WO2020000237A1

WO2020000237A1 - Enhancement for public land mobile network selection procedure followed by cell selection procedure

Info

Publication number: WO2020000237A1
Application number: PCT/CN2018/093040
Authority: WO
Inventors: Rishika TINDOLA; Ankur Srivastava; Muralidharan Murugan; Jun Deng; Hewu GU; Kishore Kumar YANNAKULA
Original assignee: Qualcomm Incorporated
Priority date: 2018-06-27
Filing date: 2018-06-27
Publication date: 2020-01-02

Abstract

Systems, apparatuses, and methods for enhancement for public land mobile network (PLMN) and cell selection procedures wherein a PLMN selection procedure is followed by a cell selection procedure. The PLMN selection procedure may incorporate a cell selection criterion, for example, as is used in the subsequent cell selection procedure, into PLMN selection, for example, to screen out certain unsuitable PLMN whose cell may likely fail the cell selection procedure. The cell selection procedure, on the other hand, may leverage information on cells and PLMNs gathered during the preceding PLMN selection procedure to aid in cell selection, for example, to reduce time and computation overhead. In addition, the information may also help a subsequent PLMN selection.

Description

ENHANCEMENT FOR PUBLIC LAND MOBILE NETWORK SELECTION PROCEDURE FOLLOWED BY CELL SELECTION PROCEDURE

BACKGROUND

This disclosure relates generally to wireless communications, and more specifically, to enhancement for public land mobile network (PLMN) selection procedure followed by cell selection procedure.

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) . Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system, or a New Radio (NR) system) . A wireless multiple-access communications system may include a number of base stations or access network nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE) .

Generally speaking, a public land mobile network is a network (operated by an operator) for purposes of providing land mobile telecommunication services to the public. A PLMN may be identified by the Mobile Country Code (MCC) and the Mobile Network Code (MNC) . Each operator providing mobile services may have its own PLMN. PLMNs may interconnect with other PLMNs and public switched telephone networks (PSTN) for telephone communications or with internet service providers for data and internet.

In some systems, a UE may perform a PLMN search procedure to select a PLMN for communication services (e.g., cell camping, registration, or other communication activities) . The PLMN selection procedure may include various operations, such as searching for a number of available PLMNs and selecting a PLMN among them. The PLMN selection procedure is generally followed by a cell selection procedure, whereby a cell of the selected PLMN (or another PLMN in some scenarios) may be chosen for communication services. In general, multiple cells may belong to a same PLMN, and multiple PLMNs may share a same cell. As used herein, the term “procedure, ” as in “PLMN selection procedure” or “cell selection procedure, ” refers to a series of actions or operations, as a whole, conducted for a specific purpose, e.g., to select a PLMN, or to select a cell, respectively.

SUMMARY

Systems, apparatuses, and methods are provided for enhancement for public land mobile network and cell selection procedures wherein a PLMN selection procedure is followed by a cell selection procedure. The PLMN selection procedure may incorporate a cell selection criterion, such as one used in the subsequent cell selection procedure, into PLMN selection, for example, to screen out certain unsuitable PLMN whose cell may fail the cell selection procedure. The cell selection procedure, on the other hand, may leverage information on cells and PLMNs gathered during the preceding PLMN selection procedure to aid in cell selection, for example, to reduce time and computation overhead. In addition, the information may also help a subsequent PLMN selection.

In an aspect, a method for wireless communications is provided. The method may be performed by a UE or component (s) thereof. A public land mobile network may be detected. It may be determined whether to add the PLMN to a list of available PLMNs for PLMN selection, based on a cell selection criterion.

In another aspect, a user equipment is provided. The UE may include a receiver and a processor coupled to a memory. The receiver is configured to receive signals from one or more base stations. The processor may be configured to detect a public land mobile network based on the received signals. The processor may be further configured to determine whether to add the PLMN to a list of available PLMNs for PLMN selection, based on a cell selection criterion.

In another aspect, an apparatus of wireless communications is provided. The apparatus may include means for detecting a public land mobile network. The apparatus may further include means for determining whether to add the PLMN to a list of available PLMNs for PLMN selection, based on a cell selection criterion.

In yet another aspect, a non-transitory computer-readable medium having instructions stored thereon is provided. The instructions may include codes executable for a user equipment to perform detecting a public land mobile network (PLMN) . The medium may further include codes for determining whether to add the PLMN to a list of available PLMNs for PLMN selection, based on a cell selection criterion.

In various aspects, the cell selection criterion for a cell may be based at least on a measurement metric of the cell and a minimal value of the measurement metric, wherein the minimal value may be signaled in a system information block by the cell.

In various aspects, the cell selection criterion is checked for each cell of one or more cells of a PLMN to determine whether the cell selection criterion is satisfied for the cell. Furthermore, whether the PLMN would be added to the list may be based on an outcome of the checking. For example, the PLMN may be determined to be added to the list if the cell selection criterion is satisfied for at least one of the one or more cells. (And if so, the cell selection criterion need not be checked for another cell of the PLMN not among the one or more cells. ) On the other hand, the PLMN may be determined to not be added to the list if the cell selection criterion is not satisfied for any of the one or more cells.

In various aspects, a PLMN may be added to the list, but with an indication of low signal strength, if the cell selection criterion is not checked for any cell of the PLMN.

In various aspects, a list of available PLMNs may be displayed to a user for manual PLMN selection before another PLMN is added to the list. The displayed list may be updated if a new PLMN is added to the list. In some examples, the list may be updated for a first PLMN before a second PLMN if the first PLMN has a higher signal quality than the second PLMN.

In still another aspect, a method of wireless communications is provided. The method may include obtaining information regarding one or more cells, corresponding to one or more public land mobile networks, during a PLMN selection procedure in which a PLMN is selected. The information may include further information relating to a cell selection criterion. The method may also include storing the information in a database. The method may further include selecting a cell of the selected PLMN based on the database.

In another aspect, a user equipment is provided. The UE may include a memory and a processor coupled to the memory. The processor may be configured to obtain information regarding one or more cells, corresponding to one or more public land mobile networks, during a PLMN selection procedure in which a PLMN is selected. The information may include further information relating to a cell selection criterion. The processor may be further configured to store the information in a database in the memory. The processor may be further configured to select a cell of the selected PLMN based on the database.

In another aspect, an apparatus of wireless communications is provided. The apparatus may include means for obtaining information regarding one or more cells, corresponding to one or more public land mobile networks, during a PLMN selection procedure in which a PLMN is selected. The information may include further information relating to a cell selection criterion. The apparatus may also include means for storing the information in a database. The apparatus may further include means for selecting a cell of the selected PLMN based on the database.

In another aspect, a non-transitory computer-readable medium having instructions stored thereon is provided. The instructions may include codes executable for a user equipment to perform obtaining information regarding one or more cells, corresponding to one or more public land mobile networks, during a PLMN selection procedure in which a PLMN is selected. The information may include further information relating to a cell selection criterion. The medium may also include codes for storing the information in a database. The medium may further include codes for selecting a cell of the selected PLMN based on the database.

In various aspects, the cell selection criterion for a particular cell may be based at least on a measurement metric of the particular cell and a minimal value of the measurement metric, wherein the minimal value may be signaled in a system information block by the particular cell.

In various aspects, the further information may include one or more parameters of the cell selection criterion obtained from a system information block of a cell of the one or more cells. For a cell of the one or more cells, the cell selection criterion may be checked to determine whether the cell selection criterion is satisfied for the cell, based at least on the one or more parameters stored in the database.

In various aspects, the further information may include an indication whether the cell selection criterion, checked during the PLMN selection procedure, is satisfied for a cell of the one or more cells. For cell selection, a first cell for which the cell selection criterion is satisfied may be prioritized over a second cell for which the cell selection criterion is not satisfied, based on the indication stored in the database.

