WO2001041471A1

WO2001041471A1 - Subscriber equipment and method for a mobile communications system

Info

Publication number: WO2001041471A1
Application number: PCT/GB2000/004570
Authority: WO
Inventors: Richard James Bailey; Graham Fischer; Stuart Shutt
Original assignee: Orange Personal Communications Services Ltd
Current assignee: Orange Personal Communications Services Ltd
Priority date: 1999-12-02
Filing date: 2000-11-30
Publication date: 2001-06-07
Anticipated expiration: 2002-06-02
Also published as: GB9928522D0; AU1538301A; GB2357009A

Abstract

A subscriber equipment set for use in a mobile communications system including a mobile communications network and a plurality of mobile stations, said network having a plurality of radio transceiving stations whereby said mobile stations receive radio communications service from said network, said set including a firs station and a second station, wherein the first station comprises a first radio transceiver, memory means for storing first subscription data and means for registering with the mobile communications network, to receive radio communications service from a radio transceiving station therein, by use of the first subscription data, wherein the second station comprises a second radio transceiver, memory means for storing second subscription data and means for registering with the mobile communications network, to receive radio communications service from a radio transceiving station therein, by use of the second subscription data, and wherein the first station is connectable to the second station to receive service in the mobile communication system via the second station.

Description

SUBSCRIBER EQUIPMENT AND METHOD FOR A MOBILE COMMUNICATIONS SYSTEM

This invention relates to subscriber equipment for a mobile communications system, a mobile communications network and a method of controlling services in a mobile communications network.

Subscriber equipment referred to as a "home base station" is known. The home base station is installed inside a building, for example the home of the subscriber owning a mobile station, for providing a cordless telephony link to the mobile station when the mobile station is within its coverage area. The

home base station is connected, via a fixed line connection, to a public services telephone network (PSTN). When outside the service area of the home base station, the mobile station receives service in a cellular mobile

communications network, via a cellular radio interface.

Home base stations have been proposed in various guises, in particular

the cordless radio interface may take various forms. For example, a combined

Global System for Mobile Communications (GSM) and Digital European

Cordless Telephone (DECT) mobile station has been proposed for use with a

DECT cordless base station. A further proposal is undergoing standardisation

at the European Telecommunications Standard Institute, and is the subject of a

project entitled "GSM Cordless Telephony System (CTS)", as detailed in

Draft GSM Technical Specifications 03.52 ("Lower Layers of the CTS Radio Interface") and 03.56 ("CTS Architecture Description") and GSM Technical Specification 03.20, Annex E ("Security Related Network Functions").

Home base stations are considered to be desirable, since it is sometimes the case that cellular radio network coverage does not extend sufficiently within in-building environments. By providing a cordless radio

communications link within the home of the subscriber, the coverage of the cellular network can be supplemented. Furthermore, the subscriber is able to use a single mobile station for two-way communications outside the home via the cellular radio network, and for two-way communications inside the home via a PSTN connection.

However, there remain drawbacks to the home base stations proposed in the past. Firstly, a subscriber must maintain two separate telephony

subscriptions; one subscription to the cellular radio network and a second subscription to the PSTN. Furthermore, the range of telecommunications

services which are supported by a cellular communications network is

generally different, and often greater, than that supported by a PSTN. Such

services are, for example, the short message service (SMS) supported by, inter

alia, the GSM system. In future, with third generation mobile radio systems,

the range of services supported is to increase, thereby exacerbating the

problem.

In accordance with one aspect of the present invention there is

provided a subscriber equipment set for use in a mobile communications

system including a mobile communications network and a plurality of mobile stations, said network having a plurality of radio transceiving stations whereby said mobile stations receive radio communications service from said network, said set including a first station and a second station, wherein the first station comprises a first radio transceiver, memory means for storing first subscription data and means for registering with the

mobile communications network, to receive radio communications service from a radio transceiving station therein, by use of the first subscription data, wherein the second station comprises a second radio transceiver, memory means for storing second subscription data and means for registering

with the mobile communications network, to receive radio communications service from a radio transceiving station therein, by use of the second subscription data, and

wherein the first station is connectable to the second station to receive

service in the mobile communications system via the second station. The second station is able to receive radio communications service in a

mobile communications network, whereby the first station is able to receive service, via the second station, from the mobile communications network.

The second station itself carries voice or other data traffic via a radio link set

up between the second station and the mobile communications network.

The second station may be located, fixedly, inside a building, such as

inside the roof space of the building, or to the exterior of the building, where

mobile network coverage is available. The connection between the second

station and the first station allows the first station when inside the building to receive service which may not be available through a direct radio link with the mobile communications network in the location of the first station.

By providing that the second station itself stores subscription data to allow the radio transceiving apparatus to independently register for service with the mobile communications system, the second station is enabled with the capability of independently performing communications with the mobile

communications system. For example, such communications may consist of the exchange of control messages necessary for the servicing of a first station via the second station. Such control messages may, for example, include instructions from the mobile communications network as to a set of one or more frequencies, within the frequency band or bands allocated to the mobile communications system for radio communications, at which the second

station is authorised to conduct radio communications with a first station.

A radio interface used between the first station and the second station may be identical with, or a modified version of, a cellular radio interface

already used by a mobile station for direct radio communications via mobile communications system, whilst interference caused by the second station is

minimised by a frequency re-use plan controlled by the mobile

communications network. The frequency re-use plan may be implemented by

the sending of control messages directly via the radio link between the mobile

communications network and the second station itself.

