Abstract:
A method and apparatus for network initiated attachment are provided. A machine-type communication (MTC) wireless transmit/receive unit (WTRU) is in a detached state. A MTC server sends a trigger request to the MTC WTRU via a network entity, such as a Home Subscriber Server (HSS), a mobility management gateway (MME), a Serving General packet radio service Support Node (SGSN), or a combination thereof. The network entity stores, updates, or obtains information associated with a current, former, or default connection status of the WTRU. The information is obtained from the WTRU attach request message, subscription information, locally stored information, or a combination thereof. The subscription information includes a subscription profile. The WTRU, upon receiving the trigger request, performs a network attachment procedure, enters an attached state and communicates with the MTC server. The WTRU performs a network detach procedure and enters a detached state after completing communications with the MTC server.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. provisional application No. 61/471,052, filed Apr. 1, 2011, the contents of which are hereby incorporated by reference herein. 
     
    
     FIELD OF INVENTION 
       [0002]    This application is related to wireless communications. 
       BACKGROUND 
       [0003]    A communication device, such as a wireless transmit/receive unit (WTRU), may communicate with a remote device via a communication system. A wireless transmit/receive unit (WTRU) may be configured to perform “machine-type communications” (MTC). MTC communication, which may be referred to as Machine-to-Machine (M2M) communication, may be performed without human interaction. A WTRU configured to perform MTC communication (MTC device) may be associated with a network and may operate in a detached or offline mode. 
       SUMMARY 
       [0004]    A method and apparatus for network initiated attachment are provided. A wireless transmit/receive unit (WTRU) may be configured to perform machine-type communication (MTC) and may operate in a detached state. A network element or remote device, such as an MTC server, may initiate an attach procedure for the WTRU. The MTC server may send a trigger request message to the MTC WTRU via a network entity, such as a Home Subscriber Server (HSS), a mobility management gateway (MME), a Serving General packet radio service Support Node (SGSN), or a combination thereof. The network entity may store, update, or obtain information associated with a current, former, or default connection status of the WTRU. The information may be obtained from the WTRU attach request message, subscription information, locally stored information, or a combination thereof. The subscription information may include a subscription profile. The WTRU, upon receiving the trigger request message, may perform a network attachment procedure and enter an attached state. The WTRU may then communicate with the MTC server. The WTRU may perform a network detach procedure and enter a detached state after communications with the MTC server are complete. The WTRU may send connection status information to the network element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein: 
           [0006]      FIG. 1A  is a system diagram of an example communications system in which one or more disclosed embodiments may be implemented; 
           [0007]      FIG. 1B  is a system diagram of an example wireless transmit/receive unit (WTRU) that may be used within the communications system illustrated in  FIG. 1A ; 
           [0008]      FIG. 1C  is a system diagram of an example radio access network and an example core network that may be used within the communications system illustrated in  FIG. 1A ; 
           [0009]      FIG. 2  shows an example diagram of a communications architecture for machine-type communication (MTC) device triggering; 
           [0010]      FIG. 3  shows an example signal flow for initiating an attach procedure for a MTC device via a Home Subscriber Server (HSS); 
           [0011]      FIG. 4  shows an example signal flow for initiating an attach procedure for a MTC device via a HSS with device pre-configuration; 
           [0012]      FIG. 5  shows an example signal flow for indicating connection status information for a MTC device; 
           [0013]      FIG. 6  shows an example signal flow for initiating an attach procedure for a MTC device via a mobility management gateway; and 
           [0014]      FIG. 7  shows an example signal flow for initiating an attach procedure for a MTC device via a Serving General packet radio service Support Node with device pre-configuration. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1A  is a diagram of an example communications system  100  in which one or more disclosed embodiments may be implemented. The communications system  100  may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system  100  may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems  100  may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), and the like. 
         [0016]    As shown in  FIG. 1A , the communications system  100  may include wireless transmit/receive units (WTRUs)  102   a ,  102   b ,  102   c ,  102   d , a radio access network (RAN)  104 , a core network  106 , a public switched telephone network (PSTN)  108 , the Internet  110 , and other networks  112 , though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs  102   a ,  102   b ,  102   c ,  102   d  may be any type of device configured to operate and/or communicate in a wireless environment. By way of example, the WTRUs  102   a ,  102   b ,  102   c ,  102   d  may be configured to transmit and/or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, consumer electronics, and the like. 
