Apparatus, method and computer program for availability of a network slice service area

Abstract

There is provided an apparatus comprising means for receiving, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, where in the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice.

Description

[0001] Title

[0002] APPARATUS, METHOD AND COMPUTER PROGRAM FOR AVAILABILITY OF A NETWORK SLICE SERVICE AREA

[0003] Field

[0004] The present application relates to a method, apparatus, system and computer program and in particular but not exclusively to steering UEs to stay in a network slice area of service.

[0005] Background

[0006] A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and / or other nodes by providing carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, video, electronic mail (email), text message, multimedia and / or content data and so on. Nonlimiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

[0007] In a wireless communication system, at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). Some wireless systems can be divided into cells, and are therefore often referred to as cellular systems.

[0008] A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and / or receive communications on the carrier. The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and / or parameters which shall be used for the connection are also typically defined. One example of a communications system is Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN) (3G radio). Other examples of communication systems are the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology and so-called 5G or New Radio (NR) networks. NR is being standardized by the 3rd Generation Partnership Project (3GPP). Other examples of communication systems include 5G-Advanced (NR Rel-18 and beyond) and 6G.

[0009] A feature of modern communication systems is known as network slicing. Network slicing is a feature that enables multiplexing of virtualized and / or independent logical networks on a physical network infrastructure. The present disclosure identifies that how to steer a UE into a network slice service area and how to prevent a UE from leaving a network slice service area may need to be addressed.

[0010] Summary

[0011] In a first aspect there is provided an apparatus comprising means for receiving, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice.

[0012] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell, a list of network slices that are unavailable at the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0013] The apparatus may comprise means for receiving the flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node, triggering means for obtaining cell load information from the second radio access node based on the received flag, receiving the cell load information from the second radio access node and based on the received cell load information, determining the at least one cell where the network slice is unavailable.

[0014] Receiving the cell load information from the second access node may comprise receiving an indication of slice unavailability information for the at least one cell.

[0015] The unavailability of a network slice at a cell may be indicated with an indication that the network slice is configured with zero resources at the cell.

[0016] The information may be received in a Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

[0017] The information may be received in a resource status update or resource update response message.

[0018] The information may be provided together with load information from the second radio access node indicating that the at least one network slice has a zero capacity value at the cell.

[0019] The apparatus may comprise means for determining, based on the information, that the cell of the radio access node is to be excluded from slice-based cell reselection by a user equipment and means for providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection.

[0020] Means for providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection comprises means for broadcasting a list of excluded cells of an network slice access group including the at least one network slice.

[0021] The apparatus may comprise means at the first radio access node for determining, based on the information, to refrain from handing over a user equipment to the cell at the second radio access node.

[0022] The apparatus may comprise means for providing to the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice at a cell of the first radio access node wherein the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources at the cell or if the cell is outside the area of service of the slice. The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell or a list of network slices that are unavailable at the cell.

[0023] In a second aspect there is provided an apparatus comprising means for providing, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0024] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available for the cell, a list of network slices that are unavailable for the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0025] The apparatus may comprise means for providing the flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node, receiving a request for cell load information from the first radio access node and providing the cell load information from the second radio access node to the first radio access node for use in determining the at least one or more cells where the network slice is available or not unavailable.

[0026] Providing the cell load information from the second access node may comprise providing an indication of network slice unavailability information for the at least one cell.

[0027] The unavailability of a network slice at a cell may be indicated with an indication that the network slice is configured with zero resources at the cell.

[0028] The information may be provided in an Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

[0029] The information may be provided in an Xn application protocol resource status update or an Xn application protocol resource status response message. The information may be provided together with an indication from the second radio access node that the at least one network slice has a zero capacity value at the cell.

[0030] The apparatus may comprise means for receiving, at the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice of a cell of the first radio access node where in the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0031] In a third aspect there is provided an apparatus comprising means for receiving information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of a radio access network node comprises an unavailable slice, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice ; and excluding the cell during a slice-based cell reselection procedure.

[0032] The apparatus may comprise means for receiving the information indicating that the at least one network slice is unavailable at the cell of the radio access network node or the at least one network slice access group supported at the cell of the radio access network node comprises an unavailable slice from a further radio access node, wherein the at least one network slice is supported by the further radio access node.

[0033] The information may comprise a broadcasted list of excluded cells of a network slice access group including the at least one network slice.

[0034] The apparatus may comprise means for receiving the information indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of the radio access network node comprises an unavailable slice from a core network node.

[0035] The cell may be identified by a cell global cell identity and triggering means for determining a physical cell identifier associated with the received cell global identity of the cell. Determining of the physical cell identifier for the cell may be based on at least one of a system information block received from a neighbouring cell or a system information block received in serving cell indicating a mapping between cell global identities and physical cell identities or in a radio resource control release message when the user equipment is sent to inactive mode.

[0036] In a fourth aspect there is provided a method comprising receiving, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0037] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell, a list of network slices that are unavailable at the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0038] The method may comprise receiving the flag indicating that the at least one slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node, triggering means for obtaining cell load information from the second radio access node based on the received flag, receiving the cell load information from the second radio access node and based on the received information, determining the at least one cell where the network slice is unavailable.

[0039] Receiving the cell load information from the second access node may comprise receiving an indication of network slice unavailability information for the at least one cell.

