Patent Publication Number: US-2012028657-A1

Title: Efficient Paging for Multiple Universal Subscriber Identity Module (USIM) Equipment in TD-SCDMA Systems

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional patent application No. 61/368,184 filed Jul. 27, 2010, in the names of CHIN et al., the disclosure of which is expressly incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to efficient paging of multiple Universal Subscriber Identity Module (USIM) user equipment in time division-synchronous code division multiple access (TD-SCDMA) systems. 
     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. One example of such a network is the Universal Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). For example, China is pursuing TD-SCDMA as the underlying air interface in the UTRAN architecture with its existing GSM infrastructure as the core network. The UMTS also supports enhanced 3G data communications protocols, such as High Speed Downlink Packet Data (HSDPA), which provides higher data transfer speeds and capacity to associated UMTS networks. 
     As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications. 
     SUMMARY 
     In one aspect of the disclosure, a method of wireless communication includes communicating with a serving node B (NB) during a call using a first international mobile subscriber identity (IMSI) of a user equipment (UE). The method also includes receiving a unicast message from the serving NB for a second call for a second IMSI of the UE. 
     In another aspect of the disclosure, a method of wireless communication includes communicating from a location area and/or a routing area to a UE during a call associated with a first international mobile subscriber identity. The method also includes transmitting a message only from a serving node B of the location area and/or routing area to the UE for a second call associated with a second IMSI of the UE. 
     In another aspect of the disclosure, a system is configured for wireless communication in a multicarrier radio access network. The system comprises means for communicating from a location area and/or a routing area to a user equipment during a call associated with a first international mobile subscriber identity. The system also includes means for transmitting a message only from a serving node B of the location area and/or the routing area to the UE for a second call associated with a second IMSI of the UE. 
     In another aspect of the disclosure, a computer program product includes a computer-readable medium having program code recorded thereon. The program code includes code to communicate from a location area and/or a routing area to a user equipment during a call associated with a first international mobile subscriber identity. The program code also includes code to transmit a message only from a serving node B of the location area and/or the routing area to the UE for a second call associated with a second IMSI of the UE. 
     In another aspect of the disclosure, a network controller for wireless communication includes at least one processor and a memory coupled to the processor. The processor is configured to communicate from a location area and/or a routing area to a user equipment during a call associated with a first international mobile subscriber identity. The processor is also configured to transmit a message only from a serving node B of the location area and/or the routing area to the UE for a second call associated with a second IMSI of the UE. 
     In another aspect of the disclosure, a user equipment (UE) is configured for wireless communication in a multicarrier radio access network. The UE has means for communicating with a serving node B (NB) during a call using a first international mobile subscriber identity (IMSI) of the UE. The UE also has means for receiving a unicast message from the serving NB for a second call for a second IMSI of the UE. 
     In another aspect of the disclosure, a computer program product includes a computer-readable medium having program code recorded thereon. The program code includes code to communicate with a serving node B during a call using a first international mobile subscriber identity of a user equipment. The program code also includes code to receive a unicast message from the serving NB for a second call for a second IMSI of the UE. 
     In another aspect of the disclosure, a user equipment for wireless communication includes at least one processor and a memory coupled to the processor. The processor is configured to communicate with a serving node B during a call using a first international mobile subscriber identity of the UE. The processor is also configured to receive a unicast message from the serving NB for a second call for a second IMSI of the UE. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram conceptually illustrating an example of a telecommunications system. 
         FIG. 2  is a block diagram conceptually illustrating an example of a frame structure in a telecommunications system. 
         FIG. 3  is a block diagram conceptually illustrating an example of a node B in communication with a UE in a telecommunications system. 
         FIG. 4  is a block diagram illustrating TD-SCDMA paging. 
         FIG. 5  is a diagram illustrating location areas and routing areas in a TD-SCDMA network. 
         FIG. 6A  is a diagram showing conventional paging of a user equipment. 
         FIG. 6B  is a diagram showing enhanced paging of a user equipment according to one aspect of the present disclosure. 
         FIG. 7  is a diagram illustrating UE data stored by a network according to one aspect of the present disclosure. 
         FIG. 8  is a call flow diagram illustrating enhanced paging of a user equipment according to one aspect of the present disclosure. 
         FIG. 9  is a flow diagram illustrating enhanced paging of a user equipment according to one aspect of the present disclosure. 
