Note: Descriptions are shown in the official language in which they were submitted.
w~ 94/OSIol ~ 1 2 ~ PCr/l~Sg3iO7~29
POE~T~LE ~0 ~DRT~BiLE COMI~ICAT~3 INA ~DLE~3
TELl~EIOl~E S~S~\I
=
This inveIltion relates generally to commurlicatioIl systems and
10 more specifically to the field of cordle~a telephone syBtems~
Portable telephone &y~ltem8, such as ~econd-generation dig~tal
cordle~8 telephoIle (CT2) system~, typically include multiple call point
15 stations each providing multiple ~ char~els. ~hese call poiIlt stationæ
al80 being referred to aæ telepoirlts or cordle~s fix0d part~ (CFPs). CFPs
allow per~ons u~ing portable telephone handsets ~al~o known as cordless
portable parts, CPP~3, t~ accesæ 1 he publî~ switshed t~lephone network
(PSI~). Acce~s to the PSTN can occur when a CPP get~ in range OI a
20 telepo;llt ~C~) and aPcer the CPP ~andset3 has establi~hed a
eYnChrOnO~1S 1irk With the CFP (base ~'dOn).
~ a CT2 ~Y~t~m, a h~ et iI~itia~I~g a ~a11 tO a ba~ n
a~YX1C~OI}OU~IY tranS~t8 Qn One ~Vai1ab1e channel Of 1 he hand~et~S
tra~sceiver, WhiCh COITe~POnd~ tO a radiO ~eq11e~CY (RF~ C~anne1 in ~he
25 ba6e ~tatiOn (eaCh ba~e 8tation being capable OI 611ppor1~ing Up to 40
Channe1~
n a tYP~ T 2 BYatem, ~e communication protoeol s~andard
inc~udes ~our m~ bur~t struct~re~, called multiple2~ 3 (MIJX 3),
multiplex 2 (MUX 2) and ~ultiplex 1 (~ 1) which is filrther ~-
30 di~rided into either multiple~ l.4 sr 1.2 ~ 1.4 or MUX 1.2). MU~ 3 isr u1;ilized~mai~1y for communication link initiation (link e~tabli~hment
`J.`~ d re-e~ Ii~ent) frcm a CPP to a G~P. MU~ used primaxily
fior communicat;on l;Dk~establishmènt ~nd ~r ~i~ initiation firom the
z ~ base ~on(CP~ The MUX 1 burst structures (MUX 1.2 and MUX 1.4)
3 5~ are used prima~ly ~r voice~data communi~ations, ~ignaling
ormatio~ control mes~a~s~ m the CPP (portalble) and CEP
(base).
.
PCI~/US93/071129
For a better understanding of the oYerall CT2 system
communication protocol, one i8 refelTed to a publication entitled,
"Common air interfiace specification to be u~ed for the interworking
between cordless telepho~e apparstu~ in the frequency band 864.1 MHz
5 to 868.1 MHzJ including public access services", Version 1.1, dated 30th
June 1991, which i~ published by the European Telecommunications
Stsndard~ Institute and i~ hereby incorporated by reference.
In present CT2 systemsJ all communications occur between the
CPPs and CFP~, w~th typically the CPPs initiating the calls to the CFPs,
10 although CFP8 call also ini'date calls to individual CPPs. Using the CT2
protocol standard (CAI), a cordle~s handset ~CPP) initiating a call,
a~ynchronously transmits using MtJX 3 on an available radio frequency
channel to the base (CFP), while the base ~tation scans in MUX 3 waiting
for a poll by one of the CPPs in the s~tem.
In FIG. 1, a table showing the typical handsbake sequences
between a cordless portable part (CPP) and tl~e telepoint base station
(C~! are shown. The matrix 100 shows the link setup direction, the
mes~a~e direction,: ~ mode, and the content of the link identification
code (LID) for each han~shake sequence. T~e LI:D code iB u~ed for the
following~
i). End point idbntification for: CPP (handset) call ~etup;
ii?. Link reference for a8soci:al~ng CPP (handset) and CE P (base) call8
duling handshake:: exchanges and link re-e~tablishments; and for
iii). Base identifier ~BID), which îs the ~inging address to which one
~ 25 or more GPP's ~ respond: to.