In various aspects, the information may further include system information obtained from one or more broadcast channels of a cell of the one or more cells.

Various features and advantages of this disclosure are described in further details below. Other features will be apparent from the description, drawings, and/or the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative and non-limiting drawings are provided to aid in the description of various aspects and implementations. Unless specified otherwise, like reference symbols indicate like elements.

FIG. 1 illustrates a wireless communications system in accordance with the present disclosure.

FIG. 2 illustrates techniques of incorporating a cell selection criterion into a PLMN selection procedure in accordance with the present disclosure.

FIG. 3 illustrates techniques of aiding cell/PLMN selection with cell/PLMN information gathered during PLMN selection in accordance with the present disclosure.

FIGs. 4 and 5 illustrate various methods that support enhancement for PLMN selection procedure followed by cell selection procedure in accordance with the present disclosure.

FIGs. 6 and 7 illustrate various apparatuses that support enhancement for PLMN selection procedure followed by cell selection procedure in accordance with the present disclosure.

DETAILED DESCRIPTION

Generally speaking, a UE may first perform a PLMN selection procedure, e.g., during an idle mode, to select a public land mobile network (which may comprise one or more cells of same or different radio access technologies) . Subsequently, the UE may employ a cell selection procedure to select a cell from the selected PLMN for camping or other communication activities.

Traditionally and in many designs, interactions between the above two selection procedures may be limited, apart from a selected PLMN being provided to the subsequent cell selection procedure by the preceding PLMN selection procedure. Although the PLMN selection procedure may assess a cell’s signal quality, its criterion may be different from a cell selection criterion, used in the subsequent cell selection procedure, which may be specific to a particular cell. Thus, in some cases, especially when a user manually selects a PLMN, the selected PLMN could be less suitable and may in some cases likely fail the later cell selection procedure. If the cell selection procedure fails, the PLMN selection procedure would be attempted again and cell camping/service may be delayed.

The above problem could be alleviated if a UE incorporates a cell selection criterion into the PLMN selection procedure. For example, after a PLMN is detected, the cell selection criterion can be checked for one or more cells of the PLMN. If none of the cells would satisfy the cell selection criterion, it may be quite likely that the PLMN, even if selected, may fail the subsequent cell selection procedure, and thus it may be beneficial not to select this particular PLMN. Such a “prescreening” may help improve user experience when the PLMN selection procedure produces PLMN selection candidates more suitable for cell selection.

Another area to enhance user experience lies in making PLMN selection more responsive to a user. In many current implementations of manual PLMN selection, a UE may display a list of available PLMNs (from which the user can select a PLMN) only after the UE completes a PLMN search. Since a PLMN search may take minutes to finish, some users may find such a waiting period less appealing. To address this problem, a UE may display a “partial” list of PLMNs, without waiting for the full list compiled at the end of the PLMN search, as the PLMN search progresses. For example, a newly detected PLMN may be displayed as soon as the PLMN passes the cell selection criterion; a user may decide to choose this PLMN and exit the PLMN selection procedure.

Moreover, information regarding cells/PLMNs, obtained during PLMN search (in the PLMN selection procedure) , may also help subsequent cell selection and PLMN selection procedures. For example, cell information, such as parameters of the cell selection criterion, may be cached during the PLMN selection procedure, as a UE scans frequency spectrum for cells and retrieves system information from a detected cell to identify the PLMN. The cached cell/PLMN information can be stored in a database and later be used during cell/PLMN selection procedures to improve operation efficiency. For example, the cached parameters of a cell may be reused without one or more channels of the cell being decoded again.

Aspects of the disclosure introduced above are described below in the context of a wireless communications system. Illustrative and non-limiting examples of designs and techniques supporting enhancement for PLMN selection procedure followed by cell selection procedure are then described. Aspects of the disclosure are illustrated by and described with reference to various apparatus diagrams, system diagrams, and flowcharts.

FIG. 1 illustrates, as an example, a wireless communications system 100 in accordance with the present disclosure. The wireless communications system 100 generally include user devices (e.g., UEs 110) and network devices (e.g., base stations 120 and entities of a core network 130) . Examples of the wireless communications system 100 may include various wireless network technologies, such as LTE or NR, as developed and standardized by the Third Generation Partnership Project (3GPP) .

A user equipment generally refers to a device (e.g., of an end-user) that utilizes wireless communication service provided by a wireless communication network. As illustrated, a UE 110 may take a variety of forms, such as a cellphone, a computation device, a machine-type-communications (MTC) or Internet-of-Things (IoT) device, or a vehicular device, and so on. UEs 110 may be dispersed throughout the wireless communications system 100, and each UE 110 may be stationary or mobile. As used herein, a “user equipment” may also be referred to as a subscriber station, an access terminal, a remote terminal, a handset, a user device, or generally a wireless communication device or some other suitable terminology in the context.

A base station generally refers to a network device that communicates wirelessly (e.g., via over-the-air radio channel) with user devices. Base stations 120 may communicate with one another and/or with the core network 130, e.g., through backhaul links or other network nodes. Base stations 120 often serve as entry points for a user equipment to access communication services provided by a wireless communication network. Base stations 120 (and in some examples, with other entities) may constitute a radio access network (RAN) , which connects UEs 110 to the core network 130 via certain radio access technology (RAT) , such as LTE or NR. As used herein, a “base station” may also be referred to as a base transceiver station, a radio base station, an access point, or some other suitable terminology in the context.

In general, a base station 120 may communicate with a UE 110 using communication resources in time, frequency, and/or space. Communications may occur in two directions: “downlink” (or “forward link” ) from the base station 120 to the UE 110; or in reverse, “uplink” (or “reverse link” ) from the UE 110 to the base station 120. Downlink and uplink transmissions may take place on same or different frequency bands and during same or different time instances. In terms of time resources, time intervals of transmission may be organized according to a “frame” structure. A frame may further be divided into a number of subframes or slots, each further containing a number of symbols, and so on. In terms of frequency resources, a variety of frequency bands (e.g., ranging from ultra-high frequency to extremely-high frequency) may be used. The frequency bands may be “licensed” (e.g., to an operator exclusively) , or “unlicensed” (or “shared” ) (e.g., shared by general users subject to interference and coexistence regulation) . On a frequency band, a “carrier” may generally refer to a set of radio frequency spectrum resources supporting uplink and/or downlink communications, such as transmission of physical signals or channels. In some examples a carrier may be made up of multiple sub-carriers (e.g., waveform signals of multiple different frequencies) . In terms of spatial resources, base stations 120 and/or UEs 110 may communicate on one or more (physical or virtual) antenna ports, for example, based on various single-user or multi-user, Multiple-Input and Multiple Output (MIMO) techniques, such as spatial diversity, multiplexing, or beamforming, and so on. Multiple antennas may be co-located or distributed in diverse geographic locations.

A base station 120 may operate one or more “cells” 122. The term “cell” generally refers to a logical entity used for communication with a base station (e.g., over one or more carriers) , and in some context, may also refer to a portion of a geographic coverage area (e.g., a sector) over which the logical entity operates. An identifier (e.g., a cell identity) may be associated with a cell to distinguish the cell from another cell. A UE 110 may register and communicate with one or more cells 122 (e.g., serving cells) while monitoring other cells 122 (e.g., neighbor cells) .

