Bandwidth provisioning in ADSL access networks

We consider an ADSL access network consisting of subscribers, digital subscriber line access multiplexers (DSLAMs), metro Ethernet switches and a broadband remote access aggregation server (BRAS). We obtain expressions for dimensioning the access network in the upstream direction. Specifically, we show that the bandwidth required at each DSLAM, metro Ethernet switch, and BRAS can be expressed as an exponential function of the subscribers in a log scale when the number of subscribers does not surpass a certain value. After this value, it grows linearly as a function of the subscribers. Copyright © 2009 John Wiley & Sons, Ltd.     

Service provisioning in an ATM-over-ADSL access network

Asymmetric digital subscriber loop technology is a new platform for delivering broadband services to homes and small businesses, thus bringing the information highway to the mass market. Successful deployment of an ADSL-based access network is not only a matter of delivering faster rates, but also offering solutions that are cost-effective and easy to use and manage. As deregulation and competition spread globally, an ADSL-based access network should also enable end users to choose their service providers dynamically, and to switch from one provider to another easily and rapidly, even on a real-time basis. In light of these requirements, this article addresses the issue of service provisioning in an ATM-over-ADSL access network. It concentrates on the provisioning of services using the PPP protocol. PPP is the common protocol for service provisioning in circuit-switched telephone networks. However, it is also considered a good choice for the delivery of broadband services since it has built-in mechanisms for IP address assignment, layer-2 security, and AAA (authentication, authorization and accounting). This article presents the problem of initiating a PPP connection at an Ethernet-based host. It presents several solutions for this problem and discusses the advantages and disadvantages of each solution     

克服蜂窝电话发展带来的挑战

过去一年的销售增长率见证了蜂窝电话的再起，这令许多曾经预料去年将会是一个销售低谷的行业分析家们十分惊讶。所以，我们有必要了解究竟发生了什么，调查其中的含义，着眼于未来，对便携式设备设计方面进行研究。     

构建个性化家庭联网应用

设计人员应采用开源软件和低成本、低功耗开放式硬件设备开发人员使用可定制开源软件与低成本低功耗开放式硬件设备,可控制整个家庭中的数字媒体,以自己想要的格式通过家庭网络高效地组织、播放和捕获各种媒体内容。联网家庭中的设备多种多样,其中包括录制最喜爱电视节目的电子设备、多房间音乐或视频播放器、网络媒体服务器乃至完整的家庭媒体中心。     

Achieving distributed user access control in sensor networks

User access control in sensor networks defines a process of granting user an access right to the stored information. It is essential for future real sensor network deployment in which sensors may provide users with different services in terms of data and resource accesses. A centralized access control mechanism requires the base station to be involved whenever a user requests to get authenticated and access the information stored in the sensor node, which is inefficient, not scalable, and is exposed to many potential attacks along long communication paths. In this paper, we propose a distributed user access control under a realistic adversary model in which sensors can be compromised and user may collude. We split the access control into local authentication conducted by a group of sensors physically close to a user, and a light remote authentication based on the endorsement of the local sensors. We implement the access control protocols on a testbed of TelosB motes. Our analysis and experimental results show that our schemes are feasible for real access control requirements.     

Deployment challenges for access/metro optical networks and services

Recent technical innovations in optical networking have altered the economics for access and metro networks and enabled new service offerings to a number of different markets. While these innovations may herald a more aggressive transformation of the network infrastructure, there remain business and technical challenges that must be addressed before wider scale deployments will occur. The challenges facing large carriers are borne mainly out of the characteristics of their existing infrastructure and the business processes that have developed over the years to support that infrastructure and the services that run over it. These challenges fall into one of four major categories: 1) ensuring service demand viability, 2) minimizing the investment risk, 3) the implied business process re-engineering, and 4) access network constraints. Opportunities for continued technical innovations to address these challenges exist; however, not all challenges are addressable with new technologies: the technical transformations of the network must be accompanied by the appropriate business transformations.     

