Abstract
An efficient optical modulation technique for multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) visible light communication system is proposed in this paper. The proposed modulation technique is termed as extended spatial-index light-emitting diode (LED) modulation. In the proposed technique, the indices (the spatial domain) of the LEDs are exploited in a dynamic style to not only get rid of the optical OFDM time-domain ( OFDM t d ) shaping problem but also to expand the LED indices spatial modulation domain. The indices of the active LEDs in the proposed technique are changed from the two LEDs active situation to the situation where all or several LEDs are active. Moreover, within the selected active LED indices, the power weight distribution and the positions of the OFDM components are varied to expand the resultant spatial domain. Therefore, the proposed technique offers a considerable spectral efficiency improvement over the up-to-date LED index OFDM modulation schemes even with a lower number of LEDs. The key idea of the proposed technique is to maximize the LEDs’ indices spatial position (spatial domain) utilization, where both the power weight allocation and the positions of the complex OFDM time domain components are varying several times over the same active LED indices combination, which improve the optical system spectral efficiency. The simulation results asserted the superiority of the proposed technique, as it improves both the average bit error rate (ABER) and the achievable data rate (R) compared with existing up-to-date OFDM-LED index modulations with even lower computational complexity.
Highlights
The last decade has witnessed a phenomenal growth in wireless communications data
Both luminaries and photo detectors (PDs) are assumed in a vertical position in aforesaid configurations; in contrast, in configuration C, the PDs are located in the center of the table with distance 0.1 m between each other, but rotated by 45◦ in the xy-plane and titled by 60◦ in the yz-plane, where it can increase the line of sight (LOS) link strength
As a fair comparison, the GLIM-orthogonal frequency division multiplexing (OFDM) system architecture is adapted to support the operation of the spatial modulation along with its conventional functions
Summary
The last decade has witnessed a phenomenal growth in wireless communications data. According to [1], mobile data traffic is expected to grow to 30.6 exabytes per month by 2020 (an eight-fold increase over 2015). The ACO-OFDM enhanced the OPE of the optical wireless communication system at the expense of reducing its spectral efficiency (SE) and degradation of its bit error rate (BER), where its data rate was reduced to half of the conventional OFDM data rate This dates back to the zero level clipping of the IFFT output signal and its output signals are restricted to be conveyed over the odd subcarrier only. MIMO-OFDM to improve the VLC system spectral and power efficiency [29,30,31,32,33], where the indices of transmit LEDs (spatial LEDs positions) were exploited to convey additional bits or to handle the complex OFDM time-domain shaping problem. A novel optical MIMO-OFDM communication modulation scheme termed as extended spatial-index light-emitting diode (ESI-LED) modulation is proposed.
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