An example embodiment of the present invention relates generally to wireless networks and, more particularly, to closed subscriber group mobility.

Background

In mobile cellular networks, such as those based on the Universal Mobile Telecommunications System (UMTS) standard, a user equipment (UE) will on occasion, such as when the UE has changed locations, be required to switch its connections between cells. This process is referred to as "reselection." In some circumstances, the cell which the UE needs to reselect to is a Closed Subscriber Group (CSG) cell. CSG cells only accept connections from approved UEs, and the process of reselecting to a CSG involves the UE undertaking steps beyond those required to reselect to a normal cell.

These additional steps mean that reselection to CSG cells is currently only possible when the UE is operating in an Idle mode, a CELL PCH Radio Resource Control (RRC) state, or a URA PCH RRC state. Reselection to a CSG cell is possible in Idle and CELL PCH states because these states provide ample Discontinuous Reception (DRX) opportunities, which allow the UE to perform an "autonomous search" for CSG cells. Currently, reselection to CSG cells is not possible in the CELL FACH state, thereby limiting instances in which reselection may be made to CSG cells. Summary

A method, apparatus and computer program product are provided according to an example embodiment in order to effect reselection to a Closed Subscriber Group (CSG) cell. In this regard, the method, apparatus, and computer program product of an example embodiment may increase the instances in which reselection may be made to CSG cells.

In one embodiment, a method for use in a user equipment is provided, the user equipment being served by a current serving cell. The method includes determining that the user equipment is in range of a CSG cell and determining, based on a gap length, whether the user equipment is capable of preparing to perform a mobility procedure with respect with respect to the CSG cell. In another embodiment, the method may further include, in an instance in which it is determined that the user equipment is capable of preparing to perform a mobility procedure with respect to the CSG cell, determining whether the user equipment is a member of the CSG cell, such as based on system information. The method also includes, in an instance in which it is determined that the user equipment is not capable of preparing to perform a mobility procedure with respect to the CSG cell, causing a request to increase the gap length to be transmitted for receipt by the current serving cell. In a further embodiment, the method may further comprise, upon the gap length being increased, determining whether the user equipment is a member of the CSG cell, such as based on system information. In another embodiment, the method may also include, in an instance in which it is determined that the user equipment is a member of the CSG cell, causing the user equipment to initiate reselection with respect to the CSG cell.

In a further embodiment, an apparatus is provided for use in a user equipment being served by a current serving cell. The apparatus includes a processing system, which may be embodied by at least one processor and at least one memory storing program code instructions therein. The processing system is arranged to cause the apparatus to at least determine that the apparatus is in range of a CSG cell and determine, based on a gap length, whether the apparatus is capable of preparing to perform a mobility procedure with respect to the CSG cell. In another embodiment, the processing system may be arranged to cause the apparatus to, in an instance in which it is determined that the apparatus is capable of preparing to perform a mobility procedure with respect to the CSG cell, determine whether the apparatus is a member of the CSG cell, such as based on system information. The processing system is arranged to cause the apparatus to, in an instance in which it is determined that the apparatus is not capable of preparing to perform a mobility procedure with respect to the CSG cell, cause a request to increase the gap length to be transmitted for reception by the current serving cell. In a further embodiment, the processing system may be arranged to cause the apparatus to, upon the gap length being increased, determine whether the apparatus is a member of the CSG cell, such as based on system information. In yet another embodiment, the processing system may be arranged to cause the apparatus to, in an instance in which it is determined that the apparatus is a member of the CSG cell, initiate reselection with respect to the CSG cell.

