WO2014045151A2

WO2014045151A2 - Apparatus and method for communication

Info

Publication number: WO2014045151A2
Application number: PCT/IB2013/058303
Authority: WO
Inventors: Sami-Jukka Hakola; Kaisu Iisakkila; Samuli Turtinen; Timo Koskela
Original assignee: Broadcom Corp
Current assignee: Broadcom Corp
Priority date: 2012-09-19
Filing date: 2013-09-05
Publication date: 2014-03-27
Anticipated expiration: 2015-03-19
Also published as: GB2521950A; WO2014045151A3; HK1206534A1; GB2521950B; GB201216736D0; DE112013004554T5; GB2506118B; GB201503716D0; GB2506118A; CN104662991A; DE112013004554B4

Description

APPARATUS AND METHOD FOR COMMUNICATION

Technical Field

The present invention relates to wireless communication networks. Embodiments of the invention relate especially to an apparatus and a method in communication networks.

Background

In radio communication networks, such as the Long Term Evolution (LTE) or the LTE-Advanced (LTE-A) of the 3rd Generation Partnership Project (3GPP), network planning comprises the use of common base stations (Node B, NB). User equipment (UE), or a user terminal (UT), may communicate with another UT via the base station(s), for example. Alternatively, it is proposed that the UTs may communicate directly with each other by applying resources dedicated by the network for a device-to-device (D2D) direct communication. The D2D communication has proven to be network efficient by offloading the traffic processed in the base station(s), for example.

One part of device-to-device (D2D) communication is discovery. The discovery means basically finding other interesting peers (in general a peer can mean an application, user, service, device, etc.) in proximity. Once discovery has been performed D2D capable UEs are aware of other corresponding UEs.

When setting up a D2D connection the setup should be as fluent as possible and require minimum modifications to current devices and procedures.

Summary

In accordance with one aspect of the present invention, there is provided a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to a more detailed description that is presented later. According to an aspect of the present invention, there is provided an apparatus for use in user equipment, comprising a processing system configured to: cause the generation of a message comprising a request to setup a device-to-device bearer, an identifier of a destination user equipment and information on the mobility management entity identifier of the destination user equipment; and control the transmission of the message.

According to an aspect of the present invention, there is provided an apparatus in a communication system, comprising a processing system configured to: receive from user equipment a message comprising a request to setup a device-to-device bearer and an identifier of a destination user equipment; and obtain information on the mobility management entity identifier of the destination user equipment.

According to another aspect of the present invention, there is provided a method in a communication system, comprising: generating a message comprising an request to setup a device-to-device bearer, an identifier of the destination user equipment and information on a mobility management entity identifier of the destination user equipment; and controlling the transmission of the message.

According to yet another aspect of the present invention, there is provided a method in a communication system, comprising: receiving from user equipment a message comprising a request to setup a device-to-device bearer and an identifier of the destination user equipment; and obtaining information on the mobility management entity identifier of the destination user equipment.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows an example of a communication environment;

Figure 2 shows a flowchart illustrating an example embodiment of the invention;

Figure 3 shows an example of the transmit power control delay calculation;

Figure 4 shows a signalling chart illustrating some embodiments; and Figures 5 A and 5B show examples of apparatuses applying some embodiments of the invention.

Detailed Description

Some embodiments of the present invention are applicable to user equipment

(UE), a base station, eNodeB, a corresponding component, and/or to any communication system or any combination of different communication systems that support required functionality.

The protocols used, the specifications of communication systems, servers and user terminals, especially in wireless communication, develop rapidly. Such development may require extra changes to an embodiment. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, embodiments.

Many different radio protocols to be used in communications systems exist. Some examples of different communication systems are the universal mobile telecommunications system (UMTS) radio access network (UTRAN), HSPA (High Speed Packet Access), long term evolution (LTE^®, known also as evolved UMTS Terrestrial Radio Access Network E-UTRAN), long term evolution advanced (LTE- A), Wireless Local Area Network (WLAN) based on IEEE 802.11 star dard, worldwide interoperability for microwave access (WiMAX^®), Bluetooth^®, personal communications services (PCS) and systems using ultra- wideband (UWB) technology. IEEE refers to the Institute of Electrical and Electronics Engineers. For example, LTE^® and LTE-A are developed by the Third Generation Partnership Project 3 GPP.

