Patent Description:
The <NUM> next generation (NG) cellular technology is designed to provide extremely high-speed mobile broadband and reliable communication services at ultra-low latency levels. This enables the <NUM> technology to cater to newer market segments such as manufacturing, automotive, transportation & logistics, healthcare, agriculture, Internet of Things (IoT), etc., resulting in the exponential growth of the <NUM> mobile devices and User Equipments (UE) including Smartphones, laptops, loT devices, connected cars, smart meters, factory automation devices, etc..

Mobile devices, e.g., UEs, connect to the <NUM> cellular networks via the Radio Access Networks (RANs) for availing services such as voice, data, multimedia, etc. Effective management and maintenance of the UE contexts are essential and complex functions of the <NUM> RAN for delivering the higher quality of service (QoS) and quality of experience (QoE) expected of the <NUM> wireless networks.

UEs connect to the <NUM> wireless network via gNodeB, where the UE contexts are maintained and managed for a time duration when active user data traffic is ongoing. Once the user activity is over, such UEs are released by the gNodeB, and corresponding UE contexts removed from the system.

However, due to multitude of reasons described in detail below, situations occur when some of these UE contexts do not get removed from the gNodeB, and these UE contexts become stale UE contexts (or stale users), wherein no signaling or data transfer happens between gNodeB and actual UE, yet these remain active in the gNodeB system.

Creation, maintenance, and release of UE contexts i) involve a variety of procedures and ii) are functionally distributed across multiple components of the gNodeB. UE contexts need to be maintained in both gNB Centralized Unit (gNB-CU) and gNB Distributed Unit (gNB-DU) network functions of the gNodeB. Some of the reasons why stale UE contexts are created in the gNodeB system include:.

Stale user contexts result in various problems affecting the normal functions of the gNodeB, including the following issues:.

3GPP specification defines certain procedures to detect user (UE) data inactivity and trigger release for such inactive UE contexts. These procedures are applicable only when the necessary Bearer Contexts are created for the user after the PDU session establishment procedure. However, such 3GPP-defined mechanism are not sufficient for maintenance of the UE contexts at gNB-CU or gNB-DU in cases when stale UEs are created before PDU Session establishment and bearer inactivity cannot be triggered at either gNB-CU or gNB-DU due to absence of any established user bearer.

In the absence of any 3GPP-specification-defined mechanism, it requires a brute-force mechanism, e.g., restart of gNB-CU and gNB-DU network functions, to clear off such stale UEs. However, as mentioned above, such brute-force mechanism also affects the active, in-service users, thereby causing major service impact to the coverage area served by the gNodeB and affecting the user QoS and QoE, all of which are quite undesirable.

Document by <NPL>, discloses that if UE access the same gNB-DU, then other vendor CU will trigger UE Context Setup procedure towards the same gNB-DU.

US2021/<NUM> relates to a method and apparatus for identifying a user and generating and transmitting an identifier by a base station (BS) in a wireless communication system.

<CIT> discloses that the UE performs mobility Registration Update procedures, performs periodic Registration Update procedures triggered by expiration of the periodic update timer (e.g., to notify the network that the UE is still active).

However, the above-mentioned issues are not solved.

Therefore, there is a need for an optimized mechanism to detect and deal with stale UE contexts present at gNB-CU and gNB-DU.

The following are example embodiments of the present disclosure, that are useful to understand the claimed invention.

According to an example embodiment of the present disclosure, for the method in which stale user context detection and removal are implemented at the gNB-CU, the gNB runs a configurable periodic timer (e.g., default value = <NUM> mins) for initiating the stale UE detection procedure.

According to an example embodiment of the present disclosure, for the method in which stale user context detection and removal are implemented at the gNB-CU, as part of the detection procedure, the gNB configures, for every UE context stored in its database, a special Event A1 with the low a1-Threshold = -<NUM> dBm, reportInterval = <NUM>, and reportAmount = <NUM>. Since the configured a1-Threshold is very low, any active UE is bound to respond with an A1 Measurement report (MR) indicating the presence of a real UE. Those UE contexts for which no MR is reported for the configured duration of time will be classified as Stale UEs and deleted from the system.

