FORM 2
THE PATENTS ACT, 1970 (39 OF 1970)
& THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
“METHOD AND SYSTEM FOR SENDING CONFIGURABLE CAUSE IN REGISTRATION REJECT RESPONSE”
We, Jio Platforms Limited, an Indian National, of Office - 101, Saffron, Nr. Centre Point, Panchwati 5 Rasta, Ambawadi, Ahmedabad - 380006, Gujarat, India.
The following specification particularly describes the invention and the manner in which it is to be performed.

METHOD AND SYSTEM FOR SENDING CONFIGURABLE CAUSE IN REGISTRATION REJECT RESPONSE
FIELD OF THE DISCLOSURE
[0001] The present disclosure relates generally to the field of wireless
communication systems. More particularly, the present disclosure relates to methods and systems for sending configurable cause in registration reject response, allowing User Equipment (UE) to connect to a lower radio network (e.g., 4G network) whenever it fails to connect to a higher radio network (e.g., 5G network),
BACKGROUND
[0002] The following description of related art is intended to provide
background information pertaining to the field of the disclosure. This section may include certain aspects of the art that may be related to various features of the present disclosure. However, it should be appreciated that this section be used only to enhance the understanding of the reader with respect to the present disclosure, and not as admissions of prior art.
[0003] Wireless communication technology has rapidly evolved over the past
few decades, with each generation bringing significant improvements and advancements. The first generation of wireless communication technology was based on analog technology and offered only voice services. However, with the advent of the second-generation (2G) technology, digital communication and data services became possible, and text messaging was introduced. 3G technology marked the introduction of high-speed internet access, mobile video calling, and location-based services. The fourth-generation (4G) technology revolutionized wireless communication with faster data speeds, better network coverage, and improved security. Currently, the fifth-generation (5G) technology is being deployed, promising even faster data speeds, low latency, and the ability to connect multiple devices simultaneously. With each generation, wireless communication

technology has become more advanced, sophisticated, and capable of delivering more services to its users.
[0004] In the fifth-generation (5G) New Radio (NR) network, it has been
observed that certain user equipment(s) (UEs) with Subscriber Permanent Identifier (SUPI) associated with Public land mobile networks (PLMN) not permitted to establish connections attempt registration on the 5G network. According to the 3GPP standards, the Access and Mobility Management Function (AMF) sends “PLMN Not Allowed” in the registration reject message whenever the SUPI’s PLMN is unauthorized for registration in the 5G network. Many operators have 4G roaming agreements in place but have yet to establish 5G roaming agreements. Consequently, when users or subscribers of such operators attempt to register on the 5G network and receive “PLMN not Allowed” rejection, they are unable to access even 4G services due to the continuous latching process on the 5G network, despite the existence of 4G roaming agreement. Thus, the UEs fail to connect to either the 4G or 5G networks to use the required services such as signal transmission, voice-over-internet calls, internet access, and the like.
[0005] Hence, in view of these and other existing limitations, there arises an
imperative need to provide an efficient solution to overcome the above-mentioned limitations and to provide a method and system to allow UEs to access network services by latching onto a lower radio access network (e.g., 4G network) in the event of a failure to connect with higher radio access network (e.g., 5G network), particularly in absence of roaming agreements between operators for the higher radio access network.
OBJECTS OF THE INVENTION
[0006] Some of the objects of the present disclosure, which at least one
embodiment disclosed herein satisfies are listed herein below.
[0007] It is an object of the present disclosure to provide a system and a method
to send configurable 5GMM cause in registration reject response in an event the

SUPI PLMN is not allowed to register in 5G Network but has a mutual roaming agreement for other (lower) radio access networks.
[0008] It is another object of the present disclosure to provide a solution that
allows the UE to connect with a mutually agreed roaming network (e.g., 4G network) to avail services in the event the SUPI PLMNs are not allowed to register in the 5G network.
SUMMARY OF THE DISCLOSURE
[0009] This section is provided to introduce certain aspects of the present
disclosure in a simplified form that are further described below in the detailed description. This summary is not intended to identify the key features or the scope of the claimed subject matter.
[00010] According to an aspect of the present disclosure, a method implemented
on a user equipment (UE) is disclosed. The method includes transmitting, to a network node of a first network, a first registration request for establishing a first connection between the UE and the first network. The first registration request comprises an identifier associated with the UE. Next, the method includes receiving, from the network node of the first network, a registration reject message in response to transmission of the first registration request. The registration reject message being indicative of a failure in establishment of the first connection. Next, the method includes transmitting, to a network node of a second network, a second registration request for establishing a second connection between the UE and the second network upon receiving the registration reject message. Thereafter, the method includes establishing the second connection.
[00011] In an aspect, the first network is the 5th Generation (5G) New Radio
network and the second network is the 4th Generation (4G) Long Term Evolution (LTE) network.

[00012] In an aspect, the network node of the first network is an Access Mobility
Function (AMF) and the network node of the second network is a Mobility Management Entity (MME).
[00013] In an aspect, the first registration request is for the establishment of an
N1 interface between the UE and the AMF.
[00014] In an aspect, disabling the capability of the UE to establish the N1
interface upon receiving the registration reject message.
[00015] In an aspect, the registration reject message comprises a 5GMM cause
element to indicate to the UE that N1 mode is not allowed for the first network.
[00016] In an aspect, the identifier is Subscriber Permanent Identifier (SUPI).
[00017] According to another aspect of the present disclosure, a User Equipment
(UE) comprising: a UE memory; and a UE processor coupled to the UE memory, wherein the UE processor causes the UE to: transmit, to a network node of a first network, a first registration request for establishing a first connection between the UE and the first network, the first registration request comprising an identifier associated with the UE; receive, from the network node of the first network, a registration reject message in response to transmission of the first registration request, the registration reject message being indicative of a failure in establishment of the first connection; transmit, to a network node of a second network, a second registration request for establishing a second connection between the UE and the second network upon receiving the registration reject message; and establish the second connection.
[00018] According to yet another aspect of the present disclosure, a method
implemented on a network node of a first network is disclosed. The method comprises: receiving, from a User Equipment (UE), a first registration request for establishing a connection between the UE and the first network, the first registration request comprising an identifier associated with the UE; analysing, by the network

