Abstract:
A mobile communication device is provided with a wireless module and a controller module. The wireless module performs wireless transmissions and receptions to and from a first Public Land Mobile Network (PLMN) and a second PLMN. The controller module performs a signaling procedure with the first PLMN via the wireless module, and performs a PLMN selection procedure via the wireless module without retrying the signaling procedure with the first PLMN, in response to the signaling procedure being failed with a rejection cause indicating a network failure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Application claims priority of U.S. Provisional Application No. 61/680,848, filed on Aug. 8, 2012, and the entirety of which is incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention generally relates to the operation of a User Equipment (UE) during a signaling procedure with a Public Land Mobile Network (PLMN), and more particularly, to apparatuses and methods for recovering service from a signaling procedure rejected with network failure. 
         [0004]    2. Description of the Related Art 
         [0005]    With growing demand for ubiquitous computing and networking, various wireless technologies have been developed, such as the Wireless Local Area Network (WLAN) technologies, including the Wireless Fidelity (WiFi) technology, Bluetooth technology, and the Zigbee technology, etc., and also, the cellular technologies, including the Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, Time-Division LTE (TD-LTE) technology, and LTE-Advanced technology, etc. 
         [0006]    For user convenience and flexibility, most User Equipments (UEs) (or may be referred to as Mobile Stations (MSs)) nowadays support more than one wireless technology, and most Public Land Mobile Networks (PLMNs) support multiple wireless technologies for providing wireless services to the UEs. Taking a UE supporting the GSM/GPRS/EDGE technology, the WCDMA technology, and the LTE technology for example, it may camp on a PLMN to obtain wireless services using one of the supported wireless technologies. While the UE is camped on a PLMN, it may perform signaling procedures, such as attach procedures, location update procedures, routing area update procedures, and/or tracking area update procedures, with the PLMN. 
         [0007]    However, there are situations where the network element(s), e.g., Base Station (BS), Node-B, or others, of the PLMN in the area of the UE&#39;s location may be under maintenance, e.g., backbone environment fixing or system configuration updates. In such cases, the signaling procedure performed with the PLMN by the UE will be rejected due to network failure, and according to chapter 5 of the 3GPP TS 24.301 specification and chapter 4 of the 3GPP TS 24.008 specification, the UE will keep retrying the signaling procedure for several times with the same PLMN using the same wireless technology as it earlier used for camping on the PLMN. Unfavorably, during this time, the UE cannot obtain wireless services, and even worse, the maintenance of the network element(s) may take a long time. As a result, the user of the UE may unexpectedly experience a long break of services. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    In order to solve the aforementioned problem, the invention proposes apparatuses and methods for a UE to recover service from a signaling procedure rejected with network failure, by performing a PLMN selection procedure with different PLMNs or with the same PLMN using different wireless technologies without retrying the signaling procedure. 
         [0009]    In one aspect of the invention, a mobile communication device is provided. The mobile communication device comprises a wireless module and a controller module. The wireless module performs wireless transmissions and receptions to and from a first Public Land Mobile Network (PLMN) and a second PLMN. The controller module performs a signaling procedure with the first PLMN via the wireless module, and performs a PLMN selection procedure via the wireless module without retrying the signaling procedure with the first PLMN, in response to the signaling procedure being failed with a rejection cause indicating a network failure. 
         [0010]    In another aspect of the invention, a method for a mobile communication device to recover service from a signaling procedure rejected with a network failure is provided. The method comprises the steps of performing the signaling procedure with a first PLMN; and performing a PLMN selection procedure without retrying the signaling procedure with the first PLMN, in response to the signaling procedure being failed with a rejection cause indicating a network failure. 
         [0011]    Other aspects and features of the present invention will become apparent to those with ordinarily skill in the art upon review of the following descriptions of specific embodiments of the mobile communication devices and the methods for recovering service from a signaling procedure rejected with a network failure. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]    The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a block diagram of a wireless communications environment according to an embodiment of the invention; 
           [0014]      FIG. 2  is a block diagram illustrating the mobile communication device  110  according to an embodiment of the invention; 
           [0015]      FIG. 3  is a flow chart illustrating the method for a mobile communication device to recover service from a signaling procedure rejected with network failure according to an embodiment of the invention; and 
           [0016]      FIG. 4  is a flow chart illustrating the method for a mobile communication device to recover service from a signaling procedure rejected with network failure according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. It should be understood that the embodiments may be realized in software, hardware, firmware, or any combination thereof. 
