CA2197642A1 - Communication system and call establishment methods - Google Patents
Communication system and call establishment methodsInfo
- Publication number
- CA2197642A1 CA2197642A1 CA002197642A CA2197642A CA2197642A1 CA 2197642 A1 CA2197642 A1 CA 2197642A1 CA 002197642 A CA002197642 A CA 002197642A CA 2197642 A CA2197642 A CA 2197642A CA 2197642 A1 CA2197642 A1 CA 2197642A1
- Authority
- CA
- Canada
- Prior art keywords
- pabx
- base station
- subscriber
- station controller
- communication network
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/10—Small scale networks; Flat hierarchical networks
- H04W84/16—WPBX [Wireless Private Branch Exchange]
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
- Telephonic Communication Services (AREA)
- Telephone Function (AREA)
Abstract
The invention relates to a communication system and call establishment methods. A communication system comprising a cellular mobile communication network, which includes a mobile services switching center (MSC), a base station controller (XBSC) and base stations (BTS), as well as a private branch exchange system (PABX) having at least one base station (PABX_BTS). In the invention, the base station controller of the mobile communication network is provided with an interface to which the extension side of the PABX is coupled.
The interface between the base station controller and the PABX is a standard PABX signalling interface towards the extensions. The trunk line side of the PABX is connected e.g. to a PSTN local exchange. The base station (PABX_BTS) under control of the base station controller is placed in that space or building which is the desired location for an office cell of the wireless PABX. Between the base station controller and the base stations there exists a standard signalling interface of the mobile communication network, and the base station of the office cell (10) has a standard interface of the mobile communication network. This concept makes it possible to provide a radio interface of the mobile communication system for a standard PABX of the fixed network.
The interface between the base station controller and the PABX is a standard PABX signalling interface towards the extensions. The trunk line side of the PABX is connected e.g. to a PSTN local exchange. The base station (PABX_BTS) under control of the base station controller is placed in that space or building which is the desired location for an office cell of the wireless PABX. Between the base station controller and the base stations there exists a standard signalling interface of the mobile communication network, and the base station of the office cell (10) has a standard interface of the mobile communication network. This concept makes it possible to provide a radio interface of the mobile communication system for a standard PABX of the fixed network.
Description
2~ ~76~2 097/~s88 ~ rl,.
Communication system and call establishment methods Field of the Invention The present invention relates to a communication system comprising a cellular mobile communication network, which includes a mobile services switching center, a base station controller and base stations, as well as a private branch exchange (PB~) system having at least one base station.
sackground of the Invention The conventional access technique to a fixed telephone network is a subscriber line (2-wire line) extending from a local exchange all the way to a subscriber's telephone. Presently, however, wireless access techniques are the fastest growing area within data communication. As a result, an ever increasing portion of new subscriber connections to the communication network will be wireless. The first generation of wireless subscriber connections consisted of analogue cordless phones (the CT1 system, for example), which consisted of a base station connected to a wired subscriber line of a public switched telephone network (PSTN), and a hand-held handset. The succeeding generation consisted of a digital cordless phone, known as the CT2 system. In addition to the conventional cordless phone, the CT2. system offered a telepoint service and a wireless Private Automatic sranch exchange (P~B~). Furthermore, a standard is being developed for a European digital wireless telephone system, knowr. by the abbreviation DECT. To a large extent, DECT is similar to the CT2, but utilizes TDMA technique.
Additionally, cordless systems based on radio interfaces of mobile commur.ication systems, such as the NMT system, have been realized wherein a subscriber's mobility related features are limited or completely non-existent.
One form of wireless communication is represented ~ ~ 97~4~
W097l00~88 l~llrl._ 4 by mobile communication systems which do not provide the subscribers with a fixed access point in the network at all. Instead, the subscribers may communicate with the network via an~ of the base stations of the network. In order to route mobile termln~ing calls to a correct point at any one time, the network r~;nt~;nq, at the subscriber database, the location information of the subscriber. As a mobile terminating call is received by the networ~., the first MSC in the network carries out an enquiry to the subscriber database, and is provided with the routing addre~s in the network.
An interesting area within wireless communication is represented by wireless PABXs. PABXs (or PBXs) are, as known, a type of office-specific private telephone exchanges that have a plurality of extensions and a smaller number of trunk lines to the locaI exchange. At the PABX, in~r~ncive ~free) internal calls can be set up from an extension to another, and external calls can be set up between an extension and a PSTN trunk line. A
2C wireless PABX is typically, as tO its basic structure, a conventional "wired" PAsx, but the cabling within the building is partly or entirely replaced with radio connections. The radio standards potentially applicable to PAs~ applications are represent for example by the aforementioned CT2 and D~CT, or solutions evolving from the Pan-European digital mobile communication system GSM.
The advantages of wireless PABXs are claimed to include:
- Mobilit~ of terminal e~uipments. The user no longer needs to be at a specific place in the building.
- Location of the personnel. It will be easier to contact people who are outside their offLce buildings.
- Reduced investments in cabling inside the building.
- No costs regarding re-arrangins or maintaining the cabling at the extension end of the PARX.
W097/00588 .~I/r~ '~ 4 As noted in the above, a wireless PABX is typically implemented by using the CT2 or ~ECT radio interface at the extension end of the exchange. The trunk line of the PABX is in the conventional way connected to a PSTN local exchange. Consequently, the freer mobility provided by a wireless PABX is iimited to the area covered by the base stations of the PA3X itself, i.e. the office environment Using phones outside the office is confined to telepoint services.
In order to extend the mobility of wireless subscriber stations several solutions have been proposed in which the wireless PABX is integrated as a part of a mobile commur.ication system. In such a case, the trunk line end of the wireless PABX is connected to the BSC or the MSC in the place of a conventional base station. The extension end of the PABX is implemented with CT2, DECT or similar radio interfaces similarly as in wireless P~3Xs connected to the PSTN network. As far as location management is concerned, wireless subscribers are managed like ordinary mobile subscribers in the mobile communication network. In principal, this enables a wireless subscriber to move from a wireless P~3X to another if both PABXs are connected to the mobile communication network. In addition, prior art phones may be dual-mode devices so that they can operate both via the base stations of the wireless PABX and via the base stations of the mobile communication network.
Consequently, one subscriber equipment provides mobility within the entire mobile communication network and inexpensive PABX internal calls in the office. These solutions, however, utilize procedures of the mobile ~ communication network for establishing externals calls, making them more expensive. In addition, special solutions are typically required ir, the signalling between the elements of the mobile communication network and the WC)97~0~X8 r~llr~
signalling used in the radio interface of the PAsx.
Furthermore, dual-mode subscriber equipments are requ1red in order to be able to utilize all the features o~ the mobile communication network, increasing the costs of the subscriber equipments.
Disclosure Or the Invention An object of the present invention is a communication system in which a wireless pri~ate exchange can be implemented in association with a mobile 1~ communication network in a way that requires less changes than before in the PAsX or the mobile communication network.
It is also an object of the invention to pro~iide inexpensive internal and external calls at a wireless PAsX
connected to a mobile communication network.
Yet another object of the invention is a communication system having similar radio interfaces and similar subscriber e~i c at the mobile communication network and the wireless PAsX.
2~ These objects are achie~ed by means of a communication system comprising a cellular mobile communication network, which includes a mobi~e services switching center, a base station controller and base stations, as well as a private exchange system having at least one base station. According to the invention the system is characterized in that the subscriber side of the PABX system is connected to the BS~ and the trunk side is connected to another communication networki the PAsX base station is connected to the base station controller; t h e base station controller is arranged to route subscriber calls originating from the PAsX base station to the PABX
system, and calls coming in via the PA~X system to the P~3X base station.
The invention also relates to a method for establishing an outgoing call in a communication system Zl i~7~2 O971OOsa8 I.l/rl:.t 5~
comprising a cellular mobile communication network which contains a mobile services switching center, a base station controller and base stations, as well as a private branch (PABX) system having at least one base station, the method comprising the steps of transmitting a connection request from the subscriber to the base station controller via the PABX base station; activating call set-up.
According to the invention, the method is characterized by checking at the base station controller whether the transmitting party of the connection request is a PABX
subscriber or a standard subscriber of the mobile communication network; routing the call of the PABX
subscriber from the base station controller to the PABX
system, whose subscriber side is connected to the base lS station controller and the trunk side to another communication network; connecting the call to the mobile services switching center if the subscriber is not a PA~X
subscriber.
The invention also relates to a method for establishing a terminating call in a wireless communication system comprising a cellular mobile communication network which contains a mobile services switching center, a base station controller and base stations, as well as a private branch (PABXI system having at least one base station, in which method a call terminating to PABX subscriber is received in the PABX
system. According to the invention, the method is characterized by the steps of initiating, from the private branch exchange system, call establishment at the base station controller to which the subscriber side of the PABX system and said PA3X base station are coupled;
transmitting from the base station controller a paging message to said PABX subscriber via the PAF3X base station;
receiving an acknowledgement message from the PABX
subscriber; establishing a connection according to the W097~ 8 P~l/r~ Y ~ ~
mobile communication network between the base station controller and the PABX subscriber; and connecting a speech connection between the PABX subscriber and said PABX system via the base station controller and the P~X
base station.
