WO2009112323A1

WO2009112323A1 - Method and apparatus for controlling access to a cellular communication network

Info

Publication number: WO2009112323A1
Application number: PCT/EP2009/051701
Authority: WO
Inventors: David Neil
Original assignee: Ip.Access Limited
Priority date: 2008-03-12
Filing date: 2009-02-13
Publication date: 2009-09-17
Also published as: GB2458449B; GB0804544D0; GB2458449A

Abstract

A network element for providing access to a cellular communication network via a communication cell, the network element comprising signal processing logic arranged to broadcast within the communication cell an access control indicator, and upon receipt of a cell-based message from a wireless communication unit within the communication cell, to determine whether to provide the wireless communication unit access to the cellular communication network via the communication cell. If it is determined not to provide the wireless communication unit access, the signal processing logic is further arranged to reject the wireless communication unit.

Description

METHOD AND APPARATUS FOR CONTROLLING ACCESS TO A CELLULAR COMMUNICATION

NETWORK

Field of the invention The field of the invention relates to a method and apparatus for controlling access to a cellular communication network, and more particularly to a method and apparatus for controlling access to a cellular communication network on a cellular level.

Background of the Invention Wireless communication systems, such as the 3^rd Generation (3G) of mobile telephone standards and technology, are well known. An example of such 3G standards and technology is the Universal Mobile Telecommunications System (UMTS), developed by the 3^rd Generation Partnership Project (3GPP) (www.3qpp.org).

Typically, wireless subscriber communication units, or User Equipment (UE) as they are often referred to in 3G parlance, communicate with a Core Network (CN) of the 3G wireless communication system via a Radio Network Subsystem (RNS). A wireless communication system typically comprises a plurality of radio network subsystems, each radio network subsystem comprising one or more cells to which UEs may attach, and thereby connect to the network.

The 3^rd generation of wireless communications has been developed for macro-cell mobile phone communications. Such macro cells utilise high power base stations (NodeBs in 3GPP parlance) to communicate with UEs within a relatively large coverage area.

Lower power (and therefore smaller coverage area) femto cells or pico-cells are a recent development within the field of wireless cellular communication systems. Femto cells or pico-cells (with the term femto cells being used hereafter to encompass pico-cells or similar) are effectively communication coverage areas supported by low power base stations (otherwise referred to as Access Points (APs)). These femto cells are intended to be able to be piggy-backed onto the more widely used macro-cellular network and support communications to UEs in a restricted, for example 'in-building', environment.

In this regard, a femto cell that is intended to support communications according to the 3GPP standard will hereinafter be referred to as a 3G femto cell. Similarly, an access controller intended to support communications with a low power base station in a femto cell according to the 3GPP standard will hereinafter be referred to as a 3^rd generation access controller (3G AC). Similarly, an Access Point intended to support communications in a femto cell according to the 3GPP standard will hereinafter be referred to as a 3^rd Generation Access Point (3G AP). Typical applications for such 3G femto cell APs include, by way of example, residential and commercial (e.g. office) locations, 'hotspots', etc, whereby an AP can be connected to a core network via, for example, the Internet using a broadband connection or the like. In this manner, femto cells can be provided in a simple, scalable deployment in specific in-building locations where, for example, network congestion at the macro-cell level may be problematic. Typically, each 3G femto cell AP is owned by a member of the public, as opposed to a

Network Operator, and the owner of the 3G AP pays for the network resources, such as Digital Subscriber Line (DSL) bandwidth, used through the femto cell. As a result, it is undesirable for unauthorised UEs to use the femto cell as it will result in the owner paying for the network resources utilised. Accordingly, it is desirable for access control to be provided on a cellular level, enabling an owner of, for example, a femto cell AP to be able to control which UEs are able to access the network via the femto cell.

In a traditional macro-cellular network, since base stations (Node Bs) are generally owned and operated by the Network Operator, it has not been necessary to provide cell level access control. Instead, access control is provided on a network level basis. Furthermore, as will be appreciated by a skilled artisan, it is desirable to minimise communication between a UE and the network, in order to allow resources there between to be used more efficiently, and to avoid excessive signalling load on the network. Thus access control on the cellular level has been considered undesirable to a large extent for traditional macro networks.

As known by a skilled artisan, each cell within a UMTS network is assigned a Location Area Code (LAC), and each time a UE moves to a new cell comprising a different LAC to that of the cell from which it has moved, the UE sends a Location Update Request message to the core network. Consequently, the ability of the network to determine the location of a particular UE is dependent on the granularity of location areas. As will be appreciated by a skilled artisan, location areas are typically planned to cover geographical areas large enough to minimise unnecessary communication between UEs and the network for the purpose of location updates, whilst still enabling sufficient granularity for the purpose of routing calls, etc. to/from the UEs.

