HFC双向传输网络的特殊故障解析

当前 ,有线电视网络正朝着双向、宽带、高速的方向发展 ,ＨＦＣ网络结构成为有线电视升级改造的主要模式。改造过程中或升级之后网络故障率有所降低 ,稳定性有很大的提高 ,但也存在一些问题。笔者就近几年ＨＦＣ网络升级改造过程中遇到的问题与大家一起探讨。1　因光设备不配套而引起的雪花干扰故障现象如下 :某小区许多用户反映有雪花干扰。经测试 ,用户电平普遍下降了十个分贝。故障分析 :由于此小区网络结构为ＨＦＣ结构 ,且被干扰用户分布于多个光节点之后 ,表明此故障点不可能出现在电缆部分 ,很可能是光链路上的问题。检查光接收机 ,…     

对双向传输技术的探讨

本对HFC双向传输网络的技术发展情况介绍了个人见解，并介绍双向传输网的功能、回传方式、指标要求、并重点分析了回传噪声产生的原因，在改造大型CATV网络时应选取哪种传输方式提出了一些看法。     

CATV网络建设和改造中应把握的几个问题

1 CATV网络的现状和未来 就大部分县市级而言,现存的CATV网络通常是一种树枝型结构,这种网络只适合于从前端到用户传输广播电视信号,由放大器的特性决定大部分网络的频率范围在45～450MHz,真正达到550MHz甚至750MHz的极少.虽然有的放大器指标能达到这一标准,但就整个网络而言还是达不到这一标准。 随着我国有线电视事业的快速发展,人们对有线电视功能的认识也在不断深化。从最初的有线电视能增加节目套数,改善接收信号质量,到今天把它作为一个宽带综合信息网,已经产生了质的飞跃。     

有线电视网络HFC双向传输初探

本文综合介绍了山东定陶有线电视网络目前实施的系统组成,特别是光纤同轴电缆混合网络-HFC宽带接入网的拓扑结构,频率规划及双向传输的实现方式。     

双向HFC网络的规划思路

以海门市有线电视ＨＦＣ网络规划为例,介绍了ＨＦＣ网络结构,提出了双向ＨＦＣ网络规划的基本思路。     

HFC有线电视网的双向改造

高度发达的经济社会需要有高质量的多种多样的信息服务。有线电视网经过改造 ,可成为比现有的电信网、计算机网更具发展前景的信息网。致力于有线电视事业的广电人士以极高的热情倾注于有线电视网的发展 ,为有线电视综合业务网描绘了一幅美好的前景 :从综合业务机顶盒下载数据 ,其下载速度可达 30Ｍｂ/ｓ以上 ,上行速率达 2Ｍｂ/ｓ ,能够满足几乎所有多媒体业务的需要。使用综合业务机顶盒的有线电视用户 ,可以享受优质的交互式电视、高速数据以及话音等全方位服务。但是 ,要把单向传输的ＨＦＣ有线电视网改造成宽带高速综合信息网 ,并保留…     

CATV 网络改造的关键技术

ＣＡＴＶ网走过了半个世纪的历程 ,由共用天线系统到电缆电视系统 ,由现在的ＣＡＴＶ到未来的信息高速公路 ,从其发展轨迹中我们看到了 2 1世纪的世界大网。由于它具有得天独厚的带宽资源 ,令信息产业界纷纷抢占 2 1世纪网络要地 ,在国际上掀起了收购有线电视网的热潮 ,在国内更是各路兵马各显神通 ,纷纷在ＣＡＴＶ网上描绘未来信息高速公路的蓝图 ,一时间有线电视网成为国内乃至国际热点。未来的有线电视网不只是宽带接入网 ,而且是多媒体传输平台 ,集接入、交换、传输于一体。下面将介绍国际特别是在国内开发ＣＡＴＶ网络带宽资源方面的动…     

