Beam information exchange between base stations

1. A method comprising:

a) receiving from a first node, at least one message comprising at least one index identifying a subset of a second plurality of beamforming codewords, each of said second plurality of beamforming codewords being identifiable by an index presented by a number of bits, said number of bits being:

i) greater than or equal to log 2 (N), N being number of said second plurality of beamforming codewords; and

ii) less than number of bits in representation of a corresponding beamforming codeword;

b) transmitting to a second node signals employing a first plurality of beamforming codewords being selected, at least in part, employing said subset of said second plurality of beamforming codewords.

2. The method of claim 1 , wherein each of said plurality of indexes refers to a locally unique beamforming codeword.

3. The method of claim 1 , further comprising said first plurality of beamforming codewords are selected to reduce inter-cell interference.

4. The method of claim 3 , further comprising computing inter-cell interference employing information received from at least one wireless device.

5. The method of claim 1 , wherein:

a) a first beamforming codebook comprises said first plurality of beamforming codewords;

b) said first beamforming codebook is related to a first number of transmit antennas;

c) a codeword in said first plurality of beamforming codewords comprises a number of rows or columns equal to said first number of transmit antennas;

d) a second beamforming codebook comprises said second plurality of beamforming codewords;

e) said second beamforming codebook is related to a second number of transmit antennas;

f) a codeword in said second plurality of beamforming codewords comprises a number of rows or columns equal to said second number of transmit antennas.

6. The method of claim 5 , further comprising constructing codewords for a subset of transmit antennas employing a subset of rows or columns of said codewords.

7. The method of claim 5 , wherein said first beamforming codebook or said second beamforming codebook is defined for a number of layers.

8. A base station comprising:

a) one or more communication interfaces;

b) one or more processors; and

c) memory storing instructions that, when executed, cause said base station to:

i) receive from a first node at least one message comprising at least one index identifying a subset of a second plurality of beamforming codewords, each of said second plurality of beamforming codewords being identifiable by an index presented by a number of bits, said number of bits being:

(1) greater than or equal to log 2 (N), N being number of said second plurality of beamforming codewords; and

(2) less than number of bits in representation of a corresponding beamforming codeword;

ii) transmit to a second node signals employing a first plurality of beamforming codewords being selected, at least in part, employing said subset of said second plurality of beamforming codewords.

9. The base station of claim 8 , wherein said at least one message further comprises:

a) a cell ID for each cell in a second base station; and

b) the frequency of at least one downlink carrier and at least one uplink carrier of said second base station.

10. The base station of claim 8 , wherein:

a) a first beamforming codebook comprises said first plurality of beamforming codewords;

b) said first beamforming codebook is related to a first number of transmit antennas;

c) a codeword in said first plurality of beamforming codewords comprises a number of rows or columns equal to said first number of transmit antennas;

d) a second beamforming codebook comprises said second plurality of beamforming codewords;

e) said second beamforming codebook is related to a second number of transmit antennas;

f) a codeword in said second plurality of beamforming codewords comprises a number of rows or columns equal to said second number of transmit antennas.

11. The base station of claim 10 , wherein said instructions, when executed, further cause said base station to construct codewords for a subset of transmit antennas employing a subset of rows or columns of said codewords.

12. The base station of claim 10 , wherein said first beamforming codebook or said second beamforming codebook is defined for a number of layers.

13. The base station of claim 12 , wherein said instructions, when executed, further cause said base station to construct codewords for a subset of layers by employing a subset of columns or rows of said codewords.

14. A method in a network comprising a first base station, a second base station and at least one wireless device, the method comprising:

a) receiving by said first base station from said second base station, at least one message comprising at least one index identifying a subset of a second plurality of beamforming codewords, each of said second plurality of beamforming codewords being identifiable by an index presented by a number of bits, said number of bits being:

i) greater than or equal to log 2 (N), N being number of said second plurality of beamforming codewords; and

ii) less than number of bits in representation of a corresponding beamforming codeword;

b) transmitting by said first base station to said at least one wireless device, signals employing a first plurality of beamforming codewords being selected, at least in part, employing said subset of said second plurality of beamforming codewords.

15. The method of claim 14 , further comprising said first plurality of beamforming codewords are selected to reduce inter-cell interference.

16. The method of claim 14 , wherein:

a) a first beamforming codebook comprises said first plurality of beamforming codewords;

b) said first beamforming codebook is related to a first number of transmit antennas;

c) a codeword in said first plurality of beamforming codewords comprises a number of rows or columns equal to said first number of transmit antennas;

d) a second beamforming codebook comprises said second plurality of beamforming codewords;

e) said second beamforming codebook is related to a second number of transmit antennas;

f) a codeword in said second plurality of beamforming codewords comprises a number of rows or columns equal to said second number of transmit antennas.

17. The method of claim 16 , further comprising constructing codewords for a subset of transmit antennas employing a subset of rows or columns of said codewords.

18. The method of claim 16 , wherein said first beamforming codebook or said second beamforming codebook is defined for a number of layers.

19. The method of claim 16 , further comprising said second base station transmitting said second beamforming codebook to a plurality of base stations.

20. The method of claim 19 , further comprising said plurality of base stations selecting respective plurality of beamforming codewords based on information received from said second base station.