WO2014087229A2

WO2014087229A2 - Method of device-to-device communication controlled by cellular mobile communication network

Info

Publication number: WO2014087229A2
Application number: PCT/IB2013/002902
Authority: WO
Inventors: Kaibin Zhang; Feng Han; Qi JIANG; Wu Zheng
Original assignee: Alcatel Lucent
Priority date: 2012-12-05
Filing date: 2013-11-27
Publication date: 2014-06-12
Also published as: CN103856527B; TW201427470A; WO2014087229A3; CN103856527A

Abstract

The present invention relates to a method of device-to-device communication controlled by a cellular mobile communication network. At the user equipment side, the user equipment receives a reconfiguration message from the base station for indicating a first IP service flow transported between a first user equipment and a second user equipment to be moved from a first interface to a second interface, the first interface and the second interface being respectively one of a cellular interface for an access to the cellular mobile communication network and a device-to-device interface for the device-to-device communication between the first user equipment and the second user equipment, the reconfiguration message including information for indicating the first IP service flow and information for indicating a second L2 protocol entity, and the second L2 protocol entity being used for transporting the first IP service flow via the second interface; and the user equipment de-associates a radio bearer carrying the first IP service flow from a first L2 protocol entity and associates the radio bearer with the second L2 protocol entity in response to the reconfiguration message, the first L2 protocol entity being used for transporting the first IP service flow via the first interface.

Description

Method of Device-to-Device Communication Controlled by Cellular Mobile Communication Network

Field of the invention

The present disclosure relates to device-to-device communication in a cellular mobile communication network and particularly to a method of device-to-device communication controlled by a cellular mobile communication network. Background of the invention

In a conventional cellular mobile communication network, data communication has to go through a central node such as a Base Station (BS) even if a source and a destination of the data communication are in close proximity, which results in inefficient utilization of radio resources. As a very promising means to improve the utilization ratio of a network spectrum of the cellular mobile communication network, Device-to-Device (D2D) communication (also commonly referred to as D2D communication) has gained increasingly wide attention.

Fig. l illustrates a schematic diagram of device-to-device communication in a cellular mobile communication network. A user Equipment (UE) 3 is a typical user equipment accessing the cellular mobile communication network and communicating with a base station 110 via a radio link 120 of the cellular mobile communication network. Alike a user equipment 1 and a user equipment 2 can access the cellular network and also can communicate directly with each other over a D2D radio link 130.

Unlike conventional cellular mobile communication, D2D users perform inter-user equipment direct communication underlay by the existing cellular network instead of communication via the central base station. With reuse of radio resources of the cellular users to access the cellular mobile communication network, D2D communication can significantly improve the throughput of the system and the utilization ratio of energy. Numerous international standardization organizations (including IEEE and 3 GPP) have initiated their related studies and standardization work.

A common demand is for the possibility of data flow mobility between cellular communication and D2D communication. Fig.2 illustrates a user plane protocol stack of an existing solution to data flow mobility. The user plane protocol stack generally includes a Layer 2 (L2) protocol layer (also referred to as a data link layer), an IP layer and an Application (App) layer. The L2 protocol layer generally includes a Packet Data Convergence Protocol (PDCP) sub-layer, a Radio Link Control (RLC) sub-layer and a Medium Access Control (MAC) sub-layer. The user equipment 1 and the user equipment 2 are capable of direct D2D communication. The user equipments each are provided with two air interfaces, which are a device-to-device interface (i.e., a D2D interface) Ud and a cellular interface Uu. The D2D interface may be provided with the same radio technology as the cellular interface. As illustrated in Fig.2, in the existing solution, a new dedicated IP address IP_d is allocated for the D2D interface by a mobile network element, e.g., a Mobility Management Entity (MME) in addition to an IP address IP_C allocated for the cellular interface.

