118 research outputs found

    Studies on Core-Based Testing of System-on-Chips Using Functional Bus and Network-on-Chip Interconnects

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    The tests of a complex system such as a microprocessor-based system-onchip (SoC) or a network-on-chip (NoC) are difficult and expensive. In this thesis, we propose three core-based test methods that reuse the existing functional interconnects-a flat bus, hierarchical buses of multiprocessor SoC's (MPSoC), and a N oC-in order to avoid the silicon area cost of a dedicated test access mechanism (TAM). However, the use of functional interconnects as functional TAM's introduces several new problems. During tests, the interconnects-including the bus arbitrator, the bus bridges, and the NoC routers-operate in the functional mode to transport the test stimuli and responses, while the core under tests (CUT) operate in the test mode. Second, the test data is transported to the CUT through the functional bus, and not directly to the test port. Therefore, special core test wrappers that can provide the necessary control signals required by the different functional interconnect are proposed. We developed two types of wrappers, one buffer-based wrapper for the bus-based systems and another pair of complementary wrappers for the NoCbased systems. Using the core test wrappers, we propose test scheduling schemes for the three functionally different types of interconnects. The test scheduling scheme for a flat bus is developed based on an efficient packet scheduling scheme that minimizes both the buffer sizes and the test time under a power constraint. The schedulingscheme is then extended to take advantage of the hierarchical bus architecture of the MPSoC systems. The third test scheduling scheme based on the bandwidth sharing is developed specifically for the NoC-based systems. The test scheduling is performed under the objective of co-optimizing the wrapper area cost and the resulting test application time using the two complementary NoC wrappers. For each of the proposed methodology for the three types of SoC architec .. ture, we conducted a thorough experimental evaluation in order to verify their effectiveness compared to other methods

    Design and protection algorithms for path level aggregation of traffic in WDM metro optical networks

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    Wavelength Division Multiplexing (WDM) promises to offer a cost effective and scalable solution to meet the emerging demands of the Internet. WDM splits the tremendous bandwidth latent in a fiber into multiple non-overlapping wavelength channels, each of which can be operated at the peak electronic rate. Commercial systems with 128 wavelengths and transmission rates of up to 40 Gbps per wavelength have been made possible using state of the art optical technologies to deal with physical impairments. Systems with higher capacities are likely to evolve in the future. The end user requirements for bandwidth, on the other hand, have been ranging from 155 Mbps to 2.5 Gbps. Dedicating a wavelength for each end user will lead to severe underutilization of WDM channels. This brings to forefront the requirement for sharing of bandwidth in a wavelength among multiple end users.;The concept of wavelength sharing among multiple clients is called grooming. Grooming can be done purely at the optical layer (optical grooming) or it can be done with support from the client layer (electronic grooming). The advantage of all optical grooming is the ease of scalability due to its transparency as opposed to electronic grooming which is constrained by electronic bottlenecks. Efforts towards enhancing optical grooming is pursued through increasing optical switching speeds. However, technologies to make optical switches with high speeds, large port counts and low insertion losses have been elusive and may continue to remain so in the near future.;Recently, there have been some research into designing new architectures and protocols focused on optical grooming without resorting to fast optical switching. Typically, this is achieved in three steps: (1) configure the circuit in the form of a path or a tree; (2) use optical devices like couplers or splitters to allow multiple transmitters and/or receivers to share the same circuit; and (3) provide an arbitration mechanism to avoid contention among end users of the circuit. This transparent sharing of the wavelength channel utilizes the network resources better than the conventional low-speed circuit switched approaches. Consequently, it becomes important to quantify the improvement in achieved performance and evaluate if the reaped benefits justify the cost of the required additional hardware and software.;The contribution of this thesis is two fold: (1) developing a new architecture called light-trails as an IP based solution for next generation WDM optical networks, and (2) designing a unified framework to model Path Level Aggregation of Traffic in metrO Optical Networks (PLATOONs). The algorithms suggested here have three features: (1) accounts for four different path level aggregation strategies---namely, point to point (for example, lightpaths), point to multi-point (for example, source based light-trails), multi-point to point (for example, destination based light-trails) and multi-point to multi-point (for example, light-trails); (2) incorporates heterogenous switching architectures; and (3) accommodates multi-rate traffic. Algorithms for network design and survivability are developed for PLATOONs in the presence of both static and dynamic traffic. Connection level dedicated/shared, segregated/mixed protection schemes are formulated for single link failures in the presence of static and dynamic traffic. A simple medium access control protocol that avoids collisions when the channel is shared by multiple clients is also proposed.;Based on extensive simulations, we conclude that, for the studied scenarios, (1) when client layer has no electronic grooming capabilities, light-trails (employing multi-point to multi-point aggregation strategy) perform several orders of magnitude better than lightpaths and (2) when client layer has full electronic grooming capabilities, source based light-trails (employing point to multi-point aggregation strategy) perform the best in wavelength limited scenarios and lightpaths perform the best in transceiver limited scenarios.;The algorithms that are developed here will be helpful in designing optical networks that deploy path level aggregation strategies. The proposed ideas will impact the design of transparent, high-speed all-optical networks.</p

