RU2731557C2 - Wireless device, network nodes and corresponding methods for processing device-to-device communication (d2d) during handover in a wireless communication network - Google Patents

Abstract

FIELD: wireless communication.

SUBSTANCE: first wireless device performs "device-to-device" (D2D) communication processing with a second wireless device during handover of the first wireless device from the source network node to the target network node in the wireless communication network. First wireless device terminates D2D communication, determines first uplink timing difference as difference between uplink scheduling for source network node and uplink scheduling for target network node, reconfigures the D2D link based on the first uplink timing difference and restarts the D2D link in accordance with the reconfiguration.

EFFECT: technical result consists in provision of efficient use of resources and mutual interference processing.

10 cl, 16 dwg

Description

FIELD OF TECHNOLOGY

Embodiments of the present invention relate to device-to-device (D2D) communication in a wireless communication network. In particular, embodiments of the present invention relate to D2D communication processing during handover of a wireless device in a wireless communication network.

LEVEL OF TECHNOLOGY

In wireless networks, the latest developments in the LTE 3GPP project provide the ability to access local IP-based services at home, in the office, at a public access point or even outdoors. One area in which the access and local connectivity of these IP-based local services can be exploited is in direct communication between wireless devices in close proximity to each other. In this case, immediate proximity can usually be considered a distance of less than several tens of meters, and sometimes up to several hundred meters.

This direct mode or device-to-device (D2D) communication can demonstrate many potential advantages over traditional cellular communications. This is because D2D devices are much closer together than other cellular devices that need to communicate through a cellular access point, such as a radio network node such as an eNodeB.

However, it should be noted that it is preferable to provide D2D communication processing from a network point of view in order to ensure efficient resource use and interference handling.

In these mixed cellular and D2D wireless networks, it has been proposed to arrange D2D communications on cellular uplink (UL) resources such that time division duplex (TDD) is a D2D duplex scheme. This means that cellular uplink resources will be allocated for both uplink and downlink D2D communications between each pair of D2D wireless devices in time division multiplexing (TDM) mode.

Once the wireless devices detect proximity to each other, the wireless devices and / or the network can initiate a D2D link between the two wireless devices. This is commonly referred to as D2D bearer setup and will not be discussed further here.

However, once a D2D link is established between the two wireless devices, there is a problem in how to handle D2D communication when one of the wireless devices moves from the cellular coverage of its current cell to the cellular coverage of another cell, i.e. during handover. Thus, there is a need to provide a method for handling D2D communication during handover of a wireless device in a wireless communication network.

WO 2011/109027 A1 describes the handover of a pair of D2D wireless devices between different cells. However, in this case, both of the wireless devices of the D2D pair are part of the handover, and control of the D2D communication network can simply be transferred from the network node of the source cell to the network node of the target cell.

SUMMARY OF THE INVENTION

An object of embodiments of the present invention is to provide a method for handling D2D communication during handover of a wireless device in a wireless communication network.

In accordance with a first aspect of embodiments of the present invention, the object is achieved by a method performed by a first wireless device to process device-to-device (D2D) communication with a second wireless device during handover of the first wireless device from a source network node to a target network node in the network wireless communication. The first wireless device interrupts D2D communication. The first wireless device then determines the first uplink timing difference as the difference between the uplink timing for the source network node and the uplink timing for the target network node. Next, the first wireless device reconfigures D2D communication based on the first uplink timing difference. The first wireless device then restarts the D2D communication according to the reconfiguration.

In accordance with a second aspect of embodiments of the present invention is achieved by a first wireless device for processing D2D communication with a second wireless device during handover of the first wireless device from a source network node to a target network node in a wireless communication network. The first wireless device comprises processing circuitry configured to first terminate D2D communication. The processing circuitry is configured to then determine the first uplink timing difference as the difference between the uplink timing for the source network node and the uplink timing for the target network node. Next, the processing circuit is configured to reconfigure the D2D communication based on the first uplink timing difference and restart the D2D communication according to the reconfiguration.

In accordance with a third aspect of embodiments of the present invention, the object is achieved by a method performed by a target network node to process D2D communication between a first wireless device and a second wireless device during handover of the first wireless device to a target network node from a source network node in a wireless communication network. The target network node, upon completion of the handover, receives at least a first uplink timing difference of the first wireless device from the first wireless device. In addition, the target network node determines a D2D communication scheduling scheme based on at least a first uplink timing difference of the first wireless device, the first uplink timing difference being the difference between the first wireless device's uplink timing for the source network node and the uplink timing. communication lines of the first wireless device for the target network node.

In accordance with a fourth aspect of embodiments of the present invention, an object is achieved by a target network node for processing D2D communication between a first wireless device and a second wireless device during handover of the first wireless device to a target network node from a source network node in a wireless communication network. The target network node comprises processing circuitry adapted, upon completion of the handover, to receive at least a first uplink timing difference of the first wireless device from the first wireless device. The processing circuit is further configured to determine a D2D communication scheduling scheme based on at least a first uplink timing difference of the first wireless device, the first uplink timing difference being the difference between the first wireless device's uplink timing for the source network node and the uplink timing. communication lines of the first wireless device for the target network node.

In accordance with a fifth aspect of embodiments of the present invention, the object is achieved by a method performed by a source network node to process D2D communication between a first wireless device and a second wireless device during handover of the first wireless device from a source network node to a target network node in a wireless communication network. The source network node sends an indication to terminate the D2D communication to at least the second wireless device prior to initiating the handover. Then, upon completion of the handover, the source network node determines a D2D scheduling scheme based on at least a first uplink timing difference of the first wireless device, the first uplink timing difference being the difference between the uplink timing of the first wireless device for the source network node and uplink timing of the first wireless device to the target network node.

In accordance with a sixth aspect of embodiments of the present invention, the object is achieved by a source network node for processing D2D communication between a first wireless device and a second wireless device during handover of the first wireless device from a source network node to a target network node in a wireless communication network. The source network node comprises processing circuitry configured to transmit an indication to terminate D2D communications to at least a second wireless device prior to initiating a handover. The processing scheme is further configured to determine, upon completion of the handover, a D2D communication scheduling scheme based on at least a first uplink timing difference of the first wireless device, wherein the first uplink timing difference is the difference between the uplink timing of the first wireless device for the original network node and uplink timing of the first wireless device for the target network node.

By providing the wireless devices that participate in D2D communications, for the target network node, the uplink timing differences between the source network node and the target network node when performing a handoff from the source network node to the target network node, the network nodes involved in communication control D2D can define a D2D communication scheduling scheme to be used after the handover is completed. Thus, based on the uplink timing differences, network nodes can agree on the timing to be used for scheduling D2D communications. This scheduling scheme will thus effectively avoid collisions when there is a split network control point, ie, two network nodes managing D2D communications that are scheduling resources for D2D communications and cellular communications. Therefore, a method is provided for handling D2D communication during handover of a wireless device in a wireless communication network.

BRIEF DESCRIPTION OF DRAWINGS

The features and advantages of the embodiments will become apparent to those skilled in the art from the following detailed description of illustrative embodiments thereof with reference to the accompanying drawings.

FIG. 1 is a block diagram illustrating embodiments in a wireless communication network.

FIG. 2A-2B are flow charts illustrating a first D2D handover scenario in accordance with some embodiments.

