Method and system for determining correct escape mechanisms and controlling interference in third generation wireless systems

• US 7,133,673 B2
• Filed: 06/27/2003
• Issued: 11/07/2006
• Est. Priority Date: 06/28/2002
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Zeira, Eldad, Hunkeler, Teresa
• Primary Examiner(s): D AGOSTA, STEPHEN M
• Application Number:
  US10/608,280
• Publication Number:
  US 20040092232A1
• Time in Patent Office: 1,229 Days
• Field of Search: 455/436, 455/453, 455/437, 455/438, 455/439, 455450-4522, 455/509, 455/512, 370/330, 370/331, 370/329, 370/337, 370/319, 375/148
• US Class Current: 455/436
• CPC Class Codes: H04W 16/14 Spectrum sharing arrangements between different networks
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 36/20 for optimising the interference level

Abstract

A correct escape mechanism is determined according to interference type. Transmission is arranged so that interference may be measured at all time slots as needed to compute a measure of variance in interference in time slots. If the variance is above a predetermined value, time division duplex escape mechanisms are employed. If the variance is below a predetermined value, appropriate escape mechanisms are employed depending on whether the escape mechanism is being implemented during an uplink or downlink. Interference causing FDD WTUs may be handed over to carrier bands to control interference experienced by TDD users.

Claims

1. A method for minimizing interference in a wireless communication system employing both time division duplex (TDD) and frequency division duplex (FDD) modes, wherein a transmission between at least one base station and at least one wireless transmit/receive units (WTRUs) occurs in a plurality of time-slots, the method comprising:

measuring interference in at least two of said time slots;

computing the variance of said measured interference between said time slots if said measured interference in active slots is above a first predetermined value (to determine if the interference is continuous or discontinuous);

employing TDD escape mechanisms if the variance is above a second predetermined value indicating the measured interference is discontinuous; and

employing a handover escape mechanism if the variance is below the second predetermined value indicating the measured interference is continuous.

2. The method of claim 1 wherein the measure of variance is computed based on downlink time slots.

3. The method of claim 1 wherein the measure of variance is computed based on downlink time slots and uplink time slots.

4. The method of claim 1, wherein the TDD escape mechanism comprises time slot reallocation.

5. The method of claim 1, wherein the TDD escape mechanism comprises dynamic channel allocation.

6. The method of claim 1, wherein the TDD escape mechanism comprises dynamic channel selection.

7. The method of claim 1, wherein the handover escape mechanism comprises inter-frequency handover.

8. The method of claim 1, wherein the WTRU experiencing the continuous interference is dual mode capable, and the handover escape mechanism comprises inter-mode handover.

9. A method for evaluating uplink interference to determine a correct escape mechanism according to interference type in a wireless communication system employing both time division duplex (TDD) and frequency division dunlex (FDD) modes, the method comprising:

arranging uplink transmissions so that interference may be measured at all time slots;

measuring interference to obtain a sampling of interference in the uplink time slots;

computing a measure of variance between time slots if interference in active slots is above a first predetermined value;

employing time division duplex escape mechanisms if the computed variance is not below a second predetermined value; and

reducing cell load if the variance is below the second predetermined value.

10. The method of claim 9 wherein the measure of variance is computed based on uplink time slots.

11. The method of claim 9 wherein the measure of variance is computed based on uplink time slots and downlink time slots.

12. A method for determining an appropriate escape mechanism based on a type of interference encountered during a transmission, the method comprising:

receiving transmissions of a predetermined signal category;

arranging said transmissions to a predetermined group of slots, so that interference may be measured at all of said slots;

measuring interference at all of said slots;

time averaging the measured interference to create time averaged values, and transmitting the time averaged values to a radio network controller;

evaluating the time averaged interference measurements with respect to a first predetermined value;

in the case of the interference measurements being below the first predetermined value, accepting the transmissions;

in the case of the interference measurements being above the first predetermined value, computing a measure of variance between slots and evaluating the variance with respect to a second predetermined value;

in the case of the interference variance being below the second predetermined value, executing a handover as an escape mechanism;

in the case of the interference variance being above the second predetermined value for the variance, executing a TDD escape mechanism for discontinuous interference.

13. The method of claim 12, wherein the execution of the handover includes changing to a different carrier frequency.

14. The method of claim 12, wherein the execution of the handover includes changing to a different access mode.

15. The method of claim 12 comprising making the determination of the appropriate escape mechanism for an uplink transmission.

16. The method of claim 12 comprising making the determination of the appropriate escape mechanism for a downlink transmission.

17. The method of claim 12, wherein the measured interference includes uplink interference or downlink interference.

18. The method of claim 12 further comprising:

determining if an FDD carrier band from a FDD WTRU exists in a TDD area and thereby causing said interference;

determining a location of the FDD WTRU;

communicating the location to a radio controller able to provide control of said FDD WTRU; and

enabling a handover action for said FDD WTRU carrier band, thereby

reducing interference caused by communications of the FDD WTRU.

19. The method of claim 12, wherein the TDD escape mechanism comprises:

handing over WTRUs located in an area with TDD and FDD service and operating in a carrier band that is adjacent to a TDD carrier band from the adjacent carrier band to a carrier band that is alternate to the TDD carrier; and

handing over WTRUs located in an area with FDD service and operating in the alternate carrier band from the alternate carrier band to the adjacent carrier band.

20. A dual mode wireless transmit and receive unit (WTRU) capable of operating in time division duplex (TDD) and freauencv division duplex (FDD) modes for implementing an escape mechanism according to interference type, the WTRU comprising:

an uplink transmitter;

a circuit for measuring interference in a plurality of uplink time slots;

a circuit for transmitting the measured interference to a radio network controller through the uplink transmitter, wherein the radio network controller computes a measure of variance between the time slots if interference in active time slots exceeds a predetermined value (to determine whether the interference is continuous or discontinuous); and

a circuit for employing time division duplex escape mechanisms if the variance is above the predetermined value indicating the interference is discontinuous and employing a handover escape mechanism if the variance is below the predetermined value indicating the interference is continuous.

21. A radio network controller (RNC) for minimizing interference in a wireless communications network employing both time division duplex (TDD) and freauencv division duplex (FDD) modes in which a plurality of wireless transmit and receive units (WTRUs) communicate with a plurality of base stations, and the WTRUs utilize an escape mechanism according to interference type, the RNC comprising:

a circuit for scheduling transmission so that interference may be measured at all of a predetermined group of time slots;

a circuit for providing measured interference to a radio network controller and computing a measure of variance between the time slots if interference in active time slots is above a predetermined value (to determine if the interference is continuous or discontinuous); and

a circuit for employing TDD escape mechanisms in the case of the variance being above a predetermined value indicating the measured interference is discontinuous, and employing a handover escape mechanism in the case of the variance being below a predetermined value indicating the measured interference is continuous.