KR20160018353A - Method and apparatus for device to device communication - Google Patents

Abstract

According to the present invention, a device-to-device (D2D) communications method comprises the following steps: a first terminal receives a first timing advance (TA) value from a base station; the first terminal includes a second TA value, obtained based on the first TA value, in a scheduling assignment (SA) signal; the first terminal transmits the SA signal to a second terminal at a downlink (DL) timing for receiving a downlink signal of the base station in cellular communications; and the first terminal transmits data of D2D communications to the second terminal at a first timing obtained by applying the second TA value to the DL timing when the length of cyclic prefix (CP) set for the D2D communications and the length of the CP set for the cellular communications are different.

Description

TECHNICAL FIELD [0001] The present invention relates to a direct communication method and apparatus,

The present invention relates to a D2D (Device to Device) communication method in which a terminal directly communicates with another terminal without passing through a base station, and a device supporting the same.

The 3rd Generation Partnership Project (3GPP) standard group is based on the Long-Term Evolution (LTE) standard, and provides a Rel-to-Device (D2D) -12 Standardization is underway. D2D communication technology supports data to be transmitted directly to an adjacent terminal without passing through a base station.

The D2D communication method under consideration by 3GPP is a mode 1 communication in which a D2D transmission resource is allocated by a base station or a repeater, and a mode 2 communication in which a terminal selects a direct transmission resource. Mode 1 communication can be used only by an in-coverage terminal and Mode 2 communication can be used with an in-coverage terminal, a part-coverage terminal, or an out-of-coverage ) Terminal. ≪ / RTI > Herein, the reference of the in-coverage may include a case of satisfying the cell selection condition based on the reference signal reception power and / or the reference signal reception quality. An in-coverage terminal means a terminal located within a cell coverage. The partial-coverage terminal means a terminal that receives only the synchronization signal and the system information of the base station without being within the cell coverage. The out-of-coverage terminal means a terminal outside the cell coverage which is not synchronized with the base station in the cell and can not receive the system information.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for transmitting and receiving D2D communication capable of improving the performance of D2D communication and cellular communication when resources for D2D communication and resources for cellular communication are multiplexed in D2D communication .

According to the embodiment of the present invention, a D2D (Device to Device) communication method is provided in which a first terminal directly communicates with a second terminal without passing through a base station. Wherein the D2D communication method of the first terminal comprises: receiving a first TA (Timing Advance) value from the base station; Including a second TA value based on the first TA value in a Scheduling Assignment (SA) signal; Transmitting the SA signal to the second terminal in a downlink (DL) timing for receiving a downlink signal of the base station in cellular communication; And when the length of a CP (Cyclic Prefix) set for the D2D communication is different from the length of a CP set for the cellular communication, at a first timing obtained by applying the second TA value to the DL timing, And transmitting data of the D2D communication to the second terminal.

The D2D communication method of the first terminal may further include a D2D communication method in which when the CP length for the D2D communication is equal to the CP length for the cellular communication, at a second timing obtained by applying the first TA value to the DL timing, And transmitting data of the communication to the second terminal.

Even if the first cell to which the first terminal belongs and the second cell to which the second terminal belong have different cell coverage, the timing adjustment step size for the first cell is the timing adjustment step size for the second cell ≪ / RTI >

The step of transmitting the SA signal may include the step of including a first timing adjustment step size used by the first terminal in the SA signal.

The step of including the first timing adjustment step size in the SA signal may include setting a value of one bit included in the SA signal to a value indicating the first timing adjustment step size.

If the CP for the D2D communication is a normal CP, the first timing adjustment step size may be one of 16 * sampling time and 1/2 of the normal CP length.

When the CP for D2D communication is an extended CP having a length greater than the normal CP, the first timing adjustment step size is one half of the extended CP length and one third of the extended CP length Lt; / RTI >

The D2D communication method of the first terminal may further include transmitting a cell-specific reference signal for demodulating the SA signal to the second terminal.

The timing adjustment step size of the cell to which the first terminal belongs may be transmitted to the second terminal by the base station.

The step of transmitting the SA signal may include the step of including the terminal identifier of the first terminal belonging to the first cell in the SA signal.

The terminal identifier of the terminals belonging to the first cell and the timing adjustment step size of the first cell can be transmitted to the second terminal by the base station.

The number of bits representing the second TA value may be smaller than the number of bits representing the first TA value.

The D2D communication method of the first terminal may further include the step of allocating resources for transmitting the SA signal and resources for transmitting data of the D2D communication from the base station.

According to another embodiment of the present invention, there is provided a D2D (Device to Device) communication method in which a first terminal directly communicates with a second terminal without passing through a base station. Wherein the D2D communication method of the first terminal comprises: selecting a first resource for transmitting a Scheduling Assignment (SA) signal and a second resource for transmitting data of the D2D communication among resources; When a first timing for transmitting data of the D2D communication is set to DL (Downlink) timing for receiving a downlink signal of the base station in cellular communication, a first TA (Timing Advance) value included in the SA signal To zero; And transmitting the SA signal to the second terminal using the first resource.

The D2D communication method of the first terminal may further comprise the step of transmitting the first timing to the DL of the first terminal even if the RRC (Radio Resource Control) state of the first terminal is in an RRC connected state as well as in an RRC idle state, And setting the timing as a timing.

The D2D communication method of the first terminal may include setting the first timing to a timing obtained by applying a first timing adjustment value to the DL timing when the RRC state of the first terminal is in the RRC connected state; And setting the first timing to the DL timing when the RRC state of the first terminal is the RRC idle state.

