Showing papers on "Bit error rate published in 1978"

Cosmic Ray Induced in MOS Memory Cells

Abstract: A model for estimating the cosmic ray induced bit error rate in dynamic MOS RAMs is developed and used to calculate the bit error rate in NMDS dynamic RAMs used in an operating satellite system. The calculated error rate agrees sufficiently well with the observed error rate to conclude that cosmic ray ionization is a likely cause of observed satellite bit errors. The susceptibility of M1S RAMs to cosmic ray induced error is a result of the small charge (sub-picocoulamb) typically stored on a MDS gate to represent a data bit. Relatively small energy deposition (a few MeV) can discharge a storage node, resulting in a bit error. The heavy ion particles present in galactic cosmic rays can provide this energy, resulting in a significant bit error rate for large nmeory systems in satellites. The dynamic RAM operational factors and design factors affecting ionization-induced bit error rates are discussed.

Space optical communications with the Nd: YAG laser

Abstract: The development of a Nd : YAG space laser communication system is discussed with respect to history, potential applications, and present status. The basic design of an Air Force Space Communications Flight Test operable at a data rate of 1000 Mbit/s is described at both the system and component level. An engineering feasibility model of this system has been completed, and the results of tests data are reported. Communications at 1000 Mbit/s with a receiver sensitivity of 20 photoelectrons/bit was demonstrated for a bit error rate of 10-6, interterminal tracking with angle erros less than 1 µrad, and station to station acquisition in less than 6 s. A simulated range of 40 000 km was used.

Measurement and Generation of Error Correcting Codes for Package Failures

Abstract: Error correcting codes have been successfully employed to correct errors associated with failures in computer memories. A typical code which has found wide application is the binary Hamming code. This code corrects single bit errors. With the advent of large-scale integration (LSI) storage array technology, the likelihood of errors which exceed the correction and detection capability of such a code is significant. A serious and heretofore unanswered question is the error detection capability of a given code which is implemented and decoded for single error correction, particularly when a storage array chip or card carrying multiple bits from the codeword has failed. In order to identify this capability, a new reliability parameter called package detectability is defined. This paper also presents a method for computing package detectability. The analysis has been performed on a number of codes in order to optimize the packaging for maximum detectability. In addition, a class of distance 3 codes with maximal b-bit package detectability is given.

Method and apparatus for fault detection in PCM muliplexed system

Abstract: An idle channel test is provided for a digital time division multiplex and time switching network telecommunications system to detect and diagnose faults in an information path which routes digital information in dedicated channel time slots to and from a "time" switching network. In order to detect and diagnose faults in the information path which includes multiplex/demultiplex circuitry, an idle channel is selected as a test channel at the input to the multiplexer which in turn is the input to the switching network, a test pattern including a bit pattern and a parity bit is inserted into the test channel, the test pattern is connected via the switching network back to one of the demultiplexers and the bit pattern and parity bit are monitored for errors. The idle channel test also allows for the deliberate insertion of a bit pattern error or a parity bit error so the loop from multiplexer, through the switching network and back to any one of a plurality of predetermined demultiplexers can be marked by the propogation of the inserted bit pattern or parity bit error for isolating a fault in the loop.

On-Line Pseudo-Error Monitors for Digital Transmission Systems

Abstract: Pseudo-error detectors are devices which show great potential for the measurement of the bit error rate of an on-line digital communications link. They are implemented in the form of a second detector (in addition and in parallel to the traffic data bit detector) which is very perturbation-sensitive. They do not compromise the traffic handling capacity of the system. Four methods of generating the pseudo-error characteristic are described: i) shifted detection threshold; ii) intersymbol interference enhancement; iii) noise addition; iv) sampling phase offset. Practical considerations generally govern the choice of method. Experimental results of pseudo-error detector behavior in the presence of Gaussian noise show that stable characteristics can be achieved to estimate a wide range of bit error rate (BER's) in very modest time intervals. In addition, experimental results in a real complex environment consisting of a 1.544 Mbits/s T1 capacity digital link using QPSK modulation techniques, including both Gaussian and non-Gaussian perturbations, show pseudo-error detection to be reliable for the measurement of BER and for controlling channel switching.

