Abstract:
A technique for tuning the receiver (RX) synthesizer independently from the transmitter (TX) synthesizer helps a mobile communication device with multiple SIMs to concurrently monitor the paging channel of a first network associated with one SIM while transmitting on a second network associated with a second SIM. By independently tuning the RX and the TX synthesizers, each SIM card can maintain synchronization with the network without disruption of service in either network. As a result, the mobile communication device exhibits an increased ability to maintain communication sessions for two different networks, without the need for a second set of TX/RX synthesizer hardware.

Description:
PRIORITY CLAIM 
       [0001]    This application claims the benefit of priority to the following U.S. provisional patent applications: 
         [0000]    U.S. patent application No. 61/569,621, filed 12Dec. 2011, under attorney docket number 14528.00045;
 
U.S. patent application No. 61/587,521, filed 17Jan. 2012, under attorney docket number 14528.00425; and
 
U.S. patent application No. 61/595,546, filed 6Feb. 2012, under attorney docket number 14528.00460.
 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates to communication devices with multiple Subscriber Identity Modules (SIMs). The disclosure also relates to, in communication devices with multiple SIMs, concurrent use of transmit (TX) and receive (RX) synthesizers for a communications network associated with a first SIM and for a communications network associated with a second SIM. 
       BACKGROUND 
       [0003]    Rapid advances in electronics and communication technologies, driven by immense customer demand, have resulted in the widespread adoption of mobile communication devices. The extent of the proliferation of such devices is readily apparent in view of some estimates that put the number of wireless subscriber connections in use around the world at nearly 80% of the world&#39;s population. Furthermore, other estimates indicate that (as just three examples) the United States, Italy, and the UK have more mobile phones in use in each country than there are people living in those countries. 
         [0004]    Relatively recently, cellular phone manufactures have introduced phone designs that include multiple SIM cards. Each SIM card facilitates a separate connection to the same network or different networks. As a result, the SIMs provide the owner of the phone with, for example, two different phone numbers handled by the same phone hardware. Accordingly, the multiple SIM approach alleviates to some degree the need to carry different physical phones, and improvements in multiple SIM communication devices will continue to make such devices attractive options for the consumer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The innovation may be better understood with reference to the following drawings and description. In the figures, like reference numerals designate corresponding parts throughout the different views. 
           [0006]      FIG. 1  shows an example of user equipment with multiple SIMs. 
           [0007]      FIG. 2  is an example of a block diagram of the communications interface and system logic of user equipment with multiple SIMs. 
           [0008]      FIG. 3  shows various examples of TX/RX frequency pairs when employing a fixed offset between a TX frequency and its corresponding RX frequency. 
           [0009]      FIG. 4  shows one example of the various frequency offsets when concurrently using a single TX/RX synthesizer pair for SIM1 and SIM2. 
           [0010]      FIG. 5  shows an example of frequency control logic that a user equipment may implement, in hardware, software, or both. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The discussion below makes reference to user equipment. User equipment may take many different forms and have many different functions. As one example, user equipment may be a cellular phone capable of making and receiving wireless phone calls. The user equipment may also be a smartphone that, in addition to making and receiving phone calls, runs general purpose applications. User equipment may be virtually any device that wirelessly connects to a network, including as additional examples a driver assistance module in a vehicle, an emergency transponder, a pager, a satellite television receiver, a networked stereo receiver, a computer system, music player, or virtually any other device. The discussion below addresses how to configure a single TX/RX synthesizer pair in user equipment that includes multiple (e.g., two) SIMs. 
         [0012]      FIG. 1  shows an example of user equipment  100  with multiple SIMs, in this example the SIM1  102  and the SIM2  104 . An electrical and physical interface  106  connects SIM1  102  to the rest of the user equipment hardware, for example, to the system bus  110 . Similarly, the electrical and physical interface  108  connects the SIM2 to the system bus  110 . 
