CA2115657C

CA2115657C - Dual system cellular cordless radiotelephone apparatus with sub-data channel timing monitor

Info

Publication number: CA2115657C
Application number: CA002115657A
Authority: CA
Inventors: Michael J. Schellinger; Stefan G. Littig
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1992-06-23
Filing date: 1993-06-01
Publication date: 1998-07-07
Anticipated expiration: 2013-06-01
Also published as: ITRM930405A0; IT1262367B; CN1085706A; WO1994000946A1; US5442680A; CN1033838C; FR2693067A1; MX9303781A; FR2693067B1; CA2115657A1; ITRM930405A1

Abstract

A cellular cordless telephone may receive cellular telephone calls via a cellular telephone system and receive telephone calls on a system having a limited radio coverage area. To reduce the amount of time spent in monitoring the sub-data channel of the limited coverage area system, a timing signal is generated which represents the period of time spent monitoring the radio channel. During the monitoring, a predetermined number of data words transmitted on the limited radio coverage area radio channel system are received. When a first received data word is detected, an allowed monitoring time value is adjusted to be the sum of the value of the timing signal and the product of a determined number of received words to be detected and the time required for each word. This adjusted value of the monitoring time value is compared to the value of the timing signal and when the adjusted monitoring time value equals or exceeds the timing signal value, the monitoring of the radio channel ceases.

Description

&

DUAL ~:;Y~'l'~ CELLULAR CORDLESS
S RADIOTELEPHONE APPARATUS Wl'l'~l SUB DATA
-C~IANNEL TIMING MONlIOR

Field of the Iuv~Lion - 10 The present ~ve~.Lion relates generally to portable teleph~nes, and more particularly to an i~ploved portable t~leFhnne that may leCeiVe calls in both cordless and cellular telephone :~y8lel~1S.

1 5 R~t ~ lou~d of the Invention A cordless telephone system ty-pically includes a portable cordless h~nrlRet and a cordless base station connected to a telephone cnmr~ny phone ~y~ (TELCO) by telephone l~n~ nes. The cordless base st~tion has an 2 5 ~RsiEne~ nl11ine telephone number that allows the user to place and receive calls using the cordless portable handset within a limited range of the cordless base station, such as in a home. Howev~r, due to their li...ite~ range, the cordless portable handset provides the user with relatively local 3 0 radiotelephone commllnication.
Radiotelephone co~ on outside the range of the cordless telephone system may also be provided to the user via a cellular telephone system. A cellular telephnne system typically includes cellular subscriber units (mobile or portable) 3 5 and cellular base st~ nR connecte~l to the TELCO via one or -2- 211)3~7 more cellular swit~-hin~ nelwolks. Each cellular subscriber unit has an ~R~igne~l cellular t~le.rhone nllmher that allows the user to place and lec~ive calls within a--widespread range of the cellular base stations, such as throughout a S metropQliton area. Howevdr, the cost of using the cellular tel~rh~ ne ser~ice is generally ~eater than the cordless telephone serv-ice.
To reduce t_is problem, a radiotelephone may access hoth the wide area cçlllllAr telephone sy~ and the lower 1 0 cost cordless base station at the user's home. It is also pos~ible to access a microcellular t~lepl ~n~ system in thoge loç~inn~
where such a system offers radio cu~elage.
A rA-liotelerhnne which transmits and receives calls in both a cellular and a cordless sy~a 1 should have the 1 5 rApAkility of selec1;ng a system into which it is to opelate. An AlltQm~1;C hy~ se1ect;~n should be made on parameters a-lv~ - -t~cous to the user. It i8 i- '~JOl ~ that the radiotelerh~ns, le~aldless of which ~y~le is selecte~l) not miss calls directed to it.
2 0 Accordingly, there is a need for a radiotelephone system that Pn~hle~ a user to leceive inc~ming calls via both a short range system such as a cordless By~lem and a wide area ~ybl. ~ like a cellular telephone system without çYce~sive 1088 of incoming calls.
SllmmAry of the Invention A radiotelephone al,~ald~us lec.:ives meEsages ~lererably on a radiotelephone system having a limited radio 3 0 coverage area and alternatively lec~:ives messages on a cellular radiotelephone sy~tem having a limited radio covelage area. The telephone apl,~atus est~ hes a value for the time to monitor a radio rh~nnel ~ssor;~ts~3 with the limited coverage area system and cQmmences monitoring 3 5 that system. A timing signal is generated w_ich represents 3- ~ 7 the period of time spent ...n-.;t~.Lug th-e radio &' - el.
During the m ~;lc~ g~ a predetermined nllmhçr of data words trans_itted on the radio chqnnel A~so~ts~l with the - limite l radio co~e,age area system are ~eca;v~d. When a first 5 rcce.vad data word is ~lp-tsctsll~ the m~ nitQring time value is readjusted to be the sum of the value of the generated ti_ing signal and the product of a dete~ ;..e~ mlmhç~r of received words to be fl?t~cts~l and a ~le~tc ~ e 1 value of time for each word. This readjusted value of the mo...l~l~ time 1 0 value is ~ O~ JA ~ ad to the value of the generated timing ~i~n~l, The m~ ,~g of the radio chAnne] ceases when the readjusted m~nitoring time value equals or çycee~l~ the generated timing signal value.

1 S ' Brief Description of the Drawings FIG. 1 is a block diagram of an operating configuration for a portable radiot~lephnne in which several systems, including both a cellular ~y~lel-l and a cordless system, may 2 0 be Acc~se~l by the same portable radiotelephone.
FIG. 2 is a dia~l .. 9.~;~1 map which shows a typical arrangement of coverage areas for the cordless, microcellular and cellular systems.
FIG. 3 is a block diagram of a cordless base ets~ l;on 2 5 which may employ the lJrese~t illVH~ n.
FIG. 4 is a block diagram of a portable radiotelephone which may employ the present illve..t:nn FIGs. 5 and 6 are flowcharts for the process used by the portable radiotelephone of FIG. 4 when the portable 3 0 radiotelephone is not engaged in a call.
FIG. 7 is a timing diagram of the data format outbound on the sub-data rh~nnel from the cordless base station.
FIGs. 8, 9, and 10, taken together is a flowchart for the process of ..~;..;...;~n~ the monitoring time of an alternate 3 5 system çh~nnel by the portable radiotele}!hQne of FIG. 4.

~ 4 2 ~ 3 7 FIG. 11, 12, and 13 are, t~hor, a ~iowchart dia~lr.. ;.. ~ the process of ~y~ prioriity selectiQn w_ic_ may be employed in thie portable r.~s-~liot~!iephen.e of FIG. 4.
- FIG. 14 is a timing diagram of the system sc?nninie S ~l~ass w_ichi may be employed in thie portable radiot~lerhnne of FIG. 4.

