Jesús Llor

Bio: Jesús Llor is an academic researcher from Universidad Miguel Hernández de Elche. The author has contributed to research in topics: Network simulation & Underwater acoustics. The author has an hindex of 5, co-authored 6 publications receiving 95 citations.

Underwater Wireless Sensor Networks: How Do Acoustic Propagation Models Impact the Performance of Higher-Level Protocols?

Abstract: Several Medium Access Control (MAC) and routing protocols have been developed in the last years for Underwater Wireless Sensor Networks (UWSNs). One of the main difficulties to compare and validate the performance of different proposals is the lack of a common standard to model the acoustic propagation in the underwater environment. In this paper we analyze the evolution of underwater acoustic prediction models from a simple approach to more detailed and accurate models. Then, different high layer network protocols are tested with different acoustic propagation models in order to determine the influence of environmental parameters on the obtained results. After several experiments, we can conclude that higher-level protocols are sensitive to both: (a) physical layer parameters related to the network scenario and (b) the acoustic propagation model. Conditions like ocean surface activity, scenario location, bathymetry or floor sediment composition, may change the signal propagation behavior. So, when designing network architectures for UWSNs, the role of the physical layer should be seriously taken into account in order to assert that the obtained simulation results will be close to the ones obtained in real network scenarios.

Analyzing the behavior of acoustic link models in underwater wireless sensor networks

Abstract: In the last years, wireless sensor networks have been proposed for their deployment in underwater environments where a lot of applications like aquiculture, pollution monitoring and offshore exploration would benefit from this technology. Despite having a very similar functionality, Underwater Wireless Sensor Networks (UWSNs) exhibit several architectural differences with respect to the terrestrial ones, which are mainly due to the transmission medium characteristics (sea water) and the signal employed to transmit data (acoustic ultrasound signals). So, the design of appropriate network architecture for UWSNs is seriously hardened by the specific characteristics of the communication system. In this work we analyze several acoustic channel models for their use in underwater wireless sensor network architectures. For that purpose, we have implemented them by using the OPNET Modeler tool in order to perform an evaluation of their behavior under different network scenarios. Finally, some conclusions are drawn showing the impact on UWSN performance of different elements of channel model and particular specific environment conditions

Statistical modeling of large-scale signal path loss in underwater acoustic networks.

Abstract: In an underwater acoustic channel, the propagation conditions are known to vary in time, causing the deviation of the received signal strength from the nominal value predicted by a deterministic propagation model. To facilitate a large-scale system design in such conditions (e.g., power allocation), we have developed a statistical propagation model in which the transmission loss is treated as a random variable. By applying repetitive computation to the acoustic field, using ray tracing for a set of varying environmental conditions (surface height, wave activity, small node displacements around nominal locations, etc.), an ensemble of transmission losses is compiled and later used to infer the statistical model parameters. A reasonable agreement is found with log-normal distribution, whose mean obeys a log-distance increases, and whose variance appears to be constant for a certain range of inter-node distances in a given deployment location. The statistical model is deemed useful for higher-level system planning, where simulation is needed to assess the performance of candidate network protocols under various resource allocation policies, i.e., to determine the transmit power and bandwidth allocation necessary to achieve a desired level of performance (connectivity, throughput, reliability, etc.).

Performance evaluation of underwater wireless sensor networks with OPNET

Abstract: One of the main difficulties when modeling Underwater Wireless Sensor Network (UWSN) has to do with the environment characteristics and the acoustic signal typically used. As stated in other works, the accuracy of the acoustic propagation model and the network scenario conditions are critical to obtain reliable results. In this work we proposed a simulator framework for UWSN modeling. For that purpose we have considered the information provided by global databases (temperature, salinity, etc.) located within the network. Namely, the bathymetry and floor sediment, node depth, wave effect, and other factors may affect to the underwater signal propagation behavior. The propagation model is calculated using Bellhop ray tracing tool in order to get the closest representation to the real behavior of the acoustic signal propagation. All these tools are integrated in OPNET Modeler. Finally, we have run several experiments in different locations testing network performance with a simple MAC protocol.

A simulation analysis of large scale path loss in an underwater acoustic network

Abstract: Propagation conditions in an underwater acoustic channel are known to vary in time, causing the received signal strength to deviate from the nominal value predicted by a deterministic propagation model. To facilitate large-scale system design in such conditions (e.g. power allocation), we develop a statistical propagation model in which the transmission loss is treated as a random variable. By repetitive computation of acoustic field using ray tracing for a set of varying environmental conditions (surface height, wave activity, small displacements of transmitter and receiver around nominal locations), an ensemble of transmission losses is compiled which is then used to infer the statistical model parameters. A reasonable agreement is found with log-normal distribution, whose mean obeys a log-distance increases, and whose variance appears to be constant for a certain range of inter-node distances in a given deployment location. The statistical model is deemed useful for higher-level system planning, where simulation is needed to assess the performance of candidate network protocols under various resource allocation policies, i.e. to determine the transmit power and bandwidth allocation necessary to achieve a desired level of performance (connectivity, throughput, reliability, etc.).