Wherein the step of setting the first timing to a timing obtained by applying the first timing adjustment value to the DL timing comprises: when the CP length for the D2D communication is equal to the CP length for the cellular communication, Calculating the first timing adjustment value for obtaining a Physical Uplink Shared Channel transmission timing based on a second TA value received from the base station; And calculating the first TA value based on the first timing adjustment value.

Wherein the step of setting the first timing to a timing obtained by applying the first timing adjustment value to the DL timing comprises: obtaining a PUSCH transmission timing when the CP length for the D2D communication and the CP length for the cellular communication are different Calculating a second timing adjustment value for the base station based on a second TA value received from the base station; Calculating the first TA value based on the second timing adjustment value; And calculating the first timing adjustment value based on the first TA value.

The step of transmitting the SA signal may include the step of including a first timing adjustment step size used by the first terminal in the SA signal.

The D2D communication method of the first terminal may further include a step of including a first timing adjustment step size used by the first terminal in a synchronization channel of the D2D communication.

According to another embodiment of the present invention, there is provided a D2D (Device to Device) communication method in which a first terminal directly communicates with a second terminal without passing through a base station. Wherein the D2D communication method of the first terminal comprises: receiving, from the second terminal, a Scheduling Assignment (SA) signal including a first TA (Timing Advance) value at a first timing; From at least one of a first signal received through an SIB (System Information Block) or RRC (Radio Resource Control) signaling of the base station, a SA signal, and a D2D communication synchronization channel received from the second terminal, Obtaining a step size; Calculating a second timing using the first timing, the first TA value, and the first timing adjustment step size; And receiving data of the D2D communication at the second timing.

Wherein the step of acquiring the first timing adjustment step size comprises the steps of: when the cyclic prefix (CP) for the D2D communication is a normal CP, Determining a value corresponding to a value of one bit included in the first timing adjustment step size having a unit of seconds as the first timing adjustment step size; And a CP for D2D communication is an extended CP having a length longer than the normal CP, and a 1 bit included in the SA signal from 1/2 of the extended CP length and 3/4 of the extended CP length, And a value corresponding to the value of the first timing adjustment step size having the unit of seconds.

According to the embodiment of the present invention, when the resources for D2D communication and the resources for cellular communication are multiplexed, the transmission timing of the D2D communication can be adjusted to improve the performance of the D2D communication and the cellular communication.

Also, according to an embodiment of the present invention, when the D2D transmitting terminal and the D2D receiving terminal belong to different cells, the D2D receiving terminal may receive the TA (Timing Advance) granularity , Timing adjustment step size) information.

According to the embodiment of the present invention, uplink timing (UL) is applied according to the difference in the CP (Cyclic Prefix) length between D2D communication and WAN (Wide Area Network) communication in mode 1 communication or mode 2 communication D2D data reception and UL WAN reception performance can be improved.

According to the embodiment of the present invention, in Mode 2 communication, D2D data reception and UL WAN reception performance can be improved by applying appropriate transmission timing according to the RRC (Radio Resource Control) state of the terminal.

Further, according to the embodiment of the present invention, a partial coverage or an out-of-coverage terminal can obtain the TA granularity of the D2D transmitting terminal during the D2D reception, thereby preventing the D2D reception performance deterioration.

1 is a flowchart showing a process of adjusting the D2D transmission / reception timing.
2 is a diagram showing transmission / reception timing applied to the SA message and the D2D data.
3 is a diagram illustrating a configuration of a terminal according to an embodiment of the present invention.
4 is a diagram illustrating a configuration of a base station according to an embodiment of the present invention.
5 is a diagram of a computer system according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, a terminal is referred to as a mobile terminal (MT), a mobile station (MS), an advanced mobile station (AMS), a high reliability mobile station ), A subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE) MS, AMS, HR-MS, SS, PSS, AT, UE, and the like.

In addition, the base station (BS) includes an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B an eNodeB, an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) a BS, an ABS, a HR-BS, a Node B, an eNodeB, a BS, a BS, a BS, a relay station (RS), a high reliability relay station (HR- AP, RAS, BTS, MMR-BS, RS, HR-RS, small base station, macro base station, and the like.

1 is a flowchart showing a process of adjusting the D2D transmission / reception timing.

Prior to transmitting D2D data, a transmitting terminal (hereinafter referred to as 'D2D transmitting terminal') for D2D communication in a mode 1 communication mode or a mode 2 communication mode transmits scheduling information including resource allocation information for D2D data transmission and link adaptation information Through a Scheduling Assignment (SA) message (signal) (or SCI (Sidelink Control Information) format 0). SCI format 0 is transmitted through a Physical Sidelink Control Channel (PSCCH). In addition, the Cyclic Redundancy Check (CRC) bits included in the SA message are scrambled using the L1 (physical layer) identifier. When a receiving terminal for D2D communication (hereinafter referred to as a 'D2D receiving terminal') successfully decodes an SA message using an L1 identifier corresponding to a D2D group to which it belongs, Try to receive.

(Hereinafter referred to as a 'D2D data resource') for transmitting and receiving an SA message (hereinafter referred to as 'SA resource') and a D2D data (hereinafter referred to as a 'D2D data resource'), the D2D transmitting terminal and the D2D receiving terminal transmit an uplink Some UL subframes of a TDD (Time Division Duplexing) frame may be used. (D2D communication resources, D2D communication resources include SA resources and D2D data resources), D2D transmitting terminals and D2D receiving terminals are used for cellular communication (or WAN (Wide Area Network) communication, And transmitted through a base station). Therefore, multiplexing between D2D communication resources and WAN communication resources (hereinafter, referred to as 'WAN communication resources') is required. In view of the terminal, only TDM (Time Division Multiplexing) is supported. In terms of the system, TDM and FDM (Frequency Division Multiplexing) Can be supported at the same time. For example, in the same subframe, the first terminal may transmit UL Control Channel in the 0th RB (Resource Block) and the second terminal may transmit the D2D SA message or data in the 10th RB.