node, the identifier to determine whether the establishment of connection between the UE and the first network is feasible; and transmitting, to the UE, a registration reject message on determining that the establishment of the connection between the UE and the first network is not feasible.
[00019] According to yet another aspect of the present disclosure, a network
node of a first network is disclosed. The network node comprises: a receiving unit configured to receive, from a User Equipment (UE), a first registration request for establishing a connection between the UE and the first network, the first registration request comprising an identifier associated with the UE; an analysis unit configured to analyse the identifier to determine whether the establishment of the connection between the UE and the first network is feasible; and a transmitting unit configured to transmit, to the UE, a registration reject message on determining that the establishment of the connection between the UE and the first network is not feasible.
[00020] According to yet another aspect of the present disclosure, a non-
transitory computer-readable storage medium storing instructions for configurable error mapping for network registration in a wireless communication system is disclosed. The instructions include executable code which, when executed by a processor, may cause the processor to receive a first registration request for establishing a connection between the UE and the first network, the first registration request comprising an identifier associated with the UE; analyse the identifier to determine whether the establishment of the connection between the UE and the first network is feasible; and transmit a registration reject message on determining that the establishment of the connection between the UE and the first network is not feasible.
BRIEF DESCRIPTION OF DRAWINGS
[00021] The accompanying drawings, which are incorporated herein, and
constitute a part of this disclosure, illustrate exemplary embodiments of the disclosed methods and systems in which like reference numerals refer to the same

parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Some drawings may indicate the components using block diagrams and may not represent the internal circuitry of each component. It will be appreciated by those skilled in the art that disclosure of such drawings includes disclosure of electrical components, electronic components or circuitry commonly used to implement such components.
[00022] FIG. 1 illustrates an exemplary block diagram representation of 5th
generation core (5GC) network architecture, in accordance with exemplary embodiment of the present disclosure.
[00023] FIG. 2 illustrates an exemplary block diagram of a network node in
communication with a UE, in accordance with exemplary embodiments of the present disclosure.
[00024] FIG. 3 illustrates an exemplary sequence flow diagram illustrating the
signalling of configurable cause in a registration reject response, in accordance with exemplary embodiments of the present disclosure.
[00025] FIG. 4 illustrates an exemplary method flow diagram indicating the
process for receiving configurable cause in a registration reject response by a UE, in accordance with exemplary embodiments of the present disclosure.
[00026] FIG. 5 illustrates another exemplary method flow diagram indicating
the process for sending configurable cause in a registration reject by a network node, in accordance with exemplary embodiments of the present disclosure.
[00027] The foregoing shall be more apparent from the following more detailed
description of the disclosure.
DESCRIPTION

[00028] In the following description, for the purposes of explanation, various
specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, that embodiments of the present disclosure may be practiced without these specific details. Several features described hereafter can each be used independently of one another or with any combination of other features. An individual feature may not address any of the problems discussed above or might address only some of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein. Example embodiments of the present disclosure are described below, as illustrated in various drawings in which like reference numerals refer to the same parts throughout the different drawings.
[00029] The ensuing description provides exemplary embodiments only, and is
not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the exemplary embodiments will provide those skilled in the art with an enabling description for implementing an exemplary embodiment. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the disclosure as set forth.
[00030] It should be noted that the terms "mobile device", "user equipment",
"user device", “communication device”, “device” and similar terms are used interchangeably for the purpose of describing the invention. These terms are not intended to limit the scope of the invention or imply any specific functionality or limitations on the described embodiments. The use of these terms is solely for convenience and clarity of description. The invention is not limited to any particular type of device or equipment, and it should be understood that other equivalent terms or variations thereof may be used interchangeably without departing from the scope of the invention as defined herein.
[00031] Specific details are given in the following description to provide a
thorough understanding of the embodiments. However, it will be understood by one

of ordinary skill in the art that the embodiments may be practiced without these specific details. For example, circuits, systems, networks, processes, and other components may be shown as components in block diagram form in order not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.
[00032] Also, it is noted that individual embodiments may be described as a
process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed but could have additional steps not included in a figure.
[00033] The word “exemplary” and/or “demonstrative” is used herein to mean
serving as an example, instance, or illustration. For the avoidance of doubt, the subject matter disclosed herein is not limited by such examples. In addition, any aspect or design described herein as “exemplary” and/or “demonstrative” is not necessarily to be construed as preferred or advantageous over other aspects or designs, nor is it meant to preclude equivalent exemplary structures and techniques known to those of ordinary skill in the art. Furthermore, to the extent that the terms “includes,” “has,” “contains,” and other similar words are used in either the detailed description or the claims, such terms are intended to be inclusive—in a manner similar to the term “comprising” as an open transition word—without precluding any additional or other elements.
[00034] As used herein, an “electronic device”, or “portable electronic device”,
or “user device” or “communication device” or “user equipment” or “device” refers to any electrical, electronic, electromechanical and computing device. The user device is capable of receiving and/or transmitting one or parameters, performing function/s, communicating with other user devices and transmitting data to the other user devices. The user equipment may have a processor, a display, a memory,