The control messages may also include messages used for

authentication of a first station wishing to register for service via the second station. The second station may pass authentication challenges from the mobile communications network to the first station and authentication responses generated in the first station to the network, and receive confirmation of the authentication of the first station from the mobile network

to judge whether the first station should receive service from it.

Since the second station stores subscription data, and has the capability to authenticate with the mobile communications network itself, a secure

encrypted communications session between the second station and the mobile communications network becomes possible. Once the second station has

itself authenticated, by use of the subscription data it stores, with the mobile communications network, secure data, for example authenticating data allowing the radio transceiving apparatus to authenticate a first station directly, may be transmitted via an encrypted communications link from the

mobile communications network to the radio transceiving apparatus to be stored securely thereon. The second station may include a secure storage

module, such as a subscriber identity module (SIM), on which such secure

data may be stored along with the subscription data for the second station

itself.

Furthermore, by allowing the second station to itself register with the

mobile communications network, the radio interface between the second

station and the mobile communications network may be the same as that used

between standard mobile stations and the mobile communications network.

The radio interface technology already used for the radio interface over which the mobile stations in the network receive service may thus be re-used for the radio interface between the second station and the mobile communications system. One or more of a range of services supported by that standard radio interface, and also the standard mobile stations, may thus be provided by communications via the radio transceiving apparatus.

According to a further aspect of the invention there is provided a

method of controlling services in a mobile communications system including a mobile communications network having a plurality of network entities providing services to a plurality of radio stations which include mobile stations, said method comprising:

providing a radio station having a radio communications interface, means for storing subscription data whereby said radio station is to register for

service with said communications network via said radio communications interface, and a local communications interface for communicating with one or more external devices,

allowing an external device to register with said radio station,

storing service data in a network entity indicating that said external

device is registered with said radio station, to allow said network entity to

provide service to said external device via said radio station.

The network entity may thus communicate, or control communications

with, the external device via the radio station.

According to a further aspect of the invention there is provided a

subscriber station comprising a radio interface for communicating with a mobile communications network, a local device interface for communicating with one or more local devices, and a portable storage module arranged to hold authentication data for authenticating said one or more local devices.

A portable storage module may thus be used to securely store the authentication data for a local device in the subscriber station.

According to a further aspect of the invention there is provided a subscriber station comprising a radio interface for communicating with a mobile communications network and a local device interface for communicating with one or more local devices, wherein said subscriber

station is adapted to intermediate between said mobile communications network and said one or more local devices in a process or processes whereby said one or more local devices are authenticated in said network.

Authentication of a local device may thus be performed in the mobile communications network.

According to a further aspect of the invention there is provided a

mobile communications network adapted to transmit authentication data to a

subscriber station communicating with said mobile communications network

via a radio interface, said authentication data being for one or more devices

local to a subscriber station, whereby said subscriber station is made capable

of authenticating said one or more devices.

Authentication data for a local device may thus be transmitted over-

the-air to the subscriber station. According to a further aspect of the invention there is provided a mobile communications network adapted to communicate with a subscriber station which is authenticated with the network, and to conduct authentication of one or more devices local to said subscriber station, by transmission of control messages over a radio interface between said network and said subscriber station.

According to a further aspect of the invention there is provided a fixed station for use in a cellular communications system including a cellular communications network and a plurality of mobile stations, said fixed station comprising:

memory means for storing subscription data; radio communications means whereby the fixed station is capable of

registering for radio communications service from the cellular communications network;

local communications means for forming communications links with a plurality of home appliances; and

interworking means operating between the radio communications

means and the local communications means for detecting incoming

communications from the cellular communications network via said radio

communications means, and in response thereto selectively communicating with one of said plurality of home appliances via said local communications means.

Control of and/or reading of data from individual home appliances may thus be performed via the fixed station and the cellular communications

system.

According to a further aspect of the invention there is provided a home base station including means for registering and receiving radio communications service in a mobile communications system.

A fixed line link is thus not required for the receipt of service via the home base station, whilst if the home base station is correctly positioned, the

home base station can provide service not otherwise available to a mobile station capable of operating in the mobile communications system.

Further features and advantages of the present invention will become apparent with reference to the following description of preferred embodiments

of the invention, made with reference to the accompanying drawings:

Figure 1 is a schematic illustration of a cellular radio network arrangement in accordance with an embodiment of the present invention;

Figure 2 is a schematic illustration of a standard mobile station used in

the cellular radio network illustrated in Figure 1 ;

Figure 3 shows a schematic illustration of radio transceiving

apparatus, used in the cellular radio network of Figure 1 ;

Figure 4 shows a mobile station/cordless station used in the cellular radio network illustrated in Figure 1 ; and Figure 5 shows a home appliance/cordless station used in the cellular radio network illustrated in Figure 1.

A cellular radio network, also referred to as a public land mobile network (PLMN), in accordance with an embodiment of the present invention, is schematically illustrated in Figure 1.

In this embodiment the PLMN is a GSM network. A mobile switching

centre (MSC) 2 is connected via communication links to a base station controller (BSC) 4. The BSC 4 is one of a number of BSCs dispersed geographically across areas served by the mobile switching centre 2. The

BSC 4 controls a plurality of public radio transceiving stations 6, referred to as base transceiver stations (BTSs), located remote from, and connected by further communication links to, the BSC 4. The BTS 6 transmits radio signals

to, and receives radio signals from, cellular mobile stations 8 which are in an area served by that BTS. That area is referred to as a "cell". A PLMN is

provided with a large number of such cells, which are ideally contiguous to provide continuous coverage over the whole network territory. The radio

signals are transmitted via a standard radio interface 9, having a cellular

protocol, which is standardised both at the physical layer level and the logical layer level.

