Patent Description:
This section introduces aspects that may facilitate better understanding of the disclosure.

With the evolution of wireless communication, a requirement for supporting device to device (D2D) communication or "sidelink" features which targets at both commercial and Public Safety applications has been proposed. In the Third Generation Partnership Project (3GPP), the D2D communication feature has been introduced during the development of Release <NUM> (Rel-<NUM>) of the Long Term Evolution (LTE) standard. Some applications enabled by Rel-<NUM> LTE include device discovery, where devices are able to sense the proximity of another device and an associated application by broadcasting and detecting discovery messages that carry device and application identities. Another application, for example proximity-based service (ProSe), consists of direct communication based on physical channels terminated directly between devices, mainly optimized for Mission Critical Push To Talk (MCPTT) services, that is, voice traffic for public safety cases.

In 3GPP LTE Rel-<NUM>, an extension for the D2D work consists of supporting Vehicle-to-X (V2X) communication, which includes direct communication among vehicles, pedestrians and infrastructure, for example, vehicle to vehicle (V2V), vehicle to pedestrians (V2P) and vehicle to infrastructure (V2I). V2X communications may carry both non-safety and safety information, where each of applications and services may be associated with a specific set of requirements, e.g., in terms of latency, reliability, capacity, etc..

V2X communication may take advantage of a network (NW) infrastructure, when available, but at least basic V2X connectivity should be possible even in the case of lacking network coverage. A network-based, for example LTE-based, V2X interface may be economically advantageous because of the LTE economies of scale and capability of tighter integration between communications with LTE NW infrastructure and V2X communications, as compared to using a dedicated V2X technology.

To benefit from the network-assisted D2D communication (i.e., D2D communication at least partly configured by the network), for example V2X communication, a terminal device capable of D2D communication may need to select a proper serving network.

<CIT> relates to a method and apparatus for configuring transmission of device-to-device (D2D) control information in a wireless communication system. "Support Multi-carrier Multi-PLMN Operations for PC5 Based V2X", 3GPP TSG RAN WG2 Meeting #<NUM>, R2-<NUM> relates to potential issues for multi-carrier and multi-PLMN operations for PC5-based V2X. <CIT> relates to a system and method for using carrier aggregation for device-to-device communications.

Various embodiments of the present disclosure mainly aim at providing methods, apparatuses and computer programs for network selection in a wireless communication system, particularly a wireless system supporting V2X communications. Other features and advantages of embodiments of the present disclosure will also be understood from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the present disclosure.

In a first aspect of the disclosure, there is provided a method implemented at a terminal device. The method comprises obtaining an indication of a first carrier that provides cross-carrier configuration of a second carrier for D2D communication and selecting, from a list of authorized networks, a serving network based on the second carrier and the obtained indication.

In one embodiment, the obtaining of the indication of the first carrier may be based on at least one of a pre-configuration, a signaling from a controlling network element in a core network, and a signaling from a serving network node of the terminal device. In another embodiment, the signaling from the controlling network element or the signaling from the serving network node may indicate at least one of: whether current network or cell supports said D2D communication or said cross-carrier configuration of the second carrier; a carrier that supports said cross-carrier configuration of the second carrier; and a network or cell associated with the carrier that supports said cross-carrier configuration of the second carrier. In a further embodiment, obtaining an indication of a first carrier may include obtaining the indication of the first carrier for a network in the list of authorized networks.

In some embodiments, selecting a serving network based on the second carrier and the obtained indication may include selecting one of a first network operating on the second carrier for the D2D communication, a second network operating on the first carrier providing cross-carrier configuration of the second carrier, and a third network if the first network and the second network are unavailable. In one embodiment, the selecting may include selecting the first network with a higher priority than the second network if the first network provides the cross-carrier configuration of the second carrier for D2D communication, and/or, selecting the second network with a higher priority than the first network if the first network does not provide the cross-carrier configuration of the second carrier for D2D communication.

In one embodiment, selecting a serving network may comprise selecting a serving PLMN and selecting a cell associated with the selected serving PLMN. In another embodiment, selecting of the cell may be based on at least one of: quality of a link from the cell to the terminal device, and a D2D communication mode supported by the cell.

It should be appreciated that in some embodiments, the second carrier or a serving network may not be associated with a PLMN, and in this case, the operation of selecting a PLMN may be omitted.

In a further embodiment, the method may further include searching for a network operating on the first carrier or the second carrier, with the selection of the third network.

In an embodiment, the selected serving network may not be operator managed.

