Pulse Position Modulation Signals Research Articles

Measuring Detection Efficiency of High-Residency Acoustic Signals for Estimating Probability of Fish–Turbine Encounter in a Fast-Flowing Tidal Passage

Semidiurnal tidal currents can exceed 5 ms−1 in Minas Passage, Bay of Fundy, where a tidal energy demonstration area has been designated to generate electricity using marine hydrokinetic turbines. The risk of harmful fish–turbine interaction cannot be dismissed for either migratory or local fish populations. Individuals belonging to several fish populations were acoustically tagged and monitored by using acoustic receivers moored within the Minas Passage. Detection efficiency ρ is required as the first step to estimate the probability of fish–turbine encounter. Moored Innovasea HR2 receivers and high-residency (HR) tags were used to obtain detection efficiency ρ as a function of range and current speed, for near-seafloor signal paths within the tidal energy development area. Strong tidal currents moved moorings, so HR tag signals and their reflections from the sea surface were used to measure ranges from tags to receivers. HR2 self-signals that reflected off the sea surface showed which moorings were displaced to lower and higher levels on the seafloor. Some of the range testing paths had anomalously low ρ, which might be attributed to variable bathymetry blocking the line-of-sight signal path. Clear and blocked signal paths accord with mooring levels. The application of ρ is demonstrated for the calculation of abundance, effective detection range, and detection-positive intervals. High-residency signals were better detected than pulse position modulation (PPM) signals. Providing that the presently obtained ρ applies to tagged fish that swim higher in the water column, there is a reasonable prospect that probability of fish–turbine encounter can be estimated by monitoring fish that carry HR tags.

Theoretical analysis and experimental demonstration of gain switching for a PPM based UWOC system with picosecond pulses.

Shortening pulse width can improve the power efficiency and data rate of a pulse position modulation (PPM) based underwater wireless optical communication (UWOC) system at a fixed average optical power, which is more suitable for the energy-limited underwater environment. As a common method to generate short pulses, gain switching has the advantages of a tunable switching frequency and simple structure, facilitating the generation of high-order PPM signals. However, the output characteristics of electrical gain switching seriously affect the demodulation of PPM signals and limit the data rate. To study the performance of gain switching on a PPM communication system, simulation models of the semiconductor laser diode and the driving circuit are built to describe the generation of electrical and optical pulses. The pulse width, pulse peak value, and peak position of optical pulses are analyzed under different symbol durations and PPM orders. Furthermore, a 64-PPM/150-Mbps UWOC system with a 200-ps optical pulse width is demonstrated by using a gain-switched blue GaN-based laser diode in a water tank. The peak average power ratio (PAPR) is 19.5 dB. Via the statistical analysis of experiment results and the output characteristics of electrical gain switching, the main factor limiting the data rate attributes to the time delay fluctuation of gain switching. To the best of our knowledge, this is the first time that gain switching has been experimentally demonstrated and analyzed in a high-order PPM based UWOC system.

Modulation Scheme Analysis for Low-Power Leadless Pacemaker Synchronization Based on Conductive Intracardiac Communication.

Conductive intracardiac communication (CIC) has been demonstrated as a promising concept for the synchronization of multi-chamber leadless cardiac pacemakers (LLPMs). To meet the 2-5 μW power budget of a LLPM, highly specialized CIC-transceivers, which make optimal use of the cardiac communication channel, need to be developed. However, a detailed investigation of the optimal communication parameters for CIC-based LLPM synchronization is missing so far. This work analyzes the intracardiac communication performance of two low-power modulation techniques, namely On-Off-Keying (OOK) and Manchester-encoded baseband transmission (BB-MAN), as a function of the transmitted bit-energy. The bit error rate (BER) of a prototype dual-chamber LLPM was determined both in simulation and in-vitro experiments on porcine hearts. A BER of 1e -4 was achieved with a median bit-energy in the range of 3-16 pJ (interquartile range: 4-15 pJ) for data rates from 75-500 kbps and a receiver input noise density of 7 nV/ √{Hz}. Both modulation schemes showed comparable performance, with BB-MAN having a slight bit-energy advantage (1-2 dB at 150-500 kbps) under equalized transceiver characteristics. This study demonstrates that reliable CIC-based LLPM synchronization is feasible at transmitted power levels 10 nW under realistic channel conditions and receiver noise performance. Therefore, modulation techniques such, as BB-MAN or OOK, are preferable over recently proposed alternatives, such as pulse position modulation or conductive impulse signaling, since they can be realized with fewer hardware resources and smaller bandwidth requirements. Ultimately, a baseband communication approach might be favored over OOK, due to the more efficient cardiac signal transmission and reduced transceiver complexity.

