United States Patent [19J
`Rautiola et al.
`
`I 1111111111111111 11111 111111111111111 1111111111 1111111111 111111111111111111
`US005949775A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,949,775
`Sep.7,1999
`
`[54] OFFICE COMMUNICATION SYSTEM
`
`[75]
`
`Inventors: Markku Rautiola; Jouni Mikkonen,
`both of Tampere, Finland
`
`[73] Assignee: Nokia Mobile Phones Ltd., Salo,
`Finland
`
`[21] Appl. No.: 08/697,784
`
`[22] Filed:
`
`Aug. 30, 1996
`
`[30]
`
`Foreign Application Priority Data
`
`Sep. 29, 1995
`
`[FI]
`
`Finland .................................... 954638
`
`Int. Cl.6
`....................................................... H04Q 7/24
`[51]
`[52] U.S. Cl. ............................................. 370/338; 370/401
`[58] Field of Search ..................................... 370/395, 338,
`370/400, 401, 315, 328, 452, 349; 455/552,
`553
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,175,758
`5,257,257
`5,321,542
`5,473,669
`5,475,689
`5,598,407
`
`12/1992 Levan to et al. ... ... ... ... .... ... ... ... .. 379 /57
`10/1993 Chen et al.
`. ... ... ... ... ... .... ... ... ... .. 370/18
`6/1994 Freitas ..................................... 370/338
`12/1995 Kanada et al. ............................ 379/59
`12/1995 Kay ......................................... 370/338
`1/1997 Bud ......................................... 370/330
`
`5,737,333
`5,771,459
`
`4/1998 Civanlar .................................. 370/352
`6/1998 Demery ................................... 370/401
`
`FOREIGN PATENT DOCUMENTS
`
`2131349
`0 526 106 A2
`44 06 505 Al
`
`5/1995 Canada .
`2/1993 European Pat. Off ..
`8/1995 Germany .
`
`Primary Examiner-Chau Nguyen
`Assistant Examiner-Thinh Vu
`Attorney, Agent, or Firm-Perman & Green, LLP
`ABSTRACT
`
`[57]
`
`The invention relates to integrated office communication
`systems employing a local area network (LAN) for intra(cid:173)
`office communications. In the arrangement according to the
`invention, no other internal networks are needed in the office
`because computers (10) are connected to the local area
`network and telephones (5, 7) are either mobile or cordless
`phones for which there are low-power room-specific base
`stations ( 4, 6) in the local area network (LAN). Connections
`to the outside world are made via a gateway computer (1)
`and public cellular radio network. Inside the office, the
`coverage areas of the small base stations ( 4, 6, 8) are
`nanocells ( 4a) of one or a few rooms. A home or small office
`user has a similar small base station (14) which is cotifected
`to said local area network via a public communication
`network (15) and a gateway equipment (13).
`
`15 Claims, 4 Drawing Sheets
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`Ex.1005
`APPLE INC. / Page 1 of 13
`
`

`

`U.S. Patent
`
`Sep. 7, 1999
`
`Sheet 1 of 4
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`5,949,775
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`Ex.1005
`APPLE INC. / Page 2 of 13
`
`

`

`U.S. Patent
`
`Sep.7,1999
`
`Sheet 2 of 4
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`5,949,775
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`Ex.1005
`APPLE INC. / Page 3 of 13
`
`

`

`U.S. Patent
`U.S. Patent
`
`Sep.7,1999
`Sep. 7, 1999
`
`Sheet 3 of 4
`Sheet 3 of 4
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`5,949,775
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`Ex.1005
`APPLEINC./ Page 4 of 13
`
`Ex.1005
`APPLE INC. / Page 4 of 13
`
`
`
`

`

`U.S. Patent
`U.S. Patent
`
`Sep. 7, 1999
`Sep.7,1999
`
`Sheet 4 of 4
`Sheet 4 of 4
`
`5,949,775
`5,949,775
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`Ex.1005
`APPLEINC./ Page 5 of 13
`
`Ex.1005
`APPLE INC. / Page 5 of 13
`
`

