Showing papers on "Channel state information published in 1988"
TL;DR: The performance of 8-PSK and 8-DPSK trellis codes is presented for a class of fast fading, land mobile satellite communication channels and optimality is found to be dependent on the presence of lognormal shadowing.
Abstract: The performance of 8-PSK and 8-DPSK trellis codes is presented for a class of fast fading, land mobile satellite communication channels. The fading model is Rician but, in addition, the line-of-sight path is subjected to a fast lognormal attenuation that represents tree shadowing. The fading parameters used in this study represent the degree of shadowing and are based on measured data. The primary application considered is for digital speech transmission and thus, bit error probabilities in the order of 10/sup -3/ are emphasized. Sensitivity of the bit error probability to amplitude fading, amplitude and phase fading, and decoding delay is presented. Performance is determined via digital computer simulation. Optimal four- and eight-state codes are determined and optimality is found to be dependent on the presence of lognormal shadowing. >
78 citations
15 Jun 1988
TL;DR: A 9600-b/s 16-QAM data system is used together with the transparent tone-in-band (TTIB) reference processing technique and excellent performance under both static and fading conditions is observed.
Abstract: The transmission of high-speed data to and from a mobile terminal is considered to be far from simple. Practical results for one solution to the problem, namely reference-base channel sounding, are presented. A 9600-b/s 16-QAM data system is used together with the transparent tone-in-band (TTIB) reference processing technique. Excellent performance under both static and fading conditions is observed. >
38 citations
TL;DR: Large and rapid timing fluctuations of eye pattern due to severe delay distortion of the multipath channel was found to be the most dominant source of error.
Abstract: The so-called irreducible error due to frequency-selective fading is known to have a serious effect on mobile radio communication systems. Thus, the analysis of such errors is a prerequisite for making high-speed digital signal transmission over a fading channel feasible. The authors attempted to elucidate the physical mechanisms causing such errors using laboratory measurements of microscopic bit error rate. The results clarified some sources of burst errors in a multipath fading channel. In particular, large and rapid timing fluctuations of eye pattern due to severe delay distortion of the multipath channel was found to be the most dominant source of error. >
27 citations
28 Nov 1988
TL;DR: The authors present the measured average bit error and block error ratio performance of a coherent burst time-division multiple-access radio link in a simulated flat Rayleigh fading environment using a unique technique for implementing two-branch selection diversity.
Abstract: The authors present the measured average bit error and block error ratio performance of a coherent burst time-division multiple-access radio link in a simulated flat Rayleigh fading environment using a unique technique for implementing two-branch selection diversity The link consists of a 500-kb/s quadrature amplitude modulation burst transmitter and a coherent receiver with a fast carrier recovery circuit The receiver is switched between two signals which are corrupted by uncorrelated Rayleigh fading If the transmitter is on before the actual data burst, received signal measurement and selection can be performed just before the reception of a data burst This way, when data is to be demodulated, the receiver is already switched to the branch with the higher power With this technique, the performance of selection diversity is achieved with only one receiver chain Experimental results are presented showing link performance as functions of Rayleigh fading rate and the time delay between signal measurement/diversity selection and the actual data burst >
24 citations
15 Jun 1988
TL;DR: The authors highlight the need for soft decisions and soft channel state information to extract the maximum benefit from Viterbi decoding on a channel as harsh as the one with Rayleigh fading.
Abstract: A study is reported of the unequal error protection capabilities of convolutional codes belonging to the family of rate-compatible punctured convolutional codes. The performance of these codes is analyzed and simulated for the fast-fading Rice and Rayleigh channels with differentially coherent 4-phase modulation. Interleaving performed over one or two blocks of 256 channel bits to mitigate the effect of fading. Examples are provided to show that it is possible to accommodate widely different error protection levels within short information blocks. The effect of the code and channel parameters is considered, such as the encoder memory, the code rate, interleaver depth, fading bandwidth, and the contrasting performance of hard and soft decisions on the received symbols. The authors highlight the need for soft decisions and soft channel state information to extract the maximum benefit from Viterbi decoding on a channel as harsh as the one with Rayleigh fading. >
24 citations
12 Jun 1988
TL;DR: For the Rayleigh fading model, it is found that, when the automatic gain control of the receiver is off, the received signal fades as in real-life transmission, as expected.
Abstract: Several fading models, including the general fading model, the Rayleigh fading model, and the simple three-path fading model are simulated to study the effect of fading in radio communication links. These models are implemented in hardware using computer control. The effect of fading is demonstrated using speech as the test signal. For the Rayleigh fading model, it is found that, when the automatic gain control (AGC) of the receiver is off, the received signal fades as in real-life transmission. When the AGC is on, the effect of fading is not noticeable most of the times but the noise level goes up when fading occurs, as expected. When the fading is severe, it is found that AGC cannot totally compensate for the fading; this is also expected. Other models are tested in a similar manner and yield expected results. >
8 citations
12 Jun 1988
TL;DR: A digital carrier recovery structure which allows coherent detection on frequency-nonselective fading channels is presented and it is shown that the structure is superior to a phase-locked loop and well suited for a fully digital realization.
Abstract: A digital carrier recovery structure which allows coherent detection on frequency-nonselective fading channels is presented. The synchronizer estimates the multiplicative distortion introduced by the channel. It is shown that the structure is superior to a phase-locked loop and is well suited for a fully digital realization. A detailed synchronizer design and simulation results are presented for a land-mobile radio channel. This includes a novel scheme for a fully digital frequency offset estimation and correction. >
8 citations
15 Jun 1988
TL;DR: The performance of an adaptive multipath diversity receiver, operating in a quasi-static frequency selective Rayleigh fading channel, is considered and probability-of-error expressions are presented for channels with uniform and nonuniform delay cross power spectra.
