The dissertation presents a connected vehicle based traffic signal control model (CVTSCM) for signalized arterials. The model addresses different levels of traffic congestion starting with the initial deployment of connected vehicle technologies focusing on two modules created in CVTSCM. For near/under-saturated intersections, an arterial-level traffic progression optimization model (ALTPOM) is being proposed. ALTPOM improves traffic progression by optimizing offsets for an entire signalized arterial simultaneously. To optimize these offsets, splits of coordinated intersections are first adjusted to balance predicted upcoming demands of all approaches at individual intersections. An open source traffic simulator was selected to implement and evaluate the performance of ALTPOM. The case studies’ field signal timing plans were coordinated and optimized using TRANSYT-7F as the benchmark. ALTPOM was implemented with connected vehicles penetration rates at 25% and 50%, ALTPOM significantly outperforms TRANSYT-7F with at least 26.0% reduction of control delay (sec/vehicle) and a 4.4% increase of throughput for both directions of major and minor streets. This technique differs from traditional traffic coordination which prioritizes major street traffic, and thereby generally results in degrading performance on minor streets. ALTPOM also provides smooth traffic progression for the coordinated direction with little impact on the opposite direction. The performance of ALTPOM improves as the penetration rate of connected vehicles increases. For saturated/oversaturated conditions, two queue length management based Active Traffic Management (ATM) strategies are proposed, analytically investigated, and experimentally validated. The first strategy distributes as much green time as possible for approaches with higher saturation discharge rate in order to reduce delay. For the second approach, green times are allocated to balance queue lengths of major and minor streets preventing queue spillback or gridlock. Both strategies were formulated initially using uniform arrival and departure, and then validated using field vehicle trajectory data. After validation of the modules, the effectiveness of CVTSCM is proven. Then, conclusions and recommendations for future researches are presented at the end.

No / The use of queue thresholds is a well known technique for network traffic congestion control. This motivates the study of a single server queue with R(R ¿ 2) distinct priority classes under Head of Line (HoL) service priority discipline, Partial Buffer Sharing (PBS) scheme and a finite capacity vector N, representing a sequence of thresholds (N1, N2, ¿ , NR) for each class jobs. The external traffic is modelled using the compound Poisson process or generalised exponential (GE) distribution which can capture the bursty property of the network traffic. The transmission times have also been modelled using the GE distribution to depict the bulk departures from the system. Using a GE/GE/1/N approximation, a closed form cost-effective analytical solution is obtained using the principle of maximum entropy (ME). The forms of the joint, aggregate and marginal state probabilities, as well as basic performance measures such as utilisation and blocking probabilities are analytically established at equilibrium via appropriate mean value constraints and the generating function approach. Consequently, efficient recursive expressions of low computational cost are determined. Typical numerical experiments are included to illustrate the credibility of the proposed mechanism in the context of different QoS grades for various network traffic classes. This model, therefore, can be used as a powerful tool to provide a required grade of service to a particular class of traffic in any heterogeneous networks.

No description available.

No / Quality of Service (QoS) is of extreme importance in accommodating the increasingly diverse range of services and types of traffic in present day communication networks and delay is one of the most important QoS metrics. This paper presents a new approach for constraining queueing delay in a buffer to a specified level as the arrival rate changes with time. A discrete-time control algorithm is presented that operates on a buffer (queue) which incorporates a moveable threshold. An algorithm is developed that controls the delay by dynamically adjusting the threshold which, in turn, controls the arrival rate. The feasibility of the system is examined using both theoretical analysis and simulation.