The core network 130 may include a network of servers, gateways, or other devices, which may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. Examples of the core network 130 may include an evolved packet core (EPC) in a LTE network. A base station 120 may communicate with a gateway 132 to access the core network 130. The gateway 132 may incorporate a mobility management entity (MME) and/or a serving gateway (SGW) , and implement control plane and/or user plane protocols. The gateway 132 may manage non-access stratum (e.g., control plane) functions such as mobility, authentication, and bearer management for UEs 110 served by the base station 120. The gateway 132 may also route user IP data to another gateway 134 connected to a packet data network (PDN) 140. The gateway 134, such as a PDN gateway (PGW) , may transport IP packets between the PDN 140 and a UE 110 accessing the PDN 140 via a base station 120 and the core network 130. The gateway 134 may also provide IP address allocation as well as other functions. The core network 130 may also include other nodes or entities. For example, subscriber information or user profile may be stored in a server 136, such as a home subscriber server (HSS) , which may be queried, e.g., for user authentication, registration, or billing, etc.

In general, a packet data network may be any packet (e.g., IP) based network. A UE 110 may communicate with the PDN 140 for a variety of applications or services. Examples of the PDN 140 may include an operator’s service network, an IP Multimedia Subsystem (IMS) , or generally the Internet. The IMS may provide voice, video, or other multimedia applications (such as voice over IP call) across various types of communication networks.

The wireless communications system 100 may be a packet-based network that operate according to a layered protocol stack. In the user plane, communications on a bearer at Packet Data Convergence Protocol (PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may in some cases perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, a Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 110 and a base station 120 or core network 130 supporting radio bearers for user plane data. At a Physical (PHY) layer, transport channels may be mapped to physical channels, which are transmitted over a physical wave-propagation medium (e.g., over the air or space) .

Besides communicating with a wireless wide area network (WWAN) , a UE110 may communicate with a wireless local area network (WLAN) , such as a Wireless-Fidelity (Wi-Fi) network. A WLAN 150 may include a wireless access point (AP) , such as a wireless “hotspot” or “router” coupled to the Internet. A user device served by a wireless access point may also be referred to as an access terminal (AT) . An AP 152 may wirelessly communicate with a UE 110 and may relay packetized communication data (e.g., IP packets) between the UE 110 and the Internet (or another AT) . A WWAN (e.g., the core network 130) may support inter-networking (including aggregation) with a WLAN, and a UE 110 may communicate with both a base station 120 and an AP 152.

For illustrative purposes, the following examples and figures may be described with reference to the user or network devices of FIG. 1; however, other types of user or network devices may be used in same or other examples without limiting the scope of the present disclosure.

FIG. 2 illustrates, as an example, techniques of incorporating a cell selection criterion into a PLMN selection procedure in accordance with the present disclosure. Viewed from perspectives of layered protocol stacks, PLMN selection may generally involve operations from both an access stratum (AS) layer 210 and a non-access stratum (NAS) layer 220. The AS layer 210 generally refers to protocol stacks between a UE and a radio access network (e.g., a base station) , while NAS layer 220 between a UE and a core network. At a UE 110, the NAS layer 220 may initiate PLMN selection by requesting the AS layer 210 to report a list of available PLMNs (e.g., a PLMN list 230) , from which a PLMN is to be selected for a subsequent cell selection procedure.

At the AS layer 210, to generate the PLMN list 230, a PLMN searcher 212 may scan a number of frequency channels within supported frequency bands for potential cells/PLMNs. As illustrated in this example, a UE 110 may receive signals from multiple cells (e.g., corresponding to multiple base stations 120) , based on which the UE 110 may detect the presence of one or more cells, measure signal quality of the cells, obtain system information from the cells (e.g., by decoding one or more broadcast channels of the cells) , and so on. In some systems, a UE 110 may read a list of PLMN identities, e.g., MCCs/MNCs, from a system information block transmitted by a cell; for example, system information block 1 (SIB1) in LTE (transmitted in a broadcast channel) may contain identities of one or more PLMNs to which the cell belongs (i.e., the same cell can be shared by multiple PLMNs) . Having detected a cell, a UE 110 may identify the associated PLMNs. In some cases, a UE 110 may read a list of PLMNs from the strongest cell on each carrier. A new PLMN may be added to the PLMN list 230 as the search progresses.

In addition, the PLMN searcher 212 may also measure signal quality of a PLMN (that is, of a cell of the PLMN) . Generally speaking, the signal quality may be based on a measurement metric on a reference signal of a cell of the PLMN. The reference signal may generally refer to any signal transmitted to support cell measurement. An example of a measurement metric may be reference signal received power (RSRP) , which may be defined as a linear average of received energy on resource elements of an OFDM symbol carrying a reference signal. Another example of a measurement metric may be reference signal received quality (RSRQ) , which may be defined as a ratio between RSRP and an averaged received total power of an OFDM symbol carrying a reference signal. Compared to RSRP, RSRQ may reflect a level of signal to noise and inference ratio with respect to a reference signal.

If a UE 110 measures multiple cells for a same PLMN, the UE 110 may choose a higher (or highest) measurement value to represent the signal quality of the measured PLMN. In some examples, A PLMN whose RSRP is greater than or equal to a threshold (e.g., -110 dBm) may be designated as having “high quality” and reported as such to the NAS layer 220, while a “low quality” PLMN (i.e., not meeting the above “high quality criterion” ) may be reported along with its measured signal quality (e.g., RSRP values) .

Nevertheless, the “high quality criterion” for a PLMN, used during the PLMN selection procedure, may not fully align with a cell selection criterion used in a subsequent cell selection procedure; there is a risk that a PLMN may be selected but its cells may fail the cell selection procedure.

Generally speaking, a cell selection criterion tailors to a specific cell, which may broadcast one or more parameters to control whether a UE can select the cell (e.g., for camping or service) when receiving the cell’s signal at a certain quality level. For example, the cell selection criterion may be based at least on a measurement metric of the cell and a minimal value of the measurement metric as signaled in a system information block by the cell. In some systems, a cell selection criterion (also known as the “S” criterion) may be defined as:

Srxlev > 0 and Squal > 0

where Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) –Pcompensation; and

Squal = Qqualmeas – (Qqualmin + Qqualminoffset) .

The Qrxlevmeas is the RSRP measured by the UE. Qrxlevmin is the minimum required RSRP signaled within SIB1. Qrxlevminoffset is a measurement offset optionally included within SIB1. Pcompensation is defined as a maximal value between Pemax-Pumax and 0, where Pemax is the maximum allowed uplink transmit power within the cell, and Pumax is the maximum transmit power capacity of the UE. For a UE having insufficient transmit power (such that Pumax is less than Pemax) , a positive value of Pcompensation may make the cell selection criterion more difficult to achieve, thus thwarting the UE from camping on the cell. The Pemax parameter is included in SIB1. The Qqualmeas is RSRQ measured by the UE. Qqualmin is the minimum required RSRQ signaled within SIB1, and Qqualminoffset is optionally included within SIB1. Additional offsets (other than Qrxlevminoffset and Qqualminoffset) may also be used in the cell selection criterion.

If a cell selection criterion is satisfied (e.g., Srxlev and Squal are both greater than 0) , the cell may be selected subject to other conditions of the cell selection procedure (e.g., cell not barred and belonging to at least one tracking area which is not forbidden) ; on the other hand, if the cell selection criterion is not satisfied, the cell may not be selected.

Typically a UE 110 can obtain the (cell-specific) parameters of a cell selection criterion from a system information block (e.g., SIB1) transmitted by a cell. Because in some systems both the PLMN identities and the parameters of cell selection criterion are contained in the same system information block (e.g., SIB1) , a UE 110 may read the cell selection criterion parameters along with the PLMN identities during the PLMN search without extra efforts (e.g., by reading both information from a decoded SIB1 from a detected cell) . Furthermore, checking whether a cell selection criterion is satisfied (or passed) may not incur significant overhead because the cell selection criterion may reuse measurement metrics already obtained for PLMN selection purposes (e.g., RSRP) .

