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Showing papers on "Pulse-position modulation published in 1980"


Journal ArticleDOI
TL;DR: The cutoff rate is derived for a digital communication system employing an optical carrier and direct detection and the coordinated design of the encoder, optical modulator, and demodulator is studied using the cutoff rate as a performance measure rather than the more commonly employed error probability.
Abstract: The cutoff rate is derived for a digital communication system employing an optical carrier and direct detection. The coordinated design of the encoder, optical modulator, and demodulator is then studied using the cutoff rate as a performance measure rather than the more commonly employed error probability. Modulator design is studied when transmitted optical signals are subject simultaneously to average-energy and peak-value constraints. Pulse-position modulation is shown to maximize the cutoff rate when the average-energy constraint predominates, and the best signals when the peak-value constraint predominates are identified in terms of Hadamard matrices. A time-sharing of these signals maximizes the cutoff rate when neither constraint dominates the other. Problems of efficient energy utilization, choice of input and output alphabet dimension, and the effect of random detector gain are addressed.

45 citations




Patent
12 Sep 1980
TL;DR: In this paper, a method for simultaneously transmitting a plurality of data streams over one transmission channel with the aid of modems is proposed, where in order to synchronize the receiver for the purpose of device-specific modulation, a small additional modulation is applied in the transmitter, with the frequency of the additional modulation being equal to the transmitter modulation rate divided by a whole number, and the added modulation is demodulated in the receiver by multiplying the associated values obtained from the scanning clock pulse by the difference between the associated and actual values received.
Abstract: A method for simultaneously transmitting a plurality of data streams over one transmission channel with the aid of modems, wherein in order to synchronize the receiver for the purpose of device-specific modulation, a small additional modulation is applied in the transmitter, with the frequency of the additional modulation being equal to the transmitter modulation rate divided by a whole number, and the additional modulation is demodulated in the receiver by multiplying the associated values obtained from the scanning clock pulse by the difference between the associated and actual values received, and the resulting parameter is freed of interference with the aid of a band pass filter or a phase control loop.

15 citations


15 Mar 1980
TL;DR: In this paper, the feasibility of using optical communication systems for data telemetry from deep space vehicles to Earth-based receivers is evaluated, and the effects of background interference and weather on receiver performance are evaluated.
Abstract: The feasibility of using optical communication systems for data telemetry from deep space vehicles to Earth based receivers is evaluated. Performance analysis shows that practical, photon counting optical systems can transmit data reliably at 30 to 40 dB high rates than existing RF systems, or can be used to extend the communication range by 15 to 20 dB. The advantages of pulse-position modulation (PPM) formats are discussed, and photon counting receiver structures designed for PPM decoding are described. The effects of background interference and weather on receiver performance are evaluated. Some consideration is given to tracking and beam pointing operations, since system performance ultimately depends on the accuracy to which these operations can be carried out. An example of a tracking and pointing system utilizing an optical uplink beacon is presented, and it is shown that microradian beam pointing is within the capabilities of state-of-the-art technology. Recommendations for future theoretical studies and component development programs are presented.

5 citations



15 Dec 1980
TL;DR: This article shall expand on Massey’s suggestion and show that interleaved binary block codes can, for a given decoder complexity, perform even better than RS codes.
Abstract: It is shown that interleavel binary block codes combined with pulse position modulation give the best practical coded systems yet devised for optical communication with photon detection. Linear block codes rather than convolutional codes are considered.

3 citations


Proceedings ArticleDOI
01 Jan 1980
TL;DR: In this article, an analog encoded transmission system is presented, which operates with linear FM (chirp) pulses that are position-modulated according to the sampled baseband data.
Abstract: An analog encoded transmission system is presented, which operates with linear FM (chirp) pulses that are position-modulat ed a ccording to the sampled baseband data. Chirp duration and sampling rate are p roperly chosen to yield permanent overlapping of several FM pulses. To recover the baseband signal in the r eceiver, separation of consecutive chirps by pulse compression in a matched filter is required. S ynchronization is attained by phaselocking the receiver reference quartz oscillator to the pulse position modulation (PPM) mean frequency. A conversion of PPM into pulse a mplitude modulation (PAM) in the r eceiver demodulation process permits a maximum information bandwidth to be transmitted at a given sampling rate. In our system,using SAW dispersive delay lines with a timebandwidth product of 180 centered at 60MHz, we achieve a signal bandwidth f rom 200Hz to 570kHz with a sampling rate of 1.35MHz. The dynamic range is greater than 40dB and the amplitude c haracteristic is constant within 0.5dB over the entire desired baseband signal s pectral range.

2 citations


01 Jan 1980
TL;DR: In this paper, the capacity of a free space optical channel using a direct detection receiver was derived under both peak and average signal power constraints and without a signal bandwidth constraint, and it was shown that the addition of instantaneous noiseless feedback from the receiver to the transmitter does not increase the channel capacity.
Abstract: The capacity of a free space optical channel using a direct detection receiver is derived under both peak and average signal power constraints and without a signal bandwidth constraint The addition of instantaneous noiseless feedback from the receiver to the transmitter does not increase the channel capacity In the absence of received background noise, an optimally coded PPM system is shown to achieve capacity in the limit as signal bandwidth approaches infinity In the case of large peak to average signal power ratios, an interleaved coding scheme with PPM modulation is shown to have a computational cutoff rate far greater than ordinary coding schemes

2 citations


01 Oct 1980

2 citations