Patent Publication Number: US-2016227500-A1

Title: Efficient method to perform acquisition on gsm subscription in multi-subscriber identity module device

Description:
BACKGROUND 
     In a Global System for Mobile Communications (GSM) network, the identity, configuration, and capabilities of a base transceiver station (BTS) may be conveyed to a mobile communication device in various types of system information (SI) messages. For example, one type of SI message may provide the absolute radio frequency channel number (ARFCN) and random access channel (RACH) parameters of the BTS. A mobile communication device may decode SI messages before the mobile communication device is able to acquire a communication network (e.g., a public land mobile network (PLMN)) and camp on a BTS. 
     SI messages may be transmitted on the broadcast control channel (BCCH). The BCCH is a logical channel that is broadcast by the BTS using the same frequency (e.g., beacon frequency) as other control channels including, for example, but not limited to, the frequency correction channel (FCCH), synchronization channel (SCH), and common control channel (CCCH). Data bursts that correspond to different control channels may be transmitted according to a predetermined scheduling pattern. In order to decode BCCH data (e.g., SI messages), the mobile communication device may require information from the FCCH and SCH to synchronize to the frequency and timing of BTS. Thus, the mobile communication device may need to decode the FCCH and SCH data broadcast by a BTS before decoding BCCH data. 
     However, in a conventional multi subscriber identity module (SIM) mobile communication device having a shared radio frequency (RF) chain, BCCH decoding on the GSM subscription may not always take place immediately after FCCH and SCH decoding. Instead, after FCCH and SCH data is decoded to obtain synchronization information, BCCH decoding may be postponed while one of the other subscriptions utilizes the RF chain to perform a higher priority activity (e.g., voice call, short message service (SMS)). When the GSM subscription regains the RF chain, the synchronization information obtained earlier may have become stale and BCCH decoding may fail using the stale synchronization information. The GSM subscription may consequently be unable to acquire a communication network and camp on a corresponding BTS. As a result, the GSM subscription may remain in an out of service (OOS) state for a prolonged period of time. 
     SUMMARY 
     Apparatuses and methods for efficiently performing acquisition on a GSM subscription in multi-SIM devices are provided. 
     According to the various embodiments, there is provided a method. The method may include: decoding FCCH data and SCH data transmitted by a first BTS to obtain a first set of synchronization information; determining whether BCCH data transmitted by the first BTS was successfully decoded using the first set of synchronization information; and in response to a determination that the BCCH data transmitted by the first BTS was not successfully decoded using the first set of synchronization information: determining a cause of a BCCH decoding failure; and in response to a determination that the cause of the BCCH decoding failure is stale synchronization information in the first set of synchronization information, repeating a decoding of the FCCH data and the SCH data transmitted by the first BTS to obtain a second set of synchronization information. 
     According to the various embodiments, there is provided a mobile communication device. In some embodiments, the mobile communication device may include a control unit and an RF chain. 
     The control unit may be configured to: decode FCCH data and SCH data transmitted by a first BTS to obtain a first set of synchronization information; determine whether BCCH data transmitted by the first BTS was successfully decoded using the first set of synchronization information; and in response to a determination that the BCCH data transmitted by the first BTS was not successfully decoded using the first set of synchronization information: determine a cause of a BCCH decoding failure; and in response to a determination that the cause of the BCCH decoding failure is stale synchronization information in the first set of synchronization information, repeat a decoding of the FCCH data and the SCH data transmitted by the first BTS to obtain a second set of synchronization information. 
     Other features and advantages of the present inventive concept should be apparent from the following description which illustrates by way of example aspects of the present inventive concept. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects and features of the present inventive concept will be more apparent by describing example embodiments with reference to the accompanying drawings, in which: 
         FIG. 1  is a diagram illustrating a network environment for various embodiments; 
         FIG. 2  is a block diagram illustrating a mobile communication device according to various embodiments; 
         FIG. 3  is a flowchart illustrating a process for optimizing an acquisition of a communication network on a GSM subscription according to various embodiments; 
         FIG. 4A  is a flowchart illustrating a process for determining a cause of BCCH decoding failure according to various embodiments; 
         FIG. 4B  is a flowchart illustrating a process for determining a cause of BCCH decoding failure according to various embodiments; and 
         FIG. 5  is a flowchart illustrating a process for determining a cause of BCCH decoding failure according to various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     While a number of embodiments are described herein, these embodiments are presented by way of example only, and are not intended to limit the scope of protection. The apparatuses and methods described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and changes in the form of the example apparatuses and methods described herein may be made without departing from the scope of protection. 
