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Based on the orbital angular momentum and pulse position modulation, we present a novel passive measurement-device-independent quantum key distribution (MDI-QKD) scheme with the two-mode source. Combining with the tight bounds of the yield and error rate of single-photon pairs given in our paper, we conduct performance analysis on the scheme with heralded single-photon source. The numerical simulations show that the performance of our scheme is significantly superior to the traditional MDI-QKD in the error rate, key generation rate and secure transmission distance, since the application of orbital angular momentum and pulse position modulation can exclude the basis-dependent flaw and increase the information content for each single photon. Moreover, the performance is improved with the rise of the frame length. Therefore, our scheme, without intensity modulation, avoids the source side channels and enhances the key generation rate. It has greatly utility value in the MDI-QKD setups.

This study presents two receivers for visible light communication (VLC) systems. First, modified pulse position modulation (PPM) (MPPMD) and variable pulse position modulation (VPPM) (MVPPMD) demodulators are considered for MPPM and traditional VPPM schemes. The aim of this study is to minimise complexity at the receiver. On the basis of the derived mathematical framework, the multiplication stage is removed from the coherent detector architecture. Moreover, the generation of mask signals is unnecessary for the proposed receiver because they would be multiplied by the modulated signal for the traditional coherent detector. The simulation results show that MPPMD has the same bit error rate (BER) performance compared with the traditional coherent demodulators. Additionally, the resource utilisation of MPPM and VPPM receivers is dramatically reduced with removing the multiplication stage and the mask generator. Second, an accelerated VPPM (A-VPPM) algorithm is proposed to achieve a fast demodulation of the VPPM signal under the unknown dimming-level condition. Compared with the earlier VPPM receivers, the A-VPPM receiver can also demodulate the VPPM signal without any iteration stage and the mask generator. The BER performance of A-VPPM receiver is close to that of the traditional VPPM demodulator at 30 and 70% dimming levels.

The ultraviolet (UV) scattering communication can be applied in military networked on-the-move and unattended ground sensor networks. This paper focuses on the connectivity properties of unmanned aerial vehicles (UAVs) network based on UV communication that ensures the secret communications between UAVs. UAVs network is consisting of a group of UAVs, each of which moving according to a particular mobility model. We discuss random waypoint (RWP) mobility model and circle movement based model (CMBM), which can describe the actual movement of UAVs, respectively. In this paper, the approximations of the probability that the network is k-connected are provided with consideration of transmission using on–off keying and pulse position modulation. More precisely, we evaluate the effects of node density, transmission power, and data rate on k-connectivity. The numerical examples show that the mobility degrades the connectivity probability. When the numbers of nodes $$n=500$$ and data rate $$R_b =10\,\hbox {kbps}$$ , the required transmission power for nodes moving according to RWP is lower than CMBM in order to achieve 2-connectivity of the UAVs network, but it is about twice that for uniformly distributed nodes.

Research of impulse radio ultra-wideband (IR- UWB) systems has been extensively increasing in recent years due to their high power efficiency, high data rates and low hardware complexity. The choice of the modulation scheme used in an IR-UWB system has a great impact on its overall performances. In this paper, the biorthogonal pulse position modulation (BPPM) scheme for the application in transmitted reference (TR) IR-UWB communication systems is proposed. Performances of the BPPM scheme over two different IEEE 805.15.3a channel models in a multi-user environment are analyzed and compared to the performances of the pulse position modulation (PPM) scheme. The results show that the BPPM scheme outperforms the PPM scheme in terms of bit error rate (BER), data rate and hardware complexity. Additionally, the influence of different system parameters on the BPPM performances in TR IR-UWB systems is analyzed and possible trade-offs are proposed.

