Access Network

Passive optical network (PON) is one of the most successful broadband access architectures being deployed worldwide. PONs provide high capacity, increased reach, and low-power consumption at a very reasonable cost, on par with the cost of DSL deployments today. This paper provides an overview of present and emerging PON technologies, and discusses PON's important role in the evolution of optical access from the architectural perspective. While describing the evolution of optical access architecture, we present two important integration options: optical+wireless access integration and metro+access integration. Potential PON capacity upgrades are discussed with special emphasis on achieving a seamless upgrade. We evaluate different PON evolution strategies in the context of next-generation PON, where gradual, demand-based migration demonstrates a number of significant benefits.

The Internet Protocol (IP) is currently used to provide internetworking among heterogeneous access networks. However, the evolution of and the innovation within these networks is greatly hindered by the geographical and topological rigidness of the protocol implementation that hinders the support for flexible unstructured communication paradigms. To broaden the user's innovation space and to efficiently embrace the characteristics of these emerging unstructured networks, clean-slate architectural approaches are being pursued. In this paper, we present the Persistent Identification and NeTworking research framework (PINT); an implementation of the Transient Network Architecture (TNA) currently being developed between the University of New Mexico and the Corporation for National Research Initiatives. PINT provides the research community with a modular and extensible set of networking components and primitives that enable novel research and experimentation atop a persistently identified networking platform. This technology provides a ground for inter-networking of heterogeneous communication networks where novel networking primitives are exposed through the Persistent Identification and Networking Layer (PINL), allowing mobile and stationary entities to communicate securely based on persistent identifiers that are location independent.

In this paper we argue that service-based competition may deter (or delay) facility-based competition. Hence, to the extent that service-based and facility-based entry are perceived as substitute strategies by the entrants, regulatory policies that are aimed at each one of them may exhibit conflicts. We develop our arguments on the basis of our formal studies, , where an incumbent and an entrant compete for providing high-bandwidth services. We claim that an incumbent who faces an effective threat of facility-based competition can strategically delay facility-based entry by providing attractive terms of access to its facilities. The delay that is introduced by attractive terms of access is by virtue of a replacement effect, which may also affect the choice of technology to be eventually built by the entrant. * Dogan thanks ENST -Paris for its hospitality during the time part of this research was conducted.

The home gateway integrates heterogeneous home network environments and interconnects the home network and the public access networks. It is natural that users want to see the visual contents on the home network from outside the home. However, there exist significant differences in network capability and computing power of users. Video transcoding technique is an efficient mechanism to deliver visual contents to a variety of users who have different network conditions or terminal devices with different display capabilities. In this paper, we propose an efficient video transcoding technique as the key component of the home gateway architecture. It consists of two types of transcoding methods for adapting the bitrate of streaming video to the bandwidth of the transmission channel; spatial resolution reduction transcoding and temporal resolution reduction transcoding. The two transcoding methods are alternatively or simultaneously operated according to the requirements of users. Experimental results show that the proposed transcoding methods can preserve image quality while transcoding to the low bitrate 1 .

Abstract—A hybrid fiber–radio access network architecture for simultaneous wireline and wireless transmissions of Data-Over-Cable Service Interface Specification (DOCSIS) signals is pre-sented. An all-optical harmonic up-conversion technique using a dual-drive ...

We present a model of energy consumption in IP networks. Using this model, we identify energy ldquohotspotsrdquo and estimate how energy consumption will grow with increasing network capacity. Todaypsilas Internet uses less than 1% of the available electricity supply. However, network energy consumption could grow substantially as access rates increase.

