Showing papers on "Pulse-position modulation published in 1989"
TL;DR: In this article, multiple pulse position modulation (MPPMPM) is proposed as a modulation method to improve the band-utilization efficiency in optical PPM, where multiple pulses are transmitted using different combinations of the positions of these pulses.
Abstract: Multiple pulse position modulation (MPPM) is proposed as a modulation method to improve the band-utilization efficiency in optical pulse position modulation (PPM). Optical PPM gives higher transmission efficiency (bit/photon) in optical communications but degrades band-utilization efficiency. The proposed method reduces the required transmission bandwidth in optical PPM to about half with the same transmission efficiency, thus increasing band-utilization efficiency. While in conventional optical PPM, only one optical pulse is transmitted in every signal block, multiple pulses are transmitted using this method. Information is represented by different combinations of the positions of these pulses. The principle of bandwidth reduction applied, the transmission characteristics of the proposed method, and examples of improvement in band-utilization efficiency are also shown. >
245 citations
TL;DR: The impact of pointing and tracking errors on the design of direct-detection pulse-position modulation and heterodyne noncoherent frequency-shift keying systems is analyzed and it is shown that in the limit of large spatial tracking errors, the advantage in receiver sensitivity for theheterodyne system is quickly offset by the smaller antenna gain and the higher power penalty due to tracking errors.
Abstract: Given the RMS transmitter pointing error and the desired probability of bit error (PBE), it can be shown that an optimal transmitter antenna gain exists which minimizes the required transmitter power. Given the RMS local oscillator tracking error, an optimum receiver antenna gain can be found which optimizes the receiver performance. The impact of pointing and tracking errors on the design of direct-detection pulse-position modulation (PPM) and heterodyne noncoherent frequency-shift keying (NCFSK) systems is then analyzed in terms of constraints on the antenna size and the power penalty incurred. It is shown that in the limit of large spatial tracking errors, the advantage in receiver sensitivity for the heterodyne system is quickly offset by the smaller antenna gain and the higher power penalty due to tracking errors. In contrast, for systems with small spatial tracking errors, the heterodyne system is superior because of the higher receiver sensitivity. >
173 citations
15 Oct 1989
TL;DR: A modulation recognizer that automatically reports modulation types of constant-envelope modulated signals is developed using zero-crossing techniques, and results demonstrate that reasonable average probability of correct classification is achievable at CNR=15 dB and higher.
Abstract: A modulation recognizer that automatically reports modulation types of constant-envelope modulated signals is developed using zero-crossing techniques. The zero-crossing sampler, as a signal conditioner, has the advantage of providing accurate phase transition information over a wide dynamic frequency range. Signal parameters, such as zero-crossing variance, carrier-to-noise ratio (CNR), and carrier frequency, are estimated. Phase-difference and zero-crossing-interval histograms play the roles of features for modulation recognition. The classifier performance is given in the form of a confusion matrix. The obtained simulation results demonstrate that reasonable average probability of correct classification is achievable at CNR=15 dB and higher. >
98 citations
TL;DR: Consideration is given to the optical direct-detection channel, and it is shown how simple trellis-coded modulation (TCM) can be used to improve performance or increase throughput without bandwidth expansion or performance loss.
Abstract: Consideration is given to the optical direct-detection channel, and it is shown how simple trellis-coded modulation (TCM) can be used to improve performance or increase throughput (in bits per second) without bandwidth expansion or performance loss. In fact, a modest performance gain can be achieved. Although the approach can be used with other signal constellations, the authors concentrate on signals derived from the pulse-position modulation (PPM) format by allowing overlap. Theoretical motivation for using this signal set, known as overlapping PPM (OPPM), was recently given by I. Bar David and G. Kaplan (1984), who showed a capacity gain when overlap is introduced. >
55 citations
TL;DR: In this article, the frequency modulation and amplitude modulation responses of a 1.5- mu m distributed feedback (DFB) laser were measured to 15 GHz and the magnitude of the FM response was flat out to 12 GHz.
Abstract: The frequency modulation (FM) and amplitude modulation (AM) responses of a 1.5- mu m distributed feedback (DFB) laser were measured to 15 GHz. At 9-mW output power, the magnitude of the FM response was flat out to 12 GHz, and there was a 15-25-ps delay between the FM and AM responses. Computer simulation techniques indicate that the measured FM response is adequate to produce good eye patterns for frequency-shift-keying modulation at data rates up to 20 Gb/s. The high-speed frequency-shift-keying modulation capability of this 1.5- mu m DFB laser was experimentally confirmed at 11 Gb/s. >
52 citations
TL;DR: A comparative evaluation of the various strategies for combining convolutional codes and pulse position modulation in a direct-detection optical channel offers a comparison of bit error probability and achievable coding gain for different code structures and decoding schemes.