         [0017]    The communications systems  100  may also include a base station  114   a  and a base station  114   b . Each of the base stations  114   a ,  114   b  may be any type of device configured to wirelessly interface with at least one of the WTRUs  102   a ,  102   b ,  102   c ,  102   d  to facilitate access to one or more communication networks, such as the core network  106 , the Internet  110 , and/or the networks  112 . By way of example, the base stations  114   a ,  114   b  may be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a site controller, an access point (AP), a wireless router, and the like. While the base stations  114   a ,  114   b  are each depicted as a single element, it will be appreciated that the base stations  114   a ,  114   b  may include any number of interconnected base stations and/or network elements. 
         [0018]    The base station  114   a  may be part of the RAN  104 , which may also include other base stations and/or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station  114   a  and/or the base station  114   b  may be configured to transmit and/or receive wireless signals within a particular geographic region, which may be referred to as a cell (not shown). The cell may further be divided into cell sectors. For example, the cell associated with the base station  114   a  may be divided into three sectors. Thus, in one embodiment, the base station  114   a  may include three transceivers, i.e., one for each sector of the cell. In another embodiment, the base station  114   a  may employ multiple-input multiple output (MIMO) technology and, therefore, may utilize multiple transceivers for each sector of the cell. 
         [0019]    The base stations  114   a ,  114   b  may communicate with one or more of the WTRUs  102   a ,  102   b ,  102   c ,  102   d  over an air interface  116 , which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface  116  may be established using any suitable radio access technology (RAT). 
         [0020]    More specifically, as noted above, the communications system  100  may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station  114   a  in the RAN  104  and the WTRUs  102   a ,  102   b ,  102   c  may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface  116  using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink Packet Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA). 
         [0021]    In another embodiment, the base station  114   a  and the WTRUs  102   a ,  102   b ,  102   c  may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface  116  using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A). 
         [0022]    In other embodiments, the base station  114   a  and the WTRUs  102   a ,  102   b ,  102   c  may implement radio technologies such as IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like. 
         [0023]    The base station  114   b  in  FIG. 1A  may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, and the like. In one embodiment, the base station  114   b  and the WTRUs  102   c ,  102   d  may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In another embodiment, the base station  114   b  and the WTRUs  102   c ,  102   d  may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station  114   b  and the WTRUs  102   c ,  102   d  may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) to establish a picocell or femtocell. As shown in  FIG. 1A , the base station  114   b  may have a direct connection to the Internet  110 . Thus, the base station  114   b  may not be required to access the Internet  110  via the core network  106 . 
         [0024]    The RAN  104  may be in communication with the core network  106 , which may be any type of network configured to provide voice, data, applications, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs  102   a ,  102   b ,  102   c ,  102   d . For example, the core network  106  may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and/or perform high-level security functions, such as user authentication. Although not shown in  FIG. 1A , it will be appreciated that the RAN  104  and/or the core network  106  may be in direct or indirect communication with other RANs that employ the same RAT as the RAN  104  or a different RAT. For example, in addition to being connected to the RAN  104 , which may be utilizing an E-UTRA radio technology, the core network  106  may also be in communication with another RAN (not shown) employing a GSM radio technology. 
         [0025]    The core network  106  may also serve as a gateway for the WTRUs  102   a ,  102   b ,  102   c ,  102   d  to access the PSTN  108 , the Internet  110 , and/or other networks  112 . The PSTN  108  may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet  110  may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and the internet protocol (IP) in the TCP/IP internet protocol suite. The networks  112  may include wired or wireless communications networks owned and/or operated by other service providers. For example, the networks  112  may include another core network connected to one or more RANs, which may employ the same RAT as the RAN  104  or a different RAT. 
         [0026]    Some or all of the WTRUs  102   a ,  102   b ,  102   c ,  102   d  in the communications system  100  may include multi-mode capabilities, i.e., the WTRUs  102   a ,  102   b ,  102   c ,  102   d  may include multiple transceivers for communicating with different wireless networks over different wireless links. For example, the WTRU  102   c  shown in  FIG. 1A  may be configured to communicate with the base station  114   a , which may employ a cellular-based radio technology, and with the base station  114   b , which may employ an IEEE 802 radio technology. 
         [0027]      FIG. 1B  is a system diagram of an example WTRU  102 . As shown in  FIG. 1B , the WTRU  102  may include a processor  118 , a transceiver  120 , a transmit/receive element  122 , a speaker/microphone  124 , a keypad  126 , a display/touchpad  128 , non-removable memory  106 , removable memory  132 , a power source  134 , a global positioning system (GPS) chipset  136 , and other peripherals  138 . It will be appreciated that the WTRU  102  may include any sub-combination of the foregoing elements while remaining consistent with an embodiment. 