The rapid proliferation of the Internet over recent years has roused the research community's interest in QoS guarantees to IP traffic. The integration of new satellite technologies with terrestrial broadband networks can provide worldwid reachability to a wide range of IP-based multimedia applications and services. Thus, a great deal of research is being conducted to extend IP technology with QoS guarantees to satellite links. The purpose of this article is to contribute to this issue. In fact, the main focus is on the satellite access network of an integrated terrestrial-satellite multimedia platform. In this scenario, effective solutions to transport real-time IP traffic with quality of service (QoS) guarantees are proposed, and their effectiveness is assessed. Real-time IP services with different traffic descriptors and delay requirements are considered, and therefore the best transport solution (in terms of guaranteed quality and efficiency in satellite resource utilization) over permanent or semi-permanent satellite connections is identified.

The power consumption of wireless access networks will become an important issue in the coming years. In this paper, the power consumption of base stations for mobile WiMAX, fixed WiMAX, UMTS, HSPA, and LTE is modelled and related to the coverage. A new metric, the power consumption per covered area P C area , is introduced, to compare the energy efficiency of the considered technologies for a range of bit rates. Assuming the model parameters are correct, the conclusions are then as follows. For a 5 MHz channel, UMTS is the most energy-efficient technology until a bit rate of 2.8 Mbps, LTE between 2.8 Mbps and 8.2 Mbps, fixed WiMAX between 8.2 Mbps and 13.8 Mbps and finally mobile WiMAX for bit rates higher than 13.8 Mbps. Furthermore, the influence of MIMO is investigated. For a 2x2 MIMO system, P C area decreases by 36 % for mobile WiMAX and by 23 % for HSPA and LTE compared to the SISO system, resulting in a higher energy efficiency. The power consumption model for base stations is used in the deployment tool GRAND (Green Radio Access Network Design) for green wireless access networks. GRAND uses a genetic based algorithm and is applied on an actual case for the Brussels Capital Region, showing the possibilities of energy-efficient planning.

The EU Commission published a second, substantially revised, version of the draft recommendation for the regulation of next generation access networks for public consultation in June 2009. The Recommendation includes a large set of regulatory tools suitable for the emerging NGA environment. This second draft takes into account a large number of comments received in response to a previous EU Commission document of autumn 2008 dealing with the same topic, but with different focal points. The research question discussed in this paper is whether the revised Draft Recommendation is consistent with the current regulatory framework, i.e. whether the approach is an incremental step complementing the existing regulation, or whether the Recommendation lays the foundation for a new and innovative regulatory strategy in the EU. The conclusion of the paper is that the EU Commission aims to continue and further develop current regulation, and that the development of access regulation will remain dynamic, but at the cost of simplicity and straight-forwardness. This approach will test the current regulatory regime's ability to adapt to changes in technology and economic parameters and flexibility to deal with both legacy as well as new networks.

Providing seamless mobility support is one of the most challenging problems towards the system integration of fourth generation (4G) wireless networks. Because of the transparency to the lower layer characteristics, application-layer mobility management protocol like the Session Initiation Protocol (SIP) has been considered as the right candidate for handling mobility in the heterogeneous 4G wireless networks. SIP is capable of providing support for not only terminal mobility but also for session mobility, personal mobility and service mobility. However, the performance of SIP, operating at the highest layer of the protocol stack, is only as good as the performance of the underlying transport layers in such a heterogeneous environment. In this paper we analyze the handoff performance of SIP in a IP-based 4G network with Universal Mobile Telecommunication System (UMTS) and Wireless LAN (WLAN) access networks. Analytical results show that the handoff to a UMTS access network introduces a minimum delay of 1.4048 s for 128 kbps channel, while for handoff to a WLAN access network the minimum delay is 0.2 ms. In the former case the minimum delay is unacceptable for streaming multimedia traffic and requires the deployment of soft-handoff techniques in order to reduce the handoff delay to a desirable maximum limit of 100 ms.

