Communication method and communication device for handling insufficient network support

Abstract

A communication method for handling insufficient network support in a user equipment (UE) is disclosed. The UE has selected a first public land mobile network (PLMN) and initiates a registration procedure with the first PLMN. The method comprises the following steps: receiving a confirmation message corresponding to the registration process from the first PLMN; and in response to the confirmation message indicating that the first PLMN does not support a service required by the UE, performing a PLMN selection process after the registration process is completed, and regarding the first PLMN as the lowest priority.

Description

[0001] Cross-references

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 520,666, filed August 21, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a communication method and a communication device for a wireless communication system, and more specifically, to a communication method and a communication device for handling insufficient network support. Background Technology

[0004] Wireless communication networks have experienced exponential growth in recent years. Long-Term Evolution (LTE) systems offer high peak data rates, low latency, improved system capacity, and low operating costs due to a simplified network architecture. LTE systems, also known as 4G systems, also provide seamless integration with legacy wireless networks such as GSM, CDMA, and UMTS. In LTE systems, the evolved universal terrestrial radio access network (E-UTRAN) comprises multiple evolved Node-Bs (eNodeBs or eNBs) that communicate with multiple mobile stations (called user equipments (UEs)). 3GPP networks typically consist of a hybrid of 2G / 3G / 4G systems. The Next Generation Mobile Network (NGMN) Committee has decided to focus future NGMN activities on defining the end-to-end requirements for 5G new radio (NR) systems.

[0005] 5G systems are the new generation of mobile network technologies being rolled out globally. It is generally considered as the key technology for the future digital society. Compared to previous generations, 5G systems are no longer focused on traditional mobile phone use cases. Instead, its main targets are to provide gigabit data rates for terminal devices (Enhanced Mobile Broadband (eMBB)), connect an ever-increasing number of smart devices (Massive Machine Type Communications (mMTC)), and provide service attribute guarantees for time-critical applications (ultra-reliable low-latency communication (URLLC)).

[0006] As 5G systems are crucial for the digital mobile society, Mobile Network Operators (MNOs) are expected to transition from 4G to 5G Stand-Alone (SA) networks. However, during this transition, 5G Non-Stand-Alone (NSA) networks are widely used. SA is a fully independent 5G deployment that utilizes 5G Radio Access Network (RAN) and 5G core network, thus supporting advanced functions such as network slicing and improved Internet of Things device support. On the other hand, NSA is based on existing 4G LTE infrastructure, using 4G core network to perform basic functions while adding 5G Radio Access Network (RAN), which can help MNOs quickly transition from 4G to 5G while reusing existing 4G facilities.

[0007] NSA provides a stage for the transition from 4G to 5G. However, according to current 3GPP technical specifications, under 5G NSA networks, UEs can not be able to effectively obtain certain 5G services, such as non-Internet Protocol (non-IP), Ethernet, or Unmanned Aerial Systems (UAS) services.

[0008] Therefore, there is an urgent need for a solution. SUMMARY

[0009] Therefore, the present application aims to provide a communication method and a communication device to improve the defects of the prior art.

[0010] One embodiment of the present invention discloses a method for handling network support insufficiency in a user equipment (UE), wherein the UE has selected a first public land mobile network (PLMN) and initiated a registration procedure with the first PLMN. The method comprises receiving an acknowledgement message corresponding to the registration procedure from the first PLMN; and in response to the acknowledgement message indicating that the first PLMN does not support a service required by the UE, performing a PLMN selection procedure after completion of the registration procedure and considering the first PLMN as a lowest priority.

[0011] Another embodiment of the present invention discloses a communication device for handling network support insufficiency, wherein the communication device has selected a first public land mobile network (PLMN) and initiated a registration procedure with the first PLMN. The communication device comprises a storage device; and a processing circuit coupled to the storage device, wherein the processing circuit receives an acknowledgement message corresponding to the registration procedure from the first PLMN; and in response to the acknowledgement message indicating that the first PLMN does not support a service required by the communication device, performs a PLMN selection procedure after completion of the registration procedure and considers the first PLMN as a lowest priority.

