Showing papers on "Pulse-position modulation published in 2018"
TL;DR: In this article, the design and performance enhancement of the power penalty in a dense wavelength division multiplexing based on free space optical communication (FSOC) link using digital pulse position modulation (DPPM) and on-off keying (OOK) modulation is presented.
Abstract: This paper presents the design and performance enhancement of the power penalty (PP) in a dense wavelength division multiplexing based on free space optical communication (FSOC) link using digital pulse position modulation (DPPM) and on–off keying (OOK) modulation. Such a system has a high performance, low cost, robust and power efficient, reliable, excessive flexibility, and higher data rate for access networks. The system performance is evaluated for an 8-channel wavelength-division-multiplexing for hybrid fiber FSOC system at 2.5 Gbps on widely accepted modulation schemes under various atmospheric turbulence (AT) regimes conditions. The performance of system is introduced in terms of PP, bit-error rate (BER), transmission distance and the average received optical power. The numerical results shows that the improvement of the PP using DPPM modulation of 0.2–3.0 dB for weak turbulence (WT) regimes for BER of 10−6 and above 20, 25 dB for strong turbulence (ST) regimes are reported for BER of 10−6 and 10−9, as respectively (depending on the AT level). Further, we develop of improvement the PP caused by multiple-access interference about 6.686 dB which is predicted for target BER of 10−9 in WT and 1 dB at target BER of 10−6 in ST when the 8 user are active on the system of optical network units. Additionally, the optical power budget and margin losses of a system are calculated with different link length. The proposed approach of DPPM merges superiority with higher enhancement of PP about 0.8 dB for BER equal 10−9 at FSO link length lfso = 2000 m compared to OOK at 1 dB for WT. An improvement of 2 dB is observed using the DPPM scheme over an OOK due to capability of detect pulses under background noise conditions with increased receiver sensitivity.
45 citations
TL;DR: A 46-m UWOC system based on PPM and MPPC was proposed and experimentally demonstrated with ultra-low transmitting power into the underwater channel with data rates of Mbps level.
Abstract: The transmission distance of underwater wireless optical communication (UWOC) is severely limited by the rapid decay of light intensity in water. Power-efficient pulse position modulation (PPM) and ultra-sensitive multi-pixel photon counter (MPPC) open the door toward designing long-reach UWOC systems. In this paper, a 46-m UWOC system based on PPM and MPPC was proposed and experimentally demonstrated with ultra-low transmitting power into the underwater channel. Clear eye diagrams without any slot error for ten different PPM signals were obtained in the 46-m experiment with data rates of Mbps level. The received optical power was as low as -39.2 dBm for the 10-MHz 4-PPM signal, when the laser worked under the stimulated state. Meanwhile, the received optical power can be reduced to -62.8 dBm, for the 5-MHz 64-PPM signal when the laser worked under the spontaneous state.
45 citations
TL;DR: In this paper, an underwater wireless optical communication (UWOC) system consisting of an M-ary pulse position modulated (PPM) Gaussian optical beam at the transmitter and an avalanche photodiode (APD) at the receiver is considered.
29 citations
09 Jul 2018
TL;DR: To overcome the channel degradation resulting from the turbulence effects and the PE, the single-input multiple-output (SIMO) system with maximal ratio combining (MRC) diversity is used and optimal values of the system parameters are found.
Abstract: Free space optics (FSO) communication links are impaired by the fading due to turbulence and misalignment. In this paper, we theoretically analyze the pointing error effects on performance of FSO systems using multi-pulse pulse position modulation (MP-PPM) over the Gamma-Gamma turbulence channel. We consider the moderate and strong atmospheric turbulence regimes with the combined effect of the pointing errors (PEs), and study the link average symbol error rate (ASER) and the outage probability. The numerical results are presented to show the impact of the pointing error on the ASER and the system outage. However, to overcome the channel degradation resulting from the turbulence effects and the PE, the single-input multiple-output (SIMO) system with maximal ratio combining (MRC) diversity is used. Exact close-form expressions for ASER and outage probability are derived and verified by using Monte Carlo simulation. We concluded that the optimal values of the system parameters are, the transmitted power is 20 dBm, jitter variance should be less than 0.5 m and laser beam width equals 0.2 cm. These values are significantly reduced the impacts of misalignment and fading whereas outage probability is less than at maximum jitter variance.
