Showing papers on "Bit error rate published in 1986"

Optimum Multiuser Asymptotic Efficiency

Abstract: The degradation in bit error rate due to the presence of multiple-access interference in a white Gaussian channel can be measured by the multiuser asymptotic efficiency, defined as the ratio between the SNR required to achieve the same uncoded bit error rate in the absence of interfering users and the actual SNR. In this paper, the asymptotic efficiency of the optimum multiuser demodulator (a bank of matched filters followed by a Viterbi algorithm) is investigated and compared to that of the conventional single-user matched filter receiver. The computation of the optimum asymptotic efficiency of any given user is equivalent to the minimization of the Euclidean distance between any pair of multiuser signals which differ in at least one of the symbols of that user. It is shown that the optimum multiuser efficiency of asynchronous systems is nonzero with probability 1, and therefore the optimum demodulator does not become multiple-access limited in contrast to the single-user receiver. A class of signal constellations with moderate cross-correlation requirements is shown to achieve unit optimum multiuser efficiencies and, hence, to be equivalent to orthogonal signal sets from the viewpoint of performance of the optimum multiuser detector.

Computation of the Bit Error Rate of Coherent M-ary PSK with Gray Code Bit Mapping

Abstract: Efficient computation of the bit error rate (BER) for the coherent M -ary PSK signals with Gray code bit mapping is considered A closed-form expression for the exact BER of 8-ary PSK is presented Tight upper and lower bounds on BER are also obtained for M -ary PSK with larger M

Data communications system

Abstract: A data communications system employing sliding window protocol where the size of the window of the sending or receiving station can be made selectable by the user according to the speed, length or error rate of the communication link or the frame size used to maximize the utilization of the communication link. The negative acknowledgements sent by the receiving station specifies the upper and lower limit of a range of identification numbers of frames unsuccessfully received to increase efficiency. Before data is transmitted, the sending and receiving stations exchange the preferred sets of link parameters and generate a modified set of link parameters to resolve potential conflicts. Either the sending or the receiving station stores a table defining the frame sizes for use with different bit error rates of the communication link. The station then evaluates the current bit error rate to select the optimum frame size from the table and adjust the frame size accordingly.

Antijam Performance of Fast Frequency-Hopped M-ary NCFSK--An Overview

Abstract: The antijam performance of M -ary noncoherent FSK with fast frequency hopping (one or more hops per symbol) is studied. A summary of terminology, definitions, and an overview of the literature is given. A general analysis method based upon circularly symmetric signal theory is presented. It provides a means for exact analysis of performance for M -ary operation with any combination of signal tone distribution (frequency bins contiguously or noncontiguously spaced), jamming distribution, jamming form (partial-band noise or multitone), and receiver system noise. Some previous results are derived as subcases of the general theory. A simple robust diversity combining technique of transmitting a symbol on L hops followed by a majority vote decision is found to provide significant performance improvements. This improvement is comparable to that obtained by most error-correction coding methods. Illustrative calculations of performance were chosen to indicate trends rather than to be exhaustive. Performance is usually presented as probability of bit error versus fraction of the band jammed to emphasize worst-case operation.

Adaptively coded data communication system with half duplex and/or full duplex function

Abstract: An error correcting encoding method and a vehicle data communication apparatus based on the same for use in data communication via fading communication channels dominated by burst errors in the data communication among vehicles such as automobiles are disclosed. The error correction encoding method detects, as data sent from a transmitting side is received by a receiving side, any error contained in the received data as a frame error rate of error frames involved in block data or a bit error rate of error bits involved in the block data and selects an error correcting code in response to the frame error rate for encoding. The vehicle data communication apparatus according to the present invention profitably employs the method, and changes an error correcting code to be used on the transmitting side in response to the extent of errors involved in the received data detected by the receiving side of a remote apparatus.

Signals in mobile communications: A review

Abstract: The signals in mobile communications are reviewed both in terms of the physical scenario and as the basis of the transfer function of the mobile channel. The transfer function is arranged to demonstrate the inherent limitations (the irreducible bit error rate effect) resulting from using single port antennas, in both narrow- and wide-band systems. A new model for the average source scenario at the urban-based (vehicular) mobile is determined and an analogous model for the base station is formulated. The models are useful for deriving diversity antennas.