According to an example embodiment of the present disclosure, for the method in which stale user context detection and removal are implemented at the gNB-CU, during initial User admission procedure, the gNB configures a special Event A1 with the low a1-Threshold = -<NUM> dBm, reportInterval = <NUM> minute, and reportAmount = infinity. Those UE contexts for which no MR is reported for the configured duration of time will be classified as stale UEs and deleted from the system.

According to a second example embodiment of the present disclosure, a method is presented in which stale user context detection and removal are implemented at O-RAN Distributed Unit (gNB-DU) network function of gNodeB. According to the second example embodiment, stale UE contexts can be identified at the gNB-DU based on periodic Channel State Information (CSI) reports. In this example embodiment, during initial UE context setup, the gNB shall configure csi-ReportConfigToAddModList with reportConfigType set to periodic in the Radio Resource Control (RRC) Setup Request or RRC Reconfiguration message towards the UE, thereby causing active UE(s) to periodically report the CSI. In this example embodiment, the gNB-DU shall monitor the periodic CSI reports received from the UE. If consecutive "n" number (which can be specified) of periodic CSI reports are not received at the gNB-DU for any UE context, then such UE context is classified as inactive, and DU-initiated UE release procedure (as specified in 3GPP TS <NUM>) between gNB-DU and gNB-CU is employed for deleting the stale UE context.

According to a third example embodiment of the present disclosure, which is not part of the present invention, a new audit mechanism is provided between gNB-CU and gNB-DU for active user context synchronization and maintenance. According to a first variant of the third example embodiment, new audit mechanism involves changes to F1AP protocol specification according to 3GPP TS <NUM>. According to this variant of the third example embodiment, new interface management procedure and messages are introduced in "Section <NUM>. <NUM> Interface Management messages" for implementing the audit mechanism between gNB-CU and gNB-DU for active user context synchronization and maintenance. This procedure uses non-UE-associated signaling and can be triggered by both gNB-CU and gNB-DU network functions of the gNB to exchange the information about the UE Contexts maintained individually at both gNB-CU and gNB-DU.

According to a second variant of the third example embodiment of the present disclosure, which is not part of the present invention, a new audit mechanism is provided between gNB-CU and gNB-DU for active user context synchronization and maintenance, which new audit mechanism involves changes to E1AP protocol specification according to 3GPP TS <NUM>. According to this variant of the third example embodiment, new interface management procedure and messages are introduced in "Section <NUM>. <NUM> Interface Management messages" for implementing the audit mechanism between gNB-CU Control Plane (gNB-CU-CP) and gNB-CU User Plane (gNB-CU-UP) functions for active user context synchronization and maintenance. This procedure uses non-UE-associated signaling and can be triggered by both gNB-CU and gNB-DU network functions of the gNB to exchange the information about the UE Contexts maintained individually at both gNB-CU-CP and gNB-CU-UP.

According to a first example embodiment of the present disclosure, a method is presented in which stale user context detection and removal are implemented at Open Radio Access Network (O-RAN) Centralized Unit (gNB-CU) network function of gNodeB. According to a first variant of the first example embodiment, the gNB runs a configurable periodic timer (e.g., default value = <NUM> mins) for initiating the stale UE detection procedure. As part of the stale UE detection procedure, the gNB configures, for every UE context stored in its database, a special Event A1 with the low a1-Threshold = -<NUM> dBm, reportInterval = <NUM>, and reportAmount = <NUM>. Since the configured a1-Threshold is very low, any active UE is bound to respond with an A1 Measurement report (MR) indicating the presence of a real UE. Those UE contexts for which no MR is reported for the configured duration of time will be classified as stale UEs and deleted from the system.

According to a second variant of the first example embodiment, stale UE detection mechanism can be based on a periodic Event A1 configured during initial User admission procedure. During the initial User admission procedure, the gNB configures a special Event A1 with the low a1-Threshold = -<NUM> dBm, reportInterval = <NUM> minute, and reportAmount = infinity. All the UE contexts present at the gNB-CU network function can be maintained based on the periodic measurement reports (MRs) reported by active users. Those UE contexts for which no MR is reported for the configured duration of time will be classified as stale UEs and deleted from the system.