FIG. 3 is a signaling diagram depicting signaling in accordance with some embodiments in the first D2D handover scenario shown in FIG. 2.

FIG. 4A-4B are flow diagrams illustrating a second D2D handover scenario in accordance with some embodiments.

FIG. 5 is a signaling diagram depicting signaling in accordance with some embodiments in the second D2D handover scenario shown in FIG. 4.

FIG. 6A-6B are flow diagrams illustrating a third D2D handover scenario in accordance with some embodiments.

FIG. 7 is a signaling diagram depicting signaling in accordance with some embodiments in the third D2D handover scenario shown in FIG. 6.

FIG. 8 is a flowchart depicting embodiments of a method in a wireless device.

FIG. 9 is a flowchart depicting embodiments of a method at a target network node.

FIG. 10 is a flowchart depicting embodiments of the method at a home network node.

FIG. 11 is a block diagram depicting embodiments of a wireless device.

FIG. 12 is a block diagram depicting embodiments of a target network node.

FIG. 13 is a block diagram depicting embodiments of a home network node.

DETAILED DESCRIPTION

The figures are schematic and simplified for clarity, and only show details that are important to understanding the embodiments presented herein, while other details have not been taken into account. Throughout the same reference numbers are used for identical or corresponding parts or steps.

FIG. 1 depicts a wireless communication network 100 in which embodiments of the present invention may be implemented. In some embodiments, the wireless communication network 100 may be a wireless communication network such as LTE (e.g., LTE FDD, LTE TDD, LTE HD-FDD), WCDMA, UTRA TDD, GSM network, GERAN network, accelerated GSM evolution data transmission (EDGE), a network consisting of any combination of wireless access technologies (RAT), such as multi-standard radio base stations (MSR), multi-wireless access technology base stations, etc., any 3GPP cellular network, Wimax or any cellular network or system.

The wireless communication system 100 includes a first radio network node 110, which is a base station and thus may also be referred to as a radio base station or base station. The network node 110 serves the first cell 115. The network node 110 in this example, for example, may be an eNB, an eNodeB or a Home Node B, a Home eNodeB, a femto base station, a pico base station, or any other network unit capable of serving a wireless device or a machine-type communication device in a wireless communication system, such as a device such as a cluster head.

The first wireless device 121 is located in the first cell 115. The wireless device 121 is configured to communicate within the wireless communication system 100 via the radio network node 110 over the radio link 130 when present in the first cell 115 served by the radio network node 110. The first wireless device 121 is capable of communicating with other wireless devices, such as the second wireless device 122, which will be described below, using D2D wireless communication via a D2D link 140 (dashed arrow in FIG. 1).

In this example, the second wireless device 122 is also located in the first cell 115. However, in other embodiments, the second wireless device 122 may be located in a different cell, such as, for example, a second cell 116 served by a different, second radio network node 111 that is adjacent with a first cell 115. The second wireless device 122 is configured to communicate within a wireless communication system 100 through a first radio network node 110 over a radio link, such as, for example, a radio link 150 when present in a first cell 115 served by a base station 110. The second wireless device 122 is capable of communicating with other wireless devices, such as the first wireless device 121, using D2D wireless communications via a D2D link 140.

It should be noted that the first wireless device 121 and the second wireless device 122, for example, may be wireless devices, for example, mobile terminals or wireless terminals, mobile phones, computers such as, for example, laptops, personal digital assistants (PDAs) or tablets. wireless-capable computers, machine-to-machine (M2M) devices, or any other radio network unit capable of communicating over a radio link in a communication network.

It should also be noted that a large number of wireless devices may be located in the communications network 100. The first and second wireless devices 121, 122 may be considered one pair of D2D wireless devices among many other pairs of D2D wireless devices located in the communication network 100.

However, when one of the wireless devices, such as the first wireless device 121, moves from the cellular coverage of the first cell 115 to the cellular coverage of another cell, such as the second cell 116, the first radio network node 110 may no longer be able to manage scheduling of D2D communications if subsequently, a handover of the first wireless device 121 to the second radio network node 111 is performed.

Thus, in this case, the D2D network control point between wireless devices must be split between the first and second radio network nodes 110, 111. Thereby, collision avoidance becomes a problem, i.e., when the first radio network node performs scheduling for D2D communication and the second radio network node performs scheduling for cellular communication with the scheduling resources of a split network control point for cellular communication and a D2D link. This problem will appear for both synchronized and non-synchronized neighbor cells. For the unsynchronized case, there is also the problem that the cell timing is different for the two cells and is unknown to the pair of D2D wireless devices, i.e. A D2D pair of wireless devices is one transmit / receive pair of devices, and thus, the D2D communication between these wireless devices must be synchronized.

This problem is solved by the embodiments described herein by providing the wireless devices 121, 122 that participate in D2D communication with the uplink timing differences between the uplink timing for the source network node, i.e., the network node of their respective current cell. , and uplink timing for the target network node, i.e., the network node of the cell to which they move, when performing a handover from the source network node to the target network node. Thus, the network nodes involved in the management of D2D communications can determine the D2D communications scheduling scheme to be used after the handover is complete. Thus, based on the uplink timing differences, network nodes can agree on the timing to be used for scheduling D2D communications. This scheduling scheme will thus effectively avoid collisions when there is a split network control point that schedules resources for the D2D link and the cellular. Therefore, a method is provided for handling D2D communication during handover of a wireless device in a wireless communication network.

Three different D2D handover scenarios are described in more detail below with reference to FIG. 2-7, which illustrate different handover situations that are handled by the embodiments presented herein for D2D communications. Thereafter, embodiments are also described with reference to FIG. 8-13.

FIG. 2A-2B show a first D2D handover scenario in accordance with some embodiments. FIG. 2A, the first wireless device 121 participates in D2D communications with the second wireless device 122 over the D2D link 140. In this first D2D handover scenario, the first wireless device 121 then begins to move from the cellular coverage of its current cell, i.e., the first cell 115 served by the first network node 110, to the cellular coverage of the second cell 116, served by the second network node 111 (as shown by an arrow with a double dashed line). The first network node 110 in this scenario may be referred to as the source network node and the second network node 111 may be referred to as the target network node. This may trigger the signaling of the embodiments, described in detail below with reference to FIG. 3.

As shown in FIG. 2B, once the signaling shown in FIG. 3 has been completed, the first wireless device 121 will perform a handover from the first network node 110 to the second network node 111. This means that the first wireless device 121 is now located in the second cell 116 and served by the second network node 111. As a result of the signaling of FIG. 3, the first wireless device 121 will also continue to participate in D2D communications with the second wireless device 122 over D2D link 140, with the second wireless device 122 still located in the first cell 115 and served by the first network node 110.

FIG. 3 shows signaling of some embodiments initiated by the first D2D handover scenario shown in FIG. 2A. The signaling can be described by three main signaling units: a D2D handover prepare stage 301, a D2D handover perform stage 302, and a D2D scheduling stage 303.

As shown in FIG. 3, prior to signaling, the first wireless device 121 participates in D2D communications with the second wireless device 122 over the D2D link. Each of the first and second wireless devices 121, 122 also has an established cellular link with the first network node 110, i.e., the source network node 110. In this example, the source network node 110 and the target network node 111 are not synchronized with each other. ...

