Method, user equipment, and non-transitory computer-readable medium for adaptive UE capability message compaction

Abstract

The UE performs a threshold number of attempts to send a default capability message to a base station, the default capability message indicating a default set of CA combinations supported by the UE. If the transmission is unsuccessful, the UE switches to a compact capability mode, in which the UE attempts to send compact UE capability messages indicating successively smaller subsets of the default set of CA combinations until the base station successfully receives the capability message or performs a second threshold number of unsuccessful transmission attempts. To facilitate configuration of the initial compact capability message, the UE maintains a PC list that lists one or more cells that have been previously identified as being unable to receive a default-sized capability message, and further identifies representations of a limited subset of CA combinations to include in capability messages sent to the corresponding listed cells.

Description

Background Art

[0001] When a connection is established between a mobile wireless device or other user equipment (UE) and a serving cell of a wireless network, the UE and the cell's base station participate in a capability transfer process in which the base station sends a query about the UE's capabilities (generally referred to as a UECapabilityEnquiry message in various cellular specifications), and the UE replies with a response summarizing the UE's relevant capabilities (generally referred to as a UECapabilityInformation message in various cellular specifications). Assuming the UECapabilityInformation message is successfully received at the base station, the base station configures the air interface between the UE and the base station based on the identified capabilities.

[0002] Some wireless network protocols, such as the fourth generation (4G) Long Term Evolution (LTE) Advanced (LTE-Advanced) protocol and the fifth generation (5G) New Radio (NR) protocol promulgated by the Third Generation Partnership Project (3GPP), employ carrier aggregation (CA), in which two or more individual carriers (each called a "component carrier" or "CC") are aggregated to provide an aggregate bandwidth with a higher bit rate. In the case where both the UE and the network support carrier aggregation, the UE capability information sent from the UE to the base station includes a list or other indication of the specific CA combinations that the UE is capable of supporting. As wireless protocols have evolved, the number of possible CA combinations has increased significantly. For example, LTE-Advanced supports aggregation of up to 5 component carriers in any given CA combination, while 5G NR supports up to 16 component carriers in any given CA combination. Dual Connectivity (DC) mode in 5G NR further increases the complexity of CA combinations because it allows carrier aggregation of LTE and 5G NR component carriers.

[0003] The increase in the number of possible CA combinations supported by a UE has led to a commensurate increase in the size of the UE capabilities message sent from the UE to the base station—initially tens of bytes before CA implementation, now up to tens of kilobytes in current implementations using CA in 5G, and expected to increase further as CA technology continues to evolve. This significant increase in the size of the UE capabilities message puts the UE capabilities message at risk of not being successfully received by the base station. In some cases, the base station may not be configured to accept UE capabilities messages of the size necessary to represent the UE's full CA capabilities. In other cases, the base station may be able to handle the size of such a UE capabilities message, but uplink channel conditions may prevent the UE capabilities message from being transmitted within the time allotted for sending the message (e.g., 5 milliseconds in some wireless specifications). If the base station does not successfully receive the UE capabilities message after a UE capabilities query, it will immediately release the UE following the UE capabilities transfer procedure. The UE and base station will repeat this setup and release scenario until a threshold number of failed transmission attempts is reached, at which point the UE will block the radio access technology (RAT) associated with the cell (typically by prohibiting further connection attempts) and fall back to using the legacy RAT. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] By referencing the accompanying drawings, the present disclosure will be better understood, and its numerous features and advantages will become apparent to those skilled in the art.The use of the same reference numerals in different drawings indicates similar or identical items.

[0005] Figure 1 is a block diagram of a cellular network with a UE employing an adaptive UE capabilities message compaction procedure in accordance with some embodiments.

[0006] Figure 2 is a block diagram of a hardware configuration of a UE according to some embodiments.

[0007] Figure 3 is a flow chart illustrating a method for adaptive UE capability message compaction at a UE according to some embodiments. Summary of the Invention

[0008] In the example described herein, a UE performs up to a threshold number of attempts to transmit a default capability message to a base station, the default capability message indicating a default set of CA combinations supported by the UE. If the transmission is unsuccessful, the UE switches to a compact capability mode, in which the UE attempts to transmit compact UE capability messages indicating successively smaller subsets of the default set of CA combinations until the base station successfully receives the capability message or a second threshold number of unsuccessful transmission attempts have been performed. To facilitate the configuration of the initial compact capability message, the UE maintains a PC list that lists one or more cells that have been previously identified as being unable to receive a default-sized capability message, and further identifies representations of a limited subset of CA combinations to include in capability messages sent to the corresponding listed cells.

[0009] In a first aspect, a method for capability transfer by a user equipment (UE) in a cellular network is provided, the method comprising: in a first mode, attempting to send a capability message representing successively smaller subsets of a set of carrier aggregation (CA) combinations from the UE to a base station of a serving cell of the cellular network until the base station successfully receives the capability message or a first threshold number of unsuccessful attempts to send the capability message has been performed.

[0010] The connection between a mobile wireless device or other user equipment (UE) and a serving cell of a wireless network can therefore be improved by compensating for problem cells.Bandwidth and network usage can also be reduced by sending successively smaller capability messages during the connection process.

[0011] Optionally, the method further includes, in a second mode preceding the first mode, attempting to send a capability message representing the CA combination set from the UE to the base station until a second threshold number of unsuccessful attempts to send the capability message have been performed; and, entering the first mode in response to the second threshold number of unsuccessful attempts having been performed.

