Method for eliminating multiple-access interference and a mobile station

• US 5,799,004 A
• Filed: 07/02/1996
• Issued: 08/25/1998
• Est. Priority Date: 10/27/1993
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Telecommunications Limited (Nokia Corporation)
• Inventors: Kiema, Arto, Keskitalo, Ilkka, Jolma, Petri, Savusalo, Jari
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US08/637,659
• Time in Patent Office: 784 Days
• Field of Search: 455/422, 455/423, 455/454, 455/501, 455/515, 455/524, 455/63, 455/303, 455/304, 455/305, 370/320, 370/335, 370/342, 375/200, 375/346, 375/349
• US Class Current: 370/335
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

A mobile station, and a method for eliminating multiple-access interference in a CDMA cellular radio system having a plurality of cells each having at least one base station communicating with mobile stations residing in the respective cell and informing the respective mobile stations of at least one spreading code used in a neighboring cell, the mobile stations measuring the code phase and power level of a channel of the neighboring cell using the known spreading code. To reduce the effect of multiple-access interference, the signal received at the mobile station is utilized in the detection of the desired signal by using the code phase and power level of the measured channel using the known spreading code of the neighboring cell.

Claims

1. A method for eliminating multiple-access interference in CDMA cellular radio system having a plurality of cells each comprising at least one base station arranged for communicating by CDMA with mobile stations present in a geographic area covered by the respective cell, comprising the steps of:

at least one said base station of one said cell, being a presently dedicated base station relative to at least a respective one of said mobile stations and being bordered by at least another, neighboring said cell having a respective neighboring base station, informing said mobile station of at least one CDMA spreading code used in said one cell and at least one CDMA spreading code used in at least one said neighboring cell;

said one base station and at least one said neighboring base station respectively transmitting components of a desired signal and a signal to be measured, on respective channels, using respective CDMA spreading codes;

said mobile station measuring the code phase and power level of a respective channel of each of said one cell and said at least one neighboring cell, using respective CDMA spreading codes as made known to said mobile station by said practicing of said informing step; and

said mobile station detecting, from signal components thereby received, said desired signal, by eliminating interference from said signal components as received by said mobile station, based on said measuring.

2. The method of claim 1, wherein said detecting by eliminating comprises:

said mobile station estimating interference caused by at least one said respective channel of said at least one neighboring cell using a DMS spreading code for the respective neighboring cell as made known to said mobile station by said practicing of said informing step, by;

calculating a cross-correlation between components of said desired signal as detected from respective transmissions of said one base station and said at least one neighboring base station, and

weighting said cross-correlation with respective power levels obtained in said measuring step; and

said mobile station subtracting interference thereby estimated, from the signal components received, to obtain the desired signal.

3. The method of claim 1, wherein:

said at least one CDMA spreading code used in said at least one said neighboring cell, of which said base station informs said mobile station in said informing step comprises a spreading code used on a traffic channel of a respective neighboring cell.

4. The method of claim 1 wherein:

said at least one CDMA spreading code used in said at least one said neighboring cell, of which said base station informs said mobile station in said informing step comprises a spreading code used on a pilot channel of a respective neighboring cell.

5. The method of claim 1, wherein:

in conducting said informing, said base station transmits to said mobile station on a control channel.

6. The method of claim 1, wherein:

in conducting said informing, said base station informs said mobile station in regard to less than all spreading codes in use by said at least one neighboring cell, by including at least one more likely to correlate with multiple-access interference, and by excluding at least one less likely to correlate with multiple-access interference, as experienced by said mobile station.

7. The method of claim 6, wherein:

said including and excluding is practiced at least in part based on relative power levels of transmissions by the at least one neighboring base station.

8. The method of claim 6, further comprising:

a base station controller in control of said base station determining for said base station which CDMA spreading codes said base station will inform said mobile station of in said informing step.

9. The method of claim 1, further comprising:

practicing of said informing step being initiated by said mobile station requesting said base station to so inform said mobile station.

10. The method of claim 1, wherein:

said base station is a presently dedicated base station as to at least another respective one of said mobile stations; and

said informing step is practiced by said base station in regard to less than all of said mobile stations for which said base station is a presently dedicated base station, depending on relative likelihood of experiencing multiple-access interference.

11. A mobile station useable for eliminating multiple-access interference when communicating in a CDMA cellular radio system having a plurality of cells each comprising at least one base station arranged for communicating by CDMA with mobile stations present in a geographic area covered by the respective cell, when said base station is performing as a dedicated base station relative to at least one mobile station, including said base station, and while bordered by at least another, neighboring said cell having a respective neighboring base station, said mobile station comprising:

receiver means for causing said mobile station to become informed by said base station of at least one CDMA spreading code used in said one cell and at least one CDMA spreading code used in at least one said neighboring cell, and for detecting components of a desired signal and a signal to be measured, respectively transmitted by said base station and said at least one neighboring base station, on respective channels, using respective CDMA spreading codes;

measuring means arranged for measuring the code phase and power level of a respective channel of each of said one cell and said at least one neighboring cell, using respective CDMA spreading codes as made known to said mobile station by said practicing of said informing; and

detecting by eliminating means for detecting, from signal components thereby received, said desired signal, by eliminating interference from said signal components as received by said mobile station, based on said measuring.

12. The mobile station of claim 11, wherein said detecting by eliminating means is arranged for:

estimating interference caused by at least one said respective channel of said at least one neighboring cell as made known to said mobile station by said practicing of said informing, by;

calculating a cross-correlation between components of said desired signal as detected from respective transmissions of said one base station and said at least one neighboring base station, and weighting said cross-correlation with respective power levels obtained in said measuring; and

for

subtracting said mobile station interference thereby estimated, from the signal components received, to obtain the desired signal.

13. The mobile station of claim 11, further including:

storage means for storing information about the CDMA spreading codes in use on connectors of said at least one neighboring base station which are capable of interfering with reception by said mobile station of said desired signal;

said mobile station being arranged for using said information as stored by said storage means, in practicing said eliminating.