Patent Publication Number: US-2015065106-A1

Title: Linking user equipment contexts associated with the same physical device

Description:
BACKGROUND 
     1. Field 
     Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to management of wireless devices that support multiple subscriptions. 
     2. Background 
     Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. Examples of such networks may be based on the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS Terrestrial Radio Access Network (UTRAN), which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, including Time Division—Synchronous Code Division Multiple Access (TD-SCDMA), and code division multiple access (CDMA) or one of its variants such as Wideband-Code Division Multiple Access (W-CDMA). UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks. 
     Some wireless devices can support multiple subscriptions. Each subscription may be associated with a subscriber identity module or subscriber identification module (SIM). A wireless device may be referred to by the term user equipment (UE), or by some other terminology. Some wireless devices may support two or more SIMs in a multi-SIM device. When a wireless device has two SIMs installed, and both SIMs are active at the same time, the network may consider the connections associated with the two SIMs as relating two separate devices. In particular, a “UE Context” is tied to an international mobile subscriber identity (IMSI), rather than to physical user equipment. As a result, multi-SIM devices may perform duplicate device-specific procedures and may suffer unnecessary increased power consumption and the network may suffer unnecessary signaling load. 
     SUMMARY 
     In an aspect of the disclosure, methods, computer program products, and apparatus are provided. The apparatus may comprise a modem, an access terminal, an access point and/or a network entity. 
     In an aspect of the disclosure a method of managing multiple contexts for a wireless device includes the steps of determining a link between a first context of a UE and a second context of the UE at a network entity, and combining procedures related to the first and the second contexts when the first context and the second context are linked. The first context and the second context may be associated with a common international mobile equipment identity (IMEI) of the UE and different IMSIs. 
     In an aspect of the disclosure, combining procedures related to the first and the second contexts includes synchronizing procedures related to the different IMSIs. 
     In an aspect of the disclosure, combining procedures related to the first and the second contexts includes performing a device-specific procedure in relation to the first context, and refraining from performing the device-specific procedure in relation to the second context. A result of the device-specific procedure may be propagated between the first context and the second context. The procedures may include at least one radio resource procedure. In one example, the radio resource procedure may include a UE capability exchange. In another example, the radio resource procedure may include a handover of the UE between base stations. In another example, the radio resource procedure may include one or more of a tracking area update procedure, a location area update procedure, and a routing area update procedure. 
     In an aspect of the disclosure, combining procedures related to the first and second contexts may include initiating a measurement reporting procedure at the UE. The measurement reporting procedure may be adapted to minimize a drive tests procedure. 
     In an aspect of the disclosure, combining procedures related to the first context and the second context includes causing the UE to monitor pages corresponding to both the first context and the second context during a single paging occasion in a discontinuous reception (DRX) cycle. 
     In an aspect of the disclosure, assignment of resources for the first context and the second context are coordinated. The resources may be assigned based on a power constraint of the UE. 
     In an aspect of the disclosure, the first context and the second context are determined to be linked based on an information exchange between the network entity and another network entity, the information relating the first context and the second context to a unique identifier of the UE. The information exchanged between the network entity and another network entity may include information relating the first context and the second context transmitted in an attach or registration update message by a home subscriber server. The unique identifier comprises an IMEI. 
     In an aspect of the disclosure, the network entity comprises a home subscriber server, a home location register, or one or more of a Node B, a radio network controller, a mobile switching center, an evolved Node B and a mobility management entity. 
     In an aspect of the disclosure, the network entity comprises an apparatus configured to perform mobility management functions or radio resource management functions for the UE. 
     In an aspect of the disclosure, a method for maintaining connections related to multiple subscriptions includes the steps of maintaining a first wireless communications link corresponding to a first subscription and a second wireless communications link corresponding to a second subscription, refraining from performing a first radio resource procedure in relation to the first subscription after performing a similar radio resource procedure in relation to the second subscription, and synchronizing performance of a second radio resource procedure in relation to the first subscription with performance of the second radio resource procedure in relation to the second subscription. The first subscription and the second subscription may be associated with a common IMEI and different IMSIs and the contexts corresponding to the different IMSIs may be linked based on the IMEI. 
     In an aspect of the disclosure, the first radio resource procedure may comprise one or more of a UE capability exchange, a handover of the UE between base stations and a measurement reporting procedure. The measurement reporting procedure may relate to a drive tests procedure. The first radio resource procedure may comprise one or more of a tracking area update procedure, a location area update procedure and a routing area update procedure. 
     In an aspect of the disclosure, the performance of the second radio resource procedure is synchronized by monitoring pages corresponding to both the first subscription and the second subscription during a single paging occasion in a discontinuous reception cycle. 
     In an aspect of the disclosure, an apparatus for managing multiple contexts for a wireless device includes means for determining a link between a first context of a UE and a second context of the UE at a network entity, and means for combining procedures related to the first and the second contexts when the first context and the second context are linked. 
     In an aspect of the disclosure, an apparatus for wireless communication, includes a communications interface, and a processing circuit. The processing circuit may be configured to determine a link between a first context of a UE and a second context of the UE at a network entity, and combine procedures related to the first and the second contexts when the first context and the second context are linked. 
     In an aspect of the disclosure, a processor-readable storage medium includes one or more instructions which, when executed by at least one processing circuit, cause the at least one processing circuit to determine a link between a first context of a UE and a second context of the UE at a network entity, and combine procedures related to the first and the second contexts when the first context and the second context are linked. 
     In an aspect of the disclosure, a UE is configured to maintain connections related to multiple subscriptions. The UE may include a modem configured to communicate with a radio access network, and a processing system. The processing system may be configured to maintain a first wireless communications link corresponding to a first subscription and a second wireless communications link corresponding to a second subscription, refrain from performing a first radio resource procedure in relation to the first subscription after performing a similar radio resource procedure in relation to the second subscription, and synchronize performance of a second radio resource procedure in relation to the first subscription with performance of the second radio resource procedure in relation to the second subscription. 
     In an aspect of the disclosure, a UE configured to maintain connections related to multiple subscriptions, includes means for maintaining first and second wireless communications links corresponding to first and second subscriptions, respectively, and means for performing radio resource procedures. The means for performing radio resource procedures may be configured to refrain from performing a first radio resource procedure in relation to the first subscription after performing a similar radio resource procedure in relation to the second subscription. The means for performing radio resource procedures may be configured to synchronize performance of a second radio resource procedure in relation to the first subscription with performance of the second radio resource procedure in relation to the second subscription. 
     In an aspect of the disclosure, a processor-readable storage medium has one or more instructions which, when executed by at least one processing circuit, cause the at least one processing circuit to maintain a first wireless communications link corresponding to a first subscription and a second wireless communications link corresponding to a second subscription, refrain from performing a first radio resource procedure in relation to the first subscription after performing a similar radio resource procedure in relation to the second subscription, and synchronize performance of a second radio resource procedure in relation to the first subscription with performance of the second radio resource procedure in relation to the second subscription. The first subscription and the second subscription may be associated with a common IMEI and different IMSIs. The contexts corresponding to the different IMSIs may be linked based on the IMEI. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified schematic diagram illustrating an example of a radio access network. 
         FIG. 2  is a simplified block diagram depicting certain elements of a networking environment based on UMTS. 
         FIG. 3  is a block diagram illustrating an access terminal that supports multiple SIMs and connects to a plurality of networks. 
         FIG. 4  is a block diagram illustrating a wireless network including radio access networks operated using different radio access technologies. 
         FIG. 5  illustrates a network that includes entities configured to maintain context for connected user equipment. 
         FIG. 6  is a flow diagram illustrating an example in which multiple contexts may be linked or combined in a consolidated context. 
