Sònia P. Mansilla

Construction of k -arc transitive digraphs

Abstract A digraph is k -arc transitive if it has a group of automorphisms which acts transitively on the set of k -arcs. Unlike the undirected case, in which the cycles are the only k -arc transitive finite graphs for k⩾8 , there are k -arc transitive finite digraphs with arbitrary out-degree for every positive integer k . We show that every regular finite digraph admits a covering digraph which is k -arc transitive. The result provides a technique to construct k -arc transitive digraphs from arbitrary regular digraphs. Some examples are given from complete graphs with and without loops.

Analysis of Consecutive Idle Time Slots in Mobile Networks

In this paper, we address the issue of the radio resource allocation in a cellular mobile network. We propose a new method to reach high peak rates which improves the requirements of mobile users. The method consists of managing the available time slots, in order to obtain groups of idle consecutive time slots to allocate them in a sequential order. We develop an analytical closed expression for the probabilities of finding these groups of idle consecutive time slots. The results are useful to a network operator to reconfigure radio resources, fulfilling the quality of service (QoS) requirements to serve both voice and data traffic

A telemetry modeling for intelligent UAV monitoring

An Unmanned Aerial Vehicle, UAV for short, is able to fly autonomously during all phases of flight, but has to be monitored from an operator station. In this article a better avionic system is proposed to optimize this process reducing the channel usage without quality degradation. The information related to the aircraft position is called telemetry. This early avionic system is tested in the longitudinal mode of a high wing model unmanned aircraft system in an open source flight simulator.

Radio Resource Allocation Strategies to Guarantee Data Traffic in Cellular Networks

In this paper, we focus on different strategies of radio resource allocation in cellular mobile networks. The paper proposes two models of ordered allocation of the time slots in a frame (with or without time slots reserved for data traffic) and in such a way that the available resources for an user can be maximized if we take into account the number of consecutive idle time slots. The analytical model is presented and the probabilities of finding any given number of consecutive idle time slots for the different models are shown. The results are presented for three different scenarios, which have two, one or none reserved resources available just for data traffic. For the different scenarios the quality of service requirements of data traffic is compared, without degrading in any case the voice service.

UAS behavior modeling based on high level abstraction

This paper presents a telemetry compression algorithm for Unmanned Aerial Vehicles (UAV) based on high level abstraction. A typical communication channel usage is not optimized when it is used for telemetry because it requires persistent communications to the ground station. This method spends large bandwidth in the communication channel having an inefficient cost in terms of power consumption. We have noticed that unmanned aerial vehicles behave following patterns easy to describe by a characterizer abstracting the trajectory of the maneuvers. This behavior is also valid for aircrafts commanded by the autopilot or when the aircraft is flying a 4D navigation. The aim of this algorithm is not only to have an efficient channel usage but to reduce the delay due to the distance and to increase the accuracy without increasing the sampling rate. It is possible to rebuild the trajectory from a small amount of information if we have a good model of our aircraft and this might be very helpful for collision avoidance. Let us recall that inferring intent is a big issue in UAS detect sense and avoid. The solution presented in this paper uses a so called PID characterizer. The PID characterizer is a method which solves the six degrees of freedom motion equations for a small time interval while flying. These equations are modeled in a transfer function designed by a set of parameters that we called ephemeris. The channel usage will be low because only the ephemeris will be sent to the ground station. This algorithm is useful for monitoring the vehicle position and attitude but nevertheless, it is not so useful for remote control due to the stochastic nature of the control loop. Sudden trajectory changes need to be recalculated in flight when a significant disagreement with the predicted trajectory is detected. Transition motion and stochastic sequences must be covered by traditional telemetry.

Improved channel allocation for voice and data traffic with resource reservation for voice traffic in EDGE system

This paper makes two main contributions. The first is a method that combines TDMA time slots for voice and data packet services to offer high peak rates and guarantee packet connectivity in the case of cell congestion. The method can also be used to analyse time slot reservation for voice or data packet services. The second contribution is a novel method for analysing the system. In addition to the traditional approach that consists in solving a large system of equations to compute state probabilities, a combinatorial method that simplifies the analysis and that can be applied to larger and more complex systems is introduced.

Improving EDGE for rural environments through channel allocation for voice and data traffic

In this paper, we focus on improving EDGE technology with the aim that the benefits of mobile communication reach rural environments and isolated areas. We present a method of channel allocation that provides both voice and data services, improving data traffic transmission without putting aside the QoS of voice traffic. Firstly, a general analytical model is presented. Secondly, allocating sequentially the time slots, we study the best way of using few reserved time slots just for voice calls, in order to get greater probabilities of higher throughput. Finally, the results obtained are analysed and using them, the network operator can schedule the channel allocation of their users according to the QoS requirements of each of them.

An infinite family of sharply two-arc transitive digraphs

Abstract We disclaim Conjecture 1 posed by Seifter in [N. Seifter, Transitive digraphs with more than one end, Discrete Math., to appear], that stated that a connected locally finite digraph with more than one end is either 0-, 1- or highly arc transitive. We describe in this work an infinite family of 2-arc transitive two-ended digraphs, that are not 3-arc transitive.

Exactly k-arc Transitive Covers

A mechanical in-line sector scanner is provided in which the ultrasonic transducer pivots about an axis. The transducer is oscillated through an arc about the axis by reciprocating pins, which alternately push the transducer in opposite directions of scanning. The pins are reciprocated by a continuously turning cam having a cam surface obliquely oriented with respect to the longitudinal axis of the pins.