In a further embodiment, a computer program product is provided for execution by a user equipment being served by a current serving cell, the computer program product comprising a set of instructions, which, when executed by the user equipment, causes the user equipment to perform the steps of: determining that the user equipment is in range of a CSG cell and determining, based on a gap length, whether the user equipment is capable of preparing to perform a mobility procedure with respect to the CSG cell. In another embodiment, the set of instructions, when executed by the user equipment, cause the user equipment to, in an instance in which it is determined that the user equipment is capable of preparing to perform a mobility procedure with respect to the CSG cell, determine whether the user equipment is a member of the CSG cell, such as based on system information. The set of instructions, when executed by the user equipment, also cause the user equipment to, in an instance in which it is determined that the user equipment is not capable of preparing to perform a mobility procedure with respect to the CSG cell, cause a request to increase the gap length to be transmitted for reception by the current serving cell. In a further embodiment, the set of instructions, when executed by the user equipment, causes the user equipment to, upon the gap length being increased, determine whether the apparatus is a member of the CSG cell, such as based on system information. In yet another embodiment, the set of instructions, when executed by the user equipment, causes the user equipment to, in an instance in which it is determined that the user equipment is a member of the CSG cell, initiate reselection with respect to the CSG cell.

In yet another embodiment, an apparatus is provided that includes means for determining that an apparatus is in range of a CSG cell and means for determining, based on a gap length, whether the apparatus is capable of preparing to perform a mobility procedure with respect to the CSG cell. In another embodiment, the apparatus may further include means for determining whether the apparatus is a member of the CSG cell in an instance in which it is determined that the apparatus is capable of preparing to perform a mobility procedure with respect to the CSG cell. The apparatus also includes means for causing a request to increase the gap length to be transmitted in an instance in which it is determined that the apparatus is not capable of preparing to perform a mobility procedure with respect to the CSG cell. In a further embodiment, the apparatus may further comprise means for determining whether the apparatus is a member of the CSG cell, such as based on system information, upon the gap length being increased. In another embodiment, the apparatus may also include means for initiating reselection with respect to the CSG cell in an instance in which it is determined that the apparatus is a member of the CSG cell.

Brief Description of the Drawings

Having thus described certain example embodiments of the present disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

Figure 1 is an illustration of a system depicting communications between user equipment and a network via a plurality of cells in which closed subscriber group cell reselection may be configured in accordance with an example embodiment of the present invention;

Figure 2 is a block diagram of an apparatus that may be configured in accordance with an example embodiment of the present invention;

Figure 3 is a timing diagram depicting an overview of operations carried out in accordance with example embodiments of the present invention;

Figure 4 is a flowchart depicting the operations performed by an apparatus embodied by or otherwise associated with the user equipment in accordance with one embodiment of the present invention; and

Figures 5-8 are signaling diagrams depicting communications between a user equipment, an initial cell, and a closed subscriber group cell performed in accordance with various embodiments of the present invention.

Detailed Description

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

As used in this application, the term "circuitry" refers to all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions ofprocessor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of "circuitry" applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or application specific integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device.

Referring now to Figure 1 , a system that supports communications between user equipment 10 and a network 14, such as a Universal Mobile Telecommunications System (UMTS) network, a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, a Global Systems for Mobile communications (GSM) network, a Code Division Multiple Access (CDMA) network, e.g., a Wideband CDMA (WCDMA) network, a CDMA2000 network or the like, a General Packet Radio Service (GPRS) network or other type of network, via a base station 15 is shown. Various types of user equipment may be employed including, for example, a mobile communication device such as, for example, a mobile telephone, portable digital assistant (PDA), pager, laptop computer, a tablet computer, or any of numerous other hand held or portable communication devices, computation devices, content generation devices, content consumption devices, or combinations thereof. Regardless of the type of user equipment, the user equipment may communicate with the network via an initial cell 12 comprising at least one base station 15, such as a Node B, an evolved Node B (eNB) or other type of access point. The communications between the user equipment 10 and the base station 15 may include the transmission of data via an uplink that is granted between the user equipment 10 and the base station 15.

The user equipment 10 may, on occasion, move 9, so as to be in range of a closed subscription group (CSG) cell 13. Thus, the user equipment may implement example embodiments of the method, apparatus and computer program product in order to transition to the CSG cell 13. As such, the user equipment 10 may embody or otherwise be associated with an apparatus 20 that is generally depicted in Figure 2 and that may be configured in accordance with an example embodiment of the present invention as described below, such as in conjunction with Figure 4 from the perspective of the user equipment. However, it should be noted that the components, devices or elements described below may not be mandatory and thus some may be omitted in certain embodiments. Additionally, some embodiments may include further or different components, devices or elements beyond those shown and described herein.