`

`5,949,775
`
`1
`OFFICE COMMUNICATION SYSTEM
`
`BACKGROUND OF THE INVENTION
`
`The invention relates to integrated office communication
`systems which provide, in addition to conventional tele-
`phone services, data communication services and other
`advanced communication services for users in offices and
`other working environments.
`In present-day office work it is necessary to arrange for
`employees versatile communication connections capable of
`transmitting speech, faxes, e-mail and other data, which
`usually is in digital form. Communication is needed inside
`an office or sinilar working environment for communication
`between the employees, communication between different
`offices of a company which may be located in different cities
`or even in different countries, and for communication
`between the office and the "outside world". Here and
`throughout the text to follow, an "office" means a multi-user
`environment wherein the users in some way belong together
`and which is physically located in a relatively small area.
`There has been a tendency in the field toward integrated
`systems, in which different forms of transmission can be
`managed as a whole.
`A conventional implementation of such an integrated
`office communication system comprises a private branch
`exchange and telephones connected to it with twisted-pair
`lines in order to provide telephone services, and a separate
`local area network (LAN) which contains applications for
`advanced communication services and the intelligence
`needed to use them. The local area network is connected to
`the private branch exchange via a telephony server which
`supports the traditional client/server architecture in which
`the clients are users' computers connected to the local area
`network. The telephony server can combine e.g. the office's
`phone call, data, fax, e-mail and voice mail services. In an
`integrated system, the users may also manage the telephone
`services via their computer terminals connected to the local
`area network. The whole integrated office communication
`system is connected to a public telephone network via the
`private branch exchange.
`FIG. 1 shows an example of a known integrated office
`communication system, in which users' telephones TP are
`connected via wired connections to a private branch
`exchange PBX connected to a public switched telephone 45
`network PSTN, and a local area network LAN is connected
`to it via a telephony server TS. Servers implementing
`different applications, such as a database server DBS, voice
`server VS and an e-mail server EMS, are connected to the
`local area network, as are the users' computers PC The 50
`problem associated with this kind of implementation is that
`even though a user's telephone TP and computer PC are
`usually located side by side on the same desk, they must
`have separate wired connections from the private branch
`exchange PBX on one hand and from the telephony server 55
`TS of the local area network LAN on the other. Building and
`maintaining two overlapping communication networks is
`naturally costly.
`The problem of overlapping communication networks is
`made worse by the rapid growth in the number of portable 60
`mobile stations utilizing radio communication. Because of
`mobile work, many office workers need a mobile phone and
`often also a portable fax and/or a combination of a portable
`computer and a mobile phone. To make these devices
`useable also inside buildings, where the structures attenuate 65
`radio signals, it has been proposed, for example, that the
`mobile communication network be supplemented with small
`
`5
`
`15
`
`2
`base stations covering an office or even a room in an office,
`which would be connected either directly or via a wired
`telephone network to the switching systems of the mobile
`network. That network of small base stations would consti-
`tute a third overlapping transmission network in an office,
`and therefore it is clear that in an advantageous solution, at
`which the present invention is aimed, an arrangement which
`supports radio communication devices should be realized by
`substantially the same means as the rest of the communica-
`10 tions in the office.
`It is a challenge for the communication systems that more
`and more work is being done in the small office, home office
`(SOHO) environment. There, too, there is often a need for
`advanced office communication services, and it is particu(cid:173)
`larly advantageous if there is a flexible system which can be
`used both in the office and at home. The present systems,
`which require overlapping connections for the mobile com(cid:173)
`munication services, ordinary telephone services and fast
`data transmission services, are rather inflexible as far as
`20 working in a small or home office is concerned.
`To describe the prior art we will next briefly discuss some
`solutions related to integrated communication systems. PCT
`application document WO 94/14291 discloses an arrange(cid:173)
`ment the purpose of which is to simplify and automatize the
`25 use of services ordered by phone. The publication discloses
`an embodiment, wherein a user makes a phone call from a
`wired telephone to an automatic exchange and indicates with
`a push-button code that she wants to order a taxi. The
`number of said wired phone is automatically conveyed to the
`30 exchange which checks the location of the phone from a
`suitable database. Then the exchange checks from an
`( automatically updated) taxi database which taxi is geo(cid:173)
`graphically closest to the caller in question and can provide
`the desired lift. To update the taxi database and make
`35 connections to taxis, each taxi has a mobile station using
`radio connection. For transmission, the exchange and its
`auxiliary equipment, such as the unit answering calls, the
`databases and the base stations maintaining the radio links,
`are interconnected via a local area network which can
`40 transmit voice information in addition to data. Unlike the
`present invention, the system is not aimed at reducing
`overlapping communication networks, but its stated inten(cid:173)
`tion is to substitute computers for human labour in an
`exchange conveying taxi services.
`EP application document no. 599,632 discloses a wireless
`local area network the purpose of which is to replace a
`current wired network (such as Ethernet and Token Ring,
`both registered trademarks) with a radio network, which in
`a way constitutes a cellular radio system of its own, intended
`for data transmission, inside a company. Said application
`document concentrates mainly on the handling of problems
`caused by multipath propagation in a wireless local area
`network and proposes a solution wherein the data transmis(cid:173)
`sion time constant of the system, or the inverse of the bit
`rate, is smaller than the typical delay caused by multipath
`propagation.
`EP application document no. 462,728 discloses an intel(cid:173)
`ligent base station controller which controls at least one base
`station of a radio-based communication system and which is
`capable of transmitting calls coming from a certain mobile
`station via a base station directly to a wired telephone
`network. The idea of the system is that since a call directed
`directly to a wired network does not utilize the database
`services of a mobile telephone exchange or the long trans(cid:173)
`mission connections to the exchange, a lower price can be
`set for it. If the base station controller in question is located
`in a company's telephone exchange and its base stations
`
`Ex.1005
`APPLE INC. / Page 6 of 13
`
`

