KR20140060232A - Method of direct communication by terminal - Google Patents

Abstract

According to an embodiment of the present invention, a method is provided in which a first terminal communicating with a base station performs direct communication with a second terminal. The first terminal determines a first point of time to transmit or receive a first signal to or from the base station. The first terminal determines a second time point at which a second signal for terminal search is transmitted to the second terminal. The first terminal changes one of the first viewpoint and the second viewpoint when the first viewpoint and the second viewpoint overlap each other.

Description

[0001] METHOD OF DIRECT COMMUNICATION BY TERMINAL [0002]

The present invention relates to a direct communication method between a terminal (or a device, a device). More particularly, the present invention relates to a method for providing an inter-terminal communication service in a wireless communication system.

In the wireless communication system, a method of forming a direct link between terminals for supporting neighboring services is currently being proposed in IEEE 802.11 (PAD), 802.15 (TG8, Peer Aware Communication; PAC), 802.16 (GRIDMAN TG) and 3GPP Proximity-based Service (ProSe).

The service through direct link formation between terminals under discussion / development can be used in public safety, disaster relief, and proximity-based service (LTE Device to Device Proximity Discovery). In order to form a direct link, possibility of direct link formation is determined through searching between neighboring terminals.

However, in the related art, only a method of performing a terminal search operation (for example, transmission of a reference signal, report after signal strength measurement, etc.) is requested at the request of the base station. According to this conventional technique, the neighboring terminal search affects the existing service between the base station and the terminal. In particular, the prior art causes a lot of problems when a resource serving as a resource for a lower terminal (e.g., a terminal registered in a base station) of a base station is used as a resource for terminal search (terminal search for forming a direct link).

SUMMARY OF THE INVENTION It is an object of the present invention to provide an efficient terminal search method for establishing a direct link between terminals and a method of searching for a terminal and forming a direct link while continuously providing a communication service between the base station and the terminal.

According to an embodiment of the present invention, a method is provided in which a first terminal communicating with a base station performs direct communication with a second terminal. The direct communication method comprising the steps of: determining a first point of time to transmit or receive a first signal to or from the base station; Determining a second time to transmit a second signal for terminal search to the second terminal; And changing one of the first viewpoint and the second viewpoint when the first viewpoint and the second viewpoint overlap each other.

The first signal may be a feedback signal transmitted to the base station and a data signal transmitted to the base station every first period.

Wherein the modifying comprises: receiving first view change information from the base station; And changing the first viewpoint based on the first viewpoint change information.

The changing step may include changing the first time point to a predetermined time point.

The predetermined time may be an uplink time point after K (K is a natural number) after the second time point, or a Kth previous uplink time point from the second time point.

The direct communication method may further include transmitting the first signal to the base station at every predetermined period after transmitting the first signal at the predetermined time.

The first signal may be a signal related to an operation based on time synchronization during a Hybrid Automatic Repeat Request (HARQ) operation.

The first signal may be a signal associated with a persistent resource allocation operation.

The first signal may be a signal related to a group resource allocation operation.

The direct communication method may further include receiving from the base station first information indicating whether or not direct communication is possible based on the strength of the second terminal receiving the second signal.

The direct communication method may further comprise setting a first link for direct communication with the second terminal if the first information indicates that direct communication with the second terminal is possible.

Wherein the setting step comprises the step of, when the first communication is performed with the second terminal through the relay of the base station, transmitting a request message for changing the second link corresponding to the first communication to the first link, As shown in FIG.

The request message may include a service connection identifier indicating the second link.

Wherein the setting step includes the step of, when the second link corresponding to the first communication, which is the communication with the second terminal performed through the relay of the base station, is not set, To the base station.

According to another embodiment of the present invention, there is also provided a method for a first terminal communicating with a base station to perform direct communication with a second terminal. The direct communication method comprising the steps of: determining a first point of time to transmit or receive a first signal to or from the base station; Determining a second time point at which to receive a second signal for terminal search from the second terminal; And changing one of the first viewpoint and the second viewpoint when the first viewpoint and the second viewpoint overlap each other; And reporting the reception strength of the second signal to the base station.

Wherein the reporting step comprises: a first reporting method of reporting the reception strength of the second signal each time the second signal is received; a second reporting method of reporting the reception strength of the second signal when the reception intensity of the second signal is greater than a threshold value; A second reporting method reporting an intensity, and a third reporting method reporting an average received intensity value of the second signal received during the first time.