`~ Row 102~ows~a~ basic:sequence on how a handset (CPP)
: ; establi~hes co=cations ~with a telepoiIlt ~C~EP), row 104 shows how a
~ ~ .. telepoint:station establi~hes co=cations with a handset~ and row
~ 106 ~howfi ~how ~ a co=cation ~ k is re-e~tabli~hed in ca8e the link is
~: - 30 ~ disrupted duling an ~going comm~ication ~e~Bion.~ Lo-oking foexa~mple at row~ 102,~the sequence of events which occur in order to
establish a co=cation link between a~ particulal hand~et (CPP) and
ba~e 8tation~(CE'P), i~ shown. The requesting~hand~et (CPP) transmits
in ~ 3 a msssage including the identification number of the handset
3~ (end point ID).:~This-~is~:followed by the ba~e station transmitting in MUX
~: : 2 a message with the: LID having the commuI~îcation link reference
identificatio~ number which info~ms the handset that the link has been
granted.
~ .-
~1
WO 9-1/05101 , 2 1 2 ~ ~2~3 9 ~ ~ ' PCr/US93/07029
,- 3
Once the communic~tion link establishment has occurred
between the two units, the units go to the MUX 2 protocol where the CFP
tran~mits a supervisory message and acknowled~ent. The capab;lities
of both the CPP and CF l? are determined, and authorization to use the
5 system is determined by the CFP. The two uI~its then move on to the
MUX 1 protocol by a request from the CE~ and an acknowled~ent by
the CPP. Once in M~lX 1, dial tone i8 ~ent out by the CFP? the CPP then
dials the telephone number hs wishes to access. Finally, this is followed
by a voice communication link being established between the CPP and
10 the party at the dialed num~er telephone number. The voice messages
are either transmitted using MUX 1.2 or MUX 1.~ format.depending on
the specific ~ystem 100 being utilized.
As mentioned previously, in present CT2 systems CPPs are OD~y
capable of communicating with CFPs, although as also mentioned
15 before, either device can initiat0 a call to the other. As CT2 sy~tems
become more widely used, a need thus e~ists for a way of allowing for
CPPs to conununicate directly wi~ other CPPs wit~out having to go
through a CFP. It would also be desirable to be able to achieve t}lis goal
while ~till operating under the CT2 conununication protocol ~tandard.
20 Thi~ providing for added capabilities and benefit~ to CT2 handset users.
- ,
FIG. 1 6ho~ws a; ma~rix ~of the pr~or art handshake sequence
between the cordless tel~phone dévice (CPP) and the telepoint base
25 ~ stahon (CFP3.
FIG.~ 2 shows~a ~diagran~ of a ~ al CT2 By~tem in accordance
wi~ the present~inveniion.~
FIG. 3 ~ is~a diagrum ~howing;the CPP to CPP registration process
in accordance with the p~re~ent invention. - --
30~ FIG. 4 shows~a~ diagram;of a CPP to CPP li~k establishment in
;;.acc~rdance with the pre~ent in~re~tion.
.ri~ EIG. 5~is~a~block diag~m~ofa cordle~s telepholle in accordance
the present invention.
; 35
Referring now t~ the drawings and in particular to FIG. 2, tbere is
shown a comnr~cation syste,m ~uch as a cordless telephone system 200
in accordance with ~he pre~ent inve~tion. Cordless telephone sy~tem 200
:`
, ~
::
wo 94/05101 2 ~ ~ t ~ ~ 9 Pcr/uss3/o7~29
is preferably a second gene~ation cordle~s telephone system, betterknown as a CT2 ~ystem. (~ordles~ telephone 8ystem 200 compr~es one or
more base sta~on8 (CEP~) 204 and 208, and one or more haDdsets ~CPP~)
210, 212, 214 and 216. Each of ~he CFP8 204 a~d 208 are coupled to a
5 public ~witched telephone network (PSTN) 220. Once a handset gather~
acces~ to one of the RF channels pro~ided by a parti~ular base ~ta'don,
the base ~tation ~ets up the commun~cation link between the reque~ting
hand~et a~d 'Lhe PSTN 210, ther~by allounng a handset user to make a
~tandard telephone call to a land-line party. In system 200, base station
10 204 is shown to have ~ t~pical operating range shown by commuI~ication
coverage area 202, while ba~e sta'don 7.08 has a coverage area 206.
