Surf Africa [telecommunications and Internet infrastructure]

Africa lit a shiny new fiber-optic undersea cable almost two years ago - so why are so few Africans using it? This article describes the telecommunications infrastructure in Africa, both cable and satellite, and the financial and bureaurocratic problems which prevent widespread Internet access.     

SingAREN: the Singapore Advanced Research and Education Network

Singapore is the first country in the world to have a nationwide broadband network infrastructure deployed. What started as an experimental ATM testbed network in 1995 has now become a nationwide broadband infrastructure called Singapore ONE, launched in 1997 to provide residential broadband access via ADSL or CATV cable modem technologies, and business access via ATM. As of June 1998, Singapore ONE supported more than 10,000 users with over 120 commercial applications. More than 100,000 users are projected by the end of 1999, increasing to 400,000 by the year 2001. In order to support the technological needs of broadband communications under Singapore ONE, and to address the national R&D agenda in this area, an advanced research network called the Singapore Advanced Research and Education Network (SingAREN) was established in late 1997. This article gives an overview of the broadband infrastructure initiatives in Singapore, focusing on the SingAREN project. The goals of SingAREN, its network configuration, the research programs and activities to date, and plans for the future are described     

Applying WDM technology to undersea cable networks

WDM technology is now being applied to international undersea fiber optic cable networks in order to provide enhancements such as increased network capacity and greater network flexibility. This article looks at what WDM technology can provide, the progress being made, and the special challenges in its application in undersea networks. We then describe several international undersea networks that, when completed by the end of 1999, will use WDM technology and will serve as a major part of the global undersea fiber optic infrastructure connecting the world     

An efficient and intelligent routing strategy for vehicular delay tolerant networks

The vehicular delay-tolerant network is the real-life application based area of Delay tolerant network where communication takes place using vehicular nodes and roadside units. The topology used in vehicular networks is highly dynamic by architecture due to the use of moving vehicular nodes. It operates in such a scenario where a direct path between source and destination remains absent on the most piece of the time. In case of non-existence of connected path vehicular delay-tolerant network works opportunistically and uses the same store, carry, and forward paradigm as Delay Tolerant Network. However, the routing protocols designed for vehicular delay-tolerant network faces crucial challenges like inadequate relay node, incomplete data transfer, a large number of packet drop, and uncertain delivery time. In this research paper, we propose a novel routing strategy for the vehicular delay-tolerant network. The proposed routing strategy selects efficient vehicular relay node for complete packet transfer and intelligently reduces the packet drop for timely packet delivery. We implement the proposed routing strategy in the ONE simulator; the ONE simulator provides an opportunistic environment for nodes. We analyze the performance of the proposed strategy under various simulations results using different parameters. The results show that the proposed strategy outperforms standard routing protocols in terms of considered parameters and provide an efficient solution for the problem of disconnection.

     

The FLAG cable system

The Fiberoptic Link Around the Globe (FLAG) cable system is a 10 Gb/s synchronous digital hierarchy (SDH) based undersea fiber optic network. When fully operational, FLAG will connect 12 countries with over 120000 voice channels via 27000 km of mostly undersea cable. FLAG will incorporate a new generation of undersea fiber optic system that uses erbium-doped fiber amplifiers and will be jointly supplied by AT&T Submarine Systems Incorporated (SSI) and KDD-Submarine Cable Systems (SCS) Inc. When completed, FLAG will meet or exceed all relevant international performance standards, have greater reliability and availability than previous systems in the region, and conform to all ISO 9000 quality standards with respect to design, development, production, installation, and service     

Highly reliable optical bidirectional path switched ring networks applicable to photonic IP networks

The reliability of the optical bidirectional path switched ring (OBPSR) network is studied by using optical networking equipment (ONE) with microelectromechanical system (MEMS)-based optical switching fabrics. The reliability of the wavelength path in OBPSR networks is shown to be highly dependent on redundant schemes of switching fabrics in the ONE. This study proposes a new redundant scheme utilizing optical couplers together with controlled switch fabrics without using active selectors, and shows that reliability of the wavelength path can be remarkably improved. A fast redundant switching operation of 10 ms was experimentally confirmed with a prototype of the ONE based on the proposed redundant switching fabrics. Furthermore, interworking operations in terms of the protection and restoration between the optical layer and the Internet protocol (IP) layer are experimentally investigated. In a 500-km optical ring network, fast wavelength path protection switching was confirmed without reconfiguring the link state database of the IP layer, and the measured protection time in the IP layer was as short as 21 ms.     

Sip-empowered optical networks for future it services and applications - [Topics in optical communications]

This article presents a novel applicationaware network architecture for evolving and emerging IT services and applications. It proposes to enrich an optical burst switching network with a session control layer that can close the gap between application requests and network control. The session control layer is implemented using the Session Initiation Protocol, giving birth to what is called a SIP-OBS architecture. The article discusses the important added value of this architecture, and shows that it may support a number of end-to-end resource discovery and reservation strategies (for both network and non-network resources). Finally, it presents a testbed implementation where this approach was experimentally validated.     