Further, according to another embodiment of the present invention, a terminal is provided. The terminal includes a radio frequency converter; And a processor coupled to the radio frequency translator, for controlling direct communication with the first terminal and communication with the base station. Wherein the processor is configured to determine a first point of time to transmit or receive a first signal as a communication signal with the base station to the base station or to receive from the base station a second signal to search for the first terminal, , And changes the first viewpoint and the second viewpoint when the first viewpoint and the second viewpoint overlap each other.

According to the embodiment of the present invention, when the inter-terminal data exchange is to be performed through the wireless direct link, the terminal search for direct link formation can be efficiently performed.

Also, according to the embodiment of the present invention, the terminal search can be performed while continuously supporting the service between the base station and the terminal.

1 illustrates a procedure of searching for a terminal according to an embodiment of the present invention.
FIG. 2A illustrates an example of a terminal search process of FIG. 1; FIG.
FIG. 2B illustrates another example of the terminal search process of FIG. 1. FIG.
FIG. 3A and FIG. 3B are diagrams illustrating inter-terminal services through direct communication with inter-terminal services through relaying a base station according to an embodiment of the present invention;
4 illustrates a terminal 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 station (MS), a mobile terminal (MT), an advanced mobile station (AMS), a high reliability mobile station (HR- May refer to a subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE) , AMS, HR-MS, SS, PSS, AT, UE, device, device, and the like.

Also, a base station (BS) is an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B, eNodeB), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) a high-reliability relay station (HR-RS) serving as a base station, a home node B, a home eNodeB (HeNB) BS, etc.) and may include all or some of the functions of ABS, Node B, eNodeB, AP, RAS, BTS, MMR-BS, RS, HR-RS, HNB, HeNB, small BS, .

FIG. 1 is a diagram illustrating a procedure of searching for a terminal for forming a direct link between terminals according to an embodiment of the present invention.

FIG. 1 shows a base station 100 and terminals 200_1 to 200_5 for exchanging data through wireless communication. The terminals 200_1 to 200_5 have a function of exchanging data by forming a direct link with the neighboring terminals 200_1 to 200_5 in addition to the function of exchanging data with the base station 100. [

The terminal 200_1 transmits a reference signal (ranging preamble signal) for terminal search to the neighboring terminals 200_2 to 200_5. The neighboring terminals 200_2 to 200_5 receive the reference signal, measure the reception strength of the reference signal, and report the measurement result to the base station 100.

Meanwhile, a terminal search for forming a direct link between terminals may include a search by a request of a base station, a search by a terminal request, and a search by a terminal search by a terminal. The terminal search process will be described in more detail with reference to FIG.

FIG. 2A is a diagram specifically illustrating a terminal search process of FIG. 1. FIG. Specifically, FIG. 2A illustrates a procedure for performing a search by request between the base station 100 and the terminals 200_1 to 200_4 (i.e., searching for a terminal by request of the base station 100 and searching for a terminal by request of the terminal 200_1) .

1. Search by request of the base station 100

When data exchange is performed between a terminal (for example, 200_1) and a terminal (for example, 200_2 to 200_4) by relaying the base station 100 in the service area 300 of the base station 100, (Tl, T6, T7) to the terminals 200_2 to 200_4 to form a direct link to the terminal 200_1 to form a link, and transmits a reference signal from the terminal 200_1 to the terminals 200_2 to 200_4 (T 2, T 3, T 4) to report the measurement result to the base station 100 (T 8, T 9, T 10). Specifically, the base station 100 transmits a request message including information on whether to report the reception strength of the reference signal to the base station 100 or to report to the terminal (for example, 200_1) (E.g., 200_2) receiving the reference signal. The base station 100 determines the possibility of forming a direct link between the terminal 200_1 and the terminals 200_2 to 200_4 based on the measurement results reported from the terminals 200_2 to 200_4.

On the other hand, the terminals 200_1 to 200_4 receiving the request from the base station 100 can start, refuse, or postpone the terminal search through a response such as acceptance, rejection, or postponement of the request. If the terminal 200_1 to 200_4 refuses the request, the response message for the request may include a reason for rejection (e.g., insufficient battery capacity, etc.).

2B, when the terminal 200_1 transmits a reference signal (T13) in order to measure the signal strength between the terminals, the terminal 200_2 receives the reference signal and measures the measured reception strength The terminal 200_1 reports the measured reception strength to the base station 100 and reports the measured reception strength to the base station 100 in step T16. (T11, T12) to the terminals 200_1 and 200_2. On the other hand, when it is necessary to report the reception strength of the reference signal between terminals, the terminal (for example, 200_2) receiving the reference signal transmits the reference signal to the terminal (e.g., 200_1) (Eg, feedback). The terminal 200_1 that has received the reference signal strength measured from the terminal 200_2 may report the received signal strength of the reference signal to the base station 100. [ To this end, the base station 100 receives a reference signal from a terminal (for example, 200_1) that transmits a reference signal and receives a reference signal from a terminal (e.g., 200_2) 200_1).