[0040] The unavailability of a network slice at a cell may be indicated with an indication that the network slice is configured with zero resources at the cell.

[0041] The information may be received in a Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

[0042] The information may be received in an Xn application protocol resource status update or an Xn application protocol resource status response message. The information may be provided together with load information from the second radio access node indicating that the at least one network slice has a zero capacity value at the cell.

[0043] The method may comprise determining, based on the information, that the cell of the radio access node is to be excluded from slice-based cell reselection by a user equipment and providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection.

[0044] Providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection may comprise broadcasting a list of excluded cells of a network slice access group including the at least one network slice.

[0045] The method may comprise determining, based on the information, to refrain from handing over a user equipment to the cell at the second radio access node.

[0046] The method may comprise providing to the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice at a cell of the first radio access node wherein the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources or if the cell is outside the area of service of the slice.

[0047] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell or a list of network slices that are unavailable at the cell.

[0048] In a fifth aspect there is provided a method comprising providing, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0049] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available for the cell, a list of network slices that are unavailable for the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0050] The method may comprise providing the flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node, receiving a request for cell load information from the first radio access node and providing the cell load information from the second radio access node to the first radio access node for use in determining the at least one or more cells where the network slice is available or not unavailable.

[0051] Providing the cell load information from the second access node may comprise providing an indication of network slice unavailability information for the at least one cell.

[0052] The unavailability of a network slice at a cell may be indicated with an indication that the network slice is configured with zero resources at the cell.

[0053] The information may be provided in a Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

[0054] The information may be provided in an Xn application protocol resource status update or resource status response message.

[0055] The information may be provided together with an indication from the second radio access node that the at least one network slice has a zero capacity value at the cell.

[0056] The method may comprise receiving, at the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice of a cell of the first radio access node where in the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources at the cell or if the cell is outside the area of service of the slice.

[0057] In a sixth aspect there is provided a method comprising receiving information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of a radio access network node comprises an unavailable slice, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice; and excluding the cell during a slice-based cell reselection procedure.

[0058] The method may comprise receiving the information indicating that the at least one network slice is unavailable at the cell of the radio access network node or the at least one network slice access group supported at the cell of the radio access network node comprises an unavailable slice from a further radio access node, wherein the at least one network slice is supported by the further radio access node.

[0059] The information may comprise a broadcasted list of excluded cells of a network slice access group including the at least one network slice.

[0060] The method may comprise receiving the information indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of the radio access network node comprises an unavailable slice from a core network node.

[0061] The cell may be identified by a cell global cell identity and triggering means for determining a physical cell identifier associated with the received cell global identity of the cell.

[0062] Determining of the physical cell identifier for the cell may be based on at least one of a system information block received from a neighbouring cell or a system information block received in serving cell indicating a mapping between cell global identities and physical cell identities or in a radio resource control release message when the user equipment is sent to inactive mode.

[0063] In a seventh aspect there is provided an apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to receive, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice.

[0064] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell, a list of network slices that are unavailable at the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0065] The apparatus may be caused to receive the flag indicating that the at least one slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node, trigger means for obtaining cell load information from the second radio access node based on the received flag, receive the cell load information from the second radio access node and based on the received information, determine the at least one cell where the slice is unavailable.

[0066] Receiving the cell load information from the second access node may comprise receiving an indication of network slice unavailability information for the at least one cell.

[0067] The unavailability of a network slice at a cell may be indicated with an indication that the network slice is configured with zero resources at the cell.

[0068] The information may be received in a Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

[0069] The information may be received in an Xn application protocol resource status update or an Xn application protocol resource status response message.

[0070] The information may be provided together with load information from the second radio access node indicating that the at least one network slice has a zero capacity value at the cell.

[0071] The apparatus may be caused to determine, based on the information, that the cell of the radio access node is to be excluded from slice-based cell reselection by a user equipment and provide an indication to the user equipment that the cell is to be excluded from slice-based cell reselection.

[0072] Providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection comprises broadcasting a list of excluded cells of an network slice access group including the at least one slice.

[0073] The apparatus may be caused to determine, based on the information, to refrain from handing over a user equipment to the cell at the second radio access node. The apparatus may be caused to provide to the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice at a cell of the first radio access node wherein the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0074] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell or a list of slices that are unavailable at the cell.

[0075] In an eighth aspect there is provided at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to provide, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice.

[0076] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available for the cell, a list of network slices that are unavailable for the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0077] The apparatus may be caused to provide the flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node, receiving a request for cell load information from the first radio access node and providing the cell load information from the second radio access node to the first radio access node for use in determining the at least one or more cells where the network slice is available or not unavailable.

[0078] Providing the cell load information from the second access node may comprise providing an indication of network slice unavailability information for the at least one cell. The unavailability of a network slice at a cell may be indicated with an indication that the network slice is configured with zero resources at the cell.

[0079] The information may be provided in an Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

[0080] The information may be provided in an Xn application protocol resource status update or an Xn application protocol resource status response message.

[0081] The information may be provided together with an indication from the second radio access node that the at least one network slice has a zero capacity value at the cell.

[0082] The apparatus may be caused to receive, at the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice of a cell of the first radio access node where in the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources or if the cell is outside the area of service of the slice.

[0083] In a ninth aspect there is provided an apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to receive information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of a radio access network node comprises an unavailable slice, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice and exclude the cell during a slice-based cell reselection procedure.