In a D2D handover preparation step 301, a normal wireless device measurement report by the first wireless device 121 may initiate a handover procedure for both the source network node 110 and the target network node 111.

Action 301a. The first wireless device 121 may transmit a measurement report to the home network node 110. The measurement report may be based on certain Radio Resource Control (RRC) Information Elements (RRC) MeasConfig and ReportConfig. These information elements may be previously transmitted to the first and second wireless devices 121, 122 by the home network node 110.

Upon receiving the measurement report from the first wireless device 121, the source network node 110 is notified that the first wireless device 121, which is involved in D2D communication with the second wireless device 122, intends to change the serving cell, i.e., move out of the coverage area. the source network node 110 into the coverage area of the target network node 111.

Action 301b. In response to the measurement report, the source network node 110 sends a handover request to the target network node 111 via the X2 interface. In this case, the source network node 110 may add information to the handover request that the first wireless device 121 is a D2D-capable wireless device and that there is ongoing D2D communication related to the first wireless device 121. This allows the target network node 111 decide whether to receive the first wireless device 121 based on the capabilities of the target network node 111, eg, based on whether it can handle D2D communication and the current network load.

Action 301c. In response to the handover request, the target network node 111 may send an acknowledgment (ACK) of the handover request to the source network node 110. This handover request acknowledgment indicates to the source network node 110 that the target network node 111 is ready to receive the handover of the first wireless device 121. B In some embodiments, the MobilityControllnfo information element may be embedded in this signaling. Otherwise, it will be sent to the first wireless device 121 later to access the target network node 111.

Then, in a step 302 of performing a D2D handover, by a command from the source network node 110, the first wireless device 121 may switch the serving network node to the target network node 111. In this step, in accordance with some embodiments, the primary purpose of the first wireless device 121 is to measure the uplink timing difference between the source network node 110 and the target network node 111 during handover and report it. The uplink timing difference here is the difference between the uplink timing for the source network node 110 and the uplink timing for the target network node 111.

Action 302a. The originating network node 110 may in this case transmit a message indicating to the first and second wireless devices 121, 122 that the D2D communication should be terminated before initiating a handover. In response to receiving this message, the first and second wireless devices 121, 122 may interrupt or temporarily suspend D2D communications between the first and second wireless devices 121, 122.

However, it should be noted that if D2D communication is based on dynamic scheduling that is performed on short time intervals, for example based on the transmission time interval, i.e., 1 ms, then there is no need for independent signaling to stop the D2D communication. The source network node 110 may simply stop scheduling D2D communications. On the other hand, if D2D communication is based on semi-persistent scheduling (SPS), which is performed at long intervals, for example, about 100 ~ 500 ms, it may be necessary to temporarily interrupt or temporarily suspend the semi-persistent scheduling.

In some embodiments, the message may be a semi-persistent scheduling release in a PDCCH message. It can be sent and received by the first and second wireless devices 121, 122 to free up resources, for example, using a shared radio network temporary identifier (RNTI) for D2D communication (D2D_RNTI).

Action 302b. In this action, the source network node 110 may send a message to the first wireless device 121 indicating that the first wireless device 121 should switch the serving network node from the source network node 110 to the target network node 111, i.e., switch the serving cell. Relevant information to perform the handover may be contained in a message, for example, as the MobilityControllnfo information element received by the source network node 110 from the target network node 111. In accordance with some embodiments, this message may also direct the first wireless device 121 to perform uplink timing measurements for the source and target network nodes 110, 111, and to report the uplink timing difference between the source and target network nodes 110, 111. The message, for example, may be an RRC connection reconfiguration message.

Action 302c. Through the RACH procedure with the target network node 111, the first wireless device 121 can retrieve the uplink timing of the target network node 111 via a random access response (RAR) message from the target network node 111. The first wireless device 121 can then compare the uplink timing of the target network node 111 with the uplink timing of the source network node 110 and thereby determine the uplink timing difference between the source and target network nodes 110, 111.

It should be noted that the content of this uplink timing difference may be different. For scheduling coordination between source and target network nodes 110, 111, it may be sufficient to extract an uplink timing difference of the order of the number of subframes.

However, for example, for peer-to-peer acquisition between cells or for coordination of mutual interference, the accuracy of the uplink timing difference may have a higher level of granularity, for example, at the symbol, count, etc. level. Thus, the embodiments of the present invention should not be construed as limited to a particular uplink timing difference quantification scheme.

Action 302d. In this action, the first wireless device 121 may send a message to the target network node 111 indicating a successful handover to the first wireless device 121. This message may also contain a specific uplink timing difference between the source and target network nodes 110, 111, and thereby inform the target network node 111 of the determined uplink timing difference. For example, the message may be an RRC connection reconfiguration complete message.

In D2D scheduling step 303, the source and target network nodes 110, 111 may agree on a D2D communication scheduling scheme, i.e. in which subframes the transmission resources for D2D communication should be allocated, for example, based on the time division between the current cellular mode and the D2D communication and cell timing of source and target network nodes 110, 111, respectively. The resulting D2D scheduling scheme is then sent to both the first and second wireless devices 121, 122 to restart the D2D communication again. It should also be noted that this procedure is applicable to both synchronized and non-synchronized cells.

Actions 303a-303b. In these actions, the source and target network nodes 110, 111 can send cell-to-cell coordination messages to each other via the X2 interface. For example, the messages can be scheduling coordination request messages and scheduling coordination request confirmation messages. The source and destination network nodes 110, 111 need to agree on the timing of the subframes to be used for D2D communication. Otherwise, the source network node 110 may schedule a subframe for D2D communication, while the target network node 111 schedules the same subframe for cellular communication, which would cause a scheduling collision.

It should also be noted that the content of the X2 signaling between the source and target network nodes 110, 111 may be different. For example, it can be a numeric or binary value for each subframe, for example, 0 for a cellular subframe, 1 for a D2D subframe. According to another example, more information may be contained there, for example a value of 2 for a matching subframe. This can be useful as the source network node 110 may have its own preference for subframe allocation for D2D communication.

In addition, the procedure for this agreement may be different. For example, it can be initiated by the source network node 110 or the target network node 111 and accepted / rejected by another of them. Other negotiation procedures can also be contemplated.

Actions 303c-303d. When the D2D scheduling scheme has been negotiated by the source and target network nodes 110, 111, the source and target network nodes 110, 111 may send the D2D scheduling scheme to the second and first wireless devices 121, 122, respectively. This can be done through an SPS procedure, for example, PDDCH SPS activation messages can be used by the source and target network nodes 110, 111.

In response to receiving the D2D scheduling scheme, the first and second wireless devices 121, 122 may restart D2D communication based on the received D2D scheduling scheme. In addition, subsequently, the first and second wireless devices 121, 122 may then, based on the TDD configuration of the D2D bearer, decide on additional aspects of D2D communication such as, for example, resource location, HARQ timing, and so on.

It should be noted that the term "restarted" as used in all embodiments of the present invention is to be interpreted as continuing the D2D communication from the time it was interrupted.

FIG. 4A-4B show a second D2D handover scenario in accordance with some embodiments. FIG. 4A, the first wireless device 121 participates in D2D communication with the second wireless device 122 over the D2D link 140. In this case, the first wireless device 122 is located in a different cell relative to the second wireless device 122, i.e., in the second cell 116 served by the second network node 111. This situation may occur, for example, as a result of the above-described first scenario.

