The Graph Signal Processing (GSP) is a mathematical framework that extends the Discrete Signal Pr... more The Graph Signal Processing (GSP) is a mathematical framework that extends the Discrete Signal Processing (DSP) tools such as filtering and signals decomposition to graph data structures. In this paper, we explore the application of the GSP framework to distributed wireless sensor networks to reduce the measured noise and/or estimate the signal of missing sensors. The context is that of distributed monitoring applications, such as the monitoring of large buildings, such as hospitals, public areas and farmlands. Using simulation tools, we analysed the ability of GSP in reducing the noise and in estimating sensor's data in different WSN scenarios. We modelled the sensor networks as Graph structures and apply Graph Shift and Graph Laplacian operations on such graph signals. The analysis of obtained results shows that GSP may represent a valuable tool in the considered scenarios with outstanding performance.
Wireless mesh networks (WMN) provide rapidly deployable, cost effective and flexible communicatio... more Wireless mesh networks (WMN) provide rapidly deployable, cost effective and flexible communication infrastructures. WMNs are particularly useful in the case of disaster, allowing rescuers to build communication infrastructures that may facilitate their work and help them in saving lives. IEEE 802.11s is today the reference standard for wireless mesh networks (WMNs). The aim of this paper is to evaluate the performance of IEEE 802.11s in disaster scenarios when a robust Wireless infrastructures has to be built quickly out of nothing. In such scenarios, parameters like the time elapsed from the distribution of nodes in the area and the successful transmission of the first data packet, or the network delay, may be essential in order to save lives. The aim of this paper is to evaluate such parameters.
LoRaWAN is a Low Power Wide Area Network (LPWAN) technology which enables low cost and low power ... more LoRaWAN is a Low Power Wide Area Network (LPWAN) technology which enables low cost and low power IoT device communication even in dense urban areas. LoRa modulation is capable of extracting data from a weak signal in noisy environments. This modulation technique can be useful for the delivery of critical data in the noisy environment. In this study, we investigate LoRaWAN technology in the context of data transmission for health care systems (or critical health data in disaster environments). In the study, we explore the standard and evaluate data frame transmission in LoRaWAN with a custom test-bed system.
International Journal of Communication Systems, 2017
Summary Wireless hotspots, ie, infrastructures composed of several IEEE 802.11 access points (APs... more Summary Wireless hotspots, ie, infrastructures composed of several IEEE 802.11 access points (APs), are today the most common solution in providing Internet access to a wide and rapidly changing population of users. According to common device implementation, stations establish associations with APs based on the measured strongest Received Signal Strength Indicator level. This usually leads to an uneven distribution of users to APs, increasing the chances of local network congestion. Load balancing (LB) solutions aim at mitigating this problem controlling the distribution of users. The LB algorithms enforce stations to associate with APs that manage a low number of users and/or that have a low traffic load. Usually, LB solutions do not consider traffic priorities or they assume some a priori quality of service (QoS) configuration for users. In this study, we propose a QoS-LB solution based on the cell breathing technique with the goal of balancing the load in IEEE 802.11e Enhanced Distributed Channel Access (EDCA) Hotspots. The proposed algorithm explores the space of possible power/EDCA configurations by using a branch and bound approach that reduces the number of analyzed configurations and, hence, the time required to find the global optimal solution. The algorithm has been analytically defined and its performance evaluated through simulations and tests in a real test bed. The results prove that the proposed solution is effective in solving the optimal QoS-LB configuration problem in WiFi hotspots of average size.
2014 11th International Symposium on Wireless Communications Systems (ISWCS), 2014
Access Point (AP) selection in WiFi hotspots is driven by stations and it is based on the measure... more Access Point (AP) selection in WiFi hotspots is driven by stations and it is based on the measured strongest RSSI (Received Signal Strength Indicator) level: any station connects to the AP that provides the higher physical data rate. Although simple and effective in low crowded scenarios with low-medium traffic load, this strategy performs inefficiently when the number of mobile users is high and their distribution among APs is unbalanced, i.e. when network congestion becomes an issue. Load Balancing (LB) solutions aim at solving this problem by enforcing the connection of stations to the AP having either the smallest number of associated stations or the lowest traffic load. However, LB solutions do not account for traffic priorities or, when they consider them, they do not deal with the joint configuration of QoS (Quality of Service) and LB parameters. In this study we present a framework for modeling, analyzing and designing QoS-aware LB solutions. The proposed framework assumes that stations implement the Enhanced Distributed Channel Access (EDCA) mechanism of the IEEE 802.11e standard. Moreover, in order to make the framework concrete, we assume that the QoS goal is the weighted fair allocation of wireless resources. However, the framework is not restricted to this goal and can be easily extended in order to deal with a different cost function. The proposed framework is validated through simulations in a typical indoor LB scenario. The results show that the model is effective in capturing network performance and in designing LB solutions that account for traffic priorities and the configuration of QoS parameters.
