WO2015072782A1

WO2015072782A1 - Apparatus and method for performing a handover in communication system supporting device to device scheme

Info

Publication number: WO2015072782A1
Application number: PCT/KR2014/010970
Authority: WO
Inventors: Anil Agiwal; Young-Bin Chang
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2013-11-14
Filing date: 2014-11-14
Publication date: 2015-05-21
Also published as: KR102262994B1; KR20150056073A

Abstract

A method for performing a handover by a user equipment (UE) in a communication system supporting a device to device (D2D) scheme is provided. The method includes receiving a direct connection reconfiguration message from an enhanced node B (eNB), wherein the direct connection reconfiguration message includes information on each of direct connections of the UE, and wherein the information on each of the direct connection includes a UE identifier (ID) and connection parameters.

Description

APPARATUS AND METHOD FOR PERFORMING A HANDOVER IN COMMUNICATION SYSTEM SUPPORTING DEVICE TO DEVICE SCHEME

The present disclosure relates to an apparatus and method for performing a handover in a communication system supporting a device to device (D2D) scheme.

In a communication system supporting a D2D scheme, two devices, e.g., two user equipments (UEs) may discover each other, and direct communication may be established between the two devices.

An operating scenario for direct communication that two UEs are served by the same enhanced Node B (eNB) or the same base station in a conventional communication system supporting a D2D scheme will be described with reference to FIG. 1.

FIG. 1 schematically illustrates an operating scenario for direct communication that two UEs are served by the same eNB or the same base station in a conventional communication system supporting a D2D scheme.

Referring to FIG. 1, the communication system includes an eNB 111, a UE#1 113, and a UE#2 115. The UE#1 113 and the UE#2 115 are included in a UE pair.

The UE#1 113 and the UE#2 115 included in the UE pair communicate with the eNB 111 using a downlink (DL) frequency F1 and a uplink (UL) frequency F2. The UL frequency F2 is used for direct communication between UEs included in the UE pair, i.e., the UE#1 113 and the UE#2 115. Resources are controlled by the eNB 111 in the UL frequency F2.

An operating scenario for direct communication that two UEs are served by the same eNB or the same base station in a conventional communication system supporting a D2D scheme has been described with reference to FIG. 1, and mechanisms which enable UE-eNB communication and UE-UE communication in a service coverage of an eNB will be described below.

a) a distinct cell radio network temporary identifier (C-RNTI) for UE-eNB communication and UE-UE communication

Different C-RNTIs are allocated from an address space by an eNB for the UE-eNB communication and the UE-UE communication. A C-RNTI is allocated to a UE pair for the UE-UE communication. The C-RNTI is used for identifying a resource for the UE-eNB communication and a resource for the UE-UE communication. Information on the resource for the UE-eNB communication and information on the resource for the UE-UE communication are transmitted to the UEs included in the UE pair through a single control channel which uses the C-RNTI which is allocated to the UE pair.

b) a reserved C-RNTI for UE-UE communication of all UE pairs and a UE pair ID for each UE pair

A C-RNTI is reserved from a C-RNTI address space, and indicates information on resources for all UE-UE communication pairs in a service coverage of an eNB. A UE pair ID as a new ID is allocated to each UE pair by the eNB, and the UE pair ID identifies a related UE pair from other UE pair. That is, the UE pair ID is used for identifying a UE pair. Information on resources is transmitted to UEs included in a related UE pair through a single control channel which uses a reserved C-RNTI and a UE pair ID which are allocated to the related UE.

c) a unified C-RNTI for UE-eNB communication and UE-UE communication and C-RNTI exchange between UEs included in a UE pair

One C-RNTI is allocated to each UE regardless of a type of communication, i.e., communication between each UE and an eNB, communication between each UE and other UE, or both the communication between each UE and the eNB and the communication between each UE and the other UE. During direct connection establishment, C-RNTIs for UEs included in the UE pair are informed to the UEs each other. A C-RNTI for one of the UEs included in the UE pair is used for signaling resource allocation information for direct communication. In this way, it will be noted that time durations for direct communication are specifically reserved.

The described mechanisms provide schemes of identifying UE pair communication which is performed in a service coverage of an eNB from communication among the eNB and other UEs (the other UEs are not related to direct communication).

The schemes of identifying the UE pair communication which is performed in the service coverage of the eNB from the communication among the eNB and the other UEs identify the UE pair communication from communication among the eNB and UEs included in the UE pair. The schemes of identifying the UE pair communication which is performed in the service coverage of the eNB from the communication among the eNB and the other UEs identify arbitrary UE pair communication from other UE pair communication.

Recently, based on simulation results published in a paper ‘User association for device to device (D2D) direct communication’, R1-131990 which is published in 3GPP TSG RAN WG1 Meeting #73 Fukuoka, Japan, May 20-24, 2013, it is observed that direct links between UEs which belong to different cells is feasible. In fact, in certain scenarios, the direct links between the UEs which belong to the different cells are more dominant.

An example of relation between the number of D2D links and a threshold value of reference signal received power (RSRP) in a conventional communication system supporting a D2D scheme will be described with reference to FIG. 2.

FIG. 2 schematically illustrates an example of relation between the number of D2D links and a threshold value of RSRP in a conventional communication system supporting a D2D scheme.

Referring to FIG. 2, a graph in FIG. 2 is a simulation graph which is presented in a paper ‘User association for device to device (D2D) direct communication’, R1-131990, which is published in 3GPP TSG RAN WG1 Meeting #73 Fukuoka, Japan, May 20-24, 2013.

In a graph in FIG. 2 indicates relation between the number of D2D links and a RSRP threshold value assuming a 2GHz carrier frequency, 500m infrastructure service discovery (ISD), an inter-cell D2D link, and an intra-cell D2D link.

If the RSRP threshold value is too large, for example, if the RSRP threshold value is in a range from -80 dBm to -100 dBm, there are not enough D2D links formed, so relative many UEs do not find any pairing UE for D2D link association as described in FIG. 2.

If the RSRP threshold value is less than or equal to -110dBm, almost all of UEs are related to D2D link associations.

A proportion of inter-cell D2D links or intra-cell D2D links among all D2D links is illustrated in FIG. 2. An intra-cell D2D links denotes a D2D link between two UEs in the same cell, and an inter-cell D2D link links denotes a D2D link between two UEs in different cells.

As described in FIG. 2, for a relative high RSRP threshold value, the number of intra-cell D2D links is more than the number of inter-cell links. However, if the RSRP threshold is less than -110dBm, it will be understood that an inter-cell D2D link is dominant, and the dominance becomes stronger if the RSRP threshold value becomes lower.

An example of relation between the number of D2D links and a threshold value of RSRP in a conventional communication system supporting a D2D scheme has been described with reference to FIG. 2, and another example of relation between the number of D2D links and a threshold value of RSRP in a conventional communication system supporting a D2D scheme will be described with reference to FIG. 3.

FIG. 3 schematically illustrates another example of relation between the number of D2D links and a threshold value of RSRP in a conventional communication system supporting a D2D scheme.

Referring to FIG. 3, a graph in FIG. 3 is a simulation graph which is presented in a paper ‘User association for device to device (D2D) direct communication’, R1-131990, which is published in 3GPP TSG RAN WG1 Meeting #73 Fukuoka, Japan, May 20-24, 2013.

In a graph in FIG. 3 indicates relation between the number of D2D links and a RSRP threshold value assuming a 700MHz carrier frequency, 1732m ISD, an inter-cell D2D link, and an intra-cell D2D link.

If the RSRP threshold value is too large, for example, if the RSRP threshold value is in a range from -80 dBm to -100 dBm, there are not enough D2D links formed, so relative many UEs do not find any pairing UE for D2D link association as described in FIG. 3.

A proportion of inter-cell D2D links or intra-cell D2D links among all D2D links is illustrated in FIG. 3. An intra-cell D2D links denotes a D2D link between two UEs in the same cell, and an inter-cell D2D link links denotes a D2D link between two UEs in different cells.

As described in FIG. 3, for a relative high RSRP threshold value, the number of intra-cell D2D links is more than the number of inter-cell links. However, if the RSRP threshold is less than -110dBm, it will be understood that an inter-cell D2D link is dominant, and the dominance becomes stronger if the RSRP threshold value becomes lower.

Another example of relation between the number of D2D links and a threshold value of RSRP in a conventional communication system supporting a D2D scheme has been described with reference to FIG. 3, and an example of essential issues for resource allocation for inter-cell D2D communication in a conventional communication system supporting a D2D scheme will be described with reference to FIG. 4.

FIG. 4 schematically illustrates an example of essential issues for resource allocation for inter-cell D2D communication in a conventional communication system supporting a D2D scheme.

Referring to FIG. 4, the communication system includes an eNB#1 411, an eNB#2 413, a UE#1 415, a UE#2 417, a UE#3 419, a UE#4 421, a UE#5 423, a UE#6 425, a UE#7 427, a UE#8 429, and a UE#9 431.

The first issue for the resource allocation for the inter-cell D2D communication is for identifying resources (in control signaling) for communication between UEs included in a UE pair and resources for other UEs in a service coverage of the eNB#1 411 and a service coverage of the eNB#2 413.

An example of the first issue is for identifying resources for communication of a UE#1-UE#2 pair and resources for the UE#3 419 in the service coverage of the eNB#1 411, and for identifying resources for the UE#4 421 in the service coverage of the eNB#2 413.

The second issue for the resource allocation for the inter-cell D2D communication is for identifying resources (in control signaling) for communication of a UE pair and resources for UEs included in a UE pair for communication with the eNBs, i.e., the eNB#1 411 and the eNB#1 413.

An example of the second issue is for identifying resources for communication of the UE#1-UE#2 pair and resources for UE#1-eNB#1 (or UE#2-eNB#2) communication.

The third issue for the resource allocation for the inter-cell D2D communication is for identifying resources (in control signaling) for communication of an arbitrary UE pair and resources for communication of other UE pair (in the service coverage of the eNB#1 411, the service coverage of the eNB#2 413, or both of the service coverage of the eNB#1 411 and the service coverage of the eNB#2 413).

An example of the third issue is for identifying resources for communication of the UE#1-UE#2 pair and resources for communication of a UE#5-UE#6 pair in the service coverage of the eNB#1 411, for identifying resources for communication of a UE#7-UE#8 pair in the service coverage of the eNB#2 413, and for identifying resources for communication of a UE#9-UE#10 pair in both of the service coverage of the eNB#1 411 and the service coverage of the eNB#2 413.

An example of essential issues for resource allocation for inter-cell D2D communication in a conventional communication system supporting a D2D scheme has been described with reference to FIG. 4, and another example of essential issues for resource allocation for inter-cell D2D communication in a conventional communication system supporting a D2D scheme will be described with reference to FIG. 5.

FIG. 5 schematically illustrates another example of essential issues for resource allocation for inter-cell D2D communication in a conventional communication system supporting a D2D scheme.

Referring to FIG. 5, the first issue for resource allocation for inter-cell D2D communication is for coordinating a resource between eNBs for direct communication.

The second issue for the resource allocation for the inter-cell D2D communication is for signaling resource allocation information for UEs included in a UE pair for transmitting/receiving (TX/RX).

For example, it will be assumed that a resource for a UE#1-UE#2 pair is allocated in a UL sub-frame (SF)#n.

In this case, it becomes the second issue for the resource allocation for the inter-cell D2D communication how information on a resource which is allocated in the UL SF#n is signaled to both of a UE#1 and a UE#2.

The third issue for the resource allocation for the inter-cell D2D communication is for identifying a TX/RX role between the UEs included in the UE pair during direct communication.

The fourth issue for the resource allocation for the inter-cell D2D communication is for identifying a TX resource of the UE#1 and RX resources of the UE#2 from a RX resource of the UE#1 and TX resources of the UE#2.

For example, a resource for a UE#1-UE#2 pair is allocate a UL SF#n.

In this case, the UE#1 has to perform a TX operation through the resource which is allocated in the UL SF#n, and the UE#2 has to perform a RX operation through the resource which is allocated in the UL SF#n.

So, for the UL SF#n, the UE#1 has to exist in a TX mode, and the UE#2 has to exist in a RX mode.

For another example, the resource for the UE#1-UE#2 pair is allocated in a UL SF#n+2.

In this case, the UE#1 has to perform a TX operation through the resource which is allocated in the UL SF#n+2, and the UE#2 has to perform a RX operation through the resource which is allocated in the UL SF#n+2.

So, for the UL SF#n+2, the UE#2 has to exist in a TX mode, and the UE#1 has to exist in a RX mode.

As described above, a communication system supporting a D2D scheme supports inter-cell D2D communication and intra-cell D2D communication, so there is a need for exactly identifying a UE, a UE pair, UE-UE communication, and UE-eNB communication according to a situation in the inter-cell D2D communication and intra-cell D2D communication. However, in the communication system supporting the D2D scheme, there is no scheme of exactly identifying the UE, the UE pair, the UE-UE communication, and the UE-eNB communication according to the situation in the inter-cell D2D communication and intra-cell D2D communication.

Further, the communication system supporting the D2D scheme has to be implemented by considering various issues related to a resource allocation operation. However, in the communication system supporting the D2D scheme, there is no scheme of allocating the resource by considering the various issues.

During direct communication between a UE#1 and a UE#2 associated with different eNBs, the eNBs coordinate with each other to allocate resources for the direct communication. A logical connection is established between the eNBs at time of direct connection establishment. One or both UEs involved in a direct communication may be mobile in nature. As a result, during the direct communication between the UEs, the association of UEs with the eNB keeps changing. Some of scenarios which are possible are as follows:

1. A UE#A and a UE#B are associated with an eNB#1 before a handover. After the handover, the UE#A is associated with the eNB#1 and the UE#B is associated with eNB#2.

