High efficiency wireless optical links in high transmission speed wireless optical communication networks

Power link budgets are prepared for wireless optical communication systems to illustrate the optical losses that happen during transmission. This paper has presented optical wireless links, which offer ultra multi gigabit per second data rates and low system complexity. For ground space and/or terrestrial communication systems, these links suffer from atmospheric loss mainly due to fog, and scintillation. Optical wireless links provide high bandwidth solution to the last mile access bottleneck. However, an appreciable availability of the link is always a concern. Wireless optical links are highly weather dependent, and fog is the major attenuating factor reducing the link availability. Link margin, received signal power, transmission bit rate, bit rate distance product, signal‐to‐noise ratio, and BER are the major interesting design parameters in the current study. Copyright © 2013 John Wiley & Sons, Ltd.     

Realization of large capacity ATM switches

Large-capacity ATM switches, with switching capacity in excess of 40 Gb/s or 100 Gb/s, are becoming an essential part of network growth. To realize such switches requires technology know-how as well as implementation trade-off considerations. This article provides a system-level exploration of large-capacity ATM switches in terms of switch fabric scalability, cell buffer management, buffer design trade-off, call processing capabilities, and future trends in switch design     

Full service optical access networks: ATM transport on passiveoptical networks

Multimedia communication has become the driving force for installing broadband systems in the public network. Different alternative solutions have been presented to realize a broadband interactive access network, such as installing optical fiber or upgrading the existing copper network with ADSL for twisted pair or hybrid fiber coax for CATV networks. Among these alternatives, optical fiber access networks are seen as the most future-safe solution. Especially, passive optical networks prove to be a cost-effective way to introduce fiber into the access network. This article presents ATM-based transport on passive optical networks, starting with a current implementation of an ATM-PON (APON) system that has already been installed for various trials. It further describes the evolution of APON systems to high-splitting, long-range PONs. The increase in both number of subscribers and distance range is discussed in combination with some specific technological issues such as upstream burst mode optical amplification. Special emphasis is placed on the work carried out within the scope of the ACTS PLANET project     

High performance real-time neural scheduler for ATM switches

Input-buffered asynchronous transfer mode (ATM) packet switches are simpler than output-buffered switches. However, due to HOL blocking, their throughput is poor. Neural schedulers represent a promising solution for high throughput input-buffered switching, but their response time variance is too high for realistic hard real-time constraints. To overcome this problem, we formulate and evaluate a new neural scheduler with bounded response time     

Liquid crystal-based optical space switches fordwdm networks

This paper addresses the issue of using conventional liquid crystal materials as reconfigurable holographic or diffractive phase elements within optical space switches and the resulting constraints in their choice and use in a telecommunication environment. We discuss the advantage of this technology for implementing holographic-based approaches with respect to other techniques. As an illustration we give two examples which illustrate two generic architectures and complementary use of liquid crystal to implement them. Finally, we give some trends on implementations of high channel capacity space switches based on this technology.     

Virtual path and link capacity design for ATM networks

A path and link capacity design method for asynchronous transfer mode (ATM) networks using statistical multiplexing of cells is proposed. By developing the design method, the statistical cell multiplexing effect can be exploited to significantly reduce required network resources. The necessary design procedures are identified. A simple and effective policing mechanism is proposed. An analytical method for the evaluation of cell multiplexing characteristics using declared parameters is provided. Path and link capacity design algorithms that use these techniques are proposed. The effectiveness of the proposed design procedure is confirmed by comparing analytical results to those from a computer simulation     

Multiwavelength cross-connects for optical transport networks

Multiwavelength cross-connects (M-XCs) will play a key role in future optical multiwavelength transport networks. In this paper, we propose a class of optical wavelength interchange devices that can be used as basic building-blocks for multiwavelength optical cross-connects. We describe three different multiwavelength cross-connect structures that can be constructed using these building blocks. We investigate their blocking performance and examine issues such as complexity, modularity, and wavelength channel spacing associated with the proposed cross-connect structures     

Performance evaluation of high speed TCP over optical burst switching networks

Study of TCP performance over OBS networks has been an important problem of research lately and it was found that due to the congestion control mechanism of TCP and the inherent bursty losses in the Optical Burst Switching (OBS) network, the throughput of TCP connections degrade. On the other hand, High Speed TCP (HSTCP) was proposed as an alternative to the use of TCP in high bandwidth-delay product networks. HSTCP aggressively increases the congestion window used in TCP, when the available bandwidth is high and decreases the window cautiously in response to a congestion event. In this work, we make a thorough simulation study of HSTCP over OBS networks. While the earlier works in the literature used a linear chain of nodes as the network topology for the simulation, we use the popular 14-node NSFNET topology that represents an arbitrary mesh network in our study. We also study the performance of HSTCP over OBS for different bandwidths of access networks. We use two different cases for simulations where in the first HSTCP connections are routed on disjoint paths while in the second they contend for resources in the network links. These cases of simulations along with the mesh topology help us clearly distinguish between the congestion and contention losses in the OBS network and their effect on HSTCP throughput. For completeness of study, we also simulate TCP traffic over OBS networks in all these cases and compare its throughput with that of HSTCP. We observe that irrespective of the access network bandwidth and the burst loss rate in the network, HSTCP outperforms TCP in terms of the throughput and robustness against multiple burst losses up to the expected theoretical burst loss probability of 10⁻³.     