In this second D2D handover scenario, the first wireless device 121 then begins to move from the cellular coverage of its current cell, i.e., the second cell 116 served by the second network node 111, to the cellular coverage of the first cell 115, served by the first network node 110 (as shown by an arrow with a double dashed line). This means that the first wireless device 121 is roaming into the cell of the second wireless device 122.

The second network node 111 in this scenario may be referred to as the source network node, and the first network node 110 may be referred to as the target network node. This may trigger the signaling of the embodiments, described in detail below with reference to FIG. five.

As shown in FIG. 4B, once the signaling shown in FIG. 5 has been completed, the first wireless device 121 will perform a handover from the second network node 111 to the first network node 110. This means that the first wireless device 121 is then located in the first cell 115 and served by the first network node 110. As a result of the signaling in FIG. 5, the first wireless device 121 will also maintain D2D communication with the second wireless device 122 over D2D link 140. Since both the first and second wireless devices 121, 122 are now located in the same cell, i.e., in the first cell 115, the first network node 110 will now form a single D2D network control point and can schedule D2D communications independently.

FIG. 5 shows signaling of some embodiments triggered by the second D2D handover scenario shown in FIG. 4A. Signaling can be described by two main signaling units: a D2D handover prepare stage 501 and a D2D handover perform stage 502.

As shown in FIG. 5, prior to signaling, the first wireless device 121 participates in D2D communication with the second wireless device 122 over a D2D communication link in two different cells. Each of the first and second wireless devices 121, 122 also has an established cellular link with the second and first network nodes 111, 110, respectively, ie, with the source and target network nodes. In this example, the source network node 111 and the target network node 110 are out of sync with each other.

In preparation step 501 for D2D handover, a normal wireless device measurement report by wireless device 121 may initiate a handover procedure for both the source network node 111 and the target network node 110.

Action 501a. The first wireless device 121 transmits the measurement report to the home network node 111. Upon receiving the measurement report from the first wireless device 121, the source network node 111 is notified that the first wireless device 121 that participates in D2D communication with the second wireless device 122 intends to change the serving cell, i.e., moves from the coverage area of the source network node 111 to the coverage area of the target network node 110.

Action 501b. In response to the measurement report, the source network node 111 sends a handover request to the target network node 110 via the X2 interface. In this case, the source network node 111 may add information to the handover request that the first wireless device 121 is a D2D-capable wireless device.

Action 501c. In response to the handover request, the target network node 110 may send an acknowledgment (ACK) of the handover request to the source network node 111. This handover request acknowledgment indicates to the source network node 111 that the target network node 110 is ready to accept the handover of the first wireless device 121.

Then, in a step 502 of executing a D2D handover, by a command from the source network node 111, the first wireless device 121 can switch the serving network node to the target network node 110. However, in this second scenario, the first wireless device 121 does not need to measure and report any difference uplink timing as it moves to the same cell as the second wireless device 122 and under the control of the same network node. This means that there is no longer any difference in uplink timing since both wireless devices are served by the same network node.

Action 502a. The originating network node 111 may transmit a message indicating to the first wireless device 121 that the D2D communication should be terminated before initiating a handover. In response to receiving this message, the first wireless device 121 may interrupt or temporarily suspend D2D communications between the first and second wireless devices 121, 122.

Action 502b. The target network node 110 may transmit a message indicating to the second wireless device 122 that the D2D communication should be terminated before initiating a handover. In response to receiving this message, the second wireless device 122 may interrupt or temporarily suspend D2D communications between the first and second wireless devices 121, 122.

Action 502c. In this action, the source network node 111 may send a message to the first wireless device 121 indicating that the first wireless device 121 should switch the serving network node from the source network node 111 to the target network node 110, i.e., switch the serving cell. For example, the message may be an RRC connection reconfiguration message.

502d action. In this action, the first wireless device 121 can perform a random non-contention or contention channel (RACH) procedure with the target network node 110 without having to retrieve any uplink timing.

Action 502e. In this action, the first wireless device 121 may send a message to the target network node 110 indicating a successful handover of the first wireless device 121. For example, the message may be an RRC connection reconfiguration complete message.

Action 502f. The target network node 110 can now determine a scheduling scheme for D2D communications. The resulting D2D scheduling scheme is then sent to both the first and second wireless devices 121, 122 to restart the D2D communication again. This can be done through the SPS procedure. Then, based on the TDD configuration of the D2D bearer, the first and second wireless devices 121, 122 may decide on resource location, HARQ timing, and so on. for D2D communication.

FIG. 6A-6B show a third D2D handover scenario in accordance with some embodiments. FIG. 6A, the first wireless device 121 participates in D2D communication with the second wireless device 122 over the D2D link 140. The first wireless device 121 in this case is also located in a different cell relative to the second wireless device 122, i.e., in the second cell 116 served by the second network node 110. This situation may occur, for example, as a result of the first scenario described above.

In this third D2D handover scenario, the first wireless device 121 then begins to move from the cellular coverage of its current cell, i.e., the second cell 116 served by the second network node 111, to the cellular coverage of the third cell 117, served by the third network node 112 (as shown by an arrow with a double dashed line). The second network node 111 in this scenario may be referred to as the source network node and the third network node 112 may be referred to as the target network node. This may trigger the signaling of the embodiments, described in detail below with reference to FIG. 7.

As shown in FIG. 6B, once this signaling shown in FIG. 7 has been completed, the first wireless device 121 will perform a handover from the second network node 111 to the third network node 111.

This means that the first wireless device 121 is then located in the third cell 117 and served by the third network node 112. As a result of the signaling in FIG. 7, the first wireless device 121 also communicates D2D with the second wireless device 122 over the D2D link 140, with the second wireless device 122 still located in the first cell 115 and served by the first network node 110.

FIG. 7 shows signaling of some embodiments triggered by the third D2D handover scenario shown in FIG. 6A. The signaling can be described by three main signaling stages: a D2D handover prepare stage 601, a D2D handover perform stage 602, and a D2D scheduling stage 603.

As shown in FIG. 7, prior to signaling, the first wireless device 121 participates in D2D communications with the second wireless device 122 over a D2D link between two different cells, i.e., the second and first cells 116, 115, respectively. Each of the first and second wireless devices 121, 122 also has an established cellular link with the second and first network nodes 111, 110, respectively. In this example, the considered network nodes, i.e., the first, second and third network nodes are not synchronized with each other.

In a D2D handover preparation step 701, a normal wireless device measurement report by the first wireless device 121 may initiate a handover procedure of the source network node 111, the target network node 112, and the first network node 110.

Action 701a. The first wireless device 121 may transmit a measurement report to the home network node 111. Upon receiving the measurement report from the first wireless device 121, the home network node 111 is notified that the first wireless device 121 that participates in D2D communication with the second wireless device 122 is cell 115, intends to change the serving cell, i.e., move from the coverage area of the source network node 111 to the coverage area of the target network node 112.

