Network selection with signal level criteria and operator-controlled signal threshold criteria

Abstract

This disclosure provides systems, methods, and apparatus, including computer programs encoded on a computer readable medium, for network selection by a user equipment (UE) in a wireless communication system. The UE obtains an access technology specific signal level criterion comprising at least a first technology specific signal level threshold for a first access technology (1110). The UE selects one or more Public Land Mobile Networks (PLMNs) that include one or more candidate cells having a signal metric that satisfies a network selection criterion that is based at least in part on a first technology-specific signal level threshold for a first access technology (1120). The UE registers with a first PLMN of the one or more PLMNs that meet the network selection criteria (1130). The UE sets a condition for subsequent network selection after registering with the first PLMN (1140).

Description

Technical Field

[0001] Aspects of the present disclosure generally relate to wireless communications and mechanisms for network selection in a wireless communication system. Background Art

[0002] A Public Land Mobile Network (PLMN) supports at least one Radio Access Technology (RAT) such that a User Equipment (UE) can communicate using the network nodes of the PLMN. The UE includes at least one wireless communication device (sometimes referred to as a communication module, communication unit, wireless communication interface, communication chipset, etc.) configured to transmit or receive radio frequency (RF) transmissions to or from network nodes using a specific RAT. The network nodes implement one of the RATs supported by the PLMN. Examples of RATs include fourth-generation (4G) systems such as Long-Term Evolution (LTE) systems, fifth-generation (5G) systems (which may also be referred to as New Radio (NR) systems), and future sixth-generation (6G) systems. The 3rd Generation Partnership Project (3GPP) standards body or other standards-setting organizations define various RATs.

[0003] A UE with a Home PLMN (HPLMN) of a specific wireless carrier may be permitted to roam on other PLMNs of different wireless carriers, such as one or more Visited PLMNs (VPLMNs). Network selection (which may also be referred to as PLMN selection) refers to the process by which a UE selects the PLMN for which it is to register. The UE performs network selection at various times, such as when the UE is first powered on, when recovering from an out-of-coverage condition, after a manual user input requesting network selection, due to the mobility of the UE, or periodically during normal operation. The UE generally performs PLMN selection based on PLMN prioritization before selecting a serving cell for service. The PLMN selector list includes PLMN identifiers (IDs) and indicates the priority order of one or more PLMNs over other PLMNs. The UE observes broadcast information from nearby cells to determine the PLMNs operating in an area. Using the PLMN selector list, the UE selects one PLMN (such as the HPLMN) having a higher priority than other PLMNs (such as VPLMNs). When the UE is currently roaming in a VPLMN or other lower-priority PLMN, the UE periodically repeats PLMN selection to attempt to select a higher-priority PLMN.

[0004] After selecting a PLMN, the UE selects a serving cell from among the candidate cells in the selected PLMN. Cell selection and reselection (collectively referred to as cell selection) refers to the process by which the UE selects a serving cell from among candidate cells. Since PLMN selection occurs before cell selection, PLMN selection restricts which candidate cells (i.e., those cells in the selected PLMN) are available for cell selection. During cell selection, the UE selects a suitable serving cell based on idle mode measurements of signal metrics and cell selection criteria. The cell selection criteria are typically broadcast in the System Information Block (SIB1) from each cell. Thus, the cell selection criteria can be referred to as cell-provided cell selection criteria. In some implementations, the cell-provided cell selection criteria can include a cell signal level threshold. For example, the cell signal level threshold can be the minimum required Receiver (RX) level in the cell or the minimum required quality level in the cell.

[0005] 3GPP has proposed a signal level network selection mechanism (which can be referred to as Signal Level Enhanced Network Selection (SENSE)). Using the signal level network selection mechanism, an operator (such as a wireless carrier or network operator) can configure access technology-specific criteria for network selection. The access technology-specific criteria can also be referred to as operator-provided criteria or operator-controlled signal threshold criteria. The access technology-specific criteria can be stored in the UE's memory for use during PLMN selection. The access technology-specific criteria include access technology-specific signal level thresholds that reflect the operator's prioritization of various RATs. For example, the access technology-specific criteria can be useful for prioritizing specific access technologies for Internet of Things (IoT) stationary devices or other types of UEs. Additionally, the access technology-specific criteria can accommodate multiple PLMNs, which enables network operators to collaborate more freely or support greater roaming flexibility. The access technology-specific signal level thresholds can be a supplement to or a replacement for PLMN prioritization.

[0006] Various network selection mechanisms and their criteria (such as the PLMN selector list, cell-provided cell selection criteria, or access technology-specific criteria) may conflict with each other or produce unpredictable PLMN selection results. Alternatively or additionally, depending on which type of PLMN (such as HPLMN or VPLMN) is currently serving the UE, the UE may use the PLMN selector list to periodically perform subsequent PLMN selection, which results in the UE selecting a different PLMN than the one that would be selected by the access technology-specific criteria. Summary of the Invention

[0007] The systems, methods, and devices of the present disclosure each have several innovative aspects, no single one of which is solely responsible for the desired attributes disclosed herein.

[0008] One innovative aspect of the subject matter described in this disclosure can be implemented in a method for network selection by a user equipment (UE). The method includes: obtaining access technology specific criteria, the access technology specific criteria including at least a first access technology specific signal level threshold for a first access technology. The method includes: selecting one or more public land mobile networks (PLMNs), the one or more PLMNs including one or more candidate cells having signal metrics that meet network selection criteria, the network selection criteria being at least partially based on the first access technology specific signal level threshold for the first access technology. The method includes: registering with a first PLMN among the one or more PLMNs. And the method includes: setting conditions for subsequent PLMN selection after registering with the first PLMN.

[0009] Another innovative aspect of the subject matter described in this disclosure can be implemented in a method for network selection by a UE. The method includes: obtaining access technology specific criteria, the access technology specific criteria including access technology specific signal level thresholds for each of a plurality of access technologies. The method includes: obtaining cell selection criteria provided by a cell, the cell selection criteria provided by the cell including a cell signal level threshold. The method includes: selecting a public land mobile network (PLMN) for the UE to register with. Selecting the PLMN includes: when the UE is in a first area where all candidate cells are using one access technology among the plurality of access technologies, selecting a first PLMN among the one or more PLMNs including one or more candidate cells and registering with the first PLMN, the one or more candidate cells having signal metrics that meet the access technology specific signal level thresholds for the respective access technologies for each of the one or more candidate cells. Selecting the PLMN includes: when the UE is in a first area where at least one candidate cell is using an access technology for which the access technology specific signal level threshold is not included in the access technology specific criteria, selecting a second PLMN and registering with the second PLMN, the second PLMN being based on PLMN priority ranking and including at least one candidate cell having a signal metric that meets the cell selection criteria provided by the cell.

[0010] Another innovative aspect of the subject matter described in this disclosure can be implemented in a method for network selection by a UE. The method includes: selecting a serving cell from among a plurality of candidate cells, where the serving cell has the highest signal metric among the signal metrics of the plurality of candidate cells, and where the plurality of candidate cells include candidate cells from different public land mobile networks (PLMNs) having equal priority ranking or no priority ranking in a signal quality criterion. The method includes: selecting a first PLMN including the serving cell. The method includes: registering the UE with the first PLMN.

[0011] Another innovative aspect of the subject matter described in this disclosure can be implemented in a UE. The UE includes a communication unit and a processing system. The processing system is configured to control the communication unit to implement any of the above methods.

[0012] Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the specification, the drawings, and the claims. Note that the relative dimensions of the following drawings may not be drawn to scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram conceptually illustrating an example wireless communication system.

[0014] Figure 2 A schematic diagram conceptually illustrating an example public land mobile network (PLMN) selection.

[0015] Figure 3A A block diagram conceptually illustrating an example PLMN selector list and cell selection criteria provided by a cell for a conventional PLMN selection mechanism.

[0016] Figure 3B A block diagram conceptually illustrating example access technology-specific criteria for a signal level enhanced network selection (SENSE) mechanism.

[0017] Figure 3C A block diagram conceptually illustrating cell selection criteria provided by a cell for a signal quality-centric network selection mechanism.

[0018] Figure 4 A flowchart illustrating an example process performed by a user equipment (UE) for selecting among multiple network selection mechanisms.

[0019] Figure 5 A flowchart illustrating an example process performed by a UE for coordinating network selection mechanisms.

[0020] Figure 6 A flowchart illustrating an example process performed by a UE for implementing access technology-specific signal level thresholds and cell signal level thresholds.

[0021] Figure 7 A flowchart illustrating an example process performed by a UE for implementing a signal quality-centric network selection mechanism.

[0022] Figure 8 A flowchart illustrating an example process performed by a UE for managing conditions for periodic network selection.

[0023] Figure 9 A flowchart showing another example process performed by a UE for managing conditions for periodic network selection.

[0024] Figure 10 A flowchart showing an example process performed by a UE in which access technology - specific criteria may not include an access - technology - specific signal - level threshold for the RAT of a candidate cell.

[0025] Figure 11 A flowchart showing an example process performed by a UE for signal - level network selection.

[0026] Figure 12 A flowchart showing an example process in which a UE may perform signal - level network selection or conventional PLMN selection.

[0027] Figure 13 A flowchart of an example process performed by a UE for signal - quality - centric network selection.

[0028] Figure 14 A block diagram of an example wireless communication device supporting cell reselection based on a service relationship.

[0029] Like reference numerals and names in the various figures indicate like elements. Detailed Description

[0030] The following description relates to certain implementations for the purpose of describing innovative aspects of the present disclosure. However, those of ordinary skill in the art will readily recognize that the teachings herein can be applied in many different ways. Some of the examples in the present disclosure are based on wireless communications according to 3rd Generation Partnership Project (3GPP) wireless standards such as 4G LTE and 5G NR standards. However, the described implementations can be implemented in any device, system, or network capable of transmitting and receiving radio - frequency signals according to any one of the wireless communication standards, including any one of the Institute of Electrical and Electronics Engineers (IEEE) 802.11, 802.15, or 802.16 wireless standards, or other known signals for communication within a wireless, cellular, or Internet of Things (IoT) network such as a system utilizing 3G, 4G, 5G, WiFi, or future radio technologies.

[0031] Aspects of the present disclosure relate to network selection. Network selection refers to the process by which a user equipment (UE) selects a public land mobile network (PLMN) and a serving cell for service. In a conventional network selection process, the UE selects a PLMN based on PLMN priority ranking (referred to as PLMN selection). The PLMN selector list includes a list of preferred PLMNs in order of priority. In some cases, each entry in the PLMN selector list may indicate a combination of a PLMN and a radio access technology (RAT) type. During PLMN selection when powering on or recovering from lack of coverage, the UE typically selects the PLMN with the highest priority among the available PLMNs. After selecting the highest priority PLMN, the UE uses the cell selection criteria provided by the cell to select a cell among the candidate cells in the selected PLMN (referred to as cell selection). The cell selection criteria provided by the cell may include a cell signal level threshold configured by the PLMN. Examples of the cell signal level threshold include a minimum reference signal received power (RSRP) value (sometimes referred to as the Qrxlevmin threshold), a minimum reference signal received quality (RSRQ) value (sometimes referred to as the Qqualmin threshold), etc. The UE selects a serving cell by comparing the signal metrics of the candidate cells in the selected PLMN with the cell signal level threshold.

[0032] 3GPP has proposed a signal level network selection mechanism that enables a UE to select a PLMN and a serving cell based on access technology specific criteria (which may be referred to as Signal Level Enhanced Network Selection (SENSE)). The access technology specific criteria include access technology specific signal level thresholds for various access technologies (also referred to as Radio Access Technologies (RATs)). Examples of access technologies include 5G NR, E-UTRAN, UTRAN, non-terrestrial networks (NTN) including satellites, and GSM, etc. The access technology specific signal level thresholds (sometimes also referred to as RAT specific signal level thresholds or operator controlled signal thresholds per access technology) can be configured and enabled by the network operator for the UE. The access technology specific criteria may include at least a first access technology specific signal level threshold for a first access technology (or for a first combination of PLMN and RAT) and a second access technology specific signal level threshold for a second access technology (or for a second combination of PLMN and RAT). In some implementations, a network selection list (similar to a PLMN selector list) may include entries for various combinations of PLMN and RAT and corresponding access technology specific signal level thresholds. During PLMN selection, the UE can compare the signal metric of each candidate cell with the access technology specific signal level threshold for the access technology of the candidate cell. If a PLMN and RAT combination has at least one candidate cell that meets the access technology specific signal level threshold, the UE selects that PLMN and RAT. When the signal metric of a candidate cell is equal to or higher than the access technology specific signal level threshold, the candidate cell is said to meet the access technology specific signal level threshold. After selecting a PLMN and RAT, the UE continues to compare the signal metrics to select a serving cell from among the candidate cells that meet the access technology specific signal level threshold of the selected PLMN and RAT.