Visible-light communication (VLC) is a new technique for high-speed, low-cost wireless data transmission services. One of the areas in which VLC is considered superior to traditional radio-based communication is security. The common slogan summarizing the VLC security features is WYSIWYS- “What You See Is What You Send.”However, the broadcast nature of downlink VLC makes it possible for eavesdroppers to easily intercept the light communication in various settings, e.g., offices, conference rooms, plenum spaces, and so on. Similarly to radio-based data broadcasting systems, such as Wi-Fi, VLC opens the possibilities of hiding information in the public channel. In this paper, we describe (for the first time, to the best of our knowledge) the implementation of steganographic data transmission in a VLC system called LuxSteg. This VLC system utilizes pulse position modulation and direct sequence-code division multiple access modulation. In our implementation, multiple steganographic data streams are mixed with the spreading codes and combined with the overt data stream. We achieve a steganographic transmission rate of approximately 1 Mb/s hidden in a 110-Mb/s data stream. We analyze the influence of the spreading factor, spreading code type, number of hidden data streams, and the amplitude on the achievable transmission rate, undetectability, and robustness.

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.

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 × 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 × 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. This work was supported by the Natural Sciences and Engineering Research Council of Canada, Canada. The authors would like to acknowledge the financial support from the Canada Research Chair in Smart Medical Devices and the design tools from CMC Microsystems. Scopus

In the information-oriented society, there are increasing needs to conduct data communication with nearby devices/people. In this light, vibration-based communication method was proposed as one of possible communication means between adjacent devices. This method has been expected to provide an intuitive and safe communication by propagating vibration to a receiver device. This study proposes two types of techniques, which are multi-step ASK (Amplitude Shift Keying) with pseudo clock and PPM (Pulse Position Modulation), to achieve a stable vibration-based communication simply using smart device functions. These proposed techniques are then evaluated through some experiments using several types of smart devices. In addition, the effectiveness of the proposed methods is discussed based on the experimental results.

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.

In order to further improve the performance of the phase-matching quantum key distribution (PM-QKD) protocol, in this paper, a more efficient protocol named PPM-PM-QKD is proposed which adopts pulse-position modulation (PPM) to realize the high-dimensional encoding. PPM technology utilizes the empty pulses in the weak coherent source, and can improve the performance of the protocol. The simulation results show the improvement compared with the original PM-QKD protocol. Moreover, the protocol inherits the advantages of the original PM-QKD protocol, and it can not only exceed the PLOB bound, but also has a higher robust to noise and channel disturbance.

The remote sensing and control of biomimetic robot fishes is an important but challenging task because the available underwater acoustic communication cannot accommodate their size, power consumption, and price. Hence, we propose a power-efficient, low-complexity time reversal pulse position modulation communication scheme, which partitions the available bandwidth of a transducer into several different sub-bands using different linear frequency modulated (LFM) pulses. The information is reflected by the position of the LFM pulses with different start and end frequencies for adjacent symbols. In the receiver, the Doppler factor is obtained by cross-correlating two hyperbolic frequency modulation signals transmitted before and after the modulated signal, and the channel response is estimated by match filtering the sync preamble. Furthermore, time reversal and bandpass filtering are performed to mitigate intrasymbol and intersymbol interferences caused by the multipath effects of underwater acoustic channels, respectively. The effectiveness and robustness of the proposed communication scheme are confirmed experimentally.

Nowadays, laser communication has received great achievements owing to its advantages, e.g., large channel capacity, easy miniaturization of communication system and strong anti-interference ability in different conditions. Pulse position modulation (PPM), as an important modulation technology in laser communication system that transmit signal with lower power, is attracting much attention. However, the performance of the modulation scheme highly depends on the bandwidth of transmission. To remedy this defect of PPM, the multipulse position modulation (MPPM) scheme is proposed to increase the accuracy and bandwidth limit. This modulation scheme has stronger anti-interference ability than PPM. Therefore, there has been rising interest in studying the characteristics of the multi-PPM. In this article, we developed an appropriate mathematical model to represent a PPM transmission, analyzed the spectrum of the transmission and characterized the bandwidth of this transmission. Compared with benchmarks of MPPM scheme, its performance has been discussed. According to the analysis, MPPM strongly increases band-utilization efficiency, however PPM has a better bit error rate (BER) performance than MPPM.