    Multi-ring SDH network design over optical mesh networks

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    Ankara : The Department of Electrical and Electronics Engineering and Sciences of Bilkent University, 2002.Thesis (Master's) -- Bilkent University, 2002.Includes bibliographical references leaves 84-87.The evolution of networks in telecommunications has brought on the importance of design techniques to obtain survivable and cost-effective transportation networks. In this thesis, we study Synchronous Digital Hierarchy (SDH) ring design problem with an interconnected multi-ring architecture overlaid over an optical mesh network. We decouple the problem into two sub-problems: the first problem is the SDH ring selection, and the second problem is the mapping of these rings onto the physical mesh topology. In this structure, the logical topology consists of SDH Add/Drop Multiplexers (ADMs) and Digital Cross-Connects (DXCs), and the physical topology consists of Optical Cross-Connects (OXCs). The ring selection problem is to choose the rings that give minimum inter-ring traffic in the network. Since inter-ring traffic increases the network cost and complexity, we aim to minimize the inter-ring traffic. We propose a greedy heuristic algorithm for this problem that finds a solution subject to the constraint that the number of nodes on each ring is limited. Numerical results on the ring design problem are presented for different topologies. Once the logical topology is obtained, resilient mapping of SDH rings onto the mesh physical topology is formulated as a Mixed Integer Linear Programming (MILP) problem. In order to guarantee proper operation of SDH ring protection against all single failures, each link on an SDH ring must be mapped onto a lightpath which is link and node disjoint from all other lightpaths comprising the same ring. The objective of this mapping is to minimize the total fiber cost in the network. We also apply a post-processing algorithm to eliminate redundant rings. The postprocessing algorithm is very useful to reduce the cost. We evaluate the performance of our design algorithm for different networks.Tan, Tuba AkıncılarM.S

    An Efficient NoC-based Framework To Improve Dataflow Thread Management At Runtime

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    This doctoral thesis focuses on how the application threads that are based on dataflow execution model can be managed at Network-on-Chip (NoC) level. The roots of the dataflow execution model date back to the early 1970’s. Applications adhering to such program execution model follow a simple producer-consumer communication scheme for synchronising parallel thread related activities. In dataflow execution environment, a thread can run if and only if all its required inputs are available. Applications running on a large and complex computing environment can significantly benefit from the adoption of dataflow model. In the first part of the thesis, the work is focused on the thread distribution mechanism. It has been shown that how a scalable hash-based thread distribution mechanism can be implemented at the router level with low overheads. To enhance the support further, a tool to monitor the dataflow threads’ status and a simple, functional model is also incorporated into the design. Next, a software defined NoC has been proposed to manage the distribution of dataflow threads by exploiting its reconfigurability. The second part of this work is focused more on NoC microarchitecture level. Traditional 2D-mesh topology is combined with a standard ring, to understand how such hybrid network topology can outperform the traditional topology (such as 2D-mesh). Finally, a mixed-integer linear programming based analytical model has been proposed to verify if the application threads mapped on to the free cores is optimal or not. The proposed mathematical model can be used as a yardstick to verify the solution quality of the newly developed mapping policy. It is not trivial to provide a complete low-level framework for dataflow thread execution for better resource and power management. However, this work could be considered as a primary framework to which improvements could be carried out

