Multiband multi-RAT cell search

Abstract

The present invention relates to "Multiband multi-RAT cell search." A user equipment (UE) configured to determine, for each of a plurality of radio access technologies (RATs), a first list of frequency bands on which a public land mobile network (PLMN) is expected to be deployed and a second list of frequency bands including frequency bands not included in the first list, wherein the first list is determined based on a region in which the UE is currently located and PLMN deployment information; select a search mode for performing a cell search based on a current UE scenario; perform a first stage of the cell search; and when the first stage of the cell search is unsuccessful and no cell is selected, perform a second stage of the cell search by scanning frequencies included in the second list of frequency bands for the first priority RAT or frequencies included in the first list of frequency bands for a second priority RAT.

Description

[0001] This application is a divisional application of patent application No. 202211165694.5, filed on September 23, 2022, entitled "Multi-band Multi-RAT Cell Search". Background Technology

[0002] User equipment (UE) can establish connections with at least one of several different networks or network types. Some UEs can support operation on a variety of different radio access technologies (RATs), including, for example, 5G New Radio (NR), Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS), and / or Global System for Mobile Communications (GSM) RATs. Each of these RATs is deployed on multiple frequency bands, and the frequency bands used by the UE for network operation can vary depending on the UE's capabilities, the Public Land Mobile Network (PLMN) where the RAT is deployed, and / or the country / region of operation.

[0003] To access a PLMN, the UE performs a cell search to determine which frequency band and network cell to attempt to camp on. The UE may first perform a stored-information cell selection, where it scans channels from a known list of frequency bands on which a PLMN was previously found during the UE's lifetime. If no cell is found during the stored-information cell selection, the UE may then perform a specific frequency band search, where it scans all possible frequency bands supported in the current country on a per-rate-attr basis. Specific frequency band searches can be time-consuming and energy-intensive for the UE when it can operate on multiple different frequency bands across multiple rate-attraries.

[0004] Operators may abandon the deployment of older RATs (e.g., UMTS, GSM, LTE, etc.). Frequency bands previously used by abandoned RATs may remain empty or be reused by newer RATs (e.g., NR, LTE, etc.). A scenario may arise where the stored information that the UE can use to perform cell searches does not reflect the RATs actually deployed by the operator. Using date information that does not accurately reflect the operator's actual RAT deployment may negatively impact UE cell search performance. Summary of the Invention

[0005] Some exemplary embodiments relate to a processor of a user equipment (UE) configured to perform operations. The operations include: for each of a variety of radio access technologies (RATs) supported by the UE, determining a first frequency band list on which a public land mobile network (PLMN) is expected to be deployed and a second frequency band list including frequency bands not included in the first list, wherein the first frequency band list is determined based on the area currently in which the UE is located and PLMN deployment information provided to the UE, wherein the second frequency band list is determined based on the area currently in which the UE is located; selecting a search mode for performing a cell search based on the current UE scenario; performing a first phase of the cell search by scanning frequencies included in the first frequency band list for a first priority RAT; and performing a second phase of the cell search by scanning frequencies included in the second frequency band list for the first priority RAT or scanning frequencies included in the first frequency band list for a second priority RAT when the first phase of the cell search is unsuccessful and no cell is selected, wherein the second phase of the cell search is determined based on the selected search mode.

[0006] Other exemplary embodiments relate to a processor of a user equipment (UE) configured to perform operations. These operations include generating a RAT search list based on a list of deranged radio access technologies (RATs), and performing a service interruption recovery using the RAT search list.

[0007] A further exemplary embodiment relates to a processor of a user equipment (UE) configured to perform operations. The operations include: generating a list of frequency bands to be searched based on stored information, the stored information including at least one of the following: predefined frequency band information for each Public Land Mobile Network (PLMN), predefined frequency band information for each Mobile Country Code (MCC), and frequency bands frequently detected by the UE; removing range bands from the list of frequency bands to be searched; and performing a frequency band scan using the list of frequency bands to be searched. Attached Figure Description

[0008] Figure 1 Exemplary network arrangements according to various exemplary implementations are shown.

[0009] Figure 2 Exemplary UEs according to various exemplary implementations are shown.

[0010] Figure 3 An exemplary diagram of UE cell search according to a first search mode is shown.

[0011] Figure 4 An exemplary diagram of UE cell search according to the second search mode is shown.

[0012] Figure 5 An exemplary diagram of UE cell search based on a third search mode is shown.

[0013] Figure 6 Methods for UE cell search according to various exemplary embodiments described herein are illustrated.

[0014] Figures 7a to 7b Examples of avoiding derangement radio access technology (RAT) during a cell search procedure are shown according to various exemplary implementations.

[0015] Figure 8 Methods for avoiding derangement RAT searches according to various exemplary embodiments are shown.

[0016] Figure 9 Methods for derangement band search avoidance according to various exemplary embodiments are shown. Detailed Implementation

[0017] The exemplary embodiments can be further understood with reference to the following description and related figures, wherein similar elements have the same reference numerals. Some exemplary embodiments relate to a cell search for a user equipment (UE). Some exemplary embodiments illustrate different search modes that can be used based on deployment information stored at the UE and / or based on the UE's current use case. Other exemplary embodiments illustrate techniques for derangement radio access technology (RAT) and band scan avoidance during cell search.

[0018] According to one aspect described herein, a Specific Band Search (SBS) is divided into two phases, where the first phase (SBS1) prioritizes frequency bands in which a Public Land Mobile Network (PLMN) is expected to operate in a specific country or region, and the second phase (SBS2) searches for remaining frequency bands deployed in the country / region that were not searched in the first phase. Each of the two phases of the SBS can be performed for each Radio Access Technology (RAT) supported by the UE, or only the first phase (SBS1) of the SBS can be performed for each RAT, as will be explained in detail below.