2. A UE#A and a UE#B are associated with an eNB#1 before a handover. After the handover, the UE#A is associated with an eNB#3 and the UE#B is associated with an eNB#2.

3. A UE#A and a UE#B are associated with an eNB#1 before a handover. After the handover, the UE#A and the UE#B are associated with an eNB#2.

4. A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with the eNB#1.

5. A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with an eNB#3.

6. A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with the eNB#1 and an eNB#3, respectively.

7. A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with an eNB#3 and an eNB#4, respectively.

As result of mobility when a UE moves from a serving eNB to a target eNB during direct communication, the following needs to be done:

a) The target eNB needs to establish a connection with the eNB(s) of UE(s) to which this UE is directly communicating

b) The serving eNB needs to release connection with eNB(s) of UE(s) to which this UE was directly communicating

c) The target eNB needs to release connection with serving eNB for the connection of its other UEs with this UE

d) UEs involved in direct communication needs to get new connection parameters

Further, in the communication system supporting the D2D scheme, there is no scheme related to a handover which takes care of steps a), b) and c) & d).

The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.

It is therefore an object of the present disclosure to provide an apparatus and method for performing a handover in a communication system supporting a D2D scheme, which eliminates the disadvantages of prior art.

Another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal related to a handover in a communication system supporting a D2D scheme.

A still another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal related to a handover by considering a communication type in a communication system supporting a D2D scheme.

A still another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal in a communication system supporting a D2D scheme.

A still another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal for a direct connection in a communication system supporting a D2D scheme.

A still another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal by considering a communication type in a communication system supporting a D2D scheme.

A still another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal related to direct connection establishment in a communication system supporting a D2D scheme.

A still another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal related to resource allocation in a communication system supporting a D2D scheme.

A still another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal related to a resource type of a resource in a communication system supporting a D2D scheme.

A still another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal related to a UE which will use an allocated resource in a communication system supporting a D2D scheme.

A still another object of the present disclosure is to provide an apparatus and method for transmitting/receiving a signal related to a communication type of communication which will use an allocated resource in a communication system supporting a D2D scheme.

In accordance with an aspect of the present disclosure, there is provided a method for performing a handover by a user equipment (UE) in a communication system supporting a device to device (D2D) scheme. The method includes receiving a direct connection reconfiguration message from an enhanced node B (eNB), wherein the direct connection reconfiguration message includes information on each of direct connections of the UE, and wherein the information on each of the direct connection includes a UE identifier (ID) and connection parameters.

In accordance with another aspect of the present disclosure, there is provided a method for supporting a handover by an enhanced node B (eNB) in a communication system supporting a device to device (D2D) scheme. The method includes determining that a user equipment (UE) needs to perform a handover to other eNB; and transmitting a direct connection handover request message to the other eNB, wherein the direct connection handover request message includes information on each of direct connections of the UE, and wherein the information on each of the direct connection includes a UE identifier (ID) and connection parameters.

In accordance with still another aspect of the present disclosure, there is provided a method for supporting a handover by an enhanced node B (eNB) in a communication system supporting a device to device (D2D) scheme. The method includes receiving a direct connection handover request message from other eNB, wherein the direct connection handover request message includes information on each of direct connections of a user equipment (UE), and wherein the information on each of the direct connection includes a UE identifier (ID) and connection parameters.

In accordance with a further another aspect of the present disclosure, there is provided a user equipment (UE) in a communication system supporting a device to device (D2D) scheme. The UE includes a receiver configured to receive a direct connection reconfiguration message from an enhanced node B (eNB), wherein the direct connection reconfiguration message includes information on each of direct connections of the UE, and wherein the information on each of the direct connection includes a UE identifier (ID) and connection parameters.

In accordance with a still further aspect of the present disclosure, there is provided an enhanced node B (eNB) in a communication system supporting a device to device (D2D) scheme. The eNB includes a controller configured to determine that a user equipment (UE) needs to perform a handover to other eNB; and a transmitter configured to transmit a direct connection handover request message to the other eNB, wherein the direct connection handover request message includes information on each of direct connections of the UE, and wherein the information on each of the direct connection includes a UE identifier (ID) and connection parameters.

In accordance with another aspect of the present disclosure, there is provided an enhanced node B (eNB) in a communication system supporting a device to device (D2D) scheme. The eNB includes a receiver configured to receive a direct connection handover request message from other eNB, wherein the direct connection handover request message includes information on each of direct connections of a user equipment (UE), and wherein the information on each of the direct connection includes a UE identifier (ID) and connection parameters.

a transmitter; a receiver; and a controller, wherein the transmitter, the receiver, and the controller perform a direct connection establishment process with a user equipment (UE) and at least one other UE, wherein the transmitter transmits a control channel signal including resource allocation information to the UE, and wherein the resource allocation information includes at least one of first information indicating a resource which is allocated to the UE, second information indicating a resource type of at least one resource which corresponds to the first information, and third information indicating information on a third party UE which will perform direct communication with the UE through the at least one resource among the at least one UE.

Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the disclosure.

Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms "include" and "comprise," as well as derivatives thereof, mean inclusion without limitation; the term "or," is inclusive, meaning and/or; the phrases "associated with" and "associated therewith, "as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term "controller" means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

As is apparent from the foregoing description, an embodiment of the present disclosure enables to perform a handover in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal related to a handover in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal related to a handover by considering a communication type in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal for a direct connection in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal by considering a communication type in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal related to direct connection establishment in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal related to resource allocation in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal related to a resource type of a resource in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal related to a UE which will use an allocated resource in a communication system supporting a D2D scheme.

An embodiment of the present disclosure enables to transmit/receive a signal related to a communication type of communication which will use an allocated resource in a communication system supporting a D2D scheme.

The above and other aspects, features and advantages of certain exemplary embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 schematically illustrates an operating scenario for direct communication that two UEs are served by the same eNB or the same base station in a conventional communication system supporting a D2D scheme;

FIG. 2 schematically illustrates an example of relation between the number of D2D links and a threshold value of RSRP in a conventional communication system supporting a D2D scheme;

FIG. 3 schematically illustrates another example of relation between the number of D2D links and a threshold value of RSRP in a conventional communication system supporting a D2D scheme;

FIG. 4 schematically illustrates an example of essential issues for resource allocation for inter-cell D2D communication in a conventional communication system supporting a D2D scheme;

FIG. 5 schematically illustrates another example of essential issues for resource allocation for inter-cell D2D communication in a conventional communication system supporting a D2D scheme;

FIG. 6 schematically illustrates an example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 7 schematically illustrates another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 8 schematically illustrates an example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 9 schematically illustrates another example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 10 schematically illustrates an example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 11 schematically illustrates another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 12 schematically illustrates still another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 13 schematically illustrates an example of a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 14 schematically illustrates another example of a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 15 schematically illustrates still another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 16 schematically illustrates still another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 17 schematically illustrates a handover process in a case that a UE hands over form an arbitrary eNB to other eNB during direct communication with other UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIGS. 18a and 18b schematically illustrate a handover process in a scenario#1 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIGS. 19a and 19b schematically illustrate a handover process in a scenario#2 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 20 schematically illustrates a handover process in a scenario#3 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 21 schematically illustrates a handover process in a scenario#4 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 22 schematically illustrates an inner structure of a UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure;

FIG. 23 schematically illustrates an inner structure of an eNB in a communication system supporting a D2D scheme according to an embodiment of the present disclosure; and

FIG. 24 schematically illustrates an inner structure of an MME in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces.

Although ordinal numbers such as “first,” ”second,” and so forth will be used to describe various components, those components are not limited herein. The terms are used only for distinguishing one component from another component. For example, a first component may be referred to as a second component and likewise, a second component may also be referred to as a first component, without departing from the teaching of the inventive concept. The term “and/or” used herein includes any and all combinations of one or more of the associated listed items.

The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "has," when used in this specification, specify the presence of a stated feature, number, step, operation, component, element, or combination thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, elements, or combinations thereof.

The terms used herein, including technical and scientific terms, have the same meanings as terms that are generally understood by those skilled in the art, as long as the terms are not differently defined. It should be understood that terms defined in a generally-used dictionary have meanings coinciding with those of terms in the related technology.

According to various embodiments of the present disclosure, an electronic device may include communication functionality. For example, an electronic device may be a smart phone, a tablet personal computer (PC), a mobile phone, a video phone, an e-book reader, a desktop PC, a laptop PC, a netbook PC, a personal digital assistant (PDA), a portable multimedia player (PMP), an mp3 player, a mobile medical device, a camera, a wearable device (e.g., a head- mounted device (HMD), electronic clothes, electronic braces, an electronic necklace, an electronic appcessory, an electronic tattoo, or a smart watch), and/or the like.

According to various embodiments of the present disclosure, an electronic device may be a smart home appliance with communication functionality. A smart home appliance may be, for example, a television, a digital video disk (DVD) player, an audio, a refrigerator, an air conditioner, a vacuum cleaner, an oven, a microwave oven, a washer, a dryer, an air purifier, a set-top box, a TV box (e.g., Samsung HomeSync^TM, Apple TV^TM, or Google TV^TM), a gaming console, an electronic dictionary, an electronic key, a camcorder, an electronic picture frame, and/or the like.

According to various embodiments of the present disclosure, an electronic device may be a medical device (e.g., magnetic resonance angiography (MRA) device, a magnetic resonance imaging (MRI) device, computed tomography (CT) device, an imaging device, or an ultrasonic device), a navigation device, a global positioning system (GPS) receiver, an event data recorder (EDR), a flight data recorder (FDR), an automotive infotainment device, a naval electronic device (e.g., naval navigation device, gyroscope, or compass), an avionic electronic device, a security device, an industrial or consumer robot, and/or the like.

According to various embodiments of the present disclosure, an electronic device may be furniture, part of a building/structure, an electronic board, electronic signature receiving device, a projector, various measuring devices (e.g., water, electricity, gas or electro-magnetic wave measuring devices), and/or the like that include communication functionality.

According to various embodiments of the present disclosure, an electronic device may be any combination of the foregoing devices. In addition, it will be apparent to one having ordinary skill in the art that an electronic device according to various embodiments of the present disclosure is not limited to the foregoing devices.

According to various embodiments of the present disclosure, for example, a user equipment (UE) may be an electronic device.

An embodiment of the present disclosure proposes an apparatus and method for performing a handover in a communication system supporting a device-to-device (D2D) scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal related to a handover in a communication system supporting a D2D scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal related to a handover by considering a communication type in a communication system supporting a D2D scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal in a communication system supporting a D2D scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal for a direct connection in a communication system supporting a D2D scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal by considering a communication type in a communication system supporting a D2D scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal related to direct connection establishment in a communication system supporting a D2D scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal related to resource allocation in a communication system supporting a D2D scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal related to a resource type of a resource in a communication system supporting a D2D scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal related to a UE which will use an allocated resource in a communication system supporting a D2D scheme.

An embodiment of the present disclosure proposes an apparatus and method for transmitting/receiving a signal related to a communication type of communication which will use an allocated resource in a communication system supporting a D2D scheme.

A method and apparatus proposed in an embodiment of the present disclosure may be applied to various communication systems such as an institute of electrical and electronics engineers (IEEE) 802.11ac communication system, an IEEE 802.16 communication system, a digital video broadcasting system such as a mobile broadcasting service such as a digital multimedia broadcasting (DMB) service, a digital video broadcasting-handheld (DVP-H) service, an advanced television systems committee-mobile/handheld (ATSC-M/H) service, and the like, and an internet protocol television (IPTV) service, a moving picture experts group (MPEG) media transport (MMT) system, an evolved packet system (EPS), a long term evolution (LTE) mobile communication system, an LTE-advanced (LTE-A) mobile communication system, a high speed downlink packet access (HSDPA) mobile communication system, a high speed uplink packet access (HSUPA) mobile communication system, a high rate packet data (HRPD) mobile communication system proposed in a 3rd generation project partnership 2 (3GPP2), a wideband code division multiple access (WCDMA) mobile communication system proposed in the 3GPP2, a code division multiple access (CDMA) mobile communication system proposed in the 3GPP2, an institute of electrical and electronics engineers (IEEE) mobile communication system, a mobile internet protocol (Mobile IP) system, and/or the like.

Firstly, a resource allocation scheme proposed in an embodiment of the present disclosure will be described below.

Enhanced node Bs (eNBs) which are associated with user equipments (UEs) included in a UE pair cooperate each other to determine resources for direct communication between the UEs included in the UE pair. Information on the determined resources is independently signaled to each UE. For example, for a UE pair including a UE#1 which belongs to an eNB#1 and a UE#2 which belongs to an eNB#2, the eNB#1 signals the information on the determined resources for direct communication between the UE#1 and the UE#2 to the UE#1, and the eNB#2 signals the information on the determined resources for the direct communication between the UE#1 and the UE#2 to the UE#2. The resources may be determined for each packet transmission in a direct link. For example, the resources may be determined by a semi static way, and the determined resources are available for a plurality of TX intervals. For example, the resources may be determined by a static way, and the determined resources are available for an interval of a connection between the UE#1 and the UE#2.

Signaling for resource allocation will be described below.

Information on resources for direct communication between UEs included in a UE pair is transmitted by an eNB in a downlink (DL) frequency.

In a control region in a DL frequency, information on resources for the direct communication as well as communication with the eNB is transmitted.

For the direct communication, information on resources is independently transmitted to the UEs included in the UE pair.

The information on the resources is transmitted to each UE included in the UE pair by an eNB for each UE.

