Note: Descriptions are shown in the official language in which they were submitted.
~12 vl ,S ~ 7i
SYSTEM FC)R I MPLEMENTI NG ~XTENSI ON PHON13S ~: .
WI THI N A CELLULAR RADI O TELECOMMUNI CATI QNS SYSTEM
. ~
BAC~GROUND OF THE I NVE:NTI ON -
Hi~ry o:f .th~ P;~iQr Ar~
Cellular radio commuIlication ~ervice i~ defined and
specifi d by a plurality of industxy standards adopted by
group~ coDIprised of both manufacturer~ and operators of
cellular ~y~tems. For example, the EIA/TIA requ~rements
:10 ~ as t forth in Standard IS-41-B provide that a call
within a cellular radio ~y6tem i~ initially routed to ~
particulax mobile switching center ~(MSC) in accox~ance
with location data identifying the call ed mobile s~ation
- :: (MS) wh~ch is stored in the home location regis:ter lHLR)
: of that p~rt~cular ub~criber. Thersafter, pa:ging of the
called ~obile ~tation takes place in the MSC to which the
c~ routed and, if the locatio~ data ~tored in the --
HLR i8 aorrec:t and th~ ~obile ~ta~ion i8 currantly ~n an
~: ~cti~e a~l ps:~wer~d on s~a~e, the MS respoIld~ to the page
a~d the call ~ill be co~pleted.
Another~recen~ 13IA/TIA Standard, IS-53, contemplates
that exten~ion phones may be providsd to mobile stations
.. within the cellular sy~t~m. In such a~ implementatlon,
a ~ingle directory number withir~ the 6y~tel~l would be
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associated with two or more individual mobile stations,
each of which would have a different mobile
identification number (MIN) and a different elec~ronic
serial number (ESN). Thus, in order to provide extension
phone ~ervice, the HLR must keep separate ~ets of
location data for each of the two or more mobile units
that have been: ~as~igned tho Bame directory numbGr. The
idea behind cellular exte~ion phone aer~ice specified by
; IS-53 i~ that the two or ~ore extension phones would be
:' 10: ~ paged simultaneouBly and the call would be completed to
the fir~t extension phone to respond. I f the extension
: :phones are locatod within an area served by the same MSC,
a: call~ to a directory: number associated with two or more
: ~ extension phonefi could be completed by simultaneou61y
15~ ~ pagi;ng each of thos~e extension phone~ in that MSC and
then completing~the call to the first one that re~ponds
in acaordance with:IS-41-B. However, if one or more of
:::: the extension: phone~ :a~ociated w1th the sa~e directory
number are looàted in different MSCs, such implementation
20~ o~f extension phone~service is not po~ible. That is, a
call cannot be,~routed to more than one MSC at the same
time ial current ~cellular networks.
::The~provl~ion of: extension phone service within a
:mobile radio ;oommuni~catic)n system, ~uch as a cellulax
25~ y~te~or a persona~l com~unication ~y~tem (PCSl, would ~e
very useful:in~a:number of di~f~rent applications. For
example, a cell;ular ~ sub~cribQr ~ may want to have only a
single.directory~number a~slgned:to hi8~her service, but
~:: yet receive~cal~ls o n a~obile station installed in a car
30:': when i~ is being used and on a transportabls/portable
in~trument on other occasion Thi~ would prov.ide an
optimum ~leve 1 o~ ~convenienoe for ~uch a ~ubscriber and
simplify both: the~ ~ cost and ~ervice by only requiring a
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single directory number~ In other applications of
cellular extension phone service, a Bervice provid~r such
as a delivery service, or an emergency ambul ance ser~rice,
may desire to have only a ~t ngle directory li~ting for
calls for it~ ~ervice yet have such call~ directed to and
responded to by either the UTlit which was nlO8t r~adily
available ox tha unit which was phy3ically close~t to the
perso~ reque~ting the service from the provider. Such an
imple~sntat~ on would greatly enhanc~ the efficiency of
:lO fiuch service provider~ and ~nable, ln the casQ of
: ~ e~ergency ervice~such as~ambulance, fire, poli~e, etc.,
an éfficient directing of ~ervice re~ue6ts to those able
to provide the most rapid re~ponRe.
The~ syste~ of the preæent invention enables ths
:~ 15 ~ implementation o~E extension phons ~ervice within 2 mobile
radio communication ~yRtem~ in a way which is hi~hly
: ~ efficient and effective.