In a second aspect of the disclosure, there is provided a method implemented at a network device. The method comprises transmitting, to a terminal device, an indication of a carrier providing cross-carrier configuration of a further carrier for device to device, D2D, communication. In one embodiment, the transmitting may include transmitting the indication via broadcast signaling.

In some embodiments, the D2D communication may include V2X communication.

In a third aspect of the disclosure, there is provided an apparatus that may be implemented in or as at least part of a terminal device. The apparatus comprises an obtaining unit, configured to obtain an indication of a first carrier that provides cross-carrier configuration of a second carrier for device to device, D2D, communication; and a selecting unit configured to select, from a list of authorized networks, a serving network based on the second carrier and the obtained indication.

In a fourth aspect of the disclosure, there is provided an apparatus that may be implemented at or as at least part of a terminal device. The apparatus may comprise a processor and a memory. The memory may contain instructions executable by the processor whereby the apparatus is operative to perform the method according to the first aspect of the present disclosure.

In a fifth aspect of the disclosure, there is provided an apparatus that may be implemented at or as at least part of a network device. The apparatus may comprise processing means adapted to perform the method in accordance with the second aspect of the disclosure.

In a sixth aspect of the disclosure, there is provided a computer program. The computer program comprises instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to the first aspect of the disclosure.

According to the various aspects and embodiments as mentioned above, support for D2D communication may be improved.

Hereinafter, the principle of the present disclosure will be described with reference to illustrative embodiments. It should be understood, all these embodiments are given merely for one skilled in the art to better understand and further practice the present disclosure, but not for limiting the scope of the present disclosure. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield still a further embodiment. In the interest of clarity, not all features of an actual implementation are described in this specification.

References in the specification to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic.

As used herein, the phrase "wireless communication system" or "wireless communication network" refers to a network following any suitable wireless communication standards, such as LTE-Advanced (LTE-A), LTE, Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), and so on. Furthermore, the communications between network devices or between a network device and a terminal device in the wireless communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (<NUM>), the second generation (<NUM>), <NUM>, <NUM>, the third generation (<NUM>), the fourth generation (<NUM>), <NUM>, the fifth generation (<NUM>) communication protocols, and/or any other protocols either currently known or to be developed in the future.

As used herein, the phrase "network device" refers to a device in a wireless communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS), a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a TRP (Transmission Reception Point), AN(access Node), a relay node (RN), or a low power node (LPN) such as a femto, a pico, an access point (AP) and so forth, depending on the applied terminology and technology.

The phrase "terminal device" refers to any end device having wireless communication capabilities. By way of example and not limitation, a terminal device may be referred to as user equipment (UE), which may be a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, mobile phones, cellular phones, smart phones, or personal digital assistants (PDAs), portable computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, wearable terminal devices, vehicle-mounted wireless terminal devices and the like. In the following description, the phrases "terminal device", "terminal", "user equipment" and "UE" may be used interchangeably.

For illustrative purposes, several embodiments of the present disclosure will be described in the context of a 3GPP LTE system. Those skilled in the art will appreciate, however, that the concept and principle of embodiments of the present disclosure may be more generally applicable to other wireless networks, for example <NUM> CDMA-based network or a <NUM> or Next Radio (NR) system.

<FIG> illustrates schematically a wireless communication system in which embodiments of the present disclosure may be implemented. As shown in <FIG>, the wireless communication system <NUM> may include one or more network devices, for example network device <NUM>, which may be in a form of an eNB. It would be appreciated that the network device <NUM> could also be in a form of a Node B, BTS (Base Transceiver Station), and/or BSS (Base Station Subsystem), AP and the like. The network device <NUM> may provide radio connectivity to a set of terminal devices, for example terminal devices <NUM> to <NUM>, within coverage of its cell. Each cell is associated with an operator's network, e.g., a Public Land Mobile Network (PLMN). A terminal device (e.g., terminal device <NUM>) may access the wireless communication system via the network device <NUM>, or communicate with another terminal device (e.g., terminal device <NUM> or <NUM>) directly via D2D. The term "D2D" as used herein refers to any type of device to device communication, including UE to UE communication, vehicle to vehicle communication and so on.

