GB2445004A - Controlling the use of access points in a telecommunications network - Google Patents

Abstract

In a GSM, UMTS or LTE mobile telecommunications network, the conventional radio access network comprises the base stations 3. In addition one or more access points 20 may be provided. An access point 20 is typically connected to the network core 12 by an IP transport broadband connection. The access point 20 is configured to appear to the mobile terminal 1 as a conventional base station. Arrangements are disclosed which allow the network to restrict access to the network via these access points whilst also minimising signalling requirements. In one aspect, the access points are excluded from traditional Tracking Areas, but associated therewith by a network controller in a mapping in order to notify authorised mobile terminals of the Access Point's existence.

Description

* TELECOMMUNICATIONS NETWORKS AND DEVICES

Technical Field

The present invention relates to a telecommunications network including a radio access network for wirelessly transmitting between a mobile telecommunications device and a base station. The present invention also relates to a method and arrangement for controlling communication access of a mobile device to one or more base stations.

Backgiound There have recently been proposals to allow access to the features and services provided by GSM and UMTS networks other than by accessing those networks in the conventional maimer. In this regard, the conventional maimer is by signalling between a mobile terminal and a conventional base station (macro base station) that has a dedicated connection to an MSC, and which provides coverage in the cell occupied by the mobile terminal using cellular telecommunication (e.g. GSM or UMTS) communication transport protocols. It has been proposed to increase network capacity by providing additional special base stations (micro base stations), referred to as access points (APs) or home access points (HAPs), for example at a subscriber's home. It has also been proposed to use APs in the Long Term Evolution (LTE) telecommunications network currently being developed, but not yet implemented. LTE is likely to be the next network implementation after 30.

An advantage of using an access point connected to the core network via an IP network is that existing broadband DSL connections can be used to link mobile terminals with the network core without using the capacity of the radio access network or transmission network of a mobile telecommunications network, or they are able to provide mobile network access where there is no conventional radio access network coverage. For example. UMTS coverage could be provided by an access point where there is no conventional UMTS coverage (perhaps only GSM coverage).

Since these access points are not conventional base stations, however, additional challenges arise. In particular, communications between the access point and the network are IP based communications, and may be, for example, transmitted via an ADSL backhaul connection to an IP network, such as the Internet. However, the capacity of such ADSL backhauls are limited, and not under the control of the telecommunications network provider, so there needs to be restrictions put in place on which user terminals (UEs) are able to access each AP in order to maintain an acceptable degree of service quality.

A problem that arises because of the need of such access restrictions is that UEs will be split into those which are supposed to access the AP and those which are not supposed to. Nevertheless all UEs would try to access the AP.

For instance, considering a UE in a connected state, when an AP provides the LIE with the best signal strength in a given region, the UE's current Node B/base station will attempt to hand the UE over to the AP. If the LIE is one of the UEs which is not supposed to use the AP, the handover procedure will be initiated and the core network or the AP will have to reject the handover. Similarly, considering a UE in an idle state, when the UE receives the Location Area broadcast by the AP, and notes it to be different from its previous Location Area, the UE will look to camp on the AP and request a Location Area update from the network. If the UE is not authorized to camp on the AP the update will be rejected by the core network.

These access rejections are a waste of signalling resources. This is 2..

particularly a problem where an AP exists in an area of high traffic or high S penetration of APs, as there is likely to be an unacceptable level of access attempts by UEs, many of which will result in unnecessary signalling.

There therefore needs to be a better balance between restricting access to * 5 APs and limiting the use of signalling resources in doing so.

Summary of the Invention

According to a first aspect, the present invention provides, in a telecommunications network including a radio access network comprising a plurality of base stations, each defining a cell, for wirelessly transmitting data that is receivable by one or more mobile terminals, wherein at least one of the base stations is an Access Point (AP), a method of controlling access to the telecommunications network via the at least one Access Point, the method including: defining tracking areas in the network covering one or more base station cells but excluding the at least one Access Point cells.

Preferably this method includes creating a mapping associating one of the at least one Access Points with one and more Tracking Areas, and using the mapping to perform at least one of the following: a) notify an idle mobile terminal that it is authorised to select the one Access Point when in the one or more Tracking Areas; b) trigger the establishment of a transport network connection between a base station and one of the at least one Access Points.

c) trigger the establishment of a transport network connection between an MME and one of the at least one Access Points.

d) page a mobile terminal where one of the one or more Tracking Areas was the last Tracking Area recorded for the mobile terminal; e) notify an idle mobile terminal that it is authorised to move about the mapping without performing a Tracking Area update; 1') notify a mobile terminal that it should undertake a search for transmissions by the one Access Point; g) notify a mobile terminal that it should undertake measurements of S transmission received from the one Access Point; h) notify a base station controlling handover of a mobile terminal that the mobile terminal is authorised to be handed over to the one Access * 5 Point.

In a second aspect, the present invention provides, in a telecommunications network including a radio access network comprising a plurality of base stations configured to wirelessly transmitting data that is receivable by one or more mobile terminals, wherein at least one of the base stations is an Access Point (AP), a method of restricting access to the at least one Access Point, the method including: transmitting information from each Access Point from which mobile terminals are able to determine their ability to access the given base station.