SUMMARY OF TH~ INVENTION
~: ~ 20 ~ In one aspect, the present invention provides the
assignment of a sing1e directory number to two or more
mo}:ile~ station~ each having different MINB. When a call
recsived by~ the HLR to which that directc~ry nu~er is
a~igned, a pagin g mesBage i~ ~en~ to each MSC: within
25: :~ which ~ach of ~the extension pho~e ~obile ~tations is
hown to be located:within th~ record~ of the HLR. The
mobile stations~are paged in each MSC. The call is
routed to ~he MSC within which the first mobile station
to re~pond to the~page ia located and the call completed
~30 : to tha~ station whether or not it is the only station
responding or the fir~t of a plurality stations which may
re~ pond. ~:
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In another aspect, the sy~tem of the pre6ent
invention pages each mobile station extension a~sociated
with the direatory number being called ~imultaneously,
but routes the call ~o the MSC of the mobile station
which is geographically closest to the ~all~ng party.
In a ~till further aspect, the invention include~
providing extension phone service within a mobile radio
communlcation 8ystem by as~ociating a plurality of
moblle station~, each haYing a u~iqu8 identification,
~ 10 with a slngle ~ubscriber nu~ber. A call received at an
: ~ exchange i d$rected:to the 6ubscrib~r number with which
a plurality of mobile stations are associated. A list of
parameters i8 maintained in a databaRe which identifies
each mobile ~tatlon associated with the ~ub~criber number
and the exchange within which each of ~he mobile ~tations
; is ~believed to be ourrently located. A routing request
message is sent to:the location within whlch each mobile
station 1~ ~peclfixd in the databa~e as currently being
: 1OGa~ed. Each mobile 6tation is paged in the exchang~ at
~.
~ ~which a routi~g regue~t wa~ received. An indication as
:to which one~ ~f~th~ mobile ~tatlo~s have re~ponded to a
page i received at the call recelving exchange and the
all i8 8el~tively routad to one of ~he mo~ile ~ations
a~: to which a~ page~ responae was received.
:: 25 ~ yet another aspect of the i~ye~ivn, &,all~ are
: ~ routed within a~ radl~eY~'whic~a~ingle
sub~criber number may bz associ~ted with one or more
mobile ~ta~ions, each having a unique mobile
ident$fication number. A location r~quest me~sage is
~:~ 30 received fro~ à~ intPrrogation ~xchange indicative of a
: call to a 6ub~cribar having a sLngle sub8crib~r number.
~hether or not there i~ more than ons ~obil~ station
: ~ a8~0ciated wlth the ~ingle subscriber nNmber for which
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:
the location reque~t me~sage was received is determined.
The call is completed to the mobile ~tation in re~ponse
to a determination that there is only one mobile station
a~ociat~d with th~ ingle subscriber numbe~ In
5 / response to a determlnation that th~re i~ more that one
mobile station identification number associated with the
single subscriber number, a routing request mes~age for
: ~ each o~ the assoolsted mobile station identification
numberR is sent~ to the curren~ location at which the
: mobile station ~ s believed to be located. Each mobile
tatlon identification number i~ page at the location in
response to the ~ receipt of a routing request message.
: The receipt of page re~poDses from each of the page~ is
monitored for;a preselected period of ti~e and a recovery
15~ pro~eaure is initiat~d in response to failure to receive
any:~page respon~es dur1ng ~he preselected period of time.
The call~is completed~to the mobile 6tation from which a
page re ponse i~ recs}ved in respon~e to the rec~ipt of
only~ sne page respons:e. A call routing decision is made
20~ in a~ccordancn ~wlth ~predefined criteria in r~sponse to the
receipt ~of more ;than one :page ~e3pon~e from the paged
mobile st~tions ~ and ~ the call is routed from the :
interrogatio~ exahange to one of the ~plurality of mobile
stations in aoc~rdance with thn call routing decision.
