WO2023003310A1

WO2023003310A1 - Method and apparatus for selecting frequency band for ue in a wireless network

Info

Publication number: WO2023003310A1
Application number: PCT/KR2022/010499
Authority: WO
Inventors: Varini Gupta; Aby Kanneath ABRAHAM; Ashok Kumar Nayak; Hoyeon Lee; Lalith KUMAR; Vinay Kumar Shrivastava; Danish Ehsan Hashmi
Original assignee: Samsung Electronics Co., Ltd.
Priority date: 2021-07-23
Filing date: 2022-07-19
Publication date: 2023-01-26

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Embodiments herein provide method and AMF device for redirecting a UE to a frequency band that provides service of interest. The method includes receiving the registration request message including a Requested-NSSAI information element from the UE, determining that S-NSSAIs requested by the UE is not supported in current TA of the UE and supported in other TAs of the wireless network, sending Target-NSSAI IE comprising the S-NSSAI requested by the UE not available in current TA and available in other TAs of the wireless network, zero or more S-NSSAIs requested by the UE available in the current TA, and a target-RFSP IE corresponding to the Target-NSSAI.

Description

METHOD AND APPARATUS FOR SELECTING FREQUENCY BAND FOR UE IN A WIRELESS NETWORK

The present disclosure relates to a field of network slicing in a 3rd Generation Partnership Project (3GPP), and more particularly, to a wireless network and a method of redirecting a user equipment (UE) to a frequency band that can provide all services of interest to the UE in the wireless network.

5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in “Sub 6GHz” bands such as 3.5GHz, but also in “Above 6GHz” bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

Moreover, there has been ongoing standardization in air interface architecture/protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture/service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

3GPP Release-15 introduced a concept of “Network Slicing” which allows network service providers to compartmentalise a network into multiple slices, depending on type of service. Such slices are identified using Single Network Slice Selection Assistance Information (S-NSSAIs). A user of the wireless network may be allowed to connect to many such network slices depending on the services it has subscribes to. The list of slices the user is allowed to access is also configured in a User Equipment (UE), and allows the user to indicate to the network the services it wishes to consume at any point of time.

The principal object of the embodiments herein is to provide an AMF apparatus and a method for selecting a frequency band for a UE in a wireless network.

Yet another objective is to provide an AMF apparatus and a method of redirection during handovers and service-requests using a target-Network Slice Selection Assistance Information (NSSAI). Redirecting the UE to the frequency band that can provide all services of interest to the UE in the wireless network, which entails selecting the frequency band for the UE in the wireless network.

Accordingly, the embodiment herein is to provide a method for redirecting a UE to a frequency band that provides service of interest to the UE in a wireless network. The method may include receiving, by an AMF device in the wireless network, a registration request message comprising a Requested-Network Slice Selection Assistance Information (NSSAI) information element from the UE. The Requested-NSSAI information element includes a plurality of Single-Network Slice Selection Assistance Information (S-NSSAI). The UE is served by a Next Generation NodeB (gNB) of the wireless network. The method may include determining, by the AMF device, that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE is not supported in current tracking-area (TA) of the UE, and supported in other TAs of the wireless network. The method may include sending, by the AMF device, a Target-NSSAI information element comprising the at least one S-NSSAI requested by the UE not available in current TA of the UE and available in other TAs of the wireless network, zero or more S-NSSAIs requested by the UE available in current TA, and a target-Radio Frequency Selection Priority (RFSP) information element corresponding to the Target-NSSAI, to the gNBs currently serving the UE. The method may include performing at least one of redirecting, by the gNB device, the UE to the frequency band that supports the at least one target S-NSSAI, when the at least one S-NSSAI is available in a nearby TA, and sending, by the AMF device, at least one of the same target-NSSAI and target-RFSP to the gNB serving the UE, upon every future activity by the UE, to avail the services from the wireless network, in response to detecting the Requested-NSSAI has not changed.

In an embodiment, sending, by the AMF device, at least one of the target-NSSAI and the target-RFSP to the gNB serving the UE, upon every future activity detected by the UE includes receiving, by the AMF device, a service-request message from the UE to get the at least one service when the UE is moved away from its initial location and sending, by the AMF device, the at least one of the target -NSSAI and the target-RFSP information elements to the gNB serving the UE, to intimate the services of interest at the UE.

In an embodiment, sending, by the AMF device, the at least one of the target -NSSAI and the target-RFSP information elements to the gNB serving the UE, to intimate the services of interest at the UE comprises one of: sending, by the AMF device, the at least one of the target-NSSAI and target-RFSP information elements to the gNB as part of a Downlink NAS transport message, while sending a service accept” message to the UE, and sending, by the AMF the at least one of the target-NSSAI and the target-RFSP information elements to the gNB via a new message or existing message, before or after a Service Accept message has been sent to the UE.

In an embodiment, sending, by the AMF device, at least one of the target-NSSAI and the target-RFSP to the gNB serving the UE, upon every future activity by the UE includes receiving, by the AMF device, a N2 path switch request message from another gNB as part of a Xn based inter NG-RAN handover procedure when the UE is moved away from its initial gNB, and performing at least one of sending, by the AMF device, at least one of the target -NSSAI and target-RFSP information element to the another gNB serving the UE as part of a N2 path switch request acknowledgement message, and sending, by the AMF device, at least one of the target-NSSAI and Target-RFSP information elements to the new gNB serving the UE, via a new or another existing message, before or after " N2 Path Switch Request Acknowledgement" message has been sent to the UE.