Meanwhile, the base station 100 may inform the terminal (e.g., 200_2) about the resource (location) to be used for reporting the reception strength of the reference signal (hereinafter, 'reporting resource information'). Specifically, the base station 100 allocates feedback resources (resources for receiving and receiving the reception strength of the reference signal) to the terminal (e.g., 200_2) in the terminal search request, or transmits the predefined resources (E.g., 200_2) to report the reception strength of the reference signal using a predefined resource. The terminal (eg, 200_2) receiving the resource information for reporting from the base station 100 can report the reception strength of the reference signal using the resource corresponding to the resource information for reporting. The resource (e.g., resource corresponding to the reporting resource information) used for reporting the reception strength of the reference signal is allocated to the base station 100 in addition to the above-described predefined resource and allocation for feedback MAC message or MAC header to be transmitted. Meanwhile, the terminal (eg, 200_2) may include the fact that the reporting resource information has been received in a MAC message or a MAC header to notify the base station 100 of the information by piggybacking. Meanwhile, the base station 100 periodically requests the terminal 200_1 to transmit a reference signal (hereinafter referred to as 'periodic reference signal transmission') and periodically reports the received signal strength of the reference signal to the terminals 200_2 to 200_4 (Hereinafter referred to as 'periodic reception strength report'). The base station 100 may transmit a periodic reference signal transmission request message including the period information, the end time information, or the search frequency information to the terminal 200_1 in response to the periodic reference signal transmission request. Similarly, the base station 100 may transmit a periodic reception strength report request message including the period information, the end point information, or the search frequency information to the terminals 200_2 to 200_4 at the request of the periodic reception strength report. The UEs 200_1 to 200_4 change the information included in the request message received from the base station 100 (e.g., period information, end time information, search frequency information, or reception strength reporting time information) The request can be accepted. In addition, the terminals 200_1 to 200_4 can accept the request of the base station 100 based on the information included in the request message received from the base station 100. [ For example, if the request message received from the base station 100 includes the end point information, the terminals 200_1 to 200_4 perform terminal search based on the end point information and transmit the request message received from the base station 100 If the period information is included, the terminal search is continuously performed based on the period information, and if the request message received from the base station 100 includes the search frequency information, the terminal search is performed based on the search frequency information . If the request message received from the base station 100 does not include the end point information, the period information, and the search frequency information, or the search frequency information indicates 1, the terminals 200_1 to 200_4 perform the terminal search only once .

On the other hand, when the base station 100 or the terminals 200_1 to 200_4 desires to end the continuous terminal search, the terminal search end process can be performed through the end request. When the terminal 200_1 to 200_4 makes a termination request, the terminals 200_1 to 200_4 may request termination of the terminal search by using a termination request message including a termination reason (e.g., insufficient remaining battery capacity, direct link signal quality degradation, direct link disconnection, etc.) .

On the other hand, when the base station 100 or the terminals 200_1 to 200_4 desires to change the period for periodic terminal search, the base station 100 or the terminals 200_1 to 200_4 may perform a search cycle changing process through a period change request.

Considering the mobility of the terminals 200_1 to 200_4, the base station 100 requests a terminal (for example, 200_4) capable of communicating with the base station 100 to transmit a reference signal when communication with the terminal (e.g., 200_1) Direct link formation may be induced.

Meanwhile, the terminal (e.g., 200_2) can report the received strength of the measured reference signal to the base station 100 upon receiving a report request from the base station 100. [

On the other hand, when it is necessary to report the reception strength of the reference signal between terminals, the terminal (for example, 200_2) receiving the reference signal transmits the reference signal to the terminal (e.g., 200_1) (Eg, feedback). The UE 200_1 that has received the measured reference signal strength may report the received reference signal strength to the base station 100. [ To this end, the base station 100 receives a reference signal from a terminal (for example, 200_1) that transmits a reference signal and receives a reference signal from a terminal (e.g., 200_2) 200_1), or may assign a part of resources for transmission of a reference signal to a resource for feedback (a resource for receiving and receiving a reception strength of a reference signal). Similarly, the base station 100 transmits a request message including information on whether to report the reception strength of the reference signal to the base station 100 or to report to the terminal transmitting the reference signal (for example, 200_1) To the receiving terminal (e.g., 200_2).

