Note: Descriptions are shown in the official language in which they were submitted.
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A SUBSCRIBEP~ UNIT HAYING A SLEEP MODE AND A DORMANT MOD~
~ackground of the Inven~on
The present invention relates to wireless communication systerns.
More specifically, it relates to the subscri~er units used by s~bscribers to thewlreless communication systems.
Wireless commL~nication systems are used to provide commLlnications
capa~ilities to businesses having fieets of vehicies operating in the field -- for
example, taxi companies or limousine companies. Typically, wireless
communication systems include a base station, one or more dispatch
stations and a plurality of subscriber units. All communicat~ons are routPd
thr~ugh the ~ase station. The subscriber units are moun~e~ in the vehicles
operating in the field to provide communication capabilities to the vehicle's
ocr~upan~s. The dispatch st~tions allow a dispatcher to send dispatch
communications to one or more of the subscriber units through the base
s~tion.
Today's dispatch communication systems, however, provide limited
communication capabilities. For example, deliverymen working the eight-to-
five shift turn their subscriber units off at ~;:t)O P.M. The nexr day, when
they start their new workshift, they turn their subscriber units on a short
time before 8:00 AaVl. Communications from the dispatch station are not
~ransmitted until the subscriber uni~ are turned on. If too many subscriber
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units are turned on at the same time, the communication 8y5tem can be
overloaded, thPreby crsating delays in the trsnsmissions of messages,
In view of thes~ and other iimitations, new systems and methods that
provide improved communicaticns between a dispatch station and a fleet of
subscriber units are needed.
Summary of sha invention
The present Tn~ention provides apparatus and method of proYiding
d,spatch communications in a syst~m that includes a bsse ritation, a dispatch
station and one or more ~ubscriber uni~s. In 2ccordzncs one aspect of the
lQ p!~sent invention, the ~ubscrl~er unit has four modes of operation ~hat
~onsume vsrious amountr, o~ power. The modes include a sleep mode, a
dDrmsnt mode, a power off mode and a power on mode. In the Rleep mode,
limited power is consumed while ~ ~ubscriber unit listens for
communications from tha base ~tation. In the dormant mode, the ~ubscriber
unit is essentially shut down and, therefor~, consumes rr.inimal power.
~urin~ the dormant mods, communic~tlon signals transmitted to the
subscri~er unit, includlng dispatches from a dlsp~tch stahon, are stored in a
buffer at the base ~tstion. After a predetermined time, which is preset by
the dispatch ttation or by the r~ubsrriber, ~n internal alarm clock in the
subscriber unit causes the subscriber unit to come out of the dormant mode
to initiate ~ call to the base ststion to inquire about messases which were
direcsed to ths su~scriber unit durin~ the time it W85 in the dormant mode.
SUBSTITUTE SHEET (RULE 26)
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If there are buffered communications for the subscr;ber unit, the base station
transmits the buffered communications from the base sl~lion to the
subscriber unit. The subscriber unit then returns to the dormant mode.
Tne inven~ion will now be described in connection with certain
illustratPd embodiments; however, it should be clear to those skilled in the
art that vari~us modifications, additions and subtractions can be made
without departing from the spirit and scope of the claims.
Description of the Drawings
FIG. 1 illustrates a communication system;
Fl~i. 2 illustrates a common air interface for providin~ communications
between the various components of the communicaticn system of FIG. 1;
FIG. 3 illustrates a base station in the communication system;
FIGS. 4 and 5 illustrate a s~lbscriber unit in the communicatlon
system;
FJG. 6 illustrates a dispatch station in the communication system;
FIG. 7 illustrates a bill;ng station in the communication system;
FIG. ~3 illustrates the on/off power control of the subscriber ùnit;
FIG. 9 illustrates the power control of the subscriber unit during the
sleep mode;
FIGS. 10 and 11 illustrate the steps taken by the subscriber unit in the
dormant mode; and
~ FIGS. 12 and 13 illustrate the organizalion of memory in the base
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station which is used to buffcr messages to dormant subscriber units.
