Abstract
In this article, a new modulation scheme named Direct Current biased Optical Generalised Frequency Division Multiplexing (DCO-GFDM) for Visible Light Communications (VLC) is explored. The DCO-GFDM enhances spectral efficiency by slicing both grids on the time-frequency plane and uses a circularly rotating filter for pulse shaping. In the Circular Pulse shaped DCO-GFDM (CP-DCO-GFDM), Root Raised Cosine (RRC) pulse is widely employed. This destroys the orthogonality among sub-carriers and degrades the Bit Error Rate (BER) performance. Therefore, in this work, a Linearly Pulse shaped DCO-GFDM (LP-DCO-GFDM) is proposed to retain the orthogonality among the sub-carriers and simultaneously improve BER and Peak-to-Average Power Ratio (PAPR) performance. The performance of CP/LP-DCO-GFDM is studied under double sided clipping distortion that occurs at the Light Emitting Diode (LED). Presented simulation results agree well with the theoretical results. Additionally, we present an experimental validation of the LP-DCO-GFDM on a Universal Software Radio Peripherals (USRP) based VLC test bed. The experimental results, in terms of Error Vector Magnitudes (EVM)s, the received constellations, and the received spectrum in comparison with DCO-OFDM shows improved performance.
Highlights
E MERGING technologies, such as the Internet of Things (IoT), are causing exponential growth in data traffic [1]
The Bit Error Rate (BER) performance of DCO-OFDM under double sided clipping is simulated under similar conditions for comparison purpose [15]
Along with CP-DCO-GFDM using Square Root Raised Cosine (SRRC) pulse with roll-off factor α, DCO-OFDM with the same number of sub-carriers are examined in the comparative analysis. 4-QAM and 16-QAM constellations are assumed in the implementation of the system and the Root Mean Square (RMS)-Error Vector Magnitudes (EVM) comparison of LP-DCO-GFDM with the corresponding modulation is depicted in Fig. 6 for 4-QAM constellation
Summary
E MERGING technologies, such as the Internet of Things (IoT), are causing exponential growth in data traffic [1]. Several forms of multi-carrier modulations, such as Optical-Orthogonal Frequency Division Multiplexing (O-OFDM), have been explored for VLC in literature [5]. With DCO-GFDM both the time and frequency grids are divided unlike in OFDM modulation where only the frequency grid is sliced [7] For this reason, DCO-GFDM transmits multiple symbols on each sub-carrier and uses circularly rotating prototype pulse shaping filter on each time grid. In the present work, a Linearly pulse shaped DCO-GFDM (LP-DCO-GFDM) is introduced This uses linear pulse shaping filters that offer an improved Bit Error Rate (BER) and PAPR performance by retaining the orthogonality of the sub-carriers.
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