At the AS layer 210, a UE 110 may check a cell selection criterion (or “S-check” in short) for one or more cells of a detected PLMN before adding the PLMN to the PLMN list 230. If none of the cells would pass the S-check, the PLMN may not be added to the PLMN list 230 (and thus may not be selected at the NAS layer 220) . But if at least one cell of the PLMN passes the S-check, the PLMN may be added to the PLMN list 230, and the S-check may be skipped for other cells of the same PLMN. Such a “prescreening” of a candidate PLMN based on the cell selection criterion used in the subsequent cell selection procedure may prevent an unsuitable PLMN being selected during the PLMN selection procedure. Since the PLMN search may be stopped at any time (e.g., when a user cancels the PLMN search) , and if S-check is not performed on any cell of a PLMN (including the case where the result of S-check is pending) , the PLMN may still be added to the PLMN list 230, but with an indication of “low signal strength, ” which may be used to discourage a user or the NAS layer 220 from selecting this particular PLMN.

At the NAS layer 220, a PLMN selector 222 may cause a PLMN to be selected from the PLMN list 230. As described above, the AS layer 210 may exclude some detected PLMNs from the PLMN list 230 based on a cell selection criterion. A PLMN may be selected automatically or manually. In automatic PLMN selection, the PLMN selector 222 may select a PLMN on its own (e.g., without a user’s manual input) . In contrast, in manual PLMN selection, the PLMN selector 222 may present the PLMN list 230 to a user and wait for a user to select a PLMN from the PLMN list 230. To facilitate manual selection, the PLMN selector 222 may interact with an input/output (I/O) device 240, such as a touch-screen display. For example, the PLMN selector 222 may display the PLMN list 230 on the I/O device 240 and prompt a user to select a PLMN. The I/O device 240 may then capture a user input as to which PLMN is selected by the user, for example, when the user clicks or taps to select a PLMN on the screen. The user’s manual selection is then passed by the I/O device 240 to the PLMN selector 222.

The PLMNs on the PLMN list 230 may be ordered according to certain preference or priority. In automatic PLMN selection, a PLMN with higher priority generally is selected before another PLMN with lower priority; for example, the PLMN with the highest priority among the PLMN list 230 may be selected. In manual PLMN selection, the PLMN list 230 may be displayed in the order of priority (e.g., a higher priority PLMN may be shown as positioned ahead of a lower priority PLMN) ; however, a user may be not bound to follow the priority order to select a PLMN. Various designs or definitions of PLMN priority can be used for a particular system, application, or operator, and so on. For example, the highest priority may be given to a home PLMN (HPLMN) or an equivalent HPLMN (EHPLMN) , followed by PLMN and access technology combinations, in priority order, as defined within a “user controlled PLMN selector with access technology” data file in a Subscriber Identity Module (SIM) card, then followed by PLMN and access technology combinations, in priority order, as defined within an “operator controlled PLMN selector with access technology” data file in the SIM card. Next in terms of priority may be other PLMNs reported as “high quality” (in a random order) , followed by still other PLMNs (not of “high quality” ) in order of decreasing signal quality. In some systems, a UE 110 may search all supported access technologies before a PLMN from the last two lowest ranked PLMN categories is selected.

In some implementations, a PLMN search may take up to a few minutes to complete. Such a time gap may become noticeable to a user who is waiting to select a PLMN, if a list of available PLMNs are to be shown only after the completion of PLMN search. For a better user experience, a “partial” PLMN list may be displayed while the PLMN search is still on-going, and thus a user may be allowed an opportunity to select a PLMN without waiting for the full PLMN list after the completed PLMN search.

To support displaying of partial PLMN list, the PLMN searcher 212 may update the PLMN list 230 dynamically as a detected PLMN is determined to be made available for PLMN selection, for example when a cell of the PLMN passes a cell selection criterion check as described above. The PLMN is added to the PLMN list 230, and the AS layer 210 may report the updated PLMN list 230 to the NAS layer 220. Correspondingly, the PLMN selector 222 may refresh the displayed PLMN list to be in sync with the updated PLMN list 230. Furthermore, the update on the PLMN list 230 (and its displayed version) may occur in order of decreasing signal quality of the respective PLMNs. For example, cell selection criterion may be checked for a first PLMN with higher signal quality (e.g., in RSRP measurement) before a second PLMN with lower signal quality. Thus, the first PLMN may be added to the list and be shown to a user before the second PLMN, while in the meantime the user may decide to select the first PLMN without waiting for more PLMN choices.

FIG. 3 illustrates, as an example, techniques of aiding cell/PLMN selection with cell/PLMN information gathered during PLMN selection in accordance with the present disclosure. A UE 110 may implement a PLMN selection procedure in a PLMN selection module 310 and a (subsequent) cell selection procedure in a cell selection module 320. The PLMN selection module 310 may search and select a PLMN among available PLMNs. In particular, the PLMN selection module 310 may include a PLMN searcher 212 and a PLMN selector 222, and may leverage a cell selection criterion of a subsequent cell selection procedure to enhance the PLMN selection procedure, for example, to avoid selecting a PLMN whose cells may fail the cell selection procedure, as described with reference to FIG. 2.

After the PLMN is selected, the cell selection module 320 may select a cell of the selected PLMN for services, such as camping, registration, or communication. Generally, during a cell selection procedure, a UE 110 attempts to find and select a “suitable” cell which meets certain conditions and/or preferences, such as satisfying a cell selection criterion in terms of signal quality, belonging to the selected PLMN (or the registered PLMN or an equivalent PLMN) , being not barred, and belonging to at least one tracking area which is not forbidden, and so on. The cell selection module 320 may not require any prior knowledge for purposes of cell selection and may scan all radio frequency channels for a suitable cell. Nevertheless, prior knowledge regarding cell/PLMN may facilitate cell selection, and in particular, as the PLMN selection module 310 acquires information on available cells/PLMNs, the cell selection module 320 may leverage such information during cell selection, e.g., to improve efficiency, enhance user experience, and reduce time/computation cost.

A UE 110 may maintain a PLMN database 330 for storing and retrieving information regarding a cell and/or a PLMN. The PLMN selection module 310 may update the PLMN database 330 with new or latest information obtained during the PLMN selection procedure, for example, after a cell of a PLMN is detected. The PLMN database 330 may hold a variety of information on cells and PLMNs, such as frequency carrier, physical cell identity, frequency band, energy measurement, and so on. If system information of a cell is read during the PLMN search, some or all part of the system information can be stored in the PLMN database 330.

The information stored in the PLMN database 330 may facilitate operations of cell selection in various ways. For example, parameters of a cell selection criterion, obtained during PLMN selection, may be stored in the PLMN database 330. As described above with reference to FIG. 2, these parameters may be readily obtainable when the UE 110 attempts to decode a broadcast channel for PLMN identity information (e.g., in SIB1) of a cell. During the subsequent cell selection procedure, the cell selection module 320 may use or reuse the (cached) parameters for checking the cell selection criterion, without decoding the cell’s broadcast channel again, which can help reducing the time/computation expended for checking the cell selection criterion.

As another example, if the cell selection criterion is checked for a cell during the PLMN selection, the PLMN selection module 310 may store in the PLMN database 330 the outcome or result of the S-check: whether the cell selection criterion is satisfied or not. Searching the PLMN database 330, the cell selection module 320 may know whether S-check was earlier performed on a particular cell. In some cases, the cell selection module 320 may skip checking the cell selection criterion again for a cell on which the S-check was checked before. Even if the cell selection module 320 would re-check the cell selection criterion (e.g., because radio conditions of a cell may change) , the cell selection module 320 may prioritize cells that previously passed S-check over other cells that do not. Likely a cell that passed the S-check before would pass the S-check again, and the cell selection module 320 may identify a suitable cell faster than if another cell that failed S-checked had been tried.

