WO2015112070A1 - Methods and means for handling configuration updates in device-to-device (d2d) communication - Google Patents

Abstract

Embodiments presented in this disclosure relate to Device-to-Device (D2D) communications in a wireless telecommunications network. In particular, embodiments herein relate to the handling of configuration updates in D2D communications. In one example embodiment, there is provided a method performed by a first user equipment, UE, which is adapted for D2D communications. The first UE transmits (601), to a second UE, an information message comprising an indication to the second UE that a first configuration will be replaced by a second, updated, configuration. Also, the first UE replaces (602) the first configuration with the second, updated, configuration after said transmission (601) of the information message.

Description

METHODS AND MEANS FOR HANDLING CONFIGURATION UPDATES IN DEVICE- TO-DEVICE (D2D) COMMUNICATION

TECHNICAL FIELD

Embodiments presented herein relate to Device-to-Device (D2D) communications in a wireless telecommunications network. In particular, embodiments herein relate to the handling of configuration updates in D2D communications. More specifically,

embodiments described herein relate to methods and means (e.g. user equipments (UEs)) for handling of configuration updates in D2D communications.

BACKGROUND

This section is intended to provide a background to the various embodiments of the technology that are described in this disclosure. The description in this section may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description or claims of this disclosure and is not admitted to be prior art by its mere inclusion in this section.

Traditional cellular communication in a wireless telecommunication network or terrestrial radio access networks is performed via radio links between user equipments, UEs, and radio base stations, such as, e.g. an eNodeB in an Long Term Evolution (LTE) system. However, when two UEs are in the vicinity of each other, then direct D2D communication may be considered. This type of communication between UEs may be dependent on synchronization information from either a radio base station or a different kind of radio node. One example of such a different kind of radio node is a cluster head. A cluster head may, for example, be a UE with dedicated capability providing local synchronization information, or a UE with dedicated capability and thereby enabled to relay synchronization information from a different synchronization source.

Clustering is a well-studied research area for ad-hoc networks. For example, "SURVEY OF CLUSTERING SCHEMES FOR MOBILE AD HOC NETWORKS", IEEE

Communications Surveys & Tutorials, Jane Y. Yu and Peter H. J. Chong, First Quarter 2005 provides a good overview of the current status in this field. It may be seen that a common fundamental procedure to enable all the different algorithms is beacon exchange between the peers. This beacon exchange carries a specific 'metric', which 'metric' is based on which of the devices that can decide whether to act as a cluster head itself (e.g., if it has the largest metric in the proximity area), or to act as a slave of a nearby cluster head (e.g., if the metric itself is smaller than the metric of the nearby neighboring device).

This metric may be defined according to different capabilities. Some examples of these capabilities are: whether radio access network (RAN) coverage is available (e.g. when considering the partial RAN coverage case); the different levels of maximum transmission, TX, power; the number of D2D connections the device is able to handle, etc. The metric may be used so that the devices in the wireless communication system may have a common observation of which device should be selected as the cluster head. The message exchange between devices in the cluster may either be active or passive. Active message exchange may here refer to explicit clustering control signaling between the devices, while passive message exchange may here refer to clustering via broadcast control signaling.

Figure 1 shows an example of wireless communication system in which synchronization information for D2D communication between UEs is broadcasted by radio base stations, e.g. evolved Node's (eNodeBs or eNBs), etc. This is shown by the fully drawn, continuous arrows in Figure 1. Also, in the wireless communication system of Figure 1 ,

synchronization information for D2D communication between UEs is also broadcasted by a cluster head (CH). This is shown by the dashed-dotted arrows in Figure 1. Furthermore, in the wireless communication system of Figure 1 , synchronization information for D2D communication between UEs is also broadcasted by UEs having a ProSe-capability

(where ProSe stands for Proximity Services). This is shown by the dotted arrows in Figure 1. Here, it may be noted that the lower-left UE in cell 2 receives synchronization information as a Single-Frequency Network (SFN) combination of multiple identical sync signals relayed by D2D-enabled UEs within cell 1. The role of a CH may also be seen as a synchronization information provider to UEs in the vicinity or proximity of the CH, e.g. cluster 1 in Figure 1. An example of this is further described in the 3GPP standard document R1 -134720 "Synchronization Procedures for D2D Discovery and

Communication". LTE D2D scenarios currently studied in 3GPP may be grouped in the following categories: 1) in-network (or "in coverage" (IC)), 2) out-of-network (or "out-of-coverage" (OOC)), and 3) partial-network (or, Partial coverage). In IC scenarios, all participating UEs are within network coverage. In OOC scenarios, all participating UEs are outside network coverage. Finally, in partial-network scenarios, some participating UEs are within coverage and some participating UEs are out-of-coverage. For the IC scenario, the synchronization reference is generally provided by the base station, e.g. an eNB. Also, the D2D resource pool (i.e. a set of resources to be used for transmission and/or reception for D2D purpose) is generally signaled by the base station to indicate the resources used for D2D. For the OOC D2D scenario the synchronization reference is generally provided by a CH and the D2D resource pool could be either broadcasted by the CH (in synchronization packet, cf. Figure 2) or be pre-configured.