FIG. 1 illustrates an example of a simplified message sequence chart 100 of a known location update procedure. The location update sequence starts with a UE 1 10 'camped' on a cell comprising a first LAC 'L1 ' 145. The UE 110 moves to a new communication cell, supported by Node-B 120, and comprising a second LAC 'L2', which is broadcast by a Radio Network Controller (RNC) 130 for the Node-B 120 within a system information broadcast 150.

Upon reading the system information broadcast 150, and determining that it has entered a new location area, the UE 110 establishes a Radio Resource Control (RRC) connection 155 with the RNC 130. The UE 110 then sends a Location Update Request message 160 via the RNC 130 to a Mobile Switching Centre (MSC) 140 within the core network. The UE 110 and MSC 140 perform identity and security procedures 165, as are well known in the art, before the MSC 140 sends a Location Update Accept message 170 back to the UE 110. The RRC connection is then released 175.

This location update messaging provides a coarse mechanism for network access control, since a location area typically corresponds to a geographical area covering multiple cells. Consequently, the Location Update mechanism is not appropriate for cellular level access control. In particular, this method could not realistically be scaled to provide cell level access control for individual cells, such as femto cells, since the number of femto cells (potentially in the region of millions) will significantly exceed the number of available location area codes (65,535) supported within the 3GPP standard. Support of Localised Service Area (SoLSA) was developed by 3GPP to provide cell level access control. However, SoLSA required modifications to be made at many levels within the network, including within the core network and the access network, as well as within UEs themselves. Accordingly, SoLSA has not been adopted by the manufacturers of UEs of network elements.

Thus, there exists a need for a method and apparatus for controlling access to a cellular communication network that substantially alleviates at least some of the deficiencies of known access control mechanisms and techniques hereinbefore described.

Summary of the Invention

Accordingly, the invention seeks to mitigate, alleviate or eliminate one or more of the abovementioned disadvantages, singly or in any combination. According to a first aspect of the invention, there is provided a network element for providing access to a cellular communication network via a communication cell. The network element comprises transceiver circuitry arranged to enable a connection to be established with at least one wireless communication unit located within the communication cell, and signal processing logic. The signal processing logic is arranged to broadcast within the communication cell an access control indicator; and upon receipt of a cell-based message from a wireless communication unit operational within the communication cell, determine whether to provide the wireless communication unit access to the cellular communication network via the communication cell.

In one optional embodiment of the invention, if it is determined not to provide the wireless communication unit access, the network element rejects the wireless communication unit. In this manner, a network element is able to indicate to wireless communication units entering its respective communication cell whether access control is performed for that cell. Consequently, upon entering such a communication cell in which access control at a cell level is performed, a wireless communication unit is able to read the broadcast signal comprising the access control indicator, and in response transmit a cell-based message. Accordingly, by transmitting the cell-based message, the wireless communication unit notifies the network element that it has entered its cell, and thereby enables the network element to perform access control on a cellular level.

Furthermore, by broadcasting such an access control indication to roaming wireless communication units, unnecessary communication between wireless communication units and network elements providing communication cells in which access control is not performed is substantially avoided. Moreover, by broadcasting the access control indication at the cellular level, and by performing the access control at the cellular level, excessive signalling load on the network may be substantially avoided.

According to a second aspect of the invention, there is provided a method for controlling access to a cellular communication network via a communication cell, wherein the method comprises broadcasting within the communication cell an access control indicator and upon receipt of a cell- based message from a wireless communication unit within the communication cell, determining whether to provide the wireless communication unit access to the cellular communication network via the communication cell.

If it is determined not to provide the wireless communication unit access, the method further comprises rejecting the wireless communication unit access to the communication network. According to a third aspect of the invention, there is provided a wireless communication system adapted to support the abovementioned method for controlling access to a cellular communication network via a communication cell.

According to a fourth aspect of the invention there is provided a wireless communication unit comprising transceiver circuitry arranged to receive signals broadcast by a network element of a communication cell within a cellular communication network, and signal processing logic. The signal processing logic is arranged to read a signal broadcast within a communication cell; and determine whether the broadcast signal comprises an access control indicator indicating that access control is performed for the communication cell. If the broadcast signal comprises an access control indicator indicating that access control is performed for the communication cell, the wireless communication unit transmits a cell-based message.

According to a fifth aspect of the invention there is provided a method for accessing a cellular communication network via a communication cell by a wireless communication unit. At a wireless communication unit the method comprises reading a signal broadcast within a communication cell from a network element; determining whether the broadcast signal comprises an access control indicator indicating that access control is performed for the communication cell; and transmitting a cell- based message if the broadcast signal comprises an access control indicator.

According to a sixth aspect of the invention there is provided a computer-readable storage element having computer-readable code stored thereon for programming signal processing logic to perform a method for controlling access to a cellular communication network via a communication cell, wherein the method comprises the aforementioned steps of the second aspect.

