Providing Fairness Through Detection and Preferential Dropping of High Bandwidth Unresponsive Flows

Stability of the Internet today depends largely on cooperation between end hosts that employ TCP (Transmission Control Protocol) protocol in the transport layer, and network routers along an end-to-end path. However, in the past several years, various types of traffic, including streaming media applications, are increasingly deployed over the Internet. Such types of traffic are mostly based on UDP (User Datagram Protocol) and usually do not employ neither end-to-end congestion norflow control mechanism, or else very limited. Such applications could unfairly consume greater amount of bandwidth than competing responsive flows such as TCP traffic. In this manner, unfairness problem and congestion collapse could occur. To avoid substantial memory requirement and complexity, fair Active Queue Management (AQM) utilizing no or partial flow state information were proposed in the past several years to solve these problems. These schemes however exhibit several problems under different circumstances.This dissertation presents two fair AQM mechanisms, BLACK and AFC, that overcome the problems and the limitations of the existing schemes. Both BLACK and AFC need to store only a small amount of state information to maintain and exercise its fairness mechanism. Extensive simulation studies show that both schemes outperform the other schemes in terms of throughput fairness under a large number of scenarios. Not only able to handle multiple unresponsive traffic, but the fairness among TCP connections with different round trip delays is also improved. AFC, with a little overhead than BLACK, provides additional advantages with an ability to achieve good fairness under a scenario with traffic of diff21erent sizes and bursty traffic, and provide smoother transfer rates for the unresponsive flows that are usually transmitting real-time traffic.This research also includes the comparative study of the existing techniques to estimate the number of active flows which is a crucial component for some fair AQM schemes including BLACK and AFC. Further contribution presented in this dissertation is the first comprehensive evaluation of fair AQM schemes under the presence of various type of TCP friendly traffic

A Fairness Investigation on Active Queue Management Schemes in Wireless Local Area Network

Active Queue Management (AQM) is scheme to handle network congestion before it happened by deciding which packet has to be dropped, when to drop it, and through which port have to drop when it has become or is becoming congested. Furthermore, AQM schemes such as Random Early Detection (RED), Random Early Marking (REM), Adaptive Virtual Queue (AVQ), and Controlled Delay (CoDel) have been proposed to maintain fairness when unresponsive constant bit rate UDP flows share a bottleneck link with responsive TCP traffic. However, the performance of these fair AQM schemes need more investigation especially evaluation in WLANs environment. This paper provides an experimental evaluation of different AQM schemes in WLAN environment with presence of two different types of flows (TCP flows and UDP flows) to study the behavior of these AQM schemes which might punish some flows unfairly. The simulation method has conducted in this paper by using Network Simulation 2 (ns-2) with the topology of bottleneck scenario. The result has shown that REM and AVQ both obtain higher fairness value than RED and Codel. However, CoDel has given the lowest fairness comparing with RED scheme which have given a moderated value in terms of fairness in WLANs environment. Besides, AQM schemes must be chosen not only based on its performance or capability to indicate the congestion and recovering overflow situation but also considering fairness with different types of flows and the environment as well, such as WLANs environment

Foraging Ecology, Genetic Diversity and Spatial Behaviour of Caucasian Lynx in Anatolia

