United States Patent [191
`Cosentino
`
`IIIIIIIIIIIIIIIIIIIIIIIIIIIIllllII||IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIlllllIIl
`USOO5097499A
`Patent Number:
`5,097,499
`[11]
`Mar. 17, 1992
`Date of Patent:
`[45]
`
`[54] AUTONOMOUS REGISTRATION
`OVERLOAD CONTROL FOR CELLULAR
`MOBILE RADIO SYSTEMS
`[75] Inventor:
`Phyllis Cosentino, Streamwood, Ill.
`[73] Assignee: AT&T Bell Laboratories, Murray
`‘
`Hill, NJ.
`[21] App1.No.: 570,948
`[22] Filed:
`Aug. 22, 1990
`
`[51] Int. Cl.5 .......................................... .. H04M 11/00
`[52] US. Cl. ................................... .. 379/59; 379/63
`[58] Field of Search ............. .. 379/59, 60, 63; 455/33,
`455/56
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,670,899 6/1987 Brody et a1. ..
`
`4,887,625 12/1989 Felix ........... ..
`
`379/59
`379/60
`379/63
`379/59
`
`Primary Examiner-James L. Dwyer
`Assistant Examiner-Dwayne D. Bost
`Attorney, Agent, or Firm-A. G. Steinmetz
`[57]
`ABSTRACT
`Registration signal channel overloads occurring due to
`overly numerous autonomous registration messages
`initiated by the mobile radiotelephones are averted by
`monitoring the number of autonomous registrations
`occurring or requested in a particular local cellular
`system and responding in the event of an impending
`overload by sending messages to speci?ed mobile radio
`telephones instructing them not to register at this time.
`The roamer mobile radiotelephones requesting registra
`tion within an area covered by a cellular system facing
`an impending overload are instructed, via an overhead
`message, not to register. Allowance of registration is
`not permitted until the overload condition is termi
`nated. Alternatively the period between autonomous
`registrations is increased until the overload is cleared.
`
`17 Claims, 9 Drawing Sheets
`
`I
`
`N803
`
`MEASURE THE RATE
`AT WHICH AR'S
`ARE RECEIVED
`805
`DOES AR RATE
`EXCEED THRESHOLD?
`YES #807
`TURN ROAMER
`REGISTRATION OFF
`809
`DOES AR RATE
`EXCEED THRESHOLD’?
`YES [V817
`TURN ROAMER
`REGISTRATION ON
`AND HOMER
`REGISTRATION OFF
`
`/v81 ‘I
`TURN ROAMER
`REGISTRATION ON
`
`NO 816
`DOES AR RATE \ YES
`EXCEED THRESHOLD'U
`
`W821
`TURN HOMER
`REGISTRATION
`ON
`
`YES #823
`TURN ROAMER
`REGISTRATION OFF
`I
`#825
`TURN HOMER
`REGISTRATION ON
`
`ERIC-1013
`Ericsson v. IV
`Page 1 of 16
`
`

`
`ERIC-1013
`Page 2 of 16
`
`

`
`US. Patent
`
`Mar. 17, 1992
`
`Sheet 2 of 9
`
`5,097,499
`
`mow.U
`
`@ziutEwL
`
`
`
`oz< _
`
`JOIHZOO
`
`XWEEOO
`
`JOIPZOO _
`
`GMT-0.53m
`
`9.53m Oh
`
`M23025
`
`
`
`. MZOImmImC.
`
`vEOEmZ
`
`ERIC-1013
`Page 3 of 16
`
`

`
`US. Patent
`
`Mar. 17, 1992
`
`Sheet 3 of 9
`
`5,097,499
`
`FIG. 3
`
`$302
`
`OVERHEAD MESSAGES
`
`‘I. SYSTEM IDENTIFICATION
`2- REGID
`3. REGINCR
`4. RADIO TELEPHONE
`CONTROL FREQ
`5. REGH, REGR
`
`CELL
`
`301” SITE
`
`CELL SITE
`INFORMATION STORAGE
`
`1_ MOBILE RADlO
`TELEPHONE REGISTER
`2. REGID
`3. RIDINCR
`4. REGINCR
`5. MOBILE RADIO
`TELEPHONE
`CONTROL FREQ
`6. REGH, REGR
`
`ERIC-1013
`Page 4 of 16
`
`

`
`US. Patent
`
`Mar. 17, 1992
`
`Sheet 4 0f 9
`
`5,097,499
`
`FIG. 4
`
`f/ 403
`SUBSCRIBER
`DATA
`
`/v 404
`DATA
`STORAGE
`
`/V401 W402
`CENTRAL
`CELL
`PROCESSOR DATA
`BUS‘
`
`/v406
`SIGNAL
`'NTERSACE
`T?'éiwgm'z
`
`|/v4o7
`SIGNAL
`INTERFACE
`TO
`CELL SITES
`
`501K
`CELL SITE
`PROCESSOR
`
`.