27 citations
TL;DR: Making the design of the PPM optical wireless communication system able to operate in a non-Kolmogorov atmosphere will give better BER performance if the parameters are taken into account in line with the trends presented in the results.
Abstract: The performance of atmospheric optical wireless communication systems in terms of the bit error rate (BER) is investigated when a Gaussian laser beam propagating in non-Kolmogorov turbulence is M-ary pulse-position-modulated (PPM). BER variations against the changes in different parameters such as the non-Kolmogorov power law exponent, symbol number, data bit rate, avalanche photodetector gain, equivalent load resistor, detector quantum efficiency, wavelength, turbulence structure constant, and the Gaussian beam source size are analyzed. Making the design of the PPM optical wireless communication system able to operate in a non-Kolmogorov atmosphere will give better BER performance if the parameters are taken into account in line with the trends presented in our results.
26 citations
17 Jun 2018
TL;DR: A low-complexity coding scheme to achieve covert communications over binary symmetric channels by introducing non-linearity through the use of pulse-position modulation (PPM) and multilevel coding (MLC).
Abstract: We develop a low-complexity coding scheme to achieve covert communications over binary symmetric channels. We circumvent the impossibility of covert communication with linear codes by introducing non-linearity through the use of pulse-position modulation (PPM) and multilevel coding (MLC). We show that the MLC-PPM scheme exhibits many appealing properties, in particular, the channel at a given index level remains the same as the number of level increases, which allows one to use families of capacity- and resolvability-achieving codes to concretely instantiate the covert communication scheme.
25 citations
TL;DR: Conventional PPM scheme is modified for the molecular communications channel and is shown to be better than CSK and other modulations in the literature, due to its robustness to ISI.
24 citations
TL;DR: In this article, the authors proposed a hybrid OFDM-pulse time modulation (PTM) scheme where bipolar O-OFDM samples are converted into the digital PTM formats of PWM and PPM for the intensity modulation of LEDs.
20 citations
TL;DR: The results show that the hybrid modulation technique, based on the pulse position modulation and phase-sampled Gaussian minimum shift keying technique, is an efficient technique to improve the performance of optical wireless communication for a cellular backhaul channel.
Abstract: In this study, a hybrid modulation technique called PPM–GMSK, based on the pulse position modulation (PPM) and phase-sampled Gaussian minimum shift keying (GMSK) technique, is investigated by considering log-normal and gamma–gamma turbulence as the channel-fading statistics. The analytical bit error rate (BER) and outage probability of the proposed hybrid modulation are derived. The results show that the hybrid modulation technique is an efficient technique to improve the performance of optical wireless communication for a cellular backhaul channel. Compared to 2-PPM and minimum shift keying (MSK), the proposed hybrid scheme has a less BER and a reduced amount of outage probability. Moreover, to achieve a reliable voice communication at 2 Gbps bit rate and BER of 10 − 3 under a weak turbulence effect, the PPM–GMSK has a coverage distance of about 3 km, whereas for PPM and MSK it is 2.6 and 2.4 km, respectively.
19 citations
TL;DR: Results show that adaptive PAA outperforms conventional fixed factor PAA and equal PAA obviously and obtains even better BER performance than MIMO one, at the same time reducing receiver complexity effectively.
17 citations
TL;DR: 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.
Abstract: 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
TL;DR: The performance of a distinct power saving and relatively simple design visible light communication system based on pulse position modulation (PPM) modulation scheme in a real life (i.e. diffuse) scenario can be optimized, controlled, and enhanced through using a careful choice of environmental and system parameters that can be selected from this work.