Figure 1 illustrates a simplified view of a communication environment only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown. The connections shown in Figure 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the systems also comprise other functions and structures. It should be appreciated that the functions, structures, elements and the protocols used in or for communication are irrelevant to the actual invention. Therefore, they need not to be discussed in more detail here. In the example of Figure 1 , a radio system based on LTE/SAE (Long Term Evolution/System Architecture Evolution) network elements is shown. However, the embodiments described in these examples are not limited to the LTE/SAE radio systems but can also be implemented in other radio systems.

The simplified example of a network of Figure 1 comprises a SAE Gateway

110 and a Mobility Management Entity MME 112. The SAE Gateway 110 provides a connection to Internet 114. Figure 1 shows a base station or an eNodeB 102 serving a cell 100. In this example, the eNodeB 102 is connected to the SAE Gateway 110 and the MME 112.

The eNodeBs (Enhanced node Bs) of a communication system may host the functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic Resource Allocation (scheduling). The MME 112 (Mobility Management Entity) is responsible for the overall UE control in mobility, session/call and state management with assistance of the eNodeBs through which the UEs connect to the network. The SAE GW 110 is an entity configured to act as a gateway between the network and other parts of communication network such as the Internet for example. The SAE GW may be a combination of two gateways, a serving gateway (SGW) and a packet data network gateway (PGW).

The eNodeB 102 may provide radio coverage to a cell 100. The cell 100 may be a macrocell, a microcell, or any other type of cell where radio coverage is present. Further, the cell 100 may be of any size or form, depending on the antenna system utilized. The eNodeB 102 may be used in order to provide radio coverage to the cell 100. The eNodeB 102 may control a cellular radio communication link established between the eNodeB 102 and terminal devices or user equipment 104A and 104B located within the cell 100. These communication links marked with solid arrows may be referred as conventional communication links for end-to-end communication, where the source device transmits data to the destination device via the base station 100. Therefore, the user terminals 104 A and 104B may communicate with each other via the base station 102. The terminal device may be a user equipment of a cellular communication system, e.g. a computer (PC), a laptop, a handheld computer, a mobile phone, or any other user terminal or user equipment capable of communicating with the cellular communication network. In addition to or instead of the conventional communication links, direct device-to-device (D2D) connections may be established among terminal devices. Direct communication links between two devices may be established, e.g., between terminal devices or user equipment 106 and 108 in Figure 1. A direct communication link 116 marked with a dashed arrow may be based on any radio technology such that the terminal devices or user equipment 106 and 108 involved in the direct communication may apply communication according to any of a plurality of radio access technologies. The eNodeB 102 may be responsible for controlling the direct communication link 116, as shown with dotted, bi-directional lines 118 in Figure 1. The radio access technology of the direct communication link 116 may operate on the same frequency band as the conventional communication link and/or outside those frequency bands to provide the arrangement with flexibility. Thus, the eNodeB 102 may be responsible for allocating radio resources to the direct communication link 116 as well as for the conventional communication links. Alternatively, the UT 106, 108 may perform auto-selection of D2D resources from a common pool of resources.

One part of device-to-device (D2D) communication is discovery. Discovery means basically finding other interesting peers (in general a peer can mean an application, user, service, device, etc.) in proximity. The discovery can be implemented either using the direct radio signals between the devices or it may utilise the network side in the process. The same discovery process may be utilised in relation to small cells.

In an embodiment, UEs announce in a discovery process their identifier by broadcasting a discovery message. Upon the reception of a discovery message an UE may be able to detect that it has an active application flow with the discovered UE. The UE could then indicate such an event to the network and the network may setup a D2D bearer between UEs to convey the common application flow. Furthermore, the UE may request a D2D bearer with the discovered UE without a priori common application flow.

In an embodiment, it is proposed that when the D2D bearer is to be setup, the D2D bearer is created under the existing Packet Data Network (PDN) and the same Internet Protocol (IP) address is in use. This allows the transition of application flow between D2D and Evolved Packet System (EPS) bearers within one PDN connection. In an embodiment, the UE is configured to call the network radio stack to request to setup a communication link with the detected neighbor.

Figure 2 is a flowchart illustrating an example embodiment of the invention. The apparatus employing the embodiment may be user equipment or a part of user equipment, for example. Here it is assumed that a discovery process has been performed and that a nearby UE has been detected. The process starts at step 200. In step 202, the apparatus is configured to cause the generation of a message comprising a request to setup a device-to-device bearer, an identifier of the destination user equipment and information on the mobility management entity identifier (MMEI) of the destination user equipment.