The network device <NUM> may control resource allocation for both cellular communication and D2D communication. For example, the network device <NUM> may send a resource grant (also referred to as a scheduling grant) to the terminal device <NUM>, indicating which resource the terminal device <NUM> may use for its sidelink communication. Such D2D communication with a resource allocated by the network may be referred to as Mode <NUM> D2D communication. Alternatively, the network device <NUM> may only configure a resource pool for sharing by all D2D communications. In this scenario, a terminal device may select, from the resource pool, a resource for its D2D communication automatically, based on for example channel sensing or a cognitive radio technology. Such D2D communication with a resource selected from a resource pool by the terminal device itself may be referred to as Mode <NUM> D2D communication. The Mode <NUM> D2D communication usually provides better quality of service than the Mode <NUM> D2D communication.

To benefit from the network-based D2D communication, a terminal device capable of D2D communication may need to select a proper serving network. In 3GPP, specifications with respect to related non-access stratum (NAS) and access stratum (AS) procedures have been enhanced to support the D2D communication. For example, in 3GPP TS <NUM> V13. <NUM>, section <NUM>. 1B, a PLMN selection procedure which prioritizes the PLMNs associated with a ProSe carrier is specified. The ProSe carrier is a carrier configured to support ProSe service. Some descriptions in the TS <NUM> V13. <NUM>, section <NUM>. 1B are reproduced below:.

Another example of 3GPP specification enhancement for supporting the D2D communication can be found in TS <NUM> V13. <NUM>, section <NUM>. <NUM>, where a cell selection prioritizing cells operating on the ProSe carrier is specified. Some related descriptions in the TS <NUM> V13. <NUM>, section <NUM>. <NUM> are reproduced below:
If the UE capable of sidelink communication is configured to perform sidelink communication and can only perform the sidelink communication while camping on a frequency, the UE may consider that frequency to be the highest priority.

3GPP TS <NUM> V13. <NUM>, section <NUM>. <NUM> specifies that a resource control from an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) cell is limited to a ProSe carrier, i.e.,
else (i.e. out of coverage on sidelink carrier):.

However, with an evolvement of D2D communication, the procedures specified currently in 3GPP may not be optimal any longer, and inventors of the present disclosure have realized that additional factors should be taken into account during the network selection in order to well support the D2D communication.

For example, in a future wireless communication system (e.g., when ProSe evolves to V2x in 3GPP), a feature of cross-carrier configuration may be introduced, that is, a carrier configured for D2D communication may be cross-carrier configured by another carrier, either via a physical layer scheduling signaling or via a higher layer configuration signaling, e.g., radio resource control (RRC) signaling. It means that an E-UTRAN cell may not only control a D2D communication (e.g., over a PC5 interface specified in 3GPP) via its own operating carrier frequency, but also control the D2D communication via another carrier frequency. Therefore, a related NAS/AS procedure for a sidelink may need to be changed accordingly.

In addition, a wireless communication system may include a plurality of cells and each of the cells may have different capability for supporting the D2D communication. For example, a network device (e.g., the network device <NUM> shown in <FIG>), and consequently an associated cell, may not support D2D communication, support one of Mode <NUM> and Mode <NUM> D2D communication, or support both D2D communication Modes.

By taking some of the above factors into account during a network selection, an optimized selection result may be obtained. In the present disclosure, methods, apparatuses and computer program products are provided to enable an enhanced network selection procedure. With embodiments of the present disclosure, support for D2D communication may be improved.

Reference is now made to <FIG>, which shows a flowchart of a method <NUM> according to an embodiment of the present disclosure. The method <NUM> may be implemented at a terminal device (e.g., any of the terminal devices <NUM>-<NUM> shown in <FIG>). For simplicity, the method <NUM> will be described below with reference to the terminal device <NUM> as shown in <FIG>. However, it is to be understood that the method <NUM> may also be implemented by other suitable terminal devices. In addition, though embodiments of the present disclosure can be implemented in the example network structure shown in <FIG>, the scope of the present disclosure is not limited to a specific network infrastructure.

As shown in <FIG>, at block <NUM>, the terminal device <NUM> obtains an indication of a first carrier that provides cross-carrier configuration of a second carrier for the D2D communication.

In an embodiment, at block <NUM>, the terminal device <NUM> may obtain the indication of the first carrier based on at least one of a pre-configuration (for example in the universal integrated circuit card (UICC) and/or in the mobile entity (ME) of the terminal device), a signaling from a controlling network element in a core network, and a signaling from a serving network node of the terminal device. In an embodiment, the terminal device <NUM> may receive the indication of the first carrier from a serving network node as a part of a broadcasting signaling. For example, the terminal device <NUM> may receive the indication of the first carrier from a serving network node as a part of system information, e.g., via a system information block <NUM>(SIB21) defined in 3GPP LTE. Alternatively, in another embodiment, the terminal device <NUM> may obtain the indication of the first carrier via a dedicated signaling, e.g., a dedicated radio resource control (RRC) signaling. In a further embodiment, at block <NUM>, the terminal device <NUM> may obtain the indication of the first carrier from a controlling network element in a core network, for example from a V2X control function via a V3 interface specified by 3GPP.

