Cyclical obstruction communication system
View Patent ↗Techniques for enabling broadband data rates at mobile terminals in a beyond-line-of-sight communication system are disclosed. Forward link time-diversity transmission methods and a time-diversity transmitter based upon blockage characteristics are provided. The transmitter optionally supports selective time-diversity and can operate at Ku-band or higher frequencies. A forward link time-diversity receiver and methods for receiving a forward link time-diversity signal are also disclosed. The forward link time-diversity receiver optionally provides low-jitter or low-delay characteristics. A return link transmitter and return link transmit methods which avoid blockages are also disclosed. The return link transmitter can include a signal presence detector and blockage prediction filter.
1. A method for transmitting data to helicopter based remote terminals in a satellite communication system, the data being transmitted from a gateway over a forward link communication channel, the method comprising:
receiving a data packet destined for a remote terminal that is located on a helicopter;
determining a transmit delay based upon a periodic blockage characteristic of the remote terminal that is associated with rotor blades of the helicopter;
transmitting a first copy of the data packet to the remote terminal at a first time;
scheduling the data packet for transmission to the remote terminal at a second time after the first time, the second time following the first time by the transmit delay; and
transmitting a second copy of the data packet to the remote terminal at the second time.
2. The method of claim 1 wherein the transmit delay is greater than a blockage duration of the remote terminal.
3. The method of claim 2 wherein the transmit delay is less than a blockage period of the remote terminal reduced by the blockage duration of the remote terminal.
4. The method of claim 1 , further comprising:
monitoring communication activity of the remote terminal, and wherein data from said monitoring is used to determine the transmit delay.
5. The method of claim 4 , further comprising:
dynamically updating the transmit delay based upon the data from said monitoring.
6. The method of claim 1 further comprising:
receiving a second data packet destined for a second remote terminal that is different from the first remote terminal; and
classifying the second data packet as obstructed or non-obstructed.
7. The method of claim 6 wherein the class of obstructed remote terminals includes helicopter-based communication systems and train-based communication systems.
8. The method of claim 6 , further comprising:
scheduling a burst of data packets for transmission at the first time, wherein the burst includes data packets destined for both obstructed and non-obstructed remote terminals.
9. The method of claim 1 wherein the transmit delay between the first and second time is determined based upon data received from the remote terminal.
10. The method of claim 9 wherein the data received from the remote terminal includes a blockage period of the remote terminal.
11. The method of claim 9 wherein the data received from the remote terminal includes a blockage duration of the remote terminal.
12. The method of claim 1 wherein scheduling the data packet further comprises adding the data packet to a delay buffer configured to implement the transmit delay between the first time and the second time.
13. The method of claim 1 , further comprising:
storing a copy of the data packet in a transmit buffer; and
transmitting the copy of the data packet at the second time.
14. The method of claim 13 , further comprising:
marking the data packet as an original packet; and
marking the copy of the data packet as a duplicate packet.
15. The method of claim 1 wherein the data packet is defined at the network layer.
16. The method of claim 1 wherein the data packet is defined at the transport layer.
17. The method of claim 1 , further comprising:
transmitting one or more parts of the data packet at the first time; and
transmitting said one or more parts of the data packet at the second time.
18. The method of claim 1 wherein data packets are transmitted using a continuous time-division multiplexed (TDM) signal.
19. The method of claim 1 wherein data packets are transmitted using a multiple-access communication protocol.
20. The method of claim 19 wherein the multiple access communication protocol is selected from the group consisting of time-division multiple access (TDMA) and multi-frequency time-division multiple access (MF-TDMA) protocols.
21. A method for transmitting data from a remote terminal to a gateway in a satellite communication system, the data being transmitted over a return link communication channel, the method comprising:
receiving a data packet for transmission at a remote terminal located on a helicopter;
determining a transmit delay based upon periodic blockage characteristics of the remote terminal; wherein the blockage characteristics are associated with a rotor of the helicopter;
transmitting the data packet to the gateway at a first time;
scheduling the data packet for transmission to the gateway at a second time after the first time, the second time following the first time by the transmit delay; and
transmitting the data packet to the gateway at the second time.