Multiple Pulse Position Modulation Research Articles

Analysis on improving channel capacity of MPPM

Nowadays, optical wireless communication has been widely applied and various techniques are used to achieve signals with higher quality and higher efficiency. Pulse position modulation (PPM) is a commonly used modulation scheme. However, PPM suffers from its low bandwidth efficiency and Multiple pulse position modulation (MPPM) is generated to improve the performance of signals. Further research can be carried out to figure out ways to further improve channel capacity of communication systems by combining modulation techniques together. In this paper, three different schemes are introduced, including LDPC-coded MPPM UWOC system, MIMO-MPPM WOC system, and PSM-MPPM system. Fundamental principles of these three techniques are mentioned before going through the methods used to carrying out experiments. Both simulations derived from numerical analysis and experiment results are obtained to support the results. In LDPC-coded and MIMO research, turbulence effects are considered by adopting different statistical distributions. The aim of the paper is to compare properties of three recent research and discuss how they can be applied in different scenarios to improve the communication systems.

The error rate analysis for MPPM

Multiple pulse position modulation is one of many modulation techniques that are appropriate for optical communication systems. In this paper, a brief description of MPPM is introduced. More importantly, the error rate performance of MPPM is discussed as the main topic. It is investigated in both theoretical part by mathematical models and experimental part by MATLAB tool and some other techniques. It can be found that the error rate performance of MPPM can be affected by several factors such as signal to noise ratio (SNR), the figure of chips in each symbol, the operating bit rate level and the number of optical pulses. Besides, let LPPM compared with MPPM, MPPM has higher error rate in ideal circumstances. However, there are still limitations in this paper, only preliminary works were done to analyze the MPPM error rate. Therefore, further progress can be made in this topic and other facets of MPPM can also be researched to reach an achievement.

Analysis of bit error rate of pulse position modulation in free-space optical communication

Pulse Position Modulation (PPM) modulation is a widely used modulation method in free-space optical (FSO) communication, which has many medium forms. This work introduces and summarises the three main PPM modulation methods, L-ary pulse position modulation (L-PPM), L-ary differential pulse position modulation (L-DPPM), and L-ary multiple pulse position modulation (L-MPPM), and summarises their respective characteristics and suitable usage scenarios. At the same time, this study analyzes several cases of combining coding methods with PPM modulation methods and finds that the right coding method can make PPM modulation methods more valuable. In addition, receiver diversity and/or aperture averaging can both improve the connection error performance.

Secure VLC for Wide-Area Indoor IoT Connectivity

For Internet of Things (IoT) connectivity, visible light communication (VLC) can play an important role, compared to traditional radio frequency (RF) communication. VLC does not interfere with existing RF communication, and the frequency spectrum is unregulated. Additionally, in an indoor area, VLC can provide secure communication. This study proposes an authentication-based framework that enhances security at the user end. In addition, we have modified the multiple pulse position modulation (MPPM) to map digits and send particulate matter (PM) data in broad area coverage. To reduce communication channel usage, we take the difference between two consecutive values instead of sending the whole value, which enables us to transmit the same volume of data in fewer optical signals using the proposed modulation. The comparative analysis result shows that the proposed modulation can transmit PM data more efficiently than other modulation techniques. We also provided delay analysis for proper synchronization for connectivity between nodes. The modulation was tested in the case of multihop connectivity to send data on long distance about 36 m in real time.

Position coding as a means of increasing the range of optical communications links

Subject of study. We present research on the range of atmospheric optical communications links as a function of atmospheric conditions, the types of laser beam modulation used, and the type of interference-resistant coding used. Aim. We develop an approach for increasing the range of free-space optical communications links by improving resistance to atmospheric turbulence. Methods. We show that the modulation technique and channel coding must be compatible if optimum results are to be achieved. Pulse position modulation and interference-resistant position coding are one example of such a compatible combination; a holographic code in which a sequence of pulses representing a 1D linear hologram of a single pulse replaces a single pulse in the desired position is one example of an interference-resistant code. In this case, position modulation is still being used, but in the form of multiple pulse position modulation. A holographic code takes advantage of the fact that holograms are divisible, and a fragment of the hologram can be used for recovery of transmitted data (as well as data hidden by noise). The recovery capacity of the holographic code depends on the hologram length—the number of slots per symbol interval. Main results. We show that holographic coding provides higher interference resistance and a lower probability of detector error and provides the same benefit as an increase in transmitter power. Practical significance. The benefit from holographic coding may be used to either increase the communications range or increase the communications channel reliability. Position coding has the advantages that the redundant information required for interference-resistant encoding is created within the symbol interval, does not affect the symbol repetition frequency, and has no effect on the data transmission rate.

