Showing papers on "Keying published in 1989"
TL;DR: An optimum class of pulse shapes for use in Q/sup 2/PSK format is presented and one suboptimum realization achieves the Nyquist rate of 2 b/s/Hz using binary detection.
Abstract: Quadrature-quadrature phase-shift keying (Q/sup 2/PSK) is a spectrally efficient modulation scheme which utilizes available signal space dimensions in a more efficient way than two-dimensional schemes such as QPSK and MSK (minimum-shift keying) It uses two date shaping pulses and two carriers, which are pairwise quadrature in phase, to create a four-dimensional signal space and increases the transmission rate by a factor of two over QPSK and MSK However, the bit error rate performance depends on the choice of pulse pair With simple sinusoidal and cosinusoidal data pulses, the E/sub b//N/sub 0/ requirement for P/sub b/(E)=10/sup -5/ is approximately 16 dB higher than that of MSK Without additional constraints, Q/sup 2/PSK does not maintain a constant envelope, however, a simple block coding can provide a constant envelope This coded signal substantially outperforms MSK and TFM (time-frequency multiplexing) in bandwidth efficiency Like MSK, Q/sup 2/PSK also has self-clocking and self-synchronizing ability An optimum class of pulse shapes for use in Q/sup 2/PSK format is presented One suboptimum realization achieves the Nyquist rate of 2 b/s/Hz using binary detection >
165 citations
TL;DR: The performance of trellis-coded differential octal phase-shift keying (coded 8-DPSK) with differentially coherent detection and soft-decision Viterbi decoding is investigated and the performance is determined on Rayleigh and Rician channels for various Doppler spreads and interleaver sizes.
Abstract: The performance of trellis-coded differential octal phase-shift keying (coded 8-DPSK) with differentially coherent detection and soft-decision Viterbi decoding is investigated. A suitable receiver is presented whose signal processing is based on Nyquist signaling, requiring only one complex sample per modulation interval. Symbol synchronization and automatic frequency control are performed in a decision-directed way. Bit-error-rate (BER) performance over Gaussian, Rayleigh, and Rician channels is determined by means of computer simulations. The performance of coded 8-DPSK on the Gaussian channel is shown for a four-state convolutional trellis code. The unquantized outputs of up to three symbol detectors with delays of 1, 2, and 3 symbol periods are used for metric computation. The coding gain which includes losses due to timing and frequency synchronization errors is found to be 2.5 dB at BER=10/sup -5/ with respect to uncoded 4-DPSK. Much larger gains are achieved for fading channels if interleaving is applied. Using an eight-state trellis code the performance is determined on Rayleigh and Rician channels for various Doppler spreads and interleaver sizes. >
68 citations
TL;DR: A spread-spectrum multiple-access SSMA packet radio network model is presented, which accounts for the availability of idle receivers in a finite population network and results are given which show the effects on throughput of the received energy-to-noise density ratio, the number of chips per symbol, and thenumber of radios, as well as the improvement due to error control coding.
Abstract: A spread-spectrum multiple-access (SSMA) packet radio network model is presented. The topology is a fully connected network with identical message generation processes at all radios. Packet lengths are exponentially distributed, and packets are generated from a Poisson process, resulting in a Markovian model. This network model accounts for the availability of idle receivers in a finite population network. The model also allows the performance of the radio channel to be specified in detail. The channel considered is a BPSK (binary phase-shift keying) direct-sequence SSMA radio channel with hard-decision Viterbi decoding. An analysis of the Viterbi decoder leads to a bound on its performance which is valid for a system with a varying probability of error, as is the case for the network under consideration. The approximate analysis yields lower bounds on throughput and probability of successful packet transmission. Results are given which show the effects on throughput of the received energy-to-noise density ratio, the number of chips per symbol, and the number of radios, as well as the improvement due to error control coding. >
55 citations
TL;DR: The performance of a bandwidth-efficient multiple-tone modulation scheme for M-ary frequency-shift keying (MFSK) is presented and a performance improvement comparable to that obtained by using time or frequency diversity is shown.
