4,869 research outputs found
Partially shared buffers with full or mixed priority
This paper studies a finite-sized discrete-time two-class priority queue. Packets of both classes arrive according to a two-class discrete batch Markovian arrival process (2-DBMAP), taking into account the correlated nature of arrivals in heterogeneous telecommunication networks. The model incorporates time and space priority to provide different types of service to each class. One of both classes receives absolute time priority in order to minimize its delay. Space priority is implemented by the partial buffer sharing acceptance policy and can be provided to the class receiving time priority or to the other class. This choice gives rise to two different queueing models and this paper analyses both these models in a unified manner. Furthermore, the buffer finiteness and the use of space priority raise some issues on the order of arrivals in a slot. This paper does not assume that all arrivals from one class enter the queue before those of the other class. Instead, a string representation for sequences of arriving packets and a probability measure on the set of such strings are introduced. This naturally gives rise to the notion of intra-slot space priority. Performance of these queueing systems is then determined using matrix-analytic techniques. The numerical examples explore the range of service differentiation covered by both models
Pilot interaction with automated airborne decision making systems
An investigation was made of interaction between a human pilot and automated on-board decision making systems. Research was initiated on the topic of pilot problem solving in automated and semi-automated flight management systems and attempts were made to develop a model of human decision making in a multi-task situation. A study was made of allocation of responsibility between human and computer, and discussed were various pilot performance parameters with varying degrees of automation. Optimal allocation of responsibility between human and computer was considered and some theoretical results found in the literature were presented. The pilot as a problem solver was discussed. Finally the design of displays, controls, procedures, and computer aids for problem solving tasks in automated and semi-automated systems was considered
Generalized gap acceptance models for unsignalized intersections
This paper contributes to the modeling and analysis of unsignalized
intersections. In classical gap acceptance models vehicles on the minor road
accept any gap greater than the CRITICAL gap, and reject gaps below this
threshold, where the gap is the time between two subsequent vehicles on the
major road. The main contribution of this paper is to develop a series of
generalizations of existing models, thus increasing the model's practical
applicability significantly. First, we incorporate {driver impatience behavior}
while allowing for a realistic merging behavior; we do so by distinguishing
between the critical gap and the merging time, thus allowing MULTIPLE vehicles
to use a sufficiently large gap. Incorporating this feature is particularly
challenging in models with driver impatience. Secondly, we allow for multiple
classes of gap acceptance behavior, enabling us to distinguish between
different driver types and/or different vehicle types. Thirdly, we use the
novel M/SM2/1 queueing model, which has batch arrivals, dependent service
times, and a different service-time distribution for vehicles arriving in an
empty queue on the minor road (where `service time' refers to the time required
to find a sufficiently large gap). This setup facilitates the analysis of the
service-time distribution of an arbitrary vehicle on the minor road and of the
queue length on the minor road. In particular, we can compute the MEAN service
time, thus enabling the evaluation of the capacity for the minor road vehicles
- …