According to the invention, the BSC of the mobile communication network is provided with an interface to which the extension side of the PABX is connected. The trunk line side of the P~BX is connected to a local lo exchange of tne PSTN network. One or more of the base stations under control of the BSC is placed in that space or building which is the desired location for an offlce cell of the wireless PABX. In this application, such a base station will be referred to as a PABX base station.
Between the BSC and the PA}3X base station there is a normal signalling interface oE the mobile , i~ion network, and the PABX base station has a normal radio interface of the mobile communication network. The interface between the BSC and the PAsX is also a normal PAsx signalling interface towards the extensions. In a preferred em~odiment of the invention this interface includes t.he normal P~3X extensions, which are connected to the BSC.
This concept makes it possible to cbtain, for a PABX of a conventional fixed networkr a radio interface o~
the mobile communication system without changing normal signalllng interfaces. The only element for which the invention requires additional features is the ssc.
The capacity of the BSC is shared to serve both PABX base stations and standard base stations of a mobile communication network at the same time. Thus, the probably long transmissior. connections between the BSC and the MSC
are avoided when making local calls ir. the PABX, but the standard functions of the mobile communication network, .such as authenticatlon and ciphering, are still available.
wos7/00s88 PCT~9h~0354 No special features are required of the subscriber stations of a wireless PABX; they may be ordinary mobile stations of a mobile communication network. As such, they can also operate via normal base stations of the mobile communication network. The mobile stations can also be treated as normal subscriber stations of the mobile communication network outside their home PABX base stations.
In the preferred embodiment of the invention, a standard subscriber of a mobile communication network will be made a PA3X subscriber by also allocating to him a PABX
subscriber number. This subscriber number may be a PA~X
extension number or any other identifier that associates the mobile station with a specific PABX extension. This way, the mobile subscriber's mobile station can serve as a cordless phone within the office building and as a normal mobile station outside. The routing of terminating calls is done in two ways. When a calling subscriber dials a PABX subscriber number, the public switched telephone network PSTN routes the call to the wireless PABX, and connecting the cal' to the mobile station is handled via the radio interface between the PABX and the BSC. When the calling subscriber dials a PLMN number ~e.g. a MSISDN
number1, the PSTN routes the call directly to the PLMN
where the call is terminated with the normal call establishment procedure.
Mobile originating calls coming from a home PABX
base station are routed by the BSC to the PABX on the basis of the subscriber number, whereby the PABX internal calls can be switched directly without any MSC call control functions or connections via the MSC.
Consequently, internal calls, and PSTN calls, via a PABX
base station can be more economical than in prior art ~ solutions.
2 ' ~ 2 W097/00588 l~l/rl.~.l 5~ ~
Brief Description of the Drawing~
In the following, the invention will be descrihed in closer detail with reference to the accompanyi.ng drawings, in which Figure l shows a wireleas communicatior. system according to the invention, Figure 2 is a block diagram illustration of an extended base station controller, Figure 3 is a signalling chart illustrating setting up of a mobile terminating call, and Figure ~ is a signalling chart illustrating setting up of a mobile originating call.
In practice, the preser.t inventlon is applicable to almost any mobile communication system if a wireless P~3X
or PBX is to be connected to a PAsX system.
One example is the European digital cellular mobile communicat.ion system GSM ~Global System for Mobile Communications). The basic elements of the GSM system are described in the GSM R~ tions. For a closer description of the GSM system, the GSM recommendations and ~The ~SM System for Mohile ~ommunications", by M. Mouly &
M. Pautet, Palaiseau, Frarce, 1992, IS3N: 2-9~07190-0-7 is referred to.
The GSM and a modification thereof, DCSla00 (Digital Communication System1 operating at the 1800 Mhz frequency range, are the primary targets for the invention, but it is not intended that the invention be restricted to these radio systems.
Figure l very briefly describes the basic elements of the GSM system. A mobile services switching centre MSC
handles the connecting of incoming and outgoing calls. It performs functions similar to those of an exchange of a public switched telephone network (PSTN~. In addition to these, it also performs functions characteristic of mobile ~5 communications only, such as subscriber location ~ ~ ~7642 ~ W097~0s8~ r~l/r~
management. The mobile stations MS are connected to the center MSC by base statior. systems. The base station system consists of a base station controller BSC and base stations BTS. An A interface is determined for the BSC
towards to MSC, and an Abis interface towards the BTS.
These interfaces are specified in the GSM recc. -n~tions~
As subscriber registers, the system includes the home location register HLR and the visitor location register VLR. The ~LR permanently stores the subscriber information as well as information on which VLR area the MS is located in. The visitor location register VLR, in turn, temporarily stores the subscriber information of the subscribers visiting the VLR area. In addition, the VLR
stores the subscriber~s more detailed location information, i.e. the so-called location area identification.
Figure 1 also shows an office system implemented as a wireless PABX. The office system lO comprises a conventional fixed network PABX whose extension cabling has been replaced with a radio interface. Accordingly, the office system 10 comprises at least one base station PABX_BTS under control of the PABX, the PABX_BTS creating an internal cell for the office (e.g. a building).
Cordless handsets can freely move within this cell and utilize the normal PABX functions, such as internal calls, calls to the public switched telephone network PSTN, etc.
The trunk line side of the PABX is connected in the conventional way to the trunk lines from a local exchange or an ISDN exchange (or any other type of a communication exchange) of the PSTN. As noted in the above, in the prior art solutions the extension side of the PABX is directly connected to the base station PABX_BTS. In accordance with the invention, Figure l shows the extension side of the PABX being connected to the BSC of the mobile communication network PLMN. A special interface module IF
21 ~4~
W~ 9'7~0058~!1 PCI'IF196/01~354 is provided in the BSC for this purpose. In this application, such a base station controller in accordance with the invention is referred to as an ~to~ base station contrDller XBSC. The PABX BTS, in turn, is connected to the extended base station controller by Abis, the normal BSC-BTS interface in the GSM system. Since the PABX_BTS iB a normal GSM base station, also the radio interface of the wireless PAsX in the office cell 10 ir; a GSM/DCS interface antirely in accordance with the lo rec~ ~tions. As a result, a conventional GS~DCS
mobile station can be used in the office cell lG as a cordless handset 11. However, the invention does not prevent the base station PABX_BTS of the PABX system. frow having a different radio interface (e.g. DBCT~ than standard base stations of the mobile communication network. This results in that the subscriber stations of the PABX sy3tem must be dual-mode devices 80 as to be able to operate on both radio interfaces, which is a signiEicant deterioration in comparison to the preferred ~C ~mh~S; ~~~t.
The A interface between the MSC and the extended base station controller xssc can be maintained as a normal GSM interface without any modifications. This way, by means of the present invention~ the features of the 2~ ~SM~DCS interface can be can be issued to a standard PABX
without changes in the standard signalling interfaces. The only element requiring alterations in the PLMN network is the extended base station controller XBSC. The capacity of the XBSC is shared to serve both PABX_BTS base stations and normal P~M~_BTS base stations at the same time. Thus, the probably long tr~ns~;Cc;on connections between the BSC
and the MSC are avoided when making local ~internalJ calls in the PABX. In the ofiice cell 10, the standard functions of the mo~ile communication network, such as authentication and ciphering, are still available.
2~ ~6~2 The subscribers of the mobile communication retwork have each been allocated unique identities in the mobile communication network, such as IMSI ~International Mobile Subscriber Identity) in the GSM system. According to the preferred embodiment, a mobile subscriber entitled to use the office cell is in addition allocated a PABX subscriber number, such a PA'3X subscriber number beins for example a PAsX extension number or some other suitable identification. A subscriber's mobile station MS provided with an IMSI and a PABX subscriber number can be used as a cordless handset within the office cell and as a standard mobile station of a mobile communication network outside the office cell. Routing mobile terminating calls is done in two ways. When a calling PSTN subscriber dials a PABX
subscriber number, the PSTN routes the call to the wireless PABX, and forwarding the call to the mobile station will be handled via the interface IF between the PABX and the XBSC. When the calling subscriber dials a subscriber number (such as a MSISDN number) allocated to the subscriber in the mobile commur.ication network, the PSTN routes the call directly to the gateway MSC o~ the mobile communication network. Calls made from an MS in the office cell are routed by the XBSC to the PABX. This way the PABX internal calls can be switched directly without any MSC call control functions or connections via the MSC.
Below, various call routing procedures will be described in more detail. At first, however, the structure and operation of the extended XBSC and particularly its interface module IF will be disclosed with reference to Figure 2.