Descr;pb'on of the Preferred Embodiment
Referring to FIG. 1, a communication system 1 is illustrated. The
system 1 includes a base station 2, a dispatch station 4 and a plurality of
subscriber units 6. A billing station, not shown in FIG. 1, is preferably also
pro~ided to process billing information from a plurality of communication
sys~ems 1.
The communication system 1 may be a frequency hopping syst~m
which is ciivided into Sectors 8 to 10 wherein sets of frequencies are reused
in each sector to provide wireless communications. Note, however, that the
present invention may be used on other types of communication syst~ms,
incl~ding TDMA systems, CDMA systems and even analog based systems.
The base station 2 includes the communication equipment necessary
to provide ~he ml~ltiple access communications for the plurality o~
subscribers units 6 and for the dispatch station ~. The base station 2 also
includes the communication equipment needed to provide communications
through the Public Switched Telephone ~iietwork (PSTN).
The dispatch station 4 includes equipment necessary to dispatch
cornmunications from the dispatch station 4 to a number of subscri~er units
6, commoniy referred to as point-to-muitipoint communications. It also
includes equipment needed to communicate with individual subscriber units.
The subscriber units 6 genera[ly consist of mobile or porta~le equipment
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necessary to transmit, receive and process communication signals.
Referring to FIG. 2, the communication links between the base s;~tion
2, the dispatch station 4 and the subscriber units 6 -- referred to as the
cornmon air interface -- are illustrated. The communication channels in FIG.
2 include a plurality of traffic channels (TCHs), at least one control channel
(CCH) and at least one access channel (ACH). In the communication system
1 of FIG. 1, all of thes~ channels are present in each sector 8 to 10. I he
TCHs operate in the uplirtk (~ransmissions from subscri~er units 6 to the bas~
station 2) and in the downlink (transmissions from the base station 2 to the
subscri~er units 6). The CCH and the A~H, however, operate only in one
direction -- the CCH in the downJink and the ACH in the uplink.
In ~he illustrated embodiment of FIGS. 1 and 2, ten 25 kHz frequency
channels are used to define ten uplink channels and ten 25 kHz frequency
channels are used to define ten downlink channels. In each sectar 8 to 10,
nine of the frequency channels are used to implement nine upiink TCHs and
nine of the frequency channels are used to impiement nine downlink TCHs.
In each sector 8 to 1 O, the remaining frequency channels are used to
transmit one ACH and one CCH. Voice information, data information and
in~and overhead control signals between the base station 2 and the
subscriber units 6 are transmitted over the TCHs, preferably using frequency
hoppin9 and time hopping communication methodology. T iming and control
~ signals from the base station 2 to the subscriber unit 6 are transmitted on
-
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the CCH. S;atus and operat;onal requests from the subscriber unit 6 to the
ba~e station 2 are transmitted on the ACH. Transmissions between the base
station 2 and the dispatch stat;on 4 are treated in the same fashion as
transmiss;ons between the base station 2 and the subscriber units 6 Note
tha~ this description is illustr~tive o~ one communication method and one air
interface that can be used in connection with the present invention -- many
others are possible.
Referring to FIG. 3, the base station 2 is iliustrated. The base s;ation
2 includes a first sector unit 16, a second sector unit 17, a third sectcr unit
18, a microsector unit 20, a redundant sector 21, a PABX 22, a voice mail
unlt 24, a central ~requency source unit 26, an administratlon computer 28,
a central controller 30, a database server 32, a local administra~ive computer
34 a terminal server 36, a local area network 38, a power supply 39, data
computers 40 and a modem pool 41. The base station 2 may also include a
billing station, but where the communication system 1 is part of a regional or
national system having numerous base stations, it is preferred to provide a
central billing system that serves all of the base stations. The base station 2
of FIG 3 does not include a billing station.