BEU EF DESCRI PTI OlI OF THE D~WI NGS
For a~ more cs~mplete~ under~tanding of the ~?re~ent
inyention and for:further objects and advantag~s thereof~
reference may now b~ had to the foll~owing description : ~,
3 0 : : `: taken ~ n conjunction with th~ accompanying drawing~, in
which~
. 1 1s;a;pictorial representation of a cellular ~-
radio communication syste~ including a mobile switchiny
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center, a plurality of base stations, and a plurality of
mobile stations;
FIG. 2 is a block diagram illustrating the routing
of callQ within a cellular radio telecommunications
system in acaordance with prior art routi~g standards;
FIG. 3 is a mes~ag~ ~xchange diagram illu6trating
the routi~g of a call within a cellular radio
telecommun~cations ~ystPm in accoraance with prior ar~
routing standard~;
FIG. 4 is a flow chart illu~trating cellular
extension service provided in accordance with ~he present
i nventi on; and
FIG. 5 is an illustrative diagram setti~g forth one
aspect of the in~lement:ation of extensiorl phone service
in a cellular raaio telecommunications ~ystem in
~ccordance with the teachings of the present inverltion.
; : DETAILED DESCRIPTION
Refexring fir~t to FIG. 1, there is illustrated a
conventional cellular radio communications syst~:m of the
typ~ to which the pre~ent invention generally psrtaills. ~:
In FïG. 1, an arbi~rary geographic area may be diviaed
into a plurality of continuous radio covs3rage areas, or
~: cell~ C1-C:10. ~ While the system of FIG. 1 is
us~ratively sho~ tc> i~clud~ only ~0 cell~ and 1 MSC, ::
it should b~ clearly u~d~rsts:30d that in practice, the . .-
number o~ MSC8 and cell~ within ~ach MSC will be much: ~ ~
1 axger. : - .
Associated wlth and located within each of the celLs
C1-Clû is a bass station a~signed as a corresponding one::
of a plurality of ba6e 6tation~ Bl-B10. 33ach of the ba~e :~
stations BloB10 include a tran~ter, a receiver, and a
ba~e ~tatio~ controller a~ arla well known in the art. In
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FI G. 1, the bas e 6 tati ons B 1 -B 10 are i l l u~ trati vel y
loca~ed at the center of each of the cells C1-C10,
respectively, and are equipped with omni-directional
antsnnas. However, in other configurations of a cellular
radio ~ystem, the base stations B1-B10 may be located
n ar the periphery, or otherwise away from the center~ of
the c~lls C1-C10 and ~ay illuminate the cells C1-C10 with
radio signals either omni-dir~ctionally or directionally.
Thersfore, the repre~entation of the cellular radio
ystem of FIG. 1 i~ for purposefi of illustration only and
is not intended a~ a limitation on the po~ible
implementations of the cellular radio Ry~tem within which
the By tem of the present invention i8 implemented.
With continuing reference to FIG. 1, a plurality of
: 15 mobile station~ M1-M10 may be found within the cells Cl-
C10. Again, on1y lO mobile stations a~e shown in FIG. 1
but it ~hould~ be~understood that the actual number of
mobile:station~ will be mu~h-larger in practice and will
invariably~greatly exceed the number of base ~tatio~.
2~0 ~ ~ Moreover, while none of the mobile stations M1-M10 may be .-
f~ound in ~ome of tha c~lls C1-C10, the pre~ence or
ab~ence of the~ mobile tation~ M1-M10 in any particular ~:
: : .
: o~ of the c~ C1-C1:0 should be under~tood to depend,
in prac~ice on~the individual de~ires of the mobile
~:f25 ~ statlon~ M1-MlO who may roam from one loaation in the
; cell to another~or from one c811 to an adjacent cell or
~eighbo~ing cell, ~and, in addition, from one cellular
radio ~y~tem served by a particular MSC to another ~uch
ey~tem served by a different MSC.
Each of the ~mobile stations Ml-M10 i~ ~apable of
ini~iat~ng or receivi~g a telephone call through one or
more of the ba~e~station~ Bl-B10 and a mobils ~witching
center MSC. A mobile ~wntching center MSC is connected
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by communication links, e.g., cables, to each of the
illustrative base station~ B1-B10 and to ths fixed public
~wi~ched tslephone network PSTN, not shown, or a similar
fixed network which may include an integrated services
digital network (ISDN~ facility. The MSC ~hown is al~o
connected to other MSCs making up the cellular radio
~ystem n~twork. The relevant con~ecttons between the
: mobile switch1ng center MSC and the base stations Bl-B10,
or between the: ~mobil e switching center MSC and the PSTN
or ISDN and other MSC~, are not completely ~hown in ~IG.