[0033] In an alternative network selection mechanism, which may be referred to as signal quality - centric network selection, cell selection is prioritized based on signal quality rather than the PLMN. The signal quality - centric network selection mechanism enables the UE to select a serving cell (and by extension, the PLMN of the serving cell) from among multiple PLMNs in the order of decreasing signal quality of the candidate cells. The UE may select a serving cell (and its PLMN) from among candidate cells in multiple PLMNs that have equal priority or no priority. The UE may use a signal quality criterion, such as the order of decreasing signal quality, instead of using the cell selection criterion provided by the cell or an access - technology - specific criterion to select the serving cell. In some implementations, the signal quality criterion causes the UE to ignore or disable PLMN prioritization. Instead of performing PLMN selection and cell selection as separate steps, the UE may select a serving cell based on the signal quality criterion and then register with the PLMN that includes the selected serving cell.

[0034] The present disclosure provides systems, methods, and devices for network selection. In various aspects, the present disclosure implements PLMN selection and cell selection based on various network selection mechanisms and their criteria, such as a PLMN selector list, cell - provided cell selection criteria, access - technology - specific criteria, or signal quality - centric criteria. When access - technology - specific criteria are configured and enabled in the UE, the UE may use the access - technology - specific criteria to select a PLMN and a serving cell. In some implementations, after using the access - technology - specific criteria to select a PLMN, the UE may use a combination of the cell - provided cell selection criteria and the access - technology - specific criteria to select the serving cell. For example, the UE may use the minimum, maximum, average, or union of a cell signal level threshold in the cell - provided cell selection criteria and an access - technology - specific signal level threshold in the access - technology - specific criteria for a particular access technology.

[0035] After the UE uses access-technology-specific criteria to select a PLMN and a serving cell, the UE can adjust how the UE performs periodic network selection (reselection). Typically, the UE can perform subsequent PLMN selection periodically to search for a higher-priority PLMN in the PLMN selector list, especially when the UE is roaming on a VPLMN. The subsequent PLMN selection can be referred to as periodic network selection or automatic network selection because the subsequent PLMN selection is typically triggered by a timer. Since the intent of the access-technology-specific criteria or the signal quality criteria is to enable the UE to select a PLMN and a serving cell using an operator-controlled access-technology-specific signal level threshold, the UE can modify (or set or configure) the conditions for the automatic periodic PLMN selection that would otherwise attempt to select a higher-priority PLMN. For example, in some implementations, when the selected serving cell still meets the access-technology-specific criteria, the UE disables, ignores, or defers the subsequent PLMN selection (that would otherwise occur), even if the current PLMN has a lower priority than another PLMN in the PLMN selector list. Alternatively or additionally, when the current signal metric of the serving cell becomes lower than the access-technology-specific signal level threshold, the UE can enable a timer for automatic network selection. In some aspects, the conditions for periodic network selection can depend on whether the selected serving cell is in a lower-priority PLMN (such as a VPLMN) or a higher-priority PLMN (such as an HPLMN). Thus, the UE can consider the priority of the PLMN containing the current serving cell when determining whether to perform subsequent PLMN selection.

[0036] In some aspects, when the UE does not include an access-technology-specific signal level threshold for one or more RATs in an area, the UE can determine that the access-technology-specific criteria are incomplete. In some implementations, when there is no access-technology-specific signal level threshold for a particular RAT, the UE can ignore that RAT (such as setting a very high signal level threshold or a very low priority value for that RAT). Alternatively, when the access-technology-specific signal level threshold is missing for that RAT, the UE can use the cell selection criteria provided by the cell for that RAT. In another alternative, the UE can determine that the access-technology-specific criteria are incorrectly configured and can revert to the regular PLMN selection and cell selection for that area (such as a location area or a tracking area).

[0037] In some aspects, a UE may be configured for a signal quality - centric network selection mechanism that uses signal quality criteria independent of PLMN priority. The UE may use the signal quality criteria to select a RAT and a serving cell based on signal quality metrics rather than PLMN priority ranking, cell - provided cell selection criteria, or access - technology - specific criteria. In some implementations of the signal quality - centric network selection mechanism, the UE selects the serving cell based only on the signal quality of all available RATs (or from a list of allowed RATs and PLMNs). In some implementations of the signal quality - centric network selection mechanism, the UE selects the serving cell based on a predefined RAT priority (which may be stored in the UE, the mobile equipment (ME), or the subscriber identity module (SIM)). For example, the predefined RAT priority may give 5G NR a higher priority than LTE, give LTE a higher priority than 3G, give 2G a higher priority than 3G, and so on. After selecting the serving cell, the UE registers with the PLMN that includes the selected serving cell. The UE may disable periodic network selection or set conditions for subsequent PLMN selection.

[0038] Certain implementations of the subject matter described in this disclosure may be realized to achieve one or more of the following potential advantages. In the absence of the techniques of this disclosure, a UE may experience an undesirable ping - pong effect caused by repeated different subsequent PLMN selections or unnecessary power consumption due to selection of a sub - optimal network. In some aspects of this disclosure, the UE may prevent ping - pong reselection between two or more PLMNs or serving cells due to conflicting thresholds in access - technology - specific criteria and cell - provided cell selection criteria. There may be cases where the access - technology - specific criteria do not include access - technology - specific signal level thresholds for the access technologies available in a region, which may also result in sub - optimal network selection.

[0039] Figure 1FIG. 0 is a block diagram conceptually illustrating an example of a wireless communication system 100. A wireless communication system (which may also be referred to as a wireless communication network) may include one or more radio access networks (RANs) that provide access for a UE to communicate with other nodes in the wireless communication system. A radio access network (RAN, sometimes also referred to as a radio network or access network) includes a plurality of base stations (BSs) that may support communication for multiple UEs. Different types of base stations may be referred to as Node B, LTE evolved Node B (eNB), next generation Node B (gNB), access point (AP), radio head, transmit receive point (TRP), etc., depending on the wireless communication standard supported by the base station. One or more LTE base stations may constitute an LTE RAN. The LTE RAN (sometimes also referred to as an LTE network) provides access to the wireless communication system. Similarly, one or more 5G base stations may constitute a 5G New Radio (NR) RAN and may be referred to as a 5G NR network that provides access to the wireless communication system. The LTE network and the 5G NR network are two examples of radio access networks that may be used to communicate with the core network of the wireless communication system.

[0040] The example wireless communication system 100 may be an LTE RAN or some other RAN, such as a 5G or NR RAN. The wireless communication system 100 may include a plurality of BSs 110 (shown as BS 110a, BS 110b, BS 110c, and BS 110d) and other network entities. A BS is an entity that communicates with a user equipment (UE) and may also be referred to as a base station, NR BS, Node B, gNB, 5G Node B (NB), access point, transmit receive point (TRP), etc. Each BS may provide communication coverage for a specific geographic area. In 3GPP, the term "cell" may refer to the coverage area of a BS, the BS subsystem serving this coverage area, or a combination thereof, depending on the context in which the term is used. Within each cell, the base station may operate on different frequencies for radio frequency communication between the UE and the base station. The UE may communicate with the base station via a downlink (DL) and an uplink (UL). The DL (or forward link) refers to the communication link from the BS to the UE, and the UL (or reverse link) refers to the communication link from the UE to the BS.

[0041] The BS can provide communication coverage for macro cells, picocells, femtocells, another type of cell, or a combination thereof. A macro cell can cover a relatively large geographical area (e.g., with a radius of several kilometers) and can allow unrestricted access by users with service subscriptions. A picocell can cover a relatively small geographical area and can allow unrestricted access by UEs with service subscriptions. A femtocell can cover a relatively small geographical area (e.g., a home) and can allow restricted access by UEs associated with the femtocell (e.g., UEs in a Closed Subscriber Group (CSG)). The BS of a macro cell can be referred to as a macro BS. The BS of a picocell can be referred to as a pico BS. The BS of a femtocell can be referred to as a femto BS or a home BS. In Figure 1 the example shown, BS 110a can be the macro BS of macro cell 102a, BS 110b can be the pico BS of picocell 102b, and BS 110c can be the femto BS of femtocell 102c. The BS can support one or more (e.g., three) cells. The terms "eNB", "base station", "NR BS", "gNB", "TRP", "AP", "Node B", "5G NB", and "cell" can be used interchangeably herein.

[0042] In some examples, the cell may not necessarily be stationary, and the geographical area of the cell can move according to the position of the mobile BS. In some examples, the BSs can be interconnected with each other and with one or more other BSs or network nodes (not shown) in the wireless communication system 100 through any suitable transport network via various types of backhaul interfaces such as Integrated Access and Backhaul (IAB), direct physical connections, virtual networks, or a combination thereof.

[0043] The RAN can also include relay stations. A relay station is an entity that can receive transmissions of data from an upstream station (e.g., a BS or a UE) and send transmissions of data to a downstream station (e.g., a UE or a BS). A relay station can also be a UE that can relay transmissions for other UEs. In Figure 1 the example shown, relay station 110d can communicate with macro BS 110a and UE 120d to facilitate communication between BS 110a and UE 120d. A relay station can also be referred to as a relay BS, a relay base station, a repeater, etc.

[0044] The wireless communication system 100 may include a heterogeneous network that includes different types of BSs, such as macro BSs, pico BSs, femto BSs, relay BSs, etc. These different types of BSs may have different transmission power levels, different coverage areas, and different impacts on interference in the wireless communication system 100. For example, a macro base station may have a high transmission power level (e.g., 5 watts to 40 watts), while pico BSs, femto BSs, and relay BSs may have lower transmission power levels (e.g., 0.1 watt to 2 watts).

[0045] The network controller 130 may be coupled to a set of BSs and may provide coordination and control for these BSs. The network controller 130 may communicate with the BSs via a backhaul. The BSs may also communicate with each other, e.g., directly or indirectly via a wireless or wired backhaul.

[0046] UEs 120 (e.g., 120a, 120b, 120c, 120d, 120e) may be dispersed throughout the wireless communication system 100, and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, or a station, etc. A UE may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or equipment, a biometric sensor / device, a wearable device (smart watch, smart clothing, smart glasses, smart wristband, smart jewelry (e.g., smart ring, smart bracelet)), an entertainment device (e.g., a music or video device or a satellite radio), an in-vehicle component or sensor, a smart meter / sensor, an industrial manufacturing device, a global positioning system device, or any other suitable device configured to communicate via a wireless or wired medium.

[0047] Some UEs are machine type communication (MTC) or evolved or enhanced machine type communication (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a base station, another device (e.g., a remote device), or some other entity. A wireless node may provide connectivity to a network (e.g., a wide area network, such as the Internet or a cellular network) or provide connectivity to the network, e.g., via a wired or wireless communication link. Some UEs are Internet of Things (IoT) devices or may be implemented as narrowband IoT (NB-IoT) devices. Some UEs are customer premise equipment (CPE). The UE 120 may be included inside a housing that houses components of the UE 120, such as processor components, memory components, similar components, or a combination thereof.

[0048] Generally, any number of RANs can be deployed in a given geographical area. Each RAN can support a specific RAT and can operate on one or more frequencies. The RAT can also be referred to as radio technology, air interface, etc. The frequency can also be referred to as carrier, frequency channel, etc.

[0049] The UE performs PLMN selection to select a PLMN for registration. In a conventional network selection mechanism, the UE selects a PLMN and a RAN based on priority before performing cell selection based on cell selection criteria provided by the cell. The UE restricts cell selection to candidate cells within the selected PLMN and RAN. Cell selection or reselection can involve selecting, from among the candidate cells within the selected PLMN / RAN, the candidate cell having the highest signal strength or signal quality that the UE can measure. The UE can monitor the signal strength and signal quality of multiple frequencies to select a serving cell from among the candidate cells within the selected PLMN. In some implementations, the UE can receive a System Information Broadcast (SIB) message or other types of messages filled with a Public Land Mobile Network identifier (PLMN ID) and cell-provided cell selection criteria. The UE can camp on the selected serving cell to register with the PLMN. The UE can perform a Tracking Area Registration so that the wireless communication system knows which Tracking Area to page the UE for mobile-terminated communication. Additionally, the UE can establish a Radio Resource Control (RRC) relationship with the serving cell to obtain configuration or other information about the wireless communication system. When the UE has registered with the wireless communication and has established a basic RRC relationship with the serving cell, the UE is said to be camping on that cell. The serving cell can be used for Mobile Originated (MO) or Mobile Terminated (MT) communication between the UE and the wireless communication system.

