Information dissemination using digital notice board plays an imperative role in this digital world. This work is primarily aimed at developing a wireless information board for displaying and broadcasting the announcements and notices that the user sends from the Internet using the IOT technology. By providing a sufficient power supply, the Raspberry Pi, node MCU and LED display work properly and the display is controlled by the android application. The application can be used by connecting it to the internet and this enables the admin to send the information from wherever in the planet and could be visualized in a matter of seconds. The admin uses the app by setting the correct username and password for WIFI. For sending information, PC or mobile phone are utilised and at recipient end, raspberry Pi is connected to the Web. The admin can send the data in the form of text or voice, which in turn would be displayed on the distant noticeboard. The LED display is to display the text/voice that the user has sent and the speaker is to announce the received text message. The displaying text would be scrolling in the display. By using the text to speech software, announcement the text that is scrolling on the LED screen become possible. Earlier the Wi-Fi notification board had been used and thereby experiencing a limit on coverage. In this proposed method, the Internet is used as a means of communication and no coverage problem exists.

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The obtainability of spectrum is limited for wireless communication. The inefficient usage of spectrum leads to the evolution of a new technology known as Cognitive Radio Networks. With the fixed spectrum assignment policy, most of the spectrum remains unused and remains as vacant white spaces all the time. This leads to an approach known as spectrum sensing. Spectrum sensing is the process of detecting the presence of the primary users (PUs) in a licensed spectrum and is considered as fundamental problem for cognitive radio. It is an intelligent radio communication approach where a cognitive radio device will sense the environment and carry communication using the unutilized spectrum bands. Cognitive radio technology potentially satisfies the increasing users in future. This paper provides an insight of cognitive radio knowledge- architecture, cognition cycle, functions, different spectrum sensing methods and various applications of CR.

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