These and other aspects, features and advantages of the invention will be apparent from, and elucidated with reference to, the embodiments described hereinafter.

Brief Description of the Drawings

FIG. 1 illustrates an example of a simplified message sequence chart of a known location update procedure.

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 2 illustrates an example of part of a cellular communications network adapted in accordance with some embodiments of the invention.

FIG. 3 illustrates an example of a simplified message sequence chart of a method for controlling access to a cellular communication network according to some embodiments of the invention. FIG. 4 illustrates a simplified flowchart of a method for controlling access to a cellular communication network according to some embodiments of the invention.

FIG. 5 illustrates a simplified flowchart of a method for accessing a cellular communication network via a communication cell according to some embodiments of the invention.

FIG. 6 illustrates a typical computing system that may be employed to implement signal processing functionality in embodiments of the invention. Detailed Description of Embodiments of the Invention

Referring now to the drawings, and in particular FIG. 2, an example of part of 3rd Generation Partnership Project (3GPP) network, adapted in accordance with some embodiments of the invention, is illustrated and indicated generally at 200. In particular, FIG. 2 illustrates an example of a cellular communication system 200 combining macro cells 285 and femto cells 250 in accordance with one embodiment of the invention. For the embodiment illustrated in FIG. 2, the cellular communication system 200 comprises two distinct radio network sub-system (RNS) architectures to handle the respective macro cell and femto cell communications. In the macro cell scenario, the RNS comprises a radio network controller (RNC) 236 operably coupled to a Node B 224 for supporting communications within a macro cell. The RNC 236 is further operably coupled to a core network element 242, such as a serving General Packet Radio System (GPRS) support node (SGSN)/mobile switching centre (MSC), as known.

In a 3G femto cell scenario, an RNS 210 may comprise a network element, in a form of a 3G Access Point (3G AP) 230, and a controller in a form of a 3G access control (3G AC) 240. As will be appreciated by a skilled artisan, an access point is a communication element that provides access to a cellular communication network via a communication cell, such as a 3G femto cell 250, for a wireless communication unit, UE, 214. One application is that a 3G AP 230 may be purchased by a member of the public and installed in their home. The 3G AP 230 may then be connected to a 3G AC 240 via a publicly or commercially available communication medium, such as via the Internet over the owner's broadband Internet connection 260.

Thus, a 3G AP 230 is a scalable, multi-channel, two-way communication device that may be provided within, say, residential and commercial (e.g. office) locations, 'hotspots' etc, to extend or improve upon network coverage within those locations. Although there are no standard criteria for the functional components of a 3G AP, an example of a typical AP for use within a 3GPP system may comprise some aspects of Node-B functionality and some aspects of radio network controller (RNC) 236 functionality. The 3G AP 230 further comprises radio frequency (RF) transceiver circuitry 255 arranged to enable a connection to be established with one or more wireless communication units located within the communication cell 250, such as User Equipment (UE) 214, via a wireless interface (Uu). The 3G AC 240 may be coupled to the core network (CN) 242 via an Iu interface as shown. In this manner, the 3G AP 230 is able to provide voice and data services to a cellular handset, such as UE 214, in a 3G femto cell in the same way as a conventional Node-B supports communication in a macro cell, but with the deployment simplicity of, for example, a Wireless Local Area Network (WLAN) access point. As would be appreciated by a skilled person, 3G AP 230 comprises numerous other functional and logical elements to support wireless communications and which will not be described further herein.

The UE 214 is a wireless communication unit comprising signal processing logic 218 and transceiver circuitry 216 arranged to transmit and receive signals. As would be appreciated by a skilled person, UE 214 comprises numerous other functional and logical elements to support wireless communications and functionality, which will not be described further herein. In accordance with embodiments of the invention, it is desirable for access control to a cell- based network to be provided at a cellular level, thereby enabling an owner of, for example, a 3G AP to be able to control which UEs are able to access the communication network via the femto cell. In order for such cellular level access control to be provided, it is necessary to detect and identify each UE that enters a cell where access control is required.

Thus, and in accordance with some embodiments of the invention, 3G AP 230 comprises signal processing logic 265 arranged to broadcast within the communication cell an access control indicator. Signal processing logic 265 is further arranged, upon receipt of a cell-based message from a wireless communication unit within the communication cell, such as UE 214, to determine whether to provide the wireless communication unit access to the cellular communication network via the communication cell. If it is determined not to provide the wireless communication unit access to the cellular communication network via the communication cell, the signal processing logic 265 is arranged to reject the wireless communication unit.

For clarity, the term 'reject' as used herein may refer to any action resulting in the wireless communication unit disconnecting from, or otherwise disassociating itself from, the communication cell, and attempting to reselect a different cell. It is within the contemplation of the invention that the act of rejecting a wireless communication unit may comprise simply not responding to the wireless communication unit, and thereby effectively ignoring it, as opposed to taking definitive actions to 'reject' the wireless communication unit. If no other cells are available for reselection, the wireless communication unit may remain

'camped' on the cell from which it was previously 'rejected' in order for the wireless communication unit to still be able to make emergency calls (for example in order for a user to be able to contact the police or fire services, etc.).