[0012] In a second aspect, a method for capability transfer by a user equipment (UE) in a cellular network is provided, the method comprising: maintaining, at the UE, a problem cell list identifying one or more cells previously identified as failing to receive a capability message of a default size, the problem cell list further identifying at least one of: a specific subset of carrier aggregation (CA) combinations or a corresponding maximum number of component carriers for each listed cell; and, in response to determining that a base station of a serving cell cannot receive a capability message indicating a set of CA combinations supported by the UE: determining whether the serving cell is listed in the problem cell list; and, in response to determining that the serving cell is listed, attempting to send, from the UE to the serving cell, a capability message indicating a subset of CA combinations, the CA combination subset including: only CA combinations from a set of multiple component carriers having a maximum number of component carriers not greater than the maximum number of component carriers identified in the problem cell list of the serving cell; or, a specific subset of CA combinations. DETAILED DESCRIPTION

[0013] The common practice of a UE attempting to repeatedly send a default set of CA combinations in a UE capabilities message to a base station in a serving cell that is unable to receive the UE capabilities message (due to UL conditions or the base station's own configuration) that requires the default set of CA combinations often results in the UE defaulting to another, less capable RAT after successive transmission attempts fail. To avoid this, systems and techniques are described herein for adaptively adjusting the size of the UE capabilities message using iterative compaction to better ensure successful reception of the UE capabilities message by the base station in the serving cell. The techniques are based on increasingly aggressive filtering of the CA combinations to be included in the UE capabilities message based on the observed performance of previous attempts to send the UE capabilities message to the base station using less restrictive sets of CA combinations. Consequently, connectivity between a mobile wireless device or other user equipment (UE) and a serving cell of a wireless network can be improved.

[0014] In at least one embodiment, a UE employs a set of lists, including a problem cell (PC) list (a first list) and a network maximum CC list (a second list). The PC list includes cells of the network that have been previously identified (by the UE or other network entity) as "problem cells," where the base station of the cell was previously found to be unable to receive a UE capability message of a default size (e.g., a size sufficient to represent the entire set of CA combinations supported by the UE). The PC list further includes corresponding information indicating an associated representation of a limited subset of CA combinations for the corresponding cell, where this information may indicate the size or compactness to be achieved in the CA capabilities that should be sent in the UE capability message to the corresponding base station of the listed cell. This representation of the limited subset of CA combinations may include, for example, a representation of the maximum CC combination size to be included in the UE capability message, a specification of a specific reduced subset set of CA combinations, or a combination thereof. The network maximum CC list is used to identify a network-specific CA combination configuration, representing a limited subset of CA combinations to be implemented for the associated network, either as a maximum CC combination size for a given network (e.g., a given Public Land Mobile Network (PLMN)) or as a specific subset of CA combinations that can be implemented as a starting point for an adaptive UE capability adjustment process.

[0015] When a UE first camps on a serving cell associated with a base station, in response to a UE capability query message from the base station, the UE sends a UE capability message with a default set of CA combinations. The default set may represent the entire set of CA combinations supported by the UE, or a subset of the entire set filtered based on known CA capabilities of, for example, a mobile network operator (MNO) or mobile country code (MCC) associated with the network. If the base station of the serving cell successfully receives the UE capability message and does not release the UE in response, the UE and the base station collaborate to establish an air interface based on the announced capabilities including the announced CA capabilities. In addition, if the serving cell was previously identified as a problem cell on the PC list, the UE deletes the serving cell from the PC list to reflect the most recent successful attempt to send a full-size UE capability message to the base station of the serving cell.

[0016] However, if the base station fails to successfully receive the full-size UE capability message after a first threshold number (X>=1) of attempts during normal capability mode, the UE switches to compact capability mode and implements the UE capability information compaction process in this mode. During this process, the UE initially accesses the PC list to determine whether the cell has been identified as a problem cell. If so, the UE accesses the compact CA combination information associated with the cell in the PC list and generates a compact UE capability message based on this compact CA combination information to include an initial subset of the CA combination set. In other cases, if the cell does not exist in the PC list, the UE instead uses the PLMN identifier (ID) or other network ID to access the network-specific CA combination configuration of the corresponding network from the network maximum CC list, and then generates a compact UE capability message based on this network-specific CA combination configuration. The UE then attempts to send the compact UE capability message to the base station. If successfully received at the base station, the UE and the base station can establish an air interface based on the capabilities announced in the compact UE capability message.

[0017] In other cases, if this compact UE capability message is not successfully received at the base station, the UE will continue to iteratively generate compact UE capability messages of successively smaller subsets of the CA capability default set (and therefore of smaller and smaller size) until the base station receives the compact UE capability message successively or until a second threshold number (Y>=1) of transmission attempt iterations of the compacting process have been performed. If the base station receives the compact UE capability message successively, the UE identifies the corresponding cell as a problem cell and adds the cell to the PC list, including adding information about the compact subset of CA combinations included in the successfully sent compact UE capability message. In other cases, if Y iterations have been attempted (including an initial iteration using problem cell information or network-specific information) and the base station has not successfully received the compact UE capability message, the UE disables carrier aggregation and attempts to connect to the base station using a UE capability message that does not contain any CA capability information.

[0018] Using this approach, the UE can iteratively reduce the number of CA combinations referenced in successively transmitted UE Capabilities Messages until the base station is able to receive the compact UE Capabilities Message, or until a total of X+Y unsuccessful attempts to send the UE Capabilities Message have been made. In this way, the UE can effectively "tune" the size of the UE Capabilities Message to provide a UE Capabilities Message that can be successfully received and processed by the base station in many cases, thereby avoiding the need to switch to a lower-performance RAT instead. Problem cells can thus be compensated during the connection process. Furthermore, the Non-Access Stratum (NAS) layer of a cellular protocol typically imposes a significant backoff period (e.g., 12 minutes in some implementations) after the base station has performed a third threshold number of consecutive UE releases (Z>1), meaning that the UE is prohibited from attempting to connect for an extended period of time. Therefore, given a value for Z, the values ​​of X and Y can be selected to minimize or avoid the risk of performing Z unsuccessful attempts and subsequently triggering the UE to be prohibited from attempting to connect for a significant period of time. For example, the UE can be configured to prohibit further attempts to connect to the base station after a third threshold number Z of consecutive UE releases by the base station. The sum of X and Y can be less than or equal to Z.