BER Performance Analysis of Non-Coherent Q-Ary Pulse Position Modulation Receivers on AWGN Channel.

This paper introduces the structure of a Q-ary pulse position modulation (PPM) signal and presents a noncoherent suboptimal receiver and a noncoherent optimal receiver. Aiming at addressing the lack of an accurate theoretical formula of the bit error rate (BER) of a Q-ary PPM receiver in the additive white Gaussian noise (AWGN) channel in the existing literature, the theoretical formulas of the BER of a noncoherent suboptimal receiver and noncoherent optimal receiver are derived, respectively. The simulation results verify the correctness of the theoretical formulas. The theoretical formulas can be applied to a Q-ary PPM system including binary PPM. In addition, the analysis shows that the larger the Q, the better the error performance of the receiver and that the error performance of the optimal receiver is about 2 dB better than that of the suboptimal receiver. The relationship between the threshold coefficient of the suboptimal receiver and the error performance is also given.

Compatibility in acoustic telemetry

Acoustic telemetry is widely used to investigate aquatic animal movement. Pulse position modulation (PPM) is an acoustic telemetry method that allows multiple unique identification codes to be transmitted at a single acoustic frequency, typically in the 69 kHz range. However, because the potential number of unique identification codes (i.e. tags) is ultimately limited by the number of pulses in the PPM signal, this poses a practical limitation. In addition, different manufacturers have developed different approaches to encoding the transmitted data, hampering compatibility across brands. A lack of broad compatibility across telemetry systems restricts users to a single manufacturer and operating system, reduces market competition and limits innovation. As the aquatic animal tracking research community organises towards networks of devices and data, incompatibility becomes more problematic and jeopardizes the unique scientific benefits offered by the networking approach. Here, we make a plea for collaboration among the manufacturers globally and propose a set of open protocols to ensure equipment interoperability as a medium-term solution.

Visible Light Communication for Position control of Robotic Vehicle

With increasing demand in the need for fast and secured transmission of data from one place to another in a wireless medium, many innovations open up with respect to the use of communication protocols. Of late, spectrum availability appears to be a very scarce resource and invites alternate methods of transmission to fortify the emerging challenges. The paper investigates the properties of a visible light communication (VLC) medium and develops a scheme for controlling the position of a Li-Fi-based robotic vehicle. The fast transmission properties of light signal along with its edge over radio frequency and or Wi-Fi communication augur well to exploit the potentials of the Li-Fi environment. The methodology involves the use of an Arduino microcontroller for the generation and reception of control signal at both the transmitter and receiver ends, respectively. The response to varying widths of pulse position modulation (PPM) signals bring out the ability of the scheme to respond to changes in position at varying speeds. The results envisage a new dimension to the scope of robotic vehicles for a space in automated domains in terms of faster and precise operational ambits.

Target Localization and Tracking Using an Ultra-Wideband Chaotic Radar With Wireless Synchronization Command

An ultra-wideband chaotic radar with wireless synchronization command is proposed and experimentally demonstrated for target localization and tracking. This radar uses the wideband chaotic pulse position modulation (CPPM) signal as the probe signal and the radar structure of single-transmitting-dual-receiving. The echo signal scattered from a target is collected by two receivers. The target is located and tracked accurately in two-dimensional space using the signal processing scheme. In particular, the radar receivers can directly generate the CPPM reference signals through a wireless synchronization command, so that the transceivers can be physically separated without cable or optical fiber connection. Experimental results demonstrate the proposed chaotic radar can locate and track the target accurately. A localization error of 11 cm and a detection resolution of 17 cm can be both achieved. Moreover, this radar possesses the excellent immune performance to the external electromagnetic interferences, which makes it suitable in the complex electromagnetic environment caused by the cooperative work of multiple radars.