         [0013]    The user equipment  100  includes a communication interface  112 , system logic  114 , and a user interface  118 . The system logic  114  may include any combination of hardware, software, firmware, or other logic. The system logic  114  may be implemented, for example, in a system on a chip (SoC), application specific integrated circuit (ASIC), or other circuitry. The system logic  114  is part of the implementation of any desired functionality in the user equipment. In that regard, the system logic  114  may include logic that facilitates, as examples, running applications, accepting user inputs, saving and retrieving application data, establishing, maintaining, and terminating cellular phone calls, wireless network connections, Bluetooth connections, or other connections, and displaying relevant information on the user interface  118 . The user interface  118  may include a graphical user interface, touch sensitive display, voice or facial recognition inputs, buttons, switches, and other user interface elements. 
         [0014]    The communication interface  112  may include one or more transceivers. The transceivers may be wireless transceivers that include modulation/demodulation circuitry, coders/decoders, waveform shapers, amplifiers, analog to digital and digital to analog converters and/or other logic for transmitting and receiving through one or more antennas, or through a physical (e.g., wireline) medium. As one implementation example, the communication interface  112  and system logic  114  may include a BCM2091 EDGE/HSPA Multi-Mode, Multi-Band Cellular Transceiver and a BCM59056 advanced power management unit (PMU), controlled by a BCM28150 HSPA+ system-on-a-chip (SoC) baseband smartphone processer. These integrated circuits, as well as other hardware and software implementation options for the user equipment  100 , are available from Broadcom Corporation of Irvine Calif. 
         [0015]    The transmitted and received signals may adhere to any of a diverse array of formats, protocols, modulations, frequency channels, bit rates, and encodings that presently or in the future support communications such as paging notifications, packet switched connections (e.g., for data sessions), and circuit switched connections (e.g., for voice sessions) associated with one or more SIMs. As one specific example, the communication interface  112  may support transmission and reception under the Universal Mobile Telecommunications System (UMTS). The techniques described below, however, are applicable to other communications technologies that include paging whether arising from the 3rd Generation Partnership Project (3GPP), GSM (R) Association, Long Term Evolution (LTE) (TM) efforts, or other partnerships or standards bodies. 
         [0016]    Maintaining Communications with the Network 
         [0017]    The communications interface  112  can establish network connections to SIM1 network  130 . The SIM1 network  130  may, for example, generate and manage a cell for a particular service provider. The SIM1  102  may discover, register with, and connect to the network  130  for data or voice connections, as examples. Similarly, the communications interface  112  can establish network connections to the SIM2 network  132 . The SIM2 network  132  may, for example, generate and manage a cell for the same or a different service provider than the SIM1 network  130 . Like SIM1  102 , the SIM2  104  may discover, register with, and connect to the SIM2 network  132  for data or voice connections. When a network connection is established, the network  130  or  132  may assign certain channels for the user equipment  100  to communicate with the network  130  or  132 . As examples, the channels may be traffic channels for actively transmitting or receiving data between the network  130  or  132  and the user equipment  100 , or the channels may be control channels for synchronizing with or receiving paging notifications from the network  130  or  132 . 
         [0018]    The user equipment  100  can maintain a network connection that is either in active mode or in idle mode. When the network connection is in active mode, the network  130  or  132  may have assigned traffic channels to the user equipment  100 , which may then actively transmit or receive data using the assigned traffic channels. When the network connection is in idle mode, the user equipment  100  can be in a reduced power “sleep” mode, “waking up” periodically to listen for synchronization or paging information from the network  130  or  132 . 
         [0019]    While in active mode, the network  130  or  132  maintains the established network connection while the user equipment  100  actively transmits data or receives data on the assigned channels. In some instances, if the user equipment  100  does not actively transmit data to the network  130  or  132  on the assigned channel, the network  130  or  132  may end the established network connection with user equipment  100  and reallocate the channel to another user equipment. Accordingly, when, for example, the user equipment  100  enters areas where signal coverage is not sufficient to perform its communications, the network  130  or  132  may end the connection to the user equipment  100  and provide a connection to a different device. 