    Towards a cloud enabler : from an optical network resource provisioning system to a generalized architecture for dynamic infrastructure services provisioning

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    This work was developed during a period where most of the optical management and provisioning system where manual and proprietary. This work contributed to the evolution of the state of the art of optical networks with new architectures and advanced virtual infrastructure services. The evolution of optical networks, and internet globally, have been very promising during the last decade. The impact of mobile technology, grid, cloud computing, HDTV, augmented reality and big data, among many others, have driven the evolution of optical networks towards current service technologies, mostly based on SDN (Software Defined Networking) architectures and NFV(Network Functions Virtualisation). Moreover, the convergence of IP/Optical networks and IT services, and the evolution of the internet and optical infrastructures, have generated novel service orchestrators and open source frameworks. In fact, technology has evolved that fast that none could foresee how important Internet is for our current lives. Said in other words, technology was forced to evolve in a way that network architectures became much more transparent, dynamic and flexible to the end users (applications, user interfaces or simple APIs). This Thesis exposes the work done on defining new architectures for Service Oriented Networks and the contribution to the state of the art. The research work is divided into three topics. It describes the evolution from a Network Resource Provisioning System to an advanced Service Plane, and ends with a new architecture that virtualized the optical infrastructure in order to provide coordinated, on-demand and dynamic services between the application and the network infrastructure layer, becoming an enabler for the new generation of cloud network infrastructures. The work done on defining a Network Resource Provisioning System established the first bases for future work on network infrastructure virtualization. The UCLP (User Light Path Provisioning) technology was the first attempt for Customer Empowered Networks and Articulated Private Networks. It empowered the users and brought virtualization and partitioning functionalities into the optical data plane, with new interfaces for dynamic service provisioning. The work done within the development of a new Service Plane allowed the provisioning of on-demand connectivity services from the application, and in a multi-domain and multi-technology scenario based on a virtual network infrastructure composed of resources from different infrastructure providers. This Service Plane facilitated the deployment of applications consuming large amounts of data under deterministic conditions, so allowing the networks behave as a Grid-class resource. It became the first on-demand provisioning system that at lower levels allowed the creation of one virtual domain composed from resources of different providers. The last research topic presents an architecture that consolidated the work done in virtualisation while enhancing the capabilities to upper layers, so fully integrating the optical network infrastructure into the cloud environment, and so providing an architecture that enabled cloud services by integrating the request of optical network and IT infrastructure services together at the same level. It set up a new trend into the research community and evolved towards the technology we use today based on SDN and NFV. Summing up, the work presented is focused on the provisioning of virtual infrastructures from the architectural point of view of optical networks and IT infrastructures, together with the design and definition of novel service layers. It means, architectures that enabled the creation of virtual infrastructures composed of optical networks and IT resources, isolated and provisioned on-demand and in advance with infrastructure re-planning functionalities, and a new set of interfaces to open up those services to applications or third parties.Aquesta tesi es va desenvolupar durant un període on la majoria de sistemes de gestió de xarxa òptica eren manuals i basats en sistemes propietaris. En aquest sentit, la feina presentada va contribuir a l'evolució de l'estat de l'art de les xarxes òptiques tant a nivell d’arquitectures com de provisió d’infraestructures virtuals. L'evolució de les xarxes òptiques, i d'Internet a nivell mundial, han estat molt prometedores durant l'última dècada. L'impacte de la tecnologia mòbil, la computació al núvol, la televisió d'alta definició, la realitat augmentada i el big data, entre molts altres, han impulsat l'evolució cap a xarxes d’altes prestacions amb nous serveis basats en SDN (Software Defined Networking) i NFV (Funcions de xarxa La virtualització). D'altra banda, la convergència de xarxes òptiques i els serveis IT, junt amb l'evolució d'Internet i de les infraestructures òptiques, han generat nous orquestradors de serveis i frameworks basats en codi obert. La tecnologia ha evolucionat a una velocitat on ningú podria haver predit la importància que Internet està tenint en el nostre dia a dia. Dit en altres paraules, la tecnologia es va veure obligada a evolucionar d'una manera on les arquitectures de xarxa es fessin més transparent, dinàmiques i flexibles vers als usuaris finals (aplicacions, interfícies d'usuari o APIs simples). Aquesta Tesi presenta noves arquitectures de xarxa òptica orientades a serveis. El treball de recerca es divideix en tres temes. Es presenta un sistema de virtualització i aprovisionament de recursos de xarxa i la seva evolució a un pla de servei avançat, per acabar presentant el disseny d’una nova arquitectura capaç de virtualitzar la infraestructura òptica i IT i proporcionar serveis de forma coordinada, i sota demanda, entre l'aplicació i la capa d'infraestructura de xarxa òptica. Tot esdevenint un facilitador per a la nova generació d'infraestructures de xarxa en el núvol. El treball realitzat en la definició del sistema de virtualització de recursos va establir les primeres bases sobre la virtualització de la infraestructura de xarxa òptica en el marc de les “Customer Empowered Networks” i “Articulated Private Networks”. Amb l’objectiu de virtualitzar el pla de dades òptic, i oferir noves interfícies per a la provisió de serveis dinàmics de xarxa. En quant al pla de serveis presentat, aquest va facilitat la provisió de serveis de connectivitat sota demanda per part de l'aplicació, tant en entorns multi-domini, com en entorns amb múltiples tecnologies. Aquest pla de servei, anomenat Harmony, va facilitar el desplegament de noves aplicacions que consumien grans quantitats de dades en condicions deterministes. En aquest sentit, va permetre que les xarxes es comportessin com un recurs Grid, i per tant, va esdevenir el primer sistema d'aprovisionament sota demanda que permetia la creació de dominis virtuals de xarxa composts a partir de recursos de diferents proveïdors. Finalment, es presenta l’evolució d’un pla de servei cap una arquitectura global que consolida el treball realitzat a nivell de convergència d’infraestructures (òptica + IT) i millora les capacitats de les capes superiors. Aquesta arquitectura va facilitar la plena integració de la infraestructura de xarxa òptica a l'entorn del núvol. En aquest sentit, aquest resultats van evolucionar cap a les tendències actuals de SDN i NFV. En resum, el treball presentat es centra en la provisió d'infraestructures virtuals des del punt de vista d’arquitectures de xarxa òptiques i les infraestructures IT, juntament amb el disseny i definició de nous serveis de xarxa avançats, tal i com ho va ser el servei de re-planificació dinàmicaPostprint (published version