Upon a handset coming in range of a base station coverage area
202 or 206, the handset can then a~tempt to gain access to one of the ba~e
stations communicatio~ cha~nels. Handsets are typical very low power
15 portable commuIIication units having a maximum outpu~ power rating
i~ the order OI 10 m~l watts (mW). Each base statîorl or telepoiIlt 204
and 208 can support up to a ma~imum of 40 communicativn channels.
Upon reque~ting access to a base station, ~he hand~et wil~ ~can the base
sta~on'~ RF ~els in order to get an available cha~nel ~e.g., a
20 channel wbicl~ ot busy). At which poi~t the handset tran~mits a link
request in MllX 3 which t~e ba~e ~ on can granlt UBirlg a MUX 2
retu~n traDBm~88~on. Thi~ is ~ollowed by a ~ 2 h~ndshake between
the two units and a hand~et ID check, in order to establi~h the
ide~tification of 1 he particular handset ~at i~ ori~ating t~e call. The
2~ handset :Il) is used Por both billing pul~po~e8 a~d to e~5ure that only
authorized uI~its~are u~i~g ~e sy~tem.
In order to eEtablish a hand~et to ha~d~et ~CPP to CPP~
- ~ commuI~ica~o~ according to the present invexlti~n, t~e calli~g
ha~dsèt emulates a base ~ ~on MUX 2 poll message usiIlg a BID (ba~e
30 ide~tification~n~umber) in the LIl:) field and the called handset PID l
(produ~t identificatio~ number) ~ ~e H~C (handset iden~ty code) and
. MIC ~mallufa~ identity code) fields. T he poll i8 prefera~ly sent out
wit~ a unique ~ cadence 80 that the called handset user i~ aware ~h~t
the incoming call is from a handset and not ~om a ba~e 8tati0n. Once
i
3~ the link i~ established, the harldset initiating the call con1;inue~ to
- emulate a base station t~oughout the call. This in~ludes t he handset
acting as the timing master throughout the duration of the con~ersation.
wi~ the: ~pproach of the present invell~on, a ha~dset with this ~eature
wo 94/05101 21212 ~ 9 Pcr~uss3/07029
-- 5
msy establi~h a direct liPk with any CT2 Common Air interface (C: AI)
compalible handset (CPP). The two key functions for achie~ing "CPP to
CPP calling" (will be referred to a~ "CCC") are: 1). CPP to CPP
registration; and 2). CPP to CPP link e~tablishment, both of which unl1
5 be discussed in more detail below.
In FIG. 3, a registration process 300 in accordance with~the
present inven1;ion is shown. Thé registra~on proce~ a ~et-up proces~
which enables a particular ~t of hand~et~ to talk with each other
directly. Preferably~ hand3ets featur~IIg hand~et to handLset
1 O communication capability ~CCO in accordance with the present
invention ~ontain multiple regi~tration slots a~d a r~ndo~ E~ase Iden~ty
Code (BID) which identifies a par~icular handset to other handset~
registered to receive Call8 from it. In addition, the halldset-to~ d~et
capable hand~et may contain separately portioned registration ~lots ~or
15 incoming handset calls which may be enabled and disabled at the u~ers
discretion, ~hereby bloc~ing lmwanted h~ndsets from establi~hing
~ccess wit.h the particular harldset. Typically, since CT2 handsets are
usually sold via retail outlets, t~e reg~stration proces~ as fihown in FIG.
