Showing papers on "Pulse-position modulation published in 2019"

Hybrid Modulation Scheme Combining PPM With Differential Chaos Shift Keying Modulation

Abstract: In conventional ${M}$ -ary differential chaos shift keying modulation (DCSK) systems, the distance between constellation points gets closer as ${M}$ increases, resulting in poor performance. A hybrid modulation scheme based on pulse position modulation (PPM) and DCSK is proposed in this letter to improve bit-error-rate (BER) performance. In this scheme, one part of the bits is modulated by PPM while the other part is modulated by DCSK. Thus, information bearing signals are simultaneously modulated by the information bit and the selected pulse position of PPM which is determined by extra information bits. Analytical BER performance of the proposed scheme is derived and verified by simulations. Results show that the considered scheme outperforms conventional M-DCSK, code index modulation DCSK, and commutation code index DCSK in additive white Gaussian noise and multipath Rayleigh fading channels.

Error performance of deep space optical communication with M-ary pulse position modulation over coronal turbulence channels

Abstract: Free space optical (FSO) communication is a promising technology for future deep space exploration, but it encounters coronal turbulence during superior solar conjunction. In this paper, the bit-error rate (BER) performance of deep space FSO communication systems is evaluated for optical waves propagating in the non-Kolmogorov coronal turbulence. By virtue of its high energy efficiency, the pulse position modulation (PPM) technique is adopted to mitigate the influence of turbulence under lognormal distribution channels. The effects of the parameters of the coronal turbulence and of the FSO system, such as the turbulence outer scale, spectral index, symbol number, data bit rate, equivalent load resistor, and average gain, on the BER are investigated and discussed in this paper. In addition, the performance improvement from M-ary PPM and binary phase-shift keying subcarrier intensity modulation is studied. The results of a numerical evaluation illustrate that a deep space FSO communication system with PPM scheme can well be used to mitigate the impact of coronal turbulence.

BER and channel capacity of a deep space FSO communication system using L-PPM-MSK-SIM scheme during superior solar conjunction

Abstract: Although free space optical (FSO) communication is a promising technique for deep space communication and it can help in the rapid development of space exploration missions, it encounters coronal turbulence during superior solar conjunction. To improve the bit error rate (BER) performance of FSO communication system under the influence of coronal turbulence, a hybrid modulation scheme, L-PPM-MSK-SIM-which is a combination of pulse position modulation (PPM), minimum shift keying (MSK), and sub-carrier intensity modulation (SIM) techniques-is proposed in this study. Considering various noise sources, both the BER and channel capacity of the communication system are evaluated under the lognormal (LN) turbulence channel. Our simulation results demonstrate that the BER performance with the L-PPM-MSK-SIM scheme is superior to that with L-PPM and BPSK-SIM schemes. In addition, the parameters of the coronal turbulence and FSO communication system have a tremendous influence on the link BER and channel capacity. Moreover, our results also revel that thermal noise is more predominant than the short noise and background noise for the BER performance of deep space FSO communication.

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

Abstract: 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.

Quantum Pulse Position Modulation with Photon-Added Coherent States

Abstract: Quantum communication systems exploit the quantum features of light to enhance the reliability of a classically described communication system. This paper proposes the use of photon-added coherent states (PACSs), instead of coherent states, for quantum pulse position modulation (PPM) systems. PACSs are the most simple example of non-classical non-Gaussian states of light, as they can not be described by the classical laws of physics. We show that employing PACS in a PPM communication system improves the reliability of the communication with respect to using a coherent state with the same energy.

Approaching the ultimate capacity limit in deep-space optical communication

Abstract: The information capacity of an optical channel under power constraints is ultimately limited by the quantum nature of transmitted signals. We discuss currently available and emerging photonic technologies whose combination can be shown theoretically to enable nearly quantum-limited operation of a noisy optical communication link in the photon-starved regime, with the information rate scaling linearly in the detected signal power. The key ingredients are quantum pulse gating to facilitate mode selectivity, photon-number-resolved direct detection, and a photon-efficient high-order modulation format such as pulse position modulation, frequency shift keying, or binary phase shift keyed Hadamard words decoded optically using structured receivers.