Preferably the information transmitted is an Access Indicator Field. It is also preferable that unless it is determined that the mobile terminal has a right of access to the base station, the mobile terminal does not attempt to access the base station.

The Access Indicator Field can be used by the mobile terminal to determine if it is authorised to use the Access Point without the need for the mobile terminal signalling an intent to use the AP and determining its authorisation status from the core network. This aspect of the invention therefore reduces the use of signalling resources.

According to a third aspect, the present invention provides a telecommunications network including a radio access network comprising a plurality of base stations, each defining a cell, and being configured to wirelessly transmit data that is receivable by one or more mobile terminals.

with at least one of the base stations being an Access Point (AP); and Lf wherein the radio access network is arranged in a plurality of tracking areas with each tracking areas covering one or more cells but excluding the cells of the at least one Access Point.

Preferably each Access Point is a base station connected by IF transport to the network.

According to a fourth aspect, the present invention provides a telecommunications network including a radio access network comprising a plurality of base stations configured to wirelessly transmit data that is receivable by one or more mobile terminals, with at least one of the base stations being an Access Point (AP), and wherein the least one Access Point is configured to broadcast information from which the at least one mobile terminal is able to determine if it has access rights to each of the at least one Access Points.

Preferably, according to this fourth aspect of the invention, the at least one Access Point is configured to broadcast an Access Indicator Field from which the one or more mobile terminal is able to determine if it has access rights.

For a better understanding of the present invention embodiments will now be described by way of example, with reference to the accompanying drawings, in which:

Brief Description of the Figures

Figure 1 is a diagrammatic drawing of key elements of a mobile telecommunications network for use in explaining the operation of such a network; and Figure 2 shows a modified mobile telecommunications network for receiving IF based communications from an access point in addition to communications from a conventional base station.

Figure 3 shows an exemplary signalling diagram in relation to an UE in an idle state moving into the tracking area of a new base station: and Figure 4 shows an exemplary signalling diagram in relation to a UE in an active state moving into the tracking area of a new base station.

In the drawings like elements are generally designated with the same reference sign.

Detailed Description

Key elements of a mobile telecommunications network, and its operation, will now briefly be described with reference to Figure 1.

Each base station (BS) corresponds to a respective cell of its cellular or mobile telecommunications network and receives calls from and transmits calls to a mobile terminal in that cell by wireless radio communication in one or both of the circuit switched or packet switched domains. Such a subscriber's mobile terminal (UE) is shown at 1. The mobile terminal may be a handheld mobile telephone, a personal digital assistance (FDA) or a laptop computer equipped with a datacard.

In a GSM mobile telecommunications network, each base station comprises a base transceiver station (BTS) and a base station controller (BSC). A BSC may control more than one BTS. The BTSs and BSCs comprise the radio access network.

In a UMTS mobile telecommunications network, each base station comprises a node B and a radio network controller (RNC). An RNC may (0 control more than one node B. The node B's and RNC's comprise the radio access network.

In the proposed LTE mobile telecommunications network, each base station comprises an eNode B. The base stations are arranged in groups and each group of base stations is controlled by a Mobility Management Entity (MME) and a User Plane Entity (UPE).

Conventionally, in a GSMIUMTS network, the base stations are arranged in groups and each group of base stations is controlled by one mobile switching centre (MSC), such as MSC 2 for base stations 3, 4 and 5. As shown in Figure 1, the network has another MSC 6, which is controlling a further three base stations 7, 8 and 9. In practice, the network will incorporate many more MSCs and base stations than shown in Figure 1.

The base stations 3, 4, 5, 7, 8 and 9 each have dedicated (not shared) connection to their MSC2 or MSC6 -typically a cable connection. This prevents transmission speeds being reduced due to congestion caused by other traffic.

Each subscriber to the network is provided with a smart card or SIM which, when associated with the user's mobile terminal identifies the subscriber to the network. The SIM card is pre-programmed with a unique identification number, the "International Mobile Subscriber Identity" (IMSI) which is not visible on the card and is not known to the subscriber. The subscriber is issued with a publicly known number, that is, the subscriber's telephone number, by means of which calls to the subscriber are initiated by callers.

This number is the MSISDN.

The network includes a home location register (HLR) 10 which, for each subscriber to the network, stores the IMSI and the corresponding MSISDN together with other subscriber data, such as the current or last known MSC or SGSN of the subscriber's mobile terminal.

When the subscriber wishes to activate their mobile terminal in a network (so that it may make or receive calls subsequently), the subscriber places their SIM card in a card reader associated with the mobile terminal (terminal 1 in this example). The mobile terminal 1 then transmits the IMSI (read from the card) to the base station 3 associated with the particular cell in which the terminal 1 is located, In a traditional network, the base station 3 then transmits this IMSI to the MSC 2 with which the BS 3 is registered.

In a network using the functionality described in 3GPP TS 23.236, the base station follows prescribed rules to select which MSC to use, and then transmits this IMSI to the selected MSC.

MSC 2 now accesses the appropriate storage location in the HLR 10 present in the network core 12 and extracts the corresponding subscriber MSISDN and other subscriber data from the appropriate storage location, and stores it temporarily in a storage location in a visitor location register (VLR) 14. In this way, therefore the particular subscriber is effectively registered with a particular MSC (MSC 2), and the subscriber's information is temporarily stored in the VLR (VLR 14) associated with that MSC.

