scispace - formally typeset
Search or ask a question

Showing papers on "Bit error rate published in 1980"


Journal ArticleDOI
TL;DR: A multiple-access modulation technique that uses multilevel frequency shift keying (FSK) to modulate frequency-hopped, spread-spectrum carriers is examined for possible application to digital mobile radiotelephony.
Abstract: A multiple-access modulation technique that uses multilevel frequency shift keying (FSK) to modulate frequency-hopped, spread-spectrum carriers is examined for possible application to digital mobile radiotelephony. This technique, in which all users employ the full system bandwidth simultaneously, would be resistant to the frequency-selective fading so troublesome in mobile radio. We have studied base-to-mobile communication of 32 kb/s per user in the 20-MHz (one-way) bandwidth of the 850-MHz mobile radio band. The number of users that can be served within a given bit error rate criterion depends on the quality of the radio channel. For perfect transmission, where the only degradation is mutual interference, an error rate less than 10−3 can be maintained with up to 209 simultaneous users. Transmission impairments, consisting of white Gaussian noise and frequency-selective Rayleigh fading with an average rf signal-to-noise ratio of 25 dB, reduce the number of simultaneous users to about 170. This capacity is roughly three times that of a phase-shift-keying spread-spectrum system recently proposed for mobile radio. For mobile-to-base transmission of FH-fsk, we have yet to study impairments resulting from delay spread in a synchronous system or, alternatively, the penalty for operating asynchronously. These effects would reduce the number of possible users from the estimates we have given for base-to-mobile transmission.

269 citations


Journal ArticleDOI
TL;DR: The purpose of the present article is to explore the subject of data transmission bandwidth through an examination of its various definitions, as the spectrum is finite, yet as technology manipulates it, a dazzling increase in bandwidth capability emerges.
Abstract: The engineering of data communications systems invites involvement with a number of rather refined parametric concepts, such as bit error rate (BER), antenna gain, radiated power, communication efficiency, and bandwidth. Of these, none has been the subject of more lively discussion and revision than bandwidth. The implications of bandwidth can vary considerably from context to context, as the profusion of definitions of bandwidth will attest. The purpose of the present article is to explore the subject of data transmission bandwidth through an examination of its various definitions. The spectrum is finite, yet as technology manipulates it, a dazzling increase in bandwidth capability emerges.

106 citations


Patent
30 Jun 1980
TL;DR: In this paper, a coding scheme is implemented which uses through checking parity bits appended to each byte as check bits, and the remaining check bits are generated such that the combination of through-checking parity bits and remaining check bit together provide single bit error correction and double bit error detection.
Abstract: Apparatus for and method of providing single bit error correction and double bit error detection using through checking parity bits. A coding scheme is implemented which uses through checking parity bits appended to each byte as check bits. The remaining check bits are generated such that the combination of through checking parity bits and remaining check bits together provide single bit error correction and double bit error detection.

42 citations


Patent
25 Jul 1980
TL;DR: In this article, a soft error rewrite control (SECC) is included within a memory system for rendering the semiconductor memory modules less susceptible to single bit errors produced by alpha particles and other system disturbances.
Abstract: Soft error rewrite control apparatus is included within a memory system for rendering the semiconductor memory modules less susceptible to single bit errors produced by alpha particles and other system disturbances. During a number of successive memory cycles occurring at a predetermined rate, the soft error rewrite control apparatus enables the read out of information stored within each module location, the correction of any single bit errors contained therein and the rewriting of the corrected information back into such location. Diagnostic apparatus is further included which is connected to place the memory system in a state for testing and verifying the operation of the soft error control apparatus. Also, the diagnostic apparatus is connected to condition the soft error control apparatus for operating in a high speed mode enabling the read out correction and rewriting of each location to take place within a minimum amount of time. By monitoring the status of the information being corrected, the diagnostic apparatus is able to signal whether or not the soft error control apparatus is operating properly.

36 citations


Patent
03 Jul 1980
TL;DR: In this paper, the processor memory control provides its own error detection and correction employing syndrome generating and decoding circuitry which detects both multiple and single bit errors, but only those which are found to most likely be solid errors are logged.
Abstract: Apparatus which detects and corrects both transient and single bit memory read errors while selectively logging only solid (that is, hardware-related) single bit memory read errors. Each of a plurality of memory modules directly transmits uncorrected memory data to a processor memory control while also providing for automatic local restoring of corrected data back into the memory address which produced the single bit error. The processor memory control provides its own error detection and correction employing syndrome generating and decoding circuitry which detects both multiple and single bit errors. Multiple bit errors are not corrected, but merely brought to the attention of the processor. Single bit errors are corrected, but only those which are found to most likely be solid errors are logged. A solid single bit error is recognized by detecting when two single bit errors having the same memory address occur consecutively.