Baseline ecological, genetic and behavioural information is still lacking and is urgently needed to set up an efficient conservation action plan for Caucasian lynx Lynx lynx dinniki in Turkey. This dissertation investigated the diet and foraging ecology of the three largest Caucasian lynx populations occupying three major lynx habitat types in Anatolia, the Asian part of Turkey. I also studied the spatial organisation and genetic variation as well as interactions between individuals of Caucasian lynx in a study area in northwestern Anatolia where I benefitted from long-term monitoring efforts started in 2009. In Chapter 2, I quantified the diet, prey preferences and functional response of three Caucasian lynx populations in Anatolia from a comparative perspective of European Eurasian lynx populations. The diet of the Eurasian lynx in Anatolia consists mostly of brown hares Lepus europaeus (78 % - 99 % of prey biomass consumed). Its foraging ecology fulfils expectations for a lagomorph specialist, similar to Iberian lynx Lynx pardinus and Canadian lynx Lynx canadensis in other ecosystems. Caucasian lynx in Anatolia display comparable body sizes and physiological requirements to individuals of other lagomorph specialist lynx species and consume half the daily food required to sustain a European Eurasian lynx individual. There was a high incidence of cannibalism, an aggressive behaviour that has very rarely observed in low density European lynx populations, observed in two ecosystems in Anatolia. In Chapter 3, I used nuclear molecular markers to investigate how sampling methodology can affect measures of genetic diversity if the population contains male territorial residents, other male residents and females are philopatric. I contrasted ‘invasive’ sampling, where tissue samples are obtained from individuals caught in box traps, with ‘non-invasive’ sampling, which requires the search and collection of faecal samples (in my case optimised through the training and use of a domestic dog trained to find lynx faeces) and the use of camera trapping. The results demonstrated that ‘invasive’ sampling was an inefficient technique and biased in favour of sampling particular territorial individuals and their offspring, thereby underestimating the true genetic variation in the population. ‘Non-invasive’ faecal sampling resulted in a less biased sampling of all sexes and classes of residents, an improved estimate of genetic diversity measures and a significantly higher level of genetic diversity obtained. The results indicate a high genetic diversity and no signs of inbreeding for northwest Anatolian lynx. Non-invasive faecal sampling not only provides more reliable genetic diversity measures but also delivers additional information on other important aspects of the biology and ecology of the same population, including diet, spatial organization and the presence of female philopatry, which in turn can help to inform conservation management planning. In Chapter 4, I investigated the spatial behaviour and population density of a northwest Anatolian Caucasian lynx population through GPS tracking of nine lynx individuals and camera trapping. The results indicated that Caucasian lynx in this study area have the smallest mean territorial female and male kernel density distribution (KUD) and minimum convex polygon (MCP) home ranges (females: 95% KUD = 46±8, 100% MCP = 49±16; males: 95% KUD = 176±3, 100% MCP = 183±5) ever reported for Eurasian lynx and a high density (4.9 lynx/100km2), on a level comparable to southern Anatolia. A different prey type, a high prey density and the absence of exploitation of this lynx population are likely drivers of the observed small home ranges. The detailed results revealed two male spatial tactics associated with separate life history stages – adult males start their residency in a population as resident floaters, ranging across huge home ranges and queuing for a territory, probably for several years. Territorial residents defend small territories. It is at present unclear whether territorial residents and / or floaters are candidate males to father the offspring of the resident philopatric females. A landscape fully occupied by adult territorial individuals is likely the cause of late territory establishment in male lynx and the large home range sizes of floaters. In this respect, Caucasian lynx resemble the spatial organisation of cheetahs Acinonyx jubatus, where the existence of floaters queuing for territories has also been documented in high density populations in eastern and southern Africa. This thesis sheds light on foraging ecology, diet, spatial organization and behaviour and genetic variability of Caucasian lynx in Anatolia. It also provides baseline information required to set up a conservation action plan of Caucasian lynx in Anatolia. For such an action plan to become effective, the non-invasive population genetics and density estimate methods applied in this study will be an essential tool for the assessment of the status of other Caucasian lynx populations in Anatolia and elsewhere