This existing solution suffers from the following problems. First the mobile network element is required to have the new function of allocating the IP address for the D2D interface, thus increasing the complexity. Secondly how to support seamless flow mobility between the two interfaces with the different IP addresses (i.e., the cellular interface and the D2D interface respectively with the IP addresses IP_C and IP_d) is also a very difficult problem. Furthermore the existing mobile IP technology is applicable to the situation where each mobile terminal is provided with only one IP address, so an additional mechanism has to be introduced to address this problem, thus incurring additional standardization work and further increasing the implementation complexity. Moreover it is nearly impossible to obtain such a dedicated D2D IP address in the situation of urgent D2D communication because a mobile network infrastructure may not be available any longer in the situation of a disaster so that no mobile network element, e.g., a mobility management entity can allocate an IP address for D2D communication.

Summary of the invention

In view of the foregoing technical problems, one object of the invention is to provide a solution of device-to-device communication controlled by a cellular mobile communication network so as to allow data flow mobility between cellular communication and D2D communication.

In an embodiment according to a first aspect of the invention, there is provided a method, in a first user equipment of a cellular mobile communication network, of device-to-device communication controlled by the cellular mobile communication network, the method including the steps of: a. receiving a reconfiguration message from a base station, of the cellular mobile communication network, accessed by the first user equipment, the reconfiguration message being used for instructing a first IP service flow transported between the first user equipment and a second user equipment accessing the base station to be moved from a first interface to a second interface, the first interface being one of a cellular interface for an access to the cellular mobile communication network and a device-to-device interface for the device-to-device communication between the first user equipment and the second user equipment, the second interface being the other of the cellular interface and the device-to-device interface, the reconfiguration message including information for indicating the first IP service flow and information for indicating a second L2 protocol entity, and the second L2 protocol entity being used for transporting the first IP service flow via the second interface; and c. deassociating a radio bearer carrying the first IP service flow from a first L2 protocol entity and associating the radio bearer with the second L2 protocol entity in response to the reconfiguration message, the first L2 protocol entity being used for transporting the first IP service flow via the first interface.

As such, the mobility of data flow between the cellular interface and the D2D interface is achieved by changing the association of the radio bearer carrying the IP service flow with the L2 protocol entity.

The IP service flow and the radio bearer are known to one-to-one correspond to each other, and each radio bearer is associated with a specific L2 protocol entity. In the invention, the specific L2 protocol entity is an L2 protocol entity on the cellular interface or the L2 protocol entity on the D2D interface, and the association between the radio bearer and the L2 protocol entity can be changed. When the radio bearer is associated with an L2 protocol entity on the cellular interface, the IP service flow will be transported in a conventional cellular communication mode, that is, between the user equipments via the base station; and when the radio bearer is associated with an L2 protocol entity on the D2D interface, the IP service flow will be transported in a D2D communication mode, that is, directly between the user equipments. As can be apparent, there is a common IP layer on the cellular interface and the D2D interface. Regardless of whether it is cellular communication or D2D communication, the user equipment is provided with only one IP address, that is, an IP data packet sent to the user equipment has the same destination address, and an IP data packet sent from the user equipment has the same source address.

Moreover the inventive solution has neither change nor affect the IP layer and above (e.g., the application layer), so the inventive solution is transparent to these protocol layers. Regardless of whether it is an L2 protocol entity on the cellular interface or the L2 protocol entity on the D2D interface, all the L2 protocol entities are the same from the perspective of the IP layer and above.

In a particular embodiment of the invention, between the step a and the step c, the method further includes the step of: b. stopping sending a second data packet, of the first IP service flow, to the second user equipment; and after the step c, the method further includes the step of: f. transporting the second data packet via the second interface.

Since no data packet of the IP service flow is transmitted in the step C, that is, during the movement of the IP service flow from the first interface to the second interface, the possibility of the loss of a data packet can be lowered effectively.

In a particular embodiment of the invention, when the first interface is the cellular interface, the step b further includes: receiving a first end flag from the base station and performing the step c in response to the first end flag.

As such it is possible to enable the user equipment to receive the last data packet before the opposite user equipment stops sending the data packets to thereby further lower the possibility of the loss of a data packet.