1 but are well known to those of ordinary skill in the
art. Si mi 1 arl Y, i t i s al 6 0 known to include more than
one mobil~ switching: center in a cellular radio system
~: ~ and to~connect each additional mobile switch~ng center to
15~ a different group of ba6e stations ~nd to other mobile
switching centerR ~ia cable or radio links .
Each of the ce11s C1-C10 is allocated a plurality of
voice ~or speech channel~ and at lea6t one access or
con~rol channel,~ such a~ a forward control channel
~ ~FOCC), The control channel is used to control or
: supervise the operation of mobile stations by means of
~; : information transmitted to and received from those unit~
Such i~formati;on ~may include inco~ing call signals,
outgoing call ~ignal~, page signals, pa~e response
25: ; ~ signals, location; registration ~ignals, voice channel
a~ign~ents and :maintenance instructions. The control or
voice channels may operate either in an analog or digi~l
mode or a ~combination thereof.
: ~ Ref~rring next to FIG. 2, there i3 ~hown a block
diagram of a~ :portion of a cellular radio ~y~tem
illu~tratiny the routing of inco~ing c:all~ within that
sy~tem in ac~ordance with EIA/TIA IS-41. In suah call
completion procedures, a call received for a directory
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number assigned to a mobile station is received at an
interrogation exchange 11 which ~ends a location request
~ignal 12 to the home exchange or home location register
(HLR) a~sociated with the mobile station to which the
S call i8 directed 13. rhe home exchange or HLR co~sults
its database to determlne the current phy~ical location
of the mobile station assigned to the directory number
; bein~ called and identifies a particular v~ited exchangeor visited location register within the sygtem a~ the
current location of the called mobile station. A routing
request î4 is sent to the vi~itea location register or
visited exchange 15. Referring in more detail to the
message exchange diagram ~hown in FIG. 3, the visited
: : lo~ation register or ~i~ited exchange 15 ~ends a routing
~ reque~t~rsturn :re~ult 16 to the H~R 13, such me~sage
i~cluding a temporary routing number. The HLR 13
forward the: temporary routing number in a lscation
request return result me3sage 17 to the interrogation
~ :: :: : :
exchange 11.~ ~he call i8 then ~outed to the current
: ;~ location of: the mobile 18 where it is paged 19 and the
: c:all:completed to the mobile i~ it respo~d~ to the page.
A~ illu~trated in FIGS. 2 and 3, paging of a mobile
station in~acoord~nce with IS-41 doas not occur until
after the call ha~ been rout~d to the vislted exchanse.
;25 ~ Thu8, in the ~ttemp~sd i~pla~entatio~ of extension phone
~ service within ~a cellular radlo 6y8te~ a3 func~ionally
: defined by IS-53, two aifferent mobile ~tation~ a~signed
the same directory number cannot be ~aged eimultaneously
unleRs bo~h 8tatio~B are loca~ed in the same exchange.
~, .
30 ~ Of cour~e, ona csuld first routs the call to ar~ exchanye
where a fir8t moblle station assigned to th~3 directory ;~
number waR belie~ed to b~ located, pagE3 that mobile in
~hat ~xchange and wait for it to respo~d and then, only ~-
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aftsr failure to receivs a page ~esponsQ, advise the
interrogation exchange to reroute the call to a se ond
exchange where another mobile station extension assigned
to that directory number wa6 believed to be located.
S Such a proce~s would be highly cumber~ome, ~low, ~nd
inade~uatQ to supply the needs of the ~ellular radio
industry.
~ t~chni~ue used in the ~ystem of the present
invention i6 that of paging to locate a ~obile statlon
within a visitod exchang2 prior to the routing of the
call to that exchange. Thus, if the ~obile station fails
to an~wer the page, the call i8 never routed to the
visited exchange ~aving substantial co~t and time. Such
techniqueæ arc de cribed in co-pending U.S. patent
application ~erial no. 07/756,487, filed September 25,
1991, entitled "Apparatus and Method of Directing Calls
:: to Mobile Telephone Subscribers~', in the name o~ John
.: -
~: Hayes, et al. and U. S. patent applicati~n ~erial no.
: û7~516, 122, filed April 27~ 1990, entitled "Multi~
Exchange Paging System for Locating a Mobile Telephone in
a Wide Area Telephone Network", in the na~e of ~ancy
Buhl, et al., both of which are as~igned to the as~ignee
: ~ of ~he pre~ent invention and incorporated by r~ference
here~ n.