The block diagram of Figure 2 is but one exemplary embodiment of the base station controller XBSC. ~owever, it should be understood that the invention is by no means restricted thereto, but there exists several implementations depending in particular on the type and W097/00~Y
properties of the PP~3X used. Generally spea~ing, it can be said that the interface module IF is implemente.d depending on the PABX features so that a standard PA}3X can be coupled to an extended XBSC without alterations to the signalling and subscriber connections of the PA3X. In some cases the PA;3X may be tailored as far as its signalling interface and extensions are concerned so that it i8 particularly well suitable to be connected to a base station controller. A11 the variations, however, are characterized in that the signalling and speech connections associated with the PP~3X subscriber side, i.e.
extensions, are connected to the X.5SC a~d not directly to the PAsX base station as in prior art systems.
The interface module IP of Figure 2 is implemented so that the extensions o~ a standard analog PAl3X can be coupled as such to the interface module IF. It is assumed that the PA~3X has n extensions. If that is the case, the interface module IF has N line modules, one per each PABX
extension. Each line module comprises a D~A and A~D
converter 21, a transcoder 22 a ring signal detector 23 a DTMF generator 30N and an OFF/ON-HOOK switch 24. The D~A
converter 21 converts the analog speech signal received from a PABX extension into a digital signal to be encoded in the transcoder 22 by a speech encoding method of the mobile communication system prior to sending it to the mobile communication network. In the same manner, the encoded speech signal recei~ed from the mobile communication network is decoded i~. the transcoder 22, and converted in the D/A converter 21 into an analog speech 3~ signal, which is fed to a PABX extension. The ring signal detector 23 is used in case of an incoming call to detect the ringing tone fed by the PA~3X to the extension in cluestion. Vpon detecting the ringing tone, the detector 23 provides a signal DET as an output. The switch 7.4, controlled by a control signal ~OOK, is in turn used to 2t ~7~2 ~ W097/00S88 I~/rl:.l 5 close the subscriber loop of the PABX extension similarly as in a conventional phone with a subscriber answering the call by lifting the earpiece (OFF-HOOK) or making a call, and to open the subscriber loop similarly as in a conventional phone with the subscriber replacing (ON HOOK) the earpiece onto the hook at the end of the call. A dual-tone multi frequency (DTMF) generator 30 is used for generating the tone-frequency dialling digits to be sent via the PABX extension to the wireless extension PABX, in a similar manner as dialling is carried out in an extension with a conventional phone. The generator 30 is controlled by a control signal DIA~, which in turn is generated on the basis of GSM type of dialling signalling of the mobile stations MS.
The interface module IF in addition comprises a controller 25, which is common to all the line modules.
The controller 25 comprises inputs for detection signals DETN generated by the ringing tone detectors 231-23N, and control outputs HOOK1-HOOKN for the switches 24~-24N and DIAL~-DIALN for the generators 30. The controller 25 in addition has a signalling link with a control unit 28 of the BSC. The controller 28 controls a BSC internal switch 29 and handles all the call control and signalling duties assigned to the sSC.
In the extended XBSC according to the invention, the interface module IF is additionally provided with a signalling interface 28, by means of which a signalling link is created between the BSC and the visitor location register V~R. In the preferred embodiment of the invention, the interface in question is similar to a signalling interface (B interface) defined between an MSC
and a V~R in the GSM system. The B interface is specified in the GSM recl -n~tion 0902 Chapter 2.4.3, and the signalling used therein is referred to as MAP_B
signalling. As far as the present invention is concerned, I q 7 ~097~00~ r~l~r. c~ ;4 1~
it is only significant that some kind of a VLR-BSC
signalling lin~ exists for database en~uiries c~n~rning a different kind of call set-up, such as ciphering and authenticatiom, and possibly also for location updating.
For this purpose, the MAP_B signalling interface 28 is used by the controller 28.
Furthermore, the controller 28 of the XBSC has access to a PABX/IMSI database 26 in the interface module IF. The database 26 contains the identities IMSI of the a mobile subscribers entitled to use the office cell ~0 and the PABX. In addition, the database 26 informs of mapping between each IMSI and the correspon~ing PABX subscriber number, in this case the physical PABX extension. The database 26 is also used by the controller 2S of the inter~ace module IF itself, as will be disclosed below.
The switch of the base station controller BSC may be an~ MSC e~ployed digital switch to whose ports the connections botween the BSC and the MSC are coupled:i.e.
those between the sSC and the PAsX_sTS, those between the 2~ ssc and conventional base statlons, afi well as connections between the s5c and the transcoders 22. Controlled by the controller 28, the switch 2g switches these connections to one another in such a manner that the calls can be routed according tc standard pr~cedures of the m~bile communication network and procedures of the present invention, to be disclosed below.
In the following, a more detalled description will be given of establishing a mobile terminating call and a mobile originating call with reference to the ~o~ n~
3~ of Figures 1 and 2, and the signalling charts of Figures 3 and 4.
Mobile terminating call It should be noted that the signalling chart in Figure 4 by no means i5 a comprehensive description oE
signalling associated with call establishment. The purpose 097l~s88 r~llr of Figure 3 is only to give a picture of information exchange related to call set-up to the extent necessary for describing the invention. Hence, in practical call set-up other signalling than the signalling described in Figure 3 is also present, but this is not essential to the invention.
It is assumed that a call is made to an extension l of the PABX from the PSTN or another PABX extension. As a result, the PABX must somehow inform the BSC of the incoming call in order to set up the call to the mobile station MS of the extension in question. Activating this call set-up is illustrated in the signalling chart of Figure 3 by a Set_up message transmitted by the PABX to the BSC. In some embodiments, this may be an actual message. In the preferred embodiment of the invention, in which the PABX has not been altered on account of the present invention and in which the extensions are directly connected to the interface module IE, the PABX establishes the call in a similar manner as to a conventional extension. In other words, the PABX generates a ring signal to the extension l, the ring signal being detected by the ringing tone detector 231 of the interface module IF. The detector 231 indicates to the controller 25 of having received the ring signal by activating a signal DET1. The active state of the signal DET1 indicates to the controller 25 that there is an incoming call to the extension l. The controller 25 searches from the database 26 the IMSI identifier corresponding with the PABX
extension l and identifying the mobile subscriber of the extension l. Eollowing this, the controller 25 gives the controller 28 a call set-up command, which contains the retrieved IMSI. As a result, the controller 25 transmits a Paging_command paging message via the switch 28 to the base station PABX_BTS of the office cell. The base station PABX BTS forwards the message to the mobile station MS in ~ l ~ 7 W~:~9~/~5~8 ~ r the office cell. Via the PABX_BTS, the mobile station transmits a response message, Paging Response, to the BSC.
Having received the response from the mobile station, the BSC transmits an authentication request MAP_pro-Cess_access_request (MAP_authentication) to the V~R, to which the VBR responds with a M~P pro-cess_re~uest_ack message. These messages convey the same information as normally in the GSM system between the MSC
and the V~R. In the preferred embodiment of the invention, the controller 2~ carries out this signalling via MAP
signalling interface 28.
Having received the answer from the V~R, the control.ler 28 of the BSC transmits to the MS an authenticatlon request Auth re~uest, according to the CSM
re~ tions, which is responded to by the MS with an authentication message Auth_response according to the GSM
rec. ~tions. If authenticatlon has been successful, and the mobile station MS is allowed access to the network, ciphering mode will be set. For this purpose, the ssc transmits, to the V~R, a MAP_proc_acc_req (Ciph_mode) message which is responded to by the VLR with a M~P_ proc_ acc_req ack message. These messages con~ey the same information as normally in the GSM system between the MSC
and the V~. Then, the BSC transfers the ciphering mode ~f ~5 the MS with a Ciph_mode_cmd message, acknowledged by the MS with a Ciph mode_com message.
When the cipherin~ mode has been set, a connection will be set up between the switch 29 and the MS on a traffic channel allocated to the call via the base station 3~ PABY_BTS. This is illustrated with a Set up message. The MS will be ringing, and as the subscriber answers, information on it will be conveyed to the controller 2~
which ~ ~ the controller 2S to set the switch 2~1 to OFF_HOO~ state. This will close the subscriber loop of the P~3X extension 1, and the PABX interprets this as the 2f ~42 WO 97/OOS88 1~ r ~ . .'. ~~
subscriber having answered the call at the extension. This is illustrated in Figure 3 with a Call conf message.
Information on the answering by the subscriber B can naturally also be sent by other types of messages. This way a speech connection will be established between the MS
and the PABX.
The BSC only establishes PA~3X calls within the area of the office cell 10. In the example above, no pre-checking was carried out as to whether the called MS was in the office cell 10. ~owever, it is possible to carry out a location enquiry to the VBR prior to initiating paging in order to avoid futile paging signalling.