In a particular embodiment of the invention, between the step c and the step f, the method further includes the steps of: d. sending a reconfiguration completion message, the reconfiguration completion message being for acknowledging completion of reconfiguring, at the first user equipment, the first IP service flow from the first interface to the second interface; and e. receiving a reconfiguration success message from the base station and performing the step f in response to the reconfiguration success message.

In a particular embodiment of the invention, the reconfiguration message is a Radio Resource Control (RRC) connection reconfiguration message; the reconfiguration completion message is an RRC connection reconfiguration completion message; and the reconfiguration success message is an RRC connection reconfiguration completion message.

In a particular embodiment of the invention, the information for indicating the second L2 protocol entity includes information required for establishing the second L2 protocol entity.

In a particular embodiment of the invention, the step c further includes the step of: when the second L2 protocol entity is not present, establishing the second L2 protocol entity according to the information required for establishing the second L2 protocol entity.

When an IP service flow is moved from the first interface to the second interface, the user equipment can delete or reserve an L2 protocol entity, on the first interface, corresponding to the IP service flow. If the user equipment reserves the corresponding L2 protocol entity, then the reserved L2 protocol entity can be available when the IP service flow is moved from the second interface back to the first interface without being reestablished.

In a particular embodiment of the invention, when the cellular interface and the device-to-device interface are based upon the same radio technology, communication via the cellular interface and communication via the device-to-device interface is performed in a time-division mode.

In an embodiment of a second aspect of the invention, there is provided a method, in a base station of a cellular mobile communication network, of device-to-device communication controlled by the cellular mobile communication network, the method including the steps of: A. receiving a flow mobility request message, the flow mobility request message for instructing a first IP service flow transported between a first user equipment and a second user equipment accessing the base station to be moved from a first interface to a second interface, the first interface being one of a cellular interface for an access to the cellular mobile communication network and a device-to-device interface for the device-to-device communication between the first user equipment and the second user equipment, and the second interface being the other of the cellular interface and the device-to-device interface; and B. sending a reconfiguration message to each of the first user equipment and the second user equipment, the reconfiguration message for instructing the first IP service flow to be moved from the first interface to the second interface, the reconfiguration message including information for indicating the first IP service flow and information for indicating a second L2 protocol entity, and the second L2 protocol entity being used for transporting the first IP service flow via the second interface.

In a particular embodiment of the invention, when the first interface is the cellular interface, after the step B, the method further includes the steps of: C. sending a data packet of the first IP service flow, the data packet including a first data packet, from the second user equipment, to be sent to the first user equipment and/or a second data packet, from the first user equipment, to be sent to the second user equipment; and D. determining whether there is another first data packet to be received, and if not, then sending a first end flag to the first user equipment after finishing sending the first data packet; and determining whether there is another second data packet to be received, and if not, then sending the first end flag to the second user equipment after finishing sending the second data packet.

In a particular embodiment of the invention, the method further includes the steps of: E. receiving a reconfiguration completion message from the each user equipment, the reconfiguration completion message being for acknowledging completion of reconfiguring, at the user equipment, the movement of the first IP service flow from the first interface to the second interface; and F. sending a reconfiguration success message to the each user equipment in response to the reconfiguration completion message from the each user equipment.

In a particular embodiment of the invention, after the step F, the method further includes: sending a flow mobility response message, the flow mobility response message being used for indicating completion of the movement of the first IP service flow from the first interface to the second interface.

In a particular embodiment of the invention, the flow mobility request message is sent from a network element of a mobile core network. For example, the network element of the mobile core network is a packet data network gateway.

In an embodiment according to a third aspect of the invention, there is provided a method, in a network element of a mobile core network, of device-to-device communication controlled by a cellular mobile communication network, the method including the steps of: sending a flow mobility request message to a base station of the cellular mobile communication network, the flow mobility request message being used for instructing a first IP service flow transported between a first user equipment and a second user equipment accessing the base station to be moved from a first interface to a second interface, the first interface being one of a cellular interface for an access to the cellular mobile communication network and a device-to-device interface for the device-to-device communication between the first user equipment and the second user equipment, and the second interface being the other of the cellular interface and the device-to-device interface.

