Telecommunication combination comprising a telepoint and a portable radio terminal

The invention relates to a combination of a switched telecommunication network, a telepoint connected to the network and a portable radio terminal constituting part of a residential equipment or an extension to a PABX, the portable radio terminal when served by a telepoint radio transceiver instead of its residential or exchange radio transceiver uses the telepoint and the network for calling its residential base radio station or PABX and reporting serving telepoint to a location store, calls to the portable radio terminal thereafter being transferred by the residential equipment or PABX through the network to the telepoint in accordance with information in the location store, whereby the portable radio terminal or cordless telephone may be called through the network and telepoint when in proximity of a telepoint.

TECHNICAL FIELD 
This invention relates to the technical field of telecommunication. More 
precisely the invention relates to a combination comprising a switched 
telecommunication network, a telepoint connected to the switched 
telecommunication network and a portable radio terminal. 
BACKGROUND OF THE INVENTION 
Many public switched telecommunication networks, PSTN, are in use. Recent 
switched telecommunication networks are based on digital technology and 
are designed to be able to transmit various kinds of information at 
various speeds, e.g speech or data or video. 
Public switched telecommunication networks, PSTN, generally comprise 
network subscriber stores for various information on subscribers to the 
network e.g identification, type, subscribed services, location or routing 
etc. 
Public switched telecommunication networks generally also comprise means 
for connecting subscriber equipment to the network, and means for setting 
up calls to and from connected subscriber equipment in accordance with 
information in the network subscriber store. Such means may comprise 
exchanges interconnected by trunks. 
When a public switched telecommunication network, PSTN, comprises plural 
distant local or transit exchanges there may be network subscriber stores 
at all local exchanges having allocated subscribers. 
Some subscribers to a telecommunication network may be residential 
subscribers having a residential equipment connected by cables to a local 
exchange of the network. 
Some residential subscriber equipments comprise a residential base radio 
station connected to the network by cable and a cordless telephone or 
portable radio terminal. The residential base radio station then comprises 
a residential radio transceiver for radio communication with the portable 
radio terminal or cordless telephone constituting part of the same 
subscriber residential equipment. This kind of residential subscriber 
equipment offers a user the freedom of making calls and receiving calls 
anywhere in his residence if within reach of his residential radio 
transceiver. 
Other subscribers to a switched telecommunication network may be business 
subscribers. The subscriber equipment may then be a private automatic 
branch exchange, PABX, connected by cable to the telecommunication network 
and plural terminals or telephones constituting extensions to the private 
branch exchange. 
Recently private automatic branch exchanges, PABX, comprising means for 
communication by radio with associated branch extensions have been 
suggested. The private automatic branch exchange, PABX, may then comprise 
an exchange switch connected by cable to a telecommunication network, 
exchange radio transceivers connected by cable to the exchange switch and 
portable radio terminals or cordless telephones for radio communication 
with the exchange radio transceivers. This kind of subscriber equipment 
may offer a staff the freedom of making calls and receiving calls anywhere 
in a business area of the subscriber if within reach of any of the 
exchange radio transceivers. 
Many mobile radio communication systems of various kinds have o been 
suggested and are in use for various purposes. Cellular mobile radio 
communication systems may cover a very large geographical area offering a 
user with a mobile station a possibility to make calls at office, in 
residential areas and in some vehicles. A disadvantage of some mobile 
communication systems is the high cost, weight and size of mobile 
stations, the operators high charge for becoming a subscriber and the high 
charge for a call compared to corresponding costs for a subscriber using a 
terminal connected by cable to a fixed telecommunication network. 
Telepoints have been suggested as a compromise between the low costs and 
low freedom of fixed telecommunication equipment and the high costs and 
freedom of cellular mobile radio communication systems. The telepoint 
concept offers users the possibility of small light-weight 
battery-powered- portable radio terminals for making calls anywhere via 
any fixed telepoint radio transceiver. The telepoint radio transceivers 
may be located at various places such as railway or underground stations, 
airports, pedestrian areas, squares, in official buildings etc. They are 
connected by cable to a switched telecommunication network. The telepoint 
concept requires comparatively little power consumption at the portable 
radio terminals whereby frequent change of battery is obviated. 
