CA1076210A - Message generator for a controlled radio transmitter and receiver - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
In a radio communication system having a command or base station and one or more controlled stations, the base station transmits outbound binary function messages to the controlled stations in order to make an inquiry or give a command to one or all of the controlled stations. The controlled station responds with an inbound binary message.
The outbound messages comprise a sequence of binary bits at a first rate and having a first synchronizing word of nine bits, a first address word having eight message bits and four parity bits and produced three times, a second synchronizing word that is the binary inversion of the first synchronizing word, a second address word having eight message bits and four parity bits and produced three times, a third synchronizing word that is the binary in-version of the first synchronizing word, and a command word having eight message bits and four parity bits and produced three times. If a controlled station receives and recognizes its address, it transmits a response in the form of an inbound message having a sequence of binary bits at a rate that is 11/2 times the rate of the outbound message, The inbound message comprises a sequence of a plurality of binary preamble bits of different values, the first synchronizing word, the first address word produced three times, the second synchronizing word, the second address word produced three times, the third synchronizing word, and a response word having eight message bits and four parity bits and produced three times.

Description

45~ 65 31 ~76 Our invention relates to function control apparatus~
and particularly to ~unction control apparatu~ for producing improved outbound and inbc~und mes~ages ~or controlling radio colmnunication system~.
Radio conununication sy~tems, particularly tho6e having a con~nand or base ~tation and one or more colltrolLed s~ations, ~uch as mol:~ile stations ,, are expected to provide ~any functions over and above the simple call and an~wex voice ~on~nunication) and are expected tQ e~tablish voice c:om_ munication quic:kly and reliably on one of ~everal ~r~q-tlncie~ or channels, An example of a provided function i~
where a base station needs to determine the status or s:ondi~ion of a particulax mobil~ station in the system.
An exampl~ o~ establi~hing voice co~ununication is where one of sev2ral radio ~requencies or channels i8 to be u~ed ~or ~oice communication between two stations in ~ given sy~tem, In order to provid0 these functions~ binary control signals are desira~le because of their speed and accuracy. However, when ~uch signal~ are used at radio ~requencie3, they are ~ubject ~c: .inter~erence" or noise, or fadi~g, ~ile there is ~unction control apparatu~
available for use with radio communication sy~t~ms" th~
spee~ are reliabillty o such apparatus are no~ a~ high a~ ~cme u~ers re~luire or pxe:~er.
Accoxdingly, a primary s~,bject of our invention is to provide new and improved ~unction control apparatu~
~or producing outbound and inbound binary mes~ages ~h~t permit xapid and xeliable ~ynchroniza~ion between radio stations.
Another ol3 ject o~ our invention is to provide new and improved functiol~ control apparatus that pro~u~e~
ou~bound and ir~bound birlary mes~age3 that ~re relativ~ly . . . . .

~)76i2~ 45~ -65 free from interference, noise, and fading.
Another ob ject of our invention is to provide r~ew and impxoved r'unction ~ontrol apparatu~ ~or producing outbound control me~sages and inbound re~ponse mes~ages: ~ :
both messages having a binary ormat that permits re~
latively quick ~nd reliable ~ynchronization betw~3en spaced radio ~3tations " and ~hat i~ relatively i~mnune from the effectæ cf interference, noi~e and fading when transmitted over xadio requen~::ies.
Another relatively ~pecific object of our invention is to provide appar~tus for producing outbound and in-!bound me3~ages having a new and improved binary format that i5 particularly u~ei~ul and de~;irable in controlling radio communication ~ystems.
Brie~ly" these and other object~ are achieved in accordan~:e with our invention by function control apparatu~
provided al: each staltion in a radio conumlnication system.
A base 2~tation u~ually serves a3 a canmand ~tation, and transmit~ outbound mes~age3 in binary ~it form. Each ~ .:
o~tbound me3sage compri~e~s a ~ir~t synchro~i~ing word of nine binary bit~, a ~irst addre~ woxd of eight mes~age bit~ and four parity bits and produc!ed three times, a second syncllxonizing word that i~ tlle binary inver~ion of the ~irst synchronizing word, a second addre~ word O:e eight message bits and four parity bi~s and pxoduced three ti~nss, a third ~ynchronizing word that is the binary in-ver-~ion of the first synchronizing word, and a comma~d word of eight mes~age bit~ and four binary bit~ and produced three ~ime~, When a con~rolled or mobile station receive~ ~uch an outbound me~sage and xecogni~e~ its ~ddress in the ~irst a~d second address word~, the mo~ile station tran~mit~ an iDbound messag~ in binary bit form at a xate _ 2 ~
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that i5 1~ times the binary bit rate o~ tha outbound message.
Each inbound message comprises a plurality of binary bits of different values ~orming a prea~ble, the same first synchronizing word, the same first address word produced three tLmes, the same second synchronizing word, the sama second address word produced thre~ times, th~ $ame third ~ynchxonizing word~ and a re~pon~e word of eight message bits ~nd four pari~y bits produced thr~c time~. This n~w and improved apparatus for producing such outbound and inbound me~ages provide~ more relaible and more easily synchroniz0d radio communication ~ystems, _2 a-45~MR-System ~3L(1976~

