# US 2014/0192768 A1 · Method for transmitting signal using multiple antennas

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- Number: US 2014/0192768 A1
- Document ID: US20140192768A1
- Status: Published application
- Kind: A1
- Application number: 14/146,942
- Filed: 2014-01-03
- Published: 2014-07-10
- Earliest claimed: 2013-01-04
- Assignees: Electronics and Telecommunications Research Institute
- Applicants: Electronics and Telecommunications Research Institute
- Inventors: Choong Il YEH; Jae Young AHN
- Web page: https://patentgrep.com/patent/US20140192768A1

## CPC

- H04B 7/06: at the transmitting station
- H04B 7/0469: {taking special antenna structures, e.g. cross polarized antennas into account}
- H04B 7/0478: {Special codebook structures directed to feedback optimisation}
- H04B 7/0486: {taking channel rank into account}
- H04B 7/024: Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
- H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection}
- H04B 7/065: {Variable contents, e.g. long-term or short-short}
- H04B: TRANSMISSION

## Abstract

Disclosed is a method for transmitting radio frequency signals. In the method according to the present invention, a plurality of antenna groups may be arranged for achieving array gain and multiplexing gain at the same time, and the plurality of antenna groups are located far from each other so that they have no correlation, and antennas of the same group are located adjacent to each other so that they have correlation. Accordingly, system capacity as well as capacity of data channel and control channel may be significantly increased through mitigation of inter-cell interference and enhancement of cell edge performance.

## Claims

### Claim 1

A method for transmitting radio frequency signals, wherein a plurality of antenna groups are arranged for achieving array gain and multiplexing gain at the same time, and the plurality of antenna groups are located far from each other so that they have no correlation, and antennas of the same group are located adjacent to each other so that they have correlation.

### Claim 2

A method for transmitting signals, performed in a base station, comprising:
transmitting reference signal for each antenna group and reference signal for each directional beam to a terminal;
receiving a first precoder matrix index (PMI-1) and a second precoder matrix index (PMI-2), which are calculated based on the reference signals, from the terminal; and
performing precoding on downlink data and reference signal for demodulation (DMRS) based a first precoder (P1) corresponding to the first precoder matrix index and a second precoder (P2) matrix corresponding to the second precoder matrix index.

### Claim 3 (depends on 2)

The method of claim 2, wherein the first precoder is a precoding matrix for each of a plurality antenna groups to form directional beam, and the second precoder is a precoding matrix for achieving multiplexing gain using the directional beam.

### Claim 4 (depends on 2)

The method of claim 2, wherein the reference signals are generated by using Pseudo-Noise (PN) sequence and Orthogonal Cover Code (OCC) sequence.

### Claim 5 (depends on 4)

The method of claim 4, wherein the reference signals are generated by multiplying the PN sequence and one of OCC sequences a number of which is the same as a number of antenna groups.

### Claim 6 (depends on 4)

The method of claim 4, wherein the PN sequence is initialized in each time period configured with a predetermined interval.

### Claim 7 (depends on 4)

The method of claim 4, wherein the PN sequence is initialized using at least one of a cell identifier, a beam identifier, and an index of time period.

### Claim 8 (depends on 2)

The method of claim 2, wherein the precoding on the reference signal is performed using only the first precoder P1 not the second precoder P2.

### Claim 9 (depends on 2)

The method of claim 2, wherein the reference signals are not transmitted using the same time-frequency resources at the same time in order to mitigate interference between adjacent directional beams formed by the same antenna group, and the adjacent directional beams are applied to the reference signals.

### Claim 10 (depends on 2)

The method of claim 2, wherein the reference signals are transmitted using the same time-frequency resources when beams formed by the antenna groups are toward the same direction, and each reference signal is distinguished using PN sequence and OCC sequence, and the adjacent directional beams are applied to the reference signals.

### Claim 11 (depends on 2)

The method of claim 2, wherein the performing precoding on reference signal for demodulation comprises:
generating the reference signal for demodulation by multiplying Orthogonal Cover Code (OCC) sequence and Pseudo-Noise (PN) sequence which is initialized using at least one of an identifier of the terminal, a cell identifier, a beam identifier, and an index of time period;
performing precoding on the generated reference signal for demodulation by using the first precoder P1 and the second precoder P2 which are applied to the precoding on the downlink data; and
transmitting downlink signal comprising the precoded downlink data and the precoded reference signal for demodulation to the terminal.