         [0028]    The processor  118  may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor  118  may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the WTRU  102  to operate in a wireless environment. The processor  118  may be coupled to the transceiver  120 , which may be coupled to the transmit/receive element  122 . While  FIG. 1B  depicts the processor  118  and the transceiver  120  as separate components, it will be appreciated that the processor  118  and the transceiver  120  may be integrated together in an electronic package or chip. 
         [0029]    The transmit/receive element  122  may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station  114   a ) over the air interface  116 . For example, in one embodiment, the transmit/receive element  122  may be an antenna configured to transmit and/or receive RF signals. In another embodiment, the transmit/receive element  122  may be an emitter/detector configured to transmit and/or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit/receive element  122  may be configured to transmit and receive both RF and light signals. It will be appreciated that the transmit/receive element  122  may be configured to transmit and/or receive any combination of wireless signals. 
         [0030]    In addition, although the transmit/receive element  122  is depicted in FIG.  1 B as a single element, the WTRU  102  may include any number of transmit/receive elements  122 . More specifically, the WTRU  102  may employ MIMO technology. Thus, in one embodiment, the WTRU  102  may include two or more transmit/receive elements  122  (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface  116 . 
         [0031]    The transceiver  120  may be configured to modulate the signals that are to be transmitted by the transmit/receive element  122  and to demodulate the signals that are received by the transmit/receive element  122 . As noted above, the WTRU  102  may have multi-mode capabilities. Thus, the transceiver  120  may include multiple transceivers for enabling the WTRU  102  to communicate via multiple RATs, such as UTRA and IEEE 802.11, for example. 
         [0032]    The processor  118  of the WTRU  102  may be coupled to, and may receive user input data from, the speaker/microphone  124 , the keypad  126 , and/or the display/touchpad  128  (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor  118  may also output user data to the speaker/microphone  124 , the keypad  126 , and/or the display/touchpad  128 . In addition, the processor  118  may access information from, and store data in, any type of suitable memory, such as the non-removable memory  106  and/or the removable memory  132 . The non-removable memory  106  may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory  132  may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor  118  may access information from, and store data in, memory that is not physically located on the WTRU  102 , such as on a server or a home computer (not shown). 
         [0033]    The processor  118  may receive power from the power source  134 , and may be configured to distribute and/or control the power to the other components in the WTRU  102 . The power source  134  may be any suitable device for powering the WTRU  102 . For example, the power source  134  may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like. 
         [0034]    The processor  118  may also be coupled to the GPS chipset  136 , which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU  102 . In addition to, or in lieu of, the information from the GPS chipset  136 , the WTRU  102  may receive location information over the air interface  116  from a base station (e.g., base stations  114   a ,  114   b ) and/or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU  102  may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment. 
         [0035]    The processor  118  may further be coupled to other peripherals  138 , which may include one or more software and/or hardware modules that provide additional features, functionality and/or wired or wireless connectivity. For example, the peripherals  138  may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, and the like. 
         [0036]      FIG. 1C  is a system diagram of the RAN  104  and the core network  106  according to an embodiment. As noted above, the RAN  104  may employ an E-UTRA radio technology to communicate with the WTRUs  102   a ,  102   b ,  102   c  over the air interface  116 . The RAN  104  may also be in communication with the core network  106 . 
         [0037]    The RAN  104  may include eNode-Bs  140   a ,  140   b ,  140   c , though it will be appreciated that the RAN  104  may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs  140   a ,  140   b ,  140   c  may each include one or more transceivers for communicating with the WTRUs  102   a ,  102   b ,  102   c  over the air interface  116 . In one embodiment, the eNode-Bs  140   a ,  140   b ,  140   c  may implement MIMO technology. Thus, the eNode-B  140   a , for example, may use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU  102   a.    
         [0038]    Each of the eNode-Bs  140   a ,  140   b ,  140   c  may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the uplink and/or downlink, and the like. As shown in  FIG. 1C , the eNode-Bs  140   a ,  140   b ,  140   c  may communicate with one another over an X2 interface. 
         [0039]    The core network  106  shown in  FIG. 1C  may include a mobility management gateway (MME)  142 , a serving gateway  144 , and a packet data network (PDN) gateway  146 . While each of the foregoing elements are depicted as part of the core network  106 , it will be appreciated that any one of these elements may be owned and/or operated by an entity other than the core network operator. 
         [0040]    The MME  142  may be connected to each of the eNode-Bs  142   a ,  142   b ,  142   c  in the RAN  104  via an S1 interface and may serve as a control node. For example, the MME  142  may be responsible for authenticating users of the WTRUs  102   a ,  102   b ,  102   c , bearer activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs  102   a ,  102   b ,  102   c , and the like. The MME  142  may also provide a control plane function for switching between the RAN  104  and other RANs (not shown) that employ other radio technologies, such as GSM or WCDMA. 