Abstract: This work explores the performance of a distinct power saving and relatively simple design visible light communication system based on pulse position modulation (PPM) modulation scheme in a real life (i.e. diffuse) scenario. The mathematical background for both communication and illumination performance is developed for the Sub-Carrier Pulse Position Modulation (SC-LPPM) Scheme in non-line-of-sight (NLOS) environment. An evaluative study is then carried out to provide an integrated picture for the SC-LPPM performance under several system/environmental parameters. Adding the NLOS components increases the total received power, but still, the LOS component dominates. At the corners of a typical room, the received optical power enhances by 120% when including NLOS components, while at room center the optical power enhances only by 12%. For illumination, the NLOS components improve the system’s lighting performance and ensure meeting illumination standards. It provides an extra illumination of about 260 lux at room corner and 175 lux at room center over LOS scenario. Wall reflectivity ( $\rho $ ), subcarrier modulation factor (SCMF), and the number of time slots (L) are environmental/system parameters that can significantly optimize the overall performance. For diffuse scenario, a BER of $10^{-5}$ to $10^{-7}$ with $L=4$ , normal wall reflectivity (plaster walls $\rho =0.8$ ) and 100% SCMF (i.e. 20 mW/LED) can be achieved easily at bit rates of 1 to 2 Mbps. These BER performance levels can be enhanced by selecting wall painting/ materials with high reflectivity. As a power saving scheme, increasing SCMF with low power/LED level can greatly enhance the BER performance in the diffuse scenario. A remarkable BER performance of $10^{-9}$ can be reached when increasing SCMF by 25% (i.e. to reach 25 mW/LED) under the same conditions ( $L=4$ , $\rho =0.8$ and 1–2 Mbps). At higher data rates the performance is getting worse but still can be optimized, controlled, and enhanced through using a careful choice of environmental and system parameters that can be selected from this work.
TL;DR: Time-hopping combined with M -ary pulse position modulation (PPM) is proposed as a modulation and multiple access scheme for multi-user nanocommunications systems and results show an improved energy efficiency and reduced computational complexity.
TL;DR: It is shown that the use of complete decoding, which retrieves information from all combinations of detector photocounts occurring within one PPM frame, allows one to achieve information efficiency scaling as the inverse of the square of the distance, i.e. proportional to the received signal power.
Abstract: We analyze the information efficiency of a deep-space optical communication link with background noise, employing the pulse position modulation (PPM) format and a direct-detection receiver based on Geiger-mode photon counting The efficiency, quantified using Shannon mutual information, is optimized with respect to the PPM order under the constraint of a given average signal power in simple and complete decoding scenarios We show that the use of complete decoding, which retrieves information from all combinations of detector photocounts occurring within one PPM frame, allows one to achieve information efficiency scaling as the inverse of the square of the distance, ie proportional to the received signal power This represents a qualitative enhancement compared to simple decoding, which treats multiple photocounts within a single PPM frame as erasures and leads to inverse-quartic scaling with the distance We provide easily computable formulas for the link performance in the limit of diminishing signal power
TL;DR: The performance of an M-ary pulse position modulated (PPM) optical wireless communication system operating in strong atmospheric turbulence is investigated and bit error rate (BER) is employed as the measure for the performance.
Abstract: The performance of an M-ary pulse position modulated (PPM) optical wireless communication system operating in strong atmospheric turbulence is investigated. Bit error rate (BER) is employed as the measure for the performance. In our overall performance formulation, average received power as measured by a finite-sized avalanche photodiode (APD) detector is used by the help of the extended Huygens-Fresnel principle. For the aperture averaged scintillation evaluations, the asymptotic Rytov theory with the gamma-gamma intensity statistics is utilized. Gamma-gamma statistics together with the large-scale and the small-scale log-intensity variances yield the scintillation index valid both in weak and strong atmospheric turbulence regimes. BER variations versus the plane wave scintillation index are examined at different values of receiver aperture diameters, data bit rates, M values of M-ary PPM, quantum efficiency, and average APD gain.
TL;DR: Simulation results show that the extra information carried by the BCS can be decoded with extremely low bit error rate and thus has negligible impacts on the demodulation of the ACO-OFDM signal, when the system nonlinearity is not dominating.
Abstract: In this paper, fractional reverse polarity optical orthogonal frequency division multiplexing (FRPO-OFDM) is studied to enable dimming compatible visible light communications. The scheme combines a layered asymmetrically clipped optical OFDM (ACO-OFDM) sequence with an information-carrying brightness control sequence (BCS) in the form of $M$ -ary pulse position modulation. We derive the expressions of the FRPO-OFDM signal and its achievable brightness level, and develop an effective detector which can recover information from both sequences based on maximum likelihood detection. We show that when the detector is to be implemented, the use of multi-layer ACO-OFDM imposes strong periodicity on the BCS, which leads to a trade-off between spectral efficiency and brightness resolution for dimming control. It is shown that high spectral efficiency can be achieved with practical dimming requirements. Simulation results show that the extra information carried by the BCS can be decoded with extremely low bit error rate and thus has negligible impacts on the demodulation of the ACO-OFDM signal, when the system nonlinearity is not dominating.