Virtual Private LAN Service (VPLS) provides a multipoint to multipoint connection service but current VPLS implementations do not provide multi-homing (resilient access). Spanning tree protocol (STP) at access network is thus required to provide resilient access at the cost of unused links and significant reconfiguration delays. This article describes a new protocol, the Resilience and Traffic Balance Protocol (RTBP) that provides resilience and load balance in VPLS network access. The proposed protocol balances the load fast and efficiently between all active access links. The protocol handles automatically failure and recovery of links redistributing the load between the remaining active links. The protocol is simple to deploy: only the access nodes to VPLS network require a software modification. The protocol has been implemented and several tests have been carried out. The results show that the effect of RTBP on node performance is low. The reconfiguration time is lower than for STP and very low (lower than 100 milliseconds).

Mesh networks are candidate to play the role of switched Ethernet LANs over extended areas and with a sensibly higher flexibility. Actually, mesh networks can exploit both Ethernet and wireless technologies, e.g. Wi-Fi and/or free-space optical links, to provide a high degree of redundancy in an access network, and to provide users with powerful means to connect with each other.

This paper presents the bringing of optical fibre to domestic users in the Republic of Slovenia. Slovenia has two main Fibre-to-the-Home (FTTH) providers, deploying access network infrastructure based on Point to Point (P2P) fibre links. In recent years, accelerated deployment of the optical access network and the consequent increase in the number of optical household connections has been noted. These

The introduction of FTTH leads to high costs, especially in fiber deployment. In operations we face a high complexity and corresponding high cost of fiber splicing compared to copper welding. However, fiber based access networks have less active equipment than copper based networks, leading to lower failure rates. In order to correctly calculate the business case for anew FTTH network deployment, the capital expenditures need to be balanced with the expected gains in operational expenditures compared to the current (e.g. copper based) access network.

Détection et localisation de défauts dans des réseaux filaires de topologie complexe. Auteur principal : Fabrice AUZANNEAU -CEA LIST Tél : 01 69 08 90 70 -email : [email protected] L'auteur est le responsable du Laboratoire de Fiabilisation des Systèmes Embarqués au CEA, centre de Saclay (91). Autres auteurs : Nicolas RAVOT -CEA LIST I. Résumé La réflectométrie est une méthode couramment utilisée pour déterminer l'état électrique de câbles et de lignes. Cette méthode fournit des informations pour la détection, la localisation et la caractérisation de défauts électriques. Le CEA LIST travaille sur l'implémentation de cette méthode pour le diagnostic de réseaux filaires de topologie complexe, pour des applications embarquées ou de diagnostic en ligne. Les domaines d'application concernent les télécommunications, l'automobile et les transports, la distribution d'énergie, etc.

The optical fiber based supercontinuum source has recently become a significant scientific and commercial success, with applications ranging from frequency comb production to advanced medical imaging. This one-of-a-kind book explains the theory of fiber supercontinuum broadening, describes the diverse operational regimes and indicates principal areas of applications, making it a very important guide for researchers and graduate students. With contributions from major figures and groups who have pioneered ...

One recent focus of research in international relations theory is that of "long cycle theory," associated primarily with George Modelski and William Thompson, which posits serial cycles of hegemonic dominance -Venice, Portugal, the Netherlands, Great Britain, the United States -lasting approximately for one century. These hegemonic cycles are highly correlated with, or underpinned by, maritime and commercial dominance. Some aspects of long cycle theory have been contested by the rival "world systems" theory, that has fewer cycles and a disinclination to separate the military and economic dimensions of hegemony. Heretofore, naval power, as reflected in capital ship construction and orders of battle, has been used to measure maritime dominance. This research suggests that data for rival and successive global basing access networks could be used to inform and query the basis of long cycle theory; i.e., to provide a measure of "global reach". There are additionally, interesting conceptual questions about the basis for basing access, as it has evolved historically; specifically, from a basis in conquest to one dependent upon diplomacy and various quid pro quo. The article suggests the need for more historical data collection on bases.