In an embodiment, sending, by the AMF device, at least one of the target-NSSAI and the target-RFSP to the gNB serving the UE, upon every future activity by the UE includes sending, by the AMF device, at least one of the Target -NSSAI and the target-RFSP information element to another gNB serving the UE as part of a Handover Request message or a Handover Command message, during N2 based inter NG-RAN handover procedure when the UE is moved away from its initial gNB, or sending, by the AMF device, the at least one of the Target-NSSAI and the Target-RFSP information elements to the another gNB serving the UE, via a new message or another existing message, before or after N2 based inter NG-RAN handover procedure has been completed for the UE.

Accordingly, the embodiment herein is to provide a method for redirecting a UE to a frequency band that provides a service of interest to the UE in a wireless network. The method may include receiving, by an AMF device in the wireless network, a registration request message comprising a Requested-NSSAI information element from the UE. The NSSAI includes a plurality of S-NSSAI. The UE is served by a first Next Generation NodeB (gNB) of the wireless network. The method may include determining, by the AMF device, that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE is not supported in current tracking-area (TA) of the UE, and supported in other TAs of the wireless network. The method may include sending, by the AMF device, a target-NSSAI information element comprising at least one S-NSSAI requested by the UE not available in current TA of the UE and available in other TAs of the wireless network and zero or more S-NSSAIs requested by the UE available in current TA of the UE, and a Target- Radio Frequency Selection Priority (RFSP) information element corresponding to Target-NSSAI, to the first gNBs currently serving the UE. The method may include performing at least one of redirecting, by the first gNB device, the UE to the frequency band that supports the at least one target S-NSSAI, when the at least one S-NSSAI is available in a nearby TA, and sending, by the first gNB device, at least one of the Target-NSSAI and Target-RFSP to a second gNB serving the UE, upon the movement of the UE to an area served by the second gNB, provided Requested-NSSAI has not changed.

In an embodiment, sending, by the first gNB device, at least one of the target-NSSAI and the target-RFSP to the second gNB serving the UE comprises one of sending, by the first gNB device, at least one of the Target -NSSAI and Target-RFSP information elements to another gNB serving the UE over the Xn Interface as part of Xn based inter NG-RAN handover procedure, sending, by the first gNB device, at least one of the Target-NSSAI and Target-RFSP information elements to the another gNB serving the UE via the AMF as part of N2 based inter NG-RAN handover procedure, and sending, by the first gNB device, at least one of the Target-NSSAI and Target-RFSP information elements to the another gNB serving the UE, via a new message or another existing message, before or after the completion of Xn or N2 based inter NG-RAN handover procedure.

In an embodiment, upon the movement of the UE away from the area served by the first gNB, the first gNB additionally utilizes the target-NSSAI and/or the target-RFSP information to preferentially select the new cell and new gNB.

Accordingly, the embodiment herein is to provide a wireless network for selecting a frequency band for the UE in a wireless network. The wireless network may include an AMF device and a gNB device. The AMF device may be configured to receive the registration request message comprising a Requested-NSSAI information element from the UE. The Requested-NSSAI information element includes a plurality of S-NSSAI. The UE is served by a Next Generation NodeB (gNB) of the wireless network. The AMF device may be configured to determine that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE is not supported in current tracking-area (TA) of the UE, and supported in other TAs of the wireless network. The AMF device may be configured to send the Target-NSSAI information element comprising the at least one S-NSSAI requested by the UE not available in current TA of the UE and available in other TAs of the wireless network, zero or more S-NSSAIs requested by the UE available in current TA, and a target-Radio Frequency Selection Priority (RFSP) information element corresponding to the Target-NSSAI, to the gNBs currently serving the UE. The gNB device may be configured to redirect the UE to the frequency band that supports the at least one target S-NSSAI, when the at least one S-NSSAI is available in a nearby TA. The AMF device may be configured to send at least one of the same target-NSSAI and target-RFSP to the gNB serving the UE, upon every future activity by the UE, to avail the services from the wireless network, in response to detecting the Requested-NSSAI has not changed.

Accordingly, the embodiment herein is to provide a wireless network for selecting a frequency band for the UE in a wireless network. The wireless network may include an AMF device and a gNB device. The AMF device may be configured to receive a registration request message comprising a Requested- NSSAI information element from the UE. The NSSAI may comprise a plurality of S-NSSAI. The UE may be served by a first Next Generation NodeB (gNB) of the wireless Network. The AMF device may be configured to determine that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE is not supported in current tracking-area (TA) of the UE, and supported in other TAs of the wireless network. The AMF device may be configured to send a target-NSSAI information element comprising at least one S-NSSAI requested by the UE not available in current TA of the UE and available in other TAs of the wireless network and zero or more S-NSSAIs requested by the UE available in current TA of the UE, and a Target- Radio Frequency Selection Priority (RFSP) information element corresponding to Target-NSSAI, to the first gNBs currently serving the UE. The first gNB device may be configured to redirect the UE to the frequency band that supports the at least one target S-NSSAI, when the at least one S-NSSAI is available in a nearby TA. The first gNB device may be configured to send at least one of the target-NSSAI and target-RFSP to a second gNB serving the UE, upon the movement of the UE to an area served by the second gNB, provided Requested-NSSAI has not changed.

These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the scope thereof, and the embodiments herein include all such modifications.

The method and wireless network are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

FIG. 1 is an example of representation of a wireless network where some of S-NSSAIs are available only on specific frequency bands;

FIG. 2, FIG. 3, and FIG. 4 are representation of example sequence diagrams of events that may take place during a service-request procedure in a new cell after registration in another cell, according to the embodiments disclosed herein;

FIG. 5 shows various hardware components of a AMF device, according to the embodiments as disclosed herein;

FIG. 6 shows various hardware components of a gNB, according to the embodiments as disclosed herein; and

FIG. 7 and FIG. 8 are flow chart illustrating methods for redirecting the UE to a frequency band that provides service of interest to the UE in a wireless network, according to the embodiments as disclosed herein.

