Hillllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`U8005327578A
`.
`5,327,578
`[11] Patent Number:
`{19]
`United States Patent
`it
`
`Breeden et a1.
`[45] Date of Patent:
`Jul. 5, 1994
`
`[54] RADIO TELEPHONE SYSTEM
`SUPPORTING AUTOMATIC BUSY AND
`OUT-OF-RANGE INDICATIONS
`
`8/1990 Daly etal. ............................ 379/61
`4,953,198
`9/1991 DeLuca et al.
`. 455/229 X
`5,049,875
`
`5,203,013 4/ 1993 Breeden et al.
`455/342
`
`[75]
`
`Inventors: Robert L. Breeden; Gary S. Lobe],
`bOth 0f Boynton Beach; Thomas V-
`D’Amico, Boca Raton, all of Fla.
`
`OTHER PUBLICATIONS
`MPT 1375 Common Air Interface Specification, May
`1939.
`
`[73] ' Assignee: Motorola, Inc.,’ Schaumburg, Ill.
`[ ‘ ] Notice:
`The portion of the term of this patent
`subsequent to Apr. 13, 2010 has been
`disclaimed.
`[21] APPL N0-= 935,492
`[22] Filed:
`Aug. 25, 1992
`
`,5 D
`R 1 t d US. A 1‘
`eta
`e .8 2
`pp tea on
`_
`gentsmuation 01' Set. N°~ 579:5“, SEP- 10, 1990: Pa"
`[63]
`°'
`’203'013‘
`Int. Cl.5 ............................................. H04B 17/00
`[51]
`[52] U.S. C1. ..................................... 455/342; 370/29;
`455/541, 455/617; 455/154.2
`[58] Field of Search .................... 455/32.1, 33.1, 34.1,
`455/342, 53.1, 54.1, 54.2, 56.1, 67.1, 67.7, 62,
`226.1, 154.1, 154.2, 156.1, 161.1, 161.3, 229;
`370/24, 29, 95.1, 95.3; 379/58-61, 63
`References Cited
`U.S. PATENT DOCUMENTS
`
`[56}
`
`4,851,820 7/1982 Fernandez ............................ 455/67
`4,873,711 10/1989 Roberts et al
`.. 379/58
`4,882,766 11/1989 Akaiwa ............. 455/58
`
`Primary Examiner—Reinhard J. Eisenzopf
`”1553”"! Examiner“.Chi Pharn
`Attorney, Agent, or Firm—Gregg Rasor
`[57}
`ABSTRACT
`A radio telephone communication system (200) having
`a base station (203) including at least one frequency
`agile time division duplex transceiver (207) for facilitat-
`ing communication with at lest one radio telephone
`(100) on the at least one radio frequency channel. The
`radio telephone (100) scans a plurality of channels capa-
`ble of being generated by the at least one frequency
`agile transceiver (207) to find an available channel and
`provide an indication representing a base station busy
`status when all the at least one frequency agile trans-
`ceivers are in use. A base station busy status is indicated
`when one of a bidirectional time division duplex com-
`munication including a base station identification signal
`is being communicated by the at least one frequency .
`agile transceiver or a unidirectional time division du-
`plex communication including a base station identifica-
`tion signal is being communicated by the at least one
`frequency agile transceiver (207).
`
`17 Claims, 6 Drawing Sheets
`
`PX 1008
`
`EXHIBIT
`Petitioner . Kyocera
`
`Kyocera PX 1008_1
`
`