       FIG. 1  is a diagram illustrating a network environment  100  for various embodiments. Referring to  FIG. 1 , a mobile communication device  110  may communicate with a first communication network  120  using a first subscription  142 . 
     In various embodiments, the mobile communication device  110  may be a multi-SIM mobile communication device. Thus, in addition to the first communication network  120 , the mobile communication device  110  may communicate with at least one other communication network. For example, the mobile communication device  110  may communicate with a second communication network  130  using a second subscription  144 . In various embodiments, the first communication network  120  and the second communication network  130  may each be, for example, but not limited to, a wireless or mobile communication network. 
     The first communication network  120  and the second communication network  130  may implement the same or different radio access technologies (RATs). For example, the first communication network  120  may be a GSM network and the first subscription  142  may be a GSM subscription. The second communication network  130  may also be a GSM network. Alternately, the second communication network  130  may implement another RAT including, for example, but not limited to, Long Term Evolution (LTE), Wideband Code Division Multiple Access (WCDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). 
     The first communication network  120  may include a plurality of BTSs including, for example, but not limited to, a first BTS  122  and a second BTS  124 . The second communication network  130  may also include a plurality of BTSs, including, for example, but not limited to, a third BTS  135 . A person having ordinary skill in the art can appreciate that the network environment  100  may include any number of communication networks, mobile communication devices, and BTSs without departing from the scope of the present inventive concept. 
     The mobile communication device  110  may attempt to acquire the first communication network  120  and camp on the first BTS  122 . To acquire the first communication network  120 , the mobile communication device  110  may decode data broadcast by the first BTS  122  on the FCCH and the SCH. For example, the data that is broadcast on the FCCH may include a frequency offset between the mobile communication device  110  and the first BTS  122 . Meanwhile, the data that is broadcast on the SCH may include a current frame clock and a base station identity code (BSIC) of the first BTS  122 . 
     The mobile communication device  110  may rely on data from the FCCH and SCH to synchronize to the frequency and timing of the first BTS  122 . Once the mobile communication device  110  is synchronized to the frequency and timing of the first BTS  122 , the mobile communication device  110  may decode data broadcast by the first BTS  122  on the BCCH. For example, the first BTS  122  may broadcast one or more SI messages that may inform the mobile communication device  110  whether the mobile communication device  110  may camp on the first BTS  122 . The mobile communication device  110  may decode data transmitted by the first BTS  122  on the BCCH in order to complete acquisition of the first communication network  120  and camp on the first BTS  122 . 
     The mobile communication device  110  may also attempt to acquire the second communication network  130  and camp on the third BTS  135 . A person having ordinary skill in the art can appreciate that the acquisition of the first communication network  120  performed on the first subscription  142  may be independent of the acquisition of the second communication network  130  performed on the second subscription  144 . Furthermore, the mobile communication device  110  may attempt to acquire the first communication network  120  on the first subscription  142  and the second communication network  130  on the second subscription  144  in the same or a different manner. 
       FIG. 2  is a block diagram illustrating the mobile communication device  110  according to various embodiments. Referring to  FIGS. 1 and 2 , in various embodiments, the mobile communication device  110  may include a control unit  210 , a communication unit  220 , a first SIM  240 , a second SIM  250 , a user interface  270 , and a storage unit  280 . 
     In various embodiments, the mobile communication device  110  may be any device capable of wirelessly communicating with one or more communication networks. In various embodiments, the mobile communication device  110  may be, for example, but not limited to, a smartphone, a tablet PC, or a laptop computer. 