[0050] Figure 2 FIG. 200 is a schematic diagram conceptually illustrating an example PLMN selection. When selecting a PLMN, the UE generally selects the network with the highest priority among the available PLMNs. There are two network selection modes: the automatic network selection mode and the manual network selection mode. In the automatic network selection mode, the UE searches for available networks prioritized in the following order (in decreasing priority): HPLMN (or equivalent HPLMN); User Controlled PLMN (UPLMN); Operator Controlled PLMN (OPLMN); other PLMN / access technology combinations with received high-quality signals in random order; other PLMN / access technology combinations in decreasing signal quality order; and finally, PLMNs supporting disaster roaming. After selecting a PLMN and a RAN, the UE selects a serving cell within the selected PLMN and RAN.

[0051] When selecting a serving cell, a UE typically selects the serving cell with the highest signal metric (such as signal strength or signal quality) measured by the UE, provided that the signal metric meets the cell selection criteria provided by the cell. The cell selection criteria provided by the cell typically include one or more cell signal level thresholds for one or more signal metrics. The cell selection criteria provided by the cell may also be referred to as network-provided parameters, network-broadcast thresholds, cell selection / reselection criteria, or similar terms. Examples of cell signal level thresholds may include a minimum RSRP value (sometimes referred to as the Qrxlevmin threshold), a minimum RSRQ value (sometimes referred to as the Qqualmin threshold), a minimum signal-to-interference-plus-noise ratio (SINR), or a minimum received signal strength indicator (RSSI), etc. In some implementations, the cell selection criteria provided by the cell may also include offset values (such as Qrxlevminoffset values and Qqualminoffset values). The UE may use the offset values to modify the cell signal level threshold or the measured signal metric before comparing the measured signal metric of the candidate cell with the cell signal level threshold. For example, if the UE is roaming on a VPLMN or other lower-priority PLMN, the UE may use the offset values when performing periodic network selection. The UE may periodically measure the signal quality or signal strength to determine whether another candidate cell is suitable for the UE to camp on or to determine whether to select a different PLMN.

[0052] Reference Figure 2 , UE 120 may be in the coverage areas of several base stations (such as gNB 210, eNB 212, gNB 222, gNB 224, eNB 232). Each base station operates one or more cells. In Figure 2In this case, gNB 210 and eNB 212 are using different RATs (5G NR and LTE respectively) and are part of the first PLMN 215. gNB 222, gNB 224, and eNB 232 are part of the second PLMN 225. The UE receives broadcast signals 252, 254, 222, 224, and 232 from the cells of each base station eNB 212, gNB 210, gNB 222, gNB 224, and eNB 232 respectively. The broadcast signals 252, 254, 222, 224, and 232 may include information (such as SIB messages) indicating the PLMN ID, configuration data, and cell selection criteria provided by the cell. The broadcast signals 252, 254, 222, 224, and 232 may also include reference signals for performing measurements of signal metrics. The UE may receive the broadcast signals to obtain information and measure the signal metrics for each available cell. In a conventional PLMN selection mechanism, after collecting the PLMN IDs from the available cells, if the first PLMN 215 has a higher priority than the second PLMN 225, the UE 120 may select the first PLMN 215. For example, the first PLMN 215 may be an HPLMN, while the second PLMN 225 may be a VPLMN. Additionally, the UE may select a RAT during PLMN selection. For example, 5G NR may have a higher priority than LTE. The PLMN selector list may include entries, where each entry has a combination of a PLMN and a RAT and a priority order for that entry. After selecting the first PLMN 215 and the first RAT (5G NR in this example), the UE 120 may select gNB 210 as the serving cell for the UE based on a comparison of the signal metric 254 for gNB 210 with the cell signal level threshold of the cell selection criteria provided by the cell.

[0053] Because conventional PLMN selection relies on PLMN priority as the first criterion, even when the signal metric of gNB 210 is lower than the signal metrics 253, 254, and 255 of the base stations gNB 222, gNB 224, and eNB 232 that are part of the second PLMN 225, the UE 120 may still select a serving cell (such as gNB 210) belonging to a higher priority PLMN (such as the first PLMN 215) and RAT or remain camped on that serving cell. In other words, even though a different base station (such as eNB 232) may have better signal quality or signal strength, the UE 120 may select gNB 210 as the serving cell because that gNB is in a PLMN and RAT with a higher priority compared to the second PLMN 225.

[0054] As described in this disclosure, a signal level network selection mechanism can mitigate the drawbacks of conventional PLMN selection that would otherwise be based on PLMN priority ranking. SENSE is an example signal level network selection mechanism promulgated by 3GPP. SENSE uses access technology - specific criteria as a supplement to or in place of the cell selection criteria provided by the cell. The access technology - specific criteria can include customized access technology - specific signal level thresholds for each access technology in a set of access technologies. The UE can store the access technology - specific criteria in a SIM (such as a Universal SIM (USIM)). It is expected that the UE uses the access technology - specific criteria when performing network selection. Referring again to Figure 2 , by comparing the signal metrics (such as signal metrics 270, 252, 253, 254, and 255) for each candidate cell with the access technology - specific signal level thresholds configured in the access technology - specific criteria, the UE 120 can select a PLMN and select a serving cell from among multiple candidate cells (such as gNB 210, eNB 212, gNB 222, gNB 224, eNB 232). For example, the UE can compare the signal metrics 252 and 255 for the LTE base stations eNB 212 and eNB 232 respectively with a first access technology - specific signal level threshold specific to LTE. The UE can compare the signal metrics 270, 253, and 254 for the 5G NR base stations gNB210, gNB 222, and gNB 224 respectively with a second access technology - specific signal level threshold specific to 5G NR.

[0055] The cell selection criteria provided by the cell and the access technology - specific criteria can be related to the same or different signal metrics. For example, both the cell signal level threshold in the cell selection criteria provided by the cell and the first - technology - specific threshold access technology - specific criteria can be related to RSRQ. Alternatively, the cell signal level threshold can be related to RSSI, while the first access technology - specific signal level threshold can be related to RSRQ. In some cases, in the absence of the techniques of this disclosure, the access technology - specific criteria and the cell selection criteria provided by the cell may conflict with each other or produce unpredictable network selection results. Additionally, as referenced in Figure 5 , Figure 8 and Figure 9 , the conditions for periodic network selection can be different depending on whether the PLMN was previously selected using the cell selection criteria provided by the cell or the access technology - specific criteria.

[0056] Figure 3AFIG. 300 conceptually illustrates an example PLMN selector list 310 and cell selection criteria 318 provided by a cell for a conventional PLMN selection mechanism. The PLMN selector list 310 includes entries for PLMN and RAT combinations. For example, the first entry 312 has the highest priority for a first PLMN (PLMN 1) and a first RAT (RAT ID 1). The second entry 314 has the second highest priority for the first PLMN (PLMN 1) and a second RAT (RAT ID 2). The third entry 316 has a lower priority for a second PLMN (and RAT ID 1) compared to the first PLMN prioritized by the first entry 312 and the second entry 314. The fourth entry 318 indicates a lower priority for a third PLMN (PLMN 3) compared to the first PLMN and the second PLMN. In the PLMN selector list, an HPLMN / EHPLMN can be prioritized over a user-controlled PLMN (UPLMN), which can be prioritized over an operator-controlled PLMN (OPLMN), which can be prioritized over other PLMN types.

[0057] In standardized automatic network selection, the UE shall search for PLMNs in the following order: HPLMN / EHPLMN; User-controlled PLMN (UPLMN); Operator-controlled PLMN (OPLMN); Other PLMN / access technology combinations with received high-quality signals in random order; Other PLMN / access technology combinations in the order of decreasing signal quality; and PLMNs supporting disaster roaming.

[0058] For some of the PLMN types (such as HPLMN, UPLMN, and OPLMN), the network may provide priorities for PLMN / access technology combinations. Further examples of the PLMN selector list are given below (Tables 1 to 3).

[0059] For the UPLMN, the network may configure the EF in the USIM PLMNwAcT (User-controlled PLMN selector with access technology): Table 1.

[0060] For an OPLMN, the network can configure the EF in the USIM OPLMNwACT (Operator Controlled PLMN Selector with Access Technology): Table 2.

[0061] For an HPLMN, the network can configure the EF in the USIM HPLMNwAcT (HPLMN Selector with Access Technology): Table 3.

[0062] The coding of access available technologies is illustrated in the following tables: Table 4.1 Table 4.2.5.1. Coding for E-UTRAN Table 4.2.5.2. Example Coding for Satellite Access

[0063] The UE selects the highest priority PLMN available in an area based on priority ranking when using the PLMN selector list 310. Then, the UE selects a serving cell. During cell selection, the UE also takes into account the cell selection criteria 318 provided by the cell. The cell selection criteria 318 provided by the cell include one or more cell signal level thresholds. Examples of cell signal level thresholds can include RSRQ, RSRP, or both. For 5G NR, as an example, the cell signal level threshold can be Q rxlevmin / Q qualmin threshold. The cell selection criteria 318 provided by the cell can also include a Q rxlevminoffset / Q qualminoffset offset parameter for higher priority PLMN cell selection. When the UE initiates a periodic search for a higher priority PLMN (also known as a periodic network selection attempt) while normally camped on a VPLMN, the UE will use Q rxlevmin +Q rxlevminoffset / Q qualmin +Q qualminoffset as the minimum RSRP / RSRQ value.

[0064] Figure 3BFIG. 302 is a block diagram conceptually illustrating example access technology - specific criteria for a SENSE mechanism. The access technology - specific criteria may include one or more access technology - specific signal level thresholds 320. For example, the access technology - specific signal level thresholds 320 may include a first access technology - specific signal level threshold 322 for 5G NR, a second access technology - specific signal level threshold 324 for LTE, and a third access technology - specific 326 for GSM. In some cases, the access technology - specific criteria may be associated with a specific PLMN 328. Alternatively, the access technology - specific criteria may include a list of acceptable PLMNs 328 that may not be prioritized, or the PLMNs 328 may have the same priority. In some cases, the access technology - specific criteria may indicate an access technology - specific signal level threshold for a unique combination of RAT and PLMN (or PLMN type).

[0065] Figure 3C FIG. 304 is a block diagram conceptually illustrating example signal quality criteria for a signal - quality - centric network selection mechanism. In some implementations of the signal - quality - centric network selection mechanism, the signal quality metric 338 may be the sole criterion for selecting a serving cell from among available or acceptable PLMNs. The UE may select the candidate cell with the highest signal metric, regardless of the access technology or PLMN type.

[0066] In some implementations, the signal quality criteria may include a prioritization of access technologies 330. For example, a first RAT 332 may have a higher priority than a second RAT 224, which has a higher priority than a third RAT 336. In some cases, the UE may select from any candidate cell within a list of allowed PLMNs (not shown) without preferring one type of PLMN over another.

[0067] Figure 4 FIG. 400 is a flowchart of an example process performed by a UE (such as the UE 120 described with reference to Figure 1 and Figure 2 ) for selecting among multiple network selection mechanisms. Example process 400 shows that the signal - quality - centric network selection mechanism has priority over the SENSE mechanism, and the SENSE mechanism has priority over the conventional PLMN selection mechanism. In some implementations, the prioritization of the network selection mechanisms may be sorted in a different way (such as making the SENSE prior to the signal - quality - centric network selection mechanism).

[0068] At block 410, the UE may determine whether a signal quality criterion for a signal quality - centric network selection mechanism is configured and enabled. The signal quality criterion is said to be configured and enabled when it is stored in the UE's memory and the operator has enabled the signal quality - centric network selection mechanism. For example, settings or configurations in the UE may indicate whether the signal quality - centric network selection mechanism is enabled. In some implementations, the signal quality - centric network selection mechanism may be dynamically enabled or disabled by the UE's processor. Alternatively or additionally, the signal quality - centric network selection mechanism may be manually enabled or disabled via the UE's user interface. If the signal quality criterion is configured and enabled, process 400 proceeds to block 415, where the UE uses the signal quality criterion to select a serving cell (and its PLMN) based on the highest signal quality. If the signal quality criterion is not configured or not enabled, process 400 proceeds to block 420.

[0069] At block 420, the UE may determine whether the SENSE mechanism is configured and enabled. SENSE is said to be configured and enabled when access - technology - specific criteria are stored in the UE's memory and the operator has enabled the SENSE mechanism. The SENSE mechanism may be enabled or disabled dynamically or manually, as described with reference to the signal quality - centric network selection mechanism in block 410. If the SENSE mechanism is configured and enabled, process 400 proceeds to block 425, where the UE uses the access - technology - specific criteria (such as an access - technology - specific signal level threshold) when selecting a PLMN and a suitable serving cell. If the SENSE mechanism is not configured or not enabled, process 400 proceeds to block 435.