In this manner, a network element, such as 3G AP 230, is able to indicate to wireless communication units entering its respective communication cell whether access control is performed for that cell. Consequently, upon entering such a communication cell in which access control is performed, a wireless communication unit is able to read the broadcast signal comprising the access control indicator, and in response transmit a cell-based message. Accordingly, by transmitting the cell-based message, the wireless communication unit notifies the network element that it has entered its cell, and thereby enables the network element to perform access control on a cellular level.

Furthermore, by broadcasting such an access control indication to wireless communication units, unnecessary communication between wireless communication units and network elements supporting communication in cells in which access control is not performed is substantially avoided. Moreover, by broadcasting the access control indication at the cellular level, and by performing the access control at the cellular level, excessive signalling load on the network may be substantially avoided, for example as compared with the use of known mechanisms, such as a Location Update procedure, whereby different Location Area Codes are allocated to adjacent cells in order to induce Location updates between the adjacent cells.

For the illustrated embodiment, 3G AP 230 further comprises memory element 270 for storing, by way of example, computer-readable code for programming signal processing logic 265. In accordance with some embodiments of the invention, the access control indicator may be broadcast within a system information message. System Information messages contain information that is common to all of the UEs in the cell. For example, a UMTS network utilises a Radio Resource Control (RRC) protocol. The RRC protocol is defined in the Universal Mobile Telecommunications System (UMTS) Radio Resource Control (RRC) Protocol specification (3GPP TS 25.331 ), and forms part of the network layer between the UE and the UMTS Terrestrial Radio Access Network (UTRAN). The RRC protocol comprises connection management procedures, which, in turn, comprise the broadcasting of system information by the UTRAN. More particularly, system information elements are broadcast in system information blocks, which group together system information elements of the same nature.

A generic 'SYSTEM INFORMATION' message is used to convey the system information blocks on a BCCH (Broadcast Control CHannel) logical channel, which, in turn, may be mapped onto either a BCH (Broadcast CHannel) or FACH (Forward Access CHannel) transport channel. The size of the SYSTEM INFORMATION message is configured to fit the size of a BCH or FACH transport block, as required.

The RRC layer in the UTRAN performs segmentation and concatenation of encoded system information blocks. If the encoded system information block is larger than the size of a SYSTEM INFORMATION message, it is segmented and transmitted in several messages. If the encoded system information block is smaller than a SYSTEM INFORMATION message, several system information blocks may be concatenated into the same SYSTEM INFORMATION message.

Thus, and in accordance with some embodiments of the invention, the signal processing logic 265 of 3G AP 230 may be arranged to construct a system information block comprising the access control indicator, the access control indicator being located within an information element of the system information block. The system information block may then be broadcast within one or more system information messages, on a BCCH logical channel. The system information block may then be broadcast to all the UEs in the cells coverage area.

As will be appreciated by a skilled artisan, by broadcasting the access control indicator within an RRC system information message, only slight modifications are required to be made to network elements and wireless communication units in order to implement embodiments of the invention. As will also be appreciated by a skilled artisan, system information blocks broadcast by the

RRC layer of the UTRAN comprise an 'area scope' value that specifies the area where a system information block's value tag is valid. For example, if the area scope is set to 'cell', a wireless communication unit reading the system information block shall consider the system information block to be valid only in the cell in which it was read. Thus, in accordance with some embodiments of the invention, the signal processing logic 165 may further be arranged to set an area scope of the system information block to 'cell'. In this manner, a wireless communication unit reading the system information block will treat identifiers within the system information block as being valid only for the cell in which it was read. In this manner, the broadcasting of the identifiers by the 3G AP 230 will not affect wireless communication units accessing the network 200 via neighbouring cells. It is also envisaged that the access control indicator may also comprise a flag or the like, indicating whether or not access control is required. For example, if the flag is set to T or TRUE', access control is performed, whilst if the flag is set to '0' or 'FALSE', access control is not performed. Additionally, or alternatively, the absence of an access control indication within, for example, a system information message, may in itself indicate that access control is not performed. In this manner, existing cells, such as macro cells, in which access control on the cellular level is not required, require no modification.

It is also envisaged in a further embodiment of the invention that the access control indicator may alternatively, or additionally, comprise a flag indicating that a wireless communication unit entering the communication cell is required to transmit a 'cell-based' message, without explicitly identifying the purpose of the cell-based message as being for access control.

As previously mentioned, the signal processing logic 265 of, for the illustrated embodiment, 3G AP 230, is arranged to determine whether to provide a wireless communication unit access to the network 200 upon receipt of a cell-based message therefrom. For example, the signal processing logic 265 may extract information from the received cell-based message identifying the wireless communication unit, and determine whether to provide the wireless communication unit access to the cellular communication network based at least on the extracted information identifying the wireless communication unit.

