A Framework for Efficient Modulation Techniques for Visible Light Communication Under Indoor Environment Based Iot Applications

Abstract

The Internet of Things has paved the way for several smart applications, which broadly include smart homes, smart cities, smart transports, etc. The underlying architecture of these systems typically involves sensor devices communicating data over the internet to provide some useful insight. However, as the number of devices connected to the internet is increasing, the existing backbone network infrastruc- ture is experiencing considerable challenges in the allocation of channel bandwidth for communicating devices. Moreover, it is also widely debated that prolonged ex- posure to high radio-frequency spectrum is harmful to living bodies. Thus, there is a need to have an alternative to existing radio-frequency-based communication techniques. Visible light communication is a sub-domain of optical wireless com- munication which uses an unlicensed visible light spectrum for communication. However, the domain is new and requires more work to be done with respect to designing testbeds and integration with existing Internet of Things infrastructure. Thus, there is a scope to design low-cost testbeds to test various modified versions of existing modulation techniques as well as to build new modulation techniques specific to light characteristics. This research thesis proposes various low-cost testbeds to implement exist- ing modulation techniques and compares them with the standard implementation of their simulated counterparts. The work also proposes a few new modulation techniques and describes their integration with Internet of Things applications. Depending upon the type of the receivers and the features used for generating sig- nals, the modulation techniques were divided into three major categories namely photodiode-based modulation, rolling-shutter-based optical camera communica- tion modulation, and pattern-based optical camera communication. The work also proposes photodiode-based modulation and shows an imple- mentation of a low-cost visible light communication testbed. It also highlights the implementation of On-Off keying and pulse duration modulation techniques on the proposed testbed. The work also evaluates the performance of the implemented system with its equivalent standard implementation using Matlab simulation. The iwork shows the performance of the proposed testbed is in line with the perfor- mance of the simulated counterpart with respect to the trend of increasing error rate with increasing distance. It also shows that the performance of pulse duration modulation is consistently better than that of On-Off keying in terms of the suc- cess of reception (%). The work also highlights an extension by building an image transmission application using the proposed visible light communication testbed. The research work in the thesis involves the design and implementation of the visible light communication system which uses the camera as the receiver. It highlights the use of the concept of a rolling shutter to modulate signals in terms of the blink frequency of the transmitter LED. The work proposes a novel hybrid frequency shift pulse duration modulation technique that modulated the data in terms of the duration of frequencies. The work also highlights the performance comparison of the proposed technique with other standard implementations of the modulation techniques such as On-Off keying and binary frequency shift on-off keying. An indoor positioning system application built using the testbed was also described in this work. As a part of the work on pattern-based optical camera communication mod- ulation techniques, the work proposes two novel modulation techniques, one in- spired by the nested structure of textures and the other inspired by quantum physics. The implementation of both proposed modulation techniques uses the same testbed setup. It evaluates the performance of the proposed techniques based on the visibility of the patterns, the amount of data that can be encoded, signal-to-noise ratio, and bit-error rate (%). The work also highlights the perfor- mance comparison of the proposed techniques with the other existing techniques. Finally, the testbed setup was also used to propose and build an Internet of Things application that communicates temperature and humidity data over a non-radio- frequency medium.