Figure 2 shows an example of a broadcast of synchronization information, wherein the synchronization information may comprise a synchronization signal and a synchronization message as is also described in the 3GPP standard document R1 -134720

"Synchronization Procedures for D2D Discovery and Communication". These may typically be transmitted with different periodicities. When a UE is about to transmit data, the UE may first scan for synchronization signals broadcasted from CHs or radio base stations. If the UE detects a synchronization signal, the data transmission from the UE may be related to this detected synchronization signal, possibly also based on a transmission resource pool information from the CH or radio base station. Furthermore, a UE that has detected a synchronization source, such as, for example, a radio base station or a CH, may forward such synchronization information by acting as a synchronization source relay node. If the UE does not detect any

synchronization signal, the UE may initiate synchronization signal transmission itself and relate the data transmission to the transmitted synchronization signal. The inventors have realized that existing solutions for handling configuration updates (e.g. when switching from a first (e.g. old) configuration to a second, updated (e.g. new), configuration) in D2D scenarios may be inadequate. For example, a D2D UE that is currently transmitting (e.g. relaying) synchronization information may need to change, thus update, its direct transmission configuration according to a TX re-configuration.

Another example scenario is when a UE which is participating in D2D and which is furthermore in RRC Connected Mode (RRC is an abbreviation for Radio Resource Control) performs a handover (HO) and direct signals (or channels) are re-configured, and thus changed. If, or when, the configuration updates in such D2D scenarios are handled inadequately this may lead to unnecessary service disruption and/or unnecessary latency.

SUMMARY

It is in view of these considerations and others that the various embodiments of this disclosure have been made. It is therefore a general object of the embodiments disclosed herein to improve the handling of configuration updates in D2D scenarios.

According to an aspect of embodiments disclosed herein, this general object is addressed by a method according to the independent claim 1. According to another aspect of embodiments disclosed herein, the general object is addressed by a first UE according to the independent claim 9. According to yet another aspect of embodiments disclosed herein, the general object is addressed by a method according to the independent claim 17. According to still another aspect of embodiments disclosed herein, the general object is addressed by a second UE according to the independent claim 25.

Thus, and according to one of its aspects, the technology disclosed herein concerns a method performed by a first UE, which is adapted for D2D communications. The method comprises transmitting, to a second UE which is also adapted for D2D communications, an information message comprising an indication to the second UE that a first configuration will be replaced by a second, updated, configuration. The method also comprises replacing the first configuration with the second, updated, configuration after said transmitting of the information message.

According to another aspect, the technology disclosed herein concerns a first UE adapted for D2D communications. The first UE comprises means adapted to transmit, to a second UE which is also adapted for D2D communications, an information message comprising an indication to the second UE that a first configuration will be replaced by a second, updated, configuration. The first UE also comprises means adapted to replace the first configuration with the second, updated, configuration after transmission of the information message. According to still another aspect, the technology disclosed herein concerns a method performed by a second UE, which is adapted for D2D communications. The method comprises receiving, from a first UE which is also adapted for D2D communications, an information message comprising an indication to the second UE that a first configuration will be replaced by a second, updated, configuration.

According to a further aspect, the technology disclosed herein concerns a second UE adapted for D2D communications. The second UE comprises means adapted to receive, from a first UE which is also adapted for D2D communications, an information message comprising an indication to the second UE that a first configuration will be replaced by a second, updated, configuration.

DETAILED DESCRIPTION

The technology will now be described more fully hereinafter. The technology may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the technology to those persons skilled in the art. Like reference numbers refer to like elements or method steps (or actions) throughout the description.

A general object of the technology disclosed herein to improve the handling of

configuration updates in D2D scenarios.

According to an aspect of the technology disclosed herein, this general object is addressed by a method performed by a first UE which is adapted for D2D. The first UE transmits a first configuration message related to a first configuration to a second UE (i.e. another UE) that is also adapted for D2D communication. The first UE also transmits a second configuration message related to a second, updated, configuration to the second UE. In some embodiments, the first and second configuration messages may be transmitted simultaneously, or substantially simultaneously. According to another aspect of embodiments disclosed herein, the earlier-mentioned general object is addressed by a corresponding method performed by the second UE, which is adapted for D2D communications. The second UE receives a first configuration message related to the first configuration from the first UE, which is also adapted for D2D communications. Furthermore, the second UE receives the second configuration message related to the second, updated, configuration from the first UE. In some embodiments, the first and second configuration messages may be received simultaneously, or substantially simultaneously. According to still another aspect of the technology disclosed herein, the earlier-mentioned general object is addressed by a method performed by a first UE, which is adapted for D2D. The first UE transmits, to a second UE (i.e. another UE) which is also adapted for D2D communications, an information message comprising an indication to the second UE that a first configuration will be replaced by a second, updated, configuration. According to yet another aspect of embodiments disclosed herein, the earlier-mentioned general object is addressed by a corresponding method performed by the second UE, which is adapted for D2D communications. The second UE receives, from the first UE (which is also adapted for D2D communications), an information message comprising an indication to the second UE that a first configuration will be replaced by the second, updated, configuration.

According to still a further aspect of the technology disclosed herein, the earlier- mentioned general object is addressed by a method performed by a network control node (or control node), which is adapted for D2D communications. The network control node transmits, to a first UE, an informative message comprising informative information related to a second, updated, configuration.

According to yet another aspect of the technology disclosed herein, the earlier-mentioned general object is addressed by a first UE adapted for D2D communications. The first UE comprises means adapted to transmit a first configuration message related to a first configuration to a second UE, which second UE is also adapted for D2D communications. The first UE also comprises means adapted to transmit a second configuration message related to a second, updated, configuration to said second UE. Said means are also adapted to transmit the first and second configuration messages simultaneously, or substantially simultaneously. According to yet another aspect of embodiments disclosed herein, the earlier-mentioned general object is addressed by a corresponding second UE adapted for D2D communications. The second UE comprises means adapted to receive the first configuration message related to the first configuration from a first UE, which first UE is also adapted for D2D communications. The second UE also comprises means adapted to receive the second configuration message related to the second, updated, configuration from the first UE. Said means are further adapted to receive the first and second configuration messages simultaneously, or substantially simultaneously.