         [0020]    While in idle mode, the network  130  or  132  may maintain the established network connection with the user equipment  100  by having the user equipment  100  periodically listen for synchronization or paging information from the network  130  or  132 . If the user equipment  100  does not periodically wake up to listen for the synchronization or paging information from the network  130  or  132 , the user equipment  100  may lose synchronization with the network  130  or  132 . As a result, the user equipment  100  may not receive a paging indicator from the network  130  or  132  and may miss a call, message, or data that the network  130  or  132  has designated for the user equipment  100  or the user equipment  100  may lose service. 
         [0021]    Configuring the User Equipment 
         [0022]    Once the user equipment  100  has established a network connection, the user equipment  100  may configure the communication interface  112  to operate the transceiver on a channel assigned by the network. The channel assigned by the network may be a frequency pair including a transmit (TX) frequency and a receive (RX) frequency. The frequency pair may depend on the communication standards employed by the SIM network  130  or  132 , and the frequency pair may relate to the certain channel that is assigned by the network  130  or  132 . For the particular frequency pair, the TX frequency may be spaced from the RX frequency by a fixed frequency offset. For example, SIM1 network  130  may assign to the user equipment  100  a certain channel for communicating with the SIM1 network  130 . The certain channel may be a particular frequency pair specifying a TX frequency and a corresponding RX frequency. The TX frequency is used by the user equipment  100  for transmitting data from the user equipment  100  to the SIM1 network  130 . The RX frequency is used by the user equipment  100  for receiving data at the user equipment  100  from the SIM1 network  130 . 
         [0023]      FIG. 3  shows examples of channels that correspond to the frequency pairs  302 ,  304 , and  306  where frequency is plotted on the x-axis. SIM1  102  may initially be assigned to Channel  1 , for example.  FIG. 3  shows that Channel  1  corresponds to the TX/RX frequency pair  302 , which includes TX frequency  302   a  and RX frequency  302   b.  TX frequency  302   a  is offset from RX frequency  302   b  by a fixed offset  310 . In one implementation that uses the GSM standard, for example, frequency pair  302  may correspond to an assigned GSM channel having TX frequency  302   a  of 900.0 MHz and RX frequency  302   b  of 945.0 MHz. In such a case, the fixed offset  310  is 45 MHz. 
         [0024]    The user equipment  100  may also be assigned to a different channel for the SIM2  104 , for example, and therefore a different frequency pair, as shown by Channel  2  in  FIG. 3  as TX/RX frequency pair  304 . TX/RX frequency pair  304  includes the TX frequency  304   a  and RX frequency  304   b.  Even though TX frequency  304   a  may differ from TX frequency  302   a  and RX frequency  304   b  may differ from RX frequency  302   b,  the frequency offset  310  remains the same. In one implementation that uses the GSM standard, for example, frequency pair  302  may correspond to an assigned GSM channel having TX frequency  304   a  of 915.0 MHz and RX frequency  304   b  of 960.0 MHz. In such a case, the fixed offset  310  is still 45 MHz. 
         [0025]    Similarly, at any point in time, either SIM1  102  or SIM2  104  may move to a different channel under direction of the network.  FIG. 3  shows another example in which the user equipment  100  is assigned to Channel  3  and therefore a different frequency pair, as shown by TX/RX frequency pair  306 . TX/RX frequency pair  306  includes the TX frequency  306   a  and RX frequency  306   b.  Even though TX frequency  306   a  may differ from TX frequency  304   a  and RX frequency  306   b  may differ from RX frequency  304   b,  the frequency offset  310  remains the same. In one implementation that uses the GSM standard, for example, frequency pair  306  may correspond to an assigned GSM channel having TX frequency  306   a  of 890.0 MHz and RX frequency  306   b  of 935.0 MHz. In such a case, the fixed offset  310  is still 45 MHz. In the above examples, the assigned channels, TX/RX frequency pairs, and resulting fixed offset may differ from these few examples and may depend on the communication standard employed by the particular communications network  130  or  132 . 
         [0026]    Configuring the Transceiver(s) in the User Equipment 
         [0027]    In order for the user equipment  100  to communicate on a network, the user equipment  100  may configure the communications interface  112  to use the frequency pair associated with the channel assigned to the user equipment  100  by the network  130  or  132 . In one implementation, the user equipment  100  may have one transceiver for each SIM interface  106 ,  108 . In such an implementation, each transceiver may be independently programmed to the frequency pair associated with the channel assigned to each SIM interface  106 ,  108 . 
