EP1958476A1

EP1958476A1 - Adjusting usage data of a network service provided via a first access technology when a mobile station is detected via a second access technology

Info

Publication number: EP1958476A1
Application number: EP06819472A
Authority: EP
Inventors: Roger Holmes
Original assignee: Orange SA
Current assignee: Orange SA
Priority date: 2005-11-14
Filing date: 2006-11-14
Publication date: 2008-08-20
Also published as: GB0523220D0; WO2007054588A1; GB2432281A

Abstract

A method of detecting the context of a mobile station for use in processing usage data corresponding to usage of a network service provided by a cellular mobile telephone network, the network being capable of providing the mobile station with said network service via a first terrestrial radio access technology and being arranged to generate a usage data record in respect of said usage of said network service, the method comprising the steps of: detecting a mobile station during a detection period via a second terrestrial access technology, said second access technology being different to said first terrestrial radio access technology; receiving data indicative of said detected mobile station; and for any usage data records generated in respect of usage of said network service occurring during said detection period, adjusting usage data derived from said usage data records on the basis of the received data. Embodiments of the invention are concerned with identifying the context of a subscriber via a technology different to that utilised to provide the subscriber with network services, and using the context information to determine a charge for the usage of network services; and/or to track the movements of a subscriber; and/or to determine a next task to be performed by the subscriber; and/or to verify access to various network services.

Description

ADJUSTING USAGE DATA OF A NETWORK SERVICE PROVIDED VIA A FIRST ACCESS TECHNOLOGY WHEN A MOBILE STATION IS DETECTED VIA A SECOND ACCESS TECHNOLOGY

Field of the Invention

The present invention relates to a system for, and a method of, detecting

5 the context of a mobile subscriber. Embodiments of the invention are particularly, but not exclusively, suited to detecting the context via a different access technology to that associated with usage of network services, and the detected context data can be used in conjunction with applications such as authorising access to network services; security or workflow applications; and/or call rating

10 applications.

Background of the Invention

In a wired network, calls between a calling party and a called party are either carried over a bespoke circuit set up between the respective parties, or via

15 packets that are transmitted independently of one another, and which are reassembled at a terminal associated with the called party. The former are commonly referred to as circuit-switched calls, while the latter are referred to as packet-switched calls.

With the advent and ever increasing reach of Digital Subscriber Line

20 communications technologies (e.g. ADSL, SDSL, commonly referred to by the generic term "broadband"), there is a correspondingly increasing trend to handle wired voice calls as packet switched data - using the Voice over IP (VoIP) protocol - instead of as switched circuits. Such data can be transmitted as Internet Protocol (IP) traffic over networks such as the Internet at a significantly lower

25 cost than is possible for circuit-switched calls because there is no need to occupy a circuit for the duration of the call.

Currently cellular mobile telephone networks handle voice calls by setting up circuits between the caller and calling party for the duration of the call; as wired calls are increasingly being transmitted as packets, it will therefore be

30 appreciated that mobile calls are becoming increasingly more expensive compared to their wired counterparts. Clearly when a caller is on the move, he is constrained to use the cellular - and thus circuit-switched - network, but when he is located in one location he has a choice of access technology, and, if there is a substantial difference in call costs, subscribers located in the office environment are more likely to use their wired telephone in preference to their mobile phones. It will be appreciated that mobile operators are keen to review their service offerings in light of developing technologies. Indeed, BT has recently launched a combined fixed and mobile phone service, named "Bluephone", which allows a single device to act as both a mobile phone, when users are out and about, and a landline that switches automatically onto a Broadband wired line when customers get home. The service requires a wireless hub, which uses Bluetooth to create a wireless link to the phone, and is connected to the fixed network. It will therefore be appreciated that there is a handover of calls from a cellular network (e.g. when the subscriber is out and about, and where the network service can only be provided via cellular networks) to the fixed network, this being performed under control of the hub.