[0084] In a tenth aspect there is provided a computer readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform at least the following receiving, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice. The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell, a list of network slices that are unavailable at the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0085] The apparatus may be caused to perform receiving the flag indicating that the at least one slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node, triggering means for obtaining cell load information from the second radio access node based on the received flag, receiving the cell load information from the second radio access node and based on the received cell load information, determining the at least one cell where the network slice is unavailable.

[0086] Receiving the cell load information from the second access node may comprise receiving an indication of network slice unavailability information for the at least one cell.

[0087] The unavailability of a network slice at a cell may be indicated with an indication that the network slice is configured with zero resources at the cell.

[0088] The information may be received in a Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

[0089] The information may be received in an Xn application protocol resource status update or an Xn application protocol resource status response message.

[0090] The information may be provided together with load information from the second radio access node indicating that the at least one network slice has a zero capacity value at the cell.

[0091] The apparatus may be caused to perform determining, based on the information, that the cell of the radio access node is to be excluded from slice-based cell reselection by a user equipment and means for providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection.

[0092] Providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection comprises broadcasting a list of excluded cells of an network slice access group including the at least one network slice. The apparatus may be caused to perform determining, based on the information, to refrain from handing over a user equipment to the cell at the second radio access node.

[0093] The apparatus may be caused to perform providing to the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice at a cell of the first radio access node wherein the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0094] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell or a list of network slices that are unavailable at the cell.

[0095] In an eleventh aspect there is provided a computer readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform at least the following: providing, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0096] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available for the cell, a list of network slices that are unavailable for the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0097] The apparatus may be caused to perform providing the flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node, receiving a request for cell load information from the first radio access node and providing the cell load information from the second radio access node to the first radio access node for use in determining the at least one or more cells where the network slice is available or not unavailable. Providing the cell load information from the second access node may comprise providing an indication of network slice unavailability information for the at least one cell.

[0098] The unavailability of a network slice at a cell may be indicated with an indication that the network slice is configured with zero resources at the cell.

[0099] The information may be provided in a Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

[0100] The information may be provided in an Xn application protocol resource status update or an Xn application protocol resource status response message.

[0101] The information may be provided together with an indication from the second radio access node that the at least one network slice has a zero capacity value at the cell.

[0102] The apparatus may be caused to perform receiving, at the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice of a cell of the first radio access node wherein the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0103] In a twelfth aspect there is provided a computer readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform at least the following: receiving information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of a radio access network node comprises an unavailable slice, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice and excluding the cell during a slice-based cell reselection procedure.

[0104] The apparatus may be caused to perform receiving the information indicating that the at least one network slice is unavailable at the cell of the radio access network node or the at least one network slice access group supported at the cell of the radio access network node comprises an unavailable from a further radio access node, wherein the at least one network slice is supported by the further radio access node.

[0105] The information may comprise a broadcasted list of excluded cells of a network slice access group including the at least one network slice.

[0106] The apparatus may be caused to perform receiving the information indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of the radio access network node comprises an unavailable slice from a core network node.

[0107] The cell may be identified by a cell global cell identity and triggering means for determining a physical cell identifier associated with the received cell global identity of the cell.

[0108] Determining of the physical cell identifier for the cell may be based on at least one of a system information block received from a neighbouring cell or a system information block received in serving cell indicating a mapping between cell global identities and physical cell identities or in a radio resource control release message when the user equipment is sent to inactive mode.

[0109] In a thirteenth aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to the fourth, fifth or sixth aspect.

[0110] In the above, many different embodiments have been described. It should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above.

[0111] Embodiments will now be described, by way of example only, with reference to the accompanying Figures in which:

[0112] Figure 1 shows a schematic diagram of an example 5GS communication system;

[0113] Figure 2 shows a schematic diagram of an example mobile communication device;

[0114] Figure 3 shows a schematic diagram of an example control apparatus; Figure 4 is an example signalling diagram for a slice-specific cell reselection procedure;

[0115] Figure 5 is a flowchart of a method according to an example embodiment;

[0116] Figure 6 is a flowchart of a method according to an example embodiment;

[0117] Figure 7 is a flowchart of a method according to an example embodiment;

[0118] Figure 8 is a signalling flow of a method according to an example embodiment.

[0119] Detailed description

[0120] Before explaining in detail the examples, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figure 1 , Figure 2 and Figure 3 to assist in understanding the technology underlying the described examples.

[0121] An example of a suitable communications system is the 5G or NR concept. Network architecture in NR may be similar to that of LTE-advanced. Base stations of NR systems may be known as next generation NodeBs (gNBs). Changes to the network architecture may depend on the need to support various radio technologies and finer Quality of Service (QoS) support, and some on-demand requirements for e.g. QoS levels to support Quality of Experience (QoE) for a user. Also network aware services and applications, and service and application aware networks may bring changes to the architecture. Those are related to Information Centric Network (ICN) and User-Centric Content Delivery Network (UC-CDN) approaches. NR may use Multiple Input - Multiple Output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

[0122] Future networks may utilise network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into “building blocks” or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent.

[0123] Figure 1 shows a schematic representation of a 5G system (5GS) 100. The 5GS may comprise a user equipment (UE) 102 (which may also be referred to as a communication device or a terminal), a 5G radio access network (5GRAN) 104, a 5G core network (5GCN) 106, one or more internal or external application functions (AF) 108 and one or more data networks (DN) 110.

