WO2018090274A1

WO2018090274A1 - Mobile-assisted circuit switched fall back call rate improvement in multi-sim devices

Info

Publication number: WO2018090274A1
Application number: PCT/CN2016/106207
Authority: WO
Inventors: Ang Li; Muthukumaran Dhanapal; Xuepan GUAN; Jun Deng; Hewu GU; Xiaochen Chen; Peng Hu; Haizhou LIU; Nitin Pant; Subashini Krishnamurthy; Muralidharan Murugan; Ta-Yan Siu
Original assignee: Qualcomm Incorporated
Priority date: 2016-11-17
Filing date: 2016-11-17
Publication date: 2018-05-24

Abstract

A method for circuit switched fall back (CSFB) for a multi-subscriber identity module (SIM) mobile communication device, includes: initiating a CSFB procedure; receiving an RRC Connection Release message without a redirected Carrier lnfo information element (IE); collecting neighbor cell information (NCI); and performing circuit switched (CS) call redirection to a neighbor cell based on collected NCI (CNCI).

Description

MOBILE-ASSISTED CIRCUIT SWITCHED FALL BACK CALL RATE IMPROVEMENT IN MULTI-SIM DEVICES

BACKGROUND

During a mobile originated/mobile terminated (MO/MT) circuit switched fall back (CSFB) call setup procedure in a multi-Subscriber Identity Module (SIM) mobile communication device, when an RRCConnectionRelease over-the-air (OTA) message is received by the mobile communication device, the mobile communication device will release the long term evolution (LTE) radio resource control (RRC) connection and attempt to connect to a 2G/3G cell to setup the circuit-switched (CS) call. When the information element (IE) redirectedCarrierInfo is not present in the RRCConnectionRelease message, the mobile communication device does not obtain frequency information to perform a redirection to the 2G/3G cell. As a result, a full band scan has to be performed. However, a full band scan is much more time-consuming than a redirection and can even result in a dropped call caused by a connection time-out leading to a sub-optimal user experience in a multi-SIM (MS) mobile communication device.

SUMMARY

Apparatuses and methods for mobile assisted CSFB in a multi-SIM mobile communication device are provided.

According to various aspects there is provided a method for circuit switched fallback (CSFB) for a multi-subscriber identity module (SIM) mobile communication device. In some aspects, the method may include: initiating a CSFB procedure； receiving an RRCConnectionRelease message without a redirectedCarrierInfo information element (IE) ； collecting neighbor cell information (NCI) ； and performing circuit switched (CS) call redirection to a neighbor cell based on collected NCI (CNCI) .

According to various aspects there is provided a multi-subscriber identity module (SIM) mobile communication device. In some aspects, the multi-SIM mobile communication device may include: a communication unit； a memory； and a control unit operably connected to the communication unit and the memory.

The control unit may be configured to: initiate a circuit switched fallback (CSFB) procedure； control the communication unit to receive an RRCConnectionRelease message without a redirectedCarrierInfo information element (IE) from one of the two or more communication networks； control the communication unit to collect neighbor cell information (NCI) ； and control the communication unit to perform circuit switched (CS) call redirection to a neighbor cell based on collected NCI (CNCI) .

According to various aspects there is provided a multi-subscriber identity module (SIM) mobile communication device. In some aspects, the multi-SIM mobile communication device may include: means for initiating a circuit switched fallback (CSFB) procedure； receiving an RRCConnectionRelease message without a redirectedCarrierInfo information element (IE) ； means for collecting neighbor cell information (NCI) ； and means for performing circuit switched (CS) call redirection to a neighbor cell based on collected NCI (CNCI) .

According to various aspects there is provided a non-transitory computer readable medium. In some aspects, the non-transitory computer readable medium may include instructions for causing one or more processors to perform operations including: initiating a circuit switched fallback (CSFB) procedure on a multi-subscriber identity module (SIM) mobile communication device； receiving an RRCConnectionRelease message without a redirectedCarrierInfo information element (IE) ； collecting neighbor cell information (NCI) ； and performing circuit switched (CS) call redirection to a neighbor cell based on collected NCI (CNCI) .