In a particular embodiment of the invention, the network element of the mobile core network is a packet data network gateway.

Brief description of drawings

Other features, objects and advantages of the invention will become more apparent upon review of the following detailed description of non-limiting embodiments taken with reference to the drawings in which:

Fig. l illustrates a schematic diagram of D2D communication in the cellular mobile communication network;

Fig.2 illustrates the user plane protocol stack of the existing solution to data flow mobility between cellular communication and D2D communication;

Fig.3 illustrates a user plane protocol stack of a solution to data flow mobility between cellular communication and D2D communication according to an embodiment of the invention;

Fig.4 illustrates an L2 protocol layer in a user plane protocol stack of a solution to data flow mobility between cellular communication and D2D communication according to an embodiment of the invention;

Fig.5 illustrates a flow chart of a process of data flow mobility for movement from cellular communication to D2D communication according to an embodiment of the invention; and

Fig.6 illustrates a flow chart of a process of data flow mobility for movement from D2D communication to cellular communication according to an embodiment of the invention.

Identical or similar reference numerals will denote identical or similar step features or devices/modules throughout the drawings.

Detailed description of embodiments

The invention will be described below in details with reference to the drawings. Without loss of generality, the following description will be given taking an LTE system as an example, but those skilled in the art shall appreciate that the inventive method will also be applicable to other cellular communication systems in a similar protocol framework to the LTE system.

Fig.3 illustrates a user plane protocol stack of a solution to data flow mobility between cellular communication and D2D communication according to an embodiment of the invention.

Referring to Fig.3, a user equipment 1 and a user equipment 2 each are provided with two air interfaces which are a device-to-device interface (i.e., a D2D interface) Ud and a cellular interface Uu. On one hand the user equipment 1 and the user equipment 2 can access a cellular mobile communication network, particularly a base station of the cellular mobile communication network, via the cellular interface Uu. On the other hand, the user equipment 1 and the user equipment 2 can communicate directly with each other via the D2D interface Ud. Like the cellular interface, a Layer 2 (L2) protocol layer of the D2D interface includes PDCP, RLC and MAC sub-layers.

As illustrated in Fig.3, the cellular interface and the D2D interface share the same IP layer and above (e.g., the application layer). In other words, the user equipment is provided with only the same one IP address for an IP data packet regardless of whether it is transported via the cellular interface Uu or the D2D interface Ud.

Fig.4 illustrates an L2 protocol layer in a user plane protocol stack of a solution to data flow mobility between cellular communication and D2D communication according to an embodiment of the invention.

Referring to Fig.4, an inter-layer connection point is referred to as a Service Access Point (SAP). An L2 protocol layer includes PDCP, RLC and MAC sub-layers. Specifically the MAC provides multiplexing and mapping of a logic channel to a transport channel; a service between the RLC and MAC sub-layers is a logic channel; and the PDCP sub-layer provides upward a service which is a radio bearer as well as a Robust Header Compression (ROHC) function and security. A point-to-point radio bearer is established, modified and released by a Radio Resource Control (RRC) layer in a control plane protocol stack. Moreover each radio bearer carries an IP service flow, and each radio bearer corresponds to an L2 protocol entity. All of these are well known to those skilled in the art, so a detailed description thereof will be omitted here.

Several L2 protocol entities can be established on each of the cellular interface and the D2D interface. Without loss of generality, two L2 protocol entities respectively on the cellular interface and the D2D interface are illustrated in Fig.4, but those skilled in the art shall appreciate that the number of protocol entities on each interface may be zero or may be one or more. The user equipment transports an IP service flow corresponding to a radio bearer according to an association between the radio bearer and an L2 protocol entity. As illustrated in Fig.4, radio bearers carrying IP service flows Fl and F2 are associated with L2 protocol entities on the cellular interface, so the IP service flows Fl and F2 will be transported via the cellular interface; and radio bearers carrying IP service flows F3 and F4 are associated with L2 protocol entities on the D2D interface, so the IP service flows F3 and F4 will be transported via the D2D interface.