In this study, it is aimed to investigate the required signal-to-noise ratio (SNR) that provides a sufficient bit error rate (BER) according to the zenith angle between the ground station and satellite when pulse position modulation is utilised. Many parameters such as scintillation index, link distance, wavelength, Rytov variance, Fried's parameter, aperture diameter of the receiver and zenith angle have been considered to achieve realistic results. Due to the restrictions on the system, some parameters are specified as deterministic; the obtained results suggest that the required SNR value changes in a wide range from small to large values of the zenith angle to achieve sufficient BER. Therefore, either SNR adjustment as a function of the zenith angle is provided or the interval of the zenith angles to establish the link is determined previously in order to avoid the high link margin. It is shown that, instead of the second choice, aperture diversity is utilised at the receiver to establish communication even for large zenith angles with a reasonable value of the SNR. Besides aperture diversity, channel coding with error correction codes further improves the performance.

In this letter, we propose the concept of quadrature channel modulation (QCM) by combining quadrature spatial modulation (QSM) and media-based modulation (MBM) transmission principles. The proposed QCM schemes exploit not only the in-phase and quadrature components of complex data symbols for antenna indexing but also channel states for the transmission of additional information bits through index modulation by employing a single radio frequency (RF) chain. It is shown via numerical studies that the proposed QCM schemes can outperform the existing emerging schemes such as QSM, plain MBM, and spatial modulation-based MBM, which also employ a single RF chain at their transmitters.

In this paper, we consider the scenario of N collocated users communicating over Free-Space Optical (FSO) channels. We propose a novel cooperation scheme where the users are grouped together in groups of two for the sake of achieving enhanced diversity orders in a simple manner. In this context, instead of communicating independent binary Pulse Position Modulation (PPM) symbols over each of the N available links in a non-cooperative manner, the information from the different users will be combined and encoded in a joint manner. We propose a method for performing the joint encoding and we propose the structure of the 4-ary augmented constellation to be associated with the proposed cooperation scheme. A performance analysis is conducted over gamma-gamma channels reflecting the capability of the proposed scheme in enhancing the diversity order for all levels of background radiation. In particular, we prove that the diversity order is enhanced by the factor ⌊ N 2 ⌋ + 1 .

This paper presents visible light communication (VLC) based energy efficient lighting system in indoor parking area for illumination and at the same time would offer ubiquitous data communication. Light emitting diodes (LEDs) based VLC is used for communication and illumination at the same time. We have optimized the position of LED emitters on the ceiling in the parking area to obtain the desired signal-to-noise ratio (SNR) and bit error rate (BER). Two lighting configurations in the parking area are discussed. We compared the power transmission from LED emitters, number of emitters, SNR distribution, BER and cost for both the configurations. Multi-level pulse modulations are used in this work along with simple on off keying (OOK) for modulation. We compared OOK with M-PAM, multi-level pulse position modulation and invert multi-level pulse position modulation to obtain the required SNR and power to achieve the same BER. Simulation results are presented and discussed. It is observed that the system allows uniform illumination in the parking area and at the same time high data rate communication.

In this article, the downlink bit-error-rate (BER) performance of scintillation models for a laser satellite communication system influenced by weak-to-strong turbulence on a slant path is investigated, which take optical wavelength, zenith angle, terrestrial turbulence strength and modulation schemes into account. To describe the properties of atmospheric turbulence which vary with the altitude between a satellite station and a ground station, a three-layer altitude spectrum is used. By adopting the extended Rytov theory valid in weak-to-strong turbulence, scintillation models of an unbounded plane wave for downlink path and spherical wave for uplink path are derived, respectively. The optical fading channel influenced by weak-to-strong turbulence is modeled by Gamma–Gamma distribution. The numeric results show that when the system is under strong terrestrial turbulence conditions or at large zenith angles, disparities in BER performance among different kinds of level of pulse position modulation (PPM) schemes are quite small. Under real circumstances, a longer optical wavelength and a suitable zenith angle range can be selected to reduce turbulence effects for the satellite communication system through weak-to-strong turbulence.

In the paper, a mixed-interval multi-pulse position modulation (MI-MPPM) scheme for visible light communication (VLC) system is theoretical proposed and implemented on field programmable gate array (FPGA). It has better bandwidth efficiency than PPM and MPPM. And it has better anti-jamming than MPPM. A real-time VLC link based on phosphorescent white LED is also built to measure the performance of the proposed MI-MPPM scheme. The data rate of 104 Mbps in our VLC system under the distance of 60 cm could be achieved, and bit error rate is 3 . 81 × 1 0 − 5 . As far as we know, it is the highest data rate that can be achieved in continuous real-time VLC system with phosphorescent white LED based on PPM and its derivative modulation. The performance of VLC system under different distances, advantages and the possible application scenarios of MI-MPPM are also discussed.