The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term “or” as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

As is traditional in the field, embodiments may be described and illustrated in terms of blocks which carry out a described function or functions. These blocks, which may be referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and/or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and may optionally be driven by firmware and software. The circuits may, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like. The circuits constituting a block may be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the embodiments may be physically separated into two or more interacting and discrete blocks without departing from the scope of the disclosure. Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the disclosure.

Below are the abbreviations used in the description:

a) AMF - Access and Mobility Management Function.

b) UE - User Equipment.

c) 3gpp - 3rd Generation Partnership Project.

d) NSSAI - Network Slice Selection Assistance Information.

e) S-NSSAI - Single - Network Slice Selection Assistance Information.

f) PLMN - Public Land Mobile Network.

g) NAS - Non-Access Stratum.

h) TA - Tracking Area.

i) RA - Registration Area

j) gNB - Next Generation NodeB.

k) IE - Information Element.

l) RFSP - RAT/Frequency Selection Priority (Index).

Accordingly, the embodiment herein is to provide a method and a wireless network for selecting a frequency band for the UE in the wireless network. Redirecting the UE to the frequency band that can provide all services of interest to the UE in the wireless network, which entails selecting the frequency band for the UE in the wireless network. The method includes receiving, by an AMF device in the wireless network, a registration request message comprising a Requested-NSSAI information element from the UE. The Requested-NSSAI information element includes a plurality of S-NSSAI. The UE is served by a Next Generation NodeB (gNB) of the wireless network. Further, the method includes determining, by the AMF device, that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE is not supported in current TA of the UE, and supported in other TAs of the wireless network. Further, the method includes sending, by the AMF device, a Target-NSSAI information element comprising the at least one S-NSSAI requested by the UE not available in current TA of the UE and available in other TAs of the wireless network, zero or more S-NSSAIs requested by the UE available in current TA, and a target-RFSP information element corresponding to the Target-NSSAI, to the gNBs currently serving the UE. Further, the method includes performing at least one of redirecting, by the gNB device, the UE to the frequency band that supports the at least one target S-NSSAI, when the at least one S-NSSAI is available in a nearby TA, and sending, by the AMF device, at least one of the same target-NSSAI and target-RFSP to the gNB serving the UE, upon every future activity by the UE, to avail the services from the wireless network, in response to detecting the Requested-NSSAI has not changed.

Referring now to the drawings and more particularly to FIGS. 1 through 8, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

FIG. 1 is an example of representation of a wireless network 1000 where some of the S-NSSAIs are available only on specific frequency bands.

Referring to the conventional methods and systems, the FIG. 1 illustrates a representation of an example network 1000 where some of the S-NSSAIs are available only on specific frequency bands:

a) Frequency f1 supports slice s1 and s2 and is available throughout the network.

b) Frequency f2 supports slice s1, s3, but is available only in TA5

Consider, the UE 100 may perform the registration procedure when it is served by gNB1 in TA1. It provides Requested-NSSAI = s1, s3 indicating it wants to register to these slices. However, since gNB1 only supports f1 serving slice s1 but not s3, network (e.g. AMF) can provide only “s1” as “Allowed-NSSAI” to the UE 100, indicating the UE 100 is only allowed to consume services offered by slice s1 in current area.

When the AMF device 300 sends the registration accept to the UE 100, the AMF device 300 may also provide the gNB1 with information elements called “Target-NSSAI” and/or “Target-RFSP”, which indicates to the gNB1 that the UE 100 was actually interested in “s1, s3” and when possible, move/redirect the UE 100 to a frequency/cell that supports both these slices. As part of Registration-Accept, the AMF device 300 also may provide to the UE 100, an information element called “Registration-Area”, which is the list of TAs where UE 100 does not need to perform mobility registration procedure, and all the slices in “Allowed-NSSAI” are available for use by the UE 100. In an example, the Registration-Area may be set to “TA1, TA2, TA3, and TA4” as Allowed-NSSAI “s1” is available in all these areas. Slice “s3” is provided to UE 100 in Rejected-NSSAI, indicating that as long as UE 100 is in the current Registration-Area, it cannot access “s3”.

It is noteworthy that in current state-of-art, “Target-NSSAI” and/or “Target-RFSP” are provided to the gNB 200 only during the registration procedure, specifically, while sending the registration-accept message to the UE 100 via the gNB 200. In the example of the FIG. 1, a cell supporting Slices “s1, s3” belongs to TA5, and is far from TA1. However, since the UE 100 performed the registration via the gNB1 200 in TA1, the network 1000 will try to redirect it to TA5 only when the UE 100 is in the area covered by the gNB1 200. Since TA1 and TA5 are far apart, the redirection will not happen.

As the UE 100 moves across it's the registration-area, the UE 100 may handover from the gNB1 to the gNB7, or the UE 100 may perform a service-request in the gNB7. The gNB7 is much closer to gNB9, and chances of the UE 100 getting successfully redirected to TA5 (serving slices “s1, s3”) are much more when the UE 100 is served by the gNB7. However, as long as the UE 100 does not perform a fresh registration procedure, the AMF device 300 will not provide the “Target-NSSAI” and/or “Target-RFSP” to gNB7 and hence the UE 100 cannot be redirected to f2/TA5. This is a drawback of current art, as it, probably unintentionally, restricts network from proactively trying to redirect the UE 100 to the cell where it can get all the required services.

Additionally, it may be noted that in current state-of-art, “Target-NSSAI” provided to the gNB 200 may be filtered according to the capability of the serving-gNB. In the example of FIG. 1, since gNB1 does not support slice s3, it is possible that AMF device 300 does not provide it with “Target-NSSAI” set to “s1, s3”. This is problematic, as without this information, the gNB cannot try redirecting the UE to a neighbour cell that supports slice s3 but is hosted on another gNB.