Segmented error-correction system

Abstract: In a data processing error control system for named data, a parity check matrix and apparatus for using same provides for single error correcting of the data word and for multiple error detecting in both the data word and data name. The parity check matrix and apparatus utilize two additional parity check bits (over that required by a system using a prior art SEC/DED Hamming code) to provide protection against single bit errors, eight contiguous bit errors (i.e., hardware stuck at logical one or logical zero for the whole eight contiguous bits), similar four contiguous bit errors, and faults covering the entire data name field (which could occur, for example, if a wrong data word was fetched from memory). The parity check matrix is segmented and mated to the error correctional requirements and prevalent error modes of each field being protected. In encoding, parity check bits are generated for the combined data word and associated data name field. In decoding, an overall parity check of the check bits, data word and data name is performed for distinguishing between odd and even errors. Further, the parity check matrix is invoked to generate a parity checking number for addressing a decoding table circuit (realizable as a ROM) which in turn provides the error bit location for single bit correctable errors. Given the error bit location a correction circuit corrects (i.e., complements) the detected single erroneous bit in the data word or in the generated parity check bits.

A periodic switching diversity technique for a digital FM land mobile radio

Abstract: A simple and efficient diversity technique is proposed for use in a digital FM land mobile radio communication system. This technique receives two RF signals periodically by switching two antenna branches at a rate moderately higher than the bit rate. The improved bit error rate (BER) performance resulting from the use of diversity is shown to be the effect of transforming the probability density function of the signal energy per bit to noise power density ratio to a sharper distribution. Laboratory simulation test results show that in a Manchester-coded frequency-shift keying (FSK) system with a bit rate of 600 bit/s and a frequency deviation of ±5 kHz, the diversity gain at an average BER of 1 × 10-3is about 10 dB for an optimum switching rate of about 2 kHz. This diversity improvement is also verified by the field test performed in a suburban area.

Double bit error correction using double bit complementing

Abstract: An improvement to a semiconductor memory subsystem containing single bit error correction/double bit error detection (SBC/DBD) which provides correction of double bit errors through the utilization of a modest amount of additional circuitry. The present invention accomplishes this result through the technique of sequentially complementing each double bit pair within the semiconductor memory subsystem data word determined to contain a multiple error and rechecking the modified data word with the existing SBC/DBD circuitry, one double bit pair at a time, until it is determined by the SBC/DBD circuitry that such double bit pair complementing has corrected the double bit error.

Maximum-Likelihood Decoding of Binary Convolutional Codes on Band-Limited Satellite Channels

Abstract: Viterbi decoding of binary convolutional codes on bandlimited channels exhibiting intersymbol interference is considered, and a maximum likelihood sequence estimator algorithm is derived. This algorithm might be applied either to increase the allowable data rate for a fixed power transmitter or to reduce the required power for a fixed data rate. Upper and lower bounds on the bit error rate performance of several codes are found for selected values of the ratio of information rate to channel bandwidth, and results are compared against both conventional equalization techniques and the Shannon capacity limit. Results indicate that this algorithm can provide the power saving associated with low rate (highly redundant) codes without suffering the noise enhancement of linear equalization techniques.

Apparatus for smoothing transmission errors

Abstract: An apparatus for smoothing transmission errors in a receiver in order to compensate for digital errors occurring in a transmitted signal. The apparatus includes a device to generate an output signal, which corresponds to the signal transmitted by the transmitter with a high degree of probability. The device includes a device in which a predetermined number of bits are detected and an evaluation is made whether each received bit exceeds or falls below a predetermined threshold value. For each bit or group of bits which is detected and falls below said threshold value, the redundancy of bits in the signal is used to determine the correct value of the detected low value bit. From this, a bit signal is generated which more closely corresponds to the value of the bit transmitted by the transmitter than to the received value.

Orthogonal Transform Coding System for NTSC Color Television Signals

Abstract: A two-dimensional, 32nd-order orthogonal transform coding system which performs three types of transformations in realtime for NTSC color television signals has been developed. This paper reports on a hardware realization of this system, the optimum bitassignments for 32 and 22 Mbit/s transmission rates and the effects of bit errors during transmission. Through the evaluation of picture quality, the system gave a fine quality of pictures after compressing an 8-bit digitized television signal into 3 bits/pel corresponding to 32 Mbit/s transmission, and a passable quality of pictures by 2.25 bits/ pel corresponding to 22 Mbit/s transmission.

Application of solitons to communication system

Abstract: In this letter, an experimental investigation of a p.c.m. communication system using soiltons as signal carriers is reported. The soliton is a pulse that propagates along a nonlinear dispersive line with constant velocity and without distortion. It is shown that by designing the system appropriately, it is possible to achieve a better performance as far as bit error rate is concerned than the corresponding system with linear dispersive channel.