A power waveform design based on OVSF-PPM for stress wave based wireless power transfer

The lifetime of wireless sensors and devices is restricted by their limited battery capacities, since it is quite time-consuming and costly to replace batteries. Wireless power transfer is recognized as a feasible solution to charge wireless sensors and portable devices, since it can provide energy continuously for wireless electronic devices. This paper explores a waveform design for stress wave power transfer. In the proposed method, pulse position modulation (PPM) signals are firstly designed based on orthogonal variable spreading factor (OVSF) code. Then, power transfer waveforms for multiple receivers are created via analyzing the correlation among the PPM signals. When applied in stress wave power transfer, the proposed waveform is demonstrated to effectively improve power transfer performance at the intended receiver. We investigate three different transmission schemes, namely the pulse waveform, the time reversal waveform, and the proposed power transfer waveform, by comparing and analyzing their performances in experiments when one energy transmitter and one energy transfer array are respectively used. Due to multiple stress wave modes, rich dispersion and mutual interference among energy transfer signals, energy transfer efficiencies (ETE) and peak to average power ratios (PAPR) tend to be low by using pulse waveforms or traditional time reversal waveforms to transfer stress wave energy. On the contrary, by implementing the proposed waveform in stress wave power transfer, the ETE and the PAPR are effectively improved. In the experiment, three piezoceramic transducers mounted on a pipeline are used for stress wave power transfer. The experimental results demonstrate that the proposed waveform significantly improves the ETE and the PAPR, as compared with the other two waveforms.

Analysis and Rectification of the Asynchronous Sampling Effect in the Pulse-Position Modulation Systems

Although the clock synchronization is of utmost importance in communications, it is quite difficult to achieve in practice. Consequently, the asynchronous effect emerges as a critical problem for all pulse-position modulation (PPM) systems. In this paper, the impact of the sampling-period misalignment is studied and evaluated. A new analytical model is established to govern the misalignment between the slot periods of the transmitted and received signals. The ultimate error rate related to this kind of unfavorable misalignment is also derived theoretically. Besides, we propose a new algorithm, which can adjust the onsets of the slot periods dynamically, to mitigate this misalignment and improve the error performance. To justify our new analysis and algorithm, a visible-light communication system using single-pulse PPM is taken as a practical example. Simulation results demonstrate that the effectiveness of our proposed algorithm is very promising. The frame-error rate of the rectified PPM signal is around 10−5 across all of the misalignment values.

Mark ratio modulation over pulse position modulation

• Mark ratio modulation over inverse PPM modulation is proposed for optical label switching. • Two signals are transmitted by one ASK modulation. • The mark ratio difference of PPM and inverse PPM is utilized to deliver an overlay signal. • The mark ratio modulation doesn’t degrade the PPM signal. Orthogonal modulation superimposes non-amplitude-modulated signals on Manchester coded or pulse position modulated amplitude shift keying (ASK) signals, allowing two traffic flows with different bit rates to be modulated on the same wavelength channel, and hence improving spectrum efficiency. Inspired by the orthogonal modulation, this paper proposes a novel modulation format, i.e., mark ratio modulation over pulse position modulation (PPM), which utilizes the mark ratio difference between the PPM symbols and the inverse PPM symbols to deliver an overlaid signal. Better than traditional orthogonal modulation, in the mark ratio modulation over PPM, both low-speed and high-speed traffic flows are modulated by ASK with no need to sacrifice the extinction ratio, while keeping the reception simple and easy. According to theoretical analysis and test, we found 4PPM is a good option, which can balance the trade-off between the PPM signal’s effective bit rate and the mark ratio modulated signal’s quality.

