Abstract:
Aspects of the disclosure provide a method for handling reject in wireless communication. The method includes receiving, at an electronic device, a reject message indicative of a forbidden resource of a service provider network to use by the electronic device for wireless communication, determining a reliability attribute of the reject message, storing the forbidden resource associated with the reliability attribute, and maintaining the stored forbidden resource based on the reliability attribute.

Description:
INCORPORATION BY REFERENCE 
       [0001]    This present disclosure claims the benefit of U.S. Provisional Application No. 62/287,475, “Improvement to handling of reject received from unreliable source” filed on Jan. 27, 2016, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0003]    Generally, a mobile device keeps track of forbidden resources to use for mobile communication. In an example, a mobile device keeps track of a list of forbidden tracking areas. example, the mobile device is not allowed to initiate establishment of communication service from a cell belonging to one of the forbidden tracking areas. 
       SUMMARY 
       [0004]    Aspects of the disclosure provide a method for handling reject in wireless communication. The method includes receiving, at an electronic device, a reject message indicative of a forbidden resource of a service provider network to use by the electronic device for wireless communication, determining a reliability attribute of the reject message, storing the forbidden resource associated with the reliability attribute, and maintaining the stored forbidden resource based on the reliability attribute. 
         [0005]    To store the forbidden resource associated with the reliability attribute, in an embodiment, the method includes storing an indicator that indicates the reliability attribute with the forbidden resource. In another embodiment, the method includes storing the forbidden resource in a first list when the reliability attribute is reliable and storing the forbidden resource in a second list when the reliability attribute is unreliable. In another embodiment, the method includes storing the forbidden resource in a first memory device when the reliability attribute is reliable, and storing the forbidden resource in a second memory device when the reliability attribute is unreliable. For example, the method includes storing the forbidden resource in the first memory device that is a non-volatile memory device when the reliability attribute is reliable; and storing the forbidden resource in the second memory device that is a volatile memory device when the reliability attribute is unreliable. 
         [0006]    According to an aspect of the disclosure, the forbidden resource includes at least one of a forbidden location area for general packet radio service (GPRS) services, a forbidden location area for non-GPRS service, a forbidden location area for roaming, a forbidden location area for regional provision of service, a forbidden tracking area for roaming, a forbidden tracking area for regional provision of service, and a forbidden public land mobile network (PLMN). 
         [0007]    To determine the reliability attribute of the reject message, in an embodiment, the method includes determining the reject message to be reliable when the reject message is integrity protected and determining the reject message to be unreliable when the reject message is not integrity protected. 
         [0008]    To maintain the stored forbidden resource based on the reliability attribute, in an embodiment, the method includes removing the forbidden resource from storage in response to at least one of an expiration of a timer, a power-off of the electronic device and a removal of a subscriber identify module when the reliability attribute is unreliable. 
         [0009]    Aspects of the disclosure provide an apparatus that includes a transceiver circuit, one or more memory circuits, and a processing circuit. The transceiver circuit is configured to transmit wireless signals to request resources from a service provider network for wireless communication, and receive wireless signals that carry a reject message. The processing circuit is configured to determine a reliability attribute of the reject message, control the one or two memory circuits to store the forbidden resource associated with the reliability attribute, and maintain the stored forbidden resource based on the reliability attribute. 
         [0010]    Aspects of the disclosure provide a non-transitory computer readable medium storing program instructions for causing a processor to execute operations for handling reject in an electronic device. The operations include receiving a reject message indicative of a forbidden resource of a service provider network to use by the electronic device for wireless communication, determining a reliability attribute of the reject message, storing the forbidden resource associated with the reliability attribute, and maintaining the stored forbidden resource based on the reliability attribute. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Various embodiments of this disclosure that are proposed as examples will be described in detail with reference to the following figures, wherein like numerals reference like elements, and wherein: 
           [0012]      FIG. 1  shows a block diagram of a communication system  100  according to an embodiment of the disclosure: and 
           [0013]      FIG. 2  shows a flow chart outlining a process  200  according to an embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0014]      FIG. 1  shows a block diagram of a communication system  100  according to an embodiment of the disclosure. The communication system  100  includes an electronic device  110  that requests resources from a service provider network  101  for wireless communication. The electronic device  110  may receive reject messages from the service provider network  101  that indicates forbidden resources for use by the electronic device  110  to conduct wireless communication. The electronic device  110  may also receive reject messages from a fraudulent network  102  that conducts attacks to the electronic device  110  using fake reject messages. The electronic device  110  is configured to determine reliabilities of the reject messages, store the forbidden resources associated with the reliabilities, and maintain the forbidden resources based on the reliabilities. 