In this paper, we propose novel $2\times 2$ and $3\times 3$ noncoherent space-time (ST) codes for impulse-radio ultra-wideband communications with pulse position modulation (PPM). The code design is based on existing coherent ST codes, where the associated constellation is confined in order to achieve full diversity with analog energy detectors. A comprehensive performance analysis guides this confinement and highlights the maximum rates that can be achieved by this specific layered code word structure with two and three transmit antennas. The proposed codes attain these maximum rates without introducing any expansion to the unipolar PPM signal set.

This paper describes development of a visible light 4 Pulse position modulation (4PPM) data communication device for underwater swarms using a nonlinear synchronizing system. SWARM—a group robot that uses intelligence as a group—do as ants and bees, is expected to be useful for marine resource exploration. Specifically, numerous SWARMs will be grouped to explore marine resources efficiently. An important difficulty is the change in electronic circuit characteristics because of high water pressure in the deep sea. Development of small and simple underwater SWARM communication devices must eliminate this problem without using large pressure-proof containers. As described herein, we considered nonlinear synchronizing systems as effective because they can be synchronized even if system time constants differ. Such systems resemble the glow mechanism used by fireflies. They have individuality, but they flash synchronously when in a group. We developed a visible light communication device using this nonlinear synchronization system based on the firefly concept. Test results confirmed that they are synchronized even if a time constant difference exists between them. Furthermore, we achieved 4PPM data communication using the nonlinear synchronization signal as a communication clock.

Frequency modulation continuous wave (FMCW) lasers are key components in modern optical imaging. However, current intracavity modulation lasers do not exhibit low-frequency jitter rate and high linearity due to the inherent relaxation oscillations. Although this may be compensated in a direct modulation laser diode using an optoelectronic feedback loop, the available sweep speed is moderately small. In this letter, a special external modulation method is developed to improve the performance of FMCW. Since only the first sideband optical field is used during the entire generation process, phase noise is kept to a minimum and is also independent of the sweep speed. We demonstrate that the linearity and jitter rates do not deteriorate appreciably when the sweep speed is changed over three orders of magnitude, even up to the highest sweep speed of 2.5 GHz/ $\mu \text{s}$ .

In this paper a novel channel shortening equalizer (CSE) for time hopping ultra wideband (TH-UWB) multiple access system with pulse position modulation (PPM) is presented. As UWB channels have very long impulse responses as compared to the narrow pulse width, CSE can reduce the number of correlators. In UWB systems, due to the received pulse that is very similar to the channel impulse response (CIR), the proposed algorithm maximizes the shortening signal to inter-symbol and multiuser interferences ratio (SSINR), defined as the ratio of the received signal energy inside the desired window to the energy in the wall and multiuser interference. The existence of the proposed CSE before correlation receiver decreases the complexity of the receiver architecture by significantly reducing the number of effective channel taps. Further we extend our method to derive general expression for the bit error rate (BER) performance in the presence of inter-symbol and multiuser interferences. Computer simulation results are provided to compare the performance of the proposed method with a MSSNR CSE, lower bound, also known as All-Rake, Partial-Rake, and Selective-Rake in terms of Rake operational temporal windows and BER.

Appliance state sensing is a load monitoring method that requires the ON/OFF states and global consumption measurements of appliances in order to achieve energy disaggregation. Previously proposed sensor networks employed uncalibrated, overrated, and costly wireless modules to collect appliance states. In contrast, we present a simple communication scheme, in which data are transmitted through the powerline to a main meter. For this purpose, we designed a smart sensor, the circuitry of which operates as a load signature generator. It generates fixed-amplitude and short-duration rectangular current pulses that encode information about the status of an appliance. For evaluation, we tested four sensors in a small electrical model and performed a numerical simulation using raw current waveforms contained in the reference energy disaggregation data set. The performance of the applied signal processing algorithms shows a symbol error rate of less than 1% when pulse position modulation with amplitudes of 2 A or more is used.