### Claim 12 (depends on 2)

The method of claim 2, wherein the first precoder P1 is determined according to the first precoder matrix index (PMI-1) received from the terminal as following equation,
P
1
=
{
X
0
k
;
for


antenna


group


0
X
1
n
;
for


antenna


group


1
X
2
i
;
for


antenna


group


2
X
3
j
;
for


antenna


group


3
,
wherein Xlm means a mth fixed beam of lth antenna group, PMI-1 is an element of {k, n, i, j}.

### Claim 13 (depends on 2)

The method of claim 2, wherein when PMI-1 is an element of {k, n, i, j} and a rank is 1, the precoded downlink data is represented as following equation,
{
X
0
k
·
W
m
{
1
}

(
0
)

d
;
for


antenna


group


0
X
1
n
·
W
m
{
1
}

(
1
)

d
;
for


antenna


group


1
X
2
i
·
W
m
{
1
}

(
2
)

d
;
for


antenna


group


2
X
3
j
·
W
m
{
1
}

(
3
)

d
;
for


antenna


group


3
,
wherein the XPMI-1 represents the first precoder P1 of xth antenna group for a given PMI-1, and Wm{1}(i) is a (i−1)th element of the second precoder P2, and d is the same data inputted to each antenna group.

### Claim 14 (depends on 2)

The method of claim 2, wherein when PMI-1 is an element of {k, n, i, j} and a rank is 2, the precoded downlink data is represented as following equation,
{
X
0
k
·
(
W
m
{
c
1
}

(
0
)

d

(
0
)
+
W
m
{
c
2
}

(
0
)

d

(
1
)
)
;
for


antenna


group


0
X
1
n
·
(
W
m
{
c
1
}

(
1
)

d

(
0
)
+
W
m
{
c
2
}

(
1
)

d

(
1
)
)
;
for


antenna


group


1
X
2
i
·
(
W
m
{
c
1
}

(
2
)

d

(
0
)
+
W
m
{
c
2
}

(
2
)

d

(
1
)
)
;
for


antenna


group


2
X
3
j
·
(
W
m
{
c
1
}

(
3
)

d

(
0
)
+
W
m
{
c
2
}

(
3
)

d

(
1
)
)
;
for


antenna


group


3
,
wherein the XxPMI-1 represents the first precoder P1 of xth antenna group for a given PMI-1, and the Wm{c1}(i) is a (i−1)th element of a first column of the second precoder P2, and the Wm{c2}(i) is a (i−1)th element of a second column of the second precoder P2, and d(0) and d(1) are data streams.

### Claim 15 (depends on 2)

The method of claim 2, wherein when PMI-1 is an element of {k, n, i, j} and a rank is 3, the precoded downlink data is represented as following equation,
{
X
0
k
·
(
W
m
{
c
1
}

(
0
)

d

(
0
)
+
W
m
{
c
2
}

(
0
)

d

(
1
)
+
W
m
{
c
3
}

(
0
)

d

(
2
)
)
;
for


antenna


group


0
X
1
n
·
(
W
m
{
c
1
}

(
1
)

d

(
0
)
+
W
m
{
c
2
}

(
1
)

d

(
1
)
+
W
m
{
c
3
}

(
1
)

d

(
2
)
)
;
for


antenna


group


1
X
2
i
·
(
W
m
{
c
1
}

(
2
)

d

(
0
)
+
W
m
{
c
2
}

(
2
)

d

(
1
)
+
W
m
{
c
3
}

(
1
)

d

(
2
)
)
;
for


antenna


group


2
X
3
j
·
(
W
m
{
c
1
}

(
3
)

d

(
0
)
+
W
m
{
c
2
}

(
3
)

d

(
1
)
+
W
m
{
c
3
}

(
1
)

d

(
2
)
)
;
for


antenna


group


3
,
wherein the XxPMI-1 represents the first precoder P1 of xth antenna group for a given PMI-1, and the Wm{c1}(i) is a (i−1)th element of a first column of the second precoder P2, and the Wm{c2}(i) is a (i−1)th element of a second column of the second precoder P2, and the Wm{c3}(i) is a (i−1)th element of a third column of the second precoder P2, and d(0), d(1) and d(2) are data streams.

