# US 11,452,056 B2 · Apparatus and method for configuring synchronization signal for communication between user devices

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- Number: US 11,452,056 B2
- Document ID: US11452056B2
- Status: Granted
- Kind: B2
- Application number: 17/137,240
- Filed: 2020-12-29
- Published: 2021-05-06
- Granted: 2022-09-20
- Earliest claimed: 2014-11-05
- Assignees: Innovative Technology Lab Co., Ltd.
- Applicants: Innovative Technology Lab Co., Ltd.
- Inventors: Sung Jun Yoon
- Web page: https://patentgrep.com/patent/US11452056B2

## CPC

- H04W 56/001: {Synchronization between nodes}
- H04L 27/2613: {Structure of the reference signals}
- H04L 27/2692: {with preamble design, i.e. with negotiation of the synchronisation sequence with transmitter or sequence linked to the algorithm used at the receiver}
- H04W 4/70: Services for machine-to-machine communication [M2M] or machine type communication [MTC]
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

Exemplary embodiments provide a method and apparatus for transmitting a synchronization signal for Device-to-Device (D2D) communication in a wireless communication system. The method includes: receiving, at a first UE, a D2D synchronization signal transmitted from a second UE, the D2D synchronization signal comprising a primary D2D synchronization signal (PD2DSS) and a secondary D2D synchronization signal (SD2DSS); determining a root index based on the received PD2DSS; and determining a type of a synchronization source based on the root index. The root index corresponds to an integer value X when the type of synchronization source is associated with D2DSSue_net. The root index corresponds to an integer value Y when the type of synchronization source is associated with D2DSSue_oon. Each of the integer value X and integer value Y is not an element of a set {25, 29, 34}.

## Claims

### Claim 1

A system comprising:
one or more base stations configured to transmit a downlink signal; and
a first wireless user device configured to:
receive, from a second wireless user device, one or more wireless signals for direct communication, wherein the one or more wireless signals comprises a primary synchronization signal and a secondary synchronization signal;
determine, based on the primary synchronization signal, a root index associated with the primary synchronization signal, wherein the root index associated with the primary synchronization signal has one of a plurality of integer values, and wherein each of the plurality of integer values is different from root index values associated with synchronization signals transmitted from the one or more base stations; and
determine, based on the one of the plurality of integer values, a type of a synchronization source;
determine the secondary synchronization signal that is mapped in two Single Carrier-Frequency Division Multiplexing (SC-FDM) symbols in a same subframe; and
determine, based on one of two different conditions, whether a first m-sequence of the secondary synchronization signal is mapped to first sub-carriers of the two SC-FDM symbols or mapped to second sub-carriers of the two SC-FDM symbols,
wherein indexes of the first sub-carriers are even numbers and indexes of the second sub-carriers are odd numbers.

### Claim 2 (depends on 1)

The system of claim 1, wherein the first wireless user device is configured to determine the primary synchronization signal mapped in two SC-FDM symbols in the same subframe.

### Claim 3 (depends on 1)

The system of claim 1, wherein the first wireless user device is configured to:
determine, based on the root index corresponding to a first value of the plurality of integer values, that the second wireless user device has a synchronization timing originated from a base station.

### Claim 4 (depends on 3)

The system of claim 3, wherein NID(1) and NID(2) are associated with the secondary synchronization signal,
where NID(1) is an integer selected from {0, 1, . . . , 167}, and NID(2) is 0 when the root index associated with the primary synchronization signal corresponds to the first value.

### Claim 5 (depends on 1)

The system of claim 1, wherein the first wireless user device is configured to:
determine, based on the root index corresponding to a second value of the plurality of integer values, that the second wireless user device has a synchronization timing of an independent synchronization source.

### Claim 6 (depends on 5)

The system of claim 5, wherein NID(1) and NID(2) are associated with the secondary synchronization signal,
where NID(1) is an integer selected from {0, 1, . . . , 167}, and NID(2) is 1 when the root index associated with the primary synchronization signal corresponds to the second value.

### Claim 7 (depends on 1)

The system of claim 1, wherein the first wireless user device is configured to determine whether the first m-sequence of the secondary synchronization signal is mapped to the first sub-carriers of the two SC-FDM symbols or mapped to the second sub-carriers of the two SC-FDM symbols by determining, based on a first communication mode of the two different conditions, that the first m-sequence of the secondary synchronization signal is mapped to the first sub-carriers.

### Claim 8 (depends on 1)

The system of claim 1, wherein the first wireless user device is configured to determine whether the first m-sequence of the secondary synchronization signal is mapped to the first sub-carriers of the two SC-FDM symbols or mapped to the second sub-carriers of the two SC-FDM symbols by determining, based on a second communication mode of the two different conditions, that the first m-sequence of the secondary synchronization signal is mapped to the second sub-carriers.

### Claim 9 (depends on 1)

The system of claim 1, wherein the one or more wireless signals for direct communication is a device-to-device (D2D) communication signal.