Index modulation concept has attracted considerable research interest in the past few years. As a realization of index modulation in the frequency domain, orthogonal frequency division multiplexing with index modulation (OFDM-IM) has recently been proposed, which conveys information bits through both the subcarrier activation patterns and the amplitude phase modulation constellation points. This paper proposes two enhanced OFDM-IM schemes aimed at achieving higher spectral efficiency and diversity gain, respectively. The first one, termed OFDM with hybrid in-phase/quadrature index modulation (OFDM-HIQ-IM), explores the I- and Q- dimensions jointly for index modulation, allowing transmission of more index modulation bits in each subcarrier group. The second one, termed linear constellation precoded OFDM-IQ-IM (LP-OFDM-IQ-IM), spreads information symbols across two adjacent active subcarriers through linear constellation precoding to harvest additional diversity gain. By maximizing the minimum squared Euclidean distance, two different realizations of LP-OFDM-IQ-IM are derived, which leads to a rotated and a diamond-shaped constellation, respectively. The proposed OFDM-HIQ-IM and LP-OFDM-IQ-IM, as revealed by both theoretical analyses and computer simulations, enable low-complexity detection and exhibit superior error rate performance over the existing OFDM-IM schemes.

In order to guarantee reliable data transmission, powerful channel coding techniques are usually required in noncoherent ultra- wideband (UWB) communication systems. Accordingly, several forward error correction (FEC) codes, such as Reed-Solomon and convolutional codes have been used in noncoherent UWB systems to improve the bit error rate (BER) performance. In this paper, low-density parity-check (LDPC) codes are further studied as more powerful FEC candidates for noncoherent UWB systems. Two LDPC codes and the corresponding decoding procedures are presented for noncoherent UWB systems. Moreover, performance comparison between the LDPC codes and other FEC codes are provided for three major noncoherent UWB communication systems, namely, noncoherent pulse position modulation (NC-PPM), transmitted reference (TR) and transmitted reference pulse cluster (TRPC). Both theoretical analysis and simulation results show that the two investigated LDPC codes outperform other existing FEC codes with limited penalty in terms of complexity and therefore they are promising FEC candidates for noncoherent UWB systems with low- cost and low-power consumption.

Multipath effects in airborne analogue voice amplitude modulation communications have been characterized using air-to-air communications radiofrequency recordings for the first time. The different paths followed by the direct wave and reflected waves give rise to a Doppler shift difference, which produces a characteristic noise or voice modulation depending on the fading depth, Doppler shift, and the speed of the automatic gain control of the receiver. Scattered reflected waves would also increase the perceived noise at reception.

Visible light communication (VLC) is a promising wireless communication technology that utilizes existing lighting system infrastructure. This paper presents the bidirectional VLC physical layer design that supports both pulse width modulation (PWM) and direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) for downlink, and an infrared pulse position modulation (PPM) for uplink. The physical layer consists of an analog front end (AFE) and digital signal processing (DSP) circuits on both the transmitter and the receiver. The AFE circuit on the receiver is specifically designed to compensate for impairments in optical channels, such as ambient light and uneven distribution of light intensity. The evaluation results show that the designed AFE circuit minimizes the interference in the receiver without increasing the TX power. In addition, the PWM is found to be more robust in the optical channel than the DCO-OFDM. In respect of data transmission rate, however, it is observed that the DCO-OFDM is superior to the PWM; namely, the DCO-OFDM modulation using quadrature phase shift keying (QPSK) attains a data rate of 26.8 kbps, while the 2-PWM modulation achieves a data rate of 6.2 kbps.

The fundamental properties of free space optical channels in the ultraviolet (UV) spectral range between 200 and 280 nm are the enhanced scattering and the solar blind operation. Exploiting these properties, point-to-point links in a non-line-of-sight (NLOS) regime were experimentally tested and the performance of pulse position modulation of fourth order (4-PPM) and flip–orthogonal frequency division multiplexing (Flip-OFDM) modulation formats was evaluated. At the transmitting side, light-emitting diodes (LEDs) emitting at 265 nm were used. At the receiving side, a photo-multiplier tube was combined with an optical filter. Distances up to 20 m were covered and kilobits/s rates were applied. The performance was also evaluated after modifying artificially the atmospheric conditions by the operation of a fog machine. In short, 4-PPM outperformed Flip-OFDM, whereas a medium that offers enriched scattering due to fog may boost the performance of short-range NLOS links in the UV spectral range.