Nobile originating call In the following, establishing a mobile originating PAsX call will be described in the system according to the invention with reference to the signalling chart of Figure 4. The signalling chart of Figure 4 is not intended to be a full description of call set-up signalling, either. The figure only shows the signalling to the extent that is essential in order to describe the present invention. In practice, other messages can be included in the signalling, these other messages being insignificant to the present invention.
It is assumed in the following that the user of a cordless handset MS in the office cell 10 wishes to make a call. It is typical of mobile communication networks that call set-up signalling on the radio path only begins after the user has dialled the number of the called party and pressed a specific "send" button. When the user has pressed the ~send~ button, the MS transmits to the PABX_BTS of the office cell 10 a Channel Request message which i5 forwarded to the ssc. The 3SC responds by transmitting an Immediate Assignment message. Both of these are messages in accordance with the GSM
re~. nd~tions. The next message from the MS is a CM
2 ~ ~7~
WO 97/005A8 r ~n/rl. ~ll 54 ~--Service Re~uest which includes the reason ~or the transaction This message is in accordance with the GS~I
recommendations as well Due to the connection request having been received via the PABX_BTS in the ofEice cell 1~, the controller 28 checks in the database 26 whether the IMSI belongs to a PABX subscriber If the IMSI in question is not included in the database 26, call establishment proceeds according to the standard procedures of the mobile communication network If the IMSI does belong to a PABX subscriber, the controller 28 activates the call set-up procedure of the invention, with the call being routed to the PABX At first, the BSC authenticates the sub~criber and sets the ciphering mode; similar signalling between the BSC and the VLR, as well as between the BSC and the MS, is related thereto as that which was illustrated in Figure 3. ~hen the ciphering mode has beer set, the mobile station transmits, to the sSC, a call establishment message Set_up, which also contains the dialled subscriber number s In connection with the pre~ious en~uiry to the database ~6, the controller 28 was provided with information on which PABX extension the IMSI of the subs riber in questions matches. Let us assu~e that the IMSI corresponds to the PABX extension N. Having received the Set_up message from the MS, the controller 28 c ~ the controller 25 to set the switch 24~ of the extensior. ~ to OFF_HOO~ As a result, the subscriber loop of the extension N closes The PABX reacts to this by generating a dial tone to the extension, and awaits dialling The 3~ controller 28 now provides the controller 25 with the number of the subscriber B The cor.troller 25 directs the DTMF generator 30N to generate DTMF digits according to the subscriber number B. Signalling by the subscriber B to the PABX is illustrated by a B_number message in Figure 4 }5 Haviny received the number of the subscriber B, the PA3X
2 1 ~764~
~ W097lOOs~ r~lrrl ' ;~
proceeds with call set-up as if the dialling had been made from a standard extension.
Simultaneously with the dialling, thereafter, or prior to it the BSC establishes a connection between the s switch 29 and the MS on a traffic channel allocated to the call via the PABX BTS. This is illustrated in Figure 4 with a set_up message. As soon as the number of the subscriber B has been transferred to the PABX, the controller directs the switch 29 to connect the transcoder 22~ to said traffic channel. Thus, a connection will be established between the MS and the PABX, which is illustrated in Pigure 4 with an arrow ~connection~.
Call releasq When a mobile station requests a call release, the BSC transmits a response to the mobile station, switching it to ON-HOOK state. Information on the ON-HOOK state of the MS is simultaneously signalled to the PA}3X. In the preferred embodimens of the invention, this takes place by the controller 28 cn~~~n~1 ng the controller 25 to set the switch 24 of the PABX extension in auestion to ON-HOOK
state. As a result, the subscriber loop opens and the PABX
interprets the connection as having been cut off.
Following this, the resources and connections reserved in the BSC for the call are released.
When the other party decides to end the call, the PABX generates a busy tone to the extension, also carried over to the mobile station MS. Normally this causes the MS
user to onhook, i.e. to activate the call release described above from the MS side. In addition, the interface module IF may be provided with a busy tone detector whose activation causes the controller 28 to sent a call release message in accordance with the GSM
recommendations to the mobile station. In the latter case, the ON-HOOK state of the MS is signalled to the PABX by opening the subscriber loop with the switch 24.
z ) ~
w097/0~8 r~l/rl~ 4 Call~ made to the MSIS~N of the mobile station arrive in the mobile communication network in the normal manner Inot via PABX~, and the call set-up related thereto is narmal regardless of whether the MS i8 in the office cell lQ or not.
In order to save the resources of the radio network, hando~Yers from the office cell may be restricted to minimum. In such a case, even call release can be accepted instead of a handover.
Furthermore, the mobile stations entitled to use the office cell 10 may have a specific access category. If that is the Gase, all other access categories may he prohibited from the office cell. This is how other mobile stations could be prevented from locking to the office cell. In a GSM mobile station, for example, information on the subscriber's access category is located on his SIM
card ISubscriber Identification Module), which means that the categori~ation does not require changes to the software of the mobile station.
Although the invention has been described with reference to specific embodiments, it should be understood that these are intended as examples only, and that changes and moaifications can be made thereto without departing from the score and spirit of the attached claims.
Communication system and call establishment methods Field of the Invention The present invention relates to a communication system comprising a cellular mobile communication network, which includes a mobile services switching center, a base station controller and base stations, as well as a private branch exchange (PB~) system having at least one base station.
sackground of the Invention The conventional access technique to a fixed telephone network is a subscriber line (2-wire line) extending from a local exchange all the way to a subscriber's telephone. Presently, however, wireless access techniques are the fastest growing area within data communication. As a result, an ever increasing portion of new subscriber connections to the communication network will be wireless. The first generation of wireless subscriber connections consisted of analogue cordless phones (the CT1 system, for example), which consisted of a base station connected to a wired subscriber line of a public switched telephone network (PSTN), and a hand-held handset. The succeeding generation consisted of a digital cordless phone, known as the CT2 system. In addition to the conventional cordless phone, the CT2. system offered a telepoint service and a wireless Private Automatic sranch exchange (P~B~). Furthermore, a standard is being developed for a European digital wireless telephone system, knowr. by the abbreviation DECT. To a large extent, DECT is similar to the CT2, but utilizes TDMA technique.
Additionally, cordless systems based on radio interfaces of mobile commur.ication systems, such as the NMT system, have been realized wherein a subscriber's mobility related features are limited or completely non-existent.
One form of wireless communication is represented ~ ~ 97~4~
W097l00~88 l~llrl._ 4 by mobile communication systems which do not provide the subscribers with a fixed access point in the network at all. Instead, the subscribers may communicate with the network via an~ of the base stations of the network. In order to route mobile termln~ing calls to a correct point at any one time, the network r~;nt~;nq, at the subscriber database, the location information of the subscriber. As a mobile terminating call is received by the networ~., the first MSC in the network carries out an enquiry to the subscriber database, and is provided with the routing addre~s in the network.
An interesting area within wireless communication is represented by wireless PABXs. PABXs (or PBXs) are, as known, a type of office-specific private telephone exchanges that have a plurality of extensions and a smaller number of trunk lines to the locaI exchange. At the PABX, in~r~ncive ~free) internal calls can be set up from an extension to another, and external calls can be set up between an extension and a PSTN trunk line. A
2C wireless PABX is typically, as tO its basic structure, a conventional "wired" PAsx, but the cabling within the building is partly or entirely replaced with radio connections. The radio standards potentially applicable to PAs~ applications are represent for example by the aforementioned CT2 and D~CT, or solutions evolving from the Pan-European digital mobile communication system GSM.
The advantages of wireless PABXs are claimed to include:
- Mobilit~ of terminal e~uipments. The user no longer needs to be at a specific place in the building.
- Location of the personnel. It will be easier to contact people who are outside their offLce buildings.
- Reduced investments in cabling inside the building.
- No costs regarding re-arrangins or maintaining the cabling at the extension end of the PARX.
W097/00588 .~I/r~ '~ 4 As noted in the above, a wireless PABX is typically implemented by using the CT2 or ~ECT radio interface at the extension end of the exchange. The trunk line of the PABX is in the conventional way connected to a PSTN local exchange. Consequently, the freer mobility provided by a wireless PABX is iimited to the area covered by the base stations of the PA3X itself, i.e. the office environment Using phones outside the office is confined to telepoint services.
In order to extend the mobility of wireless subscriber stations several solutions have been proposed in which the wireless PABX is integrated as a part of a mobile commur.ication system. In such a case, the trunk line end of the wireless PABX is connected to the BSC or the MSC in the place of a conventional base station. The extension end of the PABX is implemented with CT2, DECT or similar radio interfaces similarly as in wireless P~3Xs connected to the PSTN network. As far as location management is concerned, wireless subscribers are managed like ordinary mobile subscribers in the mobile communication network. In principal, this enables a wireless subscriber to move from a wireless P~3X to another if both PABXs are connected to the mobile communication network. In addition, prior art phones may be dual-mode devices so that they can operate both via the base stations of the wireless PABX and via the base stations of the mobile communication network.