The sector units 16 to 18 establish the communication channels
illustrated in FIG. 2 in the sectors 8 to 10, respectively. The microsector
unit 20 establishes communications with additional communication
equipment in trouble spots in the communication system 1. I he redundant
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sector 21 provides redundant communication channels for the sector units
16 to 18. The base station 2 provides communications with the PSTN via
the PABX 22. The PABX 22 aJso provides three way conferencing, routing,
least cost routing of long distance calls, voice mail inter~acing, dispatch
briclging, user services supporlt and meterin~ functions.
The voice mail unit 24 provides voice mail capability to the
communication sys.em 1. The central frequency sourcs unit 26 provides
timing references throughout the system. The admin;strat;ve computer 28
tracks subscri~er unit 6 configurations, tracks administrative activities,
performs network management, performs built-in-test mana~ement and
performs system initialization. The central controller 30 provides various
functions, includin~ call managem~nt, dispatch mana~ement, control OT the
PABX 2Z, voice mail interfacing, operational rnode management, subscriber
mana~ement, call mana~ement, supplies billing information, and generates
reports. The data base ser~er 32 stores user data concerning ~Iser rights,
status, calls and airtime. it also provides basic data base management and
servi~es to all datz base clients, such as the local operator, ~leet
administrators and remote operators. The local administration computer 34
provides maintenance and operational control of the base stat;on 2. The
loca~ area network 38 enables communications between the various
components connected to the networic.
Two pieces of equipment form a subscriber unit-- a subscriber
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terrn;nal 14 illustrated in FIG. 4 and a radio unit 12 iilustrated in FIG. 5. Ingeneral, the radio unit 12 provides the equipment needed to transmit, receive
and process signals over the common air interface of FIG. 2 while the
subscriber terminal 14 provides ~n inter~ace to a subscriber.
Referring to FIG. 4, the subscriber terminal 14 includes a
microprocessor 50, an oscillator circ~lit 52, a power supply circuit 54, a
serial interface clrcuit 56, a display driver circuit 58, a memory circuit 60, akeyboard interface circuit 62, an l/O decoder circuit 64, a LEI:) driver 66 and
an interface circuit 68. The subscriber terminal 14 can also include a real
time clock 70 or, alternatively, th~ base station 2 can distribute rea~ time
ciock information to each of the s~lbscriber units 6.
The memory circuit 60 inciudes a decoder circuit 76, an address latch
78 a boot ROM 80, a flash memory 82 and a static RAM 84. The boot
RO~ 80 stores the code necessary to initialize the microprocessor 50 and
l~ the circuitry of the subscriber terminal 14 as well as code necessary to
download ~uture software versions for the subscriber te~minal 14. The f~ash
memory 82 is non-volatile re-writable memory which is utilized to store
ir~formation which must be maintained even durin~ a loss of power. The
static RAM 84 is utilized as a working memory as needed.
The display driver circuit 58 includes the LCD display 24, a power
supply 86, a LCD controller 8~, a memory circuit 90 and an address
controller 92. The display driver circuit 58 is accessed by the
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r.icrocontrollt-r 50 via the 1/0 dacoder 64. The information to be displayed
isJownloaded from the microprocessor 50 to the memory circuit 9(). The
~ display of the in~ormation on the dispiay 24 is then controlled in a
conventional manner by the LCD controller 88.
The microproc9ssor 50 is responsive to the selec1:ion of the keys 30 to
34 cnd 36 to 43, as well as to the selection of the keys on the handset 2~:.
When the kzys are s~lected, selection signals are processed through the
keyboard inter~ace circuit 62 to the microprocessor 50. The microprocessor
~0 also controls the LE~s 44 through the LED driver circuit 66. T he RS-2:~2
interface 9 provides commun;cations between the subscriber terminal 14
and extern21 devices, such as notebook computers, magnetic swipe devices
used to read magnet~c strips, printers, bar code readers and serial key~oards.