         FIG. 10  is a flow diagram illustrating enhanced paging of a user equipment according to one aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts. 
     Turning now to  FIG. 1 , a block diagram is shown illustrating an example of a telecommunications system  100 . The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. By way of example and without limitation, the aspects of the present disclosure illustrated in  FIG. 1  are presented with reference to a UMTS system employing a TD-SCDMA standard. In this example, the UMTS system includes a (radio access network) RAN  102  (e.g., UTRAN) that provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The RAN  102  may be divided into a number of Radio Network Subsystems (RNSs), such as an RNS  107 , each controlled by a Radio Network Controller (RNC), such as an RNC  106 . For clarity, only the RNC  106  and the RNS  107  are shown; however, the RAN  102  may include any number of RNCs and RNSs in addition to the RNC  106  and RNS  107 . The RNC  106  is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS  107 . The RNC  106  may be interconnected to other RNCs (not shown) in the RAN  102  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  107  may be divided into a number of cells, with a radio transceiver apparatus serving each cell. A radio transceiver apparatus is commonly 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, two node Bs  108  are shown; however, the RNS  107  may include any number of wireless node Bs. The node Bs  108  provide wireless access points to a core network  104  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 user equipment (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 (AT), 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. For illustrative purposes, three UEs  110  are shown in communication with the node Bs  108 . The downlink (DL), also called the forward link, refers to the communication link from a node B to a UE, and the uplink (UL), also called the reverse link, refers to the communication link from a UE to a node B. 
     The core network  104 , as shown, includes a GSM 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 GSM networks. 
     In this example, the core network  104  supports circuit-switched services with a mobile switching center (MSC)  112  and a gateway MSC (GMSC)  114 . One or more RNCs, such as the RNC  106 , may be connected to the MSC  112 . The MSC  112  is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC  112  also includes a visitor location register (VLR) (not shown) that contains subscriber-related information for the duration that a UE is in the coverage area of the MSC  112 . The GMSC  114  provides a gateway through the MSC  112  for the UE to access a circuit-switched network  116 . The GMSC  114  includes a home location register (HLR) (not shown) containing subscriber data, such as the data reflecting the details of the services to which a particular user has subscribed. The HLR is also associated with an authentication center (AuC) that contains subscriber-specific authentication data. When a call is received for a particular UE, the GMSC  114  queries the HLR to determine the UE&#39;s location and forwards the call to the particular MSC serving that location. 
     The core network  104  also supports packet-data services with a serving GPRS support node (SGSN)  118  and a gateway GPRS support node (GGSN)  120 . GPRS, which stands for General Packet Radio Service, is designed to provide packet-data services at speeds higher than those available with standard GSM circuit-switched data services. The GGSN  120  provides a connection for the RAN  102  to a packet-based network  122 . The packet-based network  122  may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN  120  is to provide the UEs  110  with packet-based network connectivity. Data packets are transferred between the GGSN  120  and the UEs  110  through the SGSN  118 , which performs primarily the same functions in the packet-based domain as the MSC  112  performs in the circuit-switched domain. 
     The UMTS air interface is a spread spectrum Direct-Sequence Code Division Multiple Access (DS-CDMA) system. The spread spectrum DS-CDMA spreads user data over a much wider bandwidth through multiplication by a sequence of pseudorandom bits called chips. The TD-SCDMA standard is based on such direct sequence spread spectrum technology and additionally calls for a time division duplexing (TDD), rather than a frequency division duplexing (FDD) as used in many FDD mode UMTS/W-CDMA systems. TDD uses the same carrier frequency for both the uplink (UL) and downlink (DL) between a node B  108  and a UE  110 , but divides uplink and downlink transmissions into different time slots in the carrier. 
       FIG. 2  shows a frame structure  200  for a TD-SCDMA carrier. The TD-SCDMA carrier, as illustrated, has a frame  202  that is 10 ms in length. The frame  202  has two 5 ms subframes  204 , and each of the subframes  204  includes seven time slots, TS 0  through TS 6 . The first time slot, TS 0 , is usually allocated for downlink communication, while the second time slot, TS 1 , is usually allocated for uplink communication. The remaining time slots, TS 2  through TS 6 , may be used for either uplink or downlink, which allows for greater flexibility during times of higher data transmission times in either the uplink or downlink directions. A downlink pilot time slot (DwPTS)  206 , a guard period (GP)  208 , and an uplink pilot time slot (UpPTS)  210  (also known as the uplink pilot channel (UpPCH)) are located between TS 0  and TS 1 . Each time slot, TS 0 -TS 6 , may allow data transmission multiplexed on a maximum of 16 code channels. Data transmission on a code channel includes two data portions  212  separated by a midamble  214  and followed by a guard period (GP)  216 . The midamble  214  may be used for features, such as channel estimation, while the GP  216  may be used to avoid inter-burst interference. 
