In a radio network environment, reducing interference among overlapping cells

• US 9,049,715 B2
• Filed: 03/08/2012
• Issued: 06/02/2015
• Est. Priority Date: 08/04/2009
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Inventors: Xu, Ning, Yang, Jin
• Primary Examiner(s): Eng, George
• Assistant Examiner(s): HAMMONDS, MARCUS C
• Application Number:
  US13/414,799
• Publication Number:
  US 20130130699A1
• Time in Patent Office: 1,181 Days
• Field of Search: 455443-444, 455446-454, 370/322, 370/329, 370/341
• US Class Current: 1/1
• 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 located in a cell-center area of the macrocell;

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

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

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

scheduling, by the macrocell, in response to the indication, the cell-center user to communicate via one or more frequency sub-channels included in a subset of the first set of frequency sub-channels, the frequency sub-channels in the subset being assigned a higher power than the other frequency sub-channels in the first set of frequency sub-channels.

2. 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 located in a cell-center area of the macrocell, for assigning a second set of frequency sub-channels to be used by cell-edge users of the macrocell located in a cell-edge area of the macrocell, for receiving, via the transceiver from a cell-center user, a neighbor list, the neighbor list comprising the femtocell, for receiving, via the transceiver from the cell-center user, an indication of a strength of a signal received from the femtocell, and for scheduling, in response to the indication, the cell-center user to communicate via one or more frequency sub-channels included in a subset of the first set of frequency sub-channels, the frequency sub-channels in the subset being assigned a higher power than the other frequency sub-channels in the first set of frequency sub-channels.