The BER Performance of the LDPC-Coded MPPM over Turbulence UWOC Channels

Turbulence-induced fading is a critical performance degrading factor for underwater wireless optical communication (UWOC) systems. In this paper, we propose a quasi-cyclic (QC) low-density parity-check (LDPC) code with multiple-pulse-position modulation (MPPM) to overcome turbulence-induced fading. MPPM is adopted as a compromise between the low-power efficiency of on–off keying (OOK) and the low bandwidth efficiency of pulse position modulation (PPM). The bit error rate (BER) performance of LDPC-coded MPPM over turbulence UWOC channels is investigated. The log-likelihood ratio (LLR) of MPPM is derived, and a simplified approximation is used for iterative decoding. Subsequently, the closed-form expression of the BER, without forward error correction (FEC) code, is obtained for the generalized-gamma (GG) fading model. Finally, Monte-Carlo (MC) simulation results are provided to demonstrate the correctness of the derived closed-form expressions and the effectiveness of the LDPC code with simplified LLR to improve the BER performance for different MPPM formats over fading channels.

A Bandwidth Efficient Hybrid Multilevel Pulse Width Modulation for Visible Light Communication System: Experimental and Theoretical Evaluation

Visible light communication (VLC) is considered a new technology for interconnecting devices in 5G and beyond. VLC can provide additional bandwidth for communicating devices which can help to reduce the radio frequency bandwidth congestion. In this work, we aim to maximize the bandwidth usages for VLC. The proposed modulation technique can impose more bits due to the combined utilization of both pulse height and width changes. Moreover, we subdivide the single bit duration to impose more bits for data transmission. The proposed modulation is capable of transmitting more bits by utilizing fewer optical pulses than other traditional modulation techniques such as multilevel modulation, on-off keying, pulse width modulation, pulse position modulation, pulse amplitude modulation, and multiple pulse position modulation. We have evaluated the theoretical bit error rate (BER) expression in terms of average signal to noise ratio and compared the experimental BER performance for the proposed system. The experimental results demonstrate that the proposed modulation technique can achieve a communication distance of 3 m in an indoor environment.

Analisis Kinerja Multiple Pulse Position Modulation terhadap Interferensi Lampu Neon pada Sistem VLC

Visible Light Communication (VLC) technology is a wireless communication system that transmit information using the visible light spectrum. VLC has the advantage of not being affected by electromagnetic interference, but can be affected by interference from ambient light. There are two types of interference in the VLC system, namely natural interference from sunlight and ambient light interference from fluorescent or incandescent lamps. This study discusses the effect of fluorescent light interference on the VLC system using Multiple Pulse Position Modulation (MPPM) in a 10x10x3 meter room with Line Of Sight (LOS) channel. There are two scenarios carried out in this study discusses. The first scenario is the delivery of information using the VLC system without interference, while the second scenario is the delivery of information with interference from fluorescent lights. The final results of the simulations show that the VLC system in scenario I has a better performance compared to the VLC system in scenario II. This is evidenced by the results of the BER value obtained in scenario I with 2-PPM modulation obtained a value of 0.416, in 4-PPM modulation obtained a value of 0.335, and with 8-PPM modulation obtained a value of 0.231. In scenario II the BER value obtained with 2-PPM modulation is 0.466, in 4-PPM modulation is 0.432 and with 8-PPM modulation is 0.384. It also shows that 8-PPM modulation is the best modulation to transmit data compared to 2-PPM and 4-PPM modulation.

Performance analysis of a low-complexity nonorthogonal multiple access scheme in visible light communication downlinks using pulse modulations

Although Successive Interference Cancellation (SIC) decoding is widely adopted in Nonorthogonal Multiple Access (NOMA) schemes for the recovery of user data at acceptable complexity, the imperfect SIC would cause Error Propagation (EP), which can severely degrade system performance. In this work, we propose an SIC-free NOMA scheme in pulse modulation based Visible Light Communication (VLC) downlinks, including two types of users with different data rate requirements. Low bit-rate users adopt on-off keying, where as high bit-rate ones use Multiple Pulse Position Modulation (MPPM). The soft decision decoding scheme is exploited by high bit-rate users to decode MPPM signals, which could fundamentally eliminate the detrimental effect of EP; the scheme is also easier and faster to execute compared with the conventional SIC decoding scheme. Expressions of the symbol error rate and achievable data rate for two types of users are derived. Results of the Monte Carlo simulation are provided to confirm the correctness of theoretical results.