33 citations


Journal ArticleDOI
TL;DR: A performance comparison of three representative ADM systems has been made by computer simulation using real speech, and HCDM yields the best performance in signal-to-quantization noise ratio (SQNR) and dynamic range regardless of the channel bit error rate.
Abstract: A performance comparison of three representative ADM systems has been made by computer simulation using real speech. The three systems studied are continuously variable slope delta modulation (CVSD), Jayant's constant factor delta modulation (CFDM), and a modified version of Un and Magill's hybrid companding delta modulation (HCDM). Among the three systems, HCDM yields the best performance in signal-to-quantization noise ratio (SQNR) and dynamic range regardless of the channel bit error rate. Comparing CVSD and CFDM in an ideal channel, the dynamic range of the latter is significantly wider than that of the former, although their peak SQNR's are almost the same. In a noisy channel, CFDM degrades more rapidly than the other two as the bit error rate increases. In the channel with an error rate above 10-3, the use of CFDM appears to be impractical when the bit rate is below 16 khits/s. However, intelligible speech transmission is possible with HCDM or CVSD even at the error rate of as high as 10-1.

27 citations


Journal ArticleDOI
TL;DR: This paper analyzes the performance of two FHMA-PSK systems in a Rayleigh fading environment and derives expressions for the union upper bound on the bit error rate for U users, each assigned N frequencies, i.e., N chips.
Abstract: Recently, various Frequency-Hopping, Multiple-Access (FHMA) schemes have been proposed as alternatives to frequency-division (FDMA) techniques for guarding against interference from other users and multipath fading in transmitting digitized speech in mobile radio. While the advantage of frequency diversity against fading is well known, the system degradation of frame-asynchronous FHMA-PSK due to interference from other users and fading has not been studied, except by modeling the interference as additive white Gaussian noise (AWGN). In this paper, we analyze the performance of two FHMA-PSK systems in a Rayleigh fading environment. We assume that the interferers' addresses are assigned at random and derive expressions for the union upper bound on the bit error rate (P b ) for U users, each assigned N frequencies, i.e., N chips. As an example, we consider transmitting digitized speech (R = 31.25 kb/s) over the mobile radio channel (bandwidth W = 20 MHz), using orthogonal coding of rate r = 5/32 (N = 32). For the differentially coherent FHMA-PSK case, the number of users in a two-way radio system is limited to 26 by the performance of the mobile-to-base link, which corresponds to an equivalent bandwidth of 770 kHz per user.

27 citations


Patent
08 Apr 1980
TL;DR: In this article, a link performance indicator card analyzes incoming analog data from a demodulator on a bit by bit basis and compares the individual bit amplitudes with a fraction of the average bit signal levels.
Abstract: A link performance indicator card analyzes incoming analog data from a demodulator on a bit by bit basis and compares the individual bit amplitudes with a fraction of the average bit signal levels. The data bits that lack sufficient amplitude to be clear-cut "high" or "low" pulses are detected as "pseudo-errors". A bit error rate gate signal controls the detectors in order that circuits operate for only one burst or part of a burst per frame always from the same earth station. A comparator is used for comparing the output of the averaged incoming analog signal with the instantaneous value of the analog signal. Alternate clocking signals are used to perform the averaging function and the comparison function of the average signal with the instantaneous signal. This alternation of the signals frees the comparison operation from the influence of any loading on the circuit. The sample points of the incoming analog signal are adjustable by use of delays on the clock signals fed into the circuits.