An eNB which are associated with the UEs included in the UE pair transmits a control channel signal, e.g., a physical downlink control channel (PDCCH) signal through which resource allocation information is transmitted to the UEs included in the UE pair. In an embodiment of the present disclosure, the control channel through the resource allocation information is transmitted is the PDCCH, however, it will be understood by those of ordinary skill in the art that the control channel through the resource allocation information is transmitted may be other channel.

A UE identifier (ID) for a UE, e.g., a cell radio network temporary identifier (C-RNTI) is encoded in the control channel. In an embodiment of the present disclosure, the UE ID is the C-RNTI, however, it will be understood by those of ordinary skill in the art that the UE ID may be other ID. In an embodiment of the present disclosure, a cyclic redundancy check (CRC) for the control channel is masked with the UE ID.

For example, considering a UE pair, i.e., a UE#1-UE#2 pair which includes a UE#1 which belongs to an eNB#1 and a UE#2 which belongs to an eNB#2, and in which information on allocated resources needs to be signaled, the UE#1 uses the allocated resources for TX, and the UE#2 uses the allocated resources for RX. In order to transmit information on the allocated resources that the UE#1 performs a TX operation and the UE#2 performs a RX operation, the eNB#1 transmits an arbitrary PDCCH signal to the UE#1, and the eNB#2 transmits other PDCCH signal to the UE#2. The PDCCH signal which is transmitted by the eNB#1 is masked with a C-RNTI of the UE#1. The PDCCH signal which is transmitted by the eNB#2 is masked with a C-RNTI of the UE#2. Both of the PDCCH signal which is transmitted by the eNB#1 and the PDCCH signal which is transmitted by the eNB#2 may be transmitted in the same DL sub-frame, or different DL sub-frames.

For another example, considering a UE pair, i.e., a UE#1-UE#2 pair which includes a UE#1 and a UE#2 which belong to an eNB#1, and in which information on allocated resources needs to be signaled, the UE#1 uses the allocated resources for TX, and the UE#2 uses the allocated resources for RX. In order to transmit information on the allocated resources that the UE#1 performs a TX operation and the UE#2 performs a RX operation, the eNB#1 transmits an arbitrary PDCCH signal to the UE#1, and transmits other PDCCH signal to the UE#2. The first PDCCH signal which is transmitted by the eNB#1 is masked with a C-RNTI of the UE#1. The second PDCCH signal which is transmitted by the eNB#1 is masked with a C-RNTI of the UE#2. The PDCCH signals are transmitted by the eNB#1 may be transmitted in the same DL sub-frame, or different DL sub-frames.

A scheme of identifying communication related to allocated resources.

Each UE communicates with one or more UEs, and an eNB. If the UE receives and decodes a control channel signal (e.g., a PDCCH signal) which is masked with a C-RNTI of the UE, the UE needs to determine whether a related resource is for direct communication or for communicating with the eNB.

Schemes of determining whether a related resource is for direct communication or for communicating with an eNB, i.e., a scheme#1, a scheme#2, and a scheme#3 will be described below.

Firstly, the scheme#1 will be described below.

Information on resources for communication between a UE and an eNB and information on resources for communication between the UE and other UEs are transmitted different DL sub-frames. The UE knows information on sub-frames in which the information on the resources for the communication between the UE and the eNB. Further, the UE knows information on sub-frames in which the information on the resources for the communication between the UE and the other UEs.

For example, it is considered that a uplink (UL) frequency is used for direct communication. Information on resources in the UL frequency for the direct communication and information on resources in a UL frequency for communication with an eNB are signaled in other DL sub-frames. So, a UE may determine resources for communication of each type using a single C-RNTI of the UE.

Secondly, the scheme#2 will be described below.

A format of downlink control information which is transmitted in a control channel, e.g., a PDCCH in order to indicate resources for communication with an eNB is different from a format of downlink control information which is transmitted in the control channel in order to indicate resources for direct communication. A size of the format of the downlink control information which is transmitted in the control channel in order to indicate the resources for the direct communication is different from sizes of conventional downlink control information formats. Upon receiving and decoding a control channel signal, the UE may know whether the downlink control information is for indicating the resources for the direct communication.

Thirdly, the scheme#3 will be described below.

For communication with an eNB and communication with other UEs, different C-RNTIs may be allocated to a UE. The eNB and the UE will use a C-RNTI which is allocated for direct communication for a control channel, e.g., a PDCCH which transmits information on resources for the direct communication. So, the eNB will use a C-RNTI which is allocated for the direct communication for a control channel which transmits information on resources for the direct communication. The eNB will use a C-RNTI which is allocated for eNB communication in a control channel, e.g., a PDCCH which transmits information on resources for the eNB communication.

Schemes of determining whether a related resource is for direct communication or for communicating with an eNB, i.e., a scheme#1, a scheme#2, and a scheme#3 has been described above, and a scheme of identifying a resource for TX and a resource for RX in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described below.

If a UE transmits information on a resource which is allocated for direct communication, the UE needs to determine whether the resource which is allocated for the direct communication is for TX or RX. A scheme of determining whether a resource which is allocated for direct communication is for TX or RX according to an embodiment of the present disclosure will be described below.

Firstly, an eNB includes a transmitting_receiving_indicator (Tx_Rx_indicator) of one bit into a control channel signal which transmits resource allocation information. The Tx_Rx_indicator is an indicator indicating a related resource is for a TX resource or a RX resource.

(1) If a Tx_Rx_indicator is set to 1 (Tx_Rx_indicator = 1), it is indicated that a related resource is a TX resource.

(2) If a Tx_Rx_indicator is set to 0 (Tx_Rx_indicator = 0), it is indicated that a related resource is a RX resource.

In an embodiment of the present disclosure, the Tx_Rx_indicator is implemented with one bit, however, it will be understood by those of ordinary skill in the art that the Tx_Rx_indicator may be implemented with a plurality of bits.

If a UE receives a control channel signal which transmits resource allocation information using an ID of the UE, e.g., a C-RNTI, and a Tx_Rx_indicator is set to 0 in the received control channel signal, the UE may know that resources which correspond to the resource allocation information are RX resources, so the UE performs a RX operation in the resources which correspond to the resource allocation information.

If the Tx_Rx_indicator is set to 1 in the received control channel signal, the UE may know that resources which correspond to the resource allocation information are TX resources, so the UE performs a TX operation in the resources which correspond to the resource allocation information.

The Tx_Rx_indicator may be included in the control channel which transmits the resource allocation information as an information field, or a CRC mask which is used for generating a cyclic redundancy check (CRC) for a control channel.

A scheme of determining whether a resource which is allocated for direct communication is for TX or RX in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been be described above, and schemes of identifying a transmitter and a receiver if a TX resource and a RX resource are allocated to a UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described below.

Firstly, a first scheme of identifying a transmitter and a receiver if a TX resource and a RX resource are allocated to a UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described below.

(1) a scheme of identifying a transmitter if a RX resource is allocated to a UE

Each UE may be connected to a plurality of UEs. If TX resources are allocated to the UE, the UE needs to determine that the UE has to perform a TX operation with which UE using the allocated TX resources. In an embodiment of the present disclosure, a scheme of determining that the UE has to perform a TX operation with which UE using TX resources which are allocated to the UE will be described below.

Firstly, a receiving index (Rx_idx) is allocated to each UE at time of direct connection establishment.

The Rx_idx is an ID for identifying a plurality of UEs from which a related UE receives data.

For example, it will be assumed that a UE#1 is connected to a UE#2 and a UE#3. The UE#1 receives data from the UE#2 and the UE#3.

For a connection between the UE#1 and the UE#2, a Rx_idx of 0 (Rx_idx = 0) is allocated to the UE#1.

For a connection between the UE#1 and the UE#3, a Rx_idx of 1 (Rx_idx = 1) is allocated to the UE#1.

If an arbitrary UE receives a control channel signal using a C-RNTI of the UE, and a Tx_Rx_indicator is set to 0, the UE will perform a RX operation in resources which correspond to resource allocation information included in the control channel signal.

The Rx_idx may be included in the control channel, and is used for identifying a transmitter in the control channel.

The Rx_idx may be included in the control channel as an information field, or a CRC mask.

The Rx_idx is unique for a plurality of connections among other UEs and the UE. That is, the Rx_idx is independently maintained for each UE.

(2) a scheme of identifying a receiver if a TX resource is allocated to a UE

Each UE may be connected to a plurality of UEs. If RX resources are allocated to the UE, the UE needs to determine that the UE has to perform a RX operation with which UE using the allocated RX resources. In an embodiment of the present disclosure, a scheme of determining that the UE has to perform a RX operation with which UE using RX resources which are allocated to the UE will be described below.

Firstly, a transmitting index (Tx_idx) is allocated to each UE at time of direct connection establishment.

The Tx_idx is an ID for identifying a plurality of UEs to which a related UE transmits data.

For example, it will be assumed that a UE#1 is connected to a UE#2 and a UE#3, and the UE#1 transmits data to the UE#2 and the UE#3.

For a connection between the UE#1 and the UE#2, a Tx_idx of 0 (Tx_idx = 0) is allocated to the UE#1.

For a connection between the UE#1 and the UE#3, a Tx_idx of 1 (Tx_idx = 1) is allocated to the UE#1.

If an arbitrary UE receives a control channel signal using a UE ID of the UE, and a Tx_Rx_indicator is set to 1, the UE will perform a TX operation in resources which correspond to resource allocation information included in the control channel signal.

The control channel signal is used for identifying a UE to which the UE has to transmit data.

The Tx_idx may be included in the control channel as an information field, or a CRC mask.

The Tx_idx is unique for a plurality of connections among other UEs and the UE. That is, the Tx_idx is independently maintained for each UE.

A process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIGS. 6 and 7.

An example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 6.

FIG. 6 schematically illustrates an example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 6, the communication system includes a UE#A 611, an eNB#1 613, an eNB#2 615, and a UE#B 617.

The UE#A 611 is associated with the eNB#1 613, the UE#B 617 is associated with the eNB#2 615, and a direct connection is established between the UE#A 611 and the UE#B 617. In a process of establishing the direct connection, the eNB#1 613 allocates a Tx_Idx of p (Tx_Idx = p) and a Rx_Idx of r (Rx_Idx = r) to the UE#A 611 for a connection with the UE#B 617. During the direct connection establishment process, the eNB#2 615 allocates a Tx_Idx of q (Tx_Idx = q) and a Rx_Idx of s (Rx_Idx = s) to the UE#B 617 for a connection with the UE#A 611 at operation 619. The Tx_Idx and the Rx_Idx have been described above, and a description thereof will be omitted herein.

The eNB#1 613 and the eNB#2 615 coordinate each other to determine resources for direct communication between the UE#A 611 and the UE#B 617 at operation 621. For example, the eNB#1 613 and the eNB#2 615 determine to use resources which are indicated by X, and the UE#A 611 performs a TX operation for the UE#B 617 in the resources which are indicated by the X.

The eNB#1 613 transmits a PDCCH#1 signal to the UE#A 611, and a CRC for the PDCCH#1 is masked using a C-RNTI of the UE#A 611 at operation 623. A Tx_Rx_indicator is set to 1, and a Tx_Idx is set to p in the PDCCH#1. The PDCCH#1 signal includes resource allocation information for resources X for direct communication.

The UE#A 611 receives the PDCCH#1 signal, and may decode the PDCCH#1 signal using the C-RNTI of the UE#A 611. The UE#A 611 determines to use resources which correspond to the resource allocation information included in the PDCCH#1 signal for transmitting from the UE#A 611 to the UE#B 617 based on the Tx_Rx_indicator and the Tx_Idx at operation 625. That is, the Tx_Rx_indicator of 1 indicates that related resources are TX resources. If the Tx_Idx of p is allocated to the UE#A 611 for a connection with the UE#B 617, the UE#A 611 determines related resources as TX resources for transmitting to the UE#B 617. The UE#A 611 performs a TX operation using the determined TX resources at operation 627.

The eNB#2 615 transmits a PDCCH#2 signal to the UE#B 617, and a CRC for the PDCCH#2 is masked using the C-RNTI of the UE#B 617 at operation 629. The Tx_Rx_indicator is set to 0, and the Rx_Idx is set to q in the PDCCH#2 signal. The PDCCH#2 signal includes the information on the resources X for direct communication. The UE#B 617 receives the PDCCH#2 signal, and may decode the PDCCH#2 signal using the C-RNTI of the UE#B 617. The UE#B 617 determines to use resources which correspond to the resource allocation information included in the PDCCH#2 signal for receiving from the UE#A 611 based on the Tx_Rx_indicator and the Rx_Idx at operation 631.

The Tx_Rx_indicator of 0 indicates that related resources are for RX. If the Rx_Idx of q is allocated to the UE#B 617 for a connection with the UE#A 611, the UE#B 617 determines related resources as RX resources. The UE#B 617 performs a RX operation using the determined RX resources at operation 633.

That is, the same resources are indicated by the eNB#1 613 using the PDCCH#1, and by the eNB#2 615 using the PDCCH#2, the UE#A 611 transmits a packet to the UE#B 617 at operation 635.

Although FIG. 6 illustrates an example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 6. For example, although shown as a series of operations, various operations in FIG. 6 could overlap, occur in parallel, occur in a different order, or occur multiple times.

An example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 6, and another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 7.

FIG. 7 schematically illustrates another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 7, the communication system includes a UE#A 711, an eNB#1 713, an eNB#2 715, and a UE#B 717.