Abstract: Several strategies for combining convolutional codes (CCs) and pulse position modulation (PPM) in a direct-detection optical channel are considered, including binary and 2/sup n/-ary PPM with rate-1/n CCs, 2/sup m/-ary PPM with a dual-m CC, and interleaved 2/sup L/-ary PPM with a rate-1/n CC. In the latter case, J.L. Massey's (1981) concept of coding of L separate component channels constituting a 2/sup L/-ary PPM erasure channel is carried out for both the ideal photon counting and the avalanche photodetection (APD) cases, providing a comparative evaluation of the various strategies in terms of bit error probability and achievable coding gain for different code structures and decoding schemes. >
33 citations
TL;DR: In this paper, a performance analysis has been presented for digital PPM transmitted over an optical fiber channel and detected using both optimum and sub-optimum pre-detection filters.
Abstract: A performance analysis has been presented for digital PPM transmitted over an optical fibre channel and detected using both optimum and sub-optimum pre-detection filters. Receiver sensitivity calculations, carried out at a bit-rate of 140Mbit/s and a wavelength of 1.3 μm, show that the optimum digital PPM system considered offers an 8.6 dB improvement over a typical PCM system. The sub-optimum pre-detection filters considered were a matched filter, an optimised 3-pole filter and a third-order Butterworth filter. These led to sensitivity degradations of 0.4 dB, 0.9 dB and 1.1 dB respectively. This clearly illustrates that receiver complexity can be simplified without large reductions in sensitivity. In particular, the well known and simple Butterworth filter can be employed with only 1.1 dB degradation in sensitivity. The timing requirements for digital optical fibre PPM have been analysed. An original spectral characterisation of the PPM format using its cyclostationary properties has been presented. The characterisation was used to evaluate the inherent systematic jitter associated with the extracted slot clock. An optimisation of the extracted slot clock timing variance and system wrong slot errors (due to imperfect slot synchronisation) was shown to be feasible in terms of the PLL bandwidth and the PPM order. Frame synchronisation was analysed for an original class of frame synchronisers that utilises natural sequences. The extracted frame clock timing variance was evaluated and the probability of wrong slot errors due to the non-ideal frame clock was assessed. The frame clock timing variance and wrong slot errors were shown to be minimisable provided that the proper number of natural sequences is tracked and the appropriate PLL bandwidth is utilised. The analysis has provided a performance evaluation of the optical fibre PPM system in the presence of inherent systematic slot and frame jitter.
27 citations
Patent•
31 Jan 1989
TL;DR: In this article, a high frequency (HF) communications buoy that employs HF surface wave and sky wave, communication and spread spectrum modulation to suppress multipath fading and to decrease the undesired detectability of transmitted signals is presented.
Abstract: A high frequency (HF) communications buoy that employs HF surface wave, and sky wave, communication and spread spectrum modulation to suppress multipath fading and to decrease the undesired detectability of transmitted signals. The buoy comprises a water-tight floatable enclosure that may be deployed from a flying vehicle or a submerged vessel. An HF communications transceiver is disposed within the enclosure that is capable of transmitting and receiving signals employing high frequency (HF) band surface wave and sky wave propagation. The transceiver further comprises spread spectrum modulation and demodulation circuitry for modulating transmitted signals utilizing spread spectrum modulation and for demodulating received signals encoded by means of spread spectrum modulation. The spread spectrum modulation and demodulation circuitry is provided to suppress multipath fading and decrease the probability of detection of transmitted signals. An antenna is coupled to the transceiver and supports the transmission and reception of the high frequency (HF) spread spectrum modulated signals. The use of HF surface wave communications in conjunction with the spread spectrum modulation of the transmitted signals provides for networking of a plurality of buoys. The use of HF spread spectrum communications also reduces the probability of exposing the presence and location of the transmitting terminal and eliminates multipath interference between ground wave and sky wave transmissions, or transmissions reflected from different sky wave layers. In addition, utilization of the underwater communication circuitry permits a submerged vehicle to take advantage of the relatively secure communications link provided by the present invention.
22 citations
TL;DR: It appears that in systems with a high enough SNR, the loss in effective SNR could be outweighed by the decrease in average peak shift, which could be of particular interest in future systems using magnetoresistive heads which have the potential to yield substantially higher SNRs.
