SIGNAL DEMODULATION METHOD AND APPARATUS AND SIGNAL MODULATION METHOD AND APPARATUS IN RETURN LINK OF SATELLITE SYSTEM

• US 20120147939A1
• Filed: 12/08/2011
• Published: 06/14/2012
• Est. Priority Date: 12/10/2010
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Pan-Soo, Oh, Deock-Gil, Giraud, Xavier, HAN, Jae-Hee
• Granted Patent: US 8,699,628 B2
• Time in Patent Office: Days
• US Class Current: 375/224
• CPC Class Codes: H04B 7/18589 Arrangements for controlling an end to end session, i.e. for initialising, synchronising or terminating an end to end link
• CPC Class Codes: H04B 7/2125 Synchronisation
• CPC Class Codes: H04L 2027/0024 at the receiver end
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 2027/0079 Switching between loops
• CPC Class Codes: H04L 2027/0095 in a preamble or similar structure
• CPC Class Codes: H04L 7/04 Speed or phase control by synchronisation signals H04L7/0075 takes precedence

Abstract

A technology for modulating and demodulating a burst signal in a return link of a satellite system, in which the burst signal is modulated and transmitted from a transmission end of the return link and a symbol of the burst signal is identified and demodulated at a receiving end. The method includes estimating symbol timing of a burst received through the return link and synchronizing the estimated symbol timing of the burst to reference symbol timing; synchronizing a location of the timing-synchronized burst having the symbol timing synchronized to a location of a reference burst using a preamble symbol and a post-amble symbol of the timing-synchronized burst; and recovering a carrier of the location-synchronized burst whose location has been synchronized to the location of the reference burst using a pilot symbol of the location-synchronized burst.

Claims

1. A method of demodulating a signal in a return link of a satellite system, comprising:

estimating symbol timing of a burst received through the return link of the satellite system and synchronizing the estimated symbol timing of the burst to reference symbol timing;

synchronizing a location of the timing-synchronized burst having the symbol timing synchronized to a location of a reference burst using a preamble symbol and a post-amble symbol of the timing-synchronized burst; and

recovering a carrier of the location-synchronized burst whose location has been synchronized to the location of the reference burst using a pilot symbol of the location-synchronized burst.

2. The method of claim 1, wherein the recovering of the carrier comprises estimating a frequency error of the location-synchronized burst and correcting the estimated frequency error and estimating a phase error of the location-synchronized burst and correcting the estimated phase error.

3. The method of claim 2, wherein the estimating of the frequency error of the location-synchronized burst comprises estimating the frequency error using a data-aided scheme when a pilot symbol is present in the location-synchronized burst, and estimating the frequency error using a blind scheme when a pilot symbol is not present in the location-synchronized burst.

4. The method of claim 1, wherein the burst includes at least one symbol of a preamble symbol, a post-amble symbol, a payload symbol, and a pilot symbol.

5. The method of claim 1, wherein the burst includes payload symbols and pilot symbols which are alternately arranged between a preamble symbol and a post-amble symbol.

6. An apparatus for demodulating a signal in a return link of a satellite system, comprising:

a symbol timing synchronizing unit configured to synchronize symbol timing of a burst received through the return link of the satellite system to reference symbol timing;

a burst synchronizing unit configured to synchronize a location of the timing-synchronized burst of which the symbol timing has been synchronized by the symbol timing synchronizing unit to a location of a reference burst using a preamble symbol and a post-amble symbol of the timing-synchronized burst; and

a carrier recovering unit configured to recover a carrier of the location-synchronized burst of which the location has been synchronized by the burst synchronizing unit using a pilot symbol of the location-synchronized burst.

7. The apparatus of claim 6, wherein the symbol timing synchronizing unit is further configured to comprise a digital converter configured to perform analog/digital conversion on the received burst, a matched filter configured to perform matched filtering on the digitized burst, and a symbol timing corrector configured to estimate and correct a symbol timing error of the digitized burst.

8. The apparatus of claim 6, wherein the burst synchronizing unit is further configured to comprise a symbol detector configured to detect locations of a preamble symbol and a post-amble symbol of the timing-synchronized burst, a comparer configured to compare the locations of the preamble symbol and the post-amble symbol, and a location corrector configured to correct the location of the timing-synchronized burst to the location of the reference burst according to the comparison result from the comparer.

9. The apparatus of claim 6, wherein the carrier recovering unit is further configured to comprise a frequency corrector configured to estimate a frequency error of the location-synchronized burst according to the presence of the pilot symbol and correct the estimated frequency error, and a phase corrector configured to estimate and correct a phase error of the location-synchronized burst.

10. The apparatus of claim 9, wherein the frequency corrector is further configured to comprise a first estimator configured to estimate a frequency error of the location-synchronized burst using a data-aided scheme, a second estimator configured to estimate a frequency error of the location-synchronized burst using a blind scheme, and a selector configured to transmit the location-synchronized burst to the first estimator if a pilot symbol of the location-synchronized burst is detected, and transmit the location-synchronized burst to the second estimator when the pilot symbol is not detected wherein a detection signal of the pilot signal is selectively input.

11. A method of modulating a signal in a return link of a satellite system, comprising:

generating a payload symbol by modulating an encoded data bit using a predefined modulation scheme;

generating a unique word into at least one of unique symbols including a preamble symbol, a post-amble symbol and a pilot symbol according to a type of a burst; and

generating a burst by combining the payload symbol and the unique symbol.

12. The method of claim 11, further comprising:

performing baseband filtering on the generated burst.

13. The method of claim 11, wherein the generating of the payload symbol comprises modulating the encoded data bit using at least one of quadrature phase shift keying (QPSK), 8-phase shift keying (8PSK) and 16-quadrature amplitude modulation (16-QAM) schemes.

14. The method of claim 11, wherein the generating of the burst comprises combining the payload symbol and the pilot symbol in such a manner that the pilot symbol is interposed between payload symbols.

16. The apparatus of claim 11, further comprising:

a filter unit configured to restrict the burst generated by the burst generating unit to baseband frequencies.

15. An apparatus for modulating a signal in a return link of a satellite system, comprising:

a payload symbol generating unit configured to generate a payload symbol by modulating an encoded data bit using a predefined modulation scheme;

a unique symbol generating unit configured to generate the unique word into a preamble symbol, a post-amble symbol, or a pilot symbol according to a type of a burst; and

a burst generating unit configured to generate a burst by combining the symbols generated by the payload symbol generating unit and the unique symbol generating unit.