Information on UK telepoint standard may be found in "MPT 1375, COMMON AIR 
INTERFACE SPECIFICATION", DETMENT OF TRADE AND INDUSTRY, LONDON 1989. 
One major disadvantage of suggested telepoint systems is that a subscriber 
in proximity of a telepoint transceiver can not be called by an other 
subscriber to the telecommunication network to which the telepoint 
transceiver is connected. Thus a user of a radio terminal for telepoints 
can make calls but not receive calls. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide means enabling a 
subscriber to a switched telecommunication network with a portable radio 
terminal constituting part of a residential equipment or constituting an 
extension to a private branch exchange connected to the telecommunication 
network to use his portable radio terminal both for making calls and 
receiving calls at a telepoint connected to the telecommunication system. 
Another object of the present invention is to provide a roaming function 
between various kinds of subscriber equipment connected to a public 
switched telecommunication network without introducing new procedures or 
means in the switched telecommunication network. 
Still another object of the present invention is to provide means enabling 
both way call initiation at telepoints connected to a telecommunication 
network. 
According to the invention existing network subscriber stores in a 
telecommunication network and/or new location stores in private branch 
exchanges or residential base radio stations are used for keeping track of 
portable subscriber radio terminals constituting extensions to the private 
branch exchanges or part of residential equipment. 
According to the invention a portable radio terminal of a subscriber 
residential equipment comprises means for scanning of radio channels used 
by the residential radio transceiver or exchange radio transceiver or 
telepoint radio transceiver, means for receiving radio signals at scanning 
and determining from received radio signals information on identity of 
transmitting transceiver, if any, means for choosing as serving 
transceiver a transceiver of appropriate received radio signals, if any, 
and means for calling via a telepoint transceiver or a branch exchange 
transceiver the residential base radio station constituting part of the 
same subscriber equipment or the network subscriber store and reporting to 
the residential location store or the network subscriber store the 
identity of serving radio transceiver when other than the residential 
radio transceiver constituting part of the same subscriber residential 
equipment. 
According to the invention a portable radio terminal constituting an 
extension to a private branch exchange comprises means for scanning of 
radio channels used by exchange radio transceiver or telepoint radio 
transceiver, means for receiving radio signals at scanning and determining 
from received radio signals information on identity of transmitting 
transceiver, if any, means for choosing as serving transceiver a 
transceiver of appropriate received radio signals, if any, and means for 
calling via a telepoint transceiver the private branch exchange to which 
the portable radio terminal constitutes an extension or the network 
subscriber store and reporting to the exchange location store or the 
network subscriber store the identity of serving radio transceiver when 
other than one of the exchange radio transceivers constituting part of the 
same branch exchange. 
According to the invention the switched telecommunication network sets up a 
call to a subscriber according to the subscriber information in the 
network subscriber store. 
According to the invention a residential base radio station, receiving a 
call to the portable radio terminal constituting part of the same 
subscriber equipment and having reported to the residential location store 
an other serving radio transceiver than that of the same subscriber 
equipment, forwards the call to the branch exchange or telepoint 
comprising the serving radio transceiver. 
According to the invention a branch exchange, receiving a call to a 
portable radio terminal constituting an extension to the branch exchange 
and having reported to the exchange location store an other serving radio 
transceiver than one of the exchange radio transceivers of the same branch 
exchange, forwards the call to the telepoint or residential equipment 
comprising the choosen serving radio transceiver. 
According to a preferred embodiment of the invention plural telepoint radio 
transceivers are connected to the switched o telecommunication network via 
a telepoint transceiver controller.

PREFERRED EMBODIMENTS OF THE INVENTION 
FIG. 1 illustrates a public switched telecommunication network, PSTN, and 
various kinds of subscriber equipment connected to the network. The 
network comprises network local exchanges, LNX1 to LNX8, to which 
subscriber equipment may be connected by cables, network transit 
exchanges, TNX1 and TNX2, for switching calls, and network trunks, NT, for 
interconnection of local and transit exchanges. 
The local and transit exchanges may comprise multiplexors, demultiplexors, 
processors ,stores as well as other usual network means. In particular the 
network may comprise at least one network subscriber store for information 
on subscribers to the network. Each local exchange may comprise a network 
subscriber store, NSS, for information on subscribers allocated to that 
local exchange, in particular subscribers having subscriber equipment 
connected to that local exchange by cables. 
