IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
UP-0378563
(2006-03-17)
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등록번호 |
US-7643441
(2010-02-11)
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발명자
/ 주소 |
- de La Chapelle, Michael
- McLain, Christopher J.
- Niesen, Joseph W.
- Parkman, David S.
|
출원인 / 주소 |
|
대리인 / 주소 |
Harness, Dickey & Pierce, P.L.C.
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인용정보 |
피인용 횟수 :
8 인용 특허 :
4 |
초록
A satellite communications method for communicating information from a base station, via a satellite, to one or more user terminals via a single channel of a forward link.
대표청구항
▼
What is claimed is: 1. A satellite communications method for communicating information from a base station, via a satellite, to one or more user terminals via a single channel of a forward link, said method comprising: providing a satellite having a satellite transponder; determining a separate inf
What is claimed is: 1. A satellite communications method for communicating information from a base station, via a satellite, to one or more user terminals via a single channel of a forward link, said method comprising: providing a satellite having a satellite transponder; determining a separate information rate for information to be transmitted from the base station to each of the user terminals, using the satellite, such that a predetermined amount of margin above a threshold energy per bit to power spectral density noise ratio (Eb/No) is provided in the forward link; formatting data received at the base station into a continuous time division multiplexed (TDM) data stream including a plurality of data frames to be transmitted to the user terminals via the forward link, each data frame formatted to have the determined information rate of the respective user terminal that is to receive the data frame; transmitting the TDM data stream on a single carrier of the forward link, using the satellite; continuously and dynamically adjusting the information rate of subsequent data frames transmitted on the forward link from the base station, via the satellite, for each user terminal to maintain successful communication and maintain the predetermined amount of margin as operating conditions of each user terminal change; and maintaining an approximately constant occupied signal bandwidth of the TDM data stream using spread spectrum modulation as the information rate is changed from data frame to data frame. 2. The method of claim 1, wherein formatting data received comprises formatting the data frames with a substantially fixed forward error correction coding rate, and a substantially fixed modulation order that achieves the minimum threshold Eb/No and a constant direct sequence spread spectrum chipping rate, while the information rate is continuously and dynamically adjusted from frame to frame. 3. The method of claim 2, wherein formatting data received comprises: applying the forward error correction coding and modulation order that provides the minimum threshold Eb/No to all data frames for a selected group of the most disadvantaged user terminals to adapt to each disadvantaged user terminal and its link condition, and changing the forward error correction coding and modulation to dynamically adjust the information rate of data frames multiplexed into the same forward link TDM data stream for a selected group of more advantaged user terminals to adapt to each more advantaged user terminal and its link condition. 4. The method of claim 1, wherein continuously and dynamically adjusting the information rate comprises continuously and dynamically adjusting a processing gain of the spread spectrum modulation. 5. The method of claim 1, wherein the spread spectrum modulation comprises direct sequence spread spectrum having a substantially constant chipping rate. 6. The method of claim 5, wherein the method further comprises slightly varying a forward error correction code rate of the TDM signal to reduce a step size between allowable information rate values that produce the approximate constant occupied signal bandwidth signal when the direct sequence spread spectrum modulation uses a small number of chips per information bit. 7. The method of claim 1, wherein determining a separate information rate for information to be transmitted to each user terminal comprises: continuously measuring the Eb/No of the signal received at each user terminal and communicating the measured Eb/No to the base station; and calculating the margin on the forward link during transmission of the data frames to each respective user terminal by subtracting the threshold Eb/No from each measured Eb/No. 8. The method of claim 1, wherein transmitting the TDM data stream comprises transmitting information to a selected group of the user terminals using the determined information rate for the most disadvantaged user terminal of the selected group that is to receive the information. 9. The method of claim 1, wherein the method further comprises operating a signal amplifier of the satellite transponder approximately at a maximum saturation output power of the signal amplifier. 10. The method of claim 1, wherein the method further comprises operating a power amplifier of the base station approximately at a maximum saturation output power of the power amplifier. 11. The method of claim 1, wherein each data frame comprises a synchronization word, all synchronization words the same and transmitted at an information rate adapted to allow all user terminals to maintain synchronization with the forward link TDM data stream. 12. The method of claim 1, wherein the method further comprises maintaining an approximately constant occupied signal bandwidth of the TDM data stream as the information rate is changed from data frame to data frame by changing a forward error correction coding rate and a signal modulation of the TDM signal stream without the use of spread spectrum modulation. 