Showing papers on "Pulse-position modulation published in 1990"

Optical fibre digital pulse-position-modulation assuming a Gaussian received pulse shape

Abstract: The abundance in bandwidth available in the best monomode fibres may be exchanged for improved receiver sensitivity by employing digital PPM. The paper presents a performance and optimisation analysis for a digital PPM coding scheme operating over a fibre channel employing a PIN-BJT receiver and assuming a Gaussian received pulse shape. The authors present original results for a 50 Mbit/s, 1.3 mu m wavelength digital PPM system and conclude that, provided the fibre bandwidth is several times that of the data rate, digital PPM can outperform commercially available PIN-BJT binary PCM systems.

Error correction for infrared data communication

Abstract: The present invention is for a method for correcting errors in received data during transmission of infrared radiation from a transmitter to a receiver without retransmitting entire packets. The method includes the steps of detecting an error in received data. A negative acknowledgement signal is transmitted from the receiver to the transmitter. A predetermined aknowledgement is transmitted by the transmitter to indicate to the receiver that the negative acknowledgement signal has been received. The data is then retransmitted. The data is transmitted using pulse position modulation (figure 1 and figure 2). An error is detected by either sensing two pulses within one cycle or sensing no pulses within one cycle. The negative acknowledgement signal comprises transmitting a pulse several positions in duration (figure 5). The predetermined acknowledgement by the transmitter includes purposely transmitting a cycle containing a known error.

Word timing recovery in direct detection optical PPM communication systems with avalanche photodiodes using a phase lock loop

Abstract: A technique for word timing recovery in a direct detection optical pulse position modulation (PPM) communication system is described. It tracks on back-to-back pulse pairs in the received random PPM data sequences with the use of a phase locked loop. The experimental system consisted of an AlGaAs laser diode transmitter ( lambda =833 nm) and a silicon avalanche photodiode photodetector, and its used Q=4 PPM signaling at a source data rate of 25 Mb/s. The mathematical model developed to characterize system performance is shown to be in good agreement with the experimental measurements. Use of this recovered PPM word clock, along with a slot clock recovery system described previously, caused no measurable penalty in receiver sensitivity when compared to a receiver which used common transmitter/receiver clocks. The completely self-synchronized receiver was capable of acquiring and maintaining both slot and word synchronizations for input optical signal levels as low as 20 average detected photons per information bit. The receiver achieved a bit error probability of 10/sup -6/ at less than 60 average detected photons per information bit. >

Method for the coding of a digital signal, coder and decoder to implement this method, regeneration method and corresponding regenerator utilizing pulse position modulation

Abstract: Method for coding a digital signal, a coder and decoder for implementing this method, a regeneration method and a corresponding regenerator. On each bit time, a detection is made of the possible presence of a binary pattern from any number "n" of binary patterns including at least two bits; the bit time is divided into "n" equal time intervals to which "n" temporal positions are associated; a correspondence is established between each of "n" binary patterns and each of "n" temporal positions; if one of the binary patterns is present, a pulse occupying a temporal position corresponding to the binary pattern is generated and the next detection for the possible presence of a binary pattern is made from the bit following the last bit of the binary pattern whose presence is detected.

50-Mbps free-space direct detection laser diode optical communication system with Q=4PPM signaling

Abstract: A 50 Mbps direct detection optical communication system for use in an intersatellite link was constructed with an AlGaAs laser diode transmitter and a silicon avalanche photodiode photodetector. The system used a Q = 4 PPM format. The receiver consisted of a maximum likelihood PPM detector and a timing recovery subsystem. The PPM slot clock was recovered at the receiver by using a transition detector followed by a PLL. The PPM word clock was recovered by using a second PLL whose input was derived from the presence of back-to-back PPM pulses contained in the received random PPM pulse sequences. The system achieved a bit error rate of 0.000001 at less than 50 detected signal photons/information bit. The receiver was capable of acquiring and maintaining slot and word synchronization for received signal levels greater than 20 photons/information bit, at which the receiver bit error rate was about 0.01.