In yet another example, for a cell that passes S-check, the cell’s system information such as master information block (MIB) and system information block (SIB) , obtained during PLMN selection, may be stored in the PLMN database 330. If the cell’s PLMN is selected, the cell selection module 320 may use the cached system information to perform cell selection operation, without re-decoding one or more channels (e.g., physical broadcast channel (PBCH) for the MIB, and physical downlink control channel (PDCCH) and physical downlink shared channel (PDSCH) for the SIB) .

Although described in the context of assisting cell selection procedure, the PLMN database 330 may be used to help PLMN selection procedure in analogous ways. For example, a new (or subsequent) PLMN selection may reuse information gathered during a previous PLMN selection for checking cell selection criterion, identifying a cell of a previously detected PLMN, and so on.

FIG. 4 illustrates, as an example, a method 400 that supports enhancement for PLMN selection procedure followed by cell selection procedure in accordance with the present disclosure. The method 400 may encompass various aspects of the techniques described with reference to FIG 2. A UE (or one or more of its components) may implement the method 400 using hardware, firmware, or software, or a combination thereof.

At 410, a public land mobile network may be detected. The PLMN detection may be based on detection of a cell belonging to the PLMN. As generally described with reference to a PLMN searcher 212 in FIG. 2, a UE 110 may scan a number of carriers within supported frequency bands to detect a cell based on received signals from the cell. A cell may transmit various signals/channels, such as synchronization signals, reference signals, and/or broadcast channels, to support cell detection or acquisition. For example, a UE 110 may detect a synchronization signal of a cell and further decode a physical cell identity from the synchronization signal. Subsequently, the UE 110 may decode one or more channels (generally broadcast in nature) to obtain system information of the cell. In some systems, a list of identities of the PLMNs to which the cell belong is contained in a system information block (e.g., SIB1) transmitted by the cell. A PLMN is detected when a UE 110 can identify the PLMN from a detected cell, for example, when the UE 110 reads the PLMN identities from the SIB1 of the cell.

At 420, based on a cell selection criterion, a UE 110 may determine whether to add the (detected) PLMN to a list of available PLMNs for PLMN selection. As generally discussed with reference to a PLMN selector 222 in FIG. 2, a PLMN may be selected from the list of the available PLMNs (either automatically or manually with user input) , and the selected PLMN is provided to a subsequent cell selection procedure whereby a cell (generally from the selected PLMN) is selected to provide communication services (including camping, registration, data/voice communications, etc. )

The cell selection criterion used in the PLMN selection may be identical to the one used in the cell selection procedure, and hence, checking the cell selection criterion during PLMN selection procedure may prescreen out an “unsuitable” PLMN whose cells may fail to pass the same cell selection criterion during the later cell selection procedure. Generally, a cell selection criterion may be designed to impose a cell-specific requirement in terms of signal quality of a cell measured at a UE. For example, the cell selection criterion for a cell may be based at least on a measurement metric (e.g., RSRP and/or RSRQ) and a minimal value of the measurement metric, such as the “S” Criterion (Srxlev > 0 and Squal > 0) discussed with reference to FIG. 2. In some systems (e.g., LTE or NR) , the minimal value, or generally, one or more parameters of the cell selection criterion is signaled in a system information block transmitted by a cell.

For a detected PLMN, a UE 110 may check, for one or more cells of the PLMN, whether the cell selection criterion is satisfied for these cells respectively. Whether the PLMN is to be added to the PLMN list may depend on the outcome (or result) of the checking, e.g., as described with reference to FIG. 2. For example, the PLMN may be added to the list if the cell selection criterion is satisfied for at least one of cells of the PLMN. In such a case, the UE 110 may skip checking cell selection criterion for the rest of cells of the PLMN. However, if none of the detected cells of the PLMN would pass the cell selection criterion checking, the PLMN may be excluded from the PLMN list.

To handle the case where the PLMN selection procedure may be stopped prematurely before the procedure completes (e.g., as when the NAS layer or the user stops or aborts the PLMN selection) , a UE 110 may still add a PLMN to the list but with an indication of “low signal strength” if the cell selection criterion has not been checked for any cell of the PLMN, including the case when the result of a cell selection criterion check, though being performed, is not yet available. Such an indication of “low signal strength” may serve to discourage the selection of this particular PLMN.

In connection with manual PLMN selection, the list of available PLMNs generated during PLMN search may be presented to a user, e.g., as generally described with reference to a PLMN selector 222 and an I/O device 240. A UE 110 may display a partial content of the list as the PLMN search progresses. For example, if a new PLMN is added to the list, the list may be updated and displayed before another PLMN is added to the list. The UE 110 may also update the list in order of decreasing signal quality; for example, the list is updated for a first PLMN before a second PLMN, if the first PLMN has a higher signal quality than the second PLMN. Such an ordering may be achieved by prioritizing the cell selection criterion check for PLMNs of higher signal quality over those of lower signal quality.

FIG. 5 illustrates, as an example, a method 500 that supports enhancement for PLMN selection procedure followed by cell selection procedure in accordance with the present disclosure. The method 500 may encompass various aspects of the techniques described with reference to FIG 3, and may be performed in conjunction with the method 400 described with reference to FIG. 4 (e.g., when the PLMN selection procedure utilizes a cell selection criterion) . A UE (or one or more of its components) may implement the method 500 using hardware, firmware, or software, or a combination thereof.

At 510, information regarding one or more cells, corresponding to one or more public land mobile networks, is obtained during a PLMN selection procedure in which a PLMN is selected. Among the one or more cells, a cell may belong to multiple PLMNs; different cells may belong to different PLMNs. The information may include further information relating to a cell selection criterion. The PLMN selection procedure may encompass aspects of the techniques and the method 400, as described with reference to FIGs. 2 and 4, which leverage the cell selection criterion for purposes of PLMN selection.

Various types of information may be obtained, e.g., as generally discussed with reference to FIG. 3. For example, for a cell of one or more cells (detected during the PLMN search) , the information may comprise: one or more parameters of the cell selection criterion obtained from a system information block of the cell; an indication whether the cell selection criterion, checked during the PLMN selection procedure, is satisfied for the cell; and/or some or all of the system information obtained from one or more broadcast channels of the cell.

At 520, the information may be stored in a database, e.g., a PLMN database 330 described with reference to FIG. 3. The database may be located in a memory or other medium. The term “database” may generally refer to any organized collection of information, which support storing and retrieving particular information item or field from the collection. The database may further support search or query, for example, with respect to cell or PLMN identity or status of previous cell selection criterion check. The database may be updated during a PLMN search (of the PLMN selection procedure) as new or latest information is obtained.

At 530, a cell of the selected PLMN may be selected based on the database, for example, as described with reference to a cell selection module 320 in conjunction with a PLMN database 330 in FIG. 3. The information stored (or cached) in the database may facilitate the subsequent cell selection, which may lead to increased efficiency and reduced computational overhead. For example, during the cell selection, a UE 110 may check whether the cell selection criterion is satisfied for a cell using one or more parameters of the cell selection criterion previously obtained and stored in the database. In another example, during cell selection, a cell may be prioritized over, or tried earlier than, another cell, if the cell selection criterion was previously satisfied for the cell. A UE 110 may identify cells that previously pass the cell selection criterion based on indications of results on cell selection criterion check stored in the database.