Abstract: The performance of an adaptive multipath diversity receiver, operating in a quasi-static frequency selective Rayleigh fading channel, is considered. Phase coded direct sequence spread spectrum signaling is used. The receiver formulation is presented as an extension of a previously derived result by the authors (1988). Probability-of-error expressions are presented for channels with uniform and nonuniform delay cross power spectra. The performance with multiuser interference is considered by invoking the Gaussian assumption. The validity of this assumption is verified through simulation. >
7 citations
19 May 1988
5 citations
TL;DR: A simulation case study of a high capacity digital radio link subject to frequency selective fading with M-QAM modulation and different types of channel encoding and high rate cyclic and convolutional codes.
2 citations
23 Oct 1988
TL;DR: The author presents an approximate formula for MFSK (M-ary frequency shift-keying) symbol error probability in nonfrequency selective fast Rayleigh fading, referring to channel decorrelation times on the order of a symbol duration.
Abstract: The author presents an approximate formula for MFSK (M-ary frequency shift-keying) symbol error probability in nonfrequency selective fast Rayleigh fading. Here, fast fading refers to channel decorrelation times on the order of a symbol duration. At the receiver, fast fading produces attenuation in the output of the filter matched to the transmitted signal and 'crosstalk' in the other filter outputs. These effects are studied quantitatively and lead to approximations which enable a simple formula for symbol error probability to be derived. The accuracy of this formula is determined by computer simulation. >
12 Jun 1988
TL;DR: An estimator correlator receiver structure is developed based on the likelihood ratio test, and for reasonable SNRs the estimator can be realized as simple linear averaging, which is asymptotically optimal.
Abstract: Adaptive reception of binary data over a frequency selective slow Rayleigh fading communication channel, through wideband signaling, using spectral spreading codes is considered. Based on the likelihood ratio test, an estimator correlator receiver structure is developed. The receiver structure includes the effects of estimation errors, which are usually neglected. The estimator is a Wiener-Hopf filter, and for reasonable SNRs the estimator can be realized as simple linear averaging, which is asymptotically optimal. In practice, the linear averaging may have to be modified by using exponential weights to prevent runaway due to decision errors. The receiver performance is a function of estimation error variance, which depends on the channel SNR, multipath spread and profile, fade rate, and multiuser interference, when used for SSMA (satellite-switched multiaccess) applications. >
12 Jun 1988
TL;DR: Experimental results are presented for the multipath channel characterization of a 40 MHz wide RF channel in the 4 GHz band and the effects of bandwidth on in-band power-difference are described.
Abstract: Experimental results are presented for the multipath channel characterization of a 40 MHz wide RF channel in the 4 GHz band. The 40 MHz wide test signal is transmitted over a 52 km hop. The space diversity receiver combines the test signal using a continuous phase maximum power technique. Channel responses are measured on the main antenna, the diversity antenna, and the combined channel. The effects of bandwidth on in-band power-difference are also described. >
01 May 1988
TL;DR: Results indicate that impulse response extension by means of bit smearing appears to be a useful technique for correcting errors due to impulse noise or signal fading in a binary channel.
Abstract: A finite impulse response (FIR) digital smearing filter was designed to produce maximum intersymbol interference and maximum extension of the impulse response of the signal in a noiseless binary channel. A matched FIR desmearing filter at the receiver then reduced the intersymbol interference to zero. Signal fades were simulated by means of 100 percent signal blockage in the channel. Smearing and desmearing filters of length 256, 512, and 1024 were used for these simulations. Results indicate that impulse response extension by means of bit smearing appears to be a useful technique for correcting errors due to impulse noise or signal fading in a binary channel.
15 Jun 1988
TL;DR: In this article, the performance of multisubchannel direct-sequence spread-spectrum multiple-access systems in multipath fading channels was investigated, where a wideband channel is divided into several subchannels and each subchannel carries the same messages but is modulated by different pseudo-random sequences.
Abstract: The performance of multisubchannel direct-sequence spread-spectrum multiple-access systems in multipath fading channels is investigated. A wideband channel is divided into several subchannels and each subchannel carries the same messages but is modulated by different pseudo-random sequences. Independent fading in different subchannels is assumed. The upper and lower bounds of the system error probability are derived. Numerical computation shows that, over multipath fading channels, for a given system processing gain, the multisubchannel direct-sequence spread-spectrum multiple-access system has a performance advantage over the single-channel system. The results obtained also hold for conventional direct-sequence spread-spectrum multiple-access systems with diversity technique. >
28 Nov 1988
TL;DR: A two-ray model for multipath fading is described, which incorporates the effects of the angular structure of the incident signal and is, therefore, potentially suitable for angle diversity applications.
Abstract: A two-ray model for multipath fading is described. The model incorporates the effects of the angular structure of the incident signal and is, therefore, potentially suitable for angle diversity applications. The model has four variables. Adjustment of the statistical parameters of these variables makes it possible to match statistics of data obtained from experiments. Through a simulation based on this model, both the single frequency fading and IBPD (inband power difference) statistics of experimental data obtained in Gainesville, FL, for two antennas tilted at different elevation angles have been matched approximately using a single set of parameters. >