According to yet another aspect of the technology disclosed herein, the earlier-mentioned general object is addressed by a first UE adapted for D2D communications. The first UE comprises means adapted to transmit, to a second UE (which is also adapted for D2D communications), an information message comprising an indication to the second UE that a first configuration will be replaced by a second, updated, configuration. According to still a further aspect of embodiments disclosed herein, the earlier-mentioned general object is addressed by a corresponding second UE adapted for D2D communications. The second UE comprises means adapted to receive, from the first UE (which is also adapted for D2D communications), an information message comprising an indication to the second UE that the first configuration will be replaced by the second, updated, configuration. According to yet another aspect of the technology disclosed herein, the earlier-mentioned general object is addressed by a network control node (or control node) adapted for D2D communications. The network control node comprises means adapted to transmit, to a first UE, an informative message comprising informative information related to a second, updated, configuration.

In the following, various detailed example embodiments will be explained in further detail: Example Scenario 1

There exist various reasons why configuration updates may be needed, or desired. In a first scenario, a D2D UE that is currently transmitting (e.g. relaying) synchronization information may need to change, thus update, its direct transmission configuration according to a TX re-configuration. The re-configuration may include, but is not limited to, the following: - Changing the synchronization reference

Changing the resource allocation of any direct signal/channel

Changing content of the broadcast control information

Changing transmission format of a direct broadcast control channel

Moving from in coverage (IC) to out of coverage (OOC), and vice versa If there is no information of the re-configuration at a receiving D2D UE, this may generally cause service disruption and/or latency. For example, if there is a change of the synchronization, the transmitting D2D UE will transmit synchronization signals according to the new synchronization source, while the receiving D2D UE will generally fail to detect the synchronization signal (SS) since it has no information about the new, updated, SS. This may cause service discontinuity. The receiving D2D UE will thus have to blind search for new SS's. In turn, this may result in additional latency. The proposed embodiments are as follows: Figure 3 shows a flowchart of a method 300 performed by a first UE (i.e. UE-A, see Figure 5), which first UE is adapted for D2D communications. The first UE transmits 301 a first configuration message related to a first configuration to a second UE (i.e. another UE, e.g. UE-B), which second UE is also adapted for D2D communication. The first configuration message may comprise synchronization information related to the first configuration and/or broadcast information related to the first configuration. If the first configuration message comprises both the synchronization information related to the first configuration and the broadcast information related to the first configuration, it should be appreciated that the synchronization information related to the first configuration and broadcast information related to the first configuration may be transmitted simultaneously, e.g. essentially at the same time. The first UE also transmits 302 a second configuration message related to a second, updated, configuration to the second UE. The second configuration message may comprise synchronization information and/or broadcast information related to the second configuration. Similar to the first configuration message, if the second configuration message comprises both the synchronization information related to the second configuration and the broadcast information related to the second configuration, it should be appreciated that the synchronization information related to the second configuration and the broadcast information related to the second configuration may be transmitted simultaneously, e.g. essentially at the same time. Although the method steps or actions 301 and 302 are schematically illustrated to occur sequentially in figure 3 it is to be understood that the first and second configuration messages may be transmitted simultaneously (or substantially simultaneously) to the second UE. The expression "simultaneously" or "substantially simultaneously" as used herein means "at the same time" or "essentially at the same time". Thus, in this context it should be appreciated by those skilled in the art that the transmissions of the first and second configuration messages may be performed essentially at the same time. Or said differently, the first and second configuration messages may be transmitted to the second UE during a same period of time. This period of time may be pre-defined. In some embodiments, the transmission 301 of the first configuration message and the transmission 302 of the second configuration message are performed during a transition period, or transition phase.

Figure 4 shows a flowchart of a corresponding method 400 performed by the above- mentioned second UE (UE-B, see Figure 5). The first configuration message related to the first configuration is received 401 from the above-mentioned first UE. Also, the second configuration message related to the second, updated, configuration is received 402 from the first UE. The first and second configuration messages may be received

simultaneously, or substantially simultaneously. In other words, the first and second configurations may be received essentially at the same time at the receiving UE, i.e. the second UE.

This embodiment is also illustratively depicted in Figure 5. Figure 5 is a schematic signaling diagram showing example signaling according to various example

embodiments.

More particularly, and according to some embodiments, it is proposed that (e.g., at least during a certain transition phase) the first UE (i.e. UE-A) transmits (e.g. simultaneously) sync information and/or broadcast info according to both the new and the old

configurations. By doing so, the receiving UE (i.e. UE-B) has sufficient time to blindly detect the new (thus updated) configuration. One example is shown in figure 5. Please note that control node 1 and/or control 2 may be either a base station (e.g. eNB) or a CH. The first UE (UE-B) may be in the coverage of control node 1 , control node 2 or even out of coverage. The sync signal/channel broadcasted by the first UE, i.e. UE-A, (denoted sync signal/channel 3 in Figure 5) may have the same or different content as compared with the sync signal/channel received from control node 1. If there is a re-configuration at the first UE (e.g. a UE-A handover to control node 2 as is depicted in Figure 5), a message is broadcasted or transmitted from the first UE (i.e. UE-A) to indicate the reconfiguration to the second UE (i.e. UE-B). For example, both sync signal/channel 3 (e.g., as derived from sync signal 1 even if it may have different content) and sync

signal/channel 4 (e.g., as derived from sync signal 2 even if it may have different content) may be broadcasted by the first UE (i.e. UE-A). Note that the signaling between control nodes related to the handover procedure is not shown in figure 5.

