Patent Description:
In wireless communications, including mobile communications in accordance with the <NUM>rd Generation Partnership Project (3GPP) specification(s) such as the 3GPP Technical Specification (TS) <NUM> and TS <NUM>, after an inter-system change from an Evolved Packet System (EPS) to a <NUM>th Generation System (5GS) by a user equipment (UE) in an idle mode, the <NUM>th Generation Mobility Management (5GMM) layer is to include an integrity protected TRACKING AREA UPDATE (TAU) REQUEST message in a 5GMM REGISTRATION REQUEST message. The source Mobility Management Entity (MME) in the EPS integrity verifies the TRACKING AREA UPDATE REQUEST during the registration procedure and sends a failure indication to the target Access and Mobility Management Function (AMF) if the verification fails, thereby causing a 5GMM REGISTRATION REJECT message being sent to the UE. If the integrity verification in the MME is successful, the Mobility Management (MM) context is to be transferred to the target AMF and be removed from the source MME. The source MME may keep the MM context for an implementation-specific time after MM context transfer in order to allow the UE to reattempt the procedure in case of a failure. A reattempt may be necessary, for example, if the EPS tracking area updating or 5GMM registration procedure fails abnormally. The context preservation may be controlled by an implementation-specific timer.

If the 5GMM registration procedure fails abnormally, the UE is to reattempt registration after the expiry of timer T3511 (e.g., <NUM> seconds). However, if the MM context preservation timer in the MME is shorter than timer T3511, the MM context would be removed from the source MME before the new registration attempt. This would result in a failure when the MME is unable to verify the TRACKING AREA UPDATE REQUEST and thus would lead to a 5GMM registration failure. Therefore, there is a need for a solution of an improvement on the inter-system registration failure case in mobile communications.

3GPP document S3-<NUM> reflects a discussion on the handling of native non-current <NUM> NAS security context after an inter-system change from S1 mode to N1 mode in idle mode. Further, 3GPP TS <NUM> V16. <NUM> specifies the Non-Access-Stratum (NAS) protocol for <NUM> System (5GS); Stage <NUM>.

One objective of the present disclosure is to propose a method and apparatus pertaining to an improvement on the inter-system registration failure case in mobile communications. The method and an apparatus according to the invention are defined in the independent claims. The dependent claims define preferred embodiments thereof.

In one aspect, a method involves a processor of an apparatus (e.g., UE) performing a registration procedure with a wireless network after an inter-system change. The method also involves the processor detecting a failure of the registration procedure. In response to the detecting, the method further involves the processor reattempting the registration procedure earlier than expiry of a first timer T3511.

In another aspect, an apparatus includes a transceiver and a processor coupled to the transceiver. The transceiver is configured to communicate with a wireless network. The processor performs, via the transceiver, a registration procedure with a wireless network after an inter-system change. The processor also detects, via the transceiver, a failure of the registration procedure. In response to the detecting, the processor reattempts, via the transceiver, the registration procedure earlier than expiry of a first timer T3511.

It is noteworthy that, although description provided herein may be in the context of certain radio access technologies, networks and network topologies such as <NUM>/New Radio (NR) and <NUM>th Generation (<NUM>) EPS mobile networking, the proposed concepts, schemes and any variation(s)/derivative(s) thereof may be implemented in, for and by other types of wireless and wired communication technologies, networks and network topologies such as, for example and without limitation, Ethernet, Universal Terrestrial Radio Access Network (UTRAN), Evolved UTRAN (E-UTRAN), Global System for Mobile communications (GSM), General Packet Radio Service (GPRS)/Enhanced Data rates for Global Evolution (EDGE) Radio Access Network (GERAN), Long-Term Evolution (LTE), LTE-Advanced, LTE-Advanced Pro, Internet-of-Things (IoT), Industrial IoT (IIoT), Narrow Band Internet of Things (NB-IoT), and any future-developed networking technologies. Thus, the scope of the present disclosure is not limited to the examples described herein.