`

`U.S. Patent
`
`July 5, 1994
`
`Sheet 1 of 6
`
`5,327,578
`
`102
`
`ANTENNA
`
`DUPLEXER 103
`
`105
`
`FIG.l
`
`205
`,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,~
`I ,
`I
`,
`'
`' 204\
`'
`,
`'
`
`07
`
`J3
`
`(201
`
`TELEPHONE
`I
`TELEPHONE
`NETWORK
`
`202)
`
`/
`
`SYSTEM
`PROCESSOR
`
`TELEPHONE
`INTERFACE
`
`I-
`
`r-
`206
`
`1/0
`MULTIPLEXER
`
`1 -
`
`,--
`
`1-
`
`RECEIVER A
`1- TRANSMITTER A
`RECEIVERS
`1-
`TRANSMITTER B
`•
`•
`•
`1-
`RECEIVER N
`L.... TRANSMITTER N
`
`I
`
`I
`
`I
`I
`
`I
`
`I
`I
`
`I
`I
`I
`
`I
`
`•
`,
`,
`,
`,
`'
`,
`'
`,
`,
`
`•
`•
`'
`,
`,
`•
`•
`•
`,
`,
`•
`•
`,
`•
`,
`,
`,
`
`I
`
`I
`
`I
`I
`I
`
`I
`I
`
`I
`
`I
`
`I
`I
`,,,,,,,,,:;,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,~
`
`203
`
`FIG.2
`
`Kyocera PX 1008_2
`
`

`

`U.S. Patent
`
`July 5, 1994
`
`Sheet 2 of 6
`
`5,327,578
`
`302
`
`....
`I
`I
`306
`I
`~~.
`I
`I .
`I
`I
`)
`
`300
`
`307
`
`FIG.3
`
`Kyocera PX 1008_3
`
`

`

`U.S. Patent
`
`JulyS, 1994
`
`Sheet 3 of 6
`
`5,327,578
`
`400
`
`401
`
`402
`
`9-1-555-1212
`
`'
`
`BUSY
`
`OUT OF RANGE
`
`ROAM
`
`( LO CELL)
`
`(CONNECT)
`
`404
`
`403
`
`FIG.4
`
`Kyocera PX 1008_4
`
`

`

`U.S. Patent
`
`July 5, 1994
`
`Sheet 4 of 6
`
`5,327,578
`
`GUARD
`
`GUARD
`
`SIGNAL STRENGTH
`~~ (_ 502 GUARD
`- r---- ---- ,.... ___
`FIG. SA
`
`BASE
`XMITS
`
`501
`'---
`
`(503
`
`HANDSET
`XMITS
`
`BASE
`XMITS
`
`HANDSET
`_XMITS _
`
`TIME
`
`SIGNAL STRENGTH
`~~ L505 GUARD
`
`GUARD
`
`GUARD
`
`HANDSET
`HANDSET
`OR BASE
`OR BASE
`504
`XMITS
`XMITS
`'---ucr-~~~~~~~~,~r-~-~~~~====~.~
`FIG.SB
`TIME
`
`r
`
`SIGNAL STRENGTH
`
`GUARD
`
`GU~RD
`
`GUARD
`
`506
`
`'- u=~~~====~*~=:~o=====~
`FIG.SC
`
`TIME
`
`Kyocera PX 1008_5
`
`

`

`U.S. Patent
`
`July 5, 1994
`
`Sheet 5 of 6
`
`5,327,578
`
`SIGNAL
`STRENGTH
`•
`
`GUARD
`
`GUARD
`
`GUARD
`
`5 ?!_
`
`J~
`
`BASE
`BASE
`XMITS
`HANDSET
`XMITS
`XMITS
`---- ---- r - - - -
`·~
`
`a
`
`j~
`
`HANDSET
`..
`_XMITS _
`TIME
`
`507
`
`508
`
`509
`
`510
`FIG. SD
`
`SIGNAL
`STRENGTH
`h
`
`GUARD
`
`GUARD
`
`GUARD
`
`HANDSET
`OR BASE
`XMITS
`
`r-
`
`r
`
`?!_
`5
`
`h
`
`j~
`
`j
`
`HANDSET
`OR BASE
`XMITS
`
`r
`
`,
`
`r-
`
`·~
`
`-TIME
`
`507
`
`508
`
`509
`510
`FIG. SE
`
`SIGNAL
`STRENGTH
`
`~
`
`?!_
`5
`
`GUARD
`
`GUARD
`
`GUARD
`
`,,
`
`,,
`
`J
`
`j
`
`507
`
`508
`509
`510
`FIG. SF
`
`u
`
`.. -TIME
`
`Kyocera PX 1008_6
`
`