A problem with this method is that the handover of calls requires modification to the signalling and data associated with calls (since the radio access technology is changing from cellular to Bluetooth and to IP packets), potentially resulting in a loss of data contained within the call. Another problem arises from differences between network operators: notwithstanding the fact that the GSM cellular communications technology has been standardised, each network operator offers different services and the format of data can vary between networks. Accordingly, hubs will either have to be equipped with APIs corresponding to each network operator or they will only work with phones associated with a particular network operator. In situations where a hub is designed to serve several users, each of which is a subscriber of a different network operator, the latter situation will result in at least some of the users not being able to route their calls via the wired network. Summary of the Invention

In view of the complications of protocol translations and potential problems with standardisation required by intermediate devices such as the hub described above, the inventors of the present invention have taken a rather different approach to that adopted in the prior art. Instead of trying to route calls via different communications technologies, calls are handled via the cellular network - in a preferred arrangement for the duration of the call, irrespective of the location of the subscriber - and the context of the subscriber is detected independently of the call. Accordingly, in accordance with a first aspect of the present invention, there is provided a method of detecting the context of a mobile station for use in processing usage data corresponding to usage of a network service provided by a cellular mobile telephone network, the network being capable of providing a mobile station with said network service via a first terrestrial radio access technology and being arranged to generate a usage data record in respect of said usage of said network service, the method comprising the steps of: detecting a mobile station during a detection period via a second terrestrial access technology, said second access technology being different to said first terrestrial radio access technology; receiving data indicative of said detected mobile station; and for any usage data records generated in respect of usage of said network service occurring during said detection period, adjusting usage data derived from said usage data records on the basis of the received data.

In one embodiment the detection information is then used to identify whether the mobile station is present in a location in which a wired phone could be used and, if so, the call is rated accordingly. An advantage of embodiments of the invention is that, since there is no change to the way network services are provided, there is no interruption to the network services and use of existing network infrastructure is maximised. In preferred embodiments the first terrestrial radio access technology is a

GSM network and the second terrestrial radio access technology is Bluetooth or Wi-Fi or similar. In one arrangement the mobile station broadcasts data via Bluetooth, the data including an identifier associated with the mobile station. Thus in this arrangement, detection of the mobile station arises through receipt of the broadcast data. Preferably the broadcast data can be transmitted to the cellular mobile telephone network via a network node associated with a further access technology such as the Internet Protocol, and the detection period can be identified from the broadcast data - e.g. by identifying gaps between broadcasted data. Most conveniently the broadcast data are effectively relayed to the mobile communications network via the network node embodied as an IP Router and processed by the mobile communications network. However, the broadcast data could alternatively be filtered on the basis of subscription type, so that only those broadcast data corresponding mobile stations subscribing to the mobile communications network are relayed to the mobile communications network.

In one arrangement, adjustment of the usage data is performed on the basis of the identity of the network node relaying the broadcast data, and optionally the actual geographical location of the router can be identified (e.g. from a previously stored look-up table listing router identity and physical location). In this latter case the mobile communications network can select data such as location-based information and transmit this to the mobile station via the mobile communications network. The information might, for example, be transmitted as SMS messages or as a cell broadcast message. Additionally or alternatively, movement of the mobile station could be tracked on the basis of the network node identity and instructions and/or work to be performed can be transmitted to the mobile station.

According to a further aspect of the present invention there are provided system and device components corresponding to the foregoing.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings. Brief Description of the Drawings

Figure 1 is a schematic diagram showing components of a detection system according to an embodiment of the invention;

Figure 2 is a timing diagram showing transmission of data between various of the detection system components shown in Figure 1; and

Figure 3 is a schematic flow diagram showing steps performed by a usage processing system shown in Figure 1.

Detailed Description of the Invention Embodiments of the invention are concerned with identifying the context of a subscriber via a technology different to that utilised to provide the subscriber with network services, and using the context information to determine a charge for the usage of network services; and/or to track the movements of a subscriber; and/or to determine a next task to be performed by the subscriber; and/or to verify access to various network services. The following description will present operation of embodiments of the invention as they relate to using context information to rate usage of network services.

As shown in Figure 1, calls made by, and messages sent from, a subscriber 2 are handled by a cellular network 10 in the conventional way. With the exception of a base station 101 and a switch (MSC) 103 it will be noted that Figure 1 does not include any details of the radio and switching components of the cellular network 10; these components will not be described in any detail herein, since the parts are entirely conventional. The mobile station 2 is connected to a removable subscriber identity module (SIM) not shown, the SIM providing a means for the mobile station 2 to receive service from the cellular network 10.

In addition to communicating with the base station 101, the mobile station 2 is arranged to communicate with an Access Point AP 4. In one arrangement, the AP 4 is a personal computer (fixed or portable) having a wireless router embedded therein, the router being arranged to transceive in accordance with one or more of WIFI (802.11b Standard), Bluetooth or indeed any unlicensed band of frequencies. The mobile station 2 is similarly equipped to transceive in accordance with the corresponding radio access technology, and, referring to Figure 2, transmits (step S2.1) packets identifying the mobile station 2, either in response to data received from the AP 4 or by way of a periodic broadcast. The identification data can comprise any suitable identifier such as a Bluetooth identifier associated with the mobile station, the IMSI associated with the SIM, or the MSISDN associated with the subscription.