Thus, there is a need to address the above-mentioned issues.

How the AMF device 300 or the network 1000 determines “Target-NSSAI” and/or “Target-RFSP” is an existing stage-of-art and has not been explained in detail in this proposed method, as such information does not directly affect the embodiments in the proposed method.

Unlike to the conventional methods and systems, consider a proposed method, it is proposed that when the UE 100 performs service-request in the cell in 5G network, the AMF device 300 may provide the gNB 200 with “Target-NSSAI” and/or “Target-RFSP” while sending “Service Accept” message to the UE 100 as part of Downlink NAS Transport over a NG interface. Alternatively, the AMF device 300 may provide the gNB 200 with the “Target-NSSAI” and/or “Target-RFSP” via a new of another existing message over the NG interface.

Going back to the example of the FIG. 1, when the UE 100 had performed service-request in gNB 7 or gNB 9, with the additional knowledge of “Target-NSSAI” and/or “Target-RFSP”, the gNB 200 may try redirecting the UE 100 to f2/TA5, and thus the UE 100 may receive services of both slices s1 and s3 in the new cell. It is noteworthy that it is up to the gNB 200 to decide as to when it will actually perform redirection. For example, when there is ongoing data-transfer on a particular S-NSSAI, the gNB 200 may wait for the data-transfer to finish before executing redirection.

In an embodiment, the gNB 200 may utilize “Target-NSSAI” and/or “Target-RFSP” as additional input while deciding on the target-cell and/or target-gNB to handover the UE 100 to during handover procedure. If, among the candidate cells, some cells support both “Allowed-NSSAI” and “Target-NSSAI”, such cells can be preferred. From the example of the FIG. 1, when the UE 100 is in gNB7, and wants to handover to, say an area served by gNB 9, it may be preferable to handover the UE 100 to cell on frequency f2, as it supports both Allowed-NSSAI (s1) and Target-NSSAI (s1, s3), whereas cell on frequency f1 supports only the Allowed-NSSAI (s1).

In an embodiment, the AMF device 300 may provide the new gNB with “Target-NSSAI” and/or “Target-RFSP” as part of or after successful handover procedure. The information can be provided as part of “N2 Path Switch Request Ack” message sent as part of Xn-based handover procedure as defined in 3GPP TS 23.502, or it can be sent as part of “Handover Request” or “Handover Command” message sent as part of N2-based handover procedure as defined in 3GPP TS 23.502. Alternatively, the AMF device 300 may provide the gNB 200 with the “Target-NSSAI” and/or “Target-RFSP” via a new of another existing message over the NG interface. From the example of FIG. 1, with this information at hand, the new gNB (Target-gNB) may try redirecting the UE 100 to a cell supporting both slices “s1, s3”.

In an embodiment, the AMF device 300 may provide the gNB with “Target-NSSAI” which does not exclude some S-NSSAIs according to the capability of gNBs. From the example of FIG. 1, Target-NSSAI sent to the gNB1 will include “s3” even as gNB1 does not support s3.

In an embodiment, during handover procedures, source gNBs transfers “Target-NSSAI” and/or “Target-RFSP” to target gNB. The information elements can be transferred via Xn interface when it is an Xn-based handover, and via the AMF device 300 when it is an N2-based handover. The information elements can be transferred in existing or new messages exchanged as part of handover procedure. This helps target gNB pick up the cell that supports the “Target-NSSAI”, especially when the UE 100 has reported multiple cells in measurement report. This way, further redirection may be avoided.

FIG. 2 to FIG. 4 are representation of an example sequence diagrams of events that may take place during a service-request procedure in a new cell after registration in another cell, according to the embodiments disclosed herein.

Referring to the FIG. 2, the UE 100 may achieve all the services required when the UE 100 performs service-request in a cell different from the cell where registration procedure took place. The steps are as follows:

In

operations

201 and 202, the old gNB 200a and the new gNB 200b may perform a NG-Setup procedure with the AMF device 300 and inform the supported slices “s1, s2” and “s1, s3” respectively.

In operation 203, the UE 100 may connect to the network (e.g., AMF device 300) via the Old gNB 200b and send the registration-request to the AMF device 300 with the requested-NSSAI IE set to “s1, s3”.

In operation 204a, when all validations (e.g. subscription) are successful, the AMF device 300 may send the registration-accept to the UE 100. Since the old gNB 200a does not support one of the Requested S-NSSAI ("s3"), Allowed-NSSAI is set to “s1” and Rejected-NSSAI is set to “s3”. In operation 204b, the AMF device 300 also may provide the old gNB 200a with “Target-NSSAI” set to “s1, s3”, and/or “Target-RFSP”, while sending the registration-accept to the UE 100.

In operation 205, the UE 100 may move in the idle model. In operation 206, the UE 100 may wake up in the area of the new gNB 200b and send the service-request to the AMF device 300.

In operation 207a, when the AMF device 300 is able to provide the service requested by the UE 100, the AMF device may send “Service-Accept” message to the UE 100. In operation 207b, the AMF device 300 also may provide the new gNB 200b with “Target-NSSAI” set to “s1, s3”, and/or “Target-RFSP”, while sending “service-accept” message to the UE 100. When slices “s1, s3” are supported in a nearby cell, the new gNB 200b may now redirect the UE 100 to a cell supporting both slices, which was not possible earlier.

As shown in the FIG. 3, in

operations

301 and 302, the old gNB 200a and the new gNB 200b may perform the NG-setup procedure with the AMF device 300 and inform the supported slices “s1, s2” and “s1, s3” respectively. In operation 303, the UE 100 may connect to the network (e.g., AMF device 300) via the old gNB 200b and sends the registration-request to the AMF device 300 with the requested-NSSAI IE set to “s1, s3”.

