Base station apparatus and transmission method
The present disclosure provides a method of generating codebook in a wireless communication system with multiple antenna arrays, as well as a wireless communication system, base station and terminal using the codebook for communication. The method comprises steps of: providing a basic codebook which contains multiple pre-coding matrices; and assigning phase offsets to certain pre-coding matrices in the basic codebook to form a codebook with phase offset. The feedback overhead from a client to a base station side is reduced and a good precision of feedback for multi-antenna array is kept by applying the method of generating codebook and using the generated codebook in the wireless communication system, base station and terminal.
1. An integrated circuit, comprising:
control circuitry which, in operation, controls:
storing an extended codebook which is generated by combining a first basic codebook and a second basic codebook along a column direction, wherein the first basic codebook includes N groups, each consisting of four basic pre-coding column vectors (N is a natural number equal to or larger than 2), and wherein the second basic codebook is generated by applying phase offsets to the N groups, respectively, each of the phase offsets, applied to the N groups, being different from each other;
receiving, from a terminal apparatus via a multi-antenna array, information including a pre-coding matrix indicator (PMI) that identifies one pre-coding extended column vector from among 4N pre-coding extended column vectors included in the extended codebook;
pre-coding data using the pre-coding extended column vector identified by the PMI; and
at least one output, coupled to the control circuitry, which, in operation, outputs the pre-coded data for transmission via the multi-antenna array to the terminal apparatus.
2. The integrated circuit according to claim 1 , wherein:
each of the first basic codebook and the second basic codebook includes 4N basic pre-coding column vectors, each having four rows and one column; and
the extended codebook includes the 4N pre-coding extended column vectors, each having eight rows and one column.
3. The integrated circuit according to claim 1 , wherein:
the four basic pre-coding column vectors are orthogonal to each other in each of the N groups.
4. The integrated circuit according to claim 1 , wherein:
an angle difference between a basic pre-coding matrix w m and a basic pre-coding matrix w m+1 included in the first basic codebook is an integer multiple of 2π/32, wherein m is an integer.
5. The integrated circuit according to claim 1 , wherein:
the at least one output, in operation, outputs the pre-coded data for transmission from a base station apparatus using two layers,
the basic pre-coding column vectors included in the first basic codebook respectively include basic pre-coding matrix vectors w m for one of the two layers and basic pre-coding matrix vectors w′ m for another one of the two layers, where m is an integer; and
an angle difference between the vectors w m and w′ m is selected from a set of angles including: 2π/32, 4π/32 and 6π/32.
6. The integrated circuit according to claim 1 , wherein:
the integrated circuit is part of a base station apparatus that includes a plurality of array antennas; and
the PMI is for each of the plurality of array antennas.