Moreover the user equipment can have an IP service flow corresponding to a radio bearer moved on the cellular interface and the D2D interface by changing an association between the radio bearer and an L2 protocol entity. For example, the radio bearer can be de-associated from an L2 protocol entity on the cellular interface and associated with an L2 protocol entity on the D2D interface to thereby have the corresponding IP service flow moved from the cellular interface to the D2D interface.

Fig.5 illustrates a flow chart of a process of data flow mobility for movement from cellular communication to D2D communication according to an embodiment of the invention. In this embodiment, initially both the user equipment 1 and the user equipment 2 access a base station (e.g., an eNodeB) 410 of the cellular mobile communication network in a normal cellular mode. In the normal cellular mode, all the user data flows will be transported through the base station. It is assumed that there is an IP service flow between the user equipment 1 and the user equipment 2. In the normal cellular mode, the IP service flow is transported through the base station 410 and a backhaul network. Correspondingly in the user equipments, a radio bearer carrying the IP service flow is associated with a first L2 protocol entity on the cellular interface. After a period of time, it has been found in D2D neighbor discovery, mode selection and other procedures that the user equipment 1 and the user equipment 2 can establish a D2D radio link for D2D communication, and this IP service flow between the user equipment 1 and the user equipment 2 is decided to be offloaded from the cellular mobile communication network to D2D communication. The offload process will be described below with reference to Fig.5.

First in the step S501 , a network element of a mobile core network (a packet data network gateway 420 in this example) sends a flow mobility request to the base station 410, the flow mobility request instructing a first IP service flow transported between the user equipment 1 and the user equipment 2 to be moved from the cellular interface to the D2D interface.

Next in the step S503, the base station 410 sends an RRC reconfiguration message to the user equipment 1 and the user equipment 2 in response to the received flow mobility request, the RRC reconfiguration message instructing the first IP service flow transported between the user equipment 1 and the user equipment 2 to be moved from the cellular interface to the D2D interface. The RRC reconfiguration message includes information indicating the first IP service flow and information indicating a second L2 protocol entity, and the second L2 protocol entity transports the first IP service flow via the D2D interface. For example, the information indicating the first IP service flow can include identification information of the first IP service flow. For example, the information indicating the second L2 protocol entity can include information required for establishing the second L2 protocol entity.

After the user equipment 1 and the user equipment 2 receive the RRC reconfiguration message, the user equipment 1 and the user equipment 2 will stop sending a data packet of the first IP service flow in the step S507.

After sending the RRC reconfiguration message, the base station 410 continues with sending a data packet of the first IP service flow. The data packet has been sent out before the user equipments stop sending but has not been sent to the opposite user equipments through the backhaul network and the base station. For example, when the first IP service flow is bidirectional, the data packet includes a first data packet, from the user equipment 2, to be sent to the user equipment 1, and a second data packet, from the user equipment 1 , to be sent to the user equipment 2. Moreover the base station 410 determines whether there is another first data packet to be received, and if not, then the base station sends a first end flag to the first user equipment after finishing sending the first data packet; and the base station 410 determines whether there is another second data packet to be received, and if not, then the base station sends the first end flag to the second user equipment after finishing sending the second data packet.

After sending the RRC reconfiguration message, the base station 410 can continue with sending a data packet of the first IP service flow in numerous ways, for example.

In one way, after sending the RRC reconfiguration message, the base station 410 continues with sending a data packet of the first IP service flow in the normal cellular mode. In other words, the base station 410 receives a data packet from the source user equipment, sends the data packet to the backhaul network (e.g., the packet data network gateway 420), and further receives the data packet from the backhaul network, and next sends the data packet to the destination user equipment.

