Code reservation for interference measurement in a CDMA radiocommunication system

• US 7,151,761 B1
• Filed: 03/15/2000
• Issued: 12/19/2006
• Est. Priority Date: 03/19/1999
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Palenius, Torgny
• Primary Examiner(s): LEE, CHI HO A
• Application Number:
  US09/525,898
• Time in Patent Office: 2,470 Days
• Field of Search: 455/63.1, 455/67.11, 455/67.13, 455/68, 455/226.1, 455/226.2, 455/226.3, 455/278.1, 455/296, 455/115.1, 455/115.2, 455/115.3, 370/252, 370/248, 370/249, 370/251, 370/320, 370/335, 370/342
• US Class Current: 370/335
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 7/26 at least one of which is mobile
• CPC Class Codes: H04J 11/0023 Interference mitigation or co-ordination direct sequence spread spectrum [DSSS] systems H04B1/7097; frequency hopping H04B1/713; allocation criteria for ingress interference avoidance H04L5/0062; frequency allocation criteria for requirements on out-of-channel emissions H04L5/0066; arrangements for removing intersymbol interference or baseband equalisers H04L25/03006; peak power aspects in multicarrier modulation H04L27/2614; power management H04W52/00; traffic scheduling H04W72/54, H04W72/541
• CPC Class Codes: H04J 13/0044 OVSF [orthogonal variable spreading factor]
• CPC Class Codes: H04J 13/20 having an orthogonal variable spreading factor [OVSF]
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters

Abstract

Methods and structures for quickly and accurately measuring interference associated with a received signal in a CDMA radiocommunication system are described. Interference measurement is performed by despreading a received signal using a channelization code which is reserved from a finite set of orthogonal channelization codes. The reserved code is not used (or is rarely used) for spreading traffic and, therefore, provides an estimate of the interference associated with a received signal when a receiver correlates the received signal with the reserved code.

Claims

1. A method for estimating interference in a radiocommunication system comprising the steps of:

reserving at least one code in a set of codes for interference measurement only such that said at least one code is never used for transmitting signals;

receiving a composite signal that was not spread by using said at least one reserved code; and

estimating said interference at a receiver by correlating with said at least one reserved code.

2. The method of claim 1, further comprising the step of:

broadcasting information identifying said at least one code to said receiver.

3. The method of claim 1, further comprising the step of:

storing said at least one code in a terminal'"'"'s memory.

4. The method of claim 1, wherein the at least one code is reserved within a communication cell to which the receiver belongs.

5. The method of claim 1, wherein the estimating comprises despreading the received composite signal using the reserved at least one code, and the despread result contains only interference with respect to the mobile station.

6. A mobile station comprising:

a receiver for receiving a composite signal over an air interface and despreading said signal using at least one channelization code;

a processor for providing said at least one channelization code to said receiver, said at least one channelization code including a reserved code that is used only to estimate interference associated with said received signal,

wherein said reserved code is never used for transmitting said signal.

7. The mobile station of claim 6, wherein said receiver receives information over said air interface that identifies said reserved code.

8. The mobile station of claim 6, wherein said at least one channelization code also includes a code associated with a traffic channel assigned to said mobile station.

9. The mobile station of claim 6, further comprising:

a memory for storing said reserved code.

10. The mobile station of claim 6, wherein the received signal does not contain data intended for the receiver and spread with the reserved code.

11. The mobile station of claim 6, wherein the reserved code is reserved within a communication cell to which the mobile station belongs.

12. The mobile station of claim 6, wherein the receiver despreads the received signal using the reserved code, and the despread result contains only interference with respect to the receiver.

13. A mobile station comprising:

a receiver for receiving a signal over an air interface and despreading said signal using at least one channelization code; and

a processor for providing said at least one channelization code to said receiver, said at least one channelization code including a reserved code that is used only to estimate interference associated with said received signal,

wherein said at least one channelization code also includes a code associated with a traffic channel assigned to said mobile station; and

wherein said code associated with said traffic channel is selected based upon a desired user bit rate for a connection between said mobile station and a radiocommunication system.

14. A method for estimating interference in a system comprising a transmitter and a receiver, the method comprising the steps of:

reserving at least one code in a set of codes for interference measurement only, wherein the reserved at least one code is used within the system only to despread received signals and not to encode signals for transmission;

transmitting a signal that was not spread by using the reserved at least one code;

receiving the signal; and

estimating interference at the receiver by despreading the received composite signal using the reserved at least one code.

15. A method of estimating interference at a receiver in a communications system, the method comprising:

receiving a composite signal that includes a transmitted signal representing a data stream that has been spread by means of a first spreading code;

using the first spreading code to despread the composite signal and thereby retrieve the transmitted signal; and

estimating interference at the receiver by using a second spreading code to despread the composite signal, wherein the estimated interference represents interference that occurred during that part of the composite signal that includes the data stream,

wherein the second spreading code is reserved for interference measurement such that the second spreading code is not typically used for spreading traffic.

16. The method of claim 15, wherein the composite signal never includes a transmitted signal representing a data stream that has been spread by means of the second spreading code.

17. The method of claim 15, comprising:

prior to receiving the composite signal, receiving a transmitted signal that includes information identifying the second spreading code.

18. The method of claim 15, wherein each of the first and second spreading codes is an Orthogonal Variable Spreading Factor (OVSF) code selected from a code-tree.

19. The method of claim 18, wherein the second code has a spreading factor greater than or equal to 256.

20. A mobile unit for use in a communications system, the mobile unit comprising:

a receiver that receives a composite signal that includes a transmitted signal representing a data stream that has been spread by means of a first spreading code;

despreading logic that uses the first spreading code to despread the composite signal and thereby retrieve the transmitted signal; and

interference estimating logic that estimates interference at the receiver by using a second spreading code to despread the composite signal, wherein the estimated interference represents interference that occurred during that part of the composite signal that includes the data stream,

wherein the second spreading code is reserved for interference measurement such that the second spreading code is not used for spreading traffic.

21. The mobile unit of claim 20, wherein the composite signal never includes a transmitted signal representing a data stream that has been spread by means of the second spreading code.

22. The mobile unit of claim 20, comprising:

logic for retrieving, from a signal received prior to the composite signal, information identifying the second spreading code prior to receiving the composite signal.

23. The mobile unit of claim 20, wherein each of the first and second spreading codes is an Orthogonal Variable Spreading Factor (OVSF) code selected from a code-tree.

24. The mobile unit of claim 23, wherein the second code has a spreading factor greater than or equal to 256.