Sparse Recovery With Graph Constraints

Sparse recovery can recover sparse signals from a set of underdetermined linear measurements. Motivated by the need to monitor the key characteristics of large-scale networks from a limited number of measurements, this paper addresses the problem of recovering sparse signals in the presence of network topological constraints. Unlike conventional sparse recovery where a measurement can contain any subset of the unknown variables, we use a graph to characterize the topological constraints and allow an additive measurement over nodes (unknown variables) only if they induce a connected subgraph. We provide explicit measurement constructions for several special graphs, and the number of measurements by our construction is less than that needed by existing random constructions. Moreover, our construction for a line network is provably optimal in the sense that it requires the minimum number of measurements. A measurement construction algorithm for general graphs is also proposed and evaluated. For any given graph G with n nodes, we derive bounds of the minimum number of measurements needed to recover any k-sparse vector over G (M_(k,n)^G). Using the Erdõs-Rényi random graph as an example, we characterize the dependence of M_(k,n)^G on the graph structure. This paper suggests that M_(k,n)^G may serve as a graph connectivity metric

Métodos de melhoria da disponibilidade e da resiliência a desastres em redes de telecomunicações

In current societies, telecommunication networks are one of its essential components, in which different services depend on. Critical service requires these networks to provide high levels of availability between their nodes and high levels of resilient to large-scale natural disasters, either by avoiding them or quickly recover from them. Different techniques can be used to reach these goals. In this dissertation, it is considered the use of geodiversity routing to reduce the impact of large-scale disasters, with the downside of utilizing longer paths which, in turn, reduces the resulting end-to-end availability. This downside can be corrected if the availability of some network elements are upgraded so that the availability required by critical services is met, while maintaining the geodiversity required to prevent the impact of disasters. In this dissertation, different upgrade strategies are implemented to efficiently identify the network elements required to be upgraded, so that the network can provide critical services with high availability and high resilience to natural disasters.As redes de telecomunicações são um dos componentes essenciais na atual sociedade, no qual vários serviços dependem da sua funcionalidade para operarem eficientemente. O suporte de serviços críticos exige que as redes ofereçam altos níveis de disponibilidade entre os seus nós e sejam altamente resilientes a desastres de larga escala, tais como os provocados por fenómenos naturais (tremores de terra, tsunamis, etc.). Algumas técnicas podem ser implementadas para atingir estes objetivos. Nesta dissertação, considera-se o uso de encaminhamento com geodiversidade para reduzir o impacto de desastres de larga escala, com a desvantagem de exigir percursos de encaminhamento mais longos, reduzindo a disponibilidade resultante entre os nós origem-destino do encaminhamento. Assim, para obter simultaneamente alta disponibilidade e alta resiliência a desastres, é necessário melhorar a disponibilidade em alguns elementos da rede. Nesta dissertação são introduzidas diferentes estratégias para identificar eficazmente os elementos da rede que precisam de ser melhorados em termos de disponibilidade, para que a rede suporte os requisitos de disponibilidade e resiliência a desastres requeridos por serviços críticos.Mestrado em Engenharia Informátic

Failure Localization Aware Protection in All-Optical Networks

The recent development of optical signal processing and switching makes the all-optical networks a potential candidate for the underlying transmission system in the near future. However, despite its higher transmission data rate and efficiency, the lack of optical-electro-optical (OEO) conversions makes fault management a challenge. A single fiber cut can interrupt several connections, disrupting many services which results in a massive loss of data. With the ever-growing demand for time-sensitive applications, the ability to maintain service continuity in communication networks has only been growing in importance. In order to guarantee network survivability, fast fault localization and fault recovery are essential. Conventional monitoring-trail (m-trail) based schemes can unambiguously localize link failures. However, the deployment of m-trail requires extra transceivers and wavelengths dedicated to monitoring the link state. Non-negligible overhead makes m-trail schemes neither scalable nor practicable. In this thesis, we propose two Failure Localization Aware (FLA) routing schemes to aid failure localization. When a link fails, all traversing lightpaths become dark, and the transceiver at the end node of each interrupted ligthpath issues an alarm signal to report the path failure. By correlating the information of all affected and unaffected paths, it is possible to narrow down the number of possible fault locations to just a few possible locations. However, without the assistance of dedicated supervisory lightpaths, and based solely on the alarm generated by the interrupted lightpaths, ambiguity in failure localization may be unavoidable. Hence, we design a Failure Localization Aware Routing and Wavelength Assignment (FLA-RWA) scheme, the Least Ambiguous Path (LAP) routing scheme, to dynamically allocate connection requests with minimum ambiguity in the localization of a link failure. The performance of the proposed heuristic is evaluated and compared with traditional RWA algorithms via network simulations. The results show that the proposed LAP algorithm achieves the lowest ambiguity among all examined schemes, at the cost of slightly higher wavelength consumption than the alternate shortest path scheme. We also propose a Failure Localization Aware Protection (FLA-P) scheme that is based on the idea of also monitoring the protection paths in a system with path protection for failure localization. The Least Ambiguous Protection Path (LAPP) routing algorithm arranges the protection path routes with the objective of minimizing the ambiguity in failure localization. We evaluate and compare the ambiguity in fault localization when monitoring only the working paths and when monitoring both working and protection paths. We also compare the performance of protection paths with different schemes in regards to fault localization