`502
`"\
`CELL SITE
`DATA
`
`
`
`503‘ I LINE
`
`TO
`- INT RFA
`MTSO
`E
`CE
`
`FIG. 5
`
`506
`r’
`CONTROL
`CHANNEL
`“7''
`RADIO
`TRANSCEIVER :
`I
`:
`
`:
`
`l
`
`
`
`' F507 VO'CE
`
`1
`
`CHANNEL
`I
`‘
`RADIO
`TRANSCEIVER
`
`.
`
`51°
`
`508
`
`#509
`COMBINER
`
`ERIC-1013
`Page 5 of 16
`
`

`
`US. Patent
`
`Mar. 17, 1992
`
`Sheet 5 0f 9
`
`5,097,499
`
`FIG. 6
`
`I START I
`
`READ CLOCK OH TIME
`
`N605
`T
`SET INITIAL INCREMENT
`RATE RIDINCR
`W607
`DETERMINE VALUE OF
`CELL SITE CLOCK REGID
`
`W609
`EVERY RIDINCR
`OH OLD = OH TIME
`W611.
`
`CALCU LATE
`OH TIME ' OH OLD
`
`W
`
`RIDINCR
`I
`W613
`IS VALUE > 0'?
`T YES /\/615
`SET NEW CELL SITE
`CLOCK VALUE REGID
`I
`M17
`BROADCAST VALUE
`OF REGID
`
`ERIC-1013
`Page 6 of 16
`
`

`
`US. Patent
`
`Mar. 17, 1992
`
`Sheet 6 of 9
`
`5,097,499
`
`FIG. 7
`
`I START I
`
`MEASURE THE RATE
`A AT WHICH AR'S
`ARE RECEIVED
`I #705
`NO / DOES AR RATE >
`9 @XOEED THRESHOLD?
`707
`I YES N709
`TuRN ROAMER
`REGISTRATION OFF
`
`TuRN R AMER NO
`
`{V711
`0/713
`REGISCTDZATION ‘{EXCEEEEiHRSQ-ISLDQ
`
`YES
`
`719
`
`NO
`
`725
`
`YES [715
`DECREASE RATE AT
`WHICH REGID IS
`INCREMENTED
`/v717
`DOES AR RATE
`EXCEED THRESHOLD?
`
`INCREASE RATE AT
`WHICH REGID IS
`INCREMENTED
`I
`,4723
`IS REGID BEING
`INCREMENTED AT IT'S
`ORIGINAL RATE?
`I YES [727
`TURN ROAMER
`REGISTRATION ON
`W729
`SET R'EGID TO IT'S
`EXPECTED VALUE
`
`ERIC-1013
`Page 7 of 16
`
`

`
`US. Patent
`
`Mar. 17, 1992
`
`' Sheet 7 of9
`
`5,097,499
`
`FIG. 8
`
`I
`
`/\/803
`
`MEASURE THE RATE
`AT WHICH AR’S
`ARE RECEIVED
`
`*
`
`YES ,v807
`TURN ROAMER
`REGISTRATION OFF
`
`[/81 ‘I
`TURN ROAMER
`REGISTRATION ON
`
`_
`NO 816
`< DOES AR RATE > YES
`EXCEED THRESHOLD?