[0019] On the other hand, the UE selects the search mode to use based on an assessment of the current UE scenario. In the first search mode, the UE performs two phases of the SBS (SBS1 followed by SBS2) for a specific RAT (e.g., RAT-A) before continuing to perform two phases of the SBS for any other supported RAT (e.g., RAT-B, RAT-C), according to a certain priority order of the RATs. In the second search mode, the UE performs the first phase of the SBS for each supported RAT before continuing to perform the second phase of the SBS for the supported RATs. In the third search mode, the UE performs only the first phase of the SBS for each supported RAT and does not perform the second phase of the SBS.

[0020] The SBS search mode selected by the UE can vary based on the current UE scenario. For example, the first mode can be used in emergency call scenarios, where the priority is to find emergency call service on any RAT, regardless of the PLMN. The second mode can be used as the default option. The third mode can be used in various cell recovery procedures when it is only desired to select a specific PLMN (e.g., a home PLMN). These scenarios and additional scenarios, as well as various conditions that may precede the use of a specific SBS search mode, are described in detail below.

[0021] Exemplary embodiments are described with reference to operations performed by a User Equipment (UE). However, reference to the UE is provided for illustrative purposes only. Exemplary embodiments can be used with any electronic component capable of establishing a connection to a network and configured with hardware, software, and / or firmware for exchanging information and data with the network. Therefore, the UE described herein represents any suitable electronic component capable of performing cell searches.

[0022] Certain aspects of exemplary embodiments have been described with reference to 5G New Radio (NR) networks. However, the reference to 5G NR networks is provided for illustrative purposes only. As will be explained in further detail below, exemplary embodiments relate to a UE performing cell search over various radio access technologies (RATs), including, for example, 5G New Radio (NR), Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS), Global System for Mobile Communications (GSM), and / or other networks. Therefore, the network described herein can represent any network that can be searched by a UE using initial access signaling and in a similar manner as described herein.

[0023] Based on several aspects, exemplary embodiments describe techniques for avoiding derangement RATs and frequency band scans during cell search. A UE can perform cell searches based on stored information, such as, but not limited to, a pre-configured list of frequency bands for each RAT, and information identifying the RAT and frequency bands previously detected by the UE. However, for any of a variety of reasons, an operator may cease deploying a particular RAT or frequency band. Therefore, a scenario may occur where the UE is configured to rely on stored information to perform cell searches that lack data and do not accurately reflect the operator's actual deployment of the RAT and / or frequency band. This can negatively impact the UE's cell search performance. The exemplary techniques described herein allow the UE to avoid wasting time and power searching for cells in derangement RATs and / or frequency bands that the operator no longer deploys. These exemplary techniques can be used independently of each other, in conjunction with currently implemented cell search mechanisms, in future implementations of cell search mechanisms, or independently of other cell search mechanisms.

[0024] Figure 1 An exemplary network arrangement 100 according to various exemplary embodiments is shown. The exemplary network arrangement 100 includes a plurality of UEs 110, 112. Those skilled in the art will understand that the UEs can be any type of electronic component configured to communicate via a network, such as components of a connected car, mobile phone, tablet computer, smartphone, phablet, embedded device, wearable device, Internet of Things (IoT) device, etc. It should also be understood that a practical network arrangement can include any number of UEs used by any number of users. Therefore, the example with two UEs 110, 112 is provided only for illustrative purposes.

[0025] UEs 110 and 112 can communicate directly with one or more networks. In the example of network configuration 100, the networks with which UEs 110 and 112 can communicate wirelessly are 5G NR Radio Access Network (5G NR-RAN) 120, LTE Radio Access Network (LTE-RAN) 122, and Wireless Local Area Network (WLAN) 124. Therefore, UEs 110 and 112 may include a 5G NR chipset communicating with 5G NR-RAN 120, an LTE chipset communicating with LTE-RAN 122, and an ISM chipset communicating with WLAN 124. However, UEs 110 and 112 can also communicate with other types of networks (e.g., traditional cellular networks), and UEs 110 and 112 can also communicate with networks via wired connections. Referring to the exemplary aspect, UEs 110 and 112 can establish connections with 5G NR-RAN 120, LTE-RAN 122, traditional networks including UMTS and GSM, or other networks.

[0026] 5G NR-RAN 120 and LTE-RAN 122 may be portions of a cellular network that can be deployed by a cellular provider (e.g., Verizon, AT&T, T-Mobile, etc.). These networks 120, 122 may include, for example, cells or base stations (NodeB, eNodeB, HeNB, eNBS, gNB, gNodeB, macrocell base stations, microcell base stations, small cell base stations, femtocell base stations, etc.) configured to send and receive traffic from UEs equipped with appropriate cellular chipsets. WLAN 124 may include any type of wireless local area network (WiFi, hotspot, IEEE 802.11x network, etc.).

[0027] UEs 110 and 112 can connect to 5G NR-RAN 120 via at least one of Next Generation Node B (gNB) 120A and / or gNB 120B. Reference to the two gNBs 120A and 120B is for illustrative purposes only. Exemplary implementations can be applied to any suitable number of gNBs. For example, UEs 110 and 112 can simultaneously connect to and exchange data with multiple gNBs in a multi-cell CA configuration. UEs 110 and 112 can also connect to LTE-RAN 122, or any other type of RAN, as described above, via either or both of eNBs 122A and 122B. In network arrangement 100, UE 110 is shown having a connection to gNB 120A, while UE 112 is shown having a connection to gNB 120B.

[0028] gNB 120A and 120B can represent the serving cell as a PCell or SCell, or in a separate configuration with UE 110. gNB 120A and 120B can represent any access node in the 5G NR network, through which UE 110 and 112 can establish connections and manage network operations. gNB 120A and 120B may include a processor, memory layout, input / output (I / O) devices, transceivers, and other components. These other components may include, for example, audio input devices, audio output devices, batteries, data acquisition devices, and ports for electrically connecting the gNB 120A to other electronic devices.