HFC网由单向到双向的改造

关于双向业务的开展 ,前几年国内一些有实力的有线台作了有益的尝试 ,由于设备价格、用户需求以及对双向业务技术的认识等问题 ,经营好的并不多。因缺乏实践机会 ,对ＨＦＣ网双向改造中的相关技术问题了解不多。成都市龙泉宽带网的建设使我们获得了一些感性认识 ,整理出来与大家共同研讨。1　双向业务定位双向增值业务有许多种 ,建设双向网络需要投入大量资金 ,业务定位对这一建设项目快速步入良性循环至关重要。成都市龙泉驿区有线台采用了基于Ｓ -ＣＤＭＡ技术的ＣａｂｌｅＭｏｄｅｍ宽带接入系统 ,为首批用户提供高速Ｉｎｔｅｒｎｅｔ、…     

如何利用双向CATV网络来建设智能化小区

本文主要介绍在双向HFC的CATV网络上的空闲带宽传送数据、图象等信号,实现INTERNET浏览、社区联网、智能住宅的安全、通信、管理自动化。     

A data transmission scheme for CDMA wireless networks based onIS-95

Data integration into the existing cellular voice systems is an attractive approach since it can reduce an initial implementation cost of the data network and can provide voice/data integrated services. In this paper, we propose a data transmission scheme for code-division multiple-access (CDMA) cellular voice systems. The CDMA systems under consideration include IS-95 digital cellular systems using the 800-900-MHz band and J-STD-008 personal communications systems using the 1.8-2.0-GHz band. The proposed protocol and control schemes are designed for real systems based on IS-95 rather than conceptual systems and require no modifications to the existing voice mobile stations (MSs). Using computer simulation, the performance of voice and data users is evaluated. As a result, we show that the proposed scheme well meets our design goals, which are that the data transmission scheme should not only provide a good data performance, but also have little effect on the voice performance     

Novel spatial spread spectrum based fiber optic CDMA networks forimage transmission

Novel code division multiple access (CDMA) fiber optic networks based on spatial frequency spread spectrum for image transmissions are proposed. Two key technologies are the parallel fiber optic transmission of spatially encoded images and parallel access to image data through optical spatial encoding and decoding. The temporal signature sequences used in conventional time-domain CDMA are replaced by two-dimensional (2-D) signature patterns to encode and decode binary image pixels. This enables the fully parallel access and transmission of images. The fundamental rules and methodology to construct optical orthogonal signature patterns (OOSP) are presented. Furthermore, it is shown that the all-optical implementation of the proposed system is feasible by utilizing optically addressable spatial light modulators in both the spatial encoder and the decoder along with multicore fibers as the parallel image transmission medium. The predicted overall throughput can reach 10 Tb/s     

A joint source coding-power control approach for video transmission over CDMA networks

We consider future generation wireless code-division multiple-access (CDMA) cellular networks supporting heterogeneous compressed video traffic and investigate transport schemes for maximizing the number of users that can be supported in a single cell while simultaneously maximizing the reconstructed video quality of individual users. More specifically, we demonstrate that the network resources consumed by an individual user in a spread-spectrum CDMA network can be taken as the product of the allocated source-coding rate R/sub s/ and the energy per bit normalized to the multiple-access interference noise density /spl gamma//sub b/. We propose a joint source coding and power control (JSCPC) approach for allocating these two quantities to an individual user, subject to a constraint on the total available bandwidth, to simultaneously maximize the per-cell capacity while maximizing the quality of the delivered video to individual users. We demonstrate the efficacy of this approach using the ITU-T H.263+ video source coder, although the approach is generally applicable to other source-coding schemes as well. The results indicate a significant improvement in delivered quality-of-service (QoS), measured in terms of the end-user average peak signal-to-noise ratio, that can be achieved at a given level of network loading. Furthermore, we demonstrate that without an appropriate JSCPC strategy the traditional soft-capacity limit associated with CDMA networks is no longer present. Indeed, a precipitous decrease in performance can be expected with increasing load. We show that this behavior can be avoided with the proposed JSCPC approach, thereby significantly extending the useful capacity of the CDMA network while exhibiting a more graceful degradation pattern under increasing load.     