Wireless IPTV (Internet Protocol TeleVision) aims to make the traditional IPTV and related services available to users anywhere, anytime, on any device, and through any network. Mobile streaming TV is one of the alternatives to deploy such a system; others are DVB-H or MediaFLO. In this paper we propose an alternative CDN-based architecture to distribute contents to different access networks, in order to create a triple screen platform. The core elements of the system are the video streamers, acting as surrogates of the mobile CDN-based architecture, installed in the access networks (including mobile), and the transcoding servers in the premises of the content providers. The paper focused on the wireless part of the system, analyzing the architecture and performance results related with the video coding and the efficiency obtained due to the placement of the streaming servers. The system has been deployed by a Spanish media company for its use with different Telcos, ISPs and media companies.

A large variety of access network technologies and architectures that provide wide service portfolio to the customer are available for the network operators. Each of the potential access network architectures and technologies varies in complexity, network functionality, services supported and overall network costs. A detailed comparison of the economic viability of different access network scenarios is crucial for operators due to the high cost of this network segment. This paper identifies all essential elements of a general framework for the techno-economic analysis of different access network technologies and architectures, as well as describes some specific issues/problems related to the techno-economic evaluation of next generation (NG) access networks. The goal is to have at operator's disposal a methodology allowing the techno-economic comparison of the proposed access network solutions and their introduction/rollout.

Using orthogonal-frequency-division-multiplexing (OFDM) format for passive optical network (PON) is a subject of great interest for recent research works. OFDM signal has high spectral efficiency, high tolerance to the fiber chromatic dispersion and the high flexibility on both multiple services provisioning and dynamic bandwidth allocation. In this paper we study the use of OFDM signals for optical access networks, including carrier distributed PON, heterogeneous optical wired/wireless network and a 100 Gb/s OFDM-PON. We first quantify the performance of the OFDM signal when subjected to the noise produced by two different Rayleigh backscattering (RB) components that are present in the carrier-distributed PON. Then, based on these results, we also study the possibility of using OFDM for signal remodulation in a long-reach (LR)-PON. We propose carrier-distributed OFDM PONs using a dual-feeder fiber architecture and wavelength-shifting to mitigate the RB noise. Afterwards, we propose heterogeneous optical wired/wireless access networks, combining 10 Gb/s PON and 10 Gb/s OFDM radio-over-fiber (ROF) network. Finally, we propose a 100 Gb/s OFDM-PON using subcarrier multiplexing (SCM).

Since the energy crisis and environmental protection are gaining increasing concerns in recent years, new research topics to devise technological solutions for energy conservation are being investigated in many scientific disciplines. Specifically, due to the rapid growth of energy consumption in ICT (Information and Communication Technologies), lot of attention is being devoted towards "green" ICT solutions. In this paper, we provide a comprehensive survey of the most relevant research activities for minimizing energy consumption in telecom networks, with a specific emphasis on those employing optical technologies. We investigate the energy-minimization opportunities enabled by optical technologies and classify the existing approaches over different network domains, namely core, metro, and access networks. A section is also devoted to describe energy-efficient solutions for some of today's important applications using optical network technology, e.g., grid computing and data centers. We provide an overview of the ongoing standardization efforts in this area. This work presents a comprehensive and timely survey on a growing field of research, as it covers most aspects of energy consumption in optical telecom networks. We aim at providing a comprehensive reference for the growing base of researchers who will work on energy efficiency of telecom networks in the upcoming years.

The communications sector is undergoing significant changes, with the emergence of a number of platforms available to provide a different range of services. Some of these platforms are complementary to each other, while others are competitive, or can provide a valid substitute for some of the services provided. Up till now, the most important communications platform in most of the developing countries has been the public switched telecommunication network (PSTN) which provides access to all households and buildings. This universality in providing access has also meant that the network has generally been designated as one for universal service.This chapter focuses on the area where the most significant changes are taking place in the communication sector. The objective of this chapter is neither to give an overview of all communication platforms, nor is it aimed to assess the relative extent to which different platforms complement or compete with each other. The central theme of this chapter is to examine the developments in what is commonly refereed to as next generation access networks and next generation core networks and their role in convergence.

