Exhibit 1007
`
`|lllllIllllllllllllillIlllllillllllllllllllilllllllllllllllllllllllllllIIII
`U5005243530A
`,
`5 243 530
`[11] Patent Number:
`[191
`United States Patent
`9
`9
`
`Stanifer et a1.
`[45] Date of Patent:
`Sep. 7, 1993
`
`[54] STAND ALONE MULTIPLE UNIT
`TRACKING SYSTEM
`
`[75]
`
`Inventors: Samuel D. Stanifer, Camarillo;
`Mucus W. Wood-rd, Oxnard, both
`0‘ Califv
`[73] Assignee: The United States of Amer-in Is
`represented by the Secretary of the
`Navy, Washmgton, DC
`[2]] Appl. No.: 736,560
`
`Jul 26 1991
`[22] Filed-
`'
`’
`'
`60617 15/50
`[51]
`Int. Cl.5 ..................
`
`[52] US. Cl. .................................... 364/452; 364/516;
`_
`340/990
`[58] Field of Search ............... 364/452, 449, 514, 516;
`340/990, 991, 992, 993, 995; 342/389, 457;
`73/178 R; 370/941
`References Cited
`
`[56]
`
`U'S‘ PATENT DOCUMENTS
`4,318,105 3/ 1982 Brodeur .........
`--------- 342/339
`4,428,057
`1/1984 Setliff et 21.1.
`
`
`4,513,377 4/1985 Hasebe et a1
`364/“9 X
`
`4,777,489 10/ 1988 Allan ..............
`""" 32:73:
`. 364/452
`4,791,572 12/1988 Green, III et 31.
`
`
`4,989,204
`1/1991 Shimizu et a1.
`........
`.. 370/941
`
`7/1991 Velasco ....................... 342/457
`5,032,845
`
`.
`5.153.836 10/1992 Fraughton et al.
`5,155,689 10/1992 Worthham .......................... 364/449
`
`OTHER PUBLICATIONS
`GPS—Based Vessel Position Monitoring and Display
`System; Reynolds ct 11-; IEEE ABS Magazine; Jul-
`1990; PP 16-22-
`‘
`Primary Examiner—Thomas G. Black
`Assistant Examiner—Michael Zanelli
`
`Attorney, Agent. orFirm—David S. Kalmbaugh; Melvin
`J. Sliwka
`
`“WOT
`[57]
`A stand alone multiple unit tracking system which uti-
`files a packet radio link to periodically transmit infer-
`mation identifying the geographic position of ships,
`aircraft and other land mobile vehicles. The stand alone
`multiple unit tracking system comprises a base station,
`relay stations and a plurality of remote stations placed
`on board ships, aircraft or the like. The remote stations
`transmit latitude and longitude position information to
`the base station through relay stations, if required, using
`packet radio techniques.
`
`6 Claims, 8 Drawing Sheets
`
`MONITOR
`
`
` =
`
`II
`
`l
`
`I
`lI
`I
`
`LORAN c o
`
`oupuren
`
`'
`
`E"
`
`Liberty Mutual
`
`Exhibit 1007
`
`Page 000001
`
`

`

`US; Patent
`
`Sep. 7, 1993
`
`Sheet 1 of 8
`
`5,243,530
`
`OE<¢hz>
`
`¢w>_wum2(¢._.
`
`05¢:
`
`¢w>_wumz<x._.
`
`..=,.>
`
`Page 000002
`
`

`

`US; Patent
`
`Sep. 7, 1993
`
`Sheet 2 of 8
`
`5,243,530
`
`50g‘
`
`52-—56-58—mmm
`
`
`
`m--_-mm
`
`
`Fig. 3.
`
`INFORMATION
`
`STATUS
`
`INITILIZE REPORT
`TNC
`MODE
`
`POSITION
`REPORT '
`
`Inn on
`
`
`
`
`TERMINATE OUIESCENT NORMAL
`STATE
`STATE
`
`
`
`I. POSITION REPORT INDICATES A POSITION OF -||9.I223 DEGREES
`LONGITUDE BY 34.|O42 DEGREES LATITUDE.
`
`2. VALUES DEPEND ON NUMBER OF REMOTE STATIONS/SITES.
`
`3. VALUES VARY WITH REMOTE STATION POSITION.
`
`Fig. 5.
`
`Page 000003
`
`