~rief Description of ~
The s~bject matter which we regard as our invention is particularly pointed out and distinctly claimed in the claims. The structure and operation of our invention, to-gether with further objects and advantages, may be better understood from the following description given in connection with the accompanying drawing, in which:
FIGURE 1 shows a diagr~m illustrating an example of a radio communication system utilizing function control apparatu~ in accordance with our invention;
FIGURE 2 shows a schematic block diagram of a i base 3tation function control apparatu~ in accordance with . :
our invention;
FIGU~E 3 shows a schematic block diagram of a mobile station function control apparatus in accordance with our invention;
, FI~URE 4 shows the outbound message format used ', in the function control apparatus in accordance with our inventiorl;
FIGURl~ ~ shows ~he inbound message ~ormat used in the function control apparatus in acaordance with our invention;
FIGUREB6a through 6d ~hcw wave forms illustrating I certain pulses and their manipula~ion in the op~xakion of 1 25 function con~rol apparatus in accordance with~our invention;
FIGURE 7 shows a more detailed sc~hematic bloclc diagram ~f the transmit modem of our function control :
; apparatu~ of FIGURE 2;
FIGURE 8 shows a more detailed ~che,matic block ~:
~iayram of the xeceive modem of our function control 4 5 -MR-Sys t~m ~76;~
apparatus o f FIGURE 2;
FIGUKE 9 shows a more detailed schematic block diagram of the transmit and receive modem of our function control apparatus of FIGURE 3;
EIGURE 10 shows a more detailed schematic block diagram of a diphase to binary converter in accordance with our inven~ion that can be used in the modem~ vf FIGURES 8 and 9; ~ :
~IGU~ES lla through llf show wave form~ for illus-tr~ting the opera~ion of the convertex of FIGU~E 10;
FIGURE 12 shows a more detaile~ schematic block ! diagram of the encoder of our function con~rol apparatus of FIGU~ES 2 and 3; and FIGURE 13 shows a more detailed schematic block i` 15 diagram of the decoder of our function control apparatus of FIGURES 2 and 3.
Description of Preferred E~bodim~nts Introduction In the following descriptiorl, we will first give ~, 20 a genexal description of a xadio communication system having func~ion control apparatus utilizin~ our inventionO Then, we will give a more de~ailed description of the f~ction control app~ratu~ and our inventions in that apparatus.
\ General De~cription ~ FI~URE 1 shows an example of a radio con~nunication sy~tem havingl function control apparatus utilizing our ¦ invention. In the example of FI~URE 1, it is de~irable that relatively e~ficient u~e be made of ~he radio ~pectrum when : : .
~ co~r~nunicatiny between a fixed con~nand or base station and~; `
one or more controlled or mobile sta~ions, or when colmnuni- ~
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.. ~ . . '.'' ~ ' . .-, .: ' '' : ' 45-MR-System ~76~0 cating between mobile stations. The base station may be connected by telephone lines ~o other user locations in order to permit those other locations to connect with the radio transmitter and receiver at the base station for communi-cation with the mobile ~tations. While only one base sta~ion, two mobile stations, and three user telephones are shown, our apparatus can be used with more or less such stations or users, Because the mobile station transmitters are, usually, of lower power th~n the base station transmitter, satellite rad~o receivers may be strategically located 80 as to pick up transmitted si~nals from the mobile station transmitters and ~upply those signals over telepho~e lines to the base - _ .
J station. In order that communication can be established and comE~leted ~nore effie~iently between a base station and one or moxe bile stations or between mobile stations, we have provided function control apparatus for u~e with the radio communication system. Our function control apparatus utilize~relatively high speed binary or digital signals to est~blish the desired communication I or to obtain inform-ation, or to indicate a statu~ condition. Whexe there are . a relatively large nu~er of radio fre~3uency channels avail--able for communication, we pre~er t}~a~ a single channel be .dedicated for the tran~mission c: f tl~i~i binary or digital information. However, it is to be understood ~hat the binary 03r digital infonnation can be transmi tted and received on the same radio frequencie~ used for the voice communication. Ihe base station is shown with a data transmitter and several voice trarlsmitter3. The receiver~i must be able to receive on the dedicated channel, if used, and the voice channels.
The binary~ or digital information transrnitted is used to ~:

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45 -MR-System ~7~2~ ~

provide a control function, such as th~ establishment of desired communication betweenthe base station and a mobile station, or between two mobile stations, or to obtain informa-tion.
S An ~xample of ~he establishment of communisation between the base station and a mobile station i5 where a person at a fixed location connected to the base station by a telephone line desire~ to communicate with a mobile station.
Tha~ pexson can dial an appropriate number to the ba~e station.
The ~a~e s~ation computer than processes (including recording if de~ired) the information represented by the dialed number, provides switching, and transmits appropriate binary or digital in~ormation over either the dedicated ch~nnel or the ~oice channel to the desired mobile station. If the mobile sta~ion receive~ the transmi~ion and is avail~ble, the mobile stat~on tran~mits a response u~ing binary or di~ital informa-ti~n, ~he ~a~e station then direct~ the mobile station to begin co~munication with the pexson at the ixed location ei~hex on the ~re~uency used to eRtabli~h the communication, or on gome ~re~uen~y direc~ed by the ~ase ~ta~ion. In a ~imilar manner, the base ~tation can receive a re~ponse from a mobile ~ation and establi~h co~nunication between that mobile sta~ion and some o~her ~kation, f~i~her mobile or a user through the ba~e ~tation.
An example of indicating ~tatu~ or other condition i8 where a pexson at the ba~;e ~tation wishes to know whet~er a mobile station is in operation, or ~s in some othe~ condition* Such applications are co~qnon in police for~ where a~cen~ral dispatcher ~ishe~ ~o know the s~a~u~
or ao~ditio~ of o~e or more of h1s mobile police sta~ions.

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45-MR System ~Lf~ff~fff~

In such a case, the dispatcher can send out an appropria~e inquiry identifying the particular mobile s~ation, and the mobile station can, totally unknown to the mobile police officer, send out a reply indicating that the mobile station is in service and awaiting messages, or that ~he mobile station is in 50me other condition, such as off duty or unavailable.
The two relatively specific e~amples given above ; will suggest many other us~s and applications. Gener~lly, the function control apparatus of our invention can be used in many different types of radio communication systems and ~or many different purposes in such systems~ such purposes including without Iimitation the estakflishment of communica-tion between two stations on a radio frequency, or the inquiry as to the ~ituation or condition in a distant station.
FIGUR~ 2 shows a block diagram of function control apparatus in accordance with our invention for use in a base station of a radio communication sys~em. ~unctions and voice signals from either the base s~ation or a telephone line are appIiea to a compfuter and audio fcffwitcher 10. If the base sta~ion utilizes a separate frequency or the funff_tion signals and a ~eparate frequency for the voice signals, the computer 10 switches the ~unction signals to an inter~ace and encoder circuit 11. The interface portion makes whatever conversion ~ -may be needed to provide the proper electrical relations I between the computer 10 and the encoder 11. The encoder 11 i converts the unction instructions received from the computer 10 to the desired format in accordance with our invention, and then supFflies this format to a mfodem 12 for transmission by the base station data transmittex. After communication is established, if voice communication is provided, ~hen ' 45-MR-System ~L~762~

the audio switcher 10 connects the voice input to the voice transmitter. Signals from the data receiver are applied to a modem 13 which converts the received signals to binary signals for application to an inter~ace and decoder circuit 14. The decoder circuit 14 with the interface circ~it converts the binary information into the proper l~nguage for the comput~r 10. me indic:ated functions are supplied, and after communi-cation is established, if voice communication is provided, the voice receiver is connected to ~he appropriate lines for a voice outpu~ signal. ~ freguency stable clock or oscillator circui~ 15 provides timin~ signals for the various components at the base station.
~IGURE 3 shows a block diagram o function control apparatus in accordance wi~h our invention for use in a mobile station of a xadio communication sy~tem. The diagram of FIGURE 3 is similar to that of ~IGURE 2. However, because a mobile station typically has only one transmitter and one reaeiver, the data information must be transmitted and received by the~same ~ransmitter and receiver used for voice communi-cation. Typically, a mobile station does not transmit when it is receiving, and does not receive when it is trans-mitting, 90 that a single modem 16 can be used. Received data sign~ls are applied to the modem 16, and then decoded by a decoder 14 which may be similar to the decoder I4 for the base station~ Signals from the decoder 14 are applied to a control 10 which generally pr3~ides the same function~
a~ the computer and audio switcher 10 in FIGU~ 2. The data signa1s so received are utilized at the moblle station in any way desired~ such as es~ablishlng a communication channe1, or re~uesting information from th~ mo~ile station.