         [0041]    The serving gateway  144  may be connected to each of the eNode Bs  140   a ,  140   b ,  140   c  in the RAN  104  via the S1 interface. The serving gateway  144  may generally route and forward user data packets to/from the WTRUs  102   a ,  102   b ,  102   c . The serving gateway  144  may also perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when downlink data is available for the WTRUs  102   a ,  102   b ,  102   c , managing and storing contexts of the WTRUs  102   a ,  102   b ,  102   c , and the like. 
         [0042]    The serving gateway  144  may also be connected to the PDN gateway  146 , which may provide the WTRUs  102   a ,  102   b ,  102   c  with access to packet-switched networks, such as the Internet  110 , to facilitate communications between the WTRUs  102   a ,  102   b ,  102   c  and IP-enabled devices. 
         [0043]    The core network  106  may facilitate communications with other networks. For example, the core network  106  may provide the WTRUs  102   a ,  102   b ,  102   c  with access to circuit-switched networks, such as the PSTN  108 , to facilitate communications between the WTRUs  102   a ,  102   b ,  102   c  and traditional land-line communications devices. For example, the core network  106  may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the core network  106  and the PSTN  108 . In addition, the core network  106  may provide the WTRUs  102   a ,  102   b ,  102   c  with access to the networks  112 , which may include other wired or wireless networks that are owned and/or operated by other service providers. 
         [0044]    Although not shown in  FIG. 1C , it will be appreciated that the RAN  104  may be connected to other ASNs and the core network  106  may be connected to other core networks. The communication link between the RAN  104  the other ASNs may be defined as an R4 reference point, which may include protocols for coordinating the mobility of the WTRUs  102   a ,  102   b ,  102   c  between the RAN  104  and the other ASNs. The communication link between the core network  106  and the other core networks may be defined as an R5 reference, which may include protocols for facilitating interworking between home core networks and visited core networks. 
         [0045]    A WTRU, such as the WTRU  102  shown in  FIG. 1B , may be configured to perform machine-type communication (MTC) via a network, such as the network shown in  FIG. 1C . For simplicity, a WTRU configured to perform MTC communication may be referred to herein as an MTC device. The MTC device may communicate with an entity in the network, such as a server. For simplicity, the network entity may be referred to herein as an MTC server. 
         [0046]      FIG. 2  shows an example MTC device triggering architecture  2000  for MTC device triggering. MTC device triggering may include MTC addressing and Mobile Station Integrated Services Digital Network number (MSISDN)-less communications. 
         [0047]    The MTC device triggering architecture  2000  may include a device trigger gateway (DT-GW)  2005 , which may be a standalone physical entity or a functional entity. The DT-GW  2005  may include functional entities/mechanisms such as a domain name server  2006 , access stratum (AS)  2008 , a short message entity  2010  and a cell broadcast entity  2012 . The DT-GW  2005  functionality may include the following: ingress of trigger indication messages into a Public Land Mobile Network (PLMN); authorization that the trigger indication is from a trusted MTC server; authorization that the MTC device addressed in a trigger indication is from a MTC server that is authorized to trigger the addressed MTC device; selection of the delivery service and route to forward the trigger indication to for delivery to the MTC device, (e.g. based on collected reachability information and network operator policy); reformatting, as needed, of the trigger indication payload to match the format required for the selected delivery service; egress of trigger indication from the DT-GW to the to the selected delivery service entity for delivery to the MTC device; and appropriate e.g. error handling, error logging and/or error notification when trigger indication is determined to be invalid or unauthorized. 
         [0048]    At any given point of time, there is at least one globally routable DT-GW assigned for each subscribed WTRU or MTC device that supports the MTC device trigger feature. A DT-GW  2005  terminates an MTCsp interface for reception of trigger indications from a submitting node, for example, a MTC server  2015  residing in a packet data network (PDN)  2020 . The MTC server  2015  may send a trigger indication request to the appropriate DT-GW encapsulated in an IP packet. The trigger indication request could contain pertinent information needed to route the trigger, (e.g. device subscriber identity, trigger command/arguments, relevant device location information, security parameters, and the like). 
         [0049]    When a trigger indication is received from a submitting node, the DT-GW  2005  may authorize the received request to make sure it originated from a trusted MTC server and is targeted for a MTC device  2090  for which the MTC server  2015  is authorized to trigger. The DT-GW  2005  may then determine the reachability of the MTC device  2060 . To determine “how” reachable the device is, the DT-GW  2005  interrogates a Home Location Register/Home Subscriber Server (HLR/HSS)  2025  using a C and/or Sh interface. 
