Browsing by Author "Guerri, Juan Carlos"

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Altruistic networks: where every node matters
(Nova Science, 2014) Arce Vila, Pau; Guerri, Juan Carlos; González Martínez, Santiago Renán
Traditionally, wireless ad hoc networks have been used for emergency situations due to the feasibility of fast deployment and connectivity. However, multimedia services are much demanded nowadays and bandwidth and delay requirements of this kind of services are very restrictive. Offering real-time video services in wireless ad hoc networks is not an easy task because of the difficulty of guaranteeing certain quality in a shared medium. In this kind of network, nodes should be ready to route and forward data packets coming from other nodes. The cooperation of every node is essential for the proper operation of the network because there are many factors that may cause video quality degradation, from radio interferences to node mobility, which causes link breakages until a new route is calculated, producing annoying video interruptions to the receiver. The variability in network capacity and link quality, together with the dynamic network topology, has clearly influenced emerging wireless mesh networks, which tend to maintain a static backbone in order to provide sufficient Quality of Service. Moreover, since wireless propagation nature allows any node to overhear any neighbor transmission, the way opportunistic and cooperative routing protocols take advantage of the broadcast nature of wireless medium can be adopted for new routing proposals. In this sense, this chapter proposes and describes a new cross-layer mechanism for recovering lost packets by means of caching overheard packets in neighbor nodes and retransmit them to destination. Additionally, a video-aware cache is implemented in order to recover full frames and prioritize more significant frames. On the other hand, energy consumption is critical in mobile nodes because they may rely on battery power, and the whole network connectivity may be affected if some of the routing nodes run out of battery eventually. Thus, energy consumption is also taken into account in the recovering algorithm design to ensure longer network connectivity life. Finally, results show the improvement in reception, increasing the throughput as well as video quality, and reduce large video interruptions considerably. Moreover, by being aware of nodes energy consumption, the proposed algorithm is able to maintain network lifetime longer.
Buffering technique for optimizing energy consumption in the transmission of multimedia traffic in Ad-Hoc networks
(2015) González Martínez, Santiago Renán; Arce, Pau; Guerri, Juan Carlos
Energy constraints on wireless nodes represent a current field of research. Such restrictions are particularly significant because of the great amount of features and applications currently available on devices, which contribute to dramatically increase energy consumption. However, when transmitting delay-sensitive data, such as multimedia streaming, a balance between energy optimization and quality of service is required. In this sense, there are many works that address this issue from different layers of network architecture separately; however, a more efficient solution could be achieved by combining the management capabilities of the different layers and the joint use of such information, which is called a cross-layer mechanism. Moreover, despite the fact that the IEEE 802.11 standard defines an energy management mechanism at MAC level, it is envisaged only for structured networks, leaving just general guidelines for other kind of networks, such as Ad-Hoc networks. Therefore, as a first step towards the design of a cross-layer scheme, this paper analyzes the flaws of IEEE 802.11 standard as regards the infrastructureless mode and proposes an optimization mechanism for energy management in Ad-Hoc networks. The proposed approach is based on a buffering mechanism, which is able to increase power-saving periods of time in Ad-Hoc nodes. Simulations using NS3 indicate that it is possible to obtain higher levels of residual energy at the end of a transmission using the proposed scheme
Energy optimization for video monitoring system in agricultural areas using single board computer nodes and wireless ad hoc networks
(Institute of Electrical and Electronics Engineers, 2016) González Martínez, Santiago Renán; Vargas, Tito; Guerri, Juan Carlos; Arce, Pau; Vargas, Tito
This paper presents the design and implementation of a set of prototype nodes that have the ability to establish communication links in ad hoc mode. The prototypes were implemented using low cost, single board computers with embedded Linux (Raspberry Pi devices). The implemented stations aim to set a wireless sensor network for the capture of variables applied to agricultural environments. In particular, a camera module has been included on a node for remote video monitoring of farming zones, and also a GPS module for the capture of geolocation information. Nodes can be accessed remotely by means of the developed web interface. The routing process between nodes is carried out using the S-OLSR mechanism (OLSR modification) in order to set up routes taking into account the energy limitations as well as the location of each device in the topology. Results describe the contribution of this work to the design of monitoring applications on agricultural zones by means of the deployment of autonomous ad hoc nodes and energy routing optimization.
Simulation and experimental testbed for adaptive video streaming in ad hoc networks
(2016) González Martínez, Santiago Renán; Castellanos, Wilder; Guzman, Paola; Arce, Pau; Guerri, Juan Carlos
This paper presents a performance evaluation of the scalable video streaming over mobile ad hoc networks. In particular, we focus on the rate-adaptive method for streaming scalable video (H.264/SVC). For effective adaptation a new cross-layer routing protocol is introduced. This protocol provides an efficient algorithm for available bandwidth estimation. With this information, the video source adjusts its bit rate during the video transmission according to the network state. We also propose a free simulation framework that supports evaluation studies for scalable video streaming. The simulation experiments performed in this study involve the transmission of SVC streams with Medium Grain Scalability (MGS) as well as temporal scalability over different network scenarios. The results reveal that the rate-adaptive strategy helps avoid or reduce the congestion in MANETs obtaining a better quality in the received videos. Additionally, an actual ad hoc network was implemented using embedded devices (Raspberry Pi) in order to assess the performance of the proposed adaptive transmission mechanism in a real environment. Additional experiments were carried out prior to the implementation with the aim of characterizing the wireless medium and packet loss profile. Finally, the proposed approach shows an important reduction in energy consumption, as the study revealed.
Simulation and testbed evaluation for optimizing energy consumption in ad hoc networks based on OLSR protocol
(SciTePress, 2016) Arce, Pau; González Martínez, Santiago Renán; Guerri, Juan Carlos; González Martínez, Santiago Renán
This paper presents a proposal to optimize energy consumption in ad hoc networks based on the OLSR protocol. This approach focuses on the set up of routes with less congestion level and higher energy capacity. Therefore, in addition to the remaining energy of nodes, a new metric is introduced, the strategic value, which reports the importance of a specific node in the network based on the numbers of neighbors it has. In order to obtain valuable results, the evaluation was performed in a simulation environment (NS3) and on a real testbed. In that sense, an actual ad hoc network was implemented using embedded devices (Raspberry Pi). Results show a decrease in energy consumption, especially in zones with the highest device density, as well as an increase of the time of operation for nodes with higher amount of neighbors. Additionally, the performed evaluation shows a positive effect in the quality of traffic flows, avoiding route breakages and packet losses.