Method and system for providing a semi-data aided frequency estimator for OQPSK
View Patent ↗An approach for performing synchronization is provided. Phase and timing offsets are first estimated in order to calculate a frequency offset. A receiver processes a signal received from a satellite and determine offset information. The receiver includes a phase estimator for estimating a phase offset of the received signal, a timing estimator for estimating a timing offset of the received signal, and a frequency estimator for deriving a frequency offset from the phase and timing offset. A determination is made as to whether the sampling was done at a peak wave point of the data.
1. A receiver for receiving a communication signal transmitted from a satellite, said signal including data information and synchronization information, said receiver comprising:
a controller adapted to control operation of the receiver;
a phase estimator coupled to the controller and adapted to estimate a phase offset of said received signal;
a timing estimator coupled to the controller and adapted to estimate a timing offset of said received signal; and
a frequency estimator coupled to the controller and adapted to derive a frequency offset from said phase and timing offset by performing the following operations:
removing the modulation from the received signal;
sampling the received signal for information carrying data;
determining whether the step of sampling was done at a peak wave point of said data; and
repeating said step of sampling in a response to a determination that said sampling was not done at a peak wave point of said data.
2. The system of claim 1 , wherein said synchronization information comprises a unique word.
3. The system of claim 2 , wherein said unique word comprises between ten to twenty symbols.
4. The system of claim 2 , wherein said unique word comprises a known symbol arrangement between said satellite and said receiver.
5. The system of claim 2 , wherein said unique word is used to derive said phase and timing offset.
6. The system of claim 1 , wherein the process of determining said offset values comprises using a semi-data aided approach.
7. The system of claim 6 , wherein said semi-data aided approach uses less bandwidth to transmit training information than a data-aided approach.
8. The system of claim 6 , wherein said semi-data aided approach uses less time to determine synchronization information than a non-data-aided approach.
9. The system of claim 1 , wherein removing said modulation comprises squaring the value of said received signal.
10. The system of claim 9 , wherein said signal is delayed a half symbol.
11. The system of claim 10 , wherein a subtraction is performed between the non-delayed and the delayed signal.
12. The system of claim 5 , wherein said timing offset is used to adjust the sampling.
13. The system of claim 12 , wherein the phase offset is used to adjust the phase.
14. The system of claim 1 , wherein said phase and frequency offset are used to determine said frequency offset.
15. The system of claim 1 , wherein said timing offset is redetermined by assuming said timing offset was off by a quarter of a symbol.
16. The system of claim 15 , wherein said frequency derived from said original timing offset and said frequency derived from said redetermined timing offset are compared, said frequency giving better estimation is selected.
17. A method for receiving a communication signal comprising data information and synchronization information, said method comprising:
receiving said communication signal at a receiver;
determining a phase offset of said communication signal by processing the synchronization information;
determining a timing offset of said communication signal by processing the synchronization information;
removing modulation from said received communication signal;
determining whether sampling was done at a peak wave point of said data; and
repeating said step of sampling in a response to a determination that said sampling was not done at a peak wave point of said data.
18. The method of claim 17 , wherein said synchronization information comprises a unique word.
19. The method of claim 18 , wherein said unique word comprises between about ten to twenty symbols.
20. The method of claim 18 , wherein said unique word comprises a known symbol arrangement between said satellite and said receiver.
21. The method of claim 18 , wherein said unique word is used to derive said phase and timing offset.
22. The method of claim 17 , wherein the process of determining offset values comprises using a semi-data aided approach.
23. The method of claim 22 wherein said semi-data aided approach uses less bandwidth to transmit training information than a data-aided approach.
24. The method of claim 22 , wherein said semi-data aided approach uses less time to determine synchronization information than a non-data-aided approach.
25. The method of claim 17 , wherein removing said modulation comprises squaring the value of said received signal.