Survivability through pre-configured protection in optical mesh networks

Network survivability is a very important issue, especially in optical networks that carry huge amount of traffic. Network failures which may be caused by human errors, malfunctional systems and natural disaster (eg. Earthquakes and lightening storms), have occurred quite frequently and sometimes with unpredictable consequences. Survivability is defined as the ability of the network to maintain the continuity of service against failures of network components. Pre-configuration and dynamic restoration are two schemes for network survivability. For each scheme, survivability algorithms can be applied at either Optical Channel sublayer (Och) known as link-based. Or, Optical Multiplex Section sublayer (OMS) known as path-based. The efficiency of survivability algorithms can be assessed through such criteria as capacity efficiency, restoration time and quality service. Dynamic restoration is more efficient than pre-configuration in terms of capacity resource utilization, but restoration time is longer and 100% service recovery cannot be guaranteed because sufficient spare capacity may not be available at the time of failures. Similarly, path-based survivability offers a high performance scheme for utilizing capacity resource, but restoration time is longer than link based survivability

Capacity design for multiple quality of protection service classes in optical mesh networks

Along with the ever-increasing volume of Internet and other communication traffic intoday’s networks, the advancement of key technologies such as Wavelength Division Multiplexing(WDM) or Dense WDM (DWDM) could enable a tremendous improvement inutilisation of the enourmous bandwidth that optical fibres are capable of providing. Forlarge-scale transmission deployment, optical networking offers excellent solutions due toits transmission reliability; with low-bit error rate, massive capacity and high scalability.Being the backbone of the network and responsible for the distribution of huge amountof traffic, optical mesh networks are consequently faced with great expectations for thereliability of the services delivered. The failure of an optical component, such as a fibre cutor a link-down at a node, often has catastrophic consequences leading to communicationdisruption, loss of data, services and profits. For instance, according to Gartner Group,up to $500 million in US business losses would have been inflicted by network failures experiencedthrough 2004. A direct voice-call revenue loss from the failure of a major trunkgroup is frequently quoted at amounting to more than$100,000 per minute. In anothercase reported by the International Cable Protection Committee, a powerful earthquakein Taiwan in December 2006 caused damage to four major fiber optics lines as well asnine cables laid undersea. It took 49 days to repair all 21 damaged points. These casessignify that protection design against network failures has a crucial and imperative role intelecommunications networks today - being of even more significance in the case of opticalmesh networks. The central theme of this dissertation revolves around this vital researcharea.Protection design, however, can not cover for all scenarios of network failures. Indeed,the protection expectation of traffic demands is varied. Majority of these, defined as goldservice class, require an average outage period of around 5 minutes per year with fullrestorability against single span failures. Others, such as the platinum service class, mayrequire higher protection against dual span failures; or average outage period of 30 secondsper year. This thesis first studies the minimum requirements regarding the connectivity of a physical network topology to ensure the success of restoration algorithms to achieveMultiple Quality of Protection (MQoP). Furthermore, we propose the mathematical formulationfor determining the relationship between any two paths connecting each node-pair.This principle plays an important role as the core of modeling potential and eligible sets ofdisjoint and distinct path candidates for designing backup routes against network failures.On the other hand, protection design in optical transport networks can be applied ateither Optical Channel sublayer (OCh) known as span-based, or, Optical Multiplex Sectionsublayer (OMS), known as path-based. A variety of restoration techniques have beendesigned and implemented for mesh networks including span restoration, path restoration,p-cycles, etc. This thesis studies the design of these protection schemes for supportingMQoP service classes. We propose a new optimisation model for Shared Backup PathProtection (SBPP) with the objective of minimising the number of constraints and reducingthe model complexity. This model is much more tractable with large size networks. For pcycledesign, we propose a new mathematical model to construct sufficient a set of p-cyclesto protect failed working channels or flows. Unlike a conventional model which selects theoptimal set of p-cycles from all pre-determined cycles in the network, this approach usesspan-based variables to indicate whether or not a cycle crosses a span. Therefore, thecomplexity of the model is significantly reduced in large scale networks where the numberof all cycles exponentially increases with network size.Finally, it is noted that each of these protection schemes has its own advantages anddisadvantages in terms of complexity, capacity efficiency and restoration time. In addition,the use of an individual technique for MQoPs may be neither possible or efficient. Anew mathematical model is proposed based on a mixed-protection formulation to supportMQoPs. Despite of the complexity of modeling, this optimisation formulation efficientlyutilises the advantages of each protection scheme with respect to different service classesand, hence, maximise the efficiency. Consequently, the interaction between service classesis formulated and investigated to provide the minimum amount of capacity utilisation for agiven network topology. The best mixture of service classes would determine whether or notthe existing physical topology is suitable to support the known or predicted requirementsof traffic demands

A range error reduction technique for positioning applications in sports

In recent times, ultra-wideband (UWB)-based positioning systems have become popular in sport performance monitoring. UWB positioning system uses time of arrival to calculate the range data between devices (i.e. anchors, tags), and then use trilateration algorithms to estimate position coordinates. In practical applications, non-line-of-sight transmissions and multipath propagations lead to inaccurate range data and lower positioning accuracy. This paper introduces a range error minimisation algorithm to address this limitation of error in range data in UWB-based positioning system. The proposed solution analyses the range error for each anchor and sequentially reduces this error based on the distance between each anchor and the tag. This ultimately contributes to higher positioning accuracies. The authors implemented the proposed algorithm in a hardware test-bed, evaluating the positioning accuracy for an indoor sport. The proposed algorithm outperforms both the trilateration algorithm and a commercially used positioning algorithm by up to 50% and 25%, respectively