When the HLR 10 is interrogated by the MSC 2 in the manner described above, the HLR 10 additionally performs an authentication procedure for the mobile terminal 1. The HLR 10 transmits authentication data to the MSC 2 in "challenge" and "response" forms. Using this data, MSC 2 passes a "challenge" to the mobile terminal 1 through base station 3. Upon receipt of this data, the mobile terminal I passes this data to its SIM and produces a "response". This response is generated using an encryption algorithm on the SIM and a unique Ki on the SIM. The response is transmitted back to the MSC 2 which checks it against its own information for the subscriber which checks it against information that it has obtained for that subscriber z from the HLR 10 in order to complete the authentication process. If the response from the mobile terminal I is as expected. the mobile terminal 1 is deemed authenticated. At this point the MSC 2 requests subscription data from the HLR 10. The HLR 10 then passes the subscription data to the * 5 The authentication process will be repeated at regular intervals while the mobile terminal I remains activated and can also be repeated each time the mobile terminal makes or receives a call, if required.

Each of the MSCs of the network (MSC 2 and MSC 6) has a respective VLR (14 and 11) associated with it and operates in the same way as already described when a subscriber activates a mobile terminal in one of the cells corresponding to one of the base stations controlled by that MSC.

When the subscriber using mobile terminal 1 wishes to make a call, having already inserted the SIM card into the reader associated with this mobile terminal and the SIM has been authenticated in the manner described, a call may be made by entering the telephone number of the called party in the usual way. This information is received by the base station 3 and passed on to MSC 2. MSC 2 routes the call towards the called party. By means of the information held in the VLR 14, MSC 2 can associate the call with a particular subscriber and thus record information for charging purposes.

The MSCs 2 and 6 support communications in the circuit switched domain -typically voice calls. Corresponding SGSNs 16 and 18 are provided to support communications in the packet switched domain -such as GPRS data transmissions. The SGSNs 16 and 18 function in an analogous way to the MSCs 2 and 6. The SGSNs 16, 18 are equipped with an equivalent to the VLR for the packet switched domain.

From the description above, it will be understood that the coverage area of a mobile telecommunications network is divided into a plurality of cells, each of which is served by a respective base station. In order to allow a mobile terminal to maintain a call when the mobile terminal moves outside the coverage area of a cell, the call must be switched to an alternative cell automatically. The call must be routed to the new cell before handover can be effected whilst maintaining the connection with the old cell until the new connection is known to have succeeded. Handover is a time critical process requiring action to be taken before the radio link with the original cell degrades to such an extent that the call is lost. Handover requires synchronisation of events between the mobile terminal and the network.

When a calling party (whether a subscriber within the mobile telecommunications network or outside it) attempts to call a mobile terminal within the network, that mobile terminal must be paged. Paging is a process of broadcasting a message which alerts a specific mobile terminal to take some action -in this example, to notify the terminal that there is an incoming call to be received. If the network knows in which cell the mobile terminal is located, it is only necessary to page in that cell. However, if the mobile terminal is moving within the network, the precise cell in which the mobile terminal is located may not be known. It will therefore be necessary to perform paging in a number of cells. The greater the number of cells in which paging must occur, the more use of valuable signalling capacity However, if the HLR is to always have an up-to-date record of the cell in which each mobile terminal is located so that the current cell which is occupied by a terminal is always know, this will require a large amount of location updating signalling between the mobile terminal and the HLR in order that the HLR has up-to-date records of the cells occupied by each mobile terminal. This is also wasteful of valuable signalling capacity. to

S As indicated above, the HLR is updated each time a mobile terminal moves from the coverage area of one MSC to another MSC and from one SGSN to another SGSN. However, typically the area covered by a single MSC and SGSN is large, and to page all the cells covered by a single MSC and SGSN would require a significant amount of paging signalling.

In a UMTS/GSM network, the problems of excessive use of signalling capacity by paging a multiplicity of cells or performing a multiplicity of frequent location updates is solved in a known manner by dividing the coverage area of the mobile telecommunications network into a plurality of location areas (LAs) and into a plurality of routing areas (RAs). The equivalent areas in the proposed LTE network are described as tracking areas (TAs).

A location area relates to a particular geographical area for communications in the circuit-switched domain. Typically, although not necessarily, a location area is larger than the area of a single cell but is smaller than the area covered by one MSC. Each cell within the network broadcasts data indicative of the identity of its location area. The mobile terminal uses this data to determine when it has moved into a new location area. The terminal stores its last known location area on its SIM. This information stored on the SIM is compared with the location area information broadcast by the local cell. The identities of the two location areas are compared. If they are different, the mobile terminal determines that it has entered a new location area. The mobile terminal then gains access to a radio channel and requests a location update. If the MSC/VLR is the same for the new and old location areas, the network can immediately authenticate the mobile terminal and note the change of location area. However, if the mobile terminal is moved to a different MSC/VLR, the MSC/VLR addresses a message to the HLR.