`

`U.S. Patent
`
`July 5, 1994
`
`Sheet 6 of 6
`
`5,327,578
`
`FIG. 6
`
`614
`
`CLEAR
`BUSY
`FLAG.
`
`MEASURE SIGNAL STRENGT
`. BOTH DIRECTIONS .
`
`ACTIVATE OOR INDICATOR;
`DEACTIVATE BUSY INDICATOR.
`
`ALL MATCHED
`OPERATORS
`ARE BUSY.
`ACTIVATE
`BUSY
`INDICATOR.
`
`620
`
`613
`
`SET INITIAL LOGON
`FREQUENCY TO
`THAT SUGGESTED
`BY TELEPOINT.
`
`612
`
`AUTQ-SELECT
`HANDSET LOGON
`TO MATCH THE
`OPERATOR.
`
`616
`
`INDICATE
`ROAM
`PSSBL
`(5 SEC)
`
`_......~~..... __ 617
`
`611 DEACTIVATE
`BUSY
`INDICATOR.
`
`Kyocera PX 1008_7
`
`

`

`1
`
`RADIO TELEPHONE SYSTEM SUPPORTING
`AUTOMATIC BUSY AND OUT-OF-RANGE
`INDICATIONS
`
`This is a continuation of application Ser. No. 579,646,
`filed Sep. 10, 1990, now Pat. No. 5,203,013.
`
`FIELD OF THE INVENTION
`This invention relates in general to radio telephone
`communication systems, and more particularly to those
`systems that support busy (in use) and/or out-of-range
`conditions and is particularly directed toward a Time
`Division Duplex (TDD) radio telephone system sup(cid:173)
`porting busy and out-of-range functions.
`
`2
`SUMMARY OF THE INVENTION
`Briefly, according to the invention, there is provided
`a radio telephone communication system having a base
`5 station and at least one radio telephone capable of com(cid:173)
`municating with each other over at least one radio fre(cid:173)
`quency channel.
`The base station includes at least one frequency agile
`time division duplex transceiver for facilitating commu-
`10 nication with at least one radio telephone on the at least
`one radio frequency channel. The radio telephone scans
`a plurality of channels capable of being generated by the
`at least one frequency agile transceiver to find an avail(cid:173)
`able channel and provides an indication representing a
`15 base station busy status when all of the at least one
`· frequency agile transceivers are in use. The base station
`busy indication is determined when one of a bidirec(cid:173)
`tional time division duplex communication including a
`base station identification signal is being communicated
`by the at least one frequency agile transceiver on the at
`least one radio frequency channel or a unidirectional
`time division duplex communication including a base
`station identification signal is being communicated by
`the at least one frequency agile transceiver on the at lest
`one radio frequency channel.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of a radio telephone suit(cid:173)
`able for use with the present invention.
`FIG. 2 is a block diagram of a base station suitable for
`use with a Time Division Duplex (TDD) communica(cid:173)
`tion system as discussed in the present invention.
`FIG. 3 is an front isometric view of the radio tele(cid:173)
`phone of FIG. 1.
`FIG. 4 is an illustration of the information display in
`FIG. 3 showing BUSY and out-of range indicators in
`accordance with the present invention.
`FIG. SA illustrates TDD transmissions where the
`received signal strength is above the minimum thresh(cid:173)
`old for both the radio telephone and the Telepoint.
`FIG. SB illustrates TDD transmissions where the
`received signal strength is above the minimum thresh(cid:173)
`old one of either the radio telephone or the Telepoint.
`FIG. SC illustrates TDD transmissions where the
`received signal strength is below the minimum thresh(cid:173)
`old for both the radio telephone and the Telepoint.
`FIG. SD illustrates TDD transmissions and receiver
`sample points where the received signal strength is
`above the minimum threshold for both the radio tele(cid:173)