It is appreciable that the drawings are not necessarily in scale as some components may be shown to be out of proportion than the size in actual implementation in order to clearly illustrate the concept of the present disclosure.

The subject matter of the invention is described in paragraph [<NUM>] below. All other aspects of the disclosure serve to get a better understanding of the invention.

Implementations in accordance with the present disclosure relate to various techniques, methods, schemes and/or solutions pertaining to an improvement on the inter-system registration failure case in mobile communications. According to the present disclosure, a number of possible solutions may be implemented separately or jointly. That is, although these possible solutions may be described below separately, two or more of these possible solutions may be implemented in one combination or another.

Referring to <FIG>, network environment <NUM> may involve a UE <NUM> and a wireless network <NUM>, which may include a 5GS and an EPS. Depending on channel condition, availability and/or other factor(s), UE <NUM> may be in wireless communication with wireless network <NUM> via one or more network nodes as represented by a network node <NUM>. Wireless network <NUM> may also include an AMF and an MME (e.g., as part of 5GS although they are shown separate from the 5GS in <FIG>). In network environment <NUM>, UE <NUM> and wireless network <NUM> may implement various schemes pertaining to an improvement on the inter-system registration failure case in mobile communications in accordance with the present disclosure, as described below. It is noteworthy that, while the various proposed schemes may be individually or separately described below, in actual implementations each of the proposed schemes may be utilized individually or separately. Alternatively, some or all of the proposed schemes may be utilized jointly.

Under a proposed scheme in accordance with the present disclosure, in an event that a 5GMM registration procedure for inter-system change (e.g., from EPS to 5GS) when UE <NUM> is in an idle mode, UE <NUM> has an option to reattempt registration earlier than expiry of timer T3511 before the MM context is removed from the source MME. That is, under the proposed scheme, the MME would still have the MM context when the registration is reattempted by UE <NUM> so that the TRACKING AREA UPDATE REQUEST integrity verification and the 5GMM registration may be successful. Under the proposed scheme, this may be achieved in one or more ways. For instance, in a first approach, UE <NUM> may use a timer which is started after detecting the 5GMM abnormal registration failure. In some implementations, the timer may be T3511 timer with a shorter duration. In other implementations, the timer may be a new timer which is of a shorter duration than that of T3511, and this new timer may be used to trigger a new (reattempted) registration procedure.

In a second approach under the proposed scheme, UE <NUM> may restart the registration procedure immediately after detecting the 5GMM abnormal registration failure. That is, UE <NUM> may restart the registration procedure without any delay upon detection of the 5GMM abnormal registration failure. In a third approach under the proposed scheme, UE <NUM> may restart the registration procedure immediately upon release of an NR radio resource control (NRRC) connection after detecting the 5GMM abnormal registration failure. In a fourth approach under the proposed scheme, UE <NUM> may use a timer, which is started upon release of the NRRC connection after detecting the 5GMM abnormal registration failure, to trigger a new registration procedure.

It is noteworthy that the term "failure" or "abnormal failure" herein may refer to an abnormal failure that occurs despite wireless network <NUM> successfully validates the TRACKING AREA UPDATE REQUEST from UE <NUM>. Moreover, the term "failure" or "abnormal failure" herein may also refer to an abnormal failure that occurs before UE <NUM> receives a REGISTRATION ACCEPT message from wireless network <NUM>.