The UE#A 711 is associated with the eNB#1 713, the UE#B 717 is associated with the eNB#2 715, and a direct connection is established between the UE#A 711 and the UE#B 717. In a process of establishing the direct connection, the eNB#1 713 allocates a Tx_Idx of p (Tx_Idx = p) and a Rx_Idx of r (Rx_Idx = r) to the UE#A 711 for a connection with the UE#B 717. During the direct connection establishment process, the eNB#2 715 allocates a Tx_Idx of q (Tx_Idx = q) and a Rx_Idx of s (Rx_Idx = s) to the UE#B 717 for a connection with the UE#A 711 at operation 719. The Tx_Idx and the Rx_Idx have been described above, and a description thereof will be omitted herein.

The eNB#1 713 and the eNB#2 715 coordinate each other to determine resources for direct communication between the UE#A 711 and the UE#B 717 at operation 721. For example, the eNB#1 713 and the eNB#2 715 determine to use resources which are indicated by Y, and the UE#A 711 performs a TX operation for the UE#B 717 in the resources which are indicated by the Y.

The eNB#2 715 transmits a PDCCH#3 signal to the UE#B 717, and a CRC for the PDCCH#3 is masked using a C-RNTI of the UE#B 717 at operation 729. A Tx_Rx_indicator is set to 1, and a Tx_Idx is set to s in the PDCCH#3. The PDCCH#3 signal includes resource allocation information for the resources Y for direct communication.

The UE#B 717 receives the PDCCH#3 signal, and may decode the PDCCH#3 signal using the C-RNTI of the UE#B 717. The UE#B 717 determines to use resources which correspond to the resource allocation information included in the PDCCH#3 signal for TX from the UE#B 717 to UE#A 711 based on the Tx_Rx_indicator and the Tx_Idx at operation 731.

The Tx_Rx_indicator of 1 indicates to the UE#B 717 that related resources are TX resources. If the Tx_Idx of s is allocated to the UE#B 717 for a connection with the UE#A 711, the UE#B 717 determines related resources as TX resources for TX to the UE#A 711. The UE#B 717 performs a TX operation using the determined TX resources at operation 733.

The eNB#1 713 transmits a PDCCH#4 signal, and a CRC of the PDCCH#4 is masked using the C-RNTI of the UE#A 711 at operation 723. The Tx_Rx_indicator is set to 0, and the Rx_Idx is set to r in the PDCCH#4 signal. The PDCCH#4 signal includes the information on the resources Y for direct communication. The UE#A 711 receives the PDCCH#4 signal, and may decode the PDCCH#4 signal using the C-RNTI of the UE#A 711. The UE#A 711 determines to use resources which corresponds to the resource allocation information included in the PDCCH#4 signal for RX from the UE#B 717 using the Tx_Rx_indicator and the Rx_Idx at operation 725.

The Tx_Rx_indicator of 0 indicates that related resources are for RX. If the Rx_Idx of s is allocated to the UE#A 711 for a connection with the UE#B 717, the UE#A 711 determines related resources as RX resources for RX from the UE#B 717. The UE#A 711 performs a RX operation using the determined RX resources at operation 727.

That is, the same resources are indicated by the eNB#1 713 using the PDCCH#3, and by the eNB#2 715 using the PDCCH#4, and the UE#B 717 transmits a packet to the UE#A 711 at operation 735.

Although FIG. 7 illustrates another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 7. For example, although shown as a series of operations, various operations in FIG. 7 could overlap, occur in parallel, occur in a different order, or occur multiple times.

Another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 7, and a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIGS. 8 and 9.

An example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 8.

FIG. 8 schematically illustrates an example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 8, the communication system includes a UE#A 811, a UE#B 813, and an eNB 815.

The UE#A 811 and the UE#B 813 are associated with the same eNB, i.e., the eNB 815, and a direct connection is established between the UE#A 811 and the UE#B 813. In a process of establishing the direct connection, the eNB 815 allocates a Tx_Idx of p (Tx_Idx = p) and a Rx_Idx of r (Rx_Idx = r) to the UE#A 811 for a connection with the UE#B 813. During the direct connection establishment process, the eNB 815 allocates a Tx_Idx of q (Tx_Idx = q) and a Rx_Idx of s (Rx_Idx = s) to the UE#B 813 for a connection with the UE#A 811. The Tx_Idx and the Rx_Idx have been described above, and a description thereof will be omitted herein.

The eNB 815 determines resources for direct communication between the UE#A 811 and the UE#B 813. For example, the eNB 815 determines to use resources which are indicated by X. The UE#A 811 performs a TX operation to the UE#B 813 in the resources which are indicated by the X. The eNB 815 transmits a PDCCH#1 signal to the UE#A 811, and a CRC for the PDCCH#1 is masked using a C-RNTI of the UE#A 811 at operation 819. A Tx_Rx_indicator is set to 1, and a Tx_Idx is set to p in the PDCCH#1 signal. The PDCCH#1 signal includes resource allocation information for the resources X for the direct communication.

The UE#A 811 receives the PDCCH#1 signal, and may decode the PDCCH#1 signal using the C-RNTI of the UE#A 811. The UE#A 811 determines to use resources which correspond to the resource allocation information included in the PDCCH#1 signal for TX to the UE#B 813 using the Tx_Rx_indicator and the Tx_Idx at operation 821.

The Tx_Rx_indicator of 0 indicates to the UE#A 811 that related resources are RX resources. If the Tx_Idx of p is allocated to the UE#A 811 for a connection with the UE#B 813, the UE#A 811 determines related resources as TX resources for TX to the UE#B 813. The UE#A 811 performs a TX operation using the determined TX resources at operation 823.

The eNB 815 transmits a PDCCH#2 signal to the UE#B 813, and a CRC of the PDCCH#2 is masked using the C-RNTI of the UE#B 813 at operation 825. The Tx_Rx_indicator is set to 0, and the Rx_Idx is set to q in the PDCCH#2 signal. The PDCCH#2 signal includes the information on the resources X for direct communication. The UE#B 813 receives the PDCCH#2 signal, and may decode the PDCCH#2 signal using the C-RNTI of the UE#B 813. The UE#B 813 determines to use resources which correspond to the resource allocation information included in the PDCCH#2 signal for RX from the UE#A 811 using the Tx_Rx_indicator and the Rx_Idx at operation 827.

The Tx_Rx_indicator of 0 indicates that related resources are for RX. If the Rx_Idx of q is allocated to the UE#B 813, the UE#B 813 determines related resources as the RX resources. The UE#B 813 performs a RX operation using the determined RX resources at operation 829.

That is, the same resources are indicated by the eNB 815 in the PDCCH#1 and the PDCCH#2, so the UE#A 811 transmits a packet to the UE#B 813 at operation 831.

Although FIG. 8 illustrates an example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 8. For example, although shown as a series of operations, various operations in FIG. 8 could overlap, occur in parallel, occur in a different order, or occur multiple times.

An example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been be described with reference to FIG. 8, and another example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 9.

FIG. 9 schematically illustrates another example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 9, the communication system includes a UE#A 911, a UE#B 913, and an eNB 915.

The UE#A 911 and the UE#B 913 are associated with the same eNB, i.e., the eNB 915, and a direct connection is established between the UE#A 911 and the UE#B 913. In a process of establishing the direct connection, the eNB 915 allocates a Tx_Idx of p (Tx_Idx = p) and a Rx_Idx of r (Rx_Idx = r) to the UE#A 911 for a connection with the UE#B 913. During the direct connection establishment process, the eNB 915 allocates a Tx_Idx of q (Tx_Idx = q) and a Rx_Idx of s (Rx_Idx = s) to the UE#B 913 for a connection with the UE#A 911. The Tx_Idx and the Rx_Idx have been described above, and a description thereof will be omitted herein.

The eNB 915 determines resources for direct communication between the UE#A 911 and the UE#B 913. For example, the eNB 915 determines to use resources which are indicated by Y, and the UE#B 913 performs a TX operation to the UE#A 911 in the resources Y.

The eNB 915 transmits a PDCCH#3 signal to the UE#B 913, and a CRC for the PDCCH#3 is masked using a C-RNTI of the UE#B 913 at operation 919. A Tx_Rx_indicator is set to 1, and a Tx_Idx is set to s in the PDCCH#3 signal. The PDCCH#3 signal includes resource allocation information for the resources Y for the direct communication. The UE#B 913 receives the PDCCH#3 signal, and may decode the PDCCH#3 signal using the C-RNTI of the UE#B 913. The UE#B 913 determines to use resources which are indicated in the PDCCH#3 signal for TX to the UE#A 911 using the Tx_Rx_indicator and the Tx_Idx at operation 921.

The Tx_Rx_indicator of 1 indicates to the UE#B 913 that related resources are TX resources. If the Tx_Idx of s is allocated to the UE#B 913 for a connection with the UE#A 911, the UE#B 913 determines related resources as TX resources for TX to the UE#A 911. The UE#B 913 performs a TX operation using the determined TX resources at operation 923.

The eNB 915 transmits a PDCCH#4 signal to the UE#A 911, and a CRC of the PDCCH#4 is masked using the C-RNTI of the UE#A 911 at operation 925. The Tx_Rx_indicator is set to 0, and the Rx_Idx is set to r in the PDCCH#4 signal. The PDCCH#4 signal includes the information on the resources Y for the direct communication. The UE#A 911 receives the PDCCH#4 signal, and may decode the PDCCH#4 signal using the C-RNTI of the UE#A 911. The UE#A 911 determines to use resources which are indicated in the PDCCH#4 signal for RX from the UE#B 913 using the Tx_Rx_indicator and the Rx_Idx at operation 927.

The Tx_Rx_indicator of 0 indicates that related resources are RX resources. If the Rx_Idx of s is allocated to the UE#A 911, the UE#A 911 determines related resources as RX resources for RX from the UE#B 913. The UE#A 911 performs a RX operation using the determined RX resources at operation 929.

That is, the same resources are indicated by the eNB 915 in the PDCCH#3 and the PDCCH#4, so the UE#B 913 transmits a packet to the UE#A 911 at operation 931.

Although FIG. 9 illustrates another example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 9. For example, although shown as a series of operations, various operations in FIG. 9 could overlap, occur in parallel, occur in a different order, or occur multiple times.

Another example of a process of transmitting resource allocation information to UEs included in a UE pair for intra-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 9, and a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIGS. 10 and 11. A process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in each of FIGS. 10 and 11 is just an example. That is, it will be understood by those of ordinary skill in the art that a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx may be implemented with various schemes other than schemes in FIGS. 10 and 11.

FIG. 10 schematically illustrates an example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 10, the communication system includes a UE#A 1011, an eNB#1 1013, a mobility management entity (MME) 1015, and an eNB#2 1017.

It will be noted that a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in FIG. 10 is a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a case that the UE#A 1011 triggers direct connection establishment after discovering a UE#B (not shown in FIG. 10).

The UE#A 1011 transmits a direct communication request message to an eNB to which the UE#A 1011 attaches, i.e., the eNB#1 1013 at operation 1019. The UE#A 1011 includes a UE ID of the UE#B into the direct communication request message. In an embodiment of the present disclosure, the UE ID may be an ID which is allocated to a UE for proximity-based service (ProSe) communication, e.g., a ProSe UE ID. The UE ID may be an idle mode ID which is allocated to the UE, e.g., a system architecture evolution (SAE) temporary mobile subscriber identity (TMSI) (S-TMSI). In other embodiment of the present disclosure, the UE ID may be a globally unique temporary identifier (GUTI) which is allocated to the UE. In an embodiment of the present disclosure, the UE#A 1011 discovers the UE ID of the UE#B during discovering the UE#B. The UE#A 1011 may include a UE ID of the UE#A 1011 into the direct communication request message. After receiving the direct communication request message from the UE#A 1011, the eNB#1 1013 authenticates the direct communication request message, and transmits a direct communication request message including the UE ID of the UE#B to the MME 1015 at operation 1021.

After receiving from the direct communication request message from the eNB#1 1013, the MME 1015 determines a cell/eNB of the UE#B at operation 1023. When the UE#A 1011 and the UE#B are in an idle mode, the MME 1015 will page the UE#B if the UE#B and the UE#A 1011 are under the same MME, so the UE#B transits from the idle mode into a connected mode, and the UE#B is associated with a cell or an eNB.

When the UE#A 1011 and the UE#B are in the connected mode, if the UE#A 1011 and the UE#B are under the same MME, the MME 1015 knows the cell of the UE#B. If the UE#A 1011 and the UE#B are not under the same MME, the MME 1015 contacts with an MME of the UE#B in order to determine the cell of the UE#B. Upon determining the cell of the UE#B, the MME 1015 transmits a direct communication response message as a response message to the direct communication request message to the eNB#1 1013 at operation 1025.

Information on the cell/eNB information is included in the direct communication response message. The eNB#1 1013 allocates a Tx-Idx and a Rx-Idx to the UE#A 1011. The eNB#1 1013 transmits a direct communication response message including the Tx-Idx and the Rx-Idx which are allocated to the UE#A 1011 to the UE#A 1011 at operation 1027. The eNB#1 1013 includes a C-RNTI of the UE#A 1011 into the direct communication response message. In an embodiment of the present disclosure, the C-RNTI of the UE#A 1011 may be included in the direct communication response message if the C-RNTI is newly allocated to the UE#A 1011. If the C-RNTI is not allocated to the UE#A 1011, the eNB#1 1013 allocates the C-RNTI to the UE#A 1011. The eNB#1 1013 may include other parameters which are associated with direct communication into the direct communication response message.

After receiving the direct communication response message from the eNB#1 1013, the UE#A 1011 transmits a direct communication complete message as a response message to the direct communication response message to the eNB#1 1013 at operation 1029. The UE#A 1011 starts to use the allocated C-RNTI, Tx-Idx, and Rx-Idx. The C-RNTI, Tx-Idx, and Rx-Idx have been described above, and a description thereof will be omitted herein.