`phone and the Telepoint.
`FIG. SE illustrates TDD transmissions and receiver
`sample points where the received signal strength is
`above the minimum threshold one of either the radio
`telephone or the Telepoint.
`FIG. SF illustrates TDD transmissions and receiver
`sample points where the received signal strength is
`below the minimum threshold for both the radio tele(cid:173)
`phone and the Telepoint.
`FIG. 6 is a flow diagram showing a method for deter(cid:173)
`mining the acquisition status of a base station by a radio
`telephone in accordance with the present invention.
`
`DESCRIPTION OF A PREFERRED
`EMBODIMENT
`Referring to FIG. 1, a block diagram is shown of a
`battery (energy source) 101 powered radio telephone
`100. Operationally, a radio frequency signal is received
`or transmitted by the antenna 102. The antenna is cou-
`
`BACKGROUND OF THE INVENTION
`In contemporary telephone systems, the telephone
`user addresses other radio telephone units or land-line 20
`telephones by entering a telephone number that corre(cid:173)
`sponds to the phone system address of the user to be
`contacted. Once the connection is complete, two way
`voice or data communications can take place.
`With the growing use of portable radio telephone 25
`(cellular or CT-2) systems as a mode of communication,
`there are two normally occurring conditions that can
`prevent the establishment of a radio frequency link with
`a base station (e.g. Telepoint): all channels of the base
`station may be BUSY handling other calls, or the poria- 30
`ble radio telephone attempting to access the system may
`be out-of-range.
`It is desirable to be able to indicate to the user which
`of the two conditions is responsible, because in the
`BUSY case the user merely needs to wait for a channel 35
`to become available, while in the out-of-range case, the
`user needs to move closer to the Telepoint. It is easy
`enough to provide status indicators on the radio tele(cid:173)
`phone to visually indicate either the BUSY or the out(cid:173)
`of-range condition, but the Common Air Interface 40
`(CAl) specification, on which the CT-2 system is based,
`makes it difficult to determine which of the two condi(cid:173)
`tions has prevented the establishment of a link.
`The difficulty in implementing functional BUSY and
`out-of-range indicators arises because the CT-2 system 45
`uses a Time Division Duplex (TDD) transmission
`scheme on a single RF channel. TDD optimizes the use
`of the available radio frequency spectrum by allowing
`transmission of voice and data in both directions be-
`tween the Telepoint and the portable radio telephone.
`Specifically, the radio telephone and the Telepoint al(cid:173)
`ternately transmit and receive one-millisecond bursts of
`information every two milliseconds, one receiving
`while the other transmits. The CAl specification, how- 55
`ever, provides no reliable way for an unsynchronized
`receiver monitoring an active channel on which a call is
`in progress to tell whether it is monitoring a transmis(cid:173)
`sion from a radio telephone or from a Telepoint at any
`given moment in time.
`Under most circumstances, to originate a call, the
`user must travel within range of a Telepoint and acti(cid:173)
`vate a transmitter in the user's radio telephone, thus
`placing the call. However, this simple scenario does not
`address the case where the user cannot determine 65
`whether the user is in range of the Telepoint, or if the
`Telepoint has any channels available for communica(cid:173)
`tion.
`
`50
`
`60
`
`Kyocera PX 1008_8
`
`

