一种新型的宽带无线接入网

目前,随着各种通信技术的飞速发展以及Internet的迅速普及,宽带无线接入网已运渐成为具有强大市场潜力及技术基础的通信产业。从功能上看,宽带无线接入网使无线终端在一定服务质量(QoS)保证下具有高速数据及超过2Mbit／s的多媒体业务的传输能力,并具备速度受限的移动漫游能力。从技术上,宽     

降低接入网远端设备功耗的一种方法

提出降低接入网远端设备功耗的重要性,分析影响普通电话用户环路耗电的各种因素,比较在用户板更接近用户的情况下用户环路耗电与传统用户环路耗电,对接入网远端设备Z按口指标作一些理论上的探讨。     

小改均衡器解决长距离信号传输引起的凸鼓问题

现在农村有线电视不少是长距离电缆传输,由于电缆自身的特性,不可能给电缆带来平滑衰减,加上多年的使用和外界的温差变化,电缆的衰减变化更大,造成实际线路传输中间频段凸高,使后节放大器信号图像失真。不少杂志介绍过长距离电视信号引起的凸高问题,但所说的大多都是理论,现介绍一种实践中得到的简单方法。这种方法是在现有的均衡器上增加电感和电容两个元件进行改制,电感和电容串联组成一个频带陷波电路。电感用电视机中周改制,即将中周屏蔽罩去掉,将骨架上的线圈和电容撤去,用直径0.3~0.4 mm漆包线绕两圈半,电容选用1~6 pF瓷片电容,电视…     

一种新型光电复合缆在接入网中的应用

由于光电复合缆具有宽带、高可靠性数据传输、价格低、连接方便等特点，非常适合作为传输媒质来组建接入网，并且采用光电复合缆的接入网可实现电话、数据、电视、电力四网融合。为此，叙述了一种新型光电复合缆的结构和特点，简要介绍了四网融合方案采用的以太网无源光网络接入技术，展望了光电复合缆的应用前景。     

一种应用于QAM信号的新型高速均衡器

提出了一种基于新型算法SGLMS-CMA的高速QAM均衡器.SGLMS-CMA算法在stop-and-go原理指导下结合了经典CMA算法和DD-LMS算法.MATLAB仿真表明,与经典CMA算法相比,新型算法具有收敛速度快5倍,剩余MSE改善3～5dB,运算复杂度减少了82%,可纠正残留相偏的优点.综合结果表明,采用SGLMS-CMA+DD-LMS的新型均衡器与CMA+DD-LMS均衡器相比,系统中均衡器模块的硬件开销只增加5%.最后使用SMIC 0.18μm工艺库对新型均衡器进行综合,并且嵌入到QAM解调芯片中进行流片,最终测试结果表明新型均衡器性能优越.     

一种应用于QAM信号的新型高速均衡器

提出了一种基于新型算法SGLMS-CMA 的高速QAM均衡器. SGLMS-CMA 算法在stop-and-go原理指导下结合了经典CMA算法和DD-LMS算法. MATLAB仿真表明,与经典CMA算法相比,新型算法具有收敛速度快5倍,剩余MSE改善3~5dB,运算复杂度减少了82%,可纠正残留相偏的优点. 综合结果表明,采用SGLMS-CMA+DD-LMS的新型均衡器与CMA+DD-LMS均衡器相比,系统中均衡器模块的硬件开销只增加5%. 最后使用SMIC 0.18μm工艺库对新型均衡器进行综合,并且嵌入到QAM解调芯片中进行流片,最终测试结果表明新型均衡器性能优越.     

一种宽带接入网的设计方案

文章介绍了一种光纤到大楼加上多媒体引入线的宽带接入网的设计方案 ,并从接入技术、组网结构、系统配置等方面作了详细的介绍。最后给出了详细的设计方案图。     

广东省广播电视SDH数字微波电路长站距传输可靠性分析

本文对SDH微波传输电路中影响传输可靠性的原因进行了分析,介绍了广东省广播电视数字微波传输网为保证长站距传输可靠性所采取的一些技术手段,并用数据对所取得的成效进行了分析。     

SC-FDE系统的一种新型判决反馈均衡器

针对单载波频域均衡系统MMSE均衡器存在残留码间干扰的缺点,提出MMSE-RISIC判决反馈均衡器消除残留码间干扰.MMSE-RISIC均衡器采用传统MMSE均衡后的判决数据,对残留码间干扰进行估计并消除.残留码间干扰的估计主要采用FFT和IFFT运算,与其他方法相比计算量较小.对该均衡器在不同信道下进行了计算机仿真,结果表明,在频率选择性衰落信道条件下,系统性能有了较为明显的提高.     

一种新型光纤带及其在接入网中的应用

本文介绍了一种新型可卷光纤带,从不同角度分析了该光纤带的易弯曲和熔接特性,简要说明了该新型光纤带光缆在接入网中的应用优势。     

Designing long reach optical access networks

The long reach optical access concept promises to reduce the cost of a future BT network through simplification. This is achieved by extending the reach and split of today’s passive optical network systems (PONs) to 100 km and 1024 respectively, thus eliminating the need for separate backhaul equipment. Compact, low-power optical amplifiers are used at exchange locations requiring very low electrical power consumption. Ultimately this could effectively eliminate local exchange buildings and consolidate BT’s network to around a hundred metro nodes, drastically reducing operational costs. In this paper we describe research to date on the techniques to overcome physical layer impairments at costs appropriate for residential access. We also highlight from an operator’s point of view the protocol requirements of the LR-PON concept, point out the necessary changes to the GPON protocol, and describe an experiment to show its suitability to work over 100 km distances at 10 Gbit/s.     