According to a second example embodiment of the present disclosure, a method is presented in which stale user context detection and removal are implemented at O-RAN gNB Distributed Unit (gNB-DU) network function of gNodeB. According to the second example embodiment, stale UE contexts can be identified at the gNB-DU based on periodic Channel State Information (CSI) reports. In this example embodiment, during initial UE context setup, the gNB shall configure csi-ReportConfigToAddModList with reportConfigType set to periodic in the Radio Resource Control (RRC) Setup Request or RRC Reconfiguration message towards the UE, thereby causing active UE(s) to periodically report the CSI. In this example embodiment, the gNB-DU shall monitor the periodic CSI reports received from the UE. If consecutive "n" number (e.g., "n" ≥ <NUM>) of periodic CSI reports are not received at the gNB-DU for any UE context, then such UE context is classified as inactive, and DU-initiated UE release procedure (as specified in 3GPP TS <NUM>) between gNB-DU and gNB-CU is employed for deleting the stale UE context.

According to a third example embodiment of the present disclosure, which is not part of the present invention, a new audit mechanism is provided between gNB-CU and gNB-DU for active user context synchronization and maintenance. According to a first variant of the third example embodiment, new audit mechanism involves changes to F1AP protocol specification according to 3GPP TS <NUM>. According to this variant of the third example embodiment, new interface management procedure and messages are introduced in "Section <NUM>. <NUM> Interface Management messages" for implementing the audit mechanism between gNB-CU and gNB-DU for active user context synchronization and maintenance. This procedure uses non-UE-associated signaling and can be triggered by both gNB-CU and gNB-DU network functions of the gNB to exchange the information about the UE Contexts maintained individually at both gNB-CU and gNB-DU. According to this variant of the third example embodiment, periodic reporting can be configured for exchanging the UE context information periodically between gNB-CU and gNB-DU. Once the audit report is received, gNB-CU or gNB-DU can mark the unmatched contexts (UE context present only in either in gNB-CU or gNB-DU). When two or more consecutive reports specify the same inconsistency, UE context release procedure can be initiated for deleting the stale UE contexts.

In this section, active UE status request procedure will be discussed in connection with the first variant of the third example embodiment. The purpose of the Active UE Status Request procedure is to audit the active user context information stored at gNB-CU and gNB-DU. Active user context information exchanged between gNB-CU and gNB-DU is used to detect stale UE contexts and take suitable actions to remove such stale UE contexts. The active UE status request procedure i) does not affect the application-level configuration, and ii) uses non-UE associated signaling.

As shown in <FIG>, which is a diagram illustrating an example embodiment of an active UE Status Request procedure initiated from the gNB-CU (and successfully completed), gNB-CU <NUM> initiates the UE Context Audit procedure by sending the ACTIVE UE STATUS REQUEST message <NUM> to gNB-DU <NUM> to request reporting of the UE Contexts maintained at gNB-DU <NUM>. Reporting Periodicity IE can be present in the ACTIVE UE STATUS REQUEST message <NUM> to indicate the periodicity for the reporting of periodic UE Context audit report. In the case the Reporting Periodicity IE is absent, the gNB-DU <NUM> shall report once. The gNB-DU <NUM> shall include each Active UE association present in the gNB-DU <NUM> in the Active UE Status Response message <NUM> sent to the gNB-CU <NUM>, which Active UE Status Response message <NUM> contains, e.g., DU F1 Application Protocol (F1AP) UE Identifier (ID), CU F1AP UE ID, and/or (optionally) Cell Radio Network Temporary Identifier (C-RNTI).

As shown in <FIG>, which is a diagram illustrating an example embodiment of an active UE Status Request procedure initiated from the gNB-DU (and successfully completed), gNB-DU <NUM> initiates the UE Context Audit procedure by sending the ACTIVE UE STATUS REQUEST message <NUM> to gNB-CU <NUM> to request reporting of the UE Contexts maintained at GNB-CU <NUM>. Reporting Periodicity IE can be present in the ACTIVE UE STATUS REQUEST message <NUM> to indicate the periodicity for the reporting of periodic UE Context audit report. In the case the Reporting Periodicity IE is absent, the gNB-CU <NUM> shall report once. The gNB-CU <NUM> shall include each Active UE association present in the gNB-CU <NUM> in the Active UE Status Response message <NUM> sent to the gNB-DU <NUM>, which Active UE Status Response message <NUM> contains, e.g., DU F1AP UE ID, CU F1AP UE ID, and/or (optionally) C-RNTI.