Consequently, one subscriber equipment provides mobility within the entire mobile communication network and inexpensive PABX internal calls in the office. These solutions, however, utilize procedures of the mobile ~ communication network for establishing externals calls, making them more expensive. In addition, special solutions are typically required ir, the signalling between the elements of the mobile communication network and the WC)97~0~X8 r~llr~
signalling used in the radio interface of the PAsx.
Furthermore, dual-mode subscriber equipments are requ1red in order to be able to utilize all the features o~ the mobile communication network, increasing the costs of the subscriber equipments.
Disclosure Or the Invention An object of the present invention is a communication system in which a wireless pri~ate exchange can be implemented in association with a mobile 1~ communication network in a way that requires less changes than before in the PAsX or the mobile communication network.
It is also an object of the invention to pro~iide inexpensive internal and external calls at a wireless PAsX
connected to a mobile communication network.
Yet another object of the invention is a communication system having similar radio interfaces and similar subscriber e~i c at the mobile communication network and the wireless PAsX.
2~ These objects are achie~ed by means of a communication system comprising a cellular mobile communication network, which includes a mobi~e services switching center, a base station controller and base stations, as well as a private exchange system having at least one base station. According to the invention the system is characterized in that the subscriber side of the PABX system is connected to the BS~ and the trunk side is connected to another communication networki the PAsX base station is connected to the base station controller; t h e base station controller is arranged to route subscriber calls originating from the PAsX base station to the PABX
system, and calls coming in via the PA~X system to the P~3X base station.
The invention also relates to a method for establishing an outgoing call in a communication system Zl i~7~2 O971OOsa8 I.l/rl:.t 5~
comprising a cellular mobile communication network which contains a mobile services switching center, a base station controller and base stations, as well as a private branch (PABX) system having at least one base station, the method comprising the steps of transmitting a connection request from the subscriber to the base station controller via the PABX base station; activating call set-up.
According to the invention, the method is characterized by checking at the base station controller whether the transmitting party of the connection request is a PABX
subscriber or a standard subscriber of the mobile communication network; routing the call of the PABX
subscriber from the base station controller to the PABX
system, whose subscriber side is connected to the base lS station controller and the trunk side to another communication network; connecting the call to the mobile services switching center if the subscriber is not a PA~X
subscriber.
The invention also relates to a method for establishing a terminating call in a wireless communication system comprising a cellular mobile communication network which contains a mobile services switching center, a base station controller and base stations, as well as a private branch (PABXI system having at least one base station, in which method a call terminating to PABX subscriber is received in the PABX
system. According to the invention, the method is characterized by the steps of initiating, from the private branch exchange system, call establishment at the base station controller to which the subscriber side of the PABX system and said PA3X base station are coupled;
transmitting from the base station controller a paging message to said PABX subscriber via the PAF3X base station;
receiving an acknowledgement message from the PABX
subscriber; establishing a connection according to the W097~ 8 P~l/r~ Y ~ ~
mobile communication network between the base station controller and the PABX subscriber; and connecting a speech connection between the PABX subscriber and said PABX system via the base station controller and the P~X
base station.
According to the invention, the BSC of the mobile communication network is provided with an interface to which the extension side of the PABX is connected. The trunk line side of the P~BX is connected to a local lo exchange of tne PSTN network. One or more of the base stations under control of the BSC is placed in that space or building which is the desired location for an offlce cell of the wireless PABX. In this application, such a base station will be referred to as a PABX base station.
Between the BSC and the PA}3X base station there is a normal signalling interface oE the mobile , i~ion network, and the PABX base station has a normal radio interface of the mobile communication network. The interface between the BSC and the PAsX is also a normal PAsx signalling interface towards the extensions. In a preferred em~odiment of the invention this interface includes t.he normal P~3X extensions, which are connected to the BSC.
This concept makes it possible to cbtain, for a PABX of a conventional fixed networkr a radio interface o~
the mobile communication system without changing normal signalllng interfaces. The only element for which the invention requires additional features is the ssc.
The capacity of the BSC is shared to serve both PABX base stations and standard base stations of a mobile communication network at the same time. Thus, the probably long transmissior. connections between the BSC and the MSC
are avoided when making local calls ir. the PABX, but the standard functions of the mobile communication network, .such as authenticatlon and ciphering, are still available.
wos7/00s88 PCT~9h~0354 No special features are required of the subscriber stations of a wireless PABX; they may be ordinary mobile stations of a mobile communication network. As such, they can also operate via normal base stations of the mobile communication network. The mobile stations can also be treated as normal subscriber stations of the mobile communication network outside their home PABX base stations.
In the preferred embodiment of the invention, a standard subscriber of a mobile communication network will be made a PA3X subscriber by also allocating to him a PABX
subscriber number. This subscriber number may be a PA~X
extension number or any other identifier that associates the mobile station with a specific PABX extension. This way, the mobile subscriber's mobile station can serve as a cordless phone within the office building and as a normal mobile station outside. The routing of terminating calls is done in two ways. When a calling subscriber dials a PABX subscriber number, the public switched telephone network PSTN routes the call to the wireless PABX, and connecting the cal' to the mobile station is handled via the radio interface between the PABX and the BSC. When the calling subscriber dials a PLMN number ~e.g. a MSISDN
number1, the PSTN routes the call directly to the PLMN
where the call is terminated with the normal call establishment procedure.
Mobile originating calls coming from a home PABX
base station are routed by the BSC to the PABX on the basis of the subscriber number, whereby the PABX internal calls can be switched directly without any MSC call control functions or connections via the MSC.
Consequently, internal calls, and PSTN calls, via a PABX
base station can be more economical than in prior art ~ solutions.
2 ' ~ 2 W097/00588 l~l/rl.~.l 5~ ~
Brief Description of the Drawing~
In the following, the invention will be descrihed in closer detail with reference to the accompanyi.ng drawings, in which Figure l shows a wireleas communicatior. system according to the invention, Figure 2 is a block diagram illustration of an extended base station controller, Figure 3 is a signalling chart illustrating setting up of a mobile terminating call, and Figure ~ is a signalling chart illustrating setting up of a mobile originating call.
In practice, the preser.t inventlon is applicable to almost any mobile communication system if a wireless P~3X
or PBX is to be connected to a PAsX system.
One example is the European digital cellular mobile communicat.ion system GSM ~Global System for Mobile Communications). The basic elements of the GSM system are described in the GSM R~ tions. For a closer description of the GSM system, the GSM recommendations and ~The ~SM System for Mohile ~ommunications", by M. Mouly &
M. Pautet, Palaiseau, Frarce, 1992, IS3N: 2-9~07190-0-7 is referred to.
The GSM and a modification thereof, DCSla00 (Digital Communication System1 operating at the 1800 Mhz frequency range, are the primary targets for the invention, but it is not intended that the invention be restricted to these radio systems.
Figure l very briefly describes the basic elements of the GSM system. A mobile services switching centre MSC
handles the connecting of incoming and outgoing calls. It performs functions similar to those of an exchange of a public switched telephone network (PSTN~. In addition to these, it also performs functions characteristic of mobile ~5 communications only, such as subscriber location ~ ~ ~7642 ~ W097~0s8~ r~l/r~
management. The mobile stations MS are connected to the center MSC by base statior. systems. The base station system consists of a base station controller BSC and base stations BTS. An A interface is determined for the BSC
towards to MSC, and an Abis interface towards the BTS.
These interfaces are specified in the GSM recc. -n~tions~
As subscriber registers, the system includes the home location register HLR and the visitor location register VLR. The ~LR permanently stores the subscriber information as well as information on which VLR area the MS is located in. The visitor location register VLR, in turn, temporarily stores the subscriber information of the subscribers visiting the VLR area. In addition, the VLR
stores the subscriber~s more detailed location information, i.e. the so-called location area identification.
Figure 1 also shows an office system implemented as a wireless PABX. The office system lO comprises a conventional fixed network PABX whose extension cabling has been replaced with a radio interface. Accordingly, the office system 10 comprises at least one base station PABX_BTS under control of the PABX, the PABX_BTS creating an internal cell for the office (e.g. a building).
Cordless handsets can freely move within this cell and utilize the normal PABX functions, such as internal calls, calls to the public switched telephone network PSTN, etc.
