Abstract: A User Equipment (UE) including a wireless transceiver and a controller is provided. The controller obtains information indicating that the UE is not allowed to access a 3GPP core network over which one or both or none of the 3GPP access network and the non-3GPP access network. Also, the controller refrains the UE from accessing the 3GPP core network over the indicated one or both of the 3GPP access network and the non-3GPP access network in response to the information indicating that the UE is not allowed to access the 3GPP core network over one or both of the 3GPP access network and the non-3GPP access network.

Abstract: Examples pertaining to an improvement on the inter-system registration failure case in mobile communications are described. A user equipment (UE) performs a registration procedure with a wireless network after an inter-system change. In response to detecting a failure of the registration procedure, the UE reattempts the registration procedure. The UE reattempts 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.

Abstract: Examples pertaining to user equipment (UE) reachability after notification in mobile communications are described. An apparatus (e.g., UE) receives an indication to initiate a notification procedure from a network over a non-3rd Generation Partnership Project (non-3GPP) access while a 3GPP access with the network is unavailable. In response, the apparatus transmits a notification response message to the network. After the 3GPP access with the network becomes available, the apparatus indicates to the network that the apparatus is reachable over the 3GPP access.

Abstract: Examples pertaining to protocol improvement for redirection to another system in mobile communications are described. An apparatus in a 5th Generation System (5GS) receives, from a mobile network, a reject cause indicating that redirection to an Evolved Packet System (EPS) is required. Responsive to receiving the reject cause while no suitable cell of the first mobile network connected to an Evolved Packet Core (EPC) is found or while no cell of the first mobile network connected to an EPC can be selected, the apparatus enters a predefined 5th Generation Mobility Management (5GMM) state and starts a timer.

Abstract: A User Equipment (UE) including a wireless transceiver and a controller is provided. The wireless transceiver performs wireless transmission and reception. The controller selects a PLMN via the wireless transceiver, and determines whether a predetermined ciphering algorithm is adopted for a Non-Access Stratum (NAS) security context. In response to selecting the PLMN and the predetermined ciphering algorithm being adopted for the NAS security context, the controller sends an initial NAS message in which Information Elements (IEs) are in cleartext only to the selected PLMN via the wireless transceiver.

Abstract: A method executed by a User Equipment (UE) for emergency call handling during a de-registration or detach procedure is provided. The UE initiates a Mobility Management (MM) de-registration procedure or an MM detach procedure with a mobile communication network. The UE initiates an emergency service before the MM de-registration procedure or the MM detach procedure has been completed. In response to the initiation of the emergency call, the UE aborts the MM de-registration procedure or the MM detach procedure and performs local de-registration or local detach. After the local de-registration or the local detach, the UE initiates a registration procedure or an attach procedure.

Abstract: A method of supporting reception of standalone SERVICE ACCEPT message is proposed. In one embodiment, a new timer is started when the UE determines successful completion of the service request procedure and has not received SERVICE ACCEPT during the procedure. In an alternative embodiment, an existing timer T3417 or T3417ext can be used to define the allowed time window for the reception of SERVICE ACCEPT. While the timer is running, the UE can treat the SERVICE ACCEPT message as successfully received and the message does not cause protocol error.

Abstract: Various examples pertaining to improvement for incorrect key set identifier (KSI) handling in mobile communications are described. An apparatus (e.g., user equipment) receives from a wireless network an authentication challenge after the processor having completed an authentication and key agreement (AKA) procedure with the wireless network. The apparatus detects an error in the authentication challenge and handles the error in the authentication challenge. For example, the apparatus can reject the authentication challenge responsive to detecting the error. Alternatively, the apparatus can accept the authentication challenge.

Abstract: Examples pertaining to optimized allocation of new equipment identifier in mobile communications are described. An apparatus receives, from a network, an assignment of a plurality of temporary identities. The apparatus identifies itself with one of the plurality of temporary identities in performing a procedure with the network.

Abstract: Examples pertaining to protocol improvement for redirection to another system in mobile communications are described. An apparatus in a 5th Generation System (5GS) receives, from a mobile network, a reject cause indicating that redirection to an Evolved Packet System (EPS) is required. Responsive to receiving the reject cause while no suitable cell of the first mobile network connected to an Evolved Packet Core (EPC) is found or while no cell of the first mobile network connected to an EPC can be selected, the apparatus enters a predefined 5th Generation Mobility Management (5GMM) state and starts a timer.

Abstract: Methods and apparatus are provided for handling of non-integrity reject message in the 5G system. In one novel aspect, the UE upon receiving the reject message via one access without integrity protection, retries one or more other accesses for one or more times before treating the rejection genuine. In one embodiment, the UE attempts the same 5GMM procedure over another access in the same cell/tracking area (TA). The alternative access including other types of 3GPP access and non-3GPP access. Subsequently, the UE can search the service from another cell/TA or another PLMN. In one embodiment, if the UE receives reject cause invalidating the UE with one access without integrity protection, the UE tries the system a few times before treating the reject genuine by tracking an invalidating counter, which is increased by one each time the rejection is received with a cause value invalidating the UE.

