Sandra Sendra | Universidad de Granada (original) (raw)
Papers by Sandra Sendra
Cloud-based communications system is now widely used in many application fields such as medicine,... more Cloud-based communications system is now widely used in many application fields such as medicine, security, environment protection, etc. Its use is being extended to the most demanding services like multimedia delivery. However, there are a lot of constraints when cloud-based sensor networks use the standard IEEE 802.15.3 or IEEE 802.15.4 technologies. This paper proposes a channel characterization scheme combined to a cross-layer admission control in dynamic cloud-based multimedia sensor networks to share the network resources among any two nodes. The analysis shows the behavior of two nodes using different network access technologies and the channel effects for each technology. Moreover, the existence of optimal node arrival rates in order to improve the usage of dynamic admission control when network resources are used is also shown. An extensive simulation study was performed to evaluate and validate the efficiency of the proposed dynamic admission control for cloud-based multimedia sensor networks.
Sensors (Basel, Switzerland), 2011
The first step to detect when a vineyard has any type of deficiency, pest or disease is to observ... more The first step to detect when a vineyard has any type of deficiency, pest or disease is to observe its stems, its grapes and/or its leaves. To place a sensor in each leaf of every vineyard is obviously not feasible in terms of cost and deployment. We should thus look for new methods to detect these symptoms precisely and economically. In this paper, we present a wireless sensor network where each sensor node takes images from the field and internally uses image processing techniques to detect any unusual status in the leaves. This symptom could be caused by a deficiency, pest, disease or other harmful agent. When it is detected, the sensor node sends a message to a sink node through the wireless sensor network in order to notify the problem to the farmer. The wireless sensor uses the IEEE 802.11 a/b/g/n standard, which allows connections from large distances in open air. This paper describes the wireless sensor network design, the wireless sensor deployment, how the node processes the images in order to monitor the vineyard, and the sensor network traffic obtained from a test bed performed in a flat vineyard in Spain. Although the system is not able to distinguish between deficiency, pest, disease or other harmful agents, a symptoms image database and a neuronal network could be added in order learn from the experience and provide an accurate problem diagnosis.
Sensors, 2009
Forest and rural fires are one of the main causes of environmental degradation in Mediterranean c... more Forest and rural fires are one of the main causes of environmental degradation in Mediterranean countries. Existing fire detection systems only focus on detection, but not on the verification of the fire. However, almost all of them are just simulations, and very few implementations can be found. Besides, the systems in the literature lack scalability. In this paper we show all the steps followed to perform the design, research and development of a wireless multisensor network which mixes sensors with IP cameras in a wireless network in order to detect and verify fire in rural and forest areas of Spain. We have studied how many cameras, sensors and access points are needed to cover a rural or forest area, and the scalability of the system. We have developed a multisensor and when it detects a fire, it sends a sensor alarm through the wireless network to a central server. The central server selects the closest wireless cameras to the multisensor, based on a software application, which are rotated to the sensor that raised the alarm, and sends them a message in order to receive real-time images from the zone. The camera lets the fire fighters corroborate the existence of a fire and avoid false alarms. In this paper, we show the test performance given by a test bench formed by four wireless IP cameras in several situations and the energy consumed when they are transmitting. Moreover, we study the energy consumed by each device when the system is set up. The wireless sensor network could be connected to Internet through a gateway and the images of the cameras could be seen from any part of the world.