`I
`
`TuRN ROAMER
`REGISTRATION ON
`AND HOMER
`REGISTRATION OFF
`
`YES ,v823
`TURN ROAMER
`REGISTRATION OFF
`I
`W825
`TURN HOMER
`REGISTRATION ON
`
`W821
`TURN HOMER
`REGISTRATION
`ON
`
`ERIC-1013
`Page 8 of 16
`
`

`
`US. Patent
`
`Mar. 17, 1992
`
`Sheet 8 of 9
`
`5,097,499
`
`S") #3
`
`DIST
`
`$10 #4
`
`510114
`
`DIST
`
`$10 #7
`
`FIG. 9
`
`W911
`SID NXTREG
`#3
`1200
`REGR=1 /O\
`I
`W915
`
`10
`
`W919
`$10 NXTREG
`#4
`1200
`m REGR=1 m
`69/
`69/
`
`FIG. 10
`
`1010
`
`s10 NXTREG
`#4
`1200
`Q; REGR=1 @
`V I
`\_/
`
`[919
`s10 NXTREG
`#4
`1200
`REGR=0
`
`ERIC-1013
`Page 9 of 16
`
`

`
`US. Patent
`
`Mar. 17, 1992
`
`Sheet 9 of 9
`
`5,097,499
`
`REGID CLOCK = 11200
`REGINCR = 100
`
`TIME
`
`l
`
`REGID CLOCK = 12:00
`REGINCR = 100
`
`REGID CLOCK = 11:00
`REGINCR = 100
`
`TIME
`
`i
`
`REGID CLOCK = 11:50
`REGINCR = 100
`
`FIG. 11
`
`NXTREG
`1200
`(O1 REGR=1 @
`U I V
`
`. NXTREG
`1300
`m REGR=1 [X
`G/
`\O/
`
`FIG. 12
`
`1210
`
`SID NXTREG
`1200
`m REGR = 1 m
`\9/
`I
`\9/
`l
`
`NXTREG
`1200
`@9
`REGR=0 /\
`
`4)
`
`ERIC-1013
`Page 10 of 16
`
`

`
`AUTONOMOUS REGISTRATION OVERLOAD
`CONTROL FOR CELLULAR MOBILE RADIO
`SYSTEMS
`
`FIELD OF THE INVENTION
`This invention relates to cellular mobile radiotele
`phone systems and to autonomous registration of mo
`bile radiotelephones with a local cell site or ?xed site
`base station. It is particularly concerned with the con
`trol of registrations during overload conditions occur
`ring in a transmission channel handling these registra
`trons.
`
`15
`
`25
`
`BACKGROUND OF THE INVENTION
`Autonomous registration is an overhead mobile ra
`diotelephone locating function used in a cellular system
`to identify the mobile radiotelephones covered for ser
`vice within a particular local cellular service system,
`eg a cellular geographic service area. Autonomous
`registration may be time based and/or geographic
`based. In time based autonomous registration, the regis
`tration of a mobile radiotelephone is in response to the
`passage of a time interval as de?ned by a clock. Geo
`graphic based autonomous registration is based on the
`location of the mobile radiotelephone; e.g. a roamer
`(e.g., a mobile radiotelephone away from its home terri
`tory) autonomously registers when it enters the terri
`tory of a new cellular system. Detailed particulars con
`cerning the requirements and operation of autonomous
`registration in a cellular mobile radiotelephone system
`may be found in the published standard BIA-553.
`Each mobile radiotelephone, when not engaged in
`making a call, continuously listens to a set-up channel
`with control information and sends overhead messages
`via a reverse signalling channel. System identi?cation
`code signals generated by the base stations of the cellu
`lar system identify the presently serving cellular system
`to the mobile radiotelephone. These identi?cation code
`signals include time stamp signals which are periodi
`cally incremented at some speci?c rate. In a time re
`sponse autonomous registration each mobile radiotele
`phone compares a timed identi?cation stamp or marker
`(REGID) received from the base station with a stored
`value of its next registration (NXTREG) which was
`calculated from parameters received in a previous over
`head signal transmission.
`If a mobile radiotelephone begins to lose reception of
`its present identifying code signal it searches for a new
`better quality identi?cation code signal. If the new iden
`ti?cation code signal indicates that the mobile radiotele
`phone system is in a new cellular service area, the mo
`bile radio telephone automatically registers with the
`new base station.
`In registering, the mobile radiotelephones send their
`serial number and related information to the local cellu
`lar service system over a reverse radio channel dedi
`‘cated to transmitting overhead messages of this type.