In step 204, the apparatus is configured to control the transmission of the message.

The process ends in step 206.

In an embodiment, the UE requesting a D2D bearer is configured to transmit a Request Bearer Resource Modification message to the MME of the network. The message may include an indication about D2D bearer setup for a new session, denoted for instance as d2d_for_a_new_flow. The message may further comprise an identifier of the destination UE and the MME identifier (MMEI) of the destination UE.

Alternatively, a Globally Unique Mobility Management Entity Identifier (GUMMEI) may be sent in the message. This may be feasible in shared radio access network (RAN) scenario where multiple operators are sharing a common RAN but have their own core network (including own MMEs). The GUMMEI comprises MMEI as well as Public Land Mobile Network Identifier (PLMN ID).

In an embodiment, if the MME identifier is not conveyed in the message along with the UE identifier, the MME receiving the message may request the corresponding MME identifier with the UE identifier from the Home Subscriber Server (HSS) of the network.

Figure 3 is a flowchart illustrating an example embodiment of the invention. The apparatus employing the embodiment may be a Mobility Management Entity MME or a part of an MME, for example. The process starts at step 300.

In step 302, the apparatus is configured to receive from user equipment a message comprising a request to setup a device-to-device bearer, an identifier of the destination user equipment and information on the mobility management entity identifier of the destination user equipment.

In step 304, the apparatus is configured to initialize the setup of a D2D bearer on the basis of the message.

The process ends in step 306.

Figure 4 is a signalling chart illustrating some embodiments. The figure illustrates D2D bearer setup related signalling between involved UEs 400, 402 and network elements such as eNodeB 404, MME 406 of UE400, MME 408 of UE 402, SGW 410, PGW 412 and Policy and Charging Rules Function (PCRF) 414.

The UE 400 transmits a Request Bearer Resource Modification message 416 to the MME 406 of the network. The message may include an indication about D2D bearer setup for a new session, denoted for instance as d2d_for_a_new_flow. The message may further comprise an identifier of the destination UE and the MME identifier (MMEI) of the destination UE. The D2D bearer may also be setup for an existing application flow between UEs as is explained below.

If the MME identifier of the destination UE is different than MME identifier of the MME receiving the D2D bearer setup request, a sequence of messages 418 between MMEs is introduced by which the master MME 406 (in this case the MME that receives the Request Bearer Resource Modification message) can query the authorization of the destination UE for the D2D communications and the destination MME 408 sends the response.

Furthermore, the D2D bearer setup could trigger MME relocation for either of the UEs, e.g., the destination UE, if the UEs are served by different MMEs, and destination UE is authorized for D2D communication.

For the triggering, the MME 406 could indicate in the authorization query request message if the MME relocation could take place from its perspective. The MME 408 of the destination UE could then respond with the MME Relocation Request message using a new RAN cause. The cause field could be for instance "relocation_due_to_D2D_bearer_setup".

Reason for the relocation is that the mobility of application flow(s) between

D2D and EPS bearers would be easier if UEs were served by the same MME The D2D bearer setup is processed by the serving gateway (SGW) 410, packet data network gateway (PGW) 412 and Policy and Charging Rules Function (PCRF) 414 with messages 420, which may be performed for both UEs separately.

In an embodiment, when the D2D bearer is established with a given Traffic Flow Template TFT, the same bearer should be established to the PGW 412 unless a corresponding bearer already exists. Pairing between the D2D bearer and the Evolved Packet Core (EPC) routed EPS bearer may be indicated in the Bearer Setup message in order to facilitate mobility from the D2D link to the EPC routed bearer.

The MME 406 sends then a Bearer Setup Request 422 to both UEs via the eNodeB 404 indicating the D2D bearer parameters to which the UEs respond with Bearer Setup Response.

To confirm that the D2D bearer has successfully been setup the MME sends a Bearer Setup Complete message 424 to the UEs.

In an embodiment, the eNodeB is configured to 404 add D2D bearer specific Radio Network Temporary Identity (RNTI) in the message 424 for incoming control channel information such as resource allocation messages 426 sent by the eNodeB.

In an embodiment, when a D2D bearer is setup for an existing application flow conveyed over cellular EPS bearers of involved UEs, following differences for the above signaling methods are proposed:

The UE that triggers D2D bearer setup according to discovery and network configuration for active flow includes into the Bearer Resource Request message 416 the cause, for example d2d_for_active_flow, and the application flow identity.