In some embodiments, signaling may be provided by signals/channels (e.g., PD2DSCH (Physical D2D Synchronization Channel), D2DSS (D2D Synchronization Channel), SA Scheduling Assignment), and/or any Control Channel) informing the receiving UEs that the associated configuration will cease soon. Different techniques may be used for signaling that the configuration is going to be ceased. In some embodiments, signaling is provided by signals/channels (e.g., PD2DSCH, D2DSS, any Ctrl channel) informing the receiving UEs that the associated old

configuration will be replaced by another indicated configuration.

In some embodiments, signaling is provided by signals/channels (e.g., PD2DSCH, D2DSS, any Ctrl channel) informing the receiving UEs about the resource and/or format of the new configuration.

In some embodiments, the old configuration may for example be faded out with power over a certain time (the time may be signaled by the network or decided by the device autonomously), and the new configuration may be faded in or switched on immediately, or substantially immediately.

Turning now to Figure 6, a flowchart of a method 600 performed by the first UE (i.e. UE-A, see Figure 5) is illustrated. The first UE transmits 601 , to the second UE (i.e. UE-B), an information message comprising an indication to the second UE that a first configuration will be replaced by a second, updated, configuration. The information message may also comprise information about the time when the first configuration will be replaced by the second, updated, configuration. Furthermore, the method 600 may additionally comprise replacing 602 the first configuration with the second, updated, configuration after the transmission 601 of the information message. The replacement 602 may be done seamlessly, e.g. without overlap.

Figure 7 shows a flowchart of a corresponding method 700 performed by the second UE (UE-B). The second UE (i.e. UE-B) receives 701 (from the first UE (UE-A)) the information message comprising the indication to the second UE that a first configuration will be replaced by a second, updated, configuration. Furthermore, the second UE (i.e. UE-B) may subsequently replace 702 the first configuration with the second, updated, configuration. This may be done at a time indicated by the received information message. The embodiments described with respect to figures 6 and 7, respectively, may

advantageously be combined with the embodiments described in connection with figures 3, 4 and 5, respectively.

More particularly, and according to some embodiments, the first UE (i.e. UE-A) may switch from the old to the new configuration, without overlap. Prior to this switching, signaling may however be provided by signals/channels (e.g., PD2DSCH, D2DSS, and/or any Control (ctrl) Channel) informing the receiving UEs that the associated old

configuration will be replaced by another indicated configuration. In some embodiments, signaling may be provided by signals/channels (e.g., PD2DSCH, D2DSS, any ctrl channel) informing the receiving UEs of the switching time.

In some embodiments, signaling may be provided by signals/channels (e.g., PD2DSCH, D2DSS, any ctrl channel) informing the receiving UEs about the resource/format of the new configuration.

In some embodiments, signaling may be provided by signals/channels (e.g., PD2DSCH, D2DSS, any ctrl channel) informing the receiving UEs about the resource offset of the new configuration compared to the old configuration.

In at least some of the embodiments described so far, the signaling could be either explicitly or implicitly carried by signals/channels, e.g.:

- Explicitly: this signaling may e.g. be coded in the PHY (physical) channel explicitly, e.g., in the PD2DSCH or in the data and/or control channel;

- Implicitly: this information may e.g. be piggy-backed in the D2DSS, e.g., using a different format and/or resource location.

Example Scenario 2

As mentioned earlier, there exist various reasons why configuration updates may be needed, or desired. In a second scenario, a UE which is participating in D2D communications and which is furthermore in RRC Connected Mode performs a HO and direct signals (or channels) may need to be re-configured, and thus changed.

The HO may occur when a D2D UE moves between cells (or clusters). For example, a transmitting D2D UE moves from:

1) the coverage of one base station (e.g. eNB) to another base station (e.g. eNB);

2) from one cell to another cluster,

3) from one cluster to another cell, or

4) from one cluster to another cluster.

In this scenario, the synchronization source (e.g., as timing reference for D2D

communication), the resource of any direct signal/channel, the content of the broadcast control information may be different, which may thus trigger a re-configuration.

Common to at least some of the following embodiments is the fact that the new

configuration may be signaled from the target eNB to the source eNB as part of the handover signaling. In particular, for the case of X2 handover, the target eNB may include the new configuration in the Target eNB to Source eNB Transparent Container IE, sent to the source eNB in the X2AP HANDOVER REQUEST ACKNOWLEDGE message. For the case of S1 handover, the target eNB may include the new configuration in the Target to Source Transparent Container IE, sent to the MME (Mobility Management Entity) in the S1AP HANDOVER REQUEST ACKNOWLEDGE message. The MME may then include the Target to Source Transparent Container IE in the S1 HANDOVER COMMAND message to the source eNB.

The new configuration may be added as an extension to the RRC HandoverCommand message generally included in the Target eNB to Source eNB Transparent Container IE or in the Target to Source Transparent Container IE (for the case of X2 or S1 handover, respectively) or separately from the RRC HandoverCommand message (in which case it may be separately encoded before being added to the transparent containers mentioned above).

Figure 8 shows a flowchart of a method 800 performed by the control node (e.g. Control Node 1 , see Figure 5). The control node may be adapted for D2Dcommunications. An informative message comprising informative information related to a second, updated, configuration is transmitted 801 to the earlier-mentioned first UE (e.g. UE-A, cf. Figure 5). The transmission 801 of the informative message may for example be performed while a first configuration is in use. Moreover, the informative message may additionally comprise indication about the time when said first configuration is to be replaced by the second, updated, configuration.

Figure 9 shows a flowchart of a corresponding method 900 performed by the first UE (UE- A). The first UE receives 901 the above-mentioned informative message comprising informative information related to a second, updated, configuration. Subsequently, the first UE may advantageously proceed by performing the method 300 and/or method 600 described hereinabove in connection with figures 3 and 6, respectively.