Sensors (Basel, Switzerland), 2012
One of the main problems in underwater communications is the low data rate available due to the u... more One of the main problems in underwater communications is the low data rate available due to the use of low frequencies. Moreover, there are many problems inherent to the medium such as reflections, refraction, energy dispersion, etc., that greatly degrade communication between devices. In some cases, wireless sensors must be placed quite close to each other in order to take more accurate measurements from the water while having high communication bandwidth. In these cases, while most researchers focus their efforts on increasing the data rate for low frequencies, we propose the use of the 2.4 GHz ISM frequency band in these special cases. In this paper, we show our wireless sensor node deployment and its performance obtained from a real scenario and measures taken for different frequencies, modulations and data transfer rates. The performed tests show the maximum distance between sensors, the number of lost packets and the average round trip time. Based on our measurements, we provide some experimental models of underwater communication in fresh water using EM waves in the 2.4 GHz ISM frequency band. Finally, we compare our communication system proposal with the existing systems. Although our proposal provides short communication distances, it provides high data transfer rates. It can be used for precision monitoring in applications such as contaminated ecosystems or for device communicate at high depth.
Recent Advances in Communications and Networking Technology, 2014
Proceedings of the 7th International Conference on Cooperative Design Visualization and Engineering, 2010
Wireless Sensor Networks (WSNs) can be used in many applications, but it is most used in environm... more Wireless Sensor Networks (WSNs) can be used in many applications, but it is most used in environmental monitoring. The energy consumption of each node should be as low as possible, and the collaborative methods can improve their performance. In this work, we compare the energy consumption of a regular WSN with a WSN in which the nodes are organized in
Journal of Sensors
ABSTRACT
Lecture Notes in Computer Science, 2015
2015 IEEE International Conference on Communication Workshop (ICCW), 2015
ABSTRACT
Sensors, 2015
The main aim of smart cities is to achieve the sustainable use of resources. In order to make the... more The main aim of smart cities is to achieve the sustainable use of resources. In order to make the correct use of resources, an accurate monitoring and management is needed. In some places, like underground aquifers, access for monitoring can be difficult, therefore the use of sensors can be a good solution. Groundwater is very important as a water resource. Just in the USA, aquifers represent the water source for 50% of the population. However, aquifers are endangered due to the contamination. One of the most important parameters to monitor in groundwater is the salinity, as high salinity levels indicate groundwater salinization. In this paper, we present a specific sensor for monitoring groundwater salinization. The sensor is able to measure the electric conductivity of water, which is directly related to the water salinization. The sensor, which is composed of two copper coils, measures the magnetic field alterations due to the presence of electric charges in the water. Different salinities of the water generate different alterations. Our sensor has undergone several tests in order to obtain a conductivity sensor with enough accuracy.
Journal of Sensors, 2015
ABSTRACT
Peer-to-Peer Networking and Applications, 2015
IEEE Sensors Journal, 2015
ABSTRACT Due to the growing interest using underwater acoustic networks, there are more and more ... more ABSTRACT Due to the growing interest using underwater acoustic networks, there are more and more research papers about underwater communications. These papers are mainly focused on deployments and studies about the constraints of the underwater medium. The underwater acoustic channel is highly variable and the signal transmission can change according to environmental factors such as the temperature, pressure or salinity of the water. For this reason, it is important to know how these devices are developed and the maximum distance and data transfer rates they can achieve. To this end, this paper presents an exhaustive study of existing underwater acoustic modems where their main features are highlighted. We also review the main features of their hardware. All presented proposals in the research literature are compared with commercial underwater acoustic modems. Finally, we analyze different programs and improvements of existing network simulators that are often used to simulate and estimate the behavior of underwater networks.
International Journal of Distributed Sensor Networks, 2015
In last decade, there have been many research works about wireless sensor networks (WSNs) focused... more In last decade, there have been many research works about wireless sensor networks (WSNs) focused on improving the network performance as well as increasing the energy efficiency and communications effectiveness. Many of these new mechanisms have been implemented using the behaviors of certain animals, such as ants, bees, or schools of fish. These systems are called bioinspired systems and are used to improve aspects such as handling large-scale networks, provide dynamic nature, and avoid resource constraints, heterogeneity, unattended operation, or robustness, among many others. Therefore, this paper aims to study bioinspired mechanisms in the field of WSN, providing the concepts of these behavior patterns in which these new approaches are based. The paper will explain existing bioinspired systems in WSNs and analyze their impact on WSNs and their evolution. In addition, we will conduct a comprehensive review of recently proposed bioinspired systems, protocols, and mechanisms. Finally, this paper will try to analyze the applications of each bioinspired mechanism as a function of the imitated animal and the deployed application. Although this research area is considered an area with highly theoretical content, we intend to show the great impact that it is generating from the practical perspective.