         [0015]    The service provider network  101  can include any suitable service provider, such as one or more mobile service providers, a wireless communication service provider, and the like. In an embodiment, the service provider network  101  includes a mobile service provider that can be implemented using any suitable mobile communication technology, such as third generation (3G) mobile network technology, fourth generation (4G) mobile network technology, fifth generation (5G) mobile network technology, global system for mobile communication (GSM), long-term evolution (LTE), and the like. It is noted that the service provider network  101  can include interconnections that are implemented using any suitable network technology, such wired, wireless, a cellular communication technology, a local area network (LAN), a wireless LAN (WLAN), a fiber optical network, a wide area network (WAN), a peer-to-peer network, the Internet, and the like. 
         [0016]    In an example, a mobile service provider in the service provider network  101  is a facility-based provider that owns a mobile infrastructure (including both hardware and software), such as cell towers, network components that form a backbone to manage and control the services provided by the mobile service provider. In another example, a mobile service provider in the service provider network  101  is a mobile virtual network operator that does not own a mobile infrastructure, but leases telephone and data service from facility-based providers. 
         [0017]    In an embodiment, the service provider network  101  can include any suitable public land mobile network (PLMN) for providing land mobile telecommunication services to the public. In an example, the service provider network  101  includes a home public land mobile network (HPLMN) for the electronic device  110 . The electronic device  110  subscribes service from HPLMN, for example via a subscriber identity module (SIM), and the HPLMN holds a subscriber profile of the electronic device  110 . The service provider network  101  can include other PLMNs. In an example, the electronic device  110  loses coverage of the HPLMN, and the electronic device  110  can search for another public land mobile network (PLMN) for roaming service. In an example, when the electronic device  110  roams to another PLMN, the other PLMN can receive the subscriber profile of the electronic device HO from the HPLMN. 
         [0018]    According to an aspect of the disclosure, the electronic device  110  can send a request (e.g., a tracking area update request, a routing area update, a service request, a location update request, etc.) to the service provider network  101  to request resources from the service provider network  101  for wireless communication. The electronic device  110  may receive a reject message, such as an attach reject message, a tracking area update reject message, a service reject message, a location updating reject message, a routing updating reject message, and the like, from the service provider network  101  due to various reasons, such as no suitable cells, roaming not allowed, tracking area not allowed, and the like. In an embodiment, the reject message includes a cause value that indicates the reason and the forbidden resource of the service provider network  101  for use by the electronic device  110 . 
         [0019]    In an example, the electronic device  110  loses the coverage by the HPLMN, and the electronic device  110  tries to search for another PLMN for roaming service. The electronic device  110  may receive a location updating reject message with a cause value 11 from the service provider network  101 . In the example, the location updating reject message with the cause value 11 indicates that the PLMN is not allowed to the electronic device  110 . The electronic device  110  may need to search other PLMNs. 
         [0020]    In another example, the electronic device  110  may receive a location updating reject message with a cause value 12. The location updating reject message with the cause value 12 indicates that the location area is not allowed for regional provision of service. 
         [0021]    In another example, the electronic device  110  may receive a location updating reject message with a cause value 13. The location updating reject message with the cause value 13 indicates that the location area is not allowed for roaming service. 
         [0022]    In another example, the electronic device  110  may receive a location updating reject message with a cause value 15. The location updating reject message with the cause value 15 indicates that there is no suitable cell in the location area. 