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45-MR-System 76Z~

If the data signals are used to establish voice communication, a switch 17 connects voice signals from the receiver to an appropriate output such as a loudspeaker. In the other direc-tion, data signals are applied to the c:ontrol 10 and eracoded S by an encoder 11 which may be similar to the encoder 11 of FIGURE 2. These encoded signals are applied to the modem 16 and transmitted as data signal~. If information has been . requested from the mobile station, these data signals indi~ate : the status or desired information. If the function control is u~;ed to establish communication, the control 10 opsrates the switch 18 to ~onnect voice signals to the mobile station transmitter. ~nd as in the base of the base station, a frequency stable clock or oscillator circuit 15 provides the necessary timing signals for the mobile BtatiOn.
In order ~hat our function control apparatus can be used in variou~ applications such as e~tabli~hing communi-cation channels or requesting information, and in order that our function con~rol apparatus can be used in the xelatively noisy and sometimes unreliable radio frequen~y environment, we developed a function message control format to meet those requirement~ and 9till give reliable transmi~ion o~ data at a relatively rapid rate. FIGURE 4 shows the format of the function control messages used for transmission from a ba~e station to a mo~ile station. m e base s~ation may and pre~erably does transmit messages con~inuously and 1 sequentially, ~o that messa~e 2 is shown immediately I following message 1. Subsequsnt ou~bound messages would follow immediately, each outbound message having the same fonnat: but having unique or particular addross and aommand words depending on the station to which the message is . . .
_ 9 _ 45-MR-Sys tem ~6~7~

addressed and the function or inquiry desixed. If the function control apparatus is to provide colr~nunication between the stations in a radio co~nunication system, the ba~e station may send a message addreæsed ~o each mobile station in a sequence, the message inquiring whether the m~bile station desires to coImnurlicate. The sequenGe can, of course, be repeated continuously~ Or, the base station can send an addre~s to all mobile stations. When its addres3ed message is receiYed, a mobile station can re~pond to the inqui~y by sending a message (to ~e described) indicating that ~he mobile station does or doe~ not de~ire to communicate. If the function control apparatus i5 to obtain information, ~he ba~e station may send a mes~age addre~sed to a m~bile station, the message inquiring as to information about or status of the mobile ~tation. When its addres~ed message is receivedt the mobile station can respond to the in~uiry by sending a message (to be described) that answers the in~ui~y. The messages comprise binary or digital~` ~its in a train or sequenceO Message 1 i~ representa-tive of the foxmat of all outbound messages, and compxises, from left to right in time sequence, a synchronizing word (abbreviated SYN), a first address word (abbreviated ADD.l) which is produced a total of three times, a logic inverted synchronizing word (abbreviated SYN), a second address word (abbreviated ~DD~l') which is produced a total of three times, a second inverted synchronizing word (abbreviated SYN~, and a co~mand word (abbrevia~ed COM.l) which is produced a total of three times. ~he binary ox digital makeup of each address and co}~mland word comprises 8 message a~d 4 parity bits as indicated by' the arrows leading from the words. It will be ,1 30 seen that each me~sage has a total of 135 binary bits. The .

~10- ~ :
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, , , ., ~ .; : : . . - : : . , ' lC~76210 4 5 ~ MR-Sys tem SYN word comprises nine binary bits 011100100, which will be recognized as a seven ~it Barker code having a prefix O and a suffix O. The SYN word is, of course, the logic inversion of ~liS. The Barker cod~ also includes the reverse sequence - 5 which, with the added prefix O and suffix 0~ is 001001110.
This sequence may serve as the S~N word, and the SYN Word is the logic inversion of this. Hence, as used in this applica-tion, thP Barker code with prefix and ~3uffix ze:ros may be 011100100 or 001001110. And of course, persons skilled in the art will appreciate that logi~ ones and zeros may be interchanged, since they refer to two binary levels, and not to a rigid voltage polarity or magnitudeO Each of the address and command words compri~es eight message bi~s and four parity bit~ whose generator polynomial is X4 + X ~ 1.
The generator matrix i9:

0.1 0 0 0 0 0 0 0 1 1 1 G = O O 1 0 0 0 0 0 1 0 1 0 ~
O O 0 1 0 û O O 0 1 0 1 . ~.
O O O ~ 1 0 ~ û 1 0 1 1 - O O ~ O O O 1 0 0 1 1 0 The parity check matrix is:
I 1 0 1 0 1 1 0 0 1 0 0 O~ ' H = 1 1 0 1 0 1 1 0 0 1 0 ol ~S We have ~elected a bit rate of approximately 1111 bits per second, so that each message requires approximately 121. 5 milliseconds. While o~her message formats and o~her bit rates are possible, we prefer those de~cribed above and shown in FIGURE 4.
Since a typical application of our ~unction control ' ::

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45-MR-System ~6Z~

apparatus transmits outbound messages continuously, it is relatively easy for the function control in a mobile receiver to synchronize with the transmitted outbound mess~ge even though the message i5 not addressed to that receiver. On inbound messages, however, a mobile station generally does not transmit continuously, 50 that the base station has less opportunity to synchronize with an inbound message. Accord-ingly, as shown in FIGURE 5, we provide our inbound message format with a binary preamble ahead of the 135 binary bits 1~ that provide synchronization t addresses, and responses. In a preferred embodiment~ this preamble comprises 24 bits of alternate ones and zeros. However, other preambles may be used. In the inbound message, the 135 bits are substantially the same a~ the 135 bits in the outbound message format.
Thus, we prefer that the ADD.l and ADD.l' words (three times each) be identical to the outbound ADD.1 and ADD.l' words, and that the response word RESP.l (pxoduced three times~ be partly similar to the command word, and partly different to indicate the response to that command or question. However, this is a matter of choice and preference, depending upon the application and environment. Since the mobile ~tation transmits a longer message and requires some time to respond to an address and command, we provide a time interval between mobile inbound messages. Accordingly, the total of binary 159 bits in our inbound message format are transmitted approximately 1~ times faster than the outbound bits, or 1666 bits per second. Hence an inbound message requires g5.2 milliseconds, which leaves a time of 26.3 milliseconds between inbound messages. This time period of 26.3 milliseconds is adequate and desirable in order to compensate for any delays or responses of the mobile ~ .