[0019] For ease of illustration, the procedures of the present disclosure are described below in the context of an example 4G / 5G radio resource control (RRC) message exchange procedure for UE capability notification. However, these procedures are equally applicable to other UE capability notification protocols. Therefore, unless otherwise specified, references to the UECapabilityEnquiry RRC message and the UECapabilityInformation RRC message should equally apply to other equivalent UE capability query messages and UE capability messages, respectively.

[0020] Figure 1 The present invention illustrates three example scenarios in a mobile cellular system 100 that utilizes adaptive UE capability message compaction to compensate for problem cells according to some embodiments. As shown, the mobile cellular system 100 includes a user equipment (UE) 102 and a network 104, wherein the UE 102 and the network 104 are configured to communicate using one or more radio access technologies (RATs) (e.g., 4G LTE or 5G NR RATs). The UE 102 can include any of a variety of wireless communication devices, such as a cellular phone, a cellular-enabled tablet or laptop, a car or other vehicle using cellular services (e.g., for navigation, providing entertainment services, or using an in-car mobile hotspot), and the like.

[0021] Network 104 includes multiple cells 106, including cells 106-1 and 106-2, shown, connected to a core network 108, which in turn is connected to one or more wide area networks (WANs) 110, such as the Internet. Each cell 106 includes a base station 112, such as base station 112-1 for cell 106-1 and base station 112-2 for cell 106-2. In implementations where the cells implement the 5G NR protocol, the base stations are typically referred to as "5G NodeBs" or "gNBs," while when the cells implement the 4G LTE protocol, the corresponding base stations are typically referred to as "extended NodeBs" or "eNBs."

[0022] As a general operational overview, a UE 102 selects a cell 106 of a network 104 to camp on using any of a number of well-known selection procedures. As part of an initial registration procedure, the base station 112 of the selected cell 106 (i.e., the "serving cell") and the UE 102 perform a capability transfer procedure so that the UE can advertise its relevant capabilities to the base station 112, which in turn uses the capabilities to establish an air interface between the UE 102 and the base station 112 for wireless signaling of uplink (UL) and downlink (DL) radio frequency (RF) signaling representing the transfer of control and data information. To illustrate, in 4G LTE and 5G NR protocols, the capability transfer procedure is performed as an exchange of RRC messages using the RRC protocol at Layer 3 of the cellular protocol stack. First, the base station sends a UECapabilityEnquiry RRC message to the UE, to which the UE generates and sends a UECapabilityInformation RRC message (an example of a "capability message") containing the relevant UE capabilities in response. If the base station is able to receive and process the UECapabilityInformation RRC message, the base station extracts the UE capability information and establishes the air interface accordingly. The base station then sends a hybrid automatic repeat request (HARQ) acknowledgement (ACK) signal to confirm the successful receipt of the UECapabilityInformation RRC message at the base station. However, if the base station 112 is unable to fully receive and process the UECapabilityInformation RRC message, either because it is too large for the base station to process or because the UL channel conditions are poor, and therefore the transmission of the UECapabilityInformation RRC message times out based on a specified timeout timer, the base station 112 releases the UE. The UE may then retry another iteration of this capability transfer process or choose to use a different, lower-performance RAT to establish a connection with the network.

[0023] In at least one embodiment, UE 102 and network 104 are configured to support carrier aggregation (CA). Consequently, the UE capabilities signaled by UE 102 in the UECapabilityInformation RRC message include information indicating the CA combinations (i.e., aggregated combinations of component carriers) supported by UE 102. As described above, 4G LTE allows for up to five component carrier CA combinations, while 5G NR allows for up to 16 component carrier CA combinations, meaning that UE 102 may be able to support thousands of CA combinations. Consequently, including information identifying each of the numerous CA combinations that UE 102 is capable of supporting can cause the size of the UECapabilityInformation RRC message to swell, typically by tens of kilobytes. The base station 112 of the cell 106 to which UE 102 is attempting to connect may be unable to receive and fully process an RRC message of this size, or the time required to send a UECapabilityInformation RRC message of this size may exceed a timeout limit implemented for sending such messages due to poor UL channel conditions.

[0024] To illustrate, Figure 1 As shown in view 121 of FIGURE 1, cell 106-1 is considered a "no problem cell" or "non-PC," wherein UE 102 can send a default UECapabilityInformation RRC message 114 containing information indicating a default set of CA combinations supported by UE 102, and base station 112-1 of cell 106-1 can fully receive and correctly process the message without triggering base station 112-1 to release UE 102; that is, default UECapabilityInformation RRC message 114 can be "successfully sent" to base station 112-1 of non-PC cell 106-1. Default UECapabilityInformation RRC message 114 typically includes most or all of the set of CA combinations that UE 102 can support, or a subset of the set of CA combinations filtered based on the known CA capabilities of the MNO or MCC associated with network 104. In this normal capability mode, the UE can send a capability message indicating the set of CA combinations to the base station.

[0025] However, if Figure 1As shown in view 122 of FIG, cell 106-2 is considered a "problem cell" or "PC," in which UE 102 is unable to successfully transmit a default UECapabilityInformation RRC message 114, either because base station 112-2 of cell 106-2 is unable to process an RRC message of its size, or because the size of UECapabilityInformation RRC message 114 cannot be transmitted within a specified time window due to poor UL channel conditions between UE 102 and base station 112-2. Consequently, repeated attempts by UE 102 to transmit the default UECapabilityInformation RRC message 114 may result in connection delays (due to a typical 10-second wait period between each attempt), or, if a threshold number of connection failures are exceeded, may result in the NAS protocol of UE 102 prohibiting UE 102 from making any further connection attempts for a relatively long period of time.

[0026] Therefore, in at least one embodiment, rather than continuing to attempt to send a default UECapabilityInformation RRC message 114 to the problem cell 106-2, the UE 102 employs an adaptive UECapabilityInformation message compaction process that iteratively generates smaller and smaller, or increasingly compact, UECapabilityInformation RRC messages 116, as shown in view 123, by iteratively reducing the represented CA combinations supported in the compact UECapabilityInformation RRC message 116 until a compact UECapabilityInformation RRC message 116 of sufficiently small size is generated and successfully sent to the base station 112-2 of the problem cell 106-2, as shown in view 123, or until a threshold number of compaction / transmission iterations have occurred, at which point the UE 102 can switch to a different RAT or attempt a connection without CA capabilities. Note that Figure 1 The box heights of the UECapabilityInformation RRC messages 114 and 116 in FIG. 1 suggest the corresponding sizes of these messages relative to each other.