In operation 304a, when all validations (e.g. subscription) are successful, the AMF device 300 may send the registration-accept to the UE 100. Since the old gNB 200a does not support one of the Requested S-NSSAI ("s3"), Allowed-NSSAI is set to “s1” and Rejected-NSSAI is set to “s3”. In operation 304b, the AMF device 300 also may provide the old gNB 200a with “Target-NSSAI” set to “s1, s3”, and/or “Target-RFSP”, while sending the registration-accept to the UE 100. In operation 305, the old gNB 200a may try to find the cell that supports target-NSSAI to re-direct the UE 100.

In operation 306, the UE 100 may move in the idle model. In operation 307, the UE 100 may wake up in the area of the new gNB 200b and send the service-request to the AMF device 300.

In operation 308a, when the AMF device 300 is able to provide the service requested by the UE 100, the AMF device 300 may send “Service-Accept” message to the UE 100. In operation 308b, the AMF device 300 also may provide the new gNB 200b with “Target-NSSAI” set to “s1, s3”, and/or “Target-RFSP”, while sending “service-accept” message to the UE 100. When slices “s1, s3” are supported in a nearby cell, the new gNB 200b may now redirect the UE 100 to a cell supporting both slices, which was not possible earlier. In operation 309, the new gNB 200b may try to find the cell that supports the target-NSSAI to re-direct the UE 100.

As shown in the FIG. 4, in

operations

401 and 402, the old gNB 200a and the new gNB 200b may perform the NG-setup procedure with the AMF device 300 and inform the supported slices “s1, s2” and “s1, s3” respectively. In operation 403, the UE 100 may connect to the network (e.g., AMF device 300) via the old gNB 200b and send the registration-request to the AMF device 300 with the requested-NSSAI IE set to “s1, s3”.

In operation 404a, when all validations (e.g. subscription) are successful, the AMF device 300 may send the registration-accept to the UE 100. Since the old gNB 200a does not support one of the Requested S-NSSAI ("s3"), Allowed-NSSAI is set to “s1” and Rejected-NSSAI is set to “s3”. In operation 404b, the AMF device 300 also may provide the old gNB 200a with “Target-NSSAI” set to “s1, s3”, and/or “Target-RFSP”, while sending the registration-accept to the UE 100. In operation 405, the old gNB 200a may try to find the cell that supports target-NSSAI to re-direct the UE 100.

In operation 406, the UE 100 may hand over to the cell hosted in the new gNB 200b. The old gNB 200a may try to find a cell that supports Target gNB. Else, the old gNB 200a may transfer the target-NSSAI to the new gNB 200b. In operation 407, the new gNB 200b may try to find the cell that supports the target-NSSAI.

FIG. 5 shows various hardware components of the AMF device according to the embodiments as disclosed herein. In an embodiment, the AMF device 500 may include a processor 510, a communicator 520, a memory 530 and an area-specific network slices controller 540. The processor 510 may be coupled with the communicator 520, the memory 530 and the area-specific network slices controller 540.

The area-specific network slices controller 540 may receive the registration request message including the Requested-NSSAI information element from the UE 100. The Requested-NSSAI information element may include a plurality of S-NSSAI. The UE 100 may be served by a Next Generation NodeB (gNB) 200a of the wireless network 1000. In an embodiment, the area-specific network slices controller 540 may determine that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE 100 is not supported in current TA of the UE 100, and supported in other TAs of the wireless network 1000. In an embodiment, the area-specific network slices controller 540 may send the Target-NSSAI information element including the at least one S-NSSAI requested by the UE 100 not available in current TA of the UE 100 and available in other TAs of the wireless network 1000, zero or more S-NSSAIs requested by the UE 100 available in current TA, and a target- RFSP information element corresponding to the Target-NSSAI, to the gNBs 200a currently serving the UE 100. In an embodiment, the area-specific network slices controller 540 may send at least one of the same target-NSSAI and target-RFSP to the gNB 200 serving the UE 100, upon every future activity by the UE 100, to avail the services from the wireless network 1000, in response to detecting the Requested-NSSAI has not changed.

In an embodiment, the area-specific network slices controller 540 may send the at least one of the target-NSSAI and target-RFSP information elements to the gNB 200 as part of a Downlink NAS transport message, while sending a service accept message to the UE 100. In another embodiment, the area-specific network slices controller 540 may send the at least one of the target-NSSAI and the target-RFSP information elements to the gNB 200 via a new message or existing message, before or after a service accept message has been sent to the UE 100. In an embodiment, the area-specific network slices controller 540 may send at least one of the target-NSSAI and the target-RFSP information elements to another gNB 200b serving the UE 100 over the Xn interface as part of Xn based inter NG-RAN handover procedure. In an embodiment, the area-specific network slices controller 540 may send at least one of the target-NSSAI and the target-RFSP information elements to the another gNB 200b serving the UE 100 via the AMF device 300 as part of N2 based inter NG-RAN handover procedure. In an embodiment, the area-specific network slices controller 540 may send at least one of the target-NSSAI and the target-RFSP information elements to the another gNB 200b serving the UE 100, via a new message or existing message, before or after the completion of Xn or N2 based inter NG-RAN handover procedure.

In an embodiment, the area-specific network slices controller 540 may receive the service-request message from the UE 100 to obtain the at least one service when the UE 100 is moved away from its initial location. In an embodiment, the area-specific network slices controller 540 may send the at least one of the target-NSSAI and the target-RFSP information elements to the gNB 200 serving the UE 100, to intimate the services of interest at the UE 100.