SER performance investigation of a MPPM relay-aided FSO system with three decision thresholds over EW fading channel considering pointing errors

The symbol error rate (SER) performance of a multi-hop parallel free-space optical (FSO) communication system with multiple pulse position modulation (MPPM) scheme considering three different decision threshold schemes, fixed decision threshold (FDT), optimized decision threshold (ODT), and dynamic decision threshold (DDT) has been investigated over exponentiated Weibull (EW) atmospheric turbulence channel combiningthe impact of the fading induced by pointing errors. On the basis of the decode-and-forward (DF) protocol, the cumulative distribution function (CDF) and probability density function (PDF) in terms of the Meijer’ s G-function for this considered FSO communication system are derived with the max–min criterion as the best path selection scheme. After that, the closed-form SER expressions for three threshold schemes are obtained by Gauss–Laguerre quadrature function and then confirmed by Monte Carlo (MC) simulation. The SER performance is further analyzed systematically under different turbulence conditions, receiver aperture sizes, jitter variances, and structure parameters (R and C) for three decision threshold schemes. The results show that pointing errors will deteriorate the system performance, while the multi-hop parallel transmission can improve the SER performance and expand the communication range. Furthermore, ODT and DDT schemes can significantly overcome the effect of the error floor of FDT scheme. This work benefits the development of the MPPM based relay-aided FSO system.

Optical Energy-Constrained Slot-Amplitude Modulation for Dimmable VLC: Suboptimal Detection and Performance Evaluation

Energy-constrained slot-amplitude modulation (ECSAM) enables light dimming, eliminates light flicker and constrains the peak optical power while providing robust communication links. However, the complexity of the maximum-likelihood (ML) based ECSAM receiver increases exponentially with required spectral efficiency. This paper provides a comprehensive performance evaluation of ECSAM for the indoor visible light communication (VLC) channel with multipath propagation under realistic illumination constraints and imperfect channel estimation. A sub-optimal receiver that employs a slot-by-slot detection algorithm followed by a slot-correction mechanism for reducing the receiver complexity is proposed. Additionally, the method for optimal selection of parameters when designing the signal waveform is presented. The analytical upper bound on the symbol error rate of ECSAM is derived using the union-bound technique. The results show that the error performance of the sub-optimal receiver are comparable to that of the optimal ML receiver. Compared with conventional power or bandwidth efficient VLC modulation techniques such as multiple pulse position modulation (MPPM) and pulse amplitude modulation (PAM), ECSAM provides complete flexibility in modifying the signal constellation for a desired dimming level to maximise the spectral efficiency and provide a robust bit error rate performance especially in the multipath propagation channel induced intersymbol interference.

Generic evaluation of FSO system over Málaga turbulence channel with MPPM and non‐zero‐boresight pointing errors

Free space optical (FSO) communication channels are affected by fluctuations in irradiance due to atmospheric turbulence and pointing errors. Recently, a generalized statistical model knows as Malaga ( M ) was developed to describe irradiance fluctuations of the beam propagating through a turbulent medium. In this paper, an approximate finite-series probability density function (PDF) for composite M turbulence with pointing errors is verified. Considering multiple pulse-position-modulation (MPPM) with intensity modulation and direct detection, specific closed-form expressions for average symbol error rate (ASER) and outage probability are obtained. Moreover, asymptotic expressions for ASER and outage probability over the Malaga channel with pointing errors are presented. Finally, ASER and outage probability expressions are deduced in three turbulence regimes, strong, moderate, and weak. Therefore, simulation results are given to confirm the accuracy of the proposed expressions. The results show that the optimum beam divergence angle is 1 mrad for zero-boresight displacement and 2 mrad for nonzero-boresight at a distance of 1 km. By increasing the range to 5 km, atmospheric turbulence is found to have the dominant effect over boresight displacement. Moreover, the system performance at the optimized divergence angle is studied in terms of transmit power, normalized boresight, and link distance.

Performance Evaluation of MPPM-Coded Wireless Optical MIMO System with Combined Effects over Correlated Fading Channel

The performance of wireless optical MIMO system with multiple pulse position modulation (MPPM) over correlated fading channel is investigated. The combined effects of atmospheric attenuation, atmospheric turbulence, and pointing error are taken into consideration. The bit error rate (BER) and the ergodic channel capacity are analyzed by utilizing the Poisson counting model and the exponential correlation model. Moreover, their approximate expressions are derived. The simulation results demonstrate that the pointing error is the most prominent influence factor over weak correlated channel. The performance degradation caused by a high channel correlation coefficient is more than that of pointing error in strong correlated channel. Therefore, the use of pointing, acquisition, and tracking (PAT) system and reasonable arrangement of the number and spacing of antennas at the transceiver are the keys to improve system performance.