In this section, active UE status update procedure will be discussed in connection with the first variant of the third example embodiment. The purpose of the Active UE Status Update procedure is to periodically update the active user context information stored at gNB-CU and gNB-DU. This procedure i) does not affect the application-level configuration, and ii) uses non-UE associated signaling. <FIG> is a diagram illustrating an example embodiment of an active UE Status Update procedure initiated from the gNB-CU (and successfully completed). In the case the Reporting Periodicity IE in the ACTIVE UE STATUS REQUEST is present, then gNB-CU <NUM> shall periodically send the ACTIVE UE STATUS UPDATE message <NUM> to gNB-DU <NUM> to report the list of UE contexts present at GNB-CU <NUM>. The following information is provided for each UE in the list of UE contexts: DU F1AP UE ID, CU F1AP UE ID, and/or (optionally) C-RNTI.

<FIG> is a diagram illustrating an example embodiment of an active UE Status Update procedure initiated from the gNB-DU (and successfully completed). In the case the Reporting Periodicity IE in the ACTIVE UE STATUS REQUEST is present, then gNB-DU <NUM> shall periodically send the ACTIVE UE STATUS UPDATE message <NUM> to gNB-CU <NUM> to report the list of UE contexts present at GNB-DU <NUM>. The following information is provided for each UE in the list of UE contexts: DU F1AP UE ID, CU F1AP UE ID, and/or (optionally) C-RNTI.

According to an example embodiment of the present disclosure, in connection with the first variant of the third example embodiment, additional modifications are proposed in the following existing messages to indicate a new UE release cause, "UE Context Mismatch": i) UE CONTEXT RELEASE REQUEST (gNB-DU-initiated Release procedure); and ii) UE CONTEXT RELEASE COMMAND (gNB-CU-initiated Release procedure).

According to a second variant of the third example embodiment of the present disclosure, which is not part of the present invention, a new audit mechanism is provided between gNB-CU and gNB-DU for active user context synchronization and maintenance, which new audit mechanism involves changes to E1AP protocol specification according to 3GPP TS <NUM>. According to this variant of the third example embodiment, new interface management procedure and messages are introduced in "Section <NUM>. <NUM> Interface Management messages" for implementing the audit mechanism between gNB-CU Control Plane (gNB-CU-CP) and gNB-CU User Plane (gNB-CU-UP) functions for active user context synchronization and maintenance. This procedure uses non-UE-associated signaling and can be triggered by both gNB-CU and gNB-DU network functions of the gNB to exchange the information about the UE Contexts maintained individually at both gNB-CU-CP and gNB-CU-UP. In this variant of the third example embodiment, periodic reporting can be configured for exchanging the UE context information periodically between both gNB-CU-CP and gNB-CU-UP. Once the audit report is received, gNB-CU-CP or gNB-CU-UP can mark the unmatched contexts (UE context present only in either in gNB-CU-CP or gNB-CU-UP). When two or more consecutive reports specify the same inconsistency, UE context release procedure can be initiated for deleting the stale UE contexts.

In this section, active UE status request procedure will be discussed in connection with the second variant of the third example embodiment. The purpose of the Active UE Status Request procedure is to audit the active user context information stored at gNB-CU-CP and gNB-CU-UP. Active user context information exchanged between gNB-CU-CP and gNB-CU-UP is used to detect stale UE contexts and take suitable actions to remove such stale UE contexts. The active UE status request procedure i) does not affect the application-level configuration, and ii) uses non-UE associated signaling.

As shown in <FIG>, which is a diagram illustrating an example embodiment of an active UE Status Request procedure initiated from the gNB-CU-CP (and successfully completed), gNB-CU-CP 1001a initiates the UE Context Audit procedure by sending the ACTIVE UE STATUS REQUEST message <NUM> to gNB-CU-UP 1001b to request reporting of the UE Contexts maintained at GNB-CU-UP 1001b. Reporting Periodicity IE can be present in the ACTIVE UE STATUS REQUEST message <NUM> to indicate the periodicity for the reporting of periodic UE Context audit report. In the case the Reporting Periodicity IE is absent, the gNB-CU-UP 1001b shall report once. The gNB-CU-UP 1001b shall include each Active UE association present in the gNB-CU-UP 1001b in the Active UE Status Response message <NUM> sent to the gNB-CU-CP 1001a, which Active UE Status Response message <NUM> contains, e.g., gNB-CU-CP UE E1 Application Protocol (E1AP) Identifier (ID), and gNB-CU-UP UE E1AP ID.