Detsilell Descriiption of a I~efe~lad li.mho~ rnt 1 0 A generalized block diagram of an applir~tion of tbie present illivt:~lion is shown in FIG. 1. A port~suible ceDiular cord]iess (PCC) rs-liotelerhnns 101 is shown haviing thie ability to cu~ ;cste with a cullve~1;n"?1 cellular radiotelephone &y~l~ 103, which has a plurality of ceDular base sts~ionR~ 105, 15 107 lo~ste-l at geogr~rhir~slly se~alate lor~?t;nnR but arranged to pro-vide radiotelephone coverage over a wide geographic area. The ceDular base stst;QnR are co~pled to a control t';~ ---;--91 109 which pro-vides cool~ 9t;Qn ~mnng the plurality of cellular base st~tionR~ including h~n-loff of user 2 0 cellular mobile and portable eq~ ent~ and provides call switching and intercQnnert to the public switched telephone nelwolL (ident;fie-l hereinafter as "TELC0") 111.
The PCC 101 further has the capacity to co~ ic~te with a _icrocellular base st~ion 113, which is a cellular 2 5 adjunct cell having lower power and limited c~p~bilities but providing public radiotelephone service to distinct areas such as shopping malls, airports, etc. The _icrocellular base 8t~tiQn 113 is coupled to the TELC0 111 l~n~iline telephone BY8tem BO that calls can be placed to the TELC0.
3 0 The PCC 101 further has the r~p~hility to coJ~ ..... ....... ......ic~te with and place radiotelephone calls via a cordless base station 115, which provides private telephone line interconnection to the TELC0 111 for the user of the PCC
101. AB previously noted, the cordless base st~1;on 115 and the 3 5 PCC 101 together provide the limited radio range service -5- 2~ 36~7 ~ cc~v~ n~lly known as cordless telephone service. Such service has hecQme pervasive, c~llv~ nnolly using a few radio frequency rhonn~lR in the HF (high frequency) radio band.
S The user of a re-~liot~lel.l.n .e Rho~ espect tho-t ~ ~iot~~erh~ns serv-ice be av-o~ hl~ wherever he travels in the United States and that this serv-ice is provided at the lowest cost. It is also to be e~l~cle~l that ra~liotelerh~ P~ service be provided in a portable unit that is as co ~I,act and ;.~eYl~ Rive 1 0 as pos~ihle. The PCC 101 ig uniquely configured to meet this end. Furtht:l ~ole, the cordless base station 115 is uniquely dcE~n~ l to provide telephone inte~. ect to the user's home telephQne line when the user has the PCC 101 within the radio range of the cordless base stov1;Qn 115.
In ~otl~lit;Qn to ~u~ to the cellular system sign~lling rhonnalR the PCC 101 will monitor the signollin~ sub-data ~,honnel of the cordless base sto~ n 115 for ad~lit;on~
il.rol...ot;-~n If the PCC is in an area in which it has e-ccesse~
normal cellular service on a control ~honna~l~ then monitoring 2 0 the sub-data ~~.h~nn~sl involves leaving the cellular system control rh5~nnpl. By leaving the control rhonnPl, the PCC may miss i~ ol~ t control (~honnel message traffic. (An exh...l~le mes~oge may be a "page~ of the cellular phone.) Thus, the time period spent away from the control rh~nnel hecomes 2 5 critical as t_e period gets longer. The present invention qn~hles the PCC to reduce its sub-data ~h-onnel mo l~lhlg time and return to the cellular control ~-h~nnPl as soon as possihle.
FIG. 2 ~hows a typical arrangement of coverage areas 3 0 for the cordless, _icrocellular, and cellular systems. The cordless system coverage area is the sm-ollPst and can reside within the microcellular ~ytjle 1. The microcellular system has interme~ te coverage and can reside within the cellular system. The coverage area of each ~ ~ may depend upon, 3 5 but is not limited to, the mlmher of base stot;~)nR in each -6- 2113~'~7 e~y~sk~ ~..t9....~ hpieht of each base st~t;Qn and t_e power level used by each ~y~llem. The user of the PCC may relosAte bel~ the various cu~elage _reas. The PCC may change ,e~ ~y~klL~ based on but not limited to portable S radioteleFhone lorAt;on, ~y~Le~ av~ h lity~ and user felellce.
The coverage areas of the ~y~l.,~& are not lillliled to the particular arrangement as shown in FIG. 2. A cuv~:l~;e area may be indepsn~l~nt of Anotl er coverage area or may partially overlap one or more other coverage areas.
The cordless base stst;~n 115, cullce~Lually~ is a sl~hminiAt~lre cellular ~y~,em providing a gingle ~ignAlline rhAnnP,l which tran6mits o.ll~oulld data mes~aee~ in a f~4hiQn analogous to a cul.v~ Qn~l cP.lllllAr oull,ou,ld ~igngllir,e f~hsnnsl~ and ~cceives service requests from a remote unit, such as a PCC 101. I~O~:r serv-ice requests are granted with an A~ienmpnt of a voice rh~nn-p~l (made via the control l~hAnnPl) on the same or a secQn~ radio frequency to which the PCC 101 is instructed to tune for its telephone call.
2 0 The basic implPmentst;on of a cordle6~ base station is shown in FIG. 3. A collve..t;-nAl trAn~ ;ller 301 and a ~llv~-.L ~n-sl laceive~ 303 6llitshle for use in the 869 to 894 MHz and 824 to 849 MHz band of freqll~nt~ies, lc~ec~ ;vely, being u6ed for collv~lltional cellular services, are coupled to a 2 5 commnn An~nnA 305 via a ~lllplp~rp~r 307. The power oul~ul of the trall6llilLer3ol is limitell to &~ At~ly 6 milliw~ll6 so that intelre,ellce to other service6 and other cordle6s telephone 6tations is .~;n;n~ erl The rh~nnp~l frequency sêlection i6 implemPnte~l by a frequency 6ynthe8i7er309 3 0 controlled by a logic unit 311. Wil~ill the logic unit 311 is a mic~u~roce860r313,8uch as a 68HC11 available from Motorola, Inc., or similAr miclo~lûce660r, which i6 coupled to conventional mamory device6 315 which store the microproce660r ol,ela~illg program, base itlantificAtion (BID) 3 S and cnFtomi~ing personality, and other featules. Received - 7 211~6~7 and tr~nR..~ c-.1 data is çncolle ~ c2~1e~1 and coupled belwee the l~ceiver 303, the trAn~...;Ll~l 301, A~d the miclv~l~&esRor 313 by ~ign~llin~ interface ha~dw~e 317. The mic~o~,ocessor instr l~t;onR are cGllv~ed and implçmPnte~
S by control haldw~e 319. Interface with the user's home landline telephone line is co.-v .l :on~lly ~cc~ hed via a l'ELCO ;~ r~ce 321. Power is supplied from the cvllve..t;on~l AC mains and hA-~ke-l-up with a ball~-~ reserve (all ~lep;cte~ as power 323).
1 0 The PCC 101 is a portable .cLdio~ ep4-ns transceiv~r which is shown in block diagram form in FIG. 4. A portable radio lec~iver 401, cArAble of .~c~,:vi~ the band of freql~nries belwee.l 869 and 894 MHz, and a portable ~A..R...;! le.- 403, r~FAble of trAn~ with low power (a~ ;..-At~y 6 l 5 milliw~tls in t_e ~.efe..ed çmho-lim-nt) on freqll~nries between 824 and 849 MHz, are coupled to the A~t' '~A 405 of the PCC 101 by way of a ~illrle~er 407. The particular rh-snnel of radio frequency to be used by the tran~ill~. 403 and the le~ivel~ 401 iR del~r~led by the mi~"op.ucsRsor 409 and 2 0 co.lv~yt,d to the frequency ~ynt~-esi~çr 441 via the interface circuit 413. Data ~iEn~lR received by the ~c~iv~l 410 are ~l9co~le l and coupled to the micL~-wa880r 409 by the interface circuit 413 and data Rignsls to be ~,ra, s~ illed by the transmitter 403 are generated by the mic.~-ocassor 409 and 2 5 form~te l by the interface 413 before being transmitted by the tran~miller 403. Operational status of the transmitter 403 and the receiver 401 is çn~hlell or ~liR-g-hletl by the interface 413.
The interface also controls light q~ E ~iio~les~ 415 and 417, which are used to in~ic~te to the user which system the PCC
3 0 101 is currently receiving Control of user audio, the microphone output and the speaker input, is controlled by audio processinE ci~cuill ~ 419.
In the 1,l efer~ed Qmho-liment, the microprocessor 409 is a 68HC11 microprocessor, av-s-ils-hle from Motorola, Inc, 3 5 and l,e,ro.~s the necesss,ry procesRine filnrt;ons under 211~657 co~ of ~ ~8 stored in cull-v~ tional ROM421.
Ch~a~le~;zing fealulas of the PCC 101 are stored in EEPROM423 (which may also be stored in mic.~loce~ûr on-board EEPROM) and include the nnmher As~ienment (NAM) 5 l~quire~l for o~ lion in a ~ll~ Qnol cellular system and -the base identification (BID) le~luir2d for c~ ion with the user's own cordless base.
The l,L~ 403 of the PCC 101 has the ca~o-hility of tron~ g wit_ the full range of o~l~ul power which is 10 iequilc~ for u~ lion in a collve~ Qnol cellular system. This range of o~ l power cQ- RiF~ of six sets of output power maf~nit.l~e rAn~ing from a high output power level of &~ ;...At~y 600 milliw~lls to a low o~ ul power level of 6 illi~. zllls. This six set range of output power is en~hletl 15 when the PCC 101 is in the cellular system mode.
Accoldillg to the l l~rel~ed emho~lim~nt of the ~leEe.lt hlv~ ;Qn, the sAme PCC 101 is comrAll;hle with both the cordless and cellular t~lerhone s~lelll 103. This is Ac~...~ he~ by f~nAhling the PCC 101 to o~elc,te in both a 2 0 cordless and cellular telephone ~y~LelQ 103 using, in the .erelled embo~lim~nt only cellular telephone freql~ncies.
The radiotelephone arrangement has desirable a~l-v~tages for the user. Fil~lly, the PCC 101, in comhinAt;~n with the cordless base station 115, can A~ Ally route an 2 5 j~ro.~ call to the t~lerhone system in which the PCC 101 iB
lorAte-l without incollv~lliencing the user. .~econ~lly~ the PCC
101, in comhinAt;on with the cordless base et~t;~n 115, can AlltomA~;cAlly route a call in process ~ith the PCC 101 between the cordless and the cellular tçlerh~ne systems when the PCC
3 0 101 rçlocAte6 therebelweel,.
