Showing papers in "IEEE Transactions on Broadcasting in 1993"
TL;DR: The channel response results presented suggest that polarization diversity may be a useful technique for mitigating some of the channel impairments predicted by the propagation model.
Abstract: A propagation model is presented for characterizing the channel response for digital systems in urban areas where multiple reflections from buildings are encountered. A deterministic ray-tracing propagation model is used to predict the time delay and fading characteristics for the channel in a hypothetical urban area. The analysis shows that due to multiple reflection and diffraction sources, the RMS delay spread of the channel in urban areas can be several hundred nanoseconds, so that very effective equalizers will be required to achieve successful performance of high-data-rate digital systems such as 20-Mb 16-QAM digital HDTV. The channel response results presented also suggest that polarization diversity may be a useful technique for mitigating some of the channel impairments predicted by the propagation model. >
96Â citations
TL;DR: It is concluded that the power and spectrally efficient F-QPSK make it an excellent candidate for future high-capacity personal communication system (PCS) networks.
Abstract: A brief review of the principles and properties of F-QPSK (quadrature phase shift keying) modulation is given. Its spectral efficiency is compared with that of Gaussian minimum-shift keying (GMSK) using adjacent channel interference (ACI) as a parameter. It is established that in a noncellular environment, hardlimited F-QPSK has a spectral efficiency of 1.42 b/s/Hz, which is up to 51% more spectrally efficient than GMSK BT=0.5 for ACI=20 dB. F-QPSK's BER performance in AWGN and Rayleigh fading channels is shown to be superior to that of GMSK. The spectral efficiency of the modulations in cellular/microcellular environments where frequency is reused in geographically separate cells to achieve higher capacity is compared. It is shown that the application of F-QPSK in such environment would leads to a 95% increase of system capacity compared to GMSK. It is concluded that the power and spectrally efficient F-QPSK make it an excellent candidate for future high-capacity personal communication system (PCS) networks. >
70Â citations
TL;DR: Results show that in wide-area networks, very low outage probabilities may be achieved with very modest transmitter powers, which implies that good network planning results in low-power, closely spaced transmitters.
Abstract: The new digital modulation schemes (OFDM) proposed for broadcasting of sound and television allow for the use of simulcasting, i.e., letting all transmitters in a radio network transmit on the same frequency. Such single-frequency networks (SFNs) have the potential of providing good coverage and very good frequency economy in wide-area (nationwide) applications. An OFDM-based SFN is analyzed with respect to its coverage properties. The network performance is measured by the outage probability and frequency economy. Both wide and local area systems are considered. Results show that in wide-area networks, very low outage probabilities may be achieved with very modest transmitter powers. The main reason for this is the inherent diversity, the efficiency is of which is primarily dependent on the transmitter density. However, in local area systems with only a few transmitters in each region, the performance is shown to drop drastically, mainly due to the low degree of diversity. This work implies that good network planning results in low-power, closely spaced transmitters. >
67Â citations
TL;DR: The audio quality, robustness and implementational complexity of a novel mobile digital audio broadcast scheme are addressed and the audio codec proposed is based on an efficient combination of subband coding and multipulse excited linear prediction coding.
Abstract: The audio quality, robustness and implementational complexity of a novel mobile digital audio broadcast scheme are addressed. The audio codec proposed is based on an efficient combination of subband coding (SBC) and multipulse excited linear prediction coding (MPLPC). The bit allocation is dynamically adapted according to both the signal power in different subbands and a perceptual hearing model. Typically a segmental signal to noise ratio (SEGSNR) in excess of 30 dB associated with high fidelity subjective quality was achieved for 2.67-b/sample transmissions at a bit rate of 86 kb/s. Perceptually unimpaired audio quality was achieved for a bit error rate (BER) of about 10/sup -4/, when injecting random errors, which was degraded for increased BERs. In order to provide robust error protection, the audio codec was also subjected to a rigorous bit sensitivity analysis. Four different forward error correction schemes were investigated in order to explore the complexity, bit rate, and robustness tradeoffs. >
19Â citations
TL;DR: The Zenith/AT&T digital spectrum compatible high definition television (DSC-HDTV) data transmission system is currently one of the systems being evaluated for the consideration as a US broadcast standard.