Capacity and effects of Reed-Solomon codes on multi-pulse PPM in optical communications

Abstract: The capacity of multiphase pulse position modulation (MPPM) and the performance of Reed-Solomon coded MPPM in photon communications are evaluated. The transmission rate, energy efficiency, and error probability of MPPM are presented for a noiseless channel. It is shown that MPPM yields higher limits of energy efficiency and transmission rate than PPM in a band-limited channel. MPPM combined with RS codes achieves an energy efficiency more than twice that of RS-coded PPM in the practical range of error probability. >

Polarisation independent detection by synchronous intra-bit polarization switching in optical coherent systems

Abstract: A novel approach to polarization diversity transmission is discussed in connection with achieving polarization-independent coherent detection with minimum IF bandwidth, as required in high-bit-rate optical systems. This is obtained by stepping the polarization of the field between two orthogonal states at the same frequency as the bit rate. This approach is promising, avoiding complicated receivers, and particularly suitable for a distribution network where switching at the transmitter can be shared among several receivers, reducing system complexity. Computer simulations have been performed for both amplitude- and frequency-shift keying. Critical system parameters are examined and excess penalty is evaluated. In addition to square-wave modulation, sinusoidal modulation has been considered. An optimum value of the modulation depth exists for which the penalty is reduced with respect to the square-wave. >

Performance analysis of code division multiple access techniques in fiber optics with on-off and PPM pulsed signaling

Abstract: The performance of asynchronous code division multiple access (CDMA) fiber optics using noncoherent optical-signal processing is analyzed. The use of pseudo-orthogonal address codes with aperiodic and periodic correlation properties is explored for on-off and pulse position modulation (PPM). The performance of the schemes is analyzed using avalanche photodiodes (APD) in both signaling and address code formats. The bit error rate is evaluated in terms of system parameters, such as number of active users, weight and length of the address code, laser power, photodetector characteristics, and fiber length, by taking into account the effects of noise. The numerical results of these evaluations are presented. >

Jointly optimal receivers for the optical pulse-position modulation channel

Abstract: Jointly optimal receivers that make decisions in the absence of symbol synchronization are derived and analyzed for a pulse-position modulation, optical direct-detection channel. Both receivers that observe the complete sample-path (count record data) and receivers that observe histogram data are studied, and approximations to them are derived. It is seen that jointly optimal receivers are superior to conventional receivers that have separately designed synchronization and decision subsystems. However, their performance advantage is significant only at very low signal levels. Perhaps more significant is that an approximation to the jointly optimal receivers that is much easier to implement than an optimal, separately synchronized receiver achieves nearly the same performance as the latter. Simulation results indicate that the much less complicated receivers that observe histogram data perform as well as receivers that observe the complete sample path at a rather small number of bins per slot. >

Apparatus and method for decoding biphase-coded data

Abstract: There is provided a system for decoding a digital code and in particular a biphase-coded data, by detecting edges of the biphase-coded 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) 2 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.

Performance analysis of coded optical PPM system using direct and coherent detection

Abstract: Monomode optical fibres currently used in optical communication systems usually have bandwidths much greater than the information rate transmitted. This excess bandwidth can be used to improve receiver sensitivity. Pulse-position modulation (PPM) schemes are usually used in optical communication systems to improve receiver sensitivity. The paper analyses the sensitivity of the receiver of an optical PPM system, considering both wrong-slot error and false-alarm error. Coded optical PPM systems with direct and heterodyne detection are analysed. The performances of Reed-Solomon codes with different code rates are considered. Relations between bit-error probability Pb and the optimum efficiency p for the uncoded and coded systems are obtained. It is found that system performance does not necessarily improve with coding. System performance improves only for codes that are capable of reducing the minimum required number of photons sufficiently to compensate for the decrease in system efficiency resulting from coding.

Direct detection optical intersatellite link at 220 Mbps using AlGaAs laser diode and silicon APD with 4-ary PPM signaling

Abstract: A newly developed 220 Mbps free-space 4-ary pulse position modulation (PPM) direct detection optical communication system is described. High speed GaAs integrated circuits were used to construct the PPM encoder and receiver electronic circuits. Both PPM slot and word timing recovery were provided in the PPM receiver. The optical transmitter consisted of an AlGaAs laser diode (Mitsubishi ML5702A, lambda=821nm) and a high speed driver unit. The photodetector consisted of a silicon avalanche photodiode (APD) (RCA30902S) preceded by an optical interference filter (delta lambda=10nm). Preliminary tests showed that the self-synchronized PPM receiver could achieve a receiver bit error rate of less than 10(exp -6) at 25 nW average received optical signal power or 360 photons per transmitted information bit. The relatively poor receiver sensitivity was believed to be caused by the insufficient electronic bandwidth of the APD preamplifier and the poor linearity of the preamplifier high frequency response.

