CLIAMS:
1. A method of optimizing service recovery during Manual Closed Subscription Group (CSG) selection in LTE, the method comprises of:
triggering, by a User Equipment (UE), a manual selection of a Closed Subscriber Group (CSG) cell;
performing a Tracking Area Update (TAU) on the selected CSG cell;
receiving, by the UE, a registration rejection with one or more temporary causes from a network for the selected CSG cell;
checking if the registration is rejected with the temporary cause other than cause #25; and
performing service recovery of the UE with a Registered Public Land Mobile Network (RPLMN) if the temporary cause is other than cause #25.

2. The method claim 1, wherein performing service recovery of the UE comprises of:
ignoring the CSG registration reject cause;
adding a rejected CSG to a Failed Closed Subscription Group (FCSG) list; and
adding one or more Tracking Area Identities (TAIs) to a Failed Tracking Area Identity (FTAI) list.

3. The method of claim 1, further comprising performing service recovery using normal service recovery actions if the registered PLMN is not available.

4. The method of claim 1, wherein service recovery for UE during manual CSG selection is performed by at least one of:
retaining a Globally Unique Temporary ID (GUTI);
previously visited registered TAI, Key Set Identifier (KSI) and Equivalent Public Land Mobile Network (EPLMN) lists;
retrying registration multiple times on a single CSG cell;
employing a preset PLMN for recovery procedures; and
performing the TAU instead of an Attach while returning to the preset PLMN thereby reducing the delay while recovering to the preset PLMN.

5. A system for optimizing service recovery during Manual Closed Subscription Group (CSG) selection in LTE, the system comprising:
a user equipment adapted for:
triggering manual selection of a CSG cell;
performing a Tacking Area Update (TAU) on the selected CSG cell;
receiving a registration rejection with one or more temporary causes from a network for the selected CSG cell;
checking if the registration is rejected with the temporary cause other than cause #25; and
performing service recovery with a Registered Public Land Mobile Network (RPLMN). ,TagSPECI:
FIELD OF THE INVENTION
The present invention generally relates to wireless communication and particularly relates to a method and system for optimizing service recovery of User Equipments (UE) during Manual Closed Subscriber Group (CSG) selection in wireless communication.

BACKGROUND OF THE INVENTION

In an LTE system, a home base station, sometimes called a femto base station or a pico base station, is considered to be a promising solution for many issues in mobile communication networks, such as coverage, capacity, and cost. The home base station delivers a great user experience in homes, office buildings or schools, at very low cost, using customer's broadband access (e.g. digital subscriber line (DSL) or cable television backhaul). For this application, the home base station usually serves small cellular coverage that has a restricted group of users and only allows access and provides service to the restricted group of users, which can be referred as to a Closed Subscriber Group (CSG). Such cells providing the small cellular coverage are referred to as femto-cells, Home Node B (HNB) cells, Home e-Node B (HeNB) cells or, most commonly, CSG cells.

The CSG cell is accessible only for a limited set of User Equipments (UEs) (i.e. closed subscriber group). In order to prevent a UE from attempting to register on a CSG cell on which they do not have access, the UE maintains an allowed CSG list, i.e. a list of CSG identities (IDs) for which access has been granted to the UE. The CSG ID is an identifier broadcast by the CSG cell or cells and used by the UE to facilitate access for authorized members of the associated CSG.

The Closed Subscriber Group (CSG) identifies subscribers of an operator who are permitted to access one or more cells of a Public Land Mobile Network (PLMN) but which have restricted access. In automatic mode of CSG selection, the access stratum utilizes a list in the UE (combination of Operator CSG list and Allowed CSG list) to re-select/handover to a CSG cell. In Manual mode, the available CSGs are scanned and displayed to the user based on configuration by a Home Public Land Mobile Network (HPLMN) on a Universal Integrated Circuit Card (UICC). Upon manually selecting the CSG cell, the UE’s behavior is differentiated based on whether the selected CSG belongs to a registered PLMN or not.

Consider a scenario where the user selects a CSG ID from the available CSG list during manual CSG selection. The user is generally unaware of the registration status that is received due to the selection. The user’ registration onto the selected CSG cell is rejected with a particular cause value. A new cause value #25 is introduced for the CSG subscription reject cases, which allows the UE to recover and go back to a saved or previously visited PLMN without any delay. Also, during manual CSG registration the network can send any of the reject cause other than cause value #25 when the CSG subscription fails.

As per 3GPP specification, if the CSG subscription is rejected due to the user selection, the contexts in the UE like security parameters, Equivalent PLMN (ePLMN) list, Globally Unique Temporary Identifier (GUTI) etc., are deleted, Evolved Universal Terrestrial Radio Access (E-UTRA) is disabled or Subscriber Identity Module (SIM) is invalidated. This causes the UE to go to limited services and also the UE may need to switch the Radio Access Terminal (RAT) as the EUTRA is disabled. Further a fresh registration procedure needs to be performed for the recovery of the UE to receive normal services by moving back onto the saved PLMN and this will not be possible without a large delay or a power cycle.

Consider another scenario, where the UE is registered with PLMN of a first operator on a non-CSG/CSG cell and the user initiates a manual CSG selection by selecting the CSG belonging to PLMN of a second operator. In such case, if the CSG registration fails, it is rejected with temporary cause values other than #25. Further if the EUTRA is disabled or the contexts are invalidated, then the UE will take long time for recovering back to normal services.

In view of the foregoing, there exists a need for a method for optimizing manual CSG selection which enables UE to perform faster service recovery during CSG registration failure.

The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.