Abstract: The authors present results on a controlled-polarity modulation/coding scheme. They review this scheme and describe how to choose certain code parameters for the purpose of comparing the controlled polarity scheme to conventional (d,k) coding with NRZI modulation. A computer simulation is then utilized to compare the different schemes in terms of effective signal-to-noise ratio (SNR) and peak shift. It is shown that the controlled polarity schemes have less peak shift than the conventional schemes, whereas the conventional schemes have a higher effective SNR. It appears that in systems with a high enough SNR, the loss in effective SNR could be outweighed by the decrease in average peak shift. This could be of particular interest in future systems using magnetoresistive heads which have the potential to yield substantially higher SNRs. >
16 citations
Journal Article•
TL;DR: In this paper, the authors evaluate the capacite of the modulation multiple de positions d'impulsion in communications optiques, grâce a un capteur de photons, etudie l'efficacite, l'energie, la vitesse de transmission and the probabilite d'erreur.
Abstract: Evaluation de la capacite de la modulation multiple de positions d'impulsion en communications optiques, grâce a un capteur de photons. On etudie l'efficacite, l'energie, la vitesse de transmission et la probabilite d'erreur. On obtient une bonne efficacite de la probabilite d'erreur pour la modulation multiple de positions d'impulsions codee Reed-Solomon
15 citations
TL;DR: In this article, an orthogonal convolutional coding scheme is proposed, achieving better performances than previous coding alternative, over a wide range of efficiencies, achieving operation points over 3 nat/photon, with performances that cannot be obtained with other coding schemes.
Abstract: Several coding alternatives have been analyzed to improve the performance of the ideal optical pulse position modulation (PPM) optical channel, although it has been shown that performance improvements are difficult to obtain for transmission efficiencies over 1 nat/photon. In the present work, an orthogonal convolutional coding scheme is proposed, achieving better performances than previous coding alternative, over a wide range of efficiencies. Furthermore, a concatenated coding scheme using an orthogonal convolution code as an inner code and a Reed-Solomon code as an outer code is proved to be effective, achieving operation points over 3 nat/photon, with performances that cannot be obtained with other coding schemes. >
Patent•
29 Dec 1989TL;DR: In this article, a system for decoding a digital code and in particular a biphase-coded data, by detecting edges of the data and the time intervals between edge conditions, is provided.
Abstract: There is provided a system for decoding a digital code
and in particular a biphase-coded data, by detecting edges
of the biphase-code data and the time intervals between
edge conditions. A system for decoding the biphase-code
data includes a microcomputer 1 to control the system, a
remote receiver module (RRM) 3 for logicizing code data
received in infrared rays, filtering the waveform, and
applying the output to the microcomputer 1; a first remote
transmitter (RTTP) 5 for generating Pulse Position
Modulation (PPM) code; a second remote transmitter (RTTB)
7 for generating biphase-code according to the pressing of
a key; a tuner 9, display unit 11, and servo 13 operated
under the control of the microcomputer 1; and a key matrix
15 for entering key data to the microcomputer 1.
18 Dec 1989
TL;DR: Recent theoretical developments relating specifically to the transmission of video signals of PWM are discussed in this paper along with a range of practical results and measurements.
Abstract: Pulse time modulation (PTM) techniques offer attractive performance trade-offs for the transmission of analogue data over optical fibre networks In particular, pulse width modulation (PWM) emerges as a bandwidth-efficient technique capable of supporting multiple video channels inexpensively Recent theoretical developments relating specifically to the transmission of video signals of PWM are discussed in this paper along with a range of practical results and measurements >
Book•
01 Jun 1989
TL;DR: An introduction to single-SIDEBAND MODULATION and single-sideband modulation, and applications for mobile phone use and data communications.
Abstract: INTRODUCTION TO ELECTRONIC COMMUNICATION AMPLITUDE MODULATION AND SINGLE-SIDEBAND MODULATION AMPLITUDE MODULATION CIRCUITS FREQUENCY MODULATION FREQUENCY MODULATION CIRCUITS RADIO TRANSMITTERS COMMUNICATIONS RECEIVERS MULTIPLEXING ANTENNAS, TRANSMISSION LINES, AND RADIO WAVE PROPAGATION MICROWAVE TECHNIQUES INTRODUCTION TO SATELLITE COMMUNICATIONS DATA COMMUNICATION FIBER-OPTIC COMMUNICATIONS TELEVISION THE TELEPHONE SYSTEM AND ITS APPLICATIONS
11 Jun 1989
TL;DR: A practical timing recovery subsystem for a direct detection optical communication system that uses Q=4 pulse position modulation (PPM) signaling at 25 Mb/s is described.