As shown in Figure 2, the apparatus 20 may include or otherwise be in communication with a processing system including processing circuitry, such as the processor 20 and, in some embodiments, the memory 24, which is configurable to perform actions in accordance with example embodiments described herein. The processing circuitry may be configured to perform data processing, application execution and/or other processing and management services according to an example embodiment of the present invention. In some embodiments, the apparatus or the processing circuitry may be embodied as a chip or chip set. In other words, the apparatus or the processing circuitry may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus or the processing circuitry may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single "system on a chip." As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein. In an example embodiment, the processing circuitry may include a processor 22 and memory 24 that may be in communication with or otherwise control a communication interface 26 and, in some cases in which the apparatus is embodied by the user equipment 10, a user interface 28. As such, the processing circuitry may be embodied as a circuit chip (e.g., an integrated circuit chip) configured (e.g., with hardware, software or a combination of hardware and software) to perform operations described herein. However, in some embodiments taken in the context of the user equipment or the base station 15, the processing circuitry may be embodied as a portion of user equipment or the base station.

The user interface 30 (if implemented in embodiments of the apparatus 20 embodied by the user equipment 10) may be in communication with the processing circuitry to receive an indication of a user input at the user interface and/or to provide an audible, visual, mechanical or other output to the user. As such, the user interface may include, for example, a keyboard, a mouse, a joystick, a display, a touch screen, a microphone, a speaker, and/or other input/output mechanisms.

The communication interface 26 may include one or more interface mechanisms for enabling communication with other devices and/or networks. In some cases, the communication interface may be any means such as a device or circuitry embodied in either hardware, or a combination of hardware and software that is configured to receive and/or transmit data from/to a network 14 and/or any other device or module in communication with the processing circuitry, such as between the user equipment 10 and the base station 15. In this regard, the communication interface may include, for example, an antenna (or multiple antennas) and supporting hardware and/or software for enabling communications with a wireless communication network and/or a communication modem or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB), Ethernet or other methods.

In an example embodiment, the memory 24 may include one or more non- transitory memory devices such as, for example, volatile and/or non-volatile memory that may be either fixed or removable. The memory may be configured to store information, data, applications, instructions or the like for enabling the apparatus 20 to carry out various functions in accordance with example embodiments of the present invention. For example, the memory could be configured to buffer input data for processing by the processor 22. Additionally or alternatively, the memory could be configured to store instructions for execution by the processor. As yet another alternative, the memory may include one of a plurality of databases that may store a variety of files, contents or data sets. Among the contents of the memory, applications may be stored for execution by the processor in order to carry out the functionality associated with each respective application. In some cases, the memory may be in communication with the processor via a bus for passing information among components of the apparatus.

The processor 22 may be embodied in a number of different ways. For example, the processor may be embodied as various processing means such as one or more of a microprocessor or other processing element, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), or the like. In an example embodiment, the processor may be configured to execute instructions stored in the memory 24 or otherwise accessible to the processor. As such, whether configured by hardware or by a combination of hardware and software, the processor may represent an entity (e.g., physically embodied in circuitry - in the form of processing circuitry) capable of performing operations according to embodiments of the present invention while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA or the like, the processor may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor is embodied as an executor of software instructions, the instructions may specifically configure the processor to perform the operations described herein.

Figure 4 is a flowchart illustrating the operations performed by a method, apparatus and computer program product, such as apparatus 20 of Figure 2 in accordance with an example embodiment of the present invention. It will be understood that each block of the flowchart, and combinations of blocks in the flowchart, may be implemented by various means, such as hardware, firmware, processor, circuitry and/or other device associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a memory 24 of an apparatus employing an embodiment of the present invention and executed by a processor 22 in the apparatus. As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus provides for implementation of the functions specified in the flowchart blocks. These computer program instructions may also be stored in a non-transitory computer-readable storage memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage memory produce an article of manufacture, the execution of which implements the function specified in the flowchart blocks. The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart blocks. As such, the operations of Figures 3 and 4, when executed, convert a computer or processing circuitry into a particular machine configured to perform an example embodiment of the present invention. Accordingly, the operations of Figures 4 define an algorithm for configuring a computer or processing circuitry, e.g., processor, to perform an example embodiment. In some cases, a general purpose computer may be provided with an instance of the processor which performs the algorithm of Figure 4 to transform the general purpose computer into a particular machine configured to perform an example embodiment.

Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will also be understood that one or more blocks of the flowchart, and combinations of blocks in the flowchart, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions.

In some embodiments, certain ones of the operations above may be modified or further amplified as described below. Moreover, in some embodiments additional optional operations may also be included. It should be appreciated that each of the modifications, optional additions or amplifications below may be included with the operations above either alone or in combination with any others among the features described herein.

Referring again to Figure 1 , it will be understood that during, or in-between, communication sessions between the user equipment (UE) 10 and the network 14, such as through an initial cell 12 comprising at least one base station 15, the UE may move 9, placing it in range of a Closed Subscriber Group (CSG) cell 13. Thus, it may be desirable for the UE to perform a mobility procedure with respect to the CSG cell 13, e.g., to transition from communicating with the network 14 via the initial cell 12, to communicating with the network 14 via the CSG cell 13. The mobility procedure used to transition to the CSG cell may include, for example initiating a reselection procedure, initiating a redirection procedure, or initiating a handover procedure. In embodiments that utilize a redirection or handover procedure as the mobility procedure, initiating the mobility procedure may, for example, involve the UE 10 sending a report including information needed for the network to initiate the handover or redirection. It should be understood that the mobility procedure is not limited to a reselection, redirection, or handover procedure, but instead may be any suitable mobility procedure that results in terminating the connection with the initial cell and establishing a connection with the CSG cell. Regardless of the mobility procedure used, certain preparations may be required, such as, for example, reading system information (SI) to determine whether the UE 10 is a member of the CSG cell. In certain scenarios, such as, for example, when the UE 10 is operating in a CELL FACH state, these preparations may not be possible due to certain timing limitations.

For instance, referring now also to Figure 3, the periods between paging occasions 30, e.g., the DRX cycle "gaps" 31, may be too short to permit the UE 10 to prepare to perform a mobility procedure, such as by reading system information. Thus, according to an example embodiment of the present invention, upon detecting that the CSG cell 13 is in range, but that the gaps 31 are not long enough to prepare to perform a mobility procedure (see block 32), the UE 10 may request, such as via a Cell update message 61, that the length of the gaps 31 be extended. The network 14, such as through a base station 15 associated with the initial cell 12, may then respond, such as with a Cell update confirm message 62, which triggers the UE 10 to use a longer gap 36. DRX may, in some embodiments, be stopped during this exchange between the UE 10 and network 14, as indicated by block 35. During the longer gap 36, the UE may prepare to perform the mobility procedure, including, for example, reading System Information (SI) being broadcast by the CSG cell 13. The longer gap 36 may be provided as part of, for example, a 2 ^nd CELL FACH DRX cycle that may ordinarily only be available after a predetermined period of inactivity. The SI may include, for example, a CSG ID associated with the CSG 13. Thus, in certain embodiments, the UE 10 may determine whether it is a member of the CSG 13 based on the SI. For example, the UE may check the CSG ID against a "whitelist" that identifies the CSGs of which the UE is a member. The whitelist may, for example, be stored on the UE 10. The whitelist may also, for example, be stored in a server or other storage means associated with the network 14, such as a Network-attached Storage (NAS). Upon determining whether the UE 10 is a member of the CSG, such as by comparing the CSG ID to a whitelist, the UE 10 may then perform the mobility procedure with respect to the CSG cell 13 if it is a member. If the UE 10 is not a member, the UE 10 may resume communication with the network 14 via the initial cell 12 and re-enter the initial DRX cycle 30, 31. The UE 10 may also resume any pending data transmission or reception with continuous transmission or reception.