### Claim 10

A system comprising:
one or more base stations configured to transmit a downlink signal; and
a first wireless user device configured to:
transmit, to the one or more base stations, an uplink signal;
transmit, to a second wireless user device, one or more wireless signals for direct communication;
synchronize with a synchronization source based on a synchronization signal received from the synchronization source;
determine, based on the synchronization source and from a plurality of integer values, a root index of a primary synchronization signal, wherein each of the plurality of integer values is different from root index values associated with synchronization signals transmitted from the one or more base stations;
generate, based on the determined root index, the primary synchronization signal;
determine one of two different conditions;
map a secondary synchronization signal in two Single Carrier-Frequency Division Multiplexing (SC-FDM) symbols in a same subframe, wherein mapping the secondary synchronization signal comprises mapping, based on the one of the two different conditions, a first m-sequence of the secondary synchronization signal to first sub-carriers of the two SC-FDM symbols or to second sub-carriers of the two SC-FDM symbols; and
transmit, to the second wireless user device, a second synchronization signal comprising the primary synchronization signal and the secondary synchronization signal,
wherein indexes of the first sub-carriers are even numbers; and
wherein indexes of the second sub-carriers are odd numbers.

### Claim 11 (depends on 10)

The system of claim 10, wherein the generated primary synchronization signal is transmitted in two SC-FDM symbols in the same subframe.

### Claim 12 (depends on 10)

The system of claim 10, wherein the first wireless user device is configured to:
determine, based on the synchronization source that has a synchronization timing originated from a base station, a first value, of the plurality of integer values, for the root index of the primary synchronization signal.

### Claim 13 (depends on 12)

The system of claim 12, wherein NID(1) and NID(2) are associated with the secondary synchronization signal,
where NID(1) is an integer selected from {0, 1, . . . , 167}, and NID(2) is 0 when the root index of the primary synchronization signal corresponds to the first value.

### Claim 14 (depends on 10)

The system of claim 10, wherein the first wireless user device is configured to:
determine, based on the synchronization source that has a synchronization timing of an independent synchronization source, a second value, of the plurality of integer values, for the root index of the primary synchronization signal.

### Claim 15 (depends on 14)

The system of claim 14, wherein NID(1) and NID(2) are associated with the secondary synchronization signal,
where NID(1) is an integer selected from {0, 1, . . . , 167}, and NID(2) is 1 when the root index of the primary synchronization signal corresponds to the second value.

### Claim 16

A system comprising:
one or more base stations to transmit a downlink signal; and
a wireless user device configured to:
receive, from a second wireless user device, one or more wireless signals for direct communication;
receive a synchronization signal transmitted from the second wireless user device, the synchronization signal comprising a primary synchronization signal;
determine, based on the received primary synchronization signal, a root index associated with the received primary synchronization signal, wherein the root index associated with the received primary synchronization signal has one of a plurality of integer values, and each of the plurality of integer values is different from root index values associated with synchronization signals transmitted from the one or more base stations;
select the second wireless user device to be a synchronization source of the wireless user device;
generate, using the root index associated with the received primary synchronization signal, a primary synchronization signal to be transmitted to a third wireless user device;
map a secondary synchronization signal in two Single Carrier-Frequency Division Multiplexing (SC-FDM) symbols in a same subframe, wherein mapping the secondary synchronization signal comprises mapping, based on one of two different conditions, a first m-sequence of the secondary synchronization signal to first sub-carriers of the two SC-FDM symbols or to second sub-carriers of the two SC-FDM symbols; and
transmit, to the third wireless user device, the generated primary synchronization signal and the secondary synchronization signal,
wherein indexes of the first sub-carriers are even numbers; and
wherein indexes of the second sub-carriers are odd numbers.

### Claim 17 (depends on 16)

The system of claim 16, wherein the second wireless user device is directly synchronized with a base station via a primary synchronization signal (PSS) transmitted from the base station, and
wherein the root index associated with the received primary synchronization signal has a first integer value.

### Claim 18 (depends on 17)

The system of claim 17, wherein the received primary synchronization signal is received via two SC-FDM symbols in the same subframe,
wherein the first integer value is used for the received primary synchronization signal, and
wherein NID(1) and NID(2) are associated with the secondary synchronization signal,
where NID(1) is an integer selected from {0, 1, . . . , 167}, and NID(2) is 0 when the root index associated with the received primary synchronization signal corresponds to the first integer value.

### Claim 19 (depends on 16)

The system of claim 16, wherein the second wireless user device is an independent synchronization source (ISS) or synchronized with an ISS, and
wherein the root index associated with the received primary synchronization signal has a second integer value.

### Claim 20 (depends on 19)

The system of claim 19, wherein the received primary synchronization signal is received via two SC-FDM symbols in the same subframe,
wherein the second integer value is used for the received primary synchronization signal, and
wherein NID(1) and NID(2) are associated with the secondary synchronization signal,
where NID(1) is an integer selected from {0, 1, . . . , 167}, and NID(2) is 1 when the root index associated with the received primary synchronization signal corresponds to the second integer value.