TL;DR: The proposed scheme is a hybrid of a randomized modulation scheme, namely, the randomized wrapped-around pulse position modulation scheme (RWAPPM), and a noise-shaper, and an analytical expression for the input current spectrum of the hybrid scheme is derived.
Abstract: We propose a novel low-harmonics low-noise modulation scheme for switched-mode dc–dc converters. The proposed scheme is a hybrid of a randomized modulation scheme, namely, the randomized wrapped-around pulse position modulation scheme (RWAPPM), and a noise-shaper. The RWAPPM mitigates the switching-frequency harmonics in the input current, whereas the noise-shaper mitigates the low-frequency noise therein. We derive an analytical expression for the input current spectrum of the hybrid scheme. We benchmark the hybrid scheme against the conventional pulse width modulation scheme (PWM) and the RWAPPM without the noise-shaper. At 0.5 duty cycle, 3.3-V input voltage, 100-kHz average switching frequency, and with the second-order noise-shaper, the peak spectral power in the input current spectrum of the hybrid scheme is 18.1 dB lower than the PWM. Other randomized and spread-spectrum modulation schemes, in general, have undesirably higher input noise current than that of the PWM. However, the input noise current of the proposed hybrid scheme, obtained at ~73-mA rms (integrated over a 200-kHz bandwidth without an input filter), is comparable with that of the PWM, and is lower by ~16-mA rms compared with that of the RWAPPM without the noise-shaper. We also benchmark the hybrid scheme against other well known randomized and spread-spectrum modulation schemes. We further propose a novel pulse generator structure that embodies the hybrid scheme. We realize a dc–dc converter employing the pulse generator, and measure the converter to verify the derived expression and the characteristics of the hybrid scheme. We also measure the output voltage spectrum, the transient-response, and the operating range of the converter.
TL;DR: This paper presents the system architecture, modeling, and design constraints of a wireless chip-to-chip-communication transceiver as a low-power alternative to wireline links, such as PCI-Express and shows that energy efficiency better than 6 pJ/bit could be reached with the proposed architecture.
Abstract: This paper presents the system architecture, modeling, and design constraints of a wireless chip-to-chip-communication transceiver as a low-power alternative to wireline links, such as PCI-Express. On top of the potential power savings, the wireless link provides lower latency times, better flexibility, lower complexity, and easier heat diffusion. The proposed transceiver uses impulse-radio ultra-wideband communication at 10 GHz. It supports a 2.5-Gb/s data rate with pulse position modulation over short distances (~10 cm). The hardware complexity is reduced by using a modified non-coherent receiver with a rectifying RF front-end and a relative-compare analog baseband. The system performance is quantified and tradeoffs are explored with the main motivation of reducing power. A discussion of the modulation choice, the performance specifications of the receiver blocks and the clock generation principle is presented. We show that energy efficiency better than 6 pJ/bit could be reached with the proposed architecture.
01 Dec 2018
TL;DR: Numerical results show that MGSM achieves a full range of dimming with sufficiently high spectral efficiency compared to conventional techniques such as multiple pulse position modulation, overlapping pulse positionModulation, on-off keying and generalized spatial modulation (GSM).
Abstract: In this paper, we propose a modified generalized spatial modulation (MGSM) scheme with dimming support for indoor optical wireless communication (OWC) systems. The spatial indices of the active LEDs and their transmitted optical power levels are utilized to modulate data in MGSM. The key property of the signal waveforms in MGSM is that it provides the same amount of optical power emitted at any time instant that corresponds to the dimming level requested. Consequently, MGSM prevents potential health and safety concerns related to the human eye such as flickering caused by intensity modulation. The upper bound on the symbol error rate (SER) of MGSM is derived theoretically using the union bound method, which is used to verify Monte-Carlo simulations. Numerical results show that MGSM achieves a full range of dimming with sufficiently high spectral efficiency compared to conventional techniques such as multiple pulse position modulation, overlapping pulse position modulation, on-off keying and generalized spatial modulation (GSM). In terms of error performance, the SER of MGSM is compared with GSM at several dimming levels, which shows that MGSM provides an advanced and efficient modulation scheme for indoor OWC systems.