In another way, after sending the RRC reconfiguration message, the base station 410 may not necessarily send a data packet to the backhaul network but can forward the data packet directly to the destination user equipment upon reception of the data packet from the source user equipment. Moreover, after sending the RRC reconfiguration message, the base station 410 can buffer a data packet of the first IP service flow and further send the buffered data packets to the destination user equipment after finishing reception of all the data packets. This can be performed in the steps S505 to S513, for example.

In the step S505, the base station 410 will stop sending a data packet of the first IP service flow and store it in a buffer. Next the base station 410 will determine whether there is another first data packet to be received, and if no, then the base station will send the stored first data packet to the user equipment 1 (step S511) and send a first end flag to the user equipment 1 after finishing sending the stored first data packets (step S513). Similarly the base station 410 will determine whether there is another second data packet to be received, and if no, then the base station will send the stored second data packet to the user equipment 1 (step S511) and send the first end flag to the user equipment 2 after finishing sending the stored second data packets (step S513).

The base station can make the determination above in numerous ways. In an example, a user equipment will send a second end flag to the base station after stopping sending a data packet, and the base station can determine upon reception of the second end flag that the user equipment has stopped sending a data packet, that is, there will be no more data packet to be received. Referring to Fig.5, optionally after the step S507, the user equipment sends the second end flag to the base station in the step S509. The second end flag can be sent separately or together with the last data packet before stopping sending. In another example, if the base station 410 detects that no data packet from a user equipment has been received for a predetermined period of time, then the base station 410 will determine that there will be no more data packet from the user equipment.

Next in the step S515, the user equipment performs RRC reconfiguration in response to the first end flag. Specifically the user equipment de-associates the radio bearer carrying the first IP service flow from the first L2 protocol entity and associates the radio bearer with the second L2 protocol entity in response to the RRC reconfiguration message. So far the radio bearer carrying the first IP service flow will be associated with the second L2 protocol entity on the D2D interface. Optionally when the second L2 protocol entity is absent, the second L2 protocol entity is established according to the information required for establishing the second L2 protocol entity.

After finishing RRC reconfiguration, the user equipment sends an RRC connection reconfiguration completion message to the base station in the step S517.

Next in the step S519, the base station 410 sends an RRC connection reconfiguration success message to the user equipment in response to the received RRC connection reconfiguration completion message. Correspondingly the user equipment starts D2D communication upon reception of the RRC connection reconfiguration success message.

After the base station 410 sends the RRC connection reconfiguration success message to both the user equipment 1 and the user equipment 2, the base station 410 sends a flow mobility response to the packet data network gateway 420 in the step S521 , the flow mobility response indicating completion of the movement of the first IP service flow from the cellular interface to the D2D interface.

Fig.6 illustrates a flow chart of a process of data flow mobility for movement from D2D communication to cellular communication according to an embodiment of the invention. In this embodiment, initially both the user equipment 1 and the user equipment 2 communicate directly with each other in a D2D communication mode. It is assumed that there is an IP service flow between the user equipment 1 and the user equipment 2. In the D2D communication mode, the IP service flow is transported directly between the user equipment 1 and the user equipment 2. Correspondingly in the user equipments, a radio bearer carrying the IP service flow is associated with a first L2 protocol entity on the D2D interface. After a period of time, this IP service flow between the user equipment 1 and the user equipment 2 is decided to be switched from a D2D communication back to a normal cellular mode. The process will be described below with reference to Fig.6.

First in the step S601 , a network element of a mobile core network (a packet data network gateway 420 in this example) sends a flow mobility request to the base station 410, the flow mobility request instructing a first IP service flow transported between the user equipment 1 and the user equipment 2 to be moved from the D2D interface to the cellular interface. Next in the step S603, the base station 410 sends an RRC reconfiguration message to the user equipment 1 and the user equipment 2 in response to the received flow mobility request, the RRC reconfiguration message instructing the first IP service flow transported between the user equipment 1 and the user equipment 2 to be moved from the D2D interface to the cellular interface. The RRC reconfiguration message includes information indicating the first IP service flow and information indicating a second L2 protocol entity, and the second L2 protocol entity transports the first IP service flow via the cellular interface. For example, the information indicating the first IP service flow can include identification information of the first IP service flow. For example, the information indicating the second L2 protocol entity can include information required for establishing the second L2 protocol entity.