The trunk line side of the PABX is connected in the conventional way to the trunk lines from a local exchange or an ISDN exchange (or any other type of a communication exchange) of the PSTN. As noted in the above, in the prior art solutions the extension side of the PABX is directly connected to the base station PABX_BTS. In accordance with the invention, Figure l shows the extension side of the PABX being connected to the BSC of the mobile communication network PLMN. A special interface module IF
21 ~4~
W~ 9'7~0058~!1 PCI'IF196/01~354 is provided in the BSC for this purpose. In this application, such a base station controller in accordance with the invention is referred to as an ~to~ base station contrDller XBSC. The PABX BTS, in turn, is connected to the extended base station controller by Abis, the normal BSC-BTS interface in the GSM system. Since the PABX_BTS iB a normal GSM base station, also the radio interface of the wireless PAsX in the office cell 10 ir; a GSM/DCS interface antirely in accordance with the lo rec~ ~tions. As a result, a conventional GS~DCS
mobile station can be used in the office cell lG as a cordless handset 11. However, the invention does not prevent the base station PABX_BTS of the PABX system. frow having a different radio interface (e.g. DBCT~ than standard base stations of the mobile communication network. This results in that the subscriber stations of the PABX sy3tem must be dual-mode devices 80 as to be able to operate on both radio interfaces, which is a signiEicant deterioration in comparison to the preferred ~C ~mh~S; ~~~t.
The A interface between the MSC and the extended base station controller xssc can be maintained as a normal GSM interface without any modifications. This way, by means of the present invention~ the features of the 2~ ~SM~DCS interface can be can be issued to a standard PABX
without changes in the standard signalling interfaces. The only element requiring alterations in the PLMN network is the extended base station controller XBSC. The capacity of the XBSC is shared to serve both PABX_BTS base stations and normal P~M~_BTS base stations at the same time. Thus, the probably long tr~ns~;Cc;on connections between the BSC
and the MSC are avoided when making local ~internalJ calls in the PABX. In the ofiice cell 10, the standard functions of the mo~ile communication network, such as authentication and ciphering, are still available.
2~ ~6~2 The subscribers of the mobile communication retwork have each been allocated unique identities in the mobile communication network, such as IMSI ~International Mobile Subscriber Identity) in the GSM system. According to the preferred embodiment, a mobile subscriber entitled to use the office cell is in addition allocated a PABX subscriber number, such a PA'3X subscriber number beins for example a PAsX extension number or some other suitable identification. A subscriber's mobile station MS provided with an IMSI and a PABX subscriber number can be used as a cordless handset within the office cell and as a standard mobile station of a mobile communication network outside the office cell. Routing mobile terminating calls is done in two ways. When a calling PSTN subscriber dials a PABX
subscriber number, the PSTN routes the call to the wireless PABX, and forwarding the call to the mobile station will be handled via the interface IF between the PABX and the XBSC. When the calling subscriber dials a subscriber number (such as a MSISDN number) allocated to the subscriber in the mobile commur.ication network, the PSTN routes the call directly to the gateway MSC o~ the mobile communication network. Calls made from an MS in the office cell are routed by the XBSC to the PABX. This way the PABX internal calls can be switched directly without any MSC call control functions or connections via the MSC.
Below, various call routing procedures will be described in more detail. At first, however, the structure and operation of the extended XBSC and particularly its interface module IF will be disclosed with reference to Figure 2.
The block diagram of Figure 2 is but one exemplary embodiment of the base station controller XBSC. ~owever, it should be understood that the invention is by no means restricted thereto, but there exists several implementations depending in particular on the type and W097/00~Y
properties of the PP~3X used. Generally spea~ing, it can be said that the interface module IF is implemente.d depending on the PABX features so that a standard PA}3X can be coupled to an extended XBSC without alterations to the signalling and subscriber connections of the PA3X. In some cases the PA;3X may be tailored as far as its signalling interface and extensions are concerned so that it i8 particularly well suitable to be connected to a base station controller. A11 the variations, however, are characterized in that the signalling and speech connections associated with the PP~3X subscriber side, i.e.
extensions, are connected to the X.5SC a~d not directly to the PAsX base station as in prior art systems.
The interface module IP of Figure 2 is implemented so that the extensions o~ a standard analog PAl3X can be coupled as such to the interface module IF. It is assumed that the PA~3X has n extensions. If that is the case, the interface module IF has N line modules, one per each PABX
extension. Each line module comprises a D~A and A~D
converter 21, a transcoder 22 a ring signal detector 23 a DTMF generator 30N and an OFF/ON-HOOK switch 24. The D~A
converter 21 converts the analog speech signal received from a PABX extension into a digital signal to be encoded in the transcoder 22 by a speech encoding method of the mobile communication system prior to sending it to the mobile communication network. In the same manner, the encoded speech signal recei~ed from the mobile communication network is decoded i~. the transcoder 22, and converted in the D/A converter 21 into an analog speech 3~ signal, which is fed to a PABX extension. The ring signal detector 23 is used in case of an incoming call to detect the ringing tone fed by the PA~3X to the extension in cluestion. Vpon detecting the ringing tone, the detector 23 provides a signal DET as an output. The switch 7.4, controlled by a control signal ~OOK, is in turn used to 2t ~7~2 ~ W097/00S88 I~/rl:.l 5 close the subscriber loop of the PABX extension similarly as in a conventional phone with a subscriber answering the call by lifting the earpiece (OFF-HOOK) or making a call, and to open the subscriber loop similarly as in a conventional phone with the subscriber replacing (ON HOOK) the earpiece onto the hook at the end of the call. A dual-tone multi frequency (DTMF) generator 30 is used for generating the tone-frequency dialling digits to be sent via the PABX extension to the wireless extension PABX, in a similar manner as dialling is carried out in an extension with a conventional phone. The generator 30 is controlled by a control signal DIA~, which in turn is generated on the basis of GSM type of dialling signalling of the mobile stations MS.
The interface module IF in addition comprises a controller 25, which is common to all the line modules.
The controller 25 comprises inputs for detection signals DETN generated by the ringing tone detectors 231-23N, and control outputs HOOK1-HOOKN for the switches 24~-24N and DIAL~-DIALN for the generators 30. The controller 25 in addition has a signalling link with a control unit 28 of the BSC. The controller 28 controls a BSC internal switch 29 and handles all the call control and signalling duties assigned to the sSC.
In the extended XBSC according to the invention, the interface module IF is additionally provided with a signalling interface 28, by means of which a signalling link is created between the BSC and the visitor location register V~R. In the preferred embodiment of the invention, the interface in question is similar to a signalling interface (B interface) defined between an MSC
and a V~R in the GSM system. The B interface is specified in the GSM recl -n~tion 0902 Chapter 2.4.3, and the signalling used therein is referred to as MAP_B
signalling. As far as the present invention is concerned, I q 7 ~097~00~ r~l~r. c~ ;4 1~
it is only significant that some kind of a VLR-BSC
signalling lin~ exists for database en~uiries c~n~rning a different kind of call set-up, such as ciphering and authenticatiom, and possibly also for location updating.
For this purpose, the MAP_B signalling interface 28 is used by the controller 28.
Furthermore, the controller 28 of the XBSC has access to a PABX/IMSI database 26 in the interface module IF. The database 26 contains the identities IMSI of the a mobile subscribers entitled to use the office cell ~0 and the PABX. In addition, the database 26 informs of mapping between each IMSI and the correspon~ing PABX subscriber number, in this case the physical PABX extension. The database 26 is also used by the controller 2S of the inter~ace module IF itself, as will be disclosed below.
The switch of the base station controller BSC may be an~ MSC e~ployed digital switch to whose ports the connections botween the BSC and the MSC are coupled:i.e.
those between the sSC and the PAsX_sTS, those between the 2~ ssc and conventional base statlons, afi well as connections between the s5c and the transcoders 22. Controlled by the controller 28, the switch 2g switches these connections to one another in such a manner that the calls can be routed according tc standard pr~cedures of the m~bile communication network and procedures of the present invention, to be disclosed below.
In the following, a more detalled description will be given of establishing a mobile terminating call and a mobile originating call with reference to the ~o~ n~
3~ of Figures 1 and 2, and the signalling charts of Figures 3 and 4.
Mobile terminating call It should be noted that the signalling chart in Figure 4 by no means i5 a comprehensive description oE
signalling associated with call establishment. The purpose 097l~s88 r~llr of Figure 3 is only to give a picture of information exchange related to call set-up to the extent necessary for describing the invention. Hence, in practical call set-up other signalling than the signalling described in Figure 3 is also present, but this is not essential to the invention.
