Frequency offset compensation for communication systems

• US 20040067741A1
• Filed: 10/02/2002
• Published: 04/08/2004
• Est. Priority Date: 10/02/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Ho, Ming-Ju, Fei, Fan, Kim, Dukhyun, Vrijkorte, Marcel Johannes Gerhardus
• Granted Patent: US 7,269,394 B2
• Time in Patent Office: Days
• US Class Current: 455/192.1
• CPC Class Codes: H04L 2027/002 using feedback from a remote receiver
• CPC Class Codes: H04L 2027/0022 using the carrier of the associated receiver of a transceiver
• CPC Class Codes: H04L 27/2646 using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
• CPC Class Codes: H04L 27/2657 Carrier synchronisation

Abstract

In communications between a pair of stations using modulated carrier signals, a first station estimates the carrier frequency offset with respect to the second station and transmits signals that are responsive to the estimated carrier frequency offset. The first station may adjust the carrier frequency of the signals it transmits in response to the estimated carrier frequency offset, and/or transmit data to the second station representing the estimated carrier frequency offset. The second station adjusts the carrier frequency of the signals it transmits to the first station, and/or compensates for carrier frequency offset in its processing of received signals, in response to estimated carrier frequency offset data received from the first station.

Claims

1. A first station comprising:

(a) a transmitter adapted to transmit, to a second station, signals at a first carrier frequency modulated to represent first data signals; and

(b) a receiver adapted to receive, from the second station, signals at a second carrier frequency modulated by second data signals, and to generate an estimate of the carrier frequency offset between the first station and the second station,

wherein the transmitter is adapted to transmit signals that are responsive to the carrier frequency offset estimate.

2. The invention of claim 1, wherein the transmitter is adapted to adjust the first carrier frequency in response to the carrier frequency offset estimate.

3. The invention of claim 2, wherein the transmitter adjusts the first carrier frequency only if the carrier frequency offset estimate exceeds a minimum value.

4. The invention of claim 2, wherein the first carrier frequency adjustment is limited to a maximum value.

5. The invention of claim 2, wherein the carrier frequency adjustment includes rotating phases of the first data signals.

6. The invention of claim 1, wherein the first data signals include data signals representing the carrier frequency offset estimate.

7. The invention of claim 1, wherein the first station is a base station adapted to communicate with a plurality of mobile stations and to transmit wireless radio frequency carrier signals modulated by orthogonal frequency division multiplexing.

8. The invention of claim 1, wherein the first carrier frequency is substantially equal to the second carrier frequency.

9. A second station comprising:

a transmitter adapted to transmit signals to a first station at a second carrier frequency modulated to represent second data signals; and

a receiver adapted to receive signals from the first station at a first carrier frequency modulated by first data signals, and to process received signals to generate received data signals corresponding to the first data signals,

wherein the receiver is adapted to obtain, from the received data signals, data signals representing a carrier frequency offset estimate.

10. The invention of claim 9, wherein the transmitter is adapted to adjust the second carrier frequency in response to the data signals representing the carrier frequency offset estimate.

11. The invention of claim 10, wherein the carrier frequency adjustment includes rotating phases of the first data signals.

12. The invention of claim 9, wherein the receiver is adapted to adjust its processing of received signals in response to the data signals representing the carrier frequency offset estimate.

13. The invention of claim 9, wherein the second station is a mobile station adapted to communicate with a base station and to transmit wireless radio frequency carrier signals modulated by orthogonal frequency division multiplexing.

14. The invention of claim 9, wherein the first carrier frequency is substantially equal to the second carrier frequency.

15. In a communication system comprising a first station and a second station, the first station having a transmitter adapted to transmit signals to a second station at a first carrier frequency modulated by first data signals and having a receiver adapted to receive signals from the second station at a second carrier frequency modulated by second data signals, a method comprising, at the first station:

(a) generating, in the receiver, an estimate of the carrier frequency offset between the first station and the second station; and

(b) transmitting signals that are responsive to the estimated carrier frequency offset.

16. The invention of claim 15, further comprising adjusting the first carrier frequency based on the estimated carrier frequency offset.

17. The invention of claim 16, wherein carrier frequency adjustment is performed only if the estimated carrier frequency offset exceeds a minimum value.

18. The invention of claim 16, wherein the carrier frequency adjustment is limited to a maximum value.

19. The invention of claim 16, wherein the carrier frequency adjustment includes rotating phases of the first data signals.

20. The invention of claim 15, wherein the first data signals include data signals representing the estimated carrier frequency offset.

21. The invention of claim 20, wherein the method comprises, at the second station, the steps of:

(c) receiving signals from the first station;

(d) processing the signals received from the first station to generate received data signals; and

(e) obtaining, from the received data signals, data signals representing a carrier frequency offset estimate.

22. The invention of claim 21, wherein the second station adjusts the second carrier frequency in response to the data signals representing the carrier frequency offset estimate.

23. The invention of claim 21, wherein the second station adjusts its processing of signals received from the first station in response to the data signals representing the carrier frequency offset estimate.

24. The invention of claim 15, wherein the second station is a mobile station adapted to communicate with a base station and to transmit wireless radio frequency carrier signals modulated by orthogonal frequency division multiplexing.

25. The invention of claim 15, wherein the first carrier frequency is substantially equal to the second carrier frequency.

26. In a communication system comprising a first station and a second station, the second station being adapted to transmit signals to the first station at a second carrier frequency modulated by second data signals and being adapted to receive signals from the first station at a first carrier frequency modulated by first data signals, a method comprising, at the second station, the steps of:

(a) receiving signals modulated by first data signals;

(b) processing the received signals to generate received data signals corresponding to the first data signals; and

,

(c) obtaining, from the received data signals, data signals representing a carrier frequency offset estimate.

27. The invention of claim 26, further comprising adjusting the second carrier frequency based on the data signals representing the estimated carrier frequency offset.

28. The invention of claim 26, further comprising adjusting the processing of received signals in response to the data signals representing the carrier frequency offset estimate.

29. The invention of claim 26, wherein the second station is a mobile station adapted to communicate with a base station and to transmit wireless radio frequency carrier signals modulated by orthogonal frequency division multiplexing.

30. The invention of claim 26, wherein the first carrier frequency is substantially equal to the second carrier frequency.