         FIG. 7  is a message flow diagram illustrating an example of conventional handover of multiple contexts in a multiple subscription device. 
         FIG. 8  is a message flow diagram illustrating an example of handover of multiple contexts of a multiple subscription device when the contexts are linked according to certain aspects disclosed herein. 
         FIG. 9  is a flowchart illustrating a method of managing multiple contexts for a wireless device. 
         FIG. 10  is a schematic illustrating an apparatus configured to manage multiple contexts for a wireless device. 
         FIG. 11  is a flowchart illustrating a method of maintaining connections related to multiple subscriptions. 
         FIG. 12  is a schematic illustrating apparatus configured to maintain connections related to multiple subscriptions. 
         FIG. 13  is a flowchart illustrating a method for linking user equipment contexts associated with same physical device. 
         FIG. 14  is a schematic illustrating an apparatus configured to link user equipment contexts associated with same physical device. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, specific details are given to provide a thorough understanding of the various aspects of the disclosure. However, it will be understood by one of ordinary skill in the art that the aspects may be practiced without these specific details. For example, circuits may be shown in block diagrams in order to avoid obscuring the aspects in unnecessary detail. In other instances, well-known circuits, structures and techniques may not be shown in detail in order not to obscure the aspects of the disclosure. 
       FIG. 1  is a simplified schematic diagram illustrating a radio access network (RAN)  100  in a UTRAN architecture. The RAN  100  includes multiple cellular regions (cells), including cells  102 ,  104 , and  106 , each of which may include one or more sectors. Cells may be defined geographically by coverage area, and/or may be defined in accordance with a frequency, scrambling code, etc. That is, the illustrated geographically-defined cells  102 ,  104 , and  106  may each be further divided into a plurality of cells, through the use of different scrambling codes, for example. In one example, cell  104   a  may utilize a first scrambling code, and cell  104   b,  while in the same geographic region and served by the same Node B  144 , may be distinguished by utilizing a second scrambling code. 
     In a cell that is divided into sectors, the multiple sectors within a cell can be formed by groups of antennas with each antenna responsible for communication with one or more access terminals in a portion of the cell. An access terminal may be referred to as a UE, including in relation to an access terminal configured to operate in networks complying or compatible with 3GPP standards. In the depicted example, antenna groups  112 ,  114 , and  116  may each correspond to a different sector in cell  102 . In cell  104 , antenna groups  118 ,  120 , and  122  may each correspond to a different sector. In cell  106 , antenna groups  124 ,  126 , and  128  may each correspond to a different sector. 
     The cells  102 ,  104 , and  106  may include several UEs that may be in communication with one or more sectors of each cell  102 ,  104 , or  106 . For example, UEs  130  and  132  may be in communication with Node B  142 , UEs  134  and  136  may be in communication with Node B  144 , and UEs  138  and  140  may be in communication with Node B  146 . Here, each Node B  142 ,  144 , and  146  may be configured to provide an access point to a core network  204  (see  FIG. 2 ) for all the UEs  130 ,  132 ,  134 ,  136 ,  138 , and  140  in the respective cells  102 ,  104 , and  106 . 
     During a call with a source cell, or at any other time, the UE  136  may monitor various parameters of the source cell as well as various parameters of neighboring cells. Further, depending on the quality of these parameters, the UE  136  may establish and/or maintain communication with one or more of the neighboring cells. During this time, the UE  136  may maintain an Active Set, which may include a list of cells to which the UE  136  is simultaneously connected (i.e., the UTRAN cells that are currently assigning a downlink dedicated physical channel DPCH or fractional downlink dedicated physical channel F-DPCH to the UE  136  may constitute the Active Set). 
       FIG. 2  is a schematic representation of a UMTS-based system  200  according to certain aspects of the present disclosure. A UMTS network includes three interacting domains: a core network  204 , a RAN, and an access terminal  210 . The RAN may comprise the UTRAN  202 . In the depicted example, the UTRAN  202  may employ a W-CDMA air interface for enabling various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The UTRAN  202  may include a plurality of Radio Network Subsystems (RNSs) such as an RNS  207 , each controlled by a respective Radio Network Controller (RNC) such as an RNC  206 . The UTRAN  202  may include any number of RNCs  206  and RNSs  207  in addition to the illustrated RNCs  206  and RNSs  207 . The RNC  206  is an apparatus responsible for, among other things, assigning, reconfiguring, and releasing radio resources within the RNS  207 . The RNC  206  may be interconnected to other RNCs (not shown) in the UTRAN  202  through various types of interfaces such as a direct physical connection, a virtual network, or the like using any suitable transport network. 
     The geographic region covered by the RNS  207  may be divided into a number of cells, with a radio transceiver apparatus serving each cell. Such radio transceiver may be referred to as a Node B in UMTS applications, but may also be referred to by those skilled in the art as a base station (BS), a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), or some other suitable terminology. For clarity, three Node Bs  208  are shown in each RNS  207 ; however, the RNSs  207  may include any number of wireless Node Bs. The Node Bs  208  provide wireless access points to a core network  204  for any number of mobile apparatuses. Examples of a mobile apparatus include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a notebook, a netbook, a smartbook, a personal digital assistant (PDA), a satellite radio, a global positioning system (GPS) device, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device. The mobile apparatus is commonly referred to as a UE in UMTS applications, but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. 
     In the UMTS-based system  200 , the UE  210  may further include one or more universal SIM (USIM)  211 , which contains a user&#39;s subscription information to a network. For illustrative purposes, one UE  210  is shown in communication with a number of the Node Bs  208 . The downlink (DL), also called the forward link, refers to the communication link from a Node B  208  to a UE  210  and the uplink (UL), also called the reverse link, refers to the communication link from a UE  210  to a Node B  208 . 
     The core network  204  can interface with one or more access networks, such as the UTRAN  202 . As shown, the core network  204  is a UMTS core network. However, as those skilled in the art will recognize, the various concepts presented throughout this disclosure may be implemented in a RAN, or other suitable access network, to provide UEs with access to types of core networks other than UMTS networks. 
     The illustrated UMTS core network  204  includes a circuit-switched (CS) domain and a packet-switched (PS) domain. Some of the circuit-switched elements are a Mobile services Switching Centre (MSC), a Visitor Location Register (VLR), and a Gateway MSC (GMSC). The illustrated core network  204  supports packet-switched data services such as General Packet Radio Service (GPRS), which may be accessed through a Serving GPRS Support Node (SGSN) and/or a Gateway GPRS Support Node (GGSN). GPRS is designed to provide packet-data services at speeds higher than those available with standard circuit-switched data services. The GGSN  220  provides a connection for the UTRAN  202  to a packet-based network  222 . The packet-based network  222  may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN  220  is to provide the UEs  210  with packet-based network connectivity. Data packets may be transferred between the GGSN  220  and the UE  210  through the SGSN  218 , which performs primarily the same functions in the packet-based domain as the MSC  212  performs in the circuit-switched domain. Some network elements may be shared by both of the circuit-switched and packet-switched domains. 
     In the illustrated example, the core network  204  supports circuit-switched services with the MSC  212  and a GMSC  214 . In some applications, the GMSC  214  may be referred to as a media gateway (MGW). One or more RNCs, such as the RNC  206 , may be connected to the MSC  212 . The MSC  212  is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC  212  also includes a visitor location register (VLR) that contains subscriber-related information for the duration that a UE is in the coverage area of the MSC  212 . The GMSC  214  provides a gateway through the MSC  212  for the UE to access a circuit-switched network  216 . The GMSC  214  includes a home location register (HLR)  215  containing subscriber data, such as the data reflecting the details of the services to which a particular user has subscribed. The HLR  215  is also associated with an authentication center (AuC) that contains subscriber-specific authentication data. When a call is received for a particular UE  210 , the GMSC  214  queries the HLR  215  to determine the location of the UE  210  and forwards the call to the particular MSC  212  serving that location. 