Abstract: The different power measurement techniques used for NTSC (peak envelope power) and HDTV (average power and peak-to-average power ratio) are described. A brief description of a digital data transmission system is included to show why the HDTV signal is noiselike in nature and how it can be measured. A new type of RF analyzer with the ability to statistically measure peak-to-average power ratio is presented. The Zenith/AT&T digital spectrum compatible high definition television (DSC-HDTV) data transmission system is currently one of the systems being evaluated for the consideration as a US broadcast standard. Examples of signal measurement for this system are provided. >
10Â citations
TL;DR: The recently released Federal Communications Commission ATV System Recommendation put forth by the FCC's Advisory Committee on Advanced Television Service is reprinted in its entirety as discussed by the authors, which summarizes some very significant tests and highly detailed technological advances.
Abstract: The recently released Federal Communications Commission ATV System Recommendation put forth by the FCC's Advisory Committee on Advanced Television Service is reprinted in its entirety. This report summarizes some very significant tests and highly detailed technological advances. >
9Â citations
TL;DR: A highly versatile digital modulator that uses a direct digital synthesis method to perform signal modulation is described, based on directly accessing many of the digitally stored carrier modulating symbols according to the information bearing input signals.
Abstract: A highly versatile digital modulator that uses a direct digital synthesis method to perform signal modulation is described. In contrast to the customary methods of implementing I-Q modulation schemes utilizing in-phase and quadrature branches, this design approach is based on directly accessing many of the digitally stored carrier modulating symbols according to the information bearing input signals. Apart from the digital-to-analog converter, all the previous stages are digital. To demonstrate the concept, a differential 16-QAM modulator was implemented. The technique lends itself to VLSI implementation. It can be considered as a digital implementation of a digital modulator. >
7Â citations
TL;DR: An overview of test equipment and applications targeted specifically for digital broadcast signal distribution is given, and the vector generator and analyzer evaluate the constellation accuracy, give direct conclusions with regard to the source of impairments, and allow SER (symbol error rate) estimates.
Abstract: An overview of test equipment and applications targeted specifically for digital broadcast signal distribution is given. The vector generator and analyzer evaluate the constellation accuracy, give direct conclusions with regard to the source of impairments, and allow SER (symbol error rate) estimates. Peak power and peak-to-average power ratio, key parameters in digital broadcasting, are monitored with the digital video power analyzer. The power distribution functions of the power analyzer may prove useful as an economic tool for linearity and group delay adjustments. The effects of potential impairments in the transmission path, like reflections, multipath signals, or Doppler effects from antenna sway, can be evaluated with a channel simulator. The bottom line assessment of a total system's transmission quality is delivered by BER (bit error rate) measurements from modulator input to receiver demodulator output. >
7Â citations
TL;DR: It is concluded that, although RDS may be essential to the early phases of introduction of novel advanced traffic information systems (ATISs), FM subcarrier transmission does not offer a spectrum-efficient solution for large-scale ATIS datacasting.
Abstract: The paper addresses the use of the radio data system (RDS) for datacasting road traffic information. It is concluded that, although RDS may be essential to the early phases of introduction of novel advanced traffic information systems (ATISs), FM subcarrier transmission does not offer a spectrum-efficient solution for large-scale ATIS datacasting. The conclusions are believed relevant to the spectrum-efficient design of the future datacasting networks. >
6Â citations
TL;DR: An 8-14 channel coding method suitable for high density recording for digital VTRs was developed and provides simplified recording and reproduction equalization, azimuth and overwrite recording, no error propagation to any other word, and error detection.
Abstract: An 8-14 channel coding method suitable for high density recording for digital VTRs was developed. Using this coding, an 8-b data word is transformed into 14-b code word, assuming that the distance between magnetic polarity transitions is two to seven channel bits, the maximum absolute of the DSV (digital sum variation) is seven. The code has a minimum recorded wavelength 14% longer and a required bandwidth 12.5% narrower than those of S-NRZ and M/sup 2/ codes. Since it is a run-length-limited block code, it provides simplified recording and reproduction equalization, azimuth and overwrite recording, no error propagation to any other word, and error detection. The signals encoded by applying this method as well as S-NRZ and M/sup 2/ to 64-Mb/s M-sequence data were recorded and reproduced using metal particle tape and a Sendust laminated sputtered type head. The results show that the reproduced SNR of 8-14 channel coding was 2.8 dB higher than those of S-NRZ and M/sup 2/. >
5Â citations
TL;DR: In this paper, the authors proposed a scheme that combines superposed quadrature amplitude modulation (SQAM) filtering with the pi/4-shift quadratures phase-shift keying (QPSK) digital transmission format adopted for the first generation of US digital cellular systems.