24 citations


Patent
Hoogeveen Jacobus1
18 Apr 1980
TL;DR: In this article, the authors proposed a frame synchronization method based on the assumption that it is not necessary to store the partially received synchronization pattern in a store, but that the storage capacity of N×entire log 2 M is sufficient.
Abstract: The invention relates to a method of frame synchronization of a digital time-division multiplex communication system and to an arrangement for performing the method. During the search for a synchronization pattern of M bits in frames, each consisting of N time slots, a shift register of N×M bits is usually used. The method according to the invention has for its object to reduce the number of bit storage capacity required. The method operates as follows. At the start of the synchronization process the first bit of the synchronization pattern is expected. If this expectation comes true, the second bit of the synchronization pattern is expected in that time slot in the immediately subsequent frame etc. If the expectation does not come true then the (partially) received pattern is no synchronization pattern and the procedure is performed again in that time slot. The method is based on the recognition that it is not necessary to store the partially received synchronization pattern in a store, but that it is sufficient to store the numerical order of the bit of the synchronization pattern expected in the time slot of the next frame. Consequently, a storage capacity of N×entire log 2 M is sufficient. The method can be performed with a microprocessor or with "wild" logic circuits.

24 citations


Patent
21 Apr 1980
TL;DR: In this paper, a digital subscriber communications system for transmitting voice and data information is disclosed, where the signal transmissions are in an optimized sixteen bit per frame format with a framing bit in each frame.
Abstract: A digital subscriber communications system for transmitting voice and data information is disclosed. The signal transmissions, on any suitable medium, are in an optimized sixteen bit per frame format with a framing bit in each frame. The framing bit is detected with unique circuitry and used to phase a master synchronization signal for decoding the information transmitted.

22 citations


Patent
20 Aug 1980
TL;DR: In this article, a method and system for transmitting N-bit serial data (where N is a positive number) in the form of a bit serial, including a data sending circuit, a data receiving circuit and data transmission lines, is presented.
Abstract: A method and system for transmitting N-bit serial data (where N is a positive number) in the form of a bit serial, including a data sending circuit, a data receiving circuit and data transmission lines. The system includes a first data transmission line; a second transmission line; a transfer circuit, provided in the receiving means, for sending back to the data sending circuit through the second data transmission line, the bit content of received N-bit data each time one bit of the N-bit data is received through the first data transmission line; a comparison circuit, provided in the data sending circuit, for comparing the transmitted bit content and the bit content sent back on the second data transmission line; and a detection circuit provided in the data receiving circuit. The data sending circuit is adapted to transmit as a start bit a signal of a prescribed logical value before the N-bit serial data is sent, and, as an alarm bit, the results of the comparison after the N-bit serial data has been sent. The detection circuit detects whether the logical values of the start bit and the alarm bit are prescribed logical values, so that a transmission error or a break in a transmission line can be detected.

Journal ArticleDOI
TL;DR: The results show that regenerative satellites are especially effective against uplink CW interference when on-board despreading of spread spectrum signals is included as part of the satellite processing.
Abstract: We evaluate and compare bit error rates for conventional (linear and nonlinear) repeater satellites and regenerative satellites. This work is based on a new formulation for error rates using the generalized moment technique for numerical evaluation of error rates. Both coherent MPSK and noncoherent MFSK modulations are considered with regenerative satellites. The results show that regenerative satellites are especially effective against uplink CW interference when on-board despreading of spread spectrum signals is included as part of the satellite processing.

Patent
29 Dec 1980
TL;DR: In this paper, a method and apparatus for detecting and correcting bit errors in a pulse code modulated television signal is presented, which recognizes the unique spectral characteristics of isolated bit errors and utilizes that energy to detect and correct errors without the use of overhead bits.
Abstract: Method and apparatus for detecting and significantly correcting bit errors in a pulse code modulated television signal which recognizes the unique spectral characteristics of isolated bit errors in a digital bit stream, which generate spectral energy outside the frequency band of the video signal, and utilizes that energy to detect and correct errors without the use of overhead bits.

Patent
03 Jun 1980
TL;DR: In this article, a data comparator (880) detects noncoincidences of bits in the two data streams and counts such errors over a given sampling interval, providing a bit error rate.
Abstract: A muldem (100) has a monitor (101) for testing data path failures through the muldem (100) by comparing the latter's input and output. The monitor (101) includes comparing means (806, FIGS. 13a and b) with a data comparator (880, FIGS. 13b and 17) for bit error detection by comparision of a pair of data streams (A+B) processed through the monitor (101) from the input and output of the muldem (100). The data comparator (880) delays one of the data streams (A) by a fixed amount and variably delays the other data stream (B), and then slipshifts the data streams in time until they are in alignment to be compared. The data comparator (880) detects noncoincidences of bits in the two data streams and counts such errors over a given sampling interval, providing a bit error rate. If this rate is above a user selectable threshold, then a malfunction in the tested data path is probable, so the path is retested, using a longer sampling interval, to improve the statistical accuracy of the test. If the number of bit errors increases accordingly, then a malfunction is indicated and standby data path protective switching may be initiated. Return switching from standby back to the normally on-line main path is not permitted until the bit error rate drops below a second, lower threshold.