`

`US; Patent
`
`Sep. 7, 1993
`
`Sheet 3 of 8
`
`5,243,530
`
`SANTA CRUZ IS.
`
`6"
`ANACAPA Is.
`
`SANTA BASBARA IS.w
`
`SANTA CATALINA IS.
`
`SAN CLEMENTE IS.
`
`BEGGBOCK
`
`Fig.4.
`
`Page 000004
`
`

`

`US. Patent
`
`Sep. 7, 1993
`
`Sheet 4 of 8
`
`5,243,530
`
`
`
`
`
`
`
`
`
`3.8.whoa2...:
`
`
`
`
`
`
`
`
`
`mEo<¢<zo8253xmbééu«$.3330..
`
`
`
`
`
`
`
`5.55220mmu¢8<mm:EB<¢<=08933mm:u.no.
`
`“:6E029.2925um:2:3858m2
`mama~53ESwooo.
`
`
`
`cum:5:502:2gunman5&8eooo.
`
`uuzmmmummEda54.7?uozuzuummEda55-2mouo.
`
`
`Edaoznoutime02-?mm.o.
`
`
`
`am:52”5:58:5:«woo.
`
`
`
`
`
`e5...9..onQSuzammmfiwmHmamSee.
`
`Soc.
`
`
`
`
`
`cum:5:.2532.anuzSoc.38%
`
`25;
`
`5552:".mmuzofi585210«85389..ago:
`
`
`
`
`
`
`
`”.3255$322¢m8<x<xo«3:8438..
`
`was.
`
`
`
`anz.amu><4umxwoz.mmm><4wm
`
`
`
`
`
`xmaz.s.¢m><4w¢xmoz.L.¢w><4w¢h.
`
`
`
`
`
`xwho<¢<rummuzna<mm.—
`
`
`
`mutudzdxuwmwxoo<mm.“
`
`
`
`EUPO<¢<IUmmmcona
`
`
`
`zmhu<mdzuwwwxoo<
`
`
`
`xmoz._mu><4m¢xmoz..mu><uu¢
`
`xuoz.N¢m><4m¢xwoz.N¢w><4u¢
`
`xuoz.nKm><4wz
`
`xwoz.mzw><4wm
`
`$5....
`
`mnmnd
`
`~31».
`
`ooN¢.~n
`
`whooéo.
`
`¢¢_N.w~
`
`amok
`
`:bmao...
`
`xwoz.m¢m><4wmanz.w¢u><4m¢
`
`xuoz.Qzw><4w¢
`
`xmoz.e.¢m><4m¢
`
`
`hmwgllu.xuo_mm>zhm<u“awn—m.
`zn(awxmoz.nzm><4uz
`
`Page 000005
`
`
`
`
`
`
`
`
`
`
`

`

`US. Patent
`
`Sep. 7, 1993
`
`Sheet 5 of 8
`
`5,243,530
`
`§on
`«-
`
` .
` OO o
`
`52.4288
`
`04.8576
`
`
`
`§ 3
`
`§0
`«-
`
`§0
`<r
`
`co
`@-
`
`w<
`
`1-
`
`8
`
`co
`:1-
`
`a:
`c-
`
`.0002
`
`.0004
`
`.0008
`
`.00l6
`
`.0032
`
`.0064
`
`.0l28
`
`.0256
`
`.05l2
`
`|024
`
`.2048
`
`.4096
`
`.8l92
`
`l3.|072
`
`26.2!44
`
`l.6384
`
`3.2768'-96.5536
`
`E30
`E3
`
`SIXTHWORD
`
`COLUMN
`
`COLUMN
`
`.
`)
`.I
`
`ma
`
`.
`
`.6
`
`I
`
`.5.
`
`63.
`’9-
`
`
`
`SIGN'0—+NORTHl—-SOUTH
`
`SEVENTHWORl
`
`Page 000006
`
`

`

`US. Patent
`
`Sep. 7, 1993
`
`Sheet 6 of s
`
`.
`
`5,243,530
`
`'Fig[00.
`
`mI
`
`II
`I
`an:
`
`L”:—
`E!00an.
`
`2d1m!
`:l-
`
`106.
`Fig.
`
`
`
`POINTER=4 HEADPOINTER*ITAIL
`
`
`
`
`Page 000007
`
`