3 i8 required in order to enable handsets to communicate wit~ each other
20 directly. However, if it were knn~ ahead of time t~at a particular
group of han.d~ets would needed to commuDicate w~th each other dlirec~y
(CCC) the re~strstioIl info~ma1ion (e.g., ID'~ of h~ndsets whieh can
com~uI~icate directly with a particulsr handset, etc.) could be
programmed into each radio eit~er at a serv~ce BhOp or during the
25 manufacturi~g pr~cess.
The regi~tration process i6 bi^directional if both handsets are
: capable of handset^to-h~set communicatio~s (either handset can
i~t iate a c~ to the o~er) and unidirection~ if only one handset is
handset-t~^ha~se~ capable (e.g., in 1~i8 particular case, only 1~he ccc
30 -j - capable handset would be able to iDitiate the call). - ~ -
~
Tbe CPPl ha~d~et user iDitiates ~he regi~tral;ion process by. selec~ing a ~eYv r~gistration ~1ot for the~:handset he WaI~B to be able to
. ~ commurlica~e directl~ wit h ~t a later date (in this par~cular egample it
is ~dset CPP2). The user the~ presses a key sequence in his handset
35 ~ to enable the re istral ion process. At this point, handset CPPl begins
!3 MUX 3 scam~ing ~or a lihk identification code = "FFFF". Handset CPP2
at the same time selects a CFP (base station~ registration slot for handset
`~3
.1 ~
M
WO94/05101 ~12~ i - pcr/us93/o7o29
CPPl The CPP2 handset i~ then ~et to initiate a ~tandard CE P over the
air registration via the handset'~ keypad.
The over the air registr~tion step is executed by the portable
handset (CPP2) ini~ating a MUX 3 link request 302 in which ~e hand~et
5 identity code ~IIC) alld the manufacturer identity code (MIC) equals the
CPP2 portable identification c~de (PID). The link iden~ific~tion~code
(LID) for over th~ air regi~tr~tion i~ set equal to "FFE F". The channel
marker bit patter~ (CHMP) i~ al80 sent in thi~ tran~mi~sion. The
receiving }~d~et, CPPl, at the same time i~ scanning t~e availa~le
10 radio fie~uency ch~el~ in MUX 3 for a LID equal to "FFFF". Once
CPPl receives the LID, the uI~its begin commun~cating in ~ 2, as
~hown in ~tep 304. A link grallt message 30ff is then sent by CPPl, the
message inc~ude~ CPP2's PID and tbe LID, the SYNCF (~ynchronization
word from CFP), ~et equal to the link reference identification number.
15 In step 326, CPP2 sends an identi~cation received message ("ID-OK")
which include~ CPP2's PID and the SYNCP (~ynchronization word from
CPP).
CPP2 in step 308 then ~ends a layer two li~k protocol initialization
command which i8 referred to as a Set Asyllchronous Balanced Mode
20 message ~"S~M") to CPPl. This in turn i8 fo~lowed by CPPl
acknowledging ~e SABM mes~age in 8tep 310. ~teps 308 and 310 alB0
re~et all of the state va2~ables
( ~(r) = the receive local state variable and V(8) = t~le send local state
variable), as well as traIlsmission of a data establishment request
25 (DL_EST_RE:Q) and the indication of the Data Establi~hme~
(DL_EST~
-- In step 308, CPP2 se~ds:a~set asynchronous Balanced mode
~SABM) mes~age ~C~PPL SABM iB a layer two link protocol ,
: i~ti~lizal;io~ co~aIld This i8 followed b~ a SABl~ acknowledgment
30 mçssage from CPPl to C~PP2. At~ his point in t;he regi~tration proce~
t~e commul~isa1ion ~ k between CPPl and CPP2 has been ~tabli~hed.