     In various embodiments, the communication unit  220  may include an RF chain  230 . The RF chain  230  may include, for example, but not limited to, an RF module  232  and an antenna  234 . Although the mobile communication device  110  is shown to include the communication unit  220 , a person having ordinary skill in the art can appreciate that the mobile communication device  110  may include additional communication units without departing from the scope of the present inventive concept. 
     In various embodiments, the first SIM  240  may associate the communication unit  220  with the first subscription  142  on the first communication network  120  while the second SIM  250  may associate the communication unit  220  with the second subscription  144  on the second communication network  130 . 
     In various embodiments, the first communication network  120  and the second communication network  130  may be operated by the same or different service providers. Additionally, in various embodiments, the first communication network  120  and the second communication network  130  may each support the same or different RATs, including, for example, but not limited to LTE, GSM, CDMA, and TD-SCDMA. 
     In various embodiments, the user interface  270  may include an input unit  272 . In some embodiments, the input unit  272  may be, for example, but not limited to, a keyboard or a touch panel. In various embodiments, the user interface  270  may include an output unit  274 . In some embodiments, the output unit  274  may be, for example, but not limited to, a liquid crystal display (LCD) or a light emitting diode (LED) display. A person having ordinary skill in the art will appreciate that other types or forms of input and output units may be used without departing from the scope of the present inventive concept. 
     In various embodiments, the control unit  210  may be configured to control the overall operation of the mobile communication device  110  including controlling the functions of the communication unit  220 . In various embodiments, the control unit  210  may include a decoder module  212  and a causation module  214 . In various embodiments, the control unit  210  may be, for example, but not limited to, a microprocessor (e.g., general-purpose processor, baseband modem processor, etc.) or a microcontroller. 
     In various embodiments, the storage unit  280  may be configured to store application programs, application data, and user data. In various embodiments, the storage unit  280  may include a database  282  that is configured to store data indicating one or more BTSs on which the control unit  210  may have previously attempted to acquire a selected communication network (e.g., the first communication network  120  or the second communication network  130 ) on a corresponding subscription (e.g., the first subscription  142  or the second subscription  144 ). Furthermore, in various embodiments, at least some of the application programs stored at the storage unit  280  may be executed by the control unit  210  for the operation of the mobile communication device  110 . 
     In various embodiments, the control unit  210  may attempt to acquire the first communication network  120  on the first subscription  142  and camp on the first BTS  122 . The control unit  210  may decode FCCH and SCH data on the first subscription  142  in order to obtain information to synchronize the mobile communication device  110  (e.g., the RF chain  230 ) to the frequency and timing of the first BTS  122 . But the control unit  210  may subsequently determine to postpone BCCH decoding. For example, the control unit  210  may postpone BCCH decoding on the first subscription  142  in order to perform an activity on the second subscription  144 . When the control unit  210  returns to decode BCCH data on the first subscription  142 , the control unit  210  may decode FCCH and SCH data again on the first subscription  142  if BCCH decoding on the first subscription  142  fails. 
     In various embodiments, the control unit  210  may determine a cause of the failure to decode BCCH data on the first subscription  142 . The control unit  210  may selectively repeat FCCH and SCH decoding on the first subscription  142  based on the cause of the BCCH decoding failure. For example, the control unit  210  may repeat FCCH and SCH decoding on the first subscription  142  if the control unit  210  determines that the cause of the BCCH decoding failure is stale synchronization information. Alternately, the control unit  210  may not repeat FCCH and SCH decoding if the BCCH decoding failure is determined to be due to another cause including, for example, but not limited to, low signal strength from the first BTS  122 . If the control unit  210  determines that the BCCH decoding failure is not caused by stale synchronization information, the control unit  210  may attempt to acquire the first communication network  120  on the first subscription  142  and camp on a different BTS (e.g., the second BTS  124 ). 
       FIG. 3  is a flowchart illustrating a process  300  for optimizing an acquisition of a communication network on a GSM subscription according to various embodiments. With references to  FIGS. 1-3 , in various embodiments, the process  300  may be performed by the control unit  210 , for example, by the decoder module  212 . 