[0029] The processor can be configured to execute multiple engines of the gNB 120A. The functions associated with the engines can also be represented as independent integrated components of the gNB 120A, or as modular components coupled to the gNB 120A, such as integrated circuits with or without firmware. For example, the integrated circuit may include input circuitry for receiving signals and processing circuitry for processing signals and other information. Furthermore, in some gNBs, the functions described for the processor are split among multiple processors (e.g., baseband processor, application processor, etc.). Exemplary implementations can be implemented according to any of these or other configurations of the gNB.

[0030] The memory can be a hardware component configured to store data related to operations performed by UEs 110 and 112. The I / O device can be a hardware component or port enabling a user to interact with the gNB 120A. The transceiver can be a hardware component configured to exchange data with UEs 110, 112, and any other UE in system 100. The transceiver can operate on a variety of different frequencies or channels (e.g., a set of consecutive frequencies). For example, when NR-U functionality is configured, the transceiver can operate on unlicensed bandwidth. Therefore, the transceiver may include one or more components (e.g., radio components) to enable data exchange with various networks and UEs.

[0031] eNBs 122A and 122B can be configured for LTE operation similar to that of gNBs 120A and 120B described above for NR operation. Additionally, in the exemplary embodiments described herein, UEs 110 and 112 can operate with network cells configured for UMTS and / or GSM operation. In some PLMNs, the same network cell can operate on multiple different RATs. Therefore, gNBs 120A and 120B and eNBs 122A and 122B are shown for illustrative purposes only, and UEs 110 and 112 can connect to any type of network.

[0032] In addition to networks 120, 122, and 124, network deployment 100 also includes a cellular core network 130, an Internet 140, an IP Multimedia Subsystem (IMS) 150, and a network service backbone 160. The cellular core network 130 can be viewed as an interconnected collection of components that manage the operation and traffic of the cellular network (e.g., NR's 5GC). The cellular core network 130 also manages the traffic flowing between the cellular network and the Internet 140.

[0033] IMS 150 can generally be described as an architecture for delivering multimedia services to UE 110 using the IP protocol. IMS 150 can communicate with cellular core network 130 and Internet 140 to provide multimedia services to UE 110. Network service backbone 160 communicates directly or indirectly with Internet 140 and cellular core network 130. Network service backbone 160 can generally be described as a set of components (e.g., servers, network storage deployments, etc.) that implement a set of services that can be used to extend the functionality of UE 110 to communicate with various networks.

[0034] Figure 2 An exemplary UE 110 according to various exemplary embodiments is shown. Reference will be made to... Figure 1 The network layout 100 is used to describe UE 110. UE 110 can represent any electronic device and may include processor 205, memory layout 210, display device 215, input / output (I / O) device 220, transceiver 225, and other components 230. Other components 230 may include, for example, audio input devices, audio output devices, batteries providing a limited power source, data acquisition devices, ports for electrically connecting UE 110 to other electronic devices, sensors for detecting the status of UE 110, etc. Figure 2 The UE 110 shown can also represent UE 112.

[0035] Processor 205 may be configured to execute multiple engines for UE 110. For example, engines may include a Specific Band Search (SBS) engine 235 and a derangement avoidance engine 240. SBS engine 235 may perform operations including, but not limited to, determining a list of frequencies to be searched in each stage of a two-stage SBS search, determining the search mode to use based on the current UE scenario, performing SBS according to the selected search mode, and other operations described in further detail below. Derangement avoidance engine 240 may perform operations including, but not limited to, identifying derangement RATs, identifying derangement bands, and omitting identified derangement RATs and / or bands from different aspects of the cell selection procedure.

[0036] The engine described above, as an application (e.g., a program) executed by processor 205, is merely exemplary. The functionality associated with the engine may also be represented as a separate integrated component of UE 110, or as a modular component coupled to UE 110, such as an integrated circuit with or without firmware. For example, the integrated circuit may include input circuitry for receiving signals and processing circuitry for processing signals and other information. The engine may also be embodied as a single application or multiple separate applications. Furthermore, in some UEs, the functionality described for processor 205 is distributed among two or more processors, such as a baseband processor and an application processor. Exemplary implementations can be implemented according to any of these or other configurations of the UE.

[0037] Memory arrangement 210 may be a hardware component configured to store data related to operations performed by UE 110. Display device 215 may be a hardware component configured to display data to a user, while I / O device 220 may be a hardware component enabling user input. Display device 215 and I / O device 220 may be separate components or may be integrated together (such as a touchscreen). Transceiver 225 may be a hardware component configured to establish connections with 5G-NR RAN 120, LTE RAN 122, etc. Therefore, transceiver 225 can operate on various frequencies or channels (e.g., consecutive frequency groups). For example, when configured, for example, NR-U, transceiver 225 can operate on unlicensed spectrum.

[0038] The initial 5G NR access procedure typically includes the following operations. However, it should be understood that exemplary implementations are not limited to any particular access procedure or order of operations. The following is provided as an example to illustrate the procedure in which a UE performs a cell search (specifically referring to a 5G NR RAT). However, a UE may perform a cell search at other times and using other RATs, as will be explained below, and exemplary implementations are not limited to this particular procedure or RAT. For example, a UE may perform a cell search to camp on a cell regardless of its PLMN identity, enabling emergency calls. In another example, a UE may prioritize cell searches for different RATs before performing a cell search on an NR frequency.

[0039] During initial 5G NR access, the gNB periodically broadcasts System Information (SI), which can be categorized into Minimal System Information (MSI) and Other System Information (OSI) using beam sweeping. Beam sweeping typically refers to transmitting multiple transmitter beams over a specific spatial area for a predetermined duration. Each beam transmitted during transmitter beam sweeping may include a reference signal. The UE can measure one or more transmitter beams based on its corresponding reference signal and select one transmitter beam from the transmitter beams based on the measurement data.