st~p 312, CPP2 infomls CPPl of its capabilitie~ CAP,
. . ~ tenninal capabilihes):includi~g in~o~nation on a~sr activated features
via element "FA". - Also, i~ ~tep 312 CPP2 info2~ns CPPl of its
35 ma~u~acturer'~ iden~ty co~e (MANIC) a~d the manu~act~rers CPP
model iden~ity code ~MOI)EL). CPPl then ~o~s CPP2 of its
capabilities (BAS_CAP, base capabilities since CPPl in the preseIlt
invention is emulating a base station) in step 328. In step 314, CPPl
wo 94/05l01 2 1 2 ~ 2 3 g ~ ~ ~ Pcr/VS93/07029
sends a message info~ning CPP2 of its ~ ) and PID, and that it is
capable of CPP-CPP registration. CPP2 then acknowledge~ receipt of the
information in ~tep 316. CPP1 then transmits an On Air Registration
Acknowledgment (OARA) in step 318, and in step 320, CPP2
acknowledges receipt of the OARA. In ~tep 318 CPP2 ~tore~: CPP1'~ lBID
allo~ving for incoming call8 ~rom CPP1, while in step 320 CPP~ stores
CPP2's PID in the assigned registration slot. In step 32a, CPP1
tran~mits the initialization information element (INIT), and in step 324,
CPP2 acknowledges receipt of the INIT. At this point th0 registration of
CPP1 and CPP2 i8 complete, thereby allowing for the two handsets to be
able to communicate directly with each other, whenever they so chose.
Referr~ng now to FIG. 4, a CPP to CPP link establishment
procedure in accordance with the present invention i8 shown. In this
p~cedure one handset re~uests to communicate with another handset
directly~ In ~is particular example, CPP1 wants to establish a
communication link with CPP2. Link establishment protocol diagram
400 begiI~s with CPP1 selecting the CPP2 registrati:on slot previou~y
.established in the registration process. Once the CPP1 user presses the
proper key entry in (~PP1's keypad requesting to establish a
communication liDk with CPP2, the CPP1 handset in step 402 transmits
a poll message in:MUX 2. ~If the poll message is successfully received by
CPP2, CPP2 trans~ts a response to t}le poll which is al~o transmitted in
MUX 2. This is:foUowed by b~th units interchanging handshal~e lD-OK
code words in~ ~teps 404 and 406.:
: A ring sig~al message i6 t hen sent in step 408. As men1ioned
before the ~g 8ignal message can include parameters which can
i~form CPP2 to ring~in a~distinotlfashion which can inform CPP2 that
e transmission is origiDating from a handset a~d not a telepoint. In
~: ~tep~ 410 and 412 lhe two hsnd~ets interchange handshake ID-OK
messages.~ :~This~is followed by, CPP1 in step 414 tra~smitting a message
: info~g t~e nnger cir~t in GPP2 to ~:shut of ~. Steps 404 through 414
are repeated~ in :order to gene:rate a~particular ring cadence (duty cycle).
e user of the:~CPP2 hand~et at thi~ point to answer the call
a~vates 1~e ~t's "line key" switch on the handset, which generates a
35 ~: link request message in ~step 416. ~ request is a requ~st by CPP2 to
seize a commlmlcat;ion li~k. CPP1 receives the request a~d in step 416,
:~ transmits a link grant message. In this mes~age, CPP1 sends a ~FP
acknowledg~ent assigning a call reference identification number.
' WO g4/05iol 21 21 2 ~ f ~ PCI'/VS93/07029
CPP2 responds in step 418, by transmitting an identification-ok me~sage,
followed by a layer two link protocol initialization command (SABM), in
~tep 42Z. CPP1 then acknowledges this command in step 424. Once the
initialization command has been acknowledged, the communication
5 link between 1 he two handsets ha~ been established. A~ before, ~teps 422
and 424 initialize all state variables (V(s) and V(r) to zero in ord~r to keep
the communication between the two Ullit~ in ~ynchronization.