`

`5,949,775
`
`3
`cover the premises of the company, the method can be used
`to form a similar wireless local area network as the one
`described above in conjunction with EP document no.
`599,632.
`So-called, cordless systems, in which the fixed terminals
`of the conventional wired telephone network are replaced
`with corresponding radio-based devices, constitute a field of
`technology of its own. These systems have so far concen(cid:173)
`trated on standardizing the radio interface between the
`mobile terminal and the fixed station at the end of a wired
`connection. Known radio interface standards include, for
`example, DECT (Digital European Cordless
`Telecommunications) and CT2 (Cordless Telephone 2).
`They do not define the communication services offered to
`the user, but the services depend on the communication
`network (e.g. the public wired telephone network) to which
`the fixed station implementing the radio inter-face is con(cid:173)
`nected.
`Above solutions according to the prior art do not actually
`attempt to solve the aforementioned problem caused by the
`overlapping of networks required by different transmission
`formats. An object of this invention is to provide a system
`which combines all electrical communication within a given
`limited area and controls the communication directed out of
`said area and provides a chance to share data and data
`processing resources between several users. Another object
`of the invention is to provide an arrangement with which
`said communication-combining system can also serve home
`and small office users. A further object of the invention is to
`provide an arrangement like the one mentioned above in
`which the same equipment can be used everywhere as
`terminals of the communication system.
`
`4
`transmission, whereby overlapping networks are not needed.
`The invention is based on the novel idea that since an office
`interconnected by a local area network constitutes an inte(cid:173)
`grated subsystem comprising rooms, or cells, it can be
`5 connected via a gateway connection to form a component of
`the cellular radio system in the same way as an ordinary base
`station subsystem (BSS) which is controlled by a base
`station controller (BSC) and comprises several base stations
`(BS). However, the invention does not limit the external
`10 communication connections of the office to the cellular radio
`network. From the local area network there may be, in
`addition to the cellular radio network connection provided
`by the gateway machine, also other communication connec(cid:173)
`tions to the outside world, such as a connection to a wired
`15 telephone network or an asynchronous transfer mode (ATM)
`network.
`Nanocells are created in the office that cover one or a few
`rooms and that have a special very low power base station
`for serving ordinary terminals of a cellular radio system. The
`20 base stations are connected via a local area network to each
`other and to a gateway machine which provides the neces(cid:173)
`sary data transfer from the local area network to an exchange
`in the cellular radio system. It is also possible to connect
`infrared stations to the local area network which operate in
`25 the same way as the low-power radio base stations of the
`nanocells except for that instead of a radio link the connec(cid:173)
`tion to a terminal is made via an infrared link. In addition,
`stations applying cordless standards (such as DECT) can be
`connected to the local area network, whereby also terminals
`30 of cordless systems can be used in the office. Usually the
`local area network has advantageously one or more servers
`which take care of certain functions related to the distribu(cid:173)
`tion of resources, such as the database services and voice
`mail and e-mail services.
`For home and small office users and remote working, the
`communication system according to the invention advanta(cid:173)
`geously comprises a nanocell in the user's home with a
`connection to the local area network in the office. The
`connection can be realized in many ways. The most advan-
`40 tageous way is to use an existing connection in the user's
`home, such as the twin lead connection of the conventional
`telephone network. If the user's home is provided with a
`coaxial cable of a cable TV system, the transmission capac(cid:173)
`ity required can be leased from the cable TV company. In the
`45 future, as ATM and ISDN networks will become more
`widely used, these can be used especially to implement
`home connections requiring high bit rates. From the local
`area network in the office there is a bridge connection to the
`network realizing the home connection; the implementation
`50 of the bridge connection will be discussed in more detail
`later. If the user's home or small office is provided with
`many alternative connections, the user can advantageously
`choose which of the connections to the local area network in
`the office she wants to use.
`
`SUMMARY OF THE INVENTION
`These objects of the invention are achieved through an 35
`arrangement in which the core of the communication system
`is a local area network in the office and a cellular radio
`network between office units. From the point of view of the
`cellular radio system, each office constitutes a cellular
`subsystem, in which a certain so called gateway computer
`controls the connections in the direction of the cellular radio
`system exchange and in which the local area network
`connects to said gateway computer a group of base units
`serving as radio base stations.
`An integrated office communication system according to
`the invention, which includes a local area network, is
`characterized in that it also includes, connected to said local
`area network,
`gateway equipment to convey information between said
`local area network and a public cellular radio network,
`and
`low-power base station equipment to provide a radio
`interface for terminal equipment operating in a public
`cellular radio network, which radio interface is sub- 55
`stantially identical with the radio interface provided by
`conventional base station equipment in said public
`cellular radio network,
`which, ie. the gateway equipment, local area network and
`low-power base station equipment, are arranged in such 60
`a manner that within the area of said office communi(cid:173)
`cation system a connection between said terminal
`equipment and said public cellular radio network is
`made via said low-power base station equipment, said
`local area network and said gateway equipment.
`In the arrangement according to the invention, the local
`area network inside an office is used for all data
`
`65
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`The invention is described in more detail with reference
`to the advantageous embodiments presented as examples
`and to the accompanying drawing, in which
`FIG. 1 shows a known communication arrangement in an
`office environment,
`FIG. 2 shows the communication system according to the
`invention especially from the office environment standpoint,
`FIG. 3 shows the communication system according to the
`invention especially from the home or small office environ(cid:173)
`ment standpoint, and
`
`Ex.1005
`APPLE INC. / Page 7 of 13
`
`