The RRC protocol comprises a Cell Update message, whereby a wireless communication unit is able to inform the network about the communication cell on which the wireless communication unit is camped on etc. Thus, and in accordance with some embodiments of the invention, the cell-based message may comprise such an RRC Cell Update message.

Alternatively, the cell-based message may comprise an RRC Connection Request message, which also forms part of the current RRC protocol, or some other message within the RRC protocol whereby the wireless communication unit reveals its presence to the network element providing the communication cell. In a still further alternative embodiment, a new message may be defined within, for example, the RRC protocol, specifically for enabling a wireless communication unit to reveal its presence for the purpose of access control.

As will be appreciated by a skilled artisan, RRC Cell Update messages and RRC Connection Request messages, as currently defined within the 3GPP specifications (3GPP TS 25.331 ), may comprise a UTRAN Radio Network Temporary Identifier (U_RNTI). However, a network element such as 3G AP 230 may not have access to information enabling it to associate such temporary identifiers with specific wireless communication units. Accordingly, it is also envisaged that the RRC protocol may be adapted such that the Cell Update message, or Connection Request message, may comprise information relating to an identification number of the wireless communication unit available to the network element. For example, the message may comprise information relating to the International Mobile Subscriber Identity (IMSI) number, or the International Mobile Equipment Identity (IMEI) number of the wireless communication unit, or a value cryptographically derived therefrom.

Alternatively, upon receipt of a cell-based message from a wireless communication unit, the signal processing logic 265 may transmit an identification request message to the wireless communication unit. For example, the 3G AP 230 may impersonate the core network, and utilise a Mobility Management (MM) Identity Request procedure. In this manner, the signal processing logic 265 is able to obtain information identifying the wireless communication unit, and determine whether to provide the wireless communication unit access to the cellular communication network based at least on the information identifying the wireless communication unit. As previously mentioned, the 3G AP 230 comprises a memory element 270. Accordingly, information identifying the wireless communication unit, whether extracted from the cell-based message or obtained otherwise, may be compared to information stored within the memory element 270 in order to determine whether to provide a wireless communication unit access to the network.

As will be appreciated by a skilled artisan, the cell update procedure within a UMTS system serves several main purposes, and as such a wireless communication unit may transmit a cell-based message for reasons other than purely in response to an access control indicator being broadcast.

In accordance with some embodiments of the invention, the signal processing logic 265 of the 3G AP 230 may be arranged to determine whether to provide the wireless communication unit access to the cellular communication network upon receipt of a cell-based message comprising a 'Message cause' information element (IE) indicating the cause of the cell-based message as access control. In this manner, the signal processing logic 265 will only perform access control procedures when a cell- based message is received in response to the access control indicator being broadcast.

Referring now to FIG. 3, there is illustrated an example of a simplified message sequence chart 300 of a method for controlling access to a cellular communication network according to some embodiments of the invention.

The simplified message sequence starts with a network element, such as 3G AP 230, broadcasting an access control indicator. For the illustrated embodiment, the access control indicator is broadcast in the form of an RRC System Information message 310 comprising an Access Control Indicator set to TRUE'. The broadcast system information message 310 is received and read by a wireless communication unit, such as UE 214. The UE 214, in response to the Access Control Indicator being set to TRUE', transmits a cell-based message, which for the illustrated embodiment comprises an RRC Cell Update message 320.

Upon receipt of the RRC Cell Update message 320, the 3G AP 230 performs access control, and more particularly determines whether to provide the UE 214 access to the cellular communication network. For example, the 3G AP 230 may extract information from the received cell-based message identifying the UE 214, and determine whether to provide the UE 214 access to the cellular communication network based at least on the information identifying the UE 214.

Alternatively, upon receipt of a cell-based message from the UE 214, the 3G AP 230 may transmit an identification request message (not shown) to the UE 214. For example, the 3G AP 230 may impersonate the core network, and utilise a Mobility Management (MM) Identity Request procedure. In this manner, the 3G AP 230 is able to obtain information identifying the UE 214, and determine whether to provide the UE 214 access to the cellular communication network based at least on the information identifying the UE 214.

If the 3G AP 230 determines that access to the cellular communication network should be provided to the UE 214, for example due to the UE 214 being authorised as such, the 3G AP 230 transmits a confirmation message back to the UE 214, which for the illustrated embodiment is in the form of a RRC Cell Update Confirm message 340.

However, if the 3G AP 230 determines not to provide the UE 214 access to the network, the 3G AP 230 rejects the UE 214. As previously mentioned, the term 'reject' as used herein may refer to any action resulting in the wireless communication unit disconnecting from, or otherwise disassociating itself from, the communication cell, and attempting to reselect a different cell. For example, the 3G AP 230 may transmit an RRC Connection Release message back to the UE 214. However, the use of an RRC Connection Release message, as currently defined within the RRC protocol, will not prevent the UE 214 from attempting to establish a connection at a later time.