Abstract: The performance of a bandwidth-efficient multiple-tone modulation scheme for M-ary frequency-shift keying (MFSK) is presented. The use of balanced incomplete block (BIB) designs is proposed to form the signaling frames. On each symbol interval the modulator selects a group of elements from a BIB design and divides its energy into the orthogonal waveforms corresponding to these elements. The multiple-tone FSK scheme based on these block designs is shown to increase greatly the bandwidth efficiency of a conventional M-ary FSK system. An implicit diversity is incorporated in the modulation scheme. Thus, a performance improvement comparable to that obtained by using time or frequency diversity is shown on a Rayleigh fading channel and also on an interference channel with partial-band Gaussian noise. The multiple-tone scheme based on this design is compared to a multiple-tone scheme based on Hadamard matrices suggested by J.F. Pieper et al. (1978). It is shown that similar performance is achieved on a fading channel, while an advantage close to 4 dB is obtained for the proposed scheme on an AWGN (additive white Gaussian noise) channel. >
46 citations
TL;DR: In this paper, the authors describe the use and performance of CSMA (carrier-sense multiple access) with priority acknowledgements for medium access control on distribution power line communication networks, and the particular effects on performance of the power-line channel behavior are ascertained.
Abstract: The authors describe the use and performance of CSMA (carrier-sense multiple access) with priority acknowledgements for medium access control on distribution power line communication networks. Such networks suffer from highly variable, ever-changing, and unpredictable signal-to-noise ratio. The architecture of the CSMA implementation is described, along with its advantages relative to other access control schemes. The best packet length, in terms of throughput maximization, was found to approximate 1000 bits. Delay-throughput performance is measured, and the particular effects on performance of the power-line channel behavior are ascertained. Extensive tests were conducted on intrabuilding lines using channel bit rates from 1200 to 19200 bits/s, with FSK (frequency-shift keying) and spread-spectrum PSK (phase-shift keying) modems transmitting at 3 V RMS at frequencies ranging from 40 to 120 kHz. The reported results include potentially difficult cases involving transmission across power phases. >
35 citations
Patent•
23 Jan 1989
TL;DR: A secure communication system comprising signal manipulation and inverse signal manipulation means at the sending and receiving locations respectively, the signal manipulation processes being controlled by keying signals derived according to predetermined operations from another, unrelated signal, said signal being readily and reliably available at both send and receive locations.
Abstract: A secure communication system comprising signal manipulation and inverse signal manipulation means at the sending and receiving locations respectively, the signal manipulation processes being controlled by keying signals derived according to predetermined operations from another, unrelated signal, said signal being readily and reliably available at both sending and receiving locations.
35 citations
Patent•
22 Sep 1989TL;DR: An optical homodyne differential phase shift keying (DPSK) receiver for receiving and demodulating optical input signals, provided with a power splitter for splitting the input signal into first and second signals, is described in this article.
Abstract: An optical homodyne differential phase shift keying (DPSK) receiver for receiving and demodulating optical input signals, is provided with a power splitter for splitting the input signal into first and second signals, a delay is applied to the second signal, an optical amplifier optically amplifies the delayed second signal, and a balanced noise reduction circuit combines the first signal and the delayed amplified second signal to produce a demodulated output signal.
31 citations
TL;DR: In this paper, an analysis of the performance of phase diversity receivers using amplitude shift keying (ASK) and differential phase-shift keying(DPSK) is presented. But their performance is independent of the polarization state of the received signal, and the value of SNR required to obtain the BER of 10/sup -9/ is only a few tenths of a decibel greater than that needed by the phase diversity receiver.
Abstract: An analysis of the performance of phase diversity receivers using amplitude-shift keying (ASK) and differential phase-shift keying (DPSK) is presented. Both (2*2) and (3*3) multiport receivers are investigated. Asymptotic methods are used to estimate the bit error rate (BER) and signal-to-noise power ratio (SNR) dependence for each type of the receiver. The analysis favors the squarers as the demodulators for ASK whose performance approaches that of the ideal heterodyne detector in the limit of large SNR. A modification of the ASK ((3*3)) receiver which cancels the local oscillator intensity noise is proposed. Receivers which comprise polarization and phase diversity techniques are also investigated for both ASK and DPSK. Their performance is independent of the polarization state of the received signal, and the value of SNR required to obtain the BER of 10/sup -9/ is only a few tenths of a decibel greater than that needed by the phase diversity receivers. >
29 citations
Patent•
16 Nov 1989TL;DR: In this article, a first connector is provided with a polarizing structure 23 and a keying structure 28, 29, and a complementary housing with a receiving end 25 having a slidable frame 30 having complementary keying.
Abstract: A first connector 1 provided with a polarizing structure 23 and keying structure 28, 29, a complementary housing 3 provided with a receiving end 25 having a slidable frame 30 for receiving the polarizing structure 23 and the keying structure 28, 29, and the frame 30 having complementary keying means aligned with the keying structure of the first connector and aligned with a single one of the multiple connector positions.