The mobile switching centre 2 is also connected via communications

links to other mobile switching centres in the remainder of the PLMN, and to

other networks such as a public service telephone network (PSTN) 10, which provides service to fixed line terminals, such as a fixed telephone (FT) 11. The mobile switching centre 2 is connected via a signalling link to a home location register (HLR) 12 which is a database permanently storing subscriber data for subscriptions with the PLMN, including, for each subscription, the international mobile subscriber identity (IMSI), which is

unique to each mobile station in the GSM system and service data associated with the subscription. The HLR 12 is connected via a signalling link to an authentication centre (AuC) 13, which securely stores an authentication key

(Ki) against each IMSI, and provides authentication functions to the PLMN.

The IMSI and the Ki for a subscription are also securely stored along with other subscription specific information in the mobile station in a subscriber identity module (SIM) (to be described below), also referred to as a smart card. The SIM is removable such that the stored data is portable between mobile stations.

The mobile switching centre is connected to, or combined with, a visitor location register (VLR), not shown, which is a database temporarily

storing subscriber data for mobile stations registered for service in its area.

In addition, the MSC 2 and each BSC 4 are connected via signalling

links to a cordless telephone service node (CSN) 14, to be described in further

detail below.

Referring now to Figure 2, a standard, known cellular mobile station 8

used in the PLMN comprises a transmit/receive aerial 16, a radio frequency

transceiver 18, a voice coder/decoder (codec) 20 connected to a loudspeaker

22 and a microphone 24, a digital processor 26 and its associated memory 28 (which includes ROM storing the operating system of the mobile station), a display 30 and a manual input port (e.g. a keypad) 32. The mobile station is

connected to a removable SIM 34 via electrical contacts 35.

The SIM 34 connected to the mobile station is a standard component of the PLMN system, and may be inserted in any similarly standardised mobile station. The SIM 34 includes a digital processor 36 and SIM memory 38, which includes for example mask-programmed ROM containing the SEM operating system, read/write EEPROM for the non-volatile storage of

subscriber data and RAM for use by the SEM processor 36 during operations. The SEM is issued to a subscriber on taking out a subscription with the

PLMN. The SIM 34 is used for authentication functions and the storage and retrieval of data items by the processor 26 of the mobile station 8. The

command set, data file structure and data coding format for data communicated via the interface between the mobile station processor 26 and the SEM processor 36 are all standardised (see for example GSM technical

specification 11.11).

As far as authentication is concerned, the SEM 34 stores an encryption

algorithm (A3), and the subscriber's authentication key (Ki), which it applies

to a random challenge issued by the PLMN and passed to it by the mobile

station 8, in order to generate a response. The response should be verifiably

related to that computed in the AuC 13 of the PLMN, in order for

authentication to be successful. Once authentication is complete, the mobile

station 8 is granted service in the PLMN and is issued with a temporary identity (TIMSI) whereby the mobile station 8 is identified (for example in paging messages broadcast in the PLMN) during the subsequent access session.

Referring now to Figure 3, a home base station, referred to herein as a

fixed part (FP) 40 forms part of the mobile communications system in this embodiment of the invention. The FP 40 is capable of communicating via a standard PLMN radio interface 9 with a BTS 6 of the PLMN. The FP 40 is also capable of communicating via a cordless radio interface 41 with a mobile station/cordless station (MS/CS) 42 and a home appliance/cordless station (HA CS) 43, to be described in further detail below.

The FP 40 comprises a cellular radio transmit/receive aerial 44, a cellular radio frequency transceiver 46, a digital processor 48 and its

associated memory 50 (which includes ROM storing the operating system of the FP 40), whereby the FP 40 interfaces with the PLMN. The FP

communicates with the BTSs 6 of the PLMN directly using the standard radio

interface 9 of the PLMN. The FP 40 also includes a cordless radio transmit/receive aerial 62 and a cordless radio frequency transceiver 60 which

is controlled by the digital processor 48 of the FP 40. These components

provide a two-way radio link via the cordless radio interface 41. The cordless

radio interface may be a modified version of the GSM radio interface, such as

that described in Draft GSM 03.52 as referred to above.

As the FP 40 is designed to be fixedly sited, the FP 40 includes an in¬

built transformer whereby the FP 40 may be powered directly from an electrical mains supply, and no battery power pack is required. The FP 40 includes a power lead (not shown) which includes a plug adapted to be connected to a socket of the electrical mains supply, whereby the FP 40 has a permanent source of power when fixedly sited for operational use. In order to

provide functionality for subscribers having no PLMN coverage, even at rooftop level, the FP 40 may also include a fixed line interface (not shown) for performing voice and/or data communications via a fixed line network (e.g. a PSTN), for example a digital subscriber line (DSL) interface to provide high speed data communications via the fixed line network. The FP 40 may also include a satellite transceiver (not shown), whereby higher data rates are made available for services such as (near) video on demand, video streaming, large

file transfers, etc. In such a case, the satellite link may be used as a high speed data downlink whilst the radio interface 9 is used as a data uplink for carrying control messages, thereby enabling interactive video and multimedia services.