Exchanges of the network also comprise network information stores, NIS, for 
information on the network, in particular information on trunks to other 
exchanges, numbering, routing etc enabling exchange processors to set up 
calls to and from subscribers and disconnect calls. Local exchanges may 
also comprise means for transferring calls from a subscriber to an other 
subscriber. 
Eleven residential subscriber equipments, RSQ1 to RSQ11, are connected by 
cables to the local exchanges LNX1 to LNX5 and LNX8 of the network. Five 
private automatic branch exchanges, PABX1 to PABX5, are connected by 
cables to the local exchanges LNX2 and LNX5 to LNX8 of the network. Five 
telepoint radio stations, TSN1 to TSN5, are connected by cables to the 
local exchanges LNX4 and LNX5 and LNX7 of the network. Three telepoint 
transceiver controllers, TTC1 to TTC3, are connected by cables to the 
local exchanges LNX3 and LNX6 and LNX8 of the network. At least in some 
aspects the RSQ, the PABX, the TSN and the TTC may all be considered as 
various kinds of subscriber equipment connected to the PSTN. The local 
exchanges network subscriber stores NSS comprise information on the 
subscribers having the equipment connected to them. In particular the 
stores may comprise information on type of subscription, e.g residential 
or business or telepoint, type of equipment connected, eg RSQ or PABX or 
TSN or TTC, and number of lines or bandwith connected to the network, e.g 
single analogue line, 64 kbit digital line, 1 Mbit digital line etc. 
FIG. 2 illustrates a kind of residential subscriber equipment of particular 
interest to this invention connected to a PSTN. The residential equipment, 
RSQ, comprises a residential base radio station, RBS, connected to the 
PSTN by cable, and a residential portable radio terminal, PRT. The 
residential base radio station comprises a residential location store, 
RLS, for information on the portable radio terminal and a residential 
radio transceiver, RTR, for radio communication with the portable radio 
terminal. When a subscriber uses his residential portable radio terminal 
in his residence the portable radio terminal and the residential radio 
transceiver may cooperate in a well known way transmitting radio signals 
when setting up a call, during an ongoing call and when terminating a 
call. To the user the portable radio terminal and the residential radio 
transceiver may then appear to operate substantially in accordance with 
known residential cordless telephones. When a subscriber uses or has used 
his portable radio terminal distant from his residence but in proximity to 
an other radio transceiver, the portable radio terminal and the 
residential radio transceiver may however operate somewhat differently to 
be described later on. 
FIG. 3 illustrates a private automatic branch exchange, PABX, of particular 
interest to this invention connected to a PSTN by cable and portable 
exchange radio terminals, PRT, constituting extensions to the PABX. The 
PABX comprises an exchange switch, XSW, an exchange location store, XLS, 
for information on portable radio terminals constituting extensions to the 
PABX, an exchange processor, XCP, and exchange radio transceivers, XTR, 
connected to the exchange switch by cables. The exchange radio 
transceivers are preferably plural channel transceivers. The exchange 
radio transceivers are located at various sites in the business area of 
the PABX subscriber for radio communication with the portable radio 
terminals constituting extensions. When setting up a call to or from a 
proximate portable radio terminal, during an ongoing call involving a 
proximate portable radio terminal, and when terminating such a call an 
exchange radio transceiver transmits radio signals to the portable radio 
terminal and receives radio signals from the portable radio terminal in a 
way similar to what is known in connection with cellular mobile radio 
systems. The PABX and the portable radio terminals cooperate to enable 
portable radio terminal roaming and handoff within the area covered by the 
exchange radio transceivers. The radio communication between the exchange 
portables and the exchange transceivers may incorporate known dynamic 
channel allocation procedures and known roaming and handoff procedures 
appropriate in comnnection with dynamic channel allocation, in which 
procedures decision on choice of serving transceiver and channel and 
handoff is taken by portable terminal. The PSTN is not at all involved in 
channel selection, roaming or handoff for a portable radio terminal served 
by an exchange radio transceiver of the PABX. 