[0027] In this way, the UE may attempt to send a capability message representing a CA combination set from the UE to a base station (of a serving cell of a cellular network) in normal capability mode until a first threshold number of unsuccessful attempts to send the capability message have been performed. In response to having performed the first threshold number of unsuccessful attempts, the UE may enter compact capability mode. In compact capability mode, the UE may attempt to send a capability message representing successively smaller subsets of the CA combination set until the base station successfully receives the capability message or a second threshold number of unsuccessful attempts to send the capability message have been performed. Figure 3 An example implementation of an adaptive UE capability message compaction procedure is described.

[0028] Figure 2 An example hardware configuration of a UE 102 according to some embodiments is illustrated. As shown, the UE 102 includes an RF front end 202, which includes one or more antenna arrays 204 and one or more transceivers for converting digital information into RF signaling and for converting RF signaling into digital information. The UE 102 also includes one or more modems (e.g., an LTE modem 206 and a 5G NR modem 208) for controlling the RF front end 202, one or more processors 210, and one or more memories 212 or other non-transitory storage components. The one or more processors 210 shown may include, for example, an application processor and may also represent one or more modem processors of the modems 206 and 208. Similarly, the one or more memories 212 shown may include system memory for the UE 102 and one or more local memories used by the modems 206 and 208 or other components of the UE 102. In addition, it should be understood that for ease of illustration, the UE 102 may include memory from Figure 2 Additional components omitted include, for example, one or more displays, one or more touch screens, a keypad, a mouse, a touchpad, a microphone, speakers and other user input / output devices, one or more sensors, a battery or other power source, a graphics processing unit (GPU) or other co-processor, etc.

[0029] As a general operational overview, the one or more processors 210 execute instructions of a software stack stored in one or more memories 212, including an operating system (OS) (not shown) executed by an application processor, one or more user software applications (not shown) executed by the application processor, and one or more cellular protocol stacks 214, such as a 4G LTE protocol stack implemented by the LTE modem 206 and a 5G NR protocol stack implemented by the 5G NR modem 208, executed at least in part by the modem processors of the modems 206 and 208. The cellular protocol stacks 214 include multiple protocol layers, including a core network layer responsible for formatting and controlling communications between the UE and the network (e.g., the core network 108 of the network 104, Figure 1 ) and a radio resource control (RRC) protocol 218, which manages connection establishment and release functions, system information broadcast, radio bearer establishment, reconfiguration, and release, RRC connection mobility procedures, etc. In one embodiment, RRC protocol 218 includes a CA capability management module 220, which is configured to implement capability transfer of UE 102, and more specifically, the adaptive UE capability message compaction process, as described herein. In other embodiments, CA capability management module 220 is partially or completely implemented in different layers of cellular protocol stack 214.

[0030] During the execution of the adaptive UE capability message compaction process, the CA capability management module 220 utilizes various information stored in one or more memories 212 and belonging to the UE 102 or the network 104. This includes UE capability information 222 indicating the current capabilities of the UE 102, which includes CA capability information 224 indicating the set of CA combinations currently supported by the UE 102. Typically, the set of CA combinations supported by the UE 102 is determined by the hardware capabilities of the UE 102 and is therefore effectively a maximal superset. As described herein, in some embodiments, rather than using the complete set of all possible supported CA combinations as the "CA combination set," the UE 102 uses a default set of CA combinations filtered from the universe of supported CA combinations based on the CA capabilities associated with the PLMN ID of the serving cell as the "CA combination set" (where the PLMN ID is typically composed of a combination of a Mobile Country Code (MCC) and a Mobile Network Code (MNC)). These CA combinations are typically represented as CA descriptors or CA configurations that reference certain bandwidth (BW) classes and the number of component carriers in each class, such as a CA descriptor CA_1C-5A, which, for a CA combination having a total of 3 component carriers, represents two contiguous component carriers in band 1 and one component carrier in band 5. Thus, the CA capability information 224 can be implemented as a list or other data structure containing CA descriptors or other identifiers of the CA combinations supported by the UE 102.

[0031] The information used by CA capability management module 220 further includes a PC list 226, which lists cells in one or more networks that were previously identified by UE 102 or other network entities as problem cells that were unable to successfully receive and process UE capability messages, where these UE capability messages contain information indicating a default set of CA combinations supported by UE 102 (a list of one or more cells in one or more networks that were previously identified as being unable to successfully receive a default-sized capability message). PC list 226 also includes information related to each identified problem cell, including an indication of a limited subset of CA combinations previously established for the problem cell. For illustration, Table 1 below describes an example configuration of PC list 226:

[0032] Table 1: PC List

[0033]

[0034] As shown in Table 1, each entry in the PC list 226 includes a network identifier (e.g., PLMN ID) and a cell identifier for the network 104, which together uniquely identify a given cell. Each entry also includes one or both of a max_CC_num value and a specific_CA_subset field. The max_CC_num value identifies the maximum number of component carriers that can be implemented in a CA combination indicated in a compact UECapabilityInformation RRC message sent to the base station 112 of the corresponding problem cell. In other words, max_CC_num represents the maximum number of component carriers that can be present in any CA combination included in a limited subset of CA combinations sent to the corresponding problem cell. For example, while 5G NR allows up to 16 component carriers to be aggregated in a CA combination, when sending a compact UECapabilityInformation RRC message to a problem cell identified by PLMNID 387652 and cell ID 2011, the UE 102 is limited to including only those CA combinations with 10 or fewer aggregated component carriers (to reduce the size of the compact UECapabilityInformation RRC message). Instead of or in addition to limiting the maximum number of aggregated component carriers to reduce the size of the compact UECapabilityInformation RRC message, the UE 102 may instead include only a specified subset of the default set of CA combinations, where the specified subset is identified in the specific_CA_subset field as a limited sublist identifying each CA combination for inclusion in the limited subset, as shown in entries 1 and 2 of Table 1, or as an index value for indexing entries of a separate table containing different subsets of CA combinations supported by the UE 102. The list 226 thus contains an associated representation of the limited subset of CA combinations for each cell listed.