         [0023]    In another example, the electronic device  110  may receive a location updating reject message with a cause value that is domain based. For example, the cause value 2 is used for circuit switch (CS) domain, and the cause value 7 is used for packet switch (PS) domain. For example, the electronic device  110  may receive a location updating reject message with a cause value 2. The location updating reject message with the cause value 2 indicates that the non-general packet radio service (GPRS) is not available. It is noted that the cause value 2 may not affect operation of GPRS service in the PS domain. In another example, the electronic device  110  may receive a routing area updating reject message with a cause value 7. The routing area updating reject message with the cause value 7 indicates that the GPRS is not available for the subscriber. It is noted that the cause value 7 may not affect operation of non-GPRS service in the CS domain. 
         [0024]    It is noted that, in some examples, the electronic device  110  combines a cause value and other suitable information, such as ongoing procedure and the like, to determine the domain that is affected. 
         [0025]    According to an aspect of the disclosure, the reject messages can be integrity protected or non-integrity protected. In an example, the electronic device  110  and the service provider network  101  perform a security mode control procedure during an attach procedure to establish secure exchange of non-access stratum (NAS) messages via. NAS signals in LTE technology example. Before the establishment of the secure exchange of NAS messages for the NAS signals, the reject messages have no integrity protection. After successful completion of the security mode control procedure, NAS messages exchanged between the electronic device  110  and the service provider network  101  are sent integrity protected using security algorithms. In an example, at a transmitting side, the security algorithms are used to generate a hash of an original message and the hash is added in the final message to be sent to the recipient side. The recipient side can use the security algorithms to authenticate that the received message is sent by the transmitting side, 
         [0026]    It is noted that, in a 3G technology example, the secure exchange of messages is handled in access stratum (AS). The AS can indicate to the NAS whether the secure exchange is activated, and thus the NAS can determine whether the message is reliable or not. 
         [0027]    It is noted that authentication may not be possible in certain scenarios, for example when the service provider network  101  cannot access the HPLMN of the electronic device  110 . 
         [0028]    Additionally, the electronic device  110  may receive fake reject messages from the fraudulent network  102 . In an example, the fraudulent network  102  includes malicious base station that uses the fake reject messages to conduct security attacks to the electronic device  110 . The malicious base station may listen to messages sent by the service provider network  101  and form the fake reject messages accordingly. The fake reject messages are not integrity protected in an example. 
         [0029]    The electronic device  110  can be any suitable electronic device. In an example, the electronic device  110  is a terminal device used by an end-user for mobile telecommunication, such as a cell phone, a smart phone, a tablet computer, and the like. In another example, the electronic device  110  is a stationary device, such as a desktop computer. In another example, the electronic device  110  is a machine type communication device, such as a wireless sensor, an Internet of things (IoT) device and the like. 
         [0030]    According to an aspect of the disclosure, the electronic device  110  is configured to determine reliabilities of the reject messages. For example, the electronic device  110  determines whether the reject messages come from reliable sources that have accomplished a security mode control procedure with the electronic device  110 . Then, the electronic device  100  stores the forbidden resources associated with the reliabilities, and maintain the stored forbidden resources based on the reliabilities. For example, the electronic device  100  can keep the information of forbidden resources associated with reliable sources, and discard the information of forbidden resources associated with unreliable sources in response to certain trigger events. 
         [0031]    Specifically, in the  FIG. 1  example, the electronic device  110  includes a transceiver  120 , a processing circuit  130 , a card interface  150 , and a memory  170  coupled together as shown. 
         [0032]    The transceiver  120  is configured to receive and transmit wireless signals. In an example, the transceiver  120  includes a receiving circuit (not shown) and a transmitting circuit (not shown). The receiving circuit is configured to generate electrical signals in response to captured electromagnetic waves by an antenna  111 , process the electrical signals to extract digital streams from the electrical signals. In an example, the transmitting circuit is configured to receive digital streams, such as management frames, data frames, and the like from for example the processing circuit  130 , generate radio frequency (RF) signals to carry the digital streams, and emit electromagnetic waves in the air via the antenna  111  to transmit wireless signals that carry the digital streams. 