In a most basic arrangement, and in accordance with conventional processing capabilities, the mobile station 2 broadcasts identification data periodically; these data are picked up by whichever Access Point is within range of the broadcast. The AP 4 is configured with a software component (not shown) arranged to receive and store the identification data (step S2.3), together with temporal information identifying time of receipt thereof. It will be appreciated that the mobile station 2 might be located within range of an Access Point more than once in a given period, which means that some sort of post-processing of the identification data is required in order to identify actual periods of proximity in relation to a given Access Point. The post-processing can be performed by a bespoke location application 201 operating within the infrastructure of a given network operator, in which case the AP 4 simply forwards all of the identification data to a network address associated with the location application 201, via IP Router 6. The data can be transmitted either in response to detection of data newly stored in its Bluetooth stack, or periodically as part of a batch process (step S2.5).

On the basis of the destination address associated with the identification data transmitted at step S2.5, the IP Router 6 is arranged to transmit the identification data as messages to the cellular network, more specifically to the infrastructure 20 thereof, via an API 200. This API 200 includes components arranged to authenticate messages received from IP Routers 6, so as to ensure that only messages received from those Routers that have subscribed to the location service are passed to the location application 201. Many suitable encryption methods are known, and for example can include the Router 6 encrypting (step S2.7) the data using a key derived from the identity of the Router 6 and data previously transmitted from the network 20 to the Router 6 (e.g. as part of the subscription process). More specifically, encryption is preferably handled via Public Key Encryption via certificates issued by a suitable signing authority, such as Verisign™. In this way, the owner of a respective IP Router 6 is responsible for maintaining the corresponding certificate. The Router and the API 200 then negotiate using their certificates to establish the authenticity of the sending organisation (in this example IP Router 6). In addition, the API 200 may require the identification data transmitted at step S2.5 to include a name corresponding to the owner of Router 6 and a password both of which it will verify against data held by the API 200 itself.

Once the identification messages have been authenticated by the MNO API 200 (step S2.9), the API 200 passes the messages to the location application 201, for processing thereby. The role of the location application 201 is to identify periods in which a particular mobile station 2 is proximate to the IP Router 6 (in Figure 1 this is identified schematically as region R); that is to say, periods during which an Access Point 4, which is locally connected to the IP Router 6, is wirelessly communicating with the mobile station 2. This therefore excludes instances in which the mobile station 2 is a portable terminal that has remotely connected to an Access Point (via the IP Router), and instances in which the AP 4 is itself mobile, located remote from region R, and transmitting data received from mobile station 2 to the IP Router 6. Such communication attempts can be filtered out by a firewall associated with communications access to region R, e.g. by means of settings on a firewall based on destination IP address or similar.

Accordingly, assuming all of the data received by the location application 201 have been transmitted by mobile stations 2 that are local to the IP Router 6, the location application 201 proceeds to distinguish, from the received messages, a time of arrival and a time of departure of the mobile station 2 from region R. A suitable method involves comparing successively received messages in respect of a given mobile station 2: recalling that the identification messages comprise identification data, which themselves include temporal information, if the time between two successively received data messages exceeds a predetermined interval, the location application 201 might assign the first of said two successively received data to "departure" status and the second of said two successively received data to "arrival" status. Having identified a time of arrival and a time of departure for the mobile station 2 with respect to Region R, the location application 201 preferably then stores, in database 203, a presence record 300 (step S2.l l). Each presence record 300 comprises a field identifying the mobile station 301, a field identifying the Router 303, a field identifying said time of arrival 305 of the mobile station 2 at, and a field identifying said time of departure 307 of the mobile station 2 from, the region associated with the Router identified in field 303.

It is to be noted that when the mobile station is located within region R, the mobile station 2 could take up network services via the second access technology, but in fact takes up network resources via the first access technology, using the second access technology solely for the purposes of transmitting presence data. Usage data held by the provider of the first access technology can be updated to reflect the fact that the mobile station could have used an alternative access technology, but instead used (or continued to use) the first access technology. Alternatively, and in the case where the mobile station is located in region R but is not accessing either of the network services, this presence data may similarly be forwarded and tagged accordingly.