The RS-48~ ;nterface 96 and the interface circuitry 68 provides
communications between the subscriber terminal 14 and the receiver and
transmitter circ:uitry of the radio unit 12 (shown in FIG. 5).
ln FIG. ~, the circuitry of the radio unit 12 is illustrated. The rzd;o unit
1 2 includes antennas 102 and 104, a radio board 106, a bas~band unit 108,
a service board 1 10, and a GPS interface 1 1 1. The radio unit circu;try
illustrated in FIG. ~, except the antennas 102 and 104, is preferably housed
separately frorn the subscr;ber terminal 14, ~or exarnple, inside the trunk of
an automobile. The antennas 102 and 1 04 are preferably mounted
ex-emally on the automobiie.
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The radio board 106 includes transmitter and receiver circuitry. I~lore
particularly, it ;ncludes a transm;tter 1 12, two receiver channels ~ 14 and
116, a duplexer 118, a frequency synthesi2er 120, gain and frequency
control circuitry 122 and transmitter gain control circuitry 124. As
previous1y descri~ed, the circuitry of the radio board 106 preferably provides
communication via frequency hopping, that is, a communication signal is
transmitted and received by hopping the signal oYer several different
~requency channels.
The radio board 106 is interfaced with the baseband unit 108. The
baseband unit 108 includes a modem 126, a controller 128, a voice
processing package 130 and an inter~ace circuit 132 to the subscriber
terminal's 14 ci~cuitry, This baseband un;t 108 receives the signals ~o be
tran~miKed ;o the base station 2 from the subscriber terminal 14 processes
~hose signals and then sends the signals to the transmit~er 1 12 in the radio
1~ board 106 for transmission. This baseband unit 108 also receives the
signals that the radio board 106 receives from the base staticn 2, processes
the received signals and sends them to the subscriber terminal 14 through
tlleinterface 132.
Referring to Fl~i. 6, the dispatch station 4 is illustrated. The dispatch
slation 4 includes a personal computer 150, a modem 152, a radio unit 12,
a microphone 15~, a speaker 156 and an antenna 158. When the base
stat;on transmits tc the dispatch station 4, the communication s;gnaJs are
_
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received on the antenna 15~3, processed by the radio unit 12 and sent to the
computer 150 throu~h a seria~ port 160 The computer 150 determines
whether the communication is voice or data communications. If the
communication is a voice communication, then the signals are sent to a
sound card in the computer 150 for voice process;ng. The voice sisnais are
eventually sent to the speaker 156 through a port ~ 62 on the sound card so
that they can be heard by a dispatcher. If the communicat;on is a data
communication, then the computer 150 processes the data so thzt it can be
presented to the dispatcher in a desired format.
iO When the dispatcher sznds a voice or data communication signai 'rom
' the dispatch station 4 to the base station 2, the signal is senerated from themicrophone 1~;4, in the case of voice signals, or from a data file in ;he
computer 150, in the casz of data si5nals. The voice signals are preferably
processe~ throu~h the sound card in the computer 150. Then, the voice or
da~a signals are sent through the port 160 to the radio un;t 12 for
transmission by the antenna 158.
In addi~ion to voice and data, the dispatcher can send fleet
administration information to the subscriber units in the dispatcher's fleet to
control the configuration and capabilities of those subscriber !Jnits. To do
this, the dispatcher accesses the computer 150 to set the desired fleet
administration information. The fleet administration information, once
c~nfigured by the dispalcher, i5 then sent through a port 164 to the modem
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152. The modem 1~2 transmits the fleet adminlstration information to either
a central billing station or to the base sta~;on 2 over a land line.
Alternatively, the fleet administration information is transmitted over-;ne-air
to the base station 2 through the dispatch station radio unit 12. The fleet
adrninistration information can then he forwarded to the billin~ station,
whe,ther the billing station is part of the base station 2 or off-site in a centrat
location.