The TPC-5 Cable Network

The TPC-5 Cable Network (TPC-5 CN) will be the first self-healing trans-Pacific ring network. It consists of a ring of undersea cables connecting six network nodes at six cable landing sites. The TPC-5 CN brings together a unique blend of technology to achieve the architectural robustness and transmission performance needed by network users. Among the technologies used in the TPC-5 CN are erbium doped fiber optical amplifiers (EDFAs), 5 Gb/s line terminating equipment (LTE), line monitoring equipment (LME), synchronous digital hierarchy (SDH) STM-16 add/drop multiplexers (ADMs) with four-fiber-ring automatic protection switching capability, and network management equipment (NME). The article describes the operation of each of these technology and how this equipment is collectively integrated to achieve the performance and functionality of the TPC-5 CN     

Policy-based management of content distribution networks

We present a policy-based architecture for the control and management of content distribution networks that form an overlay of caching proxies over an underlying physical network. The architecture extends the policy framework used for controlling network quality of service (QoS) and security to content distribution networks. The fundamental advantage of a policy-based framework is that it allows a machine-independent scheme for managing multiple devices from a single point of control. In this article we describe this architecture and demonstrate how it enables dynamic updates to content distribution policies. Furthermore, we analyze the impact of such dynamic distribution on the cost of content serving     

A vision for residential broadband services: ATM-to-the-home

The arrival of asynchronous transfer mode (ATM) networks has enabled a wide range of new interactive multimedia applications for the residential market. The article presents a vision for supporting universal residential broadband services based on an ATM-to-the-home (ATTH) network architecture. This network architecture applies to the various residential access network (RAN) architectures being deployed today, such as hybrid fiber/coax (HFC), fiber-to-the-curb (FTTC), fiber-to-the-home (FTTH), and asymmetric digital subscriber loop (ADSL) technologies. The article addresses today's residential networks and applications, to understand why a switched broadband residential network is required to support residential broadband services. After exploring residential broadband application requirements, a new class of service is proposed to support a very important class of residential broadband applications that has been not addressed. Then, the technical and strategic motivations for using the ATTH architecture are discussed in detail. A universal model for residential broadband network architecture based on ATTH is described, which is shown to apply to various RAN architectures. Finally, it discusses the signaling requirements of residential broadband services and explain why the ATM multiconnection per-call model is much more efficient than the digital stored media command and control (DSM-CC) session control protocol approach for the ATTH architecture     

Shore-to-Undersea Visible Light Communication

In this paper, a novel visible light based shore-to-undersea (S2US) communication is proposed. It considers various properties of both maritime and undersea environments such as wave height, wind speed, and absorption. A lighthouse transmits the signal using white light emitting diodes (LEDs) and this signal is received by a buoy that acts as a beacon to relay to the undersea receiver. The beacon employs the decode-and-forward (DF) method in such a way that green LEDs transmit the DF processed signal to the undersea receivers via the undersea optical channel. The performance of the proposed S2US system was first evaluated via simulations with the JONSWAP spectrum model representing the maritime optical channel and the Jerlov water type representing the undersea optical channel. The results show that the transmitted signal undergoes significant attenuation, particularly over the undersea optical channel. At the reference distance of 1.025 km with Jerlov water type I, a bit error rate performance of 10^?4 is achieved with a data rate of 1 Mbps. The S2US was further verified with experiments in terms of received signal level on a laboratory scale. The comparative analysis demonstrates that the simulation and experiment results are in good agreement.     

Future transport network architectures

The architecture of today's long distance transmission networks, which we call the baseline architecture, is a complex and multilayered hierarchy of TDM circuits. One premise of the baseline architecture is that restoration from network failures is provided mostly by SONET/SDH rings. This article presents an alternative architecture that uses ATM and optical layer cross-connect technology for TDM services. Using a sophisticated set of network design tools developed at AT&T Labs-Research, we show that the alternative architecture offers dramatic capital savings and improved network efficiency over the baseline architecture. Most of this savings can be attributed to use of OLXC mesh network restoration, which makes more efficient use of capacity than SONET/SDH rings, and use of ATM switching for transport of TDM circuits, which consolidates the numerous TDM equipment layers inherent to the baseline architecture. In addition, motivated by the rapid growth of IP services, we analyze in the alternative architecture whether to provide restoration for IP services in the IP layer itself, by rerouting packets over precalculated restoration paths with MPLS, or to alternatively provide restoration of failed IP layer links in the OLXC layer. One potential advantage of IP layer restoration is that network operators may choose to only restore a fraction of the services, in particular the “priority” services, affected by a network failure. This article gives some methodology of how to determine this fraction at which IP layer restoration is cost-competitive with OLXC restoration     

DirMove: direction of movement based routing in DTN architecture for post-disaster scenario