The CPP2 unit then transmits a message infor~ng CPP1 of its
capabilities in step 426. In step 428, a ring termination message is sent
10 to CPP2 which cause6 ~e ringing in CPP2 to turn off completely. CPP1
follQws this message with a message informirlg CPP2 of its own
capabili~e6 in step 430. The channel control me~age ~CC) i~ then
transmitted in MUX 2, in step 432. CPP2 in step 434, acknowledges the
channel control message in MUX 1. Another channel control message
15 is sent out by CPP1 in step 436, this 1;ime using the ~UX 1 protocol. CPP2
also acknowledges this message using the MUX 1 protocol in step 438.
Once these step~ are completed, the units are connected to the B channel
which is a 32 kilobit per secor.d (kbit/s) speech or data channel which is
then used by the units to transmit their data or voice conversation. The
20 units maintaih this bi-directional MUX 1 transmission until one of the
,
~ units d~cides to hang-up from the conversation. At which point a
- - . conventional: hang-up ~routine~is followed, which releases the :B channel
and returns t~e; unit6 to t~eir stand-by states.
With the present invention, the CPP standby operation is not
25 modified for CCC capabili~y as the CCC poll is received in l~lX 2 ~step
402). Addition~ly, B~) collisions with~ CPrPs are avoided ~L~ce C~FPs
monitor;for only MU~ 3 1ink requests, this eliminating outgoing CCC
collisions. CPPs~haviDgCGC capabiliiD (in t~is particular case CPP1)
- using the present invention:monitor for only MUX 2 polls ~except for
30 registration and link re-e6tablishment~, which eliminates CFP link
.z request collis~ions. CCC link re-establishment is identical to a CPP-CFP
link w¢re the CPP- t~at~ tiates the call emulates a CPl? and SCall8 for
; ~ ~ the called :CPP MUX 3 link request dunng re-e~tablishment.
Du~ing the present inve~tion's link establishmen$ procedure, as
35 discussed above, the initiating handset (CPP1) emulate~ a CE P (base
sta~on) in order to: estab:ish~: a communication link with the second
handset (CPP2). The emulation of a CFP by CPP1 includes CPP1 being
the synchroniz~tion master for frame, burst and bit synchronization. In
wo g~ 5101 2 1 2 1 2 3 9 ~ t ~ P~/US93/070~s
the above e~ample, CPP2 ~rill synchronize it~ ~rame, burst and bit clock~
to the 8igIlal~ received from CPP1. Also, a~ part of the CP~P emulation by
CPP1, CPP1 transmits its link establishment poll ~4023 in MUX 2, a~
compared to the standard CPP to CFP link esta~ hment were th0 CPP
5 ~ran~mits the Poll in MUX 3. This allows for other CPP~ which are
usually sca~g in MU~ 2 under the CT2 protocol to be able t^b receive
the MUX 2 poll without modifying their standard mode OI operation.
The emulation of a CFP by CPl?1 a~ discus~ed above include~ .PP1
emulating ~ome the b~se station's communication protocol parameters
10 a8 established by the CT2 common air interface ~tandard (~AI), such as
transmitting a lir~ establishment poll in MUX2, being th~ timing
ma~ter and other CFP emulation as shown in FIG. 3 ~d 4. Also, the
registration process shown in FIG.3, of (: PPl scar~ g for a link request
(step 302 ) in MUX 3, i8 also aIl emulation of a CFP by CPPl, given that
15 CPPs normally do no not scan in MUX 3.
I~ FIG. 5, a simplified block diagram of a radio such as a cordless
telepho~e 500 in accordance with l~e pre~ent i~vention is ~hown.
Cordless telephone 500 comprises a well known RF transceiver 502 for
transmitting and receiving RF comrnun~cation signals via an antenna
20 504. CT2 handsets operate in accordance with the previously mentioned
"MPT13~ Common Air I~terface Specification" (~AI) which establishes
a time~divi~io~ multiple~ed protocol ha~ing altematiIlg one millisecond
receive and traDsmit frame~ separated by guard time ~egments. In one
multiplexing ~cheme each $ransmit/receive ~egment includes a B
25 chalmel ~64 bits) and ~ D chaDnel which cont~ 1 or 2 bits at each end
of ~he B channel.
