# US 10,484,152 B2 · Method and apparatus for transmitting or receiving reference signal in beamforming communication system

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- Number: US 10,484,152 B2
- Document ID: US10484152B2
- Status: Granted
- Kind: B2
- Application number: 15/767,261
- Filed: 2016-11-02
- Published: 2019-02-21
- Granted: 2019-11-19
- Earliest claimed: 2015-11-02
- Assignees: Samsung Electronics Co., Ltd.
- Applicants: Samsung Electronics Co., Ltd.
- Inventors: Hyun-Yong Lee
- Web page: https://patentgrep.com/patent/US10484152B2

## CPC

- H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)}
- H04B 7/06952: {Selecting one or more beams from a plurality of beams, e.g. beam training, management or sweeping}
- H04B 7/088: {using beam selection}
- H04L 5/0007: {the frequencies being orthogonal, e.g. OFDM(A) or DMT}
- H04L 5/0023: {Time-frequency-space}
- H04L 5/0083: {symbol-by-symbol}
- H04L 5/0094: {Indication of how sub-channels of the path are allocated}
- H04L 27/2613: {Structure of the reference signals}
- H04L 27/265: {Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators (H04L27/26524 takes precedence)}
- H04W 16/28: using beam steering
- H04W 56/001: {Synchronization between nodes}
- H04W 72/044: based on the type of the allocated resource
- H04L 5/0057: {Physical resource allocation for CQI}
- H04L 5/0073: {Allocation arrangements that take into account other cell interferences}
- H04L 27/2655: {Synchronisation arrangements}
- H04W 88/08: Access point devices
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04B: TRANSMISSION
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

The present disclosure relates to a 5G or pre-5G communication system for supporting a higher data rate beyond a 4G communication system such as LTE. Disclosed is a method and apparatus for transmitting or receiving a reference signal in a beamforming communication system. The method comprises the steps of: generating a reference signal sequence for a reference signal that can be used for beam searching; mapping the reference signal sequence to modulation symbols corresponding to resource elements having a predetermined identical subcarrier spacing among resource elements that can be used to transmit the reference signal; generating an OFDM symbol signal including the modulation symbols; and transmitting the OFDM symbol signal using at least one predetermined transmission beam among transmission beams that can be used by a base station.

## Claims

### Claim 1

A method for transmitting a reference signal by a base station in a beamforming communication system, comprising:
generating a reference signal sequence for a reference signal to be used for a beam search;
mapping the reference signal sequence to modulation symbols which correspond to resource elements with same subcarrier spacing which is predetermined on a frequency domain among resource elements to be used for transmitting the reference signal;
generating an orthogonal frequency division multiplex (OFDM) signal including the modulation symbols, wherein one OFDM symbol included in the OFDM signal comprises a sequence pattern associated with the reference signal sequence that is repeated a plurality of times over a duration of the one OFDM symbol, and wherein the duration of the one OFDM symbol corresponds to a duration of sub-symbols determined for repetition of the sequence pattern on a time domain; and
transmitting the OFDM signal using at least one transmission beam among a plurality of transmission beams.

### Claim 2 (depends on 1)

The method of claim 1,
wherein the transmitting of the OFDM signal comprises transmitting the OFDM signal during a predetermined period,
wherein the predetermined period is divided into a plurality of frame groups based on a number of transmission antennas of the base station, and different transmission beams are used for the transmission antennas during each of the plurality of frame groups, and
wherein the OFDM signal is received by a terminal during all or a part of the plurality of frame groups based on an operating mode of the terminal, and the operating mode includes one of a single input single output (SISO) mode and a multiple input multiple output (MIMO) mode.

### Claim 3 (depends on 1)

The method of claim 1, wherein the reference signal sequence is generated using at least one of a cell identifier (ID) of the base station, a subframe index, or a slot number.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
transmitting configuration information indicating at least one of a resource location or a direction of a transmission beam which are used for transmitting the reference signal through control information or upper layer signaling.

### Claim 5 (depends on 1)

The method of claim 1,
wherein the transmitting of the OFDM signal comprises transmitting the OFDM signal using different transmission beams through a plurality of transmission antennas, and
wherein each of the plurality of transmission antennas is configured to transmit the OFDM signal using all transmission beams sequentially during a predetermined period.

### Claim 6 (depends on 1)

The method of claim 1, wherein the reference signal sequence is defined as the following equation,
r
l
,
n
s
⁡
(
m
)
=
1
2
⁢
(
1
-
2
·
c
⁡
(
2
⁢
⁢
m
)
)
+
j
⁢
1
2
⁢
(
1
-
2
·
c
⁡
(
2
⁢
⁢
m
+
1
)
)
,
⁢
m
=
0
,
1
,
…
⁢
,
N
RB
DL
-
1
c
init
=
2
10
·
(
7
·
(
n
s
+
1
)
+
l
+
1
)
·
(
2
·
N
ID
cell
+
1
)
+
2
·
N
ID
cell
+
1
where the reference signal sequence is mapped to a modulation symbol according to the following equation,
{
a
k
,
l
(
p
)
=
0
,
if
⁢
⁢
k
⁢
⁢
mod
⁢
⁢
4
≠
0
a
k
,
l
(
p
)
=
r
l
,
n
s
⁡
(
m
)
,
if
⁢
⁢
k
⁢
⁢
mod
⁢
⁢
4
=
0
⁢
⁢
m
=
0
,
1
,
…
⁢
,
N
RB
DL
·
N
sc
RB
/
4
-
1
where, k and l denote indexes on the frequency domain and indexes on the time domain, respectively, p and ns denote an antenna port number and a slot number, respectively, NIDcell and NRBDL denote a cell identifier (ID) and a number of downlink resource blocks (RBs), rl,ns (m) is an mth reference signal sequence, and ak,l(p) denotes a modulation symbol which is carried through a kth subcarrier.