Ten-channel coherent optical fibre transmission

Abstract: A laboratory ten-channel coherent fibre-optic broadband transmission system is reported. The frequency-division-multiplexed optical carriers are separated by 6 GHz and are demultiplexed by a tunable heterodyne receiver having a sensitivity of -46 dBm at a bit error rate of 10-9. In this system a maximum number of 64 channels can be installed.

Multiple-access channels with point-process observations: Optimum demodulation

Abstract: The derivation and analysis of optimum multiuser detectors for additive-rate and additive-light Poisson multiple-access channels are studied. The observed point process models the output of an ideal photodetector illuminated by several synchronous or asynchronous users who modulate coherent light of the same frequency. Dynamic programming-based decision rules for the asynchronous multiple-access channel exhibit the same computational complexity as their synchronous counterparts and are shown to be optimum under the criteria of minimum error probability and maximum likelihood sequence detection. Upper and lower bounds on the minimum uncoded bit error rate achievable with arbitrary signal constellations are obtained in terms of the error probability of binary hypothesis testing problems. A particular case of these results, namely, the single-user finite-length intersymbol interference problem, solves the error rate analysis of optimum direct-detection systems for dispersive optical fibers.

Compensation of write current adn delta-V for recording component and radial position

Abstract: A magnetic disk drive channel circuitry is shown and described that generates eight incremental values of write current and eight incremental values of delta-V (the minimum voltage change per unit time which tests signals to discriminate between data and noise). Each of these variable parameter values may be program selected by a three bit bus signal. This variability testing of an adaptation to the optimum parameter value for each head media combination and by grouping tracks in contiguous data bands, the parameters may be optimized for tracks near the inner diameter, the outer diameter and in the middle band. The variable delta-V can also be used as an additional data recovery tool wherein re-reading with a lower value enhances recovery of missing bit errors and re-reading with an increased value can assist recovery from an extra bit error.

Analysis of GMSK with differential detection in land mobile radio channels

Abstract: The effect of intersymbol interference (ISI) of Gaussian filtered minimum shift keying (GMSK) on the probability of error of one bit differential detection is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels. A closed-form expression is derived for the probability of error as a function of the fading rate, IF filter bandwidth, signal-to-noise ratio (SNR) and ISI. Numerical results are presented for cases of practical interest to researchers and designers of cellular land mobile radio systems.

Bit synchronization method for a digital radio telephone system

Abstract: A method and means for maintaining continuous bit synchronization of data transmitted from a remote unit through a base unit to a landline unit is disclosed. An input data stream at a first bit rate, such as digitized or encrypted speech, is interleaved with a plurality of signalling words, and transmitted over an RF channel at a second bit rate. The base site recovers the clock of the received data, strips off the signalling word, modifies the bit rate of the received data, and adjusts the recovered clock rate to provide an output data stream which is in bit synchronization with the input data stream and within a predetermined modem specification. The encrypted data is then sent over landlines to a decryption unit which requires bit synchronization.

Performance of PLL Synchronized Optical PPM Communication Systems

Abstract: Receiver timing synchronization of an optical PPM communication system can be achieved using a phase-locked loop (PLL) if the photodetector output is properly processed. The synchronization performance is shown to improve with increasing signal power and decreasing loop bandwidth. The bit error rate performance of the PLL synchronized PPM system is analyzed and compared to that of the perfectly synchronized system. It is shown that the increase in signal power needed to compensate for the imperfect synchronization is small (less than 0.1 dB) for loop bandwidths less than 0.1 percent of the slot frequency.

