Mixed Polling with Rerouting and Applications

Queueing systems with a single server in which customers wait to be served at a finite number of distinct locations (buffers/queues) are called discrete polling systems. Polling systems in which arrivals of users occur anywhere in a continuum are called continuous polling systems. Often one encounters a combination of the two systems: the users can either arrive in a continuum or wait in a finite set (i.e. wait at a finite number of queues). We call these systems mixed polling systems. Also, in some applications, customers are rerouted to a new location (for another service) after their service is completed. In this work, we study mixed polling systems with rerouting. We obtain their steady state performance by discretization using the known pseudo conservation laws of discrete polling systems. Their stationary expected workload is obtained as a limit of the stationary expected workload of a discrete system. The main tools for our analysis are: a) the fixed point analysis of infinite dimensional operators and; b) the convergence of Riemann sums to an integral. We analyze two applications using our results on mixed polling systems and discuss the optimal system design. We consider a local area network, in which a moving ferry facilitates communication (data transfer) using a wireless link. We also consider a distributed waste collection system and derive the optimal collection point. In both examples, the service requests can arrive anywhere in a subset of the two dimensional plane. Namely, some users arrive in a continuous set while others wait for their service in a finite set. The only polling systems that can model these applications are mixed systems with rerouting as introduced in this manuscript.Comment: to appear in Performance Evaluatio

Stochastic approximation of symmetric Nash equilibria in queueing games

We suggest a novel stochastic-approximation algorithm to compute a symmetric Nash-equilibrium strategy in a general queueing game with a finite action space. The algorithm involves a single simulation of the queueing process with dynamic updating of the strategy at regeneration times. Under mild assumptions on the utility function and on the regenerative structure of the queueing process, the algorithm converges to a symmetric equilibrium strategy almost surely. This yields a powerful tool that can be used to approximate equilibrium strategies in a broad range of strategic queueing models in which direct analysis is impracticable

Queues and risk models with simultaneous arrivals

We focus on a particular connection between queueing and risk models in a multi-dimensional setting. We first consider the joint workload process in a queueing model with parallel queues and simultaneous arrivals at the queues. For the case that the service times are ordered (from largest in the first queue to smallest in the last queue) we obtain the Laplace-Stieltjes transform of the joint stationary workload distribution. Using a multivariate duality argument between queueing and risk models, this also gives the Laplace transform of the survival probability of all books in a multivariate risk model with simultaneous claim arrivals and the same ordering between claim sizes. Other features of the paper include a stochastic decomposition result for the workload vector, and an outline how the two-dimensional risk model with a general two-dimensional claim size distribution (hence without ordering of claim sizes) is related to a known Riemann boundary value problem

The Impact of Mindful Breathing on Stress of Employees Working from Home

This DNP project was designed to decrease stress among employees working from home (WFH) by educating them on mindful breathing practices. Through the implementation of a mindful breathing activity, the intended project outcome was to improve stress levels of employees working from their homes. Mindful breathing is an evidence-based strategy that has demonstrated decreased stress levels. Mindful breathing was implemented among two companies employing an estimate of 170 WFH employees to improve health and well-being with potential long-term positive impact on sustainability of organizations in the post-COVID, work from home environment. The participants were invited to perform 8-minutes of daily mindful breathing for two weeks. Project impact was measured utilizing a pre/post-survey evaluating their stress levels before and after the mindful breathing activity. Results identified moderate to high levels of stress in work from home employees at baseline and post-intervention. Additional research is indicated to increase sample size. In conclusion, implementing a mindfulness breathing technique may impact the organizations positively by decreasing the stress of the employees working from home

Using Remote Attestation of Trust for Computer Forensics

Telecommunications systems are critical systems with high quality of service constraints. In Network Function Virtualization (NFV), commonly known as the Telco Cloud, network functions are distributed as virtual machines that run on generic servers in a datacenter. These network functions control critical elements; therefore, they should be run on trusted hardware. Trusted computing concepts can be used to guarantee the trustworthiness of the underlying hardware platform running critical workload. These concepts include the Trusted Platform Module and Remote Attestation. This work identifies limitations in existing solutions and uses those as motivation for designing and implementing a finer-grained definition of trust. This thesis designs and develops a remote attestation solution, which includes a policy and rule based mechanism for determining platform trust in a trusted cloud. Additionally, it develops a fine-grained concept of trust in a cloud environment based on NFV. Finally, this thesis utilizes the remote attestation solution to develop a forensics system based on root cause analysis, which allows the investigation of attestation failures and their mitigation

Continuous Polling with Rerouting and Applications to Ferry Assisted Wireless LANs

International audienceIn almost all studied continuous polling systems, the user leaves the system after his service is completed. There are interesting applications, in which the users demand a second service (or more). For example, in a ferry assisted wireless network, for every local data transfer the ferry has to collect the data from the source and then deliver the same to the sink. This type of application can be modeled by polling systems with rerouting. In polling systems with arrivals on a continuum (on a circle), a moving server attends the users as and when it encounters one. When rerouting is supported, after the service is completed, the users can reroute to a different point in the same circle to await another service. We obtain the performance of such a system under quite general conditions, via discretization approach. The results are applied to study a ferry assisted wireless local area network. Our results rely heavily on fixed point analysis of infinite dimensional operators

Analysis and Design of Message Ferry Routes in Sensor Networks using Polling Models

RoutingInternational audienceWe consider a Ferry based Wireless Local Area Network (FWLAN), in which information is forwarded from a base station to sensors, or gathered from sensors to a base station using a moving Ferry. The sensors are scattered in a large area and do not have direct radio connectivity with the base station. The ferry thus serves as a relay that enables communication between the sensors and the base station. Our goal in this paper is to design optimal routes of the Ferry moving along which it distributes/collects the messages. Our analysis and optimization results build heavily on the theory of polling systems which we extend here in order to handle the case of continuous location of the demand. We derive optimal trajectories for various scenarios: uplink, downlink and their combination. We extend some of these results to the case of several base stations and several ferries