Apparatus and method for beamforming for downlink data transmission in wireless communication system

1 . A method performed by a user equipment (UE) supporting a beam forming in a wireless communication system, the method comprising:

receiving, from a base station, configuration information on channel state information (CSI) including parameters of a code book and a parameter (N DFT ) indicative of a maximum number of discrete Fourier transform (DFT) vectors with one signal polarization in a precoding matrix;

receiving, from the base station, CSI reference signals (CSI-RSs);

choosing a number (L) of MIMO layers;

based on the parameters of the code book, the parameter indicative of the maximum number of DFT vectors and the number (L) of MIMO layers, generating the precoding matrix including precoding vectors, wherein a number of the precoding vectors is same as the number (L) of the MIMO layers; and

based on the received CSI-RSs, transmitting, to the base station, CSI including at least one of a rank indicator (RI) of a chosen number L of multiple input and multiple output (MIMO) layers, and a precoding matrix indicator (PMI).

2 . The method of claim 1 , wherein generating the precoding matrix comprising:

in case that L≤N DFT , generating L precoding vectors by using L different DFT vectors, each being used with one signal polarization;

in case that N DFT <L≤2N DFT , generating N DFT precoding vectors by using N DFT different DFT vectors, each being used with one signal polarization, and generating further N next precoding vectors, where N next =L−N DFT , by using N next DFT vectors from the N DFT DFT vectors, each of the N next DFT vectors being used with a signal polarization different from said one signal polarization with which said DFT vector has been already used in the precoding matrix; or

in case that L>2N DFT , generating L precoding vectors by using N DFT =ceil (L/2) different DFT vectors, wherein each of floor (L/2) DFT vectors among the N DFT DFT vectors is used with two different signal polarizations to generate 2·floor (L/2) precoding vectors, and, if mod (L,2)=1, a remaining DFT vector among the N DFT DFT vectors is used with one signal polarization to generate a respective precoding vector.

3 . The method of claim 1 , wherein the parameters of the code book include at least one of a number (N 1 ) of antenna ports of the base station along a first spatial dimension and a respective oversampling parameter (O 1 ), and a number (N 2 ) of antenna ports of the base station along a second spatial dimension and a respective oversampling parameter (O 2 ), wherein a number of DFT vectors defined by the code book is equal to (N 1 ×O 1 )×(N 2 ×O 2 ).

4 . The method of claim 1 ,

wherein different DFT vectors are orthogonal DFT vectors,

wherein different signal polarizations are orthogonal signal polarizations, and

wherein the configuration information is transmitted by using at least one of downlink control information (DCI), medium access control (MAC), radio resource control (RRC) signaling.

5 . The method of claim 1 , further comprising:

determining L individual normalization parameters, wherein the individual normalization parameters are respectively individual for the L MIMO layers.

6 . The method of claim 5 ,

wherein the determining of the individual normalization parameters comprises:

determining an individual normalization parameter for each precoding vector of the precoding matrix depending on whether a same DFT vector is used with different signal polarizations both for a MIMO layer associated with precoding vector and for a MIMO layer associated with another precoding vector of the precoding matrix, and

setting an individual normalization parameter for each precoding vector of the precoding matrix to 1, and

wherein applying the normalization parameters further comprises:

multiplying the precoding vectors of the precoding matrix by the respective determined individual normalization parameters.

7 . A method performed by a base station supporting a beam forming in a wireless communication system, the method comprising:

generating configuration information on channel state information (CSI) including parameters of a code book and a parameter (N DFT ) indicative of a maximum number of discrete Fourier transform (DFT) vectors with one signal polarization in a precoding matrix and information for a power normalizing the precoding matrix;

transmitting, to a user equipment (UE), the configuration information on the CSI;

transmitting, to the UE, CSI reference signals (CSI-RSs);

receiving, from the UE, CSI including at least one of a rank indicator (RI) of a chosen number L of multiple input and multiple output (MIMO) layers, and a precoding matrix indicator (PMI);

determining normalization parameters for the generated precoding matrix based on normalizing information, wherein the determined normalization parameters include a common normalization parameter applied to the precoding matrix as a whole and an individual normalization parameter respectively applied to individual precoding vectors or groups of precoding vectors of the precoding matrix; and

applying the determined normalization parameters to the generated precoding matrix.

8 . The method of claim 7 ,

wherein L is chosen from a plurality of preset values and a maximum value of the L is 16.

9 . The method of claim 8 , further comprising:

calculating a respective common normalization parameter based on at least one of a predefined EIRP restriction, an antenna gain, a transmission power, and value of L for each value of L among a plurality of preset values; and

including the calculated common normalization parameters into the normalizing information.

10 . The method of claim 9 ,

wherein determining the normalization parameters comprises:

selecting, among the calculated common normalization parameters, a common normalization parameter corresponding to said chosen number L of MIMO layers, for being applied to the generated precoding matrix, and

wherein the applying the common normalization parameter comprises:

multiplying the precoding matrix by a normalization multiplier which includes said common normalization parameter.