26 citations
15 Oct 1989
TL;DR: The author proposes a suboptimal coded system that combines a regular convolutional code, bit interleaving, and an appropriate decoding technique, and the bounds on the error performance indicate that the best convolutionian code in conjunction with 8-PSK modulation and appropriate soft-decision metric is an attractive means of improving the reliability.
Abstract: Trellis-coding techniques are considered as a means of improving the reliability of 8-PSK (phase-shift keying). It is shown that the combination of a rate 2/3 convolution code and 3-b interleavers provides a good modulation/coding method for the Rayleigh channel. The author proposes a suboptimal coded system that combines a regular convolutional code, bit interleaving, and an appropriate decoding technique. The bounds on the error performance of this approach indicate that the best convolutional code in conjunction with 8-PSK modulation and appropriate soft-decision metric is an attractive means of improving the reliability. In particular, over a Rayleigh channel this system requires E/sub b//N/sub 0/ of about 14.5 dB to provide a bit-error rate of 10/sup -5/ (for a code with 64 states), which is 1.2 dB less than the requirement for the baseline system, which uses the optimal trellis codes for the Rayleigh channel. >
23 citations
01 May 1989
TL;DR: In this article, the authors describe a digital cellular system with linear modulation and discuss two kinds of modulation schemes-QPSK (quadrative phase-shift keying) and pi/4 shift QPSK, and two kindsof detection schemes-coherent detection and limiter-discriminator detection.
Abstract: The authors describe a digital cellular system with linear modulation. They discuss two kinds of modulation schemes-QPSK (quadrative phase-shift keying) and pi /4 shift QPSK, and two kinds of detection schemes-coherent detection and limiter-discriminator detection. The features of these modulation/detection schemes are clarified. From the collective point of view, the pi /4 shift QPSK/limiter-discriminator detection is judged to be the most advantageous. Next, the authors show examples of the radio link design for a digital cellular system with linear modulation. The system could be constructed at a transmission power of 100-200 mW. Finally, the breadboard equipment configuration and the experimental results are shown. >
01 May 1989
TL;DR: In this article, three short-block equalization techniques based on linear, nonlinear decision-directed, and maximum-likelihood estimation principles are presented. But, each data block is detected as a unit, which is considered an advantage from the adaptation point of view.
Abstract: The objective of the present study is reliable digital communications over fading channels with severe time-dispersion. The authors present three short-block equalization techniques based on linear, nonlinear decision-directed, and maximum-likelihood estimation principles. Short alternating blocks of data and training symbols are used. In contrast to the recursive symbol-by-symbol equalization approaches usually employed, each data block is detected as a unit. These schemes require an estimate of the channel impulse response. This is considered an advantage from the adaptation point of view, since channel response estimation is one of the simplest adaptation requirements of any equalization process. Performance is evaluated for QPSK (quadrature phase-shift keying) and BPSK (binary phase-shift keying) signaling using a Rayleigh fading-channel model with severe time-dispersion. The degradation from ideal for the three schemes was about 5, 2.5, and 1 dB respectively. >
TL;DR: In this paper, an experimental 155.52 Mb/s coherent broadcast network with 16 channels using a conventional distributed feedback (DFB) laser operating at 1540 nm is described, which includes absolute laser frequency stabilization, a fiber span of 74.4 km, and a balanced polarization-diversity single-filter frequency-shift keying (FSK) heterodyne receiver.
Abstract: An experimental 155.52 Mb/s coherent broadcast network with 16 channels using a conventional distributed feedback (DFB) laser operating at 1540 nm is described. It includes absolute laser frequency stabilization, a fiber span of 74.4 km, and a balanced polarization-diversity single-filter frequency-shift keying (FSK) heterodyne receiver. At a channel spacing of 8.5 GHz a power penalty of 0.3 dB is incurred due to adjacent channel crosstalk. >
TL;DR: A formula is derived for the error probability of M-ary phase-shift keying (PSK) in the satellite mobile channel when the signal is accompanied by a pilot tone which is used in the receiver for coherent detection of the signal.
Abstract: A formula is derived for the error probability of M-ary phase-shift keying (PSK) in the satellite mobile channel when the signal is accompanied by a pilot tone which is used in the receiver for coherent detection of the signal. The author computes the error probability as a function of the signal-to-noise ratio, the ratio of powers in the specular and diffused signal component, the ratio of bandwidth in the pilot tone and signal extraction filters, and the numbers of symbols, i.e. M, while optimizing the ratio of powers in the pilot tone and signal. He computes results when the diffused component is not delayed with respect to the specular component, as well as for the opposite case, i.e. when the symbol in the diffused component is independent of the symbol in the main component. >
TL;DR: The guard time effect, is used in multipath spread channels, is evaluated for frequency-selective channels, and the optimal combination of signaling rate, code rate, and guard time is presented.
