In this paper, we investigate how to reformulate the concepts of cognitive access, originally developed for radio communications, in the framework of underwater acoustic communications. A straightforward application of the classical energydetection-based cognitive approach, such as the one employed for radio communications, would result in a reduced spectrum utilization in an acoustic scenario. Actually, in the underwater scenario, acoustic signals sensed by a network node are likely to be due to communication sources as well as natural/artificial acoustic sources (e.g., mammals, ship engines, and so forth), differently from classical cognitive radio access, where each signal at the receiver is generated by a communication source. To maximize the access probability for cognitive acoustic nodes, we focus on understanding the nature of sensed interference. Toward this aim, we try to discriminate among natural and communications sources by classifying the images representing the time and frequency features of the received signals, obtained by means of the WignerVille transform. Two different classifiers are considered here. The first one is targeted on finding natural interference while the second one looks for communication. Simulation results show how the herein described approach drastically enhances the access probability in an acoustic scenario with respect to a direct rephrasing of classical cognitive access. A possible protocol for implementing cognitive access is also described and its performance evaluated.
We propose a vsible light communication scheme utilizing red, green and blue light-emitting diodes (LEDs) and three color-tuned photodiodes. Amplitude shift keying modulation is considered, and its effect on light emission in terms of flickering, dimming, and color rendering is discussed. The presence of interference at each photodiode generated by the other two colors is used to improve detection since interference is symbol-dependent. Moreover, the capability of the photodiodes to follow the LEDs speed is considered by analyzing the possibility of equalizing the received signal, and also self-interference mitigation is proposed. The system performance is evaluated both with computer simulations and tests on an Arduino board implementation.
The Internet of Things (IoT) is by now very close to be realized, leading the world towards a new technological era where people’s lives and habits will be definitively revolutionized. Furthermore, the incoming 5G technology promises significant enhancements concerning the Quality of Service (QoS) in mobile communications. Having billions of devices simultaneously connected has opened new challenges about network management and data exchange rules that need to be tailored to the characteristics of the considered scenario. A large part of the IoT market is pointing to Low-Power Wide-Area Networks (LPWANs) representing the infrastructure for several applications having energy saving as a mandatory goal besides other aspects of QoS. In this context, we propose a low-power IoT-oriented file synchronization protocol that, by dynamically optimizing the amount of data to be transferred, limits the device level of interaction within the network, therefore extending the battery life. This protocol can be adopted with different Layer 2 technologies and provides energy savings at the IoT device level that can be exploited by different applications.
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