FIG. 5 and FIG. 6 taken together is a flowchart for the process used by the PCC 101 in FIG. 4. In one çmho~liment of the present invention, the PCC 101 and the cordless base station 115 coo~e~alively operate, as ~3es~ihe~l in the flowchart 3 5 of FIGs. 5 and 6 to route an inComing call to the cordless 9 2~156S7 telerhn~e ~y~l~ or the cellular telephone system 103 acco~ g to the lor~t;on of the PCC 101.
As shown in FM. 5, the PCC 101 may be in an idle 6tate in either the cellular t~leFhlme sy~l~ 103 at block 501 or the 5 cordles6 telephone ~y~l~ at block 503. In either idle state, the PCC 101 is in a condition to le~;Ve an ;~ e ~~ E call. For ~1;RC~1RR;On purpo6e6, ~Rnme t_at the PCC 101 is in the idle state in the cellular t~lep~ nne ~y~l~ 103 at block 501. The PCC 101 ~1e~D8 at block 505 whether to ,~a~ in its idle state 1 0 in the cellular t~lcrh ~ns sy~l~ 103 by icl -- ..;..~ to block 501 or to change to the cordless tel~rt one sy~lelll by sc~nnin~ for an accept~hle cordless base stPtj"n at block 507. If the scan process loc~tes an ~eFt~ble cordless base st~ n 115, as det~ ;..e-l at block 509, the PCC 101 sends a regipter m?~~age 1 S (an ~ttempt by the PCC to register with the cordless base ~t~t;r~n) to t~e cordles6 base Bt~1;Qn 115 at block 511. Otherwise, the PCC 101 returns to the idle state in the cordless telerh~me sy~l~ at block 501.
The cordless base station 115 normally waits in an idle 2 0 state. Upon receivil g the register m~sage~ the cordless base st-o-tjnn 115 de~l ...;..es if the PCC 101 is ~cc~ hle. If the PCC
101 is acce~,able, the cordless base etotinn 115 sends an accept mgg~age to the PCC 101, sends its own lonfllin? telephone mlmh~r to the PCC 101, and le~ s to its idle state. If the 2 5 PCC 101 is not accepted 6y the cordless base st-qt;on 115, the cordless base station 115 sends a reject message (a non-registration of the PCC by the cordless base s~qt;nn) to PCC 101 and returns to its idle state.
In FIG. 5 the PCC 101 de~l~es if the acc l,I,ed (PCC
3 0 registration) me~sage is leceived at block 513. If the accepted mes~ge is leceived, the PCC 101 leceives the lon-lline telepll~ne number of the cordless base station 115 at block 515.
Otherwise, the PCC 101 returns to its idle state in the cellular telephnne system 103 at block 501. Thus, the cordless base 3 S station 115 has been notified of the PCC '8 101 deri~ion to 211.5~3 7 change to t_e cordless t~epllnns B,~ and the cordless base n 115 le8~ by giving t_e PCC 101 itg l~n-lline plerhnn? number.
In FIG. 5 the PCC 101 detennines whether the user's 5 cell~ r or l~n~lline phone nnmher has call routing prionty at block 517. Call routing priority refers to the user's ~le~.,L
,lefel~lce (cellular or l~n~lline) to which an incomine call is routed to first before tr~n~feri~ to the seC~nfl s~lelnL if the PCC 101 is not loc~te-l- Since the user iB av~ hle via both a 10 cellular and ~ line phone nllmher~ it would be c~,nve~ent to give out only one of the phone ~m~hc- D to ~n~x party to place inCo~ e calls to the user. Thus, a single phone mlmher _ay be used by the other party to reach the user's PCC 101 in either the cellular or cordless telephone system.
1 5 If the cellular phone nllmber has call routing priority, the PCC 101 fol . ~Lds the cellular phone mlmher to the ~ n~lline phone nnmher of the cordless base unit at block 519 and waits in the idle state in the cordless t~lephnne system at block 503. Thus, an incomin~ call routed to the user's cellular 2 0 phone number is alltom~ically fol w&L~ed to the l~ntiline phone nnmher of the cordless base st~ n 115 when the PCC
101 is lor~t~fl in the cordless telephon? ~y~l~ L.
If the user's l~nflline phone number has call routing priority, the PCC 101 sends a call fol ~. ~rd messa~e to the 2 5 cordless base unit instructing it to rOl ~ mLd the userg l~n~lline phone mlmher (sent to the cordless base ~t;Q~) to the l~n~lline phone number of the cordless base unit at block 521 and waits in the idle state in the cordless t~leph~ne ~ 1L at block 503.
If a call fol~.zlrd mess~e is lecei~ed by the cordless base 3 0 st~tion 115, the cordless base ~t~tiQn 115 pelrol...a a remote call fol wal lhlg of the user's l~n~lline phone number to the l~n(lline phone number of the cordless base station 115 and returns to its idle state. Thus, an inCQmine call routed to the user's l~n~lline phone number is ~ntQm~cally rolwaLded to 3 5 the l~nllline phone nu_ber of the cordless base station 115 211~7 when the PCC 101 iB loc~te-l in the cordless system If the PCC
101 is t~ e 1 off the user ~y still lcc~;ve i..co-..;.~E calls via any t~lerh~ne ~so~te 1 with the phone m~mhsr of the base et~t;nn S In FM. 6 the PCC 101 ~ ?r at block 523 whether to re_ain in its idle state in the cordless telephone sy~ n by elullli lg to block 503 or to change to the c~-llnl~r t~lephnne ~y~l~ 103 by l.;~las~ to block 525. At block 525 the PCC
101 ~let~rmines whether the cellular phone mlmher of the PCC
1 0 101 or the user's l~n~line phone mlmber has call routing prionty. If the cellular phone mlmher has call routing priority, the PCC 101 sends a cancel call ror~.a~ g msssage to the cellular 8y~lelll and the PCC 101 returns to wail~ in the idle state in the cellular ~y~l. ~ at block 501. Thus, an l 5 inr~ call routed to the user's cellular phone nnmh~r directly calls the PCC 101 lor~te-l in the cellular telephone ~y~l~ 103.
If the user's l~n(lline phone nllmher has call routing priority, the PCC 101 sends a call 1U1 ~. ~dillg msR~age to the cordless ba~e station 115 to fo~.~d the user's l~ntiline phone nnmher for the cellular phone mlmher of the PCC 101 at block 531. If the PCC 101 is lln~hle to ert~hli~h co~ cf~t;t n with the cordless base st~t;Qn 115, the PCC 101 can ~elEw~ the call fol w~ liLlg by mAking a cellular teleph~ns call. Thus, an 2 5 incomin~ call routed to the user's lAn~llin~ phone number is rul ~. ~.led to the cellular phone number of the PCC 101 locAte~
in the cellular teleph~ne ~y~lem 103.
The radiotelephone arrangement iB not limited to only cellular and cordless telephone ~y~le B. The radiotelephone 3 0 all~ent _ay operate in at least two radiotelephone ByBte_B where it would be desirable for a PCC 101 to switch be~,weell the systems. Such desirable re~CQn~ may include but are not limited to coverage area, service cost or service quality.
Since at least two systems coe~iFt (the cGllvr!~l ;on~l 3 5 cellular system and the cordless ~y~lel~l) and can have 211~6~7 overl~pring radio coverage, it is illl~Ul~Lt that a priority iei~.,hy be eE~t~hliRhetl The cordless system is e~ects~l to be a lower cost sy~ L than the co,lLvelltional cellular ~y~Leln - heCAll~e it is Attr~he 1 via the user's home l~n~lline connection S to the TELC0 public ~wilcLcd t~lerhnns, LC~Wu~h by Col~. lional wire. It is most likely t_at the cordless system would be the ~.arel,ad system when the PCC 101 is within the , area of the cordless base station 115. Thel ~rore, in the ~-afe,,~ mhollim~nt~ priority is given to the cordless 10 base service. How~var, the uRer may select other _ie,arcl,y of pnority if desired.
The cordles6 base st~t;on 115 transmits an oull~oulLd Rign~lli~ m?E~ge on a radio rhAnnel which is selecte~ to be nonin~f~"~lLg with radio ch~nnel~ in use in the local cellular 15 ~y~l~ L 103. Thi8 mefisage is ~imilpr to that transmitted in the collve~ ;nn~l system in that its ~ ose is to present the ident;ty of the cordless ~y~lel lL and aid the PCC 101 in del~ ;--;-.g it~ avAilAhility. The format of the messa~e oul~ounLd from the cordless base st~;nn 115 on its ~i n~lline 2 0 rh~nn~l is shown in FIG. 7. In the ~ felled ~mhofliment, inform~t;nn is transmitted in words on a radio rhAnnçl from the cordless base sto1;o~ 115. Each word c~-.t~ a known ~ledetel~ed sequence of data bits (S) for syncLLo .i7At;Qn followed by the data bits Cullv~yil Lg the mes~a~e (MSG).
2 5 Optionally, a word also cont~in~ a dotting sequence (D) which precedes the synchroni7At;on sequence. Words are repeAte-lly transmitted on the çhAnnal The dotting and ~yl~Lcln~;7A~;s)n are transmitted in NRZ while the m~ssage is trans_itted in MAnrhe~ter. When ~rAnning, the PCC 101 locks onto a 3 0 particular channel which may contain illfUl ..ation transmitted by the cordless base st~t;nn 115. If it is not able to ~-co-le a word within the time to transmit a cel laiu nllmher of words, it assumes that data iB not present on the rh~nnsl and continues with the sCAnning process. Since the PCC may 3 5 arrive on the çhAnn~l in the mi~l~lle of a word, it must be on 2 ~ 7 -the rh~nnel for the ~mount of time to tr~nRmit W+1 words to gu~tee being on the ch~nnp~l for W c~ ,lete words. For the purposes of this ~ cllR~ion, the term Frame will he llt;li7e~ to in~lir~te W wordg. In the ~ relled Pmho-limen~, S the Frame size is two words.
The word mes~age includes a Base IDent;ficAt;on (herein~ftsr, BID) field which ~ lates in a m~nnsr 8imil~r to the CO11V~ .L:nn~l System IDent;fic~t;c-n (herein~er, SID) in use in c~ lAr systems. The BID is ~JlO~lA~ l into the 10 cordless base st~t;~n mpmory 315 as a mlmher unique to each cordless base st~t;on This unique Bm prondes the speci~l characteri7~tion of each cordless base st~ n 80 that a user's PCC 101 and cordless base st~1;on 115 will ol.el~e to~etller without allowing lln~l~tllorized users to obtain ~es~.
l 5 To provide better 8ec~;~ and int~lfe~ ce protecti-n, the B~) is co~.l:...~ously tran& LLed sl~h~ lihly on the voice rh~nnel when voice cv~ rAt;on is occ~lillg. The PCC