a battery and an input-means such as a hard keypad and/or a soft keypad. The user equipment may be capable of operating on any radio access technology including but not limited to IP-enabled communication, Zig Bee, Bluetooth, Bluetooth Low Energy, Near Field Communication, Z-Wave, Wi-Fi, Wi-Fi direct, etc. For instance, the user equipment may include, but not limited to, a mobile phone, smartphone, virtual reality (VR) devices, augmented reality (AR) devices, laptop, a general-purpose computer, desktop, personal digital assistant, tablet computer, mainframe computer, or any other device as may be obvious to a person skilled in the art for implementation of the features of the present disclosure.
[00035] Further, the user device may also comprise a “processor”
or “processing unit”, wherein the processor refers to any logic circuitry for processing instructions. The processor may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor, a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits, Field Programmable Gate Array circuits, any other type of integrated circuits, etc. The processor may perform signal coding data processing, input/output processing, and/or any other functionality that enables the working of the system according to the present disclosure. More specifically, the processor is a hardware processor.
[00036] As portable electronic devices and wireless technologies continue to
improve and grow in popularity, the advancing wireless technologies for data transfer are also expected to evolve and replace the older generations of technologies. In the field of wireless data communications, the dynamic advancement of various generations of cellular technology are also seen. The development, in this respect, has been incremental in the order of second generation (2G), third generation (3G), fourth generation (4G), and now fifth generation (5G), and more such generations are expected to continue in the forthcoming time.
[00037] Radio Access Technology (RAT) refers to the technology used by
mobile devices/ user equipment (UE) to connect to a cellular network. It refers to the specific protocol and standards that govern the way devices communicate with

5 base stations, which are responsible for providing the wireless connection. Further,
each RAT has its own set of protocols and standards for communication, which define the frequency bands, modulation techniques, and other parameters used for transmitting and receiving data. Examples of RATs include GSM (Global System for Mobile Communications), CDMA (Code Division Multiple Access), UMTS
10 (Universal Mobile Telecommunications System), LTE (Long-Term Evolution),
and 5G. The choice of RAT depends on a variety of factors, including the network infrastructure, the available spectrum, and the mobile device's/device's capabilities. Mobile devices often support multiple RATs, allowing them to connect to different types of networks and provide optimal performance based on the available network
15 resources.
[00038] As used herein, subscription permanent identifier (SUPI) refers to a
unique identifier used in the 5G system architecture to identify mobile subscribers, as per the 3GPP (3rd Generation Partnership Project) standards. The SUPI ensures
20 the privacy and security of the subscriber's identity by preventing its exposure over
the air. The SUPI is derived from the IMSI (International Mobile Subscriber Identity), the SUPI can be formatted either as an IMSI, which combines the Mobile Country Code (MCC), Mobile Network Code (MNC), and Mobile Subscriber Identification Number (MSIN), or as a Network-Specific Identifier (NSI) for local
25 network operations.
[00039] As used herein, 5G Mobility Management (5GMM) refers to a set of
protocols and procedures used in the 5G network to manage and control the mobility and connection states of User Equipment (UE). The 5GMM includes
30 functionalities such as registration, connection management, and mobility
management, ensuring seamless connectivity and efficient handovers between different network nodes. The 5GMM protocols facilitates the UE in registering with a network, maintain its connection, and manage mobility as it moves across different geographical areas or network segments for maintaining continuous
35 service and connectivity.
11

5 [00040] As used herein, ‘cause code’, refers to a specific numerical code used
to indicate a reason for a particular event or condition. For example, the cause code
can indicate why a registration request was rejected or why a connection attempt
failed. This allows the network and the User Equipment (UE) to understand and
appropriately respond to various conditions. Examples of cause code includes but
10 not limited only to "PLMN not allowed" or "N1 mode not allowed". Cause codes
help in diagnosing issues, managing network behaviour, and ensuring seamless user experience.
[00041] As used herein, ‘public land mobile network (PLMN)’ refers to a
15 network established and operated by an administration or recognized operating
agency to provide land mobile telecommunications services to the public. Each
PLMN is uniquely identified by a combination of the Mobile Country Code (MCC)
and the Mobile Network Code (MNC). The PLMN enables mobile users to access
network services, roam across different geographical areas, and maintain
20 connectivity as they move. The PLMN thus facilitates interoperability and service
continuity across different regions and network operators.
[00042] As used herein, ‘N1 mode’ refers to an operational mode of the 5G
system architecture that pertains to the connection and communication between the
25 User Equipment (UE) and the Access and Mobility Management Function (AMF)
over the N1 interface. The N1 mode is primarily concerned with the signalling procedures related to mobility management, session management, and other control plane functions necessary for the operation of the UE within a 5G network.
30 [00043] As used herein, ‘configurable cause in registration reject response’
refers to a code that is sent by the network to the UE when a registration attempt is denied. The configurable cause code provides information about why the registration request was rejected, allowing the network to communicate precise reasons to the UE. Further, the network operators or administrators can modify the
35 cause codes based on different scenarios, policies, or operational requirement.
12