13. A satellite communications method for communicating information from a base station to one or more user terminals via a single channel of a forward link via a transponded satellite, the one or more user terminals subject to time varying losses and performance differences that affect the quality of the forward link, said method comprising: determining a separate information rate for information to be transmitted from the base station via the forward link, using the transponded satellite, to each of the user terminals, each information rate determined to allow successful communication with the respective user terminal and provide a predetermined amount of margin above a threshold energy-to-noise ratio power spectral density (Eb/No) in the forward link; formatting data received at the base station into a continuous time division multiplexed (TDM) data stream including a plurality of data frames to be transmitted to the user terminals via the forward link using the transponded satellite, each data frame formatted to have the determined information rate of the respective user terminal that is to receive the data frame; transmitting the TDM data stream using a single carrier of the forward link, via the transponded satellite link; continuously and dynamically adjusting the information rate at the boundaries of subsequent data frames being transmitted via the forward link on the single channel for each user terminal, to adapt to the time varying losses and user terminal performance differences and maintain the predetermined amount of margin for each user terminal as the operating conditions of each user terminal change; and maintaining an approximately constant occupied signal bandwidth of the TDM data stream using spread spectrum modulation as the information rate is changed from data frame to data frame. 14. The method of claim 13, wherein the spread spectrum modulation comprises direct sequence spread spectrum having a substantially constant chipping rate. 15. The method of claim 13, wherein transmitting the TDM data stream comprises maintaining a forward error correction coding rate and a signal modulation of the TDM data stream approximately constant while the information rate varies. 16. The method of claim 13, wherein transmitting the TDM data stream comprises transmitting specific data frames to more than one of the user terminals using the determined information rate for the most disadvantaged user terminal that is to receive the data frames. 17. The method of claim 13, wherein the method further comprises operating a signal amplifier of the transponded satellite approximately at a maximum saturation output power of the signal amplifier. 18. The method of claim 13, wherein the method further comprises seamlessly transitioning from varying the information rate to maintain the approximately constant occupied signal bandwidth, to changing a forward error correction coding rate and a signal modulation of the TDM signal stream to maintain the approximately constant occupied signal bandwidth, when the information rate has been varied such that the TOM data stream comprises a non-spread spectrum TOM data stream. 19. A satellite based communication system comprising: a base station configured to: communicate with one or more user terminals via single channel of a transponded satellite forward link; determine a separate information rate for information to be transmitted from the base station via the transponded satellite forward link to each of the user terminals, each information rate determined to allow successful communication with the respective user terminal and provide a predetermined amount of margin above a threshold energy per bit to noise power spectral density ratio (Eb/No) in the forward link; format data received at the base station into a continuous time division multiplexed (TDM) data stream including a plurality of data frames to be transmitted to the user terminals via the transponded satellite forward link, each data frame formatted to have the determined information rate of the respective user terminal that is to receive the data frame; transmit the TDM data stream using a single carrier forming the single channel of the forward link; continuously and dynamically adjust the information rate of subsequent data frames of the TDM data stream on the single channel of the transponded satellite forward link, for each user terminal to maintain successful communication and maintain the predetermined amount of margin as the operating conditions of each user terminal change; and maintain an approximately constant occupied signal bandwidth of the TDM data stream using spread spectrum modulation as the information rate is changed from data frame to data frame. 20. The system of claim 19, wherein the spread spectrum modulation comprises direct sequence spread spectrum having a substantially constant ‘chipping’ rate. 21. The system of claim 19, wherein to continuously and dynamically adjust the information rate, the base station is further adapted to continuously and dynamically adjust a processing gain of the spread spectrum modulation. 22. The system of claim 19, wherein to transmit the TDM data stream, the base station is further adapted to maintain a forward error correction coding rate and a signal modulation of the TDM data stream approximately constant while the information varies. 23. The system of claim 19, wherein to determine a separate information rate for information to be transmitted to each user terminal, the base station is further adapted to: receive from each user terminal measurements for the Eb/No of the signal received at each user terminal; and calculate the margin on the transponded satellite forward link during transmission of the data frames to each respective user terminal by subtracting the threshold Eb/No from each measured Eb/No. 24. The system of claim 19, wherein to transmit the TDM data stream, the base station is further adapted to transmit specific data frames to more than one of the user terminals using the determined information rate for the most disadvantaged user terminal that is to receive the data frames. 25. The system of claim 19, wherein the satellite transponder includes a signal amplifier that is operated approximately at a maximum saturation output power as the TDM data stream is relayed and distributed to the user terminals via the transponder satellite. 26. The system of claim 19, wherein the base station is further configured to seamlessly transition from varying the information rate to maintain the approximately constant occupied signal bandwidth, to changing a forward error correction coding rate and a signal modulation of the TDM signal stream to maintain the approximately constant occupied signal bandwidth, when the information rate has been varied such that the TDM data stream comprises a non-spread spectrum TDM data stream.
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