The HLR notes the new location and downloads security parameters to allow the network to authenticate the mobile. It also passes on subscription details of the user to the new VLR and informs the old VLR to delete its records.

A routing area relates to a particular geographical area for communications in the packet-switched domain. Typically, although not necessarily, a routing area is larger than the area of a single cell but is smaller than the area covered by one SGSN. A routing area is typically, although not necessarily, smaller than a location area. There may be many routing areas within one location area. Each cell within the network broadcasts data indicative of its routing area (in addition to the data mentioned above indicative of the identity of its location area). The mobile terminal uses this received data to determine when it has moved to a new routing area. The terminal stores the last known routing area on its SIM. The information stored on the SIM is compared with the routing area information broadcast by the local cell. The identities of the two routing areas are compared. If they are different, the mobile terminal determines that it has entered a new routing area. The mobile terminal then gains access to a radio channel and requests a routing area update.

The functionality just described may also apply to the proposed LTE mobile telecommunications network, with its eNode Bs performing the functionality of the base stations and the MMEJUPE performing the functionality of the MSCsIVLRs. It is also to be appreciated that the functionality just described is one example of a network in which the embodiments of the invention may be implemented.

Figure 2 shows elements for providing access to a GSM or UMTS network by both a conventional base station 3 and an access point (AP 20). The AP 20 provides a radio link 21 to mobile terminal 1. 1Z

The radio link 21 from the AP 20 to the mobile terminal I uses the same S cellular telecommunication transport protocols as the conventional base station 3 but with a smaller range -for example 25m. The AP 20 appears to the mobile terminal I as a conventional base station, and no modification to the mobile terminal I is required to operate with the AP 20. The AP 20 performs a role corresponding to that of a GSM BTS 22 and BSC 26 and/or UMTS Node B and RNC and/or an LTE Node B. Communications between the access point 20 and the core network 12 are IP based communications, and may be, for example, transmitted over a broadband IP network (and routed via the Internet). The communications are routed via MSC 32 or SGSN 34. The access point 20 converts the cellular telecommunications transport protocols used between the mobile terminal 1 and the AP 20 to IP based signalling.

The connection 23 between the access point 20 and the core network 12 may use the PSTN telephone network. Typically a DSL cable connection connects the access point 20 to the PSTN network. The data is transmitted between the access point 20 and the core network 12 by IP transportlDSL transport (a backhaul connection). The bandwidth of the cable connection between the access point and the telephone exchange is shared with multiple other users (typically between 20 and 50 other users). This means that the speed of transmission of data between the access point 20 and the telephone exchange varies significantly in dependence upon the activities of the other access point devices sharing the connection.

The access point 20 may be connected to the core network 12 by means other than a DSL cable and the PSTN network. For example, the access point 20 may be connected to the core network 12 by a dedicated cable connection that is independent of the PSTN, or by a satellite connection between the access point 20 and the network core 12. These methods of connecting the access point 20 to the network core 12 suffer from the same limitations as the DSL cable connection to the PSTN network. That is, the connection between the access point and the network core 12 is shared between multiple users and the speed of transmission of data and the quality of the connection is variable, being outside the control of the network core 12.

This variability of transmission speed between the access point 20 and the core network 12 should be contrasted with the much more consistent transmission speed between the conventional base station of a mobile telecommunications network and the core network 12. In a conventional mobile telecommunications network the base station is connected by an exclusive, dedicated connection to the MSC 2/SGSN 16/MME (not shown) and network core 12. The connection is not shared with other base stations, and therefore its speed will not depend upon other traffic of other devices.

AP 20 would typically be configured to serve a Wireless Local Area Network (WLAN) located in a home or office, in addition to GSMJUMTSILTE networks. The WLAN could belong to the subscriber of the mobile terminal 1, or be an independently operated WLAN. The owner of AP 20 can prescribe whether the AP is either open or closed, whereby an open AP is able to carry communications from any mobile device in the GSM/UMTS/LTE network, and a closed AP is only able to carry communications from specific pre-designated mobile devices.

With this background in mind, an implementation of the first embodiment of the invention will now be described, which seeks to minimise unnecessary signalling in regard to closed APs.

Conventionally, when a mobile terminal is in idle mode and moves from a first location area to a second location area, the mobile terminal detects that a different Location Area identity (LA ID) (from that stored in the mobile terminal) is being broadcast by the local base station/AP. The mobile terminal then sends a location area update request to the core network I2IMME. The request includes the first (current) LA ID and the mobile terminal's current temporary mobile subscriber identity (TMSI). The MSC/MME with which the mobile terminal is currently registered then sends a new TMSI to the mobile terminal I. When the mobile terminal moves from a first (current) location area to a second location area, and the second location area is administered by a different MSCIMME, similar steps occur and in addition the different MSCIMME requests user profile information from the original MSCIMME.

Each cell provided by the core network has a unique cell global identity (CGI), whereby the CGI is a concatenation of the Location Area ID and a Cell ID and uniquely identifies a given cell. Traditionally, each AP has its own cell and also has its own unique Tracking Area identifier, which is broadcast (along with its cell ID), so that all passing mobile terminals are able to identify the AP and to attempt to access the network via the AP. In other words, the APs are traditionally treated the same as the Node Bs.