Action 701b. In response to the measurement report, the source network node 111 sends a handover request to the target network node 112 via the X2 interface. In this case, the source network node 111 may add to the handover request the information that the first wireless device 121 is a D2D-capable wireless device and that there is ongoing D2D communication related to the first wireless device 121. This allows the target network node 112 decide whether to receive the first wireless device 121 based on the capabilities of the target network node 112, such as whether it can handle D2D communication and the current network load.

Action 701c. In response to the handover request, the target network node 112 may send an acknowledgment (ACK) of the handover request to the source network node 111. This handover request acknowledgment indicates to the source network node 111 that the target network node 112 is ready to accept the handover of the first wireless device 121. B In some embodiments, the MobilityControllnfo information element may be embedded in this signaling. Otherwise, it will be sent to the first wireless device 121 later to access the target network node 112.

Action 701d. Further in this action, the originating network node 111 may also send a message to the first network node 110 indicating a temporary release of D2D resources for D2D communication, i.e., indicating to the first network node 110 that the D2D communication should be interrupted or temporarily suspended. This is done prior to initiating the handover of the first wireless device 121.

Then, in a D2D handoff execution step 702, by a command from the source network node 111, the first wireless device 121 may switch the serving network node to the target network node 112. At this stage, in accordance with some embodiments, the primary purpose of the first wireless device 121 is to measure and report the uplink timing difference between the source network node 111 and the target network node 112 during a handover. The uplink timing difference in this case is the difference between the uplink timing for the source network node 111 and the uplink timing for the target network node 112.

Action 702a. In response to the message from the source network node 111 in action 701d, the first network node 110 may send a message indicating to the second wireless device 122 that D2D communication should be terminated before initiating a handover. In response to receiving this message, the second wireless device 122 may interrupt or temporarily suspend D2D communications between the first and second wireless devices 121, 122.

Action 702b. The originating network node 111 may transmit a message indicating to the first wireless device 121 that the D2D communication should be terminated before initiating a handover. In response to receiving this message, the first wireless device 121 may interrupt or temporarily suspend D2D communications between the first and second wireless devices 121, 122. Note that D2D communications may be interrupted by the second wireless device 122, as in step 702a, by the first wireless device 121 as described in this act 702b, or both the first and second wireless devices 121, 122.

Action 702c. In this action, the source network node 111 may send a message to the first wireless device 121 indicating that the first wireless device 121 should switch the serving network node from the source network node 111 to the target network node 112, i.e., switch the serving cell. The relevant information for performing the switch may be contained in a message, for example, as the MobilityControllnfo information element, received by the source network node 111 from the target network node 112, for example via X2 signaling. In accordance with some embodiments, this message may also instruct the first wireless device 121 to perform uplink timing measurements for the source and target network nodes 111, 112 and report the uplink timing difference between the source and target network nodes 111, 112. For example, the message may be an RRC connection reconfiguration message.

Action 702d. Through the RACH procedure with the target network node 112, the first wireless device 121 can retrieve the uplink timing of the target network node 112 via a random access response (RAR) message from the target network node 112. The first wireless device 121 can then compare the uplink timing of the target network node 112 with the uplink timing of the source network node 111, and thereby determine the uplink timing difference between the source and target network nodes 111, 112.

It should be noted that the content of this uplink timing difference may be different. To coordinate scheduling between source and target network nodes 111, 112, it may be sufficient to extract an uplink timing difference of the order of the number of subframes.

Action 702e. In this action, the first wireless device 121 may send a message to the target network node 112 indicating a successful handover of the first wireless device 121. This message may also contain a determined uplink timing difference between the source and target network nodes 111, 112, and thus the determined difference the uplink timing may be reported to the target network node 112. For example, the message may be an RRC connection reconfiguration complete message.

In D2D scheduling step 703, the target network node 112 and the first network node 110 may agree on a scheduling scheme for D2D communication, i.e., in which subframes the transmission resources for D2D communication should be allocated. This may be based, for example, on the division of time between the current cellular communication and the D2D communication mode and the cell timing of the target and first network nodes 112, 110, respectively.

This negotiation can be done through the source network node 111, which can act as a bridge between the target network node 112 and the first network node 110. The resulting D2D scheduling scheme is then sent to both the first and second wireless devices 121, 122 to restart communication again D2D via appropriate network nodes. It should also be noted that this procedure is applicable to both synchronized and non-synchronized cells.

Action 703a-703b. In these actions, the target and the first network nodes 112, 110 can send each other inter-cell coordination messages via the X2 interface. This is done through the originating network node 111, which receives and sends messages onward to the corresponding network node. For example, the messages can be scheduling coordination request messages and scheduling coordination request confirmation messages.

In this case, it should be noted that in this case, the target network node 112 can only know the uplink timing difference between the source and target network nodes 111, 112, but does not know the uplink timing of the first network node 110. However, the source network node 111 knows uplink timing difference between itself and the first network node 110. Therefore, by transmitting this information to the target network node 112, the target network node can determine the uplink timing difference between the target and first network nodes 112, 110.

The target and first network nodes 112, 110 must agree on the timing of the subframes to be used for D2D communication. Otherwise, a D2D scheduling collision may occur, as described earlier.

It should also be noted that the content of the X2 signaling between the target and the first network nodes 112, 110 may be different. For example, it can be a binary value for each subframe, for example, 0 for a cellular subframe, 1 for a D2D subframe. According to another example, more information may be contained there, for example a value of 2 for a matching subframe.

In addition, the procedure for this agreement may be different. For example, it can be initiated by the target network node 112 or the first network node 110 and accepted / rejected by another of them. According to another example, a pre-negotiation procedure may exist between the source and target network nodes to obtain uplink timing differences, or some negotiation procedures may be implemented between the first network node 110 and the source network node 111. Additional negotiation procedures with the same result.

Actions 703c-703d. When the D2D scheduling scheme has been agreed upon by the target and first network nodes 112, 110, the target and first network nodes 112, 110 may send the D2D scheduling scheme to the first and second wireless devices 121, 122, respectively. This can be done through an SPS procedure, for example, PDDCH SPS activation messages can be used by the target and first network nodes 112, 110.

In response to receiving the D2D scheduling scheme, the first and second wireless devices 121, 122 may restart D2D communication based on the received D2D scheduling scheme. In addition, subsequently, the first and second wireless devices 121, 122 can then, based on the TDD configuration of the D2D bearer, decide on additional aspects of D2D communication such as, for example, resource location, HARQ timing, and so on.

With reference now to the flowchart of FIG. 8, an exemplary embodiment of a method performed by a first wireless device 121 for handling D2D communication with a second wireless device 122 during handover of the first wireless device 121 from a source network node 110, 111 to a target network node 111, 112 in a wireless communication network will be described. one hundred.

Here, the method is discussed from the perspective of the first wireless device 121.

The method can comprise the following steps, which can be taken in any suitable order.

Step 801. In this step, the first wireless device 121 terminates the D2D communication. This may be done in response to receiving an indication to abort D2D communications from the originating network node prior to initiating a handover. For example, as described above in steps 302a, 502a, and 702b.

Act 802 In this act, the first wireless device 121 determines the first uplink timing difference as the difference between the uplink timing for the source network node and the uplink timing for the target network node.

In some embodiments, the first wireless device 121 may determine the uplink timing for the target network node as part of a random access procedure performed between the first wireless device 121 and the target network node during a handover. The uplink timing differences, for example, can be determined in magnitude of the order of the number of subframes.