[0035] The information used by the CA capability management module 220 may also include a network maximum CC list 228, an example configuration of which is shown in Table 2 below:

[0036] Table 2: Network maximum CC list

[0037] PLMN ID max_CC_num_PLMN specific_CA_subset 124724 4 1A-3A,1A-42A-42C,... 387652 10 3A-3A-20A,5A-66A-66C 874581 3 [Index 4] 988181 16 [null] ... ... ...

[0038] As shown, each entry in the network maximum CC list 228 corresponds to a network (e.g., identified by a PLMN ID) and specifies one or both of the following: the maximum number of component carriers (max_CC_num_PLMN) that can be implemented in the CA combination announced by the UE 102 to the network, or a specific subset of the default set of CA combinations for the corresponding network, as similarly described above. Note that, unlike the PC list 226, the granularity of the network maximum CC list 228 is at the network level (or MCC level) rather than at the level of a specific cell. The list 228 thus identifies one or more networks and an associated representation of a limited subset of CA combinations for each network.

[0039] Figure 3 An example method 300 illustrating an adaptive UE capability information compaction process implemented by a UE 102 according to some embodiments is illustrated. For ease of reference, refer to Figure 2 3. The method 300 is described with reference to the hardware configuration of the UE 102 depicted in FIG. 3. The method 300 begins at block 302 with the configuration of the UE 102, which includes obtaining initial versions of the PC list 226 and the network maximum CC list 228. As represented by block 303-1, in some embodiments, one or both of these lists are initially unpopulated and are built up on an entry-by-entry basis as the UE 102 interacts with cells on one or more networks. As represented by block 303-2, in other embodiments, one or both of these lists are initially populated at least when the UE 102 is provisioned by the corresponding MNO. Further, as represented by block 303-3, in some embodiments, the initial version of one or both of these lists is obtained from a remote server (i.e., "from the cloud"), such as from the WAN 110 ( Figure 1 ) is obtained from a remote server in the core network 108. To illustrate, the MNO that provides UE 102 may have developed a database of correspondences between PLMNs or MCCs and the maximum number of component carriers that can be implemented in a CA combination, prepared a version of network maximum CC list 228 based on this information, and stored a copy of this version of network maximum CC list 228 in memory 212 when UE 102 is provided. As another example, a server on the Internet or otherwise accessible to core network 108 can be used to store and provide a dynamically updated version of PC list 226. UE 102 can access and store a current copy of PC list 226 in response to a start event, a periodic trigger, or another trigger, and when UE 102 updates its local copy of PC list 226, UE 102 can transmit the update back to the server, whereupon the changes indicated by UE 102 can be propagated to other UEs, such that the identification and documentation of problem cells can be effectively tasked to any number of UEs.

[0040] At block 304, UE 102 identifies the serving cell 106 on which to camp and initiates an attempt to connect to the identified cell. This connection attempt triggers the base station 112 of the serving cell 106 to send a UECapabilityEnquiry RRC message to UE 102. In response to this message, CA capability management module 220 enters normal capability mode. In this mode, at block 306, CA capability management module 220 utilizes CA capability information 224 to identify a default set of CA combinations, generates a default UECapabilityInformation RRC message representing the identified default set of CA combinations, and UE 102 repeatedly attempts to send the default UECapabilityInformation RRC message until the default UECapabilityInformation RRC message is successfully received by the base station 112 of the serving cell 106 or a threshold number X of attempts to send the default UECapabilityInformation RRC message has been made. In some embodiments, successful reception of the default UECapabilityInformation RRC message is indicated by, for example, receiving a HARQ ACK signal from the base station 112 , indicating that the default UECapabilityInformation RRC message has been received and fully processed by the base station 112 .

[0041] The default set of CA combinations may include the entire set of CA combinations supported by the UE 102 or a filtered subset. To illustrate, in some embodiments, the MNO or other network entity may determine that cells associated with a particular cellular operator or a network associated with a particular MCC generally only support up to a certain number of component carriers in any available CA combination. Using this information, the CA capability management module 220 may identify the cellular operator or MCC associated with the camped cell 106 and remove all CA combinations that have more component carriers than the identified maximum number of component carriers for the identified cellular operator or MCC, so that the default set of CA combinations does not include any CA combinations known to be incompatible with the network 104 and thus provides a smaller default set of CA combinations. As a result, bandwidth usage may be reduced during the connection.

[0042] At block 308, the CA capability management module 220 determines whether the default UECapabilityInformation RRC message was successfully sent to the base station 112 within X attempts. If so, the CA capability management module 220 identifies the serving cell 106 as the current non-problem cell at block 310. Therefore, the CA capability management module 220 checks the PC list 226 to determine whether the serving cell 106 was previously identified as a problem cell, and if so, clears or removes the entry in the PC list 226 associated with the now non-problem serving cell 106.

[0043] In other cases, if the default UECapabilityInformation RRC message is not successfully sent to the base station 112 within X attempts, the CA capability management module 220 enters a compact capability mode in which the UE 102 iteratively attempts to send successively more compact UECapabilityInformation RRC messages until a compact UECapabilityInformation RRC message is successfully sent to the base station 112 or until a threshold number Y of transmission attempts have been made. Thus, at block 312, the CA capability management module 220 determines whether the cell 106 is on the PC list 226 and, therefore, has been identified as a problem cell. If so, at block 314, the CA capability management module 220 determines an initial compact maximum number of component carriers in the CA combination of the compact subset of the CA combination (compact_CC_num) based on the maximum number of component carriers in the CA combination identified in the max_CC_num field of the cell entry in the PC list 226; i.e., sets compact_CC_num = max_CC_num. For illustration, if the PC list 226 indicates that the max_CC_num of the cell 106 is 6, the initial maximum number of component carriers allowed in the CA combination to be included in the compact CA capability is set to 6. Alternatively, if a specific subset of CA combinations is listed in the specific_CA_subset field of the corresponding entry in the PC list 226, the CA capability management module 220 determines the compact subset of CA combinations to include the specific subset. In this manner, the UE can configure the initial capability message for transmission in the compact capability mode to indicate a subset of the set of CA combinations based on the indication of the limited subset of CA combinations associated with the serving cell.