[0070] At block 435, the UE may default to a conventional PLMN selection mechanism based on a PLMN selector list and a cell selection based on cell - provided cell selection criteria.

[0071] Figure 5 A flowchart showing an example process performed by a UE (such as UE 120 described with reference to Figure 1 and Figure 2 ) for coordinating network selection mechanisms. At block 505, the UE triggers network selection. The UE may trigger network selection for a variety of reasons, such as power - on condition, disabling of flight mode, manual user interaction, or expiration of a timer for periodic network selection, etc.

[0072] Beginning with a scenario where the signal level network selection mechanism is not configured or not enabled (the "No" branch from block 510), at block 520, the UE initiates PLMN selection using the PLMN selector list and cell selection using the cell selection criteria provided by the cell in a conventional manner. For example, the UE may compare the signal metrics of candidate cells in the PLMN sorted by the highest priority with one or more cell signal level thresholds of the cell selection criteria provided by the cell. At block 540, if the UE selects a suitable serving cell in the highest priority PLMN / RAT, the process 500 proceeds to block 550; otherwise, the process 500 may return to block 505 to trigger subsequent network selection. At block 550, the UE registers with the PLMN including the selected serving cell. For example, the UE may establish an RRC connection with the selected serving cell and perform NAS registration and / or tracking area update to the core network of the PLMN including the selected serving cell. At block 560, if the selected serving cell is in the VPLMN, the UE starts a timer (T) for periodic network selection (block 570); otherwise, if the selected serving cell is in the HPLMN (or EHPLMN), the process 500 ends until an event triggers block 505 again. From block 570, when the timer for periodic network selection expires, the process 500 returns to block 505 (or alternatively, returns to block 520). Periodic network selection is triggered after the expiration of the timer (T) such that the UE attempts to obtain service from a higher priority PLMN (higher than the current VPLMN) using the PLMN selector list and the cell selection criteria provided by the cell.

[0073] In a scenario where the signal level network selection mechanism is enabled (the "Yes" branch from block 510), the process 500 proceeds to block 515. At block 515, the UE initiates the signal level network selection mechanism. For example, the UE may compare the signal metrics of candidate cells with appropriate access technology specific signal level thresholds that match the access technology of the candidate cells. Refer to Figure 6 and Figure 7 further describes the access technology specific signal level thresholds. At block 545, if the UE fails to select a serving cell using the signal level network selection mechanism, the process 500 proceeds to block 520, where the UE performs PLMN selection and cell selection to select a serving cell. Otherwise, if the UE successfully selects a serving cell using the signal level network selection mechanism, the process 500 proceeds to block 555. At block 555, the UE registers with the PLMN including the selected serving cell. For example, the UE may establish an RRC connection with the selected serving cell and perform NAS registration and / or tracking area update to the core network of the PLMN including the selected serving cell.

[0074] At block 565, the UE modifies the conditions for periodic network selection to prevent or mitigate subsequent PLMN selection that would otherwise occur with the regular PLMN selection mechanism. Figure 8 and Figure 9 The description of

[0075] includes examples of setting the conditions for periodic network selection. The intent of the signal strength network selection mechanism is to find a suitable serving cell (such as having the highest signal metric) among candidate cells in different PLMNs. Thus, the UE can configure the periodic network selection settings that would otherwise trigger subsequent PLMN selection. For example, because the UE has selected a serving cell using the signal strength network selection mechanism, the UE disables or extends the timer for periodic network selection even if the selected serving cell is in a lower priority PLMN.

[0075] In some implementations, when the registered PLMN is not a higher priority PLMN and the signal quality of the access technology of the registered PLMN is below an access technology - specific criterion (such as an operator - controlled signal threshold according to the access technology), the UE (according to the timer for periodic network selection) triggers subsequent PLMN selection. In some implementations, if the registered PLMN is a higher priority PLMN and the signal quality of the access technology of the registered PLMN is equal to or higher than an access technology - specific criterion (such as an operator - controlled signal threshold according to the access technology), the UE avoids (according to the timer for periodic network selection) triggering subsequent PLMN selection.

[0076] Figure 6 illustrates a flowchart of an example process 600 performed by a UE (such as the UE 120 described with reference to Figure 1 and Figure 2 ) for implementing an access - technology - specific signal strength threshold and a cell signal strength threshold. At block 610, the UE determines whether SENSE is configured and enabled. For example, the UE determines whether the access - technology - specific signal strength threshold is stored in the UE's memory. Note that while Figure 6 the example refers to SENSE, the same concept can be used with a signal - quality - centered network selection mechanism. Figure 1 and Figure 2 If SENSE is not configured or not enabled (the "No" branch of block 610), then process 600 proceeds to block 630. At block 630, the UE uses regular PLMN selection and cell selection to select a serving cell from among multiple candidate cells in the highest - priority PLMN. For example, the UE compares the signal metric of candidate cells in the highest - priority PLMN with the cell signal strength threshold in the cell selection criteria provided by the cell. Figure 6 the example of

[0077] refers to SENSE, the same concept can be used with a signal - quality - centered network selection mechanism.

[0077] If SENSE is not configured or not enabled (the "No" branch of block 610), then process 600 proceeds to block 630. At block 630, the UE uses regular PLMN selection and cell selection to select a serving cell from among multiple candidate cells in the highest - priority PLMN. For example, the UE compares the signal metric of candidate cells in the highest - priority PLMN with the cell signal strength threshold in the cell selection criteria provided by the cell.

[0078] If SENSE is configured and enabled (the "Yes" branch of block 610), the UE proceeds with the SENSE mechanism using access-technology-specific criteria. There are two options (shown as blocks 620 and 640) for using the access-technology-specific signal level threshold in the access-technology-specific criteria. In one option, at block 620, the UE may use the access-technology-specific signal level threshold and ignore the cell selection criteria provided by the cell. For example, the UE compares the first signal metric of the first candidate cell with the first access-technology-specific signal level threshold for the access technology of the first candidate cell. Similarly, the UE compares the second signal metric of the second candidate cell with the second access-technology-specific signal level threshold for the access technology of the second candidate cell. In the other option, at block 640, the UE may use a combination of the access-technology-specific signal level threshold and the cell signal level threshold. The UE compares the signal metric of each candidate cell with the combination of the access-technology-specific signal level threshold and the cell signal level threshold.

[0079] Figure 6 Several example combinations of the access-technology-specific signal level threshold and the cell signal level threshold are shown (blocks 642, 644, 646, and 648). For example, at block 642, the combination may be based on the maximum of multiple thresholds (such as the access-technology-specific signal level threshold for the SENSE mechanism, the cell signal level threshold for a normal-priority PLMN, and the cell signal level threshold for a high-priority PLMN or any combination thereof). At block 644, the combination may be based on the minimum of multiple thresholds (such as the access-technology-specific signal level threshold for the SENSE mechanism, the cell signal level threshold for a normal-priority PLMN, and the cell signal level threshold for a high-priority PLMN or any combination thereof). At block 646, the combination may be based on the average of multiple thresholds (such as the access-technology-specific signal level threshold for the SENSE mechanism, the cell signal level threshold for a normal-priority PLMN, and the cell signal level threshold for a high-priority PLMN or any combination thereof). In another example (not shown), the UE may use one of the thresholds (such as the access-technology-specific signal level threshold for the SENSE mechanism, the cell signal level threshold for a normal-priority PLMN, and the cell signal level threshold for a high-priority PLMN) based on a predefined priority. For example, if the priority order is (1) the access-technology-specific signal level threshold, (2) the cell signal level threshold for a normal-priority PLMN, (3) the cell signal level threshold for a high-priority PLMN, the UE may use the access-technology-specific signal level threshold (if accessible) regardless of the values of the other thresholds.

[0080] Another example combination shown at block 648 can be based on the conjunction of multiple thresholds. For example, an access-technology specific signal level threshold can be based on a first type of signal metric (such as RSRQ), and a cell signal level threshold can be based on a different type of signal metric (such as RSRP). When combined conjunctively, the UE can select a serving cell that meets both the access-technology specific signal level threshold and the cell signal level threshold for its respective signal metric type.

[0081] Figure 7 A flowchart showing an example procedure 700 performed by a UE (such as UE 120 described with reference Figure 1 and Figure 2 to implement a signal quality centric network selection mechanism. At block 710, the UE determines whether the signal quality centric network selection mechanism is configured and enabled.

[0082] If the signal quality centric network selection mechanism is not configured or not enabled (the "no" branch of block 710), then procedure 700 proceeds to block 730. At block 730, the UE performs PLMN selection using conventional PLMN selection or using the SENSE mechanism if SENSE is configured and enabled.

[0083] If the signal quality centric network selection mechanism is configured and enabled (the "yes" branch of block 710), then the UE proceeds with the signal quality centric network selection mechanism. There are two options for using the signal quality centric network selection mechanism (shown as blocks 720 and 740). In one option, at block 720, when a first candidate cell has the highest signal metric among multiple candidate cells, the UE can select the first candidate cell as the serving cell. For example, the UE can ignore access technology and PLMN considerations (such as the PLMN selector list) when selecting a serving cell and its PLMN. In another option, at block 740, when a first candidate cell has the highest signal metric among multiple candidate cells using the highest priority ranked RAT, the UE can select the first candidate cell as the serving cell. For example, the UE can store RAT priorities and consider candidate cells from a higher priority ranked RAT first before considering candidate cells in a lower priority ranked RAT.

[0084] Figure 8 A flowchart showing an example procedure 800 performed by a UE (such as UE 120 described with reference Figure 1 and Figure 2 to manage conditions for periodic network selection. Example procedure 800 is to set conditions for periodic network selection ( Figure 5Example of the frame 565). Periodic network selection (also known as PLMN reselection) includes the possibility that subsequent PLMN selection causes the UE to select a new PLMN for registration.

[0085] At block 810, the UE determines whether the UE has selected a serving cell using a signal level network selection mechanism such as SENSE or signal quality centric network selection. If so, the process 800 proceeds to block 875; otherwise, the process 800 proceeds to block 870. At block 870 (when the serving cell is selected using conventional PLMN selection and cell selection), if the serving cell is in a VPLMN (or any PLMN type with a lower priority than the HPLMN), the UE starts a timer (T) for periodic network selection. When the timer T expires, the UE triggers subsequent PLMN selection (block 890). When the UE triggers subsequent PLMN selection, the UE may start at Figure 5 block 505. Alternatively or additionally, subsequent PLMN selection may follow the processes 400, 500, 600, or 700 described with reference to Figure 4 , Figure 5 , Figure 6 and Figure 7 respectively.

[0086] From block 810, if the UE has selected a serving cell using the signal level network selection mechanism, process 800 proceeds to block 875. At block 875, the UE starts a timer (T2) for evaluating the current serving cell prior to the periodic network selection that would normally occur for the conventional PLMN selection mechanism. In some implementations, the timer (T2) uses the same timer value (such as the value of timer (T)) that would normally be used for periodic network selection. Alternatively, the timer (T2) is an independent timer for triggering the evaluation. When the timer (T2) expires, the UE determines 880 whether the signal metric of the serving cell meets (is equal to or higher than) the access technology specific signal level threshold. Block 880 may also be referred to as the evaluation of the current serving cell. For example, if the signal metric still meets the access technology specific signal level threshold, the UE considers the serving cell suitable for service. If the serving cell remains suitable for service, the UE avoids triggering a periodic network selection and instead returns to block 875, where the UE restarts the timer (T2). Alternatively, if the signal metric of the serving cell does not meet (is less than) the access technology specific signal level threshold, process 800 proceeds to block 890, where the UE triggers a subsequent PLMN selection. Although block 880 shows an evaluation of the current serving cell based on the signal metric, the UE may alternatively or additionally use a different evaluation of the current serving cell. For example, at block 880, the UE may consider the priority of the current serving cell's RPLMN when deciding whether the current serving cell remains suitable for service. If the RPLMN is a high priority PLMN, the UE may consider the serving cell suitable for service. If the serving cell remains suitable for service, the UE avoids triggering a periodic network selection and instead returns to block 875. Otherwise, if the RPLMN is a low priority PLMN, process 800 proceeds to block 890, where the UE triggers a subsequent PLMN selection (such as by starting at Figure 5 block 505). In some implementations, the UE may evaluate the suitability of the current serving cell based on both the signal metric compared to the access technology specific signal level threshold and the priority of the serving cell's RPLMN.

[0087] Figure 9 shows a flowchart of another example process performed by a UE (such as UE 120 described with reference to Figure 1 and Figure 2 ) for managing the conditions for periodic network selection. Example process 900 is an example of setting the conditions for periodic network selection ( Figure 5 block 565).