Open technical issues in provisioning high-speed interactive dataservices over residential access networks

This article is intended as an overview of high-speed data services delivery over residential access networks. The author identifies and lists some of the most important open technical issues that deserve further investigation by members of the global technical community prior to a truly large-scale deployment of a wide variety of high-speed interactive multiple-media services over state-of-the-art residential broadband access networks. The target access options include hybrid fiber/coax, fiber in the loop, digital subscriber line, digital satellite, broadband wireless, and so forth     

On lifetime-oriented device provisioning in heterogeneous wireless sensor networks: approaches and challenges

With the promise of being a revolutionary innovation for ubiquitous surveillance and monitoring, wireless sensor networks have attracted increasing interest from both academia and industry. One of the critical challenges facing successful WSN implementation is limited lifetime, which is imposed by the limited power supply of non-replenishable batteries on devices. In this article we concentrate on the impact of device provisioning on the usable system lifetime. We introduce a device provisioning framework based on hierarchical communication architecture. The device provisioning strategies are classified into two groups based on the application scenarios: deterministic and random. We investigate and compare the latest approaches for deterministic and random device provisioning. We also discuss open issues in each category.     

认知无线电中能效优先的多用户随机接入方法

为了提高认知无线电网络中用户随机接入的能量效率,提出了一种能效优先的多用户随机接入方法.该方法基于信道的时变特性,在构建多用户随机接入能耗模型的基础上,利用最优停止理论,可实现接入算法能量效率的最大化.通过研究发现,该方法是一个基于门限的接入判决准则.在此基础上,研究了最大化能量效率和最大化吞吐量之间的关系,推导了使能量效率和吞吐量同时达到最大的充分条件.数值计算结果表明：如果传输功率远大于信道竞争功率和探测功率,则当系统实现吞吐量最大化时,能量效率损失较小.并研究了以用户为中心模式下,用户行为自私性对系统级能量效率的影响.数值结果显示,当用户数增大时,由用户行为自私性带来的相对损失百分比小于10%.     

Lighting the local area: optical code-division multiple access and quality of service provisioning

Asynchronous, high-speed multiple-access is proposed as a natural solution to achieving asynchronous, high-speed connectivity in a local area network environment. Optical CDMA is shown to be competitive with other networking technologies such as WDMA and TDMA, but has the benefit of more flexibility, simpler protocols, and no need for centralized network control. The limitations of one-dimensional optical orthogonal codes for CDMA have motivated the idea of spectral spreading in both the temporal and wavelength domains. If the constraints on constant weight in these two-dimensional codes are relaxed, differentiated levels of service at the physical layer become possible. Areas for further research are suggested which may allow quality of service levels to be guaranteed at the physical layer.     

Adaptive DC interconnection provisioning in distributed all-optical micro-datacenters using holistically SDN orchestration for dynamic access

The metro-embedded datacenter (ME-DC) architecture which is based on micro-DCs (mDC) is introduced and implemented to deliver more flexible services with less access latency. Hierarchical SDN control is employed to adaptively interconnect the distributed mDCs and the metro network slices into re-configurable virtual DC (VDC). Such an approach improves the overall resource mobility, especially for traveling users that need to dynamically access the service. In this paper, the VDC re-configuration and pre-configuration mechanisms for dynamic user access are proposed and demonstrated for the first time. In specific, by re-configuring the VDC with the most accessible resources with user location tracking, fast and flexible service is provided with consistent service access. Furthermore, by pre-configuring the VDC with user prediction, mDC and metro network resources are reserved in advance for users in order to provide seamless service. Demonstration based on the implemented ME-DC prototype shows that VDC is adaptively constructed for dynamic user access with fast and flexible service provisioning.     

Preventing unauthorized access to user accounts in a telemedicine consultation system

Problems of authentication in telemedicine systems and methods for preventing account cracking are considered. A simple approach to prevention of account-password matching without complicating the authentication procedure is proposed.     