After the user equipment 1 and the user equipment 2 receive the RRC reconfiguration message, the user equipment 1 and the user equipment 2 will stop sending a data packet of the first IP service flow to each other in the step S605, that is, the user equipment 1 will stop sending a second data packet to the user equipment 2, and the user equipment 2 will stop sending a first data packet to the user equipment 1.

Next in the step S607, the user equipment performs RRC reconfiguration. Specifically the user equipment de-associates the radio bearer carrying the first IP service flow from the first L2 protocol entity and associates the radio bearer with the second L2 protocol entity in response to the RRC reconfiguration message. So far the radio bearer carrying the first IP service flow will be associated with the second L2 protocol entity on the cellular interface. Optionally when the second L2 protocol entity is absent, the second L2 protocol entity is established according to the information required for establishing the second L2 protocol entity.

After finishing RRC reconfiguration, the user equipment sends an RRC connection reconfiguration completion message to the base station in the step S609.

Next in the step S611, the base station 410 sends an RRC connection reconfiguration success message to the user equipment in response to the received RRC connection reconfiguration completion message. Correspondingly the user equipment starts communication in the normal cellular mode upon reception of the RRC connection reconfiguration success message. In the normal cellular mode, the user equipment 1 and the user equipment 2 access the base station, and the first IP service flow is transported between the user equipment 1 and the user equipment 2 through the base station 410 and the backhaul network.

After the base station 410 sends the RRC connection reconfiguration success message to both the user equipment 1 and the user equipment 2, the base station 410 sends a flow mobility response to the packet data network gateway 420 in the step S613, the flow mobility response indicating completion of the movement of the first IP service flow from the D2D interface to the cellular interface.

Those skilled in the art shall appreciate that all of the foregoing embodiments are merely illustrative but not limiting. Different technical features appearing in different embodiments can be combined to advantage. Those skilled in the art shall appreciate and make other variant embodiments to the disclosed embodiments upon review of the drawings, the description and the claims. In the claims, the term "comprising" will not preclude another device(s) or step(s); the definite article "a" or "an" will not preclude plural; and the terms "first", "second", etc., are merely intended to designate a name but not to suggest any specific order. Any reference numerals in the claims shall not be construed as limiting the scope of the invention. The mere fact that some technical features appear in different dependent claims will not mean that these technical features can not be combined to advantage.

Claims

1. A method, in a first user equipment of a cellular mobile communication network, of device-to-device communication controlled by the cellular mobile communication network, the method comprising the steps of:

a. receiving a reconfiguration message from a base station, of the cellular mobile communication network, accessed by the first user equipment, the reconfiguration message being used for instructing a first IP service flow transported between the first user equipment and a second user equipment accessing the base station to be moved from a first interface to a second interface, the first interface being one of a cellular interface for an access to the cellular mobile communication network and a device-to-device interface for the device-to-device communication between the first user equipment and the second user equipment, the second interface being the other of the cellular interface and the device-to-device interface, the reconfiguration message including information for indicating the first IP service flow and information for indicating a second L2 protocol entity, and the second L2 protocol entity being used for transporting the first IP service flow via the second interface; and

c. deassociating a radio bearer carrying the first IP service flow from a first L2 protocol entity and associating the radio bearer with the second L2 protocol entity in response to the reconfiguration message, the first L2 protocol entity being used for transporting the first IP service flow via the first interface.

2. The method according to claim 1 , wherein between the step a and the step c, the method further comprises the step of:

b. stopping sending a second data packet, of the first IP service flow, to the second user equipment; and

after the step c, the method further comprises the step of:

f. transporting the second data packet via the second interface.