[0040] The synchronization signal block (SSB) broadcast by the gNB includes the synchronization signal (SS) (primary synchronization signal (PSS) and secondary synchronization signal (SSS)) and the physical broadcast channel (PBCH), where the PBCH transmission includes the main information block (MIB) containing the MSI. The MSI includes parameters indicating the location and resources of ControlResourceSet0 (CORESET#0) on the resource grid, and carries downlink control information (DCI) for decoding System Information Block 1 (SIB1). SIB1 may be referred to as the Residual Minimal System Information (RMSI), a subset of the MSI, and is carried on the Physical Downlink Shared Channel (PDSCH). The SSB (including the MIB) and CORESET#0 / RMSI (SIB1) are transmitted on the same beam, which will be used by the UE for random access channel (RACH) transmission when selected by the UE, until a dedicated connection is established and the beam is switched. The OSI includes SIB2 to SIB9, which can be broadcast or provided to the UE via dedicated RRC signaling.

[0041] The UE performs beam measurement, detects the optimal SSB (e.g., the strongest beam), and selects this beam. The UE then decodes the SSB and, based on the extracted MSI parameters, searches the Type 0-PDCCH common search space (CSS) of the downlink control information (DCI) on CORESET#0, then uses it to decode SIB1. The extracted SI allows the UE to initiate random access (RACH procedure) using the same beam by transmitting Msg1 of the RACH procedure (i.e., the RACH preamble) on the Physical Random Access Channel (PRACH).

[0042] Cell search refers to the procedure by which a UE attempts to detect and decode broadcasts (e.g., SSBs) from a network cell to obtain parameters for accessing the cell. Cell search can be performed during cell selection and PLMN search. In the first step of cell search, the UE performs a frequency scan. The frequency scan involves the UE tuning to each channel in the list of supported channels and measuring the strength of the detected signal on said frequency, e.g., the Reference Signal Strength Indicator (RSSI) for each channel in the scanned channels. In this step, only the signal strength (e.g., RSSI) is measured; that is, no channel decoding is performed at this stage. After the scan, the UE determines a sublist of candidate channels whose signal strength is above a threshold. This threshold, such as the RSSI threshold, may depend on the UE implementation.

[0043] After determining the sublist of candidate channels, the UE attempts to decode the PSS and SSS on each candidate frequency. This allows the UE to obtain frequency and time synchronization and detect the physical cell ID of the network cell. The UE can then select a cell and / or beam and decode the PBCH MIB and RMSI to extract the PLMN ID, cell selection parameters, and RACH parameters. When the extracted PLMN ID matches a PLMN ID in the UE's available PLMN list, the UE performs the cell selection procedure. Otherwise, the UE acquires another cell and restarts the process.

[0044] The list of frequency bands / channels scanned by the UE during cell search can depend on the type of frequency scan being performed. Types of frequency scans include Stored Information Cell Selection (SICS), where the UE scans channels within a stored list of frequencies and / or frequency bands where a PLMN was previously found during the UE's lifetime. SICS can be performed for each RAT supported by the UE according to a priority order determined based on the UE implementation. For example, the UE may prioritize the most recently camped RAT. In another example, the UE may prioritize RATs in order, such as NR, LTE, UMTS, and GSM. However, other priority orders can be used.

[0045] The second type of frequency scanning is Specific Band Search (SBS), where the UE scans for frequency bands supported by the UE in its current country / region. The third type of frequency scanning is Additional Band Search (ABS), where the UE scans for all remaining frequency bands not covered by SBS, including those not deployed in the UE's current country / region. SBS and ABS can also be performed consecutively for multiple RATs based on their priority order.

[0046] Some UEs can support network operation for multiple different Radio Access Technologies (RATs) and network types (e.g., NR, LTE, UMTS, and GSM). Each of these RATs can support multiple frequency bands, which can vary based on the PLMN (PLN) and region. For example, 57 different frequency bands can be supported on NR FR1, 6 different frequency bands on NR FR2, 88 different frequency bands on LTE, 21 different frequency bands on UMTS, and 5 different frequency bands on GSM. Multiple channels can be used within each frequency band. Worldwide, different RATs are deployed across multiple frequency bands on a per-RAT basis, which can vary based on country and region, resulting in a broad spectrum available for network operation with the UE.

[0047] According to the various exemplary embodiments described herein, cell search for a UE includes a two-phase Specific Band Search (SBS). In the first phase (SBS1) of the SBS, the UE searches only for specific frequency bands that the operator / PLMN has deployed or is expected to deploy in the UE's current location / region / country. The UE determines this first list of frequency bands based on PLMN deployment information. This information can be derived in various ways, including but not limited to i) based on historical data determined by the UE regarding the location of previously discovered PLMNs, ii) using location-based PLMN deployment data, or iii) using static / dynamic configuration data of the PLMN and its frequency band deployment stored in the UE.

[0048] In the second phase of SBS (SBS2), the UE searches for the remaining portions of frequency bands deployed in its current location / region / country that were not searched in the first SBS step. Therefore, the second list of frequency bands is determined in part based on known operating frequency bands used in said region. Information on deployed frequency bands for a country can be derived in various ways, including but not limited to using static / dynamic configuration data stored in UEs deployed based on frequency bands for each country.

[0049] According to another exemplary embodiment described herein, a cell selection and search method for a UE is described, wherein the UE uses the aforementioned two-stage SBS framework to make decisions among various search options.

[0050] In the following options, specific searches (SICS, SBS1, SBS2) are described as being performed on specific RATs (RAT-A, RAT-B, RAT-C, RAT-D). As described above, each of these searches includes scanning all frequencies on the list and generating a sublist of frequencies whose Received Signal Strength Indication (RSSI) is above a certain threshold. After generating the sublist, the UE can attempt to camp on the selected frequency. If a specific search is unsuccessful, the UE performs the next search based on predefined rules and / or the selected search mode, as described in detail below.