After receiving the direct communication complete message from each of the UE#A 1011 and the UE#B, the eNB#1 1013 and the eNB#2 1017 exchange signaling in an eNB-eNB interface in order to coordinate resource for UE#A-UE#B communication at operation 1031.

Although FIG. 10 illustrates an example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 10. For example, although shown as a series of operations, various operations in FIG. 10 could overlap, occur in parallel, occur in a different order, or occur multiple times.

An example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 10, and another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 11.

FIG. 11 schematically illustrates another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 11, the communication system includes a UE#B 1111, an eNB#1 1113, an MME 1115, and an eNB#2 1117.

It will be noted that a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in FIG. 11 is a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a case that the MME 1115 triggers an eNB which is associated with the UE#B 1111 for establishing a direct connection with a UE#A (not shown in FIG. 11).

If the MME 1115 receives a direct communication request message from an eNB or other MME, the MME 1115 is triggered. For example, when the UE#A and the UE#B 1111 are under the same MME, the MME 1115 triggers the eNB#1 1113 upon receiving a direct communication request message from the eNB#1 1113. For example, when the UE#A and the UE#B 1111 are not under the same MME, the MME 1115 is triggered upon receiving a direct communication request message from an MME of the UE#A. The MME 1115 transmits a direct communication request message to the eNB#2 1117 at operation 1119.

The MME 1115 includes UE IDs of the UE#A and the UE#B 1111 into the direct communication request message. The MME 1115 includes cell/eNB information of the UE#A into the direct communication request message. Upon receiving the direct communication request message, the eNB#2 1117 allocates a Tx-Idx and a Rx-Idx to the UE#B 1111. The eNB#2 1117 includes the Tx-Idx and the Rx-Idx into a direct communication response message as a response message to the direct communication request message to transmit the direct communication response message to the UE#B 1111 at operation 1121. The eNB#2 1117 includes a C-RNTI of the UE#B 1111 into the direct communication response message. In an embodiment of the present disclosure, the C-RNTI of the UE#B 1111 may be included in the direct communication response message if the C-RNTI is newly allocated to the UE#B 1111. If the C-RNTI is not allocated to the UE#B 1111, the eNB#2 1117 allocates the C-RNTI to the UE#B 1111. The eNB#2 1117 may include other parameters which are associated with direct communication into the direct communication response message.

After receiving the direct communication response message, the UE#B 1111 transmits a direct communication complete message as a response message to the direct communication response message to the eNB#2 1117 at operation 1123. The UE#B 1111 starts to use the allocated C-RNTI, Tx-Idx, and Rx-Idx. The C-RNTI, Tx-Idx, and Rx-Idx have been described above, and a description thereof will be omitted herein.

After receiving the direct communication complete message from the UE#B 1111, the eNB#2 1117 transmits a direct communication response message to the MME 1115 at operation 1125. After receiving the direct communication complete message from each of the UE#A and the UE#B 1111, the eNB#1 1113 and the eNB#2 1117 exchange signaling in an eNB-eNB interface in order to coordinate resource for UE#A-UE#B communication at operation 1127.

In other embodiment of the present disclosure, the Tx-Idx and the Rx-Idx are maintained by a UE. The UE allocates a Tx-Idx and a Rx-Idx for a connection between other UE and the UE, and transmits the allocated Tx-Idx and Rx-Idx to an eNB during the a connection establishment process. The eNB stores the Tx-Idx and the Rx-Idx, and uses the Tx-Idx and the Rx-Idx for transmitting a PDCCH signal to the UE. The Tx-Idx and the Rx-Idx may be transmitted to the eNB by the UE in a direct communication request message to the direct communication complete message. Here, a characteristic of the Tx-Idx and the Rx-Idx is the same regardless of whether the Tx-Idx and the Rx-Idx are allocated by the eNB or the UE.

For example, if the eNB allocates the Tx-Idx and the Rx-Idx, the eNB has to maintain information on Tx-Idxes and Rx-Idxes which are already allocated to connections of the UE, and maintain information on Tx-Idxes and Rx-Idxes which are already allocated to all UEs.

For another example, if the UE allocates the Tx-Idx and the Rx-Idx, the UE has to maintain the information on the Tx-Idxes and the Rx-Idxes which are already allocated to the connections of the UE, so load of the eNB decreases.

Although FIG. 11 illustrates another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 11. For example, although shown as a series of operations, various operations in FIG. 11 could overlap, occur in parallel, occur in a different order, or occur multiple times.

Another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 11, and still another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 12. A process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in FIG. 12 is just an example. That is, it will be understood by those of ordinary skill in the art that a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx may be implemented with various schemes other than a scheme in FIG. 12.

FIG. 12 schematically illustrates still another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 12, the communication system includes a UE#A 1211, a UE#B 1213, an eNB#1 1215, and an eNB#2 1217.

The UE#A 1211 initiates a direct communication establishment process with the UE#B 1213. That is, the UE#A 1211 transmits a direct communication request message including a UE ID of the UE#A 1211 to UE#B 1213 at operation 1219. The UE ID may be an ID which is specific to D2D communication, or other UE ID. In an embodiment of the present disclosure, the UE ID may be an ID which is allocated to the UE#A 1211 for ProSe communication, e.g., a ProSe UE ID. The UE ID may be an idle mode ID which is allocated to the UE#A 1211, e.g., an S-TMSI. In other embodiment of the present disclosure, the UE ID may be a GUTI which is allocated to the UE#A 1211. After receiving the direct communication request message from the UE#A 1211, the UE#B 1213 transmits a direct communication response message including a UE ID of the UE#B 1213 to the UE#A 1211 if the UE#B 1213 accepts the received direct communication request message at operation 1221.

The UE#A 1211 and the UE#B 1213 transmit a direct communication request message to the eNB#1 1215 and the eNB#2 1217, respectively at

operations

1223 and 1225. The UE#A 1211 is associated with the eNB#1 1215, and the UE#B 1213 is associated with the eNB#2 1217. The UE#A 1211 includes a UE ID of the UE#A 1211 into the direct communication request message, and the UE#B 1213 includes a UE ID of the UE#B 1213 into the direct communication request message. It will be noted that an order of transmitting the direct communication request message to a related eNB between the UE#A 1211 and the UE#B 1213 is not limited.

After receiving the direct communication request message from the UE#A 1211, the eNB#1 1215 authenticates the direct communication request message, and allocates a Tx-Idx and a Rx-Idx to the UE#A 1211. The eNB#1 1215 includes the Tx-Idx and the Rx-Idx which are allocated to the UE#A 1211 in a direct communication response message as a response message to the direct communication request message to transmit the direct communication response message to the UE#A 1211 at operation 1227. The eNB#1 1215 includes a C-RNTI of the UE#A 1211 into the direct communication response message. In an embodiment of the present disclosure, the C-RNTI of the UE#A 1211 may be included in the direct communication response message if the C-RNTI is newly allocated to the UE#A 1211. If the C-RNTI is not allocated to the UE#A 1211, the eNB#1 1215 allocates the C-RNTI to the UE#A 1211. The eNB#1 1215 may include other parameters which are associated with direct communication into the direct communication response message.

After receiving the direct communication request message from the UE#B 1213, the eNB#2 1217 authenticates the direct communication request message, and allocates a Tx-Idx and a Rx-Idx to the UE#B 1213. The eNB#2 1217 includes the Tx-Idx and the Rx-Idx which are allocated to the UE#B 1213 in a direct communication response message as a response message to the direct communication request message to transmit the direct communication response message to the UE#B 1213 at operation 1229. The eNB#2 1217 includes a C-RNTI of the UE#B 1213 into the direct communication response message. In an embodiment of the present disclosure, the C-RNTI of the UE#B 1213 may be included in the direct communication response message if the C-RNTI is newly allocated to the UE#B 1213. If the C-RNTI is not allocated to the UE#B 1213, the eNB#2 1217 allocates the C-RNTI to the UE#B 1213.

After receiving the direct communication response message from the eNB#1 1215, the UE#A 1211 transmits a direct communication complete message to the eNB#1 1215 at operation 1231. After receiving the direct communication response message from the eNB#2 1217, the UE#B 1213 transmits a direct communication complete message to the eNB#2 1217 at operation 1233. The UE#A 1211 and the UE#B 1213 start to use the allocated C-RNTI, Tx-Idx, and Rx-Idx. The C-RNTI, Tx-Idx, and Rx-Idx have been described above, and a description thereof will be omitted herein.

In other embodiment of the present disclosure, the Tx-Idx and the Rx-Idx are maintained by a UE. The UE allocates a Tx-Idx and a Rx-Idx for a connection between other UE and the UE, and transmits the allocated Tx-Idx and Rx-Idx to an eNB during the direct connection establishment process. The eNB stores the Tx-Idx and the Rx-Idx, and uses the Tx-Idx and the Rx-Idx for transmitting a PDCCH signal to the UE. The Tx-Idx and the Rx-Idx may be transmitted to the eNB by the UE in a direct communication request message to the direct communication complete message. Here, a characteristic of the Tx-Idx and the Rx-Idx is the same regardless of whether the Tx-Idx and the Rx-Idx are allocated by the eNB or the UE.

Although FIG. 12 illustrates still another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 12. For example, although shown as a series of operations, various operations in FIG. 12 could overlap, occur in parallel, occur in a different order, or occur multiple times.

Still another example of a process of establishing an inter-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure according to an embodiment of the present disclosure has been described with reference to FIG. 12, and an example of a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 13. A process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in each of FIG.13 is just an example. That is, it will be understood by those of ordinary skill in the art that a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx may be implemented with various schemes other than a scheme in FIG. 13.

FIG. 13 schematically illustrates an example of a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 13, the communication system includes a UE#B 1311, a UE#A 1313, an eNB#1 1315, and an MME 1317.

It will be noted that a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in FIG. 13 is a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a case that the UE#A 1313 triggers a direct connection establishment process after discovering the UE#B 1311.

The UE#A 1313 transmits a direct communication request message to an eNB to which the UE#A 1313 attaches, i.e., the eNB#1 1315 at operation 1319. The UE#A 1313 includes a UE ID of the UE#B 1311 into the direct communication request message. In an embodiment of the present disclosure, the UE ID may be an ID which is allocated to UE#B 1311 for ProSe communication, e.g., a ProSe UE ID. In other embodiment of the present disclosure, the UE ID may be a GUTI which is allocated to the UE#B 1311. In still embodiment of the present disclosure, the UE#A 1313 discovers the UE ID of the UE#B 1311 during a discovery process for the UE#B 1311. The UE#A 1313 may include a UE ID of the UE#A 1313 into the direct communication request message. After receiving the direct communication request message from the UE#A 1313, the eNB#1 1315 authenticates the direct communication request message, and transmits a direct communication request message including the UE ID of the UE#B 1311 to the MME 1317 at operation 1321.

After receiving from the direct communication request message from the UE#B 1311, the MME 1317 determines a cell/eNB of the UE#B 1311 at operation 1323. When the UE#A 1313 and the UE#B 1311 are in an idle mode, the MME 1317 will page the UE#B 1311 if the UE#B 1311 and the UE#A 1311 are under the same MME, so the UE#1311 transits from the idle mode into a connected mode, and the UE#B 1311 is associated with a cell or an eNB.

When the UE#A 1313 and the UE#B 1311 are in the connected mode, if the UE#A 1313 and the UE#B 1311 is under the same MME, the MME 1317 knows a cell of the UE#B 1311. Upon determining the cell of the UE#B 1311, the MME 1317 transmits a direct communication response message as a response message to the direct communication request message to the eNB#1 1315 at operation 1325.

Information on the cell/eNB information is included in the direct communication response message. The eNB#1 1315 allocates a Tx-Idx and a Rx-Idx to the UE#A 1313. The eNB#1 1315 transmits a direct communication response message including the Tx-Idx and the Rx-Idx which are allocated to the UE#A 1313 to the UE#A 1313 at operation 1327. The eNB#1 1315 includes a C-RNTI of the UE#A 1313 into the direct communication response message. In an embodiment of the present disclosure, the C-RNTI of the UE#A 1313 may be included in the direct communication response message if the C-RNTI is newly allocated to the UE#A 1313. If the C-RNTI is not allocated to the UE#A 1313, the eNB#1 1315 allocates the C-RNTI to the UE#A 1313. The eNB#1 1315 may include other parameters which are associated with direct communication into the direct communication response message.

After receiving the direct communication response message from the eNB#1 1315, the UE#A 1313 transmits a direct communication complete message to the eNB#1 1315 at operation 1331. The UE#A 1313 starts to use the allocated C-RNTI, Tx-Idx, and Rx-Idx. The C-RNTI, Tx-Idx, and Rx-Idx have been described above, and a description thereof will be omitted herein.

After receiving the direct communication response message from the MME 1317, the eNB#1 1315 allocates a Tx-Idx and a Rx-Idx to the UE#B 1311 if cell/eNB information for the UE#B 1311 is identical to the cell/eNB information for the UE#A 1313. The eNB#1 1315 transmits a direct communication response message including the Tx-Idx and the Rx-Idx which are allocated to the UE#B 1311 to the UE#B 1311 at operation 1329. The eNB#1 1315 includes a C-RNTI of the UE#B 1311 into the direct communication response message.

In an embodiment of the present disclosure, the C-RNTI of the UE#B 1311 may be included in the direct communication response message if the C-RNTI is newly allocated to the UE#B 1311. If the C-RNTI is not allocated to the UE#B 1311, the eNB#1 1315 allocates the C-RNTI to the UE#B 1311. The eNB#1 1315 may include other parameters which are associated with direct communication into the direct communication response message.

