Theoretical Analysis of Optical Spatial Multiple Pulse Position Modulation

Abstract

This paper proposes an advanced multi-pulse multilight emitting diodes (LEDs) modulation technique to improve the efficiency for indoor visible light communication systems. The technique is referred to as spatial multiple pulse position modulation (SMPPM), and it is developed by combining a high spectral efficiency space shift keying (SSK) with a high energy efficiency multiple pulse position modulation (MPPM). During a symbol transmission, multiple active pulse slots and active LED indices are utilized as two degrees of freedom to modulate information which in turn provides the balance between the complexity, achievable spectral efficiency and energy efficiency. The analytical expression for symbol error rate (SER) of SMPPM in a multiple input multiple output system with multi-path propagation from reflection is derived theoretically using union bound technique and validated by means of Monte-Carlo simulations. Error performance of SMPPM is then evaluated extensively for different transceiver parameters and pulse configurations. Error rate distribution in a typical indoor workspace is plotted and analyzed. The SMPPM system achieves significantly higher spectral efficiency with respect to the conventional MPPM, SSK and spatial pulse position modulation (SPPM).

A Spatial Time-Frequency Hopping Index Modulated Scheme in Turbulence-free Optical Wireless Communication Channels

“…In this Section we present simulation results for the BER and SER, along the calculated values for P b and P e using the previously developed formulas 3 . For comparison, we offer results for SMPPM [37] and I-TFH [36], as limit cases where either the FSK symbol part or the OSSK symbol part have been removed. Notice that the authors of [37] only analyzed the average symbol error probability P e of SMPPM.…”

“…For comparison, we offer results for SMPPM [37] and I-TFH [36], as limit cases where either the FSK symbol part or the OSSK symbol part have been removed. Notice that the authors of [37] only analyzed the average symbol error probability P e of SMPPM. We will give results for both the average symbol and average Reference absolute temperature T R = 290 K PD load resistor R L = 50 Ω Noise figure of the receiver electronics N F = 10 log 10 (F) = 10 dB Relative-intensity noise factor (RI N ) = −155 dB/Hz PD responsivity R = 0.5 A/W.…”

“…The possibility to communicate using this kind of compound symbol has already been studied and evaluated in a system denominated SMPPM [37]. As a way to extend the possiblities of the SMPPM symbol, and make it carry additional information, instead of just sending rectangular optical pulses within each of the w signal slots, another kind of modulated symbol may be sent by driving other properties of the signal.…”

“…where n k is a zero-mean Gaussian random variable (RV) with variance N 0 /2. As detailed in [37], the hypothetical signal slots are identified as the w slots with highest r k values (this allows the recovery of the corresponding q MPPM bits mapped in the MPPM symbol part). After this, the ML OSSK detector is applied to the selected w signal slots over the metrics r k , so as to get the corresponding q OSSK bits.…”

“…Along these ideas, we propose in this work an IM system based on Spatial MPPM (SMPPM) [37] that carries additional information during the signal slots by combining an FSK scheme, which can thus be named Frequency-Hopping Spatial Multi-Pulse Position Modulation (FH-SMPPM). We will show how its spectral and power efficiencies, its demodulator complexity, and its error rate performance, can be efficiently traded-off respecting other related IM alternatives, like I-TFH [36] and the mentioned SMPPM, which are limit cases of FH-SMPPM.…”