101 lece;vds and ~1eco~3es the BID and rhe~R for a match l~elweell the sllhAn~lihly tranall~ ed BID and the BID of its 2 0 ~sso~ted cordless ba~e st~tion 115. So long as the BIDs mAtGh, the collvelaalion on the voice rh~nn?l may c.~ e.
Upon detec1;~ n of a mi~mAtr.h, the PCC 101 l¢'C~;Ved audio is mllte~l and the PCC transmitter 403 is unkeyed. After a predetel~ed penod of i ~lol,er BID lece~ on by the PCC
2 5 101 and a subsequent lack of l~ceived tr~qnRmi~sion from the PCC 101 to the cordless base station 115, the call is tel~ Ate~
G*en that the pIiority es~hliRhP!~l for the PCC 101 is that the cordless base st~t;on 115 is the first de~h~d path for a user's telephone call and the collvf~tionql cellular (or the 3 0 microcell system) is the second choice, the process of implem~ntin~ that priority is shown in FIG. 14. The depiction in FIG. 14 is ofthe PCC l~c~iver's 401 lec~lion ofthe ou~oulld sign~llin~ rhpnnel or set of ~i n~llinE rh~nnelR
transmitted from the cellular system, the cordless base, and 3 5 the microcellular system relative to time. This diagram aids -14- 21156~7 in t_e under~nAing of t_e scA~ pnonty employed in the ~,efe~l ed emhoAim~nt of the present invention.
The PCC .ace;v~l 401 can be ~ OI ~L 1401 the - outbound me~ge ~e&-ll being tr-o-nRmitte~ from the cellular 5 system ~ignolling channel (w_ich was selected from om-lng ~the plurality of cellular ~ign-o~lling rhonnP.lg in ~jllvç-~l:on-fio~hi~n). At the a~ ,lia~e time, t_e PCC lece;ver 401 i8 instructed by its mi~o~loces~ol- 409 to tune to the frequency or one of the freql~qnries being used by the cordlesg base gts~t;~n 10 115 as a 8ignAlling sub data ch-onnPl. The PCC re~;vel 401 scans 1403 t-he cordless base oul~,ound sub data çhonnel or channels for a period of time t2. If the ~ignolling data ~l~e~
is not lec~;vt:d with sllffiripnt quality, the PCC l~c~;ver 401 is retuned to the previously selected Rignollin~ çhonnel of the l 5 cellular 8~m 103. It ram-oinR tuned to tig ~ign-olling rhonnel 1405 for a penod of time, tl, before ~ lillg another scan of a ~Rignollin~ rh-onnel of one of the alternative systems.
The rel-o-~;Qnship of tl and t2 i8 such that a cellular page messA~e (that is, a radiotelephone call or other transmitted 2 0 requil~ent) which is repeated, collvt:l~Lionally, after a 5 secQn~l pause will not be miRRe-l hecAllse the PCC lcceiver 401 was sÇAnning an alternative system during both cellular page .message tr!onRmiRRiQn t.imes. The time tl must be greater than the sum of the pause between the two pages and the 2 S typical time to tr~namit two pages. The time t2 must be less than the time between the two pages. If the pause time is 5 secQ~ and the typical time to ~ a page is 185.2 milliaecon~lR, tl must be t leater than the 5.3704 secQn~ls and t2 must be less than 5 secon~lR. After mo lilor~g the cellular 3 0 ky~le~ ~Rign~llin~ chAnnel for a time tl, the PCC leceiver 401 may be instructed to tune to the si~n~lling ~-h~nnel or to the aignslllin~ ~~h~nnela, 8eql~Qnt;f~lly, of the microcell system, as shown at 1407. If an adequate microcell aien~lline chS-nnel is not found during the scan of predete,~ed ~i~n~lling -rh~nnPl freql.~an~a~, the PCC lecc;ver 401 l~L-~..es to the cellulsr system ~ign~llin~ rh~nnel~ a8 shown at 1409.
A scan to the Rign~llin~ sub-data ch~9nn~ 1411, of the cordless base st~on 115 which discv~ a Pign~llin~ data 5 sLleal-l mo!et;nE a~lol,l;ate quality re~ ile~nant~ results in the PCC l~cc;vel- 401 cv~ ;.~ to m~nit~r the cordless 8ign~l1ing rh~nnel- The PCC lecciver 401 le~ on the cordless ~ign~lling rh~nnel without le8c~...;..~ to ~nother ~y~te~ until the PCC 101 c~nn~t lece;ve the cordless base's trans_itted signal for a ~ ~---Q~l~ 5 BecQn~l period of time.
The effect of this priority ~locess is to give priority to the cordless base Et~1;on 115 at the PCC 101. Once the sign~lling çh~nn~l of the cordless base st~t;o~ 115 is di~cv~e~e.l, the PCC
101 rem~inR tuned to this rh~nnPl Thus, when the PCC 101 1 5 is ini1;s~11y tuned to the cellular system it will ~qllt~m~tir~lly switch to the cordleBB base stPt;- n when it is possible to access the cordless base st~tiQn Once the PCC ~ecc;ve~ 401 has found the cordleBB base 8i n~llin~ sub-data rh~nnp~l~ it ram~in~ tuned to that rh~nn~l When the PCC t,~ce;vel is 2 0 first turned on, its first scan of ~ llin~ gub-data rh~nnala is the preest~hli~hed ~ign~lling rh~nnel or rh~nn~ of the cordless base station 115. Of course, the user may override the slllt~ t;C priority sc~nnin~ _ie~&lchy by e.lter,llg an override code into the PCC 101. In this m~nner~ the user may force the 2 5 sc~nning of the cellular system ~i n~lling rhs~nnel8 only, the cordless base ~i~n~lling rh~nnalR only, the microcellular byB~el-~ Bi~nS-llin~ r-hs~nnel8 oIily, or cQmhin~t;on~ of the ~y~le~s. The user may also pelrullll a call ori~in~t;on with a one time over~ide to the system of his ~hoice 3 0 Once the ~i~n~lling rh~nnel of a system iB being monitored, a visual indication iB given to the PCC transceiv~r user. In the l lerelled amho~impnt~ this in~lir~t~r iB a set of light ~ g diodes (LEDs) 415, 417, one of which uniquely illl~min~te~ to indicate to w_ich system the PCC transceiver iB
3 5 tuned. Other indicators may alternately he used to cvllvey the -16- 21156~7 same hlfo,~ n For Py~mrle~ a system ident;fisr may *h .- in the mlmhP~r display of the PCC 101, or a fl~shin~
symbol (having Ji~ c.lt rates of fl~hing) may be used.
- Nevertholess, this in~lic~ n çn~hles the user to dete,~e S which ~ he is in and decide whether he wishes to complete a radioteleph~ne call in the in~lir~qte~l sy0tem.
Tllmin~ now to FIGs. 11, 12, and 13, the process followed by the PCC 101 in re~li7ir~ the scan pnority is shown in a flow diagram. This lJ.ocass is eYecn~ l by the 10 miclo~ocessor 409 from its o~e,ati~ program stored in ROM
mPmory 421. Upon power-on, at 1101, the radio sets the cellular scan COu~ter to 0. This variable is ll~ e 1 to ensure that PYce~sive word syncln~ n losses or other re~on~
for e~ ;ve celi~ r ,e~us do not ~ e,lt the PCC 101 from 15 ~cP---.;--g for the cordless base st~ n 115 ~h~nnPlR. After resetting the cellular scan counter, the predetermined ~ign~lline /~h~nn?l (or rhsnnel~) of the cordless base st~ti(~n 115 is sc~nns~ at 1103 to de~,~c if the PCC 101 is within range of a cordless base station, whether the ~i~ns~llin~
2 0 rhnnnel leceived has the ~ e~ BID, and pote~ lly whether the ~ign~lling rh9nnel has sllffic~ent signal quality. The PCC
101 llsri~les if all the criteria have been met at 1105. If the criteria have been met, the cordless mode of ope,~Lion is entered and the user iB notified by illllminAt;on of the LED
2 5 AssociAtecl with the cordIess mode, at 1107. The PCC
transce*er rçmAin~ in the mode of proce~ing cordless functions, at 1109, including momt~l~ the cordless base ~ign~lling rhslnnel, mslring and l~ce;villg radiotelephone calls, and effecting çhsnnp~l change (hsn~lnff~ between itself 3 0 and the cordless base, until syncL~..i7At;Qr or BID is lost between the PCC 101 transceiv~l and the cordless base station 115 (as ~letecte~l at 1111).
If syncl~s..;7-s-1;Qn or BID match becQme~ lo~t, the process move~ to a check of whether the PCC 101 was engaged 3 5 in a radiotelephone call, at 1113. If the PCC 101 were not in a ~ ' -17- 211~7 call, the process moves into a scan of the cellular ~t~
~ignolling rhonn~la; if the PCC 101 were engaged in a call, several ~tt~-..p~ are made to reen~ge the call in the cordless - mode. The cordless base sr~n co .. ~- is reset at 1115 and is S rh~cL e~l at 1117 to dete~nine if the co ~ ~.te-- has gone beyond the mo~;.... nnmher of cordless base scans (m~ -.. = 2 in the l lerelled Pmho~l;...q..t). The cordless rhonnela are 8~onl~e 1 at 1119 as ~3es~ihe~ for 1103 and the results are ~' ~cL~fl at 1121. If the pign~lling channel from the cordless 1 0 base ~to1;on 115 is found, the cordless phone call ig regllmq-l Otherwise, the cordless base scan co mtqr is incremented at 1123 and is lerke~ Le~l for ~ ae~ the m~.;....-... at 1117. If the cordless base ~can counter eYc~e~a the m~ ..., the PCC 101 will abort the cordless mode and will -o~tte-npt to scan 1 5 the ~ignolling chonn~la of the cellular s~te 103.
The cellular scan is begun with ~loce88 1125 which is also entered from test 1105. First, the cordless base re~can timer is reset (set to zero) at 1125 to mark the time of the end of the last cordless co...~ -;cation. The cellular Bcan coullter is 2 0 incrPmPnte~ (1 is added) at 1127 since a cellular scan is about to begin. The PCC 101 scans the cellular ~ble I ~ign-olling rh~nnPlg, at 1129, accoldillg to co~ nol user set1;nga.
A test is l,elrwl-led at 1131 to determine if an adequate ~ignollinf~ rh~nnel is present in the list of cellular ~i~nolling 2 5 rh~nnpl frequencies sr-orine~l by the PCC 101. If no ch-onnel is ble, a "no svc" LED is illllminot~ l at 1133, and the process returns to scan the cordless Rign~ollin~ ch~nnpl~ at 1101. If a cellular &y~le~ . ~igno-lling chonr~ is found to be accelJtable~ a LED indicating an in service mode is 3 0 illllmin~te-l and all other service provider LED's are e~liahe~l, at 1135. The cellular rescan timer is reset at 1137 to determine the time at which the last cellular rescan was completed. The process then progresses to the modified cellular system "idle task", 1138.