It will be appreciated (for example with reference to Figure 1) that embodiments of the present invention may be implemented in a network architecture such that the mobile station can access network services via the first and second access technologies independently from one another. Thus, the mobile station can access both network services from the respective access technologies directly, without needing to use network services provided by the other access technology. Furthermore, the mobile station may be detected directly via a second access technology, without any signals being sent over the second access technology being sent via the cellular network service. It is to be noted from the foregoing that, in this embodiment, any mobile station 2 equipped with Bluetooth functionality will cause the Access Point 4 to generate identification data, which, in turn, will be sent as an identification message from the Router 6 to the location application 201 via the MNO API 200. Therefore in this embodiment the process performed by the location application 201 will involve an initial filtering step, in which data received from mobile stations that are not subscribers of the network 10 are discarded. This filtering process can be performed in many ways, one of which includes reviewing a look-up table matching IMSI to Bluetooth identifier for all subscribers of the cellular network 10, and which is therefore applicable in the event that the identification messages include identification data in the form of a Bluetooth identifier. In response to receipt of an identification message the location application 201 reviews a look-up table matching IMSI to Bluetooth identifier for all subscribers of the cellular network 10. Since the look-up table will only list IMSI data - and thus Bluetooth identifiers - for subscribers of the network 10, the location application 201 reviews the look-up table, and, if there are no entries corresponding to the Bluetooth identifier contained within the identification message under consideration, the identification message is discarded.

During the normal course of a day a subscriber of network 10 might leave region R - e.g. if the region R is an office building and the subscriber leaves the office to visit a shopping precinct during a lunchbreak. If the subscriber is involved in a telephone call during the transition from region R to the shopping precinct it will be appreciated that there will be no interruption to the telephone call - either actual or perceived (other than is associated with normal GSM handover between base stations) - but that data will only be transmitted from the Router 6 to the location application 201 while the subscriber is in region R. This is shown schematically in Figure 2, by means of the presence (subscriber in region R) and then absence (subscriber leaves region R) of successively broadcast identification data. Details of how the location data are processed to generate a rate for the call are described in detail below, but suffice to note at this point that the call will have at least two charging rates - a first for when the subscriber is in the region R and a second for when the subscriber is outside of region R (typically normal charging tariffs would apply in this region). As is known in the art, the MSC 103 is arranged to generate call data records in respect of calls originating at the switch 103. Usually this record comprises at least call start time, call termination time, calling and called numbers, and a cell identifier Cell ID. The MSC 103 stores the generated data records 105 and transmits a large number of the stored CDR records, en-masse, to the network infrastructure 20 (more specifically to a billing processing system 205 therein) where the billing program post-processes the call data records and generates bills to be sent to the subscribers; this is shown schematically in Figure 2 as steps performed in respect of a call that is placed while the subscriber is within, moves out of, and subsequently moves back into region R.

Turning to Figure 3, in embodiments of the invention this post-processing of call data records involves firstly selecting a call data record (step S3.1) and identifying (step S3.3) the overlap, if any, between temporal data associated with the presence records (fields 305, 307) and temporal data associated with the selected call data record. In the event that the presence record 300 identifies the subscriber via a Bluetooth identifier in field 301, the post-processing additionally involves billing application 205 retrieving data from the look-up table referred to above and matching IMSI to Bluetooth identifier. Having identified the period of overlap at step S3.3, the billing application 205 identifies, from field 303, the identity of the region R - e.g. from the identity of the Router located proximate to the subscriber during the period of overlap - and accesses a look-up table listing call rates as a function of Router ID so as to retrieve an appropriate call rate for the period of overlap (step S3.5). The billing application 205 also identifies (step S3.7) any periods within the call data record under consideration for which the subscriber was not in the vicinity of region R; in one arrangement this can be performed by subtracting the period of overlap identified at step S3.3 from the duration of the entire call detail record.

The billing application 205 then proceeds to rate the call data record (step 3.9) in accordance with whatever call rates were retrieved at step S3.5 and that apply during the periods identified during step S3.7. Having identified the appropriate rates for the call data record, the billing application 205 generates data indicative of charges for the call and stores the data for subsequent inclusion in a bill for the subscriber.