[0124] An example 5G core network (CN) comprises functional entities. The 5GCN 106 may comprise one or more Access and mobility Management Functions (AMF) 112, one or more session management functions (SMF) 114, an authentication server function (ALISF) 116, a Unified Data Management (UDM) 118, one or more user plane functions (UPF) 120, a Unified Data Repository (UDR) 122 and / or a Network Exposure Function (NEF) 124. The UPF is controlled by the SMF (Session Management Function) that receives policies from a PCF (Policy Control Function).

[0125] The CN is connected to a UE via the Radio Access Network (RAN). The 5GRAN may comprise one or more gNodeB (gNB) Distributed Unit (DU) functions connected to one or more gNodeB (gNB) Centralized Unit(CU) functions. The RAN may comprise one or more access nodes.

[0126] A User Plane Function (UPF) referred to as PDU Session Anchor (PSA) may be responsible for forwarding frames back and forth between the DN and the tunnels established over the 5G towards the UE(s) exchanging traffic with the DN.

[0127] A possible mobile communication device will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, voice over IP (VoIP) phones, portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehiclemounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart devices, wireless customerpremises equipment (CPE), or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts, and other information.

[0128] A mobile device is typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant components can be provided on an appropriate circuit board and / or in chipsets. This feature is denoted by reference 204. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and / or for connecting external accessories, for example hands-free equipment, thereto.

[0129] The mobile device 200 may receive signals over an air or radio interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

[0130] Figure 3 shows an example of a control apparatus 300 for a communication system, for example to be coupled to and / or for controlling a station of an access system, such as a RAN node, e.g. a base station, eNB or gNB, a relay node or a core network node such as an MME or Serving Gateway (S-GW) or Packet Data Network Gateway (P-GW), or a core network function such as AMF / SMF, or a server or host. The method may be implemented in a single control apparatus or across more than one control apparatus. The control apparatus may be integrated with or external to a node or module of a core network or RAN. In some embodiments, base stations comprise a separate control apparatus unit or module. In other embodiments, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 300 can be arranged to provide control on communications in the service area of the system. The control apparatus 300 comprises at least one memory 301 , at least one data processing unit 302, 303 and an input / output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The receiver and / or the transmitter may be implemented as a radio front end or a remote radio head.

[0131] The following relates to network slicing enhancements, for example Network Slice Area of Service (NS-AoS).

[0132] A network slice is a logical network that provides specific network capabilities and network characteristics. The network support for a Network Slice is defined on a per Tracking Area (TA) granularity. The area where a UE can access and get service of a particular network slice when more than zero resources are allocated to the network slice in the NG-RAN cells is called Network Slice Area of Service (NS-AoS).

[0133] Some Network Slices have a limited geographical availability that do not matching existing Tracking Area boundaries. The operator may, in this case decide to change the topology of the Tracking Areas so they match the boundaries of the Network Slice, or the operator may configure resources for the Network Slices in the cells of TAs where the Network Slices are to be available, and in areas of the TAs where the network slice is defined to be not available the cells are configured with zero resources. That is, OAM may configure radio resource management (RRM) policies for Single-Network Slice Selection Assistance Information (S- NSSAIs) on a per cell basis, i.e. , cells outside the Network Slice Area of Service while in a TA supporting the S-NSSAI are allocated with no RRM resources for the S-NSSAI. Slices which are allocated with no (zero) RRM resources may be considered to be unavailable at the cell or out of the NS-AoS.

[0134] If the service area of a network slice does not match TA boundaries, then the RAN nodes that manage cells that are outside slice service area, but still within a TA that supports the slice, are configured with zero radio resource management (RRM) resources for those cells that are outside of the slice service area. Any service related to that particular slice cannot be served in the cell, although the TA (and thus the RAN node) still reports the slice as supported in the Xn interface.

[0135] AMF may be made aware of such per-cell non-availability in the TA via 0AM. Then, AMF can configure the UE with such per-cell information via Non-access Stratum-(NAS-)level signalling such as in UE Registration Accept Message or UE Configuration Update message.

[0136] For example, the AMF may receive from the 0AM the information on availability of a network slice when the granularity is smaller than TA, i.e., if the NS-AoS includes TAs where the network slice is not available in some cells of the TA.

[0137] To optimize the end-to-end behaviour, the AMF may, based on NS-AoS information received from 0AM, configure supporting UEs with S-NSSAI location availability information, and the network may monitor the S-NSSAI usage and enforce the NS-AoS, e.g., if the UE does not support the S-NSSAI location availability information.

[0138] The AMF is configured per S-NSSAI whether to send the S-NSSAI location availability information to supporting UEs.

[0139] The S-NSSAI location availability information sent to the UE may include, for each applicable S-NSSAI of the Configured NSSAI, Location information indicating the cells of TAs in the RA where the related S-NSSAI is available if the S-NSSAI is not available in all the cells of the TA.

[0140] If the UE has indicated that the UE supports S-NSSAI location availability information in the 5GMM Core Network Capability, the AMF may, based on 0AM configuration, configure the UE with S-NSSAI location availability information for one or more S-NSSAIs when the AMF allocates an RA where the Network Slice availability does not match whole TAs, by including the S-NSSAI location availability information in the Registration Accept message or the UE Configuration Command message.