Optical beat noise suppression and power equalization in subcarrier multiple access passive optical networks by downstream feedback

This paper describes a cost-effective method of suppressing optical beat noise in subcarrier multiple access passive optical networks. The method is based on initial power equalization followed by automatic fine tuning of laser wavelengths, via downstream feedback control of their mean powers, so that the receiver noise floor level is continuously minimized. Application and performance of the method is demonstrated for a low-cost 16-channel system with uncooled Fabry-Perot lasers, utilizing narrow-band QPSK modulated subcarrier frequencies over more than one octave. In static and dynamic temperature worst-case situations a considerable reduction in the number of transmission errors caused by optical beat noise is observed, depending on the temperature change rate.     

Evaluating power saving techniques in passive optical access networks

This work proposes a resilient wheel-based wavelength-division-multiplexed passive optical network optical access network architecture for backhauling network traffic. This proposed resilient architecture can efficiently support not only the fixed users but also the mobile users in the downstream direction under normal and failure operating scenarios, while minimizing the average traffic delivery time and without using extra redundant fibers for protection purposes.

     

Sparse power equalization placement for limiting jamming attack propagation in transparent optical networks

The latest advances in Wavelength Division Multiplexing (WDM) technology are making it possible to build all-optical transparent WDM networks, which are expected to be able to satisfy the rapid growth of today’s capacity demand. However, the transparency of such networks makes them highly vulnerable to deliberate attacks, specifically targeting the physical layer. Physical-layer attacks, such as high-power jamming, can cause severe service disruption or even service denial, enhanced by their capability to propagate through a transparent optical network. Several attack-aware routing and wavelength assignment algorithms have been proposed to reduce the possible disruption caused by high-power jamming attacks. However, even with network planning approaches which take network security, specifically physical-layer attacks, into account, resilience to deliberate attacks in such scenarios remains an issue.In this paper, we propose the use of wavelength-selective attenuators as power equalizers inside network nodes to limit the propagation of high-power jamming attacks. Due to the increased cost of optical switching nodes associated with the addition of power equalizers, we aim at minimizing their number through sparse power equalization placement. We developed a set of greedy algorithms to solve what we call the Power Equalization Placement (PEP) problem with the objective of minimizing the number of power equalizers needed to reduce, to a desired level, the propagation of high-power jamming attacks for a given routing scheme. We further improved upon these results by proposing a GRASP (Greedy Randomized Adaptive Search Procedure) heuristic with a somewhat longer execution time, but with significantly superior results. The performance evaluation results indicate that the proposed GRASP heuristic can achieve the same attack propagation reduction as can be obtained by equipping all nodes with power equalizers by placing them at less than 50% of the nodes on average, potentially yielding significant cost savings.     

Developments in optical access networks

Optical fibre access network technology has become more complex over the last few years with bit rates steadily increasing. PONsystems are available with bit rates in the range 155 Mbit/s to, currently, 622 Mbit/s. Newly designed systems, both PON andpoint-to-point, will allow this trend to continue with 2.5 Gbit/s systems becoming practicable in the near future.With this increase in technology has come an increase in the opportunities for fibre systems to cost-reduce more of the network,including the metro space – a fact which increases the appeal of the technology.Some of the newer PON systems are being designed using Ethernet as the underlying technology with a promise of reducing theprice of the technology still further. How this will occur in practice, however, is still unclear.What is certain is that optical access technologies are expanding and are sure to find openings in real networks in the foreseeablefuture.     

Local access optical networks

Both broadcast CATV and switched telephony access networks have evolved, over decades, to deliver their respective services efficiently. But these networks are not necessarily optimal for services that are rapidly emerging. This suggests that the access infrastructure will likely change in the future, driven by demands for new services and the costs of providing them. Will fiber optic networks play an important role? Trade-offs in desirable network properties (low initial costs, high capacity, flexible provisioning, enhanced maintenance and operations, etc.) are strongly influenced by the network architecture. We classify architectures on two characteristics: delivery mode (i.e., broadcast vs. switched) and carrier utilization (i.e., shared vs. dedicated), examining the trade-offs these imply with several examples of existing and proposed architectures. We show that optical networks can, by virtue of recent component development, be reconfigured to change their characteristics without changing the outside plant     

Optical power budget enhancement in next-generation DDO-OFDM-based optical access networks using square root module

A passive optical network based on orthogonal frequency division multiplexing (OFDM-PON) gives improved performance for high speed optical access network due to its greater resistance to fiber dispersion and higher bandwidth efficiency. In optical fiber communication, chromatic dispersion (CD) is a linear distortion in fiber, but it is converted into nonlinear distortion due to square-law characteristic of photo diode detector at the receiver side resulting in degradation of performance. To compensate for this nonlinear distortion, we proposed to use a linearized receiver circuit with square root module (SRM) device which can improve the performance of system in terms of CD tolerance. In this paper, we have analytically analyzed the performance of OFDM-PON system with and without SRM device for direct-detection optical OFDM-PON (DDO-OFDM-PON) system. At BER of \(10^{-3}\), which is the limit of forward error correction, there is 11.1 and 13.5 dB improvement in optical budget with SRM for downstream and upstream direction, respectively, as compared to conventional DDO-OFDM-PON system.