Patent Description:
Application servers in the loT ecosystem provide information or instructions to devices in the loT ecosystem by transmitting queries. Queries are used to initiate actions such as data collection by the devices, to request transmission of the collected data from the devices to the application server, to provide data such as software upgrades to the devices, to notify devices of upcoming broadcast transmissions from the application server, and the like. Most of the queries are non-time critical queries having relatively small numbers of bytes that are transmitted to the loT devices, e.g., a request to turn on the air conditioning in a connected car. Short message service (SMS) messages provide a straightforward way to exchange small amounts of data between application servers and loT devices. The SMS messages are used to trigger actions at the loT device such as shutdown, rebooting, reconfiguration of a reporting time interval, and the like. The SMS messages are also able to instruct loT devices to establish a connection network, PDN, connection) that is subsequently used for delivery of other types of data such as software upgrade packages.

"<NPL>, discloses that the exposure of service by the network creates a toolbox of capabilities that, with proper authorisation can be used for example, to retrieve information, to request specific services, to receive notifications, to request the setting of specific parameters, etc. The service capability exposure function (SCEF) provides a means to securely expose the services and capabilities provided by 3GPP network interfaces. The SCEF provides a means for the discovery of the exposed service capabilities. The SCEF abstracts the services from the underlying 3GPP network interfaces and protocols.

"<NPL>, discloses that the Service Capability Server (SCS) is an entity which connects to the 3GPP network to communicate with UEs used for machine type communications (MTC) and the MTC-IWF and/or SCEF in the home PLMN. The SCS offers capabilities for use by one or more multiple MTC application.

"<NPL>, discloses an MT forward short message procedure. The procedure shall be used between the SMS-GMSC and the serving MME or SGSN (transiting an SMS router, if present) or IP-SM-GW to forward mobile terminated short messages.

"<NPL>, discloses a definition of data structures used in the short messaging API. Some of the structures can be instantiated as so-called root elements.

"<NPL>, discloses procedures for assessing MTC-IWF functionality via an SCEF. The SCS/AS determines the need to trigger the device. The SCS/AS sends the trigger submit request message to the SCEF. The SCEF sends a trigger submit confirmation to the SCS/AS to confirm that it has been accepted for delivery to the UE.

The invention is defined by the appended independent claims, including the methods according to claims <NUM> and <NUM>, a service capability exposure function according to claim <NUM>, and a mobility management entity according to claim <NUM>.

Conventional SMS messages are delivered using a circuit-switched architecture according to standards defined by the 3GPP. The circuit-switched path includes a service capability exposure function (SCEF) that receives SMS messages from the application server, an interworking function (IWF), a short message service center (SMSC) to store, forward, convert, and deliver the SMS messages, a mobile switching center (MSC), and a mobility management entity (MME). The conventional circuit-switched architecture also requires additional support functions for SMS messages including a charging data function (CDF) and a services capability server/application server (SCS/AS). However, the conventional circuit-switched architecture is being phased out and future networks are not expected to implement the functionality needed to support circuit-switched SMS messaging. Furthermore, deploying elements of the circuit-switched architecture to support SMS messaging to loT devices is expected to be cost prohibitive, at least in part because of the large number of loT devices that will need to be supported.

Small amounts of data are also conventionally transmitted to user equipment using non-Internet protocol (IP) data delivery between an SCEF and an MME. Non-IP data delivery can therefore be used to support exchange of small amounts of data between loT devices and an application server. However, non-IP data delivery requires establishing a PDN connection between the user equipment and a PDN, which incurs a significant amount of overhead. The user equipment is required to perform a PDN attach/connectivity procedure to register with the MME and then transmit a connection management request to the SCEF. The application server registers with the user equipment for the non-IP data delivery and the SCEF authenticates and authorizes the request on the basis of information provided by an HSS. Once the user equipment and the application server are successfully registered for non-IP data delivery using the PDN connection, the MME and the SCEF exchange messages to negotiate a connection. The PDN connection creation procedure is completed when the MME transmits an acceptance message including an identifier of a bearer to be used by the user equipment for non-IP data delivery. The overhead incurred by the PDN creation procedure is undesirable, and possibly prohibitive, when scaled to support the expected number of loT devices.