According to some embodiments, the receiving D2D UE may receive assistance signals from a transmitting D2D UE (or from the network, if a network connection is available), so that the receiving D2D UE may track the new configuration and get the resource of discovery messages, scheduling assignments, and/or data communication without necessarily interrupting the D2D communication.

In some embodiments, the receiving D2D UEs may optimize their receivers (e.g., DRX cycles) during herein described signaled reconfiguration in order to promptly acquire the synchronization reference associated with the new configuration. In more detail, receiving D2D UEs may be adapted to wake up from DRX and start searching for the new D2DSS, receiving broadcasted control information and complete the new sync procedure. The new sync searching operation may, e.g., be triggered earlier than the assistance info from the transmitting D2D UE, considering that the receiving D2D UE may receive the relayed D2DSS from UEs in the neighboring cell or cluster, so that it may reduce the re- connection latency.

With reference to fig. 10, an example implementation of the first UE (i.e. UE-A) 1000 will be described. As can be seen, the first UE 1000 may comprise a communication interface or radio circuitry 1010. The communication interface 1010 may comprise a transmitter (Tx), or transmitter circuitry. The communication interface 1010 may also comprise a receiver (Rx), or receiver circuitry. Furthermore, the first UE 1000 may comprise a processor or processing circuitry 1020. Still further, the first UE 1000 may comprise one or more memories 1030. The memory 1030 may comprise instructions executable by the processor 1020, whereby the first UE 1000 is operative to initiate the transmission, by means of the transmitter 1010, of the first configuration message related to the first configuration to a second UE (UE-B). The first configuration message may comprise synchronization information related to the first configuration and/or broadcast information related to the first configuration. The memory may further comprise instructions executable by the processor 1020, whereby the first UE 1000 is operative to initiate the transmission, by means of the transmitter 1010, the second configuration message related to a second, updated, configuration to said second UE. The second configuration message may comprise synchronization information related to the second configuration and/or broadcast information related to the second configuration. Moreover, the transmitter 1010 may be adapted to transmit the first and second configuration messages simultaneously, or substantially simultaneously. In some embodiments, the transmitter 1010 is adapted to transmit synchronization information related to the first configuration and broadcast information related to the first configuration simultaneously, i.e. essentially at the same time. Additionally, or alternatively, the transmitter 1010 may be adapted to transmit synchronization information related to the second configuration and broadcast information related to the second configuration simultaneously.

Still further, the transmitter 1010 may be adapted to transmit the first configuration message and the second configuration message during a transition period. In some embodiments, the memory 1030 may additionally, or alternatively, comprise instructions executable by the processor 1020, whereby the first UE 1000 is operative to initiate transmission (by means of the transmitter 1010) an information message to the second UE. The information message comprises an indication to the second UE that a first configuration will be replaced by a second, updated, configuration. The information message may further comprise information about the time when the first configuration will be replaced by the second, updated, configuration. Yet further, the memory 1030 may additionally comprise instructions executable by the processor 1020, whereby the first UE 1000 is operative to replace the first configuration with the second, updated, configuration after transmission of the information message. For example, the memory 1030 may comprise instructions executable by the processor 1020, whereby the first UE 1000 is operative to replace the first configuration with the second, updated, configuration seamlessly (e.g. without overlap) after transmission of the information message

With reference to fig. 1 1 , an example implementation of the second UE (UE-B) 1 100 will be described. As can be seen, the second UE may comprise a communication interface or radio circuitry 1 110. The communication interface 1 110 may comprise a transmitter (Tx), or transmitter circuitry. The communication interface 11 10 may also comprise a receiver (Rx), or receiver circuitry. Furthermore, the second UE 1 100 may comprise a processor or processing circuitry 1120. Still further, the first UE 1 100 may comprise one or more memories 1130. The memory 1130 may comprise instructions executable by the processor 1 120, whereby the second UE 1100 is operative to receive (by means of the receiver 1 110) the above- mentioned first configuration message related to the first configuration from the first UE (UE-A). Additionally, the memory 1130 may comprise instructions executable by the processor 1 120, whereby the second UE 1100 is operative to receive (by means of the receiver 1 110) the above-mentioned second configuration message related to the second, updated, configuration, from the first UE. The receiver 11 10 may be further adapted to receive the first and second configuration messages simultaneously, or substantially simultaneously.

In some embodiments, the receiver 11 10 is adapted to receive synchronization information related to the first configuration and broadcast information related to the first configuration simultaneously, i.e. essentially at the same time. Additionally, or alternatively, the receiver 1010 may be adapted to receive synchronization information related to the second configuration and broadcast information related to the second configuration simultaneously. Additionally, the receiver 1 1 10 may be adapted to receive the first configuration message and the second configuration message during a transition period. In some embodiments, the memory 1130 may additionally, or alternatively, comprise instructions executable by the processor 1120, whereby the second UE 1100 is operative to receive (by means of the receiver 11 10) the earlier-mentioned information message from the first UE. The information message comprises an indication to the second UE (UE-B) that a first configuration will be replaced by a second, updated, configuration. Also, the information message may further comprise information about the time when the first configuration will be replaced by the second, updated, configuration.

It will be appreciated that, in some embodiments, a single UE may include the functions of both the first UE (see Fig. 10) and the second UE (see Fig. 11). With reference to fig. 12, an example implementation of a control node 1200 (e.g. eNB) will be described. As can be seen, the control node may comprise a communication interface or radio circuitry 1210. The communication interface 1210 may comprise a transmitter (Tx), or transmitter circuitry. The communication interface 1210 may also comprise a receiver (Rx), or receiver circuitry. Furthermore, the control node 1200 may comprise a processor or processing circuitry 1220. Still further, the control node 1200 may comprise one or more memories 1230.