FIG. 4 illustrates a telepoint radio station, TSN, connected by cable to a 
PSTN. The telepoint radio station comprises a telepoint-network interface, 
TNI, a telepoint store, TS, a telepoint processor, TPC, and a multi 
channel telepoint radio transceiver, TTR. The telepoint radio transceiver 
may be similar to an exchange radio transceiver. When setting up or 
terminating a call from a proximate portable radio terminal the telepoint 
radio transceiver and the rest of the telepoint radio station may 
cooperate with each other and the PSTN in accordance with well known 
telepoint procedures. The telepoint radio transceiver and the rest of the 
telepoint radio station may however also cooperate with the PSTN in 
setting up a call from the PSTN to a proximate portable radio terminal in 
a way to be described later on. 
FIG. 5 illustrates a telepoint transceiver controller, TTC, connected to a 
PSTN by cable and controlling plural telepoint radio transceivers, TTR, 
connected to the telepoint transceiver controller by cables. The telepoint 
transceiver controller comprises a network-controller interface, TNI, a 
telepoint controller store, TCS, and a telepoint processor, TPC. Each 
telepoint radio transceiver connected to the transceiver may be similar to 
the radio transceiver of the telepoint station according to FIG. 4. When 
setting up or terminating a call from a portable radio terminal, in 
proximity of one of the telepoint radio transceivers connected to the 
transceiver controller, the portable radio terminal, the telepoint 
transceiver and the controller may cooperate with the PSTN in accordance 
with well known telepoint procedures. The telepoint transceiver 
controller, the telepoint radio transceivers and the portable radio 
terminals cooperate to enable portable radio terminal roaming and handoff 
when within the area covered by radio transceivers connected by cables to 
the same transceiver controller. The procedures include dynamic channel 
allocation and decision on serving radio transceiver and channel at 
portable radio terminal identical with or similar to correspondeing 
procedures at the PABX according to FIG. 3. The PSTN is not at all 
involved in radio channel selection, roaming or handoff for a portable 
radio terminal served by a radio transceiver connected by cable to the 
TTC. The transceiver controller and its connected radio transceivers may 
however also cooperate with the PSTN and a portable radio terminal in 
setting up a call from the PSTN to a portable terminal served by one of 
the radio transceivers connected to the transceiver controller in a way to 
be described later on. 
FIG. 6 illustrates a portable radio terminal PRT which may be part of a 
residential subscriber equipment according to FIG. 2 or may constitute an 
extension to a PABX according to FIG. 3. The portable radio terminal 
comprises input/output means, I/O, comprising at least one of keypad or 
microphone or display or loudspeaker or printer. The portable radio 
terminal also comprises a portable terminal store, PTS, a portable 
terminal computer, PTC, and a portable radio terminal transceiver, PTR. 
The portable radio terminal is intended to be able to be used not only at 
subscribers residence, if constituting part of residential equipment, or 
in subscribers business area, if constituting an extension to a PABX, but 
also proximate to a telepoint radio transceiver. Each residential radio 
transceiver and exchange radio transceiver and telepoint radio transceiver 
frequently scans and transmits radio signals on at least one of a 
predetermined group of radio channels. The radio signals from such a 
transceiver comprises information on transmitter identity and in 
appropriate cases PABX identity or TST identity or TTC identity. The radio 
signals may also comprise information on channels available at transceiver 
and the order in which the transceiver scans radio channels for receiving 
signals from portable radio terminals. An exchange radio transceiver or a 
telepoint radio transceiver may page a portable radio terminal by 
transmitting radio signals comprising identity of paged terminal on at 
least one of the radio channels. 
A portable radio terminal frequently scans one or more or all of the radio 
channels of the predetermined group for receiving radio signals from 
proximate residential or exchange or telepoint radio transceivers, if any. 
Sometimes there are no radio signals or all or some of the radio signals 
are too weak or disturbed by noise or interfering signals. When receiving 
appropriate radio signals the portable radio terminal determines from 
received radio signals the identity of transmitting radio transceiver and 
possible other information on channels available etc. The information is 
stored in the portable terminal store separately for all present or recent 
active transmitters and is updated with more recent corresponding 
information obtained at subsequent scanning. Based on the strength and/or 
quality of radio signals received and/or other information on transceiver 
in the portable terminal store and possibly also predetermined rules the 
portable terminal computer chooses as serving transceiver a transceiver of 
appropriate radio signals received. When there are more than one possible 
choice the rules may give priority to possible transceiver of same 
subscriber equipment. 