         [0050]    The DT-GW  2005  may use the reachability information obtained from the HLR/HSS  2025 , a Gateway General Packet Radio Service (GPRS) Support Node (GGSN)/PDN Gateway (P-GW) Radius/Diameter interface  2030  and mobile network operator (MNO) configured policy information to determine the most efficient and effective service and route to use for forwarding of the trigger indication to be delivered to the MTC device  2060 . For example, the DT-GW  2005  may forward the trigger indication to: 1) a GGSN/P-GW  2030  for delivery over an already established PDP context/PDN connection; 2) a Serving GPRS Support Node (SGSN)/Mobility Management Entity (MME)  2035  for delivery over a newly established PDP context (via a Network-Requested PDP Context Activation Procedure initiated by the DT-GW); a Serving Call State Control Function (S-CSCF)  2040  for delivery over a Session Initiation Protocol (SIP)/IP Multimedia Subsystem (IMS) (SIP/IMS) service; a Short Message Service-Service Centre (SMS-SC)  2045  for delivery over SMS; or a Cell Broadcast Centre (CBC)  2050  for broadcast delivery over cell broadcast service (CBS). 
         [0051]    An MTC device may operate in a detached or offline mode. For example, an MTC device may be in a packet mobility management (PMM) PMM-DETACHED or evolved packet system (EPS) Mobility Management (EMM) EMM-DEREGISTERED state. An offline MTC device may not be aware of its location. An entity in the network, such as a MME or SGSN, may identify a location of an offline MTC device. The location may be identified on a per Tracking Area or Routing Area identity (ID) granularity, for example when the MTC device is in an IDLE state, such as an EPS connection management (ECM) ECM-IDLE or PMM-IDLE state. The location may be identified on a per cell ID granularity, for example when the device is in a connected state, such as an ECM-CONNECTED or READY/PMM-CONNECTED state. 
         [0052]    MTC communication may include Group based optimization, MTC device communication to multiple MTC servers, Internet Protocol version 4 (IPv4) addressing, Small data transmission, including online and offline transmission, such as short message service (SMS) messaging, Low mobility, MTC subscription, MTC device triggering, Time controlled devices, MTC monitoring, Decoupling MTC server from network architecture, MTC identifiers, and Congestion and Overload control. 
         [0053]    Congestion and Overload control may include use of a low priority indicator within Access Stratus (AS) and non-access stratus (NAS) signaling to allow an MME or SGSN to reject a connection to low priority devices when congestion and overloading occurs. An MTC device may use an Over the Air (OTA) SIM or Universal SIM, or Open Mobile Alliance (OMA) Device Management (DM). 
         [0054]    As stated above, a message, such as a trigger, may be sent via the MTCsp between an MTC server and a device trigger gateway (DT-GW) within a CN. The DT-GW may use reachability, or connection status, information obtained from the HLR/HSS, a GGSN/P-GW Radius/Diameter interface, and MNO configured policy information to determine the most efficient and effective service and route to use for forwarding of the message to be delivered to the MTC device. The DT-GW may reformat and send the trigger indication to a GGSN/P-GW for delivery over a PDP context or PDN connection. The DT-GW may reformat and send the trigger indication to a GGSN for delivery over a PDP context, using, for example, a Network-Requested PDP Context Activation Procedure initiated by the DT-GW. The DT-GW may reformat and send the trigger indication to a S-CSCF for delivery using a SIP or IMS service. The DT-GW may reformat and send the trigger indication to a SMS-SC for delivery via SMS. The DT-GW may reformat and send the trigger indication to a CBC for broadcast delivery over CBS, such as where location information is available in the message request or from another source in order to limit the broadcast area. 
         [0055]    However, location information at a network entity, such as a MME or SGSN, for an offline or detached MTC device may be incomplete or inaccurate. For example, the location information may identify a last location of the MTC device before the MTC device went offline and the device may be mobile. The network entity may identify the MTC device as detached if the MTC device is not reachable, if timers expire, or the MTC device detached, such as where the HSS has an un-reachable flag. The network element may not detect that an MTC device is offline. 
         [0056]    Described herein are methods and apparatus to trigger devices used for machine-to-machine (M2M) communication that are offline, e.g. detached from the network. The methods allow the CN or the MTC server to be aware when an offline device can be triggered. In an example method, a subscription profile may be added in the HSS/HLR indicating the status of the MTC device. In another example method, the MTC device may indicate its status when attaching or detaching for the network, where status may be saved in a subscription profile. In another example, the MTC server may indicate to a 3GPP network, via the DT-GW, whether the MTC device to be triggered is online or offline. 
