学习的时变信道自动调制识别技术

自动调制识别在军事领域和民用领域都发挥了巨大作用。现有的大多数研究都是基于高斯白噪声信道,但是时变信道下的自动调制识别才更符合实际并且具有挑战性。该文针对时变信道提出了一种融合流形学习和深度学习的自动调制识别方法,第一次将格拉斯曼流形引入到信号的特征提取,通过将信号星座图建模到格拉斯曼流形上完成特征提取。分类网络由基于流形学习和深度学习的两部分组成,流形数据先经过流形学习网络进行降维,然后映射到平滑子空间,最后通过简单的卷积神经网络完成分类。实验结果表明,与传统的卷积神经网络相比该文所提出的方案具有良好的性能,同时为自动调制识别提供了新的解决思路。      

Robustness evaluation of a minimal RBF neural network fornonlinear-data-storage-channel equalisation

The authors present a performance-robustness evaluation of the recently developed minimal resource allocation network (MRAN) for equalisation in highly nonlinear magnetic recording channels in disc storage systems. Unlike communication systems, equalisation of signals in these channels is a difficult problem, as they are corrupted by data-dependent noise and highly nonlinear distortions. Nair and Moon (1997) have proposed a maximum signal to distortion ratio (MSDR) equaliser for data storage channels, which uses a specially designed neural network, where all the parameters of the neural network are determined theoretically, based on the exact knowledge of the channel model parameters. In the present paper, the performance of the MSDR equaliser is compared with that of the MRAN equaliser using a magnetic recording channel model, under Conditions that include variations in partial erasure, jitter, width and noise power, as well as model mismatch. Results from the study indicate that the less complex MRAN equaliser gives consistently better performance robustness than the MSDR equaliser in terms of signal to distortion ratios (SDRs)     

Theoretical simulation and experimental investigation on a WDMsurvivable unidirectional open ring network using tunable channelselecting receivers

In this paper theoretical and experimental investigations on a wavelength-division-multiplexed (WDM) reconfigurable open ring network are reported. The theoretical study is focused on network component characteristics and ring network structure. These aspects will form the basis of numerical modeling. A powerful computer aided design software “COMSIS” is used for the simulation. The simulation takes into account the most important parameters: node structure, link losses, EDFA characteristics, optical powers of the channels, and signal wavelength arrangements. The power of a new channel added at each node and its wavelength with respect to those present before the node are two important parameters in the performance analysis of this open ring network. If the performance criterion is to receive the channels with high signal to noise ratios (SNR) and a narrow spread ΔSNR, the optimal length of this ring network can reach 366 km for 4 nodes and 565 km for 8 nodes. The experimental demonstrator is composed of 4 secondary nodes incorporating tunable channel selecting receivers (TCSR's) and erbium doped fiber amplifiers (EDFA's). The reconfiguration and the protection of the ring is computer controlled. Experimental results of a fully connected testbed demonstrator are also presented     

Channel characterization and television field strength measurements

The new standard in North America for the advanced television (ATV) transmission system will be selected in 1996. The new ATV system is expected to co-exist with the conventional NTSC television system for many years to come. Simulcasting of the two systems will require a good understanding of the channels used. In this paper, a method to characterize a channel using the ghost canceling reference (GCR) signal is presented as well as the method used to conduct field strength measurements of television channels. The channel characterization gives us the time and frequency response of channels. The field strength measurements show the power variation of the signals that are transmitted through a channel over a period of time. The results obtained from field tests for a number of channels and with different polarization of transmitter's and receiver's antennas are then presented. The results for the channel characterization of a cable network using the GCR signal are also presented     

Bidirectional WDM passive optical network for simultaneous transmission of data and digital broadcast video service

We have demonstrated an easily upgradable bidirectional passive optical network for the simultaneous transmission of wavelength-division-multiplexing channels and digital broadcast video signals. The proposed network could transmit 15 2.5-Gb/s downstream channels, 15 155-Mb/s upstream channels, and one broadcast signal consisting of more than 70 digital video channels.     

GSM移动通信网的优化

本着重讨论GSM移动通信网络中无线网络的优化问题。提出蜂窝式移动通信网优化的必要性,无线网络在无线覆盖方面应做的工作。譬如基站覆盖信号强度测绘图的重要性,背景噪声检查的重要性等。对各种控制信道的配置方法和相关参数的设置方法,也提出了一些看法。     

基于多尺度注意力机制ResNet的雷达工作模式识别

雷达工作模式识别是解释雷达行为和功能的基本任务。现有方法难以在信号灵活、环境复杂的条件下筛除脉冲序列中不同空间和不同通道中的冗余信息。本文在深度残差网络的基础上,增加了空间自注意力模块和通道自注意力模块以适应上述信号特点。模型引入自注意力机制以实现雷达序列不同空间和通道的自适应权值分配,使网络能更有效地关注更具差异性的信息,实现了极端条件下雷达工作模式的高精度识别。同经典深度学习网络AlexNet、LeNet、VGGNet、ResNet以及常规深度卷积网络相比,该模型在0~50%漏脉冲条件下,平均识别率提升了36%,在独立测试集40%漏脉冲比例下模型仍然具备90%以上的识别率,证明了所提网络的优越性和有效性。     

Sensing throughput trade‐off for an energy efficient cognitive radio network under faded sensing and reporting channel

The trade‐off between sensing time and throughput is investigated in the context of an energy‐efficient cognitive radio network considering both the sensing and reporting channels are Rayleigh faded, while the existing literature considered the fading in sensing channel only. In this paper, such a trade‐off is re‐examined under Rayleigh faded sensing as well as reporting channel. Novel analytical expressions for overall detection probability and false alarm probability are developed under such scenario. The performance is investigated in terms of detection probability, false alarm probability, throughput and energy efficiency of the network for different sensing parameters such as sensing time, number of samples, sensing channel signal‐to‐noise ratio and reporting channel signal‐to‐noise ratio. Our analysis shows that the quality of the reporting channel significantly affects the trade‐off performance of the network. Copyright © 2015 John Wiley & Sons, Ltd.     

Experimental network synchronization via plastic optical fiber

In this paper, network synchronization of coupled Chua’s circuits in star configuration is experimentally studied. In particular, plastic optical fiber (POF) is used in the network like communication channels among chaotic nodes to achieve synchronization. The master signal is sent to multiple slaves through a fiber optical coupler with corresponding electrical/optical and optical/electrical stages. An application to encrypted chaotic communication to transmit analogical signal and image messages to multiple receivers is also given.