     The control unit  210  may decode FCCH and SCH data transmitted by a first BTS  122  to obtain a first set of synchronization information ( 302 ). For example, the control unit  210  may attempt to acquire the first communication network  120  on the first subscription  142  and camp on the first BTS  122 . The control unit  210  may decode the FCCH and SCH data broadcast by the first BTS  122  in order to obtain information required to synchronize the mobile communication device  110  (e.g., the RF chain  230 ) to the frequency and timing of the first BTS  122 . 
     In various embodiments, the control unit  210  may attempt to acquire the first communication network  120  and camp on the first BTS  122  as a result of home PLMN (HPLMN) recovery, PLMN selection, or PLMN search. A person having ordinary skill in the art can appreciate that the control unit  210  may attempt to acquire the first communication network  120  and camp on the first BTS  122  due to other communication network events without departing from the scope of the present inventive concept. 
     After decoding the FCCH and SCH data broadcast by the first BTS  122 , the control unit  210  may determine whether to postpone BCCH decoding ( 303 ). In various embodiments, the control unit  210  may determine whether to postpone BCCH decoding on the first subscription  142  based on a priority of a concurrent activity being performed on the second subscription  144 . For example, the control unit  210  may detect an activity being performed on the second subscription  144  that has a higher priority than the acquisition of the first communication network  120  on the first subscription  142 . In response, the control unit  210  may release the RF chain  230  from the first subscription  142  in order for the second subscription  144  to utilize the RF chain  230  to perform the activity having the higher priority. 
     The control unit  210  may determine not to postpone BCCH decoding ( 303 -N) and may proceed to decode BCCH data transmitted by the first BTS  122  using the first set of synchronization information ( 304 ). The control unit  210  may require the first set of synchronization information in order to decode the BCCH data broadcast by the first BTS  122 . Meanwhile, the control unit  210  may not detect an activity having a higher priority being performed on the second subscription  144 . Thus, after decoding the FCCH and SCH data broadcast by the first BTS  122  to obtain the first set of synchronization information, the control unit  210  may decode the BCCH data broadcast by the first BTS  122  using the first set of synchronization information. Since BCCH decoding on the first subscription  142  is performed after FCCH and SCH decoding, the first set of synchronization information may have remained current. Consequently, the control unit  210  may successfully decode the BCCH data broadcast by the first BTS  122  using the first set of synchronization information. 
     The control unit  210  may camp on the first BTS  122  ( 306 ). For example, by decoding the BCCH data broadcast by the first BTS  122 , the control unit  210  may obtain sufficient information on the identity, configuration, and available features of the first BTS  122  to acquire the first communication network  120  and camp on the first BTS  122 . 
     Alternately, the control unit  210  may determine to postpone BCCH decoding ( 303 -Y). For example, the control unit  210  may determine to postpone BCCH decoding on the first subscription  142  when the control unit  210  detects an activity having a higher priority being performed on the second subscription  144 . The control unit  210  may release the RF chain  230  from the first subscription  142 , and the second subscription  144  may utilize the RF chain  230  to perform the activity having the higher priority. Accordingly, BCCH decoding on the first subscription  142  may be delayed for a period of time. 
     After a period of time during which BCCH decoding is postponed, the control unit  210  may decode the BCCH data transmitted by the first BTS  122  using the first set of synchronization information ( 308 ). Since BCCH decoding on the first subscription  142  may be postponed for a period of time, at least some of the synchronization information in the first set of synchronization information may become stale during the delay. Consequently, the control unit  210  may fail to decode the BCCH data broadcast by the first BTS  122  using the first set of synchronization information. Thus, the control unit  210  may determine whether the BCCH data broadcast by the first BTS  122  was successfully decoded using the first set of synchronization information ( 309 ). 
     If the control unit  210  determines that the BCCH data broadcast by the first BTS  122  was successfully decoded using the first set of synchronization ( 309 -Y), the control unit  210  may camp on the first BTS  122  ( 306 ). For example, the control unit  210  may successfully decode the BCCH data transmitted by the first BTS  122  using the first set of synchronization information. The control unit  210  may obtain sufficient information on the identity, configuration, and capabilities of the first BTS  122  to acquire the first communication network  120  and camp on the first BTS  122 . 