5 [00044] As used herein, ‘N1 interface’ refers to the communication interface
between the UE and the AMF within the 5G core network. The N1 interface facilitates operations such as registration, authentication, connection management, mobility management, and session management.
10 [00045] As discussed in the background section, a problem arises when
operators have mutual agreements for one radio access technology (e.g., 4G) but fail to connect due to repetitive attempts by UEs to access a higher radio access technology (e.g., 5G) where operators do not have any roaming agreement.
15 [00046] In fifth-generation (5G) New Radio (NR) networks, it has been
observed that certain user equipment(s) (UEs) with Subscriber Permanent Identifier (SUPI) associated with Public Land Mobile Networks (PLMNs) not permitted to establish connections attempt registration on the 5G network. According to the 3GPP standard, the Access and Mobility Management Function (AMF) sends a
20 “PLMN Not Allowed” cause in registration reject message whenever the SUPI’s
PLMN is unauthorized for registration in the 5G network. Many operators have 4G roaming agreements in place but have yet to establish 5G roaming agreements. Consequently, when users or subscribers of such operators attempt to register on the 5G network and receive “PLMN not Allowed” rejection, they are unable to
25 access even 4G services due to the continuous latching process on the 5G network,
despite the existence of 4G roaming agreement. Thus, the UEs fail to connect to either the 4G or 5G networks to use the required services such as signal transmission, voice-over internet calls, internet access, and the like.
30 [00047] The present disclosure aims to overcome the above-mentioned and
other existing problems in this field of technology by providing a solution of sending a configurable cause in the registration reject response so that such UE(s) may at least attach on lower radio access network (e.g., 4G network) without any delay.
35
[00048] In an example, operator ‘X’ only has a 4G roaming agreement with
operator ‘Y’, but does not have any roaming agreement on 5G technology. When
13

5 users or UEs of such operator, say operator ‘X’, attempt to register on the 5G
network of the operator ‘Y’, they are rejected with the cause “PLMN not Allowed”. This also leads to the unavailability of even 4G services for UE(s) even though a 4G roaming agreement is there between operator ‘X’ and operator ‘Y’. Thus, UE is unable to latch on both 4G and 5G networks. To tackle this issue, the present
10 disclosure allows the AMF to send configurable cause in the Registration Reject so
that at least 4G service of such users will not be impacted. In the present disclosure, AMF is configured to send “N1 Mode not Allowed” cause so that such devices can disable N1 capabilities and can attach on a 4G network without any issue. Hence, they (users or UEs of operator ‘X’) can continue using 4G service while roaming
15 with operator ‘Y’.
[00049] Hereinafter, exemplary embodiments of the present disclosure will be
described with reference to the accompanying drawings.
20 [00050] FIG. 1 illustrates an exemplary block diagram representation of 5th
generation core (5GC) network architecture, in accordance with exemplary embodiment of the present disclosure. As shown in FIG. 1, the 5GC network architecture [100] includes a user equipment (UE) [102], a radio access network (RAN) [104], an access and mobility management function (AMF) [106], a Session
25 Management Function (SMF) [108], a Service Communication Proxy (SCP) [110],
an Authentication Server Function (AUSF) [112], a Network Slice Specific Authentication and Authorization Function (NSSAAF) [114], a Network Slice Selection Function (NSSF) [116], a Network Exposure Function (NEF) [118], a Network Repository Function (NRF) [120], a Policy Control Function (PCF) [122],
30 a Unified Data Management (UDM) [124], an application function (AF) [126], a
User Plane Function (UPF) [128], a data network (DN) [130], wherein all the components are assumed to be connected to each other in a manner as obvious to the person skilled in the art for implementing features of the present disclosure.
35 [00051] The User Equipment (UE) [102] interfaces with the network via the
Radio Access Network (RAN) [104]; the Access and Mobility Management Function (AMF) [106] manages connectivity and mobility, while the Session
14

5 Management Function (SMF) [108] administers session control; the service
communication proxy (SCP) [110] routes and manages communication between network services, enhancing efficiency and security, and the Authentication Server Function (AUSF) [112] handles user authentication; the Non-Standalone Access Architecture Function (NSSAAF) [114] for integrating the 5G core network with
10 existing 4G LTE networks i.e., to enable Non-Standalone (NSA) 5G deployments,
the Network Slice Selection Function (NSSF) [116], Network Exposure Function (NEF) [118], and Network Repository Function (NRF) [120] enable network customization, secure interfacing with external applications, and maintain network function registries respectively; the Policy Control Function (PCF) [122] develops
15 operational policies, and the Unified Data Management (UDM) [124] manages
subscriber data; the Application Function (AF) [126] enables application interaction, the User Plane Function (UPF) [128] processes and forwards user data, and the Data Network (DN) [130] connects to external internet resources; collectively, these components are designed to enhance mobile broadband, ensure
20 low-latency communication, and support massive machine-type communication,
solidifying the 5GC as the infrastructure for next-generation mobile networks.
[00052] Radio Access Network (RAN) [104] is the part of a mobile
telecommunications system that connects user equipment (UE) [102] to the core
25 network (CN) and provides access to different types of networks (e.g., 5G network).
It consists of radio base stations and the radio access technologies that enable wireless communication.
[00053] Access and Mobility Management Function (AMF) [106] is a 5G core
30 network function responsible for managing access and mobility aspects, such as UE
registration, connection, and reachability. It also handles mobility management procedures like handovers and paging.
[00054] Session Management Function (SMF) [108] is a 5G core network
35 function responsible for managing session-related aspects, such as establishing,
modifying, and releasing sessions. It coordinates with the User Plane Function
(UPF) for data forwarding and handles IP address allocation and QoS enforcement.
15

5
[00055] Service Communication Proxy (SCP) [110] is a network function in the
5G core network that facilitates communication between other network functions by providing a secure and efficient messaging service. It acts as a mediator for service-based interfaces. 10
[00056] Authentication Server Function (AUSF) [112] is a network function in
the 5G core responsible for authenticating UEs during registration and providing security services. It generates and verifies authentication vectors and tokens.
15 [00057] Network Slice Specific Authentication and Authorization Function
(NSSAAF) [114] is a network function that provides authentication and authorization services specific to network slices. It ensures that UEs can access only the slices for which they are authorized.
20 [00058] Network Slice Selection Function (NSSF) [116] is a network function
responsible for selecting the appropriate network slice for a UE based on factors such as subscription, requested services, and network policies.
[00059] Network Exposure Function (NEF) [118] is a network function that
25 exposes capabilities and services of the 5G network to external applications,
enabling integration with third-party services and applications.
[00060] Network Repository Function (NRF) [120] is a network function that
acts as a central repository for information about available network functions and
30 services. It facilitates the discovery and dynamic registration of network functions.
[00061] Policy Control Function (PCF) [122] is a network function responsible
for policy control decisions, such as QoS, charging, and access control, based on subscriber information and network policies. 35
16