Analytic and simulative comparison of turbulent FSO system with different modulation techniques

Abstract: In this paper, we characterize the performance of Intensity Modulation/Direct Detection (IM/DD) and coherent detection modulation techniques in free-space optical (FSO) communication system in terms of bit error rate (BER). The system of interest includes M-ary Pulse Position Modulation (M-PPM) in correspondence to IM/DD and M-ary Phase Shift Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) with respect to coherent detection. The system is subjected to weak turbulence regime of log-normal channel with scintillation index less than 0.75. Coherent techniques involve the amount of signal pulses transmitted in a particular time as the major component of their generation, except IM/DD which is a result of photon intensity, i.e. the number of photons forming a pulse. It is worth mentioning that in previous studies, the performance of IM/DD techniques had been evaluated in terms of photon-count fluctuation statistics and thus the impact of fading strength of channel on signal intensity was not discussed anywhere. In this work, an objective equivalence has been achieved between these two kinds of detection by deriving the BER expression of M-PPM in terms of probability density function of signal intensity, while considering fading strength, scintillation index, thermal noise and outage probability as system parameters for numerical analysis.

Multi-rate OCDMA system BER performance evaluations for different ML-code sequences

Abstract: This paper analyzes Bit Error Rate (BER) of Optical Code Division Multiple Access (OCDMA) networks for different class of services which are data, voice, and video; whereas Multi-Length Weighted Modified Prime Code (ML-WMPC) sequences are utilized as a spreading code in with respect to previously used ML-Optical Orthogonal codes. Due to variations in bit rates between the mentioned services, each of them assigns a different WMPC sequence length. In addition, the shot noise, thermal noise, and the Multiple Access Interference (MAI) are included and considered as sources of noise in the BER performance analysis. Furthermore, Pulse Position Modulation, Manchester encoding and MAI cancellation (MAIC) technique are utilized to improve the network performance at a higher number of active users. For analysis, the BER performance calculations are investigated for three types of OCDMA receivers such as simple receiver, receiver with MAIC technique, and receiver with MAIC and Manchester encoding. Moreover, the BER mathematical models have been introduced for different bit rates according to the type of service in the presence of the ML-WMPC and the last of three mentioned OCDMA receivers. Finally, these models and their results are compared with the other existing models, where the results show an improvement in BER performance in the proposed approach.

Performance analysis of optical code division multiple access networks for multimedia applications using multilength weighted modified prime codes

Abstract: The bit error rate (BER) performance of the incoherent synchronous pulse position modulation optical code division multiple access (PPM-OCDMA) network has been analyzed using a multilength weighted modified prime code (ML-WMPC) for three different multimedia services, such as data, voice, and video. Each service has a different bit rate than the other services and, hence, a different WMPC code length. In the network performance calculations, the multiple access interference (MAI) is included and considered as the only source of noise. In addition, to improve the network performance, the Manchester encoding and the MAI cancellation techniques are used with the WMPC at a higher number of active users. The network performance calculations are introduced in terms of BER for three kinds of PPM-OCDMA receivers, such as a simple receiver, receiver with MAI cancellation (MAIC), and receiver with MAIC and Manchester encoding technique. Finally, the BER calculation has been investigated at different bit rate according to the type of service provided by the network in the presence of the ML-WMPC and the third PPM-OCDMA receiver.

The Impact of Optical Beam Position Estimation on the Probability of Error in Free-Space Optical Communications

Abstract: Optical beam position on a detector array is an important parameter that is needed to optimally detect a pulse position modulation (PPM) symbol in free-space optical communications Since this parameter is generally unknown, it is essential to estimate the beam position as accurately as possible In this paper, we examine that an accurate estimate of the beam position is required in order to minimize the probability of PPM symbol detection error Furthermore, we employ different estimators/trackers of the beam position (which could be stationary or time-varying), and compare the probability of error performance of the detectors using those estimators The probability of error is calculated with the help of Monte Carlo simulations for the uncoded 8-PPM and 16-PPM systems, each of which employ photon counting maximum likelihood receivers It is found out that the probability of error is minimum for the maximum likelihood estimate of the stationary beam position Moreover, for the dynamically varying beam position, a particle filter with a sufficiently large number of particles provides a close-to-optimal probability of error performance

Performance analysis of various pulse modulation schemes for a FSO link employing gain switched quantum cascade lasers