<FIG> disclose techniques for exchanging SMS message among application servers and user equipment without incurring the overhead of the conventional 3GPP SMS architecture or the connection establishment procedure used for non-IP data delivery by conveying SMS messages between an MME and an SCEF associated with the user equipment on the basis of a unique identifier of the user equipment, such as an international mobile subscriber identity (IMSI), without establishing a PDN connection for the user equipment. The MME selects the SCEF in response to receiving an attach message from the user equipment including a request for SMS messaging and the SCEF notifies the application server that the user equipment is available for SMS messaging. The user equipment is identified to the application server using an external identifier such as a mobile station international subscriber directory number (MSISDN) and the SCEF is configured to map the external identifier to the unique identifier of the user equipment. The MME routes SMS messages on the basis of the unique identifier and the SCEF is able to route messages on the basis of either the unique identifier or the external identifier, depending on the direction of the SMS message.

Mobile-terminated SMS messages including the external identifier are received by the SCEF, which maps the external identifier to the unique identifier and identifies the MME on the basis of the unique identifier. The SCEF then selectively forwards the SMS message depending on the operational status of the user equipment. If the user equipment is in an active mode and able to receive SMS messages, the SCEF forwards the SMS message to the MME, which sends the message to the user equipment on the basis of the unique identifier. If the user equipment is in an idle mode and available to be paged, the SCEF forwards the SMS message to the MME, which pages the user equipment and then sends the message to the user equipment when the user equipment responds to the page. If the user equipment is in a power saving mode and only available for paging at specific time intervals, the SMS message is buffered in either the SCEF or the MME. The buffered SMS message is then provided at the next paging opportunity, if possible. If the user equipment cannot be reached within a predetermined time interval, then the MME notifies the SCEF that the user equipment is not reachable.

Mobile originated SMS messages including the unique identifier of the user equipment are transmitted from the user equipment to the MME. The unique identifier is used to identify the SCEF that is registered with the user equipment to provide SMS messaging. The MME then forwards the SMS message to the identified SCEF, which maps the unique identifier to an external identifier. The SCEF uses the external identifier to identify the application server and then forwards the SMS message to the identified application server using the external identifier.

<FIG> illustrates a wireless communication system <NUM> that supports delivery of SMS messages according to the Third Generation (<NUM>) standards defined by the Third Generation Partnership Project (3GPP). The wireless communication system <NUM> includes a radio access network (RAN) <NUM> that provides wireless connectivity to one or more user equipment <NUM> (only one user equipment is illustrated in <FIG> in the interest of clarity) within a geographic area or cell over a corresponding air interface <NUM>. The radio access network <NUM> can implement one or more base stations (not shown in <FIG>). As used herein, the term "base station" refers to any entity or device capable of providing wireless connectivity including eNodeBs, macrocells, access points, small cells, microcells, picocells, femtocells, and the like. As used herein, the term "user equipment" refers to any device or entity capable of accessing network services by establishing a wireless connection over the air interface <NUM> with the radio access network <NUM>. For example, the user equipment <NUM> can include devices that are used to facilitate communication between people, such as cell phones, smart phones, tablet computers, wireless-enabled laptops, and the like. For another example, the user equipment <NUM> can include physical devices such appliances, vehicles, buildings, and other items that are embedded with electronics, software, sensors, actuators, and network connectivity that enable the devices to collect and exchange data over the Internet. The user equipment <NUM> can therefore be used as part of an "Internet of Things.

