Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Application claims priority of U.S. Provisional Application No. 61/101,147, filed Sep. 29, 2008. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention generally relates to handling an attach procedure, and more particularly, to methods, apparatus, and system for handling an attach procedure in a mobile communication system environment. 
         [0004]    2. Description of the Related Art 
         [0005]    In a typical mobile communication system environment, a mobile user equipment (UE) communicates with one or more mobile communication systems via the radio access networks of the mobile communication systems. A UE comprises various types of equipment such as a mobile telephone (also known as cellular or cell phone), a laptop with wireless communication capability, a personal digital assistant (PDA) etc. The equipment may be portable, handheld, pocket-sized, installed in a vehicle etc and communicate voice and/or data signals with the radio access network. 
         [0006]    A universal mobile telecommunications system (UMTS) is a third generation mobile communication system that has evolved from the Global System for Mobile communications (GSM) system. The UMTS is a European standard which aims to provide better mobile communication services based on the GSM core network and wideband code division multiple access (W-CDMA) technology. Although UMTS delivers high data transfer rates, wireless data usage is expected to increase significantly over the next few years. For this reason, concepts for UMTS Long Term Evolution (LTE) have been proposed and the objective is to further improve UMTS to achieve high-data-rates, low-latency and packet-optimized radio access technology. The improved UMTS technology is called Evolved Universal Terrestrial Radio Access (E-UTRA) and the system employing the E-UTRA technology is called an Evolved Packet System (EPS). 
         [0007]    For a UE, which complies with the 3GPP specifications for the E-UTRA protocol, the 3GPP TS 24.301 specification, v.1.0.0, referred to herein as the 24.301 specification, addresses the subject of the Non-Access-Stratum (NAS) protocol requirements for the EPS and the UE. 
         [0008]    After the UE is powered on and connects to the EPS, it will need to perform an attach procedure to register itself to the EPS so that it can start a packet data session over the EPS. As illustrated in  FIG. 1 , the attach procedure starts by the UE sending an ATTACH REQUEST message to the EPS (step S 101 ). The ATTACH REQUEST message may be sent combined with a PDN CONNECTIVITY REQUEST message indicating that the UE wishes to start a packet data session with the EPS. When the EPS receives the ATTACH REQUEST message, it authenticates the UE, checks if the UE is authorized to have access to packet data services, and performs a security mode control procedure to activate the encryption on subsequent messages (step S 102 ). If none of the checks fails, the EPS accepts the attach request by sending an ATTACH ACCEPT message to the UE. The ATTACH ACCEPT message may be sent combined with an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message if the PDN CONNECTIVITY REQUEST message is found in the ATTACH REQUEST message (step S 103 ). The ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message contains the configuration used to activate the default bearer for the packet data session. When the UE receives the ATTACH ACCEPT message, it checks the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message to see if the configuration within is acceptable. If the UE accepts the configuration specified in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message, it applies the configuration, resets the counters associated with the attach procedure, including the attach attempt counter and the tracking area updating attempt counter, enters the EMM-REGISTERED state, and sets the EPS update status to EU1 UPDATED (step S 104 ). The UE then responds to the EPS with an ATTACH COMPLETE message to acknowledge that it has received and accepted the ATTACH ACCEPT message (step S 105 ). The ATTACH COMPLETE message may be sent combined with an ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT message indicating that the UE has accepted the configuration of the default bearer from the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message. At last, the EPS receives the ATTACH COMPLETE message combined with the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT message and the attach procedure ends successfully. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    Accordingly, embodiments of the invention provide an apparatus, system, and methods for handling attach procedure in a mobile communication system. In one aspect of the invention, a user equipment handling an attach procedure with a service network is provided. The user equipment comprises a wireless module and a controller. The wireless module transmits an attach request message to the service network and receives an attach accept message replied to the attach request message from the service network. The controller determines whether to accept the attach accept message, sends an attach complete message, via the wireless module, to the service network in response to the attach accept message being accepted, and resends the attach request message, via the wireless module, to the service network in response to the attach accept message not being accepted. 
         [0010]    In another aspect of the invention, a method for a user equipment to handle an attach procedure with a service network is provided. The method comprises sending an attach request message to the service network, receiving an attach accept message replied to the attach request message from the service network, determining whether to accept the attach accept message, and sending an attach complete message to the service network in response to the attach accept message being accepted, and resending the attach request message to the service network in response to the attach accept message not being accepted. 