       FIG. 3  is a diagram illustrating an access terminal  302  adapted to operate concurrently in multiple networks. The access terminal  302  may receive services provided by core networks  314  and  316 . The access terminal  302  may communicate with a first access point  304  to obtain services from a first network  314 . The access terminal  302  may communicate with a second access point  306  to obtain services from a second network  316 . The access terminal  302  may obtain services from a single network  314  or  316  through two or more access points  304 ,  306  and/or  308 . For example, the access terminal  302  may communicate with the second access point  306  and the third access point  308  to obtain services from the second network  316 . Each network  314  and  316  may provide voice and/or data services through one or more RANs operated by the same or different network operators. 
     The access terminal  302  may be adapted or configured to support two or more SIMs  328  that can be used to identify and authenticate subscribed users of the different services offered by network operators. In one example, each SIM  328  may store an IMSI  326  and related keys that can uniquely identify and authenticate a user of the access terminal  302  and subscribed services available to the user through the networks  314  and/or  316 . Each SIM  328  may be associated with a telephone number or other network identifier different from telephone numbers or other identifiers associated with the other SIMs  328 . In one example, an access terminal  302  comprises a mobile telephone device equipped with two or more SIM cards  328  that enable the establishment of calls on two or more different voice and/or data networks, and to maintain two or more active calls concurrently. The use of multiple SIM cards  328  may permit a user of the access terminal  302  to access and use features of different subscriptions to reduce costs, obtain superior service, etc. 
     The access terminal  302  may support a variety of operational modes when multiple SIMs  328  are installed in the access terminal  302 . For example, in dual SIM stand-by (DSS) mode, the access terminal  302  may initially be in standby mode for two different subscriptions. After establishing a call through one network  314  or  316 , the access terminal  302  may cause the connection between the access terminal  302  and the other networks  316  or  314  to enter an inactive state. 
     In dual SIM dual active (DSDA) mode, the access terminal  302  may be concurrently connected to two different subscribed networks  314  and  316 . A DSDA-enabled access terminal  302  may be capable of switching between two active calls and/or connecting two active calls at the access terminal  302 . In DSDA mode, the access terminal  302  may establish a first active call on a first subscribed network  314 , while remaining idle on a second subscribed network  316 . While a call is active on a first subscribed network  314  or  316 , a DSDA-enabled access terminal  302  may receive a second call through a second subscribed network  316  or  314 . If calls are active on the first and second subscribed networks  314  and  316 , a user may switch between the two calls as desired, and/or may connect the two calls at the access terminal  302 . When more than two SIMs  328  are installed in the access terminal  302 , other modes of operation may be defined, including triple SIM dual active (TSDA) mode, quad SIM dual active (QSDA) mode, for example. 
     A DSDA-enabled access terminal  302  may have a plurality of radio frequency (RF) chains  322  and  324 . Each RF chain  322  and  324  may be operated and used for establishing and maintaining an active connection with an access point  304 ,  306 , or  308 . The plurality of RF chains  322 ,  324  may be embodied in one or more RF modems. An RF modem may comprise one or more RF chains  322 ,  324 , each having at least one power amplifier (PA). In the example depicted in  FIG. 3 , the access terminal  302  may employ two RF chains  322 ,  324  to support concurrent connections to different access points  304  and  306  corresponding to networks  314  and  316 , respectively. An RF modem may additionally comprise one or more processors, non-transitory storage and logic configured to process, transmit and receive signals, and to encode and decode data transmitted and received by the access terminal  302 . 
     In triple SIM dual active (TSDA) mode, the access terminal  302  may support three subscriptions but can be connected to only two different ones of access points  304 ,  306 ,  308  concurrently. Typically, TDSA mode is adopted when an access terminal  302  is provided with only two RF chains  322  and  324  in order to optimize power consumption of the access terminal  302 . In quad SIM dual active (QSDA) mode, the access terminal  302  may support four subscriptions but can be concurrently connected to only two different ones of access points  304 ,  306 ,  308 . A QDSA-enabled access terminal  302  may be provided with only two RF chains  322  and  324  in order to optimize power consumption of the access terminal  302 . 
       FIG. 4  is a block diagram  400  illustrating a simplified wireless internetworking environment. An access terminal  402  may be associated with one or more access points  404 ,  410  that may be operated by the same or different network operators and that may operate using the same or different network technology. The access point  404  and/or  410  may comprise, or be referred to, as a base station, a base transceiver station, a radio access point, an access station, a radio transceiver, a basic service set, an extended service set, a Node B, an evolved Node B (eNB), or some other suitable terminology. Each access point  404 ,  410  may provide a radio interface in a RAN that provides access to core network services provided by one or more network operators. RANs may be implemented using any suitable radio access technology (RAT) and telecommunication standards employing a variety of modulation and multiple access techniques. By way of example, RANs associated with access points  404 ,  410  may comprise one or more networks based on UTRAN, GSM, Long Term Evolution (LTE) which includes a set of enhancements to UMTS, Evolved UTRA (E-UTRA) network, IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and/or Flash-OFDM employing OFDMA. RANs may also comprise one or more Evolution—Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB) networks. 
     In the depicted example, the access terminal  402  may be associated with a PS network, such as LTE, through an eNB  404  and with a CS network for data and voice calls through the base station  410 . Access terminal  402  may be registered with an E-UTRAN (through the eNB  404 ) and a packet data network (PDN) gateway  410  may provide connectivity between the access terminal  402  and one or more external packet data networks  416 . The access terminal  402  may be registered with a 1xRTT CS network (which may be referred to as a 1x network) through base station  410  in order to obtain voice and data services through a CDMA-2000 network. GPRS permits 2G, 3G and W-CDMA mobile networks to transmit Internet Protocol (IP) packets to external networks such as the Internet  416  using a gateway function which may comprise a SGSN  414 , which provides certain interworking services enabling communication between the GPRS system and an external packet switched network  416 . Certain aspects of the invention are equally applicable to other combinations of PS and CS networks, including GSM for example. 
     In the example depicted in  FIG. 4 , the MME  406  serves as a control node for LTE traffic related to access terminal  402 . The MME  406  typically processes signaling between the access terminal  402  and a core network, providing bearer and connection management services. In some embodiments, an interworking server (IWS)  408  may perform a single radio voice call continuity interworking solution function between UTRAN and E-UTRAN access networks. Accordingly, backhaul communications may be available between LTE and lx networks. The mobile switching center (MSC)  412  may control network switching elements used in the provision of 1xRTT voice services through base station  410 . 
     The access terminal  402  may be deployed in a location where multiple accessible cells or RANs are available and the access terminal  402  may use different frequencies and/or different RATs to access a core network that provides mobility management, session management, transport for IP packet services, and other services. RATs may be based on UMTS, TD-SCDMA, GSM, CDMA2000 and/or WiMAX, for example. 
       FIG. 5  is a block diagram  500  illustrating a network in which various entities may be configured to maintain subscription information related to user equipment  502 . A core network entity may provide a centralized subscription manager comprising a database function that maintains subscription information, including subscriber profiles and information identifying subscriber location and IP connection information. The core network may distribute and/or delegate subscription management to one or more subscription management functions deployed across one or more network entities. A subscription manager may be associated with a database function that may be configured or adapted to implement, manage and/or control certain authentication and authorization of users in a wireless network. For example, a subscription manager and/or its associated subscription database function may be provided on one or more of a home subscriber server (HSS)  520  and a home location register (HLR)  518 . The location and operation of the subscription manager and its associated subscription database function may be determined or selected based on the type of RAT used in the network and preferences of a network operator. The master user database may interact with subscriber information databases maintained by other network entities and elements of an IP multimedia core network subsystem (IMS)  540 . 