The radio access network <NUM> is connected to a mobility management entity (MME) <NUM>. The MME <NUM> is responsible for paging idle user equipment, performing bearer activation/deactivation, authenticating user equipment, and the like. The MME <NUM> is also a terminating node for NAS signaling. The MME <NUM> is connected to a mobile switching center (MSC) <NUM>, which is implemented in a circuit-switched portion <NUM> of the wireless communication system <NUM>. The MSC <NUM> controls elements of a network switching subsystem for the wireless communication system <NUM>. The MSC <NUM> is connected to a short message service (SMS) server <NUM> that is used to receive, store, and transmit SMS messages, which can be short messages that are constrained to include a maximum of <NUM> alphanumeric characters. The SMS server <NUM> is configured to receive and transmit the SMS messages along control plane paths in a circuit-switched network.

The portion <NUM> of the wireless communication system includes a home subscriber server (HSS) <NUM>, which is a master user database that stores subscription-related information such as subscriber profiles associated with the user equipment <NUM>. The HSS <NUM> also performs authentication and authorization of users and provides location and IP information for the user. A charging data function (CDF) <NUM> in the portion <NUM> is used to gather charging information for online charging or off-line charging for usage of the resources of the wireless communication system <NUM> by the user equipment <NUM>. The CDF <NUM> can use the charging information to generate a call detail record (CDR), which can be sent to a billing system for the wireless communication system <NUM>. A service capability server (SCS) <NUM> provides middleware that serves third-party value-added services and applications. The SCS <NUM> can be owned or leased by a mobile network operator or other network service provider and is accessible through application programming interfaces (APIs). The SMS <NUM>, the HSS <NUM>, the CDF <NUM>, and the SCS <NUM> are connected to an interworking function <NUM> that provides interworking between the portion <NUM> and external networks such as packet-switched networks.

The SCS <NUM> communicates with a service capability exposure function (SCEF) <NUM> over a corresponding user plane path. The SCEF <NUM> is configured to securely expose the services and capabilities provided by network interfaces in the wireless communication system <NUM>. For example, the SCEF <NUM> provides an interface for small data transfers and control messaging between the user equipment <NUM> and one or more application servers <NUM>. The SCEF <NUM> provides APIs to the application server <NUM> for the small data transfers and control messages.

In order to receive SMS messages via the circuit-switched portion <NUM> of the wireless communication system <NUM>, the user equipment <NUM> is required to establish a connection with a packet data network (PDN) <NUM>. The user equipment <NUM> is identified using an IP address associated with the PDN connection. One or more bearers are used to convey the SMS messages using control plane signaling along a circuit-switched path that is supported by one or more of the bearers in the PDN connection. The circuit-switched path includes the SCEF <NUM> that receives SMS messages from the application server <NUM> or the MME <NUM>. The circuit-switched path also includes the IWF <NUM>, the HSS <NUM>, the SMS <NUM>, the MSC <NUM>, and the MME <NUM>.

<FIG> illustrates a wireless communication system <NUM> that supports delivery of SMS messages over an interface <NUM> between an MME <NUM> and an SCEF <NUM> that does not require establishing a PDN connection according to some embodiments. The wireless communication system <NUM> includes a radio access network (RAN) <NUM> that provides wireless connectivity to one or more user equipment <NUM> (only one user equipment is illustrated in <FIG> in the interest of clarity) within a geographic area or cell over a corresponding air interface <NUM>. An HSS <NUM> provides a master user database that stores subscription-related information such as subscriber profiles associated with the user equipment <NUM>. An application server <NUM> generates mobile-terminated SMS messages for transmission to the user equipment <NUM> and receives mobile-originated SMS messages from the user equipment <NUM>.