The FP 40 is also connected to a removable SIM 52 via electrical contacts 54. The SIM 52 provides all SEM-related functions required in order

for the FP to receive radio communications service, in a similar manner as a

mobile station 8, within the PLMN via the standard radio interface 9 of the

PLMN. The SIM 52 may be a standard SIM as used in a standard mobile

station 8. The SIM 52 includes a digital processor 56 and SIM memory 58,

which includes for example mask-programmed ROM containing the SIM

operating system, read/write EEPROM for the non-volatile storage of

subscriber data and RAM for use by the SIM processor 56 during operations. The SIM 52 is used for authentication functions and the storage and retrieval of data items by the processor 48 of the FP 40. The SEVI is issued when an FP subscription is taken out by a subscriber, and subscription data corresponding to that stored in the SIM 52 is stored in the HLR 12 and AuC 13 of the PLMN.

As far as authentication is concerned, the SEM 52 stores an encryption algorithm (A3), and an authentication key (Ki) of the FP 40, which it applies to a random challenge issued by the PLMN and passed to it by the FP 40, in order to generate a response. The response should be verifiably related to that computed in the AuC 13 of the PLMN, in order for authentication of the FP to

be successful. Once authentication is complete, the FP 40 is granted service in the PLMN and is issued with a temporary identity (TEMSE) whereby the FP 40 is identified (for example in paging messages broadcast in the PLMN) over

the PLMN radio interface 9 during the subsequent access session. The mobile station 8 also has a session key resulting from the authentication procedure,

whereby to encrypt and decrypt radio communications with the PLMN.

During both the authentication phase and the subsequent access session, the

FP 40 communicates with a BTS of the PLMN using the standard radio

interface 9 of the PLMN.

The digital processor 48 of the FP 40 provides digital processing and

control functions supporting the individual setting up, and functioning, of

radio links via the radio frequency transceivers 46 and 60. For the cellular

radio interface 9, these processing and control functions are similar to that used in a standard mobile station 8. For the cordless radio interface 41, those processing and control functions are similar to that used in a base station of the PLMN. In addition, the digital processor 48 provides an interworking function between the radio interfaces 9 and 41 , which will be described in

further detail below. The interworking function processes control messages received over either one of the radio interfaces 9, 41 and reacts by transmitting control messages over the other of the radio interfaces 41, 9. In addition, the interworking function relays traffic data, such as voice traffic data or data traffic data, received over one of the radio interfaces 9, 41 , to the other of the radio interfaces 41, 9.

The MS/CS 42, as illustrated in Figure 4, preferably includes all of the components of a standard mobile station 8. For conciseness, it is to be understood that in this embodiment the MS/CS 42 includes all of the components described in relation to the mobile station 8, and that in Figure 4

those components are referenced with the same reference numerals as those

used in Figure 2, although incremented by 100. In addition, the MS/CS 42 includes functionality, programmed in the software used by the digital

processor 126 and stored in memory 128, which allows the MS/CS 42 to

communicate via the cordless radio interface 41 directly with the FP 40.

The HA/CS 43, as illustrated in Figure 5, preferably includes all of the

components and functionality of the MS/CS 42 as described above, except for

the man machine interface components (the speaker 122, the display 130, the keypad 132 and the microphone 124), and the voice codec 120. For conciseness, it is to be understood that the components of the HA/CS 43 illustrated in Figure 5 which are the same as those of the MS/CS 42 of Figure 4 are referenced with the same reference numerals as those used in Figure 4, although incremented by 100. The HA/CS may have only the capability to transmit and/or receive data (i.e. not voice) traffic data to and/or from the

PLMN via the FP 40 over a cordless radio interface 41 which is preferably substantially identical with the cordless radio interface 41 between the MS/CS

42 and the FP 40. The capability to communicate directly with the PLMN via a cellular radio interface is not provided for the HA/CS 43, since the device is intended to be permanently located in the vicinity of the home of the subscriber, thereby allowing all communications to occur via the FP 40.

The HA/CS 43 shown is a module to be connected to a home appliance by means of a data input/output port 240. Alternatively, the HA/CS

43 may be built into a home appliance. Examples of appliances which may be connected to, or include, a HA/CS 43 include a lighting control module, a

video tape recorder, a heating and/or air conditioning control module, a

refrigerator, an electricity or gas meter, a personal computer, etc. The HA CS

43 may also take the form of a cordless telephone, in which case it is provided

with all of the man machine interface components illustrated in Figure 4 and a

voice codec and the capability to transmit and receive voice data.

The HA/CS 43 provides the capability to control the appliance

remotely and/or receive data remotely from the appliance, via the PLMN, by

means of the FP 40. The FP 40 may act as a hub for communications with a plurality of HA/CSs 43, which may each individually send data messages to a receiving unit (such as a mobile station) serviced by the PLMN via the FP 40 and/or individually receive data messages from a transmitting unit (such as a mobile station) serviced by the PLMN. A selective forwarding function, to be

described below, may be used for the forwarding of data to an individual

HA/CS 43 by the FP 40.

In the following description, reference is made to a "CS", which reference is intended to apply to both an MS/CS 42 and a HA/CS 43. Where reference is to be made to one of these types of station specifically, such specific reference will be made.

Initialisation of FP

The FP is designed to be installed in a fixed location. In order to set up the FP 40 for use, the FP is placed, or securely mounted, in a fixed location

which is within coverage of the PLMN. The location of the FP 40 is selected to provide in-building coverage to the CS. If the FP is placed within a

subscriber's home, the FP may for example be placed on an upper floor,

within the roof space, or an external wall or on the roof of the house, such that

the FP is operable even where PLMN coverage is not available in other

locations of the house. The FP 40 is then connected directly to the mains power supply.

