Methods for reducing overhead of NR type II channel state information feedback using angle and delay reciprocity
A method, network node and wireless device for reducing overhead of New Radio (NR) Type II channel state information (CSI) feedback using angle and delay reciprocity are disclosed. According to one aspect, a method in a wireless device (WD) includes receiving a configuration of CSI report setting that indicates frequency domain basis vectors from a discrete Fourier transform, CSI reference signal (RS) ports and a subset of pairs of spatial domain and frequency domain vectors for the N CSI-RS CSI-RS ports. The method also includes determining linear combination coefficients corresponding to the selected frequency domain basis vectors and the selected subset of CSI-RS ports, determining linear combination coefficients corresponding to the selected frequency domain basis vectors and the selected subset of pairs of vectors in the spatial domain and the frequency domain.
1 . A network node configured to communicate with a wireless device (WD), the network node comprising:
processing circuitry configured to configure the WD with a channel state information (CSI) report setting, the CSI report setting including at least one of:
a CSI reference signal (CSI-RS) resource with N CSI-RS CSI-RS ports for channel measurement, each of the N CSI-RS ports being associated with a pair of spatial domain (SD) and frequency domain (FD) vectors;
a first subset of length N3 frequency domain, FD, FD basis vectors of a discrete Fourier transform, the first subset comprising N basis vectors, one of which is a direct current (DC) basis vector containing all ones, where 1<=N<=N3; and
a number M of FD basis vectors of a second subset of M FD basis vectors, the second subset being determined by the WD from the first subset of FD basis vectors, one of the M FD basis vectors being the DC basis vector, where M<=N; and
a radio interface in communication with the processing circuitry and configured to:
transmit a CSI-RS to the WD;
request the WD to feedback a CSI based on a CSI-RS and according to the CSI report setting;
receive from the WD a CSI report comprising:
an indication of a number of transmission layers;
an indication of a selection by the WD of a subset of the N CSI-RS CSI-RS ports;
an indication of a selection by the WD of M FD basis vectors out of the N FD basis vectors;
an indication of a set of linear combination coefficients associated with the selected subset of the CSI-RS ports and the selected M frequency domain basis vectors per transmission layer; and
an indication of a total number of non-zero linear combination coefficients associated with all the M frequency domain basis vectors; and
the reporting being associated with N p,sel /2 pairs of vectors that are common to two polarizations out of a total of N p N CSI-RS /2 pairs of vectors using at most
⌈
log
2
(
(
N
p
N
CSIRS
/
2
N
p
,
sel
/
2
)
)
⌉
bits
,
wherein N p,sel is a total number of ports to be selected for both polarizations, and N p =1.
2 . The network node of claim 1 , wherein the radio interface is further configured to receive a non-zero coefficient (NZC) bitmap, for each transmission layer, wherein each bit in the bitmap is associated with one of the selected CSI-RS ports and one of the M FD basis vectors.
3 . The network node of claim 1 , wherein the radio interface is configured to receive from the WD an indication of a selection by the WD of the M frequency domain basis vectors only when N is greater than one and M is less than N.
4 . A method in a network node configured to communicate with a wireless device (WD), the method comprising:
configuring the WD with a channel state information (CSI) report setting, the CSI report setting including at least one of:
a CSI reference signal (CSI-RS) resource with N CSI-RS CSI-RS ports for channel measurement, each of the N CSI-RS ports being associated with a pair of spatial domain (SD) and frequency domain (FD) vectors;
a first subset of length N3 (FD) basis vectors of a discrete Fourier transform, the first subset comprising N basis vectors, one of which is a direct current (DC) basis vector containing all ones, where 1<=N<=N3; and
a number M of FD basis vectors of a second subset of M FD basis vectors, the second subset being determined by the WD from the first subset of FD basis vectors, one of the M FD basis vectors being the DC basis vector, where M<=N;
transmitting a CSI-RS to the WD;
requesting the WD to feedback a CSI based on a CSI-RS and according to the CSI report setting;
receiving from the WD a CSI report comprising:
an indication of a number of transmission layers;
an indication of a selection by the WD of a subset of the N CSI-RS CSI-RS ports;
an indication of a selection by the WD of M FD basis vectors out of the N FD basis vectors;
an indication of a set of linear combination coefficients associated with the selected subset of the CSI-RS ports and the selected M frequency domain basis vectors per transmission layer; and
an indication of one of a total number of non-zero linear combination coefficients (NZC) per transmission layer associated with non-DC frequency domain basis vectors in the M frequency domain basis vectors, and an indication of a total number of non-zero linear combination coefficients associated with all the M frequency domain basis vectors; and
the reporting being associated with N p,sel /2 pairs of vectors that are common to two polarizations out of a total of N p N CSI-RS /2 pairs of vectors using at most
⌈
log
2
(
(
N
p
N
CSIRS
/
2
N
p
,
sel
/
2
)
)
⌉
bits
,
wherein N p,sel is a total number of ports to be selected for both polarizations, and N p =1.