`

`5,949,775
`
`5
`FIG. 4 shows known relationships between certain admin(cid:173)
`istrative areas.
`Above, in conjunction with the description of the prior art,
`we referred to FIG. 1 and so, below, in the description of the
`invention and its advantageous embodiments, we will refer
`mainly to FIGS. 2 to 4. In the figures, like parts are denoted
`by like reference numbers and letters.
`
`DETAILED DESCRIPTION OF IBE
`INVENTION
`
`10
`
`6
`means primarily that certain protocol conversion tasks are
`transferred from the mobile switching centre MSC to the
`gateway computer 1. From the point of view of the switch(cid:173)
`ing centre all communication operations occurring under the
`5 control of the gateway computer 1 occur in a certain location
`area 3 corresponding to the office in question. It could also
`be said that from the point of view of the switching centre
`the systems operating under the gateway computer consti(cid:173)
`tute a base station subsystem (BSS).
`The interface between the gateway computer 1 and the
`local area network LAN depends on the implementation of
`the local area network and on the protocols and application
`programming interfaces (API) used for maintaining local
`area network traffic. Known network protocols include e.g.
`15 TCP/IP (Transmission Control Protocol/Internet Protocol)
`and Novell Netware SPX/IPX (Sequenced Packet
`Exchange/Internetwork Packet Exchange). A known API
`interface is e.g. NetBIOS (Network Basic Input/Output
`System).
`A wide variety of equipment can be connected to the local
`area network LAN in an office. Low-power base units 4
`(BU) serving one or a few rooms are essential from the point
`of view of the invention. These are small base stations that
`constitute a coverage area consisting of nanocells, covering
`25 the whole office. Each base unit 4 includes a network adapter
`part (not shown in the drawing), which is similar to known
`network adapter cards widely used in computers and which
`takes care of the practical implementation of the communi-
`cation between a base unit 4 and the local area network.
`Thus, a nanocell 4a refers to the coverage area of a base unit
`4, which is a miniaturized equivalent of the coverage area of
`a base station BS in an ordinary cellular system. In an
`advantageous embodiment, each base unit 4 operates on
`only one transmission and one reception frequency, whereby
`35 one base unit can simultaneously serve a maximum of seven
`mobile stations 5-when applying an 8-channel time divi(cid:173)
`sion multiple access (TDMA) known from the GSM system,
`wherein one channel is reserved as a control channel. For the
`useability of the system it is essential that except for the
`40 transmission power the radio interface offered to mobile
`stations 5 by the base units 4 is identical with the radio
`interface offered by an ordinary base station BS so that the
`system sets no additional requirements on existing mobile
`stations.
`Base units 4 can handle the communication required by
`all those mobile stations 5 that use the radio interface
`according to a public cellular radio system and which
`therefore can be used also outside the office environment in
`a coverage area of the public cellular radio system. These
`50 devices include e.g. mobile phones, portable fax machines,
`and computers utilizing a digital communication connection
`formed by means of a data adapter. Base units 4 offering
`different radio interfaces can also be connected to the same
`local area network for those users who use mobile stations
`according to the DCS 1800 standard, for example.
`Usually, however, it is not economical to purchase rela(cid:173)
`tively expensive mobile phones for office employees if they
`need the telephone connection only within the office area.
`Then a more advantageous solution is to connect base units
`6 complying e.g. with the radio interface standard of a
`cordless telephone system, such as DECT, to the local area
`network LAN, and thus create through these base units a
`cordless telephone connection for the whole office area,
`utilizing cordless telephones 7, which usually are cheaper
`than mobile phones. Compared to a conventional wired