When the FP 40 is switched on, with its SEM 52 inserted, the FP

monitors the broadcast control channels (BCCHs) of a number of the PLMN's

BTSs within its range, and selects the strongest signal. The FP 40 then establishes radio contact with the selected BTS, and requests authentication. The BTS 6 then transmits an authentication request towards the AuC 13. The IMSI of the FP 40 is included in the authentication request. The EMSI is that stored in the S M 52 of the FP 40, which is the IMSI of the separate subscription held by the FP 40 in the PLMN. In response, the AuC 13

forwards a challenge message to the BTS 6, which transmits the challenge message over the PLMN radio interface 9 to the FP. The challenge message is passed by the FP to the SEM 52, which conducts the encryption function using the stored authentication key Ki, and transmits an authentication response to the BTS 6. Once the authentication response is validated in the PLMN, the

FP 40 is granted service in the PLMN, and the subscription details necessary to control service of the FP 40 in the PLMN are downloaded from the HLR to

the VLR of the serving MSC 2. From this point, the FP 40 receives service from the BTS 6 similarly to the manner in which a conventional mobile station 8 receives such service, in an encrypted communications session.

Once authentication of the FP 40 is complete, a message is transmitted

from the BTS 6 serving the FP 40 requesting a group frequency list (GFL) for

the FP 40 to the CSN 14. The CSN 14 holds a frequency re-use plan for the

entire PLMN, with details of all frequencies, all of which are within the

frequency band allotted to the PLMN, used by each BTS 6 in the network.

The CSN 14 also holds sets of group frequency lists (GFLs) specifically

allocated for use by FPs in their cordless radio links. These lists consist of a

sub-set of the frequencies within the allotted PLMN frequency band, and are selected to minimise interference caused by the cordless radio transmissions to the normal PLMN radio transmissions. On receipt of the GFL request, the CSN selects an appropriate GFL for the serving BTS 6, taking into account the frequencies used by the serving BTS 6 and adjacent BTSs, and transmits

same to the serving BTS. The serving BTS then transmits a control message to the FP 40, containing the selected GFL. On receipt of the message containing the selected GFL, the FP 40 monitors ambient signal strengths at the frequencies within the list, and selects one or more frequencies, whereby to communicate with CSs being served by the FP, from the GFL at which least interference is experienced.

The CSN 14 also provides the FP 40, by means of a control message transmitted over the cellular radio interface 9, with a unique FP identity to be

transmitted by the FP 40 on its own BCCH. Such transmission is intended to prevent CSs which are not affiliated to the FP 40 from attempting to register on the FP 40 for service. As an alternative to transmitting the unique FP

identity over-the-air, the unique FP identity may be preprogrammed in the

SIM 52 of the FP 40.

Affiliation of CS

The CS in its affiliation phase becomes associated with an FP 40 from

which it is intended to receive cordless radio service. In the case of an MS/CS

42, once the FP 40 is initialised, the CSN 14 may transmit a message, via the

cellular radio interface 9 to the MS/CS 42, containing the unique FP identity

of the FP 40 with which it is to be affiliated. The MS/CS 42 places the unique FP identity in a preferred FP list held in the SEM 134. The MS/CS 42 may use its PLMN authentication key (Ki) as the CS authentication. The CS authentication key (KCS), if this is different from the PLMN authentication key, is also transmitted in a control message and securely stored in the SIM

134 of the MS/CS 42. Such a message may be encrypted between the AuC 13 and the SIM 134, using an encryption key known only by the AuC and the SIM 134.

In the case of a HA CS 43, the unique FP identity and the CS

authentication key are preprogrammed on the SIM 234. Such provision may also be used in the case of an MS/CS 42 in an alternative to the over-the-air provision described above.

Following affiliation when a CS is switched on inside, or enters, the coverage area of the FP on the radio interface 41, the CS can detect the presence of the FP to which it is affiliated on the BCCH broadcast by the FP 40, and attempt to register with the FP 40.

Registration of CS with FP

With the modified GSM radio interface, as described in Draft GSM

03.52, the FP 40 uses discontinuous BCCH broadcast, to prevent standard

mobile stations attempting to register with the FP 40. However, each CS has

the capability of monitoring and decoding the discontinuous BCCH of the FP

40. On detection of the FP 40, a CS may automatically, or under manual

control by the subscriber, attempt to register with the FP 40 in preference to

obtaining service directly from the PLMN. In order to register with the FP 40, the CS transmits an authentication request, containing its IMSI, to the FP 40 on the cordless radio interface 41. Authentication of a CS may be carried out by the FP itself, or may be carried out in the PLMN, by the FP 40 acting as an intermediary for authentication challenges and responses carried in control

messages over both the radio interfaces 9, 41. In the case of the FP 40 conducting CS authentication itself, the FP 40 must be provided with the necessary CS authentication key or keys for the one or more CSs with which it is to be affiliated. One alternative for providing the FP 40 with the CS authentication key or keys is by transmitting the data in an over-the-air control

message from the network to allow the data to be stored in the SEM 52 of the

FP 40. Alternatively, the CS authentication key or keys may be preprogrammed on the SEM 52 of the FT¹ 40. In either case, the SIM 52 of the FP 40 securely stores the CS authentication key or keys in a secure data file

which cannot be accessed by querying the SEVI, except perhaps using a high level SIM unblocking PEN. An exemplary form of such a data file contains a

plurality of individual CS authentication key records (KCS1, KCS2, ...,

KCSn).