Abstract: A User Equipment (UE) communicates with one or both of a first 3GPP core network and a second 3GPP core network over one or both of a 3GPP access and a non-3GPP access. The communication includes: receiving, from the first 3GPP core network, a reject message; and searching for another suitable cell or another suitable Access Point (AP), when the reject message is received over the 3GPP access or the non-3GPP access and the UE is registered with the first 3GPP core network or the second 3GPP core network over the 3GPP access or the non-3GPP access.

Abstract: Examples pertaining to improved Globally Unique Temporary Identity (GUTI) allocation after establishment of mobile-terminated connection in mobile communications are described. An apparatus implemented in a UE receives a paging message from a network node of a wireless network. The apparatus then transmits a request to the network node responsive to receiving the paging message. In response to transmitting the request, the apparatus receives a signaling from the network node, with the signaling indicating a new temporary identity of the UE.

Abstract: Examples pertaining to user equipment (UE) reachability after notification in mobile communications are described. An apparatus (e.g., UE) receives an indication to initiate a notification procedure from a network over a non-3rd Generation Partnership Project (non-3GPP) access while a 3GPP access with the network is unavailable. In response, the apparatus transmits a notification response message to the network. After the 3GPP access with the network becomes available, the apparatus indicates to the network that the apparatus is reachable over the 3GPP access.

Abstract: Various examples pertaining to application of non-access stratum (NAS)-level congestion control timer values at intersystem change in mobile communications are described. A user equipment (UE) receives an indication of a NAS-level congestion control from a first type of wireless network. The UE starts a timer responsive to the receiving of the indication of the NAS-level congestion control. The UE then performs an intersystem change from the first type of wireless network to a second type of wireless network different from the first type by utilizing the timer.

Abstract: Examples pertaining to no subscription permanent identifier (SUPI) or no non-3GPP coverage in 5G mobile communications are described. A processor controls a communication device of a UE to connect to one or more wireless networks and receive one or more 5GS services via a 3GPP access and a non-3GPP access. The processor performs either a first procedure or a second procedure. The first procedure involves: (i) detecting either no Subscriber Identity Module (SIM) being inserted in the UE or a SIM inserted in the UE being invalid; and (ii) entering the UE into a 5G no-SUPI substate responsive to the detecting. The second procedure involves: (i) performing registration or determining that the UE is registered to one or more 5GS services over the non-3GPP access; (ii) detecting an absence of non-3GPP coverage; and (iii) entering the UE into a no access point available substate responsive to the detecting.

Abstract: A method of supporting reception of standalone SERVICE ACCEPT message is proposed. In one embodiment, a new timer is started when the UE determines successful completion of the service request procedure and has not received SERVICE ACCEPT during the procedure. In an alternative embodiment, an existing timer T3417 or T3417ext can be used to define the allowed time window for the reception of SERVICE ACCEPT. While the timer is running, the UE can treat the SERVICE ACCEPT message as successfully received and the message does not cause protocol error.

Abstract: A User Equipment (UE) including a wireless transceiver and a controller is provided. The wireless transceiver performs wireless transmission and reception to and from a service network. The controller transitions the UE from a Radio Resource Control (RRC) idle state to an RRC connected state, and after transitioning the UE from the RRC idle state to the RRC connected state, sends an initial Non-Access Stratum (NAS) message comprising a limited set of Information Elements (IEs) in cleartext, which are required to establish security between the UE and the service network, and a container IE carrying an initial NAS message Protocol Data Unit (PDU) ciphered with NAS security context to the service network via the wireless transceiver.

Abstract: Aspects of the disclosure provide a method for avoiding reselection of fake cell. The method includes transmitting a first request for network service of a wireless communication network in a first cell from user equipment, receiving a first reject message without integrity protection, adding the first cell to a set-aside cell list, and selecting a cell from other cells that are not included in the set-aside cell list to request network service.

Abstract: A User Equipment (UE) including a wireless transceiver and a controller is provided. The wireless transceiver performs wireless transmission and reception to and from a first service network utilizing a first Radio Access Technology (RAT) and a second service network utilizing a second RAT. The controller starts a Mobility Management (MM) back-off timer in response to a first MM procedure with the first service network being rejected, determines whether both the UE and the first service network support a dual registration mode in response to starting the MM back-off timer, and initiates a second MM procedure with the second service network via the wireless transceiver when the MM back-off timer is running, in response to determining that both the UE and the first service network support the dual registration mode.