Other features and advantages should be apparent from the following description which illustrates by way of example aspects of the various teachings of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects and features of the various embodiments will be more apparent by describing examples with reference to the accompanying drawings, in which:

FIG. 1A is a block diagram illustrating a mobile communication device according to various embodiments；

FIG. 1B is a diagram illustrating a network environment for various embodiments；

FIG. 2 is a sequence diagram illustrating a CNCI based redirection procedure in accordance with certain aspects of the disclosure；

FIG. 3 is a flowchart illustrating a method for CNCI collection in accordance with certain aspects of the disclosure； and

FIG. 4 is a flowchart illustrating a method for CNCI Prioritization in accordance with certain aspects of the disclosure.

DETAILED DESCRIPTION

While certain embodiments are described, these embodiments are presented by way of example only, and are not intended to limit the scope of protection. The apparatuses, methods, and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and changes in the form of the example methods and systems described herein may be made without departing from the scope of protection.

FIG. 1A is a block diagram illustrating a mobile communication device 100 according to various embodiments. As illustrated in FIG. 1A, the mobile communication device 100 may include a control unit 110, a communication unit 120, an antenna 130, a first subscriber identity module (SIM) 140, a second SIM 150, a user interface device 170, and a memory 180.

The mobile communication device 100 may be, for example but not limited to, a mobile telephone, smartphone, tablet, computer, etc., capable of communications with one or more wireless networks. One of ordinary skill in the art will appreciate that the mobile communication device 100 may include one or more communication units and may interface with one or more antennas without departing from the scope of protection.

The communication unit 120 may include, for example, but not limited to, a radio frequency (RF) module 121. The RF module 121 may include, for example, but not limited to a transceiver 122. An RF chain 135 may include, for example, but not limited to the antenna 130 and the RF module 121.

One of ordinary skill in the art will appreciate that embodiments of the mobile communication device 100 may include more than one communication unit and/or more than one antenna without departing from the scope of protection.

A SIM (for example the first SIM 140 and/or the second SIM 150) in various embodiments may be a universal integrated circuit card (UICC) that is configured with SIM and/or universal SIM (USIM) applications, enabling access to global system for mobile communications (GSM) and/or universal mobile telecommunications system (UMTS) networks. The UICC may also provide storage for a phone book and other applications. Alternatively, in a code division multiple access (CDMA) network, a SIM may be a UICC removable user identity module (R-UIM) or a CDMA subscriber identity module (CSIM) on a card. A SIM card may have a CPU, ROM, RAM, EEPROM and I/O circuits. An integrated circuit card identity (ICCID) SIM serial number may be printed on the SIM card for identification. However, a SIM may be implemented within a portion of memory of the mobile communication device 100, and thus need not be a separate or removable circuit, chip, or card.

A SIM used in various embodiments may store user account information, an international mobile subscriber identity (IMSI) , a set of SIM application toolkit (SAT) commands, and other network provisioning information, as well as provide storage space for phone book database of the user’s contacts. As part of the network provisioning information, a SIM may store home identifiers (e.g., a system identification number (SID) /network identification number (NID) pair, a home public land mobile network (HPLMN) code, etc. ) to indicate the SIM card network operator provider.

The first SIM 140 may associate the communication unit 120 with a first subscription (Sub1) 192 associated with a first radio access technology (RAT) on a first communication network 190 and the second SIM 150 may associate the communication unit 120 with a second subscription (Sub2) 197 associated with a second RAT on a second communication network 195. When a RAT is active, the communication unit 120 receives and transmits signals on the active RAT. When a RAT is idle, the communication unit 120 may receive but not transmit signals on the idle RAT.

For convenience, the various embodiments are described in terms of dual-SIM dual-standby (DSDS) mobile communication devices. However, one of ordinary skill in the art will appreciate that the various embodiments may be extended to Multi-SIM Multi-Standby (MSMS) and/or Multi-SIM Multi-Active (MSMA) mobile communication devices without departing from the scope of protection.

