26,107 research outputs found
Case Study: Election Observation Dispatches From the Polls
Provides an overview of the diversification among poll observers, from political parties to researchers to journalists and bloggers, and what they may contribute to the voting process. Summarizes state rules on media and public access to polling places
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
Analysis of a polling system modeling QoS differentiation in WLANs
This paper investigates a polling system with a random polling scheme, a 1-limited service discipline and deterministic service requirement modeling WLANs with QoS differentation capability. The system contains high and low priority queues that are distinguished via the probability of being served next. We propose a new iteration algorithm to approximate the waiting time of customers in the high and low priority queues. As shown by simulation results, our approximation is accurate for light to moderately loaded networks
Wait-and-see strategies in polling models
We consider a general polling model with stations. The stations are
served exhaustively and in cyclic order. Once a station queue falls empty, the
server does not immediately switch to the next station. Rather, it waits at the
station for the possible arrival of new work ("wait-and-see") and, in the case
of this happening, it restarts service in an exhaustive fashion. The total time
the server waits idly is set to be a fixed, deterministic parameter for each
station. Switchover times and service times are allowed to follow some general
distribution, respectively. In some cases, which can be characterised, this
strategy yields strictly lower average queueing delay than for the exhaustive
strategy, which corresponds to setting the "wait-and-see credit" equal to zero
for all stations. This extends results of Pek\"oz (Probability in the
Engineering and Informational Sciences 13 (1999)) and of Boxma et al. (Annals
of Operations Research 112 (2002)). Furthermore, we give a lower bound for the
delay for {\it all} strategies that allow the server to wait at the stations
even though no work is present.Comment: 24p, submitte
- …