Thus, having described in general the basic functionality of the present invention, reference will now be made to Figures 4-8, so as to discuss in further detail, example embodiments of the present invention. In this regard, the apparatus may include means, such as the processing circuitry, the processor 22, the communications interface 26 or the like, for determining whether the apparatus 20 is in range of a CSG cell. See block 40 of Figure 4. Determining whether the apparatus 20 is in range of a CSG cell may, for example, involve using inter- frequency measurement, such as via the communications interface 26 or the like, to detect that a CSG cell 13 is broadcasting on a frequency other than the frequency on which the apparatus is communicating with an initial cell 12. In other embodiments, a proximity detection mechanism may instead be used to detect that the apparatus is in range of the CSG cell 13. For example, the proximity detection mechanism may include using Global Positioning System (GPS) information or Radio Frequency (RF) fingerprint matching, in which RF measurements taken from neighboring cells are stored and compared to subsequent measurements. In certain embodiments, the proximity detection mechanism may, for example, be used as a fallback when inter- frequency measurements are not possible.

The apparatus may further include means, such as the processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for determining whether the current gap length is sufficient to prepare to perform a mobility procedure. A gap may, for example, be a FACH measurement occasion or a DRX cycle gap. If the gap length is such that preparing to perform a mobility procedure is possible, then the apparatus 20 can prepare for and perform the mobility procedure. For example, if there is currently a period of low data activity, the UE 10 may have entered a 2 ^nd DRX cycle which can have gaps sufficiently long to prepare for the mobility procedure. Preparing for the mobility procedure may, for example, consist of reading system information (SI) and determining whether the UE 10 is a member of the CSG. In another embodiment, preparing for the mobility procedure may also involve performing measurements on the CSG frequency. The mobility procedure itself may involve, for example, initiating a reselection to the CSG cell 13, initiating a redirection to the CSG cell 13, or initiating a handover to the CSG cell 13, if the UE 10 is a member.

Whatever operations preparing to perform the mobility procedure may involve, determining whether the gap length is sufficient to prepare to perform the mobility procedure may, for example, involve the apparatus 20, such the processing circuitry, the processor 22, the memory 24 or the like, comparing the amount of time necessary to prepare to perform the mobility procedure to the length of the gap. The time necessary to prepare for the mobility procedure may, in some embodiments be an estimate. In some embodiments, the time necessary to prepare to perform the mobility procedure, or an estimate thereof, may be provided to the apparatus 20, such as via the communications interface 26 or the like, or stored in the memory 24 of the apparatus. In some embodiments, the estimated time necessary to prepare to perform the mobility procedure may account for radio conditions, such as accounting for multiple attempts being required to read system information do to reception errors, The gap length may be provided to the apparatus 20, such as via the communications interface 26 or the like, such as in SI broadcast by the initial cell 12 via a base station 15.

The apparatus may further include means, such as the processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for, in an instance in which the gaps are not long enough to prepare for a mobility procedure, completing a portion of the preparation. See block 45. As indicated by the dotted lines of block 45, performing a portion of preparation for the mobility procedure is not essential. Performing a portion of the preparation for the mobility procedure may allow the UE 10 to at least gain a certain amount of information to send to the network 14. For example, in certain embodiments the apparatus 20 may at least perform measurements on the CSG 13 frequency. The apparatus 20 may also, for example, detect whether a CSG cell 13 has the potential to be a member cell. In either case, the UE 10 may provide this information, such as with the communications interface 26 or the like, to the network 14, such as via a base station 15 associated with the initial cell 12. In some circumstances, no gaps at all may be provided. In this case, the UE 10 may not be able to perform the measurement and may simply inform the network 14 of, for example, the existence of the CSG cell 13, but provide no measurements. In certain embodiments, the UE 10 may, upon detecting an insufficient gap length, not attempt any portion of the reselection procedure, but rather simply inform the network 14 that longer gaps are needed. In other embodiments, the UE 10 may simply wait for long enough gaps before starting the reselection procedure.