The first communication network 190 and the second communication network 195 may be operated by the same or different service providers, and/or may support the same or different RATs, for example, but not limited to, GSM, CDMA, Time Division Synchronous CDMA (TDSCDMA) , wideband CDMA (WCDMA) , long term evolution (LTE) , and 5G.

The user interface device 170 may include an input device 172, for example, but not limited to a keyboard, touch panel, or other human interface device, and a display device 174, for example, but not limited to, a liquid crystal display (LCD) , light emitting diode (LED) display, or other video display. One of ordinary skill in the art will appreciate that other input and display devices may be used without departing from the scope of the various embodiments.

The control unit 110 may be configured to control overall operation of the mobile communication device 100 including control of the communication unit 120, the user interface device 170, and the memory180. The control unit 110 may be a programmable device, for example, but not limited to, a microprocessor (e.g., general-purpose processor, baseband modem processor, etc. ) or microcontroller.

The memory 180 may be configured to store operating systems and/or application programs for operation of the mobile communication device 100 that are executed by the control unit 110, as well as to store application data and user data.

FIG. 1B is a diagram illustrating a network environment 105 for various embodiments. Referring to FIGS. 1A and 1B, a mobile communication device 100 may be configured to communicate with a first communication network 190 on a first subscription 192 and a second communication network 195 on a second subscription 197. One of ordinary skill in the art will appreciate that the mobile communication device may configured to communicate with more than two communication networks and may communicate on more than two subscriptions without departing from the scope of protection.

The first communication network 190 and the second communication network 195 may implement the same or different radio access technologies (RATs) . For example, the first communication network 190 may be an LTE network and the first subscription 192 may be an LTE subscription. The second communication network 195 may also be an LTE network. Alternatively, the second communication network 195 may implement another RAT including, for example, but not limited to, Global System for Mobile communication (GSM) , Code Division Multiple Access (CDMA) , Wideband CDMA (WCDMA) , Time Division-Synchronous CDMA (TD-SCDMA) and 5G.

The first communication network 190 may include one or more base transceiver stations (BTSs) including, for example, but not limited to, a first BTS 193. The second communication network 195 may also include one or more BTSs, including, for example, but not limited to, a second BTS 198. A person having ordinary skill in the art will appreciate that the network environment 105 may include any number of communication networks, mobile communication devices, and BTSs without departing from the scope of the various embodiments.

The mobile communication device 100 may attempt to acquire the first communication network 190 and camp on the first BTS 193. The mobile communication device 100 may also attempt to acquire the second communication network 195 and camp on the second BTS 198. A person having ordinary skill in the art will appreciate that the acquisition of the first communication network 190 performed on the first subscription 192 may be independent of the acquisition of the second communication network 195 performed on the second subscription 197. Furthermore, the mobile communication device 100 may attempt to acquire the first communication network 190 on the first subscription 192 and the second communication network 195 on the second subscription 197.

In accordance with certain aspects of the present disclosure, a mobile communication device (e.g., the mobile communication device 100) may trigger a service request to 2G/3G with cell priority information that is derived from CNCI as an alternative manner of redirection. Certain aspects of the present disclosure use Collected Neighbor Cell Information (CNCI) to perform a redirection to a 2G/3G cell when the information element (IE) redirectedCarrierInfo is not present in the RRCConnectionRelease OTA message during a CSFB call setup procedure.

Aspects of the present disclosure may be applied to RAT1-to-RAT2 redirection scenarios where RAT1 and RAT2 may be any cellular RATs including 5G, for example, but not limited to, LTE-to-GSM, LTE-to-TDSCDMA, LTE-to-CDMA, WCDMA-to-LTE, 5G-to-LTE, etc. Redirection in accordance with certain aspects of the present disclosure may provide improved CSFB call rate for the subscription performing CSFB as well as improved page performance for the other subscription.