In one embodiment, the first carrier may be a carrier that provides physical layer cross-carrier configuration for the second carrier, that is, physical layer scheduling information of the second carrier may be provided to the terminal device <NUM> via the first carrier. In another embodiment, the first carrier may provide, to the terminal device <NUM>, cross-carrier configuration of the second carrier via a higher layer (e.g., a radio resource control (RRC) layer) signalling.

The second carrier is a carrier provisioned to the terminal device <NUM> for D2D communication, e.g., for V2X communication via the PC5 interface specified in 3GPP. In one embodiment, the second carrier may be the same carrier configured for a Prose service. In another embodiment, the second carrier may be different from the carrier for the Prose.

In one embodiment, the second carrier (and an associated network with the second carrier, e.g., a PLMN) which supports D2D communication (e.g., V2X communication over a PCS interface) may be preconfigured. The terminal device may store the pre-configuration locally, for example.

In another embodiment, the terminal device <NUM> may acquire the indication of the second carrier in a similar way as that for obtaining the indication of the first carrier. For example, the indication/configuration of the second carrier may be provided to the terminal device <NUM> by a V2X control function via a V3 interface. Alternatively, the terminal device <NUM> may learn the second carrier (and an associated PLMN) from a broadcast signaling (e.g. a SIB21) provided by its serving cell in the serving PLMN.

A serving network (e.g., a PLMN) or a serving network device (e.g., the network device <NUM> shown in <FIG>) of the terminal device <NUM> may not support the D2D communication (e.g., the V2X communication via PC5 interface) or may not provide cross-carrier configuration for a V2X carrier (e.g., the second carrier). With an embodiment of the present disclosure, in such a case, the serving PLMN or the serving network device <NUM> may indicate, to the terminal device <NUM>, which is the carrier (and a related PLMN) where the D2D communication (e.g., V2X via PC5 interface) is supported, optionally, it can also indicate, to the terminal device <NUM>, whether there is an E-UTRAN deployment on that carrier.

In another embodiment, the serving network device <NUM> may indicate, to the terminal device <NUM>, whether there are carriers in neighboring frequencies (which may possibly belong to another PLMN) where cross-carrier configuration for V2X carriers is supported. That is, in some embodiments, at block <NUM>, the terminal device <NUM> may obtain the indication of the first carrier (and/or the second carrier) based on a signaling from a controlling network element in a core network, and/or a signaling from a serving network node of the terminal device, and/or pre-configuration, for example, in the universal integrated circuit card (UICC) and/or in the mobile entity (ME) of the terminal device.

Furthermore, the signaling from the controlling network element or the signaling from the serving network node may provide one or more of the following information: whether current network or cell supports D2D communication on its operating carrier directly or it supports, on its operating carrier, cross-carrier configuration of another D2D carrier; a carrier that supports cross-carrier configuration of the second carrier; and a network or cell associated with the carrier that supports cross-carrier configuration of the second carrier. This allows the terminal device <NUM> to obtain information/indication of the first or second carrier from a network (or network device) associated with a further third carrier.

In still another embodiment, at block <NUM>, the terminal device <NUM> may obtain the indication of the first carrier for a specific network in a list of authorized networks. In other words, the indication of the first carrier obtained by the terminal device <NUM> at block <NUM> may be per-network information. It means that the indicated of first carrier may be associated with a specific network (e.g., a PLMN). In one embodiment, the network device <NUM> may transmit indications of a plurality of first carriers to the terminal devices <NUM>, each of the plurality of first carriers is capable of providing cross-carrier configuration of a D2D carrier (e.g., a carrier for V2X communication via PC5 interface) and associated with a corresponding network (e.g., a PLMN).

At block <NUM>, based on the second carrier and the obtained indication of the first carrier, the terminal device <NUM> selects a serving network from a list of authorized networks. The list of authorized networks may be preconfigured, or signaled to the terminal device, for example in a similar way as that used for indicating the first carrier or second carrier. One or more of the authorized networks in the list may be operator-managed or non-operator managed. In other words, an authorized network in the list may be operated by one or more operators, or the authorized network is not managed by any operator. As a result, the selected serving network may or may not be operator managed.