Abstract: In this paper, we analyze the performance of an FSO communication link that incorporates gain switched Quantum Cascade Lasers (QCLs) operating at 9 µm and a Quantum-Well based Infrared Photodetector (QWIP). The performance of various modulation techniques like ON-OFF Keying (OOK), Pulse Position Modulation (PPM), Dual-Header Pulse Interval Modulation (DH-PIMα), Differential Pulse Interval Modulation (DPIM) are analyzed for the FSO link with short optical pulses. It is found that DH-PIM2 satisfies most of the properties required for an efficient pulse modulation. It provides highest power efficiency, normalized packet rate (3.8 times that of PPM), possesses the lowest bandwidth requirement of 3.8 GHz and also the lowest average symbol length of 11 bits. DPPM has the highest transmission capacity that is 2 times that of PPM while PPM performs significantly better among all the modulation techniques providing an astounding BER of 10−40 under soft decoding.

Power distribution and BER in indoor VLC with PPM based modulation schemes: a comparative study

Abstract: Visible light communication (VLC) uses an intensity-modulation and direct-detection scheme to transmit data. The light source utilized in VLC structures is constantly switched on and off rapidly, resulting in flickering. Furthermore, most of illumination systems exclude dimming support to permit customers to dim the light source to the desired stage. Therefore, the modulation scheme for information transmission in VLC should consist of flicker mitigation and dimming manage abilities. Double inverse pulse position modulation (DIPPM), sub-carrier pulse position modulation (SC-L-PPM), and M-ary variable pulse position modulation (M-VPPM) are recommended for minimizing the flicker issues and supporting an excessive degree of dimming for VLC systems. In this paper, a comparison is introduced between DIPPM, SC-L-PPM, and M-VPPM according to error performance and bit rate. In addition, a simulation is carried out to measure the optical power distribution for a LED lamp in an indoor room topology for each modulation technique. The obtained results indicated that SC-L-PPM is the best choice regarding the bit error rate (BER) and optical power distribution compared to the other two schemes. A 10−6 BER is achieved with a very low power requirement at L = 8, while a remarkable power distribution of 1.5–6.5 dBm is observed from 3 × 5 × 5 m3 room corners to the center, respectively. According to the bit rate, it is noticed that, M-VPPM is the most efficient one compared to the two other schemes. It achieves 2.3 × 107 bps at a signal to noise ratio (SNR) of 22 dB and M = 8.

Free Space Optical Communication and Laser Beam Propagation through Turbulent Atmosphere: A Brief Survey

Abstract: In this survey paper, a brief survey has been performed about the free space optical communication (FSO), which has emerged as an innovative hot topic in the field of research. This paper inspected about the features and challenges faced by FSO communication. Here, it is focused about atmospheric turbulence, one of the main challenge FSO has to encounter during the propagation of laser beams through free space. The survey has also been undergone regarding the various modulation schemes, and various laser optical beam profile that can be used in FSO as optical source of propagation. The analysed techniques employed for the process of modulation are Amplitude shift keying(ASK), Binary phase shift keying(BPSK), Quadrature phase shift keying(QPSK), Pulse position modulation(PPM), Pulse amplitude modulation(PAM), Pulse width modulation(PWM). Also, investigated about the effect of different types of aberrations such a tilt, astigmatism, coma, and spherical aberrations present in a turbulent atmosphere on different laser beam profiles such as Bessel Gaussian (BG) beam, Laguerre-Gaussian (LG) beam, Hermite-Gaussian (HG) beam, Helical beam.

Optimized Beam Size of Optical Ground-to-Satellite Link over Turbulence and Beam-Wandering

Abstract: The performance of a laser beam traveling in uplink from a ground-to-satellite is subjected to turbulence, and beam wandering. This paper evaluates the performance of the optical uplink with the pulse position modulation (PPM) scheme in order to determine the optimum beam size that minimizes the symbol error rate (SER) and outage probability. Close-form expressions for SER and outage probability are derived by considering the combined effect of turbulence, and beam wandering. Appropriate simulation scenarios are applied, and numerical results are verified the accuracy of the derived close-form expressions. The results show that the optimum beam size is 2.5 with zenith angle changes from 0 to 30°. Furthermore, this paper studies the system performance on optimized beam size by considering the effect of changing the zenith angle, the transmitter power and the modulation orders.