FIG. 6 illustrates, as an example, an apparatus 600 that supports enhancement for PLMN selection procedure followed by cell selection procedure in accordance with the present disclosure. The apparatus 600 may include a receiver 610, a transmitter 620, and a PLMN selection logic 630, and may perform various aspects of the techniques and the method 400 described with reference to FIGs. 2 and 4. The apparatus 600 may be embodied by, or reside within, a UE 110 with reference to FIG. 1.

The receiver 610 may be configured to receive signals or channels carrying information such as packets, user data, or control information associated with various information channels. Information may be passed on to other components of the apparatus. The receiver 610 may utilize a single antenna or a set of multiple antennas. The receiver 610 may be configured to receive signals from one or more base stations, based on which a cell may be detected and measured, and system information of the cell may be obtained.

The transmitter 620 may be configured to transmit signals or channels generated by other components of the apparatus. In some examples, the transmitter 620 may be collocated with a receiver 610 in a transceiver module. The transmitter 620 may utilize a single antenna or a set of multiple antennas.

The receiver 610 and transmitter 620 (or a transceiver incorporating both) may be coupled to the PLMN selection logic 630 and may provide means for communications between the apparatus 600 with a base station.

The PLMN selection logic 630 may be a baseband modem or an application processor or may illustrate aspects of a baseband or application processor. The PLMN selection logic 630 or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. Software may comprise codes or instructions stored in a memory or like medium that is connected or in communication with the processor described above. The codes or instructions may cause the processor, the apparatus 600, or one or more components thereof to perform various functions described herein.

The PLMN selection logic 630 may control, coordinate, or execute various functions of PLMN selection, including, e.g., searching for potential PLMNs, identifying available PLMNs for selection, and selecting a PLMN for a subsequent cell selection procedure. The PLMN selection logic 630 may further include a PLMN searcher 632, a PLMN list manager 634, and cell selection criterion checker 636.

The PLMN searcher 632 may provide means for detecting a public land mobile network and may, for example, be configured to perform the method 400 at 410 described with reference to FIG. 4. The PLMN searcher 632 may encompass aspects of the PLMN searcher 212 described with reference to FIG. 2. For example, the PLMN searcher 632 may, in conjunction with the receiver 610, scan frequency carriers within supported bands to search for one or more cells of potential PLMNs. The PLMN searcher 632 may detect the presence of a cell, measure the cell’s signal quality, and identify one or more PLMNs to which the cell belongs, as generally described with reference to FIGs. 2 and 4.

The PLMN list manager 634 may provide means for determining whether to add a (detected) PLMN to a list of available PLMNs for PLMN selection ( “PLMN list” ) , based on a cell selection criterion. The PLMN list manager 634 may be configured to perform the method 400 at 420 described with reference to FIG. 4. The PLMN list manager 634 may also encompass various aspects of the PLMN searcher 212 and PLMN selector 222 pertaining to generating, maintaining, and presenting a PLMN list 230 described with reference to FIG. 2.

The PLMN searcher 632 and the PLMN list manager 634 may be coupled to (or contain) the cell selection criterion checker 636, which may provide means for checking a cell selection criterion for a cell, that is, determining whether the cell selection criterion is satisfied or not for the cell. The cell selection criterion may be as generally described above (e.g., the “S” criterion described with reference to FIG. 2) . For example, a cell selection criterion for a cell may be based at least on a measurement metric of the cell and a minimal value of the measurement metric, wherein the minimal value may be signaled in a system information block by the cell. In particular, the cell selection criterion may be the same criterion used in a subsequent cell selection procedure following the PLMN selection procedure.

For a detected PLMN, the cell selection criterion checker 636 may check the cell selection criterion for one or more cells of the PLMN. Depending on the outcome of the check, the PLMN list manager 634 may determine whether to add the PLMN to the PLMN list (from which a PLMN is to be selected for the subsequent cell selection procedure) as generally described with reference to FIGs 2 and 4. For example, a PLMN is to be added in the list if the cell selection criterion is satisfied for at least one of the cells of the PLMN; not to be added, on the other hand, if the cell selection criterion, when checked, is not satisfied for any of the cells of the PLMN. If a PLMN has one cell passing the cell selection criterion check, the checking for the remaining (unchecked) cells of the same PLMN may be skipped.

In some scenarios when a user stops PLMN selection, the PLMN list manager 634 may still add a PLMN to the PLMN list, but with an indication of “low signal quality, ” if none of the cells of the PLMN has its cell selection criterion checked. Such an indication may be displayed as an attribute of the accompanying PLMN, for example, as a way to alert user or discourage the user from selecting the PLMN.

The PLMN list manager 634 may also cause the PLMN list being displayed (or generally, presented) to a user during a manual PLMN selection procedure, as generally described with reference to FIG. 2 in connection with the PLMN selector 222 and the I/O device 240, and with reference to FIG. 4. For example, a “partial” list may be displayed such that the PLMN list is displayed for a PLMN before another PLMN is added to the list. The displayed list may be updated every time or if a new PLMN is added to the list. The list may be updated in order of decreasing signal quality of the PLMN; for example, the list may be updated for a first PLMN before a second PLMN if the first PLMN has a higher signal quality than the second PLMN.

FIG. 7 illustrates, as an example, an apparatus 700 that supports enhancement for PLMN selection procedure followed by cell selection procedure in accordance with the present disclosure. The apparatus 700 may include a receiver 710, a transmitter 720, and a PLMN/cell selection logic 730, and may perform various aspects of the techniques and the

methods

400 and 500 described with reference to FIGs. 2-5. The apparatus 700 may be embodied by, or reside within, a UE 110 with reference to FIG. 1.

The receiver 710 may be configured to receive signals or channels carrying information such as packets, user data, or control information associated with various information channels. Information may be passed on to other components of the apparatus. The receiver 710 may utilize a single antenna or a set of multiple antennas. The receiver 710 may be configured to receive signals from one or more base stations, based on which a cell may be detected and measured, and system information of the cell may be obtained.

The transmitter 720 may be configured to transmit signals or channels generated by other components of the apparatus. In some examples, the transmitter 720 may be collocated with a receiver 710 in a transceiver module. The transmitter 720 may utilize a single antenna or a set of multiple antennas.

The receiver 710 and transmitter 720 (or a transceiver incorporating both) may be coupled to the PLMN/cell selection logic 730 and may provide means for communications between the apparatus 700 with a base station.

The PLMN/cell selection logic 730 may be a baseband modem or an application processor or may illustrate aspects of a baseband or application processor. The PLMN/cell selection logic 730 or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. Software may comprise codes or instructions stored in a memory or like medium that is connected or in communication with the processor described above. The codes or instructions may cause the processor, the apparatus 700, or one or more components thereof to perform various functions described herein.

The PLMN/cell selection logic 730 may control, coordinate, or execute various functions of PLMN and cell selection. The PLMN/cell selection logic 730 may further include a PLMN selection module 732, a PLMN database manager 734, and a cell selection module 736.

The PLMN selection module 732 may provide means for obtaining information regarding one or more cells, corresponding to one or more public land mobile networks, during a PLMN selection procedure in which a PLMN is selected, and may, for example, be configured to perform the method 500 at 510 described with reference to FIG. 5. The PLMN selection module 732 may generally encompass various aspects of the PLMN selection module 310 described with reference to FIG. 3. In general, the PLMN selection module 732 may provide means for selecting a PLMN, for example, implementing a PLMN selection procedure as generally discussed above. In particular, the PLMN selection module 732 may encompass various aspects of the PLMN selection logic 630 described with reference to FIG. 6 (which, inter alia, may incorporate a cell selection criterion into PLMN selection) .