By providing information on the first carrier, embodiments of the present disclosure enable the terminal device <NUM> to select a network which may be more suitable for the D2D communication than that selected using a conventional solution.

In one embodiment, the selection at block <NUM> may be performed when the terminal device <NUM> is configured to perform D2D communication. In another embodiment, the selection at block <NUM> may be performed when the terminal device needs to or wishes to perform the D2D communication.

At block <NUM>, the terminal device <NUM> may select a serving network according to any suitable selection criteria, and embodiments of the present disclosure are not limited to any specific criteria or rules for the selection. Just for illustrative rather than limitation, some examples are provided below.

In one embodiment, at block <NUM>, the terminal device <NUM> may select one of the following as the serving network: a first network operating on the second carrier for the D2D communication, a second network operating on the first carrier that provides cross-carrier configuration of the second carrier, and a third network if the first network and the second network are unavailable. The third network may be considered as a fallback network.

Both the first network and the second network can provide control for D2D communication of the terminal device103, and their difference lies in that the first network provides the control via its operating carrier while the second network provide the control via cross-carrier configuration of the second carrier from the first carrier. In one embodiment, the terminal device <NUM> may select the first network with a higher priority than the second network. For example, the terminal device <NUM> may select the serving network in the following order:.

In an embodiment, the terminal device <NUM> may select the first network with a higher priority than the second network and the third network, if the first network provides the cross-carrier configuration of the second carrier for D2D communication. Alternatively, or in addition, in some embodiments, the terminal device <NUM> may select the second network with a higher priority than the first network and the third network if the first network does not provide the cross-carrier configuration of the second carrier for D2D communication.

With the above order, when both the first network and the second network are available, the terminal device <NUM> will select the first network as the serving network, and only when both the first network and the second network are unavailable, the terminal device may choose the third network as the serving network. In this case, the third network may be considered as a fallback network.

In one embodiment, the terminal device <NUM> may consider the selection of the third network as a temporary selection, and then monitors (or searches for) a network satisfying the above condition <NUM>) or <NUM>) after selecting the third network at block <NUM>. That is, the terminal device <NUM> may search for (or reselect) a network operating on the first carrier or the second carrier once the third network is selected. For example, optionally, terminal device <NUM> may search for the first network or the second network periodically at block <NUM> if a third network is selected at block <NUM>, until the first network or the second network is found, or a predefined maximum searching time threshold is reached.

Now reference is made to <FIG> which illustrates some optional implementations of block <NUM> shown in <FIG>. As shown in <FIG>, in an embodiment, selecting a serving network at block <NUM> may include selecting a serving PLMN at block <NUM>. During selection of the PLMN at block <NUM>, besides the above selection priorities, the terminal device <NUM> may optionally take more factors into account during the network selection. For example, the terminal device <NUM> may first determine a plurality of networks (e.g., PLMNs) with the above priority <NUM>), and then select a network from the plurality of networks based on a further criterion. For instance, the terminal device may further choose the PLMN by following a procedure specified in 3GPP TS <NUM>, that is, choose an allowable PLMN which:.

As shown in <FIG>, in another embodiment, selecting a serving network at block <NUM> may include selecting a serving PLMN at block <NUM> and selecting a cell associated with the selected serving PLMN at block <NUM>. However, neither block <NUM> nor block <NUM> is mandatory for the block <NUM>. Embodiments of the present disclosure are not limited to any specific way for selecting any specific network based on the second carrier and the obtained indication of the first carrier at block <NUM>. For example, in another embodiment, the selecting a serving network at block <NUM> may only include selecting a serving cell for a given PLMN at block <NUM>.

In an embodiment, there may be a plurality of cells associated with a selected/given serving network (e.g., serving PLMN). In such case, at block <NUM>, the terminal device <NUM> may select a cell associated with a selected/given serving PLMN in the following order:.

Similar to what is described with reference to a PLMN selection, at block <NUM>, the terminal device <NUM> may monitor (periodically or aperiodically) a cell satisfying the above condition a) or b) if a cell satisfying condition c) is selected at block <NUM>, in order to find/reselect a cell that can support D2D communication better. This embodiment enables the terminal device <NUM> to re-prioritize the cell selection according to the prioritization order above.

In another embodiment, when there are a plurality of cells associated with a selected/given serving network (e.g., serving PLMN), then at a block <NUM>, the terminal device <NUM> may select a cell based on quality of a link from the cell to the terminal device <NUM>, and/or based on a D2D communication mode supported by the cell.

It should be appreciated that in some embodiments, the second carrier or a serving network may not be associated with a PLMN, and in this case, the operations of selecting a PLMN and a cell associated with the PLMN in blocks <NUM> and <NUM> may be omitted.