CNCI collection may be triggered when: 1) a CSFB call is started (Or any other similar procedure is started) ； and 2) an RRCConnectionRelease OTA message is received but the IE redirectedCarrierInfo is not present in the message. In accordance with certain aspects of the present disclosure, CNCI may be collected, prioritized, and utilized to perform CNCI-based redirection. An alternative way of redirecting involves an upper layer triggering a service request to a 2G/3G cell using cell priority information that is derived from CNCI.

FIG. 2 is a sequence diagram 200 illustrating a CNCI based redirection procedure for MO CSFB in accordance with certain aspects of the disclosure. Referring to FIG. 2, a CSFB call or other similar procedure may be started or triggered when a CSFB-Started-Indicator signal 202 is sent from the non-access stratum (NAS) layer to the RRC layer of the mobile communication device 100 and the mobile communication device 100 may receive an RRCConnectionRelease OTA message 208 from a network (e.g., the first communication network 190 or the second communication network 195) without the redirectedCarrierInfo IE present in the message. The NAS comprises functions and protocols that support traffic and signaling between a terminal and a core network.

In another example, an Extended Service Request NAS message 204 may also be sent to the RRC layer. The Extended Service Request NAS message 204 may be sent to the network by the mobile communication device 100 to begin a CSFB or respond to a CSFB message from the network. In addition, the Extended Service Request NAS message 204 may be used by the mobile communication device 100 to establish NAS messaging. The mobile communication device 100 may initiate an uplink (UL) Information Transfer 206 to transfer NAS information to the mobile communication device 100 if the mobile communication device 100 is in an RRC Connected state.

At block 220 the mobile communication device 100 may initiate CNCI collection. At block 230, it may be determined whether CNCI collection succeeded. The mobile communication device 100 may determine that CNCI collection succeeded when NCI is collected from at least one neighbor cell.

In response to determining that the CNCI collection succeeded (230-Y) the mobile communication device 100 may perform CNCI-based redirection at block 240. In response to determining that CNCI collection did not succeed (230-N) , at block 250 the mobile communication device 100 may perform the RRC connection release procedure.

FIG. 3 is a flowchart illustrating a method for CNCI collection in accordance with certain aspects of the disclosure. Referring to FIG. 3, a target CSFB RAT may be determined based on the RAT priority of the serving cell public land mobile network (PLMN) stored in the mobile communication device 100. The sources of neighbor cell information (NCI) are neighbor cells (i.e., frequencies) that are configured in system information blocks (SIBs) , and neighbor cells (i.e., frequencies) that are configured via the MeasConfig IE in the RRCConnectionReconfiguration OTA message.

At block 310, the mobile communication device 100 may determine whether CSFB to 3G (i.e., universal mobile telecommunications service (UMTS) ) is preferred based upon the RAT priority of the serving PLMN. In response to determining that CSFB to 3G is preferred (310-Y) , at block 320 the mobile communication device 100 may collect 3G RAT (e.g., WCDMA, TDSCDMA, etc. ) NCI.

If the mobile communication device 100 is in connected mode with a neighbor cell, 3G NCI may be collected via the system information blocks (SIB) , for example, SIB6 for TDSCDMA/WCDMA, and/or from the MeasConfig IE in the RRCConnectionReconfiguration message. If the mobile communication device 100 is in idle mode, 2G NCI may be collected via SIBs. The CNCI may be stored in the mobile communication device 100, for example, in the memory 180.

At block 350, the mobile communication device 100 may determine whether NCI was collected from at least one neighbor cell. In response to determining that NCI was not collected from at least one neighbor cell (350-N) , the CNCI procedure fails. In response to determining that NCI was collected from at least one neighbor cell (350-Y) , the mobile communication device 100 may determine that the CNCI procedure succeeded and at block 360 may perform CNCI prioritization.

In response to determining that CSFB to 3G is not preferred (310-N) , at block 330 the mobile communication device 100 may determine that CSFB to 1x/2G (i.e., CDMA, high rate packet data (HRPD) and/or GSM EDGE Radio Access Network (GERAN) is preferred based upon the RAT priority of the serving PLMN. At block 340 the mobile communication device 100 may collect 2G RAT (e.g., GSM, CDMA, etc. ) NCI.