[0012] One embodiment of the present invention discloses a method for handling network support insufficiency in a user equipment (UE), wherein the UE has selected a first public land mobile network (PLMN) and initiated a registration procedure with the first PLMN. The method comprises receiving an acknowledgement message corresponding to the registration procedure from the first PLMN; and in response to the acknowledgement message indicating that the first PLMN does not support a service required by the UE, performing a PLMN selection procedure after completion of the registration procedure and considering the first PLMN as a lowest priority.

[0013] Another embodiment of the present invention discloses a communication device for handling network support insufficiency, wherein the communication device has selected a first public land mobile network (PLMN) and initiated a registration procedure with the first PLMN. The communication device comprises a storage device; and a processing circuit coupled to the storage device, wherein the processing circuit receives an acknowledgement message corresponding to the registration procedure from the first PLMN; and in response to the acknowledgement message indicating that the first PLMN does not support a service required by the communication device, performs a PLMN selection procedure after completion of the registration procedure and considers the first PLMN as a lowest priority.

[0014] These and other objects of the present invention will no doubt become apparent to those of ordinary skill in the art after reading the following detailed description of the preferred embodiments of the present invention, shown in a variety of contexts together with the various figures and graphs of the drawing figures. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a schematic diagram of a wireless communication system.

[0016] Figure 2 is a schematic diagram of a communication device according to an example of the invention.

[0017] Figure 3 is a flowchart according to an example of the invention.

[0018] Figure 4 and Figure 5 is a schematic diagram of handling network under-provisioning scenarios according to an example of the invention. DETAILED DESCRIPTION

[0019] Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, hardware manufacturers can refer to a component by different names. This document does not intend to distinguish between components that differ in name but not in function. In the following description and in the claims, the terms“including” and“comprising” are used in an open-ended fashion, and thus should be interpreted to mean“including, but not limited to.” Also, the term“about” means within an acceptable error range for the particular technology or technique being described, which will vary from one technology to another. Further, the term“coupled” is intended to mean either an indirect or direct connection in either a wired or wireless manner, and can further mean that intervening components, if any, can or can not be present. A direct connection occurs if there is no intervening component(s) present. Contrarily, an indirect connection occurs through one or more intervening components.

[0020] See Figure 1 . Figure 1 is a schematic diagram of a wireless communication system 10. The wireless communication system 10 is briefly composed of a plurality of user equipments (UEs) 12_1 to 12_m and a plurality of public land mobile networks (PLMNs) 14_1 to 14_n. Each UE 12_1 to 12_m can be a low-cost device (e.g., a machine-type communication (MTC) device), a device-to-device (D2D) communication device, a narrowband Internet of Things (NB-IoT), a cell phone, a laptop, a tablet, an e-book, a portable computer system, or a combination thereof. Each PLMN 14_1 to 14_n represents a network that provides various wireless communication services within a particular country, operated by a particular mobile network operator (MNO). One PLMN can support one or more cellular technologies, such as UMTS / 3G, LTE / 4G, and NR / 5G. To provide 5G services while reusing current 4G infrastructure, one or more of the PLMNs 14_1 to 14_n can support a non-standalone (NSA) version of 5G technology that is based on an existing 4G LTE infrastructure, using a 4G core network (referred to as an evolved packet core (EPC)) for basic functions while adding a 5G radio access network (RAN).

[0021] As well known to those skilled in the art, the 5G RAN consists of two types of base stations (BS): eNB and gNB. The eNB (primary node) is the LTE base station used to exchange control plane and data plane messages with the UE. In the 5G NSA architecture, the eNB performs functions such as paging, over-the-air security, and handover. The gNB (secondary node), also known as "en-gNB" or "SgNB", works in collaboration with the eNB as a 5G base station dedicated to exchanging data plane messages, mainly significantly increasing the data rate of the UE. The main components of the 4G core network include the mobility management entity (MME), the home subscriber server (HSS), the serving gateway (S-GW), and the packet data network gateway (P-GW). The MME is a central control node responsible for authenticating the UE when it connects to the network and allocating resources. The HSS is a database that stores user-related data, such as international mobile subscriber identity (IMSI), shared keys, and subscription data. The S-GW is responsible for routing and forwarding user data packets. The P-GW acts as a connection point between the core network and external networks, i.e., the Internet and other mobile networks.