Method of digital signal transmission

Abstract: A modulation method capable of high-speed or high-quality digital data transmission under a multipath fading transmission line such as a radio transmission in an urban area is a type of differential coding phase modulation and residues in the fact that the rate of change of phase varies, or the phase is discrete, but does not employ a phase transition waveform of a constant value in a time slot which is a smallest unit for transmitting one symbol of data as in conventional methods Phase transition waveforms in respective time slots which are spaced apart from each other by prescribed time slots are identical varying waveforms or discrete waveforms, and entirely shifted from each other by an amount according to the data transmitted A detecting method employed is a differential detection method using a delay line for delaying a signal for a time corresponding to the prescribed time slots In the presence of multipath propagation, a plurality of kinds of detected outputs are produced according to the multipath propagation, and the detected outputs are combined by a filter after the differential detection, producing a diversity effect for improving bit error rate characteristics This digital signal transmission method is capable of multiphase transmission and can increase spectrum utilization efficiency

Error control encoding system

Abstract: An error control encoding method and a mobile data communication system using the method in a moving body communication system such as mobile telephone for effecting data communication through a fading channel dominated by a burst error, upon receiving data transmitted from the transmitting side on the receiving side, detects any error involved in said received data as a frame error rate involved in block data or a bit error rate in the block data and thereby changes the frame length in response to the detected error rates. The mobile data communication system employs the error control encoding method wherein a frame length employed in the transmitting part is changed in response to the extent of any involved error in the received data detected by the remote receiving part.

Serial-to-parallel converter for high-speed bit streams

Abstract: A serial bit stream and a clock signal at a frequency equal to the bit rate divided by an integer n are passed in opposite directions via respective delay lines to respectively the data and clock inputs of n flip-flops, which thereby each latch a respective one of n bits of the bit stream during n/2 bit periods. During the next n/2 bit periods the outputs of the flip-flops are stable, and the n bits are latched in a parallel data latch. The delay lines comprise transmission lines terminated with their effective characteristic impedances. The converter is particularly useful for bit rates greater than 1Gb/s.

The Effects of Multipath Delay Spread on Timing Recovery.

Abstract: Equations for the recovered timing for a squaring timing recovery circuit under multipath radio propagation are derived. Both coherent and differential detections are studied. If delay spread is much smaller than the symbol duration, the recovered timing can be approximated by the centroid of the power delay profile, p(t). Two cases of timing loop bandwidth are considered. If the fading frequency is much lower than the bandwidth of the timing loop, the instantaneous sample of p(t) is used to generate the timing clock. If the fading frequency is much higher than the loop bandwidth, the ensemble average of p(t) over fading samples is used to recover the timing. A computer simulation is performed for a system operating in a frequency-selective, slowly fading environment. It is found that for root mean square (rms) delay spread less than or equal to 0.1 of the symbol duration, a squaring timing loop with either narrow or wide bandwidth can properly determine the timing detection. The main mechanism of the "irreducible bit error rate" in this case is the closure of the eye-pattern instead of timing error.

Performance of the Adaptive A/D Converter in Combined CW and Gaussian Interference

Abstract: Previous analyses are extended to give the performance of the adaptive 2 bit A/D converter in combined CW and Gaussian interference. The converter is seen to give substantial conversion gain even when the direct sequence pseudonoise (DSPN) spread signal is much weaker than the Gaussian component of interference. The upper bound on conversion gain depends primarily on the relative strengths of the Gaussian and CW components of interference. The relevant relationships are given in graphical form.

Performance Analysis of a Memory ARQ Scheme with Soft Decision Detectors

Abstract: An automatic repeat-request (ARQ) scheme with memory and soft error detectors has been recently proposed by Benelli. Its performance was studied mainly through computer simulation. In this paper, a generalized version of this ARQ scheme is examined. The selection of certain thresholds and weights to minimize the bit error rate in systems using a fixed number of packet repeats is considered. Finally, the evaluation of the average number of transmissions per packet in systems in which negatively acknowledged packets are retransmitted until successfully received is described.

Impact Of Temporal Fluctuations Of Signal-To-Noise Ratio (Burst Error) On Free-Space Laser Communications System Design

Abstract: In free-space optical communications systems, a number of mechanisms can produce a temporally fluctuating signal-to-noise ratio (SNR), giving rise to fluctuations in the bit error probability that have time constants which are extremely long in comparison to the bit length. Among these mechanisms are pointing errors and atmospheric turbulence. This paper presents simple methods of properly accounting for the fades and surges in optical communication system design through the concepts of burst error and burst error probability. Examples are given for the cases of atmospheric turbulence and pointing errors.