Performance analysis of pulse position modulation-based hybrid technique for cellular backhaul free-space optical link

Abstract: We investigate the performance of half-cosine pulse-shaped hybrid pulse position modulation-orthogonal frequency division multiplexing (HC-PPM-OFDM) under weak (i.e., log-normal) and strong (i.e., gamma–gamma) turbulence free-space optical channel. Joint impact of frequency and time offset on the performance parameters such as intercarrier interference, a symbol to interference ratio, and bit-error rate are also investigated. This research aims to improve the spectral efficiency performance of traditional PPM through the proposed hybrid technique. Further, the proposed HC-PPM-OFDM technique is compared with pulse position modulation-minimum shift keying (PPM-MSK), PPM, and hybrid PPM-OFDM. Obtained results show comprehensive improvement in the performance parameters under both weak and strong atmospheric turbulences. In addition to the above results, the upper-bound channel capacity expression is derived for log-normal as well as gamma–gamma turbulence channel models. Obtained results reveal that the proposed modulation technique outperforms PPM and PPM-MSK techniques under all turbulence conditions at a marginal cost of power penalty.

A non-linear channel code for covert communications

Abstract: This paper presents an explicit channel code design for covert communications in the Binary Symmetric Channel. The proposed architecture is composed of the serial concatenation of a linear code and a graph-based non-linear code baptized as moderate-density non-linear code. This non-linear code encompasses pulse position modulation as a particular case. In order to guarantee covertness, a scrambling sequence that is not known to the warden is employed.

High output power laser transmitter for high-efficiency deep-space optical communications

Abstract: We report on the design, development, and testing of the high-power Laser Transmitter Assembly (LTA) supporting the Deep Space Optical Communications (DSOC) demonstration hosted on the Psyche Discovery class mission, due to launch in 2022. The DSOC project, under development by NASA’s Jet Propulsion Laboratory, will test space-to-ground high-bandwidth laser communications while en route to the Psyche-16 asteroid in the main asteroid belt, in what will be the longest range high rate optical communications link in history. The LTA is based on a master-oscillator power-amplifier optical architecture, using highly-efficient cladding-pumped amplification. The transmitter is designed to deliver average optical output powers <4 W at 1550 nm for low power consumption data links at <100 Mbps. The output signal operates across multiple pulse-position modulation (PPM) orders and pulse-widths to optimize the space-to-ground link. The architecture is designed for high-reliability and radiation hardness, and features hardware interlocks and secondary signal/pumping paths to reduce single points of failure. We also detail the effective management of optical nonlinearities which could damage the LTA or impact the communications link. These include the suppression of stimulated Brillouin scattering, self-phase modulation, and pulseto- pulse energy variation (PEV), which arises from the gain dynamics of the power amplifier, and will manifest when the LTA is configured for large pulse energies and long inter-pulse delays. The LTA also incorporates hardware and software controls to enable autonomous operation, including closed-loop control of intra-stage and output power levels, modulator bias control, and detailed reporting of LTA status through telemetry.

Utilizing time-bandwidth space for efficient deep-space communication

Abstract: We discuss modulation formats that warrant high information efficiency of deep-space optical links under given power constraints. The discussion is framed using the theoretical concept of orthogonal optical modes occupying the available time-bandwidth space. With diminishing average signal power, the challenge is to concentrate the entire optical energy in very few of these modes. In the generic case of pulse position modulation (PPM), where optical modes occupy separate time bins, this results in increasing peak-to-average power ratio requirements for the transmitter light source. Equivalent information efficiency can be attained using frequency shift keying (FSK) employing modes that do not overlap in the spectral degree of freedom and have uniformly distributed instantaneous optical power in the temporal domain. Recently, efficient modulation formats have been proposed that use words composed from the binary phase shift keying (BPSK) alphabet. Such words can be converted after transmission into the PPM format with the help of structured optical receivers. Selected technical aspects of physical implementations of links based on different modulation formats are briefly reviewed.

On Optimizing the Performance of Impulse Radio Pulse Position Modulation Based on UWB Gaussian Pulse Derivatives

Abstract: In this paper, we enhance the performance of Pulse Position Modulation scheme applied with Impulse Radio Ultra WideBand transmission, while the receiver is based on non-coherent energy detection. By exploiting the time properties of Gaussian pulse derivatives, it was possible to adjust the modulation index in order to improve the data rate in compromise with the error probability. For the 5th Gaussian waveform, we succeeded in increasing the information rate by 25 % with a notable reduction in the bit error rate simultaneously. The transmission speed can be further boosted by 33 % at the cost of additional errors collected at receiver side, which depend on the signal-to-noise ratio and generated pulse dynamics.

