Interference Suppression in a Multicarrier Receiver

• US 20080298524A1
• Filed: 06/04/2007
• Published: 12/04/2008
• Est. Priority Date: 06/04/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Koorapaty, Havish, Balachandran, Kumar, Ramesh, Rajaram
• Granted Patent: US 7,796,698 B2
• Time in Patent Office: Days
• US Class Current: 375/348
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

A receiver uses knowledge of pilot symbols transmitted by a neighboring sector to reduce interference in a received data symbol. The received data symbol is transmitted on one or more data subcarriers in a first sector. Overlapping pilot symbols transmitted on overlapping pilot carriers in a second sector are determined and used to generate channel estimates for the overlapping pilot carriers. The overlapping pilot symbols and pilot channel estimates are then used to reduce interference in the received data symbol.

Claims

1. A method of reducing interference in a received data symbol, said method comprising:

receiving a data symbol transmitted on one or more data subcarriers in a first sector;

determining overlapping pilot subcarriers in a second sector;

determining one or more overlapping pilot symbols transmitted on the overlapping pilot subcarriers;

generating channel estimates associated with said overlapping pilot subcarriers in said second sector; and

reducing interference in said received data symbol based on said overlapping pilot symbols and said channel estimates.

2. The method of claim 1 wherein determining overlapping pilot subcarriers in a second sector comprises determining pilot subcarrier allocation for the second sector to identify pilot subcarriers overlapping in frequency and time with data subcarriers in the first sector.

3. The method of claim 2 wherein determining pilot subcarrier allocation for the second sector comprises determining the location of subcarrier allocation zones in a frame, and determining the pilot subcarriers in said subcarrier allocation zones.

4. The method of claim 1 wherein determining one or more overlapping pilot symbols transmitted on the overlapping pilot subcarriers comprises detecting a preamble transmitted in the second sector to obtain a sector identifier, and determining the overlapping pilot symbols based on the sector identifier.

5. The method of claim 1 wherein generating channel estimates associated with said overlapping pilot subcarriers in said second sector comprises averaging said channel estimates over a plurality of symbol periods.

6. The method of claim 1 wherein generating channel estimates associated with said overlapping pilot subcarriers in said second sector comprises computing channel estimates with a maximum likelihood estimator.

7. The method of claim 1 wherein generating channel estimates associated with said overlapping pilot subcarriers in said second sector comprises computing channel estimates with a maximum a posteriori probability estimator.

8. A mobile terminal comprising:

a receiver to receive a data symbol transmitted on one or more data subcarriers in a first sector; and

a subcarrier selector configured to;

determine overlapping pilot subcarriers in a second sector;

determine one or more overlapping pilot symbols transmitted on the overlapping pilot subcarriers;

a channel estimator to generate channel estimates associated with said overlapping pilot subcarriers in said second sector; and

an interference cancellation module to reduce interference in said received data symbol based on said overlapping pilot symbols and said channel estimates.

9. The mobile terminal of claim 8 wherein the subcarrier selector determines overlapping pilot subcarriers in a second sector by determining pilot carrier allocation for the second sector to identify pilot subcarriers overlapping in frequency and time with data subcarriers in the first sector.

10. The mobile terminal of claim 9 wherein the subcarrier selector determines pilot carrier allocation for the second sector by determining the location of subcarrier allocation zones in a frame, and determining the pilot subcarriers in said subcarrier allocation zones.

11. The mobile terminal of claim 8 wherein the subcarrier selector determines one or more overlapping pilot symbols transmitted on the overlapping pilot subcarriers by detecting a preamble transmitted in the second sector to obtain a sector identifier, and determining the overlapping pilot symbols based on the sector identifier.

12. The mobile terminal of claim 8 wherein said channel estimator averages said channel estimates over a plurality of symbol periods.

13. The mobile terminal of claim 8 wherein the channel estimator comprises a maximum likelihood estimator.

14. The mobile terminal of claim 8 wherein the channel estimator comprises a maximum a posteriori probability estimator.