For D2D communication between the terminals, the two terminals must be synchronized within a certain range. The in-coverage terminal receives synchronization signals (or synchronization signals and reference signals) of the base station and synchronizes them (including frequency synchronization and time synchronization). The in-coverage terminal uses the synchronized signal to receive downlink (DL) signals of the base station during WAN communication. This synchronized time synchronization is referred to as DL timing. The DL timing is similar to the propagation delay until the transmission signal of the base station is received at the terminal, and the point of time when the first path is detected can be defined as the DL timing. In addition, in order for the in-coverage terminal to transmit UL to the base station, a timing offset value (hereinafter referred to as 'first UL timing adjustment value') obtained based on TA (Timing Advance) signaled by the base station on the basis of DL timing, (Hereinafter referred to as a 'third UL timing adjustment value') of an offset value (hereinafter referred to as 'second UL timing adjustment value'). The pulled-in timing is referred to as UL timing. In general, the first UL timing adjustment value is a value corresponding to about twice the propagation delay. The UE can update the first UL timing adjustment value in accordance with the TA signaling transmitted by the base station and also update the first UL timing adjustment value in consideration of the DL timing changed by the UE itself. The latter can be implemented as an implementation. Hereinafter, the D2D transmission of the in-coverage terminal will be described in detail. However, the D2D receiving terminal may be an in-coverage terminal, a partial-coverage terminal, or an out-of-coverage terminal.

The SA transmission timing (timing for transmitting the SA message) follows the DL timing and the D2D data transmission timing (timing for D2D data transmission) follows the UL timing in mode 1 communication (the terminal is allocated D2D communication resources from the base station) . The D2D transmitting terminal transmits TA information to the D2D receiving terminal by including the TA information in the SA message to inform the D2D receiving terminal of the difference between the DL timing and the UL timing.

The D2D receiving terminal can receive an SA message by determining an FFT (Fast Fourier Transform) window start point based on its DL timing. Alternatively, when the DL timing acquisition is impossible, the D2D receiving terminal transmits the timing (hereinafter, referred to as 'SA receiving timing') for receiving the SA message to the D2D synchronizing signal (or the D2D receiving signal) transmitted by another D2D terminal , sidelink synchronization signal). Then, the D2D receiving terminal calculates a timing offset value (hereinafter referred to as 'first D2D receiving timing adjustment value') obtained based on the TA included in the SA message from its own SA receiving timing (for example, DL timing or timing obtained from the D2D synchronizing signal) (Hereinafter referred to as a 'third D2D reception timing adjustment value') of a fixed timing offset value (hereinafter referred to as 'second D2D reception timing adjustment value') and a fixed timing offset value Lt; / RTI >

Figure 1 illustrates this process. Specifically, when the D2D transmitting terminal is connected to the base station, the base station receives a TA value signal (S10).

The D2D transmitting terminal obtains a first UL timing adjustment value from a TA signaled from a base station (hereinafter referred to as 'base station TA'), and obtains a TA value to be included in the SA message based on the first UL timing adjustment value (S11). Herein, the base station TA can be signaled in bit form, and the base station TA corresponding to the base station TA is a value obtained by converting the signaled bits into decimal numbers.

The D2D transmitting terminal includes the TA value obtained in step S11 as a TA indication (or TA information) in the SA message, and transmits the TA indication to the D2D receiving terminal (S12). Specifically, the D2D transmitting terminal transmits the SA message at the DL timing. Here, the TA indication may be signaled in bit form, and the TA indication value corresponding to the TA indication is a value in which the signaled bits are converted to decimal.

The D2D transmitting terminal sets the D2D data transmission timing to the UL timing (S14).

The D2D transmitting terminal transmits the D2D data at the D2D data transmission timing set in the step S14 (S15).

Meanwhile, the D2D receiving terminal receives the SA message from the D2D transmitting terminal (S12).

The D2D receiving terminal obtains the TA indication from the received SA message (S13).

When receiving the D2D data, the D2D receiving terminal calculates the sum of the first D2D receiving timing adjustment value and the second D2D receiving timing adjusting value obtained based on the TA indication from the SA receiving timing (timing for receiving the SA message) The point of time that is earlier than the third D2D reception timing adjustment value is set as the D2D data reception timing (D2D data reception timing) (S16).

The D2D receiving terminal receives and demodulates the D2D data at the D2D data reception timing set in the step S16 (S17).

2 is a diagram showing transmission / reception timing applied to the SA message and the D2D data. 2 (A) shows a flow in which the D2D transmitting terminal transmits an SA message and D2D data (D2D data scheduled by the SA message), FIG. 2 (B) D2D < / RTI >

The reason why the D2D data transmission timing is set to the UL timing is that when the resources for the D2D communication and the WAN communication are FDM, the receiving point of the D2D communication signal and the base station receiving the UL WAN signal (UL signal in WAN communication) So as to match the viewpoint within a certain range. In general, if the arrival time of signals simultaneously received from a plurality of terminals by a base station deviates by more than half the CP (Cyclic Prefix) length, Inter-Symbol Interference (or ISI) Lt; / RTI > In order to prevent this, it is preferable to use the UL timing when the in-coverage terminal desires to transmit D2D data.