After receiving the direct communication response message from the eNB#1 1315, the UE#B 1311 transmits a direct communication complete message to the eNB#1 1315 at operation 1333. The UE#B 1311 starts to use the allocated C-RNTI, Tx-Idx, and Rx-Idx. The C-RNTI, Tx-Idx, and Rx-Idx have been described above, and a description thereof will be omitted herein.

In other embodiment of the present disclosure, the Tx-Idx and the Rx-Idx are maintained by a UE. The UE allocates a Tx-Idx and a Rx-Idx for a connection between other UE and the UE, and transmits the allocated Tx-Idx and Rx-Idx to an eNB during a direct connection establishment process. The eNB stores the Tx-Idx and the Rx-Idx, and uses the Tx-Idx and the Rx-Idx for transmitting a PDCCH signal to the UE. The Tx-Idx and the Rx-Idx may be transmitted to the eNB by the UE in a direct communication request message to the direct communication complete message. Here, a characteristic of the Tx-Idx and the Rx-Idx is the same regardless of whether the Tx-Idx and the Rx-Idx are allocated by the eNB or the UE.

Although FIG. 13 illustrates an example of a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 13. For example, although shown as a series of operations, various operations in FIG. 13 could overlap, occur in parallel, occur in a different order, or occur multiple times.

An example of a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure according to an embodiment of the present disclosure has been described with reference to FIG. 13, and another example of a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 14. A process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in each of FIG.14 is just an example. That is, it will be understood by those of ordinary skill in the art that a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx may be implemented with various schemes other than a scheme in FIG. 14.

FIG. 14 schematically illustrates another example of a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 14, the communication system includes a UE#A 1411, a UE#B 1413, and an eNB 1415.

The UE#A 1411 initiates a direct communication establishment process with the UE#B 1413. That is, the UE#A 1411 transmits a direct communication request message including a UE ID of the UE#A 1411 to the UE#B 1413 at operation 1417. The UE ID may be an ID which is specific to D2D communication, or other UE ID. In an embodiment of the present disclosure, the UE ID may be an ID which is allocated to the UE#A 1411 for ProSe communication, e.g., a ProSe UE ID. In other embodiment of the present disclosure, the UE ID may be an idle mode ID which is allocated to the UE#A 1411, e.g., an S-TMSI. In still other embodiment of the present disclosure, the UE ID may be a GUTI which is allocated to the UE#A 1411. After receiving the direct communication request message from the UE#A 1411, the UE#B 1413 transmits a direct communication response message including the UE ID of the UE#B 1413 to the UE#A 1411 upon accepting the direct communication request message received from the UE#A 1411 at operation 1419.

The UE#A 1411 and the UE#B 1413 transmit a direct communication request message to the eNB 1415 at

operations

1421 and 1423. The UE#A 1411 and the UE#B 1413 are associated with the same eNB, i.e., the eNB 1415. The UE#A 1411 and the UE#B 1413 include a UE ID of the UE#A 1411 and a UE ID of the UE#B 1413 into the direct communication request message, respectively. It will be noted that an order of transmitting the direct communication request message to the eNB 1415 between the UE#A 1411 and the UE#B 1413 is not limited.

Upon receiving the direct communication request message from the UE#A 1411, the eNB#1 1415 authenticates the direct communication request message, and allocates a Tx-Idx and a Rx-Idx to the UE#A 1411. The eNB#1 1415 transmits a direct communication response message including the Tx-Idx and the Rx-Idx which are allocated to the UE#A 1411 to the UE#A 1411 at operation 1425. The eNB#1 1415 includes a C-RNTI of the UE#A 1411 into the direct communication response message. In an embodiment of the present disclosure, the C-RNTI of the UE#A 1411 may be included in the direct communication response message if the C-RNTI is newly allocated to the UE#A 1411. If the C-RNTI is not allocated to the UE#A 1411, the eNB#1 1415 allocates the C-RNTI to the UE#A 1411. The eNB#1 1415 may include other parameters which are associated with direct communication into the direct communication response message.

Upon receiving the direct communication request message from the UE#B 1413, the eNB#1 1415 authenticates the direct communication request message, and allocates a Tx-Idx and a Rx-Idx to the UE#B 1413. The eNB#1 1415 transmits a direct communication response message including the Tx-Idx and the Rx-Idx which are allocated to the UE#B 1413 to the UE#B 1413 at operation 1427. The eNB#1 1415 includes a C-RNTI of the UE#B 1413 into the direct communication response message. In an embodiment of the present disclosure, the C-RNTI of the UE#B 1413 may be included in the direct communication response message if the C-RNTI is newly allocated to the UE#B 1413. If the C-RNTI is not allocated to UE#B 1413, the eNB#1 1415 allocates the C-RNTI to the UE#B 1413.

After receiving the direct communication response message from the eNB#1 1415, each of the UE#A 1411 and the UE#B 1413 transmits a direct communication complete message to the eNB#1 1415 at

operations

1429 and 1431. Each of the UE#A 1411 and the UE#B 1413 starts to use the allocated C-RNTI, Tx-Idx, and Rx-Idx. The C-RNTI, Tx-Idx, and Rx-Idx have been described above, and a description thereof will be omitted herein.

Although FIG. 14 illustrates another example of a process of establishing an intra-cell direct connection and allocating a Tx-Idx/Rx-Idx in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 14. For example, although shown as a series of operations, various operations in FIG. 14 could overlap, occur in parallel, occur in a different order, or occur multiple times.

The first scheme of identifying a transmitter and a receiver in a case that a TX resource and a RX resource are allocated to a UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described above, and the second scheme of identifying a transmitter and a receiver in a case that a TX resource and a RX resource are allocated to a UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described below.

Firstly, a connection_index (connection_idx) is allocated to each UE at time of direct connection establishment. The connection_idx is unique for a plurality of connections among other UEs and a UE. That is, the connection_idx is independently maintained for each UE. The connection_idx of the UE identifies which UE among a plurality of UEs performs a RX operation or TX operation. For example, a UE#1 is connected to a UE#2 and a UE#3. A connection_idx of 0 (connection_idx = 0) is allocated to the UE#1 for a connection between the UE#1 and the UE#2. A connection_idx of 1 (connection_idx = 1) is allocated to the UE#1 for a connection between the UE#1 and the UE#3.

(1) a scheme of identifying a transmitter if a RX resource is allocated to a UE

Each UE may be connected to a plurality of UEs. If TX resources are allocated to a related UE, the UE needs to determine that the UE has to perform a TX operation with which UE using the allocated TX resources. In an embodiment of the present disclosure, a scheme of determining that a UE has to perform a TX operation with which UE using TX resources which are allocated to the UE will be described below.

If a UE receives a control channel signal, e.g., a PDCCH signal using a C-RNTI of the UE, and a Tx_Rx_indicator is set to 0, the UE will perform a RX operation in resources which correspond to resource allocation information included in the control channel signal.

A connection_idx is used for identifying a transmitter in the control channel.

For example, it will be assumed that a UE#1 is connected to a UE#2 and a UE#3. For a connection between the UE#1 and the UE#2, a connection_idx of 0 (connection_idx = 0) is allocated to the UE#1. For a connection between the UE#1 and the UE#3, a connection_idx of 1 (connection_idx = 1) is allocated to the UE#1. If the UE#1 receives a control channel signal using a C-RNTI of the UE#1, and a Tx_Rx_indicator is set to 0, the UE#1 will perform a RX operation in resources which correspond to resource allocation information included in the control channel signal.

The connection_idx may be included in the control channel as an information field, or a CRC mask.

(2) a scheme of identifying a receiver if a TX resource is allocated to a UE

Each UE may be connected to a plurality of UEs. If RX resources are allocated to a related UE, the UE needs to determine that the UE has to perform a RX operation with which UE using the allocated RX resources. In an embodiment of the present disclosure, a scheme of determining that a UE has to perform a RX operation with which UE using RX resources which are allocated to the UE will be described below.

If a UE receives a control channel signal, e.g., a PDCCH signal using a C-RNTI of the UE, and a Tx_Rx_indicator is set to 1, the UE will perform a TX operation in resources which correspond to resource allocation information included in the control channel signal.

A connection_idx is used for identifying a UE with which the UE has to perform a TX operation in a control channel signal.

For example, it will be assumed that a UE#1 is connected to a UE#2 and a UE#3. For a connection between the UE#1 and the UE#2, a connection_idx of 0 (connection_idx = 0) is allocated to the UE#1. For a connection between the UE#1 and the UE#3, a connection_idx of 1 (connection_idx = 1) is allocated to the UE#1. If the UE#1 receives a control channel signal using a C-RNTI of the UE#1, and a Tx_Rx_indicator is set to 1, the UE#1 will perform a TX operation in resources which correspond to resource allocation information included in the control channel signal.

In other embodiment of the present disclosure, the connection_idx is maintained by a UE. The UE allocates a connection_idx for a connection between other UE and the UE, and transmits the allocated connection_idx to an eNB during a direct connection establishment process. The eNB stores the connection_idx, and uses the connection_idx for transmitting a PDCCH signal to the UE. The connection_idx may be transmitted to the eNB by the UE in a direct communication request message to the direct communication complete message. Here, a characteristic of the connection_idx is the same regardless of whether the connection_idx is allocated by the eNB or the UE.

For example, if the eNB allocates the connection_idx, the eNB has to maintain information on connection_idxes which are already allocated to connections of the UE, and maintain information on connection_idxes which are already allocated to all UEs.

For another example, if the UE allocates the connection_idx, the UE has to maintain the information on the connection_idxes which are already allocated to the connections of the UE, so load of the eNB decreases.

A process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIGS. 15 and 16.

Still another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 15.

FIG. 15 schematically illustrates still another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 15, the communication system includes a UE#A 1511, an eNB#1 1513, an eNB#2 1515, and a UE#B 1517.

Operations 1519 to 1535 in FIG. 15 are identical to operations 619 to 635 in FIG. 6 except in a case that a connection_idx is used instead of a Tx-Idx and a Rx-Idx.

Although FIG. 15 illustrates still another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 15. For example, although shown as a series of operations, various operations in FIG. 15 could overlap, occur in parallel, occur in a different order, or occur multiple times.

Still another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 15, and still another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 16.

FIG. 16 schematically illustrates still another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 16, the communication system includes a UE#A 1611, an eNB#1 1613, an eNB#2 1615, and a UE#B 1617.

Operations 1619 to 1635 in FIG. 16 are identical to operations 719 to 735 in FIG. 7 except in a case that a connection_idx is used instead of a Tx-Idx and a Rx-Idx.

Although FIG. 16 illustrates still another example of a process of transmitting resource allocation information to UEs included in a UE pair for inter-cell direct communication in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 16. For example, although shown as a series of operations, various operations in FIG. 16 could overlap, occur in parallel, occur in a different order, or occur multiple times.

The second scheme of identifying a transmitter and a receiver in a case that a TX resource and a RX resource are allocated to a UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described above, and a handover scheme in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described below.

Firstly, UEs which communicates with each other using device to device communication may be mobile. Due to mobility, the UE will move from an enhanced node B (eNB) to another eNB. As a result, an association among an eNB and UE during direct communication between the UEs is continuously changed. A part of possible scenarios will be followed.

(1) scenario#1

A UE#A and a UE#B are associated with an eNB#1 before a handover. After the handover, the UE#A is associated with the eNB#1, and the UE#B is associated with an eNB#2.

(2) scenario#2

A UE#A and a UE#B are associated with an eNB#1 before a handover. After the handover, the UE#A is associated with an eNB#3, and the UE#B is associated with an eNB#2.

(3) scenario#3

A UE#A and a UE#B are associated with an eNB#1 before a handover. After the handover, the UE#A and the UE#B are associated with an eNB#2.

(4) scenario#4

A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with the eNB#1.

(5) scenario#5

A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with an eNB#3.

(6) scenario#6

A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with the eNB#1 and an eNB#3, respectively.

(7) scenario#7

A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with an eNB#3 and an eNB#4, respectively.

A handover process in a case that a UE hands over form an eNB to other eNB during direct communication with other UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 17.

FIG. 17 schematically illustrates a handover process in a case that a UE hands over form an arbitrary eNB to other eNB during direct communication with other UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 17, the communication system includes a UE#A 1711, an eNB#1 1713, an eNB#2 1715, and an MME 1717.

The UE#A 1711 transmits a measurement report message to the eNB#1 1713 at operation 1719. After receiving the measurement report message from the UE#A 1711, the eNB#1 1713 determines that there is a need of a handover for the UE#A 1711 based on the measurement report message at operation 1721, and transmits a direct connection handover request message to the eNB#2 1715 at operation 1723. The direct connection handover request message includes information on each of direct connections of the UE#A 1711. For example, the information on the direct connection may include a UE ID of a UE which is connected to the UE#A 1711, connection parameters identifying the connection of UE #A 1711 with other UEs, and the like.

After receiving the direct connection handover request message from the eNB#1 1713, the eNB#2 1715 performs an admission control operation for the UE#A 1711 at operation 1725, determines an eNB/cell of each of UEs with which the UE#A 1711 is directly communicating at operation 1727, and transmits a UE cell information request message to the MME 1717 if eNB/cell information is not available at operation 1729. The UE cell information request message includes a UE ID of each of the UEs with which the UE#A 1711 is directly communicating. After receiving the UE cell information request message from the eNB#2 1715, the MME 1717 transmits a UE cell information response message as a response message to the UE cell information request message to the eNB#2 1715 at operation 1731. The UE cell information response message includes information on the eNB/cell of each of the UEs with which the UE#A 1711 directly communicates.

