Delay based approach to support low priority users in preemptive wireless networks

Title from PDF of title page, viewed on January 27, 2012Thesis advisor: Cory C. BeardVitaIncludes bibliographic references (p. 39)Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2011At times of serious disasters (natural or man-made), wireless networks are quickly congested due to the sheer volume and stress on network resources, and, preferential treatment is necessary for National Security/Emergency Preparedness (NS/EP) users to combat the disaster by responding effectively and potentially save many lives. Under such circumstances, with scarce resources, the new request for sessions are denied and worse even, active sessions are dropped for general public whilst they have come to rely on these resources and depend on them especially during distressed times. Prior research has been conducted to examine upper limit (UL) and preemptive approaches to support emergency users but the traditional approach of blocking the capacity for emergency users is, from one perspective, restrictive to the general public. In this thesis, we propose the delay-based soft preemptive approach to support the low priority users and provide an alternative to several preemptive policies by further examining them. We provide a queuing algorithm in the network that warns the low priority users with an active session of scarce resources thereby giving them an opportunity to complete their session prior to reducing the quality of service (QoS) of their session and moving their bandwidth to emergency users, if blocked. The emergency users in turn wait for the resources to become available and are on hold until resources become available. By creating a queuing modeling system for this algorithm, we present simulation model in C with results of our delay-based soft preemptive approach and examine other preemptive approaches to provide a comparative analysis. The results demonstrate that increasing the warning time also increases the number of sessions blocked for emergency users as well as general public due to further constraining the resources, however, this reduces the inconvenience of preemption caused to the low priority users.Introduction -- Related work -- Algorithm and simulations -- Analysis and results -- Conclusio

Reliability Guided Resource Allocation for Large-scale Supercomputing Systems

In high performance computing systems, parallel applications request a large number of resources for long time periods. In this scenario, if a resource fails during the application runtime, it would cause all applications using this resource to fail. The probability of application failure is tied to the inherent reliability of resources used by the application. Our investigation of high performance computing systems operating in the field has revealed a significant difference in the measured operational reliability of individual computing nodes. By adding awareness of the individual system nodes\u27 reliability to the scheduler along with the predicted reliability needs of parallel applications, reliable resources can be matched with the most demanding applications to reduce the probability of application failure arising from resource failure. In this thesis, the researcher describes a new approach developed for resource allocation that can enhance the reliability and reduce the costs of failures of large-scale parallel applications that use high performance computing systems. This approach is based on a multi-class Erlang loss system that allows us to partition system resources based on predicted resource reliability, and to size each of these partitions to bound the probability of blocking requests to each partition while simultaneously improving the reliability of the most demanding parallel applications running on the system. Using this model, the partition mean time to failure (MTTF) is maximized and the probability of blocking of resource requests directed to each partition by a scheduling system can be controlled. This new technique can be used to determine the size of the system, to service peak loads with a bounded probability of blocking to resource requests. This approach would be useful for high performance computing system operators seeking to improve the reliability, efficiency and cost-effectiveness of their systems

Call admission control for interactive multimedia satellite networks.

Master of Science in Engineering (Electronic). University of KwaZulu-Natal, Durban 2015.Satellite communication has become an integral component of global access communication network due mainly to its ubiquitous coverage, large bandwidth and ability to support for large numbers of users over fixed and mobile devices. However, the multiplicity of multimedia applications with diverse requirements in terms of quality of service (QoS) poses new challenges in managing the limited and expensive resources. Furthermore, the time-varying nature of the propagation channel due to atmospheric and environmental effects also poses great challenges to effective utilization of resources and the satisfaction of users’ QoS requirements. Efficient radio resource management (RRM) techniques such as call admission control (CAC) and adaptive modulation and coding (AMC) are required in order to guarantee QoS satisfaction for user established connections and realize maximum and efficient utilization of network resources. In this work, we propose two CAC policies for interactive satellite multimedia networks. The two policies are based on efficient adaptation of transmission parameters to the dynamic link characteristics. In the first policy which we refer to as Gaussian Call Admission Control with Link Adaptation (GCAC-LA), we invoke the central limit theorem to statistically multiplex rate based dynamic capacity (RBDC) connections and obtain an aggregate bandwidth and required capacity for the multiplex. Adaptive Modulation and Coding (AMC) is employed for transmission over the time-varying wireless channel of the return link of an interactive satellite network. By associating users’ channel states to particular transmission parameters, the amount of resources required to satisfy user connection requirements in each state is determined. Thus the admission control policy considers in its decision, the channel states of all existing and new connections. The performance of the system is investigated by simulation and the results show that AMC significantly improves the utilization and call blocking performance by more than twice that of a system without link adaptation. In the second policy, a Game Theory based CAC policy with link adaptation (GTCAC-LA) is proposed. The admission of a new user connection under the GTCAC-LA policy is based on a non-cooperative game that is played between the network (existing user connections) and the new connection. A channel prediction scheme that predicts the rain attenuation on the link in successive intervals of time is also proposed. This determines the current resource allocation for every source at any point in time. The proposed game is played each time a new connection arrives and the strategies adopted by players are based on utility function, which is estimated based on the required capacity and the actual resources allocated. The performance of the CAC policy is investigated for different prediction intervals and the results show that multiple interval prediction scheme shows better performance than the single interval scheme. Performance of the proposed CAC policies indicates their suitability for QoS provisioning for traffic of multimedia connections in future 5G networks