### Claim 7

A method for receiving a reference signal by a terminal in a beamforming communication system, comprising:
receiving, from a base station, an orthogonal frequency division multiplex (OFDM) signal including a reference signal sequentially using a plurality of reception beams, wherein the OFDM signal is configured such that a sequence pattern associated with the reference signal is repeated a plurality of times over a duration of one OFDM symbol included in the OFDM signal, and wherein the duration of the one OFDM symbol corresponds to a duration of sub-symbols determined for repetition of the sequence pattern on a time domain;
performing fast fourier transform (FFT) operations on signals of the sub-symbol durations of the OFDM signal;
generating channel information which corresponds to the plurality of reception beams using signals which are obtained through the FFT operations; and
selecting a reception beam from among the plurality of reception beams using the channel information.

### Claim 8 (depends on 7)

The method of claim 7,
wherein the receiving of the OFDM signal comprises receiving the OFDM signal during all or a part of a plurality of frame groups based on an operating mode of the terminal, the operating mode including one of a single input single output (SISO) mode and a multiple input multiple output (MIMO) mode, and
wherein the plurality of frame groups are generated by dividing a predetermined period based on a number of transmission antennas of the base station, and different transmission beams are used for the transmission antennas during each of the plurality of frame groups.

### Claim 9 (depends on 7)

The method of claim 7, further comprising:
receiving, from the base station, configuration information indicating at least one of a resource location or a direction of a transmission beam which are used for transmitting the reference signal through control information or upper layer signaling.

### Claim 10 (depends on 7)

The method of claim 7, wherein the receiving of the OFDM signal comprises:
receiving a signal of a first sub-symbol duration which starts after a predetermined cyclic prefix (CP) duration or a duration which corresponds to pre-measured channel delay spread on a time domain in the OFDM symbol signal using a first reception beam; and
receiving a signal of a second sub-symbol duration which is after at least beam transition time from the first sub-symbol duration using a second reception beam.

### Claim 11 (depends on 10)

The method of claim 10, wherein performing the FFT operations comprises performing FFT on samples included in a signal of each sub-symbol duration and performing phase correction on a signal obtained through the FFT operation.

### Claim 12 (depends on 10)

The method of claim 10, wherein the first sub-symbol duration is determined to be started from a sum of the pre-measured channel delay spread and a timing margin which corresponds to arrival time difference among neighbor base stations in the OFDM symbol signal.

### Claim 13 (depends on 7)

The method of claim 7, wherein receiving of the OFDM signal comprises:
in a case that terminal operates in a single input single output (SISO) mode, receiving the OFDM signal during one frame group among a plurality of frame groups, and
in a case that the terminal operates in a multiple input multiple output (MIMO) mode, receiving the OFDM signal during the plurality of frame groups,
wherein the plurality of frame groups are generated by dividing a predetermined period based on a number of transmission antennas of the base station, and different transmission beams are used for the transmission antennas during each of the plurality of frame groups.

### Claim 14 (depends on 7)

The method of claim 7, further comprising:
receiving the OFDM signal using one fixed reception beam; and
performing synchronization with the base station using the OFDM signal which is received using the one fixed reception beam.

### Claim 15

A base station in a beamforming communication system, the base station comprising:
at least one processor configured to:
generate a reference signal sequence for a reference signal to be used for a beam search, to map the reference signal sequence to modulation symbols which correspond to resource elements with same subcarrier spacing which is predetermined on a frequency domain among resource elements to be used for transmitting the reference signal, and
generate an orthogonal frequency division multiplex (OFDM) signal including the modulation symbols, wherein one OFDM symbol included in the OFDM symbol signal comprises a sequence pattern that is repeated a plurality of times over a duration of the one OFDM symbol, and wherein the duration of the one OFDM symbol corresponds to a duration of sub-symbols determined for repetition of the sequence pattern on a time domain; and
a transceiver configured to transmit the OFDM signal using at least one transmission beam among a plurality of transmission beams.

### Claim 16 (depends on 15)

The base station of claim 15,
wherein the transceiver is further configured to transmit the OFDM signal during a predetermined period,
wherein the predetermined period is divided into a plurality of frame groups based on a number of transmission antennas of the base station, and different transmission beams are used for the transmission antennas during each of the plurality of frame groups, and
wherein the OFDM signal is received by a terminal during all or a part of the plurality of frame groups based on an operating mode of the terminal, and the operating mode includes one of a single input single output (SISO) mode and a multiple input multiple output (MIMO) mode.