Radio data transmission system

Abstract: In a mode switching control for controlling the tap weighing of a transversal automatic equalizer in a radio data transmission system using multivalued amplitude modulation, the improvement wherein a bit error rate (BER) is found by using pseudo-error pulses, and a threshold value (BER 1) for switching from the normal mode to the reset mode is set to be different from a threshold value (BER 2) for switching from the reset mode to the normal mode, so that the mode switching control can be effected finely and stably with a simple circuit.

M-ary FSK Performance for Coherent Optical Communication Systems Using Semiconductor Lasers

Abstract: This paper describes the design and performance of an M ary frequency shift keyed (FSK) signaling and demodulation scheme for an optical communication system using semiconductor lasers and heterodyne detection. Frequency or phase noise in semiconductor lasers causes spectral spreading, producing a nonzero linewidth laser signal. This degrades communication performance when compared to a system using an ideal laser with zero linewidth. We present estimates of the bit error rate (BER) performance of M -ary frequency shift keying (FSK) with noncoherent demodulation in the presence of white Gaussian frequency noise and additive channel noise. This is typical of an optical system using semiconductor lasers and heterodyne detection. Estimates use the union-Chernoff bound with a simplified channel model to predict the effects of frequency noise. Two effects of frequency noise are identified: signal attenuation or suppression, and crosstalk. These cause an offset in the BER curve from the BER in the absence of frequency noise, and an error rate floor, respectively. The error rate floor is lower than previously predicted. When performance is not crosstalk limited, M -ary FSK is found to perform better than binary FSK with the same system bandwidth constraints, as would be predicted if ideal lasers are used. Theoretical results are compared with Monte Carlo simulations of the system.

Digital scrambling without error multiplication

Abstract: The present invention describes a circuit which allows a data stream to be scrambled by continuously running uninterrupted Pseudo Random sequence without multiplying errors. This is accomplished by allowing a register in the Pseudo Random scrambling receiver to acquire synchronization with a register in the Pseudo Random scrambling transmitter such that the two registers run independently through the same maximal length Pseudo Random sequence without further need for communication with each other. Bit errors occurring between the transmitter and receiver do not cause the scrambling registers at the two ends to become out of synchronization and they remain in synchronism unless a timing slip occurs to cause the transmitter and receiver to lose synchronization. While the present invention is primarily directed toward providing a circuit for performing maximal length Pseudo Random scrambling without error multiplication, the invention is particularly advantageous in reducing the error rate under conditions in which a majority of the error bursts are comprised of one or a small number of error bits such as occurs in transmission loops where impulse noise is a problem.

A Concatenated Coding Scheme for Error Control

Abstract: In this paper, a concatenated coding scheme for error control in data communications is presented and analyzed. In this scheme, the inner code is used for both error correction and detection; however, the outer code is used only for error detection. A retransmission is requested if either the inner code decoder fails to make a successful decoding or the outer code decoder detects the presence of errors after the inner code decoding. Probability of undetected error (or decoding error) of the proposed scheme is derived. An efficient method for computing this probability is presented. Throughput efficiency of the proposed error control scheme incorporated with a selective-repeat ARQ retransmission strategy is also analyzed. Three specific examples are presented. One of the examples is proposed for error control in the NASA Telecommand System.

The effect of sample timing on bit error rate performance in a multipath fading channel

Abstract: Digital mobile radio often suffers from fatal effects caused by frequency-selective fading, resulting in severe bit error rate (BER) degradation. The feasibility of digital mobile radio largely depends on the multipath-distortion tolerant capability of modulation technique. The BER performance is compared among four digital modulation techniques in a frequency selective fading channel with large multipath delay spread. In particular, taking the timing fluctuation of eye patterns due to delay distortion of a fading channel into account, the effect of sample timing on BER is analyzed. The analyses have revealed that BER performance markedly depends on the choice of sample timing, and also an interesting fact that BPSK is outstanding in the multipath-distortion tolerance, if coupled with adaptive sampling, and its BER curves remain almost the same as that of frequency-flat fading as long as multipath delay difference is less than a bit interval.