`

`U.S'. Patent
`
`Sep. 7, 1993
`
`Sheet 7 of 8
`
`5,243,530
`
`
`
`
`
`
`
`
`
`auaammaalaaaaana—
`“flflflflfiflfiflflflflflfiflflfl_
`-nnnnunnnnunnnnnn—
`nannnnnnanaannanam
`Wflflflflfllflfiflflflflflfiflfl
`unuauannnnnanauaam
`Hflflflflflflflflflflflflflflflfl
`“flflflflflflflflflfiflflflflflflm
`-EEIEEDIIDEIIEIIIIEIEEE_
`"flflflflflfllfllflflflflflflflfl—
`-EHEHIIEIIIIIIIEIIIIIIHEH-
`uflflflflflllflllflllllllllflflfl—
`
`-EHEEIEIIIEIIEIIIIIIIIIEEE—
`
`Hflflflflflflflflflflflflflflflfi
`
`-_flflflflflllllllllllflllflflfifl
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`3000
`
`|000
`
`2000
`
`l000
`
`2000
`
`3000
`
`Fig. II.
`
`Page 000008
`
`

`

`US; Patent
`
`Sep. 7, 1993
`
`Sheet 8 of 8
`
`5,243,530
`
`V / 23
`
`37
`
`
`
`
`“_
`
`VHF RADIO
`TRANSCEIVER
`
`FM. l2.
`
`Page 000009
`
`

`

`STAND ALONE MULTIPLE UNIT TRACKING
`SYSTEM
`
`5
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates generally to navigational sys-
`tems for use with ships or aircraft and more particularly
`to an aircraft or ship navigation system which uses
`packet radio technology to remotely report position 10
`information.
`‘
`2. Description of the Prior Art
`Prior art methods of remotely determining the posi-
`tion of ships or aircraft normally involve the use of
`systems with a beacon on the ship or aircraft whose 15
`position is being tracked and then reported, or radar
`systems which track a ship or aircraft by means of mi-
`crowave energy reflected from the ship or aircraft
`being tracked. Other methods involve multilateration of
`a beacon signal from multiple receiving sites. Using 20
`these prior art methods, a complex and expensive
`ground station sends interrogation signals to ships or
`aircraft being tracked. Return signals indicate ranges to
`the beacon on the ship or aircraft whose position is
`being tracked. Actual geographic or relative position of 25
`the aircraft or ship is then calculated by computers
`inherent within these systems. These systems tend to be
`complex, physically large, expensive and are not easily
`deployed.
`Systems used for remote position monitoring/track-
`ing of ships and aircraft in weapons test and evaluation
`applications are typically radars and multilateration
`tracking systems. Test ranges incorporate various types
`of radar for surface and air surveillance or precision
`tracking of vehicles under test. These radars are nor-
`mally shore-based and their coverage does not extend
`above the horizon. Multilateration systems can extend
`their coverage over the horizon only if a complex and
`expensive transponder is installed in the unit
`to be
`tracked as well as aboard a relay aircraft.
`Packet systems have been known for several years:
`see for example “Computer Networks” by Andrew S.
`Tanenbaum, published by Prentice Hall
`(1981) and
`"Advances in Packet Radio Technology” by R. E.
`Kahn et. al., Proc. IEEE, Vol. 66 (November 1978), 45
`pages 1468-1496. A packet radio system is a data com-
`munications radio network comprising a plurality of
`stations.
`Generally, packet radio communication systems in-
`clude a plurality of stations each covering a respective 50
`zone. A data message to be communicated is divided
`into discrete segments of fixed length, called “packets”.
`Packets are transmitted from a station of origin to a
`destination station and if the packets are received by the
`destination station without error, an acknowledgement 55
`is provided by the destination station. Thus, two way
`communication may be accomplished by two or more
`stations within a network.
`Specifically, packet radio communications systems
`may have a central station that administers a plurality of 60
`remote stations each covering a respective zone. In
`response to a polling packet from the central station,
`data packets are assembled at the remote stations and