Meanwhile, the D2D transmitting terminal inserts the TA information into the SA message and transmits it at the SA transmission timing (TT1a). The SA transmission timing (TT1a) follows the DL timing. The TA information included in the SA message has a limited bit size due to the limitation of the SA message size. For example, the TA indication included in the SA message may have a size smaller than 11 bits (e.g., a size of 6 bits).

Meanwhile, a TA (hereinafter referred to as a 'first base station TA') signaling through a RAR (Random Access Response) MAC (Media Access Control) payload to a UE has a size of 11 bits, and a corresponding TA value is 0 to 1282 Lt; / RTI > Also, a TA (hereinafter referred to as 'second base station TA') signaled by a base station through a MAC (Control Element) TA command (Timing Advance Command) has a size of 6 bits, and its TA value is in a range of 0 to 63 . For two types of TA (first base station TA and second base station TA), the granularity of TA has a value of 16 占 퐏 (unit: second) or 16 (unit: Ts). The granularity units of the TA described below are assumed to be Ts unless the unit is specifically specified. Here, Ts is a sampling time and is defined as 1/30720000 seconds (sec).

The D2D transmitting terminal obtains the first UL timing adjustment value N_TA from the base station TA to obtain the UL timing. Where the value of N_TA is an integer ranging from 0 to 20512. Specifically, when the D2D transmitting terminal has signaled the first base station TA, the first base station TA x 16 is substituted into the N_TA (i.e., N_TA = the first base station TA value x 16). Or when the D2D transmitting terminal has signaled the second base station TA, by adding (the second base station TA value - 31) x 16 to the current N_TA value, the N_TA value is updated to a new value. On the other hand, if the DL timing is changed but the D2D transmitting terminal does not receive the signal from the base station TA from the base station and the compensation for the changed DL timing is not sufficiently performed, the D2D transmitting terminal can update the N_TA value by itself. The D2D transmitting terminal uses the point in time that is earlier by (N_TA + N_TA_offset1) x Ts from the DL timing as the UL timing. Here, N_TA_offset1 is set as a second UL timing adjustment value, 0 for FDD, and 624 for TDD.

The D2D transmitting terminal transmits the SA message at the SA transmission timing (TT1a). The D2D transmitting terminal sets the SA transmission timing to the DL timing. The D2D transmitting terminal sets the D2D data transmission timing (TT2) to the UL timing. Therefore, the difference AT1 between the D2D data transmission timing TT2 and the SA transmission timing TT1b corresponds to the third UL timing adjustment value.

On the other hand, the D2D receiving terminal receives the SA message from the D2D transmitting terminal at the SA receiving timing (TR1a). The SA reception timing TR1a is roughly the time elapsed by the propagation delay time PD1 in the SA transmission timing TT1a. The SA reception timing TR1a may be obtained from the D2D synchronization signal transmitted by another D2D terminal (which may also be a D2D transmitting terminal) in accordance with the DL timing or when the DL timing acquisition is impossible. The D2D receiving terminal adjusts the D2D data receiving timing based on the TA indication obtained from the SA message. Specifically, the D2D receiving terminal sets a point at which the D2D receiving timing is advanced from the SA receiving timing (TR1b) by the third D2D receiving timing adjustment value (TA indication value TA granularity + N_TA_offset2) Ts, to the D2D data receiving timing (TR2) . Here, (TA indication value x TA granularity) corresponds to the first D2D reception timing adjustment value, and N_TA_offset2 corresponds to the second D2D reception timing adjustment value. N_TA_offset2 is set to 0 when the D2D receiving terminal is an in-coverage terminal, if the cell to which the D2D receiving terminal belongs is set to FDD, and to 624 if it is set to TDD. If the D2D receiving terminal can not receive the system information from the neighboring base station, N_TA_offset2 is set to zero. For example, when the TA granularity is set to 16, the D2D receiving terminal belonging to the FDD cell is advanced from the SA receiving timing by the third D2D receiving timing adjustment value (TA indication value x 16 + N_TA_offset 2) x Ts Time is used as the D2D data reception timing. The D2D receiving terminal receives the D2D data at the D2D data receiving timing (TR2).

On the other hand, when the TA indication transmitted through the SA message has a granularity of 16 and a size of less than 11 bits, it can represent a timing adjustment value corresponding to cell coverage of up to 100 km supported by the LTE standard none. Therefore, the granularity of the TA can be set based on the coverage of the cell to which the D2D terminal belongs. As one of such setting methods, a base station has a length of 16 占,, a half of a length of a normal CP (hereinafter referred to as 'NCP'), a half of a length of an extended CP (hereinafter referred to as 'ECP'), (Unit: second) of the TA granularity. If you want to change the granularity of TA Granules from seconds to Ts, divide the granularity of TA granules by seconds into Ts and round down the result. In this way, a TA granularity value in units of Ts can be generated. The base station can transmit the TA granularity thus set to the D2D terminal through SIB (System Information Block) or RRC signaling, and the terminal can use it.

