A proposal of an ATM wireless access system for tetherless multimedia services

This paper proposes an ATM wireless access system for tetherless multimedia services. The proposed system is intended to provide ATM-based high-speed transmission capability for tetherless multimedia services by wireless media in private LAN/WAN environments as well as public environments. To enable high-speed transmission, this paper proposes the utilization of the SHF band taking advantage of its wide frequency spectrum availability. However, the propagation feature of the SHF band limits the wireless terminal mobility in the proposed system compared with current cellular phone systems. This paper discusses the concept and system architecture of the proposed ATM wireless access system, including its ATM transport based on ATM/TDMA conversion using a time stamp scheme.     

A WDM-based optical access network for wide-area gigabit access services

This article proposes and demonstrates a WDM-based access network that directly connects end users over a wide area to the center node and provides guaranteed full-duplex Gigabit Ethernet access services to each of over 100 users. The center node employs an optical carrier supply module that generates not only the optical carriers for the downstream signals but also those for the upstream signals. The latter are supplied to optical network units (ONUs) at users' homes/buildings via the network. Since the ONUs simply modulate the optical carriers supplied from the center node via the network, they are wavelength-independent.     

承载多媒体业务的光接入系统设计

文章设计完成了DVB、IPTV两种多媒体业务的光接入解决方案,根据不同的接入环境可以灵活选择最合适的光接入技术.系统支持广播和点播两种收看方式,并且实现有线和无线接入的融合.同时系统最大限度地利用了已有的入户线资源,降低建设成本.     

面向云网融合的传输接入及SDN部署策略研究

云业务是运营商实现政企业务突破的关键入口,大力发展云业务驱使运营商快速提升云网一体化服务能力,提供高品质云专线。本文提出面向云网融合的传输OTN、SPN接入方案及传输网络SDN部署策略,为现阶段基于传送网的云网融合部署提供参考借鉴。     

A signaling protocol for complex multimedia services

The author introduces a signaling protocol for user applications that invokes multimedia services provided by the EXPANSE research prototype, a broadband ISDN testbed. A generic framework that flexibly accommodates a wide variety of services involving multiple parties with heterogeneous terminals is described. The author describes the generic services supported, introduces the EXPANSE call model, discusses syntax and message flow procedures, and relates EXPANSE signaling to the ISDN signaling control part (ISCP) and long-term broadband ISDN signaling work currently under study by CCITT     

A signaling architecture for wireless ATM access networks

A multiservice wireless Asynchronous Transfer Mode (ATM) access system is considered from a signaling protocol viewpoint. In an attempt to generalize and extend results and experiences obtained from the specification, design, and implementation of fixed ATM‐based access networks, we extend the concept of the broadband V interface (referred to as VB) for application to wireless ATM access networks. The proposed architecture follows the signaling structure of Broadband ISDN (B‐ISDN) User–Network Interface (UNI), thus offering the possibility for integration of the wireless ATM access system into fixed B‐ISDN. It is shown that the use of the proposed access signaling architecture provides cost effective implementations without degrading the agreed Quality of Service (QoS), and simplifies call/connection and handover control. The evaluation of the proposed access signaling protocol structure yields results that fall within acceptable ATM signaling performance measures. A performance comparison of our approach with an alternative access signaling configuration is also carried out to quantify the relative gains. This revised version was published online in August 2006 with corrections to the Cover Date.     

FODA/IBEA-TDMA: A flexible fade countermeasure system for integrated services in user-oriented networks

A flexible, processor based, TDMA station has been implemented. This station and its associated variable data rate modem enables users to implement very complex frame structures under software control. Burst rates of 512 kb/s-8-192 Mb/s and different coding rates are possible allowing the transmitted bit energy from each station in the network to be adapted to prevailing conditions. The proposed application of the station is the transmission of mixed stream and packet traffic, in a LANs interconnection via satellite environment, using a modification of the FODA¹ technique. The association of the up-link power control feature with the bit and coding rate variation gives the system an interesting ability to cope with fade conditions. The link outage probability is investigated for the Olympus transponder in k_a band. The ability of the system, together with the good performance of Olympus, shows that the K_a band is usable for the above mentioned types of networks without prohibitive fade degradation, at least for limited coverages.     