According to the first embodiment of the invention, APs are configured to broadcast an indication in the downlink from which each UE is able to determine if they have the right to access the network via the AP or not. The APs and eNode Bs broadcast system information to the UEs in idle mode, so that the UEs are able to assess the network conditions and be ready to access the network by the most appropriate route. UEs are often described as "camping" on an AP or Node B when that AP or Node B provides the most suitable prospective access point.

In idle mode, the UE may be stationary, or be moving throughout the network. In whatever location the UE is, the UE will be able to receive Ic system information broadcast from Node Bs and APs that are in range.

According to this first embodiment of the invention, the information which the APs broadcast includes an Access Indicator Field, which is broadcast in addition to the APs' cell ID and TA ED. Other information, such as a Neighbouring Cell List may also be broadcast. This Access Indicator serves to prevent the UEs from treating the AP in the same manner as an eNode B and ensures that the UEs determine if they are authorised to access the network via the AP before attempting to do so.

Considering a UE in idle mode detecting the signal broadcast by the AP, the UE will note the different Tracking Area from its previously recorded position. Rather than immediately requesting a TA area update, however, the UE will note the Access Indicator Field and determine from this field and the CGI field if it is authorised by the network to access the network via this AP. In addition, the Access Indicator Field may include a decryption key

that the UE uses to decrypt an access password previously stored on the UE, to determine if the user has previously authorised usage of this cell, or it may be an encrypted code which the UE needs to use its own previously stored decryption key to decode. The Access Indicator Field may even be a simple password which the UE needs to match with a pre-stored password to determine if access to the network via the AP has previously been granted.

If the UE determines that it is not authorised to use this AR, the UE will simply treat the AP as a cell from a forbidden TA (i.e. it will not perform future measurements of the AP) and maintain its existing Tracking Area record. If it is authorised, however, then the UE may request a TA update from the MME. Therefore it is apparent that the broadcast Access Indicator Field can be used by the UE to determine if it is authorised to use the AP without the need for the UE signalling an intent to use the AP and determining its authorisation status from the core network/MME.

When the TA update is performed, the MME may also create a mapping between the AP and the last recorded Cell's Tracking Area and provide a copy of this mapping to the UE. This mapping can then be used by the UE to restrict the number of TA updates that it performs, by not requiring a TA update to occur when the UE moves between the AP and the UE's last recorded TA. This mapping is recognition of the fact that the range of the AP is typically small, so the likelihood of the UE moving out of the range of the UE and back into the range of the previously recorded Cell is high.

The mapping can therefore be used to further minimise signalling between the UE and the MME.

According to a second embodiment of the invention, APs are excluded from the predefined location areas/tracking areas (LAs/TAs) configured by the operator. By excluding the APs from the TAs it is possible to control a UE's ability to access the APs. The Tracking Areas are hence restricted to eNode Bs in the macro-layer.

Therefore according to this second embodiment of the invention, the APs are not given a LA ID/TA ID or their LA ID/TA ID is set to "null". Each AP in this embodiment only broadcasts its Cell ID, and not a unique LA/TA ID. Since the APs only have a unique cell global identity, the UEs do not consider them to be accessible merely by virtue of the information broadcast. Therefore, by virtue of not broadcasting a TA ID, the UEs will not consider the AP as a possible point of access; further information needs to be acquired by the UE before the AP will be considered a possible point of access. In other words, since there is no unique LA/TA ID information, the UE will initially treat the AP as if it belonged to a Forbidden LA/TA. t-1

An example of the signalling that may occur in the idle state situation for this second embodiment of the invention is illustrated in Figure 3 in relation to the UE moving into the TA of a new base station/eNode B of an LIE network. This Figure illustrates how the UE is made aware of the AP if it is a possible point of access to the network.

The eNode B broadcasts system information which includes the eNode B's Cell ID and Location Area/Tracking Area ID, as well as possibly a "Neighbour Cell List" in the system information. The UE uses the tO broadcasted system information to know which cells to monitor, such as by keeping a record of signal strength and/or interference parameters. This system information only includes information about neighbouring eNode B's and perhaps nearby open APs; nearby closed APs are excluded. It is however preferable that all nearby APs are excluded, due to their more limited capacity, so the rest of this embodiment will be described with this presumption.

The UE will know that it has moved to a new TA, as the TA broadcast by the eNode B will be different to its last recorded eNode B. The UE will therefore perform a Mobility Management (MM) Procedure, such as a location area/tracking area update, so that the network knows the new location of the UE, for future paging requirements. With reference to Figure 3, to perform the Tracking Area Update, the UE transmits a "Tracking Area Update" request message to the eNode B to which it has moved.

Once received, the eNode B forwards the "Tracking Area Update" message to the MME. The MME stores a record of the new TA, and also refers to a list of APs accessible to the UE from the new location (if any). In this regard the MME preferably has a list of all APs accessible in each of its location areas/tracking areas, and all UEs that are authorised to access each of those APs. The MME will create a mapping between the new Tracking Area of the UE and the accessible APs associated with that TA, and S included in the UE context. The UE context will be stored at the MME and a copy forwarded to the eNode B in the Tracking Area Accept" update message. The mapping is stored at the MME for future use, and can be updated as new information is received. For instance, the stored UE context can be used during handover to selectively download information to the new eNode B/AP for use in subsequent handovers.