Providing channel error protection for a 2400 bps linear predictive coded voice system

Abstract: The U.S. Government has developed a real-time 2400 bps Linear Predictive Coded (LPC) voice algorithm which was designed to provide maximum intelligibility and quality within the time and accuracy limitations imposed by modern high-speed minicomputers. The algorithm which resulted provides excellent intelligibility and quality when transmitted over an ideal channel. However, the speech is significantly degraded in an error environment. This paper describes several techniques for reducing the effect of channel bit errors on the synthesized speech. These techniques cause no measurable degradation of the LPC speech transmitted over an error-free channel and they require less than a one percent increase in computer execution time.

Digital transmission system having direct bit extraction from scrambled bit streams

Abstract: Direct bit extraction from a scrambled bit stream for a digital transmission system in which a bit stream is divided into consecutive transmission frames, extra bits are inserted in given bit position of each transmission frame, the bit stream is scrambled in a transmitter terminal station and transmitted via a plurality of regenerative repeaters to a receiver terminal station in which the transmitted bit stream is descrambled and the inserted extra bits are selected from the bit stream. Both the scrambler and the descrambler include a generator for generating a given fixed scramble pulse pattern and a transmission clock pulse counter which, on attaining its final counting position, supplies a setting pulse which adjusts the pulse pattern generators in the scrambler and the descrambler to an initial generation state. By choosing a fixed relation between this final counting position and the number of bit positions per transmission frame it is possible to select with simple means the extra bits, inserted in the consecutive transmission frames, in the repeaters and the receiver terminal station without the necessity of first descrambling the received scrambled bit stream.

Periodic switching diversity effect on co-channel interference performance of a digital FM land mobile radio

Abstract: The effect of periodic switching diversity on the bit error rate (BER) performance of a binary frequency-shift keying (FSK) system in the presence of co-channel interference is described. The distribution of the signal-to-interference energy ratio per bit presented to the FM detector is found and the diversity effect on the BER performance in a Rayleigh fading environment is analyzed. The diversity effect on the BER performance in a Manchester-coded FSK system with limiter-discriminator detection is verified by laboratory simulation tests using a Rayleigh fading simulator.

Imperfect Carrier Recovery Effect on Filtered PSK Signals

Abstract: Coherent demodulation of a PSK signal requires the generation of a local carrier phase reference. Methods are given to determine the detection loss caused by noisy phase recovery and its use in the coherent detection of filtered BPSK and QPSK signals. It is assumed that the phase noise can have a static part and a random component with a Tikhonov-type distribution. The static part is mostly due to offset frequency tracking of the PLL used to recover the carrier, while the random component is due to thermal noise present in the carrier recovery loop and is also due to the random nature of the phase modulation. It is shown that the probability of error of BPSK and QPSK can be expressed as a finite sum of a set of strictly alternating converging series when the number of ISI terms is finite. Upper and lower bounds on the probability of error have been derived when this number becomes infinite and we show how this error rate can be computed with any desired accuracy. Numerical results are presented for various values of static error and phase noise variance when the transmit and receive filters are 4-pole Butterworth filters. For filtered PSK signals and for a bit error rate of 10-6, our results show that the additional degradation in presentday receiver systems due to imperfect carrier recovery can be less than 0.1 dB for BPSK and less than 1 dB for QPSK.

Triple random error correcting convolutional code

Abstract: Disclosed are methods and apparatus for transmitting information bits in a new error correcting code. Also disclosed are methods and apparatus for recovering the transmitted information bits after they have been received with errors. Utilizing the disclosed methods and apparatus, up to three errors in any twenty-six consecutive bits may be corrected. To encode the information bits for transmission, one parity bit is generated for each information bit. Each parity bit is a function of six information bits. To detect and correct an erronously received information bit, thirteen received information bits and thirteen received parity bits are examined.

A 105 Mbit/s Error Correcting Codec

Abstract: A 105 Mbit/s experimental error correcting encoder/ decoder is described. The device exhibits a coding gain of 1.9 dB at a 10-5bit error rate and has a 25 percent parity bit overhead. The decoder was constructed without syndrome reset. This allowed the operating speed to be more than doubled, while only sustaining a negligible loss in performance.

Circuit with separating filter measuring interference pulses - uses frequency band in interference pulse spectrum which is separated and excluded from analogue signal

Abstract: the interference pulses are generated during operation by bit errors, and appear at the receiver analogue output of a digital signal transmission system. A measuring device (9) for analogue signals is connected to the analogue input through a parallel separating filter (8) which selects, for the measurement only the frequency band from the spectrum generated by the interference pulses. This frequency band is excluded from the analogue signal. The filter (8) is pref. a narrow band, low frequency pass type.