[0051] In the first search mode, the UE performs two steps of SBS for each supported RAT on a per-RAT basis. Each RAT is searched in priority order, with the first phase of SBS performed by the UE for the first RAT, and the second phase of SBS performed by the UE for the same RAT before moving to the next RAT. The first search mode can be considered the default option, where the UE continuously searches for frequency bands deployed in the country on a per-RAT basis. In this option, the optimization of the SBS search can be limited relative to the second and third search modes discussed below.

[0052] Figure 3 An exemplary diagram of UE cell search according to a first search mode is shown. The diagram is described with respect to four RATs (i.e., RAT-A, RAT-B, RAT-C, and RAT-D). In the exemplary diagram, RAT-A corresponds to NR, RAT-B to LTE, RAT-C to UMTS, and RAT-D to GSM. However, depending on the UE implementation, different numbers of RATs and / or different priority orders may be used.

[0053] In 305, the UE performs SICS on available RATs based on priority. The UE first searches the stored frequency bands on RAT-A, for example, scanning the frequencies in the list to perform RAT-A SICS, and attempts to camp on the frequency / cell and perform the initial access procedure to register with the network. If the cell selection procedure fails for all listed frequencies on RAT-A, or if no cell is found that meets the signal strength threshold, the UE proceeds to RAT-B, RAT-C, and RAT-D, performing the same procedure of scanning and attempting to camp on the frequencies / cells of the corresponding RAT.

[0054] If no cell is visited in 305, the UE proceeds to 310. In 310, the UE performs the first phase of SBS (SBS1) for RAT-A. As discussed above, in SBS1, the UE searches for frequency bands where it is known that the frequency band will be deployed or expected to be deployed in the current location by the PLMN being searched.

[0055] If no cell is accessed in 310, the UE proceeds to 315. In 315, the UE performs the second phase of SBS (SBS2) for RAT-A. The UE searches for all frequency bands deployed in the country that were not searched in SBS1 for RAT-A in 310.

[0056] If no cell is visited in step 315, the UE continues to search for the remaining RATs. That is, the UE proceeds to the first phase of performing SBS for RAT-B (step 320), the second phase of performing SBS for RAT-B (step 325), the first phase of performing SBS for RAT-C (step 330), the second phase of performing SBS for RAT-C (step 335), the first phase of performing SBS for RAT-D (step 340), and the second phase of performing SBS for RAT-D (step 345).

[0057] The first cell search mode illustrated in the figure can be primarily used in scenarios where the UE is unaware of the PLMN deployment. Therefore, the UE may not yet have a list of stored frequency bands for the PLMN used in SBS1. In this case, SBS1 is not executed, and the search begins in SBS2. Thus, in these scenarios, the search process can be similar to traditional SBS, where the UE searches all frequency bands of the country without any prior knowledge of the PLMN deployment.

[0058] In the second cell search mode, before performing the second step of SBS for any RAT, the UE performs the first step of SBS for each supported RAT on a per-RAT basis. Each RAT is searched in priority order, with the first phase of SBS performed by the UE for RAT-A, RAT-B, RAT-C, and RAT-D, and then the second phase of SBS performed by the UE for RAT-A, RAT-B, RAT-C, and RAT-D.

[0059] Figure 4 An exemplary diagram of UE cell search according to the second search mode is shown. Similar to the diagram described above, the diagram is described with respect to four RATs (i.e., RAT-A, RAT-B, RAT-C, and RAT-D), where RAT-A corresponds to NR, RAT-B to LTE, RAT-C to UMTS, and RAT-D to GSM. However, depending on the UE implementation, different numbers of RATs and / or different priority orders may be used.

[0060] In 405, the UE performs SICS on available RATs based on priority, similar to 405. The UE first searches the stored frequency bands on RAT-A, for example, scanning the frequencies in the list to perform RAT-A SICS, and attempts to camp on the frequency / cell and perform the initial access procedure. If the cell selection procedure fails for all listed frequencies on RAT-A, or if no cell is found that meets the signal strength threshold, the UE proceeds to RAT-B, RAT-C, and RAT-D, and performs the same procedure of scanning and attempting to camp on the frequencies / cells of the corresponding RAT.

[0061] If no cell is accessed in 405, the UE proceeds to 410. In 410, the UE performs the first phase of SBS (SBS1) for RAT-A, similar to 310. As described above, the UE searches for frequency bands on RAT-A, where the known frequency bands will be deployed or expected to be deployed in the current location by the PLMN being searched.

[0062] If no cell is accessed in step 410, the UE continues to the remaining RAT to perform SBS1. That is, the UE proceeds to perform SBS1 for RAT-B (step 415), for RAT-C (step 420), and for RAT-D (step 425).

[0063] If no cell is accessed in 415-425, the UE proceeds to 430. In 430, the UE performs the second phase of SBS (SBS2) for RAT-A. As discussed above, the UE searches for all frequency bands deployed in the country that were not searched in SBS1 for RAT-A in 410.

[0064] If no cell is accessed in step 430, the UE continues to the remaining RAT to perform SBS2. That is, the UE proceeds to perform SBS2 for RAT-B (step 435), for RAT-C (step 440), and for RAT-D (step 445).

[0065] In the third cell search mode, the UE performs the first phase of SBS for each supported RAT on a per-RAT basis, but does not perform the second phase of SBS. Therefore, the third cell search mode is similar to the second cell search mode, but only includes SBS1.

[0066] Figure 5An exemplary diagram of UE cell search according to a third search mode is shown. Similar to the diagram described above, the diagram is described with respect to four RATs (i.e., RAT-A, RAT-B, RAT-C, and RAT-D), where RAT-A corresponds to NR, RAT-B to LTE, RAT-C to UMTS, and RAT-D to GSM. However, depending on the UE implementation, different numbers of RATs and / or different priority orders may be used.