For example, the terminal device may select a cell supporting mode <NUM> D2D communication with a higher priority than a cell only supporting mode <NUM> D2D communication. Since when a V2V carrier is congested, the usage of a mode-<NUM> resource pool may not ensure a satisfactory QoS for D2D communication. In one embodiment, a network device (e.g., an eNB) may indicate, to the terminal device <NUM>, that cross-carrier configuration (e.g., including cross-carrier scheduling in physical layer and/or higher layer configuration) over the V2X carrier is supported but it does not provide any mode-<NUM> pool configuration for operating over the V2X carrier. In such case, the UE may need to request dedicated resources from an E-UTRAN to operate on the V2X carrier on PC5 interface.

In another embodiment, in case the terminal device <NUM> is in coverage of multiple cells, and all of the multiple cells are capable of providing cross-carrier configuration for the V2X carrier, the UE may prioritize selection of a cell providing mode-<NUM> cross-carrier configuration, e.g., via physical layer cross-carrier scheduling signaling. In a further embodiment, when there are multiple cells providing mode-<NUM> (or mode-<NUM>) cross-carrier configuration, the terminal device <NUM> may prioritize selection of a cell with better quality (e.g. RSRP) according to cell (re)selection criteria. For example, the terminal device <NUM> may select a cell with maximum received RSRP as the serving cell.

Some of the embodiments for cell selection enable the terminal device <NUM> to select a cell that can provide higher QoS for the D2D communication.

Now reference is made to <FIG> which shows a flowchart of a method <NUM> according to an embodiment of the present disclosure. The method <NUM> may be implemented at or as at least part of a network device (e.g., the network device <NUM> shown in <FIG>). For simplicity, the method <NUM> will be described below with reference to the network device <NUM> shown in <FIG>. However, it is to be understood that the method <NUM> may also be implemented by any other suitable network devices.

As shown in <FIG>, at block <NUM>, the network device <NUM> transmits, to a terminal device, an indication of a carrier that provides cross-carrier configuration of a further carrier for D2D communication. The method <NUM> enables the terminal device to be aware of another carrier that can control the D2D communication, besides the carrier provisioned to it for D2D communication. This information can be taken into account during a network selection procedure for an enhancement of the selection.

In one embodiment, the further carrier for D2D communication may be preconfigured and thus known to the terminal device without additional signaling. Alternatively, the network device <NUM> may indicate the further carrier to the terminal device via a broadcast or dedicated signaling, for example at block <NUM>.

In one embodiment, the carrier and the further carrier may be the first carrier and the second carrier described with reference to method <NUM>, and therefore, descriptions with respect to approaches for communicating the first carrier and the second carrier provided with reference to method <NUM> and <FIG> and <FIG> also apply here and details will not be repeated.

In one embodiment, the indication of the carrier transmitted by the network device <NUM> at block <NUM> may be per-network information, that is to say, the carrier indicated may be associated with a specific network. Then in one embodiment, at block <NUM>, the network device <NUM> may transmit indications of a plurality of carriers to the terminal devices <NUM>, each of the plurality of carriers is capable of providing cross-carrier configuration of a D2D carrier (e.g., a carrier for V2X communication via PC5) and associated with a corresponding network (e.g., a PLMN).

In another embodiment, at an optional block <NUM>, the network device <NUM> may transmit a list of authorized networks to the terminal devices for the terminal device to select from. Such an operation can be avoided in another embodiment where the list of authorized networks is preconfigured.

<FIG> illustrates a schematic block diagram of an apparatus <NUM> implemented in/as at least part of a terminal device, for example, one of the terminal devices <NUM>-<NUM> shown in <FIG>. The apparatus <NUM> is operable to carry out the example method <NUM> described with reference to <FIG> and <FIG> and possibly any other processes or methods. It is also to be understood that the method <NUM> is not necessarily carried out by the apparatus <NUM>. At least some blocks of the method <NUM> can be performed by one or more other entities.

As illustrated in <FIG>, the apparatus <NUM> includes an obtaining unit <NUM>, configured to obtain an indication of a first carrier that provides cross-carrier configuration of a second carrier for D2D communication; and a selecting unit <NUM>, configured to select, from a list of authorized networks, a serving network based on the second carrier and the obtained indication. The selected serving network may be an operator managed network, or a network not managed by any operator.