[0044] In other cases, if the cell is not on the PC list 226 and therefore has not been recently identified as a problem cell, then at block 316, the CA capability management module 220 instead turns to the network maximum CC list 228 to determine the max_CC_num_PLMN of the network 104 or the MCC associated with the cell 106, and sets compact_CC_num equal to max_CC_num_PLMN from the entry in the network maximum CC list 228 associated with the network 104. In this way, the UE can configure the initial capability message to be sent in compact capability mode to represent a subset of the set of CA combinations based on the representation of a limited subset of CA combinations associated with the network. If the cell 106 is associated with a network that is not listed in the network maximum CC list 228, then in one embodiment, the capability management module 228 sets compact_CC_num equal to the maximum number of component carriers present in the default set of CA combinations used in normal mode minus one.

[0045] At block 318, the CA capability management module 220 generates (or configures) a compact UECapabilityInformation RRC message (initial capability message) that includes a filtered or limited subset of the default set of CA combinations and attempts to send the compact UECapabilityInformation RRC message to the base station 112 serving the cell 106. In at least one embodiment, the filtered subset of the default set of CA combinations is generated by removing any CA combinations in the default set that include a number of component carriers greater than the initial value of compact_CC_num set at blocks 314 or 316. For illustration, if compact_CC_num is initially set to 4 component carriers, any CA combinations in the default set that have 5 or more component carriers are omitted from the filtered subset of CA combinations included in the compact UECapabilityInformation RRC message. By filtering the set of CA combinations in this manner, the total size of the generated compact UECapabilityInformation RRC message including the filtered subset is reduced compared to the size of a default UECapabilityInformation RRC message including the default set of CA combinations, and is therefore more likely to be successfully transmitted to the base station 112.

[0046] At block 320, CA capability management module 220 determines whether the compact UECapabilityInformation RRC message generated at block 318 was successfully sent to base station 112. If so, CA capability management module 220 has determined that base station 112 cannot receive the default UECapabilityInformation RRC message with the default set of CA combinations, but can receive the compact UECapabilityInformation RRC message with the current limited subset of CA combinations. Therefore, at block 322, CA capability management module 220 notifies NAS protocol 216 of the reduced CA capabilities implemented for the air interface established between base station 112 and UE 102 based on the compact UECapabilityInformation RRC message. Typically, base stations such as base station 112 only seek capability information from a UE when the UE initially attaches to the base station or moves through a predefined boundary area. Therefore, in such cases, the UE may be restricted to using a relatively smaller carrier component allocation for a relatively longer period of time. However, problem cells are typically isolated issues; that is, nearby cells are typically not problematic. Therefore, to facilitate faster restoration of optimal CA capabilities, in some embodiments, whenever the UE 102 subsequently camps on another cell other than the current problem cell, the NAS protocol 218 of the UE 102 is configured to trigger the sending of a Location Area Update (LAU) message that includes a flag that triggers the receiving base station to re-initiate the UE capability query procedure so that the UE 102 does not stay in the same CA configuration that was implemented when attached to the current problem cell.

[0047] Additionally, at block 322, CA capability management module 220 also identifies cell 106 as a problem cell as a result of it being able to receive only a compact subset of CA capabilities, and therefore adds cell 106 to PC list 226, setting the max_CC_num field to the current value of compact_CC_num.

[0048] In other cases, if at block 320 the CA capability management module 220 determines that the transmission of the initial compact UECapabilityInformation RRC message was unsuccessful, the CA capability management module 220 prepares to transmit further compact UECapabilityInformation RRC messages. Therefore, at block 324, the CA capability management module 220 (iteratively) decrements the current value of compact_CC_num by one or some other specified value K (i.e., compact_CC_num=compact_CC_num-1, or more generally, =compact_CC_num-K, where K is an integer greater than or equal to 1) and increments the attempt counter compact_attempts by one (i.e., compact_attempts=compact_attempts+1) to reflect the most recent failed attempt to transmit the compact UECapabilityInformation RRC message.

[0049] At block 326, the CA capability management module 220 determines whether a threshold number of compact UECapabilityInformation RRC message transmissions have been attempted unsuccessfully (i.e., whether compact_attempts = Y). If not, the method 300 returns to block 318, whereupon the CA capability management module 220 generates another compact UECapabilityInformationRRC message that includes a further filtered subset of the default set of CA combinations, excluding all CA combinations having more component carriers than the current value of compact_CC_num, and performs another iteration of the transmission attempt and evaluation process represented by blocks 318, 320, 322, 324, and 326. In this way, the UE can attempt to transmit capability messages representing successively smaller subsets of the set of CA combinations to the base station in compact capability mode. This transmission attempt and evaluation process is repeated for increasingly compact UECapabilityInformation RRC messages in each iteration (this is because compact_CC_num is reduced with each iteration, thereby excluding more and more CA combinations from the filter subset included in the compact UECapabilityInformation RRC message) until one of the iterations produces a compact UECapabilityInformation RRC message that is small enough to be successfully received by the cell's base station, or until a threshold number Y of compact transmission attempts have been performed.