Act 803 Based on the first uplink timing difference, the first wireless device 121 reconfigures D2D communication.

In some embodiments, this may be accomplished by the first wireless device 121 by transmitting the determined first uplink timing difference to the target network node upon completion of the handover. For example, as described above in steps 302d, 502e, and 702e.

In some embodiments, this may be accompanied by the first wireless device 121 also transmitting the second uplink timing difference to the target network node. This may occur when the second uplink timing difference has been determined by the first wireless device 121 for D2D communication, and the second uplink timing difference is the difference between the uplink timing for the original network node and the uplink timing for the third network node. For example, as described in step 702e above.

Then, in response, the first wireless device 121 may receive the D2D communication scheduling scheme from the target network node. The scheduling scheme here indicates the positions in time of the subframes at which transmission resources can be allocated for D2D communication. For example, as described above in steps 303d, 502f and 703d.

Act 804 In this act, the first wireless device 121 restarts the D2D communication in accordance with the reconfiguration in act 803.

With reference now to the flowchart of FIG. 9, an example of embodiments of a method performed by a target network node for processing D2D communication between a first wireless device 121 and a second wireless device 122 during handover of the first wireless device 121 to a target network node from a source network node in a wireless communication network 100 will be described.

In this case, the method is discussed from the point of view of the target network node. The target network node in this case may be the second radio network node 111 in the first D2D handover scenario shown and described above with reference to FIG. 2-3, the first radio network node 110 in the second D2D handover scenario shown and described above with reference to FIG. 4-5, or the third radio network node 112 in the third D2D handover scenario shown and described above with reference to FIG. 6-7.

The method can include the following steps, which can be applied in any suitable order.

Act 901. In this act, the target network node, after completing the handover, receives at least the first uplink timing difference of the first wireless device 121 from the first wireless device 121. For example, as described above in actions 302d, 502e, and 702e. In some embodiments, the target network node may also receive the second uplink timing difference of the first wireless device 121 from the first wireless device 121. For example, as described above in act 702e.

Act 902. In this act, the target network node determines the D2D scheduling scheme based on at least the first uplink timing difference of the first wireless device 121. The first uplink timing difference is the difference between the uplink timing of the first wireless device 121 for the source network node and uplink timing of the first wireless device 121 for the target network node.

In some embodiments, this may be done by the target network node by determining, through communication with the source network node on the X2 interface, the time positions of the subframes at which transmission resources can be allocated for D2D communication. For example, as described above in acts 303a-303b and acts 703a-703b.

In some embodiments, when the target network node has also received the second uplink timing difference of the first wireless device 121 from the first wireless device 121, this may further be done by the target network node also based on the second uplink timing difference of the first wireless device 121. The second the uplink timing difference of the first wireless device 121 in this case may be the difference between the uplink timing of the first wireless device 121 for the source network node and the uplink timing of the first wireless device 121 for the third network node. For example, as described above in steps 703a-703b.

In addition, the determination can also be made by the target network node by communicating with the third network node when the third network node is serving the second wireless device 121. For example, as described above in steps 703a-703b.

Act 903 In this act, the target network node may transmit the D2D communication scheduling scheme to the first wireless device 121. For example, as described above in steps 303d, 502f, and 703d.

With reference now to the flowchart of FIG. 10, an example of an embodiment of a method performed by a source network node for processing D2D communication between a first wireless device 121 and a second wireless device 122 during handover of the first wireless device 121 from a source network node to a target network node in wireless network 100 will be described.

In this case, the method is discussed from the point of view of the original network node. The home network node in this case may be the first radio network node 110 in the first and second D2D handover scenario shown and described above with reference to FIG. 2-5, or the second radio network node 111 in the third D2D handover scenario shown and described above with reference to FIG. 6-7.

The method can comprise the following steps, which can be taken in any suitable order.

Act 1001. In this act, the originating network node sends an indication to terminate the D2D communication to at least the first wireless device 121, 122 before initiating the handover. For example, as described above in steps 302a, 502a, and 702b.

Act 1002. In this act, upon completion of the handover, the source network node determines scheduling schemes for D2D communication based on at least the first uplink timing difference of the first wireless device. The first uplink timing difference is the difference between the uplink timing of the first wireless device 121 for the source network node and the uplink timing of the first wireless device 121 for the target network node.

In some embodiments, this may be accomplished by the target network node by determining, via communication with the target network node via the X2 interface, the time positions of the subframes at which transmission resources can be allocated for D2D communication. For example, as described above in acts 303a-303b and acts 703a-703b.

Act 1003. In this act, the source network node may transmit the D2D communication scheduling scheme to the second wireless device 122. For example, as described above in step 303c and step 703c.

To perform the steps of a method for processing D2D communication with a second wireless device 122 during a handover of a first wireless device 121 from a source network node to a target network node in a wireless communication network 100, the first wireless device 121 may comprise the following configuration shown in FIG. eleven.

FIG. 11 shows a block diagram of embodiments of a first wireless device 121.

The first wireless device 121 includes a processing unit 1110, which may also be referred to as a processing circuitry or processor. The processing unit 1110 may comprise an interrupt / restart unit 1101, a determining unit 1102, a reconfiguration unit 1103, and a transmitting and receiving unit 1104, or be configured to be connected thereto.

Interrupt / restart unit 1101 may be configured to interrupt D2D communication. In some embodiments, this may be done in response to receiving an indication to abort D2D communications from the originating network node prior to initiating a handover. In addition, the interrupt / restart unit 1101 may also be configured to restart the D2D communication when it has been reconfigured.

The determiner 1102 may be configured to determine the first uplink timing difference as the difference between the uplink timing for the source network node and the uplink timing for the target network node. In some embodiments, the transmit and receive unit 1104 may be configured to transmit the determined first uplink timing difference to the target network node upon completion of the handover. Then, in some embodiments, the transmit and receive unit 1104 may receive a D2D communication scheduling scheme from a target network node that indicates the locations in time of subframes at which transmission resources may be allocated for D2D communication.

In some embodiments, determining unit 1102 may also be configured to determine a second uplink timing difference by the first wireless device 121 for D2D communication. In this case, the receiving and transmitting unit 1104 may be further configured to transmit the second uplink timing difference to the target network node. The second uplink timing difference is the difference between the uplink timing for the original network node and the uplink timing for the third network node.

The reconfiguration unit 1103 is configured to reconfigure D2D communication based on the first uplink timing difference.

Embodiments of the present invention for processing D2D communication in the first wireless device 121 may be implemented through one or more processors, such as processing unit 1110, in the first wireless device 121 shown in FIG. 11, together with computer program code for performing the functions and acts of embodiments of the present invention. The above program code may also be provided as a computer program product, for example, as a storage medium containing computer program code for carrying out embodiments of the present invention when loaded into the first wireless device 121. The computer program code, for example, may be provided as program code, which does not change during execution, in the wireless device 121 or on the server and downloaded to the wireless device 121.

The first wireless device 121 may further comprise a memory 1120 comprising one or more memories. Memory 1120 may be configured to be used to store data, such as, for example, information regarding one or more intervals in which the energy of transmission bursts must be increased to a second energy level in order to perform the methods of the present invention when executed on a first wireless device 121.