[0088] At block 910, the UE determines whether the UE has selected the serving cell using a signal level network selection mechanism such as SENSE or signal quality centric network selection. If so, process 900 proceeds to block 920; otherwise, process 900 proceeds to block 970. At block 970 (when the serving cell is selected using the conventional PLMN selection mechanism), if the serving cell is in a VPLMN (or any PLMN type with a lower priority than the HPLMN), the UE starts a timer (T) for periodic network selection. When the timer T expires, the UE triggers a subsequent PLMN selection (block 990).

[0089] From block 910, if the UE has selected the serving cell using a signal level network selection mechanism, process 900 proceeds to block 920. At block 920, the UE disables the timer (T) that would otherwise be used to trigger a subsequent PLMN selection for the conventional PLMN selection mechanism. At block 940, the UE monitors the signal metrics of the serving cell. At block 950, the UE evaluates whether the current serving cell remains suitable for service in a manner similar to that described for block 880 Figure 8 as described.

[0090] At block 978, the UE enables and starts a timer (T) for periodic network selection, similar to block 875. When the timer (T) expires, the UE triggers a subsequent PLMN selection (block 990). In some implementations, the UE may perform an evaluation of the current serving cell (as shown at block 980) before triggering a subsequent PLMN selection, similar to block 880. For example, at block 980, the UE determines whether the current signal metrics of the serving cell meet the access technology specific signal level threshold. If the signal metrics meet the access technology specific signal level threshold (the "yes" branch of block 980), the UE restarts the timer (T) (block 960) without triggering a subsequent PLMN selection. Alternatively, the UE may disable the timer (T) (block 920). Thus, if the current signal metrics improve after the timer (T) is enabled at block 978, the UE prevents the triggering of periodic network selection. However, at block 980, if the current signal metrics still do not meet the access technology specific signal level threshold (the "no" branch of block 980), process 900 proceeds to block 990, where the UE triggers a subsequent PLMN selection. When the UE triggers a subsequent PLMN selection, the UE may start at Figure 5 block 505. Alternatively or additionally, the UE may follow the processes 400, 500, 600, or 700 described with reference to Figure 4 respectively, Figure 5 respectively, Figure 6 and Figure 7 respectively.

[0091] Figure 10A flowchart showing an example process in which access - technology - specific criteria may not include an access - technology - specific signal - level threshold for the RAT of a candidate cell. In some implementations, Figure 10 one or more of the process blocks may be performed by a UE (such as the UE 120 described with reference to Figure 1 and Figure 2 ). Process 1000 is described with reference to access - technology - specific criteria but may also be used in conjunction with signal - quality criteria for a signal - quality - centric network - selection mechanism. Process 1000 may be used when the access - technology - specific criteria (for SENSE) include access - technology - specific signal - level thresholds for some but not all of the RATs used in a particular area. For example, the access - technology - specific criteria may include an access - technology - specific signal - level threshold for LTE but may not include an access - technology - specific signal - level threshold for GSM or another access technology.

[0092] At block 1010, the UE determines whether the access - technology - specific criteria (also referred to as SENSE criteria) are configured and enabled. In this case, if the access - technology - specific criteria include at least one access - technology - specific signal - level threshold for an access technology, the access - technology - specific criteria are configured, even if there may be candidate cells using different access technologies near the UE. If the access - technology - specific criteria are at least partially configured and enabled, process 1000 proceeds to block 1020; otherwise, process 1000 proceeds to block 1015. At block 1015, the UE uses the PLMN selector list and the cell - provided cell - selection criteria (along with cell - signal - level thresholds) to perform PLMN selection and cell selection.

[0093] At block 1020, the UE determines whether the access technology specific criteria omit the access technology specific signal level threshold for the RAT of the candidate cell. For example, the access technology specific criteria may include a first access technology specific for a first RAT, but may not include a second access technology specific for a second RAT. Alternatively, the access technology specific criteria may carry a value with an invalid value or a predetermined disabled value (such as null or ∞) to indicate that the second RAT is not a preferred or a disabled access technology specific. The UE determines which RATs are available in its area (and optionally, within the permitted PLMN list), and whether the access technology specific criteria include the access technology specific for each of those available RATs. If the access technology specific criteria do not include the access technology specific (or include an invalid value or a predetermined disabled value) for one of the available RATs, the access technology specific criteria may be referred to as being partially configured or incomplete. If the access technology specific criteria include valid access technology specific for all available RATs, the process 1000 proceeds to block 1025, where the UE uses the access technology specific criteria for signal level network selection. If the access technology specific criteria are partially configured or incomplete, the UE may perform one of several options (as shown in blocks 1032, 1034, and 1036).

[0094] In a first option shown in block 1032, the UE may exclude those candidate cells that use a particular RAT (from being selected as a serving cell) for which the access technology specific criteria do not have an access technology specific signal level threshold, or for which the access technology specific signal level threshold is invalid, missing, or has a predetermined disabled value. For example, the UE may continue with SENSE on the remaining candidate cells (such as using a first RAT), while excluding those candidate cells that use a second RAT (not configured or disabled in the access technology specific criteria).

[0095] In a second option shown in block 1034, the UE may use a valid first access technology specific signal level threshold for candidate cells that use the first RAT (appropriately configured in the SENSE parameters), and use the cell signal level threshold from the cell selection criteria provided by the cell for candidate cells that use a second RAT (not appropriately configured in the access technology specific criteria). For example, the UE may use the cell signal level threshold from the cell selection criteria provided by the cell to fill in the gaps in the access technology specific criteria.

[0096] In the third option shown in block 1036, the UE may disable SENSE and instead use the regular PLMN selection mechanism and cell selection to select a serving cell. For example, the UE may assume that the access technology - specific criterion format is incorrect and disable the SENSE mechanism. To enable network selection to continue, the UE may fallback to using the regular PLMN selection using the PLMN selector list and cell selection using the cell - provided cell selection criteria.

[0097] Figure 11 A flowchart illustrating an example process 1100 for signal - level network selection. In some implementations, Figure 11 one or more of the process blocks may be performed by a UE (such as the UE 120 described with reference to Figure 1 and Figure 2 ). In block 1110, the UE obtains access - technology - specific criteria that include at least a first access - technology - specific signal - level threshold for a first access technology. In block 1120, the UE selects one or more public land mobile networks (PLMNs) that include one or more candidate cells having a signal metric that meets network - selection criteria that are at least partially based on the first access - technology - specific signal - level threshold for the first access technology. In block 1130, the UE registers with a first PLMN among the one or more PLMNs. In block 1140, the UE sets conditions for subsequent PLMN selection after registering with the first PLMN.

[0098] Figure 12 A flowchart illustrating an example process 1200 in which a UE may perform signal - level network selection or regular PLMN selection. In some implementations, Figure 11 one or more of the process blocks may be performed by a UE (such as the UE 120 described with reference to Figure 1 and Figure 2The described UE 120) performs. In block 1210, the UE obtains access technology - specific criteria, which include access - technology - specific signal - level thresholds for each of a plurality of access technologies. In block 1220, the UE obtains cell - provided cell - selection criteria, which include a cell - signal - level threshold. In block 1230, the UE selects a public land mobile network (PLMN) for registration by the UE, where selecting the PLMN may include block 1240 or 1250. In block 1240, when the UE is in a first region where all candidate cells are using one of the plurality of access technologies, the UE selects a first PLMN among one or more PLMNs that include one or more candidate cells and registers with the first PLMN, where the one or more candidate cells have signal metrics that meet the access - technology - specific signal - level thresholds for the respective access technology of each of the one or more candidate cells. In block 1250, when the UE is in a first region where at least one candidate cell is using an access technology for which the access - technology - specific signal - level threshold is not included in the access - technology - specific criteria, the UE selects a second PLMN and registers with the second PLMN, where the second PLMN is based on PLMN priority ranking and includes at least one candidate cell having a signal metric that meets the cell - provided cell - selection criteria.

[0099] Figure 13 is a flowchart of an example process 1300 for signal - quality - centered network selection. In some implementations, Figure 11 one or more of the process blocks may be performed by a UE (such as the UE 120 described with reference to Figure 1 and Figure 2 ). In block 1310, the UE selects a serving cell from among a plurality of candidate cells, where the serving cell has the highest signal metric among the signal metrics of the plurality of candidate cells, and where the plurality of candidate cells include cells from different public land mobile networks (PLMNs) having equal priority ranking or no priority ranking. In block 1320, the UE selects a first PLMN that includes the selected serving cell. In block 1330, the UE registers with the first PLMN.

[0100] Although Figures 11 to 13 shows example blocks of processes 1100, 1200, and 1300, in some implementations, compared to the blocks depicted in Figures 11 to 13 , processes 1100, 1200, and 1300 may include additional blocks, fewer blocks, different blocks, or blocks arranged in a different manner. Additionally or alternatively, two or more of the blocks of processes 1100, 1200, or 1300 may be performed in parallel.

[0101] Figure 14 FIG. 1400 is a block diagram illustrating an example wireless communication device that supports cell reselection based on a serving relationship. In some implementations, the wireless communication device 1400 may be an example of a device for use in a UE (such as the UE 120 described above with reference to Figure 1 and Figure 2 ). The wireless communication device 1400 is capable of transmitting and receiving wireless communications (or outputting wireless communications for transmission).

[0102] The wireless communication device 1400 may be or may include a chip, a system-on-chip (SoC), a chipset, a package, or a device. The term "system-on-chip" (SoC) is used herein to refer to a group of interconnected electronic circuits that typically but not exclusively includes one or more processors, memories, and communication interfaces. An SoC may include various different types of processors and processor cores, such as general-purpose processors, central processing units (CPUs), digital signal processors (DSPs), graphics processing units (GPUs), accelerated processing units (APUs), subsystem processors, auxiliary processors, single-core processors, and multi-core processors. The SoC may further include other hardware and hardware combinations, such as field-programmable gate arrays (FPGAs), configuration and status registers (CSRs), application-specific integrated circuits (ASICs), other programmable logic devices, discrete gate logic components, transistor logic components, registers, performance monitoring hardware, watchdog hardware, counters, and time references. The SoC may be an integrated circuit (IC) that is configured such that the components of the IC reside on the same substrate, such as a single piece of semiconductor material (such as, for example, silicon).

[0103] The term "system-in-package" (SIP) is used herein to refer to a single module or package that may contain two or more IC chips, multiple resources, computing units, cores, or processors on a substrate or an SoC. For example, an SIP may include a single substrate on which multiple IC chips or semiconductor dies are stacked in a vertical configuration. Similarly, an SIP may include one or more multi-chip modules (MCMs) on which multiple ICs or semiconductor dies are encapsulated into a unified substrate. An SIP may also include multiple independent SoCs that are coupled together via high-speed communication circuitry and tightly packaged, such as on a single motherboard or in a single mobile communication device. The proximity of the SoCs facilitates high-speed communication as well as memory and resource sharing.

[0104] The term "multi-core processor" is used herein to refer to a single IC chip or chip package that includes two or more independent processing cores (e.g., CPU cores, IP cores, GPU cores, etc.) configured to read and execute program instructions. An SoC may include multiple multi-core processors, and each processor in the SoC may be referred to as a core. The term "multi-core processor" may be used herein to refer to a system or device that includes two or more processing units configured to read and execute program instructions.

[0105] The wireless communication device 1400 may include one or more modems 1402. In some implementations, one or more modems 1402 (collectively referred to as "modems 1402") may include a WWAN modem (e.g., a 3GPP 4G LTE or 5G compatible modem). In some implementations, the wireless communication device 1400 further includes one or more radio components (collectively referred to as "radio components 1404"). In some implementations, the wireless communication device 1400 further includes one or more processors, processing blocks, or processing elements (collectively referred to as "processing system 1406") and one or more memory blocks or elements (collectively referred to as "memory 1408"). In some implementations, the processing system 1406 may include the memory 1408.

[0106] The modem 1402 may include intelligent hardware blocks or devices, such as, for example, an application specific integrated circuit (ASIC), etc. The modem 1402 is generally configured to implement the PHY layer. For example, the modem 1402 is configured to modulate packets and output the modulated packets to the radio component 1404 for transmission over the wireless medium. The modem 1402 is similarly configured to obtain the modulated packets received by the radio component 1404 and demodulate the packets to provide demodulated packets. In addition to the modulator and demodulator, the modem 1402 may further include digital signal processing (DSP) circuitry, automatic gain control (AGC), a code processor, a decoder, a multiplexer, and a demultiplexer. For example, when in the transmit mode, the data obtained from the processing system 1406 is provided to the code processor, which encodes the data to provide encoded bits. The encoded bits are mapped to points in the modulation constellation (using the selected MCS) to provide modulated symbols. The modulated symbols may be mapped to multiple spatial streams (NSS) or multiple space-time streams (NSTS). The modulated symbols in the corresponding spatial stream or space-time stream may be multiplexed, transformed via an inverse fast Fourier transform (IFFT) block, and then provided to the DSP circuitry for Tx windowing and filtering. The digital signal may be provided to a digital-to-analog converter (DAC). The resulting analog signal may be provided to a frequency upconverter and ultimately to the radio component 1404. In implementations involving beamforming, the modulated symbols in the corresponding spatial stream are precoded via a steering matrix before they are provided to the IFFT block.