Abstract: A strategy that reduces the spectral spreading when an ideal hard-limiter is used as a first approximation to a fully saturated power amplifier is presented. This strategy combines superposed quadrature amplitude modulation (SQAM) filtering with the pi /4-shift quadrature phase-shift keying (QPSK) digital transmission format adopted for the first generation of US digital cellular systems. Simulation results showed that this pi /4 SQAM filtering strategy increased capacity by 35% in comparison to hard-limited pi /4 QPSK. Using computer-aided design, a receive filter that would limit the degradation of E/sub b//N/sub 0/ to less than 1.4 dB at a bit error rate of P/sub e/=10/sup -4/ was selected. >
TL;DR: In this article, a method for feeding the elements of an antenna array with a lossy transmission line section is presented, and the behavior of the system in a frequency band around the design frequency is studied.
Abstract: A method for feeding the elements of an antenna array with a lossy transmission line section is presented. Four examples showing the applicability of the method are given. The behavior of the system in a frequency band around the design frequency is studied. Besides changes of physical length, changes in the frequency bandwidth of the antennas are observed. >
TL;DR: In this article, a Gaussian minimum-shift keying (GMSK) modem with built-in fade canceler is proposed narrowband mobile digital broadcasting systems, which combines DC suppressing line code and high-pass filters to create a spectral null at the carrier frequency of the transmit GMSK signal spectrum.
Abstract: A Gaussian minimum-shift keying (GMSK) modem with built-in fade canceler is proposed narrowband mobile digital broadcasting systems. The proposed scheme combines DC suppressing line code and high-pass filters to create a spectral null at the carrier frequency of the transmit GMSK signal spectrum. This enables an unmodulated carrier pilot tone to be transmitted with the digital broadcast signal without mutual interference. In the receiver, the recovered pilot is used to coherently demodulate the received signal without phase ambiguity. The pilot can be also be used to track and cancel out the random phase noise induced by fast fading. The scheme is applied to a 16 kb/s BT=0.25 GMSK signal with B/sub v/=800 Hz, and its performance over a fast Rayleigh fading channel is investigated using computer simulation. The results demonstrates that the proposed coherent modem is capable of significantly outperforming conventional differential detection in fast fading environments such as a broadcasting channel for mobile reception. >
TL;DR: In this paper, it was found that the two-dimensional Fourier transform of a picture impaired by intermodulation beat products contains distinguishable pulses with special characteristics, and based on these properties, a method was designed which can detect these pulses, even if the picture is also impaired by snow as long as the inter modulation impairment is visible to the human eyes.
Abstract: It was found previously (Ward and Zhang 1992) that the two-dimensional Fourier transform of a picture impaired by intermodulation beat products contains distinguishable pulses. Each product results in four pulses with special characteristics. The authors further analyze and study the intrinsic properties of these pulses. Based on these properties a method is designed which can detect these pulses, even if the picture is also impaired by snow as long as the intermodulation impairment is visible to the human eyes. >
TL;DR: Several aspects of terrain databases used in radio communication system planning tools are considered and it has been found that parameters like grid size, interpolation methods, propagation models, etc. used in this type of application differ from one application to another.
Abstract: Several aspects of terrain databases (TDBs) used in radio communication system planning tools are considered. It has been found that parameters like grid size, interpolation methods, propagation models, etc. used in this type of application differ from one application to another. Some of these parameters are analyzed in order to evaluate their influence on the overall prediction error. >
TL;DR: An introduction is given to the principles of digital modulation as it is being applied to advanced television by comparison with the way in which chrominance information modulates the NTC color subcarrier.
Abstract: An introduction is given to the principles of digital modulation as it is being applied to advanced television by comparison with the way in which chrominance information modulates the NTC color subcarrier. The concept of the unit circle in constellation diagrams is explained for both signal-to-noise ratio and signal-to-interference. Using constellation diagrams, the effects of AM/AM and AM/PM and their combined effects are shown in terms of reducing noise/interference margins. it is seen that the dynamic range of the ATV transmitter must be sufficient to handle the transient peak power which results from filtering to constrain the data to the 6-MHz channel. Out-of-channel spectral components are generated by intermodulation in the high-power amplifier, as are in-channel intermodulation components which are responsible for reducing the eye opening. This results in reduction in noise/interference margins. It is shown that nonlinear amplification of the transient peaks results in intermodulation products that may cause interference to a signal on adjacent channels and reduce expected coverage. >
TL;DR: In this paper, the frequency performance of a Wilkinson power divider with tightly coupled wires in ferrite is obtained using the theory of coupled distributed lines and the lowest and highest frequencies are connected to ferrite performance and electrical angle of the wires.