Write policies for multicast ATM switches

A unicast and multicast-pushout write policy for shared-memory ATM switches is proposed. The scheme allocates buffers based on the service rates of unicast and multicast cells to ensure that maximum throughput can be maintained     

ATM passive optical networks and integrated VDSL

VDSL offers a cost effective solution for the provision of a full-service broadband access network. Standards are emerging that will define the line code, duplexing method, and spectrum requirements for VDSL. VDSL chipsets and modules are becoming available that allow the technology to be evaluated in the field. This article describes the architecture and hardware integration that has been performed in integrating VDSL technology into an ATM PON system     

A large ATM switch based on memory switches and optical starcouplers

The authors propose a large asynchronous transfer mode (ATM) switch architecture based on memory switches of the type being developed by several research groups and on optical star couplers. Fast contention resolution makes it possible to combine a number of these modules, memory switches, and optical stars in order to attain a capacity of 2.5 Tb/s. This switch architecture has a relatively small failure group size of 128 STS-3 lines out of a total of 16384. The scaling of the switch to smaller capacities is discussed, showing how tradeoffs in the various parameters can be used to overcome particular technological limitations. Fault tolerance and recovery schemes are presented, showing that with minimal increase to the switch complexity and cost, a very reasonable fault recovery scheme is available for almost every sort of failure     

高速光调制器

文章分析了适用于40Gbit／s等高速光传输系统的MZ和EA调制器的性能特点、现状及技术发展动向。     

Network architecture for optical path transport networks

This paper proposes a new layered transport network architecture on which the WDM optical path network can be effectively created. The optical path network will play a key role in the development of the transport network that will realize the bandwidth-abundant B-ISDN. This paper extends the layered transport network architecture described in ITU-T Recommendation G.803 which is applied in existing SDH networks. First, we elucidate an application example of WDM optical path networks. Next, we propose a new layered architecture for WDM-based transport networks that retains maximum commonality with the layered architectures developed for existing B-ISDN networks. The proposed architecture is composed of circuit layer networks, electrical path layer networks, optical layer networks, and physical media (fiber) networks. The optical layer is divided into an optical path layer and an optical section layer. The optical path layer accommodates electrical paths. Optical section layer networks are divided into optical multiplex section (OMS) layer networks and optical repeater section (ORS) layer networks. The OMS layer network is concerned with the end-to-end transfer of information between locations transferring or terminating optical paths, whereas the ORS layer is concerned with the transfer of information between individual optical repeaters. Finally, a detailed functional block model of WDM optical path networks, the function allocation of each layer, and an optical transport module (OTM) are developed     

Reliability performances of optical ATM switches based on differentrouting and buffering schemes

Reliability performances of seven equal-capacity optical asynchronous transfer mode switches based on different routing and buffering schemes are compared. Calculations are based on available reliability data for commercial components as well as expected life lengths for new components and systems. In general, for switching systems, the average downtime is required to be held below 3 min/year. However, our results indicate that the average downtime for the proposed configurations is much longer than requested, over ten times longer for the best case and over 1500 times longer for the worst case. Therefore, the multiplane structures (i.e., multiplying of the entire systems) have to be provided for the switching systems investigated here in order to satisfy reliability requirements     

An efficient architecture for fault-tolerant ATM switches

A cost-effective fault-tolerant architecture called FAUST is presented for ATM switches. The key idea behind the architecture is the incorporation of spare units and associated commutation logic into strategic partitions of the switching system. The definition of a replaceable unit is flexible, and based on packaging considerations. The commutation logic can switch in a spare unit in place of a failed one at cell rate, and is distributed entirely in the existing switch control units. So the additional overhead is almost entirely in the spare modules provided. The technique is far superior to a duplex configuration in terms of reliability improvement vs. component redundancy, and can be applied to established architectures for ATM switches, including multistage sort and shared memory based architectures. Its scalability also makes it applicable to system sizes from a few tens of lines to a few thousand     

Provisioning QoS features for input-queued ATM switches

A new scheduling algorithm is proposed to improve on existing algorithms designed for input-queued ATM switches. By assigning a session weight according to its queue length normalised by its rate and using maximum weight matching to obtain a match, the proposed algorithm can avoid starvation of slow sessions, thus providing good delay properties as well as fair services, and at the same time reducing traffic burstiness     

Optimum architecture for input queuing ATM switches

An input queueing ATM switch architecture employing the contention resolution called 'scheduling algorithm' is described. A high efficiency of over 90% can be achieved without any considerable increase in the amount of hardware or contention control speed.<>     

Fault-tolerant multicasting in MINs for ATM switches

This article proposes a fault-tolerant multicast routing algorithm in multistage interconnection networks (MINs) for ATM switch architectures. It employs both region and cube encoding schemes as the header encoding scheme. A multicast packet can be routed to its destinations in only two phases through the MIN having a single faulty element     

Very high speed and high capacity packet switching for broadbandISDN

The authors discuss and propose a very-high-speed and high-capacity packet-switching (HPS) architecture for a future broadband ISDN (integrated-services digital network). The HPS network accommodates various communication services, such as voice, high-speed data, high-speed still picture, and video services. The proposed architecture has three significant principles: a high-speed oriented simple network protocol, separation of signaling and network control from data transfer, and hardware switching. These principles provide fast- and high-throughput transmission for data packets and reliable transmission and processing for call-control packets. The HPS protocol structure is addressed, which provides high flexibility for various communications services as well as high-speed capability. A 3-Gb/s capacity and building-block-structured packet-switching system architecture, using bus- and loop-type switch fabric, is also presented     

Parallel-stage-based reconfigurable optical add-drop multiplexer for WDM optical transport networks

This letter proposes a simple and flexible reconfigurable optical add-drop multiplexer (ROADM) based on parallel-stage configuration using Mach-Zehnder-based fiber gratings, 1/spl times/2 optical switches, and Y-model combiners. The proposed ROADM with four-stage parallel configuration is designed and experimentally investigated to show its performance in full wavelength selection and advantages in reducing the discrepancy of the insertion loss between channels and upgrading.