In an embodiment, the area-specific network slices controller 540 may receive a N2 path switch request message from another gNB 200b as part of an Xn based inter NG-RAN handover procedure when the UE 100 is moved away from its initial gNB 200a. In an embodiment, the area-specific network slices controller 540 may send at least one of the target-NSSAI and a target-RFSP information element to the another gNB 200b serving the UE 100 as part of a N2 path switch request acknowledgement message, and/or send at least one of the target-NSSAI and the target-RFSP information element to the new gNB 200b serving the UE 100 via a new message or existing message, before or after N2 path switch request acknowledgement message has been sent to the UE 100.

In an embodiment, the area-specific network slices controller 540 may be physically implemented by analog and/or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and may optionally be driven by firmware.

In an embodiment, the processor 510 may be configured to execute instructions stored in the memory 530 and to perform various processes. The communicator 520 may be configured for communicating internally between internal hardware components and with external devices via one or more networks. The memory 530 may store instructions to be executed by the processor 510 and/or the area-specific network slices controller 540. The memory 530 may include non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories.

In an embodiment, the memory 530 may, in some examples, be considered a non-transitory storage medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term “non-transitory” should not be interpreted that the memory 530 may be non-movable. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in Random Access Memory (RAM) or cache).

Although the FIG. 5 shows various hardware components of the AMF device 300 but it is to be understood that other embodiments are not limited thereon. In an embodiment, the AMF device 300 may include less or more number of components. In an embodiment, the labels or names of the components are used only for illustrative purpose and does not limit the scope of the invention. One or more components can be combined together to perform same or substantially similar function in the AMF device 300.

FIG. 6 shows various hardware components of the gNB according to the embodiments as disclosed herein. In an embodiment, the gNB 200 may include a processor 610, a communicator 620, a memory 630 and an area-specific network slices controller 640. The processor 610 may be coupled with the communicator 620, the memory 630 and the area-specific network slices controller 640.

The area-specific network slices controller 640 may receive at least one of the target-NSSAI and target-RFSP and redirects the UE 100 to the frequency band that supports the at least one target S-NSSAI, when the at least one S-NSSAI is available in a nearby TA.

In an embodiment, the area-specific network slices controller 640 may receive the target-NSSAI information element and redirects the UE 100 to the frequency band that supports the at least one target S-NSSAI, when the at least one S-NSSAI is available in a nearby TA.

In an embodiment, the area-specific network slices controller 640 may receive the target-NSSAI information element and sends at least one of the Target-NSSAI and the Target-RFSP to a second gNB 200b serving the UE 100, upon the movement of the UE 100 to an area served by the second gNB 200b, provided Requested-NSSAI has not changed.

The area-specific network slices controller 640 may be physically implemented by analog and/or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and may optionally be driven by firmware.

In an embodiment, the processor 610 may be configured to execute instructions stored in the memory 630 and to perform various processes. The communicator 620 may be configured for communicating internally between internal hardware components and with external devices via one or more networks. The memory 630 may store instructions to be executed by the processor 610.

The memory 630 may include non-volatile storage elements. Examples of such non-volatile storage elements may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In an embodiment, the memory 630 may, in some examples, be considered a non-transitory storage medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term “non-transitory” should not be interpreted that the memory 630 may be non-movable. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in Random Access Memory (RAM) or cache).

Although the FIG. 6 shows various hardware components of the gNB 200 but it is to be understood that other embodiments are not limited thereon. In an embodiments, the gNB 200 may include less or more number of components. The labels or names of the components are used only for illustrative purpose and does not limit the scope of the invention. One or more components can be combined together to perform same or substantially similar function in the gNB 200.

FIG. 7 and FIG. 8 are flow charts S700 and S800 illustrating methods for redirecting the UE 100 to a frequency band for the UE 100 in the wireless network 1000, according to the embodiments as disclosed herein.

Referring to the FIG. 7, in operation S702, the area-specific network slices controller 540 may receive the registration request message comprising the Requested-NSSAI information element from the UE 100. The Requested-NSSAI information element may include a plurality of S-NSSAI, wherein the UE 100 may be served by the Next Generation NodeB (gNB) 200a of the wireless network 1000. In operation S704, the area-specific network slices controller 540 may determine that the at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE 100 is not supported in current TA of the UE 100, and supported in other TAs of the wireless network 1000.

In operation S706, the area-specific network slices controller 540 may send the Target-NSSAI information element including the at least one S-NSSAI requested by the UE 100 not available in current TA of the UE 100 and available in other TAs of the wireless network 1000, zero or more S-NSSAIs requested by the UE 100 available in current TA, and the target-RFSP information element corresponding to the Target-NSSAI, to the gNBs 200a currently serving the UE. In operation S708, the area-specific network slices controller 540 may send the at least one of the same target-NSSAI and target-RFSP to the gNB 200a serving the UE 100, upon every future activity by the UE 100, to avail the services from the wireless network 1000, in response to detecting the Requested-NSSAI has not changed.

In operation S710, the area-specific network slices controller 640 may redirect the UE 100 to the frequency band that supports the at least one target S-NSSAI, when the at least one S-NSSAI is available in a nearby TA.

Referring to the FIG. 8, in operation S802, the area-specific network slices controller 540 may receive the registration request message including a Requested-NSSAI information element from the UE 100. The NSSAI may include the plurality of S-NSSAI. The UE 100 may be served by the first Next Generation NodeB gNB of the wireless network 1000. In operation S804, the area-specific network slices controller 540 may determine that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE 100 is not supported in current tracking-area (TA) of the UE 100, and supported in other TAs of the wireless network 1000. In operation S806, the area-specific network slices controller 540 may send the target-NSSAI information element including at least one S-NSSAI requested by the UE 100 not available in current TA of the UE 100 and available in other TAs of the wireless network 1000, the zero or more S-NSSAIs requested by the UE 100 available in current TA of the UE 100, and the target-RFSP information element corresponding to the target-NSSAI, to the first gNBs 200a currently serving the UE 100.