On the other hand, the base station of each cell can set the TA granularity to have the smallest step size (with maximum cell coverage) while including cell coverage to optimize the performance of UL WAN reception or D2D reception of the base station. have. If adjacent cells have different coverage, UEs belonging to different cells can be configured with different TA granularities. In this case, even if the D2D receiving terminal successfully decodes the SA message of the D2D transmitting terminal belonging to the cell adjacent to the D2D receiving terminal, due to the different TA granularity, the TA indication included in the SA message is transmitted to the D2D transmitting terminal It may be interpreted differently from the one applied. As a result, the D2D receiving terminal may not be able to successfully decode the D2D data, or it may be necessary to readjust the reception FFT window starting point through additional calculation to decode it. Hereinafter, a method for solving the problem will be described in detail. A method for adjusting the D2D data transmission timing according to whether the CP length for WAN communication and the CP length for D2D communication is different will be described in detail.

On the other hand, in the mode 2 communication (the terminal directly selects the D2D communication resource), the SA transmission timing follows the DL timing like the mode 1 communication. Hereinafter, a method of adjusting the D2D data transmission timing for optimizing the D2D performance and the UL WAN performance according to the RRC (Radio Resource Control) state of the terminal in mode 2 communication will be described in detail. In Mode 2 communication, a method of adjusting the D2D data transmission timing according to whether the CP length for WAN communication and the CP length for D2D communication is adjusted will be described in detail. In addition, when the D2D receiving terminal does not set the TA granularity to be equal to the TA granularity of the D2D transmitting terminal, the D2D data receiving performance may deteriorate, and a method for solving this problem will be described in detail .

First, the transmission timing in mode 1 communication will be described.

As described above, in the mode 1 communication, the D2D transmitting terminal follows the DL timing at the SA transmission timing and follows the UL timing at the D2D data transmission timing. Meanwhile, UL timing according to the base station TA (UL timing calculated using the UL timing adjustment value obtained based on the base station TA, e.g., UL timing calculated using N_TA) is used for PUSCH (Physical Uplink Shared Channel) transmission, Hereinafter, UL timing according to the base station TA is referred to as PUSCH timing. The PUSCH timing is distinguished from the timing according to the TA indication (the timing obtained based on the TA indication). The base station TA may have a granularity of 16, while the TA indication transmitted by the D2D transmitting terminal via the SA message may have a granularity of more than 16, depending on the cell coverage.

The D2D transmitting terminal selects the value closest to the PUSCH timing as the TA indication transmitted through the SA message. Specifically, the D2D transmitting terminal can select a value closest to the N_TA value used for calculating the PUSCH timing among the TA indication candidates included in the SA message. More specifically, the D2D transmitting terminal calculates TA indication candidates (TA indication candidate value × TA granularity) for the TA indication candidates and selects the value closest to the N_TA value used in calculating the PUSCH timing among the calculated values And the TA indication candidate used for the determined value can be included in the SA message. Alternatively, the D2D transmitting terminal can determine the TA indication using Equation (1) below.

In Equation (1), floor () is the descending function, N_TA is the first UL timing adjustment value used in the PUSCH timing calculation, and TA granularity is the TA granularity used by the D2D transmitting terminal.

The D2D transmitting terminal transmits the TA indication thus selected or determined by including it in the SA message. Therefore, when the D2D transmitting terminal transmits D2D data at the PUSCH timing and the D2D receiving terminal determines the receiving FFT window starting point (or the D2D data receiving timing) based on the TA indication included in the SA message for receiving the D2D data (Unit: Ts) of the maximum and the TA granularity may occur. If the D2D transmitting terminal sets the D2D transmission timing based on the TA indication transmitted through the SA message, the D2D data reception timing set by the D2D receiving terminal may not generate or reduce the error. Thus, the D2D receiving terminal can receive the D2D data while lowering the complexity, and the D2D receiving performance can be improved. On the other hand, when the D2D transmission timing is set based on the TA indication, the D2D data is shifted by a maximum value by half the granularity (unit: Ts) as compared with the case of setting the D2D transmission timing with the PUSCH timing The UL WAN reception performance may be degraded due to interference with the UL WAN reception or collision with the last OFDM symbol of the previous subframe.

The D2D transmitting terminal can determine whether there is a difference between the CP length of the D2D communication and the CP length of the WAN communication, and determine the D2D data transmission timing according to the determination result.

If the CP lengths of the D2D communication and the UL WAN communication are set differently, the D2D transmission can generate ICI for UL WAN reception, which can be mitigated by setting the power control or protection band. Therefore, when the CP lengths of the D2D communication and the UL WAN communication are set differently, in order to improve the D2D reception performance, the D2D transmitting terminal transmits the D2D data transmission timing to the timing according to the TA indication TA indication UL timing "), which is calculated by using the TA indication included. Specifically, the TA indication UL timing is a time point advanced from the SA transmission timing (or DL timing) by (TA indication value TA granularity + N_TA_offset1) x Ts. If the CP lengths of the D2D communication and the UL WAN communication are set to be the same, the D2D transmitting terminal uses the PUSCH timing with the D2D data transmission timing.

On the other hand, in the mode 1 communication, TA granularity can be set according to the cell coverage. When different TA granules are set in the neighbor cells having different cell coverage, the D2D receiving terminal is adjacent to the D2D receiving terminal The TA indication included in the SA message transmitted by the D2D transmitting terminal belonging to the cell can be interpreted differently from the D2D transmitting terminal. As a result, the data reception performance may deteriorate. To solve this problem, four methods can be used.

The first method is to set the TA granularity of the cells to the same value even if the cell coverage of the cells is different. For example, a TA granularity can be set for each cell with a value that can support the widest cell coverage or average cell coverage. According to the first method, the D2D receiving terminal can interpret the TA indication transmitted from the D2D transmitting terminal belonging to an arbitrary cell without error, and can use it when receiving D2D data.

