Methods and systems for reducing interference across coverage cells

• US 20030003906A1
• Filed: 06/19/2001
• Published: 01/02/2003
• Est. Priority Date: 06/19/2001
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Telcordia Technologies Incorporated (Telefonaktiebolaget LM Ericsson)
• Inventors: Demers, Stephanie, Moshavi, Shimon, Zablocky, Paul G.
• Granted Patent: US 6,771,934 B2
• Time in Patent Office: Days
• US Class Current: 455/424
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: H04W 72/54 based on quality criteria

Abstract

Methods and systems are provided for reducing interference across coverage cells using base stations interconnected by a packet network. A wireless device monitors the channel signal strength of its serving cell and its neighboring cell. The serving cell collects measurements from the wireless devices within its cell and informs its neighboring cell when one of the wireless device may be causing significant interference to the neighboring cell. The neighboring cell collects this information and executes a multi-user detection and cancellation algorithm on a subset of these interfering wireless devices.

Claims

1. A method for reducing interference in a wireless communication system, comprising the steps of:

receiving, at a first cell, measurement information from a first wireless device served by the first cell while the first wireless device is at the first cell;

determining that the first wireless device causes interference at a second cell, serving wireless devices other than the first wireless device, based on the measurement information;

sending to the second cell information about the interference;

receiving the interference information at the second cell;

determining a signal based on the interference information; and

subtracting the signal at the second cell to reduce the interference.

2. The method of claim 1, wherein the step of receiving measurement information is responsive to a measurement request from the first cell.

3. The method of claim 1, wherein the step of receiving measurement information comprises the step of receiving measurement information that includes signal strength measurements on the first and second base stations and the transmit power of the first wireless device.

4. The method of claim 1, wherein the step of receiving measurement information comprises the step of receiving measurement information that includes signal-to-noise ratio measurements on the first and second base stations and the transmit power of the first wireless device.

5. The method of claim 3, wherein the location of the first wireless device is measured based on strength and interference impact of a channel signal from the second cell and received by the first wireless device.

6. The method of claim 1, wherein the steps of claim 1 is repeated for a second wireless device.

7. The method of claim 6, wherein the subtracting step comprises the steps of:

determining an approximate interference impact of the first and second wireless devices;

ranking the first and second wireless devices based on their respective approximate interference impact;

creating a list of wireless devices based on the interference impact of the first and second wireless devices; and

subtracting the signals of the wireless devices on the list.

8. The method of claim 6, wherein the subtracting step comprises the steps of:

determining a measured interference level of the first and second wireless devices;

ranking the first and second wireless devices based on their respective measured interference level;

creating a list of wireless devices based on the measured interference level of the first and second wireless devices; and

subtracting the signals of the wireless devices on the list.

9. The method of claim 7, wherein the step of creating a list of wireless devices is further based on processing burden of the first and second wireless devices, loading in the first and second cells, desired capacity at the second cell, and processing power availability at the second cell.

10. The method of claim 7, wherein the subtracting step comprises the steps of:

demodulating signals of the wireless devices on the list;

determining a bit estimate and a channel estimate for the demodulated signals of the wireless devices on the list; and

determining that the signals of the wireless devices on the list meet a goodness metric.

11. The method of claim 10, wherein only the signals of the wireless devices on the list meeting the goodness metric are subtracted.

12. The method of claim 10, wherein the step of determining a bit estimate is performed at the first cell when the signal is undetectable by the second cell.

13. The method of claim 10, wherein the step of determining a bit estimate is performed at the first cell and the bit estimate is transmitted from the first cell to the second cell when the signal is undetectable by the second cell.

14. The method of claim 10, wherein the goodness metric includes a CRC error check.

15. The method of claim 10, wherein the goodness metric includes a coding path difference.

17. The method of claim 16, wherein the sending step further comprises sending the information to the second cell through a packet network.

18. The method of claim 16, wherein the step of determining that the signal interferes comprises the step of receiving, at the first cell, measurement information from the first wireless device.

20. The method of claim 19, further comprising the step of creating a list of wireless devices based on interference impact of the plurality of wireless devices, loading at the first and second cells, desired capacity at the second cell, processing burden of the plurality of wireless devices, and processing power availability at the second cell.

21. The method of claim 20, further comprising the step of only demodulating the wireless devices on the list.

16. A method for reducing interference in a wireless communication system, comprising the steps of:

receiving a signal from a first wireless device served by a first cell while the first wireless device is at the first cell;

determining that the signal interferes with at least one other wireless device at a second cell serving wireless devices other than the first wireless device;

sending information about the first wireless device to the second cell; and

reducing the interference caused by the signal at the second cell based on the transmitted information.

19. A system for reducing interference between wireless devices, comprising:

a plurality of wireless devices including a first wireless device;

a plurality of cells including a first cell and a second cell; and

a packet network;

wherein the first cell receives measurement information from the first wireless device, determines that the first wireless device causes interference at the second cell, and transmits information about the interference to the second cell through the packet network; and

wherein the second cell receives the interference information from the first cell, and cancels the interference caused by the first wireless device based on the interference information.

22. A method for canceling interference between wireless devices, comprising the steps of:

providing a plurality of cells that serve a plurality of wireless devices;

monitoring signal strengths of the cells;

collecting, at the serving cells, information about the plurality of wireless devices;

determining that one or more of the wireless devices causes interference in one or more of the serving cells neighboring another one of the serving cells that serve the one or more wireless devices; and

transmitting information about the interference to the neighboring serving cells to cancel the interference.