         [0033]    The card interface  150  is suitably configured to accept a smart card, such as a universal integrated circuit card (UICC) card  155  provided by a wireless telecommunication service provider, such as the HPLMN service provider, and couple the UICC card  155  with other components in the electronic device  110 , such as the processing circuit  130 . Generally, the UICC card  155  includes a processing circuit (e.g., central processing unit not shown) and a memory (not shown). Generally, the memory is a non-volatile memory, such as a flash memory, and the like on the UICC card  155 , and can keep the stored information when the UICC card  155  is not electronically coupled to an electronic device, such as the electronic device  110 . The memory stores various information corresponding to the wireless telecommunication service provider, such as instructions for a subscriber identity module (SIM) application, instructions for a universal subscriber identity module (USIM) application, international mobile subscriber identity (IMSI) and related security authentication and ciphering information, user data (e.g., address book), and the like. The memory can also store temporary information related to a local network, such as a list of PLMNs, wireless access technologies, carrier frequency information, and the like. 
         [0034]    In an example, based on the information stored in the UICC card  155 , the electronic device  110  is able to perform wireless communication with another electronic device (not shown) under the management of the service provider network  101 . The service provider network  101  manages and controls the wireless communication between the electronic device  110  and the other device. For example, the service provider network  101  determines paths for the wireless communication and allocates resources to enable the wireless communication. In another example, the service provider network  101  can forbid the electronic device  110  to use certain resources, and send reject messages to the electronic device  110  to indicate the forbidden resources. 
         [0035]    The processing circuit  130  includes suitable circuits to perform various baseband processing operations, such as voice signal processing, control operations for the electronic device  110 , execution of applications, and the like. In the  FIG. 1  example, the processing circuit  130  includes a reject controller  140  configured to manage reject messages. In an example, the reject controller  140  is implemented using circuits. In another example, the reject controller  140  is implemented as a processor executing software instructions. 
         [0036]    According to an aspect of the disclosure, the reject controller  140  is configured to determine a reliability attribute of the reject message, for example whether the reject message comes from a reliable source. In an example, the reject controller  140  determines whether the reject message is integrity protected. When the reject message is integrity protected, the reject controller  140  can authenticate the reject message, and determines that the reject message comes from a reliable source. Thus, the reliability attribute of the reject message is reliable. When the reject message is not integrity protected, the reject controller  140  determines that the reject message comes from an unreliable source. Thus, the reliability attribute of the reject message is unreliable. 
         [0037]    Further, in an embodiment, the reject controller  140  determines the forbidden resource from the reject message. In an example, the reject controller  140  is configured to determine the forbidden resource based on cause value in the reject message. 
         [0038]    For example, the reject controller  140  determines that the forbidden resource is a forbidden location area that is not allowed for regional provision of service when the cause value is 12; the reject controller  140  determines that the forbidden resource is a forbidden location area that is not allowed for roaming service when the cause value is 13; the reject controller  140  determines that the forbidden resource is a forbidden location area that has not suitable cells when the cause value is 15; the reject controller  140  determines that the forbidden resource is a forbidden location area that is not allowed for non-GPRS services when the cause value is 2 (or 3 or 6). 
         [0039]    According to an aspect of the disclosure, the electronic device  110  is configured to keep track of the forbidden resources, not to request the resources in the forbidden resources. For example, when the electronic device  110  is in a location area in the forbidden location areas for non-GPRS services, the electronic device  110  is configured not to initiate a mobility management procedure; and when the electronic device  110  is in a location area in the forbidden location areas for GPRS services, the electronic device  110  is configured not to initiate a GPRS mobility management procedure. 
         [0040]    In an embodiment, the reject controller  140  is configured to control memory devices, such as the memory  170 , the memory in the UICC card  155 , and the like to store the forbidden resource associated with the reliability attribute, and then the reject controller  140  can handle the forbidden resource based on the reliability attribute. 
         [0041]    In the  FIG. 1  example, the memory  170  is configured to store the forbidden resource associated with the reliability attribute. The memory  170  can include any suitable memory devices, such as a static random access memory (SRAM), a dynamic random access memory (DRAM), a flash memory, and the like. In an example, the memory  170  is a volatile memory that loses the store the information when the electronic device  110  is powered off. In another example, the memory is non-volatile memory that can keep the stored information when the electronic device  110  is powered off. 