On Integrating Failure Localization with Survivable Design

In this thesis, I proposed a novel framework of all-optical failure restoration which jointly determines network monitoring plane and spare capacity allocation in the presence of either static or dynamic traffic. The proposed framework aims to enable a general shared protection scheme to achieve near optimal capacity efficiency as in Failure Dependent Protection(FDP) while subject to an ultra-fast, all-optical, and deterministic failure restoration process. Simply put, Local Unambiguous Failure Localization(L-UFL) and FDP are the two building blocks for the proposed restoration framework. Under L-UFL, by properly allocating a set of Monitoring Trails (m-trails), a set of nodes can unambiguously identify every possible Shared Risk Link Group (SRLG) failure merely based on its locally collected Loss of Light(LOL) signals. Two heuristics are proposed to solve L-UFL, one of which exclusively deploys Supervisory Lightpaths (S-LPs) while the other jointly considers S-LPs and Working Lightpaths (W-LPs) for suppressing monitoring resource consumption. Thanks to the ``Enhanced Min Wavelength Max Information principle'', an entropy based utility function, m-trail global-sharing and other techniques, the proposed heuristics exhibit satisfactory performance in minimizing the number of m-trails, Wavelength Channel(WL) consumption and the running time of the algorithm. Based on the heuristics for L-UFL, two algorithms, namely MPJD and DJH, are proposed for the novel signaling-free restoration framework to deal with static and dynamic traffic respectively. MPJD is developed to determine the Protection Lightpaths (P-LPs) and m-trails given the pre-computed W-LPs while DJH jointly implements a generic dynamic survivable routing scheme based on FDP with an m-trail deployment scheme. For both algorithms, m-trail deployment is guided by the Necessary Monitoring Requirement (NMR) defined at each node for achieving signaling-free restoration. Extensive simulation is conducted to verify the performance of the proposed heuristics in terms of WL consumption, number of m-trails, monitoring requirement, blocking probability and running time. In conclusion, the proposed restoration framework can achieve all-optical and signaling-free restoration with the help of L-UFL, while maintaining high capacity efficiency as in FDP based survivable routing. The proposed heuristics achieve satisfactory performance as verified by the simulation results

A novel approach for failure localization in all-optical mesh networks

Abstract—Achieving fast and precise failure localization has long been a highly desired feature in all-optical mesh networks. M-trail (monitoring trail) has been proposed as the most general monitoring structure for achieving unambiguous failure localization (UFL) of any single link failure while effectively reducing the amount of alarm signals flooding the networks. However, it is critical to come up with a fast and intelligent m-trail design approach for minimizing the number of m-trails and the total bandwidth consumed, which ubiquitously determines the length of the alarm code and bandwidth overhead for the m-trail deployment, respectively. In this paper, the m-trail design problem is investigated. To gain a deeper understanding of the problem, we first conduct a bound analysis on the minimum length of alarm code of each link required for UFL on the most sparse (i.e., ring) and dense (i.e., fully meshed) topologies. Then, a novel algorithm based on random code assignment (RCA) and random code swapping (RCS) is developed for solving the m-trail design problem. The prototype of the algorithm can be found in [1]. The algorithm is verified by comparing to an Integer Linear Program (ILP) approach, and the results demonstrate its superiority in minimizing the fault management cost and bandwidth consumption while achieving significant reduction in computation time. To investigate the impact of topology diversity, extensive simulation is conducted on thousands of random network topologies with systematically increased network density. Index Terms—monitoring trails, failure localization, combinatorial group testing I