Maritime threat response

This report was prepared by Systems Engineering and Analysis Cohort Nine (SEA-9) Maritime Threat Response, (MTR) team members.Background: The 2006 Naval Postgraduate School (NPS) Cross-Campus Integrated Study, titled “Maritime Threat Response” involved the combined effort of 7 NPS Systems Engineering students, 7 Singaporean Temasek Defense Systems Institute (TDSI) students, 12 students from the Total Ship Systems Engineering (TSSE) curriculum, and numerous NPS faculty members from different NPS departments. After receiving tasking provided by the Wayne E. Meyer Institute of Systems Engineering at NPS in support of the Office of the Assistant Secretary of Defense for Homeland Defense, the study examined ways to validate intelligence and respond to maritime terrorist attacks against United States coastal harbors and ports. Through assessment of likely harbors and waterways to base the study upon, the San Francisco Bay was selected as a representative test-bed for the integrated study. The NPS Systems Engineering and Analysis Cohort 9 (SEA-9) Maritime Threat Response (MTR) team, in conjunction with the TDSI students, used the Systems Engineering Lifecycle Process (SELP) [shown in Figure ES-1, p. xxiii ] as a systems engineering framework to conduct the multi-disciplinary study. While not actually fabricating any hardware, such a process was well-suited for tailoring to the team’s research efforts and project focus. The SELP was an iterative process used to bound and scope the MTR problem, determine needs, requirements, functions, and to design architecture alternatives to satisfy stakeholder needs and desires. The SoS approach taken [shown in Figure ES-2, p. xxiv ]enabled the team to apply a systematic approach to problem definition, needs analysis, requirements, analysis, functional analysis, and then architecture development and assessment.In the twenty-first century, the threat of asymmetric warfare in the form of terrorism is one of the most likely direct threats to the United States homeland. It has been recognized that perhaps the key element in protecting the continental United States from terrorist threats is obtaining intelligence of impending attacks in advance. Enormous amounts of resources are currently allocated to obtaining and parsing such intelligence. However, it remains a difficult problem to deal with such attacks once intelligence is obtained. In this context, the Maritime Threat Response Project has applied Systems Engineering processes to propose different cost-effective System of Systems (SoS) architecture solutions to surface-based terrorist threats emanating from the maritime domain. The project applied a five-year time horizon to provide near-term solutions to the prospective decision makers and take maximum advantage of commercial off-the-shelf (COTS) solutions and emphasize new Concepts of Operations (CONOPS) for existing systems. Results provided insight into requirements for interagency interactions in support of Maritime Security and demonstrated the criticality of timely and accurate intelligence in support of counterterror operations.This report was prepared for the Office of the Assistant Secretary of Defense for Homeland DefenseApproved for public release; distribution is unlimited

Fast RFID counting under unreliable radio channels.

Sze, Wai Kit.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.Includes bibliographical references (leaves 77-83).Abstracts in English and Chinese.Abstract --- p.iAcknowledgement --- p.viChapter 1 --- Introduction --- p.1Chapter 2 --- Background and Related Work --- p.8Chapter 3 --- RFID Tag-set Cardinality estimation based on a Two-parameter implicit Channel Model --- p.13Chapter 3.1 --- System Model --- p.14Chapter 3.2 --- Number of Empty Slots Observed by the Reader --- p.16Chapter 3.3 --- Estimator Accuracy and Performance Analysis --- p.25Chapter 3.4 --- Results and Discussions --- p.32Chapter 3.5 --- Chapter Summary --- p.41Chapter 4 --- RFID Tag-set Cardinality estimation over Unknown Channel --- p.42Chapter 4.1 --- System Model --- p.43Chapter 4.2 --- Baseline: The Union-based approach --- p.45Chapter 4.2.1 --- Motivation --- p.46Chapter 4.2.2 --- Union Algorithm --- p.46Chapter 4.2.3 --- Analysis of the Union algorithm --- p.47Chapter 4.3 --- "Probabilistic Tag-counting over Lossy, Unknown channels via the Mh model" --- p.52Chapter 4.3.1 --- "Novel Interpretation of Mh for RFID Counting over Lossy, Unknown Channels" --- p.52Chapter 4.3.2 --- The Moment Estimator --- p.55Chapter 4.3.3 --- Sample Coverage Estimator --- p.57Chapter 4.3.4 --- Estimating the overall Tag population t --- p.59Chapter 4.4 --- Performance Validation and Comparison --- p.62Chapter 4.5 --- Chapter Summary --- p.65Chapter 5 --- Conclusions and Future Work --- p.73Chapter A --- Proof of Equation (3.6) in Chapter 3 --- p.75Bibliography --- p.7

Occlusion handling in multiple people tracking

Object tracking with occlusion handling is a challenging problem in automated video surveillance. Occlusion handling and tracking have always been considered as separate modules. We have proposed an automated video surveillance system, which automatically detects occlusions and perform occlusion handling, while the tracker continues to track resulting separated objects. A new approach based on sub-blobbing is presented for tracking objects accurately and steadily, when the target encounters occlusion in video sequences. We have used a feature-based framework for tracking, which involves feature extraction and feature matching