    A flexible, abstract network optimisation framework and its application to telecommunications network design and configuration problems

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    A flexible, generic network optimisation framework is described. The purpose of this framework is to reduce the effort required to solve particular network optimisation problems. The essential idea behind the framework is to develop a generic network optimisation problem to which many network optimisation problems can be mapped. A number of approaches to solve this generic problem can then be developed. To solve some specific network design or configuration problem the specific problem is mapped to the generic problem and one of the problem solvers is used to obtain a solution. This solution is then mapped back to the specific problem domain. Using the framework in this way, a network optimisation problem can be solved using less effort than modelling the problem and developing some algorithm to solve the model. The use of the framework is illustrated in two separate problems: design of an enterprise network to accommodate voice and data traffic and configuration of a core diffserv/MPLS network. In both cases, the framework enabled solutions to be found with less effort than would be required if a more direct approach was used

    Using GRASP and GA to design resilient and cost-effective IP/MPLS networks

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    The main objective of this thesis is to find good quality solutions for representative instances of the problem of designing a resilient and low cost IP/MPLS network, to be deployed over an existing optical transport network. This research is motivated by two complementary real-world application cases, which comprise the most important commercial and academic networks of Uruguay. To achieve this goal, we performed an exhaustive analysis of existing models and technologies. From all of them we took elements that were contrasted with the particular requirements of our counterparts. We highlight among these requirements, the need of getting solutions transparently implementable over a heterogeneous network environment, which limit us to use widely standardized features of related technologies. We decided to create new models more suitable to fit these needs. These models are intrinsically hard to solve (NP-Hard). Thus we developed metaheuristic based algorithms to find solutions to these real-world instances. Evolutionary Algorithms and Greedy Randomized Adaptive Search Procedures obtained the best results. As it usually happens, real-world planning problems are surrounded by uncertainty. Therefore, we have worked closely with our counterparts to reduce the fuzziness upon data to a set of representative cases. They were combined with different strategies of design to get to scenarios, which were translated into instances of these problems. Finally, the algorithms were fed with this information, and from their outcome we derived our results and conclusions