This chapter reviews the current developments in access network architectures and protocols to communicate dynamically the emerging broadband services to end-users at low cost. Following a summary of Gigabit Ethernet and Passive Optical Network (PON) standards and deployment issues with reference to Ethernet (EPON) and Gigabit-capable PON (GPON) infrastructures, an original transparent network architecture is presented to allow interoperability of time division multiplexing (TDM) and wavelength division multiplexing (WDM) PONs, by means of coarse routing. To provide flexible connectivity at extended service reach hybrid wireless and free space optic technologies have been investigated to terminate mobile end users to high bandwidth PON terminals. To demonstrate independent bandwidth management of the constituent sectors of such architectures developed dynamic bandwidth allocation (DBA) algorithms are summarised followed by an original control plane to coordinate the various mandatory access control (MAC) protocols. Finally, to provide reliable service delivery several protection schemes have been analysed.

Mesh networks are multi-hop wireless networks that can be used as a low cost infrastructure for community and city-wide access networks. In this context, support for killer applications such as cooperative services and mobile multimedia applications are in great demand. This mini-course presents the main challenges and solutions for providing mobility, quality of service (QoS) and multicasting in wireless mesh

The integration of optical and wireless systems is considered to be one of the most promising solutions for increasing the existing capacity and mobility as well as decreasing the costs in next-generation optical access networks. In this paper, several key enabling technologies for hybrid optical-wireless access networks are described, including optical millimeter-wave (mm-wave) generation, upconversion, and transmission in a downlink direction, and full-duplex operation based on wavelength reuse by using a centralized light source in an uplink direction. By employing these enabling technologies, we design and experimentally demonstrate an optical-wireless testbed that is simultaneously delivering wired and wireless services in the integrated optical-wireless and wavelength-division-multiplexing passive-optical-network access networks. The actual applications consisting of 270-Mb/s uncompressed standard-definition TV signal and 2.5-Gb/s data channels for downstream are successfully transmitted over a 25-km fiber and a 10.2-m indoor wireless link with less than a 1.5-dB power penalty. The results show that this integrated system is a practical solution to deliver superbroadband information services to both stationary and mobile users.

We report on a hybrid DWDM-TDMA optical access network that provides a route for integrating access and metro networks into a single all-optical system. The greatest challenge in using DWDM in optical access networks is to precisely align the wavelength of the customer transmitter (Tx) with a DWDM wavelength grid at low cost. Here, this was achieved using novel tunable, external cavity lasers in the optical network units (ONUs) at the customer's end. To further support the upstream link, a 10 Gb/s burst mode receiver (BMRx) was developed and gain-stabilized erbium-doped fiber amplifiers (EDFAs) were used in the network experiments. The experimental results show that 10 Gb/s bit rates can be achieved both in the downstream and upstream (operated in burst mode) direction over a reach of 100 km. Up to 32 50 GHz spaced downstream wavelengths and another 32 50 GHz spaced upstream wavelengths can be supported. A 512 split per wavelength was achieved: the network is then capable of distributing a symmetric 320 Gb/s capacity to 16384 customers. The proposed architecture is a potential candidate for future optical access networks. Indeed it spreads the cost of the network equipment over a very large customer base, allows for node consolidation and integration of metro and optical access networks into an all-optical system.

Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. They provide network access for both mesh and conventional clients. The integration of WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be accomplished through the gateway and bridging functions in the mesh routers. Mesh clients can be either stationary or mobile, and can form a client mesh network among themselves and with mesh routers. WMNs are anticipated to resolve the limitations and to significantly improve the performance of ad hoc networks, wireless local area networks (WLANs), wireless personal area networks (WPANs), and wireless metropolitan area networks (WMANs). They are undergoing rapid progress and inspiring numerous deployments. WMNs will deliver wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. Despite recent advances in wireless mesh networking, many research challenges remain in all protocol layers. This paper presents a detailed study on recent advances and open research issues in WMNs. System architectures and applications of WMNs are described, followed by discussing the critical factors influencing protocol design. Theoretical network capacity and the state-of-the-art protocols for WMNs are explored with an objective to point out a number of open research issues. Finally, testbeds, industrial practice, and current standard activities related to WMNs are highlighted.