Abstract: The generalized cutoff rate of time- and frequency-selective fading channels is evaluated for M-ary frequency-shift keying (MFSK) and M-ary differential phase-shift keying (MDPSK) modulation with soft decoding. The optimal signaling rate and code rate for dispersive channels are evaluated. The guard time effect, is used in multipath spread channels, is evaluated for frequency-selective channels, and the optimal combination of signaling rate, code rate, and guard time is presented. Special attention is given to CCIR (International Radio Consultative Committee) HF channel models. >
TL;DR: It is shown that heterodyne detection for lightwave signals of this kind can be made highly robust to phase noise, in contrast to the case of binary phase-shift keying.
Abstract: The decision of on-off keying (OOK) and frequency-shift keying (FSK) is considered for coherent lightwave communications in which the optical pulses are corrupted by the phase noise associated with nonzero laser linewidths. Heterodyne lightwave detection is assumed, followed by intermediate frequency filtering, envelope detection, and postdetection low-pass filtering. Using analytical results published previously, theoretical minimum values of the required average power are obtained in photons/bit, for achieving a bit error rate of 10/sup -9/. Numerical results are given as functions of laser linewidth-to-bit-rate ratio for OOK, binary FSK (or 2-FSK), and 8-FSK. It is shown that heterodyne detection for lightwave signals of this kind can be made highly robust to phase noise, in contrast to the case of binary phase-shift keying. >
11 Jun 1989
TL;DR: The authors consider the differential detection of the OQPSK (offset quadrature phase-shift keying) signal and propose a method for the differential coding of the binary message as well as a suitable decoding technique.
Abstract: The authors consider the differential detection of the OQPSK (offset quadrature phase-shift keying) signal and propose a method for the differential coding of the binary message as well as a suitable decoding technique. It is shown that the coding of OQPSK for differential detection can be done either by double differential encoding of the binary message m(t) before driving the demultiplexer at the transmitter or by differential coding on each channel I(t) and Q(t) obtained by demultiplexing the message m(t). On the receiver side, it is shown that it is possible to use two lines of BPSK (binary PSK) differential detection. Doing so makes possible a decision on the polarity of the received data by simultaneous sampling of the inphase and quadrature channels. Like the minimum shift keying signal, the OQPSK signal can be detected with a delay of one or two bit time duration. >
27 Nov 1989
TL;DR: A compact-spectrum and interference-resistant digital video transmission system which employs an offset QPSK (quadrature-phase shift keying) modulation scheme and a 32-Mb/s video codec followed by a high-coding-rate and high-gain Viterbi decoder is proposed.
Abstract: A compact-spectrum and interference-resistant digital video transmission system which employs an offset QPSK (quadrature-phase shift keying) modulation scheme and a 32-Mb/s video codec followed by a high-coding-rate and high-gain Viterbi decoder is proposed. The system achieves a signal-to-noise ratio of higher than 52 dB (weighted) and a protection ratio of 20 dB higher against cochannel interference than that of conventional analog FM systems. It can transmit a high-quality NTSC video signal over nonlinearity amplified narrow-bandwidth satellite channels with high-security digital encryption. >
02 Apr 1989
TL;DR: The work carried out shows how direct-sequence baseband spread-spectrum techniques, using sequence inversion keying of unipolar code sequences, may be applied to the CDMA protocol for an optical fibre LAN.
Abstract: Presents a resume of the work on the application of CDMA techniques in optical fibre LANs. The work carried out shows how direct-sequence baseband spread-spectrum techniques, using sequence inversion keying (SIK) of unipolar code sequences, may be applied to the CDMA protocol for an optical fibre LAN. A mathematical model of the optical CDMA system is presented and used to derive performance measures for the system. A new algorithm for choosing suitable sets of code sequences is presented and a new class of code sequences for use with an optimum matched filter detector in a CDMA system is described.<
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TL;DR: It is shown that in principle T-user CCMA permits higher transmission rates than time-division multiple-access (TDMA) employing the same signal alphabet.