     Multiple UE contexts may reside in the same database in the HSS  518  and/or the HLR  520 . If these multiple UE contexts are not linked, duplicative radio resource management and mobility procedures may be performed in relation to the UE  502  by or on behalf of the respective network elements  504 ,  506 ,  510 ,  512 ,  514  and/or  520 . According to certain aspects disclosed herein, the HLR  518  and/or HSS  520  may be configured to propagate UE contexts (or subsets thereof), which correspond to two or more simultaneously active SIM cards  522  and  524  in the UE  502 , into network entities such as eNB  502 , MME  506 , Base Station  510 , MSC  512 , SGSN  514 . The network entities may include entities that handle certain aspects of calls established by or on behalf of access terminals  502  using core network PS and CS services. 
     According to certain aspects disclosed herein, the HLR  518  and/or HSS  520  may be configured to propagate UE contexts (or subsets thereof) between entities of a core network, an IMS  540 , and entities that provide interfaces between core networks and an IMS  540 . For example, an entity that performs a call session control function (CSCF)  516  may comprise a session initiation protocol (SIP) server that handles session control functions for SIP terminals and exchanges user profiles with HSS  520 . The HSS  520  and/or the HLR  518  may be configured to distribute context information to one or more application servers  542 ,  544  and  546  of the IMS  540 . In one example, a presence server  546  may maintain information correlating user identities with subscription information. In another example, an instant messaging server  544  may support messaging services for subscribed users. Other application servers (AS)  542  may maintain or access subscription information for network users. 
     The HSS  520 , which may also be referred to as a user profile server function (UPSF), is a network entity comprising a master user database that may support the IMS  504  and core network entities that establish, maintain, terminate and otherwise handle calls on behalf of UE  502 . The HSS  520  may maintain subscriber profiles and other subscription-related information, and the HSS  520  may authenticate and authorize network access by the user. The HSS  520  may also maintain and deliver information related to the location of the UE  502 , and information related to connections and services provided to a subscriber associated with the UE  502 . The HLR  518  is a central database that maintains information related to a subscriber of the UE  502  who is authorized to use a GSM/GPRS core network. A plurality of HLRs  518  may be provided in a public land mobile network (PLMN). The HLR  518  may perform functions similar to those performed by the HSS  520 . 
     A database record may be maintained by a network entity  520 ,  506 ,  518 ,  512 ,  510 ,  504  and/or  514  for each active user known to the network entity. The user may be identified through one or more SIMs  522 ,  524  installed in UE  502 . The database record may comprise one or more UE Contexts corresponding to the UE  502 . Each UE Context may define certain operational parameters associated with the UE  502 , conditions reported by the UE  502 , characteristics of the radio and/or IP bearer service and network internal routing information. A UE Context may be linked or tied to a subscription of the UE  502  identified by one of the SIMs  522  and  524 . In one example, a UE Context may be referenced using an IMSI, which may be stored on a SIM  522  or  524 . 
     Conventional networks may maintain overlapping UE Contexts for a single multi-SIM UE  502  and information regarding the UE  502  is frequently duplicated in the overlapping UE Contexts. In one example, a first UE Context corresponding to a first SIM  522  and a second UE Context corresponding to a second SIM  524  may be maintained by the network. The two UE Contexts may include certain identical or nearly identical copies of the same information, including information related to radio conditions, battery level, current location and radio access capabilities of the UE  502 , for example. In some networks, radio resource management procedures, mobility and call/session management procedures are performed on a “per-UE Context” basis, founded on a conventional understanding of standards that contemplate that a UE  502  has only one attached SIM  522  or  524  at any time. Accordingly, duplicative radio resource management, mobility and call/session management procedures may be performed in relation to a UE  502  that supports multiple SIMs  522  and/or  524 . 
     According to certain aspects disclosed herein, a consolidated context may be maintained for a multi-SIM UE  502 . The consolidated context may associate multiple subscription-based UE Contexts with the UE  502 . The subscription-based UE Contexts may be obtained from one or more network entities that maintain subscription information for different core networks, different RANs and/or different RATs. In one described example, UE Contexts for UE  502  may be maintained on an HLR  518 /HSS HSS  520 , where both UE Contexts may include duplicate records describing radio conditions, battery level, current location and radio access capabilities of the UE  502 . These duplicate records may be updated from time to time and updates may involve performing certain procedures to obtain network and other measurements. 
     According to certain aspects disclosed herein, network entities may link, combine and/or synchronize multiple UE Contexts associated with a single UE  502  in order to obtain a consolidated context for the UE  502 . This consolidated context may be employed as a single reference point for the context of a UE  502 . In one example, the consolidated context may comprise a UE Context that is modified to include links to one or more other UE Contexts corresponding to the SIMs  522 ,  524 . In another example, the consolidated context may be a UE Context that is modified to include the contents of multiple subscription-based UE Contexts corresponding to two or more SIMs  522 ,  524 . A network entity may create a consolidated context by associating multiple subscriptions with an identifier that uniquely identifies the UE  502 . The unique identifier may comprise one or more of an IMEI, a serial number of the UE  502 , or other such identifier of the UE  502  or information identifying a user of the UE  502 . 
     The use of a consolidated context can enable the sharing of information and the updating of information between the subscriptions, and can reduce or avoid duplicate performances of procedures by the UE  502 . For example, duplicate measurement procedures by the UE  502  may be avoided when a UE  502  is connected to one or more base stations  510  and/or eNBs  504 . The UE  502  may measure radio conditions once, and the measurements can be provided to any connected base station  510  or eNB  504 . 
     According to certain aspects disclosed herein, the performance of certain procedures related to UE  502  can be coordinated, synchronized and/or limited when a plurality of UE Contexts are linked or consolidated for the same UE  502 . Such procedures may include UE capability exchange procedures, handover procedures, DRX procedures and minimization of drive test (MDT) procedures. In one example, a single DRX paging occasion may be assigned for use with multiple subscriptions of the UE  502 . DRX is a procedure that can reduce power consumption when one or more subscriptions of the UE  502  are in an idle mode. DRX enables the UE  502  to power down an RF chain  322 ,  324  (see  FIG. 3 ) that is associated with an idle network connection for significant portions of a paging interval. The UE  502  powers up the RF chain only during paging occasions when UE  502  needs to monitor a paging channel for a page corresponding to its subscription. When DRX is coordinated for multiple subscriptions, the UE  502  can monitor a paging channel for pages corresponding to more than one subscription in one paging occasion per DRX cycle. In another example, MDT may be employed in LTE and UMTS RATs to exploit the measurement capabilities and geographical spread of commercially deployed UEs  130 ,  132 ,  134 ,  136 ,  138  and  140  (see  FIG. 1 ) to collect radio measurements. When UE Contexts are consolidated, the UE  502  may refrain from acquiring more than one set of MDT measurements, regardless of the number of active subscriptions supported by the UE  502 , when the same measurements would otherwise be acquired by the UE  502  for the different subscriptions. 
     According to certain aspects disclosed herein, multiple UE Contexts associated with a UE  502  may be linked at one or more network entities. The network entities may identify a UE Context associated with the UE  502  based on an IMSI corresponding to a SIM  522 ,  524  installed in the UE  502 . When the UE  502  has a plurality of installed SIMs  522 ,  524 , each SIM  522 ,  524  is typically associated with a different IMSI and the network identities may create Device Contexts for the plurality of SIMs  522  and  524 . These Device Contexts may be linked in a consolidated context, and IMSI-specific procedures may be distinguished from device-specific procedures such that duplicate procedures may be suppressed. 