TL;DR: In the scenario of first laser communication relay satellite being launched into geostationary earth orbit, it is seen that the transmitter diversity or multiple input single output technique reduces the uplink minimum transmitter power requirement, whereas for downlink aperture averaging and receiver diversity or single input multiple output techniques can achieve the same.
Abstract: In the scenario of first laser communication relay satellite being launched into geostationary earth orbit, we evaluate the reduction in transmitter power requirement for earth-to-satellite and satellite-to-earth free space optical links in presence of turbulence and various weather conditions using spatial diversity technique. In channel modeling, Beer Lambert Law incorporates the weather effects. The log-normal probability density function (pdf) models weak turbulence and gamma–gamma pdf moderate to strong turbulence. Using the combined channel state pdf, bit error rate (BER) expressions are derived for on-off keying (OOK), M-ary pulse position modulation (M-PPM) and M-ary differential PPM (M-DPPM) schemes. From the BER plots, we evaluate the minimum average received power required to achieve a desired BER for all three schemes for different channel conditions. Subsequently, minimum transmitter power requirement is evaluated for both uplink and downlink using the range equation. It is observed that presence of moderate, light and thin fog cause additional power requirement. Also, among the three schemes, M-PPM scheme requires the least transmitter power, followed by M-DPPM and OOK schemes. Further, it is seen that the transmitter diversity or multiple input single output technique reduces the uplink minimum transmitter power requirement, whereas for downlink aperture averaging and receiver diversity or single input multiple output techniques can achieve the same. The power requirement for uplink is 8–10 dB more as compared to downlink in presence of turbulence and various weather conditions.
Dissertation•
01 May 2018
TL;DR: Noise power in tuned receivers is significantly reduced for all examined configurations and under different conditions compared to non-tuned receivers, and the overall receiver performance is improved by over 3dB in some cases.
Abstract: The aim of this work is to investigate the use of tuned front-ends with OOK and PPM schemes, in addition to establish a theory for baseband tuned front end receivers. In this thesis, a background of baseband receivers, tuned receivers, and modulation schemes used in baseband optical communication is presented. Also, the noise theory of baseband receivers is reviewed which establishes a grounding for developing the theory relating to optical baseband tuned receivers.
This work presents novel analytical expressions for tuned transimpedance, tuned components, noise integrals and equivalent input and output noise densities of two tuned front-end receivers employing bi-polar junction transistors and field effect transistors as the input. It also presents novel expressions for optimising the collector current for tuned receivers. The noise modelling developed in this work overcomes some limitations of the conventional noise modelling and allows tuned receivers to be optimised and analysed.
This work also provides an in-depth investigation of optical baseband tuned receivers for on-off keying (OOK), Pulse position modulation (PPM), and Di-code pulse position modulation (Di-code PPM). This investigation aims to give quantitative predictions of the receiver performance for various types of receivers with different photodetectors (PIN photodetector and avalanche photodetector), different input transistors (bi-polar junction transistor BJT and field effect transistor FET), different pre-detection filters (1st order low pass filter and 3rd order Butterworth filter), different detection methods, and different tuned configurations (inductive shunt feedback front end tuned A and serial tuned front end tuned B). This investigation considers various optical links such as line of sight (LOS) optical link, non-line of sight (NLOS) link and optical fibre link.
All simulations, modelling, and calculations (including: channel modelling, receiver modelling, noise modelling, pulse shape and inter-symbol interference simulations, and error probability and receiver calculations) are performed by using a computer program (PTC Mathcad prime 4, version: M010/2017) which is used to evaluate and analyse the performance of these optical links.
As an outcome of this investigation, noise power in tuned receivers is significantly reduced for all examined configurations and under different conditions compared to non-tuned receivers. The overall receiver performance is improved by over 3dB in some cases. This investigation provides an overview and demonstration of cases where tuned receiver can be optimised for baseband transmission, offering a much better performance compared to non-tuned receivers. The performance improvement that tuned receivers offers can benefit a wide range of optical applications. This investigation also addresses some recommendations and suggestions for further work in some emerging applications such as underwater optical wireless communication (UOWC), visible light communication (VLC), and implantable medical devices (IMD).
Keyword: Optical communications, Baseband receivers, Noise modelling, tuned front end, pulse position modulation (PPM).