The apparatus may further include means, such as the processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for requesting an increased gap length in an instance in which a longer gap is needed. See block 46. In some embodiments, requesting an increased gap length may take the form of, for example, providing an indication to the network 14, such as via a base station 15 associated with the initial cell 12, of the potential that the CSG cell 13 is a member cell. The UE 10 may also provide measurements, if any have been taken. This information may be provided to the network 14 in a Cell Update message. In one embodiment, the Cell Update message may be an enhanced Cell Update message. Thus, for example, the Cell Update message may contain a new cause. In another embodiment, the measurements may even be included in the Cell Update message. The Cell Update message may then be interpreted as a request for a longer gap length. In other embodiments, the request for a longer gap length may, for example, be included as part of a Measurement Report or a Signaling Connection Release Indication. In other embodiments, a Measurement Report or a Signaling Connection Release Indication may be interpreted as a request for a longer gap length, without including an explicit request therein.

After the UE 10 requests a longer gap length, the network 14 may reconfigure to provide a longer gap length. The network 14 may, for example, provide a longer DRX cycle length. In other embodiments, the network 14 may, for example, "allow" the UE 10 to use a longer gap length either on a temporary basis, or a more permanent basis. In certain situations, the UE 10 may be engaged in ongoing data transmission or reception and, in this case, the ongoing transmission/reception may be suspended temporarily. In some embodiments, the UE 10 may already have 2 ^nd DRX cycle configuration and, therefore, the UE 10 may simply use a Cell Update procedure to suspend data in order to enter the 2 ^nd DRX cycle. In certain embodiments, the UE 10 may enter the longer DRX mode upon reception of a corresponding command from the network 14. The UE 10 may, for example, enter the longer DRX mode at the time of the start of the next DRX cycle. Thus, the UE 10 may, for example, not need wait for the expiration of an inactivity timer, such as a T321 inactivity timer, to transition to the longer DRX mode.

The apparatus may further include means, such as the processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for preparing to perform a mobility procedure either after the gap length has been increased, or after it was determined that the current available gap length was sufficient. Preparing to perform the mobility procedure may, for example, consist of reading system information (SI) and determining whether the UE 10 is a member of the CSG. See blocks 42 and 43. In another embodiment, preparing to perform the mobility procedure may also involve performing measurements on the CSG frequency. The SI may, for example, be broadcast by the CSG cell and may include, for example, a CSG ID and/or Public Land Mobile Network (PLMN) ID. In some embodiments, determining whether the UE 10 is a member of the CSG may, for example, involve determining, such as with the processor 22, the memory 24, the communications interface 26 or the like, whether the CSG ID and/or PLMN ID are contained in a "whitelist," which is a list of allowed CSG and/or PLMN IDs. In another embodiment, if the apparatus 20 determines that the UE 10 is not a member of the CSG 13, then the apparatus 20, such as the processing circuitry, the processor 22, the communications interface 26 or the like, may cause the UE 10 to return to the initial cell 12. The apparatus 20 may then, for example, cause the UE 10 to monitor a Paging Indicator Channel (PICH) or High Speed Shared Control Channel (HS-SCCH) on the next scheduled paging occasion. Thus, the network 14 may, in some embodiments, never have known that the UE 10 prepared to perform a mobility procedure with respect to a non-member CSG cell 13, as it may not have missed any scheduled transmissions from the network 14. In other embodiments, the UE 10 may cause a failed report to be transmitted to the network 14, such as via a base station 15 associated with initial cell 12. See block 47. The failed report may, for example, be transmitted via a cell update. In yet another embodiment, the UE 10 may report, such as with the communications interface 26 or the like, to the initial cell 12 and await a confirmation before performing a mobility procedure with respect to the CSG cell 13. The reporting and confirmation may be provided, for example, via a Cell Update procedure. The confirmation may, for example, take the form of an acknowledgement in CELL Update Confirm. In another embodiment, the mobility procedure may involve being caused to transition to a CELL DCH state and being caused to take part in a Packet Switched (PS) handover to the CSG cell 13.

The apparatus may further include means, such as the processing circuitry, the processor 22, the memory 24, the communications interface 26 or the like, for performing the mobility procedure with respect to the CSG cell, in an instance in which the UE 10 is determined to be a member of the CSG cell. See block 44. Performing the mobility procedure may involve, for example, initiating a reselection to the CSG cell 13, initiating a redirection to the CSG cell 13, or initiating a handover to the CSG cell. The mobility procedure may also involve any other operation which may result in the UE 10 transitioning to the CSG cell 13.

