Apparatus and method for controlling forward error correction encoding in a very small aperture terminal
First Claim
1. A method for adjusting the forward error encoding rate of a VSAT each station digital data transmission comprising:
- measuring at a hub station the level of an echo signal produced in response to a transmission from said hub station to a satellite transponder;
determining from said level an indication of propagation conditions;
transmitting a signal from said hub station to a plurality of VSAT earth stations, said signal comprising said indication of propagation conditions; and
altering the forward error correction rate (FEC) of said VSAT earth station transmission in accordance with said indication of propagation conditions such that the bit error rate for said VSAT earth station transmissions is maintained below a predefined value.
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Accused Products
Abstract
A system for controlling forward error correction of a VSAT earth station is disclosed. A hub earth station communicating with the VSAT earth station transmits digital data representing a propagation condition measured at the hub earth station. The VSAT earth station computes an estimated inroute fade from the transmitted information, as well as from the VSAT demodulator'"'"'s estimate of propagation condition. When the total inroute fade is below a selected margin, a higher FEC encoding rate is selected for the VSAT transmitter in which to transmit its data packets to the hub earth station. As the estimated inroute fade exceeds a high FEC rain margin, a lower rate of FEC encoding is employed at the VSAT earth station. By permitting a higher FEC encoding rate, digital throughput is increased between the VSAT earth station and the hub station.
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Citations
13 Claims
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1. A method for adjusting the forward error encoding rate of a VSAT each station digital data transmission comprising:
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measuring at a hub station the level of an echo signal produced in response to a transmission from said hub station to a satellite transponder; determining from said level an indication of propagation conditions; transmitting a signal from said hub station to a plurality of VSAT earth stations, said signal comprising said indication of propagation conditions; and altering the forward error correction rate (FEC) of said VSAT earth station transmission in accordance with said indication of propagation conditions such that the bit error rate for said VSAT earth station transmissions is maintained below a predefined value. - View Dependent Claims (2, 3)
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4. A system for controlling the forward error correcting rate of a VSAT comprising:
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a hub earth station having an outroute transmitter for forwarding digital data modulated on an outroute carrier signal; a transmit power control for changing the level of power being transmitted by said hub earth station; an encoder means for generating from said level a data packet representing said level and for combining said packet with said digital data; a VSAT earth station for receiving said outroute carrier signal; a demodulator at said VSAT earth station for removing said packet from said digital data; an inroute transmitter for forwarding digital data from said VSAT earth station to said hub station over an inroute carrier; a forward error correcting encoder for encoding said VSAT digital data at multiple rates selectable by a control signal; and means for supplying said control signal to said forward error correcting encoder based on said data packet. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A VSAT earth station having an FEC encoding rate which varies in accordance with propagation conditions comprising:
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a radio frequency converter for providing an IF signal from a received outroute signal transmitted by a hub earth station via a satellite transponder, and providing an inroute radio frequency carrier signal for transmitting a data signal to said hub earth station; an outroute IF signal demodulator connected to receive said IF signal and to remove digital data packets contained in said IF signal; a baseband signal processor connected to receive said digital data packet from said outroute IF signal demodulator and to produce inroute digital data packets for transmission to said hub station; an FEC encoder for encoding said inroute digital data packets at a selectable FEC rate; means for estimating propagation conditions and supplying a signal for selecting said FEC rate based on said propagation conditions; and an inroute modulator for receiving said encoded inroute digital data packets and modulating said inroute radio frequency carrier with said encoded inroute digital data packets. - View Dependent Claims (11, 12, 13)
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Specification