Abstract: The collaborative coding multiple-access (CCMA) technique potentially permits efficient simultaneous transmission by several users sharing a common channel, without subdivision in time or frequency. The capacity of a T-user binary adder multiple-access channel is calculated for additive white Gaussian noise (AWGN) conditions. The capacity in bits/ channel use for different numbers of users is derived by simulation for the baseband antipodal and bandpass on-off keying systems with coherent and noncoherent combining. It is shown that in principle T-user CCMA permits higher transmission rates than time-division multiple-access (TDMA) employing the same signal alphabet.
01 Jul 1989
TL;DR: The NASA Lewis Research Center has developed a unique capability for evaluation of the microwave components of a digital communication system that features a continuous data digital BER test set, a data processor, a serial minimum shift keying modem, noise generation, and computer automation.
Abstract: The NASA Lewis Research Center has developed a unique capability for evaluation of the microwave components of a digital communication system. This digitally modulated bit-error-rate (BER) measurement system (DMBERMS) features a continuous data digital BER test set, a data processor, a serial minimum shift keying (SMSK) modem, noise generation, and computer automation. Application of the DMBERMS has provided useful information for the evaluation of existing microwave components and of design goals for future components. The design and applications of this system for digitally modulated BER measurements are discussed.
27 Nov 1989
TL;DR: Different schemes that make it possible to compensate both phase-noise and polarization fluctuations due to single mode fibers are presented and are suitable for long-haul applications and local and metropolitan area networks.
Abstract: Different schemes that make it possible to compensate both phase-noise and polarization fluctuations due to single mode fibers are presented. The first two systems, double-frequency phase shift keying (DFPSK) and Jones matrix inversion PSK (JMPSK) rely on the principle of transmitting a reference carrier to compensate for the phase noise effect at the receiver. The polarization independence is attained in DFPSK by polarization diversity detection and in JMPSK by the electronic feedforward technique. The second pair of systems, antipodal Stokes parameters shift keying (ASPSK) and differential Stokes parameters shift keying (DSPSK), is based on polarization modulation and Stokes parameter detection. Because the Stokes parameters are independent of the phase terms common to both polarization components, the systems are widely tolerant with respect to the phase noise. The polarization fluctuation insensitivity is realized in ASPSK by means of a feedforward electronic control circuit, while in DSPSK the adopted decision criterion allows instantaneous polarization fluctuation compensation. The first class of systems is suitable for long-haul applications, the second class for local and metropolitan area networks. >
Patent•
21 Nov 1989
TL;DR: In this article, a case for receiving a control circuit plate is attached to the machine frame, and the circuit plates and the case are provided with coded keying means in the form of pins and holes to guarantee the fastening of a control plate matching a particular model of the sewing machine.
Abstract: In a computer-controlled sewing machine including a standard machine frame and exchangeable electronic control circuit plates inclusive of an operation board, a case for receiving a control circuit plate is attached to the machine frame. The circuit plates and the case are provided with coded keying means in the form of pins and holes to guarantee the fastening of a control plate matching a particular model of the sewing machine.
15 Oct 1989
TL;DR: Results show that bit-by-bit error under fast varying fade can predict the exact location of error bits among the sequence of transmitted data, which cannot be done by using average BER.
Abstract: Aspects of error performance of the land mobile satellite system (LMSS) using QPSK (quaternary phase-shift keying) and MSK (minimum shift keying) under fading channel conditions have been studied. In contrast to the sole use of average bit-error rate (BER) as a performance measure, bit-by-bit-error rates are calculated for the sequence of transmitted data under various fading conditions by computer simulation. For this purpose, various measured data from field experiments are collected and processed to yield the scaled version of fade amplitudes and phases for several data transmission cycles. Under the condition of a moving vehicle at a speed of 55 m.p.h. at 850-MHz transmission, a series of 256-b data streams at the rate of 2.4 kb/s are simulated using coherent QPSK and MSK. A total of 203.2 wavelength fade data is used to give actual fading effects. Results show that bit-by-bit error under fast varying fade can predict the exact location of error bits among the sequence of transmitted data, which cannot be done by using average BER. >
Patent•
14 Sep 1989
TL;DR: In this article, a method and apparatus for keying digital color TV signals without exceeding the normal sampling frequency (13.5 MHz) and without obtaining a degraded image was presented, where a digital keying signal and a digital TV signal are supplied to upsamplers (10,12), respectively, which double the sampling frequency of the incoming signal by linear interpolation.