If UE cell information is changed, the MME 1717 may update the eNB#2 1715 at operation 1733. The operation 1733 may be optionally performed. The eNB#2 1715 may inform to the MME 1717 to not send the updated eNB/cell information if the UE#A 1711 hands over to other eNB, or a connection between the UE#A 1711 and other UE is closed.

After determining an eNB/cell of each of UEs with which the UE#A 1711 is directly communicating, the eNB#2 1715 transmits a direct connection handover request acknowledgement (ACK) message to the eNB#1 1713 at operation 1735. The direct connection handover request ACK message includes a C-RNTI of the UE#A 1711 and other direct connection parameters. After receiving the direct connection handover request ACK message from the eNB#2 1715, the eNB#1 1713 transmits a direct connection reconfiguration message including the C-RNTI of the UE#A 1711 and the other direct connection parameters to the UE#A 1711 at operation 1737. After transmitting the direct connection reconfiguration message, the eNB#1 1713 releases a logical connection with other eNB(s) for a direct connection among other UEs and the UE#A 1711 at operation 1739.

After receiving the direct connection reconfiguration message from the eNB#1 1713, the UE#A 1711 transmits a direct connection reconfiguration complete message to the eNB#2 1715 at operation 1741. The direct connection reconfiguration complete message includes the C-RNTI of the UE#A 1711. After receiving the direct connection reconfiguration complete message, the eNB#2 1715 establishes a logical connection with an eNB(s) of a UE(s) with which the UE#A 1711 directly communicates at operation 1743. It will be noted that the operation 1743 is performed if the eNB(s) of the UE(s) with which the UE#A 1711 directly communicates is not the eNB#2 1715. For e.g. UE#A 1711 is directly communicating with UE C associated with eNB 3. So when UE#A 1711 handovers to eNB#2 1715, eNB#2 1715 establishes connection with eNB3. The eNB#2 1715 releases a logical connection of the eNB#2 1715 with other eNB for a UE(s) which is associated with the eNB#2 1715 and directly communicating with UE#A 1711 at operation 1745. For e.g. UE B belongs to eNB#2 1715 and is communicating with UE#A 1711 associated with eNB#1 1713. When UE A handovers to eNB#2 1715, eNB#2 1715 releases the logical connection with eNB#1 1713 for UEA-UEB connection.

Although FIG. 17 illustrates a handover process in a case that a UE hands over from an eNB to other eNB during direct communication with other UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 17. For example, although shown as a series of operations, various operations in FIG. 17 could overlap, occur in parallel, occur in a different order, or occur multiple times.

In an embodiment of the present disclosure, a source eNB may transmit a direct handover request message to a target eNB through an MME.

In an embodiment of the present disclosure, information on eNB/Cell information of an eNB(s) of a UE(s) with which a UE#A directly communicates may be transmitted from an eNB#1 to an eNB#2 through a direct connection handover request message.

A handover process in a scenario#1 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIGS. 18a and 18b.

FIGS. 18a and 18b schematically illustrate a handover process in a scenario#1 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIGS. 18a and 18b, the communication system includes a UE#A 1811, a UE#B 1813, an eNB#1 1815, an eNB#2 1817, and an MME 1819. The UE#A 1811 and the UE#B 1813 are associated with the eNB#1 1815 before a handover. The UE#A 1811 and the UE#B 1813 perform direct communication each other, and the eNB#1 1815 allocates resources, to the UE#A 1811 and the UE#B 1813 at operation 1821.

The UE#B 1813 transmits a measurement report message to the eNB#1 1815 at operation 1823. After receiving the measurement report message from the UE#B 1813, the eNB#1 1815 determines that there is a need of a handover for the UE#B 1813 based on the measurement report message at operation 1825, and transmits a direct connection handover request message to the eNB#2 1817 at operation 1827. The direct connection handover request message may include a UE ID of the UE#A 1811, connection parameters identifying the connection of UE #B 1813 with UE#A 1811, and the like.

After receiving the direct connection handover request message from the eNB#1 1815, the eNB#2 1817 performs an admission control operation for the UE#B 1813 at operation 1831, and determines an eNB/cell of the UE#A 1811 with which the UE#B 1813 directly communicates at operation 1833. The eNB#2 1817 transmits a UE cell information request message to the MME 1819 at operation 1835 if eNB/cell information is not available.

The UE cell information request message includes a UE ID of the UE#A 1811. After receiving the UE cell information request message from the eNB#2 1817, the MME 1819 transmits a UE cell information response message as a response message to the UE cell information request message to the eNB#2 1817 at operation 1837. The UE cell information response message includes eNB/cell information of the UE#A 1811, i.e., information on the eNB#1 1815.

If UE cell information for the UE#A 1811 is changed, the MME 1819 may update the eNB#2 1817 at operation 1839. The operation 1839 may be optionally performed. The eNB#2 1817 may inform MME 1819 to not send the updated eNB/cell information if the UE#B 1813 hands over to other eNB, or a connection between the UE#A 1811 and the UE#B 1813 is closed.

After determining an eNB/cell of UE#A 1811 with which the UE#B 1813 is directly communicating, the eNB#2 1817 transmits a direct connection handover request ACK message to the eNB#1 1815 at operation 1841. The direct connection handover request ACK message includes a C-RNTI of the UE#B 1813 and other direct connection parameters. After receiving the direct connection handover request ACK message from the eNB#2 1817, the eNB#1 1815 transmits a direct connection reconfiguration message including the C-RNTI of the UE#B 1813 and the other direct connection parameters to the UE#B 1813 at operation 1843.

After receiving the direct connection reconfiguration message from the eNB#1 1815, the UE#B 1813 transmits a direct connection reconfiguration complete message to the eNB#2 1817 at operation 1845. The direct connection reconfiguration complete message includes the C-RNTI of the UE#B 1813. After receiving the direct connection reconfiguration complete message, the eNB#2 1817 establishes a logical connection with the eNB#1 1815 at operation 1847.

A logical connection establishment process that coordinates resources for direct communication between the UE#A 1811 and the UE#B 1813 is performed between the eNB#1 1815 and the eNB#2 1817 at operation 1849. Resource coordination is performed between the eNB#1 1815 and the eNB#2 1817 at operation 1851. The eNB#1 1815 transmits information on the determined resources to the UE#A 1811 at operation 1853. The eNB#2 1817 transmits the information on the determined resources to the UE#B 1813 at operation 1855. The eNB#2 1817 uses the same connection identifiers indtifying connection between UEA and UE B, and uses a new C-RNTI for allocating resources.

Although FIGS. 18a and 18b illustrate a handover process in a scenario#1 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIGS. 18a and 18b. For example, although shown as a series of operations, various operations in FIGS. 18a and 18b could overlap, occur in parallel, occur in a different order, or occur multiple times.

A handover process in a scenario#1 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIGS. 18a and 18b, and a handover process in a scenario#2 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIGS. 19a and 19b.

FIGS. 19a and 19b schematically illustrate a handover process in a scenario#2 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIGS. 19a and 19b, the communication system includes a UE#A 1911, a UE#B 1913, an eNB#1 1915, an eNB#2 1917, an eNB#3 1921, and an MME 1921.

Firstly, the UE#A 1911 and the UE#B 1913 are associated with the eNB#1 1915 before a handover. The UE#A 1911 and the UE#B 1913 directly communicate each other, and the eNB#1 1915 allocates resources, to the UE#A 1911 and the UE#B 1913 at operation 1923. The UE#B 1913 hands over from the eNB#1 1915 to the eNB#2 1917 using a process in a scenario#1 at operation 1925.

The UE#A 1911 transmits a measurement report message to the eNB#1 1915 at operation 1927. After receiving the measurement report message from the UE#A 1911, the eNB#1 1915 determines that there is a need of a handover for the UE#A 1911 based on the measurement report message at operation 1929, and transmits a direct connection handover request message to the eNB#3 1919 at operation 1931. The direct connection handover request message may include a UE ID of the UE#B 1913, connection parameters identifying the connection of UE #B 1913 with UE#A 1911, and the like.

After receiving the direct connection handover request message from the eNB#1 1915, the eNB#3 1919 performs an admission control operation for the UE#A 1911 at operation 1933, and determines an eNB/cell of the UE#B 1913 with which the UE#A 1911 directly communicates at operation 1935. The eNB#3 1919 transmits a UE cell information request message to the MME 1921 at operation 1937 if eNB/cell information is not available. The UE cell information request message includes a UE ID of the UE#B 1913. After receiving the UE cell information request message from the eNB#3 1919, the MME 1921 transmits a UE cell information response message as a response message to the UE cell information request message to the eNB#3 1919 at operation 1939.

The UE cell information response message includes eNB/cell information of the UE#B 1913, i.e., information on the eNB#2 1917. If UE cell information for the UE#B 1913 is changed, the MME 1921 may update the eNB#3 1919 at operation 1941. The operation 1941 may be optionally performed. The eNB#3 1919 may inform MME 1921 to not send the updated eNB/cell information if the UE#A 1911 hands over to other eNB, or a connection between the UE#A 1911 and the UE#B 1913 is closed.

After determining an eNB/cell of UE#B 1913 with which the UE#A 1911 is directly communicating the eNB#3 1919 transmits a direct connection handover request ACK message to the eNB#1 1915 at operation 1943. The direct connection handover request ACK message includes a C-RNTI of the UE#A 1911 and other direct connection parameters. After receiving the direct connection handover request ACK message from the eNB#3 1919, the eNB#1 1915 transmits a direct connection reconfiguration message including the C-RNTI of the UE#A 1911 and the other direct connection parameters to the UE#A 1911 at operation 1945. The eNB#1 1915 releases a logical connection with the eNB#2 1917 at operation 1947.

After receiving the direct connection reconfiguration message from the eNB#1 1915, the UE#A 1911 transmits a direct connection reconfiguration complete message to the eNB#3 1919 at operation 1949. The direct connection reconfiguration complete message includes the C-RNTI of the UE#A 1911. After receiving the direct connection reconfiguration complete message from the UE#A 1911, the eNB#3 1919 establishes a logical connection with the eNB#2 1917 at operation 1951. A logical connection establishment process that coordinates resources for direct communication between the UE#A 1911 and the UE#B 1913 is performed between the eNB#2 1917 and the eNB#3 1919 at operation 1953. The eNB#2 1917 releases a logical connection with the eNB#1 1915 at operation 1955.

Resource coordination is performed between the eNB#2 1917 and the eNB#3 1919 at operation 1957. The eNB#2 1917 transmits information on the determined resources to the UE#B 1913 at operation 1959. The eNB#2 1917 uses the same connection identifiers identifying connection between UEA and UE B, and uses a new C-RNTI for allocating resources. The eNB#3 1919 transmits the information on the determined resources to the UE#A 1911 at operation 1961. The eNB#3 1919 uses the same connection identifiers identifying connection between UEA and UE B, and uses a new C-RNTI for allocating resources.

Although FIGS. 19a and 19b illustrate a handover process in a scenario#2 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIGS. 19a and 19b. For example, although shown as a series of operations, various operations in FIGS. 19a and 19b could overlap, occur in parallel, occur in a different order, or occur multiple times.

A handover process in a scenario#2 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIGS. 19a and 19b, and a handover process in a scenario#3 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 20.

FIG. 20 schematically illustrates a handover process in a scenario#3 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 20, the communication system includes a UE#A 2011, a UE#B 2013, an eNB#1 2015, and an eNB#2 2017.

The UE#A 2011 and the UE#B 2013 are associated with the eNB#1 2015 before a handover. The UE#A 2011 and the UE#B 2013 perform direct communication each other, and the eNB#1 2015 allocates resources, to the UE#A 2011 and the UE#B 2013 at operation 2019. The UE#B 2013 hands over from the eNB#1 2015 to the eNB#2 2017 using a process in a scenario#1 at operation 2021.

The UE#A 2011 transmits a measurement report message to the eNB#1 2015 at operation 2023. After receiving the measurement report message from the UE#A 2011, the eNB#1 2015 determines that there is a need of a handover for the UE#A 2011 based on the measurement report message at operation 2025, and transmits a direct connection handover request message to the eNB#2 2017 at operation 2027. The direct connection handover request message may include a UE ID of the UE#B 2013, connection parameters identifying the connection of UE #B 2013 with UE#A 2011, and the like.

After receiving the direct connection handover request message from the eNB#1 2015, the eNB#2 2017 performs an admission control operation for the UE#A 2011 at operation 2029, and determines an eNB/cell of UEB with which the UE#A 2011 directly communicates at operation 2031. Since the UE B is with eNB#2 there is no need to request MME for eNB/Cell information. The eNB#2 2017 transmits a direct connection handover ACK message to the eNB#1 2015 at operation 2033. The direct connection handover ACK message includes a C-RNTI of the UE#A 2011 and other direct communication parameters.

After receiving the direct connection handover ACK message from the eNB#2 2017, the eNB#1 2015 transmits a direct connection reconfiguration message to the UE#A 2011 at operation 2035. The direct connection reconfiguration message includes the C-RNTI of the UE#A 2011 and the other direct communication parameters. The eNB#1 2015 releases a logical connection with the eNB#2 2017 at operation 2037.

After receiving the direct connection reconfiguration message from the eNB#1 2015, the UE# 2011 transmits a direct connection reconfiguration complete message as a response message to the direct connection reconfiguration message to the eNB#2 2017 at operation 2039. The direct connection reconfiguration complete message includes the C-RNTI of the UE#A 2011. After receiving the direct connection reconfiguration complete message from the UE#A 2011, the eNB#2 2017 releases a logical connection with the eNB#1 2015 at operation 2041, and transmits information on resources for the UE#A 2011 and the UE#B 2013 at operation 2043.