It is assumed that a call is made to an extension l of the PABX from the PSTN or another PABX extension. As a result, the PABX must somehow inform the BSC of the incoming call in order to set up the call to the mobile station MS of the extension in question. Activating this call set-up is illustrated in the signalling chart of Figure 3 by a Set_up message transmitted by the PABX to the BSC. In some embodiments, this may be an actual message. In the preferred embodiment of the invention, in which the PABX has not been altered on account of the present invention and in which the extensions are directly connected to the interface module IE, the PABX establishes the call in a similar manner as to a conventional extension. In other words, the PABX generates a ring signal to the extension l, the ring signal being detected by the ringing tone detector 231 of the interface module IF. The detector 231 indicates to the controller 25 of having received the ring signal by activating a signal DET1. The active state of the signal DET1 indicates to the controller 25 that there is an incoming call to the extension l. The controller 25 searches from the database 26 the IMSI identifier corresponding with the PABX
extension l and identifying the mobile subscriber of the extension l. Eollowing this, the controller 25 gives the controller 28 a call set-up command, which contains the retrieved IMSI. As a result, the controller 25 transmits a Paging_command paging message via the switch 28 to the base station PABX_BTS of the office cell. The base station PABX BTS forwards the message to the mobile station MS in ~ l ~ 7 W~:~9~/~5~8 ~ r the office cell. Via the PABX_BTS, the mobile station transmits a response message, Paging Response, to the BSC.
Having received the response from the mobile station, the BSC transmits an authentication request MAP_pro-Cess_access_request (MAP_authentication) to the V~R, to which the VBR responds with a M~P pro-cess_re~uest_ack message. These messages convey the same information as normally in the GSM system between the MSC
and the V~R. In the preferred embodiment of the invention, the controller 2~ carries out this signalling via MAP
signalling interface 28.
Having received the answer from the V~R, the control.ler 28 of the BSC transmits to the MS an authenticatlon request Auth re~uest, according to the CSM
re~ tions, which is responded to by the MS with an authentication message Auth_response according to the GSM
rec. ~tions. If authenticatlon has been successful, and the mobile station MS is allowed access to the network, ciphering mode will be set. For this purpose, the ssc transmits, to the V~R, a MAP_proc_acc_req (Ciph_mode) message which is responded to by the VLR with a M~P_ proc_ acc_req ack message. These messages con~ey the same information as normally in the GSM system between the MSC
and the V~. Then, the BSC transfers the ciphering mode ~f ~5 the MS with a Ciph_mode_cmd message, acknowledged by the MS with a Ciph mode_com message.
When the cipherin~ mode has been set, a connection will be set up between the switch 29 and the MS on a traffic channel allocated to the call via the base station 3~ PABY_BTS. This is illustrated with a Set up message. The MS will be ringing, and as the subscriber answers, information on it will be conveyed to the controller 2~
which ~ ~ the controller 2S to set the switch 2~1 to OFF_HOO~ state. This will close the subscriber loop of the P~3X extension 1, and the PABX interprets this as the 2f ~42 WO 97/OOS88 1~ r ~ . .'. ~~
subscriber having answered the call at the extension. This is illustrated in Figure 3 with a Call conf message.
Information on the answering by the subscriber B can naturally also be sent by other types of messages. This way a speech connection will be established between the MS
and the PABX.
The BSC only establishes PA~3X calls within the area of the office cell 10. In the example above, no pre-checking was carried out as to whether the called MS was in the office cell 10. ~owever, it is possible to carry out a location enquiry to the VBR prior to initiating paging in order to avoid futile paging signalling.
Nobile originating call In the following, establishing a mobile originating PAsX call will be described in the system according to the invention with reference to the signalling chart of Figure 4. The signalling chart of Figure 4 is not intended to be a full description of call set-up signalling, either. The figure only shows the signalling to the extent that is essential in order to describe the present invention. In practice, other messages can be included in the signalling, these other messages being insignificant to the present invention.
It is assumed in the following that the user of a cordless handset MS in the office cell 10 wishes to make a call. It is typical of mobile communication networks that call set-up signalling on the radio path only begins after the user has dialled the number of the called party and pressed a specific "send" button. When the user has pressed the ~send~ button, the MS transmits to the PABX_BTS of the office cell 10 a Channel Request message which i5 forwarded to the ssc. The 3SC responds by transmitting an Immediate Assignment message. Both of these are messages in accordance with the GSM
re~. nd~tions. The next message from the MS is a CM
2 ~ ~7~
WO 97/005A8 r ~n/rl. ~ll 54 ~--Service Re~uest which includes the reason ~or the transaction This message is in accordance with the GS~I
recommendations as well Due to the connection request having been received via the PABX_BTS in the ofEice cell 1~, the controller 28 checks in the database 26 whether the IMSI belongs to a PABX subscriber If the IMSI in question is not included in the database 26, call establishment proceeds according to the standard procedures of the mobile communication network If the IMSI does belong to a PABX subscriber, the controller 28 activates the call set-up procedure of the invention, with the call being routed to the PABX At first, the BSC authenticates the sub~criber and sets the ciphering mode; similar signalling between the BSC and the VLR, as well as between the BSC and the MS, is related thereto as that which was illustrated in Figure 3. ~hen the ciphering mode has beer set, the mobile station transmits, to the sSC, a call establishment message Set_up, which also contains the dialled subscriber number s In connection with the pre~ious en~uiry to the database ~6, the controller 28 was provided with information on which PABX extension the IMSI of the subs riber in questions matches. Let us assu~e that the IMSI corresponds to the PABX extension N. Having received the Set_up message from the MS, the controller 28 c ~ the controller 25 to set the switch 24~ of the extensior. ~ to OFF_HOO~ As a result, the subscriber loop of the extension N closes The PABX reacts to this by generating a dial tone to the extension, and awaits dialling The 3~ controller 28 now provides the controller 25 with the number of the subscriber B The cor.troller 25 directs the DTMF generator 30N to generate DTMF digits according to the subscriber number B. Signalling by the subscriber B to the PABX is illustrated by a B_number message in Figure 4 }5 Haviny received the number of the subscriber B, the PA3X
2 1 ~764~
~ W097lOOs~ r~lrrl ' ;~
proceeds with call set-up as if the dialling had been made from a standard extension.
Simultaneously with the dialling, thereafter, or prior to it the BSC establishes a connection between the s switch 29 and the MS on a traffic channel allocated to the call via the PABX BTS. This is illustrated in Figure 4 with a set_up message. As soon as the number of the subscriber B has been transferred to the PABX, the controller directs the switch 29 to connect the transcoder 22~ to said traffic channel. Thus, a connection will be established between the MS and the PABX, which is illustrated in Pigure 4 with an arrow ~connection~.
Call releasq When a mobile station requests a call release, the BSC transmits a response to the mobile station, switching it to ON-HOOK state. Information on the ON-HOOK state of the MS is simultaneously signalled to the PA}3X. In the preferred embodimens of the invention, this takes place by the controller 28 cn~~~n~1 ng the controller 25 to set the switch 24 of the PABX extension in auestion to ON-HOOK
state. As a result, the subscriber loop opens and the PABX
interprets the connection as having been cut off.
Following this, the resources and connections reserved in the BSC for the call are released.
When the other party decides to end the call, the PABX generates a busy tone to the extension, also carried over to the mobile station MS. Normally this causes the MS
user to onhook, i.e. to activate the call release described above from the MS side. In addition, the interface module IF may be provided with a busy tone detector whose activation causes the controller 28 to sent a call release message in accordance with the GSM
recommendations to the mobile station. In the latter case, the ON-HOOK state of the MS is signalled to the PABX by opening the subscriber loop with the switch 24.
z ) ~
w097/0~8 r~l/rl~ 4 Call~ made to the MSIS~N of the mobile station arrive in the mobile communication network in the normal manner Inot via PABX~, and the call set-up related thereto is narmal regardless of whether the MS i8 in the office cell lQ or not.
In order to save the resources of the radio network, hando~Yers from the office cell may be restricted to minimum. In such a case, even call release can be accepted instead of a handover.
Furthermore, the mobile stations entitled to use the office cell 10 may have a specific access category. If that is the Gase, all other access categories may he prohibited from the office cell. This is how other mobile stations could be prevented from locking to the office cell. In a GSM mobile station, for example, information on the subscriber's access category is located on his SIM
card ISubscriber Identification Module), which means that the categori~ation does not require changes to the software of the mobile station.
Although the invention has been described with reference to specific embodiments, it should be understood that these are intended as examples only, and that changes and moaifications can be made thereto without departing from the score and spirit of the attached claims.
Claims (12)
1. A communication system comprising a cellular mobile communication network, which includes a mobile services switching center (MSC), a base station controller (XBSC) and base stations (BTS), as well as a private exchange system (PABX) having at least one base station (PABX_BTS), c h a r a c t e r i z e d in that the subscriber side of the PABX system (PABX) is connected to the (XBSC) and the trunk side is connected to another communication network (PSTN), the PABX base station (PABX_BTS) is connected to the base station controller (XBSC), the base station controller (xbsc) is arranged to route subscriber calls originating from the PABX base station to the PABX system, and calls coming in via the PABX system to the PABX base station.
2. A system as claimed in claim 1, c h a r a c t e r i z e d in that the base station controller has a signalling link (28) to a subscriber database (VLR) of the mobile communication network, in order to, for example, authenticate the subscriber.
3. A system as claimed in claim 1 or 2, c h a r a c t e r i z e d in that the extensions of the PABX system (PABX) are connected to the base station controller (XBSC).