In an embodiment, the network may have set a detection threshold for the received discovery message for the decision whether an UE can request a D2D bearer with a discovered UE if it has detected that it has an active application flow with that UE. There may be two conditions: First, the UE has a common application flow with the discovered UE. Second, the signal quality of received discovery message of the discovered UE is above a preconfigured threshold.

If network decides to setup D2D bearer, the Bearer Setup Request 422 sent by MME 406 includes information about application flow identity to both UEs 400, 402. Upon the reception of the Bearer Setup Complete 424 message, the UEs make a path switch for the given application flow and the path switch is in effect after the UEs receive the first radio resource grant for the D2D bearer from the serving eNodeB.

Figure 5A illustrates a simplified example of a device in which some embodiments of the invention may be applied. In some embodiments, the device may be a Mobility Management Entity MME or a respective network element a communication system or network. The device may be a part or a section of an MME.

Figure 5B illustrates a simplified example of a device in which some embodiments of the invention may be applied. In some embodiments, the device may be user equipment UE or a respective device communicating with a communications system. The device may be a part or a section of user equipment.

It should be understood that the apparatuses are depicted herein as examples illustrating some embodiments. It is apparent to a person skilled in the art that the devices may also comprise other functions and/or structures and not all described functions and structures are required. Although the devices have been depicted as single entities, different modules and memory may be implemented in one or more physical or logical entities. In addition, each device may be a part of another device.

Referring to Figure 5A, the device of the example includes one or more control circuitries or processing circuits (CNTL) 500 configured to control at least part of the operation of the device.

The device may comprise one or more memories (MEM) 502 for storing data.

Furthermore the memory may store software (PROG) 504 executable by the control circuitry 500. The memory may be integrated in the control circuitry.

The device may comprise an interface (IF) 506. The interface is operationally connected to the control circuitry 500. The device may be connected to other network elements of the communication system or network via the interface.

The software 504 may comprise a computer program comprising program code means adapted to cause the control circuitry 500 of the device to receive from user equipment a message comprising a request to setup a device-to-device bearer, an identifier of the destination user equipment and information on the mobility management entity identifier of the destination user equipment.

Figure 5B illustrates a simplified example of user equipment UE or a respective device. The device of the example includes one or more control circuitries or processing circuits (CNTL) 520 configured to control at least part of the operation of the device.

The device may comprise one or more memories (MEM) 522 for storing data. Furthermore the memory may store software (PROG) 524 executable by the control circuitry 520. The memory may be integrated in the control circuitry.

The device may comprise a transceiver (TRX) 526. The transceiver is operationally connected to the control circuitry 520. It may be connected to an antenna arrangement (not shown). The device may also comprise a connection to a transceiver instead of a transceiver.

The software 524 may comprise a computer program comprising program code means adapted to cause the control circuitry 520 of the device to control a transceiver 526.

The software 524 may comprise a computer program comprising program code means adapted to cause the control circuitry 500 of the device to cause the generation of a message comprising a request to setup a device-to-device bearer, an identifier of the destination user equipment and information on the mobility management entity identifier of the destination user equipment; and to control the transmission of the message.

The device may further comprise user interface (UI) 528 operationally connected to the control circuitry 520. The user interface may comprise a display which may be touch sensitive, a keyboard or keypad, a microphone and a speaker, for example.

The steps and related functions described in the above and attached figures are in no absolute chronological order, and some of the steps may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between the steps or within the steps. Some of the steps can also be left out or replaced with a corresponding step.

The apparatuses or controllers able to perform the above-described steps may be implemented as an electronic digital computer, processing system or a circuitry which may comprise a working memory (RAM), a central processing unit (CPU), and a system clock. The CPU may comprise a set of registers, an arithmetic logic unit, and a controller. The processing system, controller or the circuitry is controlled by a sequence of program instructions transferred to the CPU from the RAM. The controller may contain a number of microinstructions for basic operations. The implementation of microinstructions may vary depending on the CPU design. The program instructions may be coded by a programming language, which may be a high-level programming language, such as C, Java, etc., or a low-level programming language, such as a machine language, or an assembler. The electronic digital computer may also have an operating system, which may provide system services to a computer program written with the program instructions.