     Alternately, if the control unit  210  determines that the BCCH data broadcast by the first BTS  122  was not successfully decoded using the first set ( 309 -N), the control unit  210  may determine a cause of the BCCH decoding failure ( 310 ). The control unit  210  may be configured to determine whether the cause of the BCCH decoding failure is stale synchronization information in the first set of synchronization information ( 311 ). 
     If the control unit  210  determines that the cause of the BCCH decoding failure is not stale synchronization information in the first set of synchronization information ( 311 -N), the control unit  210  may attempt to acquire the first communication network  120  on the second BTS  124  ( 316 ). 
     The BCCH decoding on the first subscription  142  may have failed due to causes other than stale synchronization information in the first set of synchronization information. For example, BCCH decoding may fail due to low signal strength as the mobile communication device  110  travels beyond the coverage area of the first BTS  122 . If the BCCH decoding failed not because of stale synchronization information, then the control unit  210  may attempt to acquire the first communication network  120  on a different BTS. 
     For example, the control unit  210  may attempt to acquire the first communication network  120  on the second BTS  122 . The control unit  210  may decode the FCCH and SCH data transmitted by the second BTS  124  to in order to obtain information required to synchronize the mobile communication device  110  (e.g., the RF chain  230 ) to the frequency and timing of the second BTS  124 . The control unit  210  may use the synchronization information to decode the BCCH data transmitted by the second BTS  124  and camp on the second BTS  124   
     Alternately, if the control unit  210  determines that the cause of the BCCH decoding failure is stale synchronization information in the first set of synchronization information ( 311 -Y), the control unit  210  may repeat decoding of the FCCH and SCH data transmitted by the first BTS  122  to obtain a second set of synchronization information ( 312 ). The control unit  210  may decode the BCCH data transmitted by the first BTS  122  using the second set of synchronization information ( 314 ) and then camp on the first BTS  122  ( 306 ). 
     Since the second set of synchronization information may be a current set of synchronization information for the first BTS  122 , the control unit  210  may successfully decode the BCCH data broadcast by the first BTS  122  using the second set of synchronization information. By successfully decoding the BCCH data broadcast by the first BTS  122 , the control unit  210  may obtain sufficient information on the identity, configuration, and capabilities of the first BTS  122  to acquire the first communication network  120  and camp on the first BTS  122 . 
     For clarity and convenience, the process  300  is described with respect to the first subscription  142 . However, a person having ordinary skill in the art can appreciate that the control unit  210  may also perform the process  300  with respect to the second subscription  144  instead of or in addition to the first subscription  142  without departing from the scope of the present inventive concept. 
       FIG. 4A  is a flowchart illustrating a process  400  for determining a cause of BCCH decoding failure according to various embodiments. With reference to  FIGS. 1-4A , in various embodiments the process  400  may be performed by the control unit  210 , for example, by the causation module  214 , and may implement operation  310  of the process  300 . 
     The control unit  210  may measure one or more received signal strength indicators (RSSIs) of a signal transmitted by a BTS ( 402 ). For example, the control unit  210  may measure one or more RSSIs of the signal transmitted by the first BTS  122 . In various embodiments, the control unit  210  may measure RSSIs after postponing BCCH decoding but prior to decoding the BCCH data broadcast by the first BTS  122 . Alternately, the control unit  210  may measure RSSIs during or subsequent to the decoding of the BCCH data broadcast by the first BTS  122 . 
     The one or more RSSIs may include, for example, but not limited to, a received signal level (RxLev) and a received signal quality (RxQual). A person having ordinary skill in the art can appreciate that the control unit  210  may measure other or additional RSSIs without departing from the scope of the present inventive concept. A person having ordinary skill in the art can appreciate that the control unit  210  may measure a signal to noise ratio (SNR) instead of or in addition to RSSIs without departing from the scope of the present inventive concept. 