Pulse position modulation (PPM) has been used in the radio-frequency (RF) domain to achieve both low-dissipation requirements and provide precision ranging. In ultrawideband (UWB) architectures, it underpins an asynchronous receiver, multiple access environments, and interference-resistant transmission. When combined with frequency hopping (FH), it allows for an additional level of immunity to jamming and low probability of intercept. Realization of a FH-PPM transceiver poses a practical challenge, particularly in the UWB RF range. With UWB pulses reaching the multi-gigahertz range, FH adds to the effective bandwidth at which the receiver must be operated, exceeding the performance of a modern quantizer and digital demodulation backplane. This study describes a new photonics-assisted FH-PPM receiver architecture that rests on mutually coherent frequency combs. The performance of the new receiver was characterized by receiving and decoding an 80–Mb/s rate FH-PPM UWB signal.

This paper studies and compares the performance of on-off keying (OOK), pulse position modulation (PPM), digital pulse interval modulation (DPIM) and dual-header pulse interval modulation (DH-PIM) schemes in FSO channels in the presence of different weather conditions. The bit error rate (BER) curves for these modulations are simulated. Moreover, a performance comparison between these modulation techniques is provided. Generally, in the absence of turbulence OOK-NRZ (non-return-to-zero) and PPM is found to achieve a better BER performance as compared to DPIM and DHPIM. In the presence of fog, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 1 dB at BER 1e-3. While, in case of rain, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 1.5 dB at BER 1e-3. Moreover, in case of snow, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 1.7 dB at BER 1e-3. Additionally, in the presence of turbulence, in case of weak turbulence, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 8 dB and 10 dB, respectively at BER 1e-3. Furthermore, in case of moderate turbulence, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 6 dB and 8 dB, respectively at BER 1e-3. Finally, in case of strong turbulence, OOK-NRZ and PPM is better than DPIM and DH-PIM by approximately 3 dB and 4 dB, respectively at BER 1e-3.

In this paper, the fully integrated CMOS current mode PLL with current input injects at the place of input or output of the loop filter without summing amplifier circuit. It functions as PPM and PWM circuit is present. In addition, its frequency response is an analysis which electronic tuning BPF and LPF are obtained. The proposed circuit has been designed with 0.18 μm CMOS technology. The simulation results of this circuit can be operated at 2.5 V supply voltage, at center frequency 100 MHz. The linear range of input current can be adjusted from 43 μA to 109 μA, and the corresponding duty cycle of pulse width output is from 93% to 16% and the normalized pulse position is from 0.93 to 0.16. The power dissipation of this circuit is 4.68 mW with the total chip area is 28 μm × 60 μm.

Impulse radio ultra wideband (UWB) signals are used in various applications which require joint localization and communication. Due to the large bandwidth of the UWB signal, the estimation of time of arrival (TOA) and data symbols requires high sampling rates. This letter describes a sub-Nyquist rate receiver, which can jointly estimate TOA and data symbols. We first represent the received UWB signal in a new domain in which it is sparse. Then, we design physical layer waveforms and estimation algorithms to exploit this sparsity for joint estimation of TOA and pulse position modulation data symbols. The performance of the receiver is compared against the maximum likelihood (ML)-based receiver using an IEEE 802.15.4a CM1 line of sight UWB channel model. The proposed algorithm yields performance similar to the ML-based algorithms with only a fraction of sampling rate at high SNRs (> 25 dB).

In wireless optical systems, Visible Light Communication (VLC) is one of the most popular communication systems. In this study, a Bit Error Rate (BER) performance comparison is given for Variable On-Off Keying (VOOK) and Variable Pulse Position Modulation (VPPM) which are extensively used in VLC systems. According to simulation and theoretical results, it is shown that the BER performances of systems are similar. In this paper, an ambient light noise is added to Additive White Gaussian Noise to extend the BER performance analysis. From simulation results, it is obtained that the impact of ambient light noise is very high for VOOK while it is quite poor for VPPM. Hence, the BER performance of VPPM has better than that of VOOK under ambient light noise.