25~ In the present yste~, ~hen a call direct~d to a : mobile ~ubscriber i~ received at an inte~rog~ion
..
exchange, the HLR~ of that ~ubscriber i~ consulted to `.
obtain information . identify1 ng the MSC ~erving its
present location. ~ That MSC is then requested to page the
: 30 mobile ~ta~ion: and then re~poIld to ~he HI.R with an ~ -
i~dication as ~o whether or not the mobile station was ~ -
~ound. If tha mobile s~ation has responded to the page, -
the call i8 ~heIl routed ts tha~ MSC fQr completion of ~he
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call to the mobile station. This concept of paging a
mobile 6tation prior to routing the call was introduced
primarily to overcome the uncertainties in the location
data stored in the HLR for a cellular subscriber and
S ~ minimize needless routing of cal~s to improper locations
and the attendant circuit time associated therewith. The
paging prior to routing concept is expanded in the system
of the pre~ent invention to provide efficient
implementation of extension phone 6ervice within a
cellular radio telephone system.
~In the pres~ent 6ystam, a home location register
maintains location data independently for each mobile
station~within a group of mobile stations a~signed to the
same directory~number. Upon the rece$pt of a call to be
15~ terminated to ~th:at directory number, the interrogation
~exchange reguest the MSCs identiied in the HLR location
:: : : :
data correspondi~ng to the belie~ed current location of
ea~ch ~mobile station to page each mobi~e ~tation in
accordance with 1ts~MIN/ESN. All of the MSCs then page
20 ~ the relevant moblle stations in a quasi-simultaneous
fashiQn~rega~rdles 8 to their proximity to or 5 eparation
from one~another.~ Since each mobile unit being paged is
identifi~ed by~a~separate MINJESN, all of the moblle units
associated with~;the dlrectory number may be located in
25~ the saMe MSC and~paged there ~imultaneou~}y. Similarly,
all mobi1e~units~ may be located;i~ diferent MSCs and
each page~ separately~in itfi respective MSC. Al~ paging
requests from the interrogation exchange to th~ MSCs are
treated independently~from one another since eaah MS is
:30: ~ identified~: by~ a~ specific MIN/ESN combination, or
: otherwi~e, by speci~ic data u~ed on the air interface of
the ~ystem~
.
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Af~er ~he page reque~ts are executed, each MSC ln
which an MS was paged reports to the interrogation
exchange a3 to whether or not a page respons e has been
received from the paged mobile station. The
interrogation exchange then routeB the ca~l to one of the
: MSCs which has received a page respon~e f~om the paged
mobile station. Different techniques can be u~ed to
select which ~obile station extension phone the call is
: to be routed to in the event more than on6 mobile station
~ an wered ~he page from its a~sociated MSC. Several
~: different criteria can be used by the HLR to make the
6election. For example, the interrogation exchangQ may
salect to route the call toward the MSC which first send~
:: : it~ a positive acknowledgement indicat~ng that the paged
mobi1e station~has;answered the page and/or been placed
on a voice channel in that MSC. In addition, ~ach mobile
tation in a group o~ mobile 6 tati on8 aa ~ i g~ed as
.~ .
extension pho~es to~ the ~ame directory rlumber may have ~ :~
prea8signed prioritiPs and the H~R ~ay treat multiple
~ responses in accorda~ce with these assigned priorities. ~ -
The a6~igrled priorities may be permanen~ly fixed aB to
the: re~pect1ve exten~ion phones or they may be ~bject to ~:
ch~ ge withln the~ databa~e in accsrdance wi~h a ~:
pre~elected priority modification algorithm. Fur~her, ::~
25~ : : : the interrogatio~ MSC may analyze: the location of the ~:
c~ll1ng ~ party by ~ using the MSC identity of the
origin~ting I~SC :and th~ location where th~ page respo~ae
was received using the MSC-ID of the MSC having obtained
the page responses:. : The~e data ~ay be u~3d ln order to
~- route the call ~oward ths responding mobile station that
i3 close t to~the cal1er. Thi~ woul~ be a particularly ;-
useful call routing scheme in th~ ca~e o~ emergsncy ~:
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s ervi ces S Uch a5 the Ufi e of extenS i on phone~ i n
ambulances, police C ars, etc.