In the Figure 3 example, the UE is allowed to access the Home AP, and so the MME will map an association between the Home AP and the current macro-layer TA. Therefore, when the MME transmits the "Tracking Area Accept" update message back to the UE, via the eNode B, this message includes the UE context, as well as the Cell ID of the Home AP, being Cell [D#2, and the appropriate macro-layer Tracking Area, being TA ID# 1. The inclusion of the AP's cell ID in this message is used to inform the UE that an AP cell is available and that it should look for that AP in addition to the cells controlled by neighbouring eNode Bs identified in the system information. This therefore induces the UE to do a search for the AP in order to detect its broadcast signal.

Therefore, in this way the network notifies the UE as to which APs it is able to access. By doing so, the typical "trial and error" signalling approach is avoided, as the UEs will not try to access an AP until they have been notified that they can access the AP. A further advantage of excluding the APs from the Tracking Areas, is that more efficient searching can be achieved, as the UEs do not consider APs as possible points of access until told by the network.

Once the UE is notified of the existence of the Home AP, and that it is an AP that the LIE is allowed to access, the LIE adds the Home AP to its list of entities on which it keeps a measurement report. The UE also utilises the mapping between the Home AP and the Tracking Area of the Node B to restrict the number of TA updates that it performs, by not requiring a TA update to occur when the UE reselects between the Home AP and the last recorded Cell's Tracking Area. This mapping is recognition of the fact that the range of the AP is typically small, so the likelihood of the UE moving out of the range of the UE and back into the range of the previously recorded Cell is large. The mapping can therefore be used to further minimise signalling between the UE and the MME.

It is to be appreciated that the UE may have a stored list of which APs it is allowed to use, but it is preferred that the information on accessible APs comes from the network, rather than the UE determining this itself, although this is possible. This ensures signalling is kept to a minimum. The UE will mainly use the stored list of APs for keeping a record of access passwords and the like.

The mapping between the Home AP and the Tracking Area of the eNode B has an additional advantage from the MME's perspective. In this regard, if a communication arrives for the UE, the MME will send a paging message in both the last recorded Tracking Area for the UE, being TA ID#l, and to the Home AP. This allows the MME to trace the UE if it has camped on the AP, despite the AP being not part of a Tracking Area. The mapping therefore effectively creates a new Tracking Area, including accessible APs, which is unique to the UE.

When the UE moves to a geographical location where the UE could handover or reselect to the Home AR, the MME is responsible for ensuring that the necessary connection between the new geographic location and the Home AP exists.

In general, if the number of APs with which the UE can associate is small z.o (i.e. one or two), or where a single AP is seen as the default home AP. then the network can also have a default position where it always pages the UE in the Home APs" as well as the Tracking Area where the UE was last registered. *5

There are various other possibilities to keep the paging load to a minimum.

For instance, if there are a greater number of APs with which the UE is registered, then the MME can page the UE in its current Tracking Area and a subset of the APs. In a further variation, the size of the Macro-layer Tracking Area may be varied by the MME, depending upon the number of APs which the UE is allowed to access in an area. Finally, in the situation of a UE being permanently associated with a Home AP, it may be more efficient and secure to provision this information in the UE by utilising Over-The-Air (OTA) to the UE's SIM.

This description of the first and second embodiments, with the UE operating in Idle mode, has assumed that the UE is only associated with a single Tracking Area at any one time. However it is possible that the UE is associated with more than one Tracking Area. In this implementation, the identifiers of multiple Tracking Areas are broadcast in the system information of a cell. When the UE performs a Mobility Management (MM) procedure, such as a Tracking Area Update, the UE will become associated with more than one TA within which the idle mode UE is free to move within without contacting the network. When the UE is allocated multiple Tracking Areas, the MME needs to maintain a list of which TA lDs have been allocated to the UE. This is because, when it becomes necessary for the MME to page the UE, the MME would look up which eNode Bs form part of the Tracking Areas allocated to the UE in order to page them. The paging message would be passed to all the applicable eNode Bs in order to locate the UE. 2I

The physical size of a Tracking Area is typically decreased in urban areas in order to maintain a similar level of paging load to less-populated areas, as the concentration of UEs in urban areas is dramatically increased. One problem that arises from smaller Tracking Areas, however, is that for fast moving UEs. a higher signalling load on the core network results.

Therefore, alternatively, or in addition, Tracking Areas for a UE can be determined based upon its speed. so that the faster the UE is travelling, the larger the physical Tracking Area allocated to the UE. In an implementation of this, eNode Bs will broadcast a number of different sizes of Tracking Areas, such as a smaller one for low mobility UEs and a larger one for higher mobility UEs.

Once the UE is in a connected state, the mobility of the UE is managed by the network, and so there are different considerations in regard to how the APs with no allocated Tracking Area ID, are managed. In this regard, in a connected state, the UE will be connected to the network via an eNode B or AP which provides the best signal. When the signal falls below a certain threshold, the UE will handover its connection to an alternative eNode B or AP.