[0022] The NSA provides a step for transitioning from 4G to 5G, allowing UEs to experience 5G applications under the 4G LTE infrastructure, such as extended protocol configuration options (ePCO).

[0023] In the field of mobile communications, protocol configuration options (PCO) in 4G networks play a key role in customizing and optimizing network connections for UEs. These options allow dynamic adjustment of network settings, such as IP address allocation, domain name system (DNS) server addresses, and quality of service (QoS) parameters. The flexibility of PCO ensures that devices can efficiently communicate with the network, adapting to different conditions and user needs.

[0024] When transitioning to 5G, extended protocol configuration options (ePCO) further extend this functionality, providing more granular control over network configuration. ePCO supports advanced features such as network slicing, where a single physical network can be divided into multiple virtual networks, each tailored to specific service requirements. This is crucial for 5G's promise to support a wide range of applications, from high-speed mobile broadband to mission-critical communication systems.

[0025] With ePCO, UEs can access non-Internet Protocol (non-IP), Ethernet, and unmanned aerial system (UAS) services. However, according to current 3GPP technical specifications, UEs may not be able to efficiently initiate these 5G services.

[0026] In particular, if a UE supports ePCO, this support must be signaled in the Attach Request message during the Attach procedure. The Attach procedure is the procedure by which a UE registers with a PLMN (in particular, an MME) to establish an Evolved Packet System Bearer (EPS Bearer) enabling it to send and receive data. If the MME of the PLMN supports ePCO and receives an indication of ePCO support from the UE (through the Attach Request message), the MME shall confirm this support in the Attach Accept message (feedback to the UE). Furthermore, a UE needs to support ePCO if it establishes a packet data network connection to a non-IP or Ethernet Access Point Name (APN), or for UAS services. When a UE supporting ePCO attempts to use a non-IP / Ethernet / UAS APN but the MME does not support ePCO, the UE knows that the MME does not support ePCO upon receiving the Attach Accept message. However, current 3GPP technical specifications do not detail the subsequent operation of the UE in this case, which can result in the UE staying connected to a PLMN that does not support ePCO and being unable to receive non-IP, Ethernet, or UAS connection services.

[0027] In short, a User Equipment (UE) and a Mobility Management Entity (MME) can receive an indication of Extended Protocol Configuration Option (ePCO) support from each other through the Attach Request message and the Attach Accept message during the Attach procedure, and the indication of ePCO support does not directly affect the outcome of the Attach procedure. However, current 3GPP technical specifications do not detail the case where a UE supporting ePCO attempts to use a non-Internet Protocol (non-IP) / Ethernet / Unmanned Aircraft System (UAS) Access Point Name (APN) but the MME of the Public Land Mobile Network (PLMN) selected by the UE does not support ePCO, resulting in the UE staying in the PLMN without being able to obtain non-Internet Protocol, Ethernet, or Unmanned Aircraft System services.

[0028] In another example, a UE can be registered to one MME and moves to an area served by a new MME of the same PLMN, where the original MME can support ePCO but the new MME does not support ePCO. The UE can initiate a Tracking Area Update (TAU) procedure to inform the new MME of its new location. The UE can learn whether the new MME supports ePCO through the TAU Accept message during the TAU procedure. However, the above-mentioned deficiency can occur, i.e., current 3GPP technical specifications do not detail the case where a UE supporting ePCO attempts to use a non-Internet Protocol (non-IP) / Ethernet / Unmanned Aircraft System (UAS) Access Point Name (APN) but the (latest) MME of the PLMN serving the UE does not support ePCO, resulting in the UE staying in the PLMN without being able to obtain non-Internet Protocol, Ethernet, or Unmanned Aircraft System services.

[0029] To remedy the deficiencies of current 3GPP technical specifications, the present application provides a method enabling a UE to accurately perform PLMN selection when the PLMN serving the UE does not support a service required by the UE.