TL;DR: Using bipolar M-ary pulse position modulation (PPM) signaling in conjunction with the code-interleaving (CI) technique to address the inter-core XT problem in MCF-based optical code-division multiple-access (OCDMA) passive optical networks (PONs) with spectral-amplitude coding employed as the coding scheme.
Abstract: Inter-core crosstalk (XT), caused by closely spaced cores, is the principal challenging issue of implementing multicore fiber (MCF)-based optical networks as it limits the network performance severely. In this paper, we propose and demonstrate using bipolar M-ary pulse position modulation (PPM) signaling in conjunction with the code-interleaving (CI) technique to address the inter-core XT problem in MCF-based optical code-division multiple-access (OCDMA) passive optical networks (PONs) with spectral-amplitude coding employed as the coding scheme. The bit error rate of the proposed network is derived based on an accurate analysis for the statistics of the decision random variables, i.e., mean and variance. The analysis accounts for inter-core XT, optical beat noise, and receiver noise. In addition, a comparison between the performance of core-multiplexed OCDMA PON adopting the newly proposed techniques, namely, unipolar on-off keying (OOK) with CI and bipolar 2-PPM with CI and that adopting unipolar OOK without CI, is presented under both data rate and average photons per bit constraints. The obtained results show that bipolar 2-PPM and CI are capable of reducing the inter-core XT impact on the performance of MCF-based OCDMA PONs. Furthermore, bipolar 2-PPM with CI outperforms other schemes in terms of the number of supportable users and energy efficiency.
07 May 2018
TL;DR: A novel modulation scheme is presented, which can be efficiently used in body-centric terahertz (THz) nanonetworks and is a combination of the time-spread On-Off keying (TS-OOK) and the pulse position modulation (PPM).
Abstract: In body-centric communications, energy efficiency is the most critical parameter, while the maximum 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. This scheme is a combination of the time-spread On-Off keying (TS-OOK) and the pulse position modulation (PPM). The new modulation scheme presents lower energy consumption levels at a small cost to the achievable data rate. Furthermore, another important aspect is that, due to the nature of noise in THz communications, the proposed modulation is affected in a much smaller way by the noise. Finally, we present analytical and simulation results in order to compare the new scheme with TS-OOK.
TL;DR: A unique technique of mimicking genuine sea-piling sounds as carrier to convey information is presented, which differs from traditional low signal to noise ratio covert underwater acoustic communication.
TL;DR: This study analyses the outage performance of the indoor relay-assisted hybrid radio frequency (RF)/visible light communication (VLC) systems and derives closed-form expressions for the outage probability of the end-to-end signal- to-noise ratio using the differential evolution algorithm.
Abstract: In this study, the authors analyse the outage performance of the indoor relay-assisted hybrid radio frequency (RF)/visible light communication (VLC) systems. They derive closed-form expressions for the outage probability of the end-to-end signal-to-noise ratio. Then they obtain the optimal approximation parameter with optimising the outage probability using the differential evolution algorithm. Moreover, they analysed the average bit error rate (BER) performance of the hybrid RF/optical system using pulse position modulation method while assuming the timing error in synchronisation. Finally, they present some numerical results utilising the newly derived exact closed-form expressions.
TL;DR: The main aim of this paper is to improve the performance of Ultra Wideband multiple access modulation system with a newly Proposed combined pulse, generated using a modified random pulse combining of the first five Gaussian derivative pulses with optimal shaping factors as basic functions.
Abstract: Ultra-Wideband (UWB) technology uses very narrow pulses of nano-seconds duration to provide very high data rates. The pulses to be used for the UWB are very important and should meet the emission mask regulatory requirements to get good performance when transmitted over the channel. To meet these requirements, a combination of higher order derivatives of Gaussian pulses can be considered to form a combined pulse instead of transmitting them separately. The main aim of this paper is to improve the performance of Ultra Wideband (UWB) multiple access modulation system with a newly Proposed combined pulse, generated using a modified random pulse combining of the first five Gaussian derivative pulses with optimal shaping factors as basic functions. In order to meet the UWB power spectrum regulations, the power spectral utilization of the newly designed pulse is calculated and the bit error rate performance of the pulse position modulation time hopping system using the newly proposed pulse is analyzed in a multi-path channel environment using RAKE receiver. The simulation results carried out in MATLAB software shows that the new proposed combined pulse has higher pulse energy matching the spectral limits of UWB and an improved bit error rate performance as compared to the previous literature results.
