Xarxa de comunicacions de la UdG

La Universitat de Girona disposa d'una xarxa física de comunicacions que uneix tots els campus. Es tracta d'un avantatge important que permet la transmissió de dades i telefonia de manera segura i fiable, sense haver de llogar els enllaços a operadors externs

Immersió lingüística, cultural i acadèmica per a estudiants de Telecomunicació

L’Escola Tècnica Superior d’Enginyers de Telecomunicació (ETSET) de la Universitat Politècnica de València (UPV) promou la mobilitat dels seus estudiants i professors, no només a través de programes nacionals –SICUE-Sèneca– o internacionals (ERASMUS, PROMOE), sinó també per la realització de viatges de pràctiques de llengua estrangera. D’aquesta manera, els estudiants matriculats en les assignatures de francès, anglès o alemany poden beneficiar- se d’una estada a França, Gran Bretanya o Alemanya, visitant-ne les universitats i empreses del sector. En aquesta comunicació ens remetem a l’últim viatge realitzat a París al març passat, durant el qual quinze estudiants de l’ETSET, matriculats en els cinc grups de les assignatures de francès (nivell bàsic, intermedi i avançat), van visitar una Grande École, l’ENSEA (École Nationale Supérieure de l’Électronique et de ses Applications). La visita, coordinada i programada entre els professors responsables d’ambdues escoles, va consistir a efectuar presentacions institucionals (escola, universitat d’origen) i generals (informació sobre la ciutat i la seua cultura) per part dels mateixos estudiants espanyols i francesos en els diferents grups de les assignatures d’espanyol. Per a fer-ho, cada grup havia preparat la presentació en PowerPoint de la seua escola o ciutat en la llengua d’estudi. Aquest tipus d’activitats facilita la immersió lingüística, cultural i acadèmica dels estudiants, de manera que els permet rebre informació de primera mà sobre el panorama dels seus estudis en un altre país, i alhora patrocinen la seua pròpia escola entre els estudiants estrangers

Estimation of zero-sequence impedance of undergrounds cables for single-phase fault location in distribution systems with electric arc

This paper focus on the problem of locating single-phase faults in mixed distribution electric systems, with overhead lines and underground cables, using voltage and current measurements at the sending-end and sequence model of the network. Since calculating series impedance for underground cables is not as simple as in the case of overhead lines, the paper proposes a methodology to obtain an estimation of zero-sequence impedance of underground cables starting from previous single-faults occurred in the system, in which an electric arc occurred at the fault location. For this reason, the signal is previously pretreated to eliminate its peaks voltage and the analysis can be done working with a signal as close as a sinus wave as possible

AXARM : una aplicació eXtensible per assistència remota i monitorització

Un dels camps que aquest projecte ha estat treballant és el de la telemedicina. Aquest projecte presenta una aplicació per assistir al personal mèdic rehabilitador en tasques de telerehabilitació (i teleassistència) fent servir una connexió bàsica ADSL i hardware comú. És la continuació del projecte TeleRehabilitació i Esclerosi Múltiple (TRiEM), un esforç conjunt entre el grup de recerca Comunicacions i Sistemes Distribuïts (BCDS en anglès) de la Universitat de Girona (UdG) i de la Fundació Esclerosi Múltiple (FEM) per desenvolupar una eina per ajudar a tasques de rehabilitació de l’Esclerosi Múltiple. L’aplicació AXARM és una iniciativa del grup de Comunicacions i Sistemes Distribuïts de la Universitat de Girona per impulsar una eina d’assistència telemàtica entre doctors i pacients. Facilita una eina útil als especialistes d’un centre per realitzar tasques de rehabilitació, assistència remota o monitorització (sanitària, assistencial o d’una altra mena) amb pacients que es trobin en un altre punt físic a través d’Internet

Disseny i implementació d’un sistema experimental de telefonia IP per a la Unitat de Tecnologies de la Informació i Comunicació de l’Institut Català de la Salut a Girona

L'objectiu d'aquest projecte és dissenyar i implementar un servei de telefonia IP per a la Unitat de Tecnologies de la Informació i Comunicació (UTIC) de l'Institut Català de la Salut (ICS) a Girona. En primer lloc, es descriu el funcionament actual del servei de telefonia de l'ICS a Girona i la seva infraestructura de xarxa. A continuació s’estudia els fonaments de la VoIP. Es segueix amb el disseny, les eines escollides i la implementació realitzada, per acabar amb les conclusions

ToIP: Implementació d'un identificador de trucades

El principal objectiu d’aquest projecte és desenvolupar una aplicació client en .NET que sigui capaç de processar les trucades IP entrants que pugui rebre un usuari al llarg de la seva jornada laboral. L’empresa per la qual es desenvoluparà aquest projecte és Caixa Girona, una empresa dedicada a la banca, fundada l’any 1940 per la Diputació de Girona i que disposa d’una plantilla d’uns 1300 empleats repartits entre unes 250 oficines disposades arreu del territori català i uns Serveis Centrals (SSCC) situats a la ciutat de Girona

Evaluating the probability and the impact of a failure in GMPLS based networks

In this paper, we define a new scheme to develop and evaluate protection strategies for building reliable GMPLS networks. This is based on what we have called the network protection degree (NPD). The NPD consists of an a priori evaluation, the failure sensibility degree (FSD), which provides the failure probability, and an a posteriori evaluation, the failure impact degree (FID), which determines the impact on the network in case of failure, in terms of packet loss and recovery time. Having mathematical formulated these components, experimental results demonstrate the benefits of the utilization of the NPD, when used to enhance some current QoS routing algorithms in order to offer a certain degree of protection