If the FP 40 is provided with the ability to authenticate a CS directly,

the FP 40 requests from its SEM 52 an authentication challenge message

containing a substantially random number generated in the SEVI 52. The

authentication challenge message is transmitted over the cordless radio

interface 41, and the CS responds in the same manner in which such an

authentication challenge received from the PLMN is responded to, using the stored encryption algorithm (A3) on a key, except using the CS authentication key if different to the PLMN authentication key. That is, the SEM of the CS generates a response, and the response is transmitted to the FP 40, and checked in the SIM 52 of the FP. The response is checked in the SEM 52 by

applying the stored encryption algorithm (A3), and the stored CS authentication key, to the authentication challenge, and comparing the result with the returned response. Once authentication is completed, the FP 40 transmits a registration confirmation to the CS, which is then able to receive service in the PLMN via the FP 40.

In the alternative that the FP 40 acts as an intermediary in the authentication of CS, on receipt of the authentication request over the cordless radio interface 41, the FP 40 transmits a corresponding authentication request, containing the IMSI of the CS, to the PLMN via the cellular radio interface 9. Such authentication request is passed to the CSN 14, which requests an

authentication challenge from the AuC 13. The AuC 13 returns the

authentication challenge to the CSN 14, which is then passed to the serving

BTS 6 for transmission over the cellular radio interface 9. On receipt of the

authentication challenge the FP 40 relays the challenge to the CS over the

cordless radio interface 41, and the SEM 134 of the CS computes a response,

which is transmitted over the cordless radio interface 41 to the FP 40. The FP

40 then relays the response to the PLMN over the cellular radio interface 9

and the PLMN checks the response against a result calculated by using the

appropriate encryption key (KCS) stored in the authentication centre AuC 13. If correct, the FP 40 receives a confirmation of authentication from the PLMN. On receipt of the confirmation of authentication from the PLMN, the FP 40 transmits a registration confirmation over the cordless radio interface 41 to the CS, which then camps on to the FP 40. Because the FP 40 is itself

already authenticated, and the control messages sent between the FP 40 and the PLMN for authentication of the CS are encrypted, such registration procedures are also known to be secure and reliable.

On registration of the CS with the FP 40, the FP 40 transmits a message to the PLMN over the PLMN radio interface 9 indicating that the CS is now to receive service via the FP 40. In response, the PLMN activates a

Follow-me service, to be controlled by the CSN 14, for the CS in question. The Follow-me service is an intelligent network (EN) service which allows

incoming calls for a particular directory number, such as that of a CS, to be forwarded automatically to a different directory number. In this case, when

the CS registers with the FP the Follow-me service is set up to forward all incoming calls addressed to the CS to the directory service number of the FP

40. When a CS deregisters from the FP 40, the Follow-me service is

deactivated. Deregistration from the FP 40 may be activated by the

subscriber, or caused by a CS being switched off or leaving the coverage area

of the FP 40. Deregistration from the FP 40 may be signalled by the FP 40

sending a deregistration message to the CSN 14. Reception of Incoming Calls via FT*

On receipt of an incoming call, for example from the FT 1 1, at the MSC 2 when the CS is currently registered with the FP 40, an intelligent network trigger for the Follow-me service causes the MSC 2 to hand control of the call to the CSN 14. The CSN 14 responds by signalling to the MSC 2 that the call is to be forwarded to the FP 40. Accordingly, the call is forwarded to the FP 40, which causes a paging message to be transmitted by

the serving BTS 6 to the FP 40 on the PLMN radio interface 9. In response, the FP 40 transmits a similar paging message on the cordless radio interface 41, to which the CS may respond with an acknowledgement message, which is relayed by the FP 40 to the PLMN. The call is then connected to the FP 40, and in its function as a two-way relay, the FP 40 passes all traffic data

between the CS and the PLMN for the remainder of the call. On completion of the call, the FP 40 intermediates between the PLMN and the CS to signal

the end of the call in both directions.

Making Outgoing Calls via FP

To make an outgoing call on the CS whilst the CS is registered with

the FP 40, the CS sets up a call over the cordless radio interface 41, and the

FP 40 correspondingly sets up a call over the PLMN radio interface 9.

Throughout the call, the FP acts in its function as a two-way relay to pass

traffic data between the CS and the PLMN. Short Messages

Data messages in the form of short messages (i.e. text messages) may be transmitted by, and received by a CS when it is registered with the FP 40.

For a mobile-originated short message, the CS transmits the short message signal to the FP 40 over the cordless radio interface 41 and the FP 40 transmits a corresponding short message signal to the PLMN over the PLMN

radio interface 9. To handle the case of mobile-terminating short messages, a short message service centre (SMSC) of the PLMN, not illustrated in Figure 1, is informed by the CSN 14 of the FP 40 identity for forwarding of incoming

messages when a CS registers with the FP 40. The SMSC stores service data indicating that incoming short messages should be sent via the FP 40. Incoming short messages which are addressed to the CS when registered with the FP 40 are redirected by the SMSC to the FT* 40, which retransmits the

short message to the CS over the cordless radio interface 41. The SMSC is also informed by the CSN when the CS deregisters from the FT* 40.

Another example of a service which may be provided via the FP 40 is

the GSM/UMTS General Packet Radio Service (GPRS), whereby packet data

messages may be transmitted to and from the MS/CS in an "always on" mode.

To handle the case of mobile-terminating GPRS data, a GPRS service node

such as a gateway node (GGSN) of the GPRS network, not illustrated in

Figure 1, is informed by the CSN 14 of the FP identity for forwarding of

incoming data packets thereto by an address mapping function when a CS registers with the FP 40. In this case the FP 40 appropriately relays GPRS data packets between the network and the CS in both directions. The GPRS service node is also informed by the CSN when the CS deregisters from the FP 40.