[0030] Referring to Figure 2 , which is a schematic diagram of a communication device 20 according to an example of the present application. The communication device 20 can be any one of the UEs 12_1 to 12_m shown in Figure 1 , but is not limited thereto. The communication device 20 can include at least one processing circuit 200, such as a microprocessor or an Application Specific Integrated Circuit (ASIC), at least one storage device 210, and at least one communication interface device 220. The at least one storage device 210 can be any data storage device that can execute processing or store program code 214, accessed and executed by the at least one processing circuit 200. Examples of the at least one storage device 210 include, but are not limited to, a Subscriber Identity Module (SIM), a Read-Only Memory (ROM), a flash memory, a Random-Access Memory (RAM), a Compact Disc Read-Only Memory (CD-ROM), a Digital Versatile Disc-ROM (DVD-ROM), a Blu-ray Disc-ROM (BD-ROM), a hard disk, an optical data storage device, a non-volatile memory device, a non-transitory computer readable medium (e.g., a tangible medium), and the like. The at least one communication interface device 220 is preferably at least one transceiver for transmitting and receiving signals (e.g., data, messages, and / or data packets) according to the processing results of the at least one processing circuit 200.

[0031] Figure 3 is a flowchart of a process 30 according to an example of the present application. The process 30 can be used in a UE (e.g., Figure 1 , or Figure 2communication device 20 in FIG. 1), the UE has selected a first PLMN and initiated a registration procedure with the first PLMN. The procedure 30 can handle a network support deficiency issue, i.e., the first PLMN does not support a service required by the UE. For example, the UE can support ePCO in a 5G non-standalone (NSA) network, and the service required by the UE can be a non-Internet Protocol (non-IP), Ethernet packet data network type, or unmanned aerial system (UAS) service, while the first PLMN does not support ePCO. The procedure 30 can be compiled into program code 214 stored in at least one storage device 210 shown in FIG. 2 and / or executed by at least one processing circuit 200, including the following steps: Figure 2 The procedure 30 shown in FIG. 3 can be compiled into program code 214 stored in at least one storage device 210 shown in FIG. 2 and / or executed by at least one processing circuit 200, including the following steps: Step 300: Start.

[0032] Step 302: Receive a confirmation (e.g., accept) message corresponding to the registration procedure from the first PLMN.

[0033] Step 304: In response to the confirmation message indicating that the first PLMN does not support the service required by the UE, perform a PLMN selection procedure after completing the registration procedure, and consider the first PLMN as a lowest priority.

[0034] Step 306: End.

[0035] According to the procedure 30, after the UE selects a first PLMN and initiates a registration procedure with the first PLMN, if a confirmation message corresponding to the registration procedure received from the first PLMN (step 302) indicates that the first PLMN does not support the service required by the UE, the UE can perform a PLMN selection procedure after completing the registration procedure, and consider the first PLMN as a lowest priority (step 304). As the first PLMN is considered as a lowest priority, the UE can not select the first PLMN in the PLMN selection procedure, and can select a second PLMN, which can support the service required by the UE. Therefore, the UE can obtain the required service through the second PLMN. If the PLMN selection candidate of “considering the first PLMN as a lowest priority” is not considered, according to the conventional PLMN selection, the registration PLMN (the first PLMN in which the UE has successfully registered) is the highest priority PLMN selection candidate in the conventional PLMN selection procedure.

[0036] In one example, a user equipment (UE) supports extended protocol configuration options (ePCO) in a 5G non-standalone (NSA) network, and the service required by the UE is one or more of the following: non-internet protocol (non-IP), Ethernet packet data network type (Ethernet PDN type), and unmanned aerial system (UAS) service, while the first public land mobile network (PLMN) does not support ePCO. In this case, the registration procedure can be an ATTACH procedure, and the confirmation message can be an ATTACH accept message of the ATTACH procedure. Since the first PLMN does not support ePCO, the extended protocol configuration options (ePCO) bit in the evolved packet system (EPS) network function support information element (IE) in the ATTACH accept message is not set to “extended protocol configuration options supported”. Therefore, after the UE receives the ATTACH accept message from the first PLMN, the UE knows that the first PLMN does not support ePCO and cannot provide the service required by the UE, so that according to the procedure 30, a PLMN selection procedure is performed after the completion of the ATTACH procedure, and the first PLMN is regarded as the lowest priority. As a result, the UE will not stay in the first PLMN after the PLMN selection procedure, and can select a second PLMN that supports the service required by the UE.