The user equipment <NUM> is identified to the MME <NUM>, the SCEF <NUM>, and the HSS <NUM> by a unique identifier that is allocated to the user equipment <NUM>. For example, the user equipment <NUM> is allocated an International Mobile Subscriber Identity (IMSI) that is used to identify the user equipment to the MME <NUM>, the SCEF <NUM>, and the HSS <NUM>. An external identifier is used to identify the user equipment <NUM> to external entities such as the application server <NUM>. One example of an external identifier is a mobile station international subscriber directory number (MSISDN). The SCEF <NUM> is configured to map the external identifier to the unique identifier of the user equipment <NUM>. The MME <NUM> routes SMS messages on the basis of the unique identifier and the SCEF <NUM> is able to route messages on the basis of either the unique identifier or the external identifier, depending on the direction of the SMS message.

Mobile-terminated SMS messages are generated by the application server <NUM> for transmission to the user equipment <NUM>. The mobile-terminated SMS messages therefore include the external identifier of the user equipment <NUM>. The SCEF <NUM> receives the mobile-terminated SMS message and maps the external identifier to the unique identifier of the user equipment <NUM>. The SCEF <NUM> also uses the unique identifier to identify the MME <NUM> that is connected to the RAN <NUM> that is serving the user equipment <NUM>. Depending on the operational status of the user equipment <NUM>, the SCEF <NUM> selectively forwards the SMS message.

Some embodiments of the user equipment <NUM> support three operational modes that indicate different statuses: an active mode in which the user equipment <NUM> is able to receive SMS messages, an idle mode in which the user equipment <NUM> is not able to receive SMS messages but is available to be paged, and a power saving mode in which the user equipment <NUM> is not able to receive SMS messages and is only available to be paged at certain paging time intervals. If the user equipment is in the active mode, the SCEF <NUM> forwards the SMS message to the MME <NUM>, which sends the SMS message to the user equipment <NUM> on the basis of the unique identifier. If the user equipment is in the idle mode, the SCEF <NUM> forwards the SMS message to the MME <NUM>, which pages the user equipment <NUM>. If the user equipment <NUM> responds to the page, the MME <NUM> transmits the SMS message to the user equipment <NUM>. If the user equipment is in the power saving mode, the SMS message is buffered in either the SCEF <NUM> or the MME <NUM>. The MME <NUM> transmits a message to notify the SCEF <NUM> that the SMS message will be successfully delivered. The message also indicates a time of delivery. The buffered SMS message is then provided at the next paging opportunity, if possible. For example, the MME <NUM> pages the user equipment <NUM> at the next paging interval and forwards the SMS message if the user equipment <NUM> responds to the page. If the user equipment <NUM> cannot be reached within a predetermined time interval, then the MME <NUM> notifies the SCEF <NUM> that the user equipment <NUM> is not reachable. In that case, the SMS message is discarded.

The user equipment <NUM> generates mobile-originated SMS messages that include the unique identifier of the user equipment <NUM>. The user equipment <NUM> transmits the mobile-originated SMS message to the MME <NUM>, which uses the unique identifier included in the SMS message to identify the SCEF <NUM> that is registered with the user equipment <NUM> to support SMS messaging. The MME <NUM> forwards the SMS message to the identified SCEF <NUM>, which maps the unique identifier to an external identifier. The SCEF <NUM> uses the external identifier to identify the application server <NUM> and then forwards the SMS message to the identified application server <NUM> using the external identifier.

<FIG> is a block diagram of a communication system <NUM> according to some embodiments. The communication system <NUM> includes an MME <NUM> that is used to implement some embodiments of the MME <NUM> shown in <FIG>. The communication system <NUM> also includes and SCEF <NUM> that is used to implement some embodiments of the SCEF <NUM> shown in <FIG>.

The MME <NUM> includes a transceiver <NUM> that is used to support communication over an interface <NUM> with the SCEF <NUM>. The interface <NUM> is used to implement some embodiments of the interface <NUM> shown in <FIG>. Some embodiments of the transceiver <NUM> are implemented using one or more receivers and one or more transmitters. The MME <NUM> also includes a processor <NUM> and a memory <NUM>. The processor <NUM> is configured to execute instructions such as instructions stored in the memory <NUM> and the memory <NUM> is configured to store instructions, data that is to be operated upon by the instructions, or the results of instructions performed by the processor <NUM>.

