Method of minimizing reverse channel interference caused by an abnormally high number of access attempts in a wireless communications system

• US 7,228,134 B2
• Filed: 06/17/2003
• Issued: 06/05/2007
• Est. Priority Date: 06/17/2003
• Status: Active Grant

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Gandhi, Asif D, Zhu, Lily H, Thomas, Mathew
• Primary Examiner(s): SMITH, CREIGHTON H
• Application Number:
  US10/463,995
• Publication Number:
  US 20040259528A1
• Time in Patent Office: 1,449 Days
• Field of Search: 455/452.1, 455/452.2, 455/453
• US Class Current: 455/434
• CPC Class Codes: H04W 48/06 based on traffic conditions
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 74/002 Transmission of channel access control information
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access

Abstract

When an overload condition is determined to exist at a base station in a wireless communications system based on the number of unsuccessful access attempts to access the system relative to the successful access attempts to access the system, the base station broadcasts a message to each mobile terminal within its coverage area that changes at least one access probe-related parameter associated with at least one of: the number, the frequency, and the power intensity of the access probes made by these mobile terminals as they attempt to establish access to the wireless network. By so limiting these access probes in some manner when an overload condition is present, the interference caused on the reverse link by many mobile terminals attempting access is reduced.

Claims

1. A method in a wireless communications system in which one or more mobile terminals attempt to establish communications with a base station through at least one access attempt, the method comprising the steps of:

when an overload condition is determined to be present, sending in a message information for controlling the access attempt,

wherein the access attempt comprises one or more access probes transmitted by the mobile terminal and the information in the message is for controlling the transmission of at least one of;

the number of access probes, the frequency of the access probes, and the intensity of the access probes, and

wherein an overload condition is determined to be present when a number of seizures relative to a number of assignments recorded by the base station over a predefined period of time is greater than a predetermined threshold.

2. The method of claim 1 wherein the message is an overhead message that is continuously transmitted on a paging channel.

3. The method of claim 1 wherein an overload condition is determined to be present only when the difference between the number of seizures and the number of assignments is greater than a predetermined number.

4. The method of claim 1 wherein the information in the message is used to change the value of at least one probe-related parameter related to at least one of:

number of access probes, the frequency of the access probes, and the intensity of the access probes, so as to reduce the number and/or the frequency, and/or to vary the intensity of the probes transmitted by the mobile terminal from a default value of the same parameter used when an overload condition is not present in the system.

5. The method of claim 4 further comprising the step of:

when an overload condition is determined to be easing, sending in a message information to change in a direction towards, its default values the value of at least one of the probe-related parameters that was changed in response to the overload condition.

6. The method of claim 1 wherein the information in the message is directed to a specific mobile terminal to inhibit that mobile terminal from attempting access for a period of time.

7. The method of claim 6 wherein the information in the message is directed to a specific mobile terminal to inhibit that mobile terminal from attempting access for a new connection for a period of time after that mobile terminal has completed a previous connection.

8. The method of claim 6 wherein the information in the message is directed to a specific mobile terminal to inhibit that mobile terminal from re-attempting access for a period of time after a previous unsuccessful access attempt.

9. The method of claim 1 wherein the information in the message redirects access requests made by a subset of the mobile terminals to a wireless system that is unavailable as a redirection target system.

10. The method of claim 9 wherein the message is a Global Service Redirection (GSR) message.

11. The method of claim 10 wherein the GSR message is repeatedly transmitted for a predetermined time period, after which a new GSR message is sent to redirect access requests made by a different subset of the mobile terminals to the unavailable redirection target system.

12. A method in a wireless communication system in which one or more mobile terminals attempt to establish communications with a base station through an access attempt, the method comprising the steps of:

at a mobile terminal, making an access attempt in response to information in a message received from the base station that is transmitted to control the making of the access attempt when the base station determines that an overload condition is present, the base station determining that an overload condition is present when a number of seizures relative to a number of assignments recorded by the base station over a predefined period of time is greater than a predetermined threshold,

wherein making an access attempt comprises transmitting one or more access probes and the information in the message controls the transmission of at least one of;

the number of access probes, the frequency of the access probes, and the intensity of the access probes.

13. The method of claim 12 wherein the message is an overhead message that is continuously received over a paging channel.

14. The method of claim 12 wherein the information in the received message is used to change the value of at least one probe-related parameter related to at least one of:

number of access probes, the frequency of the access probes, and the intensity of the access probes, so as to reduce the number and/or the frequency, and/or to vary the intensity of the transmitted probes from a default value of the same parameter used when an overload condition is not present.

15. The method of claim 14 further comprising the step of:

in response to information in a message received when an overload condition is determined to be easing, changing in a direction towards its default value the value of at least one of the probe-related parameters that was changed in response to the overload condition.

16. The method of claim 12 wherein the information in the message inhibits making any access attempts for a specified period of time.

17. The method of claim 12 wherein the information in the message redirects a subsequent access request by the base station to an unavailable redirection target.

18. The method of claim 17 wherein the message is a Global Service Redirection message.

19. A method in a wireless communications system in which one or more mobile terminals attempt to establish communications with a base station through at least one access attempt, the method comprising the steps of:

when an overload condition is determined to be present, sending in a message information for controlling the access attempt,

wherein the access attempt comprises one or more access probes transmitted by the mobile terminal and the information in the message is for controlling the transmission of at least one of;

the number of access probes, the frequency of the access probes, and the intensity of the access probes, and

wherein an overload condition is determined to be present based on the number of unsuccessful attempts by mobile terminals to access the system relative to the number of successful attempts to access the system over a predetermined period of time.