[0067] In 505, the UE performs SICS on the available RATs based on priority order, similar to 305 and 405.

[0068] If no cell is accessed in 505, the UE proceeds to 510. In 510, the UE performs the first phase of SBS (SBS1) for RAT-A, similar to 410. As described above, the UE searches for frequency bands on RAT-A, where the frequency bands are known to be deployed or expected to be deployed in the current location by the PLMN being searched.

[0069] If no cell is accessed in step 510, the UE continues to the remaining RAT to perform SBS1. That is, the UE proceeds to perform SBS1 for RAT-B (step 515), for RAT-C (step 520), and for RAT-D (step 525).

[0070] Each of the search modes described above can be suitable for use by the UE in different situations. To select a search mode during a PLMN search, consider the following scenarios.

[0071] In one scenario, a limited service PLMN search is performed using the first search mode. For this type of search, the UE's priority is to find services on any RAT for emergency or public alert system (PWS) purposes, such as earthquake and tsunami warning systems (ETWS). Therefore, PLMNs do not need to be prioritized.

[0072] In another scenario, a manual PLMN search is performed using the first search mode. For this type of search, the UE prioritizes detecting PLMNs from the better serving RAT, for example, in the order of NR to LTE to UMTS to GSM. Therefore, PLMNs do not need to be prioritized.

[0073] In another scenario, an out-of-coverage (OOC) recovery PLMN search is performed using the second search mode. For this type of search, the RRC of the corresponding RAT will benefit from the mutual exclusion frequency (MFE), and the probability of finding a significant PLMN in a known frequency band is higher. Therefore, PLMNs can be given priority.

[0074] In all other scenarios where PLMN search is not mentioned, the UE's default behavior is to use the second search mode.

[0075] To use the second search mode, some additional conditions may be required. In one example, the second search mode can only be used if the UE is located in its home country and not near the border. In another example, the second search mode can only be used if the SICS frequency for PLMN / RAT is available for xRRC. In yet another example, the second search mode can only be used if location-specific PLMN information data is available for the PLMN location.

[0076] To select a search mode during the neighborhood selection process, consider the following scenarios.

[0077] In one scenario, the first cell search mode is used to perform cell selection for emergency calls, limited service scenarios, or emergency 911 calls. For this type of search, the UE prioritizes finding services on any RAT for emergency or public alarm system (PWS) purposes, such as earthquake and tsunami warning systems (ETWS), based on call type preferences. Therefore, PLMN does not need to be prioritized.

[0078] For the following scenarios where the third search mode is used, the following conditions may be required for its use: In one example, the third search mode can be used only when the UE is located in its home country and not near a border. In another example, the third search mode can be used only when the SICS frequency for PLMN / RAT is available for xRRC. In yet another example, the third search mode can be used only when APACS data is available for the PLMN location. In yet another example, the third search mode can be used only when it is enabled.

[0079] In one scenario, an OOC recovery cell selection attempt is performed using a third search mode. When the UE is located in its home country and not near the border, the probability that any other operator will be able to provide service is very low. Therefore, it is better to check the registered PLMN (RPLMN) in another RAT before performing the PLMN search cycle.

[0080] In another scenario, when reselection / redirection fails, a circuit-switched backoff (CSFB) is performed using a third search mode to resume cell selection. In this type of search, the UE is only interested in its home PLMN (HPLMN).

[0081] In another scenario, when reselection / redirection fails, an Evolved Packet System Backoff (EPSFB) attempt to restore cell selection is performed using a third search mode. In this type of search, the UE is only interested in the RPLMN or equivalent PLMN (EPLMN) list.

[0082] In another scenario, a prioritized RAT to NR cell selection attempt is performed using a third search mode. In this type of search, the UE is only interested in the NR PLMN.

[0083] In another scenario, network-based rejection leads to the use of a third search mode for cell selection. In this type of search, the UE is only interested in cell selection for the specific PLMN.

[0084] In another scenario, the N1 / LTE mode being disabled causes cell selection to be performed using a third search mode. In this type of search, the UE is only interested in cell selection for the specific PLMN.

[0085] In all other scenarios where PLMN search is not mentioned, the UE's default behavior is to use the second search mode.

[0086] Figure 6 A method 600 for UE cell search according to various exemplary embodiments described herein is illustrated.

[0087] In step 605, the UE determines a list of first frequency bands to be used in the first phase of SBS and a list of second frequency bands to be used in the second phase of SBS. The UE can determine these lists based on the UE's PLMN deployment information.

[0088] In 610, the UE selects the search mode to use based on the current UE scenario and / or by evaluating the current conditions, as explained above.

[0089] In 615, the UE performs cell search according to the selected search mode.

[0090] According to several aspects, exemplary embodiments describe techniques for derangement RATs and frequency band scan avoidance. As described above, UE 110 can perform cell search based on stored information. The stored information may include, but is not limited to, a predefined list of frequency bands for each RAT and / or region, and information identifying the frequency bands of different RATs of each operator previously detected by UE 110. As will be described in more detail below, a particular RAT or frequency band can be deranged by the operator. A scenario may occur where the stored information that can be used by UE 110 to perform cell search may include information about derangement RATs or frequency bands. This may negatively impact UE 110 performance and power consumption during cell search.

[0091] Operators may abandon the deployment of older RATs (e.g., UMTS, GSM, LTE, etc.). The frequency bands previously used by the abandoned RATs can remain empty or be reused by newer RATs (e.g., NR, LTE, etc.). For example, an operator may shut down the deployment of a particular RAT, or all operators in a region (e.g., a country) may cease deploying a particular RAT. The operator can then deploy a newer RAT on frequencies previously used by the abandoned RAT. The process of deploying RATs on frequency bands previously occupied by different RATs can be called "refarming." Additionally, a scenario may occur where one or more frequency bands of a RAT are abandoned, but the remaining frequency bands of the RAT are still deployed.