A ~me division mul~ple~er (TDD) 506 is coupled to transce*er 502
for pro~iding 1;ime-divi~io~ multiple~g and receive/transmit f~aming
o~t~e digital sigIlals. An ADPCM/CODEC 508 rece*es ~ice 8igI-alS
30 ge~erated by a microp!hone 510 and proce~ses them for transmi~sion.
: The APCl~!UCODEC 508 also provides voice sign~ls to be rendered audible
via a speaker~512.~
A oo~trol me~n6 such as controller 514 which is pro~rammed in a
;knowIl ~èr e~cept for the modific~tions to obtain 1~e present
35~ ention'~ capabilities, provides operational control ~or the cordless
telephone 500. Controller 514 can be any one of a~ number of
microprocessors or microcontrollers, the controller preferably having
input~output capabilities and built-in memo~y. Controller 514 executes
~ Wo 94/05101 2 1 2 1 2 3 9 10 P~/VS93/07029
the program which modifie~ the operat~on of cordles~ telephone 500
whenever telephorle 500 needs to communicate directly with ano~her
cordless telephone. Controller 514 automa~cally modifies such
com~unication protocol parameters a~; which MUX level to use, what
5 information packets to ~end, as well as other parameters which are
required for telephone ~00 to emulate in or~er for it to b~ able to-
comn~unica$e directly with other telephones, while still a11Owing
telephone 500 to maintaîn compliance with the CT2 communication
protocol standara (CAI).
For example, con*oller 514 modi~es the operation of telephone 500
to transmit a link establishment message (as shcwn in ste~ 402) which
substantially emulates a message transmitted by a telepoint, in order for
telephone 500 to be able to commuI~icate directly with another telephone.
Controller 514 also allows telephone 500 to re~ster with another
15 telephone by emula~ng a ba~e station in the area of scanning in MUX 3
~r a link request Inessage (as 8hown in 8tep 302 in FI(:. 3) which is
eomething a CT2 telephone does not per~o~m.
A ~ub~c~ber int~r cta with the cordless telephone via a keypad
516. Keypad 516 allow& t~e device user to enable operational features of
20 1~he tel~phone 500 ~uch as CCC (handset-to-handset communications) as
taught by the preaent invention. A display 520 provides visual
intera~on for t~e ~ubscriber. ~ memory block 522 ~uch as an
electrically ~rasa~le prog~mmabl0 read-only memo~y (EEPl~OM),
provides storage of ~e hand~etis ID nuunber and ot~er important
25 information. Memory block 522 can also inc~ude a RAM portion for the
temporar~T storage of informa~on.
The present ixlvention e~t~nds GT2 handset ~unclioIlality to allow
for cQmmurlicationfi~ directly between hand~ets without the RF link
,
. passi~g ~hrough a CFP, while at the same time m~ntaining fi~ll
. 30 ~ compliance with t~he CT2 Commoll Air I~erface (CAI) protocol
~i . . s~dard. In order to estab~ish a CPP to CPP lillk, the calling CPP
. . . .
. e~nulatss a CFP MIJX 2 poll Witl;h a BID in the LID field and 1;he called
CPP PID iIl tthe ~IIC and~MIC fields. The poll is thell sent out optionally
with a unique ring cadeIlce ~o: that the called CPP user is aware that the
3~ incomi~g call is ~rom a handset. Once t~he link is established, the CPP
initiating the call ~ontinues to emulate a CFP t~oughout 1 he call. With
,t3 the approach of the present invention, a handset with this feature may
;~ establish a direct link with any CT2 CAI compatible handset.
.~
.t
Wo 94/05101 11 2 l 2 ~ Pcl/us93/o7o2s
In summa2y, t~e present invention allows for a cordless telephone
handset which operates using the CT2 standard common air interface
standard to be able to communicate with another handset direc~ly
~nthout disturbing the CT2 communica~on ~tandard in any fashion.
5 The present invention also allows f~r a more flexible communication
sy~tem since handset users can not only link up to 1 he PSTN bût to other
handset users directly.
What i8 claimed is:
.
'
:~
~'