`‘This reverse channel is normally used for a variety of
`purposes, e.g. control messages sent for the purpose of
`originating phone calls, in addition to the registration of
`mobile radiotelephones with the base station.
`Since the transmission capacity of the reverse chan
`65
`nel is limited, the need to process a large number of
`autonomous registrations will fill the reverse channel to
`capacity and block or severely limit transmissions of the
`
`1
`
`5,097,499
`2
`other overhead messages that operate to originate calls
`and perform other support services.
`
`SUMMARY OF THE INVENTION
`Registration signal channel overloads occuring due
`to overly numerous autonomous registration messages
`initiated by the mobile radiotelephones are averted in
`accord with the principles of the invention by monitor
`ing the number of autonomous registration messages
`occurring in a particular local cellular system and re
`sponding in the event of an impending overload by
`sending messages to speci?ed mobile radiotelephones
`instructing them not to register at this time. In one
`particular illustrative implementation disclosed herein
`the roamer mobile radiotelephones requesting registra
`tion within an area covered by a cellular system experi
`encing an immediate or an impending overload are
`instructed, via an overhead message, not to register.
`Normal registration service is not resumed until the
`overload condition is terminated.
`Additional features of the system to prevent autono
`mous registration message overloads include the capa
`bility to limit registration by homers (e.g., a mobile
`radiotelephone in its home territory) and roamers (e. g.,
`a mobile radiotelephone in a foreign territory) to pre
`vent an overload in the reverse channel by restricting
`the rates of autonomous registration. This is achieved in
`the illustrative embodiment by dilating the time of the
`generation of timing stamps on markers, e.g. REGID,
`by the local cellular access station and transmitting
`these altered timing markers to the mobiles so that the
`mobile radiotelephones experience a longer time inter
`val betweenautonomous registrations.
`These terminations of roamer and homer mobile ra
`diotelephone registrations and dilations of roamer and
`homer registration timing marks is controlled by a
`stored program control which is operative to actively
`preserve sufficient capacity on the reverse channel for
`the call originations from mobile radiotelephone and
`other cellular overhead activities.
`
`BRIEF DESCRIPTION OF THE DRAWING
`In the Drawing:
`FIG. 1 is a schematic of a typical cellular system
`geographical layout;
`FIG. 2 is a schematic of the interconnections in a
`cellular radiotelephone system between a mobile radio
`telephone and a telephone network;
`FIG. 3 is a schematic listing of the overhead messages
`and information involved in autonomous registration of
`mobile radiotelephones;
`FIG. 4 is a block diagram of parts of a control system
`used in cellular systems for controlling autonomous
`registrations;
`FIG. 5 is a block diagram of a cell site radio transmis
`sion system;
`FIG. 6 is a flow diagram executed by the control
`system of FIG. 4 in handling messages between a radio
`telephone and a cell site;
`FIG. 7 is a flow diagram of a process included within
`the control system of FIG. 5 to prevent autonomous
`registration overloads;
`FIG. 8 is a ?ow diagram of another process included
`within the control system of FIG. 5 to prevent autono
`mous registration overloads;
`FIGS. 9, 10, 11 and 12 are schematics representing
`various aspects of a mobile radiotelephone overhead
`data storage content.
`
`ERIC-1013
`Page 11 of 16
`
`

`
`3
`DETAILED DESCRIPTION
`A schematic of a typical geographical layout of a
`cellular radiotelephone system is illustrated in FIG. 1.
`The radiotelephone service area is divided into a plural
`ity of cells 101 each covering a de?ned and substantially
`contiguous geographical area as illustrated by the geo
`metric tiled hexagons 102. Each cell 101 includes a cell
`site 103 or base station which is a wireless communica
`tion and switching center for providing air communica
`tion with mobile radiotelephones. The cell sites 103
`each include air radio communication equipment, in
`cluding antennas, and land communication equipment
`including trunk connections to a mobile telephone
`switching office 105 which couples the cell site to a
`public switched land telephone network 106 which is
`typically the normal public switched telephone system.
`An understanding of this cellular concept may be at
`tained from the article “The Cellular Concept” by V.
`H. McDonald, Bell System Technical Journal, January
`1979, pages 15-41, Vol. 58, No. 1.
