A flexible medium access control framework for multimedia application support in wireless ATM

Includes bibliographical references.The field of wireless communications has seen phenomenal development over the last decade. With the current abundance of applications that use broadband multimedia over wired networks it is logical that users will want to have access to these same multimedia streams [rom a mobile terminal. Wireless solutions for connectivity to networks such as Ethernet networks already exist, however, a method of supporting access to an ATM network from a mobile terminal has not yet been standardised. Transporting ATM data over the wireless medium poses a number of problems. The Medium Access Control (MAC) layer of any proposed wireless ATM network would be responsible for resolving many of these problems. Unfortunately, research into MAC layers is hampered by the fact that most existing MAC layers cannot be modified in order to experiment with the effectiveness of the many MAC protocol techniques that exist

Optical Packet Switching Contention Resolution Based On A Hybrid Wavelength Conversion-Fiber Delay Line Scheme

Due to the convergence of computer communication and telecommunication technology, data traffic exceeds the telephony traffic. Thus, existing connection oriented and circuit switched network will need to be upgraded toward optical packet switched network. Optical packet switching has characteristics like high speed, data rate/data format transparency and configurable. Wavelength Division Multiplexing is the technology of combining a number of wavelengths in a single fiber. It is a tremendous trend to harness larger bandwidth for enormous delivery. WDM optical devices for multiplexing and switching in simple configuration are now available at a reasonable cost. It is a very appealing solution for development of optical packet switching. The issue of contention arises when two or more packets contend for the same output port in a switch with the same wavelength, which results to packet loss. The packet loss probability is addressed as the most inevitable and significant measurable performance parameter with QoS provisioning that is dominated by wavelength contention in optical packet switches. In electronic domain packet switched network, the contention is resolved by store and forward technique using the available electronic random access memory (RAM). Due to the immaturity of optical memory storage technology, there is no available ready-to-use optical random access memory. In order to overcome this bottleneck, several approaches have been adopted to resolve the contention problem from three domains: time, space and wavelength as stated: fiber delay line (time), deflection routing (space) and wavelength conversion (wavelength). Consequently, contention resolution in wavelength domain has attracted considerable interest among the optical communications community instead of implementing optical buffering and deflection routing that have been studied previously. This thesis proposes a bufferless, single stage, non-blocking fully connected optical packet switch for synchronous optical packet switching network, followed by a prioritized scheduling algorithm in association with hybrid contention resolution schemes. This iterative prioritized scheduling comprises of a set of preemptive selective policies for contention resolution. It is a hybrid technique that integrates wavelength conversion with feedback mechanism realized by fiber delay lines (FDL). By means of simulation, the proposed scheme has been investigated and compared with the conventional baseline scheme. A sensitive description of the satisfied packet loss probability and average packet delay as a function of main design parameters such as switch size, number of wavelengths, traffic load, degree of conversion and number of fiber delay lines have been carried out with significant improvement.Simulation results proved that the proposed scheme is an efficient approach in resolving packet contention with less complexity in execution. Relatively, number of wavelength, traffic load and degree of conversion has significant impact to packet loss ratio. The implementation of fiber delay lines results on average packet delay. Simulation results demonstrated that the switch size mildly affect the performance parameter. Respectively, packet loss ratio below 10-10 is obtained via simulation by the means of wavelength conversion without conventional buffering delay. The packet loss ratio is further reduced with the method as aforementioned with the insertion of fiber delay lines where PLR below 10-13 is achieved, which is much lower than the benchmark value. Furthermore, the obtained simulation results show that by classifying packet priority, the proposed scheduling scheme and architecture are able to offer differentiated class of service

Isochronets: a High-Speed Network Switching Architecture

Traditional switching techniques need hundred- or thousand-MIPS processing power within switches to support Gbit/s transmission rates available today. These techniques anchor their decision-making on control information within transmitted frames and thus must resolve routes at the speed in which frames are being pumped into switches. Isochronets can potentially switch at any transmission rate by making switching decisions independent of frame contents. Isochronets divide network bandwidth among routing trees, a technique called Route Division Multiple Access (RDMA). Frames access network resources through the appropriate routing tree to the destination. Frame structures are irrelevant for switching decisions. Consequently, Isochronets can support multiple framing protocols without adaptation layers and are strong candidates for all-optical implementations. All network-layer functions are reduced to an admission control mechanism designed to provide quality of service (QOS) guarantees for multiple classes of traffic. The main results of this work are: (1) A new network architecture suitable for high-speed transmissions; (2) An implementation of Isochronets using cheap off-theshelf components; (3) A comparison of RDMA with more traditional switching techniques, such as Packet Switching and Circuit Switching; (4) New protocols necessary for Isochronet operations; and (5) Use of Isochronet techniques at higher layers of the protocol stack (in particular, we show how Isochronet techniques may solve routing problems in ATM networks)