Underwater Acoustic Wireless Sensor Networks: Advances and Future Trends in Physical, MAC and Routing Layers

Abstract: This survey aims to provide a comprehensive overview of the current research on underwater wireless sensor networks, focusing on the lower layers of the communication stack, and envisions future trends and challenges. It analyzes the current state-of-the-art on the physical, medium access control and routing layers. It summarizes their security threads and surveys the currently proposed studies. Current envisioned niches for further advances in underwater networks research range from efficient, low-power algorithms and modulations to intelligent, energy-aware routing and medium access control protocols.

An Energy Efficient Localization-Free Routing Protocol for Underwater Wireless Sensor Networks

Abstract: Recently, underwater wireless sensor networks (UWSNs) have attracted much research attention from both academia and industry, in order to explore the vast underwater environment. UWSNs have peculiar characteristics; that is, they have large propagation delay, high error rate, low bandwidth, and limited energy. Therefore, designing network/routing protocols for UWSNs is very challenging. Also, in UWSNs, improving the energy efficiency is one of the most important issues since the replacement of the batteries of underwater sensor nodes is very expensive due to the unpleasant underwater environment. In this paper, we therefore propose an energy efficient routing protocol, named (energy-efficient depth-based routing protocol) EEDBR for UWSNs. EEDBR utilizes the depth of sensor nodes for forwarding data packets. Furthermore, the residual energy of sensor nodes is also taken into account in order to improve the network lifetime. Based on the comprehensive simulation using NS2, we observe that EEDBR contributes to the performance improvements in terms of the network lifetime, energy consumption, and end-to-end delay. A previous version of this paper was accepted in AST-2011 conference.

EEDBR: Energy-Efficient Depth-Based Routing Protocol for Underwater Wireless Sensor Networks

Abstract: Recently, Underwater Wireless Sensor Networks (UWSNs) have attracted much research attention from both academia and industry, in order to explore the vast underwater environment However, designing network protocols is challenging in UWSNs since UWSNs have peculiar characteristics of large propagation delay, high error rate, low bandwidth and limited energy In UWSNs, improving the energy efficiency is one of the most important issues since the replacement of the batteries of such nodes is very expensive due to harsh underwater environment Hence, in this paper, we propose an energy efficient routing protocol, named EEDBR (Energy-Efficient Depth Based Routing protocol) for UWSNs Our proposed protocol utilizes the depth of the sensor nodes for forwarding the data packets Furthermore, the residual energy of the sensor nodes is also taken into account in order to improve the network life-time Based on the comprehensive simulation using NS2, we observe that our proposed routing protocol contributes to the performance improvements in terms of the network lifetime, energy consumption and end-to-end delay

A survey on deployment techniques, localization algorithms, and research challenges for underwater acoustic sensor networks

Abstract: Summary In recent years, wireless sensor networks (WSNs) have attracted the attention of both the research community and the industry, and this has eventually lead to the widespread use of WSNs in various applications. The significant advancements in WSNs and the advantages brought by WSNs have also enabled the rapid development of underwater acoustic sensor networks (UASNs). In UASNs, in addition to deployment, determining the locations of underwater sensor nodes after they have been deployed is important since it plays a critical role in many applications. Various localization techniques have been proposed for UASNs, and each one is suitable for specific scenarios and has unique challenges. In this paper, after presenting an overview of potential UASN applications, a survey of the deployment techniques and localization algorithms for UASNs has been presented based on their major advantages and disadvantages. Finally, research challenges and open research issues of UASNs have been discussed to provide an insight into future research opportunities.

A reliable energy-efficient pressure-based routing protocol for underwater wireless sensor network

Abstract: Recently, Underwater Wireless Sensor Networks (UWSNs) has witnessed significant attention from both academia and industries in research and development, due to the growing number of applications for wide range of purposes including commercial, scientific, environmental and military. Some of the major applications include pollution monitoring, tactical surveillance, tsunami warnings and offshore exploration. Efficient communication among sensors in UWSNs is a challenging task due to the harsh environments and peculiar characteristics of UWSNs. Therefore, design of routing protocol for efficient communication among sensors and sink is one of the fundamental research themes in UWSNs. In this context, this paper proposes a location-free Reliable and Energy efficient Pressure-Based Routing (RE-PBR) protocol for UWSNs. RE-PBR considers three parameters including link quality, depth and residual energy for balancing energy consumption and reliable data delivery. Specifically, link quality is estimated using triangle metric method. A light weight information acquisition algorithm is developed for efficient knowledge discovery of the network. Multi-metric data forwarding algorithm is designed based on route cost calculation which utilizes residual energy and link quality. Simulations are carried out in NS-2 with Aqua-Sim package to evaluate the performance of RE-PBR. The performance of the proposed protocol is compared with the stat-of-the-art techniques: DBR and EEDBR. The comprehensive performance evaluation attests the benefit of RE-PBR as compared to the state-of-the-art techniques in terms of network lifetime, energy consumption, end-to-end delay and packet delivery ratio.