Showing papers on "Channel state information published in 1976"

Convolutional Code Performance in the Rician Fading Channel

Abstract: The performance of short constraint length convolutional codes in conjunction with binary phase-shift keyed (BPSK) modulation and Viterbi maximum likelihood decoding on the classical Rician fading channel is examined in detail. Primary interest is in the bit error probability performance as a function of E_{b}/N_{0} parameterized by the fading channel parameters. Fairly general upper bounds on bit error probability performance in the presence of fading are obtained and compared with simulation results in the two extremes of zero channel memory and infinite channel memory. The efficacy of simple block interleaving in combating the memory of the channel is thoroughly explored. Results include the effects of fading on tracking loop performance and the subsequent impact on overall coded system performance. The approach is analytical where possible; otherwise resort is made to digital computer simulation.

Performance of Phase-Locked Loops in the Presence of Fading Communication Channels

Abstract: An approach is presented for the analysis of phase-locked loops whose input signal has passed through time-varying channels. The specific channels considered in detail are the Rice-Nakagami, Rayleigh, and lognormal fading channels. Loop performance is characterized in terms of the steady-state probability density function of the reduced phase error process. The basic parameters which characterize performance include the loop signal-to-noise ratio (SNR) and the variance and bandwidth of the fading components introduced by the channel. Particular channel models are used to illustrate the theory for the firstorder loop. The results are also applied to the analysis of the PSK noisy reference problem in the presence of these time-varying channels.

An h.f. channel simulator using a new Rayleigh fading method

Abstract: The paper describes a new method of producing a discrete-level approximation to a Rayleigh fade by means of a quasi-random digital process. This offers considerable advantages over existing methods in cost, simplicity and flexibility, having an exactly repeatable fading pattern and a fading rate which may be easily changed by varying the digital clock rate. Mathematical analysis and experimental evidence show that the output closely approximates to a Rayleigh fade in all respects. A description is given of a prototype h.f. ionospheric channel simulator incorporating the design. In addition to Riceian fading the prototype allows the simulation of two-path propagation, Doppler shift, and additive Gaussian noise. Some practical applications of the simulator are discussed.

A Simple Buffer Control for Variable-Rate Communication Systems

Abstract: Transmission of data with receiver-controlled bit rate is an effective way to reduce the effect of signal-to-noise ratio (SNR) fluctuations, as in a fading channel. All previous publications on this subject ignore the critical topic of buffer size. This concise paper summarizes the results of the first study of the effect of finite buffers on a variable-rate system for fading channels.

On the steady-state error of the fading memory filter

Abstract: The steady-state error of the fading memory filter is studied for stable, two-dimensional models with an uncertainty in the form of a constant, unknown control input. For a set of these models, it is observed that any age-weighting of the data can cause an error greater than that of the Kalman filter. This contradicts previous assumptions about the fading memory filter.

A Study of Signal Decorrelation Through the Ionosphere

Abstract: Signals in a satellite-earth communication link pass through the ionosphere where there may exist random irregularities. These random irregularities will scatter and distort the Signal, producing a fading channel. Such a channel is generally characterized by the symmetric and asymmetric correlation functions. Approximate solutions for these functions have been obtained and the results plotted for typical ionospheric parameters. Some of the results are shown in terms of coherence bandwidth.

Buffer Requirements for Intermittent Data Transmission Over a Rayleigh Fading Channel

Abstract: Intermittent data transmission, that is, sending data only when the signal strength is above a desired threshold, has been shown to be extremely effective at combatting the effects of signal fading. However, such a system must usually interface with a uniform data source and sink by the use of finite buffers. When the buffer fills, transmission must occur during bad signal conditions and when it empties, no transmission can occur. The effect of such a finite buffer on system performance is derived and these theoretical results are validated using computer simulation. Finally, adaptive methods to improve performance are investigated and two areas of application of an intermittent System are examined.

Target Tracking Over Fading Channels

Abstract: The problem of tracking a target in a multitarget environment when the observations are received over a fading channel is considered. The optimal Bayes solution to the tracking problem in such cases involves growing memory and hence is not feasible. A particularly effective suboptimal scheme uses a probabilistic judgment at each stage of the observations to overcome this problem. This concise paper presents an evaluation of the scheme in terms of mean-square error performance when the observations are received over fading channels.