Abstract: A practical timing recovery subsystem for a direct detection optical communication system that uses Q=4 pulse position modulation (PPM) signaling at 25 Mb/s is described. The system consists of an AlGaAs laser diode transmitter and an avalanche photodiode (APD) photodetector. The PPM slot clock is recovered with a transition detector followed by a phase lock loop (PLL). The PPM word clock is recovered by tracking pairs of back-to-back PPM pulses in the received random PPM data sequences with another PLL. The system is capable of acquiring and maintaining slot and word synchronization at greater than 20 average detected photons per information bit (40 photons/PPM pulse). >
11 Jun 1989
TL;DR: Trellis-coded modulation techniques are considered for use in a digital microwave radio (DMR) system employing high-level M-QAM modulation and it is found that the TCM system always outperformed the uncoded system under deep selective fades.
Abstract: Trellis-coded modulation (TCM) techniques are considered for use in a digital microwave radio (DMR) system employing high-level M-QAM modulation. Emphasis is placed on whether the coding gain offered at high signal-to-noise ratio is also in effect during deep selective fades. A specific Ungerboeck code, used in a 512-cross modulation scheme was found to have a lower probability of outage (for a bit-error-rate (BER) threshold of 10/sup -3/), than an uncoded 256-QAM system having the same symbol rate. The same linear adaptive finite-tap transversal equalizer was used in both the uncoded and the coded systems. Further work was done to see what effect various code parameters had on the fade performance. The result was that the TCM system always outperformed the uncoded system (up to a BER of 10/sup -3/) under deep selective fades. >
01 Jun 1989
TL;DR: A modified version of pulse position modulation, asynchronous digital pulse interval modulation (PIM), is examined, which strengthens the viability of using LEDs as sources on a single mode fiber system, by allowing an increase in the peak power coupled into the fiber.
Abstract: A modified version of pulse position modulation (PPM), asynchronous digital pulse interval modulation (PIM), is examined. The modulation scheme strengthens the viability of using LEDs as sources on a single mode fiber system, by allowing an increase in the peak power coupled into the fiber. First, an overview of the PIM code is provided. This is then followed by a detailed description of the 3B17P PIM code, which was implemented in an experimental 90-Mb/s communication system. Experimental results of the system's bit error rate (BER) versus the average received power were obtained for both the PIM and NRZ code over a coaxial cable link. The results are compared and discussed. The PIM code has a power advantage of up to 3.5 dB over the NRZ binary code. At a constant peak received power, the effect of the threshold level on the BER is similar for both codes at a high SNR. At a low SNR, there appears to be an optimal threshold level that depends on the duty cycle of the received code. >
Journal Article•
TL;DR: In this article, a power combiner is proposed in which the signaling frames are obtained from a code set formed by nonorthogonal constant-weight codewords, and the rate improvements of multiple-diode schemes using the combiner are presented.
Abstract: A power combiner is proposed in which the signaling frames are obtained from a code set formed by nonorthogonal constant-weight codewords The rate improvements of multiple-diode schemes using the combiner are presented, as compare to a single-diode pulse position modulation (PPM) scheme Comparisons are made assuming the same alphabet size, and the same peak power per diode As a function of the number of diodes, optical systems based on this combining scheme are shown to provide data rate improvements about 40% higher than a conventional orthogonal combiner Because of the reduction of the signaling frame length, this combining technique provides substantial rate improvements as a function of the input alphabet size >
06 Oct 1989
TL;DR: In this paper, a theoretical investigation on optical transmission schemes for free-space applications is carried out, and the receiver sensitivity of direct detection schemes like NRZ and QPPM (quaternary pulse position modulation) is evaluated.
Abstract: A theoretical investigation on optical transmission schemes for free-space applications is carried out. Receiver sensitivity of direct detection schemes like NRZ and QPPM (quaternary pulse position modulation) are evaluated. For bit rates between 10 and 65 Mbit/s, QPPM outperforms NRZ by up to 2.0 dB.
01 Dec 1989
TL;DR: In this article, the authors discuss schemes for pulse position modulation of neodymium: yttrium aluminum garnet (Nd:YAG) lasers for optical transmission of data between distant spacecraft and stations on Earth.