基于FPGA的大型柔性太阳翼展开控制系统实现

为了保证大型柔性太阳翼的伸展机构能够实现可靠、重复、平稳的展开和收拢功能,提出了采用PID调节器完成速度、电流双闭环的控制系统。为了提高控制系统的可靠性同时降低控制电路的复杂度,提出了以单片反熔丝型FPGA为控制处理器的外围电路、驱动电路及位置检测电路,实现了一种基于FPGA的大型柔性太阳翼展开控制系统的设计。通过样机验证表明,该系统能够使大型柔性太阳翼的伸展机构反复平稳地展开与收拢,有效地抑制了由于展开过程的扰动引起的不稳定,速度稳定度优于5%。该设计具有一定的应用价值,为后续工程应用提供了参考。     

A CPCH access method for prioritized services in W-CDMA

Common packet channel (CPCH) access is an efficient approach to support packet data transmissions in a wideband code-division multiple-access (W-CDMA) system. This letter introduces a simple access control method for CPCH, which results in higher throughput. This method also provides prioritized services for different traffic classes. Each traffic class is assigned a distinct transmit permission probability that is determined at the new call initiation stage based on the status of CPCH channel occupancy. The differentiated service qualities, which correspond to different transmit permission probabilities, are evaluated in terms of packet blocking rates. The overall system performance is also evaluated in terms of normalized throughput.     

A flexible multicarrier CDMA system with time‐varying data rates and services

We consider an enhanced multicarrier code‐division multiple access (CDMA) system that performs the spreading in the time and frequency domains simultaneously, where time‐domain spreading codes are used as a main code and frequency‐domain spreading codes (FDSCs) are used as a subcode. By allocating the FDSCs to users, rates and services can be dynamically matched to users' needs. The resulting system can support different time‐varying source rates and, therefore, enable multimedia applications. In addition, since the proposed scheme uses multiple carriers, it has some advantages such as the mitigated multipath fading, frequency/path diversity and narrowband interference suppression capability, in contrast to a single carrier (SC) system such as the multicode CDMA scheme. Finally, the closed‐form expression for probability of bit error is derived for a frequency‐selective Rayleigh fading channel. It has been also shown that the proposed system has outperformed the conventional SC RAKE system if the available bandwidth is fixed. Copyright © 2008 John Wiley & Sons, Ltd.     

Adaptive access points deployment for Indoor bluetooth positioning accuracy enhancement

The indoor positioning system based on fingerprint receives more and more attention due to its high positioning accuracy and time efficiency. In the existing positioning approaches, much consideration is given to the positioning accuracy improvement by using the angle of signal, but the optimization of access points (APs) deployment is ignored. In this circumstance, an adaptive APs deployment approach is proposed. First of all, the criterion of reference points (RPs) effective coverage is proposed, and the number of deployed APs in target environment is obtained by using the region partition algorithm and full coverage algorithm. Secondly, the wireless signal propagation model is established for target environment, and meanwhile based on the initial APs deployment, the simulation fingerprint database is constructed for the sake of establishing the discrimination function with respect to fingerprint database. Thirdly, the greedy algorithm is applied to optimize APs deployment. Finally, the extensive experiments show that the proposed approach is capable of achieving adaptive APs deployment as well as improving positioning accuracy.     

The Satchel system architecture: Mobile access to documents and services

Mobile professionals require access to documents and documentrelated services, such as printing, wherever they may be. They may also wish to give documents to colleagues electronically, as easily as with paper, facetoface, and with similar security characteristics. The Satchel system provides such capabilities in the form of a mobile browser, implemented on a device that professional people would be likely to carry anyway, such as a pager or mobile phone. Printing may be performed on any Satchelenabled printer, or any fax machine. Scanning, too, may be accomplished at any Satchelenabled scanner. Access rights to individual documents may be safely distributed, without regard to document formats. Access to document services is greatly simplified by the use of context sensitivity. The system has been extensively tested and evaluated. This paper describes the architecture of the Satchel system.     