[0141] A slice-specific cell reselection mechanism may enable a UE to reselect a cell on a band that is preferred by the operator based on the most important slice(s) for the UE. However, it may not be guaranteed that the UE reselects the “best” cell from the slice perspective, e.g., a cell that supports all the allowed slices or the most important slices. Initial cell selection (e.g., when UE powers on) is not in the scope of the mechanism. For example, Cell 1 and Cell 2 are in the same TA1. Cell 1 is included in the service area of slice 1 (NS-AoS), but Cell 2 is not.

[0142] Cell 2 will be given zero resources for this slice via RRM policy configuration. AMF will be made aware that NS-AoS of Slice 1 includes Cell 1 , but not Cell 2. UE will be provided with the list of cells where the slice is not available in the TA via NAS signalling by the AMF in case its RA comprises TA1.

[0143] Slice support information is shared among neighbor gNBs on a per Tracking Area level granularity. In other words, Xn information exchange regarding slice support of a gNB is on tracking area level. Therefore, a gNB that has zero RRM resources for a slice can still indicate the slice as “supported”. It is not possible for a gNB to learn that a neighbor is out of NS-AoS of a particular slice using such information.

[0144] Slice support and slice availability are two different concepts. Slice support is still per TA granularity, but slice availability may be different in the cells of the same TA. Information exchange regarding slice support cannot be reused for the latter.

[0145] Network slice “support” or where a network slice is “supported” means that a network node such as gNB is configured with one or more parameters corresponding to the network slice, such as an S-NSSAI and / or parameters regarding service level agreement (SLA). In other words, it may be considered that the gNB has sufficient information in order to provide services associated with the network slice. Network slice support may be homogeneous or constant within a whole tracking area.

[0146] Network slice “availability” is where there are more than zero-resources assigned to a network slice. Then, the network slice is available for use e.g. by one or more UEs. This availability may be cell-based, i.e. , a network slice can be available in cell granularity. Where no resources are assigned to a network slice, that network slice will not be available for use. An operator may configure resources for one or more network slices in the cells of TAs where the one or more network slices are to be available. In areas of the TAs where one or more network slices are to be defined to be not available the cells are configured with zero resources for those one or more network slices. It is possible that a network slice may not be available (e.g. where zero-resources are assigned to it), even where a network slice is supported in a cell of a tracking area.

[0147] Concepts of network slice availability (which may also be referred to as a network slice area of service) and network slice support are also discussed in 3GPP TS 23.501 .

[0148] For a UE that is connected mode, handover (HO) may be used to keep the UE in the network slice service area or steer the UE to enter the network slice service area as long as radio conditions allow it.

[0149] For a UE that is in Inactive or Idle mode, a Slice-specific Cell Reselection Mechanism may be used. gNB that has zero RRM resources for a slice may still indicate the slice as “supported”. This feature enables a UE to reselect a cell on a band that is preferred by the operator based on the most important slice(s) for the UE. However, it is not guaranteed that the UE reselects the “best” cell from the slice perspective, e.g., a cell that supports all the allowed slices or the most important slices.

[0150] Figure 4 shows a signalling flow for an example Slice-specific cell Reselection mechanism.

[0151] The concept of slice groups (e.g., NSAG (Network Slice AS Group)) was introduced to enable signaling optimization (especially for broadcast) and to remove security concerns on advertising S-NSSAIs.

[0152] The solution is based on existing cell reselection procedure, where frequency band priorities are used, and assumes that all cells in a TA support the same slices. It is not possible for a gNB to learn that a neighbor is out of NS-AoS. Therefore, the gNB is not able to properly steer the UEs to cells where the slice is available with cell granularity in a TA, because currently slice availability per neighbor cells is not available to the gNB.

[0153] One option to provide NG-RAN with information about the cells that are inside / outside NS- AoS is to rely on the Slice Available Capacity Downlink. However, this is only a temporary indication of load and does not guarantee that a slice has been configured with zero resources.

[0154] Figure 5 shows a flowchart of a method according to an example embodiment. The method may be performed at a RAN node, e.g. a gNB. In 501 , the method comprises receiving, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice.

[0155] Figure 6 shows a flowchart of a method according to an example embodiment. The method may be performed at a RAN node, e.g., a gNB.

[0156] In 601 , the method comprises providing, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0157] Figure 7 shows a flowchart of a method according to an example embodiment. The method may be performed at a UE.

[0158] In 701 , the method comprises receiving information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of a radio access network node comprises an unavailable slice, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice and excluding the cell during a slice-based cell reselection procedure.

[0159] The information may comprise at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell, a list of network slices that are unavailable at the cell or a flag indicating that the at least one slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0160] The information may be received at the first RAN node from the second RAN node in a Xn application protocol setup message or a radio access network configuration update message. Alternatively, or in addition, the information is provided received in a resource status update or resource update response message.

[0161] In an example embodiment, an information element in Xn relevant messages is added, so that a gNB can indicate slice availability per cell (on top of slice support per TA) to its neighbors.

[0162] A list of cells may be added under TAI slice support list of the XnAP Setup message or the RAN configuration update message, where those cells are the cells where the corresponding slice is available (or alternatively cells the slice is not available). This is an example of a list of cells where the at least one network slice is available or a list of cells where the at least one network slice is unavailable.

[0163] A list of slices may be added under List of Served Cells NR in the XnAP Setup message or the RAN configuration update message, where those slices are the slices that are available (or alternatively not available in the corresponding cell). This is an example of a list of network slices available at the cell or a list of network slices that are unavailable at the cell.