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station~.
If a base station send~ a me~sag~ 1 ko a given mobile station, its outbound me~age format will comprise the synchronizing word 011100100, followed by an ~ddress wor~
for the mobile station tran~mit~ed a tot~l of three times.
Then the inverted synchronizing code ~ord 100011011 is ænt, foll~wed by a 3econd addre~s word for ~hg ~bile station tran~
mitted ~ t~t21 of three times. Thon, the inve~d ~ynchronl~ing word 100011011 is sent followed by the comm~nd word transmitted a total of three times. The given mobile ~tation respond~ to it~ addre~s words and command word by ~endi~g lt~ inbound message having a preamble (preferably having 24 bit~ of alter-nate zeros and ones) to enable the ba~e station to bit synchron-ize with the inbound message. Thi~ is necessary becau~e an ., 15 inbound message will not be repeated ~til a sub~equent out-bound message addressed for the given mobile i~ r~ceived.
Aft~r the preamble, the inbound me~sag~ h~s the synchronizing word 011100100 followed by an addre~s word transmitted a total of ~hree ~imes, the inverted ~ynchronlzing word, the 2Q second addres~ word transmitted a total of three times, the inverted synchronizing wordl and finally th~ response trans-mitted a total of three times. And a~ mentioned eaxlier, this inbound me3sage bit rate i9 1~ time~ fa~ter than the outbound message bit rate, namely 1666 bits per ~econd. ~hus, the inbound message only requires 95.2 milliseconds, leaving a 1 26. 3 milliseconds space for the next message from a mobile ! 9tation. Of course, while the given mobile station is trans-~i~ mitting its message 1, the base st~tion may be transmitting , it~ message 2 to another mobile station. However, the given mobile station generally will have its receiver disconnected .., ~, .
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from the antenna when its tran~mitte~ i~3 operating. Hence, message 2 should not be addre~sed to ~he ~e given mobile station, but should be for a different mobile station.
The triple transmission of each address word ADD.l, each address word ADD.l', and each command word COM.l ox response word RESP.l was provided becau~e of the nature of radio communicationc Such communication i~ subject to impulse noise and fading because of bridg~, build1ngs~ and other . objects. Hence, the triple tran~m~aion provides added assurance that the message will be received. When a message i~ received, and the receiving station i~in ~ynchronization with the message, corresponding bits of e~ch repeated word are stored, and the majori~y of ~imilar bit~ (that is 2 or more of the 3 corresponding bits) i5 ~elected by a digital or logic voting process. Thus, if the fir~t bit of the first and second words of ADD.l are a logic 1 but th~ first bit of the thixd word of ADD~ a logic 0, th~n our system selects the majority and decides that ~he fir~t bit of ADD.l is properly . . .
a logic 1. The remainder of the bit~ of each word are correspondingly selected, and after such ~election, the ~elected :.
bits are combined and utilized as the propcr logic sequence of hits. As for synchronization, we as~ume that if, in a given ~ :
me~sage, the synchronizing wor~ SYN ~nd the logic inverted synchronizing word ~Y~ are received in sequence, then the receiving mobile station is in message synchronization with :
the transmitting base station. The mobile station is considered I to remain in synchronization until fiva sequential synchronizing ; . words.are incor~ectly received. This is possible because the mobile s~ation is constantly receiving messages from th~ base station. At the base station, h~wever, a mobile only tran~mit3 _ 1 4--: '' :
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~5-M~-System 6;~

its inbound message one time in response to an outbound message, so that the base station must synchronize on that one inbound message if at all pdssible. Hence, we have provided the inbound message pre~nble which aids bit synchronization, and alerts the ba~e s~a~ion ~o an inbound message. The base station then att~mpts to ~esaage synchron-ize on the remainder of the inbound m~s~age, and considers a mes~ag~ properly received if it r~c~ s th~ first ~ynchron-izing word S~N properly.
From ~his general description of our function control apparatus, it will be seen that w~ prefer that only a base or cen~ral station transmit addr~e~ me~sages inquiring from or directing mobile station~ in ~ communication ~y~tem.
Each mobile station in the system r~pond~ only to me~sage~
addre~ed to that mobile station (or to an all-station m~ag~), such respon~e being any desired function such as qwitching to a communication ~requency or indicat~ng a ~tatus or con~ition.
~owever, we contemplate that other stations (base or mobile) in a communication~ system may have the ability to send the in~uiring or directing messages i~ de~ired.
Detailed Description - Computer and_Audio Switchin~; Control We have not shown a more detailed diagram of the computer and audio switcher 10 of FIGURE 2 ox the control 10 of FIGURE 3 since such devices are known and may take many di~ferent ~orms, depending upon the features and arrangements desired in the function control apparatus. It is for this ~eason that the computex and control have been given the same reference numexal 10. In the base station, the designated block lû has beell called a computer because it may have to hold more information and perform more functions than it would ;.
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in a mobile station. Both the computer and control 10 store addresses and commands or responses which have a predetermined code, and which are looked up and produced in response to a relatively simple signal. For example, if a user requests his base station to connect him with a designated mobile station, he may send a simple signal that means call mobile station 1. The computer 10 would look up the address of mobile station 1 and prepare the designated code for mobile station 1 and send it through the interface and encoder 11 and the modem 12 to the data transmitter. All mobile stations may receive the transmitted message, and those that do receive the message compare its address with the stored mobile address.
We prefer that each mobile station have a uni~ue address, so that only one mobile station acts on a particular message.
However, a unique address for all mobile stations may be provided to call all mobile stations simulkaneously. Mobile ; station 1 compares the transmitted address with its address, and finding them the same, transmits a reply. On receiving this reply, the base station computer 10 would compare the mobile station reply with the information transmitted and if the signals transmitted and received are proper, the computer 10 would operate its audio switcher and connect the user to mobile station 1. The computer 10 may also make a record of the call or operation. A similar operation may be pro~
vided by the control 10 in the mobile station. We have shown separate switches 17, 18 for the mobile station, but they perorm essentially the same function as the audio;~ ;
switcher in the computer 10. The audio switcher in the -~
computer 10 may be a more complicated device, since it may switch a number of incoming lines to a number of out- -: ' : , "'' , ~15~ Syst0~
31L~7~2~ `