Additional Details and Alternatives In the above embodiment it is assumed that the location application 201 analyses the identification messages in order to determine periods within which a subscriber is present within region R. A disadvantage of this arrangement is that the IP Router 6 transmits a significant number of identification messages, regardless of whether they correspond to subscribers of the network 10, and/or whether a call has been made during periods in which the mobile station is in the vicinity of region R. However, from the point of view of scalability, upgrading and compatibility, this is a particularly advantageous distribution of the various processing means, since that the Access Point 4 and IP Router 6 only need to be configured with basic store and forward functionality, these typically being included as standard features of such devices. Furthermore, should more than one network operator offer such a service, this arrangement is sufficiently flexible to allow the Router 6 to encrypt and transmit identification messages to infrastructure corresponding to different respective network operators.

However, notwithstanding these disadvantages and advantages, either of the access point 4 or IP Router 6 could alternatively be configured to distinguish, from the broadcast identification data, a time of arrival and departure accompanying presence of a mobile station 2 within region R. For example, the AP 4 could itself determine whether the mobile station 2 had arrived or departed from its vicinity and only send messages to the location application 201 when either of these events is deemed to have occurred (based, for example, on the time period between potential arrival and departure events).

Accordingly the identification messages transmitted at step S2.7 comprise the presence records 300 and the location application 201 only has to filter the identification messages so as to discard those corresponding to mobile stations that are not subscribers of the network 10. A particular advantage of using two different access technologies to determine a rate for a call is that data generated in relation to one of the access technologies can be used to corroborate data generated in respect of the other. More specifically, cell ID data associated with the CDRs generated by the MSC 103 can be used to verify the location data field 303 in given presence records 300; such a verification step could be performed on the basis of correlation techniques, preferably on the basis of data received from a plurality of different access points AP 4 within region R and as a precursor to step S3.3.

In the above-described embodiments the access point 4 and/or Router 6 are described as batch-forwarding identification messages to the API 200; alternatively these messages could be relayed to the API 200 and thence to the location application 201 in real time. An advantage of such an arrangement is that the location application 201 can generate and send an SMS message or cell broadcast message to the mobile station 2 (via the cellular network 10), alerting the subscriber to the fact that he is moving in and out of different charging areas. Moreover, if the location application 201 has access to geographical location data associated with Router ID, the message could additionally include information such as directions to services in the vicinity of the subscriber, this information having been retrieved from appropriate information sources accessible by the location application 201 in accordance with the geographical location and predetermined profile information associated with the subscriber.

Whilst in the above embodiments the context information contained within presence records 300 is used to determine a charge to be applied in respect of usage of network services, the presence records 300 could alternatively be used by a security system, in which packages - equipped with the required broadcasting functionality - can communicate with the access point 4 in the manner described above. In such an arrangement, instead of the presence records 300 being accessed by a billing processing system 205, a security tracking system could retrieve the records and process the same for the purposes of verifying that the person associated with the package - who is making calls via the cellular network 10 - is in the building in which he purports to be located, and for the purposes of providing directions as to a next job. Alternatively or additionally the presence records 300 could be used as part of a work-scheduling system, for the purposes of allocating a next task and/or providing appropriate directions in relation thereto. It will be appreciated that one or more of these latter uses (security, workforce scheduling) of the presence records 300 can be made independently of the subscriber making calls. As a further alternative use of the presence records, the network 10 could authorise a subscriber's current or requested access to various location-constrained services, e.g. the work line of a Line 2 subscription.

In the above-embodiments the region R is identified on the basis of the identity of an IP Router 6, since an IP network provides a fast and reliable conduit for the identification messages. However, the region R could be identified on the basis of different types of devices - and indeed different criteria such as geographical location - such as a GPS receiver associated with the AP 4.

In the above-embodiments the AP 4 is described as a laptop computer; however, it will be appreciated that it could alternatively be embodied as a dedicated processing node, a wireless and/or IP router, or a fixed computer.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. A method of detecting the context of a mobile station for use in processing usage data corresponding to usage of a network service provided by a cellular mobile telephone network, the network being capable of providing the mobile station with said network service via a first terrestrial radio access technology and being arranged to generate a usage data record in respect of said usage of said network service, the method comprising the steps of: detecting a mobile station during a detection period via a second terrestrial access technology, said second access technology being different to said first terrestrial radio access technology; receiving data indicative of said detected mobile station; and for any usage data records generated in respect of usage of said network service occurring during said detection period, adjusting usage data derived from said usage data records on the basis of the received data.

2. A method according to claim 1, in which the mobile station broadcasts data via said second terrestrial access technology, said data being broadcast including an identifier associated with the mobile station, the method including receiving the broadcast data and thereby detecting the mobile station.