-18- 211~6~7 The idle task, 1138, first determines if it is time for a forced cordless rescan at 1139. A forced cordless rescan occurs if the cordless base rescan timer is grester than CBRT.
- CBRT i8 the cordless base rescan l,i~lleou~ and is set to 605 seconds in the ~rarel~ad emho~ Pnt~ In order for the forced cordless rescan to occur, the cellulsr scan counter must çYceeA the m~;.... ~ mlmher of cQ-~ec~ ve cellular scans which is set to 6 in the ~.are.,ed emhoAim--lt The forcing of the rescan is done since the PCC 101 could get stuck in an 1 0 Pn~lle88 loop if the check were not there and the radio ..I:n.~ously ac~luiled the cellular channel and lost word ..;7~ n- If the forced cordless rescan is not ..ece~ry~ the PCC 101 goes to the test at 1141 to ~ "~ e if cellular word syncl.,~-.i7~ n is present. If word 15 syncL~ ;7~ n is not present, the PCC 101 resc~nR the cPlllll~r system by ~ Lillg at 1127. The ~e~el~ of the cordless base rescan timer at 1125 iB shi~l since the cordless base was not gc~nne-l If word synd~,Q--i7~tion i8 present, a detel --~ *~n of 2 0 whether a system access i8 necessary (that is, a call origin~t;on~ a call page re~o~se, or other dile~,led cellular system access) is made at 1143. If a by~ . access is ne~e~ry an ~tte-npt is made to c~,lv~..t;Qn~lly access the cellular ~y~. at 1146. A sncces~ful access results in a post 2 5 power on return to the process. An unsllrcessfi~l ~cce~s, such as a lece~lion of a page request but an nncllcces~ thmpt to ,eg~o..~l, as determined at 1148, results in a return to the cellular system ~i~n~lling ch~nn91 scan.
If a system access was not ~leems~l nscess~qry at 1143, a 3 0 test is ~,rol~ed at 1145 to de~el~e if a cellnl~r rescan should occur. A cellular rescan occurs if the cellular rescan timer çycee~l~ 300 seconds and the cordles~ rescan timer esceeds the mi-.i-.. --.. - rescan time. The .. ;.. ;.... rescan time is the minimllm value of tl which was 5.3704 secQnrlq in 3 5 the earlier es~mrle. re~ru~ g the test of the cordless -19- 21156~7 -EC~ timer enQ7ures that the PCC 101 has a ch~ncP to ~ace;ve one of the two l,olq~ l tronRmiRR~iQnR of the same page.
When a cellular rescan occurs, the PCC 101 goes to 1127 thus QL ;l~ ~; the l ~Be~ of the cordless base rescan timer at 1125.
If the cellular rescan is not neceQ7Q-Ary, a test is .e. f~)....~ at 1147 to ~leter~ ; if a cordless base rescan should occur. A cordless base leec~ occurs if the cordless base rescan timer ~cae~l4 CBRT and the cellular rescan 1 0 timer is ~71eater than the ..-;..;....~... rescan time. The ...;..;..-.-... rescan time is 5.3704 8econ~18. P~rful~ the test of the ce~ r rescan timer ensures that the PCC 101 hss a rhon~e to l. ceive one of the two pot~n*ol trAnpmiQsjanQ of the same page. The value of CBRT (cordless base leec~ timer) l 5 must be greater th~n tl which is 6.3704 seconds. A value of 60 s7econ~1Q is picked for CBRT for the ~ fe~ed amho~lim~nt~ If a cordlees base rescan i8 not necesRAry, the process starts back at the l e~;"";"~ of the idle task, 1138. This is the test at 1139.
If a cordless rescan is nP~ce~sAry~ the process begins by 2 0 resetting the cellular scan counter at 1149. This is also the first stste of a forced cellular rescan which is deci~lP~l at 1139.
The cellular scan co ...te.- is reset at 1149 to assure that a forced cordless scan is not needlessly de~ 9~l upon at 1139.
After the reset~;n~ of the cellular scan coUllter, the Rign~llin~
2 5 sub-data ~h~nnel or chAnnPl~ of the cordless base 8t~t;0n 115 are sCAnne~l at 1151 as descnbed for 1103. If the test at 1153 ~e~e--~.;..es that the base was found, the cordless mode is entered and the user is notified at 1107. If the cordless base were not found, the PCC 101 must return to the previous 3 0 control rhAnn~l at 1155. It then delays to ~equile word &~ll~o--;7A~ion at 1157. The cordless base l'eE~C~ timer is reset at 1159 to in~ Ate the time that the last cordless base rescan oc~ led. Finally, the process resllmes at the top of the idle task, 1138, at test 1139.