     According to certain aspects disclosed herein, session and/or mobility management entities including MME  506 , MSC  512 , SGSN  514 , HLR  518  and/or HSS  520  may link UE Contexts tied to the same UE  502  to obtain a single consolidated context for a multi-SIM UE  502 . The UE  502  may be uniquely identified, cross-referenced and/or linked using a common IMEI, serial number, or other such unique identifier tied to the UE  502 . Links between UE Contexts may be implemented using pointers that identify the existence and location of related UE Contexts. UE Contexts may be linked by sharing information between network entities, including MME  506 , MSC  512 , SGSN  514 , HLR  518  and HSS  520 . 
     According to certain aspects disclosed herein, signaling protocols between network entities may be extended and/or enhanced to include information related to linked IMSIs. For example, during Attach/Registration_Update procedures, Authentication_Information_Response and/or Update_Location_Ack messages related to UE  502  may include information identifying and/or describing one or more other SIMs  522 ,  524  linked to the IMEI of the UE  502 . In one example, the messages may be transmitted from HSS  520  to MME  506 . A data structure may be employed to link multiple contexts associated with a single UE  502 . The data structure may comprise class inheritance etc. 
     According to certain aspects disclosed herein, core network procedures may be optimized by linking UE Contexts in the core network. In an example where UE  502  has established a connection on behalf of a first SIM  522 , paging may be optimized for a second SIM  524  by directing pages for the second SIM  524  to a specific cell and/or access point through which the connection for the first SIM  522  is established. In another example, a DRX cycle may be established in which the UE  502  receives pages at the same time for two or more connections corresponding to multiple SIMs  522 ,  524  supported by the UE  502 . In another example, the existence of a preexisting MDT session for a first SIM  522  may preclude the need to initiate an MDT session for one or more other SIMs  524  associated with the same UE  502 , because the other MDT sessions can be expected to produce near identical MDT measurements and logs as produced by the preexisting MDT session. 
     The processing overhead and power consumption associated with mobility management procedures may be reduced by sharing UE Contexts for multiple subscriptions. Mobility management procedures are used to track locations of UE  502  and procedures performed for different subscriptions related to the UE  502 . Location area update (LAU), routing area update (RAU) and tracking area update (TAU) procedures may be initiated by the UE  502  when it detects a new tracking area, location area or routing area. The LAU procedure is typically used by a UE  502  to inform the network when the UE  502  moves from one location area to the next. In one example, a UE  502  may determine that a current location area code differs from a previously reported location area code, and the UE  502  may initiate a LAU procedure by sending the network a location update request that includes the previous and current location area codes with a Temporary Mobile Subscriber Identity (TMSI) issued in the current area. The RAU procedure is used in packet-switched networks in a manner that is equivalent to the use of the TAU. A routing area may be defined as a subdivision of a location area and may be used when UE  502  is connected in a GPRS network. The TAU procedure is used in LTE networks and corresponds to the LAU and RAU procedures used in UMTS networks. The UE  502  may refrain from initiating more than one of the LAU, RAU and TAU procedures, regardless of the number of active subscriptions supported by the UE  502 , when the same procedure would otherwise need to be performed by the UE  502  for the different subscriptions. In one example, the initiation by the UE  502  of a LAU/RAU/TAU procedure for a first SIM  522  may cause the network entity responsible for mobility management procedures to update the location associated with one or more other SIMs  524  associated with the same UE  502 , because the one or more other SIMs  524  are known by virtue of linked UE contexts to physically reside within the same UE  502 . 
     According to certain aspects disclosed herein, radio access capabilities of a UE  502  can be reported once for all subscriptions of the UE  502 . Radio access capabilities may be used to provision services for the UE  502  in a RAN. In a UMTS network, a RNC  206  is a governing entity in a UTRAN  202  that controls a plurality of Node Bs  208  (see  FIG. 2 ) and performs radio resource management functions, including certain mobility management functions. In the UMTS network, UE Contexts may be linked by the RNC  206  of the UTRAN  202  or by an MSC  212  of the core network  204 . 
     Multiple contexts associated with a single UE  502  may be linked in other control entities of a RAN, including in an eNode Bs  504  or an MME  506  in an LTE network. A consolidated device context for UE  502  may link UE contexts that correspond to the same IMEI. Certain types of information may be copied between a plurality of Device Contexts corresponding to the same IMEI and network entities may maintain an index or other data structure linking local Device Context to other Device Contexts, IMSIs, and networks associated with the same IMEI. 
     Information may be exchanged using internetworking messages and existing message types to transfer information between network entities. In the example of an LTE RAN, S 1  signaling between eNB  504  and MME  506  may be extended to include information related to linked SIMs  522 ,  524 . In one example, a message sent from MME  506  to eNB  504  requesting a setup of a new UE context associated with one or more SIMs  522 ,  524  associated with the UE  502 , such as an initial UE_Context_Setup_Request message, may include information identifying and/or characterizing one or more other SIMs  522 ,  524  linked to the IMEI corresponding to the UE  502 . 
     Certain radio resource management (RRM) procedures in a RAN may be optimized by linking different contexts associated with UE  502 . In one example, scheduling may be coordinated for two or more subscriptions corresponding to SIMs  522 ,  524 . Coordinated scheduling for UE  502  may involve consideration of power constraints as applied to multiple connections, battery condition, carrier assignments, etc. Resource grants and carrier assignments may be configured to allow each connection to transmit when the other connections are not transmitting such that each connection can transmit data with the full power in the power pool available to the UE  502 . In another example, a common paging occasion may be assigned for all SIMs  522 ,  524  associated with the UE  502 . UE capability reporting may be provided by one of the IMSIs  522  or  524 . One set of measurements may be configured for each UE  502 , and handovers may be optimized. 
     According to certain aspects disclosed herein, the UE  502  may be made aware that UE context is linked in the core network and/or in the RAN. In some embodiments, links may be established between protocol stacks at the RRC and Non-Access Stratum (NAS) layers. The RRC protocol handles the control plane signaling by which the RAN controls the behavior of the UE  502 . RRC signaling encompasses various functional areas including system information related to broadcasting, connection control including certain handovers between cells, network-controlled inter-RAT mobility and measurement configuration. NAS comprises protocols which operate between the UE  502  and a core network, and NAS typically involves protocols which are not specific to a particular RAT. When the UE  502  is aware that contexts are linked to the extent necessary to support combined and/or optimized network procedures, the UE  502  may refrain from performing duplicative procedures such as radio measurements and capability reporting. The UE  502  may use the same paging occasions for all SIMs  522 ,  524 . In some embodiments, UE  502  may perform a combined handover of connections corresponding to two or more SIMs  522 ,  524 . 
     Linking UE Contexts tied to the same UE  502  may provide benefits that include prolonged battery life for UE  502 , reduced over-the-air signaling and faster mobility procedures. The level of benefits accrued may depend upon the extent to which UE Contexts tied to the same device are linked and the degree of modification of procedures to take advantage of multi-SIM awareness in the core network. 