`A cell site communicates with a plurality of mobile
`radiotelephones via a plurality of different radio chan
`nels. Sorne channels are dedicated to voice transmis
`sions and others are dedicated various overhead control
`message transmissions. In FIG. 2 an overhead air radio
`transmission channel 210 established between a mobile
`radiotelephone 202 and a cell site 201 is schematically
`illustrated. A radio channel for overhead messages di
`rected from the mobile radiotelephone 202 to the cell
`site 201 is designated as a reverse control channel. Au
`tonomous registrations are normally transmitted over
`this reverse control channel. Call setups, including cell
`site identi?cation information, are transmitted from the
`cell site 201 to the mobile radiotelephone over a setup
`
`5
`
`25
`
`35
`
`5,097,499
`4
`GINCR de?ning the maximum interval between regis
`trations of the mobile radiotelephones 302.
`Each mobile radiotelephone unit 910, as shown in
`FIG. 9, stores the transmitted overhead message data in
`its mobile unit. This data includes certain data items
`concerning the system identi?cation number (SID), the
`sum of the most recently transmitted time stamped re
`gistration ID (REGID) and the increment REGINCR,
`which establishes NXTREG, the next time of normal
`registration and the registration enabling/disabling con
`trol bits or flags (REGH;REGR). The storage of these
`system data messages is schematically shown for a
`roamer mobile radiotelephone 910 as shown in FIG. 9.
`The mobile radiotelephone unit 910 illustrated is pres
`ently registered in the system identi?ed by the illustra
`tive number #3. This identi?cation number of the sys
`tem is stored in its memory 911 and its ability to autono
`mously register is enabled since the flag REGR is set to
`an enabling one. The mobile crosses a geographic bar
`rier 915 to a service area bearing a different identi?ca
`tion (SID) number, e.g. #4 and the overhead signal
`channel is switched to a system #4 frequency. The
`mobile radiotelephone unit 910 autonomously registers
`in the new service area and stores the new identi?cation
`(SID) number #4 in its memory 911.
`In FIG. 10 a roamer mobile radiotelephone unit 1010
`has its registration enabling flag REGR initially set to
`one (enabling autonomous registration) and is in the
`service area identified by the illustrative identi?cation
`number (SID) #4. It moves to a new service area #7,
`that is experiencing an overload in its overhead message
`transmission channels. This service area is hence trans
`mitting autonomous registration disabling messages to
`the roamer mobile radiotelephones. The enabling ?ag
`REGR of the mobile radiotelephone is set to zero by the
`new system and the mobile radiotelephone is disabled
`from autonomous registration by the setting of the
`REGR flag to zero. Hence the mobile radiotelephone
`unit is prohibited from registering and its stored SID
`value is not changed.
`A homer mobile radiotelephone 1110, as shown in
`FIG. 11 is in a service area presently free of overloads
`on the overhead message channels. The present time is
`some illustrative value 1100 and the increment RE
`GINCR is set at 100 thereby establishing the next regis
`tration time, NXTREG, at 1200 for this mobile radio
`telephone. At the occurrence of 1200 at the normal
`increment rate the mobile radiotelephone autonomously
`registers with the system and inserts the new incre
`mented time value NXTREG=1300 into its memory.
`In FIG. 12 an overload has resulted in the control
`equipment. The system for preventing autonomous
`registration overload slows the rate at which the
`REGID value is incremented. Accordingly the
`REGID value is not incremented suf?ciently to permit
`the mobile radiotelephone to register at the occurrence
`of the actual time value 1200.
`An MTSO site controller is shown in FIG. 4 and
`includes a central processor 401 which includes stored
`program controls to control the interface between the
`public switched telephone network and the cell site
`locations. Included are a cell data base 402 used for cell
`site control. Its data identifies the cells and their control
`functions. This data is used for various additional pur
`poses such as radio channel management. A subscriber
`data base 403 permits location of roamer and homer
`mobile radiotelephone units by identifying the various
`homer subscribers both active and inactive and also
`
`60
`
`channel. _
`
`.
`
`As shown in FIG. 2 the cell site 201 is connected with
`a plurality of other cell sites including cell site 204 to a
`switching and control MTSO 205 which is intercon
`nected to a public switched telephone network. If the
`mobile radiotelephone 202 leaves the area covered by
`the cell site 201 and enters the area covered by the cell
`site 204, the mobile loses the setup and reverse control
`of cell site 201. The new identifying information on the
`corresponding set up channel of cell site 204 may cause
`it to register in the new cell. If on the other hand it
`remains in the cell area of cell site 201, the time informa
`tion provided by the cell site 201 causes it to periodi
`cally register.