[0037] The above examples can be combined with the examples in Figure 1 and explained in detail by Figure 4 . As Figure 4As shown, the UE 12_x in the wireless communication system 10 selects the PLMN 14_a (step 400) and initiates an attach procedure by sending an ATTACH request message to the PLMN 14_a (step 402), where the UE 12_x supports ePCO and wants to obtain non-IP, Ethernet PDN type or UAS service, while the PLMN 14_a does not support ePCO. According to the ATTACH request message, the PLMN 14_a accepts the request and returns an ATTACH accept message (step 404). Since the PLMN 14_a does not support ePCO, the ePCO bit in the EPS network function support information element (IE) in the ATTACH accept message is not set to "extended protocol configuration options supported", which means the PLMN 14_a does not support ePCO. Then, the UE 12_x sends an ATTACH complete message to complete the attach procedure (step 406) and performs a PLMN selection procedure according to the procedure 30 and considers the PLMN 14_a as the lowest priority (step 408). Since the PLMN 14_a is considered as the lowest priority, the UE 12_x does not select the PLMN 14_a and selects the PLMN 14_b (step 410) to perform another attach procedure (steps 412-416). If the PLMN 14_b supports ePCO, the UE 12_x can obtain non-IP, Ethernet PDN type or UAS service through the PLMN 14_b after attaching to the PLMN 14_b.

[0038] In another example, a user equipment (UE) supports extended protocol configuration options (ePCO) in a 5G non-standalone (NSA) network, and the service required by the UE is a non-internet protocol (non-IP), Ethernet packet data network type (Ethernet PDN type), or unmanned aerial system (UAS) service, while one or more mobile management entities (MMEs) in a first public land mobile network (PLMN) support ePCO, while one or more MMEs do not support ePCO. The registration procedure can be a tracking area update procedure (TAU procedure), and the acknowledgment message can be a tracking area update accept message (TAU accept message) of the tracking area update procedure. For example, the UE can register to an ePCO-supporting MME and move to an area served by a new MME of the first PLMN that does not support ePCO. The UE can desire to obtain the non-IP, Ethernet PDN type, or UAS service after moving to the area and thus initiates a tracking area update procedure to inform the new MME of its new location. Since the new MME of the first PLMN does not support ePCO, the ePCO bit in the EPS network function support information element (IE) in the tracking area update accept message is not set to “extended protocol configuration options supported.” Thus, upon receiving the tracking area update accept message from the new MME of the first PLMN, the UE knows that the first PLMN does not support ePCO and is unable to provide the service required by the UE, and thus performs a PLMN selection procedure after completing the tracking area update procedure according to procedure 30 and considers the first PLMN as the lowest priority. As a result, the UE does not stay in the first PLMN after the PLMN selection procedure and can select a second PLMN that supports the service required by the UE.

[0039] The above examples can be combined with the examples in Figure 1 and explained in detail by Figure 5 . As Figure 5As shown, a user equipment (UE) 12_y in the wireless communication system 10 has selected and registered to a first mobility management entity (MME) of a public land mobile network (PLMN) 14_c that supports extended protocol configuration options (ePCO) and moved to an area served by a second MME of the PLMN 14_c that does not support ePCO (step 500). The UE 12_y supports ePCO and wishes to use non-internet protocol (non-IP), Ethernet packet data network type, or unmanned aerial system (UAS) services in the area served by the second MME. Accordingly, the UE 12_y initiates a tracking area update (TAU) procedure to inform the second MME of the PLMN 14_c of its new location by sending a TAU request message to the second MME (step 502). In response to the TAU request message, the second MME of the PLMN 14_c returns a TAU accept message (step 504). Since the second MME of the PLMN 14_c does not support ePCO, the ePCO bit in the evolved packet system (EPS) network function support information element (IE) in the TAU accept message is not set to "Supports Extended Protocol Configuration Options", which means that the PLMN 14_c does not support ePCO. The UE 12_y then completes the TAU procedure (by sending or not sending a TAU complete message to the PLMN 14_c (step 506)) and performs a PLMN selection procedure according to the procedure 30, considering the PLMN 14_c as the lowest priority (step 508). Since the PLMN 14_c is considered as the lowest priority, the UE 12_y does not select the PLMN 14_c and instead selects the PLMN 14_d (step 510) for another attach procedure (steps 512-516). If the PLMN 14_d supports ePCO, the UE 12_y can use the non-internet protocol (non-IP), Ethernet packet data network type, or unmanned aerial system (UAS) services of the PLMN 14_d after attaching to the PLMN 14_d.