going base station~transmitters and receivar~ such a~ shown in FIGURE 1.
q~e computer or control 10 is the elenænt where functions and command~ are initiated and manife~ted. ThiB
includes an in~uiry from the ba~e ~tation to the mo~ile station; comparisons of addr~es and commands; ~st~blish-ment of a co~snunication chann~l, on either he dzlta de~ignated channel Qr on ~nother channel, betwe~n the b~se ~t~tion and a mobile station or b~twe~n mobile statiorl~; and ~ny olther unctions which might b0 desired in a cu~tomer-sub~criber arrangem~nt. Hence the nu~ffler of function~ desired determine the capabilities which the computer or control 10 must providè.
It i~ for this rea~on that we have ~imply d~signated the input and outputs to the computer or control as a functlon in or a function out. Such function~ can be o~ ~lmost any type, depending upon the applicdtion or purpo8e o~ the r~dio co~-muniaation ~y~te~. Such techniqu~s ar~ well kn~wn to p~rson~
skilled in ~he.art, and nq~d not be described.
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i At this point, it is appropriate to de~cribe the binary bits or pulses which we pre~ar ~o be used in our function control apparatus. The pulse~ are shown in the wavefo.rms of FIGU~E 6 which are plotted along a common time axis. In FIGURE 6(a), we have shown what we consider binary pulses, that i~ pulses which alternate betw~en ~wo value~ designated a loglc Q and a logic 1. It is im~aterial whekher the upper value i~ considered a logic 1 and ~he lower values a logic 0, ~ or whether the upper value is con~idered a logic 0 and the ; lower value is considered a logic lo We have a~sumed that the upper value is a binary logic 1/ and the lower ~alua is a .
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2~L~

binary logic 0~ The pulses ~hown in FIGU~E 6 (a) r~present ~
typical train of binary pulses which would be produc:ed by the computer or control 10 and the encoder 11. Such pul~ea are not desirable when ~hey have to be tran~m:Ltted ~ver a radio or other pa~h~ whic~ cannot e~sily tran~mit dire~t current.
A~cordingly, the binary pulses of FIGU~E 6 (a) are converted to what w,o call diphase pulse~ a~ hawn in FIGURE 6 ~b) . Corr~s-ponding binary and diphase plllse~ are re3p~ctiv~1y abov~ and below each other. ~he diphase pul~es carry th~ informa-tion, but have a voltage transition at the end Qf each b~n~ry pul~e, and a voltage transition in th~ middle of ei ther a binary logic O or a binary logic 1. In FIGURE 6(b), w~ h~VQ
assumed that the middle trimRition i~ provid~d ~or ~ binary logic 1. Hence, it will be seen that the~ diphase pul~s ha~o }5 a tran~ition, either up or dawn, at th- ~nd of e~ch binary pulse, ~nd al~o have a transition, eith~r up or down, Elt approx~- :
mately the middle of each logic 1 binary pulse. These add~d transition~ provide more alternating current compon~nts, and are readily adaptable to being tran~mitted by radio paths or communication paths which are intended to carry altornating current signals. Conversion from binary to diphase pulses and from diphase to binary pulQes i8 a known technigue.
FIGVRES 6 (c) and 6 (d) will be discussed sub~equen~ly.
, With xespect to FIGURE 2, we have assumed that the base station is constantly transmitting outbound messages and is or may be constantly receiving inbound mes~ages.
Accordingly, the base station of FIGllRE ~ has a transmitting , modem 12 and a receiving modem 13. On the other hand, we have assumed ~hat the mobile station i~ either transmitting or receiving, so that the common modem 16 may be provided . .
- , . .

;' ' , ,' '.
~ ' , , :: ' ' ' ~ ' ' , ' ' -~7~

for the mobile station as shown in FIGURE 3. The following description covers the transmitting and receiving modems.
It should be pointed out that at a given station, the modems may be combined or may be separate, depending upon the circum-stances and needs at that station.
FIGURE 7 shows a block diagram of the transmit modem 12 used in the base station. This modem receives binary pulses, such as shown in FIGURE 6(a), from the encoder 11, and these pulses are applied to a binary to diphase converter 30. The converter 30 transforms the binary pulses to diphase pulses as shown in FIGURE 6(b). This transforma-tion is made by any of the known converter circuits, utilizing clock pulses at the 1111 bits per second or Cllll rate. As used in this application, clock pulses are indicated by the prefix C followed by a number which indicates the frequency.
Thusr C400,000 indicates clock pulses at the rate of 400,000 pulses per second. The C400,000 clock pulses are provided by the clock 15 in the base station, and these pulses are divided by a 360 divider 31 to produce the Cllll pulsesO
FIGURE 8 shows a block diagram of the receive modem 13 for the base station. FIGURE 8 includes more blocks or components, because this modem 13 provides synchronizing signals and adjusted clock signals. Its primary function however, is to convert diphase pulses, such as shown in FIGURE 6(b), to binary pulses, such as shown in FIGURE 6(a), for use in the base station decoder 14. The received diphase pulses are converted to binary pulses by a converter 35 which may be of a known type or one to be described hereinafter. The binary pulses are applied to a nine bit shift register 36 which is used in 41 5-~-Sy~tem ~7~Z~) voting on the pulses in the SYN word to prtrvide am I indication that the base station apparatus i9 Yynchroniz~3d with the in-bound message from the mobile station.
A primary requisite for thi~ ~ynchronlzation is that a stable frequency having the 9~le bit xate and pha~s as the incoming diphase pulses be supplied tc: the base station function control apparatus~ mi5 ~r~quency i~ ac:hie~l by means of the clock 15 which supplies th~ C400,000 pul~
These pulses are divided and converted to ~wo sets of pul~o~
preferably ha~ing a 180 degree phase relation, by m~an~ of a divide by six divider 37 which provides C66666~1 and C66666~2 pulses, where ~1 and ~2 may indicate 0 and 180 :
degree phases respectively. The~e pulses are respectively applied to a normally open gate 38 and a normally closed gate 39. The normally open gate 38 mAy be closed by a lead signal produced by a phase comparator 40, and the normally closed gate 39 may be opened by a: lag ~ignal produced by the phase comparator 40. The C66666~1 and C66666~2 pulses passed by the gates 38, 39 are combined sequentially in an ., 20 adder 41 and then divided by a divide by 10 divider 42 to ! produce a sequence of C6666 pulse~. These pulses are further ~ ;
divided by dividers 43, 4~ to supply adjusted clock pul~es C1666. These adjusted ~lock pulses are utilized in the decoder and other parts of the base station receive apparatus and are . also applied to one input of the phase comparator 40. The ....
received diphase pulses at the nominal 1666 bits per second rate are applied to a data xate converter 45 which may take , a nu~her of known forms. ~he converter 45 senses the data rate of the diphase pul~es of FIGURE 6(b), and omits the intermediate logic 1 transitions. The output of the .~ .