Radiotelephone system employing digitized speech/data and embedded signalling

Abstract: A radiotelephone system in which the signalling protocol for the system is embedded in the frame synchronization of the digital messages transmitted on the system. System state communication is achieved by utilizing a sequence of normal synchronization words and their ones complement inverses. Reliability of the coding is achieved by detecting normal or inverse words as binary levels when fewer than a predetermined number of bit errors exist in the bit sequence. If the predetermined number of bit errors is exceeded, a selected binary one or zero is subtituted (3003). This selected sequence of binary levels is decoded (3101) and the Hamming distance between a masked decoded sequence and a masked selected sequence is calculated (3207). If the Hamming distance calculation yields a number greater than the error correction capability of thge coding function, a new set of substituted binary levels is tried (3205), otherwise the decoded sequence is accepted as correct.

Received signal processing apparatus

Abstract: An apparatus for processing a digital signal which is transmitted from a transmit station by a radio equipment and contains the same repetitive information employs the principle of decision by majority. A particular signal pattern with the least error rate is determined by majoiry. Noncoincident bits between the determined signal pattern and each of the repeatedly received patterns are counted and, then, the number of noncoincident bits is determined on each of a predetermined number of patterns which are selected by a selector out of the repeatedly received ones. When the number is smaller than a predetermined one, the pattern is allowed for processing. That is, the signal pattern is processed by measuring the bit error rate in a transmission path with the signal pattern equivalently used as a reference.

Method for determining reliability of high speed digital transmission by use of a synchronized low speed side channel

Abstract: The reliability of a high-speed digital data traffic channel is determined by establishing end-to-end synchronization by use of confirming error detecting data transmitted on a side channel from an originating end, comparing the traffic data and the error detecting data and from time to time re-confirming the validity of the synchronization.

Novel receiver structures for systems using differential detection

Abstract: Novel receiver structures are introduced which improve the bit error rate performance of differentially detected MSK and QPSK systems. These new receiver structures are based on 1) combining with feedback, 2) a simple Viterbi decoder which uses one- and two-bit detector outputs for maximum-likelihood sequence estimation, and 3) using the correlation of noise for the partial removal of its effect prior to decision. The new receiver structures presented are useful in mobile radio and mobile satellite communications where power efficiency, synchronization, and implementation complexity are of primary concern.

Analog-to-digital conversion apparatus with dither signal

Abstract: Analog-to-digital converters are subject to errors including the known half least significant bit quantization error and also bit weighting errors due to lack of an ideal binary relationship between the transition points of all the bits. The known statistical average error reduction method in which a relatively small dither component is added to the analog input signal can only fractionally reduce overall error and has little effect on bit weighting errors. Herein the analog signal is added to a dither signal, for example a ramp signal, which varies through half the peak to peak digitization range of the converter so that irrespective of the input signal all output signal bits, other than the most significant bit, are "on" for one half of the sampling period. The result is that all the less significant bit errors are cancelled leaving only the easily compensated most significant bit error. A random component can be added to the dither signal to reduce the quantization error.

Combination of cancelling intersymbol interference and decoding of error-correcting code

Abstract: The paper proposes and investigates a new type of nonlinear adaptive canceller of intersymbol interference (ISI) called `ACDEC'. The ACDEC uses an automatic equaliser including a decoder of an error-correcting code (AEDEC), to obtain more reliable preliminary decisions than those by the linear equaliser used in the linear adaptive canceller of Gersho and Lim. By using the modified structure and incorporating one more decoder, the tap values of both the canceller's delay line and the adaptive matched filter are correctively updated with reduced final decision errors in the same manner as AEDEC. The theoretical calculation of the error probability in the joint repetitive scheme of both cancelling ISI and decoding indicates that two repetitions, i.e. ACDEC, can provide considerable improvement in the error probability performance in the steady state without excessive complexity of implementation. Moreover, computer simulations show that an ACDEC achieves stable convergence and exhibits better adaptability in noisy and time-varient channels.