`transmitted to the central station. When the packets
`arrive at the central station, the central station transmits 65
`an acknowledgement of that fact.
`Packet radio systems have many uses in the commu-
`nications field, such as, providing mobile battlefield
`
`3O
`
`35
`
`40
`
`1
`
`5,243,530
`
`2
`data users with a common communications service
`which is comparable in terms of service and reliability
`to a static system. U.S. Pat. No. 4,989,204 to T. Shimizu
`et. al. is illustrative of a packet radio communication
`system which provides for mobile stations and may be
`used in tactical mobile areas of a forward battlefield.
`However, packet radio technology has not been utilized
`to remotely report aircraft or ship locations.
`SUMMARY OF THE INVENTION
`
`It is therefore an object of the present invention to
`provided a relatively simple, inexpensive and easy to
`install position reporting system.
`It is another object of the present invention to pro-
`vide an autonomous means of position reporting inde-
`pendent of other ship/aircraft systems which would
`interface with on board ship/aircraft navigation sys-
`terns.
`
`It is yet another object of the present invention to
`provide a position reporting system whereby external
`monitoring of transmitted radio packets is permitted
`which allows for ships and aircraft to be tracked and
`displays to be provided showing the position of each
`ship and aircraft in the area.
`It is still another object of the present invention to
`provide a position reporting system which would allow
`for rapid and inexpensive setup for aircraft tracking and
`control at small airports where radars are not in the
`vicinity or cannot be justified in terms of cost.
`It is a further object of the present invention to pro-
`vide a low cost tracking system for offshore vessels in
`congested areas with fixed site local hazards being per-
`manently entered into shore station monitoring stations
`to be transmitted to ships at periodic intervals.
`These and other objects of the present invention are
`accomplished by a stand alone multiple unit tracking
`system which utilizes packet radio technology to peri-
`odically transmit
`information identifying the geo-
`graphic position of ships, aircraft and other land mobile
`vehicles by means of a packet radio link. The stand
`alone multiple unit tracking system of the present inven-
`tion comprises a base station, relay stations and a plural-
`ity of remote sites or stations placed on board ships,
`aircraft or the like. The base station includes a VHF
`radio transceiver, a terminal node controller, a cathode
`ray tube display device and a personal computer, while
`each remote station includes a Loran-C device, a per-
`sonal computer, a terminal node controller and a radio
`transceiver.
`The packet radio links which transmit position infor-
`mation/data between the remote sites and the base sta-
`tion operate on a simplex channel, that is, one channel is
`used to both transmit and receive information. Each
`station within the stand alone multiple unit tracking
`system of the present invention monitors the simplex
`channel and when it has information to send‘checks to
`see if the channel is busy transmitting or receiving. If
`the channel is busy, the station with information to send
`or transmit waits until the channel is clear. When the
`simplex channel clears, the station transmits and if the
`transmission is successful an acknowledge message will
`be provided by the receiving station. If two or more
`stations transmit at the same time, then the data from
`both stations collides and the transmitting stations will
`not receive an acknowledge message, each station then
`waits a programmed time period and transmits again.
`Time periods are different at each station which allows
`
`Page 000010
`
`