`Registration is a procedure enabling a cell site to
`determine the identity of and the presence of mobile
`telephones within its geographical radio transmission
`boundary. Both the cell site and mobile radiotelephone
`store and transmit registration information. Each cell
`site 301 as shown in FIG. 3 maintains a register of the
`mobile radiotelephones 302 it services. Calls originating
`at the public switched land line network are connected
`to the dialed mobile radiotelephone through the partic
`ular cell site with which it is registered. The cell site 301
`generates system identi?cation, information and control
`signals such as shown in FIG. 3. It periodically trans
`mits a system overhead message to the mobile radiotele
`phone which includes a system identi?cation number
`(SID), a time stamped registration ID (REGID), a bit
`or flag enabling/disabling control de?ning the ability of
`the mobile radiotelephone 302 to register (REGH for
`homer mobile radiotelephones and REGR for roamer
`radio mobile radiotelephones) and a number RE
`
`45
`
`55
`
`65
`
`ERIC-1013
`Page 12 of 16
`
`

`
`5
`maintaining a temporary data base of roamer subscrib
`ers being serviced. Additional data storage 404 is pro
`vided for cell management and cell maintenance func
`tions. Signal interface 406 interconnects the MTSO
`with the public switched telephone network and the
`signal interface 407 connects it to the various cell sites.
`The cell site apparatus is disclosed in FIG. 5 and
`includes a local cell site processor 501 and a local data
`storage apparatus 502. The local cell communicates
`with the MTSO of FIG. 5, via a line interface 503,
`which is_connected in turn to the radio transceivers of
`the radio frames 506 and 507 which are both under the
`control of the cell site processor 501. The processor 501
`is operative to control message reception and transmis
`sion, setup channel control, and radio tuning. The ra~
`dios include a control channel radio frame 506 and a
`voice channel frame 507. The autonomous registration
`functions are controlled through radio frame 506 over
`the setup and reverse control channels. An ampli?er
`508 and combiner 509 couple the radios of the frames
`506 and 507 to an antenna 510.
`A flow chart delineating the registration process is
`shown in FIG. 6. The process begins by reading a con
`tinuous clock of the cell site (block 603) to establish the
`value OH TIME which represents the value of time pres~
`ently maintained in the cell site control. An initial value
`is set for the rate RIDINCR at which the broadcast
`time stamp of the cell REGID is to be incremented
`(block605). The value of REGID is determined in block
`607 by evaluating the function:
`
`6
`uates if that AR rate threshold has been exceeded. If the
`threshold AR rate is not exceeded the process flow path
`returns, via path 707, to the monitoring function as
`expressed by block 703. If the AR rate threshold, de
`?ned by block 703, has been exceeded as determined by
`the step enumerated in block 705 the autonomous regis
`trations of all the roamer radiotelephones covered by
`the service area are inhibited by setting the ?ags REGR
`of each of the roamer radiotelephones to zero by means
`of an overhead control message broadcast to all the
`mobile radiotelephones.
`The rate of autonomous registration messages is re
`evaluated with respect to the AR rate threshold by the
`step enumerated in the decision block 711. If the rate of
`autonomous registration messages is below the thresh
`old rate the autonomous registration of roamer radio
`telephones is again enabled, according to instructions
`enumerated in block 713, by setting the flags REGR of
`the mobile radiotelephones to a 1 value.
`If the rate of autonomous registration messages is
`determined by the procedure of decision block 711 to
`exceed the threshold rate, the process ?ow continues to
`the block 715 which enumerates program instructions
`for decreasing the rate at which the time stamp REGID
`is incremented. The REGID increment rate is de
`creased by increasing the value of the registration ID
`increment rate RIDINCR to a new value RIDINCR“.
`The new values of REGID are designated REGID“.