Differential coding system

Abstract: PURPOSE:To improve the bit error rate, by realizing the differential coding in which only the difference of one bit is in existence between the adjacent code vector, in the differential coding system for QAM.

Some Effects of Phased-Array Dispersion on Digital Error Rates

Abstract: Some calculations of the effect of phased-array dispersion on degrading phase-shift-keyed (PSK) error rates are presented. The results are given in the form of curves of the bit error rate versus the ratio of array "fill-time" (propagation time across the array) to signaling interval. Values of this ratio in the range 0.5 to 0.8 are required to degrade the error rate by a factor of 2. These results were obtained for both linear and square arrays, and for rectangularpulse signaling over single-pole and two-pole Butterworth equivalent low-pass channels, as well as for impulsive signaling over an idealized channel with a raised-cosine frequency response.

High-Speed Communication Detector Characterization By Bit Error Rate Measurements

Abstract: Performance data taken on several candidate high data rate laser communications photodetectors is presented. Measurements of bit error rate versus signal level were made in both a 1064 nm system at 400 Mbps and a 532 nm system at 500 Mbps. RCA silicon avalanche photodiodes are superior at 1064 nm, but the Rockwell hybrid 3-5 avalanche photodiode preamplifiers offer potentially superior performance. Varian dynamic crossed field photomultipliers are superior at 532 nm, however, the RCA silicon avalanche photodiode is a close contender.

Bit error rate measuring instrument

Abstract: PURPOSE:To simultaneously observe entire reception burst and shorten the required time in error rate measurement by providing counters counting bit number, a memory circuit and a counting circuit and counting the times of reference timings and the times of bit errors.

Digital carrier-concentrator system with TASI

Abstract: In a digital carrier-concentration system, utilizing time slot assignment, comprises a delta modulator operable to convert analog signals into a digital binary bit stream, the modulator being responsive to the bit stream to decode a coincident pulse whenever a predetermined number of "ones" or "zeros" occur in the bit stream, a voice detect circuit responsive to the coincident pulse to provide a voice detect output, and a control assigns the stream a time slot in a high bit rate data channel in response to detection of the voice detect output, after a predetermined interval.

Application of forward-error correction to a Rayleigh fading h.f. communication channel

Abstract: The performance is assessed of a Rayleigh fading hf communication channel which transmits binary data using a selection of forward-error correction systems The criteria adopted are the probabilities of no character error, and not more than one character error in a message containing a specified number of characters, each character consisting of five information bits The basic standards for comparison are taken to be the start/stop telegraphy mode of transmission and the synchronous transmission of pure information The error-correction systems studied are tor, autospec and BCH(31, 21), all employing block coding Where interleaving is applicable the improvement obtained is assessed The advantages of employing space diversity are also assessed The case of a constant signal is included for completeness It is assumed that the probability of an element error is related to channel signal/noise by an exponential modem curve The calculations are part probabilistic, part simulation Errors and efficiency of the method are discussed

Probability of error of a binary infinite impulse train signal over a random parallel channel

Abstract: The two-filter model of an underwater acoustical communication channel is analyzed for a randomly varying indirect signal path. Expressions are derived for biterror probability given a binary signal.

System response and extra bit errors

Abstract: A simplified model of a digital disc system and its response to an extra bit error is examined. Calculations of the resultant bitshift of a 2-F waveform peak as a function of extra bit pulse amplitude and timing are presented. The detection of extra bits on a system is discussed.

Statistical analysis of error correcting schemes of stationary head digital audio recorders

Abstract: In spite of the great advance in performance, digital audio recorders have some critical points in handling and reliability resulted from the code errors These code errors are caused by (1) drop outs of tapes, by (2) peak, shift, jitter or noise, and by (3) finger prints, injuring tape edge, or dusts. (1) and (3) will cause rather burst errors and (2) will cause random errors. But, in effect, the burst and random errors cannot be separated discretely, and the trend is described by one parameter “bit error correlation coefficient.” In this paper, the changes of parameters of a statistical model of errors of magnetic tapes are discussed due to the increase of packing density. That is not only the increase of error rate but also the decrease of bit error correlation coefficient. Various error correcting schemes are evaluated by means of computer simulation for various values of error rate and bit error correlation coefficient. Another important point to increase the reliability of the systems is error interpolation ability when errors exceed the ability of error correcting schemes. These simulations will be helpful to determine the tape formats for digital audio recorders with stationary head.