[0050] If the CA capability management module 220 detects in the iteration of block 326 that the threshold number Y of compact attempts has been performed, the CA capability management module 220 stops attempting to establish a connection with the base station 112 that includes CA capabilities and instead disables carrier aggregation at the UE 102 at block 328 and generates and sends a UECapabilityInformation RRC message that does not advertise any CA capabilities at block 330 in an attempt to send a relatively smaller UECapabilityInformationRRC message that should be received and successfully processed by the base station 112, albeit at the expense of losing CA capabilities, while maintaining the ability to use the higher performance RAT provided by the air interface with the cell 106. Thereafter, the method 300 flows to block 322, where the CA capability management module 220 notifies the NAS protocol 216 of the elimination of the CA capabilities of the air interface established between the base station 112 and the UE 102.

[0051] As described above, in some embodiments, UE 102 utilizes a PC list 226 initially populated with problem cell information obtained from a shared resource, such as a shared PC list stored at a remote server and updated by multiple UEs. In this case, at block 332, UE 102 can send any updates to its local copy of PC list 226 to the remote server, including the addition of newly encountered problem cells and the removal of previously problematic cells that no longer behave like problem cells, and these updates can be propagated to other UEs. Sending updates can be performed each time a change is made to PC list 226, in response to a periodic trigger or in response to a threshold number of changes being made, etc. The initial version of network maximum CC list 228 can also be populated from a shared resource at the remote server and updated in a similar manner.

[0052] As shown in method 300, during normal capability mode, the CA capability management module 220 attempts up to X times to transmit a default UECapabilityInformation RRC message for successful reception by the base station 112 (i.e., without triggering a subsequent release of the UE 102 by the base station 112). If successful, if the cell 106 is on the PC list 226, the associated cell is removed from the PC list 226. If the X attempts are unsuccessful, the CA capability management module 220 enters a compact capability mode and makes up to Y+1 attempts to successfully transmit the UECapabilityInformation RRC message by successively reducing the number of CA combinations represented in the UE capability information of each message for each successive attempt. In the above example, for each attempt, increasingly reducing or filtering the CA combinations is accomplished by reducing the maximum number of component carriers that can be represented in the included CA combinations for each iteration. For example, attempting to transmit capability messages representing successively smaller subsets of the set of CA combinations may include, for each successive capability message, successively reducing the maximum number of component carriers that can be present in any CA combination within the subset of the CA combinations represented in the capability message. However, as described above, the PC list 226 and the network maximum CC list 228 may instead begin by identifying a particular subset of CA combinations, and each iteration may further reduce the number of CA combinations included in the particular subset by filtering more and more aggressively (e.g., removing 20% ​​of the CA combinations from the particular subset in the first iteration, 40% of the CA combinations in the next iteration, etc.). For example, attempting to send capability messages representing successively smaller subsets of the set of CA combinations may include identifying an initial subset of the set of CA combinations, and for each successive capability message, successively reducing the number of CA combinations from the initial subset represented in the capability message.

[0053] Method 300 provides for up to X+Y+1 attempts to successfully send a UECapabilityInformationRRC message to base station 112, including up to X attempts to send a default UECapabilityInformationRRC message during normal capability mode, and up to Y attempts to send increasingly compact UECapabilityInformationRRC messages during compact capability mode, and if that fails, a final UECapabilityInformationRRC message that does not include any CA capabilities. Consistent with several cellular protocols, NAS protocol 216 will typically allow up to Z consecutive releases from a base station before NAS protocol 216 will prohibit UE 102 from attempting to connect to the base station again for a significant duration. For example, 4G LTE and 5G NR specifications specify that after 5 consecutive releases from a base station, NAS will prohibit a UE from attempting to connect to the base station for 12 minutes. Therefore, to prevent NAS protocol 216 from triggering such a connection bar, the values ​​of X and Y can be set relative to Z according to the following expression: X+Y+1<=Z. Thus, assuming Z=5 for 4G LTE or 5G NR configuration, setting X to 2 would allow a second attempt to send a default UECapabilityInformation RRC message, and then allow the UE 102 to attempt to send up to two consecutive smaller UECapabilityInformationRRC messages before having to fall back to attempting to establish a connection with a base station that has abandoned the use of carrier aggregation. Similarly, setting X to 1 would allow one attempt to send a default UECapabilityInformation RRC message, and then allow the UE 102 to attempt to send up to three consecutive smaller UECapabilityInformationRRC messages before having to fall back to attempting to establish a connection with a base station that has abandoned the use of carrier aggregation.

[0054] In some embodiments, certain aspects of the above-described technology can be implemented by one or more processors of a processing system that executes software. The software includes one or more sets of executable instructions stored on a non-transitory computer-readable storage medium or tangibly embodied in other cases. The software may include instructions and certain data that, when executed by the one or more processors, manipulate the one or more processors to perform one or more aspects of the above-described technology. The non-transitory computer-readable storage medium may include, for example, a magnetic or optical disk storage device, a solid-state storage device such as flash memory, a cache, a random access memory (RAM), or other one or more non-volatile storage devices, etc. The executable instructions stored on the non-transitory computer-readable storage medium may be in source code, assembly language code, object code, or other instruction formats that are interpreted or otherwise executable by one or more processors.

[0055] Computer-readable storage media may include any storage medium or combination of storage media that is accessible by a computer system during use for providing instructions and / or data to the computer system. Such storage media may include, but are not limited to, optical media (e.g., compact discs (CDs), digital versatile discs (DVDs), Blu-ray discs), magnetic media (e.g., floppy disks, magnetic tapes, or magnetic hard drives), volatile memory (e.g., random access memory (RAM) or cache memory), non-volatile memory (e.g., read-only memory (ROM) or flash memory), or microelectromechanical systems (MEMS)-based storage media. Computer-readable storage media may be embedded in a computing system (e.g., system RAM or ROM), fixedly attached to a computing system (e.g., a magnetic hard drive), removably attached to a computing system (e.g., an optical disc or flash memory based on a universal serial bus (USB), or coupled to a computer system via a wired or wireless network (e.g., a network accessible storage (NAS)).

