Spatial Pulse Position Modulation Research Articles

Spatial pulse position modulation multi-classification detector based on deep learning

The predecessor of China Optics was China Optics and Applied Optics Digest, which was founded in 1985. At that time, it was the only retrieval journal in the field of optics in China. At the end of 2008, China Optics and Applied Optics Digest was renamed

Performance analysis of optical spatial modulation over a correlated gamma-gamma turbulence channel.

In this paper, theoretical closed expressions for the symbol error rate (SER) of two optical spatial modulation (OSM) schemes in a free-space optical (FSO) communication system-optical spatial pulse amplitude modulation (OSPAM) and optical spatial pulse position modulation (OSPPM)-over correlated gamma-gamma fading channels are derived. To study practical optical channels affected by atmospheric eddies, the effect of arbitrary atmospheric channel correlation is considered particularly, and it is shown that the correlation can degrade system performance. The parameters of atmospheric turbulence and the number of optical antennas are also under consideration in performance analysis of the FSO multiple input, multiple output system. All analytical results are validated with Monte Carlo simulations, which clearly illustrate the effect of spatial constellation and signal constellation on the average SER. In addition, it is shown by comparison that turbulence fluctuation and channel correlation have less influence on the OSPPM system than the OSPAM system. Overall, the framework proposed in this paper is proven to be effective and conducive to algorithm research on reducing the effect of correlated channels on OSM FSO systems.

Marked Multi-Layer Optical Spatial Pulse Position Modulation

Marked Multi-Layer Optical Spatial Pulse Position Modulation

Orthogonal Space Time Block Coding for Spatial Pulse Position Modulation

Orthogonal Space Time Block Coding for Spatial Pulse Position Modulation

Error Performance of Polar Coded Spatial Pulse Position Modulation Technique

The turbulence in the channel will increase the bit error rate of the FSO system, which can resist the influence of atmospheric turbulence in many ways. In this paper, spatial pulse position modulation (SPPM) is combined with Polar code to improve error performance. The influence of list length on the decoding performance of CRC-SCL and the performance changes of Polar codes at different code lengths and rates are analyzed. Monte Carlo simulation results show that Polar codes in SPPM system have similar performance changes as in single input single output system. Therefore, Higher coding gain at low code rate and long code length.

Performance enhancement of the average spectral efficiency using an aperture averaging and spatial-coherence diversity based on the modified-PPM modulation for MISO FSO links

The performance evaluation and enhancement of the proposed model for a free-space optical (FSO) communication links using the modified pulse-position modulation (MPPM) and spatial pulse-position modulation (SPPM) is analyzed in this paper. The average spectral efficiency (ASE) is investigated for the FSO communication using MPPM, SPPM, and spatial-coherence diversity in a coherent optical wireless communication (coherent OWC) systems. We proposed the hybrid MPPM/SPPM as a new modulation to improve the ASE performance of pulse-position modulation. To reduce the atmospheric turbulence (AT) effects and scintillation, the use of an aperture averaging (AA) technique has been proposed in our work. Here, we analyze the pointing error (PE) effects on the performance of M−ary MPPM based on a multiple-input single-output (MISO) of the repetition codes (RCs) and FSO systems using SPPM. The enhancement in the ASE can be accomplished with an increase in the receiver aperture and decreasing the beam radius in the presence of PEs. The ASE performances of 53 bits/s/Hz and 37 bits/s/Hz are achieved with the average transmitted optical power of 10 dBm for an aperture diameter of 10 cm over the effect of without and with PEs for coherent OWC technique, respectively. The simulation results obtained for the bit-error-rate (BER) and ASE against various AT conditions are compared with the diversity techniques and proved that both of the hybrid SPPM and MPPM/MISO−RCs based on the AA and spatial diversity offers better performance in the average channel capacity (ACC). Numerical results show that the ASE performance can be improved using the spatial-coherence diversity in coherent OWC technique. The spatial-coherence diversity in a coherent OWC system significantly outperforms on-off keying and MPPM system even in the presence of PEs under strong turbulence. Efficient estimation of the signal-to-noise ratio also allows accurate quantification of the BER and ACC for adequate quality of service and network link resource allocation.

Optical Spatial Modulation for FSO IM/DD Communications With Photon-Counting Receivers: Performance Analysis, Transmit Diversity Order and Aperture Selection

This paper investigates two pulse-based Optical Spatial Modulation (OSM) schemes as cost-efficient solutions for multi-aperture Free-Space Optical (FSO) communications with Intensity-Modulation and Direct-Detection (IM/DD). Namely, we consider Optical Space Shift Keying (OSSK) where information is encoded in the index of the pulsed optical source and Spatial Pulse Position Modulation (SPPM) where additional bits determine the position of the transmitted optical pulse resulting in higher transmission rates. A performance analysis is carried out over gamma-gamma channels with the exact Poisson photon-counting detection model. Exact Symbol Error Probability (SEP) expressions, simple upper bounds and the achievable transmit diversity orders are derived for both the open-loop and closed-loop scenarios. Based on the presented performance analysis, a transmit aperture selection scheme capable of maximizing the transmit diversity order is proposed for OSSK and SPPM in the closed-loop case. Results show that for open-loop OSSK, open-loop SPPM and closed-loop OSSK, the transmit diversity order does not depend on the severity of scintillation unlike the closed-loop SPPM case.