`The value of the expression:
`
`5,097,499
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`20
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`30
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`0H TIME
`REGID : RIDINCR
`
`(1)
`
`01! TIME — OH’OLD
`RIDINCR‘
`
`> 0
`
`(4)
`
`The present OH TIME is converted to the stored value
`OHOLD in block 609 and is used with a current OH TIME
`in the periodic calculation of block 611 in calculating
`the function:
`
`must now be evaluated in terms of the new values of
`RIDINCR“. The value OH‘OLD is the value of time
`stored the last time REGID‘ was increrr-ented. The
`new value of REGID‘ is determined by the following
`expression:
`
`011 TIME — OHOLD
`RIDINC R
`
`(2)
`
`REGID‘ = REGID‘ +
`
`0H TIME — 0H ‘01.0
`RIDINCR,
`
`(5)
`
`If the value of this expression is greater than zero
`(decision block 613) a new cell site clock value REGID
`is calculated in block 615 according to the following
`45
`equation and substitutes a new stored value for REGID
`replacing the old value:
`
`OHTJME — 01101.1)
`REGID = REGID +
`RIDINCR
`
`(3)
`
`50
`
`RIDINCR is a registration ID increment rate which
`de?nes the time interval for incrementing REGID.
`This new REGID value is broadcast throughout the
`cell area (block 617) and the ?ow routine returns to
`block 609 to determine a new value of OHOLD. If the
`value of decision block 613 is no, the ?ow path returns
`to block 609 without broadcasting the REGID value to
`the mobile radiotelephones.
`A time based technique of preventing overloads in
`overhead message channels in a cellular radiotelephone
`system is disclosed in the flow chart of FIG. 7. The
`initial step (block 703) involves the measuring of the
`rate at which autonomous registration (AR) messages
`are received. A threshold of the autonomous registra
`tion rate is established usually in terms of the number of
`autonomous registration messages within a de?nite time
`interval. The step expressed by decision block 705 eval
`
`The rate of autonomous registration messages is again
`checked, by the information of decision block 717 to see
`if the threshold AR rate is exceeded. If the AR thresh
`old rate is exceeded the process flow continues, via flow
`path 719, to the block 715 whose delineated process step
`again decreases the rate at which the value REGID is
`incremented by the method described above.
`If the rate of autonomous registration messages, mea
`sured in decision block 717, does not exceed the AR
`rate threshold the process flow continues to block 721
`which is operative to increase the rate at which
`REGID‘ is incremented by decreasing the value of
`RIDINCR". The rate of autonomous registration mes
`sages is compared to the original threshold rate by the
`instruction process of decision block 723. If the original
`rate of incrementing the standard REGID has not been
`attained the ?ow proceeds by path 725 to block 721
`which again increases the rate at which REGID‘ is
`incremented. If the original rate at which the standard
`REGID is being incremented has been attained the flow
`proceeds to the instructions of block 727 which is oper
`ative to broadcast overhead messages to again enable
`the roamer radiotelephones to register by changing the
`REGR flag to a 1 value. The original sequence of
`REGID values has been continuously maintained by
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`inhibiting acceptance of registration requests from
`the stored control program during the overload protec
`tion process and this value is now again installed as the
`mobile radiotelephones when the impending over
`operative REGID by resynchronizing the temporary
`load condition is identi?ed.
`value REGID‘ with the actual value of REGID in the
`2. A method of preventing autonomous registration
`process step of block 729 and the process ?ow returns
`overload in a cellular radio telephone system,
`to the process at block 703.
`comprising the steps of:
`An alternative geographic or system location based
`counting the number of autonomous registration mes
`process for preventing an overload due to an excess of
`sages within an initial ?xed time interval;
`autonomous registration messages is disclosed in the
`inhibiting registrations of roamer mobile radiotele‘
`?ow chart of FIG. 8. The instructions de?ned in the
`phones if the number of autonomous registration
`block 803 have the process determine the rate at which
`messages exceeds a threshold count;
`the reception of autonomous registration messages is
`counting the number of autonomous registration mes
`occurring. If the autonomous registration message rate
`sages in a ?xed time interval subsequent to the
`exceeds the preset threshold AR rate, as per block 805,
`initial ?xed time interval;
`the roamer radiotelephones are disabled from register
`allowing registrations of roamer mobile radiotele
`ing by sending an overhead control message setting the
`phones and inhibiting registrations of homer mo
`REGR ?ag to 0 as per the instructions at block 807. The
`bile radiotelephones if the number of autonomous
`instruction of subsequent decision block 809 determines
`registration messages exceeds a threshold count;
`if the rate of autonomous registration messages still
`subsequently counting the number of autonomous
`exceeds the threshold rate. If the AR rate is now under
`registration messages in a sequence of ?xed time
`the threshold rate, as determined by instructions in
`intervals; and
`decision block 809, the registrations of roamer radio
`alternately enabling and disabling allowance of regis
`telephones are again enabled by the instructions of
`trations of homer mobile radiotelephones and
`block 811 and the ?ow path returns to block 803.