Integrated services from high-altitude platforms: a flexible communication system

In this article the provision of integrated services from high-altitude platforms (HAPs) is discussed, and a flexible communication system for HAP-based communications is identified and analyzed, with particular attention to the delivery of broadband services from HAPs to highspeed trains. The high coding gain required by the proposed scenario is achieved through adaptive concatenated coding schemes, while smart antennas operating with adaptive beamforming algorithms are employed at the ground stations. The simulated system performance based on a multi-antenna model of the stratospheric channel is reported, and the use of HAPs in synergy with terrestrial and satellite systems is discussed.     

柔性信息管理系统中权限控制方法的应用

系统中的权限设计方法直接影响到系统的安全,为解决系统中权限控制的灵活性问题,结合柔性化软件开发策略提出了基于动态树模式的角色授权管理机制,系统管理员可以根据不同角色的需求,动态设置角色的权限。该授权方法突破了传统系统中角色不能更改的弊端,基于动态树模式的角色授权管理机制根据不同用户动态加载不同的菜单,实现了用户访问系统资源的可定制性、灵活性和可控性,解决了权限管理粒度与数量矛盾的问题。该方法具体应用于某高校信息管理系统中,实现了系统权限的灵活管理。     

面向5G无线接入业务的传输前传组网研究与实践

为了满足5G大带宽低延时广连接的业务特性,深入研究了C-RAN基站接入传输组网模式,并全面开展了部署和实践。针对全部基站接入业务,统一采用C-RAN传输前传组网模式,实现了降低OPEX和CAPEX的目标,同时提升了网络稳定性,解决了业务潮汐效应,加强了面向未来网络演进的快速部署能力。     

A flexible quasi-optical system for polarimetric submillimeter-wavereflectrometry

First measurements of the reflectivity of different natural and artificial materials in the 600-GHz range are reported. The investigations were carried out using a heterodyne broadband dual-polarization reflectometer which was realized in a flexible quasi-optical technique. This special construction allows the design to be changed very quickly according to the desired measurement task. The design principles of this setup are presented. Compared to Fourier-transform spectrometers the described reflectometer is capable to carry out real-time measurements even outside the laboratory. Reflectivity data of several interesting materials are presented in co- and crosspolarization     

Human-centered multimedia: culture, deployment, and access

Cultural setting is an intrinsic part of what we're trying to capture and use in muitimedia systems. However, being in our own culture (both everyday culture and professional culture) we forget that multimedia interfaces and communication are culture-specific. This article gives some great insights that stem from diversity in countries (and cultures) as well as inside the interdisciplinary multimedia community.     

Inhibitors for ubiquitous deployment of services in the next-generation network

The next-generation network is characterized by the merging of the Internet, telecommunications, and information technology. As envisioned some six years ago, the NGN was to revolutionize the lives of its users by providing them the best of the services of the PSTN and the Internet, written rapidly by IT programmers. Service providers were to be similarly affected by the increase in revenues paid by the users of these new services. Equipment vendors would have a difficult time keeping inventories of the NGN infrastructure. The truth has been somewhat different. In this article we characterize a set of inhibitors - technical, regulatory, and business-related - that are affecting the ubiquitous deployment of NGN services.     

APON接人系统的一个介质访问控制协议

作为共享介质的接入网络,APON需要介质访问控制协议用于协调各终端对介质的存取.本文提出了一个符合ITU-T建议的MAC协议,采用了时延分优先级,对高优先级的实时业务按照的均匀间隔的原则分配带宽,低优先级业务的带宽按次序循环分配.上行帧长度根据处于连接的用户数动态变化,各终端的带宽申请时隙由系统动态分配.最后给出了由该协议确定的网络性能的计算机仿真结果.