In an alternative embodiment of the invention, the 3G AP 230 may transmit a specific RRC Connection Reject message back to the UE 214, thereby causing the UE to permanently (or at least for a minimum duration) disregard the communication cell supported by the 3G AP 230 for the purpose of cell selection, and to attempt to reselect a different cell. As will be appreciated by a skilled artisan, such a message is not currently defined within the RRC protocol, and would require appropriate amendments thereto, if implemented within the RRC protocol.

Referring now to FIG. 4, there is illustrated a simplified flow chart 400 of a method for controlling access to a cellular communication network via a communication cell according to some embodiments of the invention. For example, the method of FIG. 4 may be implemented by signal processing logic within a network element, such as 3G AP 230 of FIG. 2.

The method starts at step 410 with broadcasting an access control indicator within the communication cell. For example, the method may comprise constructing a system information block comprising the access control indicator, and broadcasting the system information block within at least one system information message, for example on a Broadcast Control CHannel (BCCH). In accordance with some embodiments of the invention, the access control indicator may be located within an information element of the system information block, and an area scope of the system information block may be set to 'cell'.

As previously mentioned, the access control indicator may comprise a flag indicating that a wireless communication unit entering the communication cell is required to transmit a cell-based message.

Upon receipt of a cell-based message, from a wireless communication unit, in step 420, the method moves to step 430, where it is determined whether to provide the wireless communication unit access to the cellular communication network via the communication cell based upon the cell-based message. In accordance with some embodiments of the invention, the cell-based message may comprise an RRC Cell Update message. Furthermore, the method may comprise determining whether to provide the wireless communication unit access to the cellular communication network upon receipt of a cell-based message comprising a 'Message cause' information element, which indicates the cause of the cell-based message as access control.

For example, the method may comprise extracting information from the received cell-based message identifying the wireless communication unit, and determining whether to provide the wireless communication unit access to the cellular communication network via the communication cell based at least on the extracted information identifying the wireless communication unit.

Alternatively, the method may comprise transmitting an identification request message to the wireless communication unit from which the cell-based message was received. Accordingly, upon subsequent receipt of a message comprising information identifying the wireless communication unit, the method may comprise determining whether to provide the wireless communication unit access to the network based at least on the information identifying the wireless communication unit.

If it is determined not to provide the wireless communication unit access to the network, the method moves to step 440, and the wireless communication unit is rejected, for example in the manner previously described. The method then ends at step 450.

Conversely, if it is determined to provide the wireless communication unit access to the network, the method moves to step 460, and access to the network via the communication cell is allowed for the wireless communication unit. The method then ends at step 450.

Referring now to FIG. 5, there is illustrated a simplified flow chart 500 of a method for accessing a cellular communication network via a communication cell according to some embodiments of the invention. For example, the method of FIG. 5 may be implemented by signal processing logic within a wireless communication unit, such as UE 214 of FIG. 2.

The method starts at step 510, and moves to step 520, where a signal broadcast within a communication cell is read and processed by the UE 214, which for the illustrated embodiment comprises reading a system information broadcast.

Next, in step 530, it is determined whether the broadcast signal comprises an access control indicator indicating that access control is performed for the communication cell. If the broadcast signal does not comprise an access control indicator indicating that access control is performed, the method ends at step 550. Conversely, if the broadcast signal comprises an access control indicator indicating that access control is performed for the communication cell, the method moves to step 540, where a cell-based message is transmitted. The method then ends at step 550.

Referring now to FIG. 6, there is illustrated a typical computing system 600 that may be employed to implement signal processing functionality in embodiments of the invention. Computing systems of this type may be used in access points and wireless communication units. Those skilled in the relevant art will also recognize how to implement the invention using other computer systems or architectures. Computing system 600 may represent, for example, a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc.), mainframe, server, client, or any other type of special or general purpose computing device as may be desirable or appropriate for a given application or environment. Computing system 600 can include one or more processors, such as a processor 604. Processor 604 can be implemented using a general or special-purpose processing engine such as, for example, a microprocessor, microcontroller or other control logic. In this example, processor 604 is connected to a bus 602 or other communications medium.

Computing system 600 can also include a main memory 608, such as random access memory

(RAM) or other dynamic memory, for storing information and instructions to be executed by processor 604. Main memory 608 also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 604. Computing system 600 may likewise include a read only memory (ROM) or other static storage device coupled to bus 602 for storing static information and instructions for processor 604.