We present a hybrid dense wavelength-division-multiplexed time-division multiple access passive optical network (DWDM-TDMA PON) with record performance in terms of reach (135.1 km of which 124 km were field-installed fibers), number of supported optical network units (ONUs-8192) and capacity (symmetric 320 Gb/s). This was done using 32-, 50-GHz-spaced downstream wavelengths and another 32-, 50-GHz-spaced upstream wavelengths, each carrying 10 Gb/s traffic (256 ONUs per wavelength, upstream operated in burst mode). The 10 Gb/s downstream channels were based upon DFB lasers (arranged in a DWDM grid), whose outputs were modulated using a electro-absorption modulator (EAM). The downstream channels were terminated using avalanche photodiodes in the optical networks units (ONUs). Erbium-doped fiber amplifiers (EDFAs) provided the gain to overcome the large fiber and splitting losses. The 10 Gb/s upstream channels were based upon seed carriers (arranged in a DWDM grid) distributed from the service node towards the optical network units (ONUs) located in the user's premises. The ONUs boosted, modulated, and reflected these seed carriers back toward the service node using integrated 10 Gb/s reflective EAM-SOAs (EAM-semiconductor optical amplifier). This seed carrier distribution scheme offers the advantage that all wavelength referencing is done in the well-controlled environment of the service node. The bursty upstream channels were further supported by gain stabilized EDFAs and a 3R 10 Gb/s burst-mode receiver with electronic dispersion compensation. The demonstrated network concept allows integration of metro and optical access networks into a single all-optical system, which has potential for capital and operational expenditure savings for operators.

The increasing bandwidth needed by the business and residential users has been a challenge in recent years for telecom operators. For this reason, optical fiber became a strong candidate to access networks, allowing high transmission rates when compared with existing infrastructures, especially the twisted pair and coaxial cable or even with wireless communication systems. Optical fibers can exist in different materials: glass optical fiber (GOF) and plastic optical fiber (POF). The GOF have low attenuation allowing long-distance transmission, but are fragile. The POF currently have a higher attenuation, however is less expensive and is more flexible and robust. The purpose of this thesis is to study the feasibility of using plastic optical fiber in the access network ensuring the minimum requirements specified by the standards of technologies. For this purpose, it was used a program called VPIphotonics TM to simulate an access network with different types of fibers. Two scenarios were taken into account: the first one is an implementation of a GPON network with POF and GOF in access network and the second scenario consists on the analysis of the performance of POF in an environment where GPON and 10G-PON coexists on the same optical distribution network (ODN). It was necessary a theorical calculation of the power budget of the system, which took into account the characteristics of all passive and active components that forms the network. The fibers that were considered for testing and comparison were a singlemode fiber G.657 ClearCurve by Corning, ClearCurve multimode fiber and POF called Fontex developed by Asahi Glass. The quality of the optical received signal was analyzed using figures of merit such as BER and eye diagram. The maximum distance achieved in the last mile with POF was 115 meters to the first scenario and 40 meters for the second scenario. In the current situation, due to the high attenuation of POF is only viable when the ODN attenuation is about 15 dB.

The access network infrastructure plays an important role in the overall performance of the network, next generation access networks (NGA) must be able to access diverse services, and should incorporate adequate architectures that include mechanisms for the integration of different technologies. New optical access technologies trends are: WDM, 10 Gb/s, and longer reach/higher splits. It is also important to take

In this paper we propose a novel planning tool for Next Generation Optical Access (NGOA) networks, based on real street maps. A Geographical Information System -based tool was developed that uses OpenStreetMap (OSM) raw data to extract the network topology. Aiming to reduce the total network deployment costs in a greenfield scenario, we propose a heuristic clustering algorithm for the assignment of Optical Network Units (ONUs) to access network port and a scheme that exploits conduit sharing to find the optimum cable distribution for the working and protection paths. Our model is used to compare several variants of WDM-based NGOA system concepts with respect to their equipment, energy consumption and infrastructure costs.