Those of skill in the art will also understand that the processing unit 1110 and memory 1120 described above may refer to a combination of analog and digital circuits and / or one or more processors configured with software and / or firmware, such as stored in memory. which, when executed by one or more processors, such as processing unit 1110, performs the above execution. One or more of these processors, as well as other digital hardware, can be incorporated into a single application-specific integrated circuit (ASIC), or multiple processors and different digital hardware can be distributed across several separate components, either packaged separately or assembled into a system on microcircuit (SoC).

To perform the steps of a method for processing D2D communication between a first wireless device 121 and a second wireless device 122 during handover of the first wireless device 121 to a target network node from a source network node, the target network node may comprise the following configuration shown in FIG. 12.

FIG. 12 shows a block diagram of embodiments of a target network node. The target network node in this case may be the second radio network node 111 in the first D2D handover scenario shown and described above with reference to FIG. 2-3, the first radio network node 110 in the second D2D handover scenario shown and described above with reference to FIG. 4-5, or the third radio network node 112 in the third D2D handover scenario shown and described above with reference to FIG. 6-7.

The target network node contains a processing block 1210, which may also be referred to as a processing circuit. The processing unit 1210 at the target network node may comprise a determining unit 1201 and a transmitting and receiving unit 1202, or be configured to be coupled thereto.

The receiving and transmitting unit 1202 may be configured to receive at least the first uplink timing difference of the first wireless device 121 from the first wireless device 121 upon completion of the handover. In some embodiments, the transmit / receive unit 1202 may be configured to transmit the D2D communication scheduling scheme to the first wireless device 121. In some embodiments, the transmit / receive unit 1202 may also be configured to receive the second uplink timing difference of the first wireless device 121. from the first wireless device 121.

The determining unit 1201 is configured to determine a D2D communication scheduling scheme based on at least the first uplink timing difference of the first wireless device 121. The first uplink timing difference is the difference between the uplink timing of the first wireless device 121 for the source network node and the timing the uplink of the first wireless device 121 for the target network node. In some embodiments, determining unit 1201 may be configured to determine a scheduling scheme by determining, through communication with a home network node on an X2 interface, the time positions of subframes at which transmission resources may be allocated for D2D communication.

In some embodiments, determining unit 1201 may also be configured to determine a scheduling scheme further based on the second uplink timing difference of the first wireless device 121. The second uplink timing difference of the first wireless device 121 is in this case the difference between the uplink timing the first wireless device 121 for the source network node; and the uplink timing of the first wireless device 121 for the third network node. In some embodiments, determining unit 1201 may also be configured to determine a scheduling scheme by communicating with a third network node when the third network node is serving the second wireless device 122.

Embodiments of the present invention for processing D2D communication at a target network node may be implemented through one or more processors, such as processing unit 1210, at the target network node of FIG. 12, together with computer program code for performing the functions and acts of embodiments of the present invention. The above program code may also be provided as a computer program product, for example, as a storage medium containing computer program code for executing embodiments of the present invention when downloaded to a target network node. One such medium may be in the form of a CD-ROM. However, this is doable with other storage media such as a memory card. Computer program code, for example, can be provided as non-changeable program code at runtime at a target network node or server and downloaded to the target network node.

The target network node can further comprise memory 1220 containing one or more memory blocks. Memory 1220 can be configured to be used to store data, such as, for example, information regarding one or more intervals in which the energy of transmission packets must be increased to a second energy level in order to perform the methods of the present invention when executed at a target network node.

Those of skill in the art will also understand that processing unit 1210 and memory 1220 described above may refer to a combination of analog and digital circuits and / or one or more processors configured with software and / or firmware, such as stored in memory. which, when executed by one or more processors, such as processing unit 1210, performs the above execution. One or more of these processors, as well as other digital hardware, can be incorporated into a single application-specific integrated circuit (ASIC), or multiple processors and different digital hardware can be distributed across several separate components, either packaged separately or assembled into a system on microcircuit (SoC).

To perform the steps of a method for processing D2D communication between a first wireless device 121 and a second wireless device 122 during handover of the first wireless device 121 from a source network node to a target network node, the source network node may comprise the following configuration shown in FIG. 13.

FIG. 13 shows a block diagram of embodiments of a source network node. The home network node in this case may be the first radio network node 110 in the first and second D2D handover scenarios shown and described above with reference to FIG. 2-5, or the second radio network node 111 in the third D2D handover scenario shown and described above with reference to FIG. 6-7.

The target network node includes a processing unit 1310, which may also be referred to as a processing circuit. The processing unit 1310 at the target network node may comprise a determining unit 1301 and a transmitting and receiving unit 1302, or be configured to be coupled thereto.

The receiving and transmitting unit 1202 may be configured to transmit an indication to terminate the D2D communication to at least the second wireless device prior to initiating a handover. In some embodiments, the transmit and receive unit 1202 may be configured to transmit the D2D communication scheduling scheme to the second wireless device 122.

The determining unit 1201 is configured to determine, upon completion of the handover, a D2D communication scheduling scheme based on at least the first uplink timing difference of the first wireless device 121. The first uplink timing difference is the difference between the uplink timing of the first wireless device 121 for the initial network node and uplink timing of the first wireless device 121 for the target network node. In some embodiments, determining unit 1201 may be configured to determine a scheduling scheme by determining, by communicating with a target network node via an X2 interface, the time positions of subframes at which transmission resources may be allocated for D2D communication.

Embodiments of the present invention for processing D2D communication at a home network node may be implemented through one or more processors, such as a processing unit 1310 in the home network node shown in FIG. 13, together with computer program code for performing the functions and acts of embodiments of the present invention. The aforementioned program code may also be provided as a computer program product, for example, as a storage medium containing computer program code for carrying out embodiments of the present invention when downloaded to a home network node. One such medium may be in the form of a CD-ROM. However, this is doable with other storage media such as a memory card. Computer program code, for example, can be provided as non-changeable program code at runtime at a source network node or server and downloaded to a target network node.

The source network node may further comprise memory 1320 containing one or more memory blocks. Memory 1320 may be configured to be used to store data, such as, for example, information regarding one or more intervals in which the energy of the transmission packets must be increased to a second energy level in order to perform the methods of the present invention when executed at a source network node.

Those skilled in the art will also understand that the processing unit 1310 and memory 1320 described above may refer to a combination of analog and digital circuits and / or one or more processors configured with software and / or firmware, such as stored in memory. which, when executed by one or more processors, such as processing unit 1310, performs the above execution. One or more of these processors, as well as other digital hardware, can be incorporated into a single application-specific integrated circuit (ASIC), or multiple processors and different digital hardware can be distributed across several separate components, either packaged separately or assembled into a system on microcircuit (SoC).

It should be noted that although the target network node and the source network node have been described above as separate entities for the sake of clarity, the network node can usually be implemented as being able to be both the target network node and the source network node, depending on which of the first, second and the third D2D handover scenarios is the current case. Thus, in this case, processing unit 1210 and memory 1220 may coincide with processing unit 1310 and memory 1320.

The embodiments of the present invention are not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents can be used. Thus, the above described embodiments should not be construed as limiting.