`

`20
`
`3
`pled to the receiver 103 and transmitter 104 by a di(cid:173)
`plexer 105. The received signal is routed from the re(cid:173)
`ceiver 103 to the control circuitry 106 that recovers any
`information represented by the received signal. The
`recovered information is then used to activate functions 5
`within the radio telephone 100 such as the alert 107 (a
`ringer in the case of a radio telephone), and after an(cid:173)
`swering the call, sustain the connection. When a con(cid:173)
`nection is established, the user aurally communicates
`with the other party via the speaker 108 and a micro- 10
`phone 109. Recovered audio from the control circuitry
`106 is routed to the speaker 108 which converts electri(cid:173)
`cal energy into acoustical energy thus enabling the user
`to hear any communications. The microphone 109 is
`used to convert acoustic energy into electrical energy 15
`for use by the control circuitry 106 in modulating the
`radio frequency carrier produced by the transmitter
`104. The user may initiate a call by selecting on a key(cid:173)
`pad 205 the proper controls 110 representing the num-
`ber of a party to be contacted.
`Before dialing, the desired number is preferably pres(cid:173)
`ented on a display 111 which provides visual feedback
`for the user. If desired, the user may either place the
`call, edit the number, or abort the dialing operation.
`When a call is initiated, the transmitting means 106, 104, 25
`105, 102, broadcasts a modulated radio frequency car(cid:173)
`rier having information representative of the PSTN
`access codes, both alternate (limited or controlled ac(cid:173)
`cess) and standard (local). The radio telephone base
`(Telepoint) or an alternate unit operates to establish a 30
`communication link once proper identification is con(cid:173)
`firmed.
`Referring to FIG. 2, a block diagram is shown of a
`base station system (200). The base station's purpose is
`to establish and maintain (for the duration of a call) a 35
`communication link between a telephone (201) and a
`radio telephone as shown in FIG. 1. The telephone
`(201) communicates with the base station (203) via a
`telephone network (202). The base station is capable of
`receiving a plurality of telephone links (or lines) using 40
`its telephone interface (204) that acts to route the in(cid:173)
`coming and outgoing traffic to a transmitter/receiver
`pair as selected by the system processor (205). The
`system processor (205) controls the telephone interface
`(204) and allocates via an I/0 multiplexer (206) one 45
`transmitter/receiver pair per incoming or outgoing
`telephone line. The transmitter/receiver pairs are part
`of a bank of frequency agile modular transceivers (207)
`that can be easily expanded to meet the traffic demands
`for a particular system. In implementing a system that 50
`meets the CT-2 (cordless telephone- two) CAl specifi(cid:173)
`cation, each transmitter/receiver pair must be capable
`of time division duplex operation (TDD) over the same
`radio frequency channel. TDD operation for this appli(cid:173)
`cation is defined by the alternate transmission and re- 55
`ception, by both the radio telephone and the selected
`transmitter/receiver pair at the base station, of radio
`frequency information packets (e.g., digital or analog
`modulation carrying voice or data information). That is,
`when one unit transmits, the other unit listens. This 60
`information transfer method (TDD) yields the equiva(cid:173)
`lent to a full duplex communication link, on a single
`radio frequency channel.
`Referring to FIG. 3, the front isometric view of the
`radio telephone 300 shows the antenna 301, radio tele- 65
`phone housing 302, loudspeaker 303, display 304, con(cid:173)
`trol pad including a dialing keypad 306 and associated
