Secure visible light communication systems based on the position of the user

Mousa, Farag (2017) Secure visible light communication systems based on the position of the user. Doctoral thesis, Northumbria University.

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Abstract

In the past few decades, there has been a growing demand for bandwidth in wireless communication systems due to an increase in the number of mobile users, computer network applications and high speed internet access and services. Visible light communication (VLC) is a newly emerging technology in optical wireless communication (OWC) systems to provide both illumination and high-speed data communication. In addition, it can also be used for indoor positioning or localization with wide applications that has merited a number of attractive research studies. However, security in wireless communications has become a matter of concern due to the possibility of unauthorised access to transmitted data.

This thesis investigates received optical power (ROP) distribution to achieve illumination requirements for both optimal and sub-optimal Lambertian order in single and four cell configurations. Furthermore, it proposes VLC-based indoor positioning by using the received optical power levels from the emitting LEDs. Both scenarios of line-of-sight (LOS) and line-of-sight with non-line-of-sight (LOSNLOS) positioning are considered. The performance of the proposed system is evaluated under both noisy and noiseless channel cases and the impact of different location codes on the positioning error is also investigated. An analytical model of the system with noise and the corresponding numerical evaluation for a range of signal to noise ratios (SNRs) are presented. The results show that an accuracy of 8 cm in average is achievable at an SNR of 15 dB in the LOSNLOS scenario. We also introduce a novel approach for recovering 4×4 MIMO–VLC data with partial channel state information (CSI) knowledge both in noisy and noiseless cases. In addition, the proposed indoor localization system utilizing two visible light emitting diodes for different environments offering less complexity for both LOS and LOSNLOS scenarios is offered. The results of the scheme is compared with existing trilateration techniques and the performance of the proposed system is evaluated with a reported accuracy of less than 20 cm for SNR values of greater than 13 dB.

This thesis also proposes a new secure single input single output (SISO) VLC system and investigates the bit error rate (BER) performance with and without encryption in the Media Access Control (MAC) layer and physical layer for both the LOS and LOSNLOS scenarios. For a BER of 10-3, the results show that there is 1 to ~ 3.5 dB power penalties for the secured VLC system for data rates of up to 10 Mbps. The key length impact on the error propagation is also investigated.

Finally, this thesis proposes a secure MIMO VLC system that relies on the position of the user by incorporating a new modified version of the Rivest-Shamir-Adleman (RSA) technique for encrypting the transmitted data in the MAC layer. Furthermore, the ability of the proposed system to control the size of the encrypted cell depending on the application environment is demonstrated.

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