Journal ArticleDOI
R. Steele1, N. S. Jayant
TL;DR: The statistical block protection coding scheme has been extended to accommodate DPCM-AQF encoded speech, where AQF stands for adaptive quantization with forward (explicit) transmission of step size, and perceptual improvements in decoded speech have a good correspondence with the gains in SNR.
Abstract: The statistical block protection coding scheme [2] for protecting DPCM encoded speech signals through noisy channels has been extended to accommodate DPCM-AQF encoded speech, where AQF stands for adaptive quantization with forward (explicit) transmission of step size. Signal-to-noise ratio (SNR) gains, typically 12 dB, have been achieved over a dynamic range > 20 dB for a bit error rate (BER) of 1.4 percent and the SNR improvement is found to increase with BER. Perceptual improvements in decoded speech have a good correspondence with the gains in SNR. The penalty for this substantial enhancement in the performance of the DPCM-AQF system is an increase in transmission bit rate of 3.5 percent and encoding delay of 64 ms.

Patent
07 Feb 1980
TL;DR: In this paper, a data transmission system with asynchronous-to-synchronous data conversion at the transmitter end of a data link at times removes stop bits from, and at other times adds stop bits to, a character, a receive buffer at the receive end of the data link which converts the synchronous data to asynchronous data.
Abstract: OF THE DISCLOSURE In a data transmission system, in which asynchronous-to-synchronous data conversion at the transmitter end of a data link at times removes stop bits from, and at other times adds stop bits to, a character, a receive buffer at the receive end of the data link which converts the synchronous data to asynchronous data. The receive buffer investigates the end of each character for missing stop bits and reinserts a stop bit where it finds a lack of one, and adds other stop bits to speed up the data rate from the nominal synchronous data bit transmission rate to the nominal asynchronous data bit output rate. The inserted stop bits are of a constant bit width which is the same as the character identification bit width, and the entire asynchronous data output stream has a constant bit rate.

Journal ArticleDOI
TL;DR: Two known methods of pseudoerror generation, namely, threshold modification and sampling offset, are compared with two new monitors using controlled amounts of amplitude and phase distortion, finding the threshold modification monitor is most robust to channel degradations, while amplitude or phase distortion monitors seem to be more accurate in estimating the actual error rate but less robust.
Abstract: Pseudoerror monitoring techniques, besides providing a precursive, measure of system degradation, can also be used in extrapolation schemes to estimate the actual bit error rate of a digital link. This study examines pseudoerror techniques as applied to a precoded, modified duobinary system. Two known methods of pseudoerror generation, namely, threshold modification and sampling offset, are compared with two new monitors using controlled amounts of amplitude and phase distortion. The threshold modification monitor is most robust to channel degradations, while amplitude or phase distortion monitors seem to be more accurate in estimating the actual error rate but less robust. The sampling offset monitor seems to be less robust than the other monitors due to its unavoidable sensitivity to degradations affecting the system phase. Methods of improving the estimation accuracy by the choice of degradation parameters are also examined.

Journal ArticleDOI
A. Weinberg1
TL;DR: This paper examines the cumulative impact of nine forms of distortion induced by the repeater on BPSK and QPSK signals, which include frequency offset, filter amplitude and phase ripple, phase noise, spurious phase modulation, AM/AM and AM/PM conversion, incidental AM, and spurious outputs.
Abstract: The bit error rate (BER) performance analysis of a data communication system is generally based on the assumption that signal waveforms are ideal and hardware-induced distortion is absent. In a satellite communication system, such distortion arises in the satellite repeater, as well as in the transmitter and receiver portions. NASA, which is in the process of developing its Tracking and Data Relay Satellite System (TDRSS), is very much interested in understanding the impact of numerous hardware constraints, that have been identified, on BER performance. The present paper, which treats one segment of this broad problem area, examines the cumulative impact of nine forms of distortion induced by the repeater on BPSK and QPSK signals. These include frequency offset, filter amplitude and phase ripple, phase noise, spurious phase modulation (PM), AM/AM and AM/PM conversion, incidental AM, and spurious outputs. For the present analysis, the transmitter and receiver are assumed to operate in essentially ideal fashions and thermal noise is introduced at the receiver front end only. Computed results indicate that BPSK and QPSK performances are impacted in substantially different manners, with QPSK generally more sensitive to a given form of distortion. One noteworthy example is the combined impact of the phase noise and spurious PM parameters which affect BPSK only slightly, but lead to very rapid QPSK performance degradation as the parameter values increase. This and the other distortion effects are illustrated via computed parametric performance curves. Results also demonstrate the need to account for interactions among distortion parameters.