Mesh networks are multi-hop wireless networks emerging as a low cost infrastructure for community access networks and digital cities. In this context, support for killer applications such as cooperative services and mobile multimedia applications are the in great demand. This mini-course aims at presenting, in a theoretical way, main problems, solutions and challenges for providing security in wireless mesh networks. The course has three main focuses: the mesh networks contextualization; Security issues in wireless mesh networks, with your challenges and deficiency and; the main proposals found in the literature.

For realization of future high performance integrated networks, broadband distribution and access networks and to meet the increasing demand of multimedia services with a guaranteed quality of service, RoF technology comes out as the most promising technology that combines the capacity of optical networks with the flexibility and mobility of wireless networks. Reduction in complexity at the antenna site, reduction in installation cost of access networks, possibility of dynamically allocation of radio carriers to different antenna sites, transparency and scalability are the few advantages of radio-over-fiber (RoF) technology. In this paper, we review the different challenges that limit the probable capabilities of RoF communication networks and different mitigation techniques to combat with these challenges to realize high-performance RoF links.

Due to the rapid growth of Internet with new generation of services and applications, demand for faster and cheaper access network has been rising. To address the present and future demand, broadband fiber access technologies such as passive optical networks (PONs) are a potential solution. Mostly, time division multiplexed (TDM)-PON is deployed in all parts of the world. In order to mitigate the future demand, some next-generation PON systems have been investigated by the researchers. In this paper, we examine the current status of PONs and investigate the probable future PONs. We also explain the smooth migration process from the current status to the future technologies. Architecture of a self-restored tree-type hybrid wavelength division multiplexed/TDM-PON (WDM/TDM-PON) has been proposed, for migrating from TDM to WDM-PON. Due to the restorable capacity of the architecture, the availability of the system is increased. In addition, cost analysis of different PON architectures are performed and compared with the cost of the proposed architecture. It is found that, the proposed architecture provides more cost effective solution.

In a passive optical network with a hybrid wavelength division multiplexing time division multiple-access scheme, implementing reconfigurable wavelength assignment is complex; hence the need to determine the conditions for which the capacity improvements justify requiring reconfigurability over adopting a more inexpensive fixed wavelength assignment. Fixed and reconfigurable approaches to wavelength assignment are modeled and evaluated under nonstationary traffic conditions. The performance improvement is obtained in terms of bit rate gain relative to the nominal bandwidth and depends on the number of wavelength channels as well as the magnitude of the load offered by the optical network units. In addition, frame delay and frame loss in relation to the bit rate performance are obtained for Pareto and exponentially distributed traffic. Simulations show that when introducing reconfigurability, typical peak bit rate gains with respect to the fixed case are 17%, and maxima of 175% are potentially possible when traffic demands are particularly uneven.

The access network infrastructure plays an important role in the overall performance of the network, next generation access networks (NGA) must be able to access diverse services, and should incorporate adequate architectures that include mechanisms for the integration of different technologies. New optical access technologies trends are: WDM, 10 Gb/s, and longer reach/higher splits. It is also important to take into account the evolution of the installed legacy PONs to the next generation optical access networks. The present paper goes through such topics, focusing on the research being carried out to develop dynamic bandwidth algorithms for the 10 Gb/s new EPON standard (IEEE 802.3av). We summarize results and point out issues that will require further investigation. Postprint (published version)

Passive Optical Networks are thought to be the next step in the development of Access Networks and providing broadband access in the "last mile" area. Ethernet PONs (EPON) gain the most attention from the industry as they offer highly flexible, cost effective solution. In this paper we propose algorithms that provide Dynamic Bandwidth Allocation and shift the burden of queue