5 [00062] Unified Data Management (UDM) [124] is a network function that
centralizes the management of subscriber data, including authentication, authorization, and subscription information.
[00063] Application Function (AF) [126] is a network function that represents
10 external applications interfacing with the 5G core network to access network
capabilities and services.
[00064] User Plane Function (UPF) [128] is a network function responsible for
handling user data traffic, including packet routing, forwarding, and QoS
15 enforcement.
[00065] Data Network (DN) [130] refers to a network that provides data services
to user equipment (UE) in a telecommunications system. The data services may include but are not limited to Internet services, private data network related services.
20
[00066] The present disclosure first receives, via AMF, a registration request
from the UE. Next, the AMF checks whether the SUPI PLMN received in the registration request is allowed or not in the current serving PLMN. In case the SUPI PLMN is not allowed in the serving PLMN then the AMF is configured to send a
25 registration reject with a configurable cause “N1 mode not allowed” to the UE.
Next, the UE disables N1 capabilities and tries to attach in 4G. Next, the UE sends an attachment request to MME. Thereafter, the UE connects with the 4G network to avail the 4G services after performing the initial attach procedure with MME. Thus, the present invention is configured to allow the UE to use uninterrupted
30 network services in 5G or 5G networks depending upon the roaming agreement
between various operators. The present invention, via the AMF, responds to the rejection of the registration request with reasons so that the UE may latch to the lower radio networks (such as 4G, 3G) in case of failure to latch to 5G or upper radio networks.
35
[00067] As used herein, a Mobility Management Entity (MME) is a part of
3GPP Long-Term Evolution (LTE) networks or 4G Architecture. The primary tasks
17

5 of MME include but are not limited to managing sessions, authentication, paging,
mobility, bearers, and roaming handling.
[00068] FIG. 2 illustrates an exemplary block diagram [200] of a network node
(such as AMF [106]) in communication with a UE, in accordance with exemplary
10 embodiments of the present disclosure. As shown in FIG. 2, the block diagram [200]
includes a UE [102] which comprises a UE processor [202a], a UE memory [202b], a receiving unit [202c], and a transmitting unit [202d]. Further, the block diagram [200] of a network node (such as AMF [106]) is shown. The network node comprises an analysis unit [206a], a memory [206b], a receiving unit [206c], and a
15 transmitting unit [206d]. Further, said units may communicate with each other via
interconnections to implement the features of the present invention.
[00069] The receiving unit [206c] within the network node (such as AMF [106])
is configured to receive a request for the establishment of a connection between the
20 User Equipment (UE) [102] and a first network, such as a 5th Generation (5G)
network. The receiving unit [206c] is specifically configured to handle incoming communication from the UE [102], which is seeking to access the network’s services. The primary function of the receiving unit [206c] is to receive the registration request from the UE [102]. The registration request is a communication
25 sent by the transmitting unit [202d] of UE [102] to the network, indicating its desire
to establish a connection with the first network. The registration request typically contains essential information about the UE [102], such as its identity, SUPI, PLMN information, and the type of services it wishes to access. Upon receiving the registration request, the receiving unit [206c] processes the incoming
30 communication and transmits the relevant information to other components within
the network node (such as AMF [106]), such as the analysis unit [206a]. The analysis unit [206a] analyses the received SUPI PLMN information to check whether the connectivity establishment in the network is feasible.
35 [00070] The analysis unit [206a] analyses the information received from the UE
in the registration request (such as identity, SUPI, PLMN information, and the type of services) to check if the specific UE is allowed to register to the 5G network or
18

5 not. In an exemplary implementation, the analysis unit considers the data associated
with roaming agreement between the operators to check if the requested UE is eligible to register to the 5G network or not.
[00071] The network node has the memory [206b] to store data associated with
10 registration requests, UE parameters, roaming agreement-related information, and
the like to process the registration request of the UE. Based upon the analysis, the
network node may either connect the UE with the core network or may initiate
subsequent steps in the registration reject process towards the UE [102] with a
configurable cause of denial, so that UE [102] may establish connectivity with a
15 second network such as 4th Generation (4G) network.
[00072] Referring to FIG. 3, a sequence flow diagram for sending configurable
cause in a rejection reject is shown, in accordance with the exemplary embodiments
of the present invention. As shown in FIG. 3, the sequence diagram [300] includes
20 the UE [102], a Mobility Management Entity (MME) [304], and the AMF [106].
The sequence of steps is performed by the UE [102], the MME [304], and the AMF [106] for signaling of configurable cause in rejection reject.
[00073] At step S1, the UE [102] sends a registration request to AMF [106] to
25 establish a connection with the 5G network. This is the initial step where the UE
[102] indicates its intention to connect to the network (such as a 5G network).
[00074] Next, at step S2, upon receiving the registration request, the AMF [106]
checks or analyses whether SUPI PLMN received in the registration request is
30 allowed or not in the current serving PLMN. In case the SUPI PLMN is not allowed
in the serving PLMN, then the AMF [106] is configured to send a registration reject to the UE [102].
[00075] Next, at step S3, the AMF [106] sends a registration rejection message
with a configurable 5G mobility management (5GMM) cause i.e., “N1 mode not
35 allowed” to the UE [102].
19