`

`3
`for successful transmission by each station within the
`system.
`The Loran C device at each remote station provides
`position data that is the latitude and longitude of the
`remote station as well as data which indicates the qual-
`ity of the position data being provided. The computer at
`the remote station generates “packet” radio frames in
`accordance with the AX.25 Amateur Packet-Radio
`Link-Layer Protocol to transmit latitude and longitude
`position data from the remote station to the base station. 10
`The terminal node controllers at the remote stations
`function as modems passing the “packets” of position
`data between the remote station computer and the
`transceiver, provide for transceiver control so that each
`remote station may be successfully linked to reliably 15
`transport position data between the stations and provide
`a High Level Data Link Control ('l-IDLC) frame cheek
`sequence for error free transmission of position data
`between stations.
`When the base station receives the “packets” of posi- 20
`tional data from the remote sites, the computer at the
`base station will sift through the positional data and
`correlate the data so that it may be combined into a
`single intelligible form for presentation by the cathode
`ray tube display.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`5
`
`25
`
`35
`
`FIG. 1 is a functional block diagram of the base sta-
`tion of the present invention;
`FIG. 2 is a functional block diagram of a remote 3O
`station of the present invention;
`FIG. 3 is an illustration of the AX.25 Amateur Pack-
`et-Radio Link-Layer Protocol frame employed by the
`present
`invention during the transmit and receive
`modes of the base and remote stations;
`FIG. 4 illustrates a rangemap which appears on a
`monitor at the base station and which depicts the loca-
`tion of the base station and each remote station of the
`present invention;
`FIG. Sis a table illustrating the message formats used 40
`by the multiple unit tracking system of the present in-
`vention;
`FIGS. 6A and 6B illustrate the binary format for
`longitude and latitude positional data provided by a
`remote station of the present invention;
`FIG. 7 defines the user table for the base station and
`remote station software;
`FIG. 8 is an example of the user table of FIG. 7 for
`the base station;
`FIG. 9 is an example of the user table of FIG. 7 for a 50
`remote station;
`FIG. 10(A)-10(D) is an example illustrating the use
`of the output buffers for the computers at the base and
`remote stations of the present invention;
`FIG. 11 illustrates the binary data file used to gener- 55
`ate the map of FIG. 4; and
`' FIG. 12 is a functional block diagram of a relay sta-
`tion of the present invention.
`
`45
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`60
`
`Referring first to FIGS. 1 and 2 the multiple unit
`tracking system 18 of the present invention comprises a
`base station 20 and one or more remote stations 22 with
`the base station 20 being adapted to receive positional 65
`data from each remote station 22 and then sift through
`the positional data and correlate the data so that it may
`be combined into a single intelligible form for viewing
`
`5,243,530
`
`4
`on a cathode ray tube display 24 or such other devices
`as are customarily used to display information to an
`operator.
`At each remote station 22, a personal computer 28
`accepts data from a Loran-C 30 which establishes the
`longitudinal and latitudinal position of a ship. an aircraft
`or a vehicle respectively on the sea, in the air or on land.
`Personal computer 28 assembles the positional data into
`a “packet" or frame format, provides the “packet” to a
`terminal node controller 32 and coordinates with the
`base station 20 the transmission of positional data pro-
`vided by Loran-C 30. Terminal node controller 32, in
`turn, controls the transmission of this positional data by_
`a VHF radio transceiver 34 to the base station 20 by
`keying transceiver 34 whenever transceiver 34 needs to
`send data.
`Referring to FIGS. 4 and 12. it should benoted at this
`time that the multiple unit tracking system of the pres-
`ent
`invention may utilize repeater/relay stations 23
`which relay position data from a remote station 22 to
`the base station 20. The relay station 23 utilizes the same
`computer equipment as the remote station, but gener-
`ally does not include a Loran-C 30 since its function is
`to relay information or data "packets” between the
`base station and the remote stations. However, it should
`also be understood that a remote station 22 may also be
`utilized as a relay station 23. Further, it should be under-
`stood that a relay station 23 may require only a VHF
`transceiver 37 and a terminal node controller 39 to relay
`information when the terminal node controller adheres
`to AX.25 Amateur Packet-Radio Link-Layer Protocol.
`Referring to FIGS. 1 and 2, base station 20 includes a
`VHF radio transceiver 36 for receiving positional infor-
`mation packets/frames transmitted by each remote sta-
`tion 22, a terminal node controller 38 which provides
`the positional information in the “packet” format to a
`personal computer 40. Personal computer ‘0 then disas-
`sembles and processes the positional information for a
`map display on cathode ray tube display 24 or for dis-
`play by printer 26.
`In the preferred embodiment of the present invention
`remote station equipment does not require operator
`intervention. Upon application of power, the remote
`site Loran C 30, computer 28, terminal node controller
`32 initialize and remain quiescent until activated by base
`station 22. Base station 22, following power up and
`software loading, interacts with a human operator uti-
`lizing a keyboard 35 to identify the remote station links
`and relay stations 23 to be used by multiple unit tracking
`system 18 Base station 20 next attempts to establish
`contact with each remote station 22 and inform the
`operator of the remote station’s status. If the operator
`instructs system 18 to continue, base station 20 instructs
`each remote station 22 to transmit its position to the
`base station, which is overlaid on a range map 42, FIG.
`4, appearing on monitor 24.
`'
`Base station 20 also performs a link monitoring func-
`tion. Base station 20 maintains for each remote station
`22 a built-in software time period which is up to five
`times the remote station’s reporting period. If a remote
`station's message is not received within this time period
`the operator is informed of a time-out or inactivation of
`the remote station 22 and the base station 20 periodi-
`cally transmits a request for status to the remote station
`22 in an attempt to reactivate station 22.
`The reporting period in seconds for each remote
`station 22 is calculated as follows:
`
`Page 000011
`
`

