Shahrokh Marzban; Kamal Mohamedpour; Somye Pirzadi
Volume 5, Issue 3 , October 2012, , Pages 21-31
Abstract
After setteling the LEO satellite in the given circuit, the ground station needs to communicate with it for the received of information and control of its subsystems. Due to the fact that satellite communication channels are influenced by shadowing conditions, if a line of sight (LOS) signal exists between ...
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After setteling the LEO satellite in the given circuit, the ground station needs to communicate with it for the received of information and control of its subsystems. Due to the fact that satellite communication channels are influenced by shadowing conditions, if a line of sight (LOS) signal exists between the receiver and the transmitter, then the radio channels conditions are good and the Additive White Gaussian Noise channel is modeled as Rician distribution. However, under poor conditions and in the lack of LOS, channel model is Rayleigh, and due to the radio link conditions the channel will be switched between these two models. In a proper model, the time varying behavior of the station – satellite radio link should be considered. The importance attached to this issue is due to its considerable effect on the selection of modulation type, design of channel access method, and error control. In this view, the present study has sought to momentarily determine the range of variations in error probability. Through calculations and simulation, the Bit Error Rate received during the satellite trajectory has been obtained for any given moment and its range of variations has been determined.
SH. Marzban; K. Mohamedpour
Volume 2, Issue 1 , April 2009, , Pages 1-12
Abstract
Aeronautical telemetry system is applied to real flight conditions and movements so as to test the efficiency of different parts of an air vehicle such as an airplane, a missile, and a space shuttle during the flight. In order to study, determine and lessen the deleterious effects of the air vehicle's ...
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Aeronautical telemetry system is applied to real flight conditions and movements so as to test the efficiency of different parts of an air vehicle such as an airplane, a missile, and a space shuttle during the flight. In order to study, determine and lessen the deleterious effects of the air vehicle's flight maneuvers upon the aeronautical telemetry radio link, an urgent need for measuring the instantaneous communication angles between the telemetry receiver antenna and the transmitter antenna mounted on the air vehicle is highlighted. In the context of the values of these instantaneous communication angles, the gain from the telemetry receiver antenna and from the transmitter antenna throughout the flight trajectory can be obtained. It should be noted that in most previous studies, however, the gain from the receiver antenna during the test has been assumed to remain constant because the telemetry receivers have been provided with a system of auto-tracking the air vehicles. In order to study the improvements suggested by using coding, modulation, and other communication techniques and methods in the aeronautical telemetry radio link, a suitable model of real telemetry canal should be developed. By use of particular aeronautical navigation equations, the present paper is going to first develop an algorithm for measuring the instantaneous communication angles between the telemetry receiver antenna and the air vehicle during the flight. The equations are thus solved. After working out the equations, the value of the instantaneous power received by the receiver at any instant of the flight can be determined. On the basis of the suggested algorithm and through the simulation of the radio link (along the entire flight trajectory of an assumed air vehicle) the probability of the bit error rate of the collected data for some propagation environment of aeronautical telemetry can be found.