The computing system 600 may also include information storage system 610, which may include, for example, a media drive 612 and a removable storage interface 620. The media drive 612 may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical disk drive, a compact disc (CD) or digital video drive (DVD) read or write drive (R or RW), or other removable or fixed media drive. Storage media 618 may include, for example, a hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by media drive 612. As these examples illustrate, the storage media 618 may include a computer-readable storage medium having particular computer software or data stored therein.

In alternative embodiments, information storage system 610 may include other similar components for allowing computer programs or other instructions or data to be loaded into computing system 600. Such components may include, for example, a removable storage unit 622 and an interface 620, such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units 622 and interfaces 620 that allow software and data to be transferred from the removable storage unit 618 to computing system 600.

Computing system 600 can also include a communications interface 624. Communications interface 624 can be used to allow software and data to be transferred between computing system 600 and external devices. Examples of communications interface 624 can include a modem, a network interface (such as an Ethernet or other NIC card), a communications port (such as for example, a universal serial bus (USB) port), a PCMCIA slot and card, etc. Software and data transferred via communications interface 624 are in the form of signals which can be electronic, electromagnetic, and optical or other signals capable of being received by communications interface 624. These signals are provided to communications interface 624 via a channel 628. This channel 628 may carry signals and may be implemented using a wireless medium, wire or cable, fiber optics, or other communications medium. Some examples of a channel include a phone line, a cellular phone link, an RF link, a network interface, a local or wide area network, and other communications channels.

In this document, the terms 'computer program product' 'computer-readable medium' and the like may be used generally to refer to media such as, for example, memory 608, storage device 618, or storage unit 622. These and other forms of computer-readable media may store one or more instructions for use by processor 604, to cause the processor to perform specified operations. Such instructions, generally referred to as 'computer program code' (which may be grouped in the form of computer programs or other groupings), when executed, enable the computing system 600 to perform functions of embodiments of the present invention. Note that the code may directly cause the processor to perform specified operations, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so. In an embodiment where the elements are implemented using software, the software may be stored in a computer-readable medium and loaded into computing system 600 using, for example, removable storage drive 622, drive 612 or communications interface 624. The control logic (in this example, software instructions or computer program code), when executed by the processor 604, causes the processor 604 to perform the functions of the invention as described herein.

It will be appreciated that, for clarity purposes, the above description has described embodiments of the invention with reference to different functional elements and processors. However, it will be apparent that any suitable distribution of functionality between different functional elements or processors, for example with respect to the access point or controller, may be used without detracting from the invention. For example, it is envisaged that functionality illustrated to be performed by separate processors or controllers may be performed by the same processor or controller. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization. Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented, at least partly, as computer software running on one or more data processors and/or digital signal processors. Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units.

Although one embodiment of the invention describes an access point for a UMTS network, it is envisaged that the inventive concept is not restricted to this embodiment.

It is envisaged that the aforementioned embodiments aim to provide at least one or more of the advantages of: (i) a network element able to indicate to wireless communication units entering its respective communication cell whether access control is performed for that cell;

(ii) upon entering a communication cell in which access control is performed, a wireless communication unit is able to read the broadcast signal comprising the access control indicator, and in response transmit a cell-based message, notifying the network element that it has entered its respective cell, and thereby enabling the network element to perform access control on a cellular level;

(iii) by broadcasting an access control indication to wireless communication units, unnecessary communication between wireless communication units and network elements supporting communication in cells in which access control is not performed is substantially avoided; and

(iv) by broadcasting an access control indication at the cellular level, and by performing the access control at the cellular level, excessive signalling load on the network may be substantially avoided.

Although the invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term 'comprising' does not exclude the presence of other elements or steps.

Moreover, an embodiment can be implemented as a computer-readable storage element having computer readable code stored thereon for programming a computer (e.g., comprising a signal processing device) to perform a method as described and claimed herein. Examples of such computer-readable storage elements include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and integrated circuits (ICs) with minimal experimentation.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to 'a', 'an', 'first', 'second' etc. do not preclude a plurality.

Thus, a method and apparatus for controlling access to a cellular communication network have been described, which substantially addresses at least some of the shortcomings of past and present access control techniques and/or mechanisms.

Claims

1. A network element for providing access to a cellular communication network via a communication cell, the network element comprising: transceiver circuitry arranged to enable a connection to be established with at least one wireless communication unit located within the communication cell; and signal processing logic operably coupled to the transceiver circuitry, wherein the signal processing logic is arranged to: initiate a broadcast of an access control indicator within the communication cell; and upon receipt of a cell-based message from the at least one wireless communication unit received in response to the broadcast access control indicator, determine whether to provide the wireless communication unit access to the cellular communication network via the communication cell.

2. The network element of Claim 1 wherein the signal processing logic is arranged to construct a system information block comprising the access control indicator, and to broadcast the system information block within at least one system information message.

3. The network element of Claim 2 wherein the access control indicator is located within an information element of the system information block.

4. The network element of Claim 2 or Claim 3 wherein the signal processing logic is arranged to set an area scope of the system information block to a cell-based value.

