Methods and apparatus for mobile station to mobile station communications in a mobile satellite communication system
First Claim
1. In a mobile satellite communications system, a method for providing communications via a communications satellite relay station between a first mobile station conditioned to transmit a first signal having a first TDMA signal format and a first bandwidth and a second mobile station conditioned to receive a second signal having a second TDMA signal format, the method comprising:
- receiving in the satellite relay station the first signal having the first TDMA signal format and the first bandwidth from the first mobile station;
sampling the received first signal at a first rate to produce a first bitstream having a first number of samples per second;
storing, in a buffer, the first bitstream;
clocking out of the buffer the first bitstream at a second rate, which is different from the first rate, to produce a second bitstream having a second number of samples per second which is different from the first number of samples per second of the first bitstream, the samples in both the first and second bitstreams being representative of the received first signal; and
transmitting from the satellite relay station to the second mobile station the second bitstream as the second signal using the second TDMA format at a second bandwidth which is different from the first bandwidth of the first signal.
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Accused Products
Abstract
Methods and apparatus for mobile station to mobile station communications in a mobile satellite communications system include an asymmetrical TDMA formatting scheme. According to exemplary embodiments, a first mobile station broadcasts a first signal to an orbiting satellite using a first TDMA format. The satellite receives the first signal, maps the first TDMA format to a second TDMA format and broadcasts a second signal having the second TDMA format to a second mobile station. Advantageously, exemplary embodiments utilize an elastic buffer to allow the satellite to map the uplink TDMA format to the downlink TDMA format without having to demodulate and re-modulate communications signals.
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Citations
37 Claims
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1. In a mobile satellite communications system, a method for providing communications via a communications satellite relay station between a first mobile station conditioned to transmit a first signal having a first TDMA signal format and a first bandwidth and a second mobile station conditioned to receive a second signal having a second TDMA signal format, the method comprising:
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receiving in the satellite relay station the first signal having the first TDMA signal format and the first bandwidth from the first mobile station; sampling the received first signal at a first rate to produce a first bitstream having a first number of samples per second; storing, in a buffer, the first bitstream; clocking out of the buffer the first bitstream at a second rate, which is different from the first rate, to produce a second bitstream having a second number of samples per second which is different from the first number of samples per second of the first bitstream, the samples in both the first and second bitstreams being representative of the received first signal; and transmitting from the satellite relay station to the second mobile station the second bitstream as the second signal using the second TDMA format at a second bandwidth which is different from the first bandwidth of the first signal. - View Dependent Claims (2, 3, 4)
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5. A communications satellite relay station for providing communications between a first mobile station conditioned to transmit a first signal having a first TDMA format and a first bandwidth and a second mobile station conditioned to receive a second signal having a second TDMA format, the satellite relay station comprising:
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a receiver for receiving the first signal having the first TDMA signal format and the first bandwidth; an analog to digital converter for sampling the received first signal at a first rate to produce a first bitstream having a first number of samples per second; a buffer for receiving the first bitstream and clocking out the first bitstream at a second rate, which is different from the first rate, to produce a second bitstream having a second number of samples per second which is different from the first number of samples per second of the first bitstream, the samples in both the first and second bitstreams being representative of the received first signal; and a transmitter for transmitting the second bitstream as the second signal using the second TDMA format at a second bandwidth which is different from the first bandwidth of the first signal. - View Dependent Claims (6, 7, 8, 9)
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10. In a mobile satellite communications system, a method for providing communications via a communications satellite relay station between a first mobile station conditioned to transmit a first signal having a first TDMA format and a first bandwidth BW and a second mobile station conditioned to receive a second signal having a second TDMA format, the method comprising:
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receiving, in the satellite relay station the first signal having the first TDMA signal format and the first bandwidth BW from the first mobile station; downconverting the first signal to a first IF signal; sampling the first IF signal at a rate N×
BW, where N is greater than or equal to 2, to produce a first bitstream having at least N×
BW samples per second with the samples being representative of the received first signal;storing, in a buffer, the first bitstream; clocking out of the buffer the first bitstream at a rate M×
N×
BW, where M is greater than or equal to 2 to produce a second bitstream having at least M×
N×
BW samples per second with the samples being representative of the received first signal;filtering the second bitstream to produce a second IF signal; upconverting the second IF signal to produce an output signal; formatting the output signal into the second TDMA format to produce the second signal; and transmitting the second signal from the satellite relay station to the second mobile station. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method for supporting calls between two mobile stations within a satellite communication system, comprising the steps of:
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transmitting signals from a first mobile station to a satellite relay station using a narrowband time division multiple access transmission format; sampling and digitizing signals received from said first mobile station; storing said sampled and digitized signals in a buffer means at a first rate; reading out of said buffer means said stored signals at a faster rate than said first rate and modulating said stored signals onto a downlink frequency to create a wideband time division multiple access transmission format; transmitting said modulated signals to a second mobile station; receiving and decoding said modulated signals at said second mobile station. - View Dependent Claims (17, 18)
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19. A satellite transponder for supporting calls between two mobile stations within a satellite communication system, comprising:
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receiving means for receiving signals being transmitted using a narrowband time division multiple access transmission format; means for sampling and digitizing said received signals; means for storing said sampled and digitized signals at a first rate; means for reading out said stored signals at a faster rate than said first rate and modulating said stored signals onto a downlink frequency to create a wideband time division multiple access transmission format; and transmitting means for transmitting said modulated signals to a second mobile station. - View Dependent Claims (20, 21)
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22. A method for supporting calls between two mobile stations within a satellite communication system, comprising the steps of:
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receiving narrow band time division multiple access (TDMA) signals from said mobile stations at a satellite relay station; relaying the received narrowband TDMA signals to at least one ground station; digitizing some of the received narrowband signals; time compressing said digitized signals; multiplexing said time compressed signals into a wideband TDMA downlink format along with other signals from said at least one ground station; and transmitting said multiplexed signals to one of said mobile stations. - View Dependent Claims (23, 24, 25)
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26. A communications satellite relay station for providing communications between a first mobile station conditioned to transmit a first signal having a first TDMA format and a second mobile station conditioned to receive a second signal having a second TDMA format, the satellite relay station comprising:
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a receiver for receiving the first signal having the first TDMA signal format and a first bandwidth BW and downconverting the first signal to a first IF signal; an analog to digital converter for sampling the first IF signal at a rate N×
BW, where N is greater than or equal to 2 to produce a first bitstream having at least N×
BW samples per second with the samples being representative of the received first signal;a buffer for receiving the first bitstream and clocking out the first bitstream at a rate M×
N×
BW, where M is greater than or equal to 2 to produce a second bitstream having at least M×
N×
BW samples per second with the samples being representative of the received first signal;a low pass filter for filtering the second bitstream to produce a second IF signal; an upconverter for upconverting the second IF signal to produce an upconverted output signal; and a transmitter for transmitting the upconverted output signal using the second TDMA format. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33)
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34. A satellite transponder for supporting calls between two mobile stations within a satellite communication system, comprising:
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means for receiving narrow band time division multiple access (TDMA) signals from said mobile stations at a satellite relay station; means for relaying the received narrowband TDMA signals to at least one ground station; means for digitizing some of the received narrowband signals; means for time compressing said digitized signals; means for multiplexing said time compressed signals into a wideband TDMA downlink format along with other signals from said at least one ground station; and means for transmitting said multiplexed signals to one of said mobile stations. - View Dependent Claims (35, 36, 37)
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Specification