As used in this application, the term 'circuitry' refers to all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of circuits and software (and/or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s)/software including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of 'circuitry' applies to all uses of this term in this application. As a further example, as used in this application, the term 'circuitry' would also cover an implementation of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and/or firmware. The term 'circuitry' would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or another network device.

An embodiment provides a computer program embodied on a distribution medium, comprising program instructions which, when loaded into an electronic apparatus, are configured to control the apparatus to execute the embodiments described above.

The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, and a software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers.

The apparatus may also be implemented as one or more integrated circuits, such as application- specific integrated circuits ASIC. Other hardware embodiments are also feasible, such as a circuit built of separate logic components. A hybrid of these different implementations is also feasible. When selecting the method of implementation, a person skilled in the art will consider the requirements set for the size and power consumption of the apparatus, the necessary processing capacity, production costs, and production volumes, for example.

It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. An apparatus for use in user equipment, the apparatus comprising a processing system (500) configured to:

cause the generation (202) of a message comprising a request to setup a device-to-device bearer (116), an identifier of a destination user equipment (106) and information on a mobility management entity (1 12) identifier of the destination user equipment (106); and

control the transmission (204) of the message.

2. The apparatus of claim 1 , the apparatus being configured to generate a message comprising an indication that the bearer is for an existing network application flow to the destination user equipment (106) and the identity of the application flow identity.

3. The apparatus of claim 1 or 2, wherein the information on the mobility management entity (112) identifier of the destination user equipment (106) is the mobility management entity (112) identifier of the destination user equipment (106).

4. The apparatus of claim 1 or 2, wherein the information on the mobility management entity (112) identifier of the destination user equipment (106) is the globally unique mobility management entity (112) identifier of the destination user equipment (106).

5. The apparatus of any preceding claim, the apparatus being configured to

receive a message indicating bearer parameters of the device-to-device bearer (116) to be setup.

6. The apparatus of claim 5, wherein the bearer parameters comprise of the identity of the existing application flow identity.

7. The apparatus of any preceding claim, the apparatus being configured to:

receive a message indicating a device-to-device bearer (116) setup has been completed;

receive a radio resource grant for the device-to-device bearer (116); and switch an active application flow to use the device-to-device bearer (116).

8. The apparatus of any preceding claim, wherein the message comprising a request to setup a device-to-device bearer (116) is generated on the basis of a device-to-device discovery performed by the apparatus.

9. The apparatus of claim 7, wherein the apparatus is configured to send the message comprising a request to setup a device-to-device bearer (116) only if the device-to-device discovery indicated that the quality of the device-to-device bearer (116) would be above a given threshold.

10. The apparatus of any preceding claim, wherein the apparatus is user equipment.

11. The apparatus of claim 10, wherein the user equipment is a mobile device.

12. The apparatus of any preceding claim, wherein the apparatus is user equipment of a Long Term Evolution or a Long Term Evolution Advanced based communication system.

13. An apparatus in a communication system, the apparatus comprising a processing system (500) configured to:

receive (302) from user equipment a message comprising a request to setup a device-to-device bearer (116) and an identifier of a destination user equipment (106); and obtain information on the mobility management entity (112) identifier of the destination user equipment (106).

14. The apparatus of claim 13, the apparatus being configured to:

obtain the information on the mobility management entity (112) identifier from the message.

15. The apparatus of claim 13, the apparatus being configured to:

obtain the information on the mobility management entity (112) identifier from a network side entity.

16. The apparatus of any of claims 13 to 15, the apparatus being configured to:

determine the mobility management entity (112) of the destination user equipment (106) identified in the received message; and

send the mobility management entity (112) of the destination user equipment (106) a query regarding the device-to-device properties of the destination user equipment (106).

17. The apparatus of any of claims 13 to 16, the apparatus being configured to:

send the mobility management entity (112) of the destination user equipment (106) a query to relocate the destination user equipment (106) under the same mobility management entity (112) as the user equipment requesting the setting up the device-to-device bearer (116);

receive a relocation request from the mobility management entity (112) of the destination user equipment (106); and

perform the relocation with the mobility management entity (112) of the destination user equipment (106).

18. The apparatus of any of claims 13 to 17, wherein the message received from user equipment comprises an indication that the bearer is for an existing network application flow to the destination user equipment and the identity of the application flow identity.

19. The apparatus of any of claims 13 to 18, the apparatus being configured to

transmit user equipment a message indicating bearer parameters of the device- to-device bearer (1 16) to be setup.

