# Patent

## Title
Apparatuses and methods for handling attach procedure in a mobile communication system

## Abstract

A user equipment for handling an attach procedure with a service network is provided. In the user equipment, a 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, while a controller determines whether to accept the attach accept message according to a first parameter accompanying the attach accept message and sends an attach complete message, via the wireless module, to the service network in response to the attach accept message being accepted.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a Continuation of U.S. patent application Ser. No. 12/465,824, filed on May 14, 2009 and entitled “Apparatus, System, and Methods for Handling Attach Procedure in Mobile Communication System”, now U.S. Pat. No. 8,135,404, which claims the benefit of U.S. Provisional Application No. 61/101,147 filed on Sep. 29, 2008 and entitled “Pseudo-CR on The UE does not accept ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST in attach procedure”, the entirety of which is incorporated by reference herein.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to handling an attach procedure, and more particularly, to apparatuses and methods for handling an attach procedure in a mobile communication system environment.
2. Description of the Related Art
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, and installed in a vehicle etc and communicate voice and/or data signals with the radio access network.
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).
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.
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 S101). 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 S102). 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 S103). 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 S104). 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 S105). 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
Accordingly, embodiments of the invention provide an apparatuses 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 according to a first parameter accompanying the attach accept message and sends an attach complete message, via the wireless module, to the service network in response to the attach accept message being accepted.
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 according to a first parameter accompanying the attach accept message, and sending an attach complete message to the service network in response to the attach accept message being accepted.
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 apparatuses and methods for handling an attach procedure in an E-UTRA system environment.



BRIEF DESCRIPTION OF DRAWINGS
The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
FIG. 1 is a message sequence chart illustrating a successful attach procedure in an EPS environment;
FIG. 2 is a block diagram illustrating a UE in accordance of an embodiment of this present invention;
FIG. 3 is a message sequence chart illustrating the UE and EPS handling an attach procedure according to an embodiment of the invention; and
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
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.
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.
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.
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 S301). 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 S302). 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 S303). 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 S304). 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 S305). 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 S306). 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 S307). 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 S308) by sending a new ATTACH ACCEPT message combined with a new ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message to the UE 210 (step S309). 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 S310). Afterward, the UE sends an ATTACH COMPLETE message combined with the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT message to the EPS (step S311). Once the EPS 220 receives the ATTACH COMPLETE message, the attach procedure ends successfully.
In other embodiments, the UE 210 may rejects the new ATTACH ACCEPT message again and thus the operations in step S305 ̃S307 are repeated. In this case, step S305 ̃S307 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.
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 S401), 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 S402). 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 5403) by sending a new ATTACH ACCEPT message combined with a new ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message to the UE 210 (step S404). If the UE 210 rejects the ATTACH ACCEPT message again (step S405), then the retry process (step S401 ̃S404) 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 S406) 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 S407). Upon receiving the DETACH REQUEST message, the EPS 220 aborts the attach procedure (step S408) and responds by sending a DETACH ACCEPT message to the UE 210 (step S409). Afterward, the attach procedure ends by being considered as failed by both the UE 210 and the EPS 220.
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.

## Claims

1. A user equipment, handling an attach procedure with a service network, comprising:
a wireless module configured to transmit an “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message in accordance with the 3rd Generation Partnership Project (3GPP) technical specifications to the service network and configured to receive an attach accept message replied to the “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message from the service network; and
a controller configured to determine whether to accept the attach accept message according to a first parameter accompanying the attach accept message, and in response to the attach accept message not being accepted, the controller configured to resend, via the wireless module, the “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message with a Resent cause Information Element (IE) indicating that the “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message is being resent due to the attach accept message not being acceptable, to the service network, thereby enabling the service network to adjust the first parameter to be included in another attach accept message corresponding to the resent attach accept message.

2. The user equipment of claim 1, wherein the attach request message is accompanied with a packet data network connection request.

3. The user equipment of claim 2, wherein the packet data network connection request is used to request a connection to an Evolved Packet System in accordance with the 3rd Generation Partnership Project (3GPP) technical specifications.

4. The user equipment of claim 1, wherein the request conforming to “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” is for negotiating bearer configuration.

5. The user equipment of claim 1, wherein the controller performs at least one of the following steps in response to the attach accept message being accepted:
resetting an attach attempt counter and a tracking area updating attempt counter;
entering an EMM-REGISTERED state;
setting an EPS update status to EU1 UPDATED; and
applying configuration specified in the first parameter, wherein the EMM-REGISTERED state and EU1 UPDATED state are in accordance with the 3rd Generation Partnership Project (3GPP) technical specifications.

6. The user equipment of claim 1, wherein the wireless module is further configured to send an attach complete message to the service network in response to the attach accept message being accepted.

7. The user equipment of claim 6, wherein the attach complete message is accompanied with a second parameter corresponding to the first parameter.

8. The user equipment of claim 7, wherein the second parameter is comprised in a response conforming to “ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT” in accordance with the 3rd Generation Partnership Project (3GPP) technical specifications.

9. The user equipment of claim 8, wherein the response conforming to “ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT” is for informing the service network of the acceptance of the first parameter.

10. A method for a user equipment to handle an attach procedure with a service network, comprising:
sending an “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” in accordance with the 3rd Generation Partnership Project (3GPP) technical specifications message to the service network;
receiving an attach accept message replied to the “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message from the service network;
determining whether to accept the attach accept message according to a first parameter accompanying the “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message; and
in response to the attach accept message not being accepted, resending the “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message with a Resent cause Information Element (IE) indicating that the “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” message is being resent due to the attach accept message not being acceptable, to the service network, thereby enabling the service network to adjust the first parameter to be included in another attach accept message corresponding to the resent attach accept message.

11. The method of claim 10, wherein the attach request message is accompanied with a packet data network connection request.

12. The method of claim 11, wherein the packet data network connection request is used to request a connection to an Evolved Packet System in accordance with the 3rd Generation Partnership Project (3GPP) technical specifications.

13. The method of claim 10, wherein the request conforming to “ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST” is for negotiating bearer configuration.

14. The method of claim 10, further comprising performing at least one of the following steps in response to the attach accept message being accepted:
resetting an attach attempt counter and a tracking area updating attempt counter;
entering an EMM-REGISTERED state;
setting an EPS update status to EU1 UPDATED; and
applying configuration specified in the first parameter, wherein the EMM-REGISTERED state and EU1 UPDATED state are in accordance with the 3rd Generation Partnership Project (3GPP) technical specifications.

15. The method of claim 10, further comprising sending an attach complete message to the service network in response to the attach accept message being accepted.

16. The method of claim 15, wherein the attach complete message is accompanied with a second parameter corresponding to the first parameter.

17. The method of claim 16, wherein the second parameter is comprised in a response conforming to “ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT” in accordance with the 3rd Generation Partnership Project (3GPP) technical specifications.

18. The method of claim 17, wherein the response conforming to “ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT” is for informing the service network of the acceptance of the first parameter.