Referring next to the flow chart shown in FIG~ 4,
there i8 illustrated a procedure by which extension
5phone~ within a cellular radio system may be implemented
in accorda~ce with the teachings of the present
invention. In FIG~ 4, the system receives at 21 a
location request~m~ssage regarding a call to a subscri~er
with a given sub~criber number. At 221 the system
::~ 10determine~ whether or not more than one mobile
::~ identification number (MIN)~ exists for the subscriber
number to which the call is directed. If not, the system
move~ to 23 at~whlch the call i8 delivered to the mobile
stati~n corre~ponding to th~ MIN a~signed to the
~15 ~ ~ subscrlber number to which~the call is direc~ed and i~
accordance with the~procedure speci~ied in ~IA/TIA IS-41,
or example. If, ~ however, at 22, it i~ determined that
more than one mabils~tation identi~led by more than one
MI;N ha~ been~as~igned to the ~ub~cri~er dixectory number
20 ~to;which the~call~ was directed, the ~ystem move~ to 24
and :the ~HLR of ~ the ~ directory number sends a routing
reque~t message;~for each MIN to the V~R or vigited MSC
ide;~tified in~the~H~LR database as being the current
location of ea~ch:~of the mobile gtations corresponding to
~;25~e~ach MIN aesig~ed;to that ~ubseribsr nu~ber. At 25, eaoh
mob11e;station corresponding to each MIN i8 then paged at
the relevant VLR/MSC~for each of ~he routing mes~ages
received by it rom; the interrogation exchange sending
the multipl~ ~me~sages. At 26, the HLR monitor~ the
~: 30 ~respon8es~ rece1ved fro~ the routing requests s~nt out to
the several VLR/MSCs for a selected period o time.
If, at 26,~ tbe HLR receives no signals in re~pon~e
to the routing regue8t messages it sent to each MSC
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identified as the current location of a mobile station
corresponding to each MIN, then the system moves to 27
and initiates recovery procedures for no page response
~uch as, for example, call transfer to another number or
a no re~pon~e ~ignal to the calling party. Thereafter,
the routing ends at 28. I f, at 26, only one response was
. ,~
received hy the HI,R, indicating that only one of thP
paged MSæ re~ponded by sending a page respon~e signal to
it:5 paging MSC:, then the ~y6tem moves to 29 and the call
is delivered to the extension phone of the mobile station
identified by the MIN responding to the page at the MSC
where it is currently located.
l f, at 26, the HLR receives two or more messages
indicating the receipt of page re~ponse~ from the paged
MS~, the system moves to 31 at which routing decision~
~ased upon pr~defined criteria are evaluated for this
particular su~:scriber number. For example, th~3 system
~ight move to ~2 at which ~he call ~ould l:>e rou~e~ toward
the MSC as60ciated with ths mobile station having the MIN
20 ~ ~ ~ which fir~t responded to a page after the rou~ing
requests were sent from the HLR. In ~uch a ca~e, the
ystem would then deliver the cail to the extensio~ phone
: of th~ mobile ation having the MIN first responding to
~: th~ pag~ at 33 and ~hen end at 28. Alternatively, the
~ sy~te~ could move from the routing deci~ion at 31 to a
cr1terion beginning at 34 in whioh the c:all was to be
routed in accordance with certain priorities assigned to
th~ ~ariou~ MINs asRociated with the various plurality of
ext2nsion phone mobile statiQns as~igned to the
~ subscriber number. At 35, th~ re~ponse6 are arranged in
priority order after they havs been received from the
MSCs at which page xespo~se6 w~rs recal~sd for each MIN.
Finally, at 36, the call i~ dalivered to ~he extension
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Docket #17227jO026
phone corresponding to the MIN with the highest priority
responding to th~e page and then the routine ends at 28.
By way of further alternative, the routing decision
~ ~ contained within the criteria at 31 may include movement
: ~ 5~ to 37 at which the call i8 to be routed toward the mobile
tation Iocated clo~est to the calling 6ubs riber. In
thls case, the~; ~ 8y8~tem then mQves to 38 at which it
oalculates the~di~stancea between t~e lnterrogation
exchange a~d the~ VLR~SC at which page re6ponse6 were
10~ received from th~mobile extension phones having MINs as
to ~which a ~ page ~response was received. This can be
implem0nted by~means~ of a lookup table or a predefined
algorithm dri~ven~by the location of the interrogating
exchange and~the location of the various MSCs. Finally,
15~ the~call is~del~ivered to the ext~nsion phone which is
olosest~to the~ca11ing subscriber. The latter technique
of~call~routing~may~be~ particularly applicable in the
ase~ of~ ~emergéncy~services such as police, fire,
~ ambulance, etc.