Wireless signals present particular behaviour in indoor environments. Walls, roofs and floors gen... more Wireless signals present particular behaviour in indoor environments. Walls, roofs and floors generate reflections and refractions that conduce to constructive and destructive interferences due to the multipath effect. In this paper, we perform an analytical study based on the signal strength generated by an access point (AP) inside a building. The evolution of the signal strength allows us to move away the sensors from the AP without reducing the signal level and link quality. We study the IEEE 802.11 technology. These results are compared with the theoretical distribution channels to know what should be followed to avoid interferences. Finally, taking as a reference the measures provided, we develop a method for estimating indoor signal strength that will help us determine the best position for wireless sensors. Our method will allow saving 15% of sensors. The reduction in the number of sensors provides us economic and energy savings, allowing us to prolong the network lifetime.
Nowadays, Wireless Sensor Networks are a hot research topic in the scientific community. Research... more Nowadays, Wireless Sensor Networks are a hot research topic in the scientific community. Researchers seek to maximize their autonomy while paying attention to their limited resources, few computing capacity and low energy consumption. Security mechanisms must be deployed in the architecture of almost all Wireless Sensor Networks. Several research papers have verified that group-based communications improve the efficiency of the network. For this reason, a secure group-based architecture for wireless sensor networks is described in this paper. First, we will explain the methods of key creation and how they are used. Then, the key management method, which is used to determine the tasks performed by the nodes to maintain the keys updated, is detailed. The process of secure communication between groups is also explained. Finally, energy consumption measurements for each protocol operation are shown.
2014 IEEE 16th International Conference on e-Health Networking, Applications and Services (Healthcom), 2014
Lecture Notes in Computer Science, 2015
Cloud-based communications system is now widely used in many application fields such as medicine,... more Cloud-based communications system is now widely used in many application fields such as medicine, security, environment protection, etc. Its use is being extended to the most demanding services like multimedia delivery. However, there are a lot of constraints when cloud-based sensor networks use the standard IEEE 802.15.3 or IEEE 802.15.4 technologies. This paper proposes a channel characterization scheme combined to a cross-layer admission control in dynamic cloud-based multimedia sensor networks to share the network resources among any two nodes. The analysis shows the behavior of two nodes using different network access technologies and the channel effects for each technology. Moreover, the existence of optimal node arrival rates in order to improve the usage of dynamic admission control when network resources are used is also shown. An extensive simulation study was performed to evaluate and validate the efficiency of the proposed dynamic admission control for cloud-based multimedia sensor networks.
Sensors (Basel, Switzerland), 2011
The first step to detect when a vineyard has any type of deficiency, pest or disease is to observ... more The first step to detect when a vineyard has any type of deficiency, pest or disease is to observe its stems, its grapes and/or its leaves. To place a sensor in each leaf of every vineyard is obviously not feasible in terms of cost and deployment. We should thus look for new methods to detect these symptoms precisely and economically. In this paper, we present a wireless sensor network where each sensor node takes images from the field and internally uses image processing techniques to detect any unusual status in the leaves. This symptom could be caused by a deficiency, pest, disease or other harmful agent. When it is detected, the sensor node sends a message to a sink node through the wireless sensor network in order to notify the problem to the farmer. The wireless sensor uses the IEEE 802.11 a/b/g/n standard, which allows connections from large distances in open air. This paper describes the wireless sensor network design, the wireless sensor deployment, how the node processes the images in order to monitor the vineyard, and the sensor network traffic obtained from a test bed performed in a flat vineyard in Spain. Although the system is not able to distinguish between deficiency, pest, disease or other harmful agents, a symptoms image database and a neuronal network could be added in order learn from the experience and provide an accurate problem diagnosis.