For high photon-efficiency deep space or low power optical communications links, such as the Orion Artemis-2 Optical Communications System (O2O) project, the received optical signal is attenuated to the extent that single- photon detectors are required. For direct-detection receivers operating at 1.55 µm wavelength, single-photon detectors including Geiger-mode InGaAs avalanche photon diodes (APDs), and in particular superconducting nanowire single-photon detectors (SNSPDs) offer the highest sensitivity and fastest detection speeds. However, these photon detectors exhibit a recovery time between registered input pulses, effectively reducing the detection efficiency over the recovery interval, resulting in missed photon detections, reduced count rate, and ultimately limiting the achievable data rate. A method to overcome this limitation is to divide the received optical signal into multiple detectors in parallel. Here we analyze this approach for a receiver designed to receive a high photon efficiency serially concatenated pulse position modulation (SCPPM) input waveform. From measured count rate and efficiency data using commercial SNSPDs, we apply a model from which we determine the effective detection efficiency, or blocking loss, for different input signal rates. We analyze the scalability of adding detectors in parallel for different modulation orders and background levels to achieve desired data rates. Finally we show tradeoffs between the number of detectors and the required received optical power, useful for real link design considerations.

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is developing a low cost, scalable, photon-counting receiver prototype for space-to-ground optical communications links. The receiver is being tested in a test bed that emulates photon-starved space-to-ground optical communication links. The receiver uses an array of single-pixel fiber-coupled superconducting nanowire single-photon detectors. The receiver is designed to receive the high photon efficiency serially concatenated pulse position modulation (SCPPM) waveform specified in the Consultative Committee for Space Data Systems (CCSDS) Optical Communications Coding and Synchronization Blue Book Standard. The optical receiver consists of an array of single-pixel superconducting nanowire detectors, analog phase shifters for channel alignment, digitizers for each detector channel, and digital processing of the received signal. An overview of the test bed and arrayed receiver system is given. Simulation and system characterization results are presented. The data rate increase of using a four-channel arrayed detector system over using one single pixel nanowire detector is characterized. Results indicate that a single-pixel detector is capable of receiving data at a rate of 40 Mbps and a four-channel arrayed detector system is capable of receiving data at a rate of 130 Mbps.

In this paper, a high capacity wavelength division multiplexing (WDM) for high data rate optical communications, a WDM with 2-dimensional M-PPM to achieve a higher number of bits per photon transmission, an optical wavelength division multiple access (WDMA) for multiple CubeSats/small spacecraft for deep space optical communications, and a combined optical WDMA with optical code division multiple access (CDMA) are investigated. The signal processing components required for successful operation of above mentioned optical systems are defined. For WDMA, the performance of the uncoded case for N SmallSats/CubeSats is obtained. Software simulations are used to obtain the performance of N SmallSats/CubeSats using a coded optical WDMA multiple access scheme. Results from successful completion of this investigation might be used in the future for deep space optical communication scenarios that require science data from SmallSats/CubeSats to be transmitted to Earth. An M-ary Pulse Position modulation (PPM) format is considered. For a hard decision optical receiver with photon counting detectors, a rate compatible protograph code is proposed. The code is optimized using the reciprocal channel approximation, which is a one-dimensional density evolution. The performance analysis is provided for the uncoded and simulated coded optical WDMA under background noise for up to N=16 SmallSat/CubeSats. Our results show, for example, that in the case of 2-PPM there is a 7 dB coding gain (with respect to the uncoded case) at a FER of 10−6, for a rate 0.8 code, and 12 dB coding gain for a rate 1/6 code, depending on the received background noise intensity. Leveraging existing laboratory hardware to test the deep-space optical WDMA concept, an experiment is performed. Finally the concept of combining WDMA with optical CDMA to support more users is analyzed using short signature sequences and uncoded 2-PPM modulation and simulations are performed for coded system.