In operation S808, the area-specific network slices controller 540 may perform at least one of: redirect the UE 100 to the frequency band that supports the at least one target S-NSSAI, when the at least one S-NSSAI is available in a nearby TA, and send at least one of the Target-NSSAI and the Target-RFSP to the second gNB 200b serving the UE 100, upon the movement of the UE 100 to the area served by the second gNB 200b, provided Requested-NSSAI has not changed.

The various actions, acts, blocks, steps, or the like in the flow charts S700 and S800 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some of the actions, acts, blocks, steps, or the like may be omitted, added, modified, skipped, or the like without departing from the scope of the invention

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the embodiments as described herein.

Claims

A method for selecting a frequency band for a user equipment (UE) in a wireless network, wherein the method comprises:

receiving, by an Access and Mobility Management Function (AMF) device in the wireless network, a registration request message comprising a Requested-Network Slice Selection Assistance Information (NSSAI) information element from the UE, wherein the Requested-NSSAI information element comprises a plurality of Single-Network Slice Selection Assistance Information (S-NSSAI), wherein the UE is served by a Next Generation NodeB (gNB) of the wireless network;

determining, by the AMF device, that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE is not supported in current tracking-area (TA) of the UE, and supported in other TAs of the wireless network;

sending, by the AMF device, a Target-NSSAI information element comprising the at least one S-NSSAI requested by the UE not available in current TA of the UE and available in other TAs of the wireless network, zero or more S-NSSAIs requested by the UE available in current TA, and a target-Radio Frequency Selection Priority (RFSP) information element corresponding to the Target-NSSAI, to the gNBs currently serving the UE; and

sending, by the AMF device, at least one of the same target-NSSAI and target-RFSP to the gNB serving the UE, upon every future activity by the UE, to avail the services from the wireless network, in response to detecting the Requested-NSSAI has not changed.
The method as claimed in claim 1, wherein sending, by the AMF device, at least one of the target-NSSAI and the target-RFSP to the gNB serving the UE, upon every future activity detected by the UE comprises:

receiving, by the AMF device, a service-request message from the UE to get the at least one service when the UE is moved away from its initial location; and

sending, by the AMF device, the at least one of the target -NSSAI and the target-RFSP information elements to the gNB serving the UE, to intimate the services of interest at the UE.
The method as claimed in claim 2, wherein sending, by the AMF device, the at least one of the target -NSSAI and the target-RFSP information elements to the gNB serving the UE, to intimate the services of interest at the UE comprises one of:

sending, by the AMF device, the at least one of the target-NSSAI and target-RFSP information elements to the gNB as part of a Downlink NAS transport message, while sending a service accept message to the UE; and

sending, by the AMF, the at least one of the target-NSSAI and the target-RFSP information elements to the gNB via a new message or existing message, before or after a service accept message has been sent to the UE (100).
The method as claimed in claim 1, wherein sending, by the AMF device, at least one of the target-NSSAI and the target-RFSP to the gNB serving the UE, upon every future activity by the UE comprises:

receiving, by the AMF device, a N2 path switch request message from another gNB as part of a Xn based inter NG-RAN handover procedure when the UE is moved away from its initial gNB ; and

performing at least one of:

sending, by the AMF device, at least one of the target -NSSAI and a target-RFSP information element to the another gNB serving the UE as part of a N2 path switch request acknowledgement message, and

sending, by the AMF device, at least one of the target-NSSAI and the target-RFSP information element to the new gNB serving the UE via a new message or existing message, before or after N2 path switch request acknowledgement message has been sent to the UE.
The method as claimed in claim 1, wherein sending, by the AMF device, at least one of the target-NSSAI and the target-RFSP to the gNB serving the UE, upon every future activity by the UE comprises:

sending, by the AMF device, at least one of the target -NSSAI and the target-RFSP information element to another gNB serving the UE as part of a handover request message or a handover command message, during a N2 based inter NG-RAN handover procedure when the UE is moved away from its initial gNB ; or

sending, by the AMF device, the at least one of the target-NSSAI and the target-RFSP information elements to the another gNB serving the UE, via a new message or existing message, before or after N2 based inter NG-RAN handover procedure has been completed for the UE.
A method for selecting a frequency band that provides a service of interest to the UE in a wireless network, wherein the method comprises:

receiving, by an Access and Mobility Management Function (AMF) device in the wireless network, a registration request message comprising a Requested- Network Slice Selection Assistance Information (NSSAI) information element from the UE, wherein the NSSAI comprises a plurality of Single-Network Slice Selection Assistance Information (S-NSSAI), and wherein the UE is served by a first Next Generation NodeB (gNB) of the wireless network;

determining, by the AMF device, that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE is not supported in current tracking-area (TA) of the UE, and supported in other TAs of the wireless network;

sending, by the AMF device, at least one of a target-NSSAI information element comprising at least one S-NSSAI requested by the UE not available in current TA of the UE and available in other TAs of the wireless network, a zero or more S-NSSAIs requested by the UE available in current TA of the UE, and a Target- Radio Frequency Selection Priority (RFSP) information element corresponding to Target-NSSAI, to the first gNBs currently serving the UE; and

sending, by the AMF device, at least one of the Target-NSSAI and the Target-RFSP to a second gNB serving the UE, upon the movement of the UE to an area served by the second gNB, provided Requested-NSSAI has not changed.
The method as claimed in claim 6, wherein sending, by the first gNB device, at least one of the target-NSSAI and the target-RFSP to the second gNB serving the UE comprises one of:

sending, by the first gNB device, at least one of the target-NSSAI and the target-RFSP information elements to another gNB serving the UE over the Xn interface as part of Xn based inter NG-RAN handover procedure;