     The control unit  210  may determine whether the one or more RSSIs exceed corresponding predetermined thresholds ( 403 ). The predetermined threshold for RxLev may be, for example, equal to or less than −90 decibel-milliwatts (dBm) or another threshold value. The predetermined threshold for RxQual may be, for example, a Bit Error Rate (BER) of equal to or greater than 3.2% or another threshold value. Alternatively or additionally, the control unit  210  may determine whether the SNR exceeds a predetermined threshold value. 
     A failure to decode the BCCH data broadcast by the first BTS  122  may be attributable to poor signal quality and not stale synchronization information. The control unit  210  may determine that the one or more RSSIs do not exceed the corresponding thresholds ( 403 -N). For example, the control unit  210  may determine that the RxLev of the signal from the first BTS  122  is less than or equal to −90 dBm (or other thresholds) and/or that the RxQual of the signal has a BER of equal to or greater than 3.2% (or other thresholds). As a result, the control unit  210  may determine that the cause of the BCCH decoding failure is low signal strength ( 404 ). 
     Alternately, the failure to decode the BCCH data broadcast by the first BTS  122  may be attributable to stale synchronization information for the first BTS  122 . For example, the control unit  210  may have decoded the FCCH and SCH broadcast by the first BTS  122  to obtain information to synchronize the mobile communication device  110  to the frequency and timing of the first BTS  122 . However, BCCH decoding may have been postponed for a period of time thereafter. As a result, the synchronization information for the first BTS  122  may have become stale during the delay and the control unit  210  may be unable to decode the BCCH data broadcast by the first BTS  122 . 
     The control unit  210  may determine that the one or more RSSIs do exceed the corresponding thresholds ( 403 -Y). For example, the control unit  210  may determine that the RxLev of the signal from the first BTS  122  is greater than −90 dBm (or other thresholds) and/or that the RxQual of the signal has a BER of less than 3.2% (or other thresholds). Accordingly, the control unit  210  may have failed to decode the BCCH data broadcast by the first BTS  122  because the synchronization information became stale during the delay to decode BCCH data. Thus, the control unit  210  may determine that the cause of the BCCH decoding failure is stale synchronization information in the first set of synchronization information ( 406 ). 
       FIG. 4B  is a flowchart illustrating a process  450  for determining a cause of BCCH decoding failure according to various embodiments. With reference to  FIGS. 1-3 and 4B , in various embodiments the process  400  may be performed by the control unit  210 , for example, by the causation module  214 , and may implement operation  310  of the process  300 . 
     The control unit  210  may take a first measurement of one or more RSSIs of a signal transmitted by a BTS ( 452 ). For example, the control unit  210  may measure one or more RSSIs of the signal from the first BTS  122 . In various embodiments, the control unit  210  may take the first measurement of one or more RSSIs before or during the decoding of FCCH and SCH data broadcast by a BTS. Alternately, the control unit  210  may take the first measurement of after FCCH and SCH decoding but before postponing BCCH decoding. For example, the control unit  210  may take the first measurement of one or more RSSIs before, during, or after the decoding of FCCH and SCH data broadcast by the first BTS  122 . 
     The control unit  210  may take a second measurement of the one or more RSSIs of the signal transmitted by the BTS ( 454 ). The control unit  210  may take the second measurement of one or more RSSIs before, during, or after the decoding of BCCH data. For example, the control unit  210  may again measure the one or more RSSIs of the signal from the first BTS  122 . The control unit  210  may take the second measurement of one or more RSSIs after postponing BCCH decoding but prior to decoding the BCCH data broadcast by the first BTS  122 . Alternately, the control unit  210  may take the second measurement of one or more RSSIs during or after the decoding of the BCCH data broadcast by the first BTS  122 . 
     The one or more RSSIs may include, for example, but not limited to, a received signal level (RxLev) and a received signal quality (RxQual). A person having ordinary skill in the art can appreciate that the control unit  210  may measure other or additional RSSIs without departing from the scope of the present inventive concept. Furthermore, a person having ordinary skill in the art can appreciate that the first measurement and the second measurement may be taken of the same or different RSSIs without departing from the scope of the present inventive concept. 