### Claim 16 (depends on 2)

The method of claim 2, wherein when PMI-1 is an element of {k, n, i, j} and a rank is 3, the downlink data is represented as following equation,
{
X
0
k
·
(
W
m
{
c
1
}

(
0
)

d

(
0
)
+
W
m
{
c
2
}

(
0
)

d

(
1
)
+
W
m
{
c
3
}

(
0
)

d

(
2
)
+
W
m
{
c
4
}

(
0
)

d

(
3
)
)
;
for


antenna


group


0
X
1
n
·
(
W
m
{
c
1
}

(
1
)

d

(
0
)
+
W
m
{
c
2
}

(
1
)

d

(
1
)
+
W
m
{
c
3
}

(
1
)

d

(
2
)
+
W
m
{
c
4
}

(
0
)

d

(
3
)
)
;
for


antenna


group


1
X
2
i
·
(
W
m
{
c
1
}

(
2
)

d

(
0
)
+
W
m
{
c
2
}

(
2
)

d

(
1
)
+
W
m
{
c
3
}

(
1
)

d

(
2
)
+
W
m
{
c
4
}

(
0
)

d

(
3
)
)
;
for


antenna


group


2
X
3
j
·
(
W
m
{
c
1
}

(
3
)

d

(
0
)
+
W
m
{
c
2
}

(
3
)

d

(
1
)
+
W
m
{
c
3
}

(
1
)

d

(
2
)
+
W
m
{
c
4
}

(
0
)

d

(
3
)
)
;
for


antenna


group


3
,
wherein the XxPMI-1 represents the first precoder P1 of xth antenna group for a given PMI-1, and the Wm{c1}(i) is a (i−1)th element of a first column of the second precoder P2, and the Wm{c2}(i) is a (i−1)th element of a second column of the second precoder P2, the Wm{c3}(i) is a (i−1)th element of a third column of the second precoder P2, and the Wm{c3}(i) is a (i−1)th element of a fourth column of the second precoder P2, and d(0), d(1), d(2), and d(03) are data streams.

### Claim 17

A method for transmitting signals, performed in a base station, comprising:
transmitting reference signals through directional beams formed by each of a plurality of antenna groups;
receiving information on rank, a first precoder matrix index, and a second precoder matrix index of MIMO channels between the base station and a plurality of terminals which are determined based on the reference signals from the plurality of terminals; and
determining MIMO transmission method for at least one of the plurality of terminals based on the information on rank, a first precoder matrix index, and a second precoder matrix index.

### Claim 18 (depends on 17)

The method of claim 17, wherein when the first precoder matrix indexes reported from at least two terminal are different or when the first precoder matrix indexes reported from at least two terminal are the same and the second precoder matrix indexes reported from at least two terminal are different, Multi User MIMO (MU-MIMO) is performed, or Single User MIMO (SU-MIMO) and MU-MIMO are performed simultaneously in order to transmit downlink data.

### Claim 19

A method for transmitting cooperative signals, performed in a first base station and a second base station, comprising:
determining, by a terminal, first precoder matrix indexes and second precoder matrix indexes for the first base station and the second base station based on reference signals transmitted for the first base station and the second base station, and reporting, by the terminal, the first precoder matrix indexes and the second precoder matrix indexes to the first base station or to the first and the second base stations;
reporting, by the first base station, the first precoder matrix indexes and the second precoder matrix indexes to the second base station via an interface between the first and the second base stations; and
performing, by the first and the second base stations, Single User MIMO (SU-MIMO) and Multi User MIMO (MU-MIMO) based on the first precoder matrix indexes and the second precoder matrix indexes.

### Claim 20

A method for transmitting control channel performed in a base station,
wherein the base station transmits the same control data which omni-directional precoding is applied to by using a plurality of antenna groups, and
wherein the base station transmits antenna group specific reference signals for control channel demodulation multiplexed by using at least one of time division multiplexing (TDM), code division multiplexing (CDM), and frequency division multiplexing (FDM) in order to enable transmit diversity of control channel, so that a terminal discriminates each reference signal for each of the plurality of antenna groups.