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VINAY KUMAR SINGH1,* , U. D. DALAL1
- Sardar Vallabhbhai National Institute of Technology, Surat, Gujarat, India
To alleviate the effects of the intersymbol interference (ISI) in the multicarrier system it is impetus to incorporate the cyclic prefix (CP) whose length is determined by the worst channel impulse response (CIR) duration. A nearly ISI devoid communication system can be attained for CP length more than the CIR. Such a system is power and bandwidth inefficient. In the Visible light communication (VLC) system employing optical orthogonal frequency division multiplexing (O-OFDM) the effect of such an ISI would deteriorate the received signal. In this paper we propose a technique of adapting the CP length as per the CIR which eliminates the ISI and further increases the bit rate in O-OFDM in VLC transmission systems. A mathematical model is developed to evaluate the optimal CP length based on the channel capacity. This proves to be computationally complex, so we then propose a simplified mathematical model based on the lower & the upper bound of the channel capacity and also on the delay spread of the channel. These techniques are then compared with the conventional predetermined CP length spanning 25% of the OFDM symbol based on signal to interference noise ratio (SINR) and the overall throughput of the system. A maximum improvement of 5.2% of throughput is obtained when the CP length based on channel capacity is adopted as compared to the CP length spanning 25% of the OFDM symbol..
Visible Light Communication (VLC), OFDM, Intersymbol Interference (ISI), Optical Wireless Channel (OWC).
Submitted at: April 26, 2017
Accepted at: Nov. 28, 2017
VINAY KUMAR SINGH, U. D. DALAL, Cyclic prefix adaptation based on channel capacity of the optical wireless channel for OFDM signals in the VLC system for enhancing the throughput and to mitigate ISI, Journal of Optoelectronics and Advanced Materials Vol. 19, Iss. 11-12, pp. 709-718 (2017)
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