[0107] When in the receive mode, the digital signal received from the radio component 1404 is provided to the DSP circuitry, which is configured to acquire the signal, for example, by detecting the presence of the received signal and estimating the initial timing and frequency offset. The DSP circuitry is further configured to digitally condition the digital signal, for example, by using channel (narrowband) filtering, analog impairment conditioning (such as correcting I / Q imbalance), and applying digital gain to ultimately obtain a narrowband signal. The output of the DSP circuitry may be fed to the AGC, which is configured to determine an appropriate gain, for example, using information extracted from the digital signal in one or more received training fields. The output of the DSP circuitry is also coupled to a demodulator, which is configured to extract the modulated symbols from the signal and, for example, calculate the log-likelihood ratio (LLR) of each bit location for each subcarrier in each spatial stream. The demodulator is coupled to a decoder, which may be configured to process the LLRs to provide decoded bits. The decoded bits from all spatial streams are fed to a demultiplexer for demultiplexing. The demultiplexed bits may be descrambled and provided to the MAC layer (processing system 1406) for processing, evaluation, or interpretation.

[0108] The radio component 1404 generally includes at least one radio frequency (RF) transmitter (or “transmitter chain”) and at least one RF receiver (or “receiver chain”) that can be combined into one or more transceivers. For example, the RF transmitter and receiver can include various DSP circuitry that respectively includes at least one power amplifier (PA) and at least one low noise amplifier (LNA). The RF transmitter and receiver can in turn be coupled to one or more antennas. For example, in some implementations, the wireless communication device 1400 can include multiple transmit antennas (each transmit antenna having a corresponding transmit chain) and multiple receive antennas (each receive antenna having a corresponding receive chain) or be coupled to multiple transmit antennas and multiple receive antennas. The symbols output from the modem 1402 are provided to the radio component 1404, which transmits the symbols via the coupled antennas. Similarly, the symbols received via the antennas are obtained by the radio component 1404, which provides the symbols to the modem 1402.

[0109] The processing system 1406 can include intelligent hardware blocks or devices designed to perform the functions described herein, such as, for example, processing cores, processing blocks, central processing units (CPUs), microprocessors, microcontrollers, digital signal processors (DSPs), application specific integrated circuits (ASICs), programmable logic devices (PLDs) (such as field programmable gate arrays (FPGAs)), discrete gate or transistor logic components, discrete hardware components, or any combination thereof. The processing system 1406 processes the information received through the radio component 1404 and the modem 1402, and processes the information to be output through the modem 1402 and the radio component 1404 for transmission through the wireless medium. In some implementations, the processing system 1406 can generally control the modem 1402 to cause the modem to perform the various operations described herein. For example, the processing system 1406 in conjunction with the modem 1402 can implement any of the features described with reference to Figures 4 to 13 any one of those described.

[0110] The memory 1408 can include a tangible storage medium, such as random access memory (RAM) or read only memory (ROM) or a combination thereof. The memory 1408 can also store non-transitory processor or computer executable software (SW) code containing instructions that, when executed by the processing system 1406, cause the processor to perform the various operations for wireless communication described herein, which operations include the generation, transmission, reception, and interpretation of MPDUs, frames, or packets. For example, the various functions of the components disclosed herein or the various blocks or steps of the methods, operations, processes, or algorithms disclosed herein can be implemented as one or more modules of one or more computer programs.

[0111] Figures 1 to 14 The operations described herein are examples intended to assist in understanding the example implementations and should not be used to limit potential implementations or the scope of the claims. Some implementations may perform additional operations, fewer operations, perform operations in parallel or in a different order, and perform some operations in a different manner.

[0112] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit aspects to the precise forms disclosed. Modifications and variations may be made in light of the above disclosure, or may be obtained from practice of the aspects. While aspects of the present disclosure have been described with respect to various examples, any combination of aspects from any of the examples is also within the scope of the present disclosure. The examples in the present disclosure are provided for illustrative purposes only. Alternatively, or in addition to the other examples described herein, the examples include any combination of the following implementation options (enumerated as clauses for clarity). Clause

[0113] Clause 1. A method for network selection by a user equipment (UE), comprising: obtaining access technology-specific criteria, the access technology-specific criteria including at least a first technology-specific signal level threshold for a first access technology; selecting one or more public land mobile networks (PLMNs), the one or more PLMNs including one or more candidate cells having a signal metric that meets network selection criteria, the network selection criteria being at least partially based on the first access technology-specific signal level threshold for the first access technology; registering with a first PLMN among the one or more PLMNs; and setting conditions for subsequent PLMN selection after registering with the first PLMN.

[0114] Clause 2. The method according to clause 1, further comprising: selecting a cell from among the one or more candidate cells by comparing a first signal metric of the cell with the first access technology-specific signal level threshold; and selecting the first PLMN based on the selected cell, wherein the first PLMN includes the cell and the first signal metric exceeds the first access technology-specific signal level threshold.

[0115] Clause 3. The method according to any one of clauses 1 to 2, further comprising: obtaining cell-provided cell selection criteria from the one or more PLMNs, wherein the cell-provided cell selection criteria includes a cell signal level threshold, and wherein the network selection criteria is based on a combination of the first access technology-specific signal level threshold and the cell signal level threshold.

[0116] Clause 4. The method as described in Clause 3, wherein the network selection criteria include: a first criterion based on one of a minimum value, a maximum value, or an average value of a cell signal level threshold and a first access technology - specific signal level threshold, and wherein the cell signal level threshold and the first access technology - specific signal level threshold are for the same signal metric.

[0117] Clause 5. The method as described in Clause 3, wherein the network selection criteria at least include: a first criterion based on a first access technology - specific signal level threshold for a first signal metric; and a second criterion based on a cell signal level threshold for a second signal metric.

[0118] Clause 6. The method as described in any one of Clauses 1 to 5, wherein when the first signal metric of at least a first candidate cell of a first PLMN satisfies the first access technology - specific signal level threshold, one or more PLMNs include the first PLMN, wherein when the second signal metric of at least a second candidate cell of a second PLMN satisfies the first access technology - specific signal level threshold, one or more PLMNs include the second PLMN, and wherein one or more candidate cells include the first candidate cell and the second candidate cell.

[0119] Clause 7. The method as described in any one of Clauses 1 to 5, wherein the access - technology - specific criteria include a second access technology - specific signal level threshold for a second access technology, and wherein selecting one or more PLMNs includes: comparing the first signal metrics of a first plurality of candidate cells for the first access technology with the first access technology - specific signal level threshold; and comparing the second signal metrics of a second plurality of candidate cells for the second access technology with the second access technology - specific signal level threshold, wherein when a first PLMN includes at least one candidate cell among the first plurality of candidate cells having a first signal metric that satisfies the first access technology - specific signal level threshold, one or more PLMNs include the first PLMN; and wherein when a second PLMN includes at least one candidate cell among the second plurality of candidate cells having a second signal metric that satisfies the second access technology - specific signal level threshold, one or more PLMNs include the second PLMN.

[0120] Clause 8. The method as described in Clause 7, wherein the access - technology - specific criteria do not include a third access technology - specific signal level threshold for a third access technology, and the method further includes: when selecting one or more PLMNs, excluding a third plurality of candidate cells for the third access technology from consideration.

[0121] Clause 9. The method as described in Clause 7, wherein the access technology specific criterion does not include a third access technology specific signal level threshold for a third access technology, the method further comprising: obtaining cell-provided cell selection criteria from one or more candidate cells of the third access technology, the cell-provided cell selection criteria including a cell signal level threshold; configuring the third access technology specific signal level threshold based on the cell signal level threshold; and obtaining a third signal metric for a third plurality of candidate cells of the third access technology, wherein when a first signal metric of a third candidate cell of a third PLMN meets the third access technology specific signal level threshold, one or more PLMNs include the third PLMN.

[0122] Clause 10. The method as described in Clause 7, wherein the access technology specific criterion does not include a third access technology specific signal level threshold for a third access technology, the method further comprising: obtaining cell-provided cell selection criteria from one or more candidate cells of the third access technology; ignoring the access technology specific criterion for the third access technology in the network selection criterion; and configuring the network selection criterion based on the PLMN selector list and the cell-provided cell selection criteria.

[0123] Clause 11. The method as described in any one of Clauses 1 to 10, wherein the setting condition includes: triggering subsequent PLMN selection when a first PLMN has a lower priority than a second PLMN and a current signal metric of a serving cell of the first PLMN is lower than the first access technology specific signal level threshold.

[0124] Clause 12. The method as described in any one of Clauses 1 to 11, wherein the setting condition includes: disabling a timer for subsequent PLMN selection.

[0125] Clause 13. The method as described in any one of Clauses 1 to 12, wherein the subsequent PLMN selection is a periodic network selection attempt that typically occurs upon expiration of a timer; wherein the setting condition includes: avoiding triggering subsequent PLMN selection upon expiration of the timer when a first PLMN has a higher priority than other PLMNs in one or more PLMNs and a current signal metric of a serving cell of the first PLMN is equal to or higher than the first access technology specific signal level threshold.

[0126] Clause 14. The method as described in Clause 13, further comprising: at expiration of the timer, when the current signal metric of the serving cell is equal to or higher than the first access technology specific signal level threshold, restarting the timer without triggering a periodic network selection attempt.

[0127] Clause 15. The method as described in Clause 13, wherein the setting conditions include: when the first PLMN has a lower priority than the second PLMN and the current signal metric of the serving cell of the first PLMN is lower than the first access technology-specific signal level threshold, triggering a periodic network selection attempt, wherein the periodic network selection attempt includes at least one of the following: using the access technology-specific criteria to perform subsequent PLMN selection when the access technology-specific criteria remain enabled at the UE; or using the cell selection criteria provided by the cell to perform subsequent PLMN selection when the access technology-specific criteria are disabled or no longer exist at the UE.

[0128] Clause 16. The method as described in any one of Clauses 1 to 15, wherein the setting conditions include: disabling a timer (T) that would otherwise trigger subsequent PLMN selection; enabling the timer when the first signal metric of the serving cell of the first PLMN has changed such that the first signal metric no longer meets the first access technology-specific signal level threshold; and triggering subsequent PLMN selection when the first signal metric of the serving cell does not meet the first access technology-specific signal level threshold after the expiration of the timer.

[0129] Clause 17. The method as described in any one of Clauses 1 to 16, wherein the setting conditions include: disabling or setting subsequent PLMN selection when the serving cell is in the home PLMN (HPLMN); and enabling subsequent PLMN selection when the serving cell is roaming in a visited PLMN (VPLMN).

[0130] Clause 18. A method for network selection by a user equipment (UE) includes: obtaining access technology specific criteria including access technology specific signal level thresholds for each of a plurality of access technologies; obtaining cell provided cell selection criteria including a cell signal level threshold; and selecting a public land mobile network (PLMN) for registration by the UE, where selecting the PLMN includes: when the UE is in a first area where all candidate cells are using one of the plurality of access technologies, the UE selects a first PLMN among one or more PLMNs including one or more candidate cells and registers with the first PLMN, the one or more candidate cells having signal metrics that meet the access technology specific signal level thresholds for the respective access technologies of each of the one or more candidate cells; and when the UE is in a first area where at least one candidate cell is using an access technology for which the access technology specific signal level threshold is not included in the access technology specific criteria, the UE selects a second PLMN and registers with the second PLMN, the second PLMN being based on PLMN priority ranking and including at least one candidate cell having a signal metric that meets the cell provided cell selection criteria.

[0131] Clause 19. The method according to clause 18 further includes: when the UE moves from the first area to the second area or from the second area to the first area, selecting a new PLMN using the access technology specific criteria in the first area or the cell provided cell selection criteria in the second area.

[0132] Clause 20. The method according to clause 18 further includes: based on selecting the first PLMN and registering with the first PLMN, setting conditions for periodic network selection attempts for selecting a new PLMN, where setting the conditions for periodic network selection attempts includes at least one of the following: triggering a periodic network selection attempt when the first PLMN has a lower priority than another PLMN and the current signal metric of the serving cell of the first PLMN is below the access technology specific signal level threshold for the serving cell; or avoiding triggering a periodic network selection attempt when the first PLMN has a higher priority than other PLMNs and the current signal metric of the serving cell of the first PLMN is equal to or higher than the access technology specific signal level threshold.