[0164] Alternatively, XnAP Setup message or the RAN configuration update message may be enhanced to include a flag indicating that although slice support is reported, some slices that are reported to be supported can be unavailable. This is an example of a flag indicating that the at least one slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

[0165] The first RAN node may configure / identify load measurements to determine such unavailability from gNB2 (note that load information is sent from gNB2 to gNB1 only when gNB1 configures it) via using load reports. The method may comprise receiving the flag indicating that the at least one slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node, triggering means for obtaining cell load information from the second radio access node based on the received flag, receiving the cell load information from the second radio access node and based on the received information, determining the at least one cell where the slice is unavailable.

[0166] Receiving the cell load information from the second access node may comprise receiving an indication of slice unavailability information for the at least one cell.

[0167] This embodiment may be useful if per slice information is not acceptable, since current load reporting procedures among gNBs can continue to be used. The unavailability of a network slice at a cell may be indicated with an indication that the slice is configured with zero resources at the cell. The information may be provided together with load information from the second radio access node indicating that the at least one slice has a zero-capacity value at the cell.

[0168] For example, to assist a gNB understand in the Slice Available Capacity IE of XnAP (which may be sent in XnAP Resource Status Update / Response) an information element may be added per slice to indicate that the cell is configured with zero resources. This information element may be named “slice not available” or “slice configured with zero resources”. This is an example of an indication that the slice is configured with zero resources at the cell.

[0169] Such an information element may be signaled together with the slice available capacity value downlink / uplink IE which may be set to zero as well. If the existing slice available capacity value downlink / uplink IE are also signaled at zero, the information element may be named “configured capacity” to reflect that the indicated zero capacity value represents a value forced by configuration and differentiate from a zero-capacity value due to lack of resources. This is an example where the information is provided together with load information from the second radio access node indicating that the at least one slice has a zero-capacity value at the cell.

[0170] If a gNB receives the current Rel-18 signalling without such additions as proposed above, it understands that the slice is available in all the cells of the neighbor gNB.

[0171] Reception of such cell level availability information per neighbor cell may be a trigger for the first gNB to consider such information in the handovers to steer the UE in RRC_CONNECTED state handovers, e.g., to prioritize the neighbor cells where the slice is available, compared to cells where the slice is not available. This is an example of determining, based on the information, to refrain from handing over a user equipment to the cell at the second radio access node.

[0172] The method may comprise determining at the first RAN node, based on the information, that the cell of the radio access node is to be excluded from slice-based cell reselection by a user equipment and providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection. Providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection may comprise broadcasting a list of excluded cells of an network slice access group including the at least one slice. For example, the first RAN node may put the cells where the slice is not available to exclude- list for slice-specific cell-reselection (or remove them from allowed list).

[0173] Alternatively, the UE may put the cell into the exclude-list by itself, as the UE knows from AMF the NS-AoS. This is an example of receiving the information indicating that at least one network slice is unavailable at a cell of a radio access network node from a core network node. The cell may be identified by a cell global cell identity and triggering determining a physical cell identifier associated with the received cell global identity. Determining of the physical cell identifier for the cell may be based on at least one of a system information block received from a neighbouring cell or a system information block received in serving cell indicating a mapping between cell global identities and physical cell identities or in a radio resource control release message when the user equipment is sent to inactive mode.

[0174] In this example embodiment, since the UE receives Cell Global IDs (CGIs) from the core network regarding NS-AoS, the UE does not know the Physical Cell IDs (PCIs), which are used during cell reselection (e.g., in exclude and allowed lists).

[0175] To map CGI to PCI in the UE, the UE may use previous knowledge of the CGIs (e.g., from previous connections) or the UE may decodes SIB1 of the best possible neighbor cell (that was found in steps of slice-based cell reselection), if the UE has some area of service information for that slice or CGI to neighbor PCI mapping may be signalled via SIB or in RRC release when sending the UE to RRC_IN ACTIVE. The RRC release option would cover current neighbors (or may be configured by GAM for cells that do not have resources available also slice is supported).

[0176] A UE would then not prioritize the cells where the slice is supported but not actually available, when performing cell reselection in RRC_INACTIVE / IDLE state.

[0177] A gNB is informed that a neighbor is out of AoS of a particular slice and may be able to steer the UEs into the network slice AoS or prevent the UE from leaving network AoS with minimal specification changes. To steer the UEs in RRCJNACTIVE / IDLE states, several methods are provided for flexibility of implementation.

[0178] For a UE that is in RRC_CONNECTED state, the first RAN node may consider such information in handovers to steer the UE in RRC_CONNECTED state handovers, e.g., to prioritise neighbor cells where the slice is available, compared to cells where the slice is not available Figure 8 shows a signalling diagram between a UE, a first RAN node (gNB1) and a second RAN node (gNB2). gNB1 and gNB2 are both in TA1. gNB1 supports slice 1 in cell 1 with greater than 0 resources (i.e. , slice 1 is available in cell 1 of gNB1). gNB2 has 0 resources for slice 1 in cell 2 (i.e., slice 1 is unavailable in cell 2 of gNB2).

[0179] In step 1 , the UE is in RRC_INACTIVE / IDLE state camping in gNB1 Cell 1. The UE previously received the NS-AoS of Slice 1 , indicating Cell 2 has no resources available for the slice (the UE may know the CGI of Cell 2, but not the physical cell identifier (PCI)).