Abstract: Report discusses schemes for pulse-position modulation of neodymium: yttrium aluminum garnet (Nd:YAG) lasers for optical transmission of data between distant spacecraft and stations on Earth.
TL;DR: In this paper, the development of single-sideband broadcasting and the short-wave super transmitter is discussed, and the use of pulse duration modulation to reduce energy costs is discussed.
Abstract: The author discusses the development of single-sideband broadcasting and the short-wave super transmitter. The use of pulse duration modulation to reduce energy costs is discussed. Other energy saving methods such as dynamic amplitude modulation are also discussed. The author describes single-tube-equipped 500 kW transmitter technology. >
01 May 1989
TL;DR: In this article, the authors concentrate on signals derived from the pulse-position modulation (PPM) format by allowing overlap, and show that a modest performance gain can be achieved when overlap is introduced.
Abstract: Consideration is given to the optical direct-detection channel, and it is shown how simple trellis-coded modulation (TCM) can be used to improve performance or increase throughput (in bits per second) without bandwidth expansion or performance loss. In fact, a modest performance gain can be achieved. Although the approach can be used with other signal constellations, the authors concentrate on signals derived from the pulse-position modulation (PPM) format by allowing overlap. Theoretical motivation for using this signal set, known as overlapping PPM (OPPM), was recently given by I. Bar David and G. Kaplan (1984), who showed a capacity gain when overlap is introduced. >
TL;DR: In this paper, a closed-loop control system was used to produce a small variation in the energy consumption of a cavity-dumped laser system with pulse position modulation (PPM).
02 Jun 1989
TL;DR: It will be shown that in order to meet the size and weight constraint of the optical package and the requirement of the transmitting laser, suboptimal designs may be necessary for ISL applications.
Abstract: Communications via optical cross-link between two satellites require reciprocal spatial beam tracking. For intersatellite links (ISL) operating at narrow beamwidths, the line-of-sight pointing error at both satellite stations will have a significant impact on the system communication performance. Large pointing error on either end of the system can combine to impose higher power penalty at the transmitter, and can severely degrade the receiver performance. Tradeoffs in the required optical power and the size of the receiver aperture can be made while keeping the communication bit error rate constant. An approach to the selection of the optimal system parameters is presented. Given the tracking error statistics at each end of the link, and the desired probability of bit error rate (PBE), the combination of optical apertures are found that minimizes the required laser power. A tight error upper bound for direct-detection PPM system were developed for the bit error rate calculation. The spatial angle tracking error statistics modeled for each station are identical Rician distribution with static pointing errors. The product of optical apertures and the RMS tracking error, and the ratio of the required laser power and the RMS tracking error, are found to be constants, which are independent of the actual RMS tracking error for fixed PBE and static pointing error. Practical ISL parameters are used in the selection of the pair of optical apertures. It will be shown that in order to meet the size and weight constraint of the optical package and the requirement of the transmitting laser, suboptimal designs may be necessary for ISL applications. Sets of curves illustrating the impact of tracking error on the design parameters and the associated laser power penalty for different aperture gains and power requirement will be presented.
07 Mar 1989
TL;DR: The guard time effect, employed to combat multipath, is evaluated for frequency-selective channels and the optimal combination of signalling rate, code rate and guard time is presented.
Abstract: The generalized cut-off rate of time- and frequency-selective fading channels is used to the optimal signalling rate and code rate. Two modulation types, M-ary frequency shift keying (MFSK) and M-ary differential phase shift keying (MDPSK) with soft decoding are investigated as well as three dispersive channels. The guard time effect, employed to combat multipath, is evaluated for frequency-selective channels and the optimal combination of signalling rate, code rate and guard time is presented. Special attention is given to CCIR (International Radio Consultative Committee) HF channel models.
01 Jun 1989
TL;DR: In some rural communication systems, BPSK modulation is used for transmission of a pseudo-ternary primary multiplex PCM signal, but a trellis-coded modulation system with rate R=1/2 convolutional coding and QPSk modulation is found to be superior.
Abstract: In some rural communication systems, BPSK modulation is used for transmission of a pseudo-ternary primary multiplex PCM signal. In general the application of BPSK modulation has been appropriate, since BPSK modulation yields reasonable bandwidth utilization at low system complexity. However, a trellis-coded modulation system with rate R=1/2 convolutional coding and QPSK modulation is found to be superior. This system has a coding gain compared to BPSK modulation of approximately 3.3 dB, assuming ideal QPSK (de)modulation. >