The SCEF <NUM> includes a transceiver <NUM> that is used to support communication over an interface <NUM> with the MME <NUM>. Some embodiments of the transceiver <NUM> are implemented using one or more receivers and one or more transmitters. The SCEF <NUM> also includes a processor <NUM> and a memory <NUM>. The processor <NUM> is configured to execute instructions such as instructions stored in the memory <NUM> and the memory <NUM> is configured to store instructions, data that is to be operated upon by the instructions, or the results of instructions performed by the processor <NUM>.

<FIG> illustrates a message flow <NUM> that is used to register a user equipment for SMS messaging according to some embodiments. The message flow <NUM> is implemented in some embodiments of the wireless communication system <NUM> shown in <FIG>.

The UE transmits a message <NUM> such as an attach or combined attach message that includes an indication that the UE is requesting SMS service. In response to receiving the message <NUM>, the MME selects (at block <NUM>) an SCEF to serve the UE. Some embodiments of the MME select the SCEF based on local provisioning rules established for SMS services. Some embodiments of the MME also perform authentication and authorization of the UE using information stored in the HSS.

The MME transmits a message <NUM> to the SCEF that includes a connection management request to register the UE for SMS messaging. Some embodiments of the message <NUM> use a modified format of the connection management request that includes information used to request SMS messaging for the UE. In response to receiving the message <NUM>, the SCEF transmits a message <NUM> to notify the application server that the UE is available for SMS messaging. The application server transmits a response message <NUM> to the SCEF to acknowledge that the application server received the message <NUM> including the notification that the UE is available for SMS messaging.

The SCEF transmits a message <NUM> to the MME that includes a connection management answer including information indicating that the SCEF has registered the UE for SMS messaging and that the SCEF has notified the appropriate application server. In response to receiving the message <NUM>, the MME transmits a message <NUM> indicating that the MME has accepted the UE request to attach and to receive SMS messaging. At this point, the UE is registered to exchange SMS messaging with the application server via the MME and the SCEF. Registering the UE in this manner does not require establishing a PDN connection to convey the SMS messaging.

<FIG> illustrates a message flow <NUM> that is used to convey a mobile-originated SMS message from a user equipment to an application server according to some embodiments. The message flow <NUM> is implemented in some embodiments of the wireless communication system <NUM> shown in <FIG>.

The user equipment transmits a message <NUM> including the SMS message that is destined for the application server. Some embodiments of the message <NUM> are a downlink non-access stratum (NAS) message or a control plane service request that includes an NAS message container. The user equipment is identified in the message <NUM> using a unique identifier of the user equipment such as an IMSI. The MME forwards (at block <NUM>) the SMS message to the SCEF. For example, the MME can forward the NAS message container to the SCEF.

The MME transmits a message <NUM> that includes a mobile-originated SMS delivery request, which identifies the application server using a destination address. In response to receiving the message <NUM>, the SCEF routes (at block <NUM>) the SMS message to the application server identified by the destination address. As discussed herein, the SCEF routes the SMS message by mapping the unique identifier of the user equipment to an external identifier such as an MSISDN.

The SCEF transmits a mobile-originated SMS delivery message <NUM> that includes the SMS to the application server, which responds with a message <NUM> to acknowledge reception of the SMS message. The mobile-originated SMS delivery message <NUM> is directed to the application server on the basis of the external identifier of the UE. The SCEF then transmits a mobile-originated SMS data delivery acknowledgment <NUM> to the MME, which transmits an acknowledgment message <NUM> in response to receiving the acknowledgment <NUM>. Some embodiments of the acknowledgment message <NUM> are uplink NAS transport messages that include an NAS message container containing an acknowledgment packet.