       FIG. 3  is a block diagram of a node B  310  in communication with a UE  350  in a RAN  300 , where the RAN  300  may be the RAN  102  in  FIG. 1 , the node B  310  may be the node B  108  in  FIG. 1 , and the UE  350  may be the UE  110  in  FIG. 1 . In the downlink communication, a transmit processor  320  may receive data from a data source  312  and control signals from a controller/processor  340 . The transmit processor  320  provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals). For example, the transmit processor  320  may provide cyclic redundancy check (CRC) codes for error detection, coding and interleaving to facilitate forward error correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), and the like), spreading with orthogonal variable spreading factors (OVSF), and multiplying with scrambling codes to produce a series of symbols. Channel estimates from a channel processor  344  may be used by a controller/processor  340  to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor  320 . These channel estimates may be derived from a reference signal transmitted by the UE  350  or from feedback contained in the midamble  214  ( FIG. 2 ) from the UE  350 . The symbols generated by the transmit processor  320  are provided to a transmit frame processor  330  to create a frame structure. The transmit frame processor  330  creates this frame structure by multiplexing the symbols with a midamble  214  ( FIG. 2 ) from the controller/processor  340 , resulting in a series of frames. The frames are then provided to a transmitter  332 , which provides various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through smart antennas  334 . The smart antennas  334  may be implemented with beam steering bidirectional adaptive antenna arrays or other similar beam technologies. 
     At the UE  350 , a receiver  354  receives the downlink transmission through an antenna  352  and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver  354  is provided to a receive frame processor  360 , which parses each frame, and provides the midamble  214  ( FIG. 2 ) to a channel processor  394  and the data, control, and reference signals to a receive processor  370 . The receive processor  370  then performs the inverse of the processing performed by the transmit processor  320  in the node B  310 . More specifically, the receive processor  370  descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the node B  310  based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor  394 . The soft decisions are then decoded and deinterleaved to recover the data, control, and reference signals. The CRC codes are then checked to determine whether the frames were successfully decoded. The data carried by the successfully decoded frames will then be provided to a data sink  372 , which represents applications running in the UE  350  and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a controller/processor  390 . When frames are unsuccessfully decoded by the receiver processor  370 , the controller/processor  390  may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames. 
     In the uplink, data from a data source  378  and control signals from the controller/processor  390  are provided to a transmit processor  380 . The data source  378  may represent applications running in the UE  350  and various user interfaces (e.g., keyboard, pointing device, track wheel, and the like). Similar to the functionality described in connection with the downlink transmission by the node B  310 , the transmit processor  380  provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, spreading with OVSFs, and scrambling to produce a series of symbols. Channel estimates, derived by the channel processor  394  from a reference signal transmitted by the node B  310  or from feedback contained in the midamble transmitted by the node B  310 , may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor  380  will be provided to a transmit frame processor  382  to create a frame structure. The transmit frame processor  382  creates this frame structure by multiplexing the symbols with a midamble  214  ( FIG. 2 ) from the controller/processor  390 , resulting in a series of frames. The frames are then provided to a transmitter  356 , which provides various signal conditioning functions including amplification, filtering, and modulating the frames onto a carrier for uplink transmission over the wireless medium through the antenna  352 . 
     The uplink transmission is processed at the node B  310  in a manner similar to that described in connection with the receiver function at the UE  350 . A receiver  335  receives the uplink transmission through the smart antennas  334  and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver  335  is provided to a receive frame processor  336 , which parses each frame, and provides the midamble  214  ( FIG. 2 ) to the channel processor  344  and the data, control, and reference signals to a receive processor  338 . The receive processor  338  performs the inverse of the processing performed by the transmit processor  380  in the UE  350 . The data and control signals carried by the successfully decoded frames may then be provided to a data sink  339  and the controller/processor  340 , respectively. If some of the frames were unsuccessfully decoded by the receive processor  338 , the controller/processor  340  may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames. 
