Systems and methods for making channel assignments to reduce interference and increase capacity of wireless networks

• US 7,257,376 B2
• Filed: 06/30/2005
• Issued: 08/14/2007
• Est. Priority Date: 06/30/2005
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Adaptix, Inc. (Acacia Research Corporation)
• Inventors: Reudink, Douglas O.
• Primary Examiner(s): Feild, Joseph
• Assistant Examiner(s): MEHRA, INDER P
• Application Number:
  US11/172,604
• Publication Number:
  US 20070004420A1
• Time in Patent Office: 775 Days
• Field of Search: 455/62, 455/63.1, 455/450, 455/452.1, 455/451, 455/509, 455/513
• US Class Current: 455/63.1
• CPC Class Codes: H04J 11/003 at the transmitter transmission to multiple receive units in multiple input multiple output [MIMO] H04B7/0452; transmit antenna weighting H04B7/0615
• CPC Class Codes: H04J 11/0056 Inter-base station aspects
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0073 Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 72/54 based on quality criteria
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 72/542 using measured or perceived quality

Abstract

There is disclosed a system and method for improving wireless system capacity by reducing collisions where the Signal to Interference Ratio (SIR) is high in systems having a channel reuse of 1. By ordering the channel assignment in each of the interfering cells according to a pattern, for example, according to the distance from a base station (determined by power levels), the mobile stations will become paired on the same channel in a manner to reduce interference between them. In one embodiment, this intelligent assignment is accomplished by assigning mobile stations in one cell such that the mobile station having the strongest signal is assigned channel A while in the interfering cell the mobile station with the weakest signal is assigned to channel A. In another embodiment, certain preferred mobile stations are assigned either interference-free channels or channels paired with weak interference mobile stations.

Claims

1. A method for assigning channels in a wireless system, said method comprising:

determining at a given point in time in interfering cells which mobile stations (MSs) in each said cell are communicating with the highest signal strength; and

assigning channels to said MSs based on said determined signal strength;

wherein said assigning comprises;

in one of said cells making the channel assignment such that a MS with a highest signal strength is assigned a particular channel and in the interfering cell the assignment is that a MS with a lowest signal strength is assigned said particular channel.

2. A method for assigning channels in a wireless system, said method comprising:

determining at a given point in time in interfering cells which mobile stations (MSs) in each said cell are communicating with the highest signal strength; and

assigning channels to said MSs based on said determined signal strength;

in one of said cells making the channel assignment such that preferred MSs are assigned to certain channels and in the interfering cell said certain channels are reserved.

3. The method of claim 2 wherein said reserved channels are maintained in at least one cell without any MS assignments.

4. The method of claim 3 wherein said reserved channels are limited to a certain power level.

5. The method of claim 2 wherein the determined MSs with the weakest receiver power are assigned to said reserved channels.

6. The method of claim 2 where preferred MSs are allocated additional transmit power.

7. A method of assigning channels to MSs, said method comprising:

in a pair of potentially interfering cells, establishing an assignment order of channels such that with respect to an ordered series of channels in each cell a first cell will assign MSs to channels according to a particular assignment pattern while in the second of said cells the assignment will be in the mirror image of the assignment in said first cell, wherein said particular pattern is in the order of strongest to weakest signal strength with respect to said first cell and said channel assignment is in the order of weakest to strongest with respect to the same ordered series of channels in said second cell.

8. The method of claim 7 further comprising:

in each cell making a determination of MS signal strength on a periodic basis; and

making said assignment of said MS signal according to each said determination.

9. The method of claim 8 wherein said periodic basis is on the order of 5 MS.

10. The method of claim 8 wherein said periodic basis is on the order of 10 MS.

11. The method of claim 7 wherein said particular pattern is such that a first group of channels of said ordered channels in said first cell is reserved for particular MSs and a last group of channels of said ordered channels in said second cell is reserved for said particular MSs.

12. The method of claim 11 wherein said first group of channels of said ordered channels in said second cell is reserved for the weakest signal strength receivers.

13. The method of claim 12 further comprising:

in each cell making a determination of MS signal received signal strength on a periodic basis; and

making said assignment of said MSs according to each said determination.

14. The method of claim 7 further comprising:

changing from time to time the power levels of the base station (BS) with respect to certain MSs.

15. A wireless system comprising:

at least two BSs each defining a cell, said BSs using an N=1 repeat pattern;

means for determining relative signal strength among MSs communicating with each said BS; and

means for assigning MSs according to a pattern designed to minimize interference between MSs in each of said cells using the same channels; and

means for assigning an order to said channels in each said cell such that in one cell the weakest signal strength MSs are assigned from one end of said channel order and the strongest signal strength MSs are assigned from the other end of said channel order.

16. The system of claim 15 further comprising:

means for designating certain of said MS as preferred MSs; and

means for pairing preferred MSs in one of said cells with weak signal strength MS, in the other of said cells.

17. The system of claim 16 further comprising:

means operative from time to time for modifying the power level between a BS and one or more MS, in order to optimize capacity across both of said cells.