         [0042]    According to an aspect of the disclosure, the reject controller  140  can control the memory  170  to store various forbidden resources by list. For example, the memory  170  stores a list of forbidden location areas for general packet radio service (GPRS) services, a list of forbidden location areas for non-GPRS services, a list of forbidden location areas for roaming, a list of forbidden location areas for regional provision of service, and the like. 
         [0043]    In an embodiment, the reject controller  140  is configured to store a forbidden resource with a reliability indicator for the forbidden resource in the memory  170 , as shown by  171 . The reliability indicator can indicate the reliability attribute for the reject message (and the reject source). For example, the reject controller  140  controls the memory  170  to store forbidden resources in lists. A list of forbidden resources includes a plurality of entries. Each entry can store an identification of a forbidden resource, such as an identification of a location area, and the like, and a reliability indicator associated with the forbidden resource. The reliability indicator indicates the reliability attribute for the forbidden resource. 
         [0044]    In the example, when the electronic device  110  receives a first reject message (e.g., a fake reject message) that is sent by the fraudulent network  102 , the electronic device  110  detects that the first reject message is not integrity protected, thus the first reject message is unreliable. The reject controller  140  determines a first forbidden resource (e.g., fake forbidden resource) for example based on a cause code in the first reject message, and then stores the first forbidden resource with the reliability indicator to indicate the unreliable attribute in the list of forbidden resources. 
         [0045]    In the example, when the electronic device  110  receives a second reject message (e.g., a genuine reject message) that is sent by a base station in the service provider network  101  that has established secure exchange of messages with the electronic device  110 , the electronic device  110  detects that the second reject message is integrity protected, thus the second reject message has the reliable attribute. The reject controller  140  determines a second forbidden resource (e.g., genuine forbidden resource) for example based on a cause code in the second reject message, and then stores the second forbidden resource with the reliable attribute in the list of forbidden resources. 
         [0046]    Then, the reject controller  140  handles the forbidden resources based on the reliabilities of the forbidden resources in response to trigger events, such as an expiration of a timer, a power-off of the electronic device  110 , a removal of the UICC card  155 , and the like. In an example, the processing circuit  140  includes a timer  160  (e.g., T3247 timer) to track a back-off time for forbidden resources. When the timer  160  expires, the reject controller  140  removes forbidden resources with unreliable attribute from the list of forbidden resources, and keeps forbidden resources with reliable attribute in the list of forbidden resources. For example, the reject controller  140  removes the first forbidden resource with the unreliable attribute from the list of forbidden resources, and keeps the second forbidden resource with the reliable attribute in the list of forbidden resources. Then, the electronic device  110  can again request the removed forbidden resources, such as the first forbidden resource and the like, that are previously in the list of forbidden resources and now are removed from the list of forbidden resources, and the electronic device  110  can continue not to request the forbidden resources, such as the second forbidden resource, that are still in the list of forbidden resources. In this manner, the electronic device  110  can alleviate the attacks by the fraudulent network  102 , and can reduce unnecessary signaling load that may drain battery. 
         [0047]    In another example, the memory  170  is a non-volatile memory. In the example, at a power-off of the electronic device  110 , the electronic device  110  performs a power-off procedure. During the power-off procedure, the reject controller  140  removes forbidden resources with unreliable attribute from the list of forbidden resources, and keeps forbidden resources with reliable attribute in the list of forbidden resources. For example, the reject controller  140  removes the first forbidden resource with the unreliable attribute from the list of forbidden resources, and keeps the second forbidden resource with the reliable attribute in the list of forbidden resources. 
         [0048]    In another example, when the UICC card is detached from the card interface  150 , for example being removed from the card interface  150 , the reject controller  140  removes forbidden resources with unreliable attribute from the list of forbidden resources, and keeps forbidden resources with reliable attribute in the list of forbidden resources. For example, the reject controller  140  removes the first forbidden resource with the unreliable attribute from the list of forbidden resources, and keeps the second forbidden resource with the reliable attribute in the list of forbidden resources. 
         [0049]    In a related exemplary device, a list of forbidden resources that includes both fake forbidden resources and genuine forbidden resources is removed in response to the one or more trigger events, thus the related exemplary device later conducts additional signaling to re-determine the genuine forbidden resources. 