Referr;ng to FIG. ?, a central biiling station 170 is illustrated. The
bil~ina s~ation 170 includes a server 172, a gateway 174, a local area
network 176 and a rcuter 178 to a wide area network. The s~rver 172 has
a database that keeps track of information concerning all users of the
communication system 1, including all of the dispatchers and all of the
subscribers. The information tracked includes the services that the users
ha~ Igned up to use, the payment histor;es of the users, the configurations
of thP users of the system 1 and current bill;ng informatlon. The gateway
174 is a switch thzt provides a signal pat~l to and from the local area
netv~rork 176. A router 178 then routes these signals to a wide area
network ~or distribution to and from the local area network 38 of the base
station 2.
In accordance with the present invention, the subscriber unit 6
pre~erably has four different modes of operation, each o~ w~ich consume
differing amounts of power. In the first rnode, power off, all components in
_
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the subscriber unit 6 are turned off and no power is consumed. In ~he
second mode of operation, power on, all components in the subscriber unit 6
are turned on and maximum power is consumed. In the third mode, the
dormant mode, all compcnents except those responsible for "waking up~ the
subscrjber unit 6 at a preset time are turned off. The subscriber unit 6
wakes up at a preselected time to query the base station 2 for messages.
Once in the dormant mode, however, the subscriber unit 6 will not resume
nornlal operation until the unit is turned on by the cubscriber. In the four~h
mode, the sleep mode, subscriber unit 6 turns power off to all components
except those necessary to receive signa~s from the base s.ation 2. Then,
when signals are r-~ceived, the subscriber unit 6 again wakes up to process
those si~3nals. The subscriber unit 6 exits the sleep mode whenever any key
on the keypad 24 is touched.
These modes of operation are illustrated in FIGS. 8 to 11. Referring to
FlG. 8, the steps taken by the subscriber unit 6 when turning power on ar~d
off are illustrated. In step 200, the microprocessor 50 in the subscriber
terminai 14 determ;nes that the power control key on the subscriber terminal
14 has been selected. If the power is being turned on, then in steps 202
and 204, the controller 128 and the microprocessor 50 cause the power to
the radio unit 12 and to the subscriber terminal 14, respectively, to be
turned on. If the power is being turned off, then in steps 206 and 208, the
controller 128 and the microprocessor 50 cause the power to th~ radio unit
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1~ and to the subsc.iber terminal 1 A~ respectiveiy~ to be turned off.
Referring to FIG. 9, the 5.eps taken b~/ the subscr;ber unit ô in the
sleep rnoc~e are iilus~rated. In step 220, the microprocessor cO receives an
instruction from a subscriber that causes the subscriber unit 6 to enter the
slee~ mode. In step 222, the microprocessor 50 sends an instruction to the
controlier 128 in the radio unit 12 that tells the radio unit 12 to enter ;he
sle~p mod~. Then, in st-p 224, the processor 50 causes powef to .he
su~scriber terminal 14 to be turned off. In step 226, the controller 7 28
causes power ;o be turned off .o selected compcnents but allows power to
supplied to o.her components The controller 128 turns power of~ to all
components not needed to receive communication signals from the base
station 2. Therefore, in the radio unit 12 (FIG. 5), the reccivers 1 14 and
11~;, the synthesizer 120, the frequency and gain control cir~uit 122, the
modem 126 and the controller 128 remain powered during the sleep mode.
Thus, the subscriber unit 6 can receive signals when in the sleep mode.
When signzls are recPived or when a subscriber touches a key cn the keypad
26, the subscriber unit 6 returns to normal operation and proc~sses any
received or ;ransmitted communic~tions.
Referring to FIG. 10, the s.eps taken to enter the dormant mode are
2~ illustrated. in step ~C0, the subscri~er depresses keys on the keyboard 2
on the subscriber ter~inal 14 to instruct the subscriber uni~ 6 t~ enter a
dormant n cde of operation. Tr)e microprocessor 50 reads the depressed
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keys, interprets the dormant mode instructions and notifie5 the contro~Jer
128 In the radio unit 12 that the subscriber unit 6 has been instructed to
en~er the dormant mode of operation.
Then, in step 302, in one embodiment o~ the present invention, the
controller 1.Z8 causes a commun~cation signal to be sent by the subscriber
unit's transmitter 1 12 to the base station 2. The communication s;gnaJ is
pref~rably sent on the ACH, but may also be sent on the uplink TCH as well.
