Papers by Fernando Cerdan
Counters-Based Modified Traffic Conditioner
Lecture Notes in Computer Science, 2002
Traffic conditioners play a key role in implementing the Assured Service in the framework of the ... more Traffic conditioners play a key role in implementing the Assured Service in the framework of the DiffServ approach. In this paper, we propose a traffic conditioner for the Internet Assured Service called Counters-Based Modified (CBM) that strictly guarantees target rates and performs a fair share of the excess bandwidth among TCP sources. The fairness in the outbound bandwidth distribution is met by probabilistically dropping OUT packets in the traffic conditioner. To determine the dropping probability of an OUT packet, some sort of signaling is needed. Although, it results more feasible than other proposed intelligent traffic conditioners. The CBM traffic conditioner is evaluated under different conditions by simulation using TCP Reno sources.
DISEÑO Y ESPECIFICACIÓN DE UN PROTOCOLO DE CONEXIÓN DE TERMINALES MÓVILES FUERA DE COBERTURA
DYNA NEW TECHNOLOGIES, 2015
Simulation of 3G DCHs Supporting TCP Traffic: Design, Experiments and Insights on Parameter Tuning
Proceedings of the First International ICST Conference on Simulation Tools and Techniques for Communications Networks and Systems, 2008
... Technical University of Cartagena Plaza del Hospital, 1, 30202 Cartagena, SPAIN 34 968326544 ... more ... Technical University of Cartagena Plaza del Hospital, 1, 30202 Cartagena, SPAIN 34 968326544 {juan.alcaraz, gaspar.pedreno, fernando.cerdan, joang.haro ... properly, but to find a valid configuration for a wide range of situations, eg frame error ratio (FER), Doppler frequency ...
A Mobile Approach for a Physical Simulation Model in Wimax
2009 Fifth International Conference on Networking and Services, 2009
... Cerdán, Andrés Cabrera-Lozoya, Sergio Luján-Fernandez Department of Information Technologies ... more ... Cerdán, Andrés Cabrera-Lozoya, Sergio Luján-Fernandez Department of Information Technologies and Communications Polythecnic University of Cartagena Plaza del Hospital, 1, 30202 CARTAGENA E-mail: {sergio.almagro, fernando.cerdan, andres.cabrera, sergio.lujan ...
Deeploc: Discreet Indoor People Location Application
2011 4th IFIP International Conference on New Technologies, Mobility and Security, 2011
... Muro, Andrés Cabrera-Lozoya, Fernando Cerdan Information and Communication Technologies, ... more ... Muro, Andrés Cabrera-Lozoya, Fernando Cerdan Information and Communication Technologies, Electronic Technology Polytechnic University of Cartagena Plaza del Hospital, 1, 30202 Cartagena, Spain {sergio.lujan, juan.suardiaz, andres.cabrera, fernando.cerdan ...
Computers & Education, 2012
Current e-learning forms are commonly based on improving the learning process through the enhance... more Current e-learning forms are commonly based on improving the learning process through the enhancement of certain skills in students, such as collaborative, competitive or problem-based learning. However, it seems that there is still no e-learning formula that gathers the implementation of a number of more generic educational principles in a single e-learning system or platform. Therefore, this paper presents a web-based framework for the creation, development and implementation of heterogeneous learning environments called CADI. It offers a graphical user interface for students to interact with only the need for any generic WiFi compliant device. Its innovative design allows the instructor to select and combine the developed resources to create varied activities, providing content adapted to every single device. The usefulness of the system was tested by introducing a case study to a group of senior college students. The experience showed that the use of the system helped students to achieve better results in their evaluation. It also showed that the students had no problems interacting with it from the outset, promoting their active learning. Design, implementation and assessment results of the system are also presented and analyzed.
Computer Communications, 2009
Transport channel synchronization is a function of 3G access networks that operates in the link b... more Transport channel synchronization is a function of 3G access networks that operates in the link between Radio Network Controllers (RNCs) and Base Stations (Nodes B) and is required to support macro-diversity in the downlink direction. Its objective is to assure that every frame sent by the RNC arrives at the Node B on time to be transmitted over the air interface avoiding excessive buffering at the Node B. This is achieved by means of a timing adjustment algorithm that tracks the delay of the link and corrects the sending time of the frames in the RNC. However, when the link experiences abrupt delay variations, e.g. because of a sudden traffic increment in an intermediate node, the classic algorithm may loss frames and, depending on its configuration and the transport delay, it can show an undesired oscillatory behaviour. In this paper we analyze the response of this mechanism under sudden delay increments, providing useful guidelines to configure it in order to prevent oscillations, avoiding excessive signalling and eventual frame losses. Moreover, we propose a simple algorithm that overcomes the limitations of the classic scheme. The configuration of our proposal is addressed by means of discrete-time control theory focusing on stability and performance considerations. We show the influence of the delay on these issues and present an adaptive strategy to make the system robust under delay variations. (
A new algorithm for traffic conditioners to improve proportional fairness in IP networks
AEU - International Journal of Electronics and Communications, 2006
The current trend in telecommunications networks addresses an All-IP vision, since most user appl... more The current trend in telecommunications networks addresses an All-IP vision, since most user applications are based on IP, and additionally, IP networks operation is simpler than other more complex ones. These new trends in multimedia communications are giving rise to an increasing need of quality of service (QoS). The Differentiated Services (DiffServ) QoS architecture will provide the means to help
Lecture Notes in Computer Science, 2000
As Internet is rapidly growing and receiving traffic from multimedia applications which are sensi... more As Internet is rapidly growing and receiving traffic from multimedia applications which are sensitive to available bandwidth and delay experienced in the network, there is a strong need for quality of service (QoS) support . The Integrated and Differentiated Service models are two approaches for adding QoS to Internet. The Assured Service is an end-to-end service based on the Differentiated Service architecture. Since ATM is widely deployed in Internet backbones, traffic management for Internet traffic over ATM is becoming an important issue. In this paper we present a simulation analysis of an Assured service mapped on the ATM GFR service category. We study the problem of guarantying individual target rates to an aggregated IP stream. Aggregated streams are mapped with a MCR according to the QoS requested.