       FIG. 6  is a simplified flow diagram  600  illustrating an example in which UE Contexts  602  and  604  may be linked or combined in a consolidated context  608 . In the illustrated example, UE Contexts  602  and  604  relate to SIMs  522  and  524  installed in the multi-SIM UE  502  depicted in  FIG. 5 . In one example, the UE Contexts  602 ,  604  may be maintained in the form of a data structure populated for each SIM  522  and  524 , where each SIM  522  and  524  is identified with an IMSI or other unique identifier corresponding to the subscription associated with the SIM  522  or  524 . Each UE Context  602  and  604  may be populated with parameters that define the configuration and operational status of the subscription associated with the SIM  522  or  524  and/or the UE  502  in which the SIM  522  or  524  is installed. The parameters may include device-specific parameters including an IMEI or other unique identifier of the UE  502 , UE capabilities, MDT session context, DRX cycle, defined paging occasions, etc. The parameters may also include IMSI-specific parameters including the IMSI, call/connection status, QoS profile, security parameters, etc. Certain device-specific context parameters may be duplicated between UE Contexts  602  and  604 . 
     According to certain aspects disclosed herein, a network entity  606  may link and/or combine parameters from UE contexts  602  and  604  into a consolidated device context  608 . In one example, the device context  608  may include sets of parameters  610 ,  612  and  616  that include device-specific set  610  and IMSI-specific sets  612  and  614 . The device-specific set  610  may define UE capabilities, MDT session context, DRX context, paging occasion, etc. and other elements common to all UE Contexts  602  and  604 . In one example, the device-specific set  610  may implicitly include the IMEI that is common to all Device Contexts  602  and  604  combined or linked in the device context  608 . In another example, the IMEI may be included in a field in the device-specific set  610  and/or in the IMSI-specific sets  612  and  614 . IMSI-specific sets may include parameters and variables that are defined independently for each subscription associated with a SIM  522  or  524  installed in the UE  502 . The IMSI-specific parameters may relate to call status, call configuration such as QoS parameters and security parameters defined for the subscription. 
     The network entity  606  may create a data structure  608  that maps the UE Contexts  602  and  604  and elements of the UE Contexts  602  and  604  onto a device context  608 . In one example, the network entity  606  may initialize the device context  608  by copying parameters from the UE Contexts  602  and  604  into the device context  608 . The network entity  606  may synchronize the parameters within the device context  608  with the contents of the UE context  602  and the UE Context  604 . The device context  608  and/or the UE Contexts  602  and  604  may be synchronized by updating device-specific parameters. When corresponding fields of UE Context  602 , UE Context  604  and/or the device context  608  have different values, conflicts may be resolved using timestamps to determine which context  602 ,  604  or  608  has the most recently obtained value. Thus, for example, a current network measurement obtained in relation to UE Context  602  may be copied to device context  608  and thence to UE context  604  when the network measurement in UE context  602  is more recently obtained than the corresponding values found in device context  608  and/or UE Context  604 . 
     In some embodiments, conventional UE Contexts  602  and  604  may be adapted and/or expanded to obtain the device-context data structure  608  that includes a device-specific set of parameters  610  and IMSI-specific sets of parameters  612 ,  614  for each SIM  522  and  524  installed in the UE  502 . Accordingly, a single modified context may be replicated throughout the network, with updates being propagated by a context manager, which may be incorporated in network entity  606 . In some embodiments, UE Contexts  602  and  604  may be mapped and/or indexed using the IMEI of UE  502 , whereby a network entity  606  may track all instances of UE Contexts  602  and  604  and may synchronize the device-specific content of the different UE Contexts  602  and  604 . In one example, an IMEI may be used as a pointer to the storage locations where linked UE Contexts  602  and  604  are stored. 
       FIG. 7  is a simplified message flow diagram  700  illustrating an example of conventional handover of multiple contexts in a multiple subscription device, such as the UE  702 . In the example, two or more SIMs  708  are installed in the UE  702 , each SIM identifying a subscription of the UE  702 . The UE  702  is initially associated and/or in communication with a source base station  704  for a first subscription of the UE  702 , and the context for the first subscription is handed over to a target base station  706 . As described herein, the UE  702  may receive a measurement control message S 1 - 1  for the first subscription, which is associated with a first one of the SIMs  708 . The measurement control message S 1 - 1  may be accompanied by and/or be followed by an uplink allocation to permit the UE  702  to transmit measurement reports for the first subscription in an uplink message S 1 - 2 . The source base station  704  may determine that a handover should be initiated based on the content of the measurement reports. Accordingly, the source base station  704  may send a handover request S 1 - 3  for the first subscription to the target base station  706 , which may be identified based on the measurement reports for the first subscription. In the illustrated example, the target base station  706  sends a handover request acknowledgement message S 1 - 4  to the source base station  704 , which may then transmit a handover command S 1 - 5  to the UE  702 . The UE  702  then attempts to acquire the target base station  706  and one or more synchronization transmissions and/or messages S 1 - 6  may be exchanged between the UE  702  and the target base station  706  on behalf of the first subscription. The handover of the first subscription is completed when the UE  702  sends a handover confirm message S 1 - 7  to the target base station  706 . 
     In a conventional system, the handover procedure is performed twice, and the two performances may occur in parallel or sequentially for the same UE  702 . As illustrated in  FIG. 7 , the UE  702  is also initially associated and/or in communication with the source base station  704  for a context associated with a second subscription of the UE  702 , and the context for the second subscription is handed over to a target base station  706 . As described herein, the UE  702  may receive a measurement control message S 2 - 1  for the second subscription, which is associated with a second one of the SIMs  708 . The measurement control message S 2 - 1  may be accompanied by and/or be followed by an uplink allocation to permit the UE  702  to transmit measurement reports for the second subscription in an uplink message S 2 - 2 . The source base station  704  may determine that a handover should be initiated based on the content of the measurement reports for the second subscription. In this example, the source base station  704  independently decides that a handover should occur for both subscriptions, based on their respective measurement reports S 1 - 2  and S 2 - 2 , which typically include the same measurement information. The source base station  704  may send a handover request S 2 - 3  for the second subscription to the target base station  706 , which is identified based on the measurement reports for the second subscription. In the illustrated example, the target base station  706  sends a handover request acknowledgement message S 2 - 4  to the source base station  704 , which may then transmit a handover command S 2 - 5  to the UE  702 . The UE  702  then attempts to acquire the target base station  706  and one or more synchronization transmissions and/or messages S 2 - 6  may be exchanged between the UE  702  and the target base station  706  on behalf of the second subscription. The handover of the second subscription is completed when the UE  702  sends a handover confirm message S 2 - 7  to the target base station  706 . 
     Each message in the message flow chart is associated with a single UE Context. Accordingly, the number of transmissions is at least doubled and the time required to execute a handover of both contexts may be doubled if the handovers for the two contexts are handled separately. 
       FIG. 8  is a simplified message flow diagram illustrating an example of handover of multiple contexts of a multiple subscription device when the contexts are linked according to certain aspects disclosed herein. In the example, the UE  802  is associated and/or in communication with a source base station  804  for two contexts associated with first and second subscriptions of the UE  802 , and the context for both subscriptions is handed over to a target base station  806  in a consolidated process. The consolidation is achieved by identifying the contexts for both subscriptions in each message. As described herein, the UE  802  may receive a measurement control message M- 1  to configure measurement reports to be sent from the UE  802  to the source base station  804 . The measurement control message M- 1  may be associated with the first or second subscription. The UE  802  may determine if measurement reports have been recently transmitted on behalf of the other subscription and may refrain from sending a duplicate measurement report. Alternatively, the measurement control message may be a consolidated message associated with both subscriptions. The UE  802  may respond to the measurement control message M- 1  by transmitting measurement reports in an uplink message M- 2 . The measurement reports may be a consolidated message associated with both subscriptions. The source base station  804  may determine that a handover should be initiated based on the content of the measurement reports. In this example, the source base station  804  decides that a handover should occur for both subscriptions, based on a single consolidated measurement report M- 2 . The source base station  804  may send a handover request M- 3  identifying the device context and/or an identification of the linked context information maintained by a network entity. In the illustrated example, the target base station  806  sends a handover request acknowledgement message M- 4  to the source base station  804 , which may include the device context. The source base station  804  may then transmit a single consolidated handover command M- 5  to the UE  802 . The UE  802  may attempt to acquire the target base station  806  for both UE contexts. The handover is completed when the UE  802  sends a single consolidated handover confirm message M- 6  to the target base station  806 . 