[0180] In step 2, gNB1 sends the slice support information for slice 1 to gNB2. In this example embodiment, gNB1 sends no additional information, since slice 1 is both supported and available for Cell 1. Alternatively, gNB1 may send additional information including a list of cells where slice 1 is available. This is an example of providing to the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice at a cell of the first radio access node where in the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources.

[0181] In step 3, similarly to step 2, gNB2 sends slice support information for slice 1 to gNB1. In addition, gNB2 sends a list of cells where Slice 1 available and / or not available (e.g., cell 2), a list of slices that has 0 resources in the served cell(s) (e.g., slice 1) or a flag indicating that for at least one slice that is supported by the gNB, the slice is not available. This is an example of providing, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, where in the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources

[0182] In step 4, gNB1 considers the information received (e.g., the unavailability of slice 1 in cell 2) in the handover decisions. This is an example of determining, based on the information, to refrain from handing over a user equipment to the cell at the second radio access node.

[0183] If gNB1 receives a flag from gNB2 in step 3, indicating that for at least one slice that is supported by the gNB, the slice is not available, gNB1 configures gNB2 to provide load measurements to determine which cell has zero resources available. This is an example of triggering means for obtaining cell load information from the second radio access node based on the received flag, receiving the cell load information from the second radio access node; and based on the received information, determining the at least one cell where the slice is unavailable.

[0184] One example implementation comprises steps 5 to 8.

[0185] In step 5, based on the received information at Step 3, gNB1 decides to put Cell 2 on exclude / black -list of NSAG of Slice 1 (which is signalled in SIB16) (or refrain from including the cell to an include list of NSAG of slice 1). This is an example of providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection by broadcasting a list of excluded cells of an network slice access group including the at least one slice.

[0186] In step 6 to 8, the UE does not prioritize the frequency of Cell 2 while performing cell reselection. For example, if the best cell on the frequency of Cell 2 is found as Cell 2, UE does not prioritize the frequency.

[0187] An alternative example implementation option is shown in steps 9 to 11.

[0188] In step 9, if the UE is signalled CGIs rather than PCIs within received NS-AoS from the core network (as mentioned in step 1), the UE needs to know the PCI otherwise the UE would be unaware of PCIs before decoding SIB1 of the corresponding cells.

[0189] If the UE was connected before to Cell 2, it knows the CGI. Alternatively, UE reads SIB1 of the best cell found during slice-specific cell reselection algorithm to learn about the CGI and check NS-AoS information or CGI to PCI mapping of neighbor cells is signalled by gNB1 Cell 1 in broadcast messages, e.g., in SIB. This is an example of determining of the physical cell identifier for the cell is based on at least one of a system information block received from a neighbouring cell or a system information block received in serving cell indicating a mapping between cell global identities and physical cell identities or in a radio resource control release message when the user equipment is sent to inactive mode.

[0190] Steps 10 to 11 are then the same as steps 6 to 8 in example implementation 1 .

[0191] An apparatus may comprise means for receiving, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice.

[0192] Alternatively, or in addition, an apparatus may comprise means for providing, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

[0193] The apparatus may comprise the RAN node, such as a gNB, be the gNB or be comprised in the gNB or a chipset for performing at least some actions of / for the user gNB.

[0194] Alternatively, or in addition, an apparatus may comprise means for receiving information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of a radio access network node comprises an unavailable slice, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the slice; and excluding the cell during a slice-based cell reselection procedure.

[0195] The apparatus may comprise the user equipment, such as a mobile phone, be the user equipment or be comprised in the user equipment or a chipset for performing at least some actions of / for the user equipment.

[0196] It should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and / or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities.

[0197] It is noted that whilst some embodiments have been described in relation to 5G networks, similar principles can be applied in relation to other networks and communication systems such as 6G networks or 5G-Advanced networks. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

[0198] It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

[0199] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0200] In general, the various embodiments may be implemented in hardware or special purpose circuitry, software, logic or any combination thereof. Some aspects of the disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0201] As used in this application, the term “circuitry” may refer to one or more or all of the following:

[0202] (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and

[0203] (b) combinations of hardware circuits and software, such as (as applicable):

[0204] (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and

[0205] (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

[0206] I hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.”

[0207] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0208] The embodiments of this disclosure may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and / or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computerexecutable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

[0209] Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e. , tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0210] The memory 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 devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

[0211] Embodiments of the disclosure may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0212] The scope of protection sought for various embodiments of the disclosure is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the disclosure.

[0213] The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this disclosure. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this disclosure will still fall within the scope of this invention as defined in the appended claims. Indeed, there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

Claims1 . An apparatus comprising means for: receiving, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

2. The apparatus according to claim 1 , wherein the information comprises at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell, a list of network slices that are unavailable at the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

3. The apparatus according to claim 2, comprising means for: receiving the flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node; triggering means for obtaining cell load information from the second radio access node based on the received flag; receiving the cell load information from the second radio access node; and based on the received cell load information, determining the at least one cell where the network slice is unavailable.

4. The apparatus according to claim 3, wherein receiving the cell load information from the second access node comprises receiving an indication of network slice unavailability information for the at least one cell.

5. The apparatus according to claim 1 to 4 wherein the unavailability of a network slice at a cell is indicated with an indication that the network slice is configured with zero resources at the cell.