[0040] It is noted that the implementation of the procedure 30 is not limited to the above description. Those skilled in the art can combine, modify, and / or change the above description and examples. For example, according to the procedure 30, the UE will consider a first PLMN that does not support a service required by the UE as the lowest priority. In one example, the UE can further set the priority of the first PLMN as the lowest. The method of setting the priority of the first PLMN as the lowest is not limited to any step. For example, the UE can set the priority of the first PLMN by managing at least one parameter corresponding to the first PLMN in a universal subscriber identity module (USIM). For example, the parameter can be, but is not limited to, a "user controlled PLMN with access technology" parameter EF_PLMNwACT, which is used to set the preferred PLMNs in priority order.

[0041] In another example, considering the first PLMN as the lowest priority or setting its priority to the lowest involves determining the first PLMN as the lowest priority. In other words, step 304 can be replaced by step 304', as follows: Step 304': in response to the confirmation message indicating that the first PLMN does not support a service required by the UE, performing a PLMN selection procedure after completing the registration procedure, and determining the first PLMN as the lowest priority.

[0042] The above description, steps and / or procedures contain suggested steps, which can be implemented by hardware, software, firmware (i.e. a combination of hardware devices and computer instructions and data existing as read-only software on the hardware devices), electronic systems, or a combination thereof. One example is the communication device 20.

[0043] Examples of hardware can include analog circuits, digital circuits, and / or mixed circuits. For example, the hardware can include an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable logic device, coupled hardware components, or a combination thereof. In another example, the hardware can include a general-purpose processor, a microprocessor, a controller, a digital signal processor (DSP), or a combination thereof.

[0044] Examples of software can include a set of codes, a set of instructions, and / or a set of functions stored in a storage unit (e.g. a computer readable medium). The computer readable medium can include a SIM, a ROM, a flash memory, a RAM, a CD-ROM / DVD-ROM / BD-ROM, a magnetic tape, a hard disk, an optical data storage device, a non-volatile storage unit, or a combination thereof. The computer readable medium (e.g. the storage unit) can be coupled to the at least one processor internally (e.g. integrated) or externally (e.g. separated). The at least one processor can include one or more modules and can (e.g. be configured to) execute the software in the computer readable medium. The set of codes, the set of instructions, and / or the set of functions can cause the at least one processor, the module, the hardware, and / or the electronic system to perform the relevant steps.

[0045] Examples of electronic systems can include a system on chip (SoC), a system in package (SiP), a computer on module (CoM), a computer program product, a device, a mobile phone, a notebook computer, a tablet computer, an e-book, or a portable computer system, as well as the communication device 20.

[0046] In summary, the present application provides a communication device and method for handling network support deficiency. When receiving an acknowledgement message corresponding to a registration procedure from a first PLMN indicates that the first PLMN does not support a service required by the communication device, the communication device and method perform a PLMN selection procedure after completing the registration procedure and regard the first PLMN as a lowest priority. Therefore, the communication device can select a second PLMN which can support the service required by the communication device, so that the communication device can obtain the required service through the second PLMN. Thus, the problem of network support deficiency is solved.

[0047] Those skilled in the art will readily observe that numerous modifications and substitutions can be effected without departing from the spirit of the application. Consequently, all such modifications and substitutions are intended to be encompassed within the scope of the following claims.

