OFDM system with reverse link interference estimation

• US 7,860,176 B2
• Filed: 10/14/2005
• Issued: 12/28/2010
• Est. Priority Date: 12/10/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Wu, Jianming, Zhu, Peiying, Tong, Wen
• Primary Examiner(s): PHU, PHUONG M
• Application Number:
  US11/791,339
• Publication Number:
  US 20070297525A1
• Time in Patent Office: 1,901 Days
• Field of Search: 375/260, 375/227, 375/285, 375/261, 375/268, 375/298, 375/300, 375/346, 375/349, 455/522, 370/334
• US Class Current: 375/260
• CPC Class Codes: H04B 17/26 using historical data, averaging values or statistics
• CPC Class Codes: H04B 17/309 Measuring or estimating channel quality parameters
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04B 17/382 for resource allocation, admission control or handover
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0643 block codes
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic

Abstract

A new method of performing interference estimation to allow the data packets to be efficiently delivered in an OFDM system. The interference estimation is performed on average over each frame for each mobile station individually in both frequency and time domains. Based on the estimated interference, the CIR can be determined by the BTS based on channel response estimates made by the BTS, or by the MS based on channel response estimates made for the uplink assuming a symmetrical channel. Numerical results show that the CIR estimation error could be very small if a sub-channel is considered as the minimum transmission unit. In terms of the aggregate throughput, the interference estimation method can provide a significant gain.

Claims

1. A method comprising:

determining, by a base station, an interference estimate of an interference component of an OFDM signal received from a mobile station;

the base station determining channel estimates for sub-carriers used by the mobile station;

using the interference estimate and the channel estimates, the base station determining a carrier-to-interference ratio (CIR) for at least one sub-carrier and/or for at least one sub-channel for the mobile station; and

the base station sending the determined CIR to the mobile station.

3. The method of claim 1 wherein the CIR is determined by:

determining a desired signal power by subtracting the respective channel estimate from a transmitted signal power for each sub-carrier used by the mobile station;

determining the CIR for each sub-carrier by dividing the desired signal power by the interference estimate and/or determining the CIR for each sub-channel by summing desired signal powers of sub-carriers of the sub-channel and dividing the sum by the interference estimate.

8. The method of claim 1 further comprising:

using the CIR to perform AMC (adaptive modulation and coding).

9. The method of claim 1 further comprising:

using the CIR to perform sub-channel selection.

10. The method of claim 1 implemented for each of a plurality of mobile stations in a coverage area of a base station.

11. A base station adapted to implement the method of claim 1.

2. A method comprising:

determining an interference estimate of an interference component of an OFDM signal received from a mobile station;

using the interference estimate, determining a carrier-to-interference ratio (CIR) for at least one sub-carrier and/or for at least one sub-channel for the mobile station,

wherein determining the estimate is performed by a base station, and determining the CIR is performed by the mobile station; and

the base station sending the interference estimate to the mobile station.

12. A base station and mobile station in combination adapted to implement the method of claim 2.

4. A method comprising:

determining an interference estimate of an interference component of an OFDM signal received from a mobile station;

using the interference estimate, determining a carrier-to-interference ratio (CIR) for at least one sub-carrier and/or for at least one sub-channel for the mobile station;

the mobile station determining downlink channel measurements, the downlink channel estimates being representative of uplink channel estimates;

wherein determining the CIR is performed by the mobile station using the downlink channel estimates.

5. The method of claim 4 wherein the CIR is determined by:

determining a desired signal power by subtracting the respective channel estimate from a transmitted signal power for each sub-carrier used by the mobile station;

determining the CIR for each sub-carrier by dividing the desired signal power by the interference estimate and/or determining the CIR for each sub-channel by summing desired signal powers of sub-carriers of the sub-channel and dividing the sum by the interference estimate.

6. A method comprising:

determining an interference estimate of an interference component of an OFDM signal received from a mobile station;

using the interference estimate, determining a carrier-to-interference ratio (CIR) for at least one sub-carrier and/or for at least one sub-channel for the mobile station,

wherein determining the interference estimate of the interference component of the OFDM signal received from the mobile station comprises;

measuring a received signal strength on sub-carriers used by the mobile station;

estimating a desired signal strength of a desired signal component of each sub-carrier used by the mobile station;

subtracting the desired signal strength from the received signal strength;

averaging over all of the sub-carriers to yield an average.

7. The method of claim 6 further comprising combining the average with at least one previous interference estimate to produce a long-term average.

13. A method for execution by a mobile station comprising:

receiving, by the mobile station from a base station, an interference estimate of an interference component of a received version of an OFDM signal transmitted by the mobile station, wherein the interference estimate is determined at the base station;

using the interference estimate, determining, by the mobile station, a carrier-to-interference ratio (CIR) for at least one sub-carrier and/or for at least one sub-channel for the mobile station.

14. A mobile station adapted to implement the method of claim 13.

15. An apparatus comprising:

a base station having an interference estimator, a channel estimator, and a carrier-to-interference ratio (CIR) estimator;

wherein the interference estimator is configured to determine an interference estimate of an interference component of an OFDM signal received from a mobile station;

wherein the channel estimator is configured to perform channel estimation of an uplink channel from the mobile station; and

wherein the CIR estimator is configured to use the interference estimate and the channel estimation to determine a CIR for at least one sub-carrier and/or for at least one sub-channel for the mobile station, the CIR for forwarding to the mobile station.

16. An apparatus comprising:

a mobile station;

a base station;

an interference estimator adapted to determine an interference estimate of an interference component of an OFDM signal received from the mobile station;

a CIR estimator adapted to use the interference estimate to determine a carrier-to-interference ratio (CIR) for at least one sub-carrier and/or for at least one sub-channel for the mobile station;

wherein the interference estimator is part of the base station, and the CIR estimator is part of the mobile station, the mobile station further comprising a channel estimator configured to perform channel estimates of a downlink channel to the mobile station for use by the CIR estimator as if the downlink channel estimates were uplink channel estimates.