Claims (38)

1. A method of handling device-to-device (D2D) communication performed by a first wireless device (121) with a second wireless device (122), the second wireless device being served by a first network node, during a handover of the first wireless device (121) from a source network node (110, 111), and the source network node may be the first network node or another network node, to the target network node (110, 111, 112) in the wireless network (100), characterized in that the method comprises the steps of which interrupt (801) D2D communication and determining (802) the first uplink timing difference as the difference between the uplink timing for the source network node (110, 111) and the uplink timing for the target network node (110, 111, 112); reconfiguring (803) the D2D communication based on the first uplink timing difference, and restarting (804) the D2D communication, in accordance with the reconfiguration, with the second wireless device, the second wireless device being served by the first network node after the handover, wherein the reconfiguration step (803) also contains the steps at which: transmitting the determined first uplink timing difference to the target network node (110, 111, 112) after the handover has been completed; and receiving a scheduling scheme for D2D communication from a target network node (110, 111, 112), the scheduling pattern indicating positions in time of subframes at which transmission resources may be allocated for D2D communication. 2. A first wireless device (121) for handling device-to-device (D2D) communication with a second wireless device (122), the second wireless device being served by a first network node, during a handover of the first wireless device (121) from a source network node (110, 111), where the source network node may be the first network node or another network node, to the target network node (110, 111, 112) in the wireless network (100), characterized in that the first wireless device (121) comprises a processing circuit (1110) configured to: interrupt D2D communication; determine the first uplink timing difference as the difference between the uplink timing for the source network node (110, 111) and the uplink timing for the target network node (110, 111, 112); reconfigure D2D communication based on the first uplink timing difference by transmitting the determined first uplink timing difference to the target network node (110, 111, 112) after the handover has been completed, and receiving a scheduling scheme for D2D communication from the target network node (110, 111, 112), where the scheduling pattern indicates positions in time of subframes at which transmission resources can be allocated for D2D communication; and restart the D2D communication in accordance with the reconfiguration with the second wireless device, the second wireless device being served by the first network node after the handover. 3. The first wireless device (121) of claim 2, wherein the processing circuitry (1110) is also configured to terminate D2D communications in response to receiving an indication to terminate D2D communications from a source network node (110, 111) prior to initiating a handover. 4. The first wireless device (121) of claim 3, wherein the processing circuitry (1110) is also configured to transmit the second uplink timing difference to the target network node (110, 111, 112) when the second uplink timing difference was determined by the first wireless device (121) for D2D communication, the second uplink timing difference being the difference between the uplink timing for the source network node (110, 111) and the uplink timing for the third network node. 5. A method performed by a target network node (110, 111, 112) of processing a device-to-device (D2D) communication between a first wireless device (121) and a second wireless device (122), the second wireless device being served by the first network node, during the handover of the first wireless device (121) to the target network node (110, 111) from the source network node (111, 112), where the source network node may be the first network node or another network node, in the wireless network (100) , the second wireless device being served by the first network node after the handover, the method comprising the steps of upon completion of the handover, receive (901) at least a first uplink timing difference of the first wireless device (121) from the first wireless device (121); and determine (902) a scheduling scheme for D2D communication based on at least the first uplink timing difference of the first wireless device (121), the first uplink timing difference being the difference between the uplink timing of the first wireless device (121) for the original network node (110, 111) and uplink timing of the first wireless device (121) for the target network node (110, 111, 112); and transmit (903) the D2D communication scheduling scheme to the first wireless device (121), wherein the step of determining (902) the scheduling scheme also comprises determining, by communicating with the source network node (110, 111) over the X2 interface, the time positions of the subframes in which transmission resources can be allocated for D2D communication. 6. A target network node (110, 111, 112) for handling device-to-device (D2D) communication between a first wireless device (121) and a second wireless device (122), the second wireless device being served by the first network node during transmission serving the first wireless device (121) to the target network node (110, 111) from the source network node (111, 112), and the source network node may be the first network node or another network node in the wireless communication network (100), the second the wireless device is served by the first network node after handover, characterized in that the target network node (110, 111, 112) contains processing circuitry (1210), configured to, upon completion of the handover: receive at least a first uplink timing difference of the first wireless device (121) from the first wireless device (121); determine a scheduling scheme for D2D communication based on at least a first uplink timing difference of the first wireless device (121), the first uplink timing difference being the difference between the uplink timing of the first wireless device (121) for the source network node (110 , 111) and the uplink timing of the first wireless device (121) for the target network node (110, 111, 112) and the position in time of subframes at which transmission resources can be allocated for D2D communication, where the positions in time are determined by communication with the original network node (110, 111) via the X2 interface; and transmit the D2D communication scheduling scheme to the first wireless device (121). 7. The target network node (110, 111, 112) of claim 6, wherein the processing circuit (1210) is also configured to receive the second uplink timing difference of the first wireless device (121) from the first wireless device (121) and determine a scheduling scheme further based on the second uplink timing difference of the first wireless device (121), wherein the second uplink timing difference of the first wireless device (121) is the difference between the uplink timing of the first wireless device (121) for the source network node (110 , 111) and uplink timing of the first wireless device (121) for the third network node. 8. The target network node (110, 111, 112) of claim 7, wherein the processing circuit (1210) is also configured to determine a scheduling scheme by communicating with the third network node when the third network node is serving the second wireless device (122). 9. A method performed by a source network node (110, 111) processing a device-to-device (D2D) communication between a first wireless device (121) and a second wireless device (122), the second wireless device being served by the first network node, during handover of the first wireless device (121) from the source network node (110, 111), where the source network node may be the first network node or another network node, to the target network node (110, 111, 112) in the wireless network (100) , and the second wireless device is served by the first network node after the handover, characterized in that the method comprises the steps of transmitting (1001) an indication to terminate the D2D communication to at least the second wireless device (121, 122) before initiating the handover; upon completion of the handover, a scheduling scheme for D2D communication is determined (1002) based on at least the first uplink timing difference of the first wireless device (121), the first uplink timing difference being the difference between the uplink timing of the first wireless device (121 ) for the source network node (110, 111) and uplink timing of the first wireless device (121) for the target network node (110, 111, 112); and transmit (1003) the D2D communication scheduling scheme to the second wireless device (121), wherein the step of determining (1002) the scheduling scheme also comprises determining, by communicating with the target network node (111, 112) via the X2 interface, the time positions of the subframes in which transmission resources can be allocated for D2D communication. 10. Source network node (110, 111) for handling device-to-device (D2D) communication between the first wireless device (121) and the second wireless device (122), the second wireless device being served by the first network node, during the handover of the first wireless device (121) from the source network node (110, 111), where the source network node can be the first network node or another network node, to the target network node (110, 111, 112) in the wireless network (100), the second the wireless device is served by the first network node after the handover, characterized in that the source network node (110, 111) contains a processing circuit (1310) configured to transmit an indication to terminate the D2D communication to at least the second wireless device (122) prior to initiating the handover; determine, upon completion of the handover, a scheduling scheme for D2D communication based on at least a first uplink timing difference of the first wireless device (121), the first uplink timing difference being the difference between the uplink timing of the first wireless device (121) for the original network node (110, 111) and the uplink timing of the first wireless device (121) for the target network node (110, 111, 112), and the position in time of subframes at which transmission resources can be allocated for D2D communication, with positions in the time is determined by communication with the target network node (110, 1112) via the X2 interface; and transmit the D2D communication scheduling scheme to the second wireless device (122).

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