,~ 20~ Referring~ next~;to FIG. 5, there is shown a block
diagram/flow diagram, in which a sequence of steps are
illustrated~ln;ithe~implementatlon of extension phone
s~rvloe within a~cellular radio system in accordance with
the~teachings~o~ the present inve:ntion. As shown in FIG.
2~ 4,~a call i8~received a~ an interrogatlon exchange or
;gateway~MSC-41~for~a~pa~rticular directory number to w~i¢h
a~plurality~of extension phones, ~each having different
identification criteria such a~ differen~ MIN~, ESNs,
etc., are a~fiigned. Next, lnfor~at~on related to the
30~ Gall is sent~at;~;;42 to the HLR 43 corre~ponding to the
directory nu~ber for which the aall i~ intended.
A8~u~ing there~ are two extension phone mQbile sta~ions,
MSl and MS2, ~ ldentifled ~ within the HhR a~ being
~ ~ :
:
-16- Patent Application
Docket #17227/0026
associated with the directory number for which the call
. is intended, the HLR then forwards the call information
; at 44 and 45 to MSC1 46 and MSC2 47 identified,
re6pectively, in the databa6e of the HLR as being the
current location of MS1 and MS2, respectively. Next,
: : : : MSC:l page~ MSl:wit~hin its location and MSC2 pages MS2 in
its location. ; AB illustrated, no page response is
received f~om ~MS1 at MSCl, but a page respon6e is
receiv~d from MS2 at MSC2. Thus, a no routing message 48
~ 10 ~ is :~ent~ from~MSCl to H~R 43 while a routing number
: mes6age 49 i5 sent:from MSC2 to the HLR 43. The routing
number is forwarded:in a message 51 from the HLR 43 tO
: the gateway MSC 4:1 and, thereafter, the incoming call to
: the gateway ~MSC~41 $s~routed at 52a-c to MSC2 47 for
; 15~ completion of the call:to MS2.
Thus, lt~can be seen~from the above description that
r~ extension phone;servi~e within a cellular radio system
: may: be enabled in a logical and orderly manner in
:accordance wi:th the teaching of the pre~ent invention.
20~ The pre~ent~invention provides optimized cellular radio
e~xten~ion phone~:s:ervice in a~manner which can be flexibly
configured in~àocordance with the particular nee~s of the
oellular radio s~ubscri~ber reque6ting such service.
For~n~tanoê, ~the inventlon de~crlbed herein could
25~ :be~appll~d wit~h~the~same method and principles to other
:: :types o f ~oblle :~ radio co~mun1cation such as tho~e
: ~ propo~ed for Personal Communication~ Servlces ~PCS). PCS
may provi~e call delivery in a manner ~imilar to that of
::
cellular radlo.systems bu~ employ other air interface
30 ~ ~ technique~ not currently con~idered " cellular~ uch as
CT2, ~CT2~+, CT3, ~DECT and others. The present system for
:: implementing exten~ion pho~e 6ervice could be implemented
: : : `: : :
: ~ within ~uch~ PCS 6ystems. In another example, the method ~
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~ ~ h 3 ~ 5 ~
-17- Patent Application
Docket #17227/0026
and principles of the present invention described herein
could use an implem~ntation whereby, upon detection of a
call to a ~ingle directory number, the HLR consults
another database called a Service Control Point ~SCP) to
obtain the list of MINs atta~hed to ths directory number
along with the criteria for selection of a page re~ponse,
priority for each MIN~ geographical data ana any other
~elat~d information. The SCP ~an ~e co-located with ~n
H~R or can be a di~tinct node within the cellular
network.
It i6 believed that the operation and construction
of the present invention will be apparent from the
foregoing description. While the method and apparatus
shown a~d described ha~ been characterized a~ i8 being
preferred, obvious change~ and modification~ may be made
: therein without departing from the 6pirit and scope of
the inYention as defined in the following claim~.
.