Selective Forwarding

More than one CS may be able to register with a single FP 40. In this case, it is desirable to allow the appropriate one of the CSs registered with the FP 40 to selectively receive an incoming call or other service which is received by the FP 40. The FP 40 may have only a single subscription with

the PLMN. In such case, distinction between the multiple CSs registered with the FP 40 is not possible by distinguishing between subscriptions over the cellular radio interface 9.

The FP 40 may be informed of the identity of the CS in question for

which an incoming call is received by means of a suffix or a prefix in the form of a selected one of a plurality of identity codes of equal length which are consistently added to the calling line identifier (CLI) by the CSN 14 on

processing a Follow-me call forwarded to the FP 40, to indicate the identity of

the CS for which the incoming call is being processed. Accordingly, the FP

40 may, on receipt of the call-related signalling, which contains the CLI,

selectively page the correct CS. A similar functionality may be employed in

order to selectively transmit a short message to one of the CSs registered with

the FP 40. In this case, the SMSC may consistently add a suffix or prefix,

containing the appropriate identity code, to the originating address for all short

messages transmitted via the FP 40. Accordingly, by the FP 40 reading the prefix or suffix which identifies the corresponding CS, the FP 40 is able to forward the short message onto the correct CS.

In the alternative, a multiple subscriber profile (MSP) function may be used in communications with the FP in order to distinguish between different CSs which are registered with the FP 40. With multiple subscriber profiles, each subscription may be allotted a number of different "subscriber profiles",

whereby a plurality of identities may be associated in a single subscription with each bearer service, such as voice telephony and short message service. The different subscriber profiles are identified by the use of different identity codes used in the signalling for each bearer service. Different identities may thus be signalled to the FP 40 by use of different subscriber profiles to

indicate different CSs for which the incoming service request is being processed.

Locating Subscriber at Home

By allowing a subscriber to receive service via the FP 40 rather than via a direct radio link with the PLMN, the location of the subscriber within

their "home" site, which is defined by the service area of the FP 40, can be

readily detected by the mobile communications system. The information as to

whether the subscriber is present within that area is available, from the CSN.

Using such information, different services, quality of service and/or charging

tariffs, compared to that provided in the case of a direct radio link with the

mobile communications link, may be provided when the mobile station

receives service via the FP 40. Location-based services, such as home messaging of information specific to the home area, and home appliance control functions via a HA/CS 43, may be automatically provided when the subscriber is detected to be at home from data in the CSN 14. Other Embodiments

In the above-described embodiments, the cordless radio interface 41 is such that the same range of services offered to a mobile station over the cellular radio interface may be obtained by a CS when registered for service with the FT* 40 via the cordless radio interface 41. However, the cordless radio interface 41 may be provided with limited functionality compared to that

provided directly by the PLMN. The FP 40 may have an alerting function, to alert the subscriber using an MS/CS 42 registered with the FP 40 that a

service unavailable via the FP 40 is currently waiting for the MS/CS 42, to indicate that the MS/CS should be registered with the PLMN directly. The waiting alert may be provided via the short message service, the SMSC being

used to transmit an informational short message addressed directly to the FP

40, which alerts the subscriber, for example with an audible tone and a displayed message, to the waiting service.

In the above-described embodiment, the cellular radio interface 9 and

the cordless radio interface 41 are provided for in the FP 40 by means of

separate radio frequency transceivers 46, 60 and separate aerials 44, 62.

However, a single, combined, radio frequency transceiver and aerial set may

be used where the protocols and frequencies used in both radio interfaces are similar. The FP 40 may then be realised by the suitable reprogramming of conventional mobile station equipment.

In the above-described embodiment, control of a HA/CS 43 is by means of the CSN forwarding calls or redirecting data messages, which are originally directed to the HA/CS, to the FP 40 for relaying to the appropriate

HA/CS. Alternatively, the CSN may conduct a control dialogue with a user device (such as a mobile station 8) directly, and subsequently generate a data message to be sent to the appropriate HA/CS or HA CS s via the FP 40.

Although the cordless radio interface 41 in the embodiments described

is a modified version of the cellular radio interface 9, the cordless radio interface 41 may be realised using different protocols. The cordless radio interface 41 may alternatively be a short-range radio interface, such as a standard "Bluetooth" (TM) radio interface, operating at entirely different

frequencies than the PLMN (2.4 GHz compared to for example a GSM radio frequency of 900-1900 MHz). A radio interface according to other standards,

such as the Home RF standard, the Wireless LAN (EEEE 802.11) standard and

the HiperLAN (ETSI) standard, may also be used between the FP and CSs. In

all such cases, the relevant standard's authentication procedures may be used

in place of the authentication procedures described above between the FP and

CS. The appropriate authentication key or keys may then be securely stored,

in the case of the FP and the MS/CS, on its SIM, and in the case of the HA/CS

in a smart card like a SIM, but which does not necessarily store PLMN

subscription data. In fact, the link between the FP 40 and one or more of the CSs need not be a radio interface. A CS may be connected to the FP 40 via a fixed-line link, in the case of the MS/CS 42 by use of a docking port when the subscriber is in the area of the FP 42.

Although in the above-described embodiments the subscriber equipment includes both an MS/CS and a HA/CS, only one of these types of

subscriber equipment may be provided for.

Standard GSM voice and/or data channels may be used in the radio interfaces; alternatively other GSM channel types, such as GPRS, HSCSD, and EDGE, may be used in one or more of the radio interfaces. Although the

mobile communications system in the above-described embodiments is a GSM PLMN, the invention is applicable to other mobile communications systems, such as third generation cellular radio systems (e.g. wideband

CDMA, IMT 2000, UMTS) and satellite mobile communications systems, in which subscription-based services are provided.