         [0057]    A subscription profile, which may be maintained at an entity in the network, such as an HSS/HLR, may indicate whether a MTC device is “online” or “offline” by default. The term “by default” may mean that a device is always in an offline or online state. For example, the network operator may indicate in the subscription profile that a particular device is pre-configured to be always offline or online. The default status may be obtained via different methods. In an example, the device itself may indicate its default status. In another example, an operator, such as a mobile network operator (MNO), may always have such devices offline and the HSS may have subscription information that such devices are always offline and also location information that would assist in paging the devices. In another example, the MTC server may indicate to the network operator via the MTCsp interface the status of a device and the location information that would assist in the paging the device. 
         [0058]    The subscription profile may be included in a user subscription or MTC device subscription profile. Alternatively, the MTC device may include a parameter, indicating whether the device is offline or online by default, in a message, such as in an Attach Request or Detach Request. In this case, the network entity, which may be an SGSN/MME, may store the default connection state information. The network entity may inform other network entities, such as an HSS/HLR, about the default connection state information for the device. Alternatively, the MTC server may indicate to a CN a connection state of a device, which may include location information, via an interface, such as the MTCsp interface. A network entity in the CN, such as an HSS, may store the connection state information in, for example, a subscription profile. 
         [0059]    A subscription profile may be used, for example by a network element such as an HSS, to store device status information, location information, or both, for a detached device. Table 1 shows an example format for subscription data including MTC device status information. 
         [0000]    
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Field 
                 Description 
               
               
                   
               
             
             
               
                 MTC Device Status or Low 
                 Indicates whether MTC device is online 
               
               
                 Priority Device Status 
                 “0” or offline “1” by default 
               
               
                 MTC Device location or Low 
                 Offline device location (Tracking Area Id 
               
               
                 Priority Device location 
                 or Routing Area Id) 
               
               
                   
               
             
          
         
       
     
         [0060]    An MTC device operating in a detached mode may respond to, or be triggered by, a network. For example, an MTC server may trigger an MTC device that is offline, for example detached from the network. The MTC server may send a MTC trigger towards an MTC device or a group of MTC devices, (i.e., for the MTC device(s) to attach to the network), to an entity in a network, such as an HSS/HLR or a MME/SGSN. In the case of the HSS/HLR, the MTC server may send the MTC trigger to the HSS/HLR, for example, via a triggering gateway. The HSS/HLR may update internal information and may send a message to a MME/SGSN indicating the MTC trigger and a status of the MTC device. In the case of the MME/SGSN, the MTC server may send the MTC trigger to the MME/SGSN, for example via a triggering gateway. The MME/SGSN may send a default status request for the device to the HSS/HLR. 
         [0061]      FIG. 3  shows an example signal flow  3000  for triggering a MTC device  3010 , (for the MTC device  3010  to attach to the network), via an HSS  3020 . The MTC server  3030  may send a MTC trigger to the HSS  3020  ( 3100 ). The MTC trigger may indicate a connection status of the MTC device  3010 , for example, the MTC trigger may indicate that the MTC device  3010  is offline. The MTC trigger may indicate a location of the detached MTC device  3010 . The contents of the MTC trigger or messages derived from the MTC trigger may be referred to as “information” in the context of the signal flow diagrams described herein below, as applicable. 
         [0062]    The HSS  3020  may receive the MTC trigger from the MTC server  3030  and may update or store status information for the MTC device  3010  ( 3150 ). For example, the HSS  3020  may determine whether connection status information for the MTC device  3010  was previously stored. The HSS  3020  may send at least the MTC trigger to the MME/SGSN  3040  ( 3200 ). For example the HSS  3020  may send the MTC trigger received from the MTC server  3030  or the HSS  3020  may generate a message that may include a request to page the detached MTC device  3010 , the MTC trigger, MTC device status and/or subscriber data, (which may be referred to as an HSS message). 
         [0063]    The MME/SGSN  3040  may receive the MTC trigger or HSS message from the HSS  3020  and may update or store the information associated with the MTC device  3010  ( 3250 ). The MME/SGSN  3040  may send an acknowledgement (ACK) message to the HSS  3020  ( 3300 ). The MME/SGSN  3040  may then send a paging message to the MTC device  3010  ( 3350 ). For example, the MME/SGSN  3040  may send the paging message using the stored location information or using a last known location of the MTC device  3010 . 