`operational controls 305 such as a clear key, function
`
`5,327,578
`
`4
`key, recall key, and function key, and a microphone
`307. Electrical contacts (not shown) located on the back
`ofthe radio telephone 300 are provided for charging the
`removable power source in the radio telephone. For
`example, charging is accomplished by folding the lower
`articulated portion upward against the control pad 305
`then inserting the folded unit into a charging apparatus
`(not shown). Alternatively, a portable power adapter
`can be coupled into a power jack located on the radio
`telephone 300 for charging the power source or supply(cid:173)
`ing external power.
`When the user invokes the call mode on the radio
`telephone 300, the controller circuitry 106 scans the
`controls 110. Preferably, the user may abort the call
`mode at any time by entering an "escape" keystroke or
`waiting for the entry mode to "time out." When the
`user enters initial digits, the controller processes this
`first information for acceptance as valid digits and dis(cid:173)
`plays the digits. When a valid access code or number
`has been entered, it is presented, thus providing feed(cid:173)
`back and allowing the user to accept or reject the code
`entered. If the digits entered are incorrect the user may
`press the CLR (clear) function key clearing the present
`entry and returning to enter new digits. If the digits
`displayed are correct, the user may choose to dial the
`number by depressing the SND (send) function key
`which initiates transmission of the call information. The
`user may optionally replace the displayed number with
`a stored number by activating the RCL (recall) function .
`key, entering the stored number's code or memory num(cid:173)
`ber, determining if the code is correct and valid, and
`displaying the newly recalled stored number. The num(cid:173)
`ber to be dialed is then presented on a display to the user
`for verification. The user can then accept or reject the
`transmission of the number. When the user is ready to
`transmit the number (initiate a call), the SND (send)
`function is selected and transmission of the calling infor(cid:173)
`mation takes place. If the user rejects transmission or,
`after dialing has been completed, the call initiation se(cid:173)
`quence returns control to normal standby radio tele(cid:173)
`phone functions.
`Referring to FIG. 4, an information display (400) is
`shown that comprises a character display means (401), a
`BUSY (402), an OUT-OF-RANGE (403) indicator, and
`a ROAM (404) indicator. The character display means
`(401) is capable of presenting either numeric or alphanu(cid:173)
`meric information representing a phone number or an
`alias (i.e., a name or phrase) to a phone number.
`Referring to FIG. SA, if a radio telephone is able to
`fmd a channel on which adequate signal strength
`(greater than a predetermined amplitude, 501) is present
`in both directions (i.e., continuous bidirectional trans(cid:173)
`missions with no 1 mS gaps), then it is reasonable to
`assume that the radio telephone is monitoring transmis(cid:173)
`sion from both another radio telephone (502) and a base
`station (503).
`Referring to FIG. 5B, when a radio telephone has
`scanned all possible CT-2 channels and found no chan(cid:173)
`nel upon which adequate signal strength (504) is present
`in both directions, but has found one or more channels
`on which there is adequate signal strength in one direc(cid:173)
`tion (505) (i.e., 1 mS signals with 1 mS gaps), an uncer(cid:173)
`tainty exists.
`Referring to FIG. SC, when a radio telephone has
`scanned all possible CT-2 channels found no channel on
`which adequate signal strength (506) is present in either
`direction, it is apparent that the radio telephone is out(cid:173)
`of-range.
`
`Kyocera PX 1008_9
`
`