If the mobile communication device 100 is in connected mode with a neighbor cell, 2G NCI may be collected via the SIBS, for example SIB7 for GSM, and/or from the MeasConfig IE in the RRCConnectionReconfiguration message. Similarly, 1x may be collected via the SIBS, for example SIB8, and/or from the MeasConfig IE in the RRCConnectionReconfiguration message. If the mobile communication device 100 is in idle mode, 2G NCI or 1x NCI may be collected via SIBs. The CNCI may be stored in the mobile communication device 100, for example, in the memory 180.

Each neighbor cell may operate on more than one frequency for the target RAT. Signal strength measurements may be made on only one frequency for the target RAT but additional frequency information may be received from the CNCI.

FIG. 4 is a flowchart illustrating a method for CNCI Prioritization in accordance with certain aspects of the disclosure. Referring to FIG. 4, the order of the collected neighbor cells (i.e., CNCI Prioritization) may be determined by: 1) connected mode neighbors with higher most recent signal strength measurement result； and 2) idle mode neighbors with higher most resent signal strength measurement result. If signal strength measurement results between two neighbors have a same value, for example -98 dBm or another value, then prioritization may be determined based on the presence of the target RAT frequency for the neighbor cell in a target RAT acquisition database stored on the mobile communication device 100 and/or information on the historical number of successful redirections/reselections to the target RAT frequency for the neighbor cell stored on the mobile communication device 100.

At block 410, the control unit 110 may obtain neighbor cell target RAT information stored in the target RAT acquisition database. At block 420, the control unit 110 may obtain the historical number of successful neighbor cell redirections/reselections to the target RAT frequency. At block 430 the control unit 110 may obtain CNCI for connected mode neighbor cells stored on the mobile communication device 100. At block 440 the control unit 110 may obtain CNCI for idle mode neighbor cells stored on the mobile communication device 100.

The control unit 110 may perform CNCI prioritization in order of CNCI for connected mode neighbors, historical number of successful redirections/reselections and/or presence in the target RAT acquisition database for connected mode neighbors, the CNCI for idle mode neighbors, and historical number of successful redirections/reselections and/or target RAT acquisition database for idle mode neighbors.

At block 450, the control unit 110 may determine whether CNCI for connected mode neighbors has been obtained. In response to determining that CNCI for connected mode neighbors has been obtained, the control unit 110 may determine which connected mode neighbor cell has the highest signal strength for the target RAT frequency. The control unit 110 may select the connected mode neighbor cell having the highest signal strength for the target RAT frequency for redirections/reselection.

In response to determining that two or more connected mode neighbor cells have substantially same signal strengths for the target RAT frequency, the control unit 110 may select the connected mode neighbor cell having a higher historical number of successful redirections/reselections. In response to determining that the two or more connected mode neighbor cells have a same historical number of successful redirections/reselections, the control unit 110 may select the connected mode neighbor cell having a presence in the target RAT acquisition database. In response to determining that the two or more connected mode neighbor cells have a presence in the target RAT acquisition database, the control unit 110 may randomly select one of the connected mode neighbor cells for redirections/reselection.

In response to determining that CNCI for connected mode neighbors has not been obtained, at block 460 the control unit 110 may determine whether successful redirections/reselections have been performed for connected mode neighbor cells. The control unit 110 may select the connected mode neighbor cell having successful redirections/reselections with the highest signal strength for redirections/reselection. In response to determining that two or more connected mode neighbor cells have a substantially same signal strength, the control unit 110 may select the connected mode neighbor cell having a higher number of successful redirections/reselections. In response to determining that two or more connected mode neighbor cells have a same number of successful redirections/reselections, the control unit 110 may select the connected mode neighbor cell having a presence in the target RAT acquisition database. In response to determining that the two or more connected mode neighbor cells have a presence in the target RAT acquisition database, the control unit 110 may randomly select one of the connected mode neighbor cells for redirections/reselection.