         [0018]      FIG. 1  is a block diagram of a wireless communications environment according to an embodiment of the invention. The wireless communications environment  100  comprises a mobile communication device  110  and two PLMNs  120  and  130 , wherein the mobile communication device  110  may selectively camp on one of the PLMNs  120  and  130  to obtain wireless services. Each of the PLMNs  120  and  130  comprises at least two service networks utilizing different wireless technologies. Specifically, the PLMN  120  comprises the service networks  121  and  122 , and the PLMN  130  comprises the service networks  131  and  132 , wherein each of the service networks  121 ,  122 ,  131 , and  132  comprises an access network and a core network. 
         [0019]    For example, the PLMN  120  may be deployed by an operator A, and the service network  121  may be a Universal Mobile Telecommunications System (UMTS), wherein the access network  11  may be a Universal Terrestrial Radio Access Network (UTRAN) and the core network  12  may be a General Packet Radio Service (GPRS) core which includes a Home Location Register (HLR), at least one Serving GPRS Support Node (SGSN), and at least one Gateway GPRS Support Node (GGSN), while the service network  122  may be an LTE/LTE-Advanced system, the access network  21  may be an Evolved-UTRAN (E-UTRAN) and the core network  22  may be an Evolved Packet Core (EPC) which includes a Home Subscriber Server (HSS), Mobility Management Entity (MME), Serving Gateway (S-GW), and Packet Data Network Gateway (PDN-GW or P-GW). 
         [0020]    The PLMN  130  may be deployed by an operator B, and the service network  131  may be a GPRS/EDGE system, wherein the access network  31  may be a Base Station Subsystem (BSS) and the core network  32  may be a GPRS core which includes an HLR, at least one SGSN, and at least one GGSN, while the service network  132  may be a UMTS, and the access network  41  may be a UTRAN and the core network  42  may be a GPRS core which includes an HLR, at least one SGSN, and at least one GGSN. 
         [0021]    The mobile communication device  110  may be a smart phone, a panel Personal Computer (PC), a laptop computer, or any computing device supporting at least two of the wireless technologies utilized by the service networks  121  and  122  of the PLMN  120  and the service networks  131  and  132  of the PLMN  130 .  FIG. 2  is a block diagram illustrating the mobile communication device  110  according to an embodiment of the invention. The mobile communication device  110  comprises a wireless module  210  and a controller module  220 . The wireless module  210  is responsible for performing the functionality of wireless transmissions and receptions to and from the service networks  121  and  122  of the PLMN  120  and the service networks  131  and  132  of the PLMN  130 . The controller module  220  is responsible for controlling the operations of the wireless module  210 , and other functional components (not shown), such as a display unit and/or keypad serving as the Man-Machine Interface (MMI), a storage unit storing the program codes of applications or communication protocols, or others. Also, the controller module  220  controls the wireless module  210  for performing the method for recovering service from a signaling procedure rejected with network failure. 
         [0022]    To further clarify, the wireless module  210  may be a Radio Frequency (RF) unit (not shown), and the controller module  220  may be a general-purpose processor or a Micro Control Unit (MCU) of a baseband unit (not shown). The baseband unit may contain multiple hardware devices to perform baseband signal processing, including analog to digital conversion (ADC)/digital to analog conversion (DAC), gain adjusting, modulation/demodulation, encoding/decoding, and so on. The RF unit may receive RF wireless signals, convert the received RF wireless signals to baseband signals, which are processed by the baseband unit, or receive baseband signals from the baseband unit and convert the received baseband signals to RF wireless signals, which are later transmitted. The RF unit may also contain multiple hardware devices to perform radio frequency conversion. For example, the RF unit may comprise a mixer to multiply the baseband signals with a carrier oscillated in the radio frequency of the mobile communication system, wherein the radio frequency may be 900 MHz, 1800 MHz, or 1900 MHz utilized in the GPRS/EDGE technology, 900 MHz, 1900 MHz, or 2100 MHz utilized in the WCDMA technology, or 900 MHz, 2100 MHz, or 2.6 GHz utilized in LTE/LTE-Advanced technology, or others depending on the wireless technology in use. 