This paper presents a new analytical framework for the congestion control of Internet traffic using a queue threshold scheme. This framework includes two discrete-time analytical models for the performance evaluation of a threshold based congestion control mechanism and compares performance measurements through typical numerical results. To satisfy the low delay along with high throughput, model-I incorporates one threshold to make the arrival process step reduce from arrival rate ¿1 directly to ¿2 once the number of packets in the system has reached the threshold value L1. The source operates normally, otherwise. Model-II incorporates two thresholds to make the arrival rate linearly reduce from ¿1 to ¿2 with system contents when the number of packets in the system is between two thresholds L1 and L2. The source operates normally with arrival rate ¿1 before threshold L1, and with arrival rate ¿2 after the threshold L2. In both performance models, the mean packet delay W, probability of packet loss PL and throughput S have been found as functions of the thresholds and maximum drop probability. The performance comparison results for the two models have also been made through typical numerical results. The results clearly demonstrate how different load settings can provide different tradeoffs between throughput, loss probability and delay to suit different service requirements.

The effects of weigh-in-motion (WIM) systems on traffic operations and weight enforcement were compared and evaluated. The systems studied included high speed WIM, medium speed WIM and conventional static scales alone. The major measurements of effectiveness were traffic delay, queue, and the avoidance rate for overweight vehicles. Four weighing facilities from both the eastern and western United States were chosen as the real life bases for the study. Queuing theories, probability and statistics were the major methodologies employed in the study. The characteristics of queuing systems, such as traffic arrival patterns, weight enforcement processing time distribution, and capacity of the static scales at each weigh station were determined through field data collection at weigh stations. The proportion of the vehicle population directed to the static scale by WIM screening was analyzed, based on WIM accuracy and truck weight distributions at or near each weigh facility. By considering delay, queue, and the avoidance rate of overweight vehicles comprehensively, optimal weighing systems are proposed for different V/C ratios, i.e., the ratio of traffic volume at a specific site to the actual capacity of the static scale. When the V/C ratio is less than 1, a weighing facility using a static scale alone is most cost effective; when the V/C ratio is between 1 and 1.5, a medium speed WIM is suggested. High speed WIM is recommended only when the V/C ratio is larger than 1.5. / Master of Science

Att vänta i kö är något som de flesta människor inte tycker om, speciellt långa köer där väntan drar ut på tiden. I ett försök att minska väntetiden för kunder har företag börjat utveckla nya typer av köhanteringssystem vilka stödjer smartphonebaserade nummerlappar. Företagen erbjuder smartphonebaserade nummerlappar på olika sätt; antigen via sms eller en mobilapp. De smartphonebaserade nummerlapparna ger användarna, i tillägg till den vanliga funktionalitet som traditionella köhanteringssystem har, möjlighet att bland annat få uppdateringar om kön, ansluta sig till en kö utan att fysiskt vara på plats och att informera systemet om att de lämnar kön.Syftet med studien var att undersöka om smartphonebaserade nummerlappar påverkar kundernas kundnöjdhet jämfört med traditionella system. Det ansågs finnas ett behov av att undersöka detta eftersom köhanteringssystem som stödjer smartphonebaserade nummerlappar är relativt nya och att det inte har påträffats någon forskning som undersöker de mobila nummerlapparnas påverkan på kundnöjdheten. Den fråga som ställdes var: Påverkar en smartphonebaserad nummerlappsapp kundens kundnöjdhet i förhållande till ett traditionellt system?Studien använde en experimentell strategi för att besvara frågeställningen. Ett fältexperiment genomfördes i studentexpeditionen vid Högskolan i Borås där besökarna fick välja en mobilnummerlappsapp eller en pappersnummerlapp. Efter att besökarens betjäntas i kassan erbjöds denne att besvara en enkät om kundnöjdhet. Resultaten från enkäten användes för att beräkna en kundnöjdhetspoäng för respektive respondent och för att jämföra svaren från grupperna med olika nummerlappstyper. Även gruppernas medelkundnöjdhetspoäng beräknades och jämfördes med hjälp av independent samples t-test.Resultaten i studien visade att appanvändarna var signifikant mer nöjda än pappersanvändarna i den totala jämförelsen. För de enskilda frågorna visade resultatet att kundnöjdheten i vissa fall påverkades positiv men även att kundnöjdheten i vissa fall inte påverkades alls. Slutsatsen som drogs var att en smartphonebaserade nummerlappsapp påverkar kundnöjdheten positivt i förhållande till traditionella system. / Waiting in lines is something that most people do not like, especially waiting in long queues where the waiting drags on. In an attempt to reduce the waiting time for customers companies have begun to develop new types of queue management systems which support smartphone based queue tickets. The companies offer the smartphone based queue tickets in different ways, either by SMS or a mobile application. In addition to the usual functionality that traditional queue management systems offers the smartphone-based queue tickets provide users, with the ability to receive updates about the queue, connect to a queue without being physically on the site and inform the system that they left the queue.The purpose of this study was to investigate if smartphone based queue tickets affect the customer satisfaction compared to traditional systems. There was a need for such an investigation because the queue management system that support smartphone based queue tickets are relatively new and no research which examines the affect that smartphone based queue tickets has on customer satisfaction could be found. The question asked was: Does a smartphone based queue ticket application affect the customer satisfaction of the customer compared to a traditional system?The study used an experimental approach to answer the question. A field experiment was conducted in the student office at the University in Borås were the visitors could choose either a mobile application or a paper queue ticket. When the visitors’ had been served they were asked to answer a questionnaire about customer satisfaction. The results from the survey were used to calculate a customer satisfaction scores for each respondent and to compare the responses of the groups with different queue ticket types. The mean of the customer satisfaction scores of each group were also calculated and compared using independent samples t-test.The results of the study showed that the users of mobile application queue tickets were significantly more satisfied than those who used paper queue tickets. The results of the individual questions showed that for some questions the customer satisfaction were positively affected but for other questions the customer satisfaction were not affected. The overall conclusion was that a smartphone based queue ticket application affects the customer satisfaction positively compared to a traditional queue management system.