         [0050]    In another embodiment, the reject controller  140  is configured to store forbidden resources to different lists based on respective reliability attributes. For example, the memory  170  stores a first list and a second list as shown by  172 . The first list is configured to store forbidden resources of reliable attribute, and the second list is configured to store forbidden resources of unreliable attribute. 
         [0051]    In the example, when the electronic device  110  receives a first reject message (e.g., a fake reject message) that is sent by the fraudulent network  102 , the electronic device  110  detects that the first reject message is not integrity protected, thus the first reject message is unreliable. The reject controller  140  determines a first forbidden resource (e.g., fake forbidden resource) for example based on a cause code in the first reject message, and then stores the first forbidden resource in the second list. 
         [0052]    In the example, when the electronic device  110  receives a second reject message (e.g., a genuine reject message) that is sent by a base station in the service provider network  101  that has established secure exchange of messages with the electronic device  110 , the electronic device  110  detects that the second reject message is integrity protected, thus the second reject message has the reliable attribute. The reject controller  140  determines a second forbidden resource (e.g., genuine forbidden resource) for example based on a cause code in the second reject message, and then stores the second forbidden resource in the first list. 
         [0053]    Then, the reject controller  140  handles the forbidden resources based on the reliabilities of the forbidden resources in response to trigger events, such as an expiration of a timer, a power-off of the electronic device  110 , a removal of the UICC card  155 , and the like. In an example, when the timer  160  expires, the reject controller  140  removes the second list from the memory  170 , and keeps the first list in the memory  170 . 
         [0054]    In another example, the memory  170  is a non-volatile memory. In the example, at a power-off of the electronic device  110 , the electronic device  110  performs a power-off procedure. During the power-off procedure, the reject controller  140  removes the second list from the memory  170 , and keeps the first list in the memory  170   
         [0055]    In another example, when the UICC card is detached from the card interface  150 , for example being removed from the card interface  150 , the reject controller  140  removes the second list from the memory  170 , and keeps the first list in the memory  170 . 
         [0056]    In another embodiment, the reject controller  140  is configured to store forbidden resources to different memory devices based on respective reliability attribute. For example, the reject controller  140  is configured to store forbidden PLMNs in the UICC card  155  when the reject attribute is reliable, and store forbidden PLMNs in the memory  170  as an extension to the UICC card  155  when the reject attribute is unreliable as shown by  173 . 
         [0057]    For example, when the electronic device  110  receives a first reject message (e.g., a fake reject message) that is sent by the fraudulent network  102 , the electronic device  110  detects that the first reject message is not integrity protected, thus the first reject message is unreliable. The reject controller  140  determines a first forbidden PLMN (e.g., fake forbidden PLMN) for example based on a cause value 11 in the first reject message, and then stores the first forbidden PLMN in the memory  170 . 
         [0058]    In the example, when the electronic device  110  receives a second reject message (e.g., a genuine reject message) that is sent by a base station in the service provider network  101  that has established secure exchange of messages with the electronic device  110 , the electronic device  110  detects that the second reject message is integrity protected, thus the second reject message has the reliable attribute. The reject controller  140  determines a second forbidden PLMN (e.g., genuine forbidden resource) for example based on a cause value 11 in the second reject message, and then stores the second forbidden PLMN in the memory of the card  155 . 
         [0059]    Then, the reject controller  140  handles the forbidden resources based on the reliabilities of the forbidden resources in response to trigger events. 
         [0060]    In an example, the memory  170  is a volatile memory. In the example, the electronic device  110  experiences an unexpected power-off. Due to the power off, the forbidden PLMNs that have unreliable attribute are removed from the electronic device  110 , and the forbidden PLMNs that have reliable attribute are still stored in the UICC card  155 . In another example, when the UICC card  155  is detached from the card interface  150 , for example being removed from the card interface  150 , the reject controller  140  removes the forbidden PLMNs from the memory  170 . 