It is received and processed by the appropriate seclor unit 16 to 18 or 20.
The sector unit ~ 6 to 18 or 20 proc2sses ~he signal by examinin~ a control
field ;n the communication s;gnal to determine what type of communication
was received. In this case, the control field indicates tha~ the
communication signal is from a particul~r su~scriber unit that is entering the
dormant mode.
The sector unit 16 to 18 or 20, from the received cc~mmunication
1a signals, determines which subscriber unit is entering the dormant mode.
This information is transmitted to the database 32 and the administrative
computer 2~ under the control of the central controller 30. The information
concerning the status of the subscriber unit 6 in the database 32 and the
administrative computer 28 is updated to reflect the dormant status. Thus,
the base station 2 knows which subscriber unlts 6 are in the dormant state.
In an alternate ~mbodiment of the present invention, step 302 is
sk;pped. Then, th~ base sta~ion 2 is not notified that the subscriber unit 6 is
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entering the dormant mode of cperation Thus, upon attempting 2
communic.a.ion ~ith a dormant subscriber unit 6, the base sta;ion 2 ~,viil only
know ;ha, ~he subscriber unit 6 is not receiving the commurication.
In response to the dormancy message, the base station 2 can aend a
message to the su~scriber unit ~ instructing the subscriber unit 6 to s.ay
awake for a preselected or an ins.ructed period of time. Tile base stztion 2
can issue this instruction i~ i. wants to broadcast a message to rnany
subscriber units 6 or for any other reason.
In step 30¢, the subscriber unit 6 checks its controller 12~ rr,emGry to
determine how long the subscriber unit 6 should ~nter the dormant moce. In
one embodiment, the length of time is set in the controller 128 memory 30
that every subscriber ~nit 6 enters the dormant mode for the same lensth of
tirre. In an alternate embodiment, the subscriber can enter the length of
time that the subscriber unit 6 should stay ;n the dormant mode throus;~l the
keyboard 26 on the sui~scriber terminal 14. In this case, the microprocessor
50 ~eads this information (the length o~ time) from the keyboard and
transmits it to the controller 128, where it is stored in memory.
In ano~her embodiment, however, the length of time that a su.,~-r ~er
nit 6 stays in th~ c'crmant mode is programmable by a dispatcher â~ e~
~'' dispa,ch s;ation ~. To do this, the dispatcher accesses the computer 1 5~J.
One of the options ~he computer 1~0 offers as part of a fieet administratior.
pack2se is to alio~,v tine dispatcher to select the length of time the subscr;~e~
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unit remains dormant once the subscriber places the unit ;n the dormant
mode. When the dispatcher selects this option, the computer 150 prompts
the dispatcher to enter the length of t;me. Once the dispatcher enters the
length of time, the computer 150 stores this parameter in its memory.
When the dispatcher cornpletes the entry, the dispatcher enters an
instruction that causes the computer 150 to send this information to the
base station Z. This inforrnation is preferably sent to the base staticn with
the other dispa~cher controlled fleet administration in~ormation that
configures and controls the subscriber units 6. Examples of the information
that can be con;rolled inciude groupings of su~scriber units, PSTN
assignments to subscr;ber units, and subscr;~er unit telephony configurations
and quick dial iists.
Re~erring to FIG. 6, when the dispatcher instructs the computer 150
to send the fl~et administration information, includlng the dormancy time in
accordance with the present invention, the computer 150 sends the
information tllrough a port ~ 64 to a modem 1~2 in the dispatch station 4.
The modem 152 preferably transmits the flee~ administration information
over a land line to the modem pool 41 in the base station 2. Alternatively,
the computer 150 can route the fleet administration information through the
2d radio unit 12 so that the transmission is over-the-air, via the TCH or the ACH, to one of the sectors 16 to 18 in ~he base station 2.