Sensors, 2009
Forest and rural fires are one of the main causes of environmental degradation in Mediterranean c... more Forest and rural fires are one of the main causes of environmental degradation in Mediterranean countries. Existing fire detection systems only focus on detection, but not on the verification of the fire. However, almost all of them are just simulations, and very few implementations can be found. Besides, the systems in the literature lack scalability. In this paper we show all the steps followed to perform the design, research and development of a wireless multisensor network which mixes sensors with IP cameras in a wireless network in order to detect and verify fire in rural and forest areas of Spain. We have studied how many cameras, sensors and access points are needed to cover a rural or forest area, and the scalability of the system. We have developed a multisensor and when it detects a fire, it sends a sensor alarm through the wireless network to a central server. The central server selects the closest wireless cameras to the multisensor, based on a software application, which are rotated to the sensor that raised the alarm, and sends them a message in order to receive real-time images from the zone. The camera lets the fire fighters corroborate the existence of a fire and avoid false alarms. In this paper, we show the test performance given by a test bench formed by four wireless IP cameras in several situations and the energy consumed when they are transmitting. Moreover, we study the energy consumed by each device when the system is set up. The wireless sensor network could be connected to Internet through a gateway and the images of the cameras could be seen from any part of the world.
Sensors (Basel, Switzerland), 2012
One of the main problems in underwater communications is the low data rate available due to the u... more One of the main problems in underwater communications is the low data rate available due to the use of low frequencies. Moreover, there are many problems inherent to the medium such as reflections, refraction, energy dispersion, etc., that greatly degrade communication between devices. In some cases, wireless sensors must be placed quite close to each other in order to take more accurate measurements from the water while having high communication bandwidth. In these cases, while most researchers focus their efforts on increasing the data rate for low frequencies, we propose the use of the 2.4 GHz ISM frequency band in these special cases. In this paper, we show our wireless sensor node deployment and its performance obtained from a real scenario and measures taken for different frequencies, modulations and data transfer rates. The performed tests show the maximum distance between sensors, the number of lost packets and the average round trip time. Based on our measurements, we provide some experimental models of underwater communication in fresh water using EM waves in the 2.4 GHz ISM frequency band. Finally, we compare our communication system proposal with the existing systems. Although our proposal provides short communication distances, it provides high data transfer rates. It can be used for precision monitoring in applications such as contaminated ecosystems or for device communicate at high depth.
Recent Advances in Communications and Networking Technology, 2014
Proceedings of the 7th International Conference on Cooperative Design Visualization and Engineering, 2010
Wireless Sensor Networks (WSNs) can be used in many applications, but it is most used in environm... more Wireless Sensor Networks (WSNs) can be used in many applications, but it is most used in environmental monitoring. The energy consumption of each node should be as low as possible, and the collaborative methods can improve their performance. In this work, we compare the energy consumption of a regular WSN with a WSN in which the nodes are organized in
Journal of Sensors
ABSTRACT
Lecture Notes in Computer Science, 2015
2015 IEEE International Conference on Communication Workshop (ICCW), 2015
ABSTRACT
Sensors, 2015
The main aim of smart cities is to achieve the sustainable use of resources. In order to make the... more The main aim of smart cities is to achieve the sustainable use of resources. In order to make the correct use of resources, an accurate monitoring and management is needed. In some places, like underground aquifers, access for monitoring can be difficult, therefore the use of sensors can be a good solution. Groundwater is very important as a water resource. Just in the USA, aquifers represent the water source for 50% of the population. However, aquifers are endangered due to the contamination. One of the most important parameters to monitor in groundwater is the salinity, as high salinity levels indicate groundwater salinization. In this paper, we present a specific sensor for monitoring groundwater salinization. The sensor is able to measure the electric conductivity of water, which is directly related to the water salinization. The sensor, which is composed of two copper coils, measures the magnetic field alterations due to the presence of electric charges in the water. Different salinities of the water generate different alterations. Our sensor has undergone several tests in order to obtain a conductivity sensor with enough accuracy.
