Ioannis Glaropoulos

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Cognitive radio operation with opportunistic spectrum access has been proposed to utilize spectrum holes left unused by a primary system owning the spectrum license. The key of cognitive radio operation is the ability to detect weak primary signals and to control the transmission of cognitive users in a way that interference between the two systems is(More)
In the future Internet of Things (IoT), battery-powered devices equipped with short range radios may need to communicate with each other over multi-hop links. This may significantly increase their energy consumption. Whereas most research on IoT assumes that the devices use energy-efficient IEEE 802.15.4 wireless transceivers, we focus on IEEE 802.11(More)
The Future Internet of Things (IoT) will connect billions of battery-powered radio-enabled devices. Some of them may need to communicate with each other and with Internet gateways (border routers) over multi-hop links. While most IoT scenarios assume that for this purpose devices use energy-efficient IEEE 802.15.4 radios, there are use cases where IEEE(More)
In this paper we design a cognitive access scheme for WSNs that coexist with WLANs, considering the problem of blind and hidden WLAN terminals. The cognitive access scheme relies on a-priory known WLAN idle time distribution functions and repeated channel measurements to optimize the size of the transmitted data unit and the transmission distance, such that(More)
In this paper we evaluate the delay and sensing performance of distributed cooperative sensing in wireless sensor networks assisting cognitive secondary operation. We propose a time division multiple access protocol to exchange sensing information among neighboring sensors, that is tunable in terms of sensing cooperation range and frequency reuse distance.(More)
Efficient communication in the crowded ISM band requires the communication networks to be aware of the networking environment and to control their communication protocols accordingly. In this paper we address the issue of efficient WSN communication under WLAN interference. We propose analytic models to describe the WLAN idle time distributions as observed(More)
In this work we evaluate the efficiency of cooperative spectrum sensing to support cognitive radio operation, when sensing is assigned to the cognitive users, randomly located in the area of a primary network. We derive analytic expressions for sensing performance based on the traditional metrics of missed detection and false alarm probabilities, and show(More)
Access to unused spectrum bands of primary networks requires a careful optimization of the secondary cooperative spectrum sensing, if the transmission powers in the two networks are comparable. In this case the reliability of the sensing depends significantly on the spatial distribution of the cooperating nodes. In this paper we study the efficiency of(More)
The limited spectrum resources and dramatic growth of high data rate communications have motivated opportunistic spectrum access using the promising concept of cognitive radio networks. Although this concept has emerged primarily to enhance spectrum utilization, the importance of energy consumption poses new challenges, because energy efficiency and(More)