2. Search by request of terminal (for example, 200_1)

When the terminal (e.g., 200_1) requests the terminal search, it includes a case for forming a direct link and a case for managing a direct link already formed (re-searching due to disconnection, etc.).

The terminal search in the case of forming a direct link can be performed by requesting the base station 100 to allocate data for reference signal transmission (T0) to the terminal (eg, 200_1) The process after the request T0 is similar to the above-described search process by the request of the base station 100. [

Meanwhile, it is difficult to maintain a direct link due to attenuation of signal strength while data is being exchanged between a terminal (eg, 200_1) and a terminal (eg, 200_2) through a direct link, or a direct link with a new terminal The terminal search (T0) may be performed by the terminal (e.g., 200_1) to the base station 100 in order to perform the terminal search. In this case, the terminal search can be performed, changed, or terminated through the same process as all or a part of the search process by the request of the base station 100 described above.

Meanwhile, the base station 100 requests the other terminal (e.g., 200_2) other than the terminal (e.g., 200_1) requesting the terminal search (T0) to transmit the reference signal and requests the terminal search (E.g., 200_1) that has received the request (T0).

On the other hand, the self-search (not shown) of the terminal can be performed as follows.

3. Self-exploration of terminal (eg, 200_1)

(Eg, 200_1) in a situation where there is no base station 100 or the base station 100 does not participate (for example, when it is necessary to maintain or manage a direct link between terminals without involvement of the base station 100) Terminal search can be performed. In this case, the terminal (e.g., 200_1) spontaneously transmits the reference signal, and the terminal (e.g., 200_2) receives the reference signal and forms a direct link with the terminal (e.g., 200_1) Communication can be performed. On the other hand, the terminal (e.g., 200_2) receiving the reference signal measures the strength of the reference signal and reports the received strength of the reference signal to the terminal (e.g., 200_1) that transmitted the reference signal. In this case, the terminal search operation (e.g., transmission / reception of a reference signal) may be performed through a direct link established between the two terminals (e.g., 200_1 and 200_2) A previously allocated resource by the base station 100 or a resource previously allocated for terminal discovery). Meanwhile, the terminal (e.g., 200_2) may indicate a resource (location) to report the received strength of the measured reference signal to the terminal (e.g., 200_2) And report the reception strength to the terminal (e.g., 200_1). In addition, when the terminal (eg, 200_1) reports the reception strength of a reference signal using a predefined resource, it indicates only the fact (the fact that the reception strength of the reference signal is reported using the predefined resource) And report the reception strength of the reference signal using the resource. Meanwhile, in the case of self-exploration of the terminal, the terminal search can be performed, changed, or terminated through the same process as all or a part of the search process by the request of the base station 100 described above.

Next, a process of receiving a reference signal from a terminal (e.g., 200_2) and measuring the reception intensity of the reference signal and reporting the measurement result will be described.

The method of measuring and reporting the reception intensity of the reference signal includes a method of measuring the reception intensity after each reception of the reference signal, reporting the reception intensity of the reference signal when the reception intensity of the reference signal is out of the threshold, And a method of reporting a value obtained by averaging the reception intensity of the reference signal. On the other hand, when the reference signal is transmitted periodically and the reference signal is periodically received to report the reception strength of the measured reference signal, the reliability and accuracy of the terminal search can be improved.

Next, a method of performing terminal search for direct link formation in a situation where data exchange is performed between the base station 100 and terminals (e.g., 200_1 and 200_2) will be described. The terminal search must be performed to minimize the influence of data exchange between the base station 100 and the terminals (e.g., 200_1 and 200_2). For example, when a terminal (e.g., 200_1) transmits a reference signal using downlink resources of the base station 100, the base station 100 transmits a reference signal to the base station 100 in order to minimize the interference with the downlink of the base station 100 A data area for signal transmission may be allocated or a corresponding downlink resource may not be used. If the UE 200_1 transmits a reference signal using the uplink resource of the Node B 100, the Node B 100 transmits the uplink resource to another UE (e.g., 200_2 through 200_4) (Eg, 200_2) receives the reference signal instead of transmitting the uplink data to the base station 100 at the time of the uplink resource. Therefore, when an operation based on time synchronization (for example, periodic or timing-based data transmission / reception) is required between the base station 100 and the terminals (e.g., 200_1 and 200_2), the base station 100 transmits / (For example, 200_1) can not receive data from the base station 100 at the time of transmission of the reference signal, and the terminal (e.g., 200_2) receiving the reference signal transmits data to the base station 100 at the time of receiving the reference signal Can not. Specifically, when the terminal 200_1 transmits a reference signal using uplink resources of the base station 100, the terminal 200_1 may not transmit data to the base station 100, and the terminal 200_1 transmits a reference signal The base station 100 may not receive the data. When the terminal 200_2 receives the reference signal using the uplink resource of the base station 100, the terminal 200_2 may not transmit data to the base station 100 and the terminal 200_2 receives the reference signal using the downlink resource It is possible to receive data from the base station 100. However, when data reception from the base station 100 and reference signal reception from the terminal 200_1 are performed in the same data area, reception may be difficult.