Patent
14 Nov 1980
TL;DR: In this article, a time division demultiplexer is provided which reassigns clock positions to the various channels in a serial data stream such that different data bit positions may be assigned to a channel.
Abstract: A time division demultiplexer is provided which reassigns clock positions to the various channels in a serial data stream such that different data bit positions may be assigned to a channel. This enables each channel to be independent. A single channel can access any data bit position in the serial data stream, and several or all the channels can access the same data bit position.

Patent
06 Aug 1980
TL;DR: In this article, the authors proposed a switchable p.c. multiplex protocol where all the 32 channels of the p.m. CDMA network must be switchable, and the switching of channel zero relates to the "spare bits" not defined for synchronization purposes.
Abstract: It is an emerging international telecommunications requirement that all 32 channels of the p.c.m. multiplex must be switchable. The switching of channel zero relates to the "spare bits" not defined for synchronization purposes and these bits may be used as a data-bearer for network administration or control purposes. Digital telecommunication switching network, therefore, must be capable of concentrating channel assemblies of these spare bits into one transmit multiplex which may be connected to a spare bit data processor remote from the switching network or co-located with it. The passing of channel zero into the switch block, however, is dangerous because if this data is passed across the switch block to another digital line termination unit DLT in a time slot other than channel zero, then that receiving DLT will be called upon to transmit data containing two valid sets of sync and non-sync patterns which could confuse the synchronization circuits associated with the digital transmission system connected to that DLT. Such an arrangement is prevented using equipment in the receive and transmit DLT's. In the receive DLT after the incoming synchronization channel has fulfilled its synchronization purpose it is deliberately modified such that when switched to a transmit multiplex it will not be erroneously recognized as a sync channel. The modification does not of course cause loss of information contained in the spare bits or alarm bit. At the transmit DLT a decision is made as to whether the international bit in the sync pattern and the international bit and spare bits in the non-sync pattern should be transmitted to line as data ones or the patterns received.

Journal ArticleDOI
On-Ching Yue1
TL;DR: Close-form bounds on the bit error rate are derived for flat, Rayleigh, and Rician fading conditions for spread-spectrum system for mobile communication and are more useful than computer simulations for analyzing system performance.
Abstract: Previous results on the spread-spectrum system for mobile communication proposed by Cooper and Nettleton have been obtained by computer simulation. In this paper, closed-form bounds on the bit error rate are derived for flat, Rayleigh, and Rician fading conditions. For more general types of fading, the saddle point method is used. Since the bounds are easily computed, they are more useful than computer simulations for analyzing system performance.

Patent
24 Nov 1980
TL;DR: In this paper, a process for the transmission of data from a plurality of data sources utilizes a start-stop signal whose signal frame contains one code bit and data bits from each of the data sources between a start bit and a stop bit.
Abstract: A process for the transmission of data from a plurality of data sources utilizes a start-stop signal whose signal frame contains one code bit and data bits from a plurality of data sources between a start bit and a stop bit. Here, the code bits indicate the assignment of the data bits to the individual data sources.

Proceedings ArticleDOI
01 Apr 1980
TL;DR: A channel vocoder has been developed to operate in environments of high acoustic noise and high bit error rates and it is implemented almost entirely digitally by using an lntel 8085 microprocessor system and a special purpose digital filter bank.
Abstract: A channel vocoder has been developed to operate in environments of high acoustic noise and high bit error rates. The 2400 b/s vocoder incorporates a robust pitch extractor and regenerator, automatic speech level control and forward error correction. It is implemented almost entirely digitally by using an lntel 8085 microprocessor system and a special purpose digital filter bank. The vocoder is currently packaged in a 1/4 ATR case (short) which occupies a volume of approximately 250 cubic ins, and it will meet full military environmental conditions. The first section of this paper deals with basic channel vocoder operation. The next section covers the implementation in the digital filter bank and microprocessor. The paper concludes with a brief description of the equipment and its performance in adverse conditions.