01 Dec 2018
TL;DR: An advanced multi-pulse multi-light emitting diodes (LEDs) modulation technique to improve the efficiency for indoor visible light communication systems and achieves significantly higher spectral efficiency with respect to the conventional MPPM, SSK and spatial pulse position modulation.
Abstract: This paper proposes an advanced multi-pulse multi-light 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).
01 Dec 2018
TL;DR: This paper investigates the key requirements of the modulation wave form when using a DVS camera-based receiver, and proposes a new pulse wave form that maintains the same average luminance level while extending the operational range of the system.
Abstract: State-of-the-art vehicular visible light communication (V2LC) systems utilize either a photodiode or a camera as the receiver, while both have their drawbacks. A photodiode-based receiver lacks the capability to separate signals from sources transmitting at the same time and is more vulnerable to interference. On the other hand, a camera-based receiver suffers from low system throughput, resulting from the low image frame rate of commodity cameras. In this paper, we investigate a solution which attempts to combine the best of both, and mitigate their drawbacks.We propose to use a new type of CMOS vision sensor: a dynamic vision sensor (DVS). Instead of recording still frames, a DVS only generates outputs when it senses a significant change of brightness in a pixel. The output of a DVS is a stream of events on the pixel basis with 1 μs resolution, which greatly increase the bandwidth. We investigate the key requirements of the modulation wave form when using a DVS camera-based receiver, and propose a new pulse wave form that maintains the same average luminance level while extending the operational range of the system. Preliminary experimental results show that the proposed wave form nearly triples the range to 8 m, compared to the range of 3 m when using the conventional inverse pulse position modulation wave form.
TL;DR: In this paper, the asymptotic dark count estimate of superconducting nanowire single photon detector (SNSPD) is introduced and an average bit error expression is established based on SNSPD and pulse position modulation optical communication system over Double Generalized Gamma channel firstly.
Abstract: Optical communication has a broad prospect in deep space communication. The mechanism and the asymptotic dark count estimate of superconducting nanowire single photon detector (SNSPD) are introduced. Considering the detector bias current, an average bit error expression is established based on SNSPD and pulse position modulation optical communication system over Double Generalized Gamma channel firstly. Numerical results show that both the bias current and the atmospheric turbulence intensity have influence on the BER performance. The uncoded BER can achieve 10-5 in 32-PPM scheme with Ibias/Iv = 0.85 when SNR = 8 dB under weak atmospheric turbulence. This work can be utilized in deep space optical communication and benefits downlink communication system design.
15 Feb 2018
TL;DR: In this article, an Er-doped, Very Large Mode Area (VLMA) fiber amplifier, pumped by a 1480 nm Raman fiber laser, was used for high peak power and minimal spectral broadening.
Abstract: Fiber amplifiers have been used in many laser communication applications due to their compactness and high efficiency. However, fiber amplifiers for free space laser communications have been limited to low peak power communication formats due to nonlinear effects such as Self Phase Modulation (SPM). At high peak powers, SPM can broaden the spectrum of free space laser communication signals to an unacceptable degree, moving much of the transmitted power outside the receiver’s designed bandwidth. The Laser Communication Relay Demonstration (LCRD) needed a fiber amplifier that could amplify a 3.5 GHz wide signal to peak powers of nearly a kilo-Watt with little to no spectral broadening due to SPM. We tested several different commercial amplifiers and found an Er-doped, Very Large Mode Area (VLMA) fiber amplifier, pumped by a 1480 nm Raman fiber laser, met the needs for both high peak power and minimal spectral broadening. The high peak power performance of the VLMA amplifier is enabled by the large effective area of ~ 1100 μm 2 . We will present a detailed analysis of the effects of SPM on the amplified signal spectrum for both pulse position modulation (PPM) and differential phase shift keyed (DPSK) communication formats at peak powers up to 1 kW. Additionally, Bit Error Ratio (BER) performance data taken with the LCRD modem showed the signal did not suffer a measureable penalty from amplification with the VLMA amplifier. The ability to reach the required high peak power with this fiber amplifier makes it possible to consider its use for deep space laser communication, e.g. with high order M-ary PPM formats where such high peak powers are needed.