The performance of M-ary pulse position modulated (PPM) optical wireless communication (OWC) systems in atmospheric weak turbulence medium is evaluated by using adaptive optics corrections. Piston, tilt, defocus and coma components of adaptive optics corrections are applied to the avalanche photodetector (APD) type of receiver and the results are obtained depending on various turbulence and receiver parameters. The lognormal channel distribution is used to model the weak atmospheric turbulence conditions. Adaptive optics correction increases the bit-error-rate (BER) performance of an OWC system operating in atmospheric turbulence conditions. Piston component yields the highest BER performance, followed by the tilt, defocus and coma adaptive optics correction components respectively.

We present analytical results on the average probability of error (PER) performance of an optically pre-amplified pulse-position modulation (PPM) receiver under Malaga- M fading. The results are in the form of a finite sum whose number of terms depends on the PPM modulation order and the noise modes of the amplifier, enabling the efficient calculation of the average PER. In addition, we utilized the presented analysis to evaluate the performance of a equal-gain-combining (EGC) diversity receiver that operates in conjunction with optical amplification and PPM. The results show that the utilization of diverse and relatively low PPM orders achieves a drastic reduction in the average PER.

Presented are simulation and experimental results that provide duplex optical-free space communication links with minimal power and pointing requirements by using a modulated retro-reflector (MRR) for planetary communications. The design is the MRR resides on the surface of a planet or moon, where energy is scarce, while the source of the communication laser resides on an orbiter to achieve satellite-to-ground communications. Also, a simulated scenario using the Mars Reconnaissance Orbiter (MRO) is provided for real world potential results. The information sent through this communication path can range from raw scientific data to multimedia files such as videos and pictures. Bidirectional communications is established with the MRR by using a nested pulse position modulation (PPM) structure. This modulation scheme is then evaluated for its validity in a proof-of-concept experiment. Initial results indicate a promising return-link performance of at least 300 kbps in the nested arrangement.

International audience; To enhance the error performance of impulse radio UWB transceivers, we introduce in this manuscript a novel modulation scheme based on exploiting the symmetry properties of transmitted waveforms. Parity Modulation utilizes odd versus even pulses to represent binary data, while the detector relies on a time reverser and non-coherent cross correlator. The analytical expression of power spectral density has been derived; then, considering different orders of Gaussian derivatives as pulse waveforms, the spectral characteristics have been optimized to comply with the UWB emission regulation. The bit error rate formula in an AWGN channel has been developed, while our simulation measurements showed a significant performance gain for 2 Gbps Parity over 1 Gbps Pulse Position Modulation and 2 Gbps On Off Keying. A reference-based parity scheme has been eventually proposed to enhance robustness against multi-path effects, interesting results have been achieved in terms of error probability in a realistic channel, with a compromise between data rate and complexity.

We apply a multi-layer perceptron as the timing error detector for PPM signal clock recovery. Simulation results show that the proposed MLP-based CDR method can improve the accuracy of phase detection with large sampling frequency offset over 1200 ppm. © 2020 The Author(s)

In the VLC context, pulse position modulation (PPM) and similar modulations are typically used when the overall complexity of the transmitter is required to be low or the system needs to support dimming, i.e., dynamically control the illumination level of the transmitter. However, despite the power efficiency of PPM, it is known to be bandwidth inefficient. Having known the trade-off between reliability and spectral efficiency, in this paper we propose a PPM-based space-time block coding (STBC) technique named as quasi-trace-orthogonal (QTO), derived from trace-orthogonal, to increase the spectral efficiency of PPM VLC’s by limiting the reliability loss. We provide Monte-Carlo simulations for a $4\times 4$ MIMO-VLC system and validate the results experimentally, and show that for a given signal-to-noise-ratio, the QTO-STBC based 4-PPM VLC system offers higher spectral efficiency at a cost of higher symbol error rate compared to trace-orthogonal STBC.

This paper introduces the use of photon-added squeezed states (PASSs) for quantum pulse position modulation (QPPM). It is shown that the use of PASSs in QPPM communication systems can reduce the symbol error probability (SEP) with respect to the use of different classes of quantum states with the same energy, including squeezed states and photon-added coherent states. The impact of thermal noise and phase diffusion on the SEP is also evaluated. The findings of this paper show the utility of PASSs in quantum communication systems.