         [0028]    However, in another implementation, the user equipment  100  may have a single transceiver that is shared by each SIM interface  106 ,  108 . In such an implementation, the transceiver can be reprogrammed to switch between the frequency pair associated with the channel assigned to the SIM1 interface  106  for communicating with the SIM1 network  130  and the frequency pair associated with the channel assigned to the SIM2 interface  108  for communicating with the SIM2 network  132 . 
         [0029]      FIG. 2  shows an example implementation of the communications interface  112 . In the example of  FIG. 2 , the system logic  114  controls the communication interface  112 . The communication interface  112  may employ, as part of a transceiver, an RX synthesizer  144  and a TX synthesizer  145 . The processor  116  may compute RX synthesizer parameters  124  and TX synthesizer parameters  125  using the frequency control logic  122 . The hardware controller  142  uses the RX synthesizer parameters  124  and the TX synthesizer parameters  125  to tune the TX synthesizer  145  and the RX synthesizer  144  to the desired frequencies. For example, the hardware controller  142  may receive from the processor  116 , in the form of control bits, a specific frequency to which the synthesizer should be tuned. The control bits may be provided to a modulation input or to a fractional input of a sigma-delta modulator. In one implementation, the control bits provided to the modulation input may be 14 bits and the control bits provided to the fractional input may be 27 bits. In other implementations, the synthesizers may be programed using control bits with other lengths or using other methods for programming the synthesizer to a desired frequency. 
         [0030]    Each synthesizer may be any type of tunable time base, such as a voltage controlled oscillator operating as part of a phase locked loop. The TX synthesizer  145  is used, for example, in combination with a mixer to modulate a signal for transmitting via antenna  202  to network  130  or  132 . The RX synthesizer  144  is used, for example, in combination with a mixer to demodulate a signal received via antenna  202  from the network  130  or  132 . As described above, the user equipment  100  may have multiple transceivers with multiple TX/RX synthesizer pairs. The implementation shown in  FIG. 2 , however, depicts a single transceiver having a single TX/RX synthesizer pair. As such, transmissions to/from the SIM1 network  130  and transmissions to/from the SIM2 network  132  may share a single TX/RX synthesizer pair. The sharing may be a time divisional sharing, coordinated by the system logic  114 , so that each SIM has the RF interface at specified times to perform transmit and receive operations. 
         [0031]    Sharing Radio Frequency Recourses with Multiple SIMs 
         [0032]    In one implementation, the system logic  114  includes one or more processors  116  and a memory  120 . The memory  120  stores, for example, frequency control logic  122  that the processor  116  executes. The memory  120  may also store RX synthesizer parameters  124  and TX synthesizer parameters  125 . As will be described in more detail below, the frequency control logic  122  facilitates the independent control of the single TX/RX synthesizer pair for concurrent use by a SIM1 network  130  and a SIM2 network  132 . 
         [0033]    In some implementations of the user equipment  100 , the SIMs share radio frequency resources, including the transmit/receive paths and synthesizers. As a result, both SIMs cannot receive at the same time or transmit at the same time. Instead, the user equipment  100  allows the SIMs to share the radio frequency resources, for example in a time division manner or by providing the transmitter to one SIM and providing the receiver to second SIM. 
         [0034]    Sharing radio frequency resources may create unique challenges for maintaining concurrent network connections for both SIMs. For example, if the network connection associated with SIM1 is in active mode, the communications interface  112  may configure the radio frequency resources, including the TX/RX synthesizer pair, to use the TX frequency and RX frequency pair corresponding to the channel assigned by SIM1 network  130 . This may prevent SIM2 from using the radio frequency resources, because if the communications interface  112  configures the radio frequency resource to use the TX frequency and RX frequency pair corresponding to the channel assigned by SIM2 network  132 , SIM1 will no longer be able to transmit information over the established network connection with SIM1 network  130 , and the network connection with SIM1 network  130  may be lost. 