`

`Report Period = (Total Number of Remote Stations + 1) +
`(Number of Relay Stations to the Remote Station x 2) +
`(User Table Column + 10)
`
`The inclusion of the factor User Table Column +10,
`where the User Table Column is the column the remote
`station appears in the base station user table illustrated
`by FIG. 8, provides a variable for calculating the re-
`porting period for each remote station: thus reducing
`the possibility that two remote stations will report dur-
`ing the same time interval.
`Base station 20 also sends an acknowledge message
`when requested by each remote stations 22. After ten
`position reports have been sent by a particular remote
`station 22, it begins to request an acknowledge from
`base station 20. If the remote station 22 does not receive
`an acknowledge message from base station 20 after
`sending twenty position messages, the remote station 22
`resets to a quiescent state. This procedure prevents the
`remote station 22 from continuing to transmit position
`messages indefinitely should the system data links fail to
`connect or not operate properly. Each remote station 22
`does not request an acknowledge after every position
`report as this would greatly increase the messages trans-
`mitted and thus increase the chances of data collision.
`The terminal node controllers 32 and 38 used in the
`preferred embodiment of the present invention operate
`at 1200 Baud, are manufactured by Kantronautics Inc.
`and are their version 2.85 Terminal Node Controller.
`Terminal node controllers 32 and 38, in turn, make use
`of the AX.25 Amateur Packet-Radio Link-Layer Proto-
`col to provide a means for the reliable transport of data
`between the base station 20.and each remote station 22.
`As is best illustrated by FIG. 3, each frame 50 or
`“packet” of data consists of a pair of eight bit flags 52
`and 54 respectively at the beginning and end of the
`frame which are generated by controllers 32 and 38 and
`which delimit the frame. For the multiple unit tracking
`system 18 flags 52 and 54 are set at 0, 1, 1, l, I, 1, 1,0.
`Frame 50 also includes an address field 56 provided
`by computers 28 and 40 which is used to identify both
`the source of the frame and the destination of the frame,
`as well as one or more intermediate stations which may
`be used to relay data from the source to the destination.
`In the AX.25 Amateur Packet-Radio Link-Layer Pro-
`tocol, the destination address subfield of the address
`field 56 consist of seven octets/eight bit bytes and is sent
`first to allow each receiving station 20 or '22 of the
`frame to check the destination address subfield to see if
`the frame 50 is being addressed to that particular receiv-
`ing station while the rest of the frame is being transmit-
`ted. The source address subfield is then sent in seven
`octets/eight bit bytes. The AX.25 Amateur Packet-
`Radio Link-Layer Protocol also provides for a repeater
`or relay address subfield consisting of seven octets-
`/eight bit bytes appended to the end of the address field.
`The link-layer AX.25 protocol further provides for up
`to eight repeaters or relay stations 23 by extending
`address field 56 to 512 binary bits. When there is more
`than one repeater or relay address in the address field
`the repeater address immediately following the source
`address subfield is considered the address of the first
`repeater or relay station 23 of a multiple relay station
`chain.
`The frame of FIG. 3 also includes an eight bit control
`field 58 which provides status and control information;
`an eight bit protocol identifier field (PID) 60 which for
`purposes of the present invention is an arbitrary eight
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`5
`
`5,243,530
`
`6
`bit digital word “F0” hexadecimal or l, 1, l, 1, 0, 0, 0,0
`binary selected to occupy the field; and an information
`field 62 which may consist of up to 256 octets/eight bit
`bytes and is used to convey latitude and longitude posi-
`tional data between the remote stations 22 and the base
`station 20 and any repeater or relay stations 23 which is
`used to relay positional information between the remote
`stations 22 and the base station 20.
`Referring to FIGS. 3 and 5, messages which are in-
`formation or status frames provided by multiple unit
`tracking system 18 conform to the AX.25 Version 2.0
`packet-radio link layer protocol except for eight bit
`control field/word 58. The address field 56 is defined by
`AX.25 Version 2.0 packet-radio link layer protocol.
`Certain bits in control field 58 have been redefined for
`‘ use by the multiple unit tracking system 18 of the pres-
`cut invention.
`The messages transmitted by each remote station 22,
`an intermediate station or base station 20 are either
`information frames or status frames as defined by bit
`zero of the control field 58. An information frame is
`identified by a zero in bit zero of control field 58, while
`a status frame is defined by a one in bit zero of control
`field 58. In accordance with the AX.25 packet-radio
`link layer protocol, bit four of a status word is used to
`request a reply or to indicate a response to a request.
`The PID field for the information frames is set to F0
`hexadecimal as is best illustrated by FIG. 5.
`The four information frames messages used by multi-
`ple unit tracking system 18 are Initialize Terminal Node
`Controller (TNC), Report Mode, Position Report and
`Terminate.
`The Initialize Terminal Node Controller message
`directs each remote station 22 to initialize its terminal
`node controller 32 with a Slottime value and a Persis-
`tence value which are contained in the message. The
`control field 58 is 10 hexadecimal which indicates an
`information frame and a request for response. The first
`word of the information field 62 is the message type of
`51»hexadecimal which is a predetermined number se-
`lected to indicate the Initialize Terminal Node Control-
`ler message, thereby informing the remote station of the
`message purpose. The second word is the Persistence
`value for the terminal node controller 32 at the remote
`station. The third word is the Slottime value for the
`terminal node controller 32 at the re-ote station.
`Terminal node controllers 32 and 38 use a mode of
`operation identified as KISS which is embedded in the
`firmware of the terminal node controller to allow com-
`munication respectively with computers 28 and 40. The
`KISS mode of operation allows terminal node control-
`lers 32 and 38 to transfer all received data respectively
`to computers 28 and 40 for processing by the comput-
`ers. In the KISS mode of operation terminal node con-
`trollers 32 and 38 each convert received HDLC type
`synchronous data frames into an asynchronous frame
`format which is then provided to the serial port of com—
`puter 28 or do; likewise asynchronous data frames from
`computers 28 and 40 are respectively transmitted by
`transceivers 34 and 36 once the data is converted from
`an asynchronous format to HDLC synchronous format
`by terminal node controllers 32 and 38. Terminal node
`controllers 32 and 38 also determine proper timing for
`channel access. It should be understood by those skilled
`in the communications art that there are a number of
`commercially available terminal node controllers which
`will convert between asynchronous data frames and a
`
`Page 000012
`
`