[0056] Note that not all of the activities or elements described above in the general description are required, a portion of a particular activity or device may not be required, and one or more other activities or included elements may be performed in addition to those described above. Furthermore, the order in which the activities are listed is not necessarily the order in which they are performed. Moreover, the concepts have been described with reference to specific embodiments. However, it will be understood by those skilled in the art that various modifications and changes may be made without departing from the scope of the present disclosure as set forth in the appended claims. Accordingly, the specification and drawings should be regarded as illustrative rather than restrictive, and all such modifications are intended to be included within the scope of the present disclosure.

[0057] Benefits, other advantages and solutions to problems have been described above with respect to specific embodiments. However, benefits, advantages, solutions to problems, and any features that may cause any benefit, advantage, or solution to a problem to appear or become more apparent should not be construed as key, required, or essential features of any or all of the claims. Furthermore, the specific embodiments disclosed above are illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners that will be apparent to those skilled in the art having the benefit of the teachings herein. Except as described in the claims below, there is no intention to be limited to the details of construction or design shown herein. It is therefore apparent that the specific embodiments disclosed above may be altered or modified, and all such variations are considered to be within the scope of the disclosed subject matter. Accordingly, the protection sought herein is as described in the appended claims.

Claims

1. A method for performing capability transfer by a user equipment (UE) in a cellular network, the method comprising: in a first mode, attempting to send, from the UE to a base station of a serving cell of the cellular network, a capability message representing a successively smaller subset of a set of carrier aggregation (CA) combinations until a capability message is successfully received by the base station or a first threshold number of unsuccessful attempts to send a capability message has been performed, The attempt to send capability messages representing successively smaller subsets of the set of CA combinations includes: For each successive capability message, the maximum number of component carriers that can be present in any CA combination included in the subset of CA combinations indicated in the capability message is successively reduced.

2. The method according to claim 1, further comprising: in a second mode preceding the first mode, attempting to send a capability message indicating the set of CA combinations from the UE to the base station until a second threshold number of unsuccessful attempts to send a capability message have been performed; as well as In response to the second threshold number of unsuccessful attempts having been performed, the first mode is entered.

3. The method according to claim 2, further comprising: maintaining a first list of one or more cells in one or more networks previously identified as being unable to successfully receive a capability message of a default size, wherein the first list contains an associated representation of a limited subset of CA combinations for each cell listed in the first list; and Entering the first mode includes: In response to determining that the serving cell is listed in the first list, based on the representation of the limited subset of the CA combinations associated with the serving cells in the first list, configuring the initial capability message sent in the first mode to represent a subset of the set of CA combinations.

4. The method according to claim 3, further comprising: maintaining a second list identifying one or more networks and an associated representation of a limited subset of CA combinations for each network listed in the second list; and Wherein, entering the first mode further includes: In response to determining that the serving cell is not listed in the first list and the cellular network is listed in the second list, configuring an initial capability message for transmission in the first mode to represent a subset of the set of CA combinations based on the representation of the limited subset of the CA combinations associated with the networks in the second list.

5. The method according to claim 4, wherein Entering the first mode further includes: In response to determining that the serving cell is not listed in the first list and the cellular network is not listed in the second list, configuring the initial capability message for transmission in the first mode to indicate a subset of the set of CA combinations, the subset of the set of CA combinations including only CA combinations having a maximum number of component carriers that is at least 1 less than a maximum number of component carriers present in the capability message transmitted in the second mode.

6. The method according to claim 4, further comprising: Obtaining an initial version of the second list from a remote server; as well as In response to determining a change in the number of CA combinations determined to be supported by the network, an update to the second list is sent to the remote server.

7. The method according to claim 3, wherein: The representation of the limited subset of CA combinations of cells listed in the first list comprises a maximum number of component carriers that can be present in any CA combination included in the limited subset.

8. The method according to claim 3, wherein: The representation of the limited subset of CA combinations of cells listed in the first list comprises a specified list of CA combinations contained in the limited subset.

9. The method according to claim 3, further comprising: In response to a capability message being successfully sent to the base station while in the second mode, the serving cell is removed from the first list.

10. The method according to claim 9, further comprising: Obtaining an initial version of the first list from a remote server; as well as In response to removing the serving cell from the first list, sending an update to the first list to the remote server.

11. The method according to claim 3, further comprising: An initial version of the first list is obtained from a remote server.

12. The method according to claim 1, wherein The set of CA combinations includes a default set of CA combinations supported by the UE.

13. The method according to claim 12, wherein: The default set of CA combinations includes: the entirety of the CA combinations supported by the UE; or a subset of the entirety of the CA combinations supported by the UE, wherein the subset of the entirety of the CA combinations includes only those CA combinations that are identified as being capable of support based on the network operator of the cellular network or the mobile country code associated with the serving cell.

14. The method according to claim 2, wherein: The UE is configured to: after the base station continuously performs a third threshold number of releases of the UE, prohibit further attempts to connect to the base station; as well as The sum of the first threshold number and the second threshold number is less than or equal to the third threshold number.

15. The method according to claim 2, further comprising: in response to performing the first threshold number of unsuccessful attempts to send a capability message, attempting to send a capability message that does not indicate any CA combination from the UE to the base station; The UE is configured to: after the base station continuously releases the UE a third threshold number of times, prohibit further attempts to connect to the base station; and The sum of the first threshold number and the second threshold number is less than the third threshold number.

16. The method according to claim 1, further comprising: In response to performing the first threshold number of unsuccessful attempts to send a capability message, attempting to send a capability message that does not indicate any CA combination from the UE to the base station.

17. The method according to claim 1, wherein Attempts to send capability messages representing successively smaller subsets of the set of CA combinations include: identifying an initial subset of the set of CA combinations; and For each successive capability message, the number of CA combinations is successively reduced from the initial subset indicated in the capability message.

18. The method according to any one of claims 1 to 17, wherein: The first mode is a compact capability mode.

19. A user equipment, configured to perform the method according to any one of claims 1 to 18.

20. A non-transitory computer-readable medium storing a set of executable instructions configured to manipulate at least one processor of a user device to perform the method according to any one of claims 1 to 18.

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