Hybrid modulation schemes for data transmission improvement of indoor visible light communication system

Abstract

This work enhances the bit rate characteristics, receiver sensitivity and power requirements of multicarrier modulation schemes (MCM) for visible light communication (VLC) dimming control system at bit error rate (BER) less than 10-3. This study develops the mathematical formulation for merging pulse position modulation (PPM) and overlapping pulse position modulation (OPPM) with M-ary quadrature amplitude modulation DC-Biased optical orthogonal frequency division multiplexing (M-QAM DCO OFDM), which can achieve efficient data transmission while maintaining communication quality. These schemes are then compared with the conventional merging (i.e M-QAM DCO OFDM with pulse width modulation (PWM)). Relating to the recent advances in the field, the additional comparative study is established with the latest merging platform (i.e. M-QAM DCO OFDM with multiple pulse position modulation (MPPM)).

Enhancing the performance of optical VLC system based on asymmetric symmetric subcarriers OFDM

“…This spectrum ranges between 400 and 800 THz (375‐750 nm), which allows transmitting high data rate. Also, there are additional motivations towards using VLC technology such as low‐cost front‐end devices (LED‐photodiode detector [PD]), no licensing requirement, an enormous amount of unregulated bandwidth, no interference with radio frequency (RF) signals, privacy, security, and dual functionality system (lighting and communication) …”

“…For using of IM/DD technique with VLC systems, at the transmitter, the optical power output is proportional to the electrical current input and the information data are modulated onto the input current intensity. The electrical current signal has to be real‐valued and positive (unipolar) . At the receiver, a direct detection operation is accomplished using a photodiode (PD) to output a current proportional to the received optical power.…”

“…Higher‐order modulation types like M ‐ary phase shift keying (M‐PSK) and M ‐ary quadrature amplitude modulation (M‐QAM) cannot be used in VLC systems directly, as they generate complex signals . Recently with the help of the OFDM technique, higher‐order modulation types can be used in VLC systems with some modifications to get real and unipolar output . In conventional OFDM scheme, inverse fast Fourier transform (IFFT) block is used to convert the complex frequency‐domain mapped symbols U ( k ) into its equivalent time‐domain samples u ( n ) that are also complex and bipolar.…”

“…According to the usage of hermitian symmetry in VLC systems based on OFDM technique, a data transmission rate reduction by a factor of 1/2 occurred, compared with the conventional OFDM technique. And so, the problem of getting real‐valued output from OFDM‐based VLC systems could be solved at a price of lowering the transmitted data rate by a factor of 1/2 due to the hermitian symmetry of the IFFT …”