For illustrative purposes only and without limiting the scope of the present disclosure, <FIG> illustrates an example scenario <NUM> in which various solutions and schemes in accordance with the present disclosure may be implemented. In scenario <NUM>, initially, a UE (e.g., UE <NUM>) may be registered in a <NUM> EPS and UE <NUM> may then change its connection from the <NUM> EPS to a 5GS. That is, UE <NUM> may be registered and in an idle mode when connected to the <NUM> EPS and then chooses to move to a 5GS cell in the idle mode. Then, the UE may initiate a registration procedure by transmitting a REGISTRATION REQUEST message (including a TRACKING AREA UPDATE REQUEST) to an AMF of the wireless network (e.g., via network node <NUM>). The AMF may, in turn, forward a context request (including the TRACKING AREA UPDATE REQUEST) to an MME of the wireless network. The MME may validate the TRACKING AREA UPDATE REQUEST successfully and, in response, send a context response (with an MM context) to the AMF. The MME may delete the MM context either immediately or upon expiry of a timer Tx (which may be started by the MME upon successful validation of the TRACKING AREA UPDATE REQUEST). On the other hand, an abnormal failure in the registration procedure may occur before the UE receives a REGISTRATION ACCEPT message from the AMF. Upon determining that there is an abnormal failure in the registration procedure, the UE may start a timer T3511 upon the expiry of which the UE may reattempt the registration procedure by transmitting another REGISTRATION REQUEST message (including a TRACKING AREA UPDATE REQUEST) to the AMF. The AMF may, in turn, forward a context request (including the TRACKING AREA UPDATE REQUEST) to the MME. However, in scenario <NUM>, as no UE information is available (since the MM context associated with the UE had been deleted), validation of the TRACKING AREA UPDATE REQUEST by the MME may result in failure. Thus, the MME sends a context response, with an indication of validation failure, to the AMF, which in turn sends a REGISTRATION REJECT message to the UE.

For illustrative purposes only and without limiting the scope of the present disclosure, <FIG> illustrates an example scenario <NUM> in which various solutions and schemes in accordance with the present disclosure may be implemented. In scenario <NUM>, initially, a UE (e.g., UE <NUM>) may be registered in a <NUM> EPS and UE <NUM> may then change its connection from the <NUM> EPS to a 5GS. That is, UE <NUM> may be registered and in an idle mode when connected to the <NUM> EPS and then chooses to move to a 5GS cell while in the idle mode. Then, the UE may initiate a registration procedure by transmitting a REGISTRATION REQUEST message (including a TRACKING AREA UPDATE REQUEST) to an AMF of the wireless network (e.g., via network node <NUM>). The AMF may, in turn, forward a context request (including the TRACKING AREA UPDATE REQUEST) to an MME of the wireless network. The MME may validate the TRACKING AREA UPDATE REQUEST successfully and, in response, send a context response (with an MM context) to the AMF. The MME may delete the MM context either immediately or upon expiry of a timer Tx (which may be started by the MME upon successful validation of the TRACKING AREA UPDATE REQUEST). On the other hand, an abnormal failure in the registration procedure may occur before the UE receives a REGISTRATION ACCEPT message from the AMF. Upon determining that there is an abnormal failure in the registration procedure, the UE may reattempt the registration procedure either: (i) immediately (e.g., without delay) upon determining or detecting the abnormal failure, or (ii) upon expiry of a timer Ty which has a duration shorter than that of timer Tx. That is, the UE may reattempt the registration procedure by transmitting another REGISTRATION REQUEST message (including a TRACKING AREA UPDATE REQUEST) to the AMF. The AMF may, in turn, forward a context request (including the TRACKING AREA UPDATE REQUEST) to the MME. In scenario <NUM>, as the UE reattempts the registration procedure before timer Tx at the MME expires, validation of the TRACKING AREA UPDATE REQUEST by the MME results in success. Thus, the MME sends a context response, with an MM context, to the AMF, which in turn sends a REGISTRATION ACCEPT message to the UE to complete the registration procedure.

<FIG> illustrates an example communication system <NUM> having at least an example apparatus <NUM> and an example apparatus <NUM> in accordance with an implementation of the present disclosure. Each of apparatus <NUM> and apparatus <NUM> may perform various functions to implement schemes, techniques, processes and methods described herein pertaining to an improvement on the inter-system registration failure case in mobile communications, including the various schemes described above with respect to various proposed designs, concepts, schemes, systems and methods described above, including network environment <NUM>, as well as processes described below.