     The controller/processors  340  and  390  may be used to direct the operation at the node 
     B  310  and the UE  350 , respectively. For example, the controller/processors  340  and  390  may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories  342  and  392  may store data and software for the node B  310  and the UE  350 , respectively. For example, the memory  392  of the UE  350  may store a multiple Universal Subscriber Identity Module (USIM) paging module  391  that, when executed by the controller/processor  390 , allows the UE  350  to receive unicast paging messages for one of its International Mobile Subscriber Identities (IMSIs) when in active communication with the node B  310  using another of the UE&#39;s IMSIs. Similarly, the memory  342  of the node B  310  may store a direct paging module  343  that, when executed by the controller/processor  340 , configures the node B  310  to identify if a desired IMSI is associated with an International Mobile Equipment Identity (IMEI) and UE that is in active communication, and execute a communication (either unicast or broadcast) to the desired IMSI through the other IMSI of the UE. A scheduler/processor  346  at the node B  310  may allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs. 
     The network may also utilize hardware or software which implements an IMSI matching module that determines if a desired IMSI is associated with an IMEI and UE in active communication with a serving node B using a different IMSI. The matching module may then direct a communication for the desired IMSI directly to the serving node B. Although the present disclosure is described with respect to IMSI, IMEI, and USIM, alternatives could also be substituted for each. 
     In TD-SCDMA, the UE in idle mode monitors a recurrent paging interval to receive paging messages. When a Core Network (CN) receives a mobile terminated call, the TD-SCDMA Radio Network Controller (RNC) issues a paging request to a set of node Bs (NBs) to page the UE. The paging message may include the following information:
         The UE identity. This may include the UE&#39;s international mobile subscriber identity (IMSI), the UE&#39;s Temporary Mobile Subscriber Identity (TMSI), or the user&#39;s Packet Temporary Mobile Subscriber Identity (P-TMSI).   The core network domain for the paging, either Circuit-Switched (CS) or Packet-Switched (PS).   The paging cause. Examples of paging causes include, but are not limited to, Terminating Conversational Call, Terminating Streaming Call, Terminating Interactive Call, Terminating Background Call, Terminating High Priority Signaling, and Terminating Low Priority Signaling.       

     In TD-SCDMA networks, to reduce power consumption in idle mode, a UE conventionally uses Discontinuous Reception (DRX) to monitor for paging messages at recurring paging intervals. To do so, the UE monitors the paging occasion during the DRX cycle on the Paging Indicator Channel (PICH) and the Paging Channel (PCH).  FIG. 4  is a block diagram illustrating a TD-SCDMA paging occasion  402  within a DRX cycle length  400 . The Paging Block  404  begins with a frame offset  406 , then includes Paging Indicator Channel frames  408 , gap frames,  410 , and Paging Channel frames  412 . The DRX cycle length is determined by a circuit switched core network in the System Information message or can be negotiated between the packet switched core network and the UE. The UE starts to listen to the PICH starting with the associated paging_occasion, given by the following formula: 
       paging_occasion=( IMSI  div  K ) mod ( DRX _cycle div  PBP )* PBP +frame_offset+ j*DRX _cycle+ p    
     The Paging Block Periodicity (PBP) is the number of frames between two paging blocks and frame_offset is frame offset of the first frame in the PBP, given in the System Information message. K is the number of Secondary Common Control Physical Channels (S-CCPCHs) that can carry the Paging Channel (PCH). 
     Each TD-SCDMA cell belongs to a Location Area (LA) and a Routing Area (RA). Location area is used for the Circuit-Switched (CS) domain and RA is used for the Packet-Switched (PS) domain. A location area can consist of a few cells and a routing area can consist of a few cells. Conventionally, one location area covers a larger area than one routing area. An RNC can request that node Bs in one or more location areas send paging messages for mobile terminated circuit switched call setup. Similarly, the RNC can request that node Bs in one or more routing areas send paging messages for mobile terminated packet switched call setup. When the network pages a particular UE, the paging signal is sent to the most recent location area and/or routing area in which the UE was known to have been located. 
     In order for the network to know the proper location area to page, the UE performs location area updating (LAU) procedures when the UE moves to a cell in a new location area different from the one in which the UE previously performed a location area update. Similarly, in order for the network to know which routing area to page, the UE performs routing area update (RAU) procedures when the UE moves to a cell in a new routing area different from the one in which the UE previously performed a RAU. 