The operation based on the time synchronization between the base station 100 and the UEs 200_1 and 200_2 typically includes a HARQ ACK / NACK feedback based on a period or a timing, a channel status report , Feedback for power control, feedback for interference control, etc.), retransmission by HARQ operation, group resource allocation (Group Resource Allocation), and periodic resource allocation (persistent resource allocation) Resource Allocation). Hereinafter, a method for efficiently performing terminal search for direct link formation while ensuring services between the base station 100 and terminals (e.g., 200_1 and 200_2) will be described in detail with reference to each operation based on time synchronization.

1. Feedback based on period or timing

The feedback based on the period or timing includes HARQ ACK / NACK feedback, feedback for channel status reporting, feedback for MIMO operation, feedback for power control, periodic ranging, periodic sounding as well as feedback for interference control As well as uplink data transfer operations based on time synchronization.

The base station 100 may allow the terminals 200_1 and 200_2 to perform a terminal search operation (e.g., reference signal transmission / reception) so as not to affect the feedback time point or the uplink data transmission time point. Or when the base station 100 overlaps the timing of the data transmission based on the timing with the search execution time (e.g., reference signal transmission time, reference signal reception time), the base station 100 may explicitly change the data transmission time, 200_2), or may allow the terminal (eg, 200_1, 200_2) to transmit the data at a time when it is implicitly set. Here, the predetermined time may be defined as K (where K is a natural number, eg, 1) -th uplink time point from the reference signal transmission / reception time point or a K-th previous uplink time point from the reference signal transmission / reception time point. Meanwhile, when periodic data exchange is performed between the base station 100 and the terminals (e.g., 200_1 and 200_2), the base station 100 allows the terminals (e.g., 200_1 and 200_2) Data transmission (transmission / reception) with the base station is performed at a predetermined time instead of the data transmission time while maintaining the period of data transmission time overlapping with the time point (for example, the reference signal transmission time and the reference signal reception time) And data exchange (transmission / reception) can be performed based on the original cycle at the next data exchange (transmission / reception) timing. On the other hand, a terminal (for example, 200_1) that transmits a reference signal can not receive data from the base station 100 at the time of transmission of a reference signal, but can transmit reference signals and transmit data to the base station 100 at the same time. Also, the terminal (eg, 200_2) receiving the reference signal can receive data from the base station 100 at the time of receiving the reference signal, but there is a restriction on transmitting data to the base station 100 at the time of receiving the reference signal .

2. Based on timing (synchronous) HARQ  action

The base station 100 may cause the operations performed based on the timing (synchronization) in the HARQ operation to be performed similar to the feedback based on the above-described period or timing (e.g., HARQ ACK / NACK feedback). That is, the base station 100 may perform a retransmission operation at a predetermined time point instead of the retransmission time point at a retransmission time point that overlaps with a terminal search execution time (e.g., a reference signal transmission time point, a reference signal reception time point). Alternatively, the base station 100 may explicitly change the retransmission time point overlapping the terminal search execution time (e.g., reference signal transmission time point, reference signal reception time point) and notify the terminals (e.g., 200_1 and 200_2).

3. Group resource allocation

When one or more terminals (eg, 200_1 and 200_2) that allocate resources to a group perform a terminal search operation (reference signal transmission / reception), the base station 100 allocates the terminals (eg, 200_1 and 200_2) It can be excluded from the allocation target. Alternatively, the base station 100 may explicitly change the resource allocation time, as in the case of feedback based on the above-described period or timing (e.g., HARQ ACK / NACK feedback) You can change it implicitly. When excluding the UEs 200_1 and 200_2 from the group resource allocation target, the BS 100 schedules the resource allocation time to a time point different from the UE search execution time, Quot; to " Meanwhile, the group resource allocation includes a case where the base station 100 allocates downlink resources and transmits data to terminals (e.g., 200_1 and 200_2) using allocated downlink resources, and allocates uplink resources to terminals (e.g., 200_1 and 200_2 May transmit data to the base station 100 using the uplink resource allocated thereto.