Performance of convolutional codes in noisy optical channels using an APD‐viterbi decoder receiver

Abstract: In this analysis, performance evaluation of orthogonal convolutional coded pulse position modulation (PPM) in a typical binary-asymmetric optical channel is presented. Then, the system performance is compared to that of the Reed-Solomon coded PPM model, where high background noise affects the channel behavior. Using an avalanche photodetector for detection, threshold decision technique is used. This treatment for the PPM orthogonal convolutional coding is more comprehensive than that described in reference 1.

Performance of convolutional codes with multipulse signaling in optical channels

Abstract: Multipulse signaling has recently become an attractive alternative format to single pulse position modulation (PPM) utilized in optical communication systems [1]. In Ref. 2, the author analyzed the performance of short constraint length convolutional codes (CC) with the standard PPM model. In this article, CC are extended to multipulse signaling applied to both self-noise limited, and degraded optical channels. Using this scheme, it is seen that gains in bandwidth expansion and peak-to-average power ratios are attainable.

Electronically Programmable Femtosecond Pulse Shaping Using a Multielement Phase Modulator

Abstract: Considerable progress has been made in developing techniques for generating ultrashort pulses with arbitrarily controllable pulse shapes [1–3]. Nevertherless, it has not generally been possible to achieve both high resolution and precision [1] and electronic programmability [2] simultaneously. In this paper we describe a programmable, high resolution, fsec pulse shaping apparatus based on a multielement liquid crystal phase modulator [4]. Applications include fsec pulse position modulation and programmable fsec pulse compression.

An error control protocol based on trellis coded modulation

Abstract: A novel rate-adaptive hybrid error control technique for mobile radio applications is presented. Instead of using a binary forward error-correcting code in conjunction with a binary modulation scheme, the error control system uses joint power and bandwidth efficient trellis-coded modulation in the inner coding subsystem. As a result, the throughput of the error control system, operating in a Rayleigh fading channel environment, is better than that of many previous systems at the ranges of signal-to-noise ratios of interest. Analytical and simulation results for the throughput of systems that use different trellis-coded modulation schemes are presented and compared with previous results. >

Performance of Convolutionally Coded OOK and PPM Signalling in a Direct Detection Optical Communication

Abstract: The performance of convolutionally coded On-Off Keying (OOK) and M-ary Pulse Position Modulation (M-PPM) systems is evaluated for avalanche photodetection receiver. Results are presented in terms o...

Error Performance Study of Constant Envelope Modulation Schemes for Digital Mobile Radio

Abstract: A digital mobile communication system, with a flat-flat fading channel model is studied. Block encoding and modulation along with maximum likelihood block correlation demodulation is considered. It is shown that for memory modulation schemes, interleaving can not be used if a soft decision maximum likelihood block correlation receiver is being used. The union bound expressions for the probability of channel code word error are derived for various modulation schemes. Simple sequential algorithms are presented to calculate the error probability for different modulation schemes and the performance of (3, 1) repetition code, (7, 4) Hamming code and (15, 5), (31, 6) BCH codes has been evaluated.

Coding for multicarrier digital radio systems

Abstract: The authors investigate the performance of systems which combine the techniques of multicarrier transmission and block-coded modulation. Coding of the subchannels in multicarrier systems is made jointly, i.e. the codewords are formed by the symbols simultaneously transmitted on the different subchannels. With respect to separate encoding of the subchannels, this technique leads to significantly better performance in the presence of multipath fading and narrowband tone interference and adjacent channel interference. Simulations made using a multipath fading channel and tone interference confirmed that coding is significantly more effective than in single-carrier systems. >

The Study of an Optical Photon-Counting Channel: Capacity and Cut-off Rate

Abstract: In optical communication, direct amplification limits the information rate to 1.44 bits/photon. To increase the capacity, the idea of a Poisson-type photon-counting channel has been conceived. In this model, the input signal modulates the envelope of the optical field which is detected at the receiver by an ideal detection device. This photon detector counts the number of photons at a rate proportional to the incident field strength. The capacity of such a channel in the average power constraint case has been found out to be 104 bits/photon. Pulse Position Modulation (PPM) technique is considered to be well-suited for such channel, with the source having peak power as well as average power limitations. Reed-Solomon coded PPM enhances the cut-off rate of the channel and exhibits better performance compared to the uncoded PPM scheme.