Network architecture based on opportunistic Delay Tolerant Network (DTN) is best applicable for post-disaster scenarios, where the controlling point of relief work is any fixed point like a local school building or a hospital, whose location is known to everyone. In this work, 4-tier network architecture for post-disaster relief and situation analysis is proposed. The disaster struck area has been divided into clusters known as Shelter Points (SP). The architecture consists of mobile Relief Workers (RW) at tier 1, Throw boxes (TB) at tier 2 placed at fixed locations within SPs. Data Mules (DM) like vehicles, boats, etc. operate at tier 3 that provide inter-SP connectivity. Master Control Station (MCS) is placed at tier 4. The RWs are provided with smart-phones that act as mobile nodes. The mobile nodes collect information from the disaster incident area and send that information to the TB of its SP, using DTN as the communication technology. The messages are then forwarded to the MCS via the DMs. Based on this architecture, a novel DTN routing protocol is proposed. The routing strategy works by tracking recent direction of movement of mobile nodes by measuring their consecutive distances from the destination at two different instants. If any node moves away from the destination, then it is very unlikely to carry its messages towards the destination. For a node, the fittest node among all its neighbours is selected as the next hop. The fittest node is selected using parameters like past history of successful delivery and delivery latency, current direction of movement and node’s recent proximity to the destination. Issues related to routing such as fitness of a node for message delivery, buffer management, packet drop and node energy have been considered. The routing protocol has been implemented in the Opportunistic Networks Environment (ONE) simulator with customized mobility models. It is compared with existing standard DTN routing protocols for efficiency. It is found to reduce message delivery latency and improve message delivery ratio by incurring a small overhead .     

ATM signaling transport network architectures and analysis

As public carriers plan to offer new broadband services and consolidate different types of services into a single ATM network platform, the identification of an appropriate target broadband signaling transport network architecture is necessary to ensure smooth and cost-effective signaling network evolution. A number of suggestions have been made for possible broadband signaling transport architectures, ranging from the retention of signal transfer points (STPs) to the adoption of a fully distributed signaling transport architecture supporting the associated signaling mode only. The purpose of this article is to describe these architecture alternatives and discuss their qualitative and quantitative tradeoffs. The authors focus on public networks only     

PTN技术发展与网络架构探讨

介绍了新型承载技术PTN的发展,深入分析了PTN的技术特点以及PTN与SDH建网的差异,论述了PTN与SDH/MSTP网络间架构的关系,对PTN与OTN组网架构、4G场景PTN组网架构进行了有益的探讨,并提出了PTN业务承载和PTN+CE建设等发展策略的建议。     

Toward an all-IP-based UMTS system architecture

Looking into the future, two main drivers for the mobile telecommunications market can be identified: third-generation mobile systems (e.g., UMTS) and the Internet (e.g., the introduction of IP technologies like voice/multimedia over IP in mobile networks). UMTS is seen as the enabler of wireless multimedia applications and portability of a personalized service set across network/terminal boundaries, as defined within the virtual home environment (VHE) system concept. In light of these evolutions, this article investigates the impact of the evolution toward an all-IP UMTS network architecture on the UMTS service architecture, which is based on the VHE concept. The article discusses two possible scenarios for supporting VoIP services in the UMTS service architecture and analyzes their applicability in an all-IP-based UMTS network. The first is based on the traditional centralized IN service architecture. The second proposes a new decentralized architecture based on direct control of VoIP call control equipment by open service architecture interfaces     

Africa and the digital divide

The digital divide is a phenomenon linked not only to the topic of access to the Internet, but also to the one of usage and usage benefit. In this paper we take a look at the global digital divide concerning Africa, we analyze the situation with the help of macro-data and by discussing specific examples (Ghana, South Africa). We also address suggestions that have been made for closing the global digital divide and point out that such solutions require more fundamental changes of society and cannot be achieved by technology alone.     

cdma2000的全IP网络体系结构

本在3GPP2最新研究成果的基础上，从整体上对3GPP2的全IP网络体系结构模型进行了描述。章首先介绍了目前我国对cdma2000进行研究的必要性，以及国际上研究cdma2000标准的概况，然后介绍了网络模型中的一个重要部分——“传统移动终端域”(Legacy Mobile Station Do-main,LMSD)，给出了cdma2000的全IP网络模型图，并逐一介绍了其中的重要网络实体，最后从不同的平面和视角，对网络实体之间的关系进行了进一步勾画。     

Cross-layer wireless resource allocation

A fundamental problem in networking is the allocation of limited resources among the users of the network. In a traditional layered network architecture, the resource to be allocated at the medium access control (MAC) and network layers utilizes communication links, viewed as "bit pipes" that deliver data at a fixed rate with occasional random errors. Though this separation has many advantages, there is a growing awareness that this simple bit-pipe view is inadequate, particularly in the context of modern wireless data networks. In this article, several basic cross-layer resource allocation problems for wireless fading channels are considered. The article focuses on the characterization of fundamental performance limits while taking into account both network layer QoS and physical layer performance.     

Unified Radio Network for Broadcasting and Broadband Wireless Access [Advances in Mobile Multimedia]

In this article we propose a unified radio network architecture, broadband wireless multimedia (BWM), which integrates broadcasting service and broadband wireless access service at both the application and physical layers. A simple, flexible, and comprehensive radio resource management framework is developed for the unified radio network. It is shown that the proposed radio network architecture has many advantages over existing ones. In addition, the new architecture is currently being considered in China for the system level design.