Abstract: A method and apparatus for keying digital color TV signals without exceeding the normal sampling frequency (13.5 MHz) and without obtaining a degraded image. A digital keying signal and a digital color TV signal are supplied to upsamplers (10,12), respectively, which double the sampling frequency of the incoming signal by linear interpolation. The 27 MHz sampled outputs are keyed in multiplier (14). In one line to a switch (24) the 27 MHz, 12 MHz bandwidth keyed signal is passed through low pass filter (16) and demultiplexer (18). The latter removes each alternate sample to provide a 13.5 MHz signal of 6 MHz bandwidth. In a second line to the switch the keyed signal is demultiplexed to provide a signal which would have resulted without upsampling, which is then delayed (22). Edge detector (26) senses high frequency keying signals and controls switch (24). In the absence of such high frequency keying signals the signal to the second line to the switch is taken. Only the presence of high frequency keying is the signal to the first line employed. The invention is thus "transparent" to the viewer in the absence of high frequency keys.
Patent•
25 Oct 1989TL;DR: In this paper, the transmission of communications using frequency shift keying, involving keying at the transmit end between two or a plurality of baseband code frequencies known at the receive end, is described.
Abstract: of EP01717781. Method for the transmission of communications using frequency shift keying, involving keying at the transmit end between two or a plurality of baseband code frequencies known at the receive end, characterised in that the code frequencies and/or the number (m) of code frequencies utilised are modified according to a time program known at the receive end.
Patent•
14 Sep 1989
TL;DR: In this article, a method and apparatus for keying digital color TV signals to avoid "stairstepping" of pixels at the edges of the key while retaining a hard switch between the keyed scenes is presented.
Abstract: A method and apparatus for keying digital color TV signals to avoid "stairstepping" of pixels at the edges of the key while retaining a hard switch between the keyed scenes. This is achieved by comparing successive digital keying signals with a desired digital clip level. In the event that the clip level occurs between two successive digital signals an interpolation of the clip level between these is created fractionally. A digital representation of this fraction is then included in the keying signal so that keying is accomplished on a sub-pixel basis without acutally increasing the frequency of sampling.
01 May 1989
TL;DR: In this article, experiments were carried out within two differently constructed buildings using a 16 kb/s FSK (frequency-shift keying) modulator, where a low power transmitter broadcast a pseudorandom binary sequence (PRBS) from a low-level antenna (4.3 m) into the building.
Abstract: Experiments were carried out within two differently constructed buildings using a 16 kb/s FSK (frequency-shift keying) modulator. A low-power transmitter broadcast a pseudorandom binary sequence (PRBS) from a low-level antenna (4.3 m) into the building. A mobile receiver traversing a preplanned route within the building along several floors recorded the field strength as well as the bit error structure, a real-time clock and distance information. The evaluation and analysis was done on an MS-DOS personal computer. Analysis of the results reveals statistical distributions from which formulas were derived to describe the propagation environment. >
01 May 1989
TL;DR: In this paper, the pseudo-error method based on amplitude threshold variation is applied to differential detection of QPSK (quaternary phase-shift keying), OQPSK, DUOMSK, and MSK signals.
Abstract: The pseudoerror method based on amplitude threshold variation is applied to differential detection of QPSK (quaternary phase-shift keying), OQPSK (offset QPSK), DUOMSK (duobinary minimum-shift keying), and MSK signals. The objective of this differential-detection estimation was to reduce the simulation time required for bit-error-rate estimation relative to the Monte Carlo method. The gain in simulation time obtained in this way was shown in a specific case to be on the order of 5.5 and 8.7 for amplitude thresholds of 10 and 15%. The small approximation error values of the order of 0.1 to 0.4 dB obtained with these thresholds lead to the conclusion that the method gives very good results, permitting performance estimates for bit error rates smaller than 10/sup -4/. >
01 May 1989
TL;DR: Experiments on QPSK (quadrature phase-shift keying) signal transmission and 8 kb/s TC-WVQ speech coding and a proposed channel structure for implementation in a frequency-efficient digital mobile radio system are presented.
Abstract: Experiments on QPSK (quadrature phase-shift keying) signal transmission and 8 kb/s TC-WVQ (transform coding with weighted vector quantization) speech coding are presented. Computer simulation of the TC-WVQ speech codec has shown that the subjective quality is comparable to that of 5-bit log PCM (pulse code modulation) at a channel bit error rate of 10/sup -2/. Computation complexity can be greatly reduced compared with that of CELP. A proposed channel structure is presented for implementation in a frequency-efficient digital mobile radio system. With QPSK and 8 kb/s TC-WVQ speech codecs, such a digital mobile radio system is as frequency-efficient existing analog systems. >