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Visible Light Communications
Published in Z. Ghassemlooy, W. Popoola, S. Rajbhandari, Optical Wireless Communications, 2019
Z. Ghassemlooy, W. Popoola, S. Rajbhandari
In today's buildings, dimming and auto turn on/off are essential features that are widely deployed. The interest in dimming control functionality has further increased in the wake of ever-increasing global energy consumption, which is expected to rise another 60% over the next 25 years [113]. For LED lights to be employed as an illumination and as a data communication source simultaneously, the dimming and communication signals must be independent and not interfere with each other. The injected current to the LEDs must, therefore, carry both the dimming and data communication signals. For visible LEDs to control the dimming level, there are a number of dimming control mechanisms that are widely used [114], [115]. Amplitude modulation–based dimming is the simplest approach, whereby modulating the intensity of the injected DC current to the LED controls the emitted luminous flux [116]. However, this approach could result in changes in the chromaticity coordinates of the emitted light. Pulse time modulation schemes (such as PWM, SWFM, etc.) introduced in Chapter 4 are very attractive for both dimming and data communications. PWM with subcarrier pulse position modulation (SC-PPM) is an alternative technique for controlling LED brightness [117]. This technique offers simplicity, but the dimming frequency is limited by the frequency of SC-PPM to guarantee reliable data link performance. In addition, the signal format based on PPM has been demonstrated [118]. In this section, a number of dimming schemes will be introduced and discussed.
Basics of Electrical Communication Systems
Published in P. S. Neelakanta, ATM Telecommunications, 2018
A salient aspect of telecommunications is representing the data generated by a discrete source efficiently so as to be most compatible for transmission. The process by which this representation is enabled is called source encoding. Relevant to digital communication, source coding refers to bit representation in a specific format of the information transmitted. The unit that performs the required representation is called a source encoder. For the source encoder to be efficient, a statistic knowledge of the source is required. For example, if some source symbols are known to be more probable than the others, then one may exploit this feature in the generation of a source code by assigning short code words to frequent source symbols, and large code words to rare source symbols. Such a source code is known as a variable-length code. As indicated earlier, the Morse code is an example of a variable-length code. In the Morse code, the letters of the alphabet and numerals are encoded into streams of marks and spaces, denoted as dots (“·”) and dashes (“-”), respectively. Since in English, the letter E occurs more frequently than the letter Q for example, the Morse code encodes E into a single dot “.#x201D;. the shortest code word in the code, and it encodes Q into “---”, a longer code word.
Visible Light Communications
Published in Z. Ghassemlooy, W. Popoola, S. Rajbhandari, ®, 2017
Z. Ghassemlooy, W. Popoola, S. Rajbhandari
In today’s buildings, dimming and auto turn on/off are essential features that are widely deployed. For LED lights to be employed as an illumination and as a data communication source simultaneously, the dimming and communication signals must be independent and not interfering with each other. The injected current to the LEDs must therefore carry both the dimming and data communication signals. For VLEDs to control the dimming level, there are a number of dimming control mechanisms that are widely used and new methods have been proposed [36,37]. The amplitude modulation- based dimming is the simplest approach where by intensity modulation of the injected DC current to the LED, the emitted luminous flux is controlled [38]. However, this approach could result in changes of the chromaticity coordinates of the emitted light. Pulse time modulation schemes (PWM, SWFM, etc.) introduced in Chapter 4 are very attractive for both dimming and data communications.
Distributed event-triggered consensus control for multiple Lur'e nonlinear systems under directed graph
Published in International Journal of Control, 2019
Xiangdong Liu, Haikuo Liu, Changkun Du, Pingli Lu
The state-dependent measurement errors and their thresholds of agents are shown in Figure 5, we know that the agents will communicate with their neighbours when the measurement errors (the red lines) reach the thresholds (the black lines). Comparing with the continuous communication scheme in Zhang et al. (2014), Zhao et al. (2013), Li et al. (2011), Wen, Yu, & Hu (2013), Lv et al. (2016) or sampled-data scheme in Wen, Duan, and Yu (2013), Zhang and Tian (2010), Figure 5 shows that the proposed event-triggered strategy can reduce much signal transmission, and thus reduce the multi-agent network communication burden and save much communication source while preserving the desired consensus performance. Furthermore, it is shown in Figure 5 that the triggering instants of each agent are finite and the communication among agents is discrete, which implies that there is no Zeno behaviour. By simulation results, the proposed approach can complete the consensus task for multiple Lur'e nonlinear systems, and have satisfactory control performance with reducing communication resource.
Energy Optimization for Smart Cities Using IoT
Published in Applied Artificial Intelligence, 2022
Mamoona Humayun, Mohammed Saleh Alsaqer, Nz Jhanjhi
The proposed model’s second essential aspect is internal energy optimization; smart homes employ a lot of energy-consuming gadgets. The proposed model would recommend connecting these household appliances with IoT-based sensors to make them more energy-efficient. These IoT-based sensors can detect motion and use artificial intelligence to make decisions following the supplied instructions. The intelligent IoT sensors will automatically put inactive household appliances into sleep mode, which will save energy. In the event of a problem with a home appliance, a notification will be sent to the user’s dashboard through the cloud via a communication source. Through a communication source, the smart home/smart building will also transfer data to the cloud.