In the second method, the D2D transmitting terminal transmits a cell-specific reference signal as a reference signal for demodulating the SA message, and the base station transmits the TA granularity of the cell adjacent to the D2D receiving terminal to the SIB or RRC signaling To the D2D receiving terminal. According to the second method, when the D2D receiving terminal successfully decodes the SA message, it determines whether the D2D terminal belonging to which cell transmitted the SA message based on the cell specific reference signal used in decoding the SA message. Then, the D2D receiving terminal obtains the TA granularity information of the neighboring cell from the SIB or RRC signaling of the base station. Then, the D2D receiving terminal finds the TA granularity of the D2D transmitting terminal that has transmitted the SA message from the acquired TA granularity information. Then, the D2D receiving terminal uses the found TA granularity when receiving D2D data.

The third method is a method in which the D2D transmitting terminal includes the TA granularity used by itself in the SA message. According to the third method, when receiving the SA message, the D2D receiving terminal acquires the TA granularity from the SA message and uses the acquired TA granularity when receiving the D2D data. On the other hand, the overhead for transmitting the TA granularity information through the SA message can be mitigated through association with other information. For example, when the TA granularity value (unit: second) that can be set in one cell is 16 占 Ts s, 1/2 of the NCP length, 1/2 of the ECP length, and ECP length 3/4. ≪ / RTI > If the CP for D2D communication is NCP, one of the 16Ts and 1/2 NCP length can be assigned to the cell as a TA Granularity value (in seconds). Alternatively, if the CP for D2D communication is ECP, one half of the ECP length and 3/4 of the ECP length may be assigned to the cell as a TA Granularity value (in seconds). If all the cells set the CP length for D2D communication to the same value or if the base station notifies the D2D receiving terminal through SIB or RRC signaling for the CP length for D2D communication of the cell adjacent to the D2D transmitting terminal, The D2D transmitting terminal can express TA granularity information included in the SA message with only one bit. For example, assuming that the CP for D2D communication is NCP, when the TA granularity (unit: second) used by the D2D transmitting terminal is 16 · Ts, the TA granularity bits (Bit size = 1) is set to 0, and the TA granularity (unit: second) used by the D2D transmitting terminal is 1/2 of the NCP length, the value of the TA granularity bit is set to 1 Can be set.

In the fourth method, the base station notifies the D2D receiving terminal of the terminal identifier of the D2D terminals belonging to the cell adjacent to the D2D receiving terminal and the TA granularity of the neighboring cell to the D2D receiving terminal through SIB or RRC signaling, Including the terminal identifier. According to a fourth method, the D2D receiving terminal receives the SA message, and obtains the terminal identifier of the D2D transmitting terminal from the SA message. Then, the D2D receiving terminal uses the obtained terminal identifier to determine the cell to which the D2D transmitting terminal belongs, and finds the TA granularity of the determined cell. The D2D receiving terminal then uses the found granularity to receive the D2D data.

The transmission timing in mode 2 communication will be described below.

In Mode 2 communication, since the D2D transmitting terminal determines the transmission resource by itself, D2D transmission can be performed not only in the RRC connection state (RRC_CONNECTED) but also in the RRC id state (RRC_IDLE) state. A terminal in the RRC_CONNECTED state can be signaled from the base station to the base station TA. However, the terminal in the RRC_IDLE state can not receive signaling from the base station TA.

As described above, when the D2D transmitting terminal transmits D2D data at the calculated UL timing using the TA, the ICI can be prevented (or mitigated) upon UL WAN reception of the base station. Therefore, the terminal in the RRC_CONNECTED state uses the UL timing in the D2D data transmission, and the terminal in the RRC_IDLE state uses the DL timing in the D2D data transmission. Alternatively, regardless of the UL WAN reception capability (or regardless of the RRC state), the D2D transmitting terminal may use the DL timing during D2D data transmission. The electronic scheme (a scheme for determining the D2D transmission timing differently according to the RRC state) and the latter scheme (the scheme for determining the D2D transmission timing independently of the RRC state) include the electronic scheme and the latter scheme There is a method of defining one in advance and a method of using one in accordance with the setting of the base station among the electronic method and the latter method. Specifically, in the method of using one according to the setting of the base station, the base station can set which one of the electronic scheme and the latter scheme to use and transmit the setting information through SIB or RRC signaling. The D2D terminal which has received the setting information from the base station can use either the electronic system or the latter system depending on the setting of SIB or RRC signaling.

On the other hand, when the D2D transmitting terminal uses the UL timing with the D2D transmitting timing (for example, the terminal in the RRC_CONNECTED state in the electronic system), TA information to be included in the SA message is obtained in the same manner as in the mode 1 communication. Specifically, the D2D transmitting terminal obtains the TA information based on the UL timing adjustment value used for obtaining the UL timing, and transmits the obtained TA information by including it in the SA message. On the other hand, when the D2D transmitting terminal uses the DL timing with the D2D transmission timing (for example, the terminal in the RRC_IDLE state in the electronic scheme or the terminal in the latter scheme), TA information set to 0 is transmitted to the SA message including the TA information .