       FIG. 5  is a diagram illustrating location areas and routing areas in a TD-SCDMA network. Particular cells (represented by the hexagonal spaces) may transmit for one location area and one routing area. However the borders for a location area and routing area may differ. A particular location area may intersect with one or more routing areas and a particular routing area may intersect with one or more location areas. In this example, three routing areas and two location areas are shown. The leftmost cells  502  belong to LA 1  and RA 1 , the middle cells  504  belong to LA 2  and RA 2 , and the right most cells  506  belong to LA 2  and RA 3 . When UE 1  moves from cell A in LA 1 , RA 1  to cell B in LA 2 , RA 2 , then UE 1  performs both location area update and routing area update procedures. When UE 2  moves from Cell D in LA 2 , RA 3  to Cell C in LA 2 , RA 2 , then UE  2  performs a routing area update procedure. 
     After the respective LAU and RAU updates described above, if the network sets up a mobile terminated circuit switched call to UE 1  in its new location in Cell B (within LA 2 ), then the RNC pages all the LA 2  cells  504  and  506  (middle and rightmost cells). If the network sets up a mobile terminated packet switched call to the UE 2  in its new location in Cell C (within RA 2 ), then the RNC pages the RA 2  cells  504 . Paging can therefore consume substantial system bandwidth to broadcast paging messages in a particular location area or routing area. 
     In certain network systems, a mobile phone may have more than one Universal Subscriber Identity Module (USIM) which enables the user to make phone calls using different phone numbers from a single UE. Each USIM has a unique International Mobile Subscriber Identity (IMSI). If a first IMSI is engaged in a voice or packet call, the UE still monitors the paging messages of the second IMSI in case a call comes in destined for the second IMSI. Conventionally, the paging process for that second IMSI is the same as the process described above. 
     In general, paging is processing and bandwidth intensive because the RNC requests that several node Bs broadcast paging messages to ensure contact with the desired UE. To allow more efficient paging when the UE has already engaged in a call, an improved paging procedure is proposed. 
     If a UE with multiple USIMs has one IMSI already engaged in the call, the network only sends the paging message for the other IMSI from the cell currently serving the UE for the first IMSI, instead of from all the cells in the location area or routing area of the second IMSI. This arrangement saves significantly on processing and bandwidth. 
       FIG. 6A  illustrates conventional methods of broadcast paging, which occurs when the RNC pages from each cell in a location area or routing area.  FIG. 6B  illustrates the enhanced method of paging, which may be utilized when the network knows what cell is serving the UE on a different IMSI. This arrangement allows the network to utilize more precise location information when the UE is in the connected mode for one of its IMSIs. Communications from the serving cell to the UE may be either broadcast pages (represented by the two unidirectional arrows in  FIG. 6B ) or a direct unicast message to the UE (represented by the single bidirectional arrow in  FIG. 6B ). 
     For the network to know that two IMSIs belong to the same UE, the network matches each IMSI with an International Mobile Equipment Identity (IMEI) which is unique to each UE. The network keeps track of the UE&#39;s IMSIs, state (e.g., idle or connected), and serving cell of the UE in connected mode.  FIG. 7  is a diagram illustrating exemplary UE data stored by the network according to one aspect of the present disclosure. For each IMEI the network tracks which IMSI is associated with the IMEI. The network also tracks the UE state and serving cell. The network can also track the current location area and routing area. If a UE is in connected mode, the network can use the above information to identify the UE&#39;s cell if the need arises to page the non-connected IMSI of the UE. The network can then page the UE from the connected cell, rather than from every cell in the location area or routing area. 
     To further speed the delivery of paging messages, the network can send the paging message as a unicast message to the connected IMSI in connected mode. In this manner the network can avoid the need to wait for the next paging occasion to broadcast the paging message, and therefore reduce the delay of paging the IMSI. 
       FIG. 8  is a call flow diagram illustrating enhanced paging of a user equipment according to one aspect of the present disclosure. A pictured UE  110  has two IMSIs, IMSI  1  and IMSI  2 . When a first call is initiated for IMSI  1  at time  810  the RNC  802  sends a paging request via the S-CCPCH to the node Bs  806 ,  808  corresponding to the location area or routing area of the UE  110 , that is each cell of the location area/routing area in which the UE is located (represented by Cells  1  and k of the location area/routing area). In  FIG. 8 , Cell  1  of the location area/routing area  808  is the cell in which the UE is located. As part of the general location area/routing area page, the paging signal is sent from Cell  1   808  to the UE  110  at time  812 . Once the UE  110  receives the page for IMSI  1 , it can exchange call setup messages with Cell  1 , which exchanges call setup messages with the RNC  802 , at time  814 . Once the call is setup the UE and network may exchange downlink/uplink data via the Downlink Dedicated Physical Channel (DPCH) through Cell  1   808 , at time  816 . 
