Showing papers on "Bit error rate published in 1976"

MSK and Offset QPSK Modulation

Abstract: Minimum shift keying (MSK) and offset keyed quadrature phase shift keying (OK-QPSK) modulation techniques are often proposed for use on nonlinear, severely band-limited communication channels because both techniques retain low sidelobe levels on such channels, while allowing efficient detection performance. A more detailed performance comparison of the two techniques on such channels is, therefore, of interest. In this paper a Markov process representation is developed which is applicable to either the MSK or OK-QPSK waveform. This representation is employed to illustrate the similarity between the modulation processes and to obtain the autocorrelations and power spectral densities of the two waveforms. This Markov process representation may be similarly employed with other modulation waveforms of the same class. The autocorrelations and power Spectral densities of MSK and offset QPSK provide initial insight to expected performance on band-limited channels. The results of a digital computer simulation are presented. The simulation compares the bit error rates (BER's) of MSK and offset QPSK on nonlinear, band-limited double-hop links such as encountered in satellite communications. The simmulation results are presented as E_{b}/N_{0} degradation with respect to ideal detection versus channel noise bandwidth. The error probability was used as a performance metric, and equal adjacent channel interference as a constraint. For the channels simulated, MSK is found to provide superior performance when the channel noise bandwidth exceeds about 1.1 times the binary data rate. For narrower bandwidths, offset QPSK provides superior performance.

The Effects of Transponder Nonlinearity on Binary CPSK Signal Transmission

Abstract: An analytical approach is developed to investigate the performance of coherent phase-shift keying (CPSK) systems transmitted through a nonlinear satellite transponder. A novel quadrature model of the satellite nonlinearity is introduced, and is found to yield an excellent fit to the actual traveling wave tube (TWT) characteristics as commonly used in a satellite transponder, with the advantage of requiring the choosing of only a few parameter values. Based on this quadrature model an expression for the bit error rate is derived in the form of an infinite series where the leading term corresponds to the error-rate for a linear channel and the remaining terms are correction terms accounting for nonlinear effects. The performance of a binary PSK system is computed and presented as a function of the up-link and down-link carrier-to-noise-power ratios (CNR) and a bandwidth spread factor.

Error checking and correcting device

Abstract: An error checking and correcting device for providing group error detection in addition to single error correction and double error detection in a codeword transmitted through a modular communication channel is disclosed. The codeword comprises a plurality of data bits and a plurality of check bits. The modular communication channel comprises a plurality of modules in each of which a group (or cluster) of bits are transferred in parallel. In the preferred embodiment, the code word contains 40 bits with 32 data bits and 8 check bits, and the modular communication channel is a computer memory comprising 10 modules with 4 bits per module. At the transmitter, the check bit generator generates the check bits from the data bits in accordance with an H-matrix which is partitioned into h-submatrices corresponding to group boundaries of the memory. The construction of the h-submatrices is in accordance with rules necessary for group error detection in addition to single error correction and double error detection. The check bits are appended to the data bits to form a 40 bit code word which is transmitted through the modular memory. At the receiver, a syndrome bit generator generates 8 syndrome bits from the received code word in accordance with the H-matrix. The output of the syndrome bit generator is coupled to both the error detection circuit and the error location circuit. Should a group in the memory be faulty in the process of transmission resulting in a number of bits in the group being in error, logic means are provided in the error detection circuit to identify correctable good data from uncorrectable bad data. According to the syndrome pattern the error detection circuit permits the utilization of received data if no error is detected, or enables the error location circuit to provide single error correction if a single error is detected; or sets an error flag to prohibit the utilization of received data if a random double error is detected or a plurality of errors in the same group are detected.