On the other hand, in the mode 2 communication, as in the mode 1 communication, the D2D transmitting terminal can set the D2D data transmission timing differently according to the CP length difference between the D2D communication and the WAN communication. Specifically, when the CP lengths of the D2D communication and the WAN communication are the same, the D2D transmitting terminal sets the D2D data transmission timing to the PUSCH timing. When the CP lengths of the D2D communication and the WAN communication are different, the D2D transmitting terminal sets the D2D data transmission timing to the TA indication UL timing obtained based on the TA indication in the SA message. Concretely, the TA indication UL timing is earlier than the SA transmission timing (or DL timing) by (TA indication value × TA granularity + N_TA_offset1) × Ts as in mode 1 communication. On the other hand, in both cases (when the CP length is the same, and the CP length is different), the D2D transmitting terminal can set the TA indication transmitted through the SA message to the value closest to the PUSCH timing. Specifically, as in Mode 1 communication, the D2D transmitting terminal can select a value closest to the N_TA value used to calculate the PUSCH timing among the TA indication candidates that may be included in the SA message. More specifically, the D2D transmitting terminal calculates TA indication candidates (TA indication candidate value × TA granularity) for the TA indication candidates and selects the value closest to the N_TA value used in calculating the PUSCH timing among the calculated values And the TA indication candidate used for the determined value can be included in the SA message. Alternatively, the D2D transmitting terminal can determine the TA indication using Equation (1).

Meanwhile, in the mode 2 communication, the D2D receiving terminal may be a partial-coverage terminal or an out-of-coverage terminal. Therefore, when the D2D receiving terminal can not obtain the TA granularity information from the base station's SIB or RRC signaling, the TA applied to the D2D transmitting terminal can not be interpreted or misinterpreted. In order to solve this problem, the D2D transmitting terminal may transmit its TA granularity information to the SA message similarly to the mode 1 communication in order to inform all D2D receiving terminals of their TA granularity. The D2D receiving terminal can interpret the TA indication included in the SA message without error by using the TA granularity information included in the SA message. Alternatively, the D2D transmitting terminal may use a D2D synchronization channel (e.g., a Physical D2D Synchronization Channel (PD2DSCH), or a Physical Sidelink Broadcast Channel (PSBCH), which is used to propagate synchronization to a partially-coverage terminal or an out- ) With its own TA granularity information. The D2D receiving terminal can acquire TA granularity information of the D2D transmitting terminal from the D2D synchronization channel.

3 is a diagram showing a configuration of a terminal 100 according to an embodiment of the present invention. The D2D transmitting terminal and the D2D receiving terminal described above may be configured to be the same as or similar to the terminal 100. [

The terminal 100 includes a processor 110, a memory 120, and a radio frequency (RF) converter 130.

The processor 110 may be configured to implement the functions, procedures, and methods associated with the embodiments of the present invention. In particular, the processor 110 may be configured to implement the functions, procedures, and methods associated with the D2D transmitting terminal described herein. Alternatively, the processor 110 may be configured to implement the functions, procedures, and methods associated with the D2D receiving terminal described herein. Each configuration of the terminal 100 can be executed by the processor 110.

The memory 120 is coupled to the processor 110 and stores various information related to the operation of the processor 110. [

RF converter 130 is coupled to processor 110 and transmits or receives radio signals. The terminal 100 may have a single antenna or multiple antennas.

4 is a diagram illustrating a configuration of a base station 200 according to an embodiment of the present invention.

The base station 200 includes a processor 210, a memory 220, and an RF converter 230.

Processor 210 may be configured to implement the functions, procedures, and methods associated with embodiments of the present invention. In particular, processor 210 may be configured to implement the functions, procedures, and methods described herein with reference to a base station. Each configuration of the base station 200 may be executed by the processor 210.

The memory 220 is coupled to the processor 210 and stores various information related to the operation of the processor 210. [

The RF converter 230 is connected to the processor 210 and transmits or receives a radio signal. The base station 200 may have a single antenna or multiple antennas.

On the other hand, embodiments of the present invention may be implemented within a computer system (e.g., computer readable media, etc.). As illustrated in FIG. 5, computer system 300 may include at least one processor 310, memory 320, and storage 330. In addition, the computer system 300 may further include a communication interface 340. The communication interface 340 may include a network interface 341 connected to the network 400. In addition, the computer system 300 may further include a user input device 350 and a user output device 360. Each configuration 310-360 may communicate via bus 370. [

 The processor 310 may be a central processing unit (CPU) or a semiconductor device that executes the memory 320 or the processing instructions stored in the storage 330. Memory 320 and storage 330 may include various forms of volatile or non-volatile storage media. For example, the memory 320 may include a read-only memory (ROM) 321 and a random access memory (RAM)

Thus, embodiments of the present invention may be implemented in a computer implemented method or in a non-transitory computer readable medium with computer executable instructions stored thereon . In an embodiment of the present invention, when computer-executable instructions are executed by the processor 310, the computer-executable instructions perform the method according to at least one aspect of the invention .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (20)