Performance Analysis of Optical Spatial Modulation in Atmospheric Turbulence Channel †

In this paper, spatial pulse position modulation (SPPM) is used as a case study to investigate the performance of the optical spatial modulation (SM) technique in outdoor atmospheric turbulence (AT). A closed-form expression for the upper bound on the asymptotic symbol error rate (SER) of SPPM in AT is derived and validated by closely-matching simulation results. The error performance is evaluated in weak to strong AT conditions. As the AT strength increases from weak to strong, the channel fading coefficients become more dispersed and differentiable. Thus, a better error performance is observed under moderate-to-strong AT compared to weak AT. The performance in weak AT can be improved by applying unequal power allocation to make free-space optical communication (FSO) links more distinguishable at the receiver. Receive diversity is considered to mitigate irradiance fluctuation and improve the robustness of the system to turbulence-induced channel fading. The diversity order is computed as half of the number of detectors. Performance comparisons, in terms of energy and spectral efficiencies, are drawn between the SPPM scheme and conventional MIMO schemes such as repetition coding and spatial multiplexing.

Performance of Optical Spatial Modulation in Indoor Multipath Channel

In this paper, the performance of optical spatial modulation (OSM) in the indoor multipath optical wireless channel is investigated. Multipath propagation of the transmitted signal results in the temporal dispersion which causes intersymbol interference (ISI) especially in high-speed communications. The OSM schemes have been investigated in line-of-sight (LOS) channels. However, given the recent trend in Gigabits/s communication, there is a need to investigate the impact of the neglected higher-order reflections. Two variants of OSM are explored as case studies: optical space shift keying and spatial pulse position modulation. The multipath-induced ISI is modeled to account for the spreading of the transmitted signal, and the analytical upper bound on the symbol error rate of both OSM schemes in the multipath channel is derived. The derived analytical bounds are validated by closely matching simulation results. Furthermore, using the spatial distributions of the multipath-induced power penalty, the LOS channel response and the delay spread across the room, we demonstrate how the interaction between these parameters impacts error performance. Multipath-induced ISI has a significant adverse impact on the performance of OSM schemes, particularly on the detection of the activated transmitter as the incurred ISI can alter the channel gain of the received symbol.

Bidirectional Parallel Capacitive Data Links: Modeling and Experimental Results

We present, in this paper, a bidirectional capacitive data link. Enhancement of the spatial pulse position modulation used on the downlink is introduced, and a load-shift keying modulation is implemented for the uplink. Different grounds on the transmitter and the receiver are discussed, and a compatible solution is proposed. A human skin electrical model is extracted using the agilent impedance analyzer 4294A while doing in vivo measurements on cheek skin and then applying curve fitting to the data between 2 and 20 MHz. Multiple geometries for the link are analyzed, and a 5-mm $\times$ 5-mm plate size is used for the design of the transceiver. The signal-to-noise ratio along with the capacity of the channel is analyzed theoretically while computing the limits for the downlink and the valid operating frequency to highlight the core parameters that affect the crosstalk interference between channels. The tradeoff in using the uplink on the same channel as the downlink is also discussed and analyzed. The operating frequency is 10 MHz, a bit-rate of 20 Mb/s is demonstrated on the uplink, and 10 Mb/s is demonstrated on the downlink. An in vivo human skin model for a 5-mm $\times$ 5-mm plate size with 21.2-mm separation is extracted, and the capacity’s equation of the channel is computed using the equations for the analysis of the system.

SM/SPPM Aided Multiuser Precoded Visible Light Communication Systems

In this paper, we propose a multiuser precoded visible light communication (VLC) system utilizing optical orthogonal frequency division multiplexing (OFDM), where optical spatial modulation (OSM) and spatial pulse position modulation (SPPM) are invoked for supporting high-rate data transmissions without compromising uniform illumination across multiple light-emitting diodes (LEDs). Both OSM and SPPM exploit the index of data streams for carrying additional information bits, whereas the multiuser interference occurring between different user equipments is mitigated by the MIMO precoder. By evaluating the performances of the proposed VLC systems, we demonstrate that the OSM-aided system is capable of achieving high data rates at sufficiently high signal-to-noise ratios (SNRs). In contrast, the SPPM-aided system has a higher effective bandwidth efficiency at low SNRs, despite the fact that its attainable peak data rate is lower than that of the SM-aided counterpart. Such tradeoffs indicate the potential application scenarios of the proposed schemes for achieving diverse design prerequisites.

Spatial Pulse Position Modulation for Optical Communications

This paper proposes a low complexity spatial modulation (SM) scheme that combines spatial shift keying (SSK) with pulse position modulation (PPM) for optical wireless communication systems. SM is a multi-transmitter technique for achieving increased data rate over the traditional on-off keying (OOK) and PPM signalling methods. Analysis of the error performance of the system in the presence of noise is presented and validated via simulations. There is a perfect agreement between the simulation and the theoretical analysis for the case of M = 2 bits/symbol and other values of M at symbol error rate (SER) of less than 10-2. At higher SER values the analytical prediction is about 1.2 dB more than that of the simulation. We also show the energy efficiency/bandwidth requirement trade-off involved when determining the system parameters such as the number of transmitters and the number of bits per symbol M. Using fewer transmitters improves the energy efficiency but requires more bandwidth. Moreover, the error performance of SPPM is dictated by both the individual channel gains of the multiple transmitters and the difference between these channel gains or path losses. Hence, distinct channel gains are a prerequisite in spatial modulation. An experimental set up to measure and show the dependence of the channel gains on the relative position of the transmitter to the receiver is also presented. These measured channel parameters are then used to evaluate the system error performance. The performance of the SPPM is also compared, in terms of energy and spectral efficiencies, with the classical SSK and repetition coded (RC) schemes in which the multiple transmitters are used to transmit the same data simultaneously. The results show the SPPM as a multi-transmitter signalling scheme that combines the energy efficiency of the PPM with the high spectral efficiency of the SSK.