Each of apparatus <NUM> and apparatus <NUM> may be a part of an electronic apparatus, which may be a network apparatus or a UE (e.g., UE <NUM>), such as a portable or mobile apparatus, a wearable apparatus, a vehicular device or a vehicle, a wireless communication apparatus or a computing apparatus. For instance, each of apparatus <NUM> and apparatus <NUM> may be implemented in a smartphone, a smart watch, a personal digital assistant, an electronic control unit (ECU) in a vehicle, a digital camera, or a computing equipment such as a tablet computer, a laptop computer or a notebook computer. Each of apparatus <NUM> and apparatus <NUM> may also be a part of a machine type apparatus, which may be an IoT apparatus such as an immobile or a stationary apparatus, a home apparatus, a roadside unit (RSU), a wire communication apparatus or a computing apparatus. For instance, each of apparatus <NUM> and apparatus <NUM> may be implemented in a smart thermostat, a smart fridge, a smart door lock, a wireless speaker or a home control center. When implemented in or as a network apparatus, apparatus <NUM> and/or apparatus <NUM> may be implemented in an eNodeB in an LTE, LTE-Advanced or LTE-Advanced Pro network or in a gNB or TRP in a <NUM> network, an NR network or an IoT network.

In some implementations, each of apparatus <NUM> and apparatus <NUM> may be implemented in the form of one or more integrated-circuit (IC) chips such as, for example and without limitation, one or more single-core processors, one or more multi-core processors, one or more complex-instruction-set-computing (CISC) processors, or one or more reduced-instruction-set-computing (RISC) processors. In the various schemes described above, each of apparatus <NUM> and apparatus <NUM> may be implemented in or as a network apparatus or a UE. Each of apparatus <NUM> and apparatus <NUM> may include at least some of those components shown in <FIG> such as a processor <NUM> and a processor <NUM>, respectively, for example. Each of apparatus <NUM> and apparatus <NUM> may further include one or more other components not pertinent to the proposed scheme of the present disclosure (e.g., internal power supply, display device and/or user interface device), and, thus, such component(s) of apparatus <NUM> and apparatus <NUM> are neither shown in <FIG> nor described below in the interest of simplicity and brevity.

In one aspect, each of processor <NUM> and processor <NUM> may be implemented in the form of one or more single-core processors, one or more multi-core processors, or one or more CISC or RISC processors. That is, even though a singular term "a processor" is used herein to refer to processor <NUM> and processor <NUM>, each of processor <NUM> and processor <NUM> may include multiple processors in some implementations and a single processor in other implementations in accordance with the present disclosure. In another aspect, each of processor <NUM> and processor <NUM> may be implemented in the form of hardware (and, optionally, firmware) with electronic components including, for example and without limitation, one or more transistors, one or more diodes, one or more capacitors, one or more resistors, one or more inductors, one or more memristors and/or one or more varactors that are configured and arranged to achieve specific purposes in accordance with the present disclosure. In other words, in at least some implementations, each of processor <NUM> and processor <NUM> is a special-purpose machine specifically designed, arranged and configured to perform specific tasks including those pertaining to an improvement on the inter-system registration failure case in mobile communications in accordance with various implementations of the present disclosure.

In some implementations, apparatus <NUM> may also include a transceiver <NUM> coupled to processor <NUM>. Transceiver <NUM> may be capable of wirelessly transmitting and receiving data. In some implementations, transceiver <NUM> may be capable of wirelessly communicating with different types of wireless networks of different radio access technologies (RATs). In some implementations, transceiver <NUM> may be equipped with a plurality of antenna ports (not shown) such as, for example, four antenna ports. That is, transceiver <NUM> may be equipped with multiple transmit antennas and multiple receive antennas for multiple-input multiple-output (MIMO) wireless communications. In some implementations, apparatus <NUM> may also include a transceiver <NUM> coupled to processor <NUM>. Transceiver <NUM> may include a transceiver capable of wirelessly transmitting and receiving data. In some implementations, transceiver <NUM> may be capable of wirelessly communicating with different types of UEs/wireless networks of different RATs. In some implementations, transceiver <NUM> may be equipped with a plurality of antenna ports (not shown) such as, for example, four antenna ports. That is, transceiver <NUM> may be equipped with multiple transmit antennas and multiple receive antennas for MIMO wireless communications.