Internet of Things (IoT) expansion led the market to find alternative communication technologies ... more Internet of Things (IoT) expansion led the market to find alternative communication technologies since existing protocols are insufficient in terms of coverage, energy consumption to fit IoT needs. Low Power Wide Area Networks (LPWAN) emerged as an alternative cost-effective communication technology for the IoT market. LoRaWAN is an open LPWAN standard developed by LoRa Alliance and has key features i.e., low energy consumption, long-range communication, builtin security, GPS-free positioning. In this paper, we will introduce LoRaWAN technology, the state of art studies in the literature and provide open opportunities.
Increasing demand on Internet of Things (IoT) requires specific communication technology to handl... more Increasing demand on Internet of Things (IoT) requires specific communication technology to handle low-cost power consumption and coverage requirements. Several Low Power Wide Area Network (LPWAN) technologies emerged; however, Long Range Wide Area Networks (LoRaWAN) is the key technology to address these issues. LoRaWAN uses a unique LoRa modulation to provide long range data communication with low power consumption; this will lead LoRaWAN to be the key technology for IoT infrastructures. In this study, LoRaWAN performance is analysed with an experimental TestBed environment by considering communication range, data rates, packet losses and energy consumption for indoor usage. Obtained results are summarized and discussed possible future research directions
For the last few years peer-to-peer (p2p) networks have become widely used tools for sharing any ... more For the last few years peer-to-peer (p2p) networks have become widely used tools for sharing any kind of information from multimedia data to text documents. The vast amount of shared information leads issues on finding relevant information over p2p networks. Existing p2p file search and information retrieval techniques are based on the name of files, which is insufficient when searching relevant documents. In this paper we present a method to perform semantic information retrieval over p2p networks. Our method semantically inspects the content of shared data in peers to generate conceptual information about documents and general information about the peer.
The Graph Signal Processing (GSP) is a mathematical framework that extends the Discrete Signal Pr... more The Graph Signal Processing (GSP) is a mathematical framework that extends the Discrete Signal Processing (DSP) tools such as filtering and signals decomposition to graph data structures. In this paper, we explore the application of the GSP framework to distributed wireless sensor networks to reduce the measured noise and/or estimate the signal of missing sensors. The context is that of distributed monitoring applications, such as the monitoring of large buildings, such as hospitals, public areas and farmlands. Using simulation tools, we analysed the ability of GSP in reducing the noise and in estimating sensor's data in different WSN scenarios. We modelled the sensor networks as Graph structures and apply Graph Shift and Graph Laplacian operations on such graph signals. The analysis of obtained results shows that GSP may represent a valuable tool in the considered scenarios with outstanding performance.
Wireless mesh networks (WMN) provide rapidly deployable, cost effective and flexible communicatio... more Wireless mesh networks (WMN) provide rapidly deployable, cost effective and flexible communication infrastructures. WMNs are particularly useful in the case of disaster, allowing rescuers to build communication infrastructures that may facilitate their work and help them in saving lives. IEEE 802.11s is today the reference standard for wireless mesh networks (WMNs). The aim of this paper is to evaluate the performance of IEEE 802.11s in disaster scenarios when a robust Wireless infrastructures has to be built quickly out of nothing. In such scenarios, parameters like the time elapsed from the distribution of nodes in the area and the successful transmission of the first data packet, or the network delay, may be essential in order to save lives. The aim of this paper is to evaluate such parameters.
LoRaWAN is a Low Power Wide Area Network (LPWAN) technology which enables low cost and low power ... more LoRaWAN is a Low Power Wide Area Network (LPWAN) technology which enables low cost and low power IoT device communication even in dense urban areas. LoRa modulation is capable of extracting data from a weak signal in noisy environments. This modulation technique can be useful for the delivery of critical data in the noisy environment. In this study, we investigate LoRaWAN technology in the context of data transmission for health care systems (or critical health data in disaster environments). In the study, we explore the standard and evaluate data frame transmission in LoRaWAN with a custom test-bed system.