3. A method according to claim 2, including deriving said detection period from the broadcast data.

4. A method according to claim 2 or claim 3, including transmitting the received broadcast data to the cellular mobile telephone network via a network node associated with a further access technology.

5. A method according to claim 4, including selectively transmitting the received broadcast data to the cellular mobile telephone network on the basis of the cellular subscription associated with the mobile station.

6. A method according to claim 4 or claim 5, including identifying the network node and adjusting the usage data derived from said usage data records on the basis of the identity of the network node.

7. A method according to any one of claim 4 to claim 6, including identifying a location of the mobile station on the basis of the network node.

8. A method according to claim 7, including selecting data related to the identified location of the mobile station and transmitting the selected data to said mobile station via the first terrestrial radio access technology.

9. A method according to any one of claim 6 to claim 8, including tracking the mobile station on the basis of the network node.

10. A method according to any one of the preceding claims, in which the second terrestrial radio access technology comprises Bluetooth or Wi-Fi.

11. A detection system for use in processing usage data corresponding to usage of a network service provided by a cellular mobile telephone network, the network being capable of providing a mobile station with said network service via a first terrestrial radio access technology and being arranged to generate a usage data record in respect of said usage of said network service, the system comprising: a detection system for detecting a mobile station during a detection period via a second terrestrial access technology, said second access technology being different to said first terrestrial radio access technology; communication means for receiving data indicative of said detected mobile station; and means for adjusting, on the basis of the received data, usage data derived from any said usage data records generated in respect of usage of said network service occurring during said detection period.

12. A system according to claim 11, wherein the detection system comprises a radio access point capable of receiving data packets and arranged to associate temporal data therewith, said data packets identifying the mobile station.

13. A system according to claim 11 or claim 12, including a network node arranged in communication with the radio access point so as to receive a message comprising identification data derived from said data packets, and the temporal data.

14. A system according to claim 13, including a storage system arranged to store adjustment data in association with network node identity for use in performing said adjustment of the usage data.

15. A system according to claim 13 or claim 14, wherein the network node comprises an Internet Protocol router.

16. A method of processing usage data corresponding to usage of a network service provided by a cellular mobile telephone network, the network being capable of providing a mobile station with said network service via a first radio access technology and being arranged to generate a usage data record in respect of said usage of said network service, the method comprising the steps of: detecting a mobile station during a detection period via a second access technology, said second access technology being different to said first radio access technology; receiving data indicative of said detected mobile station; for any usage data records generated in respect of usage of said network service occurring during said detection period, adjusting usage data derived from said usage data records on the basis of the received data, wherein said data indicative of said detected mobile station is received independently of said mobile station.

17. A method of processing usage data corresponding to usage of a network service provided by a cellular mobile telephone network, the network being capable of providing a mobile station with said network service via a first radio access technology and being arranged to generate a usage data record in respect of said usage of said network service, the method comprising the steps of: detecting a mobile station during a detection period via a second access technology, said second access technology being different to said first radio access technology; receiving data indicative of said detected mobile station, said received data not including geographical location data; and for any usage data records generated in respect of usage of said network service occurring during said detection period, adjusting usage data derived from said usage data records on the basis of the received data.

18. A method of detecting the context of a mobile station for use in processing usage data corresponding to usage of a network service provided by a cellular mobile telephone network, the network being capable of providing the mobile station with said network service via a first terrestrial radio access technology and being arranged to generate a usage data record in respect of said usage of said network service, the method comprising the steps of: detecting a mobile station during a detection period via a second terrestrial access technology, said second access technology being different to said first terrestrial radio access technology; receiving data indicative of said detected mobile station; and authorising access to a requested network service during said detection period on the basis of the received data.

19. A method according to any one of claims 1 to 10 or 16 to 18, wherein said mobile station is provided with a network service via radio access technology other than said second radio access technology during said detection period.

20. A method according to any one of claims 1 to 10 or 16 to 19, wherein said mobile station is provided with said network service via said first radio access technology during at least a part of said detection period.

21. A method according to any one of claims 1 to 10 or 16 to 20, wherein said network service from said cellular mobile network is accessible by said mobile station via said first radio access technology without using said second radio access technology.

22. A method according to any one of claims 1 to 10 or 16 to 21, wherein said step of detecting a mobile station during a detection period is performed using a network other than said cellular mobile network.