Alternatively, or additionally, each of memory <NUM> and memory <NUM> may include a UICC.

Each of apparatus <NUM> and apparatus <NUM> may be a communication entity capable of communicating with each other using various proposed schemes in accordance with the present disclosure. For illustrative purposes and without limitation, a description of capabilities of apparatus <NUM>, as a UE (e.g., UE <NUM>), and apparatus <NUM>, as a network node (e.g., network node <NUM>) of a wireless network (e.g., wireless network <NUM>), is provided below.

Under various proposed schemes in accordance with the present disclosure with respect to an improvement on the inter-system registration failure case in mobile communications, processor <NUM> of apparatus <NUM>, implemented in or as UE <NUM>, may, when in an idle mode, perform, via transceiver <NUM>, a registration procedure with a wireless network (e.g., wireless network <NUM> via apparatus <NUM> as network node <NUM>) after an inter-system change (e.g., between 5GS and EPS). Additionally, processor <NUM> may detect, via transceiver <NUM>, a failure of the registration procedure. Moreover, in response to the detecting, processor <NUM> may reattempt, via transceiver <NUM>, the registration procedure either: (i) after detecting the failure; or (ii) upon expiry of a first timer used by the UE which has a shorter duration than a second timer used by the UE.

In some implementations, in reattempting the registration procedure, processor <NUM> may restart the registration procedure without delay after detecting the failure.

In some implementations, in reattempting the registration procedure, processor <NUM> may restart the registration procedure without delay upon release of an NRRC connection after detecting the failure.

In some implementations, in reattempting the registration procedure, processor <NUM> may perform certain operations. For instance, processor <NUM> may set a shorter duration for a T3511 timer, as the first timer, to be shorter than a duration of a normal T3511 timer, as the second timer. Moreover, processor <NUM> may transmit a registration request to the wireless network upon expiry of the T3511 timer with the shorter duration.

Alternatively, or additionally, in reattempting the registration procedure, processor <NUM> may perform certain operations. For instance, processor <NUM> may start a new timer, as the first timer, having a duration shorter than that of a T3511 timer, as the second timer. Additionally, processor <NUM> may transmit a registration request to the wireless network upon expiry of the new timer.

Alternatively, or additionally, in reattempting the registration procedure, processor <NUM> may perform certain other operations. For instance, processor <NUM> may start a new timer, as the first timer, upon release of an NRRC connection after detecting the failure, the new timer having a duration shorter than that of a T3511 timer, as the second timer. Furthermore, processor <NUM> may transmit a registration request to the wireless network upon expiry of the new timer.

In some implementations, in performing the registration procedure with the wireless network after the inter-system change, processor <NUM> may perform a 5GMM registration procedure when in the idle mode after changing from an EPS to a 5GS.

In some implementations, in performing the registration procedure with the wireless network, processor <NUM> may transmit a registration request with an integrity-protected TAU request to the wireless network.

In some implementations, the failure may include an abnormal failure that occurs despite the wireless network validates the TAU request successfully. In some implementations, the failure may include an abnormal failure that occurs before receiving a registration accept message from the wireless network.