Minimum interference routing with fast protection

One of the most effective techniques offering QoS routing is minimum interference routing. However, it is complex in terms of computation time and is not oriented toward improving the network protection level. In order to include better levels of protection, new minimum interference routing algorithms are necessary. Minimizing the failure recovery time is also a complex process involving different failure recovery phases. Some of these phases depend completely on correct routing selection, such as minimizing the failure notification time. The level of protection also involves other aspects, such as the amount of resources used. In this case shared backup techniques should be considered. Therefore, minimum interference techniques should also be modified in order to include sharing resources for protection in their objectives. These aspects are reviewed and analyzed in this article, and a new proposal combining minimum interference with fast protection using shared segment backups is introduced. Results show that our proposed method improves both minimization of the request rejection ratio and the percentage of bandwidth allocated to backup paths in networks with low and medium protection requirements

CAC controlled services sharing a link with connectionless data services in an ATM network: a performance evaluation study

In the B-ISDN there is a provision for four classes of services, all of them supported by a single transport network (the ATM network). Three of these services, the connected oriented (CO) ones, permit connection access control (CAC) but the fourth, the connectionless oriented (CLO) one, does not. Therefore, when CLO service and CO services have to share the same ATM link, a conflict may arise. This is because a bandwidth allocation to obtain maximum statistical gain can damage the contracted ATM quality of service (QOS); and vice versa, in order to guarantee the contracted QOS, the statistical gain have to be sacrificed. The paper presents a performance evaluation study of the influence of the CLO service on a CO service (a circuit emulation service or a variable bit-rate service) when sharing the same link

Resource dimensioning aspect of heterogeneous traffic with different service requirements: Integration versus segregation

In this paper, we consider the ATM networks in which the virtual path concept is implemented. The question of how to multiplex two or more diverse traffic classes while providing different quality of service requirements is a very complicated open problem. Two distinct options are available: integration and segregation. In an integration approach all the traffic from different connections are multiplexed onto one VP. This implies that the most restrictive QOS requirements must be applied to all services. Therefore, link utilization will be decreased because unnecessarily stringent QOS is provided to all connections. With the segregation approach the problem can be much simplified if different types of traffic are separated by assigning a VP with dedicated resources (buffers and links). Therefore, resources may not be efficiently utilized because no sharing of bandwidth can take place across the VP. The probability that the bandwidth required by the accepted connections exceeds the capacity of the link is evaluated with the probability of congestion (PC). Since the PC can be expressed as the CLP, we shall simply carry out bandwidth allocation using the PC. We first focus on the influence of some parameters (CLP, bit rate and burstiness) on the capacity required by a VP supporting a single traffic class using the new convolution approach. Numerical results are presented both to compare the required capacity and to observe which conditions under each approach are preferred

Bandwidth allocation based on real time calculations using the convolution approach

This paper focuses on one of the methods for bandwidth allocation in an ATM network: the convolution approach. The convolution approach permits an accurate study of the system load in statistical terms by accumulated calculations, since probabilistic results of the bandwidth allocation can be obtained. Nevertheless, the convolution approach has a high cost in terms of calculation and storage requirements. This aspect makes real-time calculations difficult, so many authors do not consider this approach. With the aim of reducing the cost we propose to use the multinomial distribution function: the enhanced convolution approach (ECA). This permits direct computation of the associated probabilities of the instantaneous bandwidth requirements and makes a simple deconvolution process possible. The ECA is used in connection acceptance control, and some results are presented

Optimal Traffic Grooming in WDM using Lighttours

Recent developments in optical communications have allowed simpler optical devices to improve network resource utilization. As such, we propose adding a lambda-monitoring device to a wavelength-routing switch (WRS) allowing better performance when traffic is routed and groomed. This device may allow a WRS to aggregate traffic over optical routes without incurring in optical-electrical-optical conversion for the existing traffic. In other words, optical routes can be taken partially to route demands creating a sort of "lighttours". In this paper, we compare the number of OEO conversions needed to route a complete given traffic matrix using either lighttours or lightpaths

QoS online routing and MPLS multilevel protection: a survey

A survey of MPLS protection methods and their utilization in combination with online routing methods is presented in this article. Usually, fault management methods pre-establish backup paths to recover traffic after a failure. In addition, MPLS allows the creation of different backup types, and hence MPLS is a suitable method to support traffic-engineered networks. In this article, an introduction of several label switch path backup types and their pros and cons are pointed out. The creation of an LSP involves a routing phase, which should include QoS aspects. In a similar way, to achieve a reliable network the LSP backups must also be routed by a QoS routing method. When LSP creation requests arrive one by one (a dynamic network scenario), online routing methods are applied. The relationship between MPLS fault management and QoS online routing methods is unavoidable, in particular during the creation of LSP backups. Both aspects are discussed in this article. Several ideas on how these actual technologies could be applied together are presented and compared

Adding QoS protection in order to enhance MPLS QoS routing

In this paper, a method for enhancing current QoS routing methods by means of QoS protection is presented. In an MPLS network, the segments (links) to be protected are predefined and an LSP request involves, apart from establishing a working path, creating a specific type of backup path (local, reverse or global). Different QoS parameters, such as network load balancing, resource optimization and minimization of LSP request rejection should be considered. QoS protection is defined as a function of QoS parameters, such as packet loss, restoration time, and resource optimization. A framework to add QoS protection to many of the current QoS routing algorithms is introduced. A backup decision module to select the most suitable protection method is formulated and different case studies are analyzed

Multicast algorithms evaluation using an adaptative routing in ATM networks

This paper proposes a multicast implementation based on adaptive routing with anticipated calculation. Three different cost measures for a point-to-multipoint connection: bandwidth cost, connection establishment cost and switching cost can be considered. The application of the method based on pre-evaluated routing tables makes possible the reduction of bandwidth cost and connection establishment cost individually