3. The method according to claim 2, wherein when the first interface is the cellular interface, the step b further comprises:

receiving a first end flag from the base station and performing the step c in response to the first end flag.

4. The method according to claim 2, wherein between the step c and the step f, the method further comprises the steps of:

d. sending a reconfiguration completion message, the reconfiguration completion message being for acknowledging completion of reconfiguring, at the first user equipment, the first IP service flow from the first interface to the second interface; and

e. receiving a reconfiguration success message from the base station and performing the step f in response to the reconfiguration success message.

5. The method according to claim 4, wherein:

the reconfiguration message is an RRC connection reconfiguration message;

the reconfiguration completion message is an RRC connection reconfiguration completion message; and

the reconfiguration success message is an RRC connection reconfiguration completion message.

6. The method according to claim 1, wherein the information for indicating the second L2 protocol entity includes information required for establishing the second L2 protocol entity.

7. The method according to claim 6, wherein the step c further comprises the step of: when the second L2 protocol entity is not present, establishing the second L2 protocol entity according to the information required for establishing the second L2 protocol entity.

8. The method according to claim 1 , wherein when the cellular interface and the device-to-device interface are based upon the same radio technology, communication via the cellular interface and communication via the device-to-device interface is performed in a time-division mode.

9. A method, in a base station of a cellular mobile communication network, of device-to-device communication controlled by the cellular mobile communication network, the method comprising the steps of:

A. receiving a flow mobility request message, the flow mobility request message for instructing a first IP service flow transported between a first user equipment and a second user equipment accessing the base station to be moved from a first interface to a second interface, the first interface being one of a cellular interface for an access to the cellular mobile communication network and a device-to-device interface for the device-to-device communication between the first user equipment and the second user equipment, and the second interface being the other of the cellular interface and the device-to-device interface; and

B. sending a reconfiguration message to each of the first user equipment and the second user equipment, the reconfiguration message for instructing the first IP service flow to be moved from the first interface to the second interface, the reconfiguration message including information for indicating the first IP service flow and information for indicating a second L2 protocol entity, and the second L2 protocol entity being used for transporting the first IP service flow via the second interface.

10. The method according to claim 9, wherein when the first interface is the cellular interface, after the step B, the method further comprises the steps of:

C. sending a data packet of the first IP service flow, the data packet including a first data packet, from the second user equipment, to be sent to the first user equipment and/or a second data packet, from the first user equipment, to be sent to the second user equipment; and

D. determining whether there is another first data packet to be received, and if not, then sending a first end flag to the first user equipment after finishing sending the first data packet; and determining whether there is another second data packet to be received, and if not, then sending the first end flag to the second user equipment after finishing sending the second data packet.

11. The method according to claim 9, wherein the method further comprises the steps of:

E. receiving a reconfiguration completion message from the each user equipment, the reconfiguration completion message being for acknowledging completion of reconfiguring, at the user equipment, the movement of the first IP service flow from the first interface to the second interface; and

F. sending a reconfiguration success message to the each user equipment in response to the reconfiguration completion message from the each user equipment.

12. The method according to claim 11, wherein after the step F, the method further comprises: sending a flow mobility response message, the flow mobility response message being used for indicating completion of the movement of the first IP service flow from the first interface to the second interface.

13. The method according to claim 9, wherein the flow mobility request message is sent from a network element of a mobile core network.

14. The method according to claim 13, wherein the network element of the mobile core network is a packet data network gateway.

15. A method, in a network element of a mobile core network, of device-to-device communication controlled by a cellular mobile communication network, the method comprising the steps of:

sending a flow mobility request message to a base station of the cellular mobile communication network, the flow mobility request message being used for instructing a first IP service flow transported between a first user equipment and a second user equipment accessing the base station to be moved from a first interface to a second interface, the first interface being one of a cellular interface for an access to the cellular mobile communication network and a device-to-device interface for the device-to-device communication between the first user equipment and the second user equipment, and the second interface being the other of the cellular interface and the device-to-device interface.