, :, ~ ;; : . ., -45-MR-Sys tem ~76~

converter 45 for the applied diphase pulses i~ shown in FIGURE 6(c). This output is applied ko the other input of the phase comparator 40 which compares the phase of the adjusted clock pulses c1666 with the pha~e ~f the receiYed --S data rate pulses. If the phase of the adjusted clock pulses C1666 lag~ the phase. of the data rate pulse~, as shown in ~he left portion of FIGVRE 6 (d), th¢n the pl~ase comparator 40 prcduces a lag signal that op~ns ~he gat~ 39 ~o add ~iome C66666~2 pulses to the pulse ~rain. ~h~ added pulses, when divided, xesult in the adjusted clock signal coinciding in phase with the data rate pul~es as indicated at the time Tl in FIGURES 6(b), 6(c), and 6(d). Conver~ely, if the pha~e of the adjusted clock pulses lead~ the phase of the data r~te p-llses, a~ shown at the right portion o~ FIGURE 6(d), the phase comparator 40 produces a lead signal which closes the normally open gate 38 to block some C66666~1 pul~es. This reduc~s the nu~ber of pulses in the train. Aft~r the~e pulse~ are divided, I

~' the phase of ~he adjusted clock pulses coincides.with ~he phase of the data ratè~ pulses as indicated at the time T2 in FIGURE5 `20 ~(b), 6(c), and 6~d)~ Thus, the reliable and ~table pul~es supplied by the clock 15 have their leading edge or phase .
adjusted so that they coinci~e with the incomin~ diphase pulses from the recei~rer. These adjusted clock pulses are utilized in various part~ of the '~ apparatus, particularly the decoder 14 and an apparatus signal generator 4 7.
As mentioned prèviously, the base station ~unction control apparatus must synchronize with an inbound message very quickly, as typically the inbound message may not be .
repeated unti~l a considerable number of intervening i~bound messages have been sent to the base ~tation by other mobiLe .

.: . . .. . . . .

45-MR System 76i;~

stations. It is for this reason that we have provided the 24 bit preamble to each inbound m~ssage as shown in FIGURE 5 to assist the base station in achieving bit synchroni~ation.
Generally, the base station will have some internal timing circuit S or device that alerts the base station to the time it should be receiving a preamble from a given mobile ~tation in response to the predetermined outbound message ~o th~ given mobile station.
At the proper time, the base station begins looking for this pre~mble from the given mobile station. When received, the preamble and me~sage bits of an inbound message are pas~ed through the nine bit shift register 36. Each irst bit output, each inverted fourth bit output, and each inverted seventh bit output of the shift regi~ter 36 are applied to a voter circui~ 48. Thus, the voter circuit 48 determines the binary value of each bit in each group of three equally ~paced bits, and produces a binary value representing the majority binary value of those bits. For example, if ~wo or more af the three bits in a group are a logic 1, the vot~r circuit 48 applies a logic 1 to a three bit shift r~gister 49. If two ar more o~
the three bit~ in a group are a logic zero, the voter circuit 48 applies ~ logic zero to the three bit shi~t register 49.
The following table and explanation will explain how the base statlon operates on the ~irst synchronizing word SYN to put the . base station function control apparatus in synchronization with the inbound message: ~

. _ ~ _ æinq f _ _ = = _ 1 _2_ 1 4 ~_ 5~ 7 ~ 9 ~ieY~sJ~ _ (1) O 1 1 1 O O 1 O O
_ _ _ ._ . . ~ _ ~ __ _ . ., .
l INV. INV. .
(2) 0 _ _ 0 ~ _ 0 _ _ ~ 0 _ _ __ .

(3)- 1 1 1 0 0 1 iO~ 0 ~ .
~4) 1 _ INV. _ NV. _ - 1-_ _ . , _~ _ ._ __ _ _ ~ ^ .
- ' tS) i 1 O O 1 O' O X ....... ~_ ' _ "': ' (6) 1 _ _ INV. _ INV. _ _ = _ :~

.
"' . ' ' .' '' . ''.', , : ',',, ' .'., ','''' ' , .' ' 45~MR-System ~76Z~

As the sequence o~ ~its ~rom the converter 35 pas~es through the shift register 36 at the C1666 pul~e rate, the fir~t, fourth, and seventh bits of the shift register output are con-sidered and voted on. In line 1 of Table 1, we have assumed that our ~ine bit synchronizing code 011100100 is completely entered in ~he shift register 36. In this oon~i~ion, the first bit of the synchronizing code is at the firsk hift regi~ter output, the fourth bit of the synchronizlng code i5 ~t ~he fourth shift register output, and the ~eventh bit of the synchronizing code is at the seven~h ~ift r~ister output.
After the fourth and seventh bit~ are inverted, line 2 shows :~ . the logic on which the voter 48 vote~ A3 indicated, all three bits are at a logic 0 so th~t the voter produce~ a logic 0. In line 3, another bit X has been received by the regiater so that the firs~ bit ~a 0) of the code is shifted out. At this time, the ~econd, fifth, and eighth bits of the code word are at the first, fourth, and seventh shift re~ister ~:~
; outputs, so that these outputs are at logic 1, 0 and 0 ' respectivsly. After inversion, the voter 48 sees th~ bits shcwn in line 4, all of which are a logic 1 so that the voter 48 produces a logic 1. In line 5, an~ther bit Y is received and the second bit ta 1) of the code is shifted out. At thi~
time, the third, sixth, and ninth bits o the code word are at : the shift register output, so that after inversion, as shown in line 6, the voter 48 sees three logic 1'~ so that the voter 48 produces a logic 1. The right hand column o Table 1 ~hows that the majority vote is 011, based on the best ~wo out of three bits for each v~te. ~n ~ummary, we provide ~: an IN SYNC ~ignal if a majority vo~ed ~qu~nce of 011 i~
received after the preambleO ThiS sequence is highly unique, . :

; -23-.

45-MR System ~'~7Z~2 ~ ~

so ~hat the chances of an error are reduced considerably by ourrine bit synchronizing word 011100100. Voting of the first, fourth, and seventh bit ou~puts iS a continuous opera-tion~ but ~e uni~ueness of the synchxonizing word and the majority voting ins~re synchroni~ing on almo~t all inbound messages. The voted bi~s are ~pplied to a ~hr~ZZe bit shift register 49. W~hen the three bit shift regiZ~ter 49 shows an 011 at its outputs, an 011 detector 50 produce~3 an a~ppropriateZ
- in-synchronization signal, designa~e~ IN SYNC in FIGURE ~.
This synchronizing signal indicates tha~ a Zconunand word will begin with the next bit received after the 3ynchronizing code.
The signal is applied to the apparatus signal generator 47 along with the adjusted clock so as to provide appropriate signals for use in the base station function control apparatus.
~ 15 -It will be appreciated that in the voting process just described, ; ::.the first register output may be inverted and the fourth and seventh register outputs left normal. In this case, an IN SYNC
signal would be produced if a majority voted sequence of 100 ' is received~ If the synchronizing word is 001001110, the !1 2Q majority voted sequence-would be 001 for an inver~ed seventh register output or would be 110 for inverted first and fourth register outputs. In the above description, we refer to one c~r more of the first, ~ourth, and seventh ~hi~t register 36 outputs being inverted. The net result of this is that the first, second, ~d third code bits appear inverted if the first shift register ou~put is inverted, and the fourth th.rough i ninth code bits appear inverteZd if the fourth and seventh shift I register outputs are inverted. And in this and otheZr discussions, :; the use of logic 1 and logic O simply me~ns &ny two binary levels, such as plus and zero voltages, zero and minu3 voltag~Zs, .