In one embodiment, the obtaining unit <NUM> and the selecting unit <NUM> may be configured to perform functions/operations described with reference to block <NUM> and <NUM> of method <NUM> respectively, and therefore descriptions with respect to the first carrier, the second carrier and their acquisition provided with reference to method <NUM> and <FIG> and <FIG> also apply here and details will not be repeated for simplicity.

Just for illustration, in one embodiment, the obtaining unit <NUM> may be configured to obtain the indication based on at least one of: a pre-configuration, a signaling from a controlling network element in a core network, and a signaling from a serving network node of the terminal device. In an embodiment, the pre-configuration may be coded in the universal integrated circuit card (UICC) and/or in the mobile entity (ME) of the apparatus <NUM>. In one embodiment, the signaling from the controlling network element or the signaling from the serving network node indicates at least one of whether current network or cell supports said D2D communication or said cross-carrier configuration of the second carrier; a carrier that supports said cross-carrier configuration of the second carrier; and a network or cell associated with the carrier that supports said cross-carrier configuration of the second carrier.

In an embodiment, the obtaining unit <NUM> may be configured to obtain the indication of the first carrier for a network in the list of authorized networks. In this embodiment, the indication of the first carrier obtained by the obtaining unit <NUM> is network specific. That is to say, the indicated first carrier may be associated with a specific network (e.g., a PLMN).

In another embodiment, the selecting unit <NUM> may be configured to select one of a first network operating on the second carrier for the D2D communication, a second network operating on the first carrier providing cross-carrier configuration of the second carrier, and a third network if the first network and the second network are unavailable, as the serving network. For example, without limitation, the selecting unit may be configured to select the first network with a higher priority than the second network. In an embodiment, the selecting unit may be configured to select the first network with a higher priority than the second network and the third network if the first network provides the cross-carrier configuration of the second carrier for D2D communication, and/or, select the second network with a higher priority than the first network and the third network if the first network does not provide the cross-carrier configuration of the second carrier for D2D communication.

Optionally, the apparatus <NUM> may further comprise a reselecting unit <NUM>, configured to search for a network operating on the first carrier or the second carrier, if a third network is selected currently. The searching may be performed by the reselecting unit periodically or aperiodically by the reselection unit <NUM>. For instance, the reselecting unit <NUM> may search for the first network or the second network periodically, until the first network or the second network is found, or a predefined maximum searching time is reached.

In some embodiments, the selecting unit <NUM> may include one or both of a PLMN selecting unit <NUM> and a cell selecting unit <NUM>. The PLMN selecting unit <NUM> may be configured to select a serving PLMN, and the cell selecting unit <NUM> may be configured to select a cell associated with a selected/given serving PLMN. That is to say, the selecting unit <NUM> may be configured to select both a PLMN and an associated cell in one embodiment. In another embodiment, the selecting unit <NUM> may be configured a cell associated with a given PLMN using the cell selection unit <NUM>.

It should be appreciated that in some embodiments, the second carrier or a serving network may not be associated with a PLMN, and in this case, PLMN selecting unit <NUM> and a cell selecting unit <NUM> may be omitted.

Embodiments are not limited to any specific rules for the cell selection, and just for illustrative purpose, the cell selecting unit <NUM> may be configured to select a cell based on at least one of: quality of a link from the cell to the terminal device, and a D2D communication mode supported by the cell.

<FIG> illustrates a schematic block diagram of an apparatus <NUM> implemented in/as at least part of a network device, for example, the network device <NUM> shown in <FIG>. The apparatus <NUM> is operable to carry out the example method <NUM> described with reference to <FIG> and possibly any other processes or methods. It is also to be understood that the method <NUM> is not necessarily carried out by the apparatus <NUM>. At least some blocks of the method <NUM> can be performed by one or more other entities.

As illustrated in <FIG>, the apparatus <NUM> includes a transmitting unit <NUM> configured to transmit, to a terminal device, an indication of a carrier providing cross-carrier configuration of a further carrier for D2D communication (e.g., V2X communication via PC5 interface). The transmitting unit <NUM> may transmit the indication to the terminal device via a broadcast signaling or a dedicated signaling. The indication of the carrier may be used by the terminal device during a network selection procedure.

Optionally, in another embodiment, the apparatus <NUM> may further comprise a first configuration unit <NUM>, which is configured to indicate the further carrier for D2D communication to the terminal device <NUM>. In a further embodiment, the further carrier provisioned to the terminal device for D2D communication may be preconfigured, and in this case, the first configuration unit <NUM> may be omitted.