Abstract: The frequency performance of a Wilkinson power divider with tightly coupled wires in ferrite is obtained using the theory of coupled distributed lines. The lowest and highest frequencies are connected to ferrite performance and electrical angle of the wires. The results are relevant to the use of the divider in CATV systems. >
TL;DR: Different approaches to feeding two multiple-tuned VLF antennas with regard to antenna performance and tuning are compared, and connected element systems are particularly stable.
Abstract: Different approaches to feeding two multiple-tuned VLF antennas with regard to antenna performance and tuning are compared. Both antennas may be fed separately, or only one may be fed and the other grounded through a previously tuned coil. The antennas may either be connected or separated at their capacitive ends. The maximum bandwidth-efficiency product of all these arrangements is the same. Connected antenna systems achieve this maximum for all adjustments with in-phase base currents, and the most favorable tuning depends on the efficiency desired. If only one antenna is fed, the tuning procedure is quite simple, because only current magnitudes have to be adjusted. Retuning of the coils in the nonfed upleads is not necessary if changes are small compared with the magnitude of the antennas' coupling reactances. Connected element systems are particularly stable. These properties can be transferred to other multiple-tuned antenna systems of electrically short elements with top capacitances. >
TL;DR: In this paper, the effects of rectangular, linear, and raised cosine ramp on/off switching were examined for two prototypes using both hardware experimental methods and computer simulation for different gating rates, duty cycles, roll-off factors of transmitter filter and ramp on-off times.
Abstract: A better switching technique for combating spectral pollution i.e. spectral spreading of burst time-division multiple access (TDMA) digital FM and pi /4-QPSK (quadrature phase-shift keying) systems, is proposed. The effects of rectangular, linear, and raised cosine ramp on/off switching are examined for two prototypes using both hardware experimental methods and computer simulation for different gating rates, duty cycles, roll-off factors of transmitter filter and ramp on/off times. The measures results agree with the computer simulation results and indicate that the adjacent channel interference (ACI) caused by the burst operating in TDMA pi /4-QPSK is significantly reduced by raised cosine switching in comparison with other types of switching. >
TL;DR: Theoretical and experimental evaluation of the objective signal-to-noise performance of component video signals is described and objective noise impairments in 100% saturated primary and secondary colors have been determined.
Abstract: Theoretical and experimental evaluation of the objective signal-to-noise performance of component video signals is described. Using a mathematical model, an expression for the component video-signal-to-noise ratio, called the display-signal-to-noise-ratio (DSNR), is derived for Gaussian white noise input. Using this model the signal-to-noise performance of 100% saturated primary and secondary colors are analyzed for a PAL-I video system. In order to verify the theoretical results, an electronic color video circuit was implemented. Using this simulator, objective noise impairments in 100% saturated primary and secondary colors have been determined. >
TL;DR: In this article, computer-modeling exercises performed indicate that it is possible to add a group of four elevated radials to a pre-existing conventional AM-broadcast vertical monopole antenna system in order to restore performance to its original level (or better) in situations where the ground system has been damaged.
Abstract: Computer-modeling exercises performed indicate that it is possible to add a group of four elevated radials to a pre-existing conventional AM-broadcast vertical monopole antenna system in order to restore performance to its original level (or better) in situations where the buried-radial ground system has been damaged. A wide variety of different configurations for the elevated radials are examined, including variations in orientation, length, and height above ground. It is stressed that extensive outdoor testing should be performed in order to verify these computer predictions. The computer software used is the Numerical Electromagnetics Code. >
TL;DR: Investigation of the required cross-polar protection ratio at the terrestrial receiving antenna for satellite transmission planning provides useful and realistic results for efficient channel allocation in the spectrum band of broadcast satellite systems.
Abstract: A study including simulation and a measurement campaign using live TV broadcast satellite signals and receiving commercial equipment has been carried out to investigate the required cross-polar protection ratio at the terrestrial receiving antenna for satellite transmission planning. This experiment provides useful and realistic results for efficient channel allocation in the spectrum band of broadcast satellite systems. Among them is the frequency offset required between cross-polar channels, depending on the cross-polar rejection at the receiving antenna, for a certain degree of video signal impairment due to the cross-polar channel interference effect, and taking into account the noise contribution to the signal. A worst case in frequency offset value, i.e., larger subjective impairment of the picture at equal carrier to noise ratio (CNR), has been detected around 5 MHz (near the chroma carrier in G-PAL system 4.43 MHz) only for high values of CNR. Different subjective degradation of the image due to cross-polar channel interference and noise has been observed, and their particular contributions to impairment have been evaluated. >