`

`7
`synchronous HDLC type frame format for either trans-
`mission or reception by a radio transceiver. It should
`also be understood that while terminal node controllers
`32 and 38 are capable of performing full AX.25 Ama-
`teur Packet-Radio Link-Layer Protocol functions, pro-
`tocol responsibility is off-loaded to computers 28 and
`40.
`In the KISS mode of operation, channel access is
`determined by two settings in the terminal node con-
`trollers 32 and 38 PERSISTENCE and SLOTTIME.
`In the preferred embodiment of the present invention
`PERSISTENCE is calculated by the following expres-
`sion:
`
`10
`
`PERSISTENCE =256/(number of sites + 2)
`
`(1)
`
`15
`
`Thus, for example, if there are eight sites or stations in
`multiple unit
`tracking system 18, PERSISTENCE
`would be set at 26. SLOTTIME is a predetermined time
`period set at fifty milliseconds.
`When the terminal node controller 32, for example, at
`each remote station 22 detects that the channel is clear
`and available, that is no carrier is detected, the terminal
`node controller starts an internal timer which is set at
`fifty milliseconds (SLOTTIME). When the timer ex-
`pires the terminal node controller generates a random
`number between 0 and 255. If the generated number is
`equal to or less than the PERSISTENCE value, the
`terminal node controller 32 keys up the transceiver 34
`and sends a data packet. With a setting of 26 the odds of
`this occurring after the first slottime are about 1 in 9
`with the actual odds being the PERSISTENCE value
`plus 1 divided by 256. If the terminal node controller 32
`generated random number is greater than PERSIS-
`TENCE value, the terminal node controller 32 restarts
`the timer and waits for the timer to expire again before
`generating a new random number. This procedure is
`repeated until terminal node controller 32 gains channel
`access and sends its packet of information.
`Data received, for example, from transceiver 36 is
`converted into asynchronous format by terminal node
`controller 38 and sent to computer 40. The data actually
`sent over the serial port of the computer is formatted
`with special control information, allowing the com-
`puter to determine the type of data being received from
`the Terminal node controller.
`All information flowing from the terminal node con-
`troller to the computer in the KISS mode of operation
`is data, special messages are not sent from the terminal
`node controller to the computer in the KISS mode of
`operation. The only data flowing from the terminal
`node controller to the computer is the data received
`through the radio transceiver link. Every “frame” of
`data sent from the terminal node controller will begin
`and end with a special FEND character which is the
`ASCII code 5C0 (hexadecimal) or 192 decimal. The
`second byte of the data will be the data type, and will
`always be a $00 hexadecimal which means that the
`following information is data. If the data actually con-
`tains the FEND character (5C0) it will be necessary to
`tell the computer that the SCO the computer receives is
`not the end of the frame, but simply is more data. This
`function is accomplished by replacing the SCO charac-
`ter with a special sequence consisting of a FESC (SDB
`hexadecimal) followed by a TFEND character SDC
`hexadecimal. One final special sequence which may be
`sent from the terminal node controller to the computer
`is a FESC (SDB hexadecimal) followed by TFESC
`
`2O
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`5,243,530
`
`8
`(SDD hexadecimal) which is translated into SDB by the
`computer program.