6. The apparatus according to any of claims 1 to 5, wherein the information is received in an Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

7. The apparatus according to any of claims 1 to 5, wherein the information is received in an Xn application protocol resource status update or an Xn application protocol resource status response message.

8. The apparatus according to claim 7, wherein the information is provided together with load information from the second radio access node indicating that the at least one network slice has a zero capacity value at the cell.

9. The apparatus according to any of claims 1 to 8, comprising means for determining, based on the information, that the cell of the radio access node is to be excluded from slice-based cell reselection by a user equipment and means for providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection.

10. The apparatus according to any of claims 1 to 9, wherein means for providing an indication to the user equipment that the cell is to be excluded from slice-based cell reselection comprises means for broadcasting a list of excluded cells of an network slice access group including the at least one network slice.11 . The apparatus of any of claims 1 to 8, comprising means at the first radio access node for determining, based on the information, to refrain from handing over a user equipment to the cell at the second radio access node.

12. The apparatus according to any of claims 1 to 11 , comprising means for providing to the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice at a cell of the first radio access node wherein the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cellif it is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

13. The apparatus according to claim 12, wherein the information comprises at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available at the cell or a list of network slices that are unavailable at the cell.

14. An apparatus comprising means for: providing, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

15. The apparatus according to claim 14, wherein the information comprises at least one of the following: a list of cells where the at least one network slice is available, a list of cells where the at least one network slice is unavailable, a list of network slices available for the cell, a list of network slices that are unavailable for the cell or a flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node.

16. The apparatus according to claim 15, comprising means for: providing the flag indicating that the at least one network slice that is supported at the second radio access node is unavailable in at least one cell of the second radio access node; receiving a request for cell load information from the first radio access node; and providing the cell load information from the second radio access node to the first radio access node for use in determining the at least one or more cells where the network slice is available or not unavailable.

17. The apparatus according to claim 16, wherein providing the cell load information from the second access node comprises providing an indication of network slice unavailability information for the at least one cell.

18. The apparatus according to any of claims 14 to 17, wherein the unavailability of a network slice at a cell is indicated with an indication that the network slice is configured with zero resources at the cell.

19. The apparatus according to any of claims 14 to 18, wherein the information is provided in an Xn application protocol setup message or an Xn application protocol radio access network configuration update message.

20. The apparatus according to any of claims 14 to 18, wherein the information is provided in an Xn application protocol resource status update or an Xn application protocol resource status response message.21 . The apparatus according to claim 20, wherein the information is provided together with an indication from the second radio access node that the at least one network slice has a zero capacity value at the cell.

22. The apparatus according to claim 14 to 21 , comprising means for receiving, at the second radio access node from the first radio access node, information indicating availability or unavailability of at least one network slice of a cell of the first radio access node where in the at least one network slice is supported at the first radio access node and the at least one network slice is unavailable at the cell if it is configured with zero resources at the cell or if the cell is outside the area of service of the slice.

23. An apparatus comprising means for: receiving information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of a radio access network node comprises an unavailable slice, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice; and excluding the cell during a slice-based cell reselection procedure.

24. The apparatus according to claim 23, comprising means for receiving the information indicating that the at least one network slice is unavailable at the cell of the radio access network node or the at least one network slice access groupsupported at the cell of the radio access network node comprises an unavailable slice from a further radio access node, wherein the at least one network slice is supported by the further radio access node.

25. The apparatus according to claim 23 or claim 24, wherein the information comprises a broadcasted list of excluded cells of a network slice access group including the at least one network slice.

26. The apparatus according to claim 23 to 25, comprising means for receiving the information indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of the radio access network node comprises an unavailable slice from a core network node.

27. The apparatus according to claim 26, wherein the cell is identified by a cell global cell identity; and triggering means for determining a physical cell identifier associated with the received cell global identity of the cell.

28. The apparatus according to claim 27, wherein the determining of the physical cell identifier for the cell is based on at least one of a system information block received from a neighbouring cell or a system information block received in serving cell indicating a mapping between cell global identities and physical cell identities or a radio resource control release message when the user equipment is sent to inactive mode.

29. A method comprising: receiving, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

30. A method comprising: providing, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of acell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

31. A method comprising: receiving information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node or at least one network slice access group supported at a cell of a radio access network node comprises an unavailable slice, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice; and excluding the cell during a slice-based cell reselection procedure.

32. An apparatus comprising: at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to: receive, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

33. An apparatus comprising: at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to: provide, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

34. An apparatus comprising: at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to: receive information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice; and exclude the cell during a slice-based cell reselection procedure.

35. A computer readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform at least the following: receiving, at a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice at a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

36. A computer readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform at least the following: providing, to a first radio access node from a second radio access node, information indicating availability or unavailability of at least one network slice of a cell of the second radio access node, wherein the at least one network slice is supported at the second radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured with zero resources at the cell or if the cell is outside the area of service of the network slice.

37. A computer readable medium comprising instructions which, when executed by an apparatus, cause the apparatus to perform at least the following: receiving information at a user equipment indicating that at least one network slice is unavailable at a cell of a radio access network node, wherein the at least one network slice is supported by the radio access node and the at least one network slice is unavailable at the cell if the at least one network slice is configured withzero resources at the cell or if the cell is outside the area of service of the network slice; and excluding the cell during a slice-based cell reselection procedure.

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