End-to-end performance of DF multihop hybrid RF/FSO system using MPPM coding and MIMO technique under dependent GG turbulence channels

<p><span>The paper presents a BER analysis for hybrid Radio Frequency/multihop Free Space Optics, known as RF/FSO, communication system benefiting from Multiple Input Multiple Output (MIMO) configuration but impaired by Gamma-Gamma, known as GG, turbulence. Authors deploy Multiple Pulse Position Modulation, known as M-PPM, like a signaling technique. Furthermore, the exact as well as approximated amounts of Symbol-Error Rates, known as SERs, are both judged in this work. A closed form formula related to the whole Probability Density Function, called PDF, for our designed system is derived. Such interesting approach provides to us better quality of service by combating atmospheric turbulence.</span></p>

SmartVLC: Co-Designing Smart Lighting and Communication for Visible Light Networks

Visible Light Communication (VLC) based on LEDs has been a hot topic investigated for over a decade. However, most of the research efforts assume the intensity of LED light is constant. This hypothesis is not true when Smart Lighting is introduced to VLC, which requires LEDs to adapt their brightness based on the intensity of natural ambient light. Smart lighting saves power consumption and improves user comfort. However, intensity adaptation severely affects the throughput performance of data communication. In this paper, we propose SmartVLC , a system that can maximize the throughput (benefit communication) while still maintaining the LEDs’ illumination function (benefit smart lighting). A novel Adaptive Multiple Pulse Position Modulation (AMPPM) scheme is proposed to support fine-grained dimming levels to avoid flickering while maximizing the throughput under each dimming level. SmartVLC is implemented on off-the-shelf commodity hardware. Several real-life challenges in both hardware and software are addressed to make it a robust real-time system. Comprehensive experiments are carried out to evaluate the system performance under multifaceted scenarios. Experimental results demonstrate that SmartVLC supports a communication distance up to 3.6m, and improves the throughput achieved with two state-of-the-art approaches by 40 and 12 percent on average, respectively, without bringing any flickering to users.

Lightweight multi-hop VLC using compression and data-dependent multiple pulse modulation.

Particulate matter (PM) has a diameter of few micrometers, which causes different illnesses. We used visible light communication (VLC) to transfer PM data to a user monitoring terminal in real-time. To reduce the time and power required for communication, we compressed the PM data. Subsequently, these compressed data were transmitted using a modulation technique called data-dependent multiple pulse position modulation (DDMPPM). We evaluate the performance of DDMPPM for multi-hop communication in VLC through practical experiments. For the same data set, DDMPPM utilizes a lesser frame to transfer PM data. Using DDMPPM, we achieved a total communication distance of 48 m.

Symbol error rate of soft-decision multiple pulse position modulation over turbulent channels.

Soft-decision multiple-pulse-position modulation (MPPM) is one of the favored free-space optical communication modulations. This paper derives theoretical expressions for the symbol error rate of both fast and slow fading conditions applied for soft-decision MPPM without channel state information at the receiver as a particular case of nonmemoryless channel conditions. The theoretical expressions for lognormal and gamma-gamma modeled turbulence were successfully verified by simulation.

Performance of spectral amplitude coded multiple pulse position modulation with non-uniform energy slots and fading.

Multiple-pulse position modulation (MPPM) is an advanced modulation method for optical wireless communication (OWC), which could provide better performance when channel information is not available. We consider the evaluation of a symbol error rate (SER) expression for MPPM applied within OWC. In the proposed model, MPPM is realized by spectral-amplitude coding (SAC) with non-uniform spectral slot energies. The derived fading channel SER expression is applicable for an arbitrary fading distribution, which may be due to either atmospheric turbulence or transceiver pointing error. A detailed theoretical analysis of the SER is provided and the resulting SER expression is verified by simulation.

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

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)).

Enhanced Multiple Pulse Position Modulation Aided Reverse Polarity Optical OFDM System With Extended Dimming Control

In this paper, we propose a multiple pulse position modulation (MPPM) aided reverse polarity optical orthogonal frequency division multiplexing scheme that aims to enhance the spectral efficiency (SE) for dimmable visible light communication (VLC) systems. In this scheme, we exploit the MPPM patterns to transmit the extra information bits without the increase of the signal bandwidth and, thus, improving the SE. Specifically, for each frame, the binary information stream is divided into two parallel groups, where the first group is used to select the patterns of MPPM symbols, while the other is modulated by optical OFDM. Then, the time-domain OFDM signal is accommodated by both the “on” and “off” slots of MPPM symbols for transmissions over the VLC channel. With the aid of a forward error correction aided decision feedback approach, the system performance can be further improved. Theoretical analyses on the dimming level, the average power consumption and the frame error probability are provided and verified by simulation results. It is shown that the proposed system with extended dimming control can achieve the highest effective spectral efficiency in most scenarios without substantially increasing the computational complexity, while still maintaining a power consumption level similar to those of the reference systems.