Deep-Space Optical Communication Link Engineering: Sensitivity Analysis

As in other facets of society, the data rate requirements of science and exploration missions in deep space are ever-increasing, mostly due to the number and refinement of science instruments onboard the spacecraft. For repatriating the increased data back to Earth, the communication link is the bottleneck. To tackle this issue for future missions, space agencies in the frame of Consultative Committee for Space Data Systems finalized recently a deep-space optical specification implementing serially concatenated pulse position modulation signaling. Fully based on this standard, this paper aims to provide a comprehensive tool assessing the sensitivity of the deep-space optical link on multiple factors. It also provides a practical method to avoid lengthy BER evaluations that would be otherwise required.

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

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.

Design of a New Stress Wave-Based Pulse Position Modulation (PPM) Communication System with Piezoceramic Transducers.

Stress wave-based communication has great potential for succeeding in subsea environments where many conventional methods would otherwise face excessive difficulty, and it can benefit logging well by using the drill string as a conduit for stress wave propagation. To achieve stress wave communication, a new stress wave-based pulse position modulation (PPM) communication system is designed and implemented to transmit data through pipeline structures with the help of piezoceramic transducers. This system consists of both hardware and software components. The hardware is composed of a piezoceramic transducer that can generate powerful stress waves travelling along a pipeline, upon touching, and a PPM signal generator that drives the piezoceramic transducer. Once the transducer is in contact with a pipeline surface, the generator integrated with an amplifier is utilized to excite the piezoceramic transducer with a voltage signal that is modulated to encode the information. The resulting vibrations of the transducer generates stress waves that propagate throughout the pipeline. Meanwhile, piezoceramic sensors mounted on the pipeline convert the stress waves to electric signals and the signal can be demodulated. In order to enable the encoding and decoding of information in the stress wave, a PPM-based communication protocol was integrated into the software system. A verification experiment demonstrates the functionality of the developed system for stress wave communication using piezoceramic transducers and the result shows that the data transmission speed of this new communication system can reach 67 bits per second (bps).

Performance Enhancement of Optical PPM-CDMA Using Successive Interference Cancellation Scheme

A comprehensive mathematical model of Successive Interference Cancellation (SIC) using Direct Sequence (DS) and Spectral Amplitude Coding (SAC), which is employed in incoherent optical CDMA using On-Off Keying (OOK) Pulse Position Modulation (PPM) and On-Off Keying (OOK) considering the presence of Phase–Induced Intensity Noise (PIIN), shot noise and thermal noise is presented in this work. SIC scheme has the potential to suppress Multiple Access Interference (MAI). The concept of SIC is the following: detection is taken place in successive stages where the most reliable symbols are chosen at each stage. Where the interference contributed by the already detected symbols will be removed. It has been found out that, theoretically, the size of M-ary on optical CDMA system limits the MAI effect. Thus, the system performance improves with the increasing of M-ary PPM. Hence, the system using PPM has better performances if compared to the one using OOK, due to a lower average number of interfering optical pulses. In addition, a lot of users can be accommodated with SIC/SAC-optical CDMA based PPM signaling system instead of the SIC/SAC-optical CDMA based OOK one.

Mixed‐signal demodulator for IEEE 802.15.6 IR‐UWB WBAN energy detection‐based receiver

A mixed-signal baseband demodulator for IEEE 802.15.6 impulse-radio ultra-wideband (IR-UWB) wireless body area network (WBAN) energy detection-based receiver is presented. It considers M-ary pulse position modulation (PPM) signalling format conforming to the IEEE 802.15.6 WBAN standard. The demodulator utilises ‘integrate-and-digitise’ approach employing simple mixed-signal circuits. The design is implemented in 0.18 μm CMOS technology operating at 1.8 V supply. The demodulator consists of a mixed-signal windowed integrator, a single-ended successive approximation register analogue-to-digital converter followed by a digital back-end. Further, its performance evaluation is carried out for 2-ary and 16-ary PPM signalling in different WBAN channels.