With reference to Figure 4, the eNode B provides the UE with the best signal in this instance, and so has been handed over to it. Upon handover, the MME provides the eNode B with a "UE context", which contains information about the UE and neighbouring cells.

Since APs are not included in the Tracking Area associated with the eNode B, this UE context also contains information about any nearby APs that the UE is allowed to be connected to, which in this instance is only the Home AP.

The eNode B will provide the UE with an updated Neighbour Cell List, which includes the identities of any accessible APs, being the Home AP.

The UE can then provide a measurement report to the eNode B about the Home AP when it is discovered. During its idle time slots, a connected UE scans the Broadcast Control Channel (BCCH) of all the cells in its unique * 5 neighbouring cell list.

The UE uses this neighbour cell list to filter its measurement reports -so that it only keeps reports on entities included in this cell list. These measurement reports are provided to the eNode B, as it is the job of the eNode B to monitor the measurement reports and decide when handover is necessary.

It is to be appreciated that the details of all the accessible APs is preferably only provided to the UE when the amount of APs that the UE can access is small. If however, there are a large number of APs to which the UE can connect to, then a filtering mechanism is preferably used, whereby the MME filters which AP details will be downloaded to the UE. One approach for doing this is to build a table of Tracking Areas/eNode Bs for each AP location, which is used to control from which cells it is possible to perform a handover to the AP. This table could also be used to provide the UE with information as to which subset of APs for which it should be scanning the network. This would therefore minimise wastage of the UE' s battery, as less scanning would be required.

This list may also be used by the eNodeB to trigger the establishment of the X2 interface between the eNodeB and the AP. The X2 interface is the transport network connection between eNode Bs. It is also used for APs to communicate with eNode Bs. As APs are added to the network, the relationship between these APs and their neighbouring base stations needs to be established, and the table is a mechanism for notifying the eNode B of the existence of the AP, and enables the X2 interface to be established 2-3 between the two of them, if it has not already been done.

I

Since the eNode B is responsible for initiating handover when the UE is an active state, the eNode B uses the AP information stored in the UE context to ensure that the UE is only handed over to an AP where the network has approved the association. In other words, the UE can only be handed over to APs that are listed in this UE context".

The eNode B will trigger a handover when its broadcast system information signal, as received by the UE, falls below a predetermined quality received threshold, and where a better quality signal is available from a neighbouring base station/AP.

The base stations/Node Bs therefore rely on the MME to provide them with information on the APs that the UE can utilise, since the APs are not included in the Tracking Areas. The MME accordingly needs to have up-to-date subscription information on the authorised APs for each UE.

Therefore, it is to be appreciated that in order for a UE to be able to access one or more APs, the UE's subscription information must provide the necessary authorisation. This can be done in non-real time using written subscription information provided when the Access Point is registered (i.e. a Home AP is registered, and the occupants of that home list their mobile terminals as being authorised to access the telecommunications network via that AP).

Alternatively, this could be achieved by a UE owner purchasing the right to gain access, such through a web application or by SMS. Once this purchase is completed, the MME is notified of such, and so updates its relevant list.

and the UE also stores a record of the relevant AP's details, including, for example, as access password.

Alternatively, the owner of an AP may wish to reserve access to their AP for exclusive use of friends (e.g. for a home-located AP) or customers (e.g. for a business-located AP). A real-time registration process is therefore required. This can be achieved by the AP "registered owner" inviting a person to use the AP by sending a specially formulated SMS to the network, such as Grant Access to [telephone number]". Upon receiving this request, the MME would proceed to add the person's UE identity to its list of UE's authorised to access the particular AP.

In a further alternative, the registered owner of an AP has an access password that they are able to provide to a person to allow them to use their UE to access the AP. To effect this, the UE owner would enter the password into a third party's UE, and the UE would transmit a "Tracking Area Update" request message to the network, together with a field identifying the AP, and the AP password. This would force a Tracking Area Update in relation to the AP. The MME, upon receiving the Tracking Area Update request (via the nearest Node B) would note the inclusion of the AP and its password, verify the password and update its AP table to include the UE as an authorised user of the AP. The MME would also create a mapping between the Tracking Area of the Node B that forwarded the TA update, and the AP. The UE would then be able to utilise the AP to access the network.

The mapping of APs to tracking areas is an important component of these embodiments of the invention. It is to be appreciated that since an AP can be located in every house in a certain region, and that new APs can be added to the network at any time, the network need to keep updating its associations between tracking areas and APs to ensure that best use of APs can be made by those UEs authorised to use them. In particular, transport network connections need to be established between the new APs and other Node Bs (the X2 interface) as well as between the new APs and the controlling MME (the Si interface). The mappings can be used to establish these connections.

The X2 interfaces can be established by the eNode Bs, when they are passed the mapping information from the MME. This typically occurs when the UE is in active mode, and the eNode B's are responsible for controlling the mobility of the UE.

In regard to establishing the S I interfaces, consider the situation of a Home AP newly added to the network. This AP may have two different Tracking Areas that overlap it, or which are adjacent to it. The network will therefore need to create mappings for each of these two different Tracking Areas and the AP, so that an authorised UE in either of these two different Tracking Areas is notified of the existence of the Home AP.