<FIG> illustrates an example process <NUM> in accordance with an implementation of the present disclosure. Process <NUM> may represent an aspect of implementing various proposed designs, concepts, schemes, systems and methods described above, whether partially or entirely, including those described above. More specifically, process <NUM> may represent an aspect of the proposed concepts and schemes pertaining to an improvement on the inter-system registration failure case in mobile communications. Process <NUM> may include one or more operations, actions, or functions as illustrated by one or more of blocks <NUM>, <NUM> and <NUM>. Although illustrated as discrete blocks, various blocks of process <NUM> may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. Moreover, the blocks/sub-blocks of process <NUM> may be executed in the order shown in <FIG> or, alternatively in a different order. Furthermore, one or more of the blocks/sub-blocks of process <NUM> may be executed iteratively. Process <NUM> may be implemented by or in apparatus <NUM> and apparatus <NUM> as well as any variations thereof. Solely for illustrative purposes and without limiting the scope, process <NUM> is described below in the context of apparatus <NUM> as a UE (e.g., UE <NUM>) and apparatus <NUM> as a communication entity such as a network node or base station (e.g., network node <NUM>) of a wireless network (e.g., wireless network <NUM>). Process <NUM> may begin at block <NUM>.

At <NUM>, process <NUM> may involve processor <NUM> of apparatus <NUM>, implemented in or as UE <NUM>, performing, when in an idle mode and via transceiver <NUM>, a registration procedure with a wireless network (e.g., wireless network <NUM> via apparatus <NUM> as network node <NUM>) after an inter-system change (e.g., between 5GS and EPS). Process <NUM> may proceed from <NUM> to <NUM>.

At <NUM>, process <NUM> may involve processor <NUM> detecting, via transceiver <NUM>, a failure of the registration procedure. Process <NUM> may proceed from <NUM> to <NUM>.

At <NUM>, in response to the detecting, process <NUM> may involve processor <NUM> reattempting, via transceiver <NUM>, the registration procedure either: (i) after detecting the failure; or (ii) upon expiry of a first timer used by the UE which has a shorter duration than a second timer used by the UE.

In some implementations, in reattempting the registration procedure, process <NUM> may involve processor <NUM> restarting the registration procedure without delay after detecting the failure.

In some implementations, in reattempting the registration procedure, process <NUM> may involve processor <NUM> restarting the registration procedure without delay upon release of an NRRC connection after detecting the failure.

In some implementations, in reattempting the registration procedure, process <NUM> may involve processor <NUM> performing certain operations. For instance, process <NUM> may involve processor <NUM> setting a shorter duration for a T3511 timer, as the first timer, to be shorter than a duration of a normal T3511 timer, as the second timer. Moreover, process <NUM> may involve processor <NUM> transmitting a registration request to the wireless network upon expiry of the T3511 timer with the shorter duration.

Alternatively, or additionally, in reattempting the registration procedure, process <NUM> may involve processor <NUM> performing certain operations. For instance, process <NUM> may involve processor <NUM> starting a new timer, as the first timer, having a duration shorter than that of a T3511 timer, as the second timer. Additionally, process <NUM> may involve processor <NUM> transmitting a registration request to the wireless network upon expiry of the new timer.

Alternatively, or additionally, in reattempting the registration procedure, process <NUM> may involve processor <NUM> performing certain operations. For instance, process <NUM> may involve processor <NUM> starting a new timer, as the first timer, upon release of an NRRC connection after detecting the failure, the new timer having a duration shorter than that of a T3511 timer, as the second timer. Furthermore, process <NUM> may involve processor <NUM> transmitting a registration request to the wireless network upon expiry of the new timer.

In some implementations, in performing the registration procedure with the wireless network after the inter-system change, process <NUM> may involve processor <NUM> performing a 5GMM registration procedure when in the idle mode after changing from an EPS to a 5GS.

In some implementations, in performing the registration procedure with the wireless network, process <NUM> may involve processor <NUM> transmitting a registration request with an integrity-protected TAU request to the wireless network.

Claim 1:
A method, comprising:
performing, by a processor of a user equipment, in the following also referred to as UE, a <NUM> Mobility Management, 5GMM, registration procedure with a wireless network after an inter-system change (<NUM>); and
detecting, by the processor, a failure of the <NUM> Mobility Management, 5GMM, registration procedure (<NUM>);
characterized by:
responsive to the detecting, reattempting, by the processor, the <NUM> Mobility Management, 5GMM, registration procedure earlier than expiry of a first timer T3511 (<NUM>).