Although FIG. 20 illustrates a handover process in a scenario#3 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 20. For example, although shown as a series of operations, various operations in FIG. 20 could overlap, occur in parallel, occur in a different order, or occur multiple times.

A handover process in a scenario#3 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 20, and a handover process in a scenario#4 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 21.

FIG. 21 schematically illustrates a handover process in a scenario#4 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 21, the communication system includes a UE#A 2111, a UE#B 2113, an eNB#1 2115, and an eNB#2 2117.

The UE#A 2111 and the UE#B 2113 are associated with the eNB#1 2115 before a handover. The UE#A 2111 and the UE#B 2113 perform direct communication each other at operation 2119. The UE#A 2111 transmits a measurement report message to the eNB#1 2115 at operation 2121. After receiving the measurement report message from the UE#A 2111, the eNB#1 2115 determines that there is a need of a handover for the UE#A 2111 based on the measurement report message at operation 2123, and transmits a direct connection handover request message to the eNB#2 2117 at operation 2125. The direct connection handover request message may include a UE ID of the UE#B 2123, a connection parameters identifying the connection of UE #B 2113 with UE#A 2111 the like. After receiving the direct connection handover request message from the eNB#1 2115, the eNB#2 2117 performs an admission control operation for the UE#A 2111 at operation 2127, and determines an eNB/cell of UEs with which the UE#A 2111 directly communicates at operation 2129. The eNB#2 2117 transmits a direct connection handover ACK message to the eNB#1 2115 at operation 2131. The direct connection handover ACK message includes a C-RNTI of the UE#A 2111 and other direct communication parameters.

After receiving the direct connection handover ACK message from the eNB#2 2117, the eNB#1 2115 transmits a direct connection reconfiguration message to the UE#A 2111 at operation 2133. The direct connection reconfiguration message includes the C-RNTI of the UE#A 2111 and the other direct communication parameters. The eNB#1 2115 releases a logical connection with the eNB#2 2117 at operation 2135.

After receiving the direct connection reconfiguration message from the eNB#1 2115, the UE# 2111 transmits a direct connection reconfiguration complete message as a response message to the direct connection reconfiguration message to the eNB#2 2117 at operation 2137. The direct connection reconfiguration complete message includes the C-RNTI of the UE#A 2111. After receiving the direct connection reconfiguration complete message from the UE#A 2111, the eNB#2 2117 releases a logical connection with the eNB#1 2115 at operation 2139, and transmits information on resources for the UE#A 2111 and the UE#B 2113 at operation 2141.

Although FIG. 21 illustrates a handover process in a scenario#4 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure, various changes could be made to FIG. 21. For example, although shown as a series of operations, various operations in FIG. 21 could overlap, occur in parallel, occur in a different order, or occur multiple times.

A handover process in a scenario#4 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 21, and a handover process in each of a scenario#5 to scenario#7 in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described below.

Firstly, a handover process in a scenario#5 will be described below.

A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with an eNB#3. In this case, the UE#A hands over from the eNB#1 to the eNB#3, and the UE#B hands over from the eNB#2 to the eNB#3 using a process in FIG. 17.

Secondly, a handover process in a scenario#6 will be described below.

A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with the eNB#1 and an eNB#3, respectively. In this case, the UE#B hands over from the eNB#2 to the eNB#3 using a process in FIG. 17.

Thirdly, a handover process in a scenario#7 will be described below.

A UE#A and a UE#B are associated with an eNB#1 and an eNB#2, respectively, before a handover. After the handover, the UE#A and the UE#B are associated with an eNB#3 and an eNB#4, respectively. In this case, the UE#A hands over from the eNB#1 to the eNB#3, and the UE#B hands over from the eNB#2 to the eNB#4 using a process in FIG. 17.

An inner structure of a UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 22.

FIG. 22 schematically illustrates an inner structure of a UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 22, a UE 2200 includes a transmitter 2211, a controller 2213, a receiver 2215, and a storage unit 2217.

The controller 2213 controls the overall operation of the UE 2200. More particularly, the controller 2213 controls the UE 2200 to perform an operation related to an operation of allocating a resource and performing a handover operation according to an embodiment of the present disclosure. The operation related to the operation of allocating the resource and performing the handover operation is performed in the manner described with reference to FIGS. 6 to 21, and a description thereof will be omitted herein.

The transmitter 2211 transmits various signals, various messages, and the like to other UE, an eNB, and the like under a control of the controller 2213. The various signals, the various messages, and the like transmitted in the transmitter 2211 have been described in FIGS. 6 to 21, and a description thereof will be omitted herein.

The receiver 2215 receives various signals, various messages, and the like from the other UE, the eNB, and the like under a control of the controller 2213. The various signals, the various messages and the like received in the receiver 2215 have been described in FIGS. 6 to 21, and a description thereof will be omitted herein.

The storage unit 2217 stores various data necessary for the operation of the UE 2200, information related to the operation of allocating the resource and performing the handover operation, and the like. The storage unit 2217 stores the various signals, the various messages, and the like received in the receiver 2215.

While the transmitter 2211, the controller 2213, the receiver 2215, and the storage unit 2217 are described as separate processors, it is to be understood that this is merely for convenience of description. In other words, two or more of the transmitter 2211, the controller 2213, the receiver 2215, and the storage unit 2217 may be incorporated into a single processor.

An inner structure of a UE in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 22, and an inner structure of an eNB in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 23.

FIG. 23 schematically illustrates an inner structure of an eNB in a communication system supporting a D2D scheme according to an embodiment of the present disclosure.

Referring to FIG. 23, an eNB 2300 includes a transmitter 2311, a controller 2313, a receiver 2315, and a storage unit 2317.

The controller 2313 controls the overall operation of the eNB 2300. More particularly, the controller 2313 controls the eNB 2300 to perform an operation related to an operation of allocating a resource and performing a handover operation according to an embodiment of the present disclosure. The operation related to the operation of allocating the resource and performing the handover operation is performed in the manner described with reference to FIGS. 6 to 21, and a description thereof will be omitted herein.

The transmitter 2311 transmits various signals, various messages, and the like to a UE, other eNB, an MME, and the like under a control of the controller 2313. The various signals, the various messages, and the like transmitted in the transmitter 2311 have been described in FIGS. 6 to 21, and a description thereof will be omitted herein.

The receiver 2315 receives various signals, various messages, and the like from the UE, the other eNB, the MME, and the like under a control of the controller 2313. The various signals, the various messages and the like received in the receiver 1015 have been described in FIGS. 6 to 21, and a description thereof will be omitted herein.

The storage unit 2317 stores various data necessary for the operation of the eNB 2300, information related to the operation of allocating the resource and performing the handover operation, and the like. The storage unit 2317 stores the various signals, the various messages, and the like received in the receiver 2315.

While the transmitter 2311, the controller 2313, the receiver 2315, and the storage unit 2317 are described as separate processors, it is to be understood that this is merely for convenience of description. In other words, two or more of the transmitter 2311, the controller 2313, the receiver 2315, and the storage unit 2317 may be incorporated into a single processor.

An inner structure of an eNB in a communication system supporting a D2D scheme according to an embodiment of the present disclosure has been described with reference to FIG. 23, and an inner structure of an MME in a communication system supporting a D2D scheme according to an embodiment of the present disclosure will be described with reference to FIG. 24.

Referring to FIG. 24, an MME 2400 includes a transmitter 2411, a controller 2413, a receiver 2415, and a storage unit 2417.

The controller 2413 controls the overall operation of the MME 2400. More particularly, the controller 2413 controls the MME 2400 to perform an operation related to an operation of allocating a resource and performing a handover operation according to an embodiment of the present disclosure. The operation related to the operation of allocating the resource and performing the handover operation is performed in the manner described with reference to FIGS. 6 to 21, and a description thereof will be omitted herein.

The transmitter 2411 transmits various signals, various messages, and the like to an eNB, and the like under a control of the controller 2413. The various signals, the various messages, and the like transmitted in the transmitter 2411 have been described in FIGS. 6 to 21, and a description thereof will be omitted herein.

The receiver 2415 receives various signals, various messages, and the like from the eNB, and the like under a control of the controller 2413. The various signals, the various messages and the like received in the receiver 2415 have been described in FIGS. 6 to 21, and a description thereof will be omitted herein.

The storage unit 2417 stores various data necessary for the operation of the MME 2400, information related to the operation of allocating the resource and performing the handover operation, and the like. The storage unit 2417 stores the various signals, the various messages, and the like received in the receiver 2415.

While the transmitter 2411, the controller 2413, the receiver 2415, and the storage unit 2417 are described as separate processors, it is to be understood that this is merely for convenience of description. In other words, two or more of the transmitter 2411, the controller 2413, the receiver 2415, and the storage unit 2417 may be incorporated into a single processor.

Certain aspects of the present disclosure may also be embodied as computer readable code on a non-transitory computer readable recording medium. A non-transitory computer readable recording medium is any data storage device that can store data, which can be thereafter read by a computer system. Examples of the non-transitory computer readable recording medium include read only memory (ROM), random access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission through the Internet). The non-transitory computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, code, and code segments for accomplishing the present disclosure can be easily construed by programmers skilled in the art to which the present disclosure pertains.

It can be appreciated that a method and apparatus according to an embodiment of the present disclosure may be implemented by hardware, software and/or a combination thereof. The software may be stored in a non-volatile storage, for example, an erasable or re-writable ROM, a memory, for example, a RAM, a memory chip, a memory device, or a memory integrated circuit (IC), or an optically or magnetically recordable non-transitory machine-readable (e.g., computer-readable), storage medium (e.g., a compact disk (CD), a digital versatile disk (DVD), a magnetic disk, a magnetic tape, and/or the like). A method and apparatus according to an embodiment of the present disclosure may be implemented by a computer or a mobile terminal that includes a controller and a memory, and the memory may be an example of a non-transitory machine-readable (e.g., computer-readable), storage medium suitable to store a program or programs including instructions for implementing various embodiments of the present disclosure.

The present disclosure may include a program including code for implementing the apparatus and method as defined by the appended claims, and a non-transitory machine-readable (e.g., computer-readable), storage medium storing the program. The program may be electronically transferred via any media, such as communication signals, which are transmitted through wired and/or wireless connections, and the present disclosure may include their equivalents.

An apparatus according to an embodiment of the present disclosure may receive the program from a program providing device which is connected to the apparatus via a wire or a wireless and store the program. The program providing device may include a memory for storing instructions which instruct to perform a content protect method which has been already installed, information necessary for the content protect method, and the like, a communication unit for performing a wired or a wireless communication with a graphic processing device, and a controller for transmitting a related program to a transmitting/receiving device based on a request of the graphic processing device or automatically transmitting the related program to the transmitting/receiving device.

While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

A method for performing a handover by a user equipment (UE) in a communication system supporting a device to device (D2D) scheme, the method comprising:

receiving a direct connection reconfiguration message from an enhanced node B (eNB),

wherein the direct connection reconfiguration message includes information on each of direct connections of the UE, and

wherein the information on each of the direct connections includes a UE identifier (ID) and connection parameters.
The method as claimed in claim 1, wherein the connection parameters are used for identifying a connection of the UE with other UEs.
The method as claimed in claim 1, comprising:

transmitting a measurement report message to the eNB before receiving the direct connection reconfiguration message from the eNB.
The method as claimed in claim 1, comprising:

transmitting a direct connection reconfiguration complete message as a response message to the direct connection reconfiguration message to other eNB that the UE will perform a handover.
The method as claimed in claim 1, wherein the direct connection reconfiguration message is received if the eNB determines that the UE needs to perform a handover.
A method for supporting a handover by an enhanced node B (eNB) in a communication system supporting a device to device (D2D) scheme, the method comprising:

determining that a user equipment (UE) needs to perform a handover to other eNB; and

transmitting a direct connection handover request message to the other eNB,

wherein the direct connection handover request message includes information on each of direct connections of the UE, and

wherein the information on each of the direct connection includes a UE identifier (ID) and connection parameters.
The method as claimed in claim 6, wherein the connection parameters are used for identifying a connection of the UE with other UEs.
The method as claimed in claim 6, comprising:

receiving a measurement report message from the UE before transmitting the direct connection reconfiguration message to the UE.
The method as claimed in claim 6, comprising:

receiving a direct connection handover acknowledgement (ACK) message from the other eNB.
The method as claimed in claim 9, comprising:

transmitting a direct connection reconfiguration message to the UE,

wherein the direct connection reconfiguration message includes the information on each of the direct connections of the UE, and

wherein the information on each of the direct connection includes the UE ID and the connection parameters.
A method for supporting a handover by an enhanced node B (eNB) in a communication system supporting a device to device (D2D) scheme, the method comprising:

receiving a direct connection handover request message from other eNB,

wherein the direct connection handover request message includes information on each of direct connections of a user equipment (UE), and

wherein the information on each of the direct connection includes a UE identifier (ID) and connection parameters.
The method as claimed in claim 11, wherein the connection parameters are used for identifying a connection of the UE with other UEs.
The method as claimed in claim 11, comprising:

transmitting a direct connection handover acknowledgement (ACK) message to the other eNB.
The method as claimed in claim 11, comprising:

receiving a direct connection reconfiguration complete message as a response message to a direct connection reconfiguration message which is received from the other eNB from the UE.
A user equipment (UE) configured to perform one of methods as claimed in claims 1 to 5.
An enhanced node B (eNB) configured to perform one of methods as claimed in claims 6 to 10.