Method and Apparatus for Reducing Phase Noise in Orthogonal Frequency Division Multiplexing Systems

• US 20090110112A1
• Filed: 10/24/2007
• Published: 04/30/2009
• Est. Priority Date: 10/24/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Nordstrom, Fredrik, Wilhelmsson, Leif, Andgart, Niklas
• Granted Patent: US 7,894,540 B2
• Time in Patent Office: Days
• US Class Current: 375/296
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

Method and apparatus for reducing phase noise from a multi-carrier modulation (MCM) system, such as an orthogonal frequency division multiplexing (OFDM) system, by transmitting known data on a sub-carrier at a power level adapted to allow for accurate estimation. Preferably, the sub-carrier is the DC sub-carrier.

Claims

1. A method of reducing phase noise from a multi-carrier modulation (MCM) system, comprising the step of transmitting known data on a sub-carrier wherein the sub-carrier is a DC sub-carrier.

2. The method of claim 1, wherein the known data is transmitted at a power level adapted to allow for accurate common phase error (CPE) estimation.

3. The method of claim 1, wherein the MCM system is an orthogonal frequency division multiplexing (OFDM) system.

4. The method of claim 3, further comprising the step of transmitting on the DC sub-carrier OFDM symbols that do not contain any other reference symbols.

5. The method of claim 1, wherein the spectrum of a signal transmitted on the DC sub-carrier has substantially all of its energy away from DC.

6. A method of reducing phase noise from a multi-carrier modulation (MCM) system, comprising the steps of:

determining low frequency phase noise by determining the variance of common phase error (CPE);

determining how much CPE would cause an overly degraded level of performance;

generating known data; and

based on the level of CPE that would cause an overly degraded level of performance, transmitting the known data on a sub-carrier at a power level necessary to allow for accurate CPE estimation, wherein the sub-carrier is a DC sub-carrier.

7. The method of claim 6, wherein the MCM system is an orthogonal frequency division multiplexing (OFDM) system.

8. The method of claim 7, wherein the OFDM system is one of a 3G LTE, WiMAX or WLAN system.

9. The method of claim 7, wherein the spectrum of a signal transmitted on the DC sub-carrier has substantially all of its energy away from DC.

10. The method of claim 6, wherein the power level of the DC sub-carrier is based on the transmission format, including modulation scheme and coding algorithm.

11. The method of claim 6, further comprising the step of transmitting by a mobile terminal to a base station information adapted to allow the base station to determine and transmit a proper level of the DC sub-carrier.

12. The method of claim 6, further comprising the step of transmitting, by a base station, a signal on the DC sub-carrier in order to allow for efficient CPE estimation.

13. An apparatus for reducing phase noise from a multi-carrier modulation (MCM) system comprising:

a base station having a transmitter adapted to transmit known data on a sub-carrier at a power level necessary to allow for accurate common phase error (CPE) estimation, wherein the sub-carrier is a DC sub-carrier.

14. The apparatus of claim 13, wherein the MCM system is an orthogonal frequency division multiplexing (OFDM) system.

15. The apparatus of claim 14, wherein the OFDM system is one of a 3G LTE, WiMAX or WLAN system.

16. The apparatus of claim 13, wherein the transmitter is adapted to transmit a signal with the DC sub-carrier with a spectrum that has substantially all of its energy away from DC.

17. The apparatus of claim 16, wherein the power level of the DC sub-carrier is based on the transmission format, including modulation scheme and coding algorithm.

18. The apparatus of claim 16, in combination with a mobile terminal adapted to transmit to a base station information adapted to allow the base station to determine and transmit a proper level of the DC sub-carrier.

19. The apparatus of claim 13, wherein the transmitter is adapted to transmit a signal on the DC sub-carrier in order to allow for efficient CPE estimation.

20. An apparatus for reducing phase noise from a multi-carrier modulation (MCM) system, comprising:

means for determining low frequency phase noise by determining the variance of the common phase error (CPE);

means for determining how much CPE would cause an overly degraded level of performance;

means for generating known data; and

means for transmitting, based on the level of CPE that would cause an overly degraded level of performance, the known data on a sub-carrier at a power level necessary to allow for accurate CPE estimation, wherein the sub-carrier is a DC sub-carrier.

21. The apparatus of claim 22, wherein the MCM system is an orthogonal frequency division multiplexing (OFDM) system, wherein the OFDM system is one of a 3G LTE, WiMAX or WLAN system.

22. The apparatus of claim 20, wherein the power level of the DC sub-carrier is based on the transmission format, including modulation scheme and coding algorithm.

23. The apparatus of claim 20, further comprising means of transmitting, by a mobile terminal to a base station, information adapted to allow the base station to determine and transmit a signal on the DC sub-carrier at an appropriate power level.

24. The apparatus of claim 20, further comprising means of transmitting, by a base station, a signal on the DC sub-carrier in order to allow for efficient CPE estimation.

25. The apparatus of claim 24, wherein the spectrum of the signal transmitted on the DC sub-carrier has substantially all of its energy away from DC.