International Journal of Communication Systems, 2017
Summary Wireless hotspots, ie, infrastructures composed of several IEEE 802.11 access points (APs... more Summary Wireless hotspots, ie, infrastructures composed of several IEEE 802.11 access points (APs), are today the most common solution in providing Internet access to a wide and rapidly changing population of users. According to common device implementation, stations establish associations with APs based on the measured strongest Received Signal Strength Indicator level. This usually leads to an uneven distribution of users to APs, increasing the chances of local network congestion. Load balancing (LB) solutions aim at mitigating this problem controlling the distribution of users. The LB algorithms enforce stations to associate with APs that manage a low number of users and/or that have a low traffic load. Usually, LB solutions do not consider traffic priorities or they assume some a priori quality of service (QoS) configuration for users. In this study, we propose a QoS-LB solution based on the cell breathing technique with the goal of balancing the load in IEEE 802.11e Enhanced Distributed Channel Access (EDCA) Hotspots. The proposed algorithm explores the space of possible power/EDCA configurations by using a branch and bound approach that reduces the number of analyzed configurations and, hence, the time required to find the global optimal solution. The algorithm has been analytically defined and its performance evaluated through simulations and tests in a real test bed. The results prove that the proposed solution is effective in solving the optimal QoS-LB configuration problem in WiFi hotspots of average size.
2014 11th International Symposium on Wireless Communications Systems (ISWCS), 2014
Access Point (AP) selection in WiFi hotspots is driven by stations and it is based on the measure... more Access Point (AP) selection in WiFi hotspots is driven by stations and it is based on the measured strongest RSSI (Received Signal Strength Indicator) level: any station connects to the AP that provides the higher physical data rate. Although simple and effective in low crowded scenarios with low-medium traffic load, this strategy performs inefficiently when the number of mobile users is high and their distribution among APs is unbalanced, i.e. when network congestion becomes an issue. Load Balancing (LB) solutions aim at solving this problem by enforcing the connection of stations to the AP having either the smallest number of associated stations or the lowest traffic load. However, LB solutions do not account for traffic priorities or, when they consider them, they do not deal with the joint configuration of QoS (Quality of Service) and LB parameters. In this study we present a framework for modeling, analyzing and designing QoS-aware LB solutions. The proposed framework assumes that stations implement the Enhanced Distributed Channel Access (EDCA) mechanism of the IEEE 802.11e standard. Moreover, in order to make the framework concrete, we assume that the QoS goal is the weighted fair allocation of wireless resources. However, the framework is not restricted to this goal and can be easily extended in order to deal with a different cost function. The proposed framework is validated through simulations in a typical indoor LB scenario. The results show that the model is effective in capturing network performance and in designing LB solutions that account for traffic priorities and the configuration of QoS parameters.
Internet of Things (IoT) expansion led the market to find alternative communication technologies ... more Internet of Things (IoT) expansion led the market to find alternative communication technologies since existing protocols are insufficient in terms of coverage, energy consumption to fit IoT needs. Low Power Wide Area Networks (LPWAN) emerged as an alternative cost-effective communication technology for the IoT market. LoRaWAN is an open LPWAN standard developed by LoRa Alliance and has key features i.e., low energy consumption, long-range communication, builtin security, GPS-free positioning. In this paper, we will introduce LoRaWAN technology, the state of art studies in the literature and provide open opportunities.
Increasing demand on Internet of Things (IoT) requires specific communication technology to handl... more Increasing demand on Internet of Things (IoT) requires specific communication technology to handle low-cost power consumption and coverage requirements. Several Low Power Wide Area Network (LPWAN) technologies emerged; however, Long Range Wide Area Networks (LoRaWAN) is the key technology to address these issues. LoRaWAN uses a unique LoRa modulation to provide long range data communication with low power consumption; this will lead LoRaWAN to be the key technology for IoT infrastructures. In this study, LoRaWAN performance is analysed with an experimental TestBed environment by considering communication range, data rates, packet losses and energy consumption for indoor usage. Obtained results are summarized and discussed possible future research directions
For the last few years peer-to-peer (p2p) networks have become widely used tools for sharing any ... more For the last few years peer-to-peer (p2p) networks have become widely used tools for sharing any kind of information from multimedia data to text documents. The vast amount of shared information leads issues on finding relevant information over p2p networks. Existing p2p file search and information retrieval techniques are based on the name of files, which is insufficient when searching relevant documents. In this paper we present a method to perform semantic information retrieval over p2p networks. Our method semantically inspects the content of shared data in peers to generate conceptual information about documents and general information about the peer.
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