In one embodiment, the apparatus may include a second configuration unit <NUM> configured to indicate to the terminal device a list of authorized networks for the terminal device to select from. In another embodiment, the list of authorized networks may be preconfigured, or may be transmitted to the terminal device by the transmitting unit <NUM> or the first configuration unit <NUM>, and therefore the second configuration unit <NUM> may be omitted.

<FIG> illustrates a simplified block diagram of an apparatus <NUM> that may be embodied in/as at least part of a network device, e.g., the network device <NUM> shown in <FIG>, and an apparatus <NUM> that may be embodied in/as at least part of a terminal device, e.g., one of the terminal devices <NUM> -<NUM> shown in <FIG>.

The apparatus <NUM> may include at least one processor <NUM>, such as a data processor (DP) and at least one memory (MEM) <NUM> coupled to the processor <NUM>. The apparatus <NUM> may further include a transmitter TX and receiver RX <NUM> coupled to the processor <NUM>. The MEM <NUM> may be non-transitory machine/ processor/ computer readable storage medium and it may store a program (PROG) <NUM>. The PROG <NUM> may include instructions that, when executed on the associated processor <NUM>, enable the apparatus <NUM> to operate in accordance with the embodiments of the present disclosure, for example to perform the method <NUM>. A combination of the at least one processor <NUM> and the at least one MEM <NUM> may form processing means <NUM> adapted to implement various embodiments of the present disclosure.

The apparatus <NUM> includes at least one processor <NUM>, such as a DP, and at least one MEM <NUM> coupled to the processor <NUM>. The apparatus <NUM> may further include a suitable TX/ RX <NUM> coupled to the processor <NUM>. The MEM <NUM> may be non-transitory machine/ processor computer readable storage medium and it may store a PROG <NUM>. The PROG <NUM> may include instructions that, when executed on the associated processor <NUM>, enable the apparatus <NUM> to operate in accordance with the embodiments of the present disclosure, for example to perform the method <NUM>. A combination of the at least one processor <NUM> and the at least one MEM <NUM> may form processing means <NUM> adapted to implement various embodiments of the present disclosure.

Various embodiments of the present disclosure may be implemented by computer program executable by one or more of the processors <NUM> and <NUM>, software, firmware, hardware or in a combination thereof.

The MEMs <NUM> and <NUM> may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory terminal devices, magnetic memory terminal devices and systems, optical memory terminal devices and systems, fixed memory and removable memory, as non-limiting examples.

The processors <NUM> and <NUM> may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors DSPs and processors based on multicore processor architecture, as non-limiting examples.

Although some of the above description is made in the context of a NW controlled/assisted D2D communication scenario, it should not be construed as limiting the scope of the present disclosure. The principle and concept of the present disclosure may be more generally applicable to other scenarios.

In addition, the present disclosure may also provide a memory containing the computer program as mentioned above, which includes machine-readable media and machine-readable transmission media. The machine-readable media may also be called computer-readable media, and may include machine-readable storage media, for example, magnetic disks, magnetic tape, optical disks, phase change memory, or an electronic memory terminal device like a random access memory (RAM), read only memory (ROM), flash memory devices, CD-ROM, DVD, Blue-ray disc and the like. The machine-readable transmission media may also be called a carrier, and may include, for example, electrical, optical, radio, acoustical or other form of propagated signals - such as carrier waves, infrared signals, and the like.

The techniques described herein may be implemented by various means so that an apparatus implementing one or more functions of a corresponding apparatus described with an embodiment includes not only prior art means, but also means for implementing the one or more functions of the corresponding apparatus described with the embodiment and it may include separate means for each separate function, or means that may be configured to perform two or more functions. For example, these techniques may be implemented in hardware (one or more apparatuses), firmware (one or more apparatuses), software (one or more modules or units), or combinations thereof. For a firmware or software, implementation may be made through modules or units (e.g., procedures, functions, and so on) that perform the functions described herein.

Example embodiments herein have been described above with reference to block diagrams and flowchart illustrations of methods and apparatuses. It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by various means including hardware, software, firmware, and a combination thereof. For example, in one embodiment, each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations can be implemented by computer program instructions.

Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the subject matter described herein, but rather as descriptions of features that may be specific to particular embodiments. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

Claim 1:
A method (<NUM>) implemented at a terminal device (<NUM>, <NUM>, <NUM>, <NUM>), comprising:
obtaining (<NUM>) an indication of a first carrier that provides cross-carrier configuration of a second carrier for device to device, D2D, communication; and
selecting (<NUM>), from a list of authorized networks, a serving network based on the second carrier and the obtained indication.