     The network then determines that it will page IMSI  2  of the UE  110 . Because IMSI  1  is engaged in a call and the network knows that IMSI  2  and IMSI  1  share an IMEI, i.e., belong to the same UE, the network knows the cell that is connected to the UE associated with IMSI  2 . With this information the network does not send a page to each cell in the location area/routing area of the UE. Instead, the network can send a unicast paging message directly to the serving cell of the location area/routing area, Cell  1   808 . Thus, at time  818 , the network pages IMSI  2  directly from Cell  1   808  using the downlink DPCH. Once the IMSI  2  page is received, at time  820  the UE  110  and RNC  802  can exchange call setup messages via Cell  1   808 . Although the preceding description was with respect to a unicast message delivered at time  818 , a broadcast message can be sent from the appropriate node B in another embodiment. 
       FIG. 9  is a flow diagram illustrating enhanced paging of a user equipment according to one aspect of the present disclosure. An apparatus, such as the UE  110  is configured to communicate with a node B using a first IMSI as shown in block  902 . The UE is also configured to receive a unicast message for a second IMSI of the UE from the serving node B as shown in block  904 . 
       FIG. 10  is a flow diagram illustrating enhanced paging of a user equipment according to one aspect of the present disclosure. An apparatus, such as a node B  310  within a location area or routing area is configured to communicate with a UE  110  using a first IMSI as shown in block  1002 . The node B is also configured to transmit a message for a second IMSI of the UE as shown in block  1004 . 
     The present disclosure can allow paging messages sent to the serving cell using the connection for the other IMSI. It can save bandwidth and reduce delay of the paging procedure for a UE with multiple USIMs. 
     In one configuration, the apparatus, such as the node B  310 , is configured for wireless communication and includes means for transmitting a message, which may be a unicast message or a broadcast message, for a second IMSI of a UE while communicating with the UE using a first IMSI of the UE. In one aspect, the aforementioned means may be the antennas  334 , the transmitter  332 , the transmit frame processor  330 , the channel processor  344 , the transmit processor  320 , the controller/processor  340 , and the memory  342  storing a direct paging module  343  all of which are configured together to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a module or any apparatus configured to perform the functions recited by the aforementioned means. 
     In one configuration, the apparatus, such as the UE  350 , is configured for wireless communication and includes means for communication with a serving node B (NB) during a call using a first international mobile subscriber identity (IMSI) of a user equipment (UE); and means for receiving a unicast message from the serving NB for a second call for a second IMSI of the UE. In one aspect, the aforementioned means may be the antennas  352 , the receiver  354 , the receive frame processor  360 , the channel processor  394 , the receive processor  370 , the controller/processor  390 , and the memory  392  storing a multiple Universal Subscriber Identity Module (USIM) page module  391  all of which are configured together to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a module or any apparatus configured to perform the functions recited by the aforementioned means. 
     Several aspects of a telecommunications system have been presented with reference to a TD-SCDMA system. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards. By way of example, various aspects may be extended to other UMTS systems such as W-CDMA, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and TD-CDMA. Various aspects may also be extended to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system. 
     Several processors have been described in connection with various apparatuses and methods. These processors may be implemented using electronic hardware, computer software, or any combination thereof. Whether such processors are implemented as hardware or software will depend upon the particular application and overall design constraints imposed on the system. By way of example, a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented with a microprocessor, microcontroller, digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic device (PLD), a state machine, gated logic, discrete hardware circuits, and other suitable processing components configured to perform the various functions described throughout this disclosure. The functionality of a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented with software being executed by a microprocessor, microcontroller, DSP, or other suitable platform. 
     Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium. A computer-readable medium may include, by way of example, memory such as a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disc (CD), digital versatile disc (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, or a removable disk. Although memory is shown separate from the processors in the various aspects presented throughout this disclosure, the memory may be internal to the processors (e.g., cache or register). 
     Computer-readable media may be embodied in a computer-program product. By way of example, a computer-program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system. 
     It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein. 
     The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”