[0133] Clause 21. A method for wireless communication by a user equipment (UE), comprising: selecting a serving cell from among a plurality of candidate cells, wherein the serving cell has the highest signal metric among signal metrics for the plurality of candidate cells, wherein the plurality of candidate cells includes candidate cells from different public land mobile networks (PLMNs) having equal priority rankings or no priority rankings in a signal quality criterion; selecting a first PLMN including the serving cell; and registering the UE with the first PLMN.

[0134] Clause 22. The method according to clause 21, further comprising: after registering with the first PLMN, setting conditions for a periodic network selection attempt for selecting a new PLMN, wherein setting the conditions for the periodic network selection attempt includes at least one of the following: triggering a periodic network selection attempt when a current signal metric of the serving cell is lower than a signal level threshold of the signal quality criterion; or avoiding triggering a periodic network selection attempt when the current signal metric of the serving cell is equal to or higher than the signal level threshold.

[0135] Clause 23. The method according to any one of clauses 21 to 23, wherein selecting the serving cell includes: ignoring the PLMN priority ranking of a PLMN selector list; and selecting the plurality of candidate cells based on the signal quality criterion.

[0136] Clause 24. The method according to any one of clauses 21 to 23, wherein the signal quality criterion includes a priority ranking of access technologies, and wherein the plurality of candidate cells includes those candidate cells using the highest priority access technology in the priority ranking of access technologies.

[0137] Clause 25. A user equipment (UE), comprising: a communication unit; and a processing system configured to control the communication unit to implement any one of the methods according to clauses 1 to 24.

[0138] Another innovative aspect of the subject matter described in this disclosure can be implemented as a wireless communication device of a UE. The wireless communication device can include at least one interface and a processing system communicatively coupled to the at least one interface. The processing system can be configured to implement any one of the above clauses.

[0139] Another innovative aspect of the subject matter described in this disclosure can be implemented as a portable electronic device that includes a wireless communication device, a plurality of antennas coupled to at least one transceiver to wirelessly transmit signals output from the at least one transceiver, and a housing that encloses at least a portion of the wireless communication device, the at least one transceiver, and the plurality of antennas. The wireless communication device can include at least one interface and a processing system communicatively coupled to the at least one interface. The processing system can be configured to implement any one of the above clauses.

[0140] Another innovative aspect of the subject matter described in this disclosure can be implemented as a machine-readable medium having processor-readable instructions stored therein that, when executed by a processing system of a UE, cause the UE to implement any one of the above clauses.

[0141] Another innovative aspect of the subject matter described in this disclosure can be implemented as a device. The device can include components for implementing any one of the above clauses.

[0142] As used herein, the term "component" is intended to be broadly construed as hardware, firmware, or a combination of hardware and software. As used herein, a processor is implemented as hardware, firmware, or a combination of hardware and software. As used herein, the phrase "based on" is intended to be broadly construed to mean "at least partially based on".

[0143] Some aspects are described herein in connection with thresholds. As used herein, meeting a threshold can refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, etc.

[0144] As used herein, a phrase referring to "at least one" or "one or more" of a list of items refers to any combination of those items, including a single member. For example, "at least one of a, b, or c" is intended to cover the possibilities of: only a, only b, only c, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a, b, and c.

[0145] In this disclosure, the term "can" indicates ability, or alternatively indicates a possible implementation option. The term "may" indicates permission, or alternatively indicates a possible implementation option. The term "might" indicates a possible utilization of an implementation option.

[0146] The various illustrative components, logical elements, logical blocks, modules, circuits, operations, and algorithmic processes described in connection with the implementations disclosed herein can be implemented as electronic hardware, firmware, software, or any combination of hardware, firmware, or software, including the structures disclosed herein and structural equivalents thereof. The interchangeability of hardware, firmware, and software has been exemplified in terms of functionality and in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented as hardware, firmware, or software depends upon the particular application and design constraints imposed on the overall system.

[0147] Hardware and data processing devices for implementing the various illustrative components, logical elements, logical blocks, modules, and circuits described in connection with the aspects disclosed herein can be implemented or performed using a general-purpose single-chip or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device (PLD), discrete gate or transistor logic elements, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor or any conventional processor, controller, microcontroller, or state machine. The processor can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular processes, operations, and methods can be performed by circuitry specific to a given function.

[0148] As described above, in some aspects, implementations of the subject matter described in this specification can be implemented as software. For example, the various functions of the components disclosed herein or the various blocks or steps of the methods, operations, processes, or algorithms disclosed herein can be implemented as one or more modules of one or more computer programs. Such computer programs can include non-transitory processor or computer-executable instructions encoded on one or more tangible processor or computer-readable storage media for execution by a data processing device including the components of the apparatus described herein or for execution to control the operation of the data processing device. By way of example and not limitation, such storage media can include RAM, ROM, EEPROM, CD-ROM, or other optical disk storage, magnetic disk storage, or other magnetic storage devices, or any other medium that can be used to store program code in the form of instructions or data structures. Combinations of the above should also be included within the scope of the storage media.

[0149] As used herein, the terms "user equipment", "wireless communication device", "mobile communication device", "communication device", or "mobile device" refer to any or all of the following: cellular phone, smartphone, portable computing device, personal or mobile multimedia player, laptop computer, tablet computer, smartbook, Internet of Things (IoT) device, palmtop computer, wireless email receiver, multimedia-capable Internet-enabled cellular phone, wireless game controller, display subsystem, driver assistance system, vehicle controller, vehicle system controller, vehicle communication system, infotainment system, vehicle telematics system or subsystem, vehicle display system or subsystem, vehicle data controller or router, and similar electronic devices including a programmable processor, memory, and circuitry configured to perform the operations described herein.

[0150] As used herein, the terms "SIM", "SIM card", and "subscriber identity module" are used interchangeably to refer to a memory that may be an integrated circuit or embedded in a removable card and stores an International Mobile Subscriber Identity (IMSI), associated keys, or other information for identifying or authenticating a mobile communication device on a network and enabling communication services with the network. Because the information stored in the SIM enables the mobile communication device to establish a communication link for a particular communication service with a particular network, the term "subscription" is used herein as a shorthand reference to the communication service associated with and enabled by the information stored in a particular SIM, as the SIM and the communication network and the services and subscriptions supported by that network are interrelated. The SIM used in various examples may contain user account information, an International Mobile Subscriber Identity (IMSI), a set of SIM Application Toolkit (SAT) commands, and storage space for phonebook contacts. The SIM card may further store a home identifier (such as a System Identification Number (SID) / Network Identification Number (NID) pair, Home Public Land Mobile Number (HPLMN) code, etc.) indicating the SIM card network operator provider. An Integrated Circuit Card Identification (ICCID) SIM serial number may be printed on the SIM card for identification. However, the SIM may be implemented within a portion of the memory of the mobile communication device and thus need not be a separate or removable circuit, chip, or card.

[0151] Those of ordinary skill in the art will readily recognize various modifications to the implementations described in this disclosure, and the general principles defined herein can be applied to other implementations without departing from the spirit or scope of the disclosure. Accordingly, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with the disclosure, the principles disclosed herein, and the novel features.

[0152] Additionally, various features described in the context of separate implementations in this specification can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented separately or in any suitable sub-combination in multiple implementations. Thus, although features may be described above as acting in a particular combination and even initially claimed as such, in some cases one or more features from the claimed combination can be deleted from that combination, and the claimed combination can cover a sub-combination or a variation of a sub-combination.

[0153] Similarly, although operations are depicted in the figures in a particular order, this should not be construed as requiring that such operations be performed in the particular order shown or in sequential order, or that all of the illustrated operations be performed, to achieve the desired result. Further, the figures may schematically depict one or more example processes in the form of a flowchart or a flow diagram. However, other operations not depicted can be incorporated into the example processes schematically illustrated. For example, one or more additional operations can be implemented before, after, concurrently with, or between any of the illustrated operations. In some cases, multitasking and parallel processing may be advantageous. Additionally, the separation of various system components in the implementations described above should not be construed as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the acts recited in the claims can be performed in a different order and still achieve the desired result.

[0154] Appendix A includes examples where the UE determines whether to perform a periodic network selection based on the RPLMN and access-technology specific criteria (referred to as operator-controlled signal thresholds per access technology). Appendix A Example 1 Periodic network selection attempt

[0155] If no operator-controlled signal threshold according to the access technology is set on the USIM, the UE in automatic mode shall make periodic attempts to find a higher-priority PLMN (including associated access technology) that belongs to the same country as the currently received PLMN (including associated access technology) or to find a higher-priority PLMN (including associated access technology) that uses a shared MCC (e.g., MCC = 901). If the currently received PLMN (including associated access technology) uses a shared MCC, higher-priority PLMNs (including associated access technology) using any non-shared MCC shall also be considered. For the ranking of PLMNs, the UE shall use the order as used in clause 3.2.2.2. In the absence of an associated access technology identifier, the mobile device shall assume that all access technologies provided by the PLMN have equal priority. Furthermore, the periodic network selection shall not result in a change of the access technology within the registered PLMN.

[0156] When disaster conditions apply, a UE in automatic mode that is registered to a PLMN in the "Forbidden PLMN" data field in the SIM / USIM may make periodic attempts to find a permissible PLMN that belongs to the same country as the currently received PLMN.

[0157] In the case where the UE has stored an equivalent PLMN list, the UE shall only select a PLMN if that PLMN has a higher priority than all PLMNs that belong to the same country as the currently registered PLMN in the equivalent PLMN list.

[0158] Note 1: In the context of this 3GPP TS, the term country shall not be interpreted as a political entity, but as a single mobile country code (MCC). For example, the United States and India have multiple MCCs. In fact, such cases are considered exceptions in the 3GPP specifications. For all other countries, multiple MCCs may be used; however, the specifications have not considered this and there may be adverse effects, such as the UE being unable to detect multiple MCCs within the same country.

[0159] Note 2: There are some cases where one MCC represents multiple political entities or the MCC is not related to a political entity. Examples include shared MCCs, where international satellite operations typically use a shared MCC with the value 901.

[0160] Note 3: For the purpose of PLMN selection, the associated access technology using a shared MCC is limited to satellite NG-RAN.

[0161] In the case where multiple EHPLMNs are available, when an EHPLMN has been selected, the UE shall not attempt to select a higher-priority EHPLMN. The priority of EHPLMNs only applies when the UE is on a VPLMN and multiple EHPLMNs are available.

[0162] The UE shall make reselection attempts only when in the idle mode. In the case of a GPRS terminal, the UE shall make reselection attempts only when in the idle or standby mode. In the case of a terminal operating in E-UTRA and / or NR, the UE shall make reselection attempts only when in the idle or RRC Inactive mode.

[0163] In the case where the UE receives an eMBMS delivery service while in the idle mode, the UE may postpone higher priority PLMN searches and any reselection attempts until the eMBMS delivery service has been completed or stopped.

[0164] The interval between attempts shall be stored in the SIM / USIM.

[0165] Only the service provider shall be able to select which of the previous scenarios shall have periodic network selection attempted, and set the interval value.

[0166] For a UE that supports only access technologies other than: NB-IoT, GERAN EC-GSM-IoT, and E-UTRAN enhanced MTC category M1

[17] , the UE shall interpret the interval value as being between 6 minutes and 8 hours, in steps of 6 minutes.

[0167] For a UE that supports only any one or combination of: NB-IoT, GERAN EC-GSM-IoT

[18] , and E-UTRAN enhanced MTC category M1

[13] , the UE shall interpret the interval value as being between 2 hours and 240 hours, in steps of 2 hours between 2 hours and 80 hours, and in steps of 4 hours between 80 hours and 240 hours.

[0168] For a UE that supports a combination of IoT and non-IoT access technologies, the UE shall interpret the interval value based on the access technology currently used by the UE to determine the timer value as described above.

[0169] An interval value shall be specified to indicate that periodic attempts shall not be made.

[0170] In the case where there is no permitted value in the SIM / USIM or the SIM / USIM is Release 1 and thus does not contain a data field, a default value of 60 minutes shall be used by UEs other than those that support only any one or combination of: NB-IoT, GERAN EC-GSM-IoT

[18] , and E-UTRAN enhanced MTC category M1

[17] . For those UEs, a default value of 72 hours shall be used.

[0171] Note: Using a value less than 60 minutes may result in excessive UE battery consumption. Periodic Network Selection Based on Operator-Controlled Signal Threshold Criteria

[0172] If an operator-controlled signal threshold per access technology is set on the USIM, the UE shall perform a periodic network selection procedure considering all PLMNs in the same order as in clause 3.2.2.2 when the RPLMN is not a higher-priority PLMN and the signal quality of the access technology of the RPLMN is below the operator-controlled signal threshold per access technology.