Blind Fractionally Spaced Channel Equalization for Shallow Water PPM Digital Communications Links

Abstract: Underwater acoustic digital communications suffer from inter-symbol interference deriving from signal distortions caused by the channel propagation. Facing such kind of impairment becomes particularly challenging when dealing with shallow water scenarios characterized by short channel coherence time and large delay spread caused by time-varying multipath effects. Channel equalization operated on the received signal represents a crucial issue in order to mitigate the effect of inter-symbol interference and improve the link reliability. In this direction, this contribution presents a preliminary performance analysis of acoustic digital links adopting pulse position modulation in severe multipath scenarios. First, we show how the spectral redundancy offered by pulse position modulated signals can be fruitfully exploited when using fractional sampling at the receiver side, which is an interesting approach rarely addressed by the current literature. In this context, a novel blind equalization scheme is devised. Specifically, the equalizer is blindly designed according to a suitably modified Bussgang scheme in which the zero-memory nonlinearity is replaced by a M-memory nonlinearity, M being the pulse position modulation order. Numerical results not only confirm the feasibility of the technique described here, but also assess the quality of its performance. An extension to a very interesting complex case is also provided.

An Energy Efficient Modulation Scheme for Body-Centric Terahertz (THz) Nanonetworks

Abstract: In body-centric communications, energy efficiency is a critical performance metric, while the achievable data rate is not of primary concern. In this paper we present a novel modulation scheme, which can be efficiently used in body-centric terahertz (THz) nanonetworks. The proposed scheme is a combination of the time-spread On-Off keying (TS–OOK) and the pulse position modulation (PPM) and presents lower energy consumption, compared to other existing methods as TS–OOK, at a minor cost to the data rate. Furthermore, another important aspect is that the proposed modulation scheme can be effectively used to mitigate the impact of the specific kind of noise in THz body-centric communications, thus leading to better error performance. Finally, we present analytical and simulation results in order to compare the new scheme with the existing TS–OOK.

Performance of M-ary pulse position modulation for aeronautical uplink communications in an atmospheric turbulent medium

Abstract: This paper discusses the bit-error-rate (BER) performance of an aeronautical uplink optical wireless communication system (OWCS) when a Gaussian beam is employed and the M-ary pulse position modulation technique is used in an atmospheric turbulent medium. Weak turbulence conditions and log-normal distribution are utilized. The Gaussian beam is assumed to propagate on a slant path, the transmitter being ground-based, and the airborne receiver is on-axis positioned. Variations of BER are obtained against the variations in the link length, Gaussian beam source size, zenith angle, wind speed, wavelength, modulation order, data bit rate, equivalent load resistor, avalanche photodetector gain, and detector quantum efficiency. It is observed that the performance of the aeronautical uplink OWCS is affected from atmospheric turbulence significantly.

Real Time Photon-Counting Receiver for High Photon Efficiency Optical Communications

Abstract: We present a scalable design for a photon-counting ground receiver based on superconducting nanowire single photon detectors (SNSPDs) and field programmable gate array (FPGA) real-time processing for applications to space-to-ground photon starved links, such as the Orion EM-2 Optical Communication Demonstration (O2O) [1], and future deep space or low transmitter power missions. The receiver is designed to receive a serially concatenated pulse position modulation (SCPPM) waveform [2], which follows the Consultative Committee for Space Data Systems (CCSDS) Optical Communications Coding and Synchronization Red Book standard [3]. The receiver design uses multiple individually fiber coupled, 80% detection efficiency commercial SNSPDs in parallel to scale to a required data rate, and is capable of achieving data rates up to 528 Mbps. For efficient fiber coupling from the telescope to the array of parallel detectors that can be scaled both to telescope aperture size and the number of detectors, we use either a single mode fiber (SMF) photonic lantern or a few-mode fiber (FMF) photonic lantern [4]. In this paper we give an overview of the receiver system design, the characteristics of the photonic lanterns, the performance of the SNSPDs, and system level tests. We show that 40 Mbps can be received using a single SNSPD, and discuss aspects for scaling to higher data rates.