Hybrid TDMA/CDMA based on filtered multitone modulation for uplink transmission in HFC networks

We present a hybrid TDMA/CDMA system for uplink transmission in multiple access networks that is based on filtered multitone modulation. We consider an application to uplink transmission in hybrid fiber/coax networks. After discussing the characteristics of the proposed system, we address the problem of initial ranging and power adjustment of unregistered stations. Finally, we introduce a new collision resolution algorithm in conjunction with FMT modulation that uses iterative identification of the competing stations to achieve high throughput on the collision channel. System performance is investigated by simulations.     

基于双向耦合补偿的超材料传输/反射法

在未考虑超材料中结构单元间耦合作用的情况下,传统传输/反射法在提取整体材料的等效电磁参数时会出现误差.针对该问题,对超材料中不同方向单元耦合及其补偿方法进行了讨论,提出一种基于双向耦合补偿的改进传输/反射法.与传统方法相比,该方法可有效预测超材料中多个谐振区域,更准确地提取整体材料参数;其仿真结果能与Ansoft HFSS软件计算结果很好地吻合;由于采用了局部建模,显著降低了其相应的计算时间及硬件要求.     

A wireless multimedia CDMA system based on transmission powercontrol

This paper proposes a wireless multimedia code division multiple access (CDMA) system based on transmission power control. When we transmit multimedia information (i.e., speech, image, and data), differences in information rate, traffic performance, and required quality should be taken into account. The wireless CDMA system can achieve a flexible balance if transmission power distribution is controlled by using channel measurement information, i.e., traffic. In this paper, the optimal control of transmission power is derived by linear programming and nonlinear programming. Numerical results using a LAN demonstrate that the proposed method can satisfy the required quality     

A self-adaptive full asynchronous bi-directional transmission channel for network-on-chips

To improve two shortcomings of conventional network-on-chips,i.e.low utilization rate in channels between routers and excessive interconnection lines,this paper proposes a full asynchronous self-adaptive bi-directional transmission channel.It can utilize interconnection lines and register resources with high efficiency,and dynamically detect the data transmission state between routers through a direction regulator,which controls the sequencer to automatically adjust the transmission direction of the bi-d...     

用于片上网络的全异步自适应双向传输通道

针对传统片上网络路由节点之间通道利用率低,互连线过多的缺陷,提出了一种全异步自适应双向 传输通道。此双向传输通道可以高效利用连线和寄存器资源,并可以通过方向调节器动态检测相邻路由的 数据传输情况,从而控制序列器对双向通道的传输方向进行自动调整,以满足灵活多变的数据传输环境。 零协议逻辑的应用使电路准延时不敏感,且具有较高鲁棒性。基于SMIC 0.18μm 标准CMOS 工艺实现了 此双向传输通道,后仿真结果表明,自适应双向传输通道在吞吐量,传输灵活度及通道带宽利用率上均优 于传统的单向传输通道,且可以节省连线资源近30%,最多可利用2 倍于单向传输通道的带宽资源。此双 向传输通道适用于片上寄存器和连线资源有限的片上网络互连应用。     

Fiber-optic subcarrier multiplexed CDMA local-area networks forsubband image transmission

This paper investigates the application of subcarrier multiplexed code-division-multiple-access (CDMA) techniques to image transmission over fiber-optic local-area networks (LANs). In the hybrid scheme, CDMA is used to suppress the interference caused by the laser nonlinearity in the subcarrier multiplexing (SCM) fiber-optic communication systems. Likewise, the SCM scheme is able to increase the channel data rate of CDMA systems. This hybrid system combines the advantages of both schemes and is particularly well suited to subband coding that divides the image information into multiple parallel data streams using an analysis filter bank, each of which is transmitted via a unique subcarrier-code pair, where the spreading code and subcarrier frequency correspond to the image and one of its subbands, respectively. This hybrid scheme also allows more than one image to be transmitted and be accessed simultaneously at the same channel bandwidth, in which each image is assigned a particular spreading code added to its digital data modulating the subcarrier. After transmission, each received signal is independently recovered at a high-Q surface acoustic wave (SAW) receiver with the matching subcarrier-code pair. Other concurrent signals are rejected by the SAW. Then, all the recovered subbands are reassembled by a synthesis filter bank into a close reproduction to the original image. The image quality of subband image transmission via CDMA/SCM fiber-optic channels is evaluated and examined