Cost functions in optical burst-switched networks

Optical Burst Switching (OBS) is a new paradigm for an all-optical Internet. It combines the best features of Optical Circuit Switching (OCS) and Optical Packet Switching (OPS) while avoidmg the mam problems associated with those networks .Namely, it offers good granularity, but its hardware requirements are lower than those of OPS. In a backbone network, low loss ratio is of particular importance. Also, to meet varying user requirements, it should support multiple classes of service. In Optical Burst-Switched networks both these goals are closely related to the way bursts are arranged in channels. Unlike the case of circuit switching, scheduling decisions affect the loss probability of future burst This thesis proposes the idea of a cost function. The cost function is used to judge the quality of a burst arrangement and estimate the probability that this burst will interfere with future bursts. Two applications of the cost functio n are proposed. A scheduling algorithm uses the value of the cost function to optimize the alignment of the new burst with other bursts in a channel, thus minimising the loss ratio. A cost-based burst droppmg algorithm, that can be used as a part of a Quality of Service scheme, drops only those bursts, for which the cost function value indicates that are most likely to cause a contention. Simulation results, performed using a custom-made OBS extension to the ns-2 simulator, show that the cost-based algorithms improve network performanc

Space station data system analysis/architecture study. Task 2: Options development, DR-5. Volume 2: Design options

The primary objective of Task 2 is the development of an information base that will support the conduct of trade studies and provide sufficient data to make key design/programmatic decisions. This includes: (1) the establishment of option categories that are most likely to influence Space Station Data System (SSDS) definition; (2) the identification of preferred options in each category; and (3) the characterization of these options with respect to performance attributes, constraints, cost and risk. This volume contains the options development for the design category. This category comprises alternative structures, configurations and techniques that can be used to develop designs that are responsive to the SSDS requirements. The specific areas discussed are software, including data base management and distributed operating systems; system architecture, including fault tolerance and system growth/automation/autonomy and system interfaces; time management; and system security/privacy. Also discussed are space communications and local area networking

Loss-free architectures in optical burst switched networks for a reliable and dynamic optical layer

For the last three decades, the optical fiber has been a quite systematic response to dimensioning issues in the Internet. Originally restricted to long haul networks, the optical network has gradually descended the network hierarchy to discard the bottlenecks. In the 90's, metropolitan networks became optical. Today, optical fibers are deployed in access networks and reach the users. In a near future, besides wireless access and local area networks, all networks in the network hierarchy may be made of fibers, in order to support current services (HDTV) and the emergence of new applications (3D-TV newly commercialized in USA). The deployment of such greedy applications will initiate an upward upgrade. The first step may be the Metropolitan Area Networks (MANs), not only because of the traffic growth, but also because of the variety of served applications, each with a specific traffic profile. The current optical layer is of mitigated efficiency, dealing with unforeseen events. The lack of reactivity is mainly due to the slow switching devices: any on-line decision of the optical layer is delayed by the configuration of the. devices. When the optical network has been extended in the MANs, a lot of efforts has been deployed to improve the reactivity of the optical layer. The Optical Circuit Switching paradigm (OCS) has been improved but it ultimately relies on off-line configuration of the optical devices. Optical Burst Switching (OBS) can be viewed as a highly flexible evolution of OCS, that operates five order of magnitude faster. Within this 'architecture, the loss-free guaranty can be abandoned in order to improve the reactivity of the optical layer. Indeed, reliability and reactivity appear as antagonists properties and getting closer to either of them mitigates the other. This thesis aims at proposing a solution to achieve reliable transmission over a dynamic optical layer. Focusing on OBS networks, our objective is to solve the contention issue without mitigating the reactivity. After the consideration of contention avoidance mechanisms with routing constraints similar as in OCS networks, we investigate the reactive solutions that intend to solve the contentions. None of the available contention resolution scheme can ensure the 100% efficiency that leads to loss-free transmission. An attractive solution is the recourse to electrical buffering, but it is notoriously disregarded because (1) it may highly impact the delays and (2) loss can occur due to buffer overflows. The efficiency of translucent architectures thus highly depends on the buffer availability, that can be improved by reducing the time spent in the buffers and the contention rate. We show that traffic grooming can highly reduce the emission delay, and consequently the buffer occupancy. In a first architecture, traffic grooming is enabled by a translucent core node architecture, capable to re-aggregate incoming bursts. The re-aggregation is mandatory to "de-groom" the bursts in the core network (i.e., to demultiplex the content of a burst). On the one hand, the re-aggregation highly reduces the loss probability, but on the other hand, it absorbs the benefits of traffic grooming. Finally, dynamic access to re-aggregation for contention resolution, despite the significant reduction of the contention rate, dramatically impacts the end-to-end delay and the memory requirement. We thus propose a second architecture, called CAROBS, that exploits traffic grooming in the optical domain. This framework is fully dynamic and can be used jointly with our translucent architecture that performs re-aggregation. As the (de)grooming operations do not involve re-aggregation, the translucent module can be restricted to contention resolution. As a result, the volume of data submitted to re-aggregation is drastically reduced and loss-free transmission can be reached with the same reactivity, end-to-end delay and memory requirement as a native OBS networ