The Application of PDAs and Smartphones in the Classroom as Instruments for Improvement of Learning Monitoring
Materials Science Forum, 2009
Development of a Cooperative Application for Sending SMS on WiFi Mobile Phones
2008 The Second International Conference on Mobile Ubiquitous Computing, Systems, Services and Technologies, 2008
Most of current user mobile devices incorporate a WiFi interface. Peer communications are based o... more Most of current user mobile devices incorporate a WiFi interface. Peer communications are based on Ad-hoc network configuration, but the main handicap is the radio coverage. The success in deploying services and applications based on this concept needs the development of relay protocols and applications that allows intermediate users the reception and forwarding of information to destination users. The user
Lecture Notes in Computer Science, 2008
The main goal of Transport Channel Synchronization is that frames sent by the RNC arrive in time ... more The main goal of Transport Channel Synchronization is that frames sent by the RNC arrive in time to the Nodes B for transmission over the air interface. The 3GPP specifies a simple Timing Adjustment algorithm that tracks the delay of the Iub link (interface defined between RNC and Node B) by adding or subtracting a constant step. We show that this scheme reacts too slowly under abrupt delay variations and may become unstable in high delay scenarios. This paper proposes an alternative mechanism denominated Proportional Tracking Algorithm (PTA) which ensures stability in any scenario and improves performance compared to the classic one. The stability analysis of PTA is based on control theory and the performance is measured by means of an UTRAN simulator considering realistic traffic conditions in the Iub.
Experimental Tests on SCTP over IPSec
2008 IFIP International Conference on Network and Parallel Computing, 2008
As telecommunication technologies evolve, security in communications becomes a more and more rele... more As telecommunication technologies evolve, security in communications becomes a more and more relevant issue. IPSec is a set of protocols aiming to enhance security at the IP layer. Specifically, IPSec and IKE are important security mechanism that provide cryptographic-based protection for IP packets, and consequently for IP services. SCTP is a standardized transport protocol whose main features include multihoming and
Slope based discard
Proceeding of the 2006 international conference on Communications and mobile computing - IWCMC '06, 2006
Combining ACK rate control and AQM to enhance TCP performance over 3G links
Proceedings of the ACM international workshop on Performance monitoring, measurement, and evaluation of heterogeneous wireless and wired networks - PM2HW2N '06, 2006
Lecture Notes in Computer Science, 2006
When TCP is carried over 3G links, overbuffering and buffer overflow at the RLC layer degrades it... more When TCP is carried over 3G links, overbuffering and buffer overflow at the RLC layer degrades its performance. AQM techniques at the RLC buffer can bring noticeable enhancements to TCP performance without introducing changes in 3G specifications. We show that the optimum parameter setting of AQM algorithms in RLC buffers is strongly related to the radio bearer rate, which can be changed dynamically by control layer protocols. By means of extensive simulation experiments we propose, for each specified nominal rate, optimum configurations that keep the goodput near the maximum while the delay is reduced up to 50%. We consider two AQM schemes, an adapted RED algorithm and a novel deterministic one, SBD described in this paper. We illustrate how an automatic reconfiguration of AQM parameters avoids the degradation caused by sudden changes in the radio bearer rate.
Using Design Patterns in a HSDPA System Simulator
2006 3rd International Symposium on Wireless Communication Systems, 2006
Wireless network simulators have become a fundamental tool to study, evaluate and improve wireles... more Wireless network simulators have become a fundamental tool to study, evaluate and improve wireless networks. The quick evolution of wireless technology involves the necessity of continuous changes and updates in these simulators which makes them more complicated and time demanding. Regarding software design, wireless network simulators are generally based on the object-oriented paradigm. However, the use of more advanced programming
Improving TCP Performance over 3G Links with an ACK Rate Control Algorithm
2006 3rd International Symposium on Wireless Communication Systems, 2006
Telecommunication Systems, 2012
The quality perceived by the user, a concept known as Quality of user Experience (QoE), is gainin... more The quality perceived by the user, a concept known as Quality of user Experience (QoE), is gaining momentum. Together with the efforts of providing appropriate architectures able to deliver the expected level of Quality of Service (QoS), users' perception of the level of quality could play a key role in making a VoIP multimedia application to succeed or to fail. QoE can be measured from different approaches; subjective ones are based on polls while objective ones are mainly based on QoS network performance parameters. Although a subjective evaluation could be costly and time consuming, it gives the most accurate results. Moreover, wireless environments incorporate new challenges in terms of QoS and QoE because of inherent wireless communication characteristics. In this way, our contribution is twofold. First, we carry out a subjective QoE assessment for VoIP applications in a real wireless environment. Skype, Gizmo5, ooVoo, and Damaka are the selected VoIP applications under study. Next, we contrast QoE results with QoS evaluation from the captured video calls made during the poll. Results show that there is no precise match on both assessments, because of QoE parameters that cannot be inferred from QoS analysis, because of the different effect of some QoS parameters which prevail, or even because of the popularity of the VoIP application.
Uploads
Papers by Fernando Cerdan