`telephone system, this has the advantage that, firstly, there is
`no need for a separate office telephone network since the
`
`20
`
`FIG. 2 shows the communication system according to the
`invention especially from the office environment standpoint.
`In the figure, parts belonging to the office environment are
`separated from the other parts of the system with a dashed
`line. To illustrate the operation of the system we will first
`discuss parts not belonging to the office environment, which,
`as such, are known and belong to standardized cellular radio
`systems. In the description below, which discloses a cellular
`radio system, we will use, for the sake of illustration, names
`used in the GSM (Groupe Speciale Mobile) system, which
`is widely used in Europe, but they are in no way intended to
`limit the applicability of the invention to any one particular
`cellular radio system.
`The operational nucleus of a cellular radio system is
`constituted by the mobile switching centres MSC in con(cid:173)
`nection of which there are databases such as the subscriber
`database SDB and visitor database VDB for storing and
`using information related to the location and status of mobile
`stations. Under one MSC there are several base station 30
`controllers BSC, each of which controls one or more base
`stations BS. In the GSM system, the standardized interface
`between a switching centre MSC and base station controller
`BSC is called an A-interface.
`A mobile station MS in a cellular radio system is in radio
`connection with a base station BS, whereby the base station
`conveys the location and status information of that mobile
`station to the database means SDB or VDB in a switching
`centre MSC depending on whether the mobile station
`belongs to the subscribers of the area in question or whether
`it is a visitor in the area. The switching centre MSC uses the
`stored data for controlling paging messages directed to
`individual mobile stations. The base stations constitute loca(cid:173)
`tion areas (LA) which represent the accuracy with which the
`location of a mobile station can be determined. When a 45
`mobile station MS moves from a location area to another, its
`location information is updated and the handling of the
`connection to the switching centre MSC is transferred to a
`base station BS in the new location area with a handover
`function.
`Next, we will discuss those parts in FIG. 2 that are located
`in the office environment and that constitute an entity
`according to the invention in the embodiment depicted in the
`figure. Inside the office, all communication occurs via a local
`area network LAN. The gateway computer 1 shown in the 55
`figure acts as a link between the local area network LAN and
`a mobile switching centre MSC. The interface 2 between the
`gateway computer 1 and the mobile switching centre MSC
`complies with the same A-interface standard that defines
`communication between ordinary base station controllers 60
`BSC and a mobile switching centre MSC, and therefore,
`from the point of view of the switching centre, the gateway
`computer 1 is just as any base station controller.
`Alternatively, the interface 2 between the gateway computer
`1 and mobile switching centre MSC can be implemented as 65
`a DSS. 1 + interface, as soon as the standardization for this
`new interface is completed. The new interface definition
`
`Ex.1005
`APPLE INC. / Page 8 of 13
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`7
`base unit 6 of the cordless telephone system is connected to
`the same local area network LAN as the other communica(cid:173)
`tion devices in the office. Secondly, an employee can be
`reached throughout the whole office area if she keeps the
`cordless phone with her, which is clearly an improvement
`when compared to the use of wired telephones. The base
`units 6 of a cordless telephone system are also provided with
`network adapter parts for local area network traffic.
`In certain cases it is desirable to use terminals in which the
`communication is based on an infared link. Thus brings
`certain advantages, e.g. that outside the direct visibility
`range the infrared link does not interfere with other similar