`When data flows from the computer to the terminal
`node controller, there are five possible commands in the
`KISS mode of operation that may be provided the ter-
`minal node controller from the computer which are
`setup parameters. These parameters are commands
`needed to set TXDELAY, PERSISTENCE, SLOT-
`TIME, FULLDUP, and finally, a command to exit the
`KISS Mode of operation. The only other data which
`the computer may send to the terminal node controller
`in the KISS mode of operation is data which is to be
`transmitted over the radio transceiver (HDLC) chan-
`nel. The data'provided by the computer to the terminal
`node controller must also begin and end with the same
`FEND $00 hexadecimal character used for data com-
`ing from the terminal node controller to the computer.
`All special character sequences must also be used to
`send the FEND, and FESC characters as data.
`Each of the commands is assigned a command type
`number in hexadecimal as follows: OO-Data is to be
`transmitted; Ol-TXDELAY,
`second byte contains
`TXIDELAY in ten millisecond increments; 02-PER-
`SISTENCE, second byte contains persistence value;
`03-SLO’ITIME, second byte contains slot
`interval;
`05-FULLDUP—if second byte is 0 sets fulldup mode,
`otherwise turns fulldup off; 255-KISS, causes exit from
`KISS Mode. For example, if it is desired to send a data
`packet in the KISS mode of operation, the computer
`sends the following bytes to the terminal node control-
`ler: 00, 00, 68, 65, 6C, 6C, 6F, C0. It is important to note
`that this data packet does not contain any addressing
`information, and therefore cannot be sent via the AX.25
`protocol. All of the addressing and formatting of the
`addresses is programmed in the computer and sent as a
`data packet to the terminal node controller.
`It should also be noted that only the PERSISTENCE
`and SLOTI‘IME commands are used in the preferred
`embodiment of the present invention.
`Referring again to FIGS. 3 and 5 the Report Mode
`message directs each remote station 22 to begin sending
`position reports to base station 20. The control field 58
`is 10 hexadecimal which indicates an information frame
`and a request for response. The first word of informa-
`tion field 62 is a message of 52 decimal which is a prede-
`termined number selected to indicate Report Mode.
`The second word of the information field 62 is a value
`which is ten times the report interval of the remote
`station in seconds, that is the time required for each
`remote station 22 to transmit data to base station 20. The
`second word of the information field 62, in turn, indi-
`cates to each remote station 22 how often the remote
`station reports its position to base station 20.
`The Position Report message informs base station 20
`of the Latitude and Longitude position of the remote
`station 22. The control field 62 is either 0 or 10 hexadec-
`imal depending upon whether a response is requested or
`not. The first word of the information field 62 is the
`message type of 49 decimal which is a predetermined
`number selected to indicate Position Report. The sec-
`ond, third, and fourth words or eight bit bytes, FIG.
`6(a) of the information field 62 contain the Longitude
`position information. The least significant bit (LSB)
`values of the second, third and forth words are respec-
`tively 0.0001, 0.0256, and 6.5536 degrees. Bit seven of
`word four is set at a logic “1” state to indicate a negative
`or west Longitude and a logic “0” to indicate an east
`Longitude. In a similar manner the fifth, sixth and sev-
`
`Page 000013
`
`

`

`5,243,530
`
`9
`en