         [0064]    The MTC device  3010  may, in response, send an attach request message to the MME/SGSN  3040  ( 3400 ). The MME/SGSN  3040  may, in turn, send an attach accept message to the MTC device  3010  ( 3450 ). The MTC device  3010  may establish a connection, such as an IP connection, with the MTC server  3030  ( 3500 ). The MTC device  3010  may send data and information to the MTC server  3030 . 
         [0065]    The MTC device  3010  may enter an offline state after communications with the MTC server  3030  is complete ( 3550 ). The MTC device  3010  may send a message including its offline status, such as a Detach Request message, to the MME/SGSN  3040 . The MME/SGSN  3040  may send a message, such as a Detach Accept message, to the MTC device  3010  ( 3600 ). Although not shown, the network may initiate the detach process for the MTC device  3010 , for example, where the MTC device  3010  is in a detached state by default. The network initiated detach procedures may be carried out from, for example, the MME, SGSN or HSS, using methods and techniques known to those of ordinary skill in the art. 
         [0066]      FIG. 4  shows an example signal flow  4000  for triggering a MTC device  4010  via an HSS  4020  with device pre-configuration. The MTC server  4030  may send a MTC trigger to the HSS  4020  ( 4100 ). The HSS  4020  may receive the MTC trigger from the MTC server  4030  and may evaluate a subscription profile associated with the MTC device  3010  to determine connection status information for the MTC device  4010  ( 4150 ). The HSS  4020  may then send a HSS message to the MME/SGSN  4040  ( 4200 ). The HSS message may indicate a request to page the detached MTC device  4010 , and may include subscriber data, default connection information, or location information associated with the MTC device  4010 . 
         [0067]    The MME/SGSN  4040  may receive the HSS message from the HSS  4020  and may update or store information associated with the MTC device  4010  ( 4250 ). The MME/SGSN  4040  may then send an ACK message to the HSS  4020  ( 4300 ). The MME/SGSN  4040  may send a paging message to the MTC device ( 4350 ). For example, the MME/SGSN  4040  may send the paging message using the stored location information or using a last known location of the MTC device  4010 . 
         [0068]    The MTC device  4010  may, in response, send an attach request message to the MME/SGSN  4040  ( 4400 ). The MME/SGSN  4040  may send, in turn, an attach accept message to the MTC device  4010  ( 4450 ). The MTC device  4010  may establish a connection, such as an IP connection, with the MTC server  4030  to send data and/or information to the MTC server  4030  ( 4500 ). 
         [0069]    The MTC device  4010  may enter an offline state after communications with the MTC server  4030  is complete ( 4550 ). The MTC device  4010  may send a message including its offline status, such as a Detach Request message, to the MME/SGSN  4040 . The MME/SGSN  4040  may send a message, such as a Detach Accept message, to the MTC device  4010  ( 4600 ). Although not shown, the network may initiate the detach process for the MTC device  4010 , for example, where the MTC device  4010  is in a detached state by default. 
         [0070]      FIG. 5  shows an example signal flow  5000  for indicating connection status information for a MTC device  5010 . The MTC device  5010  may enter a detached state ( 5100 ). The MTC device  5010  may then send a message, such a Detach Request message, to the MME/SGSN  5040  ( 5200 ). The Detach Request message may include connection status information for the MTC device  5010 . 
         [0071]    The MME/SGSN  5040  may receive the Detach Request message from the MTC device  5010  and may update or store status information associated with the MTC device  5010  ( 5250 ). The MME/SGSN  5040  may also send a notification message, such as a Notify Request message, to the HSS  5020  ( 5300 ). The notification message may indicate connection status information, (i.e. that MTC device  5010  is offline), location information, or both, for the MTC device  5010 . 
         [0072]    The HSS  5020  may receive the notification message from the MME/SGSN  5040  and may update or store status information for the MTC device  5010  ( 5400 ). This may be stored, for example, is a subscription profile associated with the MTC device based on, for example, the International Mobile Subscriber Identity (IMSI). The HSS  5020  may then send a notification ACK message to the MME/SGSN  5040  ( 5600 ). The MME/SGSN  5040  may then send a message, such as a Detach Accept message, to the MTC device  5010  ( 5700 ). 
         [0073]      FIG. 6  shows an example signal flow  6000  for triggering a MTC device  6010  via a MME/SGSN  6020 . The MTC server  6030  may send a MTC trigger to the MME/SGSN  6020  ( 6100 ). The MTC trigger may indicate a connection status of the MTC device  6010 , for example, the MTC trigger may indicate that the MTC device  6010  is offline. The MTC trigger may indicate a location of the detached MTC device  6010 . 