         [0035]    Also relevant is the situation in which the SIM1 is in active mode and SIM2 is in idle mode. As described above, when in active mode, SIM1 may be actively transmitting while SIM2, when in idle mode, may need to periodically listen on the paging channel. If SIM1 fails to actively transmit, the network connection with SIM1 network  130  may be disrupted. If SIM2 fails to periodically listen on the paging channel, the SIM2 may lose synchronization with the network and may miss paging indications. As a result, user equipment  100  may miss a call, message, or data that the SIM2 network  132  has designated for the user equipment  100 .. In order to prevent disruption on the SIM1 network  130  or missed calls on the SIM2 network  132  (or to achieve other receive/transmit goals for SIM1 and SIM2), the user equipment  100  may share the radio frequency resources by configuring the synthesizers independently instead of as a pair. In this manner, the TX frequency to which the TX synthesizer  145  is tuned may no longer have a fixed offset from the RX frequency to which the RX synthesizer  144  is tuned. 
         [0036]    In user equipment  100  with multiple SIMs, in this example SIM1  102  and the SIM2  104 , the user equipment  100  may establish network connections with SIM1 network  130  or SIM2 network  132  or both. The user equipment  100  may maintain the network connection with SIM1 network  130  while concurrently maintaining the network connection with SIM2 network  132 . In order to concurrently maintain the SIM1 network connection and the SIM2 network connection, the communications interface  112  may intelligently share the single transceiver TX/RX synthesizer pair by employing frequency control logic  122  that independently programs the synthesizers. Instead of programing the TX synthesizer  145  together with the RX synthesizer  144  to a TX frequency and RX frequency pair having a fixed offset, the frequency control logic  122  may program the TX synthesizer  145  to a TX frequency and independently program the RX synthesizer  144  to an RX frequency that may not be part of a TX/RX frequency pair. As a result, the tuned TX frequency may not have a fixed offset with respect to the tuned RX frequency. 
         [0037]    In another implementation, the time during which the TX frequency and RX frequency are independently programmed may be controlled to be the time period during which SIM2 may need to concurrently use the transceiver, for example to periodically listen on the paging channel or to receive a paging indicator from the SIM2 network  132 . At times when SIM2 not need concurrently use the transceiver—for example when the paging indicator is not expected or at times when SIM2 need not listen on the paging channel—the TX frequency and RX frequency may be programmed as a TX/RX frequency pair having a fixed offset, as may be required by the SIM1 network  130 . 
         [0038]      FIG. 4  illustrates the independent tuning of the TX/RX synthesizers in the user equipment  100 . The user equipment has established a network connection with SIM1 network  130 , using SIM1  102 . SIM1 network  130  has assigned to the user equipment  100  a channel having a TX/RX frequency pair of TX frequency  404   a  and RX frequency  404   b.  The fixed offset  440  represents the frequency spacing requirements for the channel assigned to the SIM1 network connection. The user equipment has also established a network connection with SIM2 network  132 , using SIM2  104 . SIM2 network  132  has assigned to the user equipment  100  a channel having a TX/RX frequency pair of TX frequency  402   a  and RX frequency  402   b.  The fixed offset  420  represents the frequency spacing requirements for the channel assigned to the SIM2 network connection. 
         [0039]    When the user equipment  100  does not need to share concurrently the radio frequency resources, however, the communications interface  112  may program the synthesizers together as a TX/RX frequency pair, corresponding to the channel assigned to each SIM. Thus, if SIM1 is using the communications interface  112 , the hardware controller  142  may program the synthesizers together as a TX/RX frequency pair to TX frequency  404   a  and RX frequency  404   b  having fixed offset  440 . If SIM2 is using the communications interface  112 , the hardware controller  142  may program the synthesizers together as a TX/RX frequency pair to TX frequency  402   a  and RX frequency  402   b  having fixed offset  420 . 