~ `
"~'`,' .~ . . . , . :

45-MR-System 1~7~
or plus and minus voltages. I I .
From the message in-synchronization.~ign~l, and with reference to the format of FIGURE 5, the g~n-r~tor 47 produco~
a function word signal at the beginning of ~ch ~f ~he ~dro~
words and the response word, a bit voter i~nal to indic~
to the decoder 14 that three corre~ponding bit~ of ~ rop~t~
word are present and should be voted on, a p~xity signal to indicate that the four parity bits in a 12 bit word h~vo b~
xeceived and corrections should be made, an~ a fir~t word signal to indicate the first of the ~hree r~peated ~ddre~ or respon~e words.
In the description of ~he reoeive modem 13 of FIGURE
~ 8, we have used terminology and designations which, we feel, .: aid in under~tanding the modem 13. Persons skilled in the art will appreciate that other logic or operating functions can be ~ubstituted. For example, the shift register 36 actually only needs to b able to store six bits, as the ~, se~enth bit ,can be voted on as it is received fxom the i conver~er 35. Similarly, other divide circuits could be used . in order to.'achieve the desired bi~ rate. And, of course, other bit ra~es may be utilized.~i j In the mobile station, the modem is generally similar except for the ~act that a mobile statlon is usually receiving outbound messages constan~ly one after another, whether they are designated for that given mobile station or not. These outbound messages provide more opportunities for ~he mobile station to synchroni`2e its function control appar~tus : with the base station pulses or bits and messages. Anothex . . di~ference is the ~act that the mobile station receives pulses. ::
at the outbound message rate of 1111 bits per second, 2nd .

' 45 MR-System ~(~7621~ ~:

transmits pulses back at the inbound message rate of 1666 bits per second, which is 1~ times as fast. Finally, the modem for ~e mobile station may combine the tran~mitting and receiving portions, since generally the mobile s~ation is either transmitting or receiving, but not both tr~n~mitting and receiving as in ~he case of a base station.
FIGURE 9 shows a block diagram of the modem 16 for ~ mobile station. Parts corresponding to those of FIGURE 8 have been given the same reference numerals. In the lower part of FIGURE 9, the clock signals are divided ~,~;
and pulses added or deleted by the gates 38, 39 depending upon the phase relation of the clock and diphase pulses : applied to the phase comparator 40. The diphase pulses are ~ also applied to the converter 35 and the nine bit shift : 15 register 36. The ~inary pulses so produced are applied to the mobile station decoder 14. The mobile station can synchronize its function control apparatus with outbound messages more reliably, as it may be constantly receiving outbound messages even though not addressed to it. A
synchxonizing and inverted synchronizing word Sensor 55 look~
at each nine bits in the register 36. If the proper synchron-izing word 011100100 is received ~ollowed by the proper inverted synchronizing word 100011011, the sensor 55 produces an in-synchronization (IN SYNC) s~ gnal for use in the function control apparatus and in the appar~tus signal generator 47.
The.apparatus produces this in-synchronization signal until an error counter 56 receives and counts a total of five con-secutive errors in synchronizing words or inverted synchron-izing words. We prefer five consecutive errors, because of the i 30 nature of the communication medium. It is quite possible .

.

~.. . . . . . . . .

~5~MR-System ~0~62~
that several synchronizing errors could be r~caiv~d without the function control apparatus getting out of qyn~hroni~atlon.
If a correct synchronizing word or a correct invert~d synchronizing word is received before five con~ecutive errOE~
are counted, the sensor 55 produces a recount ~ignal which sets the counter 56 back to zero so th~t the error count i~
star~ed over again. However, if the counter 56 does count five consecutive synchroni~ing errors, it provides a reset signal to the sensor 55, which causes the sensor 55 to produce an out-of-synchronization signal (or remove the ln~
synchronization signal) until a correct synchronizing word foll~wed by a correct inverted synchronizing word are received.
As ~entioned before, the synchronizing code may have the bit values OOlOQlllO and inverted bi~ values 110110001.
In the transmitting directionl the binary pul~e~
from the encoder 11 at the 1~ times or 1666 bits per seccnd rate are applied to the converter 30 which is the same as the converter 30 of FIGURE 7. This converter 30 receives adjusted clock pulses C3333, since ths mobile station clock is adju~ted in accordance with outbound messages. These pulse~ are derivsd from the divide by 10 divider 42 and applied to a divide by 4 divider 57 to produce C1666 clock pul~e~ for the converter 30.
Detai_ed Descrie~ D~pL51~h~se to Binary Converter While there are known diphase to binary converters which can be used for the conver~ers 35 in FIGU~E 8 and FIGU~E 9, we have provided a converter whidh,we believe, improves the message acceptance xate when a data format such as previously described i9 used. When binary or digital pulses are trans mitted over radio paths, resultant errors are primarily due :

-27~

4 5 -MR-Sy8 tom '76Z~

to multipath ~ading of the ra~io frequen~y ~ignal~ l~on, as ..
in our function control apparatus, majority voting of repe~t~d pulse~ is used to improve the accuracy of such recaived puls~
any arrangement which produces a negative or zero correlation of errors will enhance the accuracy of the voted bit~. Non~ally the occurren~e of multipath fades is predictable; ~herefore the error~3 follow a predic:table s7r correlat~d pattern. Our diphase to binary converter will produce either zerc~ or two binary errors ~or each diphase error. The probability that 8 double bina~y error will occur when a dipha~ exror occur~
: is 0. 5 . Hence, the total number of bit errors due to multi-path fading is the same as a diphase to binary con~erter with a one~to-one error corr~spondence, but the number of voted errors is less since the error~ are not correlatad. Th~
converter shown in FIGURE 10 produces a negative or zero correlation of errors and thus improves the voted bit prob-abilit~. In FIGURE 10 we have provided three D type flip-. flop~ FFl, FF2, FF3. These flip-flop~ are of the bistable type and are trigg~red or clocked at th~ir clock input C by .. . .
pulses which have a rate twice ~he bin~ry pulse r~te. The : :
diphase pul~es :Erom the receiver are applied to the D input of the irst ~lip-flop FFl. q~he Q ou~pu~: of the first :flip~
flop FFl is applied to the D input of the second flip-flop I FF2, and the Q output of the ~econd flip-flop FF2 i9 applied to ¦ 25 the D input of the third flip-flop FF3. The Q outputs of the first and third flip-flops FFl, FF3 are applied to the two inputs of an exclusive OR gate EOR, and the output of this gate EOR is inverted. This inverted output is applied to the shift register 36 in FIGURE 8 or FI~;URE: 9. As known in the .j .
~1 30art, an exclusive OR gate produce~ a logic 0 when it~ input~
.