21156~7 Refell~ again to FIG. 7, it can be &~ o~:-s-te~l that the sub-data rh~nnel ~na;avtp of WORD traffic. The sub-data ~h~nn-l WORD hag the format of the ~ sequence (D), - followed by the 13~11dl~ ;7~91;1)n field (S), followed by the sub-S data ch~nnpl mesaa~e (MSG) data bits:

N ~u~e. of these WORDs conditutes a FRAME.

It is a feature of the ~.e~ ~t i~lv~*lion that the FRAME
10 helps determine the sub-data ~~hqnno~ (...;lo~;..g time.
order that a cPll~ gr system "page" message not be mia ell during the time period the PCC is 8~ g for the ~ai~nslling sub-data rh~nnPl of the cordless base sts~;on, the mo i~Ollllg time mu~t be less than t2. The shorter the time period, the 15 lower the likPlihootl a cellular "page" will be miase~l When the PCC leaves the control chsnnPl of the cellular system and Jt8 to ac~ r~ the sub-data rh~nnPl from which one FRAME of data may be obts; . ~e~l, the following sequence of events can be çspe~te~l to occur. Under ideal conditions, the 2 0 PCC aC~ e8 the sub-data l~h~nnel at the be~inning of a WORD suc_ that the WORD is detecte~ This yields a necesg~sry mo. ~,Ollllg time of one FRAME time, that is, the ..~;..;....-... monitoring time ~e~uired to leceive a FRAME:

2 5 M; . .; .. ~ .. lll~nilu- illg time = FRAME time.

Under other than ideal conditions the PCC acquhes the sub-data ch~nnPl sometime (705) during a WORD such that the WORD is not /lPtecte-l This yields a molli~,ol ,g time of 3 0 one FRAME time plus one WORD time, that is, the duration 707 until the next FRAME and the next WORD. The m~ mll~ monitoring time required to receive a FRAME is:

r~c~;.. Ill~lli~.i,lg time = FRAME time + 1 WORD time.

211~6~7 The prece-ling conclusions are based on certain ideal conditions. Huw~zve~, under real world co~..l;~;ona an ;..I;..;le mlmh~r of BCe.~;OB may be played out. Never~hsless, the sub-data rh~nnel monitoring time should fall withil~ the S following limits:

FRAME time S . ~ time < FRAME time + 1 WORD time.

Still further refinPm~n~ of the çYi~;n~ cQ-I~lit;nrla may be 10 applied when detel n;~ the sub-data ch~nn~l ~OllitOl~g time. The two scenarios worth e~...;..;..g are the idesl cQ "ii~;nn~ and the other than ideal co~ ;s~

Ideal conditions There are two points of interest, the entry point and the exit point. First, con~illPr the entry point. The entry point is largely determined by when the radio acquil~ the sub-data t~h~nnPl Under ideal conditions the radio would &cyui~a the 2 0 sub-data rh~nnel and detect the first WORD, yielding the following monitoring time:

- monitoring time = FRAME time 2 5 Cnn~i-lering the dotting ~D) sequence w_ich may not be essçnt;~l to detec1;n~ a valid WORD (~eppn~ling on the WORD
~letect;Qn algorithm) the mnni~ring time may be reduced to yield the following:

3 0 monitoring time = (-DOl~ING time) + FRAME time Negt, consider the exit point. The exit point time may be determined by 1 eceivillg an entire E RAME of data. However, if the synchrQni7~1;0n (S) of the last WORD of a FRAME
3 5 cannot be detected (depen-ling on the WORD detection 2115~57 al6o~ ) then the m~mit~ring time may be re-lnce-l by the m~r~ge (MSG) time, yielflin~ the following time =
5 (-DOl~ING time) + E RAME time - (WORD time - r~ A(~F time) This is the .~.;..;....~... sub-data rh~nnPl monitoring time.