5 . The method of claim 4 , further comprising receiving a non-zero coefficient NZC bitmap, for each transmission layer, wherein each bit in the bitmap is associated with one of the selected CSI-RS ports and one of the M FD basis vectors.
6 . The method of claim 4 , further comprising receiving from the WD an indication of a selection by the WD of the M frequency domain basis vectors only when N is greater than one and M is less than N.
7 . A wireless device (WD) configured to communicate with a network node, the WD comprising:
processing circuitry configured to:
receive a configuration of a channel state information (CSI) report setting, the CSI report setting including at least one of:
a CSI reference signal (CSI-RS) resource with N CSI-RS CSI-RS ports for channel measurement, each of the N CSI-RS ports being associated with a pair of spatial domain (SD) and frequency domain (FD) vectors;
a first subset of length N3 FD basis vectors of a discrete Fourier transform, the first subset including N basis vectors, one of which is a direct current (DC) basis vector containing all ones, where 1<=N<=N3; and
a number M of a second subset of M FD basis vectors, the second subset being determined by the WD from the first subset of FD basis vectors, one of the M FD basis vectors being the DC basis vector, where <=N; and
measure CSI based on the N CSI-RS CSI-RS ports and according to the CSI report setting, the measuring including at least one of:
selecting M FD basis vectors out of the N frequency domain basis vectors;
selecting a subset of CSI-RS ports out of the N CSI-RS CSI-RS ports; and
determining a set of linear combination coefficients corresponding to the selected M frequency domain basis vectors and the selected subset of CSI-RS ports;
a radio interface in communication with the processing circuitry and configured to transmit a CSI report message comprising:
an indication of the selected M frequency domain basis vectors;
an indication of the selected subset of CSI-RS ports;
an indication of the set of linear combination coefficients; and
an indication of a total number of non-zero linear combination coefficients associated with all the selected M FD basis vectors; and
the processing circuitry is further configured to choose N p,sel /2 pairs of vectors that are common to two polarizations out of a total of N p N CSI-RS /2 pairs of vectors using at most
⌈
log
2
(
(
N
p
N
CSIRS
/
2
N
p
,
sel
/
2
)
)
⌉
bits
to report for each transmission layer, wherein N p,sel is a total number of ports to be selected for both polarizations, and N p =1.
8 . The WD of claim 7 , wherein, when N=1, the first subset of frequency domain basis vectors is a set containing only the DC frequency domain basis vector.
9 . The WD of claim 7 , wherein the radio interface is configured to transmit an indication of a selection of the selected M frequency domain basis vectors only when M≠N and M is greater than one.
10 . The WD of claim 7 , wherein the processing circuitry is further configured to select a second subset of frequency domain basis vectors for frequency domain channel compression.
11 . The WD of claim 7 , wherein the selected M frequency domain basis vectors is common for all transmission layers.
12 . A method in a wireless device (WD) configured to communicate with a network node, the method comprising:
receiving a configuration of a channel state information (CSI) report setting, the CSI report setting including at least one of:
a CSI reference signal (CSI-RS) resource with N CSI-RS CSI-RS ports for channel measurement, each of the N CSI-RS ports being associated with a pair of spatial domain (SD) and frequency domain (FD) vectors;
a first subset of length N3 FD basis vectors of a discrete Fourier transform, the first subset including N basis vectors, one of which is a direct current (DC) basis vector containing all ones, where 1<=N<=N3; and
a number M of a second subset of M FD basis vectors, the second subset being determined by the WD from the first subset of FD basis vectors, one of the M FD basis vectors being the DC basis vector, where <=N; and
measuring CSI based on the N CSI-RS CSI-RS ports and according to the CSI report setting, the measuring including at least one of:
selecting M FD basis vectors out of the N frequency domain basis vectors;
selecting a subset of CSI-RS ports out of the N CSI-RS CSI-RS ports; and
determining a set of linear combination coefficients corresponding to the selected M frequency domain basis vectors and the selected subset of CSI-RS ports;
transmitting a CSI report message comprising:
an indication of the selected M frequency domain basis vectors;
an indication of the selected subset of CSI-RS ports;
an indication of the set of linear combination coefficients; and
an indication of a total number of non-zero linear combination coefficients associated with all the selected M FD basis vectors; and
choosing N p,sel /2 pairs of vectors that are common to two polarizations out of a total of N p N CSI-RS /2 pairs of vectors using at most
⌈
log
2
(
(
N
p
N
CSIRS
/
2
N
p
,
sel
/
2
)
)
⌉
bits
to report for each transmission layer, wherein N p,sel is a total number of ports to be selected for both polarizations, and N p =1.
13 . The method of claim 12 , wherein, when N=1, the first subset of frequency domain basis vectors is a set containing only the DC frequency domain basis vector.
14 . The method of claim 12 , further comprising transmitting an indication of a selection of the selected M frequency domain basis vectors only when M≠N and M is greater than one.
15 . The method of claim 12 , further comprising selecting a second subset of frequency domain basis vectors for frequency domain channel compression.
16 . The method of claim 12 , wherein the selected M frequency domain basis vectors is common for all transmission layers.