[0092] Under normal circumstances, after an operator changes the deployment of a RAT or frequency band, the stored information can trigger UE 110 to scan one or more empty frequency bands. However, this is a useless operation and may only increase the amount of time and power spent by UE 110 scanning frequencies during cell search. Similarly, after an operator changes the deployment of a RAT or frequency band, the stored information may trigger UE 110 to scan frequency bands that have already been reused, without updating the stored information to reflect the change. It has been recognized that this may lead to false alarms during frequency scanning and may only increase the amount of time and power spent by UE 110 scanning frequencies during cell search.

[0093] The exemplary implementation allows the UE to disregard deranged RATs and frequency bands that are no longer deployed during frequency scanning. When the UE 110 knows that an operator in a certain country has shut down the deployment of a certain RAT or no longer uses a specific frequency band in a certain RAT, the UE 110 can focus its search on a more suitable combination of frequency bands and RATs, rather than wasting time and power searching for potential cells on deranged RATs or frequency bands that are no longer deployed by operators.

[0094] According to some exemplary embodiments, UE 110 may maintain one or more lists, which include derangement RATs, derangement bands for each RAT, derangement bands for each PLMN, and / or derangement bands for each region (e.g., country, local region, mobile country code (MCC), etc.). From the perspective of UE 110, the application processor may maintain one or more lists. During power-on, one or more lists may be pushed to the baseband processor, where the lists are stored for subsequent use.

[0095] To implement derangement RAT search avoidance, UE 110 may consider one or more lists during cell search and / or PLMN search. For example, if any RAT is deranged for a specific PLMN, UE 110 (e.g., Non-Access Stratum (NAS)) may not trigger cell selection on a given RAT for PLMN selection. Similarly, based on location-based information from the application processor (e.g., AP-Assisted Cell Search (APACS), etc.), UE 110 (e.g., NAS) avoids scanning derangement RATs at a given location as part of a PLMN search.

[0096] To implement range-free band search avoidance, when the access layer (AS) radio resource control (RRC) of UE 110 receives an initial cell selection request to perform a band scan for a specific PLMN or MCC, the AS RRC of UE 110 can avoid performing a range-free band scan for a specific PLMN or MCC.

[0097] Under normal circumstances, UE 110 can trigger SICS, SBS, and ABS on all enabled and supported RATs for PLMN search and selection. However, UE 110 may not consider the presence of RAT / band deployments at the current location where UE 110 is operating. Figure 7a An example of this situation is shown, where UE 110 search mode 710 includes performing searches for LTE RAT, UMTS RAT, and GSM RAT. However, in this example, even though the UMTS RAT is out of range at this location, UE 110 still performs a cell search on the UMTS RAT.

[0098] According to the exemplary implementation described herein, UE 110 can avoid scanning derangement RAT. Figure 7b An example of this scenario is illustrated, where UE 110 search mode 750 includes performing searches for the LTERAT and GSM RAT at the same location as performing search mode 710. Compared to search mode 710, UE 110 does not perform a search for the UMTS RAT because the UMTS RAT has been deranged at this location. This exemplary implementation allows UE 110 to conserve resources because UE 110 does not spend time or battery power performing unsuccessful cell searches on deranged RATs.

[0099] Figure 8 A method 800 for avoiding derangement RAT searches according to various exemplary embodiments is shown. (Refer to...) Figure 1 Network layout 100 and Figure 2 The UE 110 is used to describe method 800.

[0100] In 805, UE 110 initiates preparation for a cell selection or PLMN search task. For example, UE 110 may cease service and search for cells and / or PLMNs on which to access network services. Therefore, various components of UE 110 (e.g., NAS, AS, RRC, etc.) can perform operations to prepare for cell selection and / or PLMN search.

[0101] In 810, UE 110 receives a derangement RAT list. For example, UE 110 may maintain a derangement RAT list for each PLMN and / or each MCC in non-volatile memory. NAS can retrieve the derangement RAT list from UE 110's application processor or baseband processor. Information providing the basis for the derangement RAT list can be derived at a remote server based on crowdsourced information. The server can provide derangement RAT information to UE 110 at any appropriate time and in any appropriate type of message.

[0102] In 815, UE 110 determines the current RAT deployment based on stored information. For example, the NAS can obtain current RAT deployment information for a specific PLMN or MCC from the application processor of UE 110 based on the current location of UE 110 (e.g., APACS data). At this time, the application processor can provide an updated descoped RAT list. If the application provides an updated list, the NAS updates the descoped RAT list using the list provided by the application processor.

[0103] In step 820, UE 110 prepares the RAT search list. In step 825, UE 110 determines whether a RAT from the currently deployed RAT exists in the deranged RAT list. If the RAT does not exist, step 800 continues to step 830, where UE 110 adds the RAT to the RAT search list. Returning to step 825, if the RAT exists in the deranged RAT search list, step 800 continues to step 835. In step 835, UE 110 does not add the RAT to the RAT search list because it already exists in the deranged RAT list.

[0104] Methods 800 continue from steps 830 and 835 to step 840. In step 840, UE 110 determines whether the RAT search list is complete. For example, UE 110 may determine whether the RAT search list includes the maximum number of RATs. If the number included in the RAT search list is less than the maximum number, UE 110 may perform steps 825-835 for another RAT from the current RAT deployment determined in step 815. In another example, UE 110 may determine that the RAT search list is complete because there are no more RATs from the determined current RAT deployment to evaluate in step 815. Therefore, if the RAT search list is incomplete, method 800 returns to step 825. If one or more RAT search lists are complete, method 800 continues to step 845.

[0105] In 845, UE 110 can perform searches on one or more RATs from the RAT search list. For example, the NAS mobility management component of UE 110 can attempt to perform a stop-service recovery for each RAT from the RAT search list. Separate RAT search lists may exist for different types of scans (e.g., SICS, SBS, ABS, etc.), or a single RAT search list may be used for multiple different types of searches.