SUMMARY OF THE INVENTION

The various embodiments herein provide a method for enabling faster service recovery to the User Equipment (UE) during a Manual Closed Subscription Group (CSG) selection in LTE. According to the present invention, the method comprises steps of triggering by a UE, a manual selection of a CSG cell, performing a Tracking Area Update (TAU) on the selected CSG cell, receiving by the UE, a registration rejection with one or more temporary causes from a network for the selected CSG cell, checking if the registration is rejected with the temporary cause other than cause #25 and performing service recovery of the UE with a Registered Public Land Mobile Network (RPLMN).

According to an embodiment of the present invention, performing service recovery of the UE comprises of ignoring the CSG registration reject cause, adding a rejected CSG to a Failed Closed Subscription Group (FCSG) list and adding one or more Tracking Area Identities (TAIs) to a Failed Tracking Area Identity (FTAI) list.

According to an embodiment of the present invention, the method further comprises of performing service recovery using normal service recovery actions if the registered PLMN is not available.

According to an embodiment of the present invention, service recovery for the UE during manual CSG selection is performed by at least one of retaining a Globally Unique Temporary ID (GUTI), previously visited registered TAI, Key Set Identifier (KSI) and Equivalent Public Land Mobile Network (EPLMN) lists, retrying registration multiple times on a single CSG cell, employing a preset PLMN for recovery procedures and performing the TAU instead of an Attach while returning to the preset PLMN thereby reducing the delay while recovering to the preset PLMN.

Embodiments herein further disclose a system for optimizing service recovery during Manual Closed Subscription Group (CSG) selection in LTE. The system comprises of an user equipment adapted for triggering manual selection of a CSG cell, performing a Tacking Area Update (TAU) on the selected CSG cell, receiving a registration rejection with one or more temporary causes from a network for the selected CSG cell, checking if the registration is rejected with the temporary cause other than cause #25 and performing service recovery with a Registered Public Land Mobile Network (RPLMN).

The foregoing has outlined, in general, the various aspects of the invention and is to serve as an aid to better understanding the more complete detailed description which is to follow. In reference to such, there is to be a clear understanding that the present invention is not limited to the method or application of use described and illustrated herein. It is intended that any other advantages and objects of the present invention that become apparent or obvious from the detailed description or illustrations contained herein are within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

Figure 1 is a schematic diagram illustrating a method of optimizing selection of Closed Subscriber Group (CSG) cell during manual CSG selection, according to an embodiment of the present invention.

Figure 2 is a flow chart illustrating a method of optimizing CSG cell selection during manual CSG selection, according to an embodiment of the present invention.

Although specific features of the present invention are shown in some drawings and not in others, this is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The various embodiments of the present invention disclose a method of providing service recovery to the UE during manual CSG selection in LTE. In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

The specification may refer to “an”, “one” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations and arrangements of one or more of the associated listed items.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Figure 1 is a schematic diagram illustrating a method of optimizing selection of Closed Subscriber Group (CSG) cell during manual CSG selection, according to an embodiment of the present invention. According to the present invention, the UE 102 is registered onto a Public Land Mobile Network (RPLMN) 104 of a first operator in a network. The user initiates a manual CSG selection by selecting the CSG belonging to a PLMN 106 of a second operator. Meanwhile the PLMN on which the UE is currently registered i.e., RPLMN 104 is saved for further reference. During manual CSG selection of the CSG cell, if the CSG registration on the PLMN 106 of the second operator fails, the UE 102 receives either a reject cause #25 or one or more temporary causes other than cause #25 from the network. If the UE 102 receives cause #25, the UE 102 follows the procedures as specified in the 3GPP standards 24.301 and returns to the RPLMN 104 of the first user. If the UE 102 receives temporary causes other than cause #25, then UE 102 ignores the received reject cause actions and perform the recovery procedure using the saved PLMN. If RPLMN 104 is not available, the UE 102 performs service recovery using normal recovery actions. The rejected CSGs are added to a Failed Closed Subscriber Group (FCSG) list and rejected Tracking Area Identities (TAIs) are then added to a Failed Tracking Area Identity (FTAI) list. As an optimization, during automatic CSG selection, registration of the UE will not be attempted on the CSG cells that are added to the FCSG list or FTAI list until next power cycle.

Figure 2 is a flow chart illustrating a method of optimizing CSG cell selection during manual CSG selection, according to an embodiment of the present invention. . At step 202, the UE triggers a manual selection of a CSG cell. At step 204, the UE performs a tracking area update (TAU) on the selected CSG cell. At step 206, the UE receives a registration rejection indication with a temporary cause for the selected CSG from the network At step 208, the UE checks if the temporary cause received is a cause #25 or not. If the reject cause received is other than cause #25, then UE performs the service recovery with a registered PLMN (RPLMN) at step 210. If the reject cause received is cause #25, then return to the previously visited registered PLMN at step 212.

Further, during the service recovery, the UE ignores the received CSG registration reject cause and goes back to the normal mode. The rejected CSGs are then added to a FCSG list or one or more TAIs to a FTAI list.

The embodiments as disclosed herein enables the UE to recover quickly to normal services during manual CSG selection. The GUTI, last visited registered TAI, KSI and EPLMN lists are not maintained for further reference. The rejected CSGs are added to the FCSG list to avoid multiple registrations on the same CSG cell. Further performing TAU instead of Attach while recovering to the saved PLMN (RPLMN) will reduce the delay in service recovery.

The present embodiments have been described with reference to specific example embodiments; it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments. Furthermore, the various devices, modules, and the like described herein may be enabled and operated using hardware circuitry, for example, complementary metal oxide semiconductor based logic circuitry, firmware, software and/or any combination of hardware, firmware, and/or software embodied in a machine readable medium. For example, the various electrical structure and methods may be embodied using transistors, logic gates, and electrical circuits, such as application specific integrated circuit.

Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.