`roamer mobile radiotelephones as long as the num
`If the rate of autonomous registration messages con
`ber of autonomous registration messages exceeds a
`tinues to exceed the threshold rate, as per the instruc
`threshold count.
`tions of decision block 809, the ?ow process proceeds to
`3. A method of preventing registration signal channel
`the instructions of process block 817. Here the autono
`overloads in a cellular radio telephone system in which
`mous registration of the roamer mobile radiotelephones
`is again enabled and the autonomous registration of 30 registrations of mobile radiotelephones are controlled in
`response to timing markers transmitted to the mobile
`homer mobile radiotelephones is disabled.
`radiotelephones by local cellular access stations;
`The rate of autonomous registration messages is again
`comprising the steps of:
`measured in decision block 819. If the threshold AR
`monitoring the number of autonomous registrations
`rate is not exceeded the autonomous registration of the
`homer mobile radio telephones is again enabled per the
`occurring within a set time interval in a particular
`instructions of block 821 and the flow returns to process
`local cellular system
`block 803. If the rate of autonomous registration mes
`determining if the occurrence of an overload due to
`sages continues to exceed the threshold AR rate the
`the number of autonomous registrations has oc
`flow process continues to the process block 823 and the
`curred;
`roamer mobile radio telephones are inhibited from reg~
`in the event of the occurrence of an overload reduc
`istering by the instructions of block 823. The registra
`ing the number of autonomous registrations by
`tions of homer mobile radiotelephones are again en
`dilating the time of the generation of timing mark
`abled as per block 825. The flow continues to decision
`ers and transmitting these altered timing markers to
`block 816 which determines if the threshold AR rate is
`the mobile radiotelephones.
`exceeded. If the threshold AR rate continues to be
`4. Apparatus for controlling registrations of mobile
`exceeded by the autonomous registration message rate,
`radiotelephones of a cellular telephone system, compris
`the flow continues to process block 817 and the immedi
`ing:
`ately preceding steps are repeated. If the AR rate is
`a radio communication station for coupling mobile
`below threshold, the ?ow continues to process block
`radiotelephones with a land switched telephone
`811 to again enable registration of roamer mobile radio
`network in which the radio communication station
`telephone and then returns to process block 803.
`generates timing marks;
`I claim:
`'
`means for maintaining a list of mobile radiotelephones
`1. A method of registration for mobile radiotele
`served by the radio communication station;
`phones in a wireless telephone system in which mobile
`means for broadcasting the timing marks to mobile
`radiotelephones in a system identi?ed area communi
`radiotelephones to cause available mobile radio
`cate over radio channels with a base station providing
`telephones within coverage area of the radio com
`coverage of the system identi?ed area and the wireless
`munication station to request registration permit
`telephone system is coupled in turn to a land switched
`ting an update of the means for maintaining;
`telephone network;
`means for monitoring registration requests and deter
`comprising the steps of:
`mining if an overload condition occurs;
`instructing mobile radiotelephones to register over a
`means for selectively preventing registration requests
`designated overhead radio channel;
`of the mobile radiotelephones if the means for mon
`monitoring registration requests over the overhead
`itoring determines an overload condition by dilat
`radio channel;
`ing the time of generation of timing marks.
`identifying the attainment of an impending overload
`5. A method of preventing registration signal channel
`condition in autonomous registration requests by
`counting the number of registration requests within
`overloads in a cellular radio telephone system;
`comprising the steps of:
`a de?ned time interval;
`
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`monitoring the number of autonomous registrations
`time stamp of the registration ID message when the
`occurring within a set time interval in a particular
`count exceeds the threshold count;
`local cellular system;
`reducing the interval between periodic increments of
`determining if the occurrence of an ove