Local and remote management integration for flexible service provisioning to the home

Giving the operator the ability to manage in- home devices greatly increases the potential of the cost-efficient provision of new profitable services. In this spirit, standardization undertaken by the DSL forum not only addresses remote management of the residential gateway but recently, also extends to in-house devices. We propose a solution that bridges remote management specified by CWMP with UPnP, already established inside the home environment. This approach will enable providers to remotely configure and manage in-house UPnP-enabled equipment, thus accelerating the deployment of new services. We investigate the nature of the two protocols and specify the bridging functionality, taking into consideration scalability and transparency. Experimental results support the applicability of the proposed approach, highlight the importance of message filtering, and provide general insight into the interplay intricacies of the particular protocol functions.     

Sensor-based architecture for QoS provisioning and fast handoff management in WLANs

As wireless local area networks gain popularity from network access providers and customers, supporting multimedia applications becomes a crucial yet unresolved challenge. The need to maintain quality-of-service in the presence of bandwidth limitations, increasing traffic volume and user mobility entails radical rethinking in resource management design in WLANs. The unique capabilities of wireless sensor networks constitute a promising research direction to tackle these issues. In this paper, we present a new sensor-based resource management architecture for enhanced QoS provisioning and handoff management in WLANs. Through theoretical analysis and simulations, we show that the framework can maximize bandwidth utilization while satisfying applications’ QoS requirements and significantly reduce handoff latency.     

Quality of service provisioning in 802.11e networks: challenges, approaches, and future directions

In order to support diverse application requirements, a new standard called IEEE 802.11e is being proposed to improve quality of service in wireless LAN networks. There are, however, a few remaining challenges that need to be addressed in order to enable comprehensive QoS support using 802.11e. In this article we provide an overview of a few of these challenges, describe their possible impact on QoS, and provide a survey of techniques that potentially could be used to address the identified challenges. Specifically, we focus on three challenges: handling time-varying network conditions, adapting to varying application profiles, and managing link layer resources. Additionally, we present several potential future directions toward improved QoS in wireless networks.     

A new service provisioning method in the multimedia/B-ISDN era

In the coming multimedia/B-ISDN era, customers must be able to design, define, and manage communication services based on their own concepts and knowledge of communications. This article proposes a new concept, intelligent dynamic service provisioning (IDSP), offering customers this capability. Service views of customers and carriers for multimedia services are presented. Based on these views, we propose an architecture for the IDSP system. Finally, the basic mechanism of the IDSP system and the technical issues related to this system are examined     

云存储系统中支持用户隐私保护的细粒度访问控制

从云存储实际需求出发,设计了一个云存储环境下支持用户隐私保护和用户属性撤销的多属性权威的属性加密机制,为了保证系统实现的效率和减轻数据持有者的负担,在属性撤销中,复杂的计算任务都委托给可信第三方或云服务器完成。所提方案在DBDH假设下被证明是安全的。     

Network selection in heterogeneous access networks simultaneously satisfying user profile and QoS

Multimode capability empowers mobile devices to select the appropriate network to meet the requirements of user and applications. However, network selection is a challenging task owing to heterogeneous nature of network access links. At the same time, pervasiveness of mobile communication networks accompanied by the advances in wireless devices has raised the user expectations of persistent service and quality. Therefore, it is important for a mobile device to take situation‐based and timely decisions while selecting an access network to ensure both user's and operator's demand. The existing standard, called IEEE 802.21 (media‐independent handover), considers mobile device signal‐strength parameter for network selection from a list of networks. This research has proposed a ranking algorithm to rank heterogeneous networks based on a set of parameters including user profile and QoS. It selects most suitable network owing to multiple handover scenarios. The simulation results have shown that the proposed scheme has successfully satisfied apparently the contradictory requirements related to user profiles and QoS simultaneously.