Bidirectional Audio Transmission in Optical Wireless Communication Using PWM and Class D Amplifier
Optical wireless communication (OWC) using light-emitting diode (LED) is a supplement of modern radio frequency wireless communication scheme due to high bandwidth (>300 GHz) of the optical domain. It is less harmful compared to RF wave, and it fulfill
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Abstract Optical wireless communication (OWC) using light-emitting diode (LED) is a supplement of modern radio frequency wireless communication scheme due to high bandwidth (>300 GHz) of the optical domain. It is less harmful compared to RF wave, and it fulfills both illumination and data transmission at a time in indoor. OWC experiences many schemes starting from amplitude modulation to subcarrier index modulation-orthogonal frequency division multiplexing (SIM-OFDM) technique, and improvements are still going on for achieving more secured and higher data rated (in Gigabit Class) communication system. Here, an audio transmission system in OWC using PWM and class D audio amplifier have been used. Experiments have been performed using 9 W white LEDs (correlated color temperature 2900 K) as downlink maintaining the proper light level in the work plane and 850 nm IR LED as uplink for bidirectional communication. A detailed description of optical channel modeling is also described here which is very important for illumination point of view as well as communication point of view. For transmitting voice, 50 kHz carrier frequency is used, and successfully, a distance of 8 m for communication has been achieved. Keywords Audio transmission · Class D amplifier · Optical wireless communication · PWM · Visible light communication
1 Introduction The optical wireless communication (OWC) refers to a communication technology where optical sources are used as signal transmitter, air as a transmitting medium and photodetector as a signal receiver. When a visible light source (380–780 nm) is used as signal transmitter, it is called visible light communication (VLC). In recent decades, the development of light-emitting diodes (LED) in visible spectrum replaces B. Das (B) · S. Mukherjee · S. Mazumdar Department of Electrical Engineering, Jadavpur University, Kolkata, West Bengal, India e-mail: [email protected] © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 V. Nath and J. K. Mandal (eds.), Nanoelectronics, Circuits and Communication Systems, Lecture Notes in Electrical Engineering 692, https://doi.org/10.1007/978-981-15-7486-3_14
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the incandescent bulbs and fluorescent lamps, since they have the characteristics of long lifetime, mercury free, color mixing, higher efficacy, good color rendering index (CRI) value and fast switching. Utilizing the property of fast switching of LED, VLC uses white LED as transmitter which can transmit data at very high data rate as well as fulfill the requirement of illumination in indoor. The concept of optical wireless communication is not the new one. In 1880, Grahambell invented photophone, where sun light was used as optical beam to transmit telephone signal at 200 m [1–3]. Later in 1962, MIT Lincoln Labs built an experimental OWC link using low-power GaAs LED to transmit TV signal [2, 3]. In 1994, OWC link was demonstrated using 806 nm IR LED at 2.9 m distance [4]. However after invention of LED
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