4. Periodic resource allocation

When one or more UEs (e.g., 200_1 and 200_2) that are periodically allocated resources perform a terminal search operation (reference signal transmission / reception), the base station 100 determines that the corresponding UEs (e.g., 200_1 and 200_2) Such as in the feedback (e.g., HARQ ACK / NACK feedback) based on the above-described period or timing, to change the resource allocation time or to change it implicitly. Meanwhile, the base station 100 may continuously perform the periodic resource allocation after the resource allocation time overlapping with the terminal search execution time based on the original cycle. Alternatively, the base station 100 may adjust the periodic resource allocation to be performed based on a point of time when the base station 100 does not overlap the terminal search execution time. Meanwhile, the periodic resource allocation includes a case where the base station 100 allocates downlink resources and transmits data to the terminals (e.g., 200_1 and 200_2) using allocated downlink resources, and a case where the uplink resources are allocated to the terminals (e.g., 200_1 and 200_2 May transmit data to the base station 100 using the uplink resource allocated thereto.

Next, a method of setting a direct link after the terminal search is completed will be described in detail.

The terminal (eg, 200_2) that has received the reference signal reports the received strength of the measured reference signal to the base station 100. The base station 100 determines whether direct communication is possible between the two terminals (e.g., 200_1 and 200_2) based on the received signal strength of the reference signal. If it is determined that direct communication is possible, the base station 100 may request the terminal (e.g., 200_1, 200_2) to establish a direct link. The direct link setting method will be described in detail with reference to FIGS. 3A and 3B.

3A is a diagram illustrating an inter-terminal service through direct communication with an inter-terminal service through a relay of a base station 100 according to an embodiment of the present invention.

A direct link setting method will be described by dividing the case where the link L2 is set between the two terminals 200_1 and 200_2 and the case where no link is established between the two terminals 200_1 and 200_6.

1. A link (" L2 ) Is set

The link L2 between the two terminals 200_1 and 200_2 corresponds to the communication (or service) between the two terminals 200_1 and 200_2 performed through the relay (or routing) of the base station 100. [ Before the direct communication link L1 is established, the service connection between the two terminals 200_1 and 200_2 is performed through the base station 100 and the upper layer.

If it is determined that direct communication is possible between the two terminals 200_1 and 200_2 based on the reception strength of the reference signal, the base station 100 can directly communicate with the terminals 200_1 and 200_2 between the terminals 200_1 and 200_2 (Or recommending) the terminals 200_1 and 200_2 to form a direct link, or may request to form a direct link.

The terminal 200_1 notified from the base station that the direct link can be established can continuously perform the existing service by requesting the base station 100 to change the previous link L2 directly to the link L1. The change to the direct link L1 can be performed while maintaining the setting parameters of the previous link L2 as it is. Alternatively, the change to the direct link L1 may be performed by adding / changing only the parameters necessary for the direct link L1. On the other hand, the terminal 200_1 can perform the service by setting the link L1 directly after canceling the previous link L2.

On the other hand, the terminal 200_1 transmits a message including a service connection identifier to be directly changed to the link L1 or a message specialized for direct link setting to the base station 100, Service.

On the other hand, the base station 100 may request the terminal 200_1 to wait for a predetermined time to establish a direct link with the counterpart terminal 200_2, and may transmit a result of the direct link establishment request (success or failure Etc.) to the terminal 200_1.

On the other hand, the base station 100 requesting to change the link L1 directly from the terminal 200_1 requests the neighboring terminal 200_2 to change the previous link L2 directly to the link L1. The terminal 200_2 requesting the change from the base station 100 to the direct link L1 directly links the previous link L2 to the direct link L1 in order to service through the direct link L1 instead of servicing through the previous link L2. (L1). When the direct link L1 is successfully established between the two terminals 200_1 and 200_2, the two terminals 200_1 and 200_2 can transmit / receive data via the direct link L1.

On the other hand, the base station 100 may request the terminals 200_1 and 200_2 to directly or simultaneously set the link L1. In this case, as described above, the base station 100 may cause the previous link L2 to be changed to the direct link L1 or the direct link L1 to be set after the previous link L2 is canceled. In addition, the terminal (e.g., 200_1) can directly request the base station 100 to transmit / receive data directly between the terminals 200_1 and 200_2 via the link L1. In this case, the base station 100 may change the previous link L2 to the direct link L1 in response to the request of the terminal 200_1, or may set the direct link L1 after the previous link L2 is canceled . On the other hand, the base station 100 may add the direct link L1 while maintaining the previous link L2, instead of directly changing the previous link L2 to the link L1.