     Identification of the contexts for both subscriptions in a consolidated message can be achieved by including context-related ID, such as a mobile subscriber identifier (an IMSI, a TIMSI, a P-TIMSI) or a radio network identifier (RNTI, C-RNTI, U-RNTI), for each of the two contexts in the message. Alternatively, the identification of the context for both subscriptions in a message can be achieved by including a single user equipment-related ID associated with both contexts, such as the IMEI, in the message. Accordingly, signaling procedures such as the handover procedure and the associated messages may be simplified by performing a single procedure for all contexts linked to the same device. 
       FIG. 9  is a flowchart illustrating a method of managing multiple contexts for a wireless device. Certain steps of the method may be performed by one or more network entities such as an HLR  518 , an HSS  520 , an MME  506 , an MSC  512 , an RNC  206 , an SGSN  514 , a CSCF  516  and/or an entity of an IMS  540 , for example. 
     At step  902 , the network entity may determine a link between a first context of a UE and a second context of the UE. The first context and the second context may be associated with a common IMEI of the UE and different IMSIs. 
     At step  904 , the network entity may combine procedures related to the first and the second contexts when the first context and the second context are linked. The procedures related to the first and the second contexts may be combined by synchronizing procedures related to the different IMSIs. 
     According to certain aspects disclosed herein, procedures related to the first and the second UE contexts may be combined by performing a device-specific procedure in relation to the first context, and refraining from performing the device-specific procedure in relation to the second context. A result of the device-specific procedure may be propagated between the first and second contexts. The procedures may include at least one radio resource procedure. The at least one radio resource procedure may comprise a UE capability exchange. The at least one radio resource procedure may comprise a handover of the UE between base stations. The at least one radio resource procedure may comprise one or more of a TAU procedure, a LAU procedure, and a RAU procedure. 
     According to certain aspects disclosed herein, procedures related to the first and the second UE contexts may be combined by initiating a measurement reporting procedure at the UE. The measurement reporting procedure may be adapted to minimize a drive tests procedure. 
     According to certain aspects disclosed herein, procedures related to the first and the second UE contexts may be combined by causing the UE to monitor pages corresponding to both the first context and the second context during a single paging occasion in a DRX cycle. 
     According to certain aspects disclosed herein, the network entity may coordinate assignment of resources for the first context and the second context. The resources are assigned based on a power constraint of the UE. 
     According to certain aspects disclosed herein, the first context and the second context may be determined to be linked based on an information exchange between the network entity and another network entity, the information relating the first context and the second context to a unique identifier of the UE. The information exchanged between the network entity and the other network entity may include information relating the first context and the second context transmitted in an attach or registration update message by a home subscriber server. The unique identifier may comprise an IMEI. The network entity may comprise an apparatus configured to perform mobility management functions or radio resource management functions for the UE. 
       FIG. 10  is a diagram  1000  illustrating an example of a hardware implementation for an apparatus  1002  configured to manage multiple contexts for a wireless device. The apparatus  1002  may comprise a network and/or IMS entity that performs session management and/or mobility management functions in a network that supports one or more RANs and employs one or more RATs. The processing circuit  1004  may be implemented with a bus architecture, represented generally by the bus  1030 . The bus  1030  may include any number of interconnecting buses and bridges depending on the application and attributes of the processing circuit  1004  and overall design constraints. The bus  1030  may link together various circuits including one or more processors and/or hardware modules, processing circuit  1004 , and the computer-readable medium  1006 . The bus  1030  may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. 
     The processing circuit  1004  may be coupled to one or more communications interfaces  1018 . The one or more communications interfaces  1018  may be used for communications between entities of a core network, within and between RANs and between core network entities and servers and other entities of an IMS. The one or more communications interfaces  1018  may be coupled by wired or wireless transmission media. 
     The processing circuit  1004  may include one or more processors responsible for general processing, including the execution of software stored on the computer-readable medium  1006 . The software, when executed by the one or more processors, cause the processing circuit  1004  to perform the various functions described supra for any particular apparatus. The computer-readable medium  1006  may also be used for storing data that is manipulated by the processing circuit  1004  when executing software. The processing system further includes at least one of the modules  1020 ,  1022  and  1024 . The modules  1020 ,  1022  and  1024  may be software modules running on the processing circuit  1004 , resident/stored in the computer readable medium  1006 , one or more hardware modules coupled to the processing circuit  1004 , or some combination thereof. 
     In one configuration, the apparatus  1002  for wireless communication includes means  1020  for determining a link between a first context of a UE and a second context of the UE, means  1022  for combining procedures related to the first and the second contexts when the first context and the second context are linked, and means  1024  for coordinating assignment of resources for the first context and the second context. 
       FIG. 11  is a flowchart illustrating a method of maintaining connections related to multiple subscriptions. Certain steps of the method may be performed by the UE  502 , for example. 
     At step  1102 , the UE  502  may maintain a first wireless communications link corresponding to a first subscription and a second wireless communications link corresponding to a second subscription. The first subscription and the second subscription may be associated with a common IMEI of the UE  502  and different IMSIs. The contexts corresponding to the different IMSIs may be linked in a context corresponding to the IMEI. The context corresponding to the IMEI may be maintained by a network or IMS entity. 
     At step  1104 , the UE  502  may refrain from performing a first radio resource procedure in relation to the first subscription after performing a similar radio resource procedure in relation to the second subscription. The first radio resource procedure may include one or more of a UE capability exchange, a handover of the UE  502  between base stations and a measurement reporting procedure. The measurement reporting procedure may relate to a drive tests procedure. The first radio resource procedure may include one or more of a tracking area update procedure, a location area update procedure and a routing area update procedure. 
     At step  1106 , the UE  502  may synchronize performance of a second radio resource procedure in relation to the first subscription with performance of the second radio resource procedure in relation to the second subscription. Performance of the second radio resource procedure may be synchronized by monitoring pages corresponding to both the first context and the second context during a single paging occasion in a discontinuous reception cycle. 
       FIG. 12  is a diagram  1200  illustrating an example of a hardware implementation for an apparatus  1202  employing a processing circuit  1204  and configured to maintain connections related to multiple subscriptions. The apparatus  1202  may comprise a UE  502  that supports a plurality of wireless subscriptions. The processing circuit  1204  may be implemented with a bus architecture, represented generally by the bus  1230 . The bus  1230  may include any number of interconnecting buses and bridges depending on the application and attributes of the processing circuit  1204  and overall design constraints. The bus  1230  may link together various circuits including one or more processors and/or hardware modules, processing circuit  1204 , and the computer-readable medium  1206 . The bus  1230  may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. 
     The processing circuit  1204  may be coupled to one or more communications interfaces  1218 . The one or more communications interfaces  1218  may be used for communications between entities of a core network, within and between RANs and between core network entities and servers and other entities of an IMS. The one or more communications interfaces  1218  may be coupled by wired or wireless transmission media. 
     The processing circuit  1204  may include one or more processors responsible for general processing, including the execution of software stored on the computer-readable medium  1206 . The software, when executed by the one or more processors, cause the processing circuit  1204  to perform the various functions described supra for any particular apparatus. The computer-readable medium  1206  may also be used for storing data that is manipulated by the processing circuit  1204  when executing software. The processing system further includes at least the modules  1220  and  1222 . The modules  1220  and  1222  may be software modules running on the processing circuit  1204 , resident/stored in the computer readable medium  1206 , one or more hardware modules coupled to the processing circuit  1204 , or some combination thereof. 