The memory 1230 may comprise instructions executable by the processor 1220, whereby the control node 1200 is operative to transmit (by means of the transmitter 1210) an informative message to the first user equipment (i.e. UE-A). The informative message comprises informative information related to the earlier-described second, updated, configuration. Also, the memory 1230 may comprise instructions executable by the processor 1220, whereby the control node 1200 is operative to transmit the informative message while a first configuration is in use.

In the detailed description hereinabove, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, etc. in order to provide a thorough understanding of various embodiments. In some instances, detailed descriptions of well-known devices, circuits, and methods have been omitted so as not to obscure the description of the embodiments disclosed herein with unnecessary detail. All statements herein reciting principles, aspects, and embodiments disclosed herein, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. Thus, for example, it will be appreciated by those skilled in the art that block diagrams herein may represent conceptual views of illustrative circuitry or other functional units embodying the principles of the embodiments. Similarly, it will be appreciated that any flow charts and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown. The functions of the various elements, including functional blocks, may be provided through the use of hardware such as circuit hardware and/or hardware capable of executing software in the form of coded instructions stored on computer readable medium. Thus, such functions and illustrated functional blocks are to be understood as being either hardware-implemented and/or computer- implemented, and thus machine-implemented. In terms of hardware implementation, the functional blocks may include or encompass, without limitation, digital signal processor (DSP) hardware, reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) [ASIC], and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions. In terms of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers. When provided by a computer or processor or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Moreover, use of the term "processor" or "controller" shall also be construed to refer to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

SELECTED EXAMPLE EMBODIMENTS

The technology disclosed herein thus encompasses without limitation the following example embodiments:

Example embodiment M1 : A method performed by a first user equipment, UE (UE-A), which is adapted for Device-to-Device (D2D) communications, the method comprising: transmitting (301) a first configuration message related to a first configuration to a second UE (UE-B), which second UE (UE-B) is also adapted for D2D communications; and transmitting (302) a second configuration message related to a second, updated, configuration to said second UE (UE-B).

Example embodiment M2: The method according to example embodiment M 1 , wherein the first and second configuration messages are transmitted (301 , 302) simultaneously.

Example embodiment M3: The method according to example embodiment M1 or M2, wherein the first configuration message comprises synchronization information related to the first configuration and/or broadcast information related to the first configuration.

Example embodiment M4: The method according to example embodiment M3, wherein synchronization information related to the first configuration and broadcast information related to the first configuration are transmitted simultaneously.

Example embodiment M5: The method according to any of the example embodiments M1-M4, wherein the second configuration message comprises synchronization information and/or broadcast information related to the second configuration. Example embodiment M6: The method according to example embodiment M5, wherein synchronization information related to the second configuration and broadcast information related to the second configuration are transmitted simultaneously.

Example embodiment M7: The method according any of the example embodiments M1- M6, wherein said transmitting (301) of the first configuration message and said transmitting (302) of the second configuration message are performed during a transition period.

Example embodiment M8: A method performed by a second user equipment, UE (UE-B), which is adapted for Device-to-Device (D2D) communications, the method comprising: receiving (401) a first configuration message related to a first configuration from a first UE (UE-A), which first UE (UE-A) is also adapted for D2D communications; and

receiving (402) a second configuration message related to a second, updated, configuration from the first UE (UE-A). Example embodiment M9: The method according to example embodiment M8, wherein the first and second configuration messages are received (401 , 402) simultaneously. Example embodiment M10: The method according to example embodiment M8 or M9, wherein the first configuration message comprises synchronization information and/or broadcast information related to the first configuration.

Example embodiment M1 1 : The method according to example embodiment M10, wherein synchronization information related to the first configuration and broadcast information related to the first configuration are received simultaneously.

Example embodiment M12: The method according to any of the example embodiments M8-M11 , wherein the second configuration message comprises synchronization information and/or a broadcast information.

Example embodiment M 13: The method according to example embodiment M12, wherein synchronization information related to the second configuration and broadcast information related to the second configuration are received simultaneously.

Example embodiment M14: The method according any of the example embodiments M8- M13, wherein said receiving (401) of the first configuration message and said receiving (402) of the second configuration message are performed during a transition period. Example embodiment M15: A method performed by a first user equipment, UE (UE-A), which is adapted for Device-to-Device (D2D) communications, the method comprising: transmitting (601), to a second UE (UE-B) which is also adapted for D2D communications, an information message comprising an indication to the second UE (UE- B) that a first configuration will be replaced by a second, updated, configuration.

Example embodiment M16: The method according to example embodiment M15, wherein the information message further comprises information about the time when the first configuration will be replaced by the second, updated, configuration.

Example embodiment M17: The method according to M15 or M16, further comprising: replacing (602) the first configuration with the second, updated, configuration seamlessly after said transmitting of the information message.

Example embodiment M18: A method performed by a second user equipment, UE (UE-B), which is adapted for Device-to-Device (D2D) communications, the method comprising: receiving (701), from a first UE (UE-A) which is also adapted for D2D communications, an information message comprising an indication to the second UE (UE- B) that a first configuration will be replaced by a second, updated, configuration. Example embodiment M19: The method according to example embodiment M18, wherein the information message further comprises information about the time when the first configuration will be replaced by the second, updated, configuration.

Example embodiment M20: A method performed by a network control node (Control node 1) which is adapted for Device-to-Device (D2D) communications, the method comprising: transmitting (801), to a first user equipment (UE-A), an informative message comprising informative information related to a second, updated, configuration.