         [0040]    When the user equipment  100  will concurrently share the radio frequency resources, the communications interface  112  may program the synthesizers independently. Thus, if SIM1 is using the communications interface  112  for transmitting to the SIM1 network  130 , the hardware controller  142  may program the TX synthesizer to TX frequency  404   a.  If SIM2 is expecting to receive a paging indicator or if SIM2 is required to listen to the paging channel, instead of programing the RX synthesizer to RX frequency  404   b,  the hardware controller  142  may independently program the RX synthesizer to RX frequency  402   b.  The resulting implemented offset  410  between TX frequency  404   a  and RX frequency  402   b  may not have the fixed frequency offset  440  as may be required by SIM1 network  130  or the fixed frequency offset  420  as may be required by SIM2 network  132 . 
         [0041]      FIG. 5  shows one example of the frequency control logic (FCL)  500  that may be used at the user equipment  100 . FCL  500  may determine the frequency spacing requirements ( 502 ) for SIM1. The frequency spacing requirements may be the TX frequency and RX frequency pair that is associated with the channel assigned by the SIM1 network  130 , where the TX frequency and the RX frequency may have a fixed offset. Based on the frequency spacing requirements, the FCL  500  then determines a TX frequency for SIM1 ( 504 ) and an RX frequency for SIM1 ( 506 ). Next, the FCL  500  may obtain the user equipment radio frequency resource requirements for SIM1 and SIM2 ( 508 ). For example, the FCL  500  may determine that SIM1 and SIM2 require the concurrent use of the radio frequency resources because SIM1 is scheduled to actively transmit while SIM2 is scheduled to receive a paging event. If FCL  500  determines at  510  that SIM2 has a receive event (e.g., a paging event) scheduled at the same time as SIM1 is schedule to actively transmit, the FCL  500  tunes the TX synthesizer to the TX frequency for SIM1 ( 512 ) and tunes the RX synthesizer to the RX frequency for SIM2 ( 514 ). Frequency plot  520  shows the implemented offset  526  that results if TX synthesizer is tuned to the TX frequency for SIM1  522  and RX synthesizer is tuned to the RX frequency for SIM2  524 . On the other hand, if FCL  500  determines at  510  that SIM2 does not have a paging event scheduled at the same time as SIM1 is scheduled to actively transmit, the FCL  500  tunes the TX synthesizer to the TX frequency for SIM1 ( 516 ) and tunes the RX synthesizer to the RX frequency for SIM1 ( 518 ) corresponding to the frequency spacing requirements of SIM1. Frequency plot  530  shows the fixed offset  536  that results if TX synthesizer is tuned to the TX frequency for SIM1  532  and RX synthesizer is tuned to the RX frequency for SIM2  534 . 
         [0042]    The methods, devices, techniques, and logic described above may be implemented in many different ways in many different combinations of hardware, software or both hardware and software. For example, all or parts of the system may include circuitry in a controller, a microprocessor, or an application specific integrated circuit (ASIC), or may be implemented with discrete logic or components, or a combination of other types of analog or digital circuitry, combined on a single integrated circuit or distributed among multiple integrated circuits. All or part of the logic described above may be implemented as logic for execution by a processor, controller, or other processing device and may be stored in a tangible or non-transitory machine-readable or computer-readable medium such as flash memory, random access memory (RAM) or read only memory (ROM), erasable programmable read only memory (EPROM) or other machine-readable medium such as a compact disc read only memory (CDROM), or magnetic or optical disk. Thus, a product, such as a computer program product, may include a storage medium and computer readable instructions stored on the medium, which when executed in an endpoint, computer system, or other device, cause the device to perform operations according to any of the description above. 
         [0043]    The processing capability of the system may be distributed among multiple system components, such as among multiple processors and memories, optionally including multiple distributed processing systems. Parameters, databases, and other data structures may be separately stored and managed, may be incorporated into a single memory or database, may be logically and physically organized in many different ways, and may implemented in many ways, including data structures such as linked lists, hash tables, or implicit storage mechanisms. Programs may be parts (e.g., subroutines) of a single program, separate programs, distributed across several memories and processors, or implemented in many different ways, such as in a library, such as a shared library (e.g., a dynamic link library (DLL)). The DLL, for example, may store code that performs any of the system processing described above. While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.