11 . A user equipment (UE) supporting a beam forming in a wireless communication system, the UE comprising:

a transceiver; and

a controller coupled with the transceiver, and configured to:

receive, from a base station, configuration information on channel state information (CSI) including parameters of a code book and a parameter (N DFT ) indicative of a maximum number of discrete Fourier transform (DFT) vectors with one signal polarization in a precoding matrix,

receive, from the base station, CSI reference signals (CSI-RSs),

choose a number (L) of MIMO layers,

based on the parameters of the code book, the parameter indicative of the maximum number of DFT vectors and the number (L) of MIMO layers, generate the precoding matrix including precoding vectors, wherein a number of the precoding vectors is same as the number (L) of the MIMO layers, and

based on the received CSI-RSs, transmit, to the base station, CSI including at least one of a rank indicator (RI) of a chosen number L of multiple input and multiple output (MIMO) layers, and a precoding matrix indicator (PMI).

12 . The UE of claim 11 , wherein the controller is further configured to:

in case that L≤N DFT , generate L precoding vectors by using L different DFT vectors, each being used with one signal polarization;

in case that N DFT <L≤2N DFT , generate N DFT precoding vectors by using N DFT different DFT vectors, each being used with one signal polarization, and generating further N next precoding vectors, where N next =L−N DFT , by using N next DFT vectors from the N DFT DFT vectors, each of the N next DFT vectors being used with a signal polarization different from said one signal polarization with which said DFT vector has been already used in the precoding matrix; or

in case that L>2N DFT , generate L precoding vectors by using N DFT =ceil (L/2) different DFT vectors, wherein each of floor (L/2) DFT vectors among the N DFT DFT vectors is used with two different signal polarizations to generate 2·floor (L/2) precoding vectors, and, if mod (L,2)=1, a remaining DFT vector among the N DFT DFT vectors is used with one signal polarization to generate a respective precoding vector.

13 . The UE of claim 11 , wherein the parameters of the code book include at least one of a number (N 1 ) of antenna ports of the base station along a first spatial dimension and a respective oversampling parameter (O 1 ), and a number (N 2 ) of antenna ports of the base station along a second spatial dimension and a respective oversampling parameter (O 2 ), wherein a number of DFT vectors defined by the code book is equal to (N 1 ×O 1 )×(N 2 ×O 2 ).

14 . The UE of claim 11 ,

wherein different DFT vectors are orthogonal DFT vectors,

wherein different signal polarizations are orthogonal signal polarizations, and

wherein the configuration information is transmitted by using at least one of downlink control information (DCI), medium access control (MAC), radio resource control (RRC) signaling.

15 . The UE of claim 11 , wherein the controller is further configured to:

determine L individual normalization parameters, wherein the individual normalization parameters are respectively individual for the L MIMO layers.

16 . The UE of claim 11 , wherein the controller is further configured to:

determine an individual normalization parameter for each precoding vector of the precoding matrix depending on whether a same DFT vector is used with different signal polarizations both for a MIMO layer associated with precoding vector and for a MIMO layer associated with another precoding vector of the precoding matrix, set an individual normalization parameter for each precoding vector of the precoding matrix to 1, and

multiply precoding vectors of the precoding matrix by the respective determined individual normalization parameters.

17 . A base station supporting a beam forming in a wireless communication system, the base station comprising:

a transceiver; and

a controller configured to:

generate configuration information on channel state information (CSI) including parameters of a code book and a parameter (N DFT ) indicative of a maximum number of discrete Fourier transform (DFT) vectors with one signal polarization in a precoding matrix and information for a power normalizing the precoding matrix,

transmit, to a user equipment (UE), the configuration information on the CSI,

transmit, to the UE, CSI reference signals (CSI-RSs),

receive, from the UE, CSI including at least one of a rank indicator (RI) of a chosen number L of multiple input and multiple output (MIMO) layers, and a precoding matrix indicator (PMI),

determine normalization parameters for the generated precoding matrix based on normalizing information, wherein the determined normalization parameters include a common normalization parameter applied to the precoding matrix as a whole and an individual normalization parameter respectively applied to individual precoding vectors or groups of precoding vectors of the precoding matrix, and

apply the determined normalization parameters to the generated precoding matrix.

18 . The base station of claim 17 ,

wherein L is chosen from a plurality of preset values and a maximum value of the L is 16.

19 . The base station of claim 18 , wherein the controller is further configured to:

calculate a respective common normalization parameter based on at least one of a predefined EIRP restriction, an antenna gain, a transmission power, and value of L for each value of L among a plurality of preset values, and

include the calculated common normalization parameters into the normalizing information.

20 . The base station of claim 19 , wherein the controller is further configured to:

select, among the calculated common normalization parameters, a common normalization parameter corresponding to said chosen number L of MIMO layers, for being applied to the generated precoding matrix, and

multiply the precoding matrix by a normalization multiplier which includes said common normalization parameter.