Example embodiment M21 : The method according to example embodiment M20, wherein said transmitting of the informative message is performed while a first configuration is in use.

Example embodiment M22: The method according to example embodiment M20 or M21 , wherein the informative message further comprises an indication about the time when said first configuration is to be replaced by the second, updated, configuration.

Example embodiment U1 : A first user equipment, UE (1000) adapted for Device-to-Device (D2D) communications, the first UE (1000) comprising:

means (1010) adapted to transmit a first configuration message related to a first configuration to a second UE (UE-B), which second UE (UE-B) is also adapted for D2D communications; and

means (1010) adapted to transmit a second configuration message related to a second, updated, configuration to said second UE (UE-B). Example embodiment U2: The first UE (1000) according to example embodiment U1 , wherein said means (1010) are further adapted to transmit the first and second configuration messages simultaneously. Example embodiment U3: The first UE (1000) according to example embodiment U1 or U2, wherein the first configuration message comprises synchronization information related to the first configuration and/or broadcast information related to the first configuration.

Example embodiment U4: The first UE (1000) according to example embodiment U3, wherein said means (1010) are further configured to transmit synchronization information related to the first configuration and broadcast information related to the first configuration simultaneously.

Example embodiment U5: The first UE (1000) according to any of the example embodiments U1-U4, wherein the second configuration message comprises synchronization information and/or broadcast information related to the second configuration.

Example embodiment U6: The first UE (1000) according to example embodiment U5, wherein said means (1010) are further configured to transmit synchronization information related to the second configuration and broadcast information related to the second configuration simultaneously.

Example embodiment U7: The first UE (1000) according any of the example embodiments U1-U6, wherein said means are configured to transmit the first configuration message and the second configuration message during a transition period.

Example embodiment U8: A second user equipment, UE (1 100), adapted for Device-to- Device (D2D) communications, the second UE (UE-B) comprising:

means (1 110) adapted to receive a first configuration message related to a first configuration from a first UE (UE-A), which first UE (UE-A) is also adapted for D2D communications; and

means (1 110) adapted to receive a second configuration message related to a second, updated, configuration from the first UE (UE-A). Example embodiment U9: The second UE (11 10) according to example embodiment U8, wherein said means (1 110) are further adapted to receive the first and second configuration messages simultaneously. Example embodiment U10: The second UE (1100) according to example embodiment U5, wherein the first configuration message comprises synchronization information and/or broadcast information related to the first configuration.

Example embodiment U1 1 : The second UE (1 100) according to example embodiment U10, wherein said means (1 110) are further configured to receive synchronization information related to the first configuration and broadcast information related to the first configuration simultaneously.

Example embodiment U12: The second UE (1 110) according to any of the example embodiments U8-U11 , wherein the second configuration message comprises synchronization information and/or a broadcast information.

Example embodiment U13: The second UE (1 100) according to example embodiment U12, wherein said means (1 110) are further configured to receive synchronization information related to the first configuration and broadcast information related to the first configuration simultaneously.

Example embodiment U14: The second UE (1 110) according any of the example embodiments U8-U13, wherein said means (1 110) are adapted to receive the first configuration message and the second configuration message during a transition period.

Example embodiment U15: A first UE (1000) adapted for Device-to-Device (D2D) communications, the first UE (1000) comprising:

means (1010) adapted to transmit, to a second UE (UE-B) which is also adapted for D2D communications, an information message comprising an indication to the second UE (UE-B) that a first configuration will be replaced by a second, updated, configuration.

Example embodiment U16: The first UE (1000) according to example embodiment U15, wherein the information message further comprises information about the time when the first configuration will be replaced by the second, updated, configuration. Example embodiment U17: The method according to U15 or U16, further comprising: means (1020, 1030) adapted to replace the first configuration with the second, updated, configuration seamlessly after transmission of the information message.

Example embodiment U18: A second user equipment, UE (1100), adapted for Device-to- Device (D2D) communications, the second UE (1100) comprising:

means (1 110) adapted to receive, from a first UE (UE-A) which is also adapted for D2D communications, an information message comprising an indication to the second UE (UE-B) that a first configuration will be replaced by a second, updated, configuration.

Example embodiment U19: The second UE (1 100) according to example embodiment U18, wherein the information message further comprises information about the time when the first configuration will be replaced by the second, updated, configuration.

Example embodiment N1 : A network control node (1200) adapted for Device-to-Device (D2D) communications, the network control node (1200) comprising:

means (1210) adapted to transmit, to a first user equipment (UE-A), an informative message comprising informative information related to a second, updated, configuration.

Example embodiment N2: The network control node (1200) according to example embodiment N1 , wherein said transmission of the informative message is performed while a first configuration is in use. Example embodiment N3: The network control node according to example embodiment N1 or N2, wherein the informative message further comprises an indication about the time when said first configuration is to be replaced by the second, updated, configuration.

It should be appreciated that the example embodiments listed hereinabove may be combined in various combinations. As a mere example, an example embodiment corresponding to a combination of example embodiments M1-M7 and M15-M17 is conceivable. As another illustrative example and in some scenarios any one of the example embodiments M20-22 may be combined with any of the example embodiments M1-M14. Modifications and other variants of the described embodiments will come to mind to one skilled in the art having benefit of the teachings presented in the foregoing description and associated drawings. Therefore, it is to be understood that the embodiments are not limited to the specific example embodiments disclosed and that modifications and other variants are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

A method performed by a first user equipment, UE (UE-A), which is adapted for Device-to-Device (D2D) communications, the method comprising:

transmitting (601), to a second UE (UE-B) which is also adapted for D2D communications, an information message comprising an indication to the second UE (UE-B) that a first configuration will be replaced by a second, updated, configuration; and

replacing (602) the first configuration with the second, updated, configuration after said transmitting (601) of the information message.