<FIG> illustrates a message flow <NUM> that is used to convey a mobile-terminated SMS message from an application server to a user equipment that is able to receive SMS messaging according to some embodiments. The message flow <NUM> is implemented in some embodiments of the wireless communication system <NUM> shown in <FIG>.

The application server transmits a message <NUM> that includes an SMS message addressed to the UE using an external identifier of the UE such as an MSISIDN. The SCEF maps (at block <NUM>) the external identifier to a unique identifier of the UE such as an IMSI so that the SCEF is able to identify the MME that is serving the UE. In some embodiments, the SCEF does not have the unique identifier, in which case the SCEF transmits a message <NUM> to the HSS to request that the HSS resolve the external identifier to the unique identifier of the UE. The HSS is also able to provide information identifying the MME that serves the UE. The HSS responds by transmitting a message <NUM> that includes the requested information.

The SCEF encapsulates (at block <NUM>) the mobile-terminated SMS message in a container message such as an NAS container. The SCEF then transmits a message <NUM> including the encapsulated mobile-terminated SMS message to the MME. The message <NUM> is addressed to the UE using the unique identifier of the UE.

If the UE is in an active mode and available to receive the SMS message, the MME forwards the SMS message to the UE. However, in the illustrated embodiment, the UE is in an idle mode and available to be paged by the MME. The MME therefore pages (at block <NUM>) the UE using the unique identifier of the UE. In the illustrated embodiment, the UE responds to the page in block <NUM>.

The MME transmits a message <NUM> including the encapsulated SMS message to the UE. Some embodiments of the message <NUM> are an uplink NAS transport message including an NAS message container that includes the SMS message. The MME also transmits a message <NUM> to the SCEF acknowledging that the SMS has been successfully delivered to the UE. In response to the message <NUM>, the SCEF transmits a message <NUM> to the application server acknowledging that the SMS message has been successfully delivered to the UE.

The user equipment transmits a message <NUM> to the MME including an acknowledgment of receipt of the SMS message. Some embodiments of the message <NUM> are a downlink NAS message or a control plane service request that includes an NAS message container. The MME then transmits a mobile-originated SMS data delivery request <NUM> to the SCEF, which replies with an acknowledgment message <NUM> in response to receiving the acknowledgment <NUM>.

<FIG> illustrates a message flow <NUM> that is used to buffer a mobile-terminated SMS message in an SCEF for subsequent delivery to a user equipment that is in a power saving mode according to some embodiments. The message flow <NUM> is implemented in some embodiments of the wireless communication system <NUM> shown in <FIG>.

The SCEF encapsulates (at block <NUM>) the mobile-terminated SMS message in a container message such as an NAS container. The SCEF then transmits a message <NUM> including a request to transmit the encapsulated mobile-terminated SMS message to the MME. The message <NUM> is addressed to the UE using the unique identifier of the UE.

In the illustrated embodiment, the UE is in a power saving mode and is only available to be paged at particular times indicated by a paging time interval. The MME determines that the UE is in the power saving mode at block <NUM>. The MME also determines when the next paging time interval occurs. The MME then responds to the message <NUM> with a message <NUM> indicating that the UE is temporarily not reachable (due to the UE being in the power saving mode) and indicating when the UE will next be available to be paged for delivery of the SMS message. In response to receiving the message <NUM>, the SCEF buffers the SMS message for delivery at the time indicated in the message <NUM>.

The UE contacts the network at block <NUM> to indicate that the UE is available to receive SMS messaging. In some embodiments, the UE contacts the network in response to being paged by the MME at the time determined by the paging time interval. The UE is also able to contact the network in response to the UE transitioning from the power saving mode into an idle mode or an active mode.

The MME transmits a message <NUM> including a connection management update that indicates that the UE is reachable. In response to the message <NUM>, the SCEF transmits an acknowledgment message <NUM>.