As shown in <FIG>, which is a diagram illustrating an example embodiment of an active UE Status Request procedure initiated from the gNB-CU-UP 1001b (and successfully completed), gNB-CU-UP 1001b initiates the UE Context Audit procedure by sending the ACTIVE UE STATUS REQUEST message <NUM> to gNB-CU-CP 1001a to request reporting of the UE Contexts maintained at GNB-CU-CP 1001a. Reporting Periodicity IE can be present in the ACTIVE UE STATUS REQUEST message <NUM> to indicate the periodicity for the reporting of periodic UE Context audit report. In the case the Reporting Periodicity IE is absent, the gNB-CU-CP 1001a shall report once. The gNB-CU-CP 1001a shall include each Active UE association present in the gNB-CU-CP 1001a in the Active UE Status Response message <NUM> sent to the gNB-CU-UP 1001b, which Active UE Status Response message <NUM> contains, e.g., gNB-CU-CP UE E1AP ID, and gNB-CU-UP UE E1AP ID.

In this section, active UE status update procedure will be discussed in connection with the second variant of the third example embodiment. The purpose of the Active UE Status Update procedure is to periodically update the active user context information stored at gNB-CU-CP and gNB-CU-UP. This procedure i) does not affect the application-level configuration, and ii) uses non-UE associated signaling. <FIG> is a diagram illustrating an example embodiment of an active UE Status Update procedure initiated from the gNB-CU-CP 1001a (and successfully completed). In the case the Reporting Periodicity IE in the ACTIVE UE STATUS REQUEST is present, then gNB-CU-CP 1001a shall periodically send the ACTIVE UE STATUS UPDATE message <NUM> to gNB-CU-UP 1001b to report the list of UE contexts present at gNB-CU-CP 1001a. The following information is provided for each UE in the list of UE contexts: gNB-CU-CP UE E1AP ID, and gNB-CU-UP UE E1AP ID.

<FIG> is a diagram illustrating an example embodiment of an active UE Status Update procedure initiated from the gNB-CU-UP (and successfully completed). In the case the Reporting Periodicity IE in the ACTIVE UE STATUS REQUEST is present, then gNB-CU-UP 1001b shall periodically send the ACTIVE UE STATUS UPDATE message <NUM> to gNB-CU-CP 1001a to report the list of UE contexts present at GNB-CU-UP 1001b. The following information is provided for each UE in the list of UE contexts: gNB-CU-CP UE E1AP ID, and gNB-CU-UP UE E1AP ID.

Although the example embodiments of the methods for UE context management have been described in the present disclosure in the context of <NUM> gNodeB system, the present disclosure is also applicable to <NUM> LTE eNodeB system. As in the first example embodiment of the method for stale UE detection for <NUM> gNB system, a similar Stale UE detection mechanism can be implemented for <NUM> LTE eNodeB system using a Periodic Keep Alive Check mechanism based on Event A1 configuration and reporting between the <NUM> eNodeB and UE. In addition, as in the third example embodiment of the method, which is not part of the present invention, in which an audit mechanism is provided for <NUM> gNB system, a similar audit mechanism can be implement for <NUM> LTE eNodeB system for active user context synchronization and maintenance between <NUM> eNB-CU and <NUM> eNB-DU.

Claim 1:
A method for stale user equipment, UE, context detection and removal in Open Radio Access Network, O-RAN, the method comprising:
using one of O-RAN gNB Centralized Unit, gNB-CU, or O-RAN gNB Distributed Unit, gNB-DU, to implement a reporting requirement for receiving from an active user equipment, UE, information indicating the presence of the active UE, and
deleting by the one of the gNB-CU or the gNB-DU at least one UE context for which no information indicating the presence of the active UE is received.