[0173] If no PLMN (including the RPLMN) meets the operator-controlled signal threshold criteria, the UE shall perform a normal periodic network selection (as described above) for higher-priority PLMNs without applying the operator-controlled signal threshold per access technology. Example 2 Periodic Network Selection Attempts

[0174] If no operator-controlled signal threshold per access technology is set on the USIM, a UE in automatic mode shall make periodic attempts to find a higher-priority PLMN (including associated access technology) that belongs to the same country as the currently received PLMN (including associated access technology) or to find a higher-priority PLMN (including associated access technology) that uses a shared MCC (e.g., MCC = 901). If the currently received PLMN (including associated access technology) uses a shared MCC, higher-priority PLMNs (including associated access technology) using any non-shared MCC shall also be considered. For ranking of PLMNs, the UE shall use the order used in clause 3.2.2.2. In the absence of an associated access technology identifier, the mobile device shall assume that all access technologies provided by the PLMN have equal priority. Additionally, the periodic network selection shall not cause a change in the access technology within the registered PLMN.

[0175] When disaster conditions apply, a UE in automatic mode that is registered to a PLMN in the "Forbidden PLMN" data field in the SIM / USIM may make periodic attempts to find an allowable PLMN that belongs to the same country as the currently received PLMN.

[0176] If the UE has stored an equivalent PLMN list, the UE shall only select a PLMN if that PLMN has a higher priority than all PLMNs that belong to the same country as the currently registered PLMN in the equivalent PLMN list.

[0177] Note 1: In the context of this 3GPP TS, the term country should not be interpreted as a political entity, but rather as a single Mobile Country Code (MCC). For example, the United States and India have multiple MCCs. In fact, such cases are considered exceptions in the 3GPP specifications. For all other countries, multiple MCCs may be used; however, this has not been considered in the specifications and there may be adverse effects, such as the UE being unable to detect multiple MCCs within the same country.

[0178] Note 2: There are some cases where one MCC represents multiple political entities or the MCC is not related to a political entity. Examples include shared MCCs, where international satellite operations typically use a shared MCC with the value 901.

[0179] Note 3: For the purpose of PLMN selection, the associated access technology using a shared MCC is limited to satellite NG-RAN.

[0180] In the case where multiple EHPLMNs are available, when an EHPLMN has already been selected, the UE shall not attempt to select a higher-priority EHPLMN. The priority of an EHPLMN only applies when the UE is on the VPLMN and multiple EHPLMNs are available.

[0181] The UE shall only make reselection attempts when in the idle mode. In the case of a GPRS terminal, the UE shall only make reselection attempts when in the idle or standby mode. In the case of a terminal operating E-UTRA and / or NR, the UE shall only make reselection attempts when in the idle or RRC inactive mode.

[0182] In the case where the UE receives an eMBMS delivery service while in the idle mode, the UE may defer higher-priority PLMN searches and any reselection attempts until the eMBMS delivery service has been completed or stopped.

[0183] The interval between attempts shall be stored in the SIM / USIM.

[0184] Only the service provider shall be able to select which of the previous cases shall be used for periodic network selection attempts and set the interval value.

[0185] For a UE that only supports access technologies other than: NB-IoT, GERAN EC-GSM-IoT, and Category M1 of E-UTRAN enhanced MTC

[17] , the UE shall interpret the interval value as being between 6 minutes and 8 hours, in steps of 6 minutes.

[0186] For a UE that supports only any one or combination of the following: NB-IoT, GERAN EC-GSM-IoT

[18] , and E-UTRAN enhanced MTC Category M1

[13] , the UE shall interpret the interval value as being between 2 hours and 240 hours, with a step size of 2 hours between 2 hours and 80 hours, and a step size of 4 hours between 80 hours and 240 hours.

[0187] For a UE that supports a combination of IoT and non-IoT access technologies, the UE shall interpret the interval value based on the access technology currently used by the UE to determine the timer value as described above.

[0188] An interval value shall be specified to indicate that no periodic attempt shall be made.

[0189] In the case where the permit value does not exist in the SIM / USIM or the SIM / USIM is Release 1 and thus does not contain a data field, a default value of 60 minutes shall be used by UEs other than those that support only any one or combination of the following: NB-IoT, GERAN EC-GSM-IoT

[18] , and E-UTRAN enhanced MTC Category M1

[17] . For those UEs, a default value of 72 hours shall be used.

[0190] Note: Using a value less than 60 minutes may result in excessive UE battery consumption. Periodic network selection based on operator-controlled signal threshold criteria

[0191] If the operator-controlled signal threshold according to the access technology is set on the USIM, the UE shall perform the periodic network selection process considering all PLMNs with a higher or lower priority than the current PLMN in the same order as in Clause 3.2.2.2, subject to the following conditions: - If the access technology signal quality of the target PLMN is equal to or higher than the operator-controlled signal threshold according to the access technology, the UE shall select the higher priority PLMN / access technology combination. - The UE shall select the lower priority PLMN / access technology combination only if the access technology signal quality of the RPLMN is lower than the operator-controlled signal threshold according to the access technology and the access technology signal quality of the target PLMN is equal to or higher than the operator-controlled signal threshold according to the access technology. - If the RPLMN is a higher priority PLMN and the access technology signal quality of the RPLMN is equal to or higher than the operator-controlled signal threshold according to the access technology, the UE shall not perform a periodic attempt.

[0192] If no PLMN (including the RPLMN) meets the operator-controlled signal threshold criteria, the UE shall perform normal periodic network selection for a higher priority PLMN (as described above), without applying the operator-controlled signal threshold according to the access technology.

Claims

1. A method for network selection by a user equipment UE, comprising: Obtaining a carrier-controlled signal threshold criterion, the carrier-controlled signal threshold criterion at least including a first carrier-controlled signal threshold for a first access technology; Selecting one or more public land mobile networks PLMNs, the one or more PLMNs including one or more candidate cells having a signal metric that meets a network selection criterion, the network selection criterion being at least partially based on the first carrier-controlled signal threshold for the first access technology; Registering with a first PLMN among the one or more PLMNs; And When the first PLMN is a home PLMN HPLMN and the current signal metric of the serving cell of the first PLMN is equal to or higher than the first carrier-controlled signal threshold, avoiding triggering a periodic network selection attempt.

2. The method according to claim 1, further comprising: Selecting the cell from among the one or more candidate cells by comparing a first signal metric of the cell with the first carrier-controlled signal threshold; And Selecting the first PLMN based on the selection of the cell, wherein the first PLMN includes the cell and the first signal metric exceeds the first carrier-controlled signal threshold.

3. The method according to any one of claims 1 to 2, further comprising: Obtaining a cell-provided cell selection criterion from the one or more PLMNs, wherein the cell-provided cell selection criterion includes a cell signal level threshold, and wherein the network selection criterion is based on a combination of the first carrier-controlled signal threshold and the cell signal level threshold.

4. The method according to claim 3, wherein the network selection criterion includes: A first criterion based on one of a minimum value, a maximum value, or an average value of the cell signal level threshold and the first carrier-controlled signal threshold, and wherein the cell signal level threshold and the first carrier-controlled signal threshold are for the same signal metric.

5. The method according to claim 3, wherein the network selection criterion at least includes: A first criterion based on the first carrier-controlled signal threshold for a first signal metric; And A second criterion based on the cell signal level threshold for a second signal metric.

6. The method according to any one of claims 1 to 5, Wherein when the first signal metric of at least a first candidate cell of the first PLMN meets the first carrier-controlled signal threshold, the one or more PLMNs include the first PLMN, Wherein when the second signal metric of at least a second candidate cell of a second PLMN meets the first carrier-controlled signal threshold, the one or more PLMNs include the second PLMN, and Wherein the one or more candidate cells include the first candidate cell and the second candidate cell.

7. The method according to any one of claims 1 to 5, wherein the operator-controlled signal threshold criterion includes a second operator-controlled signal threshold for a second access technology, and wherein selecting the one or more PLMNs includes: comparing a first signal metric of a first plurality of candidate cells for the first access technology with the first operator-controlled signal threshold; and comparing a second signal metric of a second plurality of candidate cells for the second access technology with the second operator-controlled signal threshold, wherein when the first PLMN includes at least one candidate cell among the first plurality of candidate cells having a first signal metric that meets the first operator-controlled signal threshold, the one or more PLMNs include the first PLMN; and wherein when a second PLMN includes at least one candidate cell among the second plurality of candidate cells having a second signal metric that meets the second operator-controlled signal threshold, the one or more PLMNs include the second PLMN.

8. The method according to claim 7, wherein the operator-controlled signal threshold criterion does not include a third operator-controlled signal threshold for a third access technology, and the method further comprises: When selecting the one or more PLMNs, the third plurality of candidate cells for the third access technology are excluded from consideration.

9. The method according to claim 7, wherein the operator-controlled signal threshold criterion does not include a third operator-controlled signal threshold for a third access technology, the method further comprising: obtaining a cell-provided cell selection criterion from one or more candidate cells for the third access technology, the cell-provided cell selection criterion including a cell signal level threshold; configuring the third operator-controlled signal threshold based on the cell signal level threshold; and obtaining a third signal metric for a third plurality of candidate cells for the third access technology, wherein when the first signal metric of a third candidate cell of a third PLMN meets the third operator-controlled signal threshold, the one or more PLMNs include the third PLMN.

10. The method according to claim 7, wherein the operator-controlled signal threshold criterion does not include a third operator-controlled signal threshold for a third access technology, the method further comprising: obtaining a cell-provided cell selection criterion from one or more candidate cells for the third access technology; ignoring any operator-controlled signal threshold criterion for the third access technology in the network selection criterion; and configuring the network selection criterion based on a PLMN selector list and the cell-provided cell selection criterion.

11. The method according to any one of claims 1 to 10, further comprising: triggering a subsequent PLMN selection when the first PLMN has a lower priority than a second PLMN and the current signal metric of a serving cell of the first PLMN is lower than the first operator-controlled signal threshold.

12. The method according to any one of claims 1 to 11, further comprising: disabling periodic network selection attempts when the current signal metric of the serving cell of the first PLMN is equal to or higher than the first operator-controlled signal threshold.

13. The method according to any one of claims 1 to 12, wherein the periodic network selection attempt includes at least one of the following: if the operator-controlled signal threshold criterion is enabled at the UE, using the operator-controlled signal threshold criterion for the subsequent PLMN selection, or if the operator-controlled signal threshold criterion is disabled or no longer exists at the UE, using the cell-provided cell selection criterion for the subsequent PLMN selection.

14. The method according to any one of claims 1 to 13, further comprising: enabling a timer T for triggering the periodic network selection attempt when the serving cell of the first PLMN has a first signal metric that no longer meets the first operator-controlled signal threshold; and triggering the subsequent PLMN selection when the first signal metric of the serving cell does not meet the first operator-controlled signal threshold after the expiration of the timer.

15. The method according to any one of claims 1 to 14, wherein setting the condition includes: enabling the periodic network selection attempt for subsequent PLMN selection when the serving cell is roaming in a PLMN having a lower priority than the HPLMN.

16. A method for network selection by a user equipment UE, comprising: obtaining an operator-controlled signal threshold criterion, the operator-controlled signal threshold criterion including an operator-controlled signal threshold for each access technology among a plurality of access technologies; obtaining a cell-provided cell selection criterion, the cell-provided cell selection criterion including a cell signal level threshold; and selecting a public land mobile network PLMN for registration by the UE, wherein selecting the PLMN includes: when the UE is in a first area where all candidate cells are using one access technology among the plurality of access technologies, selecting a first PLMN from one or more PLMNs including one or more candidate cells and registering with the first PLMN, the one or more candidate cells having a signal metric that meets the operator-controlled signal threshold for the corresponding access technology for each of the one or more candidate cells, and when the UE is in a second area where at least one candidate cell is using an access technology for which the operator-controlled signal threshold is not included in the operator-controlled signal threshold criterion, selecting a second PLMN and registering with the second PLMN, the second PLMN being based on PLMN priority ranking and including the at least one candidate cell having a signal metric that meets the cell-provided cell selection criterion.

17. The method according to claim 16, further comprising: when the UE moves from the first area to the second area or from the second area to the first area, selecting a new PLMN using the operator-controlled signal threshold criterion in the first area or the cell-provided cell selection criterion in the second area.

18. The method according to claim 16, further comprising: When the current signal metric of the serving cell of the first PLMN is equal to or higher than the operator-controlled signal threshold, avoiding triggering a periodic network selection attempt for selecting a new PLMN.

19. A user equipment UE, comprising: A communication unit; And A processing system configured to control the communication unit to implement any of the methods according to claims 1 to 18.

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