Having thus described features of the present invention in more detail, reference will now be made to Figures 5-8 in order to provide examples of the types of signaling that may take give produce some of the functionality of various embodiments.

Turning first to Figure 5, a scenario is depicted in which the UE 10 determines that it is in range of the CSG cell 13 and that the available gap length is sufficient to prepare to perform a mobility procedure. See block 50. In this embodiment, the CSG cell 13 broadcasts System Information (SI) 51, which is read by UE 10. If the UE 10 determines that it is a member of the CSG cell 13, it may, for example, transmit a Cell Update message 52 to the CSG 13 in order to initiate a mobility procedure. The CSG cell 13 may then transmit a confirmation in response, such as a Cell Update Confirm message 53. The UE 10 may then transmit a response 54, such as, for example a Universal Terrestrial Radio Access Network (UTRAN) Mobility Information Confirm message to the CSG cell 13.

Turning now to Figures 6-8, scenarios are depicted in which the UE 10 determines that it is in range of the CSG cell 13, but that the gap length is not long enough to prepare for a mobility procedure. See block 60.

Figure 6 depicts a successful transition to a CSG cell 13, such as via reselection or another mobility procedure, according to an example embodiment. Thus, in accordance with the example embodiment, upon determining that the gap length is insufficient, the UE 10 may transmit a Cell Update message 61 to the initial cell 12. The Cell Update message 61 may, for example, include measurement results and/or an indication of the CSG cell's 13 proximity to the UE 10. The Cell Update message 61 may also include measured results on a Random Access Channel (RACH). The Cell Update message 61 may also include, for example, a new "Cell Update Cause," such as, for example, that measurements are available. Thereafter, the initial cell 12 may respond with a Cell Update Confirm message 62. The Cell Update Confirm message 62 may include, for example, a longer DRX cycle configuration and/or autonomous gap configuration. In response, the UE 10 may transmit a Physical Channel Reconfiguration Complete message 63 to the initial cell 12. As indicated by the dotted line, the Physical Channel Reconfiguration Complete message 63 is optional. It may be used to confirm that the longer DRX cycle was successfully accepted, but may not be needed if autonomous gaps are being used instead. During the longer gap, the UE 10 may then read SI 51 broadcast by the CSG cell 13. See block 68. The Cell Update message 52, Cell Update Confirm message 53 and response 54 are otherwise in accordance with the embodiment depicted in Figure 5, described above.

Figure 7 depicts an unsuccessful transition to a CSG cell 13 according to another example embodiment. In accordance with the example embodiment, upon determining that the gap length is insufficient, the UE 10 and initial cell 12 may communicate similarly to the embodiment depicted in Figure 6. However, in this embodiment, the UE 10 determines, upon reading SI 51 broadcast by CSG cell 13, that it is not a member of the CSG cell 13. See block 78. Thus, according to one embodiment, the UE 10 transmits a Cell Update message 75 to the initial cell 12. The Cell Update message may, for example, indicate a membership check failure. The initial cell 12 may thereafter respond with a Cell Update Confirm message 76. The Cell Update Confirm message 76 may, for example, remove the longer gap configuration. Following receipt of the Cell Update Confirm message 76, the UE 10 may then transmit a response, such as a Physical Channel Reconfiguration Complete message 77.

Figure 8 also depicts an unsuccessful transition to a CSG cell 13. Unlike the embodiment depicted in Figure 7, the embodiment depicted in Figure 8 does not include the UE 10 providing a membership check failure indication to the initial cell 12. Instead, upon determining that a member check failure has occurred, the UE 10 returns to the initial cell and resumes normal operation 85. Normal operation may be continued, for example, after the DRX period ends. According to another embodiment, the UE 10 may, for example, re-enter a shorter DRX cycle if there is some data to transmit or receive.

Example embodiments, such as those described above, may involve a UE 10 that is operating in a CELL FACH state. These embodiments offer the advantage of enabling mobility to CSG cells 13 in a CELL FACH state. In addition, a method, apparatus, and computer program product of an example embodiment of the present invention provides a hybrid solution that utilizes reselection measurements and evaluation, while minimizing impact on ongoing service, for example by minimizing missed data packets.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.