During the PLMN selection procedure (which includes a PLMN search) , information may be obtained and stored in a PLMN database (e.g., the PLMN database 330 described with reference to FIG. 3) . The stored (or cached) information may contain further information relating to a cell selection criterion as generally described above.

The PLMN database manager 734 may provide means for storing the information in a database (i.e., the PLMN database) and may, for example, be configured to perform the method 500 at 520 described with reference to FIG. 5. The database may reside in a memory or other medium coupled with the PLMN/cell selection logic 730. The PLMN database manager 734 may provide means for reading, writing, or generally managing the information stored in the database, and may be interfaced with the PLMN selection module 732 and the cell selection module 736 for storing and retrieving PLMN/cell information.

A variety of information for a cell/PLMN (e.g., detected during PLMN search) may be stored as generally described with reference to FIG. 3 and 5. For example, the information may contain one or more parameters of the cell selection criterion obtained from a system information block of the cell. The information may also contain an indication whether the cell selection criterion, checked during the PLMN selection procedure, is satisfied for the cell. Or generally, the information may include system information obtained from one or more broadcast channels of the cell. The variety of information may be organized according to an index of PLMN or cell. In some examples, for every PLMN in the database, the database may contain a list of cells (belonging to the PLMN) that are detected during the PLMN search, and for each of these cells, the database may store the frequency or channel number on which the cell is located, energy or cell selection criterion values (e.g., Srxlev/Squal) which may determine how strong the cell was, cell timing information for faster acquisition on the cell, and/or system information such as MIB and SIB1 of the cell.

The cell selection module 736 may provide means for selecting a cell of a selected PLMN based on the database (i.e., using the information stored in the database) and may, for example, be configured to perform the method 500 at 530 described with reference to FIG. 5. The cell selection module 736 may generally encompass various aspects of the cell selection module 320 described with reference to FIG. 3. In general, the cell selection module 736 may provide means for selecting a cell based on a selected PLMN, for example, implementing a cell selection procedure as generally discussed above.

The cell selection module 736 may utilize the PLMN database, which caches information obtained during an earlier PLMN selection procedure, for purposes of cell selection. For example, the cell selection criterion for a cell may be checked using the one or more parameters of the cell selection criterion of the cell stored in the database. Furthermore, a first cell for which the cell selection criterion is satisfied may be prioritized for cell selection over a second cell for which the cell selection criterion is not satisfied, based on the cell selection criterion check indication stored in the database.

The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “exemplary” used herein means “serving as an example, instance, or illustration, ” and not “preferred” or “advantageous over other examples. ” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

As used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an exemplary step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on. ”

Also, as used herein, including in the claims, “or” as used in a list of items (for example, a list of items prefaced by a phrase such as “at least one of” or “one or more of” ) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) .

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a digital signal processor and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration) .

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described above can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media can include random access memory (RAM) , read-only memory (ROM) , electrically erasable programmable read only memory (EEPROM) , compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, digital subscriber line, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

A method of wireless communications, comprising:

detecting a public land mobile network (PLMN) ; and

determining whether to add the PLMN to a list of available PLMNs for PLMN selection, based on a cell selection criterion.
The method of claim 1, wherein the cell selection criterion for a cell is based at least on a measurement metric of the cell and a minimal value of the measurement metric, the minimal value being signaled in a system information block by the cell.
The method of claim 1, wherein said determining whether to add the PLMN to the list comprises:

checking, for each of one or more cells of the PLMN, whether the cell selection criterion is satisfied; and

determining whether to add the PLMN to the list based on an outcome of the checking.
The method of claim 3, wherein the PLMN is determined to be added to the list if the cell selection criterion is satisfied for at least one of the one or more cells.
The method of claim 4, wherein the cell selection criterion is not checked for another cell of the PLMN not among the one or more cells.
The method of claim 3, wherein the PLMN is determined to not be added to the list if the cell selection criterion is not satisfied for any of the one or more cells.
The method of claim 1, wherein said determining whether to add the PLMN to the list comprises:

adding the PLMN to the list, with an indication of low signal strength, if the cell selection criterion is not checked for any cell of the PLMN.
The method of claim 1, further comprising:

displaying the list to a user for manual PLMN selection before another PLMN is added to the list.
The method of claim 8, further comprising:

updating the displayed list if a new PLMN is added to the list.
The method of claim 9, wherein the list is updated for a first PLMN before a second PLMN, if the first PLMN has a higher signal quality than the second PLMN.
A user equipment (UE) , comprising:

a receiver configured to receive signals from one or more base stations; and

a processor coupled to a memory, the processor configured to:

detect a public land mobile network (PLMN) based on the received signals; and

determine whether to add the PLMN to a list of available PLMNs for PLMN selection, based on a cell selection criterion.
The UE of claim 11, wherein the cell selection criterion for a cell is based at least on a measurement metric of the cell and a minimal value of the measurement metric, the minimal value being signaled in a system information block by the cell.
The UE of claim 11, wherein the processor configured to determine whether to add the PLMN to the list comprises the processor configured to:

check, for each of one or more cells of the PLMN, whether the cell selection criterion is satisfied; and

determine whether to add the PLMN to the list based on an outcome of the checking.
The UE of claim 13, wherein the PLMN is determined to be added to the list if the cell selection criterion is satisfied for at least one of the one or more cells.
The UE of claim 14, wherein the cell selection criterion is not checked for another cell of the PLMN not among the one or more cells.
The UE of claim 13, wherein the PLMN is determined to not be added to the list if the cell selection criterion is not satisfied for any of the one or more cells.
The UE of claim 11, wherein the processor configured to determine whether to add the PLMN to the list comprises the processor configured to:

add the PLMN to the list, with an indication of low signal strength, if the cell selection criterion is not checked for any cell of the PLMN.
The UE of claim 11, wherein the processor is further configured to:

display the list to a user for manual PLMN selection before another PLMN is added to the list.
The UE of claim 18, the processor is further configured to:

update the displayed list if a new PLMN is added to the list.
The UE of claim 19, wherein the list is updated for a first PLMN before a second PLMN, if the first PLMN has a higher signal quality than the second PLMN.
An apparatus of wireless communications, comprising:

means for detecting a public land mobile network (PLMN) ; and

means for determining whether to add the PLMN to a list of available PLMNs for PLMN selection, based on a cell selection criterion.
The apparatus of claim 21, wherein the cell selection criterion for a cell is based at least on a measurement metric of the cell and a minimal value of the measurement metric, the minimal value being signaled in a system information block by the cell.
The apparatus of claim 21, wherein the means for determining whether to add the PLMN to the list comprises:

means for checking, for each of one or more cells of the PLMN, whether the cell selection criterion is satisfied; and

means for determining whether to add the PLMN to the list based on an outcome of the checking.
The apparatus of claim 23, wherein the PLMN is determined to be added to the list if the cell selection criterion is satisfied for at least one of the one or more cells.
The apparatus of claim 24, wherein the cell selection criterion is not checked for another cell of the PLMN not among the one or more cells.
The apparatus of claim 23, wherein the PLMN is determined to not be added to the list if the cell selection criterion is not satisfied for any of the one or more cells.
The apparatus of claim 21, wherein the means for determining whether to add the PLMN to the list comprises:

means for adding the PLMN to the list, with an indication of low signal strength, if the cell selection criterion is not checked for any cell of the PLMN.
The apparatus of claim 21, further comprising:

means for displaying the list to a user for manual PLMN selection before another PLMN is added to the list.
The apparatus of claim 28, further comprising:

means for updating the displayed list if a new PLMN is added to the list.
The apparatus of claim 29, wherein the list is updated for a first PLMN before a second PLMN, if the first PLMN has a higher signal quality than the second PLMN.
A non-transitory computer-readable medium having instructions stored thereon, the instructions comprising codes executable for a user equipment (UE) to perform:

detecting a public land mobile network (PLMN) ; and

determining whether to add the PLMN to a list of available PLMNs for PLMN selection, based on a cell selection criterion.
The non-transitory computer-readable medium of claim 31, wherein the cell selection criterion for a cell is based at least on a measurement metric of the cell and a minimal value of the measurement metric, the minimal value being signaled in a system information block by the cell.
The non-transitory computer-readable medium of claim 31, wherein the codes for determining whether to add the PLMN to the list comprises:

codes for checking, for each of one or more cells of the PLMN, whether the cell selection criterion is satisfied; and

codes for determining whether to add the PLMN to the list based on an outcome of the checking.
The non-transitory computer-readable medium of claim 33, wherein the PLMN is determined to be added to the list if the cell selection criterion is satisfied for at least one of the one or more cells.
The non-transitory computer-readable medium of claim 34, wherein the cell selection criterion is not checked for another cell of the PLMN not among the one or more cells.
The non-transitory computer-readable medium of claim 33, wherein the PLMN is determined to not be added to the list if the cell selection criterion is not satisfied for any of the one or more cells.
The non-transitory computer-readable medium of claim 31, wherein the codes for determining whether to add the PLMN to the list comprises:

codes for adding the PLMN to the list, with an indication of low signal strength, if the cell selection criterion is not checked for any cell of the PLMN.
The non-transitory computer-readable medium of claim 31, further comprising:

codes for displaying the list to a user for manual PLMN selection before another PLMN is added to the list.
The non-transitory computer-readable medium of claim 38, further comprising:

codes for updating the displayed list if a new PLMN is added to the list.
The non-transitory computer-readable medium of claim 39, wherein the list is updated for a first PLMN before a second PLMN, if the first PLMN has a higher signal quality than the second PLMN.
A method of wireless communications, comprising:

obtaining information regarding one or more cells, corresponding to one or more public land mobile networks (PLMNs) , during a PLMN selection procedure in which a PLMN is selected, wherein the information comprises further information relating to a cell selection criterion;

storing the information in a database; and

selecting a cell of the selected PLMN based on the database.
The method of claim 41, wherein the cell selection criterion for a particular cell is based at least on a measurement metric of the particular cell and a minimal value of the measurement metric, the minimal value being signaled in a system information block by the particular cell.
The method of claim 41, wherein the further information comprises one or more parameters of the cell selection criterion obtained from a system information block of a cell of the one or more cells.
The method of claim 43, wherein said selecting a cell of the selected PLMN comprises:

checking whether the cell selection criterion is satisfied for the cell of the one or more cells based at least on the one or more parameters stored in the database.
The method of claim 41, wherein the further information comprises an indication whether the cell selection criterion, checked during the PLMN selection procedure, is satisfied for a cell of the one or more cells.
The method of claim 45, wherein said selecting a cell of the selected PLMN comprises:

prioritizing for cell selection a first cell for which the cell selection criterion is satisfied over a second cell for which the cell selection criterion is not satisfied, based on the indication stored in the database.
The method of claim 41, wherein the information further comprises system information obtained from one or more broadcast channels of a cell of the one or more cells.
A user equipment (UE) , comprising:

a memory; and

a processor coupled to the memory, the processor configured to:

obtain information regarding one or more cells, corresponding to one or more public land mobile networks (PLMNs) , during a PLMN selection procedure in which a PLMN is selected, wherein the information comprises further information relating to a cell selection criterion;

store the information in a database in the memory; and

select a cell of the selected PLMN based on the database.
The UE of claim 48, wherein the cell selection criterion for a particular cell is based at least on a measurement metric of the particular cell and a minimal value of the measurement metric, the minimal value being signaled in a system information block by the particular cell.
The UE of claim 48, wherein the further information comprises one or more parameters of the cell selection criterion obtained from a system information block of a cell of the one or more cells.
The UE of claim 50, wherein the processor configured to select a cell of the selected PLMN comprises the processor configured to:

check whether the cell selection criterion is satisfied for the cell of the one or more cells based at least on the one or more parameters stored in the database.
The UE of claim 48, wherein the further information comprises an indication whether the cell selection criterion, checked during the PLMN selection procedure, is satisfied for a cell of the one or more cells.
The UE of claim 52, wherein the processor configured to select a cell of the selected PLMN comprises the processor configured to:

prioritize for cell selection a first cell for which the cell selection criterion is satisfied over a second cell for which the cell selection criterion is not satisfied, based on the indication stored in the database.
The UE of claim 48, wherein the information further comprises system information obtained from one or more broadcast channels of a cell of the one or more cells.
An apparatus of wireless communications, comprising:

means for obtaining information regarding one or more cells, corresponding to one or more public land mobile networks (PLMNs) , during a PLMN selection procedure in which a PLMN is selected, wherein the information comprises further information relating to a cell selection criterion;

means for storing the information in a database; and

means for selecting a cell of the selected PLMN based on the database.
The apparatus of claim 55, wherein the cell selection criterion for a particular cell is based at least on a measurement metric of the particular cell and a minimal value of the measurement metric, the minimal value being signaled in a system information block by the particular cell.
The apparatus of claim 55, wherein the further information comprises one or more parameters of the cell selection criterion obtained from a system information block of a cell of the one or more cells.
The apparatus of claim 57, wherein the means for selecting a cell of the selected PLMN comprises:

means for checking whether the cell selection criterion is satisfied for the cell of the one or more cells based at least on the one or more parameters stored in the database.
The apparatus of claim 55, wherein the further information comprises an indication whether the cell selection criterion, checked during the PLMN selection procedure, is satisfied for a cell of the one or more cells.
The apparatus of claim 59, wherein the means for selecting a cell of the selected PLMN comprises:

means for prioritizing for cell selection a first cell for which the cell selection criterion is satisfied over a second cell for which the cell selection criterion is not satisfied, based on the indication stored in the database.
The apparatus of claim 55, wherein the information further comprises system information obtained from one or more broadcast channels of a cell of the one or more PLMNs.
A non-transitory computer-readable medium having instructions stored thereon, the instructions comprising codes executable for a user equipment (UE) to perform:

obtaining information regarding one or more cells, corresponding to one or more public land mobile networks (PLMNs) , during a PLMN selection procedure in which a PLMN is selected, wherein the information comprises further information relating to a cell selection criterion;

storing the information in a database; and

selecting a cell of the selected PLMN based on the database.
The non-transitory computer-readable medium of claim 62, wherein the cell selection criterion for a particular cell is based at least on a measurement metric of the particular cell and a minimal value of the measurement metric, the minimal value being signaled in a system information block by the particular cell.
The non-transitory computer-readable medium of claim 62, wherein the further information comprises one or more parameters of the cell selection criterion obtained from a system information block of a cell of the one or more cells.
The non-transitory computer-readable medium of claim 64, wherein the codes for selecting a cell of the selected PLMN comprises:

codes for checking whether the cell selection criterion is satisfied for the cell of the one or more cells based at least on the one or more parameters stored in the database.
The non-transitory computer-readable medium of claim 62, wherein the further information comprises an indication whether the cell selection criterion, checked during the PLMN selection procedure, is satisfied for a cell of the one or more cells.
The non-transitory computer-readable medium of claim 66, wherein the codes for selecting a cell of the selected PLMN comprises:

codes for prioritizing for cell selection a first cell for which the cell selection criterion is satisfied over a second cell for which the cell selection criterion is not satisfied, based on the indication stored in the database.
The non-transitory computer-readable medium of claim 62, wherein the information further comprises system information obtained from one or more broadcast channels of a cell of the one or more cells.