         [0061]    In a related exemplary device, forbidden PLMNs are stored in a UICC card without identifying the reliability attribute. Further, when the UICC card is full, additional forbidden PLMNs are stored in for example a volatile memory in the related exemplary device. When the related exemplary device experiences an unexpected power off or a UICC card removal, the fake forbidden PLMNs may stay in the UICC card, and the related exemplary device lacks information (e.g., attempt counters are cleared due to power off and/or UICC card removal) to correctly handle the fake forbidden PLMNs. 
         [0062]      FIG. 2  shows a flow chart outlining a process  200  according to an embodiment of the disclosure. In an example, the process  200  is executed by the electronic device  110 . The process starts at S 201  and proceeds to S 210 . 
         [0063]    At S 210 , reject messages are received from reject sources. In the  FIG. 1  example, the transceiver  120  can transmit wireless signals to request resources from the service provider network  101  for wireless communication, and then receive wireless signals that carry one or more reject messages. 
         [0064]    At S 220 , respective reliabilities of the reject messages are determined. In the  FIG. 1  example, the reject controller  140  is configured to determine a reliability attribute of a reject message, for example whether the reject message comes from a reliable source. In an example, the reject controller  140  determines whether the reject message is integrity protected. When the reject message is integrity protected, the reject controller  140  can authenticate the reject message, and determines that the reject message comes from a reliable source. Thus, the reliability attribute of the reject message is reliable. When the reject message is not integrity protected, the reject controller  140  determines that the reject message comes from an unreliable source. Thus, the reliability attribute of the reject message is unreliable. 
         [0065]    At S 230 , forbidden resources are stored with reliabilities. For example, in an embodiment, the reject controller  140  is configured to store a forbidden resource with a reliability indicator for the forbidden resource in the memory  170 , as shown by  171 . The reliability indicator can indicate the reliability attribute for the reject message (and the reject source). 
         [0066]    In another embodiment, the reject controller  140  is configured to store forbidden resources to different lists based on respective reliability attributes. For example, the memory  170  stores a first list and a second list as shown by  172 . The first list is configured to store forbidden resources of reliable attribute, and the second list is configured to store forbidden resources of unreliable attribute. 
         [0067]    In another embodiment, the reject controller  140  is configured to store forbidden resources to different memory devices based on respective reliability attribute. For example, the reject controller  140  is configured to store forbidden PLMNs in the UICC card  155  when the reject attribute is reliable, and store forbidden PLMNS in the memory  170  as an extension to the UICC card  155  when the reject attribute is unreliable as shown by  173 . 
         [0068]    At S 240 , forbidden resources are maintained based on the reliabilities. In the  FIG. 1  example, the reject controller  140  handles the forbidden resources based on the reliabilities of the forbidden resources in response to trigger events, such as an expiration of the timer  160 , a power-off of the electronic device  110 , a removal of the UICC card  155 , and the like. 
         [0069]    In an example, in response to a trigger event, such as an expiration of a timer, a power-off of the electronic device  110 , a removal of the UICC card  155 , and the like, the reject controller  140  removes forbidden resources with indicators that indicate unreliable attribute from the list of forbidden resources  171 , and keeps forbidden resources with reliable attribute in the list of forbidden resources  171 . 
         [0070]    In another example, in response to a trigger event, such as an expiration of a timer, a power-off of the electronic device  110 , a removal of the UICC card  155 , and the like, the reject controller  140  removes the second list of  172 , and keeps the first list of  172  in the memory  170 . 
         [0071]    In another example, the memory  170  is a volatile memory. In the example, the electronic device  110  experiences an unexpected power-off. Due to the power off, the forbidden PLMNs  173  that have unreliable attribute are removed from the electronic device  110 , and the forbidden PLMNs that have reliable attribute are still stored in the UICC card  155 . 
         [0072]    Then the process proceeds to S 299  and terminates. 
         [0073]    When implemented in hardware, the hardware may comprise one or more of discrete components, an integrated circuit, an application-specific integrated circuit (ASIC), etc. 
         [0074]    While aspects of the present disclosure have been described in conjunction with the specific embodiments thereof that are proposed as examples, alternatives, modifications, and variations to the examples may be made. Accordingly, embodiments as set forth herein are intended to be illustrative and not limiting. There are changes that may be made without departing from the scope of the claims set forth below.