    Temporal analysis and scheduling of hard real-time radios running on a multi-processor

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    On a multi-radio baseband system, multiple independent transceivers must share the resources of a multi-processor, while meeting each its own hard real-time requirements. Not all possible combinations of transceivers are known at compile time, so a solution must be found that either allows for independent timing analysis or relies on runtime timing analysis. This thesis proposes a design flow and software architecture that meets these challenges, while enabling features such as independent transceiver compilation and dynamic loading, and taking into account other challenges such as ease of programming, efficiency, and ease of validation. We take data flow as the basic model of computation, as it fits the application domain, and several static variants (such as Single-Rate, Multi-Rate and Cyclo-Static) have been shown to possess strong analytical properties. Traditional temporal analysis of data flow can provide minimum throughput guarantees for a self-timed implementation of data flow. Since transceivers may need to guarantee strictly periodic execution and meet latency requirements, we extend the analysis techniques to show that we can enforce strict periodicity for an actor in the graph; we also provide maximum latency analysis techniques for periodic, sporadic and bursty sources. We propose a scheduling strategy and an automatic scheduling flow that enable the simultaneous execution of multiple transceivers with hard-realtime requirements, described as Single-Rate Data Flow (SRDF) graphs. Each transceiver has its own execution rate and starts and stops independently from other transceivers, at times unknown at compile time, on a multiprocessor. We show how to combine scheduling and mapping decisions with the input application data flow graph to generate a worst-case temporal analysis graph. We propose algorithms to find a mapping per transceiver in the form of clusters of statically-ordered actors, and a budget for either a Time Division Multiplex (TDM) or Non-Preemptive Non-Blocking Round Robin (NPNBRR) scheduler per cluster per transceiver. The budget is computed such that if the platform can provide it, then the desired minimum throughput and maximum latency of the transceiver are guaranteed, while minimizing the required processing resources. We illustrate the use of these techniques to map a combination of WLAN and TDS-CDMA receivers onto a prototype Software-Defined Radio platform. The functionality of transceivers for standards with very dynamic behavior – such as WLAN – cannot be conveniently modeled as an SRDF graph, since SRDF is not capable of expressing variations of actor firing rules depending on the values of input data. Because of this, we propose a restricted, customized data flow model of computation, Mode-Controlled Data Flow (MCDF), that can capture the data-value dependent behavior of a transceiver, while allowing rigorous temporal analysis, and tight resource budgeting. We develop a number of analysis techniques to characterize the temporal behavior of MCDF graphs, in terms of maximum latencies and throughput. We also provide an extension to MCDF of our scheduling strategy for SRDF. The capabilities of MCDF are then illustrated with a WLAN 802.11a receiver model. Having computed budgets for each transceiver, we propose a way to use these budgets for run-time resource mapping and admissibility analysis. During run-time, at transceiver start time, the budget for each cluster of statically-ordered actors is allocated by a resource manager to platform resources. The resource manager enforces strict admission control, to restrict transceivers from interfering with each other’s worst-case temporal behaviors. We propose algorithms adapted from Vector Bin-Packing to enable the mapping at start time of transceivers to the multi-processor architecture, considering also the case where the processors are connected by a network on chip with resource reservation guarantees, in which case we also find routing and resource allocation on the network-on-chip. In our experiments, our resource allocation algorithms can keep 95% of the system resources occupied, while suffering from an allocation failure rate of less than 5%. An implementation of the framework was carried out on a prototype board. We present performance and memory utilization figures for this implementation, as they provide insights into the costs of adopting our approach. It turns out that the scheduling and synchronization overhead for an unoptimized implementation with no hardware support for synchronization of the framework is 16.3% of the cycle budget for a WLAN receiver on an EVP processor at 320 MHz. However, this overhead is less than 1% for mobile standards such as TDS-CDMA or LTE, which have lower rates, and thus larger cycle budgets. Considering that clock speeds will increase and that the synchronization primitives can be optimized to exploit the addressing modes available in the EVP, these results are very promising
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