The Internet has been more and more intensively used in recent years. Although network infrastructure has been regularly upgraded, and the ability to manage heavy traffic greatly increased, especially on the core networks, congestion never ceases to appear, as the amount of traffic that flow on the Internet seems to be increasing at an even faster rate. Thus, congestion control mechanisms play a vital role in the functioning of the Internet. Active Queue Management (AQM) is a popular type of congestion control mechanism that is implemented on gateways (most notably routers), which can predict and avoid the congestion before it happens. When properly configured, AQMs can effectively reduce the congestion, and alleviate some of the problems such as global synchronisation and unfairness to bursty traffic. However, there are still many problems regarding AQMs. Most of the AQM schemes are quite sensitive to their parameters setting, and these parameters may be heavily dependent on the network traffic profile, which the administrator may not have intensive knowledge of, and is likely to change over time. When poorly configured, many AQMs perform no better than the basic drop-tail queue. There is currently no effective method to compare the performance of these AQM algorithms, caused by the parameter configuration problem. In this research, the aim is to propose a new analytical model, which mainly uses discrete-time queueing theory. A novel transient modification to the conventional equilibrium-based method is proposed, and it is utilised to further develop a dynamic interactive model of responsive traffic and bottleneck queues. Using step-by-step analysis, it represents the bursty traffic and oscillating queue length behaviour in practical network more accurately. It also provides an effective way of predicting the behaviour of a TCP-AQM system, allowing easier parameter optimisation for AQM schemes. Numerical solution using MATLAB and software simulation using NS-2 are used to extensively validate the proposed models, theories and conclusions.