### Claim 17 (depends on 15)

The base station of claim 15, wherein the reference signal sequence is generated using at least one of a cell identifier (ID) of the base station, a subframe index, or a slot number.

### Claim 18 (depends on 15)

The base station of claim 15, wherein the transceiver is further configured to transmit configuration information indicating at least one of a resource location or a direction of a transmission beam which are used for transmitting the reference signal through control information or upper layer signaling.

### Claim 19 (depends on 15)

The base station of claim 15,
wherein the RF transmitting unit is further configured to transmit the OFDM symbol signal using different transmission beams through a plurality of transmission antennas, and
wherein each transmission antenna is configured to transmit the OFDM symbol signal using all transmission beams sequentially during a predetermined beam search period.

### Claim 20 (depends on 15)

The base station of claim 15, wherein the reference signal sequence is defined as the following equation,
r
l
,
n
s
⁡
(
m
)
=
1
2
⁢
(
1
-
2
·
c
⁡
(
2
⁢
⁢
m
)
)
+
j
⁢
1
2
⁢
(
1
-
2
·
c
⁡
(
2
⁢
⁢
m
+
1
)
)
,
⁢
m
=
0
,
1
,
…N
RB
DL
-
1
c
init
=
2
10
·
(
7
·
(
n
s
+
1
)
+
l
+
1
)
·
(
2
·
N
ID
cell
+
1
)
+
2
·
N
ID
cell
+
1
where the reference signal sequence is mapped to a modulation symbol according to the following equation,
{
a
k
,
l
(
p
)
=
0
,
if
⁢
⁢
k
⁢
⁢
mod
⁢
⁢
4
≠
0
a
k
,
l
(
p
)
=
r
l
,
n
s
⁡
(
m
)
,
if
⁢
⁢
k
⁢
⁢
mod
⁢
⁢
4
=
0
⁢
⁢
m
=
0
,
1
,
…
⁢
,
N
RB
DL
·
N
sc
RB
/
4
-
1
where, k and l denote indexes on a frequency domain and indexes on a time domain, respectively, p and ns denote an antenna port number and a slot number, respectively, NIDcell and NRBDL denote a cell identifier (ID) and a number of downlink resource blocks (RBs), rl,ns (m) is an mth reference signal sequence, and ak,l(p) denotes a modulation symbol which is carried through a kth subcarrier.

### Claim 21

A terminal in a beamforming communication system, the terminal comprising:
a transceiver configured to receive, from a base station, an orthogonal frequency division multiplex (OFDM) signal including a reference signal sequentially using a plurality of reception beams, wherein the OFDM signal is configured such that a sequence pattern associated with the reference signal is repeated a plurality of times over a duration of one OFDM symbol included in the OFDM signal, and wherein the duration of the one OFDM symbol corresponds to a duration of sub-symbols determined for repetition of the sequence pattern on a time domain; and
at least one processor configured to:
perform fast fourier transform (FFT) operations on signals of the sub-symbol durations of the OFDM signal,
generate channel information which corresponds to the plurality of reception beams using signals which are obtained through the FFT operations, and
select a reception beam from among the plurality of reception beams using the channel information.

### Claim 22 (depends on 21)

The terminal of claim 21,
wherein the transceiver is further configured to receive the OFDM signal during all or a part of a plurality of frame groups based on an operating mode of the terminal, the operating mode including one of a single input single output (SISO) mode and a multiple input multiple output (MIMO) mode, and
wherein the plurality of frame groups are generated by dividing a predetermined period based on a number of transmission antennas of the base station, and different transmission beams are used for the transmission antennas during each of the plurality of frame groups.

### Claim 23 (depends on 21)

The terminal of claim 21, wherein the transceiver is further configured to:
receive a signal of a first sub-symbol duration which starts after a predetermined cyclic prefix (CP) duration or a duration which corresponds to pre-measured channel delay spread on a time domain in the OFDM symbol signal using a first reception beam, and
receive a signal of a second sub-symbol duration which is after at least beam transition time from the first sub-symbol duration using a second reception beam.

### Claim 24 (depends on 23)

The terminal of claim 23, wherein the at least one processor is further configured to perform FFT on samples included in a signal of each sub-symbol duration and perform phase correction on a signal obtained through the FFT operation.

### Claim 25 (depends on 23)

The terminal of claim 23, wherein the first sub-symbol duration is determined to be started from a sum of the pre-measured channel delay spread and a timing margin which corresponds to arrival time difference among neighbor base stations in the OFDM symbol signal.

### Claim 26 (depends on 21)

The terminal of claim 21,
wherein the transceiver is further configured to:
in a case that terminal operates in a single input single output (SISO) mode, receive the OFDM signal during one frame group among a plurality of frame groups, and
in a case that the terminal operates in a multiple input multiple output (MIMO) mode, receive the OFDM signal during the plurality of frame groups,
wherein the plurality of frame groups are generated by dividing a predetermined period based on a number of transmission antennas of the base station, and different transmission beams are used for the transmission antennas during each of the plurality of frame groups.