The base station 100 notifies each terminal 200_1 and 200_2 of the completion of the direct communication connection request to each of the terminals 200_1 and 200_2 and transmits the completion information to the terminals 200_1 and 200_2 via the direct link L1 Data transmission / reception can be enabled.

2. If no link is established between the two terminals 200_1 and 200_6

If a link (or connection) is not established between the two terminals 200_1 and 200_6, the terminal 200_1 requests the base station 100 for a service connection with the counterpart terminal 200_6.

When the base station 100 that has requested the service connection determines that the direct link establishment between the two terminals 200_1 and 200_6 is difficult or does not receive the search result according to the search result (the received signal strength of the measured reference signal) The terminal 200_1 responds to the terminal 200_1 through the relay of the terminal 200 and requests the terminal 200_6 for the service connection. The terminal 200_1 responding from the base station 100 performs the service connection and the terminal 200_6 requesting the service connection from the base station 100 responds to the base station 100 for the service connection. When the corresponding service connection is successfully completed, the two terminals 200_1 and 200_6 transmit / receive data through the relay of the base station 100. [

On the other hand, when it is determined that the direct link establishment between the two terminals 200_1 and 200_6 is possible according to the search result (the reception intensity of the measured reference signal) In response to the terminal 200_1, requests the counterpart terminal 200_6 to perform data transmission / reception with the terminal 200_1 via a direct link. The terminal 200_1 that has received the response from the base station 100 waits until the counterpart terminal 200_6 completes the link setting directly. When the direct link establishment between the two terminals 200_1 and 200_6 is successfully completed, the two terminals 200_1 and 200_6 transmit / receive data through a direct link. Meanwhile, as described above, the base station 100 requests the terminal 200_1 to wait for a predetermined time for establishing a direct link with the terminal 200_6. When the direct link establishment is completed, the base station 100 transmits the fact to the terminal 200_1 So that the terminals 200_1 and 200_6 can perform data transmission / reception via the direct link.

Next, referring to FIG. 3B, when the service connection (or link L2) between the two terminals 200_1 and 200_2 through the relay of the base station 100 is required because data transmission / reception via the direct link L1 is difficult Will be described in detail. It is assumed that data is more difficult to be transmitted / received through the direct link L1 formed between the terminals 200_1 and 200_2 as the terminal 200_2 moves from the point P1 to the point P2. The link L2 between the two terminals 200_1 and 200_2 corresponds to the communication (or service) between the two terminals 200_1 and 200_2 performed through the relay of the base station 100. [

The base station 100 may cause the link L2 to be newly set or the direct link L1 to be changed to the link L2.

Meanwhile, in order to support both data transmission / reception through the direct link L1 and data transmission / reception through the relay of the base station 100 (i.e., data transmission / reception via the link L2) 200_2 may use a service (or link) identifier or indicator (hereinafter, referred to as 'service identifier or the like') indicating the service through the direct link L1 through the relay of the base station 100. The terminal 200_1 for transmitting the data transmits the data transmission to the terminal 100 (for example, 200_2) receiving the data through the direct link L1 by using the service identifier, It indicates whether the transmission is via relay. If the terminal (e.g., 200_2) can not receive data via the direct link L1, the base station 100 can receive data from the terminal (e.g., 200_1) and relay the data to the terminal (e.g., 200_2) have. On the other hand, when the terminal (eg, 200_1) transmits data using the pre-allocated direct link resource, the service can be identified through a resource used for data transmission without a service identifier. In this case, the data transmitted through the relay of the base station 100 may include the corresponding fact (service identifier, etc.).

Meanwhile, when requesting data transmission to the base station 100, the terminal (for example, 200_1) transmitting the data informs whether the corresponding data transmission is the transmission through the relay of the base station 100 or the transmission through the direct link L1 It is possible. In this case, the service identifier or the like may not be used as in the case where the terminal (for example, 200_1) transmits data using the pre-allocated direct link resource. Meanwhile, the terminals 200_1 and 200_2 can manage the service through the relay of the base station 100 and the identifier indicating the service through the direct link L1 when the direct link L1 is set, and can use them when data is transmitted.

On the other hand, when the identifier indicating the service through the relay of the base station 100 and the identifier indicating the service through the direct link L1 are not stored / managed (e.g., some service (relay through the base station 100) (A service through a direct link L1) is decided), the terminals 200_1 and 200_2 are connected to each other through a link change (L1-> L2, L2-> L1) Or a service through a direct link L1. The link change for the service is mainly requested by the base station 100. Specifically, the base station 100 may request a link change (e.g., L1-> L2) to the terminals 200_1 and 200_2, or request a link L2 setting after canceling the direct link L1. When the link change (or service change) is completed or the link (L2) is set after the cancellation of the direct link (L1), the base station 100 can make the terminals 200_1 and 200_2 continuously perform services through resource allocation have. The base station 100 may simultaneously maintain the direct link L1 between the terminals 200_1 and 200_2 and the link L2 through the relay of the base station 100. [

4 is a diagram illustrating a terminal 200_1 according to an embodiment of the present invention.