The method according to claim 1 , wherein said replacing (602) comprises:

replacing (602) the first configuration with the second, updated, configuration seamlessly, i.e. without overlap, after said transmitting (601) of the information message.

The method according to claim 1 or 2, wherein the information message further comprises information about the time when the first configuration will be replaced by the second, updated, configuration.

The method according to any one of the claims 1-3, comprising:

transmitting (301) a first configuration message related to the first configuration to the second UE (UE-B); and

transmitting (302) a second configuration message related to the second, updated, configuration to said second UE (UE-B).

The method according to claim 4, wherein the first configuration message comprises synchronization information related to the first configuration and/or broadcast information related to the first configuration.

The method according to claim 5, wherein synchronization information related to the first configuration and broadcast information related to the first configuration are transmitted simultaneously.

7. The method according to any one of the claims 4-6, wherein the second configuration message comprises synchronization information and/or broadcast information related to the second configuration.

8. The method according to claim 7, wherein synchronization information related to the second configuration and broadcast information related to the second configuration are transmitted simultaneously.

9. A first UE (1000) adapted for Device-to-Device (D2D) communications, the first UE (1000) comprising:

means (1010) adapted to transmit, to a second UE (UE-B) which is also adapted for D2D communications, an information message comprising an indication to the second UE (UE-B) that a first configuration will be replaced by a second, updated, configuration; and

means (1020, 1030) adapted to replace the first configuration with the second, updated, configuration after transmission of the information message.

10. The first UE (1000) according to claim 9, wherein the means (1020, 1030) adapted to replace the first configuration with the second, updated, configuration is further adapted to replace the first configuration with the second, updated, configuration seamlessly, i.e. without overlap, after transmission of the information message

1 1. The first UE (1000) according to claim 9 or 10, wherein the information message further comprises information about the time when the first configuration will be replaced by the second, updated, configuration.

12. The first UE (1000) according to any one of the claims 9-11 , comprising:

means (1010) adapted to transmit a first configuration message related to the first configuration to the second UE (UE-B); and

means (1010) adapted to transmit a second configuration message related to the second, updated, configuration to said second UE (UE-B).

13. The first UE (1000) according to claim 12, wherein the first configuration message comprises synchronization information related to the first configuration and/or broadcast information related to the first configuration.

14. The first UE (1000) according to claim 13, wherein said means (1010) are further configured to transmit synchronization information related to the first configuration and broadcast information related to the first configuration simultaneously.

15. The first UE (1000) according to any one of the claims 12-14, wherein the second configuration message comprises synchronization information and/or broadcast information related to the second configuration.

16. The first UE (1000) according to claim 15, wherein said means (1010) are further configured to transmit synchronization information related to the second configuration and broadcast information related to the second configuration simultaneously.

17. A method performed by a second user equipment, UE (UE-B), which is adapted for Device-to-Device (D2D) communications, the method comprising:

receiving (701), from a first UE (UE-A) which is also adapted for D2D communications, an information message comprising an indication to the second UE (UE-B) that a first configuration will be replaced by a second, updated, configuration.

18. The method according to claim 17, wherein the information message further comprises information about the time when the first configuration will be replaced by the second, updated, configuration.

19. The method according to claim 17 or 18, further comprising:

replacing (702) the first configuration with the second, updated, configuration.

20. The method according to any of the claims 17-19, comprising:

receiving (401) a first configuration message related to the first configuration from the first UE (UE-A); and receiving (402) a second configuration message related to the second, updated, configuration from the first UE (UE-A).

21. The method according to claim 20, wherein the first configuration message comprises synchronization information and/or broadcast information related to the first configuration.

22. The method according to claim 21 , wherein synchronization information related to the first configuration and broadcast information related to the first configuration are received simultaneously.

23. The method according to any one of the claims 20-22, wherein the second configuration message comprises synchronization information and/or a broadcast information.

24. The method according to claim 23, wherein synchronization information related to the second configuration and broadcast information related to the second configuration are received simultaneously.

25. A second user equipment, UE (1100), adapted for Device-to-Device (D2D) communications, the second UE (1 100) comprising

means (1 110) adapted to receive, from a first UE (UE-A) which is also adapted for D2D communications, an information message comprising an indication to the second UE (UE-B) that a first configuration will be replaced by a second, updated, configuration.

26. The second UE (1 100) according to claim 24, wherein the information message further comprises information about the time when the first configuration will be replaced by the second, updated, configuration.

27. The second UE (1 100) according to claim 25 or 26, comprising:

means (1120, 1130) adapted to replacing (702) the first configuration with the second, updated, configuration.

28. The second UE (1 100) according to any of the claims 25-27, comprising:

means (1 110) adapted to receive a first configuration message related to the first configuration from the first UE (UE-A); and

means (1 110) adapted to receive a second configuration message related to the second, updated, configuration from the first UE (UE-A).

29. The second UE (1 100) according to claim 28, wherein the first configuration message comprises synchronization information and/or broadcast information related to the first configuration.

30. The second UE (1 100) according to claim 29, wherein said means (1 110) are further configured to receive synchronization information related to the first configuration and broadcast information related to the first configuration simultaneously.

31. The second UE (1 110) according to any one of the claims 28-30, wherein the second configuration message comprises synchronization information and/or a broadcast information.

32. The second UE (1 100) according to claim 31 , wherein said means (1 110) are further configured to receive synchronization information related to the first configuration and broadcast information related to the first configuration simultaneously.