[0106] Figure 9 A method 900 for range-band search avoidance according to various exemplary embodiments is shown. (Refer to...) Figure 1 Network layout 100 and Figure 2 The UE 110 is used to describe method 900.

[0107] In 905, UE 110 maintains a derangement band list. The derangement band list can be based on information received from the network, information learned by UE 110 during deployment, or any other suitable type of information. Information providing the basis for the derangement band list can be derived at a remote server based on crowdsourced information. The server can provide derangement band information to UE 110 at any appropriate time and in any suitable type of message.

[0108] In 910, UE 110 receives a cell selection or PLMN search request. For example, the AS of UE 110 can receive the request from the NAS of UE 110. The request can be for a specific search type (e.g., SICS, SBS, ABS, etc.).

[0109] In 915, UE 110 prepares a list of frequency bands to be searched. The list may be based on stored information, such as, but not limited to, a pre-configured list of frequency bands for each RAT, each PLMN, and each MCC, as well as information identifying frequency bands previously detected by the UE.

[0110] In step 920, UE 110 determines that the list of frequency bands to be searched includes one or more frequency bands from the derangement frequency band list. In step 925, UE 110 removes one or more frequency bands from the list of frequency bands to be searched. For example, the AS of UE 110 can remove the derangement frequency band of a requested PLMN or MCC from the list of frequency bands to be searched. In step 930, UE 110 performs a scan of the frequency bands from the list of frequency bands to be searched.

[0111] Those skilled in the art will understand that the exemplary embodiments described above can be implemented with any suitable software or hardware configuration or combination thereof. Exemplary hardware platforms for implementing the exemplary embodiments may include, for example, Intel x86-based platforms with compatible operating systems, Windows OS, Mac platforms and MAC OS, and mobile devices with operating systems such as iOS, Android, etc. In other examples, exemplary embodiments of the methods described above may be embodied as programs comprising lines of code stored on a non-transitory computer-readable storage medium, which, at compile time, can be executed on a processor or microprocessor.

[0112] Although this patent application describes various combinations of aspects, each with different features, those skilled in the art will understand that any feature of one aspect can be combined with features of other aspects or features that are not functionally or logically inconsistent with the operation or function of the device of the aspect disclosed in this invention in any manner not disclosed to be denied.

[0113] As is widely recognized, the use of personally identifiable information should comply with privacy policies and practices that are generally accepted to meet or exceed industry or governmental requirements for protecting user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of authorized use should be clearly explained to users.

[0114] It will be apparent to those skilled in the art that various modifications can be made to this disclosure without departing from its spirit or scope. Therefore, this disclosure is intended to cover all modifications and variations thereof, provided that such modifications and variations are within the scope of the appended claims and their equivalents.

Claims

1. A processor for a user equipment (UE), the processor being configured to perform operations including: Generate a RAT search list based on the range-free radio access technology RAT list; as well as Use the RAT search list to perform a service recovery after a stop.

2. The processor of claim 1, wherein the UE maintains a plurality of derangement RAT lists, each derangement RAT list corresponding to an operator, a public land mobile network (PLMN), or a mobile country code (MCC).

3. The processor of claim 1, wherein generating the RAT search list comprises: The current RAT deployment is determined based on the UE location and information stored locally at the UE, wherein the current RAT deployment includes multiple RATs; as well as Determine whether the descoped RAT list includes one of the multiple RATs from the current RAT deployment.

4. The processor according to claim 3, wherein the operation further comprises: When the deranged RAT list does not include the RAT from the plurality of RATs in the current RAT deployment, the RAT from the plurality of RATs in the current RAT deployment is added to the RAT search list.

5. The processor of claim 3, wherein when the derangement RAT list includes the one RAT from the plurality of RATs deployed in the current RAT, the UE does not add the one RAT from the plurality of RATs deployed in the current RAT to the RAT search list.

6. The processor of claim 1, wherein the UE does not trigger cell selection for a Public Land Mobile Network (PLMN) selection on a RAT included in the derangement RAT list.

7. The processor of claim 1, wherein the UE does not scan RATs included in the derangement RAT list during a Public Land Mobile Network (PLMN) search.

8. The processor according to claim 1, wherein the operation further comprises: Receive descoped RAT information from a remote server that forms the basis for the descoped RAT list, wherein the descoped RAT information is derived at the remote server based on crowdsourced data.

9. A user equipment (UE), comprising: A transceiver configured to communicate with a network; as well as The processor according to any one of claims 1 to 8 is communicatively coupled to the transceiver.

10. A processor for a user equipment (UE), the processor being configured to perform operations including: A list of frequency bands to be searched is generated based on the stored information, wherein the stored information includes at least one of the following: Predefined frequency band information for each Public Land Mobile Network (PLMN), predefined frequency band information for each Mobile Country Code (MCC), and frequency bands frequently detected by the UE; Remove the range frequency band from the list of frequency bands to be searched; as well as Perform a frequency band scan using the list of frequency bands to be searched.

11. The processor of claim 10, wherein the band scan is triggered based on a cell selection request or a PLMN search request.

12. The processor of claim 10, wherein the UE does not perform band scanning for the frequency bands of the PLMN or MCC derangement range.

13. The processor of claim 10, wherein the UE maintains at least one of the following: a derangement band list for each RAT, a derangement band list for each PLMN, and a derangement band list for each MCC.

14. The processor of claim 13, further comprising: Receive from a remote server derangement band information that provides a basis for at least one of the following: a derangement band list for each RAT, a derangement band list for each PLMN, and a derangement band list for each MCC, wherein the derangement band information is derived at the remote server based on crowdsourced data.

15. A user equipment (UE), comprising: A transceiver configured to communicate with a network; as well as The processor according to any one of claims 10 to 14 is communicatively coupled to the transceiver.

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