A Wirelessly Powered UWB RFID Sensor Tag With Time-Domain Analog-to-Information Interface

This paper presents a wirelessly powered radio frequency identification sensor tag with an analog-to-information interface. A time-domain interface, incorporating an ultra-low-power impulse radio ultra-wideband (IR-UWB) transmitter (TX), is employed. The analog signal from the sensor is compared with a triangular waveform, resulting in a pulse-position modulation signal to trigger UWB pulses. Thanks to the high time-resolution IR-UWB radio, time intervals of the impulses can be used to represent the original input value, which is measured remotely on the reader side by a time-of-arrival estimator. This approach not only eliminates the analog-to-digital converter (ADC) but also significantly reduces the number of bits to be transmitted for power saving. The proposed tag is fabricated in a 0.18-μm CMOS process with an active area of 2.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The measurement results demonstrate that a 300-kS/s sampling rate with a 6.7-bit effective number of bits (ENOB) is obtained via a UWB receiver with a sensitivity of -93 dBm and an integration window of 10 ns. The ENOB is improved to 7.3 bits when the integration window is reduced to 2 ns. The tag can be powered up by a -18-dBm UHF input signal. The power consumption of the proposed tag is 41.5 μW yielding a 1.3-pJ/conv.step figure of merit, offering 9× and 67× improvements compared with the state of the art based on an ADC and a backscattering TX, and the tag based on an ADC and a narrowband TX, respectively.

Reducing Inter-Core Crosstalk Impact via Code-Interleaving and Bipolar 2-PPM for Core-Multiplexed SAC OCDMA PON

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.

On the Design of Maximal-Rate Shape-Preserving $2\times 2$ and $3\times 3$ Space-Time Codes for Noncoherent Energy-Detection-Based PPM Communications

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.

Permutation-Based Noncoherent Space-Time Codes With Analog Energy Detection for IR-UWB Communications With PPM

In this paper, we consider the problem of space-time (ST) coding for the noncoherent ultra-wideband (UWB) systems with pulse position modulation (PPM). In particular, we propose the first known family of ST codes that lends itself to optimal decoding with the energy detectors. Energy detection avoids the sampling of the received signal where the sampling rates can be prohibitively high and escapes from the challenging task of estimating the dense multi-path UWB channel. In the absence of design criteria that are adapted to the problem under consideration, we derive two novel design criteria and propose the novel construction accordingly. The proposed code is based solely on permutations, and hence it does not introduce any constellation expansion on the totally-real and unipolar PPM signal set. In other words, the components of the constructed codewords are limited to either zero or one indicating the absence or presence of an UWB pulse in the corresponding PPM slot, respectively. The above characteristics result in a remarked simplicity of the ST encoder/decoder making it an appealing solution to low-cost and low-power UWB systems. For a system equipped with $n$ transmit antennas, we prove that the proposed code is capable of achieving a full transmit diversity order with $M$ -PPM constellations for $M>n+1$ while transmitting at the rate of $({1}/{n})\log _{2}\binom {M-1}{n}$ bits per channel use.

Temporal Spectrum Sensing for Optical Wireless Scattering Communications

Due to the unlicensed spectrum nature of the optical wireless communication, for a transceiver pair, the receiver needs to periodically sense the communication media, aiming to better schedule its transmission. Considering that the data symbols or channel parameters are unknown, we adopt a generalized likelihood ratio test (GLRT), which is known to be optimal with unknown parameters based on finite samples. This paper proposes two detection rules on whether there are optical signals falling into the receiver field of view within certain time slot(s), based on the sum number of received photons over all sensing slots, as well as the number of received photons in each slot. The formal one is named the sum-counting test and the latter one is named as the general GLRT. We design the corresponding detection schemes for both on-off keying (OOK) and pulse-position modulation (PPM) signal formats. We also provide asymptotic results on the miss detection probability. Numerical results show that, for OOK signal format, the general GLRT outperforms the sum-counting test at the cost of higher computational complexity, but for PPM signal format both detection schemes perform virtually the same.