         [0011]    In another aspect of the invention, a service network for handling an attach procedure with a user equipment is provided. The service network comprises a radio access network and a control node. The radio access network receives an attach request message from the user equipment, sends a first attach accept message to the user equipment in response to the attach request message, and receives a response message from the user equipment. The control node determines that the attach procedure has ended successfully in response to the response message being an attach complete message, aborts the attach procedure and initiates a new attach procedure by sending a second attach accept message, via the radio access network, to the user equipment in response to the response message being the attach request message resent by the user equipment, and aborts the attach procedure and sends a detach accept message, via the radio access network, to the user equipment in response to the response message being a detach request message. 
         [0012]    In another aspect of the invention, a method for a service network to handle an attach procedure with a user equipment is provided. The method comprises receiving an attach request message from the user equipment, sending a first attach accept message to the user equipment in response to the attach request message, receiving a response message from the user equipment, aborting the attach procedure and initiating a new attach procedure by sending a second attach accept message to the user equipment in response to the response message being the attach request message resent by the user equipment, and aborting the attach procedure and sending a detach accept message to the user equipment in response to the response message being a detach request message. 
         [0013]    In another aspect of the invention, a mobile communication system for handling an attach procedure is provided. The mobile communication system comprises a user equipment and a service network. The user equipment sends an attach request message, receives a first attach accept message replied to the attach request message, determines whether to accept the first attach accept message, sends an attach complete message in response to the first attach accept message being accepted, and resends the attach request message in response to the first attach accept message not being accepted. The service network receives the attach request message, sends the first attach accept message in response to the attach request message, determines that the attach procedure has ended successfully upon receiving the attach complete message, and aborts the attach procedure and initiates a new attach procedure by sending a second attach accept message to the user equipment upon receiving the attach request message resent by the user equipment. 
         [0014]    Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following descriptions of specific embodiments of an apparatus, system, and methods for handling an attach procedure in an E-UTRA system environment. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]    The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
           [0016]      FIG. 1  is a message sequence chart illustrating a successful attach procedure in an EPS environment; 
           [0017]      FIG. 2  is a block diagram illustrating a UE in accordance of an embodiment of this present invention; 
           [0018]      FIG. 3  is a message sequence chart illustrating the UE and EPS handling an attach procedure according to an embodiment of the invention; and 
           [0019]      FIG. 4  is a message sequence chart illustrating the UE and EPS aborting an unaccepted attach procedure after a predetermined number of retries according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    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. The scope of the invention is best determined by reference to the appended claims. In order to give better examples, the embodiments described below are utilized in EPS environments. In addition, 3GPP specifications are used to teach the spirit of this invention but not used to limit the scope of the present invention. 
         [0021]    There are situations where the UE may not accept the configuration specified in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message. For instance, if the bearer resources of the UE are not sufficient enough to apply a required configuration, there may be semantic errors or syntactical errors in the configuration. Additionally, other situations specified in clause 6.4.1. 4 of the 24.301 specification may also occur. If the UE does not accept the configuration, it requests a suitable or correct configuration from the EPS. Accordingly, the UE reinitiates the attach procedure. Yet, in accordance with clause 5.5.1.2.4 of the 24.301 specification, whenever the UE receives the ATTACH ACCEPT message combined with the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message, it resets the attach attempt counter and tracking area updating attempt counter, enters the EMM-REGISTERED state, sets the EPS update status to EU1 UPDATED, and applies the configuration specified in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message. After, the UE sends an ATTACH COMPLETE message combined with the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT message to the EPS. Thus, since the clause 5.5.1.2.4 of the 24.301 specification completely ignores the situation when the UE does not accept the configuration specified in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message, faulty handling of attach procedures by the UE and EPS may occur. 
         [0022]      FIG. 2  is a block diagram illustrating a UE in accordance of an embodiment of this present invention. The UE  210  has a wireless module  211  for receiving and transmitting messages propagated in radio frequency. The UE  210  also includes the NAS protocol stack  212 , which is connected to receive and transmit messages from and to the EPS  220  via the wireless module  211 . The connection between the NAS protocol stack  212  and the wireless module  211  may involve protocol stacks that are not shown in  FIG. 2 , such as the radio resource control (RRC) protocol stack, the radio link control (RLC) protocol stack, the medium access control (MAC) protocol stack, and the physical layer protocol stack. For implementation, any of the protocol stacks referred to in this specification may be realized by a combination of hardware and software. The NAS protocol stack  212  comprises a controller  213  for performing the NAS functions and handling an attach procedure. The operation of the controller  213  is explained in more detail in the following embodiments. 