     The control unit  210  may determine whether the second RSSI measurement is less than the first RSSI measurement, and whether a difference between the first RSSI measurement and the second RSSI measurement exceeds a predetermined threshold ( 455 ). When the second RSSI measurement is less than the first RSSI measurement, the difference between the first RSSI measurement and the second RSSI measurement may indicate an extent to which a quality of the signal from the first BTS  122  deteriorated between the two RSSI measurements. For example, the control unit  210  may determine whether the second RSSI measurement is less than the first RSSI measurement, and may compare the difference between the two RSSI measurements to a predetermined threshold in order to assess whether the quality of the signal from the first BTS  122  experienced significant deterioration since postponing BCCH decoding. 
     If the control unit  210  determines that the second RSSI measurement is less than the first RSSI measurement, and that the difference between the first RSSI measurement and the second RSSI measurement exceeds the predetermined threshold ( 455 -Y), the control unit  210  may determine that the cause of the BCCH decoding failure is deterioration in signal strength ( 456 ). The control unit  210  may successfully decode the FCCH and SCH broadcast by the first BTS  122  to obtain synchronization information for the first BTS  122 . 
     While the control unit  210  may postpone BCCH decoding, a subsequent failure to decode the BCCH data may be attributable to a significant deterioration in the quality of the signal from the first BTS  122  and not the synchronization information becoming stale during the delay. For example, the control unit  210  may determine that the BCCH decoding failure is not caused by stale synchronization information when a second RxLev is less than a first RxLev, and a difference between the first and the second RxLev is greater than 10 dBm (or other threshold values). The control unit  210  may also determine that the BCCH decoding did not fail due to stale synchronization information when a BER of the second RxQual is less than a BER of the first RxQual, and a difference between the BER of the first RxQual and the BER of the second RxQual is greater than 0.5% (or other threshold values). 
     Alternately, the control unit  210  may determine that the second RSSI measurement is not less than the first RSSI measurement, or that the difference between the first RSSI measurement and the second RSSI measurement does not exceed the predetermined threshold ( 455 -N). For example, the control unit  210  may determine that a second RxLev is greater than or equal to a first RxLev, or that a difference between the first RxLev and the second RxLev is less than or equal to 10 dBm (or other thresholds). Alternately, the control unit  210  may determine a BER of the second RxQual is greater than or equal to a BER of the first RxQual, or that a difference between the BER of the first RxQual and the BER of the second RxQual is less than or equal to 0.5% (or other thresholds). 
     If the second RSSI measurement is not less than the first RSSI measurement or if the difference between the two RSSI measurements does not exceed the predetermined threshold, then the quality of the signal from the first BTS  122  did not experience significant deterioration during the delay to decode the BCCH data broadcast by the first BTS  122 . Accordingly, the control unit  210  may determine that the cause of the BCCH decoding failure is stale synchronization information in the first set of synchronization information ( 458 ). 
     For clarity and convenience, the process  450  is described independently of the process  400 . However, a person having ordinary skill in the art can appreciate that either or both of the process  400  and the process  450  may implement operation  314  of the process  300 . 
       FIG. 5  is a flowchart illustrating a process  500  for determining a cause of BCCH decoding failure according to various embodiments. With reference to  FIGS. 1-5 , in various embodiments, the process  500  may be performed by the control unit  210 , for example, by the causation module  214 , and may implement operation  314  of the process  300 . 
     The control unit  210  may determine whether a BTS associated with a selected communication network is included in the database  282  ( 501 ). For example, the first communication network  120  may become a selected communication network as a result of manual or automatic communication network selection. On the one hand, manual communication network selection may be performed according to inputs from a user (e.g., via the input unit  272  of the user interface  270 ) of the mobile communication device  110 . Meanwhile, the control unit  210  may perform automatic communication network selection based on the priority of available and accessible communication networks. 
     The control unit  210  may determine whether the first BTS  122 , which is associated with the first communication network  120 , is included in the database  282 . The database  282  may store the ARFCN of at least one selected BTS on which the control unit  210  has attempted to acquire the first communication network  120 . The control unit  210  may determine whether the ARFCN of the first BTS  122  matches one of the ARFCNs stored in the database  282 . 