`

`5,327,578
`
`35
`
`5
`Referring to FIG. SD, SE, and SF, a radio telephone
`receiver begins a scan of all possible CT-2 channels to
`determine their usage status. The first step is to measure
`the signal strength on each of the 40 possible CT-2
`channels. Because the radio telephone is unsynchro- 5
`nized with the base station, a minimum of four signal
`strength measurements (507, 508, 509, 510) are prefera(cid:173)
`bly made at 500 microsecond intervals in order to deter(cid:173)
`m.iile whether the radio telephone is receiving both,
`one, or none of the possible TDD transmissions on each 10
`channel. For each of the preferably 40 channels, the
`largest of the four signal strength measurements should
`be retained along with one other measurement offset
`from it by one millisecond in either direction, while the
`remaining two measurements should be discarded.
`In a preferred embodiment of the invention, the radio
`telephone continuously scans all channels to determine
`a base station status.
`This embodiment uses the technique shown in FIGS.
`50, SE, and SF, and does not require a connection 20
`attempt to the base station. In order for the radio tele(cid:173)
`phone to uniquely identify each of the single-direction
`signals, the base station must periodically transmit a
`base station message comprising: a sync character (e.g.,
`null character or alternately any character that can be 25
`transmitted by the base station and not recognized as a
`control character by the radio telephone), and status
`messages comprising: an operator identifier, an all-tran(cid:173)
`sceivers-busy status (as applicable), and a suggested
`logon frequency on the data channel of all active radio
`telephones. If all transceivers are inactive, the base
`station must continuously· transmit the aforementioned
`information on at least one transceiver (along with
`dummy voice) so that a radio telephone logging into the
`system will always be able to obtain the information.
`Whenever a scan of all channels finds one or more
`channels having useable signal levels, the radio tele(cid:173)
`phone must synchronize itself with the data channel on
`each of the useable channels and begin searching for the
`presence of the periodically transmitted radio telephone 40
`synchronization character and status messages. If mes(cid:173)
`sages are found on the channel, then the signal must be
`from a base station, and the status messages will indicate
`the operator identification, the busy status, and the
`suggested logon frequency. If the messages are not 45
`found on the channel, then the signal must be from
`another radio telephone, and the search must proceed to
`the next channel, and continue until all channels with
`useable signals have been searched without fmding any
`messages, at which time an indication is provided repre- 50
`senting a channel out-of-range status meaning that all
`base stations are out-of-range. Accordingly, in this case,
`the user should be notified of a channel out-of-range
`status.
`,
`Referring to FIG. 7, when the handset (radio tele- 55
`phone) is powered on and idle (e.g. no communications
`are taking place) (601), the BUSY and out-of-range
`(OOR) indicators are activated (602). Step 603 sets
`(tunes) the radio telephone's receiver to frequency num(cid:173)
`ber one. Step 604 measures a power spectrum associated 60
`with the channel by sampling the power spectrum asso(cid:173)
`ciated with the channel at a predetermined time inter(cid:173)
`val. This measurement provides a signal strength indica(cid:173)
`tion for each available transmission slot (time interval)
`on the particular TDD channel. In step 605, if the signal 65
`strength in either direction determined to be above a
`predetermined magnitude, step 606 synchronizes with a
`received signal to determine if communication exists on
`
`6
`the channel. After step 606 synchronizes with the chan(cid:173)
`nel's data, step 607 attempts to recover an operator
`identifier for the base station. If an operator identifier is
`recovered in step 607, step 608 correlates the handset's
`operator identifier to the received operator identifier. If
`the correlation is successful, step 609 deactivates the
`out-of-range indicator then step 610 tests the channel's
`status message for an all-transceivers-busy status. If this
`message is not detected in step 610, step 611 deactivates
`the busy indicator, step 612 recovers a logon channel
`frequency and step 613 selects the logon channel fre-
`quency as the available channel. Step 614 then clears
`the busy flag and returns control to step 603.
`Returning to step 605, if both signal strength mea-
`IS surements are below the predetermined magnitude, step
`615 increments the frequency. Step 615 is also executed
`when no operator identification is found (step 607), a
`roam possible indication (step 616) has been executed by
`step 608 failing, or an all-transceivers-busy status (step
`610) has set the busy flag (step 617). After the frequency
`is incremented, step 618 tests for the frequency number
`being greater than the highest allotted channel in the
`system. In the present CAl specification there are a
`maximum of forty full duplex channels allowed. Obvi(cid:173)
`ously, with the extension and expansion of this system in
`the future, 'more channels may be added and can be
`easily accommodated within the scope of the embodi(cid:173)
`ment disclosed in this invention. If step 618 fails, control
`is passed to step 604. If step 618 is true, step 619 tests for
`30 the busy flag being set. If step 619 is true, all operators
`registered to the radio telephone are busy and the busy
`indicator is activated (step 620). Step 614 then clears the
`busy flag and returns control to step 603. In the case
`where step 619 is false, step 621 activates the out-of(cid:173)
`range indicator and deactivates the busy indicator. Con(cid:173)
`trol is then passed to step 603 and the channel acquisi-
`tion status is continuously updated.
`We claim:
`1. In a radio telephone communication system hav(cid:173)
`ing:
`a base station with at least one frequency agile trans(cid:173)
`ceiver capable oftime division duplex operation on
`at least one radio frequency channel for facilitating
`communication with at least one radio telephone
`on the at least one radio frequency channel, a
`method of determining acquisition status of the at
`least one frequency agile transceiver in the base
`station comprising the steps of:
`at a radio telephone:
`scanning a plurality of channels capable of being
`generated by the at least one frequency agile trans(cid:173)
`ceiver to find an available channel, the plurality of
`channels including the at least one radio frequency
`channel; and
`providing an indication representing a base station
`busy status when all of the at least one frequency
`agile transceivers are in use indicating no available
`channels as determined when one of:
`bidirectional time division duplex communication
`including a base station identification signal is being
`communicated by the at least one frequency agile
`transceiver on the at least one radio frequency
`channel; and
`unidirectional time division duplex communication
`including a base station identification signal is being
`communicated by the at least one frequency agile
`transceiver on the at least one radio frequency
`channel.
`
`Kyocera PX 1008_10
`
`