5. The network element of any of Claims 2 to 4 wherein the signal processing logic is arranged to broadcast the at least one system information message on a Broadcast Control CHannel (BCCH).

6. The network element of any preceding Claim wherein if it is determined not to provide the wireless communication unit access, the signal processing logic transmits an access reject message to the wireless communication unit.

7. The network element of any preceding Claim wherein the access control indicator comprises a flag indicating that a wireless communication unit entering the communication cell is required to transmit a cell-based message.

8. The network element of any preceding Claim wherein, upon receipt of a cell-based message from the at least one wireless communication unit, the signal processing logic is arranged to extract information from the received cell-based message identifying the at least one wireless communication unit, and to determine whether to provide the at least one wireless communication unit access to the cellular communication network via the communication cell based at least partly on the information identifying the at least one wireless communication unit.

9. The network element of any of Claims 1 to 6 wherein, upon receipt of a cell-based message from the at least one wireless communication unit, the signal processing logic is arranged to transmit an identification request message to the at least one wireless communication unit, and upon subsequent receipt of a message from the at least one wireless communication unit comprising information identifying the at least one wireless communication unit, to determine whether to provide the at least one wireless communication unit access to the cellular communication network via the communication cell based at least partly on the information identifying the wireless communication unit.

10. The network element of any preceding Claim wherein the cell-based message comprises a Radio Resource Control (RRC) cell update message.

11. The network element of any one of Claims 1 to 9, wherein the cell-based message comprises a Radio Resource Control (RRC) Connection request message.

12. The network element of any preceding Claim wherein the signal processing logic is arranged to determine whether to provide the wireless communication unit access to the cellular communication network upon receipt of a cell-based message comprising a 'Message cause' information element that indicates a cause of the cell-based message as being associated with access control.

13. The network element of any preceding Claim wherein the network element comprises an access point, and the communication cell comprises a femto cell.

14. The network element of any preceding Claim wherein the cellular communication network comprises a Universal Mobile Telecommunications System (UMTS) network.

15. A method for controlling access to a cellular communication network via a communication cell, wherein at a network element the method comprises: broadcasting an access control indicator within the communication cell; receiving a cell-based message from a wireless communication unit within the communication cell, in response to the broadcast access control indicator; and determining whether to provide the wireless communication unit access to the cellular communication network via the communication cell.

16. A wireless communication system adapted to support the method for controlling access to a cellular communication network via a communication cell of Claim 15.

17. A wireless communication unit comprising transceiver circuitry arranged to receive signals broadcast by a network element of a communication cell within a cellular communication network, and signal processing logic, wherein the signal processing logic is arranged to: read a signal broadcast within a communication cell; determine whether the broadcast signal comprises an access control indicator indicating that access control is performed for the communication cell; and if the broadcast signal comprises an access control indicator indicating that access control is performed for the communication cell, transmit a cell-based message.

18. The wireless communication unit of 17 wherein the access control indicator comprises a flag indicating that the wireless communication unit entering the communication cell is required to transmit a cell-based message.

19. The wireless communication unit of Claims 17 or 18 wherein the cell-based message comprises information identifying the wireless communication unit.

20. The wireless communication unit of any of Claims 17 to 19 wherein the cell-based message comprises a Radio Resource Control (RRC) cell update message.

21. The wireless communication unit of any one of Claims 17 to 20 wherein the cell-based message comprises a 'Message cause' information element indicating the cause of the cell-based message as access control.

22. A method for accessing a cellular communication network via a communication cell by a wireless communication unit, wherein at a wireless communication unit the method comprises: reading a signal broadcast within a communication cell from a network element; determining whether the broadcast signal comprises an access control indicator indicating that access control is performed for the communication cell; and transmitting a cell-based message if the broadcast signal comprises an access control indicator.

23. A computer-readable storage element having computer-readable code stored thereon for programming signal processing logic to perform a method for controlling access to a cellular communication network via a communication cell, wherein the method comprises: broadcasting an access control indicator within the communication cell; receiving a cell-based message from a wireless communication unit within the communication cell, in response to the broadcast access control indicator; and determining whether to provide the wireless communication unit access to the cellular communication network via the communication cell.

24. A computer-readable storage element having computer-readable code stored thereon for programming signal processing logic to perform a method for controlling access to a cellular communication network via a communication cell, wherein the method comprises: reading a signal broadcast within a communication cell from a network element; determining whether the broadcast signal comprises an access control indicator indicating that access control is performed for the communication cell; and transmitting a cell-based message if the broadcast signal comprises an access control indicator.

25. The computer-readable storage element of Claim 23 or Claim 24, wherein the computer readable storage medium comprises at least one of a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), a EPROM (Erasable Programmable Read Only Memory), a EEPROM (Electrically Erasable Programmable Read Only Memory) and a Flash memory.