In response to determining that connected mode neighbor cells have not been detected, at block 470 the control unit 110 may determine whether CNCI for idle mode neighbors has been obtained. In response to determining that CNCI for idle mode neighbors has been obtained, the control unit 110 may determine which idle mode neighbor cell has the highest signal strength for the target RAT frequency. The control unit 110 may select the idle mode neighbor cell having the highest signal strength for the target RAT frequency for redirections/reselection.

In response to determining that two or more idle mode neighbor cells have substantially same signal strengths for the target RAT frequency, the control unit 110 may select the item mode neighbor cell having a higher historical number of successful redirections/reselections. In response to determining that the two or more idle mode neighbor cells have a same historical number of successful redirections/reselections, the control unit 110 may select the item mode neighbor cell having a presence in the target RAT acquisition database. In response to determining that the two or more idle mode neighbor cells have a presence in the target RAT acquisition database, the control unit 110 may randomly select one of the mode neighbor cells for redirections/reselection.

In response to determining that CNCI for idle mode neighbors has not been obtained, at block 480 the control unit 110 may determine whether successful redirections/reselections have been performed for idle mode neighbor cells. The control unit 110 may select the idle mode neighbor cell having successful redirections/reselections with the highest signal strength for redirections/reselection. In response to determining that two or more idle mode neighbor cells have a substantially same signal strength, the control unit 110 may select the idle mode neighbor cell having a higher number of successful redirections/reselections. In response to determining that two or more idle mode neighbor cells have a same number of successful redirections/reselections, the control unit 110 may select the idle mode neighbor cell having a presence in the target RAT acquisition database. In response to determining that the two or more idle mode neighbor cells have a presence in the target RAT acquisition database, the control unit 110 may randomly select one of the idle mode neighbor cells for redirections/reselection.

After selecting a neighbor cell for redirections/reselection, the control unit 110 may control the mobile communication device 100 to perform an RRC Connection Release procedure.

The

methods

200, 300, and 400, respectively, may be embodied on a non-transitory computer readable medium, for example, but not limited to, the memory 180 or other non-transitory computer readable medium known to those of skill in the art, having stored therein a program including computer executable instructions for making a processor, computer, or other programmable device execute the operations of the methods.

The various embodiments illustrated and described are provided merely as examples to illustrate various features of the claims. However, features shown and described with respect to any given embodiment are not necessarily limited to the associated embodiment and may be used or combined with other embodiments that are shown and described. Further, the claims are not intended to be limited by any one example embodiment.

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 can 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 various embodiments.

The hardware used to implement the various illustrative logics, logical blocks, modules, and circuits described in connection with the aspects 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 aspects, 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 RAM, ROM, 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.

Claims

A method for circuit switched fallback (CSFB) for a multi-subscriber identity module (SIM) mobile communication device, the method comprising:

initiating a CSFB procedure；

receiving an RRCConnectionRelease message without a redirectedCarrierInfo information element (IE) ；

collecting neighbor cell information (NCI) ； and

performing circuit switched (CS) call redirection to a neighbor cell based on collected NCI (CNCI) .
The method of claim 1, wherein the collecting NCI comprises:

determining a preferred target radio access technology (RAT) for CSFB based upon a RAT priority of a serving public land mobile network (PLMN) stored in the multi-SIM mobile communication device.
The method of claim 1, wherein the collecting NCI comprises:

collecting NCI from system information blocks (SIBs) and a MeasConfig information element (IE) when the multi-SIM mobile communication device is in connected mode with a neighbor cell.
The method of claim 3, further comprising:

collecting NCI from only at least one of the SIBs when the multi-SIM mobile communication device is in idle mode with a neighbor cell.
The method of claim 1, further comprising:

determining the collecting NCI is successful when CNCI is obtained from at least one neighbor cell.
The method of claim 1, further comprising:

performing CNCI prioritization.
The method of claim 6, wherein the performing CNCI prioritization comprises:

obtaining neighbor cell target RAT information stored in a target RAT acquisition database stored on the multi-SIM mobile communication device and reordering neighbor cells in the target RAT acquisition database based on signal strength；

obtaining a historical number of successful neighbor cell redirections/reselections to a frequency of a target RAT stored on the multi-SIM mobile communication device and reordering neighbor cells having the historical number of successful neighbor cell redirections/reselections based on signal strength；

obtaining CNCI for connected mode neighbor cells stored on the multi-SIM mobile communication device and reordering the connected mode neighbor cells based on signal strength； and

obtaining CNCI for idle mode neighbor cells stored on the multi-SIM mobile communication device and reordering the idle mode neighbor cells based on signal strength.
The method of claim 7, wherein the performing CNCI prioritization further comprises:

prioritizing the neighbor cells for reselection in a preferred order of the connected mode neighbor cells having CNCI, the connected mode neighbor cells in the target RAT acquisition database having a historical number of successful redirections/reselections, the idle mode neighbor cells having CNCI, and the idle mode neighbor cells in the target RAT acquisition database having a historical number of successful redirections/reselections.
The method of claim 8, further comprising:

selecting a neighbor cell highest in the preferred order having a highest signal strength as the neighbor cell for reselection.
A multi-subscriber identity module (SIM) mobile communication device, comprising:

a communication unit；

a memory； and

a control unit operably connected to the communication unit and the memory, the control unit configured to:

initiate a circuit switched fallback (CSFB) procedure；

control the communication unit to receive an RRCConnectionRelease message without a redirectedCarrierInfo information element (IE) from one of two or more communication networks；

control the communication unit to collect neighbor cell information (NCI) ； and

control the communication unit to perform circuit switched (CS) call redirection to a neighbor cell based on collected NCI (CNCI) .
The multi-SIM mobile communication device of claim 10, wherein the control unit is further configured to:

determine a preferred target radio access technology (RAT) for CSFB based upon a RAT priority of a serving public land mobile network (PLMN) stored in the multi-SIM mobile communication device.
The multi-SIM mobile communication device of claim 10, wherein the control unit is further configured to:

control the communication unit to collect NCI from system information blocks (SIBs) and a MeasConfig information element (IE) when the multi-SIM mobile communication device is in connected mode with a neighbor cell.
The multi-SIM mobile communication device of claim 12, wherein the control unit is further configured to:

control the communication unit to collect NCI from only at least one of the SIBs when the multi-SIM mobile communication device is in idle mode with a neighbor cell.
The multi-SIM mobile communication device of claim 10, wherein the control unit is further configured to determine the collecting NCI is successful when CNCI is obtained from at least one neighbor cell.
The multi-SIM mobile communication device of claim 10, wherein the control unit is further configured to:

perform CNCI prioritization.
The multi-SIM mobile communication device of claim 15, wherein the control unit is further configured to perform the CNCI prioritization by:

obtaining neighbor cell target RAT information stored in a target RAT acquisition database stored on the multi-SIM mobile communication device and reordering neighbor cells in the target RAT acquisition database based on signal strength；

obtaining a historical number of successful neighbor cell redirections/reselections to a frequency of a target RAT stored on the multi-SIM mobile communication device and reordering neighbor cells having the historical number of successful neighbor cell redirections/reselections based on signal strength；

obtaining CNCI for connected mode neighbor cells stored on the multi-SIM mobile communication device and reordering the connected mode neighbor cells based on signal strength； and

obtaining CNCI for idle mode neighbor cells stored on the multi-SIM mobile communication device and reordering the idle mode neighbor cells based on signal strength.
The multi-SIM mobile communication device of claim 16, wherein the control unit is further configured to perform the CNCI prioritization by:

prioritizing the neighbor cells for reselection in a preferred order of the connected mode neighbor cells having CNCI, the connected mode neighbor cells in the target RAT acquisition database having a historical number of successful redirections/reselections, the idle mode neighbor cells having CNCI, and the idle mode neighbor cells in the target RAT acquisition database having a historical number of successful redirections/reselections.
The multi-SIM mobile communication device of claim 17, wherein the control unit is further configured to select a neighbor cell highest in the preferred order having a highest signal strength as the neighbor cell for reselection.
A non-transitory computer readable medium having stored thereon instructions for causing one or more processors to perform operations comprising:

initiating a circuit switched fallback (CSFB) procedure on a multi-subscriber identity module (SIM) mobile communication device；

receiving an RRCConnectionRelease message without a redirectedCarrierInfo information element (IE) ；

collecting neighbor cell information (NCI) ； and

performing circuit switched (CS) call redirection to a neighbor cell based on collected NCI (CNCI) .
The non-transitory computer readable medium having stored therein instructions as defined in claim 19, the instructions further including:

determining a preferred target radio access technology (RAT) for CSFB based upon a RAT priority of a serving public land mobile network (PLMN) stored in the multi-SIM mobile communication device； and

collecting NCI from system information blocks (SIBs) and a MeasConfig information element (IE) when the multi-SIM mobile communication device is in connected mode with a neighbor cell.
The non-transitory computer readable medium having stored therein instructions as defined in claim 18, the instructions further including:

collecting NCI from only the SIBs when the multi-SIM mobile communication device is in idle mode with a neighbor cell.
The non-transitory computer readable medium having stored therein instructions as defined in claim 19, the instructions further including:

performing CNCI prioritization.
A multi-subscriber identity module (SIM) mobile communication device, comprising:

means for initiating a circuit switched fallback (CSFB) procedure；

receiving an RRCConnectionRelease message without a redirectedCarrierInfo information element (IE) ；

means for collecting neighbor cell information (NCI) ； and

means for performing circuit switched (CS) call redirection to a neighbor cell based on collected NCI (CNCI) .
The multi-SIM mobile communication device of claim 23, further comprising:

means for determining a preferred target radio access technology (RAT) for CSFB based upon a RAT priority of a serving public land mobile network (PLMN) stored in the multi-SIM mobile communication device.
The multi-SIM mobile communication device of claim 23, further comprising:

means for collecting NCI from system information blocks (SIBs) and a MeasConfig information element (IE) when the multi-SIM mobile communication device is in connected mode with a neighbor cell.
The multi-SIM mobile communication device of claim 25, further comprising:

means for collecting NCI from only at least one of the SIBs when the multi-SIM mobile communication device is in idle mode with a neighbor cell.
The multi-SIM mobile communication device of claim 23, further comprising:

means for performing CNCI prioritization.
The multi-SIM mobile communication device of claim 27, wherein the means for performing CNCI prioritization comprises:

means for obtaining neighbor cell target RAT information stored in a target RAT acquisition database stored on the multi-SIM mobile communication device and reordering neighbor cells in the target RAT acquisition database based on signal strength；

means obtaining a historical number of successful neighbor cell redirections/reselections to a frequency of a target RAT stored on the multi-SIM mobile communication device and reordering neighbor cells having the historical number of successful neighbor cell redirections/reselections based on signal strength；

means for obtaining CNCI for connected mode neighbor cells stored on the multi-SIM mobile communication device and reordering the connected mode neighbor cells based on signal strength； and

means for obtaining CNCI for idle mode neighbor cells stored on the multi-SIM mobile communication device and reordering the idle mode neighbor cells based on signal strength.
The multi-SIM mobile communication device of claim 28, wherein the means for performing CNCI prioritization further comprises:

means for prioritizing the neighbor cells for reselection in a preferred order of the connected mode neighbor cells having CNCI, the connected mode neighbor cells in the target RAT acquisition database having a historical number of successful redirections/reselections, the idle mode neighbor cells having CNCI, and the idle mode neighbor cells in the target RAT acquisition database having a historical number of successful redirections/reselections.
The multi-SIM mobile communication device of claim 29, further comprising:

means for selecting a neighbor cell highest in the preferred order having a highest signal strength as the neighbor cell for reselection.