Channel state information feedback

A method implemented by a non-transitory computer readable storage medium, in which a program is saved, the program comprising instructions which, when they are executed in a programmable device, cause the provision of channel state information for a wireless communications channel between a first network node having at least M transmission antennas and a second network node having at least N reception antennas, the method, comprising:

• determining characteristics of each of a plurality of taps resolvable in the time domain of at least one sub-channel within the channel from signals received by the at least N reception antennas over the channel from the at least M transmission antennas;
• arranging a set of the characteristics of each of the plurality of taps into at least one vector;
• quantizing the at least one vector in which a set of the characteristics of each of the plurality of taps are arranged by selecting one of a plurality of codebook vectors at a first level of a hierarchical codebook of vectors;
• and
• providing, to the first network node, an indication of an index to the one of a plurality of codebook vectors,
• wherein the determining further comprises:
• determining characteristics of L taps resolvable in the time domain of each sub-channel within the channel from signals received by the at least N reception antennas over the channel from the at least M transmission antennas, where L is a positive integer.

A first network node having at least N reception antennas and operable to provide channel state information for a wireless communications channel provided between second network node having at least M transmission antennas and the first network node, the network node comprising:

• determination logic operable to determine characteristics of each of a plurality of taps resolvable in the time domain of at least one sub-channel within the channel from signals received by the at least N reception antennas over the channel from the at least M transmission antennas;
• arrangement logic operable to arrange the characteristics of each of the plurality of taps into at least one vector;
• quantization logic operable to quantize the at least one vector in which a set of the characteristics of each of the plurality of taps are arranged by selecting one of a plurality of codebook vectors at a first level of a hierarchical codebook of vectors;
• and
• provision logic operable to provide, to the another network node, an indication of an index to the one of a plurality of codebook vectors,
• wherein the determining further comprises:
• determining characteristics of L taps resolvable in the time domain of each sub-channel within the channel from signals received by the at least N reception antennas over the channel from the at least M transmission antennas, where L is a positive integer.