Claims

CLAIMS:

1. A subscriber equipment set for use in a mobile communications system including a mobile communications network and a plurality of mobile stations, said network having a plurality of radio transceiving stations whereby said mobile stations receive radio

communications service from said network, said set including a first station and a second station,

wherein the first station comprises a first radio transceiver, memory means for storing first subscription data and means for registering with the

with the mobile communications network, to receive radio communications

service from a radio transceiving station therein, by use of the second subscription data, and

wherein the first station is connectable to the second station to receive

service in the mobile communications system via the second station.

2. A subscriber equipment set according to claim 1, wherein the

second station is designed to be installed in a fixed location.

3. A subscriber equipment set according to claim 1, wherein said second station includes means for selectively communicating with one of a plurality of stations receiving service in said mobile communications system via said second station.

4. A subscriber equipment set according to any preceding claim, wherein the second station is adapted to store authentication data for the first station, and the first station is adapted to authenticate with the second station.

5. A subscriber equipment set according to claim 4, wherein said

authentication data is stored in a portable storage module in said second station.

6. A subscriber equipment set according to any of claims 1 to 3, wherein said second station is adapted to intermediate in a process whereby

said second station is authenticated by the mobile communications network.

7. A subscriber equipment set according to any preceding claim,

wherein the second station is adapted to send a control message to the network

via the second radio transceiver in response to the connection of the first

station thereto.

8. A subscriber equipment set according to any preceding claim, wherein the first station is connectable to the second station via a radio link.

9. A subscriber equipment set according to claim 8, wherein said radio link operates within a frequency range allocated to said network for use by said first and/or second radio transceiver.

10. A subscriber equipment set according to claim 8 or 9, wherein said second station is adapted to receive a control message from said network and to select a frequency or frequencies for said radio link in response to receipt of said control message.

11. A subscriber equipment set according to any of claims 1 to 7, wherein the first station is connectable to the second station via a fixed line

link.

12. A subscriber equipment set according to any preceding claim,

comprising a plurality of said first stations, the second station allowing all said

plurality of first stations to register therewith simultaneously to receive service

in the mobile communications system via the second station.

13. A subscriber equipment station according to any preceding

claim, wherein the first station is a mobile telephone.

14. A method of controlling services in a mobile communications system including a mobile communications network having a plurality of network entities providing services to a plurality of radio stations which include mobile stations, said method comprising:

providing a radio station having a radio communications interface, means for storing subscription data whereby said radio station is to register for service with said communications network via said radio communications

interface, and a local communications interface for communicating with one or more external devices,

allowing an external device to register with said radio station, storing service data in a network entity indicating that said external

device is registered with said radio station, to allow said network entity to provide service to said external device via said radio station.

15. A method according to claim 14, wherein said service data controls a call forwarding service for said external device.

16. A method according to claim 14, wherein said service data

controls a data transmission service for said external device.

17. A method according to claim 16, wherein said network entity is

a short message service (SMS) control node.

18. A method according to claim 16, wherein said network entity is a general packet radio service (GPRS) control node.

19. A method according to any of claims 14 to 18, wherein said service data is stored in response to a control message received from said radio station indicating said external device registering with said radio station.

20. A method according to any of claims 14 to 19, comprising storing service data in a plurality of network entities to allow said plurality of network entities to provide a plurality of different services to said external device.

21. A method according to any of claims 14 to 20, comprising allowing a plurality of external devices to register with said radio station and

storing service data in a network entity when said external devices are registered with said radio station, to allow said network entity to provide

service to said external devices via said radio station.

22. A subscriber station comprising a radio interface for

communicating with a mobile communications network, a local device

interface for communicating with one or more local devices, and a portable storage module arranged to hold authentication data for authenticating said one or more local devices.

23. A subscriber station according to claim 22, wherein said portable storage module is arranged to hold subscription data whereby said subscriber station is capable of registering with said mobile communications network.

24. A subscriber station according to claim 23, wherein said portable storage module is a subscriber identity module.

25. A subscriber station comprising a radio interface for communicating with a mobile communications network and a local device interface for communicating with one or more local devices, wherein said

subscriber station is adapted to intermediate between said mobile communications network and said one or more local devices in a process or

processes whereby said one or more local devices are authenticated in said

network.

26. A mobile communications network adapted to transmit

authentication data to a subscriber station communicating with said mobile

communications network via a radio interface, said authentication data being for one or more devices local to the subscriber station, whereby the subscriber station is made capable of authenticating said one or more devices.

27. A mobile communications network adapted to communicate with a subscriber station which is authenticated with the network, and to conduct authentication of one or more devices local to said subscriber station, by transmission of control messages over a radio interface between said

network and said authenticated subscriber station.

28. A fixed station for use in a cellular communications system including a cellular communications network and a plurality of mobile stations, said fixed station comprising: memory means for storing subscription data;

radio communications means whereby the fixed station is capable of

registering for radio communications service from the cellular

communications network; local communications means for forming communications links with a

plurality of home appliances; and

interworking means operating between the radio communications

means and the local communications means for detecting incoming

communications from the cellular communications network via said radio

29. A fixed station according to claim 28, wherein said one home appliance is selected in accordance with an identity code received in said incoming communications.

30. A fixed station according to claim 28 or 29, comprising a power input for receiving power directly from a mains power source.

31. A home base station including means for registering and receiving radio communications service in a mobile communications system.