Showing papers on "Path loss published in 1985"
TL;DR: It is determined that the excess path loss, or fade margin, of a Rician channel will change the envelope statistics of the received waveform from Rayleigh to a more favorable Rician distribution when coherent detection of binary phase shiftkeying or quaternary phase shift keying signals is considered.
Abstract: Excess path loss due to multipath severely restricts the performance of power limited mobile networks such as those using satellite-aided links. To reduce multipath related losses, the higher elevation angle of the spacecraft can be exploited by utilizing mobile antennas which reduce the strength of the multipath reflections in favor of the line-of-sight signal. The presence of a strong and stable path in a fading link will change the envelope statistics of the received waveform from Rayleigh to a more favorable Rician distribution. It is determined that the excess path loss, or fade margin, of a Rician channel when coherent detection of binary phase shift keying (BPSK) or quaternary phase shift keying (QPSK) signals is considered. The results are presented parametrically such that they can be applied to a wide range of propagation characteristics from heavy fading to nonfading situations. Furthermore, similar results are also given for the case where only limited coverage is provided.
33 citations
TL;DR: In this paper, a comparison of relative performance, sensitivities to meteorological inputs, and ease of computation for three standard evaporation duct models and two electromagnetic wave propagation models is presented.
Abstract: This paper will evaluate the current meteorological measurement techniques used to infer the evaporation-ducting process. Included within this study is a comparison of relative performance, sensitivities to meteorological inputs, and ease of computation for three standard evaporation duct models and two electromagnetic wave propagation models. The evaporation duct models performed reasonably and equally well when considering statistically averaged meteorological inputs, but all were extremely sensitive to point-observed meteorological input parameters. The measurement techniques employed by naval and transiting commercial vessels are not of sufficient quality to infer adequately the evaporation-ducting process. The theory behind calculation of path loss values based upon current evaporation duct inputs is statistically sound. For studies of propagation phenomena or development of electromagnetic systems, both of the compared models perform reasonably well and are accurate predictors. However, the use of either model for estimation of a single propagation range based upon a point meteorological observation is severely limited by the accuracy of the data.
12 citations
1 Oct 1985
TL;DR: A model which predicts the actual measured value is within a standard deviation of 3 dB instead of 8 dB from the predicted value is introduced, which can be used to select a new optimum site based upon the battlefield condition.
Abstract: The Longley-Rice propagation path-loss prediction model,1,2 developed by the National Telecommunications and Information Administration (NTIA) mainly for troposcatter transmission and long-range line-of-sight transmission, has often been suitable for ground mobile radio propagation by adding an adjustment factor for urban areas. Since the model was not originally developed for a mobile radio environment, it does not provide a desired mean value which should match experimental values to a standard deviation of 8 dB. Okumura's model,3 obtained from empirical data gathered in the Tokyo area, has been used for commercial mobile radio because this model was designed specifically for the mobile radio environment. Although it is not a proper model for predicting the propagation path-loss in the United States, most measured values are within 8 dB of the mean predicted value. This paper introduces a model which predicts the actual measured value is within a standard deviation of 3 dB instead of 8 dB from the predicted value. A more accurate prediction of path loss can enhance a military system's performance. In the military environment set of base station sites must be properly chosen to allow optimum connectivity for tactical mobile radio communications. This model provides such information. Each time the base station is removed to a new site, this model can be used to select a new optimum site based upon the battlefield condition.
6 citations
TL;DR: In this article, the average basic transmission loss of the scattered component, Lbs can be found if K (ratio of r.m.s. value of scattered and constant component) and the resultant Basic transmission loss Lbm are known.
Abstract: Tropospheric scatter study beyond the horizon radio link presently necessitates tests to establish the median path loss and to determine the magnitude and duration of the path loss variations. The average basic transmission loss of the scattered component, Lbs can be found if K (ratio of r.m.s. value of scattered and constant component) and the resultant basic transmission loss Lbm are known. This paper also deals with the diurnal and seasonal behaviour of signal strength, based on the ana!ysis of about ten months recording on a C band Troposcatter Link between Pilani and Delhi.
2 citations
TL;DR: In this paper, a hand-held roving transmitter and a receiver located at street-lamp elevations were made in urban and rural locations, and the propagation distance exponent was approximately 2.2, and fades 20 dB below the mean envelope level occurred 1% of the time.
Abstract: Propagation measurements of 60 GHz transmissions between a hand-held roving transmitter and a receiver located at street-lamp elevations were made in urban and rural locations. The propagation distance exponent was approximately 2.2, and fades 20 dB below the mean envelope level occurred 1% of the time.