5 [00076] Next, at step S4, the UE [102] Upon receiving the registration reject
message or response with the cause code (i.e., N1 mode not allowed), the UE [102] understands that N1 mode is not allowed and thus disables its N1 capabilities, which are related to 5G access, and instead try to latch or attach to the network using 4G capabilities at the MME [304]. 10
[00077] Next, at step S5, the UE [102] sends an attachment request to the MME
[304] after receiving the rejection from the AMF [106].
[00078] Thereafter, at step S6, the UE [102] connects with the 4G network to
15 avail 4G services after performing the initial attach procedure with MME [304].
[00079] Referring to FIG. 4, an exemplary method flow diagram [400] for
indicating the process for receiving configurable cause in a registration reject
response, in accordance with exemplary embodiments of the present invention is
20 shown. As shown in FIG. 4, the method [400] starts at step [402].
[00080] At step [404], the method [400] as disclosed by the present disclosure
comprises transmitting, to a network node (such as AMF [106]) of a first network,
a first registration request for establishing a first connection between the UE [102]
25 and the first network, the first registration request comprising an identifier
associated with the UE [102]. The first network is a 5th Generation (5G) network.
[00081] The registration request corresponds to a communication from the UE
[102]. The registration request may include necessary identification and access
30 information which the first network (such as 5G network) requires to initiate the
UE’s authentication process. The information typically includes the UE’s identity, subscription details, SUPI, PLMN information, and the type of services it wishes to access. The network node (such as AMF [106]) then processes this registration request to determine whether the UE [102] is allowed to connect to and use the
35 network services. The UE [102] sends a registration request for the establishment
of an N1 interface between the UE [102] and the AMF [106] with identifier
20

5 information such as SUPI to the network node of the first network, such as AMF
[106] node of 5G network.
[00082] Next, at step [406], the method [400] as disclosed by the present
disclosure comprises receiving, from the network node (such as AMF [106]) of the
10 first network, a registration reject message in response to the transmission of the
first registration request, the registration reject message being indicative of a failure in establishment of the first connection.
[00083] Upon receiving the registration request with SUPI information from the
15 UE [102], the analysis unit [206a] of the AMF [106] analyses the received SUPI
PLMN information in the registration request to check whether the registration is allowed or not in the current serving PLMN. The analysis unit [206a] checks the allowed SUPI PLMN information with agreement between the operators for the type of network technology. In case, the SUPI PLMN is not allowed in the serving
20 PLMN, then the transmitting unit [206d] of AMF [106] sends a registration reject
with configurable cause “N1 mode not allowed” to the UE [102]. In an exemplary aspect, the configurable cause message may be such as, but not limited to, “failure cause code”, “bad request”, “unauthorized request”, “forbidden request”, “not found”, etc., and the like. In another exemplary aspect, the cause may be configured
25 such as, but not limited to, on a demand basis, operator’s agreement basis, and the
like. The UE [102] receives the registration reject message comprising configurable 5GMM cause “N1 mode not allowed” in response to transmission of the first registration request being indicative of a failure in establishment of the first connection that N1 mode is not allowed for the first network. After receiving the
30 registration reject message, the UE [102] disables the capability of the UE [102] to
establish the N1 interface with the first network.
[00084] In an aspect, the AMF [106] sends a registration reject response with an
appropriate cause that is configurable in the AMF [106] for cases where SUPI
35 PLMN is not allowed to register in the 5G network. For in-roamers having only a
4G roaming agreement, AMF [106] can send “N1 mode not allowed” cause in
21

registration reject response so that such UE equipment [102] can at least attach to a 4G network without any concern or delay.
[00085] Next, at step [408], the method [400], as disclosed by the present
disclosure, comprises transmitting, to a network node (such as MME [304]) of a second network, a second registration request for establishing a second connection between the UE [102] and the second network upon receiving the registration reject message. After receiving “N1 mode not allowed” reject cause message from the AMF [106], the UE [102] disables N1 capabilities and tries to attach with the second network. The second network is the 4th Generation (4G) Long Term Evolution (LTE) network. The UE [102] sends an attach request to the network of the second network such as MME [304] of the 4G network to initiate the attach procedure with the 4G network.
[00086] Next, at step [410], the method [400] as disclosed by the present
disclosure comprises establishing the second connection. Thereafter, the second connection is established between UE [102] and MME [304] in the 4G network after a successful registration procedure between UE [102] and MME [304].
[00087] Thereafter, the method [400] terminates at step [412].
[00088] FIG. 5 illustrates another exemplary method flow diagram [500]
indicating the process for sending configurable cause by a network node in a registration reject, in accordance with exemplary embodiments of the present disclosure. As shown in FIG. 5, the method [500] starts at step [502].
[00089] At step [504], the method [500] as disclosed by the present disclosure
comprises receiving, from a User Equipment (UE) [102], a first registration request for establishing a connection between the UE [102] and the first network, the first registration request comprising an identifier associated with the UE [102]. The network node of the first network such as AMF [106] of the 5G network receives via receiving unit [206c] a first registration request with an identifier such as UE identifier SUPI, PLMN, type of service for establishing a connection between the

