Uplink control information

A method comprising:

• receiving, at a second device, from a first device, uplink control information comprising a strongest coefficient indicator and non-zero linear combination coefficients scaled by a maximum coefficient, wherein the coefficients are of a 2L×M matrix Ŵ2 for a pre-coder matrix indicator (PMI) matrix wherein matrix Ŵ2 has 2L spatial components and M frequency components,
• the received non-zero linear combination coefficients exclude a maximum coefficient, and
• the received strongest coefficient indicator with ┌log2 2L┐ bits indicates the index of a spatial component associated with the maximum coefficient of matrix Ŵ2 and wherein the method further comprises:
• determining state information of the channel, wherein a coefficient of matrix Ŵ2, at a position with the spatial component indicated by the strongest coefficient indicator and with a frequency component determined by a predetermined index, assumes a preconfigured value.

A first device comprising:

• at least one processor;
• and
• at least one memory storing instructions that, when executed by the at least one processor, cause the first device to perform at least:
• determining a 2L×M matrix Ŵ2 comprising linear combination coefficients for a pre-coder matrix indicator (PMI) matrix, wherein matrix Ŵ2 has 2L spatial components and M frequency components;
• determining a shifted matrix by shifting the frequency components of matrix Ŵ2 circularly, such that a maximum coefficient of matrix Ŵ2 is located in a frequency component with a predetermined index;
• generating a strongest coefficient indicator with ┌log2 2L┐ bits, indicating the index of the spatial component associated with the maximum coefficient of matrix Ŵ2;
• and
• transmitting, to a second device, uplink control information comprising the strongest coefficient indicator and non-zero linear combination coefficients, wherein the non-zero linear combination coefficients are scaled by the maximum coefficient, wherein the transmitted non-zero linear combination coefficients exclude the maximum coefficient.

A second device comprising:

• at least one processor;
• and
• at least one memory storing instructions that, when executed by the at least one processor, cause the second device to perform at least
• receiving, from a first device, uplink control information comprising a strongest coefficient indicator and non-zero linear combination coefficients scaled by a maximum coefficient, wherein the coefficients are of a 2L×M matrix Ŵ2 for a pre-coder matrix indicator (PMI) matrix, wherein matrix Ŵ2 has 2L spatial components and M frequency components,
• the received non-zero linear combination coefficients exclude the maximum coefficient, and
• the received strongest coefficient indicator with ┌log2 2L┐ bits indicates the index of a spatial component associated with the maximum coefficient of matrix z;
• and
• determining state information of the channel, wherein a coefficient of matrix Ŵ2 assumes a preconfigured value at a position determined by the strongest coefficient indicator and a predetermined index of the matrix Ŵ2.

A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least:

• determining, at a first device, a 2L×M matrix Ŵ2 comprising linear combination coefficients for a pre-coder matrix indicator (PMI) matrix, wherein matrix Ŵ2 has 2L spatial components and M frequency components;
• determining a shifted matrix by shifting the frequency components of matrix circularly, such that a maximum coefficient of matrix Ŵ2 is located in a frequency component with a predetermined index;
• generating a strongest coefficient indicator with ┌log2 2L┐ bits, indicating the index of the spatial component associated with the maximum coefficient of matrix Ŵ2;
• and
• transmitting, to a second device, uplink control information comprising the strongest coefficient indicator and non-zero linear combination coefficients of the shifted matrix, wherein the non-zero linear combination coefficients are scaled by the maximum coefficient, wherein the transmitted non-zero linear combination coefficients exclude the maximum coefficient.

A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least:

• receiving, at a second device, from a first device, uplink control information comprising a strongest coefficient indicator and non-zero linear combination coefficients scaled by a maximum coefficient, wherein the coefficients are of a 2L×M matrix Ŵ2 for a pre-coder matrix indicator (PMI) matrix wherein matrix Ŵ2 has 2L spatial components and M frequency components,
• the received non-zero linear combination coefficients exclude a maximum coefficient, and
• the received strongest coefficient indicator with ┌log2 2L┐ bits indicates the index of a spatial component associated with the maximum coefficient of matrix Ŵ2;
• and
• determining state information of the channel, wherein a coefficient of matrix Ŵ2, at a position with the spatial component indicated by the strongest coefficient indicator and with a frequency component determined by a predetermined index, assumes a preconfigured value.