METHOD FOR PERFORMING ACTIVE CANCELLATION OF INTER-CELL INTERFERENCE IN A CELLULAR WIRELESS ACCESS SYSTEM

Abstract

The present invention relates to a method for improving inter cell interference cancellation in an cellular radio communication system, said cellular radio communication system sending OFDM frames on an air interface, each OFDM frame comprising a pilot tones part and a payload part comprising a plurality of bursts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment given by the way of non-limiting illustrations, and from the accompanying drawings, in which:

FIGS. 1 a, 1b show a pilot tone arrangement according to a first embodiment of the present invention;

FIGS. 2 a, 2b show a pilot tone arrangement according to a second embodiment of the present invention;

FIGS. 3 a, 3b show a pilot tone arrangement according to a third embodiment of the present invention;

FIGS. 4 a, 4b show a pilot tone arrangement according to a fourth embodiment of the present invention;

FIG. 5 shows a base station implementing the method according to the present invention;

FIG. 6 shows a subscriber station implementing the method according to the present invention.

Claims

1/ A method for improving inter cell interference cancellation in an cellular radio communication system, said cellular radio communication system sending OFDM frames on an air interface, each OFDM frame comprising a pilot tones part and a payload part comprising a plurality of bursts, said method comprising the steps of: Sending on a sub channel a first set of pilot tones by the station sending a burst on said sub channel;Sending additionally in said frame and on said sub channel a second set of pilot tones by an additional station when a burst sent by said additional station starts on said sub channel.

2/ The method according to claim 1, wherein said first set of pilot tones is sent in a first symbol of said sub channel and said second set of pilot tones is sent on a second symbol of said sub channel.

3/ The method according to claim 1, wherein the whole or a subset of said first set of pilot tones and the whole or a subset of said second set of second pilot tones are multiplexed on a single symbol of said sub channel.

4/ The method according to claim 1, wherein said station is a subscriber station sending bursts in the uplink direction.

5/ The method according to claim 1, wherein said station is a base station sending bursts in the downlink direction.

6/ The method according to claim 1, wherein said radio communication system is using Orthogonal Frequency Division Multiple Access technology on the air interface, each frame having a time and frequency extension.

7/ The method according to claim 1, wherein said pilot tones are comprised in a 3-OFDM-symbol-broad sounding zone on each of said sub channels, one OFDM symbol being used for downlink inter cell interference cancellation according to claim 3 and two OFDM symbols being used for uplink inter cell interference cancellation according to claim 2.

8/ The method according to claim 1, wherein said pilot tones are comprised in a 3-OFDM-symbol-broad sounding zone on each of said sub channels, one OFDM symbol used for calculating a frequency response from active subscriber stations in a cell and two OFDM symbols used for uplink inter cell interference cancellation according to claim 2.

9/ The method according to claim 1, wherein said radio communication system uses beamforming technology at base stations.

10/ A subscriber station adapted to be used in a cellular radio communication system, said cellular radio communication system exchanging OFDM frames on an air interface, each OFDM frame comprising a pilot tones part and a payload part comprising a plurality of bursts, said subscriber station comprising: means for detecting if the first symbol of a burst on a given sub-channel falls or not on the first symbol of said payload part;means for sending in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel does not fall on the first symbol of said payload part.

11/ The subscriber station according to claim 10, further comprising: means for sending in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel falls on the first symbol of said payload part.

12/ The subscriber station according to claim 10, said subscriber station further comprising: means for receiving in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel falls on the first symbol of said payload part and using said pilot tones for adaptive interference cancellationmeans for receiving in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel does not fall on the first symbol of said payload part and using said pilot tones for adaptive interference cancellation.

13/ A base station adapted to be used in a cellular radio communication system, said cellular radio communication system exchanging OFDM frames on an air interface, each OFDM frame comprising a pilot tones part and a payload part comprising a plurality of bursts, said base station comprising: means for detecting if the first symbol of a burst starting on a given sub-channel falls or not on the first symbol of said payload part;means for sending in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel does not fall on the first symbol of said payload part.

14/ The base station according to claim 13, further comprising: means for sending in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel falls on the first symbol of said payload part.

15/ The base station according to claim 13, further comprising: means for receiving in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel falls on the first symbol of said payload part and using said pilot tones for adaptive interference cancellationmeans for receiving in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel does not fall on the first symbol of said payload part and using said pilot tones for adaptive interference cancellation.

16/ The base station according to claim 13, further comprising: means for directing a subscriber station to sent in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel falls on the first symbol of said payload partmeans for directing a subscriber station to sent in a predefined symbol of said sub channel a predefined set of pilot tones when the first symbol of said burst starting on a given sub-channel does not fall on the first symbol of said payload part.