Journal ArticleDOI
TL;DR: The error performance of multi-transmitter data systems is described for mobile and stationary users in overlap areas, as a function of carrier frequency and modulation timing difference, and the conclusion is reached that performance is comparable to single transmitter systems at the same signal level.
Abstract: The error performance of multi-transmitter data systems is described for mobile and stationary users in overlap areas, as a function of carrier frequency and modulation timing difference. Plots of bit error rate and error distribution are given, and the conclusion is reached that performance is comparable to single transmitter systems at the same signal level. The constraints on the choice of data modulation are discussed

DOI
01 Dec 1980
TL;DR: In this article, various methods of diversity reception are considered as a means of reducing the errors in mobile radio data data systems caused by fading and ignition noise, and three dual-diversity receivers utilising switched diversity, predetection combining and postdetection combining have been implemented.
Abstract: Various methods of diversity reception are considered as a means of reducing the errors in mobile radio data systems caused by fading and ignition noise. Data modems designed for subcarrier and direct modulation of the carrier have been built, and both binary f.s.k. and p.s.k. have been used. Three dualdiversity receivers utilising switched diversity, predetection combining and postdetection combining have been implemented, and their effectiveness has been tested in both laboratory tests and field trials at v.h.f. Significant reductions in bit error rate have been achieved.

Patent
29 May 1980
TL;DR: In this paper, a modulation and demodulation system for converting a binary sequence composed of a succession of bits, each having a value of "1" or "0", occurring in successive bit intervals, into a transmitted signal containing a representation of each bit, by representing a bit of one value as a change in the level of the transmitted signal at a time corresponding to the middle of the associated bit interval.
Abstract: In a modulation and demodulation system for converting a binary sequence composed of a succession of bits, each having a value of "1" or "0", occurring in successive bit intervals, into a transmitted signal containing a representation of each bit, by representing a bit of one value as a change in the level of the transmitted signal at a time corresponding to the middle of the associated bit interval, and representing a bit of the other value as a change in the level of the transmitted signal at a time corresponding to the end of the associated bit interval if a further bit of the other value follows, transmitted signal level changes associated with the bits of the other value are in part suppressed for causing the time period between level changes in the transmitted signal to be no longer than the period of more than two consecutive level changes at intervals equal to each bit interval and associated with the bits of the other value.

Proceedings Article
01 Jan 1980

Journal ArticleDOI
J. Gruber1
TL;DR: Results related to measurmg the error performance of an experimental 12/14 GHz satellite link established between Carleton University, Ottawa, Canada, and NASA Ames Research Center, California, in 1976-1977 are presented.
Abstract: This correspondence presents results related to measurmg the error performance of an experimental 12/14 GHz satellite link established between Carleton University, Ottawa, Canada, and NASA Ames Research Center, California, in 1976-1977. The measurements were performed on a 9.6 kbit/s voiceband data channel which supported the continuous synchronous transmission of fixed length frames (composite packets). The results include measurements of packet error rate versus uplink power settings under various atmospheric conditions, densities of packet error-free interval lengths, within-packet error statistics, and propagation delay variations.

Proceedings ArticleDOI
09 Apr 1980
TL;DR: The introduction of smoothing strategies to the basic APC vocoder added 900-1100 bps to the bit rate and resulted in significantly improved robustness in channel errors.
Abstract: A study was performed to evaluate various techniques for improving the robustness of an Adaptive Predictive Coder operating in the presence of channel errors. The communications environment consisted of a packetized, symbol oriented system in which channel errors were manifested as both 5-bit symbol errors in the received bit stream and the occasional loss of an entire packet of data. To reduce the effects of symbol errors forward error correction was applied to a selected subset of the transmitted parameter bits. At the receiver, smoothing strategies were employed to replace those parameters in which errors could be detected but not corrected and to cope with situations in which entire packets were lost. The introduction of these techniques to the basic APC vocoder added 900-1100 bps to the bit rate and resulted in significantly improved robustness in channel errors.

Journal ArticleDOI
TL;DR: In order to accurately evaluate bit error rates for a frequency-hopped d.p.k.s. system, digital computer experiments were performed and the value of Eb/N0 at the 10-3 error rate without fading was 8.4 dB.
Abstract: In order to accurately evaluate bit error rates for a frequency-hopped d.p.s.k. system, digital computer experiments were performed. The value of Eb/N0 at the 10-3 error rate without fading was 8.4 dB.