Claims

1. A communication method for handling insufficient network support in a user equipment (UE), wherein the UE has selected a first public land mobile network (PLMN) and initiated a registration process with the first PLMN, the method comprising: Receive a confirmation message corresponding to the registration process from the first PLMN; as well as In response to the confirmation message indicating that the first PLMN does not support a service required by the UE, a PLMN selection process is performed after the registration process is completed, and the first PLMN is regarded as the lowest priority.

2. The communication method of claim 1, wherein the registration process is an attachment process, and the confirmation message is an attachment acceptance message of the attachment process.

3. The communication method of claim 2, wherein an Extended Protocol Configuration Option (ePCO) bit in an Evolved Packet System (EPS) Network Function Support Information Element (IE) in the Attach Accept message is not set to "Support Extended Protocol Configuration Option" to indicate that the first PLMN does not support the services required by the UE.

4. The communication method of claim 1, wherein the registration process is a tracking area update process, and the confirmation message is a tracking area update acceptance message of the tracking area update process.

5. The communication method of claim 4, wherein an Extended Protocol Configuration Option (ePCO) bit in an Evolved Packet System (EPS) Network Function Support Information Element (IE) in the Tracking Area Update Acceptance Message is not set to "Support Extended Protocol Configuration Option" to indicate that the first PLMN does not support the services required by the UE.

6. The communication method of claim 1, wherein the service required by the UE is one or more of the following: non-IP, Ethernet packet data network type, and unmanned aerial system (UAS) service.

7. The communication method as claimed in claim 1, further comprising setting the priority of the first PLMN to the lowest.

8. A communication device for addressing insufficient network support, wherein the communication device has selected a first Public Land Mobile Network (PLMN) and initiated a registration process with the first PLMN, the communication device comprising: A storage device; as well as A processing circuit coupled to the storage device receives a confirmation message from the first PLMN corresponding to the registration process; and in response to the confirmation message indicating that the first PLMN does not support the services required by the communication device, performs a PLMN selection process after completing the registration process, and regards the first PLMN as the lowest priority.

9. The communication device of claim 8, wherein the registration process is an attachment process, and the confirmation message is an attachment acceptance message of the attachment process.

10. The communication device of claim 9, wherein an Extended Protocol Configuration Option (ePCO) bit in an Evolved Packet System (EPS) Network Function Support Information Element (IE) in the Attach Accept message is not set to "Support Extended Protocol Configuration Option" to indicate that the first PLMN does not support the services required by the UE.

11. The communication device of claim 8, wherein the registration process is a tracking area update process, and the confirmation message is a tracking area update acceptance message of the tracking area update process.

12. The communication device of claim 11, wherein an Extended Protocol Configuration Option (ePCO) bit in an Evolved Packet System (EPS) Network Function Support Information Element (IE) in the Tracking Area Update Acceptance Message is not set to "Support Extended Protocol Configuration Option" to indicate that the first PLMN does not support the services required by the UE.

13. The communication device of claim 1, wherein the service required by the UE is one or more of the following: non-IP, Ethernet packet data network type, and unmanned aerial system (UAS) service.

14. The communication device of claim 1, wherein the instruction further includes setting the priority of the first PLMN to the lowest.

15. A communication method for handling insufficient network support in a user equipment (UE), wherein the UE has selected a first public land mobile network (PLMN) and initiated a registration process with the first PLMN, the method comprising: Receive a confirmation message corresponding to the registration process from the first PLMN; as well as In response to the confirmation message indicating that the first PLMN does not support the services required by the UE, a PLMN selection process is performed after the registration process is completed, and the first PLMN is regarded as the lowest priority.

16. A communication device for addressing insufficient network support, wherein the communication device has selected a first Public Land Mobile Network (PLMN) and initiated a registration process with the first PLMN, the communication device comprising: A storage device; as well as A processing circuit coupled to the storage device receives a confirmation message from the first PLMN corresponding to the registration process; and in response to the confirmation message indicating that the first PLMN does not support the services required by the communication device, performs a PLMN selection process after completing the registration process and determines the first PLMN as the lowest priority.

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