Digital synchronizing signal recovery circuits for a data receiver

Abstract: A data signal stream includes, in a noisy signal channel, periodic word synchronization characters, and each such stream is preceded by a burst of predetermined bit rate information. An approximate bit rate timing signal is derived from the data stream and utilized for producing an initialization pulse when the predetermined bit rate information is detected. In addition, the approximate bit rate timing signal drives a digital phase-locked loop which is preset by the initialization pulse to a digital circuit state defining operation at the nominal frequency of the approximate bit rate timing signal. A stable bit clock signal provided by the phase-locked loop controls the operation of further circuits which are responsive to the baseband data stream for providing an indicator pulse each time that a synchronizing character appears in the data stream. The bit rate clock and the character indicator pulses are employed to operate a timing chain that yields word synchronization pulses in synchronism with the indicator pulses and having an extraordinarily low false-pulse rate as well as evidencing a flywheel effect to maintain word synchronization in the event that a small number of character indicating pulses are missed. If more such pulses are missed, the timing chain is resynchronized.

Digital bit rate converter

Abstract: DIGITAL BIT RATE CONVERTERby Alvin L. Pachynski, Jr. ABSTRACT OF THE DISCLOSURE In a digital communication system, apparatus for upconverting the bit rate, f1, of a digital data source to permit digital transmission at a bit rate f2, where f2 > f1. Pulse stuffing techniques are used to insert a fixed number of time slots in the digital data signal such that the ratio of information time slots to stuffed time slots remains constant.The upconverted signal, consisting of nonredundant data bits and stuffed time slots, is interleaved with framing bits prior to transmission over a digital facility. The framing bits provide the synchronization information to enable the receiver to identify the added time slots and to selectively remove the information data bits from the transmitted line signal. The desired data bits are then restored to their original f1 bit rate.

The Effect of Single Bit Errors in Standard Nonlinear PCM Systems

Abstract: The effects of independent bit errors are calculated for nonlinear PCM systems. General simplified computer formulas are given for natural binary and binary folded PCM codes. Analytical formulas are produced for μ-quantization, binary folded PCM, and speech-like input signal density functions.

On noise in digital recording

Abstract: A set of rules, equations and relations are given for the effects of coherent and statistical noise on digital recorders. Simple formulas, intended for laboratory use, are given for the change in signal to noise ratio (SNR) caused by the channel. Bit error probability is related to SNR and channel parameters for the zero-crossing detector channels typical of digital computer disk and tape recorders, and many digital instrumentation recorders. Valid and invalid ways to calculate error rate statistics are discussed for situations where bit errors are correlated, i.e. not statistically independent.

High density magnetic recording using digital block codes of low disparity

Abstract: Low disparity block codes should find use in recording digital waveforms at high bit-packing densities approaching 33 000 b/in per track. Comparative tests indicate that some fairly-easy-to-implement block codes surpass the delay modulation code in bit error rate performance.

Digital error rate performance of active phased array satellite systems

Abstract: A model for a multiple spot beam digital satellite employing an active phased array antenna with frequency reuse is proposed and applied to study the power limited down-link bit error rate performance. Since the power amplifier preceding each antenna element is generally nonlinear, intermodulation distortion is produced among the various spot beams, degrading performance. Expressions for the bit error rate are derived, averaged over an ensemble of random arrays. Typical results indicate a degradation of 1-5 dB relative to a horn-reflector antenna of the same total effective aperture with a single channel per transponder, as the number of cochannel signals and the number of antenna elements are respectively varied between 10 and 30, and 500 and 10 000. The degradation is shown to result from nonlinearly induced signal suppression and cochannel interference.

Synchronization for PCM transmission systems

Abstract: At the transmitter the synchronization information is provided by position modulation of the line transitions of at least one bit of a PCM word. The receiver is synchronized to the received coded signal by detecting the position modulation of the bit of the PCM word. This arrangement avoids the need for extra bits to convey synchronization information.

On the Use of Polarity Coincidence Correlation Techniques for Differential Phase-Shift-Keyed Demodulation

Abstract: The use of polarity coincidence correlation techniques can allow efficient use of digital logic elements for binary differential phase-shift-key demodulation. For the case of sinusoidal signals in the presence of additive Gaussian noise it is shown that an ideal hard limiter at the input to the demodulator adds no degradation to the bit error rate performance.

Measurement of Bit Errors in Data Transmission Systems

Abstract: This correspondence presents an improved technique for receive error detecting a pseudorandom digital sequence suitable for bit error performance testing of serial digital transmission systems. The method is applicable to separately located transmit and receive sites, is self-synchronizing, and can be economically constructed using logic elements and medium-scale integrated (MSI) devices from commercially available logic families.