Once the length of dormancy has ~een determined, in step 306, a
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power off timer is set. The timer determines the time that the subscriber
unit 6 spends in the dormant mode and in waking up from the dormant
mode. Then, in s.ep 308, the power to the components in the su~scriber
terminal 14 and the radio unit 12 are turned off, except power is supplied to
the microprocessor 50 in ~he subscriber terminal 14 and to the controller
12~ ;n the radio unit 12. This allows the subscriber unit to "~ake up" at a
later time and then, in turn, to wake up other components needed to receive
messages. It also allows the controller 128 to maintain the power o~F tirner.
Referring now to FIG. 1 1, dur;ng the dormancy time, the control~er
128, in step ~tO, keeps checking to see whether the dormancy time has
eiapsed. During th;s time, the base station 2 can be attempting to transmit
communication signals to the subscriber Lsnit 6 while it is in the dormant
state. If step 302 has been skipped, the base station 2 attempts to
communicate with the dormant subscriber unit 6 and detErmines that the
l~ su~scriber ~nit 6 is not responding. If step 302 is performed, the ~ase
station 2 will know ~hat the subscriber unit 6 is in the dormant mode by
checking its database.
When the base station 2 determines that the subscriber unit 6 to
which the communication is directed is not availabie, either by attempting to
communicate or by checking the database or both, the base s~ation 2 buffers
the message in the communication signal. F~GS. 12 and 13, illustrate the
buffering of these messages. In FIG. 12, the database 32 maintains a table
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of subscriber unit identification numbers, an indica~ion of whether there are
bLlffered messages and the locaticns of those buffered messages. Whenever
a message cannot be delivered by the base station 2 to the subscriber unit
6, the table of FIG. 12 is updated to indicate that the subscriber unit has a
buffered message and the location of the message. In FIG. ?3, the buffering
of the rnessage is indicated. For example, in FIG. 12, the datahase indicates
that subsrriber unit having identification number SU002 has a buffer~d
message starting at mernory location 0000. Referring to memory locat;on
0000, in FIG. 13, the buffered me-sage is found. In this case, the bu,~;ered
tC message is the next days itinerary.
Referring now back to FIG. 11, once the dormancy time has elapsed,
the c~ntro~ler 128 checks the power off timer. The power off timer keeps
track of how iong the subscriber un;t 6 has ~een in the dormant mode,
including the times that the subscriber unit 6 wakes up and then returns to
the dormant mode~ If the power off timer is less than a predetermined
amount, preferably fourteen (14) hours, in step 312, the microprocessor ~0
and the controller 128 cause power to be turned on to the subscriber
terrninal 14 and to the radio ~Jnit 12, respectjvely if the power off ~imer
exceeds the predetermined amoutnt, then the subscriber unit 6 does not
wake up. Thus, the power off timer stops tlle subscriber unit 6 from
repeatedly waking up from the dormant mode, thereby preventing the
draining of the battery of the vehicle in which the subscriber unit 6 is
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ins.alled.
Once awake, in step 314, the controller 128 causes a communication
signal to be transmitted to the base station 2 indicating that th~ subscriber
unit 6 is no longer in the dormant mode. Then the base station 2 accesses
its memory as illustrated in FIGS. 12 and 13 to determine whether there are
buffered messages. If any are found, the base station 2, in step 316,
transmits these messages to the subscriber unit 6.
Any messaae which has been directed to the dorrnant subscriber unit
6 can be buffer~d and then transmitted. The present invention, however, is
particularty useful in transmitting the next day's work orders to a sulbscriber,to transmit new user databases and to download naw software versians to
subscriber units.
Once all of the buffered messages have been transmitted, the
subscriber unit 6 returns to the dormant mode. The subscriber unit 6 is
removed from the dormant mode by power being turned on or, i~ an
alternative embodiment, by the selection of one of the keys on the keypad
24.
It is understood that changes may be made in the above description
without departing from the scope of the invention. It is accordingly intended
that all mat~er contained in the above description and in the drawings be
interpreted as illustrative rather than limiting.