Other than ideal conditions ~ gS~in, there are two points of illtel~bl~, the entry point and the egit point. First, con~ ?~ the entry point. The entry point is largely delel~ed by when the radio acquires the sub-data rh~nnPl As stated previously, under other than 1 5 ideal colldit ions the cellular radio would acquire the sub-data rh~nnel somewhere 705 in a WORD such that the word is not ~letecte~l. Under worst case conditions the entire WORD may not be delec~ed, yiellling the following 2 0 monitoring time = FRAME time + 1 WORD time This is the m~mum sub-data ch~nnel mo..;l~ g time.
Next, con~ p~r the exit point (709) when the PCC exits the sub-data r.h~nn~.l (It should be noted, of course, that if the 2 5 PCC detects a WORD having a meRsage or BID which is desired, the PCC will remain tuned to that sub-data Rign~llir~
rh~nn~.l and not return to the cellular sy~lell~). The exit point time may be determined by l~ce;villg an entire FRAME of data.
3 0 How~ver, if the SYNC of the last WORD of a FRAME
r~nnot be detected (dep~n~ling on the WORD ~letec~;on algorithm) then the monitoring time may be reduced by the meRsage time (MSG) of the last message since the lack of synchroni7~tion (S) m~lre8 the MSG portion of the last word 3 5 undetectable; thus:

21156~7 t,ime = FRAME time + 1 WORD tim~ (WORD time -MFQQAr.F t,ime) ~enr~, H~.n;.. ;ng both the ideal and the other than ideal c~n ~ onP., the sub-data rh~nnn,l mo~utoring time may be ~ ese~ts~l as follows:

(-DOITING time) + E RAME t,ime - (WORD t,ime r ~..SQ,A~.~.
1 0 time)<.. .- - .; I - .l~g time< E~RAME time + 1 WORD time The sub-data rhqnn~,? monit~l~ time should fall somewhere within the prece-ling limits.
Again, when e~.n;..ing the monitoring time, the two 1 5 points of i~telebl are the entry point (705) and exit point (709).
The entIy point, for the mo~t part iB entirely ~:lldr~, since it is ~lPpen-lp-nt upon leaving the control ~h~nnel and ac~l.~irlllg the sub-data r,hsnnal. However, the exit point iB controllable from the il follllation provided on the sub-data ch~nn~l. This 2 0 info~mation includes, the WORD format and the FRAME
format.
Thus, taking the provided illfol.n~tioJ and the monitoring time limits into consideration, the following process of FIGs. 8, 9, and 10 re~nr,es the gub-data chsnnPl 2 5 monitoring time. The two main fimct;on~ of this process are:
1) Upon ~etec1;on of the first word - recalculate the monitoring time. (The monitoring time est~hli~hsd the egit point). 2) Upon entry into t~e last poE~ihle WORD, if SYNC can not be detected by the expected time, set the exit cQn~ ;on. (The 3 0 presence or absence of SYNC in the last WORD may influence the e~it point) FIGs. 8, 9, and 10, taken together, represent a flow chart of the sub-data ~h~nn~l timing monitor process. Upon all;villg on the sub-data rh~nnP,l the ~i~ monitor will be 3 5 initiated at block 801. The fir~t time through, all ~ociqte~l - 2115~S7 -variables are ini1;~te 1 at block 803. The mol.,lo.~g time (monitor_time) i8 set to the m~

- ... o.-ilur_time = E RAME_TIME + 1 WORD_TIME.
s The rem~inin~ word count (rçm~inin~ words) and the timer count (timer_count) are cleared. The first word leceived (first_word_lece:ived) and scan complete (scan_complete) inllir~1~nn~ are set to FALSE.
1 0 The first and sllhse~uent ~Yecn~;;QnR of blocks 805 and 807 m~it~r the various e~it conditions. If at block 805 the timer count e-rAed~ the ...~--.;~c.;.~ time or at block 807 a scan comrlete indication of TRUE is detected and the sub-data rh-~nne? mnnitor process is exited at block 833. Else, a 1 5 proces~in~ status of the word fl~te~;on process is reqnPsts-l at block 809 and proc~ssine c~ es on to block 811.
If at block 811 the first word lece;v~.l inAirst;~n is FALSE and at block 813 the ~oce~;-~ status is equivalent to WORD_DETECTED. The first word lcceived indication is set 2 0 to TRUE at bloc~ 815. To deter~l~ine tlle nllmhPr of words which remain to be detected, the rem~ining word count is ~lCl-l~te l at block 817 (the r~sm~ining word count is ~ll~e-l to be l~l,resented by an integer value). The rem~ining word count is calclll~te-l from the ~lPtec*Qn time of the first word, 2 5 the m~Yimum monitoring time (monitor_time, as defaulted at block 803), and the WORD_TIME (the l~esellted division in the formula i8 an integer division):

rem~inin~ words = (.,.onilor_time - timer_count)/WORD_TIME.
Then at block 819 the calc~ tR~l rem~inin~ word count is rhel l~e~l to insure that the count is less than the FRAME_Sl~. If the entry into the data happens to fall at the he inning of a WORD, the ideal colldi~ion of equating the 3 5 monitoring time to the E RAME time may be n~ etl~ If the 211~657 -count is de~,el ...;..~~, at block 819, to be equal to the FR~Mh._SIZE, the rçm~inine word count is adjusted at block The mo.l,~ol~g time i8 rer~ te l at block 823. The S new m~ rl~lg time is c~ te~l using t_e first word l~ce;v~l time (timer_count), the rem~inin~a. word count (rem~inina words), and the WORD_TIME:

_time = timer_count + (rpn~oining words * WORD_TIME).
The effect of this reCAl~ is to reduce the period of time spent m~--.;~or~g the sub-data ch~nnal As ~hown dia~ lly in FM. 7, the exit point 709 is moved in time to exit point 715, thereby re~l~rin~ the monitor time by the 1 5 Ji~el~nca in time 717 belween the or~-n~l exit point 709 and the rec~ exit point 715. (The mnnitoring time is used a~ block 805 for exit de~l...;..~ n). Once re~lc~ te~, l~.OC~R~ e will ~,4~ e on to block 825. Else, if at block 811 the first word r~ce;ved int~ n is TRUE, or at block 811 the 2 0 first word intiic~1;on is FALSE and at block 813 the procesRin~
status does not in~lic~te a WORD_DETECTED, the proc~in~
C4~ eB to block 825.
At block 825, if the timer count is greater than or equal to the monitor time minus the Nl~..~AGE_TIME and the 2 5 ~,ocess;..~ status at block 827 indicates that SYNCpETECTED is not TRUE i.e.the sync~o~;r.At;on (S) of the la~t pos~ihle WORD cannot be detected, the Rcan comrlete inflicA1;Qn is set to TRUE, at 829. This results in the monitoring time being reduced by ~uvil~ the exit point from 3 0 point 715 to the new exit point 711 dia~ ~A.. e~l in FIG. 7.
ProcesRing cQntinlles to block 831 for a timer i~cl~ment and the entire process is repeAte-l 81~ -g with block 805. Else, if the timer count at block 825 iB less than the monitor time minus the MF-~GE_T~E, or the timer count at block 825 is 3 5 greater than or equal to the m~nitor time minus the -26- 2115~57 , ~ GE_T~IE and the l,~ 0~8~ status at block 827 in~ te~ that SYNC_DETECTED i8 TRUE, ~ C~,gR;~
continues to block 831 for a timer ~~ellt and the entire - l,.oces~ i8 re~-e~qte.l sl~l,il.g with block 805.
s We Claim:

Claims

THE EMBODIMENT OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A radiotelephone apparatus which receives messages preferably on a first radiotelephone system having a limited radio coverage area and which alternatively receives messages on a second radiotelephone system having a wide radio coveragearea, the radiotelephone apparatus interrupting its monitoring of messages from the second radiotelephone system in order to monitor the first radiotelephone system for messages the radiotelephone apparatus comprising:
means for establishing a monitoring time value;
means for monitoring for a period of time a radio channel associated with the first radiotelephone system;
means for generating a timing signal whereby the period of time spent monitoring said radio channel is measured;
means for receiving during said monitoring a predetermined number of data words transmitted on said radio channel associated with said first radiotelephone system;
means for detecting a first received data word;
means for readjusting said monitoring time value to be the sum of the value of said generated timing signal and the product of a determined number of received words to be detected and a predetermined value of time for each word;
means for incrementing said timing signal by a predetermined value;
means for comparing the value of said readjusted monitoring time value to the value of said incremented generated timing signal; and means for ceasing monitoring of said radio channel when said readjusted monitoring time value equals or exceeds said incremented generated timing signalvalue, and returning to the second radiotelephone system.

2. A radiotelephone apparatus in accordance with claim 1 further comprising means for calculating said determined number of words to be detected, said means for calculating including means for generating a difference value between said generated timing signal and said established monitoring time value and means for rounding said generated difference value to the integer value equal to or less than said generated difference value.

3. A radiotelephone apparatus in accordance with claim 1 further comprising:
means for determining that the last data word is being received;
means for determining that said last data word cannot be detected; and means, responsive to said determination that said last word cannot be detected, for ceasing monitoring of said radio channel.

4. A method of channel monitoring time period reduction for a radiotelephone apparatus which receives messages preferably on a first radiotelephone system having a limited radio coverage area and which alternatively receives messages on a second radiotelephone system having a wide range coverage area, the radiotelephone apparatus interrupting its monitoring of messages from the second radiotelephonesystem in order to monitor the first radiotelephone system for messages of the method comprising the steps of:
establishing a monitoring time value;
monitoring for a period of time a radio channel associated with the first radiotelephone system;
generating a timing signal whereby the period of time spent monitoring said radio channel is measured;
receiving, during said monitoring, a predetermined number of data words transmitted on said radio channel associated with said first radiotelephone system;
detecting a first received data word;
readjusting said monitoring time value to be the sum of the value of said generated timing signal and the product of a determined number of received words to be detected and a predetermined value of time for each word;
incrementing said timing signal by a predetermined value;
comparing the value of said readjusted monitoring time value to the value of said incremented generated timing signal; and ceasing monitoring of said radio channel when said readjusted monitoring time value equals or exceeds said incremented generated timing signal value, andreturning to the second radiotelephone system.

5. A method in accordance with the method of claim 4 further comprising the step of calculating said determined number of words to be detected by generating a difference value between said generated timing signal and said established monitoring time value and by rounding said generated difference value to the integer value equal to or less than said generated difference value.

6. A method in accordance with the method of claim 4 comprising the steps of.
determining that the last data word is being received;
determining that said last data word cannot be detected; and ceasing said monitoring of said radio channel in response to said determination that said last word cannot be detected.

7. A radiotelephone apparatus which receives messages preferably on a first radiotelephone system having a limited radio coverage area and which alternatively receives messages on a second radiotelephone system having a wide radio coveragearea, the radiotelephone apparatus interrupting its monitoring of messages from the second radiotelephone system in order to monitor the first radiotelephone system for messages the radiotelephone apparatus comprising:
means for monitoring for a predetermined monitoring time value a channel associated with the first radiotelephone system;
means for generating a timing signal;
means for receiving during said monitoring a predetermined number of data words transmitted on said channel associated with said first radiotelephone system;
means, responsive to said monitoring time value and said generated timing signal, for determining that a last data word is being received;
means for determining that said last data word cannot be detected; and means, responsive to said determination that said last word cannot be detected, for ceasing monitoring of said radio channel, and returning to the second radiotelephone system.

8. A method of channel monitoring time period reduction for a radiotelephone apparatus which receives messages preferably on a first radiotelephone system having a limited radio coverage area and which alternatively receives messages on a second radiotelephone system having a wide radio coverage area, the radiotelephone apparatus interrupting its monitoring of messages from the second radiotelephonesystem in order to monitor the first radiotelephone system for messages the method comprising the steps of:
monitoring for a predetermined monitoring time value a channel associated with the first radiotelephone system;
generating a timing signal;
receiving, during said monitoring, a predetermined number of data words transmitted on said channel associated with said first radiotelephone system;
determining, in response to said monitoring time value and said generated timingsignal, that a last data word is being received;
determining that said last data word cannot be detected; and ceasing monitoring of said radio channel in response to said determination that said last word cannot be detected, and returning to the second radiotelephone system.

9. A radiotelephone apparatus which receives messages preferably on a first radiotelephone system having a limited radio coverage area and which alternatively receives messages on a second radiotelephone system having a wide radio coveragearea, the radiotelephone apparatus interrupting its monitoring of messages from the second radiotelephone system in order to monitor the first radiotelephone system for messages the radiotelephone apparatus comprising:
means for monitoring for a predetermined monitor time a channel associated with the first radiotelephone system;
means for generating a timing signal;
means for receiving a data word from said channel associated with the first radiotelephone system;

means, responsive to said data word being received by said means for receiving, for readjusting said predetermined monitor time into a monitor time value related to said timing signal and a determined number of data words to be received from said channel associated with the first radiotelephone system;
means for incrementing said timing signal by a predetermined value to produce an incremental timing signal;
means for comparing said readjusted monitor time value to said incremented timing signal; and means for ceasing monitoring of said channel associated with the first radiotelephone system when said monitor time value exceeds said incremented timing signal, and returning to the second radiotelephone system.

10. A radiotelephone apparatus in accordance with claim 9 further comprising means for calculating said determined number of words to be detected, said means for calculating including means for generating a difference value between said timing signal and said monitor time and means for rounding said generated difference value to the integer value equal to or less than said generated difference value.

11. A radiotelephone apparatus in accordance with claim 9 further comprising:
means for determining that a last data word is being received;
means for determining that said last data word cannot be detected; and means, responsive to said determination that said last word cannot be detected, for ceasing monitoring of said channel associated with the first radiotelephone system.

12. A method of channel monitoring time period reduction for a radiotelephone apparatus which receives messages preferably on a first radiotelephone system having a limited radio coverage area and which alternatively receives messages on a second radiotelephone system having a wide radio coverage area, the method comprising the steps of:
monitoring, for a predetermined monitor time, a channel associated with the first radiotelephone system;
generating a timing signal;

receiving a data word from said channel associated with the first radiotelephone system;
readjusting said predetermined monitor time into a monitor time value related to said timing signal and a determined number of data words to be received from said channel associated with the first radiotelephone system;
incrementing said timing signal by a predetermined value to produce an incremented timing signal;
comparing said readjusted monitor time value to said incremented timing signal; and ceasing monitoring of said channel associated with the first radiotelephone system when said monitor time value exceeds said incremented timing signal, and returning to the second radiotelephone system.

13. A method in accordance with the method of claim 12 further comprising the step of calculating said determined number of words to be detected by generating a difference value between said timing signal and said monitor time and by rounding said generated difference value to the integer value equal to or less than said generated difference value.

14. A method in accordance with the method of claim 12 comprising the steps of:
determining that a last data word is being received;
determining that said last data word cannot be detected; and ceasing said monitoring of said channel in response to said determination that said last word cannot be detected.