20. The apparatus of claim 19, wherein the bearer parameters comprise of the identity of the existing application flow identity.

21. The apparatus of any of claims 13 to 20, the apparatus being configured to

transmit user equipment a message indicating a device-to-device bearer (116) setup has been completed; and

transmit user equipment a radio resource grant for the device-to-device bearer

(116).

22. The apparatus of any of claims 13 to 21, wherein the apparatus is a base station (102).

23. The apparatus of any of claims 13 to 22, wherein the apparatus is a base station (102) of a Long Term Evolution or a Long Term Evolution Advanced based communication system.

24. A method in a communication system (100), the method comprising: generating (202) a message comprising a request to setup a device-to-device bearer (1 16), an identifier of a destination user equipment (106) and information on a mobility management entity (112) identifier of the destination user equipment (106); and

controlling the transmission (204) of the message.

25. The method of claim 24, further comprising:

generating (202) a message comprising an indication that the bearer is for an existing network application flow to the destination user equipment (106) and the identity of the application flow identity.

26. The method of claim 24 or 25, further comprising:

receiving a message indicating a device-to-device bearer (116) setup has been completed;

receiving a radio resource grant for the device-to-device bearer (116); and switching an active application flow to use the device-to-device (116) bearer.

27. The method of any of claims 24 to 26, wherein the information on the mobility management entity (112) identifier of the destination user equipment (106) is the mobility management entity (112) identifier of the destination user equipment (106).

28. The method of any of claims 24 to 26, wherein the information on the mobility management entity (112) identifier of the destination user equipment (106) is the globally unique mobility management entity (112) identifier of the destination user equipment (106).

29. The method of any of claims 24 to 28, further comprising:

receiving a message indicating bearer parameters of the device-to-device bearer (1 16) to be setup.

30. The method of claim 29, wherein the bearer parameters comprise of the identity of the existing application flow identity.

31. The method of any of claims 24 to 30, further comprising:

receiving a radio resource grant for the device-to-device bearer (116); and switching an active application flow to use the device-to-device bearer (116).

32. The method of any of claims 24 to 31, wherein the message comprising a request to setup a device-to-device bearer (116) is generated on the basis of a device-to-device discovery performed by the apparatus.

33. The method of any of claims 24 to 32, further comprising:

sending the message comprising an request to setup a device-to-device bearer (116) only if the device-to-device discovery indicated that the quality of the device- to-device bearer (1 16) would be above a given threshold.

34. A method in a communication system (100), the method comprising: receiving (302) from user equipment a message comprising a request to setup a device-to-device bearer (116) and an identifier of a destination user equipment (106); and

obtaining information on a mobility management entity (112) identifier of the destination user equipment (106).

35. The method of claim 34, further comprising:

obtaining the information on a mobility management entity (112) identifier from the message.

36. The method of claim 34, further comprising:

obtaining the information on a mobility management entity (112) identifier from a network side entity.

37. The method of any of claims 34 to 36, further comprising:

determining the mobility management entity (1 12) of the destination user equipment (106) identified in the received message; and

sending the mobility management entity (1 12) of the destination user equipment (106) a query regarding the device-to-device properties of the destination user equipment (106).

38. The method of claims 34 to 37, further comprising:

sending the mobility management entity (1 12) of the destination user equipment (106) a query to relocate the destination user equipment (106) under the same mobility management entity as the user equipment (108) requesting the setting up the device-to-device bearer (116);

receiving a relocation request from the mobility management entity (112) of the destination user equipment; and

performing the relocation with the mobility management entity (112) of the destination user equipment (106).

39. The method of any of claims 34 to 38, wherein the message received from user equipment comprises an indication that the bearer is for an existing network application flow to the destination user equipment and the identity of the application flow identity.

40. The method of any of claims 34 to 39, further comprising:

transmitting user equipment a message indicating bearer parameters of the device-to-device bearer (116) to be setup.

41. The method of claim 40, wherein the bearer parameters comprise of the identity of the existing application flow identity.

42. The method of any of claims 34 to 41, further comprising:

transmitting user equipment a message indicating a device-to-device bearer

(116) setup has been completed; and

transmitting user equipment a radio resource grant for the device-to-device bearer (1 16).

43. A computer readable medium comprising a set of instructions which, when executed on a processing system causes the processing system to perform the methods of any of claims 24 to 42.