UE [102] and the first network such as 5G network. The first registration request is for the establishment of an N1 interface between the UE [102] and the AMF [106]. Examples of identifiers include but not limited only to international mobile equipment identity (IMSI), subscriber concealed identifier (SUCI), subscriber permanent identifier (SUPI), international mobile equipment identity (IMEI), and globally unique temporary identifier (GUTI).
[00090] Next, at step [506], the method [500] as disclosed by the present
disclosure comprises analysing, by the network node (such as AMF [106]), the identifier to determine whether the establishment of the connection between the UE [102] and the first network is feasible. The analysis unit [206a] analyses the received identifier such as SUPI PLMN information to determine whether the establishment of the connection between the UE [102] and the first network, such as 5G is feasible or not. The analysis unit [206a] checks SUPI PLMN information of UE [102] with operators’ roaming agreements with type of network technology support. The operators have technology support agreements between them so that they provide different services to their users even when they are present in their roaming partner’s network. If analysis unit [206a] determines that operators have no agreement for 5G technology, then analysis unit [206a] initiates the registration reject, since UE [102] is not allowed to use the requested network service.
[00091] Next, at step [508], the method [500] as disclosed by the present
disclosure comprises transmitting, to the UE [102], a registration reject message on determining that the establishment of the connection between the UE [102] and the first network is not feasible. The AMF [106] sends via transmitting unit [206d] a registration reject message on determining that the establishment of the connection between the UE [102] and the first network such as a 5G network is not feasible. The registration reject message comprises a 5GMM cause element to indicate to the UE [102] that the N1 mode is not allowed for the first network.
[00092] Thereafter, the method [500] terminates at step [510].

[00093] In an exemplary aspect of the present disclosure, the present description
is not restricted to only 5G or 4G networks. The present disclosure may be implemented between two different Network(s) (such as one may be of a higher network and the other may be of a lower network) technology with the same scope of the implementation of the invention.
[00094] In another aspect of the present disclosure, a User Equipment (UE)
[102] comprising a UE memory [202b], and a UE processor [202a] coupled to the UE memory [202b]. The UE processor [202a] causes the UE [102] to: transmit, to a network node (such as AMF [106]) of a first network (such as 5th Generation (5G) New Radio network), a first registration request for establishing a first connection between the UE [102] and the first network, the first registration request comprising an identifier associated with the UE [102]; receive, from the network node (such as AMF [106]) of the first network, a registration reject message in response to transmission of the first registration request, the registration reject message being indicative of a failure in establishment of the first connection; transmit, to a network node (such as Mobility Management Entity (MME) [304]) of a second network (such as 4th Generation (4G) Long Term Evolution (LTE) network), a second registration request for establishing a second connection between the UE [102] and the second network upon receiving the registration reject message; and establish the second connection. The UE [102] transmits the first registration request for the establishment of an N1 interface between the UE [102] and the AMF [106]. The registration request comprises Subscriber Permanent Identifier (SUPI), PLMN, and network service information. After receiving the registration reject message which comprises a 5GMM cause element to indicate to the UE [102] that the N1 mode is not allowed for the first network. The UE processor [202a] further causes the UE [102] to disable the capability of the UE [102] to establish the N1 interface upon receiving the registration reject message. In an exemplary implementation, the UE memory [202b] may be used to store the data required for the implementation of the features of the present disclosure.
[00095] In an exemplary aspect, UE processor [202a] may trigger the
transmitting unit [202d], to transmit a first registration request for establishing a

first connection between the UE [102] and the first network, the first registration request comprising an identifier associated with the UE [102] to a network node (such as Access Mobility management Function (AMF) [106]) of a first network (such as 5th Generation (5G) New Radio network). In an exemplary aspect, UE processor [202a] may trigger the receiving unit [202c] to receive from the network node (such as AMF [106]) of the first network, a registration reject message in response to the transmission of the first registration request, the registration reject message being indicative of a failure in establishment of the first connection. In an exemplary aspect, UE processor [202a] may trigger the transmitting unit [202d], to transmit to a network node (such as Mobility Management Entity (MME) [304]) of a second network (such as 4th Generation (4G) Long Term Evolution (LTE) network), a second registration request for establishing a second connection between the UE [102] and the second network upon receiving the registration reject message; and establish the second connection.
[00096] In another aspect of the present disclosure, a network node (such as
AMF [106]) includes a receiving unit [206c] configured to receive, from a User Equipment (UE) [102], a first registration request for establishing a connection between the UE [102] and the first network, the first registration request comprising an identifier associated with the UE [102]. The first registration request is for the establishment of an N1 interface between the UE [102] and the AMF [106] and the identifier is Subscriber Permanent Identifier (SUPI), PLMN, and network type services. The AMF [106] includes an analysis unit [206a] configured to analyze the identifier to determine whether the establishment of the connection between the UE [102] and the first network (5G network) is feasible. Thereafter, AMF [106] via a transmitting unit [206d] transmits to the UE [102], a registration reject message on determining that the establishment of the connection between the UE [102] and the first network is not feasible. The registration reject message comprises a 5GMM cause element to indicate to the UE [102] that the N1 mode is not allowed for the first network.
[00097] According to yet another aspect of the present disclosure, a non-
transitory computer-readable storage medium storing instructions for configurable

error mapping for network registration in a wireless communication system is disclosed. The instructions include executable code which, when executed by a processor, may cause the processor to receive a first registration request for establishing a connection between the UE [102] and the first network, the first registration request comprising an identifier associated with the UE [102]; analyse the identifier to determine whether the establishment of connection between the UE [102] and the first network is feasible; and transmit a registration reject message on determining that the establishment of the connection between the UE [102] and the first network is not feasible.
[00098] As is evident from the above, the present disclosure provides a
technically advanced solution for connecting the UE with 4G network service in the event the connection with 5G network service fails due to PLMN connecting issues or unavailability of roaming agreements between operators to 5G radio technology. Thus, in view of the above disclosure, the present disclosure overall saves the time of the UE to connect the UE with an allowed network to avail network services.
[00099] Further, in accordance with the present disclosure, it is to be
acknowledged that the functionality described for the various the components/units can be implemented interchangeably. While specific embodiments may disclose a particular functionality of these units for clarity, it is recognized that various configurations and combinations thereof are within the scope of the disclosure. The functionality of specific units as disclosed in the disclosure should not be construed as limiting the scope of the present disclosure. Consequently, alternative arrangements and substitutions of units, provided they achieve the intended functionality described herein, are considered to be encompassed within the scope of the present disclosure.
[000100] While considerable emphasis has been placed herein on the disclosed embodiments, it will be appreciated that many embodiments can be made and that many changes can be made to the embodiments without departing from the principles of the present disclosure. These and other changes in the embodiments

of the present disclosure will be apparent to those skilled in the art, whereby it is to be understood that the foregoing descriptive matter to be implemented is illustrative and non-limiting.