         [0023]      FIG. 3  is a flow chart illustrating the method for a mobile communication device to recover service from a signaling procedure rejected with network failure according to an embodiment of the invention. In this embodiment, the mobile communication device is initially camped on a PLMN. To begin, the mobile communication device performs a signaling procedure with the PLMN (step S 310 ). Specifically, the signaling procedure may be an attach procedure, a location update procedure, a routing area update procedure, or a tracking area update procedure. Next, the signaling procedure is rejected by the PLMN with a rejection cause indicating a network failure (step S 320 ). Specifically, the rejection cause may be included in an ATTACH REJECT message, a LOCATION UPDATE REJECT message, a ROUTING AREA UPDATE REJECT message, or a TRACKING AREA UPDATE REJECT message, and it is set to a value of 17 which means the signaling procedure is rejected with a network failure. 
         [0024]    In response to the signaling procedure being rejected with a network failure, the mobile communication device performs a PLMN selection procedure for other PLMNs without retrying the signaling procedure with the PLMN (step S 330 ). Note that, the PLMN selection procedure is performed for the PLMNs other than the PLMN which the mobile communication device was camped on initially. That is, the PLMN selection procedure is performed for finding any suitable PLMN other than the one for which the signaling procedure was rejected. Subsequently, it is determined whether the PLMN selection procedure is successful to find another PLMN (step S 340 ). If so, the mobile communication device camps on the found PLMN (step S 350 ). Otherwise, if the PLMN selection procedure fails, the mobile communication device sets the Subscriber Identity Module (SIM) or Universal SIM (USIM), which is coupled to the mobile communication device, as invalid, and enters the “no-service” state (step S 360 ). 
         [0025]    Note that, unlike the conventional operation of UE, the mobile communication device in the embodiment of  FIG. 3  does not retry the signaling procedure with the same PLMN and performs the PLMN selection procedure for other PLMNs in response to failure of the signaling procedure with a rejection cause indicating a network failure, so that it may camp on another PLMN to obtain wireless services as soon as possible. 
         [0026]      FIG. 4  is a flow chart illustrating the method for a mobile communication device to recover service from a signaling procedure rejected with network failure according to another embodiment of the invention. Similarly, the mobile communication device is initially camped on a PLMN. To begin, the mobile communication device performs a signaling procedure with the PLMN using one of the supported wireless technologies (step S 401 ), and the signaling procedure is rejected by the PLMN with a rejection cause indicating a network failure (step S 402 ). Specifically, the signaling procedure may be an attach procedure, a location update procedure, a routing area update procedure, or a tracking area update procedure. Next, it is determined whether there is another wireless technology supported by the mobile communication device (step S 403 ). If so, the mobile communication device performs a PLMN selection procedure for the same PLMN using another wireless technology without retrying the signaling procedure using the same wireless technology (step S 404 ). 
         [0027]    After that, it is determined whether the PLMN selection procedure for the same PLMN is successful to detect another Radio Access Technology (RAT) utilized by the PLMN (step S 405 ). If so, the mobile communication device camps on the same PLMN using the detected RAT (step S 406 ). Specifically, the detected RAT is the same as the wireless technology used in the step S 404 . Otherwise, if the PLMN selection procedure for the same PLMN fails, the method proceeds to step S 403 . 
         [0028]    Subsequent to the step S 403 , if there is no other wireless technology supported by the mobile communication device (i.e., all of the supported wireless technologies have been tried), the mobile communication device performs another PLMN selection procedure for other PLMNs (step S 407 ). Note that, the PLMN selection procedure in the step S 407  is performed for the PLMNs other than the PLMN which the mobile communication device was camped on initially. That is, the PLMN selection procedure in the step S 407  is performed for finding any suitable PLMN other than the one for which the signaling procedure was rejected. Next, it is determined whether the PLMN selection procedure is successful to find another PLMN (step S 408 ). If so, the mobile communication device camps on the found PLMN (step S 409 ). Otherwise, if the PLMN selection procedure fails, the mobile communication device sets the SIM/USIM, which is coupled to the mobile communication device, as invalid, and enters the “no-service” state (step S 410 ). 
         [0029]    Note that, unlike the conventional operation of UE, the mobile communication device in the embodiment of  FIG. 4  does not retry the signaling procedure using the same wireless technology, and instead, it performs the PLMN selection procedure for the same PLMN using another wireless technology in response to failure of the signaling procedure with a rejection cause indicating a network failure, so that it may camp on the same PLMN with another RAT to obtain wireless services as soon as possible. 
         [0030]    While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. Those who are skilled in this technology can still make various alterations and modifications without departing from the scope and spirit of this invention. Therefore, the scope of the invention shall be defined and protected by the following claims and their equivalents.