The terminal 200_1 includes a processor 210, a memory 220, and a radio frequency (RF) converter 230.

The processor 210 may be configured to implement the procedures and methods described in Figures 1 to 3B.

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.

Meanwhile, the terminal 200_1 may have a single antenna or multiple antennas.

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 method for direct communication between a first terminal communicating with a base station and a second terminal,
Determining a first point of time to transmit or receive a first signal to or from the base station;
Determining a second time to transmit a second signal for terminal search to the second terminal; And
Changing one of the first viewpoint and the second viewpoint when the first viewpoint and the second viewpoint overlap each other
/ RTI > The method according to claim 1,
The first signal
A feedback signal transmitted to the base station, and a data signal transmitted to the base station every first period,
Direct communication method. 3. The method of claim 2,
The changing step
Receiving first view change information from the base station; And
And changing the first viewpoint based on the first viewpoint change information
Direct communication method. 3. The method of claim 2,
The changing step
And changing the first time point to a predetermined time point
Direct communication method. 3. The method of claim 2,
The predetermined time
(K is a natural number) from the second time point to the K-th previous uplink time point from the second time point,
Direct communication method. 5. The method of claim 4,
Transmitting the first signal to the base station every first period after transmitting the first signal at the predetermined time
Further comprising the steps of: The method according to claim 1,
The first signal
A signal related to an operation based on time synchronization during a Hybrid Automatic Repeat Request (HARQ) operation
Direct communication method. The method according to claim 1,
The first signal
The signal associated with the persistent resource allocation operation
Direct communication method. The method according to claim 1,
The first signal
The signal associated with the operation of group resource allocation
Direct communication method. The method according to claim 1,
Receiving from the base station first information indicating whether or not direct communication is possible based on the strength of the second terminal receiving the second signal
Further comprising the steps of: 11. The method of claim 10,
Establishing a first link for direct communication with the second terminal if the first information indicates that direct communication with the second terminal is possible
Further comprising the steps of: 12. The method of claim 11,
The setting step
And transmitting to the base station a request message for changing the second link corresponding to the first communication to the first link when the first communication is being performed with the second terminal through the relay of the base station doing
Direct communication method. 13. The method of claim 12,
Wherein the request message includes a service connection identifier indicating the second link
Direct communication method. 12. The method of claim 11,
The setting step
Transmitting a request message for setting up the first link to the base station when a second link corresponding to a first communication that is a communication with the second terminal performed through the relay of the base station is not set Containing
Direct communication method. A method for direct communication between a first terminal communicating with a base station and a second terminal,
Determining a first point of time to transmit or receive a first signal to or from the base station;
Determining a second time point at which to receive a second signal for terminal search from the second terminal; And
Changing one of the first viewpoint and the second viewpoint when the first viewpoint overlaps with the second viewpoint; And
Reporting the reception strength of the second signal to the base station
/ RTI > 16. The method of claim 15,
The first signal
A feedback signal transmitted to the base station, and a data signal transmitted to the base station every first period,
Direct communication method. 17. The method of claim 16,
The changing step
Receiving first view change information from the base station; And
And changing the first viewpoint based on the first viewpoint change information
Direct communication method. 17. The method of claim 16,
The changing step
And changing the first time point to a predetermined time point,
The predetermined time
(K is a natural number) from the second time point to the K-th previous uplink time point from the second time point,
Direct communication method. 16. The method of claim 15,
The reporting step
A first reporting method of reporting the reception strength of the second signal each time the second signal is received, a second reporting method of reporting the reception strength of the second signal when the reception strength of the second signal is greater than a threshold value, And a third reporting method for reporting the average value of the reception intensity of the second signal received during the first period of time
Direct communication method. A radio frequency converter; And
And a processor coupled to the radio frequency translator and controlling direct communication with the first terminal and communication with the base station,
The processor comprising:
Determining a first time point at which a first signal, which is a communication signal with the base station, is transmitted to or received from the base station, and transmitting a second signal for searching the first terminal to a second terminal And changes at any one of the first viewpoint and the second viewpoint when the first viewpoint and the second viewpoint overlap each other
Terminal.

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