I/We Claim:
1. A method implemented on a User Equipment (UE) [102], the method
comprising:
transmitting, to a network node of a first network, a first registration request for establishing a first connection between the UE [102] and the first network, the first registration request comprising an identifier associated with the UE [102];
receiving, from the network node of the first network, a registration reject message in response to transmission of the first registration request, the registration reject message being indicative of a failure in establishment of the first connection;
transmitting, to a network node of a second network, a second registration request for establishing a second connection between the UE [102] and the second network upon receiving the registration reject message; and
establishing the second connection.
2. The method as claimed in claim 1, wherein the first network is 5th Generation (5G) New Radio network and the second network is 4th Generation (4G) Long Term Evolution (LTE) network.
3. The method as claimed in claim 2, wherein the network node of the first network is Access Mobility Function (AMF) [106] and the network node of the second network is Mobility Management Entity (MME) [304].
4. The method as claimed in claim 3, wherein the first registration request is for establishment of an N1 interface between the UE [102] and the AMF [106].
5. The method as claimed in claim 4, further comprises disabling a capability of the UE [102] to establish the N1 interface upon receiving the registration reject message.

6. The method as claimed in claim 1, wherein the registration reject message
comprises a 5GMM cause element to indicate to the UE [102] that N1 mode is not
allowed for the first network.
7. The method as claimed in claim 1, wherein the identifier is Subscriber Permanent Identifier (SUPI).
8. A User Equipment (UE) [102] comprising:
a UE memory [202b]; and
a UE processor [202a] coupled to the UE memory [202b], wherein the UE processor [202a] causes the UE [202] to:
transmit, to a network node of a first network, a first registration request for establishing a first connection between the UE [102] and the first network, the first registration request comprising an identifier associated with the UE [102];
receive, from the network node of the first network, a registration reject message in response to transmission of the first registration request, the registration reject message being indicative of a failure in establishment of the first connection;
transmit, to a network node of a second network, a second registration request for establishing a second connection between the UE [102] and the second network upon receiving the registration reject message; and
establish the second connection.
9. The UE [102] as claimed in claim 8, wherein the first network is 5th Generation
(5G) New Radio network and the second network is 4th Generation (4G) Long
Term Evolution (LTE) network.
10. The UE [102] as claimed in claim 8, wherein the network node of the first
network is Access Mobility Function (AMF) [106] and the network node of the
second network is Mobility Management Entity (MME) [304].

11. The UE [102] as claimed in claim 10, wherein the first registration request is for establishment of an N1 interface between the UE [102] and the AMF [106].
12. The UE [102] as claimed in claim 11, wherein the UE processor [202a] further causes the UE [102] to disable a capability of the UE [102] to establish the N1 interface upon receiving the registration reject message.
13. The UE [102] as claimed in claim 8, wherein the registration reject message comprises a 5GMM cause element to indicate to the UE [102] that the N1 mode is not allowed for the first network.

14. The UE [102] as claimed in claim 8, wherein the identifier is Subscriber Permanent Identifier (SUPI).
15. A method implemented on a network node of a first network, the method comprising:
receiving, from a User Equipment (UE) [102], a first registration request for establishing a connection between the UE [102] and the first network, the first registration request comprising an identifier associated with the UE [102];
analysing, by the network node, the identifier to determine whether the establishment of connection between the UE [102] and the first network is feasible; and
transmitting, to the UE [102], a registration reject message on determining that the establishment of the connection between the UE [102] and the first network is not feasible.
16. The method as claimed in claim 15, wherein the first network is 5th Generation (5G) New Radio network and the network node is Access Mobility Function (AMF) [106].
17. The method as claimed in claim 16, wherein the first registration request is for establishment of an N1 interface between the UE [102] and the AMF [106].

18. The method as claimed in claim 15, wherein the registration reject message comprises a 5GMM cause element to indicate to the UE [102] that the N1 mode is not allowed for the first network.
19. The method as claimed in claim 15, wherein the identifier is Subscriber Permanent Identifier (SUPI).
20. A network node of a first network, the network node comprising:
a receiving unit [206c] configured to receive, from a User Equipment (UE) [102], a first registration request for establishing a connection between the UE [102] and the first network, the first registration request comprising an identifier associated with the UE [102];
an analysis unit [206a] configured to analyse the identifier to determine whether the establishment of connection between the UE [102] and the first network is feasible; and
a transmit unit [206d] configured to transmit, to the UE [102], a registration reject message on determining that the establishment of the connection between the UE [102] and the first network is not feasible.
21. The network node as claimed in claim 20, wherein the first network is 5th
Generation (5G) New Radio network and the network node is Access Mobility
Function (AMF) [106].
22. The network node as claimed in claim 21, wherein the first registration request
is for establishment of an N1 interface between the UE [102] and the AMF [106].
23. The network node as claimed in claim 20, wherein the registration reject
message comprises a 5GMM cause element to indicate to the UE [102] that the N1
mode is not allowed for the first network.
24. The network node as claimed in claim 20, wherein the identifier is Subscriber
Permanent Identifier (SUPI).