4. A system as claimed in claim 1, 2 or 3, c h a r a c t e r i z e d by the base station controller (XBSC) having information (26) on which identities in the mobile communication network belong to subscribers entitled to the services of the PABX system.
5. A system as claimed in claim 4, c h a r a c t e r i z e d by the base station controller (XBSC) having mapping information (26) between the identity of the mobile communication network and the corresponding PABX subscriber number or PABX extension.
6. A system as claimed in claim 1, 2, 3, 4 or 5, c h a r a c t e r i z e d by the base station controller having a signalling unit for signalling in the direction of the PABX system in the manner required by the PABX
system, and in the direction of the mobile communication system in the manner required by the mobile communication network.
system, and in the direction of the mobile communication system in the manner required by the mobile communication network.
7. A system as claimed in claim 4, c h a r a c t e r i z e d in that terminating calls to the PABX mobile subscriber number are routed in the mobile communication network as standard terminating calls to subscribers of the mobile communication network.
8. A system as claimed in claim 1, c h a r a c t e r i z e d in that the PABX base stations and the mobile communication network have different radio interfaces, and that the PABX subscriber equipments are dual-mode devices capable of operating at both radio interfaces.
9. A method for establishing an outgoing call in a communication system comprising a cellular mobile communication network which contains a mobile services switching center, a base station controller and base stations, as well as a private branch (PABX) system having at least one base station, the method comprising the steps of transmitting a connection request from the subscriber to the base station controller via the PABX
base station, activating call set-up, c h a r a c t e r i z e d by checking at the base station controller whether the transmitting party of the connection request is a PABX
subscriber or a standard subscriber of the mobile communication network, routing the call of the PABX subscriber from the base station controller to the PABX system, whose subscriber side is connected to the base station controller and the trunk side to another communication network, connecting the call to the mobile services switching center if the subscriber is not a PABX
subscriber.
base station, activating call set-up, c h a r a c t e r i z e d by checking at the base station controller whether the transmitting party of the connection request is a PABX
subscriber or a standard subscriber of the mobile communication network, routing the call of the PABX subscriber from the base station controller to the PABX system, whose subscriber side is connected to the base station controller and the trunk side to another communication network, connecting the call to the mobile services switching center if the subscriber is not a PABX
subscriber.
10. A method as claimed in claim 9, c h a r a c t e r i z e d by the routing of the call from the base station controller to the PABX system comprising the steps of signalling off-hook information to the PABX system in order to activate the extension of the subscriber equipment in the manner required by the PABX system, for example by closing the subscriber loop at the extension, signalling the subscriber's dialling to the PABX
system in the manner required by the PABX system, for example by transmitting DTMF dialling digits to the activated extension.
system in the manner required by the PABX system, for example by transmitting DTMF dialling digits to the activated extension.
11. A method for establishing a terminating call in a communication system comprising a cellular mobile communication network which contains a mobile services switching center, a base station controller and base stations, as well as a private branch (PABX) system having at least one base station, in which method a call terminating to PABX subscriber is received in the PABX system, c h a r a c t e r i z e d by the steps of initiating, from the private branch exchange system, call establishment at the base station controller to which the subscriber side of the PABX system and said PABX base station are coupled, transmitting from the base station controller a paging message to said PABX subscriber via the PABX base station, receiving an acknowledgement message from the PABX
subscriber, establishing a connection according to the mobile communication network between the base station controller and the PABX subscriber, and connecting a speech connection between the PABX
subscriber and said PABX system via the base station controller and the PABX base station.
subscriber, establishing a connection according to the mobile communication network between the base station controller and the PABX subscriber, and connecting a speech connection between the PABX
subscriber and said PABX system via the base station controller and the PABX base station.
12. A method as claimed in claim 11, c h a r a c t e r i z e d by the base station controller maintaining, for each PABX subscriber, mapping information between the identity of the mobile communication network.
and the corresponding PABX subscriber number or PABX
extension.
and the corresponding PABX subscriber number or PABX
extension.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI953012 | 1995-06-16 | ||
| FI953012A FI101338B (en) | 1995-06-16 | 1995-06-16 | Telecommunication system and call set-up methods |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2197642A1 true CA2197642A1 (en) | 1997-01-03 |
Family
ID=8543626
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002197642A Abandoned CA2197642A1 (en) | 1995-06-16 | 1996-06-14 | Communication system and call establishment methods |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0776587A1 (en) |
| JP (1) | JPH10504165A (en) |
| CN (1) | CN1158207A (en) |
| AU (1) | AU710178B2 (en) |
| CA (1) | CA2197642A1 (en) |
| FI (1) | FI101338B (en) |
| WO (1) | WO1997000588A1 (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100464337B1 (en) * | 1997-07-11 | 2006-02-28 | 삼성전자주식회사 | Multiple Calling Method for Wired and Wireless Terminal Equipment in Switching System |
| US6073029A (en) * | 1997-07-25 | 2000-06-06 | U S West, Inc. | Method and system for providing wireless communications to a subscriber of a private wireline network |
| AT407813B (en) * | 1997-12-18 | 2001-06-25 | Ericsson Austria Ag | TELEPHONE SYSTEM |
| DE19815430B4 (en) * | 1998-04-07 | 2005-12-15 | T-Mobile Deutschland Gmbh | A method for establishing a connection from a mobile radio network to a destination number of a private communication network |
| US6263211B1 (en) | 1998-09-24 | 2001-07-17 | Telefonaktiebolaget L M Ericsson (Publ) | System and method of automatically conveying a Wireless Office System (WOS) frequency set to mobile stations |
| KR100418151B1 (en) * | 2001-04-16 | 2004-02-11 | (주) 콘텔라 | Private Telecommunication Network System |
| KR100454945B1 (en) * | 2001-11-28 | 2004-11-06 | 삼성전자주식회사 | Public land mobile network and private mobile network integration service network and system therefor |
| KR100469707B1 (en) * | 2001-12-27 | 2005-02-02 | 삼성전자주식회사 | Method for using the public e1 link efficiently in wireless pabx system |
| DE10329960A1 (en) * | 2003-07-03 | 2005-03-17 | Deutsche Telekom Ag | Switching control system is used to provide a connection between a fixed communication network and a mobile telephone network |
| US20050255840A1 (en) * | 2004-05-13 | 2005-11-17 | Markham Thomas R | Authenticating wireless phone system |
| CN101325795B (en) * | 2007-06-15 | 2011-09-21 | 中兴通讯股份有限公司 | Wireless communication device for local voice exchange |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE465992B (en) * | 1990-04-10 | 1991-11-25 | Ericsson Telefon Ab L M | MOBILE PHONE SYSTEM PROVIDED TO USE BY SUBSCRIBERS INDOOR AND OUTDOOR |
| GB2253323B (en) * | 1991-03-01 | 1995-05-17 | Racal Vodafone Ltd | Telecommunications networks and methods |
| DE4128811A1 (en) * | 1991-08-30 | 1993-03-04 | Standard Elektrik Lorenz Ag | EXTENSION SYSTEM |
| JPH0815267B2 (en) * | 1991-09-27 | 1996-02-14 | 松下電器産業株式会社 | Wireless phone |
| FI94698C (en) * | 1993-09-28 | 1995-10-10 | Nokia Telecommunications Oy | The communications network |
| GB2282730B (en) * | 1993-10-08 | 1998-01-28 | Nokia Telecommunications Oy | Dual mode subscriber terminal and a handover procedure of the dual mode subscriber terminal in a mobile telecommunication network |
| SE516006C2 (en) * | 1995-01-10 | 2001-11-05 | Ericsson Telefon Ab L M | Communication system for a company / organization |
-
1995
- 1995-06-16 FI FI953012A patent/FI101338B/en active
-
1996
- 1996-06-14 CN CN 96190745 patent/CN1158207A/en active Pending
- 1996-06-14 AU AU61282/96A patent/AU710178B2/en not_active Ceased
- 1996-06-14 EP EP96918711A patent/EP0776587A1/en not_active Withdrawn
- 1996-06-14 CA CA002197642A patent/CA2197642A1/en not_active Abandoned
- 1996-06-14 WO PCT/FI1996/000354 patent/WO1997000588A1/en not_active Application Discontinuation
- 1996-06-14 JP JP9502674A patent/JPH10504165A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FI953012A0 (en) | 1995-06-16 |
| AU710178B2 (en) | 1999-09-16 |
| WO1997000588A1 (en) | 1997-01-03 |
| FI953012A (en) | 1996-12-17 |
| FI101338B1 (en) | 1998-05-29 |
| CN1158207A (en) | 1997-08-27 |
| AU6128296A (en) | 1997-01-15 |
| JPH10504165A (en) | 1998-04-14 |
| EP0776587A1 (en) | 1997-06-04 |
| FI101338B (en) | 1998-05-29 |
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