     In one configuration, the apparatus  1202  for wireless communication includes means  1220  for maintaining first and second wireless communications links corresponding to first and second subscriptions, respectively, and means  1222  for performing radio resource procedures. 
       FIG. 13  is a flowchart illustrating a method for linking user equipment contexts associated with same physical device. Certain steps of the method may be performed by one or more network entities such as an HLR  1318 , an HSS  1320 , an MME  1306 , an MSC  1312 , an RLC, an SGSN  1314 , for example. 
     At step  1302 , a first context may be established for a UE based on a first IMSI provided by the UE. 
     At step  1304 , a second context may be established for the UE based on a second IMSI provided by the UE. 
     At step  1306 , the network entity may link the first context and the second context at the network entity. The first context and the second context may be linked by associating the first context and the second context with a common IMEI of the UE. The first context and the second context may be linked at the network entity by exchanging information with another network entity. The other network entity may maintain UE Context information related to the UE. The information may relate or bind the first context and the second context to the UE. The network entities may exchange information related to the first context and the second context in an attach or registration update message from a home subscriber server. The information relating the first context and the second context to the UE may comprise an IMEI of the UE. 
     At step  1308 , an activity related to the UE may be synchronized when the first context and the second context are linked. The activity may be synchronized by causing the UE to monitor page indicators corresponding to both the first context and the second context during a single paging occasion in a DRX cycle. The activity may be synchronized by coordinating assignment of resources for the first context and the second context. The resources are assigned based on a power constraint of the UE. 
     At step  1310 , the network entity may refrain from, or cause another entity to refrain from performing at least one radio resource procedure in relation to the UE when the first context and the second context are linked. The at least one radio resource procedure may include a UE capability exchange. The at least one radio resource procedure may include a handover of the UE between base stations. The at least one radio resource procedure may includes initiating a minimization of drive tests procedure at the UE. The at least one radio resource procedure may include one or more of a TAU procedure, a LAU procedure, and a RAU procedure. 
       FIG. 14  is a diagram  1400  illustrating an example of a hardware implementation for an apparatus  1402  employing a processing circuit  1404  and configured to link user equipment contexts associated with same physical device. The apparatus  1402  may comprise a network entity that performs session management and/or mobility management functions in a network that supports one or more RANs and employs one or more RATs. The processing circuit  1404  may be implemented with a bus architecture, represented generally by the bus  1440 . The bus  1440  may include any number of interconnecting buses and bridges depending on the application and attributes of the processing circuit  1404  and overall design constraints. The bus  1440  may link together various circuits including one or more processors and/or hardware modules, processing circuit  1404 , and the computer-readable medium  1406 . The bus  1440  may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. 
     The processing circuit  1404  may be coupled to one or more communications interfaces  1418 . The one or more communications interfaces  1418  may be used for communications between entities of a core network, within and between RANs and between core network entities and servers and other entities of an IMS. The one or more communications interfaces  1418  may be coupled by wired or wireless transmission media. 
     The processing circuit  1404  may include one or more processors responsible for general processing, including the execution of software stored on the computer-readable medium  1406 . The software, when executed by the one or more processors, cause the processing circuit  1404  to perform the various functions described supra for any particular apparatus. The computer-readable medium  1406  may also be used for storing data that is manipulated by the processing circuit  1404  when executing software. The processing system further includes at least one of the modules  1420 ,  1422 ,  1424 ,  1426 ,  1428  and  1430 . The modules  1420 ,  1422 ,  1424 ,  1426 ,  1428  and  1430  may be software modules running on the processing circuit  1404 , resident/stored in the computer readable medium  1406 , one or more hardware modules coupled to the processing circuit  1404 , or some combination thereof. The processing circuit  1404  may be a component of a UE  302  (see  FIG. 3 ). 
     In one configuration, the apparatus  1402  for wireless communication includes a module  1420  for establishing first and second contexts for a UE based on a first IMSI provided by the UE, a module  1422  for linking the first context and the second context at the network entity, and a module  1424  for exchanging UE contexts associated with a UE that supports multiple concurrently active subscriptions. The module  1424  for exchanging UE contexts may comprise a module for consolidating or otherwise combining multiple UE contexts into a single context for a multi-SIM or multi-subscription UE. The apparatus  1402  may comprise a module  1426  that determines a first set of procedures to be performed in relation to the UE that are UE-specific and a second set of procedures to be performed in relation to the UE that are IMSI-specific (i.e. related to subscriptions corresponding to fewer than all of the IMSIs associated with the UE). The apparatus  1402  may comprise a module  1428  for initiating procedures defined by the first and second sets of procedures. In one example, the module  1428  for initiating procedures may avoid duplicate procedures by causing each of the first set of procedures to be performed once for each occasion on which the procedure is to be performed while procedures identified in the second set may be performed for each IMSI or group of IMSIs that require the procedures. Accordingly, the module  1428  for initiating procedures may be configured to synchronize one or more activities related to the UE or refraining from having at least one radio resource procedure performed in relation to the UE when the first context and the second context are linked. The apparatus  1402  may comprise a module  1430  for managing communications between network entities, including communications between different RANs, RATs, core networks and IMS environments. For example, the module  1430  for managing communications may comprise an IWS  408  (see  FIG. 4 ) and CSCF  516  (see  FIG. 5 ). 
     The term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B, and object B touches object C, then objects A and C may still be considered coupled to one another—even if they do not directly physically touch each other. For instance, a first die may be coupled to a second die in a package even though the first die is never directly physically in contact with the second die. 
     One or more of the components, steps, features and/or functions illustrated in  FIGS. 1-14  may be rearranged and/or combined into a single component, step, feature or function or embodied in several components, steps, or functions. Additional elements, components, steps, and/or functions may also be added without departing from novel features disclosed herein. The apparatus, devices, and/or components illustrated in  FIGS. 1-5 ,  7 ,  8 ,  10 ,  12  and  14  may be configured to perform one or more of the methods, features, or steps described herein. The novel algorithms described herein may also be efficiently implemented in software and/or embedded in hardware. 
     Also, it is noted that the embodiments may be described as a process that is depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function. 
     Moreover, a storage medium may represent one or more devices for storing data, including read-only memory (ROM), random access memory (RAM), magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other machine readable mediums for storing information. The terms “machine readable medium” or “machine readable storage medium” include, but is not limited to portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing or carrying instruction(s) and/or data. 
     Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, or any combination thereof. When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine-readable medium such as a storage medium or other storage(s). A processor may perform the necessary tasks. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc. 
     The various illustrative logical blocks, modules, circuits (e.g., processing circuit), elements, and/or components described in connection with the examples disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic component, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing components, e.g., a combination of a DSP and a microprocessor, a number of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     The methods or algorithms described in connection with the examples disclosed herein may be embodied directly in hardware, in a software module executable by a processor, or in a combination of both, in the form of processing unit, programming instructions, or other directions, and may be contained in a single device or distributed across multiple devices. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. A storage medium may be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. 
     Those of skill in the art would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     The various features of the invention described herein can be implemented in different systems without departing from the invention. It should be noted that the foregoing aspects of the disclosure are merely examples and are not to be construed as limiting the invention. The description of the aspects of the present disclosure is intended to be illustrative, and not to limit the scope of the claims. As such, the present teachings can be readily applied to other types of apparatuses and many alternatives, modifications, and variations will be apparent to those skilled in the art.