According to the present invention a portable radio terminal, choosing as 
serving transmitter a transmitter of a telepoint radio station or a 
transmitter connected to a telepoint transceiver controller, tries to 
inform a subscriber location store on choosen transceiver. This may be 
done automatically by the portable radio terminal or only after manual 
actuation of a pushbutton by the terminal user. If the radio terminal is 
part of a subscriber residential equipment the portable radio terminal 
tries to set up a call to the corresponding residential base radio 
station. The call is set up using the telepoint radio station or 
transceiver controller of the serving radio transceiver and the PSTN. The 
call set up procedure may be in accordance with well known telepoint call 
set up procedures. When the residential base radio station answers the 
call the portable radio terminal initiates transmission of a coded message 
comprising information on identity of calling portable radio terminal, 
network subscriber number of telepoint station or controller of choosen 
serving radio transceiver, and possibly also identity of serving radio 
transceiver. The residential base radio station stores at least the 
information on network subscriber number of telepoint station or 
controller of serving radio transceiver in the residential location store. 
Whenever thereafter receiving a call for the portable radio terminal the 
residential base radio station forwards the call to the network as a call 
for the telepoint radio station or the telepoint transceiver controller of 
the serving radio transceiver in accordance with the information in the 
residential location store. 
A portable radio terminal constituting an extension to a PABX according to 
FIG. 3 tries to call the PABX after choosing as serving radio transceiver 
an other transceiver than one of the radio transceivers of the PABX. This 
is normally done automatically but may be initiated by the terminal user 
by actuating a pushbutton or other device on the terminal. The call is set 
up using the PSTN and serving transceiver and associated radio station or 
controller. The call set up procedure may be in accordance with well known 
telepoint or PABX or residential call set up procedures. When the called 
PABX answers the call the portable radio terminal initiates transmission 
of a coded message comprising at least information on identity of portable 
radio terminal and network subscriber number of residential or telepoint 
station or controller of choosen serving radio transceiver and possibly 
also identity of serving radio transceiver. The PABX stores at least 
information on identity of portable radio terminal and network subscriber 
number in the exchange location store. Whenever thereafter receiving a 
call for the portable radio terminal the PABX forwards the call to the 
network as a call for the telepoint radio station or the telepoint 
transceiver controller or the residential base radio station of the 
serving radio transceiver in accordance with the information in the 
exchange location store. 
A call for a portable radio terminal forwarded by a residential base 
station or a PABX to the network as a call for a telepoint radio station 
or telepoint transceiver controller is forwarded by the PSTN in the same 
way irrespective of which portable radio terminal is intended to be the 
final call receiver. The call is answered by the telepoint station or 
transceiver controller as any call. When the telepoint radio station or 
transceiver controller has answered the call the residential base station 
or PABX having forwarded the call transmits information on identity of the 
portable radio terminal intended to be the final receiver of the call. 
This information on identity may be the network subscriber number or the 
branch extension number of the portable radio terminal. For establishing 
contact with the portable terminal the portable radio terminal must be 
paged by serving telepoint radio transceiver. If the portable radio 
terminal is served by a radio transceiver of a telepoint station having 
only one transceiver, paging is done from this transceiver only. If the 
portable radio terminal is served by a radio transceiver of a transceiver 
controller and has reported to the location store the network subscriber 
number of the controller there is more than one possible radio 
transceiver. The transceiver controller then initiates broadcast paging of 
the portable from all radio transceivers connected to the transceiver 
controller. 
The portable radio terminal receiving the paging signals sends a response 
to its choosen serving radio transceiver. The response is forwarded by the 
radio transceiver to the transceiver controller. The transceiver 
controller then forwards the call to the serving radio transceiver for 
radio communication with the portable radio terminal. The call is then 
establised all the way to the portable radio terminal intended. 