         [0074]    The MME/SGSN  6020  may send a message to the HSS  6040  ( 6150 ). The message may include a request for status information for the MTC device  6010 . For example, the message may include a request for subscription information. The message may include a status update for the MTC device  6010 . 
         [0075]    The HSS  6040  may receive the request from the MME/SGSN  6020  and may evaluate a subscription profile associated with the MTC device  7010  to determine connection status information for the MTC device  7010  ( 6200 ). The HSS  6040  may update or store status information for the MTC device  6010 . For example, the HSS  6040  may determine whether connection status information for the MTC device  6010  was previously stored. The HSS  6040  may send a status report message to the MME/SGSN  6020  ( 6250 ). The status report message may indicate connection status information for the MTC device  6010 . The status report message may also include subscriber data, location information, or both. 
         [0076]    The MME/SGSN  6020  may receive the status report message from the HSS  6040  and may update or store status information associated with the MTC device  6010  ( 6300 ). The MME/SGSN  6020  may send a paging message to the MTC device ( 6350 ). For example, the MME/SGSN  6020  may send the paging message using the location information or using a last known location of the MTC device  6010 . 
         [0077]    The MTC device  6010  may, in response, send an attach request message to the MME/SGSN  6020  at  6400 . The MME/SGSN  6020  may, in turn, send an attach accept message to the MTC device  6010  ( 6450 ). The MTC device  6010  may establish a connection, such as an IP connection, with the MTC server  6030  ( 6500 ). The MTC device  6010  may send data and/or information to the MTC server  6030 . 
         [0078]    The MTC device  6010  may enter an offline state after communications with the MTC server  6030  is complete ( 6550 ). The MTC device  6010  may send a message including its offline status, such as a Detach Request message, to the MME/SGSN  6020 . The MME/SGSN  6020  may send a message, such as a Detach Accept message, to the MTC device  6010  ( 6600 ). Although not shown, the network may initiate the detach process for the MTC device  6010 , for example, where the MTC device  6010  is in a detached state by default. 
         [0079]      FIG. 7  shows an example signal flow  7000  for triggering a MTC device  7010  via a MME/SGSN  7020  with device pre-configuration. The MTC server  7030  may send a MTC trigger to the MME/SGSN  7020  ( 7100 ). The MME/SGSN  7020  may send a message to the HSS  7040  ( 7150 ). The message may include a request for status information for the MTC device  7010 . For example, the message may include a request for subscription information, connection status information, or both. 
         [0080]    The HSS  7040  may receive the request from the MME/SGSN  7020  and may evaluate a subscription profile associated with the MTC device  3010  to determine connection status information for the MTC device  7010  ( 7200 ). The HSS  7040  may then send a status report message to the MME/SGSN  7020  ( 7250 ). The status report message may indicate connection status information for the MTC device  7010 . For example, the HSS  7040  may report that the MTC device  7010  is offline. The status report message may also include subscriber data, location information, or both. 
         [0081]    The MME/SGSN  7020  may receive the status report from the HSS  7040  and may send an ACK message to the HSS  7040  ( 7300 ). The MME/SGSN  7020  may then update or store status information associated with the MTC device  7010  ( 7350 ). The MME/SGSN  7020  may send a paging message to the MTC device  7010  ( 7400 ). For example, the MME/SGSN  7020  may send the paging message using the stored location information or using a last known location of the MTC device  7010 . 
         [0082]    The MTC device  7010  may, in response, send an attach request message to the MME/SGSN  7020  ( 7450 ). The MME/SGSN  7020  may send an attach accept message to the MTC device  7010  ( 7500 ). The MTC device  7010  may establish a connection, such as an IP connection, with the MTC server  7030  at  7550 . The MTC device  7010  may send data and/or information to the MTC server  7030  ( 7550 ). 
         [0083]    The MTC device  7010  may enter an offline state after communications with the MTC server  7030  is complete ( 7600 ). The MTC device  7010  may send a message, such as a Detach Request message, to the MME/SGSN  7020 . The MME/SGSN  7020  may send a message, such as a Detach Accept message, to the MTC device  7010  ( 7650 ). Although not shown, the network may initiate the detach process for the MTC device  7010 , for example, where the MTC device  7010  is in a detached state by default. 
         [0084]    Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element may be used alone or in combination with any of the other features and elements. In addition, the embodiments described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals, (transmitted over wired or wireless connections), and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, a cache memory, a semiconductor memory device, a magnetic media, (e.g., an internal hard disc or a removable disc), a magneto-optical media, and an optical media such as a compact disc (CD) or a digital versatile disc (DVD). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, Node-B, eNB, HNB, HeNB, AP, RNC, wireless router or any host computer.