In other words, considering the authorised UE in idle mode moving into TA#I, which is adjacent to the AP, then when the UE performs a Tracking Area Update, the UE will be informed of the existence of the Home AP, and the MME create a mapping between TA#l and the AP. The MME will also create the Si interface between itself and the AP, if one has not already been created.

Should the UE then move into another Tracking Area, being TA#2, then the AP will again perform a Tracking Area Update and also create a mapping between TA#2 and the AP in view of their geographical proximity. At this point, the MME may also create a link between TA#l, TA#2 and the AP, so that the UE is free to move in the area covered by both Tracking Areas and the AP without the need for a Tracking Area update. Once the process has been performed for each TA, it need not be repeated. as the MME will save the mappings for future reference.

If an access point is physically moved (e.g. when someone moves home), it will be necessary to cancel the mappings recorded for the AP, and to register the new location in the network, by updating the mapping between the AP location and the terrestrial cells/tracking areas.

In the embodiments described above, the AP is configured to appear to the UE as a conventional base station that communicates with the UE using GSMIUMTSILTE protocols in accordance with the Standards (where they exist) and the licensed radio spectrum. Alternatively, the AP could communicate with the UE by any other suitable technology -for example, by a Bluetooth (RTM) connection, WiFi or another unlicensed mobile access (UMA) protocol, which allows the GSMJUMTSILTE features to be provided using a non-GSMIUMTSILTE bearer technology.

The above described embodiments have also assumed that all APs in the network require access to them to be controlled, however it is also within the scope of this invention that only a subset of all the APs are controlled.

For example, it is within the scope the present invention that some APs are given Tracking Area IDs, whereas others in the network are not. 2)

Claims (14)

1. In a telecommunications network including a radio access network comprising a plurality of base stations, each defining a cell, for wirelessly transmitting data that is receivable by one or more mobile terminals, wherein at least one of the base stations is an Access Point (AP), a method of controlling access to the telecommunications network via the at least one Access Point, the method including: defining tracking areas in the network covering one or more base station cells but excluding the at least one Access Point cells.

2. The method of claim 1 further comprising creating a mapping associating one of the at least one Access Points with one and more Tracking Areas, and using the mapping to perform at least one of the following: a) notify an idle mobile terminal that it is authorised to select the one Access Point when in the one or more Tracking Areas; b) trigger the establishment of a transport network connection between a base station and one of the at least one Access Points.

c) trigger the establishment of a transport network connection between an MME and one of the at least one Access Points.

d) page a mobile terminal where one of the one or more Tracking Areas was the last Tracking Area recorded for the mobile terminal; e) notify an idle mobile terminal that it is authorised to move about the mapping without performing a Tracking Area update; f) notify a mobile terminal that it should undertake a search for transmissions by the one Access Point; g) notify a mobile terminal that it should undertake measurements of transmission received from the one Access Point: h) notify a base station controlling handover of a mobile terminal that the mobile terminal is authorised to be handed over to the one Access Point.

3. The method of any one preceding claim further including: a mobile terminal transmitting a Tracking Area update request to a S 5 network controller; the network controller determining whether any authorised Access Points exist, in the vicinity of the mobile terminal's current Tracking Area.

through which the first mobile terminal is authorised to access the network; where one or more authorised Access Points exist, creating a mapping; and transmitting the mapping to the mobile terminal.

4. A telecommunications network including a radio access network comprising a plurality of base stations, each defining a cell, and being configured to wirelessly transmit data that is receivable by one or more mobile terminals, with at least one of the base stations being an Access Point (AP); and wherein the radio access network is arranged in a plurality of tracking areas with each tracking areas covering one or more cells but excluding the cells of the at least one Access Point.

5. The network of claim 4 wherein each Access Point is a base station connected by IP transport to the network.

6. A telecommunications network including a radio access network comprising a plurality of base stations configured to wirelessly transmit data that is receivable by one or more mobile terminals, with at least one of the base stations being an Access Point (AP), and wherein the least one Access Point is configured to broadcast information from which the at least one mobile terminal is able to determine if it has access rights to each of the at least one Access Points.

7. The network of claim 6 wherein the at least one Access Point is configured to broadcast an Access indicator Field from which the one or more mobile terminal is able to determine if it has access rights.

S 5 8. In a telecommunications network including a radio access network comprising a plurality of base stations configured to wirelessly transmitting data that is receivable by one or more mobile terminals, wherein at least one of the base stations is an Access Point (AP), a method of restricting access to the at least one Access Point, the method including: transmitting information from each Access Point from which mobile terminals are able to determine their ability to access the given base station.

9. The method of claim 8 wherein the information transmitted is an

Access Indicator Field.

10. The method of claim 8 or 9, wherein unless it is determined that the mobile terminal has a right of access to the base station, the mobile terminal does not attempt to access the base station.

11. The method of claim 2, wherein the transport network connection established between the base station and one of the at least one Access Points is the X2 interface.

12. The method of claim 2 wherein the transport network connection established between the MME and one of the at least one Access Points is the Si interface.

13. A system for performing the method according to any one of claims 1 to3or8to 12.

1 2. A method of controlling access to a telecommunications network, * substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the accompanying drawings.

1 13. A telecommunications network substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the accompanying drawings.

14. A system substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the accompanying drawings.