     If the control unit  210  has already attempted to acquire the first communication network  120  on a particular BTS, then the control unit  210  may have also already decoded the FCCH and SCH data broadcast by that BTS. Thus, if the ARFCN of the first BTS  122  matches one of the ARFCNs stored in the database  282 , then the first BTS  122  may have been a selected BTS and the control unit  210  may have already decoded the FCCH and SCH data broadcast by the first BTS  122 . 
     Although the control unit  210  may have already decoded the FCCH and SCH and obtained synchronization information for the first BTS  122 , the control unit  210  may nevertheless fail to successfully decode BCCH data broadcast by the first BTS  122 . In this case, the failure to decode BCCH data may be attributable to the synchronization information becoming stale during a delay between when FCCH and SCH data from the first BTS  122  was decoded and BCCH decoding. Thus, if the control unit  210  determines that the BTS associated with a selected communication network is included in the database ( 501 -Y), then the control unit  210  may determine that the cause of the BCCH decoding failure is stale synchronization information in the first set of synchronization information ( 502 ). 
     Alternately, the first BTS  122  may not be included in the database  282 . For example, the ARFCN of the first BTS  122  may not match one of the ARFCNs stored in the database  282 . In this case, the first BTS  122  may not have been a selected BTS and the control unit  210  may have not have already decoded the FCCH and SCH that was broadcast by the first BTS  122  to obtain synchronization information for the first BTS  122 . As such, any existing synchronization information may be for a different BTS. Therefore, if the control unit  210  determines that the BTS associated with the selected communication network is not included in the database ( 501 -N), the control unit  210  may determine that the cause of the BCCH decoding failure is the BTS not being a selected BTS ( 504 ). 
     For clarity and convenience, the process  500  is described independently of the process  400  and the process  450 . However, a person having ordinary skill in the art can appreciate that any combination of the process  400 , process  450 , and process  500  may implement operation  314  of the process  300 . 
     The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the protection. For example, the example apparatuses, methods, and systems disclosed herein may be applied to multi-SIM wireless devices subscribing to multiple communication networks and/or communication technologies. The various components illustrated in the figures may be implemented as, for example, but not limited to, software and/or firmware on a processor, ASIC/FPGA/DSP, or dedicated hardware. Also, the features and attributes of the specific example embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure. 
     The foregoing method descriptions and the process flow diagrams are provided merely as illustrative examples and are not intended to require or imply that the operations of the various embodiments must be performed in the order presented. As will be appreciated by one of skill in the art the order of operations in the foregoing embodiments may be performed in any order. Words such as “thereafter,” “then,” “next,” etc. are not intended to limit the order of the operations; these words are simply used to guide the reader through the description of the methods. Further, any reference to claim elements in the singular, for example, using the articles “a,” “an,” or “the” is not to be construed as limiting the element to the singular. 
     The various illustrative logical blocks, modules, circuits, and algorithm operations 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 operations 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. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present inventive concept. 
     The hardware used to implement the various illustrative logics, logical blocks, modules, and circuits described in connection with the various embodiments 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 device, 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 receiver devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Alternatively, some operations or methods may be performed by circuitry that is specific to a given function. 
     In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a non-transitory computer-readable storage medium or non-transitory processor-readable storage medium. The operations of a method or algorithm disclosed herein may be embodied in processor-executable instructions that may reside on a non- transitory computer-readable or processor-readable storage medium. Non-transitory computer-readable or processor-readable storage media may be any storage media that may be accessed by a computer or a processor. By way of example but not limitation, such non-transitory computer-readable or processor-readable storage media may include random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of non-transitory computer-readable and processor-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a non-transitory processor-readable storage medium and/or computer-readable storage medium, which may be incorporated into a computer program product. 
     Although the present disclosure provides certain example embodiments and applications, other embodiments that are apparent to those of ordinary skill in the art, including embodiments which do not provide all of the features and advantages set forth herein, are also within the scope of this disclosure. Accordingly, the scope of the present disclosure is intended to be defined only by reference to the appended claims.