Radio network environment, reducing interference among overlapping cells

• US 8,254,937 B2
• Filed: 03/08/2012
• Issued: 08/28/2012
• Est. Priority Date: 08/04/2009
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Inventors: Xu, Ning, Yang, Jin
• Primary Examiner(s): Addy, Anthony
• Assistant Examiner(s): Obayanju, Omoniyi
• Application Number:
  US13/414,812
• Publication Number:
  US 20120172046A1
• Time in Patent Office: 173 Days
• Field of Search: 455/443, 455/444, 455/450, 455/452.1, 455/452.2, 370/322, 370/341, 370/329
• US Class Current: 455/443
• CPC Class Codes: H04W 16/02 Resource partitioning among network components, e.g. reuse partitioning
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/27 between access points
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

Disclosed is a method for a femtocell to reduce interference with an overlapping macrocell. The femtocell determines soft-frequency-reuse (“SFR”) information of the macrocell. From that information, the femtocell determines which frequency sub-channels are assigned by the macrocell for its cell-center users and which frequency sub-channels are assigned for cell-edge users. (Cell-edge users are given a higher transmission power profile in order to overcome potential interference with neighboring macrocells.) Then, the femtocell selects from the cell-center user frequency sub-channels for transmission to the femtocell'"'"'s users. By transmitting on the cell-center user frequency sub-channels, the femtocell reduces interference with the overlapping macrocell. The femtocell continues to update its knowledge of the macrocell'"'"'s SFR information and re-assigns frequency sub-channels as the SFR changes. If the macrocell detects that one of its cell-center users is “close enough” to the femtocell, then the macrocell re-assigns the cell-center user as a cell-edge user to overcome interference.

Claims

1. A method for a macrocell to reduce signal interference with a femtocell that overlaps the macrocell, the method comprising:

assigning, by the macrocell, a first set of frequency sub-channels to be used by cell-center users of the macrocell;

assigning, by the macrocell, a second set of frequency sub-channels to be used by cell-edge users of the macrocell;

detecting, by the macrocell, that a cell-center user of the macrocell is close enough to the femtocell;

assigning, by the macrocell, higher schedule priority for the cell-center user of the macrocell that is close enough to the femtocell to a subset of the first set of frequency sub-channels than to frequency sub-channels in the first set but not in the subset; and

setting, by the macrocell, a staged power profile wherein a power assigned for the subset of the first set of frequency sub-channels is higher than a power assigned for frequency sub-channels in the first set but not in the subset.

2. The method of claim 1 wherein detecting that the cell-center user of the macrocell is close enough to the femtocell comprises:

receiving, by the macrocell from the cell-center user, a neighbor list, the neighbor list comprising the femtocell; and

receiving, by the macrocell from the cell-center user, an indication that a strength of a signal received from the femtocell is above a threshold.

3. A controller for controlling a macrocell, the controller comprising:

a transceiver; and

a processor operatively connected to the transceiver and configured for assigning a first set of frequency sub-channels to be used by cell-center users of the macrocell, for assigning a second set of frequency sub-channels to be used by cell-edge users of the macrocell, for detecting that a cell-center user of the macrocell is close enough to the femtocell, for assigning higher schedule priority for the cell-center user of the macrocell that is close enough to the femtocell to a subset of the first set of frequency sub-channels than to frequency sub-channels in the first set but not in the subset, and for setting a staged power profile wherein a power assigned for the subset of the first set of frequency sub-channels is higher than a power assigned for frequency sub-channels in the first set but not in the subset.

4. The controller of claim 3 wherein the processor is further configured for receiving, via the transceiver from the cell-center user, a neighbor list, the neighbor list comprising the femtocell, and for receiving, via the transceiver from the cell-center user, an indication of a strength of a signal received from the femtocell.