`connections and that the IR link does not reserve any radio
`frequencies. For these connections, it is possible to connect
`infrared base units 8 to the local area network LAN through
`which the communication required by terminals 9 using the
`infrared connection is directed to the local area network
`LAN.
`Naturally, in the implementation according to the inven(cid:173)
`tion it is possible to connect users' computers 10, servers 11,
`printers 12 and other such known network-compatible
`devices to the office's local area network LAN directly via
`wired connections. Particularly it is possible to connect to it
`gateway computers 13, which connect the local area network
`LAN to various public communication networks, such as a 25
`public wired telephone network, digital ISDN network,
`cable TV network or a public ATM network. Gateway
`computers and said other communication networks are espe(cid:173)
`cially used to arrange connections between home and small
`office users and the local area network in the office. We will 30
`discuss this later.
`Above, we have used the term 'local area network' in its
`current sense ( e.g. registered trademarks Ethernet and Token
`Ring). However, the transmission capacity of these known 35
`implementations is quite limited and therefore we have
`reason to assume that in the future corresponding
`transmissior-channels internal to a working environment
`will be realized as ATM connections or using other fast
`transmission methods. This will not result in changes in the 40
`architecture of the communication system according to the
`invention because the invention is not confined to any
`particular network implementation.
`FIG. 3 shows a home environment HE wherefrom the user
`has a connection to the local area network in the office in the 45
`manner according to the invention. The home environment
`includes a home base unit 14 (HEU) which is similar to
`those used as base stations for the nanocells 4a in an office
`environment. The home environment forms a special nano(cid:173)
`cell for the terminals 5 in the home environment, which
`nanocell can be placed in the system hierarchy under the
`control of the gateway computer 1 in the office and thus in
`the same location area as the base units in the office although
`it is located physically apart from them. FIG. 3 also shows
`a bridge-type gateway computer 13 which handles traffic 55
`between a public communication network 15 (not specified
`in the figure) and the local area network LAN in the office.
`The home base unit 14 is connected to the public commu(cid:173)
`nication network 15 which can be e.g. a wired telephone
`network, ISDN network, cable TV network (CATV) or an
`ATM network. It is advantageous to use a network which is
`already linked to the home environment, whereby the appli(cid:173)
`cation of the system according to the invention will not
`require the building of a new link.
`The home environment HE may also communicate with
`places other than the local area network LAN in the office.
`An ordinary wired phone TP may be connected to a wired
`
`8
`telephone network or via a local conversion unit 16 to the
`nearest base station BS of a cellular radio system and via it
`and a base station controller BSC to a mobilet switching
`centre MSC. In addition, the home base unit 14 may
`5 advantageously set up a connection via a public communi(cid:173)
`cation network 15 to any place available through it, e.g. via
`a special gateway station 17 to a mobile switching centre
`MSC.
`Next, we will discuss the practical implementation of
`10 elements in the system according to the invention and the
`characteristics required of them. The gateway computer 1
`must interconnect two very different communication
`networks, a local area network LAN and a cellular radio
`network, in this case a GSM network. From the point of
`15 view of the mobile switching centre MSC, the gateway
`computer 1 should operate just like a base station controller
`BSC and it has to carry out the necessary protocol conver(cid:173)
`sions between the GSM protocol and the protocols applied
`in the local area network LAN. Furthermore, as it operates
`20 as a base station controller between the ba