`

`15
`
`7
`Z. The method according to claim 1 wherein the
`scanning step comprises the steps of:
`tuning the radio telephone to the at least one channel;
`and
`measuring a power spectrum associated with the at 5
`least one channel to provide a signal strength indi(cid:173)
`cation.
`3. The method according to claim 2 wherein the
`measuring step further comprises the steps of:
`sampling the power spectrum associated with the at 10
`least one channel at a predetermined time interval;
`and
`synchronizing with at least one received signal to
`determine if any time division duplex communica-
`tion exists· on the at least one channel.
`4. The method according to claim 3 further compris(cid:173)
`ing the steps of:
`recovering an operator identifier from a signal validly
`transmitted on1y by the base station; and
`providing an indication representing a roam available 20
`status in response to the operator identifier differ(cid:173)
`ing from an operator identifier registered with the
`radio telephone.
`5. The method according to claim 3 further compris- 25
`ing the steps of:
`determining if the signal strength indication is below
`a predetermined magnitude; and
`providing an indication representing a base station
`to the signal 30
`out-of-range status in response
`strength indication being below the predetermined
`magnitude.
`6. The method according to claim 3 further compris(cid:173)
`ing the step of:
`providing an indication representing a base station 35
`out-of-range status when unidirectional time divi(cid:173)
`sion duplex communication exists on a channel and
`the unidirectional time division duplex communica(cid:173)
`tion lacks the base station identification signal.
`7. The method according to claim 1 further compris- 40
`ing the steps of:
`recovering a suggested logon channel frequency for
`the base station from a base station status signal;
`and
`selecting the suggested logon channel frequency as 45
`the available channel.
`8. The method according to claim 1 further compris(cid:173)
`ing the step of:
`broadcasting to the radiotelephone in a base station
`status signal a suggested logon channel frequency 50
`for the base station.
`9. In a radio telephone communication system hav(cid:173)
`ing:
`a base station with at least one frequency agile trans(cid:173)
`ceiver capable oftime division duplex operation on 55
`at least one radio frequency channel for facilitating
`communication with at least one radio telephone
`on the at least one radio frequency channel, a
`method of determining acquisition status of the at
`least one frequency agile transceiver in the base 60
`station comprising the steps of:
`at a radio telephone:
`providing an indication representing a base station
`busy status when time division duplex communica(cid:173)
`tion exists on the radio frequency channel and the 65
`time division duplex communication includes at
`least a signal validly transmitted only by the base
`station.
`
`5,327,578
`
`8
`10. A radio telephone communication system, com(cid:173)
`prising:
`a base station with at least one frequency agile trans(cid:173)
`ceiver capable of time division duplex operation on
`at least one radio frequency channel for facilitating
`communication with at least one radio telephone
`on the at least one radio frequency channel; and
`a radio telephone capable of determining an acquisi(cid:173)
`tion status of the at least one frequency agile trans(cid:173)
`ceiver in the base station, the radio telephone com(cid:173)
`prising:
`means for scanning a plurality of channels capable of
`being generated by the at least one frequency agile
`transceiver to find an available channel, the plural(cid:173)
`ity of channels including the at least one radio
`frequency channel; and
`means for providing an indication representing a base
`station busy status when all of the at least one fre(cid:173)
`quency agile transceivers are in use as determined
`by the means for scanning the plurality of channels,
`the determination indicating no available channels
`when one of:
`bidirectional time division duplex communication
`including a base station identification signal is being
`communicated by the at least one frequency agile
`transceiver on the at least one radio frequency
`channel; and
`unidirectional time division duplex communication
`including a base station identification signal is being
`communicated by the at least one frequency agile
`transceiver on the at least one radio frequency
`channel.
`11. The radio telephone communication system ac(cid:173)
`cording to claim 10 wherein the means for scanning
`comprises:
`means for tuning the radio telephone to the at least
`one radio frequency channel;
`means for sampling a power spe<;:trum associated with
`the at least one radio frequency channel deter(cid:173)
`mined by the means for tuning at a predetermined
`time interval to provide a signal strength indica(cid:173)
`tion;
`means for synchronizing with at least one received
`signal when the signal strength as indicated by the
`means for tuning is above the predetermined mag(cid:173)
`nitude for determining if time division duplex com(cid:173)
`munication exists on the channel, resultin,g in the
`indication representing the base station busy status.
`12. The radio telephone communication system ac(cid:173)
`cording to claim 11 further comprising:
`means for recovering an operator identifier from the
`base station; and
`means for providing an indication representing a
`roam available status in response to the operator
`identifier differing from an operator identifier reg(cid:173)
`istered with the radio telephone.
`13. The radio telephone communication system ac(cid:173)
`cording to claim 11 further comprising:
`means for determining if the signal strength indica(cid:173)
`tion is below a predetermined magnitude; and
`means for providing an indication representing a base
`station out-of-range status in response