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A New Algorithm for Improving the Remote Sensing Data Transmission over the LEO Satellite Channels

A New Algorithm for Improving the Remote Sensing Data Transmission over the LEO Satellite Channels. Ali Payandeh and Mohammad Reza Aref Applied Science Research Association (ASRA) Department of Electrical Engineering, K.N. Toosi University of Technology Tehran, Iran

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A New Algorithm for Improving the Remote Sensing Data Transmission over the LEO Satellite Channels

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  1. A New Algorithm for Improving the Remote Sensing Data Transmission over the LEO Satellite Channels Ali Payandeh and Mohammad Reza Aref Applied Science Research Association (ASRA) Department of Electrical Engineering, K.N. Toosi University of Technology Tehran, Iran International Conference on Engineering Education (ICEE) Silesian University of Technology, Gliwice, Poland July 2005

  2. Outline • Introduction • LEO Satellite Channel Modeling • Problem Statement • Proposed Scheme Structure • Simulation Results • Conclusions

  3. Introduction • Remote sensing imagery produces large amounts of data that needs to be reliably transmitted over a band-limited channel. • Today’s performance requirements of real time on-board satellite communication systems are demanding lower consumption energy. • During the data transmit in the communications field of view area, distance between the LEO satellite and ground station changes. • We derive an adaptive data protection method, which is based on the modeling of the channel and compensation change of distance between satellite and ground station.

  4. LEO Satellite Channel Modeling SNR in ground receiver’s input is calculated by: is the satellite transmitter power, is the satellite transmitter antenna’s gain, is the ground station antenna’s gain, is the total noise power and is the total path losses We use the following approximation equation for LEO satellite channel modeling:

  5. Problem Statement • The distance between satellite and ground station has a considerable effect on performance of the communications system. • The distance in the LEO satellite’s configuration changes continuously. • For access to the desirable image’s quality, a pre-specified bit error probability usually is enough. If bit error rate reduces from the pre-specified value, received image’s quality in practical doesn’t change considerably. • Therefore, designing the on-board data transmit system for the worst case of communications channel, concludes to a wasteful use of communication system resources. • To overcome this problem, we propose a variable error-correction coding scheme.

  6. Distance Between LEO Satellite and Ground Station Ri R90 Ri+90 R0 R180

  7. Proposed Scheme Structure • We use a variable block coding, which its bit protection can be varied in accordance with the distance, so that the bit error probability is fixed at a pre-specified value . • The design constraint is a given total received data . • Bit error probability for a block code in the case of AGWN is given by: . .

  8. For the assumed , an appropriate approximation is: • We obtain: • If varies based on above equation with elevation angle, bit error probability doesn’t change in the whole of communicate séance. • The problem is to calculate the transmission rate and power, subject to . ,

  9. A tradeoff must be done between three parameters: (coding complexity), (consumption energy) and (bandwidth). • Two special cases: • Constant and known: B. Constant and known:

  10. Simulation Results • Since the error-correction code with continuous variation isn’t discovered yet, we use a method with discrete variation in simulation. • In this method, a lookup table of various error-correction codes is used. In each step, one appropriate error-correction code is selected from table based on value. • For implementation the improved remote sensing data transmission system, we use the standard BCH codes.

  11. Type Basic system Improved system I II III Performance Comparison of the Basic and Improved Data Transmission Systems

  12. Theoretical improved system Case III Case I Case II Basic system Bit Error Rates for the Basic and Improved Data Transmission Systems Versus Elevation Angle

  13. Conclusions • We proposed an analytical approach to determine an adaptive policy for selecting the error-correction code with bit protection proportional to change of distance between the LEO satellite and ground station. • This method provides transmission rate and power better than traditional systems. • The simulation results show that this scheme is a more effective tool for the LEO satellite data transmission.

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