         [0023]      FIG. 3  is a message sequence chart illustrating the UE and EPS handling an attach procedure according to an embodiment of the invention. During the attach procedure, the UE  210  maintains an attach attempt counter, referred to herein as a retry counter, to keep track of the number of retries allowed when the attach attempt is not successful. Initially, the retry counter is set to 0 (step S 301 ). When the UE  210  wishes to register with the EPS  220  and start a packet data session with the EPS  220 , the UE  210  initiates an attach procedure by sending an ATTACH REQUEST message, with a PDN CONNECTIVITY REQUEST message combined in it, to EPS  220  (step S 302 ). After reception of the ATTACH REQUEST message, the EPS  220  performs the authentication procedure to check if the UE  210  is authorized, and the security mode control procedure to activate the encryption on the subsequent messages in the connection with UE  210  (step S 303 ). If the procedures end normally, the EPS  220  sends an ATTACH ACCEPT message, with an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message combined in it, to the UE  210  (step S 304 ). Upon reception of the ATTACH ACCEPT message by the wireless module  211 , the controller  213  retrieves the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message and determines that the default EPS bearer context activation configuration in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message is not acceptable due to the reasons as specified in clause 6.4.1. 4 of the 24.301 specification (step S 305 ). The UE  210  then checks to see if the retry counter is less than a predetermined number. If the retry counter is less than a predetermined number, the UE  210  resends the ATTACH REQUEST message combined with the PDN CONNECTIVITY REQUEST message (step S 306 ). The resent ATTACH REQUEST message includes a resent cause (IE “Resent cause”) indicating that the message is resent due to the previous ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message being rejected by UE  210 , and the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message includes an unaccepted cause (IE “ESM cause”). Upon resending the ATTACH REQUEST message, the UE  210  increments the retry counter by 1 (step S 307 ). When the EPS  220  receives the resent the ATTACH REQUEST message, it checks to see if the ATTACH REQUEST message includes a resend cause. If the ATTACH REQUEST message includes a resend cause, the EPS  220  aborts the current attach procedure and initiates a new attach procedure (step S 308 ) by sending a new ATTACH ACCEPT message combined with a new ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message to the UE  210  (step S 309 ). The configuration specified in the new ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message is adjusted by EPS  220  according to the unaccepted cause. Since the configuration specified in the new ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message is adjusted, the UE may accept the new ATTACH ACCEPT message and the new ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message. After accepting the new ATTACH ACCEPT message, the UE  210  continues with resetting the attach attempt counter and tracking area updating attempt counter, entering an EMM-REGISTERED state, setting the EPS update status to EU1 UPDATED, and applying the configuration specified in the new ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message (step S 310 ). Afterward, the UE sends an ATTACH COMPLETE message combined with the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT message to the EPS (step S 311 ). Once the EPS  220  receives the ATTACH COMPLETE message, the attach procedure ends successfully. 
         [0024]    In other embodiments, the UE  210  may rejects the new ATTACH ACCEPT message again and thus the operations in step S 305 ˜S 307  are repeated. In this case, step S 305 ˜S 307  can be repeated, until the retry counter is greater than or equal to the predetermined number or the UE  210  accepts the new ATTACH ACCEPT message. 
         [0025]      FIG. 4  is a message sequence chart illustrating the UE and EPS aborting an unaccepted attach procedure after a predetermined number of retries according to an embodiment of the invention. During an attach procedure, the UE  210  carries out the retry process by resending the ATTACH REQUEST message with a resent cause (step S 401 ), as depicted in  FIG. 3 , when not accepting the ATTACH ACCEPT message from the EPS  220 . Upon resending the ATTACH REQUEST message, the UE  210  increments the retry counter by 1 (step S 402 ). When the EPS  220  receives the resent ATTACH REQUEST message with the resent cause, it responds accordingly by aborting the current attach procedure and reinitiating a new attach procedure (step S 403 ) by sending a new ATTACH ACCEPT message combined with a new ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message to the UE  210  (step S 404 ). If the UE  210  rejects the ATTACH ACCEPT message again (step S 405 ), then the retry process (step S 401 ˜S 404 ) repeats. The maximum number of retries can be any predetermined number, or  5  in this embodiment. If the retry process fails for 4 more times (step S 406 ) which means the maximum number of retries has been reached, then the UE  210  aborts the attach procedure by sending a DETACH REQUEST message to the EPS  220  (step S 407 ). Upon receiving the DETACH REQUEST message, the EPS  220  aborts the attach procedure (step S 408 ) and responds by sending a DETACH ACCEPT message to the UE  210  (step S 409 ). Afterward, the attach procedure ends by being considered as failed by both the UE  210  and the EPS  220 . 
         [0026]    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 present invention shall be defined and protected by the following claims and their equivalents.

Technology Category: 5