Beamforming Codeword Exchange between Base Stations

A method comprising:

• a) receiving, by a first base station from a second base station, at least one application protocol message, said first base station and said second base station configured to communicate with a plurality of wireless devices employing a downlink carrier, said downlink carrier comprising a plurality of resource blocks, said at least one application protocol message comprising a downlink beamforming information element for at least one resource block in said downlink carrier, said downlink beamforming information element indicating a second beamforming codeword employed by said second base station for said at least one resource block, said second beamforming codeword referenced by an index and included in a second beamforming codebook;
• b) selecting, by said first base station for said at least one resource block, a first beamforming codeword from a first beamforming codebook, said selection being based, at least in part, on said downlink beamforming information element received from said second base station;
• and
• c) transmitting, by said first base station, employing said first beamforming codeword, signals on a subset of said at least one resource block to a wireless device.

A first base station comprising:

• a) one or more communication interfaces;
• b) one or more processors;
• and
• c) memory storing instructions that, when executed, cause said first base station to:
• i) receive from a second base station, at least one application protocol message, said first base station and said second base station configured to communicate with a plurality of wireless devices employing a downlink carrier, said downlink carrier comprising a plurality of resource blocks, said at least one application protocol message comprising a downlink beamforming information element for at least one resource block in said downlink carrier, said downlink beamforming information element indicating a second beamforming codeword employed by said second base station for said at least one resource block, said second beamforming codeword:
• (1) having a number of rows or columns equal to or less than a number of antenna ports employed by said second base station for beamforming on said downlink carrier;
• and
• (2) included in a second beamforming codebook;
• ii) select for said at least one resource block, a first beamforming codeword from a first beamforming codebook, said selection being based, at least in part, on said downlink beamforming information element received from said second base station;
• and
• iii) transmit employing said first beamforming codeword, signals on a subset of said at least one resource block to a wireless device.