A residential portable radio terminal may be served by an exchange radio 
transceiver and be called there in a similar way if reporting to its 
residential location store a network subscriber number of the PABX in a 
similar way. Furthermore a portable radio terminal constituting an 
extension to one PABX may be served by an exchange radio transceiver of an 
other PABX. For this purpose there may be a couple of vacant extension 
numbers at each or some PABX for use by visiting residential or exchange 
portable radio terminals. When served by an exchange radio terminal a 
visiting portable radio terminal may be allotted one of these vacant 
extension numbers. The visiting portable radio terminal then reports this 
alloted extension number to its residential location store. 
A portable radio terminal having reported to its residential or exchange 
location store an other serving radio transceiver than its residential or 
exchange transceiver may thereafter leave the area covered by this 
transceiver and return to the area covered by its residential transceiver 
or one of the exchange radio transceivers of its PABX. When returning and 
receiving appropriate radio signals from its residential radio transceiver 
or one of the exchange radio transceivers of its PABX the portable radio 
terminal chooses this transceiver as serving transceiver and transmits a 
radio signal comprising a particular reentry message. The reentry message 
comprises information at least on identity of portable radio terminal and 
preferably also information on previous serving transceiver. When 
receiving this information from its transceiver the residential radio base 
station or the PABX changes the information on the portable radio terminal 
concerned in its location store accordingly. 
A PABX having a couple of vacant extension numbers for temporary use by 
visiting portable terminals may have appropriate means for temporary 
withdrawing from use such a vacant extension number previously allotted to 
a visiting portable terminal when the portable terminal is no longer 
served by an exchange transceiver of the PABX. Such means may comprise 
means for paging of assumed still visiting terminals with allotted 
extension numbers in order to check whether the visiting terminal with 
allotted extension number is still in proximity of one of the exchange 
transceivers of the PABX. An assumed visiting portable terminal not 
responding to such a paging may have its allotted extension number 
wuthdrawn from use. In order to be able to later on allot the withdrawn 
extension number to an other visiting portable terminal the PABX may call 
the residential base radio station or PABX of the visiting portable 
terminal and inform its location store on the withdrawal of the use of the 
extension number by the portable terminal. The PABX does not allot the 
withdrawn extension number to an other visiting portable terminal until 
the called residential base radio station or PABX has answered the call 
regarding withdrawal of allotted extension number or after a long timeout, 
whereby two portable terminals using same extension number is avoided. 
Some PSTN comprise means for transferring calls from a called subscriber to 
another subscriber. Such call transfer means may be used by a subscriber 
visiting an other subscriber and wishing to receive his calls at the 
visiting subscriber. A PSTN comprising call transfer means comprises a 
call transfer store for receiving from subscribers information on other 
subscribers where they want their calls. For the purpose of call transfer 
a subscriber normally transmits to his local station a message comprising 
information on the network subscriber number(s) of the subscriber where he 
want his calls. After receiving such information the PSTN does not forward 
a call to a subscriber in accordance with the normal information in the 
network subscriber store but forwards any call to the subscriber in 
accordance with received information stored in the call transfer store. 
A telepoint radio station or a telepoint transceiver controller may also 
store identity of served portable radio terminals and frequently page 
assumed served portable radio terminals for checking their presence in a 
similar way. The telepoint waits for answers to such paging of assumed 
served portable radio terminals. When not receiving a response to a paging 
of a portable terminal the telepoint sets up a call for reporting to 
appropiate location store the identity of the assumed served portable 
terminal not answering to such paging. The information in the location 
store may be changed accordingly. Call transfer means in a PSTN may be 
used simultaneously with or instead of location stores in residential base 
station or PABX for transferring calls from a subscriber site to a 
telepoint station or controller. When used instead of such location stores 
the portable radio station is programmed to call a network number 
dedicated to the call transfer means instead of its owm network subscriber 
number for rapporting serving radio transceivers. Neither when the call 
transfer means of the PSTN is used together with the location store nor 
when the call transfer means of the PSTN is used instead of the location 
stores must there be any amendments of the PSTN in order to be able to 
call a portable radio terminal served by a telepoint radio transceiver. 
The invention is neither restricted to described embodiments of PRT or RBS 
or TSN or TTR or TTC or XTR or PABX nor to the particular PSTN described 
but may be implemented in somewhat different ways.