A D2D (Device to Device) communication method in which a first terminal directly communicates with a second terminal without passing through a base station,
Receiving a first TA (Timing Advance) value from the base station;
Including a second TA value based on the first TA value in a Scheduling Assignment (SA) signal;
Transmitting the SA signal to the second terminal in a downlink (DL) timing for receiving a downlink signal of the base station in cellular communication; And
When a length of a CP (Cyclic Prefix) set for the D2D communication is different from a length of a CP set for the cellular communication, at a first timing obtained by applying the second TA value to the DL timing, the D2D Transmitting data of communication to the second terminal
Wherein the D2D communication method comprises: The method according to claim 1,
When the CP length for the D2D communication is equal to the CP length for the cellular communication, data of the D2D communication is transmitted to the second terminal at a second timing obtained by applying the first TA value to the DL timing Step
Wherein the D2D communication method further comprises: The method according to claim 1,
Even if the first cell to which the first terminal belongs and the second cell to which the second terminal belong have different cell coverage, the timing adjustment step size for the first cell is the timing adjustment step size for the second cell The same as
A D2D communication method of a first terminal. The method according to claim 1,
The step of transmitting the SA signal comprises:
Including a first timing adjustment step size used by the first terminal in the SA signal
A D2D communication method of a first terminal. 5. The method of claim 4,
The step of including the first timing adjustment step size in the SA signal comprises:
And setting a value of one bit included in the SA signal to a value indicating the first timing adjustment step size
A D2D communication method of a first terminal. 6. The method of claim 5,
Wherein if the CP for the D2D communication is a Normal CP, the first timing adjustment step size is one of a 16 * sampling time and a half of the normal CP length,
When the CP for D2D communication is an extended CP having a length greater than the normal CP, the first timing adjustment step size is one half of the extended CP length and one third of the extended CP length sign
A D2D communication method of a first terminal. The method according to claim 1,
And transmitting a cell-specific reference signal for demodulating the SA signal to the second terminal,
The timing adjustment step size of the cell to which the first terminal belongs is transmitted to the second terminal by the base station
A D2D communication method of a first terminal. The method according to claim 1,
The step of transmitting the SA signal comprises:
And including the terminal identifier of the first terminal belonging to the first cell in the SA signal,
The terminal identifier of the terminals belonging to the first cell and the timing adjustment step size of the first cell are transmitted to the second terminal by the base station
A D2D communication method of a first terminal. The method according to claim 1,
The number of bits representing the second TA value is smaller than the number of bits representing the first TA value
A D2D communication method of a first terminal. The method according to claim 1,
Receiving a resource for transmitting the SA signal and a resource for transmitting data of the D2D communication from the base station
Wherein the D2D communication method further comprises: The method according to claim 1,
The step of including the second TA value in the SA signal comprises:
Calculating a first timing adjustment value used for obtaining a timing for a physical uplink shared channel (PUSCH) transmission based on the first TA value; And
And calculating the second TA value using Equation 1 below
A D2D communication method of a first terminal.
[Equation 1]
TA2 = floor (N_TA / TAS)
TAS is a timing adjustment step size used by the first terminal and has a unit of a sampling time, TA2 is the second TA value, A D2D (Device to Device) communication method in which a first terminal directly communicates with a second terminal without passing through a base station,
Selecting a first resource for transmitting a Scheduling Assignment (SA) signal and a second resource for transmitting data of the D2D communication among the resources;
When a first timing for transmitting data of the D2D communication is set to DL (Downlink) timing for receiving a downlink signal of the base station in cellular communication, a first TA (Timing Advance) value included in the SA signal To zero; And
And transmitting the SA signal to the second terminal using the first resource
Wherein the D2D communication method comprises: 13. The method of claim 12,
Setting the first timing to the DL timing even when the RRC (Radio Resource Control) state of the first terminal is in an RRC connected state as well as in an RRC idle state
Wherein the D2D communication method further comprises: 13. The method of claim 12,
Setting the first timing to a timing obtained by applying a first timing adjustment value to the DL timing when the RRC state of the first terminal is in the RRC connected state; And
Setting the first timing to the DL timing when the RRC state of the first terminal is the RRC idle state
Wherein the D2D communication method further comprises: 15. The method of claim 14,
Wherein the step of setting the first timing to the timing obtained by applying the first timing adjustment value to the DL timing comprises:
The first timing adjustment value for obtaining a Physical Uplink Shared Channel (PUSCH) transmission timing when the CP length for the D2D communication is equal to the CP length for the cellular communication, 2 TA value; And
And calculating the first TA value based on the first timing adjustment value
A D2D communication method of a first terminal. 15. The method of claim 14,
Wherein the step of setting the first timing to the timing obtained by applying the first timing adjustment value to the DL timing comprises:
Calculating a second timing adjustment value for obtaining a PUSCH transmission timing based on a second TA value received from the base station when the CP length for the D2D communication and the CP length for the cellular communication differ;
Calculating the first TA value based on the second timing adjustment value; And
And calculating the first timing adjustment value based on the first TA value
A D2D communication method of a first terminal. 13. The method of claim 12,
The step of transmitting the SA signal comprises:
Including a first timing adjustment step size used by the first terminal in the SA signal
A D2D communication method of a first terminal. 13. The method of claim 12,
Including a first timing adjustment step size used by the first terminal in a synchronization channel of the D2D communication
Wherein the D2D communication method further comprises: A D2D (Device to Device) communication method in which a first terminal directly communicates with a second terminal without passing through a base station,
Receiving, at the first timing, an SA (Scheduling Assignment) signal including a first TA (Timing Advance) value from the second terminal;
From at least one of a first signal received through an SIB (System Information Block) or RRC (Radio Resource Control) signaling of the base station, a SA signal, and a D2D communication synchronization channel received from the second terminal, Obtaining a step size;
Calculating a second timing using the first timing, the first TA value, and the first timing adjustment step size; And
Receiving data of the D2D communication at the second timing
Wherein the D2D communication method comprises: 20. The method of claim 19,
The step of acquiring the first timing adjustment step size includes:
A value corresponding to a value of 1 bit included in the SA signal from the 16 * sampling time and 1/2 of the normal CP length when the CP for the D2D communication is a normal CP, Determining a first timing adjustment step size having a unit of seconds; And
The CP for the D2D communication is an extended CP having a length longer than the normal CP, and a 1 bit included in the SA signal from 1/2 of the extended CP length and 3/4 of the extended CP length And determining a value corresponding to the value as the first timing adjustment step size having a unit of seconds
A D2D communication method of a first terminal.

Images