A Large instruction window is a key requirement to exploit greater Instruction Level Parallelism in out-of-order superscalar processors. Along with the instruction window size, the size of various other structures including the issue queue, store queue and register file need to increase as well. However, the cycle time and energy consumption of conventional large monolithic Content Addressable Memories (CAMs), the underlying structure of most conventional issue queue and store queue designs, worsen rapidly with an increase in size. This results in a three way trade-off involving ILP, clock frequency and energy consumption. In this thesis, we propose efficient designs for the issue queue and the store queue that improve the circuit latency and energy consumption while minimizing the loss in IPC. We propose the Scalable Low power Issue Queue (SLIQ) design which segments the issue queue structure to reduce the latency. This is complemented with a fast Wakeup index to a consumer in the issue queue for every instruction. As this consumer instruction can be woken up directly, without any delay, this mitigates the IPC loss faced by the pipelined issue queue. Also, as the scheme incorporates a pipelined broadcast, the indices are not required for correctness and can simply be gang invalidated on branch mispredictions. The IPC loss of an 8 segment SLIQ is Within 2.3% for the entire SPEC CPU2000 benchmark suite while achieving a 39.3% reduction in issue latency. Further, in the SLIQ design unnecessary broadcasts to the higher segments are avoided most of the time as in a large majority of the cases, an instruction has a single consumer. This consumer is woken up either by direct indexing or by broadcast in the first segment of the SLIQ. This enables the 8 segment SLIQ to significantly reduce the energy consumption and the energy-delay product by 48.3% and 67.4% respectively on an average. SLIQ also allows the architects to segment the issue queue carefully so that the latency of the issue logic is just within the per pipeline stage latency goals of the design. We also propose the Scalable Low power Store Queue (SLSQ) to address similar problems associated with the store queue data forwarding logic. We extend the state- of-the-art Store Vector based Disambiguator to also predict the index of the store that will forward to a given load. SLSQ marginally adds to the hardware budget, but predicts the store queue index of the store which will forward with an accuracy of 99.5% on an average. SLSQ, thus, eliminates unnecessary address broadcasts and Compares and reduces energy consumption of the store-to-load forwarding logic by 78.4% and 91.6% for the SPEC Int and FP suites respectively. Another variant of SLSQ, eliminates the need for a CAM in the forwarding logic and achieves a 49.9% reduction in store to load data forwarding latency while incurring a minimal IPC loss less than 0.1% on average for the entire SPEC CPU2000 benchmark suite.

Timeliness in delivering packets for delay-sensitive applications is an important QoS (Quality of Service) measure in many systems, notably those that need to provide real-time performance. In such systems, if delay-sensitive traffic is delivered to the destination beyond the deadline, then the packets will be rendered useless and dropped after received at the destination. Bandwidth that is already scarce and shared between network nodes is wasted in relaying these expired packets. This thesis proposes that a deterministic per-hop delay can be achieved by using a dynamic queue threshold concept to bound delay of each node. A deterministic per-hop delay is a key component in guaranteeing a deterministic end-to-end delay. The research aims to develop a generic approach that can constrain network delay of delay-sensitive traffic in a dynamic network. Two adaptive queue management schemes, namely, DTH (Dynamic THreshold) and ADTH (Adaptive DTH) are proposed to realize the claim. Both DTH and ADTH use the dynamic threshold concept to constrain queuing delay so that bounded average queuing delay can be achieved for the former and bounded maximum nodal delay can be achieved for the latter. DTH is an analytical approach, which uses queuing theory with superposition of N MMBP-2 (Markov Modulated Bernoulli Process) arrival processes to obtain a mapping relationship between average queuing delay and an appropriate queuing threshold, for queue management. While ADTH is an measurement-based algorithmic approach that can respond to the time-varying link quality and network dynamics in wireless ad hoc networks to constrain network delay. It manages a queue based on system performance measurements and feedback of error measured against a target delay requirement. Numerical analysis and Matlab simulation have been carried out for DTH for the purposes of validation and performance analysis. While ADTH has been evaluated in NS-2 simulation and implemented in a multi-hop wireless ad hoc network testbed for performance analysis. Results show that DTH and ADTH can constrain network delay based on the specified delay requirements, with higher packet loss as a trade-off.