The SCEF prepares the buffered SMS message for transmission to the UE at block <NUM>. The SCEF transmits a message <NUM> including a delivery request for the SMS message included in the message <NUM>. In response to receiving the message <NUM>, the MME transmits a message <NUM> including the encapsulated SMS message to the UE. Some embodiments of the message <NUM> are an uplink NAS transport message including an NAS message container that includes the SMS message. The MME also transmits a message <NUM> to the SCEF acknowledging that the SMS has been successfully delivered to the UE.

The user equipment transmits a message <NUM> to the MME including an acknowledgment of receipt of the SMS message. Some embodiments of the message <NUM> are a downlink NAS message or a control plane service request that includes an NAS message container. The MME then transmits a mobile-originated SMS data delivery request <NUM> to the SCEF, which replies with an acknowledgment message <NUM> in response to receiving the acknowledgment <NUM>. In response to the message <NUM>, the SCEF also transmits a message <NUM> to the application server acknowledging that the SMS message has been successfully delivered to the UE.

<FIG> illustrates a message flow <NUM> that is used to buffer a mobile-terminated SMS message in an MME for subsequent delivery to a user equipment that is in a power saving mode according to some embodiments. The message flow <NUM> is implemented in some embodiments of the wireless communication system <NUM> shown in <FIG>.

In the illustrated embodiment, the UE is in a power saving mode and is only available to be paged at particular times indicated by a paging time interval. The MME determines that the UE is in the power saving mode at block <NUM>. The MME also determines when the next paging time interval occurs and selectively buffers the SMS message based on whether the UE will be available within a predetermined time interval. The MME then transmits a message <NUM> including an indication of the success or failure of the request and, if successful, a time of delivery of the SMS message to the UE. For example, if the MME determines that the UE will be available to be paged within a predetermined time interval, the MME buffers the SMS message and transmits the message <NUM> including an indication of successful delivery of the SMS message and the expected time of delivery. For another example, if the MME determines that the UE will not be available to be paged within the predetermined time interval, the MME discards the SMS message and transmits the message <NUM> including an indication of a failed delivery of the SMS message. In the case of a failed delivery, the message <NUM> can also include a cause such as "UE not reachable. " In response to receiving the message <NUM>, the SCEF forwards a message <NUM> to the application server including the acknowledgment information received in the message <NUM>.

The UE contacts the network at block <NUM> to indicate that the UE is available to receive SMS messaging. In some embodiments, the UE contacts the network in response to being paged by the MME at the time determined by the paging time interval. The UE is also able to contact the network in response to the UE transitioning from the power saving mode into an idle mode or an active mode. The MME prepares the buffered SMS message for transmission to the UE at block <NUM>. The MME then transmits a message <NUM> including the encapsulated SMS message to the UE. Some embodiments of the message <NUM> are an uplink NAS transport message including an NAS message container that includes the SMS message.

Claim 1:
A method comprising:
receiving (<NUM>), at a service capability exposure function (<NUM>), from an application server (<NUM>), a first message including a short message service message addressed to a user equipment (<NUM>) using an external identifier of the user equipment (<NUM>);
identifying (<NUM>), at the service capability exposure function (<NUM>), a destination for the short message service message on the basis of a mapping between a unique identifier of the user equipment (<NUM>) and the external identifier of the user equipment (<NUM>), wherein identifying the destination for the short message service message comprises mapping the external identifier included in the short message service message to the unique identifier of the user equipment (<NUM>);
identifying a mobility management entity (<NUM>) that is serving the user equipment (<NUM>) on the basis of the unique identifier of the user equipment (<NUM>);
encapsulating (<NUM>), by the service capability exposure function (<NUM>), the short message service message in a non-access stratum container; and
transmitting (<NUM>), from the service capability exposure function (<NUM>), a second message including the encapsulated short message service message to the mobility management entity (<NUM>), wherein the second message is addressed to the user equipment (<NUM>) using the unique identifier of the user equipment (<NUM>).