Broadband digital modem

Abstract: : The objective of this program was to develop a practical modem technique providing the means to trunk a large volume of digitized vocie channels within the present FDM-FM bandwidth allocations Specifically, a bandwidth efficiency of 2 bits per hertz of RF bandwidth and a bit error of 10 to the 7th power or less at an E sub b/N sub o of 20 dB were desired These characteristics, provided in conjunction with hard-limiting radio sets, allow efficient conversion of analog FDM-FM line-of-sight microwave systems to digital operation by replacement of the modulation elements It was determined that 4- ary FSK was the best signal design, given the performance objectives and the constant-envelope constraint A continuous-phase, coherent detection, multisymbol observation modem was constructed and successfully tested The performance objective of a 10 to the 7th power bit error rate at an E sub b/N sub o of 20dB was bettered by approximately 05 db in laboratory tests

Performance of Convolutionally Encoded Noncoherent MFSK Modem in Fading Channels

Abstract: The performance of a convolutionally encoded noncoherent multiple-frequency shift-keyed (MFSK) modem utilizing Viterbi maximum-likelihood decoding and operating on a fading channel is described. Both the lognormal and classical Rician fading channels are considered for both slow and time-varying channel conditions. Primary interest is in the resulting bit error rate as a function of the ratio between the energy per transmitted information bit and noise spectral density, parameterized by both the fading channel and code parameters. Fairly general upper bounds on bit error probability are provided and compared with simulation results in the two extremes of zero and infinite channel memory. The efficacy of simple block interleaving in combatting channel memory effects are thoroughly explored. Both quantized and unquantized receiver outputs are considered.

Two‐way communication with an earth penetrator

Abstract: A telemetry link capable of communicating from a depth of 50 m to the surface is described. The buried package fits within a diameter of 100 mm and provides a bit error rate of less than 10/sup -4/ at a rate of 1000 bits per second while consuming 8 W. A control link capable of turning on and off the buried telemetry transmitter from the surface is also described together with results from typical tests in a three-layer soil. The included propagation analysis is intended for use at frequencies below 100 kHz.

Flight Tests of Digital Data Transmission at VHF.

Abstract: : This report describes the results of a series of 11 experimental flights which measured the characteristics of air-to-ground digital transmission in the VHF aeronautical mobile frequency band. The tests were conducted for the Federal Aviation Administration at National Aviation Facilities Experimental Center in Atlantic City, NJ. Digital transmission rates of 2400 and 4800 bps were used with minimum-shift-keying (MSK) as the baseband modulation format. The MSK signal was transmitted on a test frequency of 120.85 MHz using conventional, air/ground voice communication equipment. A number of parameters were measured during the flights and an extensive decription is given of the bit error rates which were encountered. Received signal level was also monitored, and data describing average signal level and signal fading are presented. Other parameters measured were clock slips, carrier lossess, distribution of errors, and signal fading caused by aircraft maneuvering. The tests show that digital transmission rates of 2400 and 4800 bps can be supported, with existing FAA and ARINC equipment, at an average bit error rate near 0.00005. (Author)

Bit Error Rate Measurement For Evaluation Of A Fiber Optic Link

Abstract: Digital fiber-optic data-link terminal modules are being developed in a number of laboratories, and often the modules take the form of black boxes without convenient access to internal signals. This paper discusses types of measurements which can be made using only the digital terminals of the link. Bit-error-rate (BER) vs signal-power data can, of course, provide a means for proving overall link performance, but it can also be used to determine certain internal parameters of the receiver. The theoretical dependence of the BER-vs-light-signal-power curve shape on receiver input-noise equivalent power and comparator slicing level is discussed. BER-vs-light-signal-power measurements obtained with an experimental link are presented and interpreted with the aid of the theoretical curves. The effects of other problems, such as hum or oscillation, on the BER data are mentioned. Sensitivity of the system BER to bit rate is also discussed, with application to determining system operating limits. Since BER measurements are simple to make and can easily be automated, they may prove to be a useful means for either laboratory evaluation or production-line acceptance testing of sealed terminal modules.