Journal of Sensors, 2015
ABSTRACT
Peer-to-Peer Networking and Applications, 2015
IEEE Sensors Journal, 2015
ABSTRACT Due to the growing interest using underwater acoustic networks, there are more and more ... more ABSTRACT Due to the growing interest using underwater acoustic networks, there are more and more research papers about underwater communications. These papers are mainly focused on deployments and studies about the constraints of the underwater medium. The underwater acoustic channel is highly variable and the signal transmission can change according to environmental factors such as the temperature, pressure or salinity of the water. For this reason, it is important to know how these devices are developed and the maximum distance and data transfer rates they can achieve. To this end, this paper presents an exhaustive study of existing underwater acoustic modems where their main features are highlighted. We also review the main features of their hardware. All presented proposals in the research literature are compared with commercial underwater acoustic modems. Finally, we analyze different programs and improvements of existing network simulators that are often used to simulate and estimate the behavior of underwater networks.
International Journal of Distributed Sensor Networks, 2015
In last decade, there have been many research works about wireless sensor networks (WSNs) focused... more In last decade, there have been many research works about wireless sensor networks (WSNs) focused on improving the network performance as well as increasing the energy efficiency and communications effectiveness. Many of these new mechanisms have been implemented using the behaviors of certain animals, such as ants, bees, or schools of fish. These systems are called bioinspired systems and are used to improve aspects such as handling large-scale networks, provide dynamic nature, and avoid resource constraints, heterogeneity, unattended operation, or robustness, among many others. Therefore, this paper aims to study bioinspired mechanisms in the field of WSN, providing the concepts of these behavior patterns in which these new approaches are based. The paper will explain existing bioinspired systems in WSNs and analyze their impact on WSNs and their evolution. In addition, we will conduct a comprehensive review of recently proposed bioinspired systems, protocols, and mechanisms. Finally, this paper will try to analyze the applications of each bioinspired mechanism as a function of the imitated animal and the deployed application. Although this research area is considered an area with highly theoretical content, we intend to show the great impact that it is generating from the practical perspective.
Wireless signals present particular behaviour in indoor environments. Walls, roofs and floors gen... more Wireless signals present particular behaviour in indoor environments. Walls, roofs and floors generate reflections and refractions that conduce to constructive and destructive interferences due to the multipath effect. In this paper, we perform an analytical study based on the signal strength generated by an access point (AP) inside a building. The evolution of the signal strength allows us to move away the sensors from the AP without reducing the signal level and link quality. We study the IEEE 802.11 technology. These results are compared with the theoretical distribution channels to know what should be followed to avoid interferences. Finally, taking as a reference the measures provided, we develop a method for estimating indoor signal strength that will help us determine the best position for wireless sensors. Our method will allow saving 15% of sensors. The reduction in the number of sensors provides us economic and energy savings, allowing us to prolong the network lifetime.
Nowadays, Wireless Sensor Networks are a hot research topic in the scientific community. Research... more Nowadays, Wireless Sensor Networks are a hot research topic in the scientific community. Researchers seek to maximize their autonomy while paying attention to their limited resources, few computing capacity and low energy consumption. Security mechanisms must be deployed in the architecture of almost all Wireless Sensor Networks. Several research papers have verified that group-based communications improve the efficiency of the network. For this reason, a secure group-based architecture for wireless sensor networks is described in this paper. First, we will explain the methods of key creation and how they are used. Then, the key management method, which is used to determine the tasks performed by the nodes to maintain the keys updated, is detailed. The process of secure communication between groups is also explained. Finally, energy consumption measurements for each protocol operation are shown.
2014 IEEE 16th International Conference on e-Health Networking, Applications and Services (Healthcom), 2014
Lecture Notes in Computer Science, 2015