Almost blank subframe allocation in heterogeneous network

1. A method comprising:

a) providing, by a first base station, an overlapping coverage area with each of a plurality of second base stations and each of a plurality of third base stations;

b) each of said plurality of second base stations:

i) allowing access to a plurality of wireless devices; and

ii) configuring a second plurality of Almost Blank Subframes, base stations in said plurality of second base stations configuring the same set of subframes as said second plurality of Almost Blank Subframes; and

c) each of said plurality of third base stations:

i) allowing access only to a restricted subset of said plurality of wireless devices; and

ii) configuring a third plurality of Almost Blank Subframes, at least two base stations in said plurality of third base stations not configuring the same set of subframes as said third plurality of Almost Blank Subframes; and

wherein during a majority of symbols of an Almost Blank Subframe of a base station: signals are transmitted at an Almost Blank Subframe power level that is substantially lower than a transmit power during a non-Almost Blank Subframe.

2. The method of claim 1 , wherein each base station in a plurality of base stations broadcasts the same system frame number if said frames are transmitted substantially at the same time.

3. The method of claim 1 , wherein each of said restricted subset of said plurality of wireless devices is configured with a closed subscriber group white-list including the closed subscriber group identity of a base station in said plurality of third base stations.

4. The method of claim 1 , wherein said at least two base stations in said plurality of third base stations broadcast different closed subscriber group identities.

5. The method of claim 1 , wherein in said Almost Blank Subframe, a common reference signal is transmitted only in a control region.

6. The method of claim 1 , further comprising, each of said plurality of third base stations broadcasting a closed subscriber group indicator and a closed subscriber group identity.

7. The method of claim 1 , wherein said first base station is of a different base station type than said plurality of second base stations and said plurality of third base stations.

8. The method of claim 1 , wherein frame and subframe transmissions of said first base station and each of said plurality of second base stations and each of said plurality of third base stations are substantially synchronized.

9. A method comprising:

a) providing, by a first base station, an overlapping coverage area with each of a plurality of second base stations and each of a plurality of third base stations;

b) each of said plurality of second base stations:

i) allowing access to a plurality of wireless devices; and

ii) transmitting, to a second plurality of wireless devices in connected mode, a second message comprising a second subframe allocation bitmap indicating a second plurality of subframes, said second plurality of subframes comprising a second plurality of Almost Blank Subframes, base stations in said plurality of second base stations identifying the same set of subframes as said second plurality of Almost Blank Subframes; and

c) each of said plurality of third base stations:

i) allowing access only to a restricted subset of said plurality of wireless devices; and

ii) transmitting to a third plurality of wireless devices in connected mode, a third message comprising a third subframe allocation bitmap indicating a third plurality of subframes, said third plurality of subframes comprising a third plurality of Almost Blank Subframes, at least two base stations in said plurality of third base stations identifying different sets of subframes as said third plurality of Almost Blank Subframes.

10. The method of claim 9 , further comprising said first base station transmitting a message to each of said plurality of second base stations, said message comprising a first pattern bitmap indicating a first Almost Blank Subframe allocation.

11. The method of claim 9 , wherein said first base station is of a different base station type than said plurality of second base stations and said plurality of third base stations.

12. The method of claim 9 , wherein during a majority of symbols of an Almost Blank Subframe of a base station: signals are transmitted at an Almost Blank Subframe power level that is substantially lower than a transmit power during a non-Almost Blank Subframe.

13. The method of claim 9 , wherein frame and subframe transmissions of said first base station and each of said plurality of second base stations and each of said plurality of third base stations are substantially synchronized.

14. The method of claim 9 , further comprising, each of said plurality of third base stations broadcasting a closed subscriber group indicator and a closed subscriber group identity.

15. The method of claim 9 , wherein said at least two base stations in said plurality of third base stations provide an overlapping coverage area in at least a region in the service area.

16. The method of claim 9 , further comprising transmitting, by said first base station, a first message to a first plurality of wireless devices in connected mode, said first message comprising a first subframe allocation bitmap indicating a first plurality of subframes, said first plurality of subframes comprising a first plurality of Almost Blank Subframes, wherein said first plurality of Almost Blank Subframes and said second plurality of Almost Blank Subframes do not have a substantial overlap in time.

17. The method of claim 16 , wherein said first message further comprises a first Almost Blank Subframe allocation period and a first Almost Blank Subframe allocation offset.

18. The method of claim 16 , wherein said first base station decreases a number of Almost Blank Subframes in said first plurality of Almost Blank Subframes after an increase in traffic load of said first base station by an amount greater than a value.

19. The method of claim 16 , wherein said first base station increases a number of Almost Blank Subframes in said first plurality of Almost Blank Subframes after a decrease in traffic load of said first base station by an amount greater than a value.

20. The method of claim 10 , wherein said message further comprises a second pattern bitmap indicating a subset of a first plurality of Almost Blank Subframes indicated by said first pattern bitmap, said second pattern bitmap being used to configure measurement parameters for a subset of said second plurality of wireless devices.