sending, by the first gNB device, at least one of the target-NSSAI and the target-RFSP information elements to the another gNB serving the UE via the AMF device as part of N2 based inter NG-RAN handover procedure; and

sending, by the first gNB device, at least one of the target-NSSAI and the target-RFSP information elements to the another gNB serving the UE, via a new message or existing message, before or after the completion of Xn or N2 based inter NG-RAN handover procedure.
The method as claimed in claim 6, wherein, upon the movement of the UE away from the area served by the first gNB, the first gNB additionally utilizes the target-NSSAI and the target-RFSP information to preferentially select the new cell and new gNB.
An Access and Mobility Management Function (AMF) device for selecting a frequency band for a user equipment in the wireless network, wherein the AMF device comprises:

a memory; and

an area-specific network slices controller, communicatively coupled to the memory, configured to:

receive a registration request message comprising a Requested-Network Slice Selection Assistance Information (NSSAI) information element from the UE, wherein the Requested-NSSAI information element comprises a plurality of Single-Network Slice Selection Assistance Information (S-NSSAI), wherein the UE is served by a Next Generation NodeB (gNB) of the wireless network;

determine that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE is not supported in current tracking-area (TA) of the UE, and supported in other TAs of the wireless network;

send a Target-NSSAI information element comprising the at least one S-NSSAI requested by the UE not available in current TA of the UE and available in other TAs of the wireless network, zero or more S-NSSAIs requested by the UE available in current TA, and a target-Radio Frequency Selection Priority (RFSP) information element corresponding to the Target-NSSAI, to the gNBs currently serving the UE; and

send at least one of the same target-NSSAI and target-RFSP to the gNB serving the UE, upon every future activity by the UE, to avail the services from the wireless network, in response to detecting the Requested-NSSAI has not changed.
The AMF device as claimed in claim 9, wherein send at least one of the target-NSSAI and the target-RFSP to the gNB serving the UE, upon every future activity detected by the UE comprises:

receive a service-request message from the UE to obtain the at least one service when the UE is moved away from its initial location; and

send the at least one of the target -NSSAI and the target-RFSP information elements to the gNB serving the UE, to intimate the services of interest at the UE.
The AMF device as claimed in claim 10, wherein send the at least one of the target -NSSAI and the target-RFSP information elements to the gNB serving the UE, to intimate the services of interest at the UE comprises one of:

send the at least one of the target-NSSAI and target-RFSP information elements to the gNB as part of a Downlink NAS transport message, while sending a service accept message to the UE; and

send the at least one of the target-NSSAI and the target-RFSP information elements to the gNB via a new message or existing message, before or after a service accept message has been sent to the UE.
The AMF device as claimed in claim 9, wherein send at least one of the target-NSSAI and the target-RFSP to the gNB serving the UE, upon every future activity by the UE comprises:

receive a N2 path switch request message from another gNB as part of a Xn based inter NG-RAN handover procedure when the UE is moved away from its initial gNB; and

perform at least one of:

send at least one of the target -NSSAI and a target-RFSP information element to the another gNB serving the UE as part of a N2 path switch request acknowledgement message, and

send at least one of the target-NSSAI and the target-RFSP information element to the new gNB serving the UE via a new message or existing message, before or after N2 path switch request acknowledgement message has been sent to the UE.
The AMF device as claimed in claim 9, wherein send at least one of the target-NSSAI and the target-RFSP to the gNB serving the UE, upon every future activity by the UE comprises:

send at least one of the target-NSSAI and the target-RFSP information element to another gNB serving the UE as part of a handover request message or a handover command message, during a N2 based inter NG-RAN handover procedure when the UE is moved away from its initial gNB; or

send the at least one of the target-NSSAI and the target-RFSP information elements to the another gNB serving the UE, via a new message or existing message, before or after N2 based inter NG-RAN handover procedure has been completed for the UE.
An AMF device for selecting a frequency band for a user equipment in the wireless network, wherein the AMF device comprises:

a memory; and

an area-specific network slices controller, communicatively coupled to the memory, configured to:

receive a registration request message comprising a Requested-Network Slice Selection Assistance Information (NSSAI) information element from the UE, wherein the NSSAI comprises a plurality of Single-Network Slice Selection Assistance Information (S-NSSAI), and wherein the UE is served by a first Next Generation NodeB (gNB) of the wireless network;

determine that at least one S-NSSAI from the plurality of S-NSSAIs requested by the UE is not supported in current tracking-area (TA) of the UE, and supported in other TAs of the wireless network; and

send a target-NSSAI information element comprising at least one S-NSSAI requested by the UE not available in current TA of the UE and available in other TAs of the wireless network, a zero or more S-NSSAIs requested by the UE available in current TA of the UE, and a Target- Radio Frequency Selection Priority (RFSP) information element corresponding to Target-NSSAI, to the first gNBs currently serving the UE.
The AMF device as claimed in claim 14, wherein send at least one of the target-NSSAI and the target-RFSP to the second gNB serving the UE comprises one of:

send at least one of the target -NSSAI and the target-RFSP information elements to another gNB serving the UE over the Xn interface as part of Xn based inter NG-RAN handover procedure;

send at least one of the target-NSSAI and the target-RFSP information elements to the another gNB serving the UE via the AMF device as part of N2 based inter NG-RAN handover procedure; and

send at least one of the target-NSSAI and the target-RFSP information elements to the another gNB serving the UE, via a new message or existing message, before or after the completion of Xn or N2 based inter NG-RAN handover procedure, and

wherein, upon the movement of the UE away from the area served by the first gNB, the first gNB additionally utilizes the target-NSSAI and the target-RFSP information to preferentially select the new cell and new gNB.