Recently both ITU and IEEE have standardized solutions for passive optical networks (PONs) operating at gigabit per second line rates and optimized for the transport of packet-based traffic to improve the efficiency of previously standardized broadband PONs, which used the ATM cell as the data transport unit. The efficiency and performance of PON systems depend on the transmission convergence layer and mainly on the implemented medium access protocol. Although the latter is not part of the standards and left to the implementer, the standards describe a set of control fields that constitute the tool-set for the media access control (MAC) operation. Though starting from a common and quite obvious basis, the two standards present significant differences with the legacy of Ethernet marking the IEEE approach, while the emphasis of ITU is on demanding services. In this paper we compare the efficiency and performance of the two systems assuming the implementation of as close as possible MAC protocols. The target is twofold: assess and compare the traffic handling potential of each of the two standards and identify the range of applications they can support. Useful insight can also be gained to the MAC tools that could be designed into the next generation extra large WDM PONs. expensive optical links compared with the conventional point-to-point (P2P) transport solutions. In addition, they inherently concentrate traffic and greatly reduce the number of input ports in the access multiplexer, both important for the cost-sensitive residential access market. Owing to these advantages, PONs have generated during the last decade substantial commercial activity also reflected in the study of several standardization bodies. Since the initial standardization of ATM-based PONs (APONs or alternatively named in ITU-T G.983.1 standard [1] Broadband PONs-BPONs) newer standards support multi-gigabit rates and better adapt to the packet-based Internet applications. In January 2003, the GPON (Gigabit PON) standards were ratified by ITU-T and were included in the G.984.x series of ITU-T Recommendations [2, 3]. Driven by a closed group of worldwide system vendors and national telecom operators, they are designed to support a mix of TDM, ATM and packet-based services, reaching symmetrical transmission rates of up to 1.244 or 2.488 Gb/s. At the same time IEEE, through the activities of Ethernet in the first mile (EFM) 802.3ah group, has standardized a Gigabit Ethernet-friendly technology [4] called Ethernet PON (EPON) with the objective to leverage the great success of Ethernet as a LAN technology and exploit the economies of scale that the dominance of Ethernet has generated. The objective of EFM efforts has been to combine a minimal set of extensions to the IEEE 802.3 media access control (MAC) and MAC control sub-layers with a family of physical (PHY) layers. In addition, a mechanism for network operations, administration and maintenance (OAM) is included to facilitate network operation and troubleshooting.

Optical access networks are considered to be a definite solution to the problem of upgrading current congested access networks to ones capable of delivering future broadband integrated services. However, the high deployment and maintenance cost of traditional point-to-point architectures is a major economic barrier. Current TDM-PON architectures are economically feasible, but bandwidth-limited. In this article we first discuss the possible role of WDM in access networks and investigate the associated issues. We then present the Stanford University Access Hybrid WDM/TDM Passive Optical Network (SUCCESS-HPON), a next-generation hybrid WDM/TDM optical access architecture that focuses on providing a smooth migration path from current TDM-PONs to future WDM-PONs. The first testbed for this architecture is described, along with the experimental results obtained, including feasibility of bidirectional transmission on the same wavelength on the same fiber for access networks and ONU modulation of upstream data on continuous waves provided by the OLT, eliminating the need for tunable components at the ONUs. The development of a second testbed and the issues it will address, including the implementability of the SUCCESS-HPON MAC protocol and scheduling algorithms, are also described.

Rapidly-increasing traffic demands will require the upgrade of optical access networks, namely deployed Passive Optical Networks (PONs), which may soon face capacity exhaustion. Such upgrade options must consider several technical and cost factors for evolution towards a shared multiple-channel PON using Wavelength-Division Multiplexing (WDM). WDM can facilitate the seamless upgrade of PONs, since capacity can be increased by adding new wavelength channels. We study the requirements for optimal migration towards higher bandwidth per user, and examine scenarios and cost-effective solutions for PON evolution.