--2 8-- .

4 5 MR-Sy~ t~m 3L~762~

have the same logic level, that is all input~ are 21t logic 0 or all inputs are at a logic 1. 1 An exclusive OR gate produce~
a logic 1 output when its inputs are at different logic level~.
The combination of the exclusive OR gate EOR and the inve:rt~r results in a logic 1 being produced when both inputs ,to the exclusive OR gate EOR are at the same logic level, and a logic 0 being produced when both input~ to the ~xclu~ive OR
gate EOR are at different logic level~.
It will be seen that the flip-flops FFl through 10 . FF3 provide a way to shift~e phase or tima delay diph~e pulses so that two signals identical to the diphase input can ~: be produced ~hat have a 360 (or one binary bit) phase relation.
The exclusive OR gate EOR provides a way to produce one binary logic output when the two inputs are diferent, and to produce the other binary logic output whe~ the two inputs are the same. Thi8 can ~e ~hown by the folIowing truth table ~1 FF3 _ ~, Q _Q OUTPUT _ . . O O _ 1 __ .

~ 0 The following explanation o~ our converter of FIGURE 10 is given with the waveforms shown in FIGURE 11. FIGURE 11( ~) shows the binary pulse rate, and this can be any rate, such a~ 1111 bits per second or 1666 bits per second, as mentioned eaxlier, The outputs of the three flip flops FFl, FF2, FF3 a~e shown in FIGURES ll(b), ll(c), and ll(d), and it will be seen ~h~at each flip-flop introduces a 180 time delay between its inpu~ and output pulses. Thus, the output of the .
, 45-MR-System 6Z~

flip-flop FF3 is 360 or one binary time period delayed Wlth respect to the output of the flip-flop FFl. FIGURE ll(e) shows the applied clock pulses, which are at twice the binary pulse rate. The inputs to the exclusi~e OR gate EOR are derived from the outputs of the fir~t and third flip-flop FFl, FF3. Just before the time Tl, it will be s~en that bo~h the~e outputs are at a logic 1, so that the exclu~ive OR gate EOP~
produces a logic 0 which is inverted by the inverter to a logic l. This logic 1 is a binary pulse and is shawn in FIGURE ll(f) prior to the time Tl. Immediately after the : time Tl, the flip-flop FFI is still producing a logic 1 but the flip-flop FF3 is pxoducing a logic 0, so that the exclu~ive OR gate produces a logic 1 which is inverted to a logic 0 as shown in FIGURE ll(f). Immediately after the time T2, the flip-fl4p FFl is producing a logic 0 but the flip-flop FF3 ' i5 producing a logic 1 so that the inverted output remain~ a : logic 0. Immediately after the time T3, the flip-flop FF1.
is producing a logic 1 and the flip-flop FF3 is producing a logi¢ 1, Hence, the binary pulse of FIGURE ll(f) switches to a logic l. Immediately after the time T4, the flip-flop FFl and the flip-flop FF3 are both producing a logic 0. The exclusive OR gate EOR produces a logic 0 which is inverted , to a logic l. Subsequent changes in ~he binary pulses are ; produce~d in a similar manner. Thus~ the diphase input, such as represented in the waveform of FIGURE ll(b~, is convexted to binary pulses as represented in ~he waveform of FIGURE ll~f).
~lthough the converter circui~ of FIGVRE 10 i~
relatively sim~le, we have found that when this converter i9 used in a voting arrangement ~uch as we utilize in our function control apparatus, the accuracy of transmitted ~inary or -30- ~

45~ 65 digital data is greatly increased, particularly where the transmission path is noisy or is subject to fading, such as in the land mobile radio frequency spectrumr Detailed Description - Encoder The encoder 11 for the base station is intended to receive words (address and command of eight bits each) from the computer 10 and generate an out-bound message format such as shown in FIGURE 4. Similarly, the encoder 11 for the mobile station receives words (address and response of eight bits each) from the control lQ and generates an inbound message format such as shown in FIGURE 5. Such encoders may take a number of known forms which, generally, provide the necessary pulse and timing sequences to produce those formats. FIGURE 12 shows a relatively simple diagram of such an encoder. Words from the computer or control 10 lS are applied to a suitable storage device 65 which retains each word for the needed length of time. ~ parity generator 66 is . connected to the storage device 65.and generates, on the basis of the stored eight bit word, the necessary sequence of four parity bits to be supplied after the eight word bits~ The storage device 65 also causes a function generator 67 to repeat the .
necessary sequence of eight word bits. Last, a preamble-synchronizing generator 68 generates the preamble bits for inbound messages, and generates the synchronizing and inverted synchron-izing bits for bokh inbound and outbound messages. The outputs from the parity.generator 66, the function generator 67, and the preamble-synchronizing generator 68 are combined in a sequencing circuit 69 in the proper sequence and under time control of either the base station clock w~ich is absolute or under control of the mobile station clock which is corrected in accordance wi~h outbound messages. Of course, the time ''~':~'' - 31 - ~:.

45-MR-Sy~tem ~62~
control provides the proper rate~ namely 1111 pul~e~ par second for outbound messages, and 1666 bits per second for inbound messages. The sequencing circuit 69 also provide~
the necessary repetition of the function words, namely addre~
1, address 1', and command or response 1. The pulse sequence so produced is applied to the modem for tran~mis~ion.

A diagram of a decoder 14 which c~n be us~d with the base station of FIGURE~ or the mobile ~t~tion of ~IGURE
9 is shown in FIG~RE 13. This decoder receives the bin~ry pulses from ~he modem shift register 36 at a function word gate 72 which permi~s only the ~unction words to pass from the shift register to a 36 bit shift register 73. At the base station, the gate 72 blocks the preamble bits. At both the base and mobile stations, the gate 72 blocks the synchronizing bits. Pulseq passed by ~he gate 72 are ~pplied to a 36 bit shift register 73. The shift regi~ter 73 need not actually hold 36 bits ~ but is being described as a 36 bit register in order to simplify the explanation. Cor-responding bits of ea ::h 12 bit word of a function address or conunand are voted on by a voting circuit 74. Thi~ voting is provided by deriving bits 1, 13 and 25 froM the shlft register 73, ~o that a~ the bits are shifted into and through the register 73, the corresponding bits (separated by 12 intermed.iate bits) are voted on. The voter 74 vo~es the majority, namely 2 out of 3, o~ the bits present at ~he 1, 13 and 25 outputs of the register 73, and supplies the majority voted bit to another 12 bi* shift register 75. Th~ register 75 store~ the voted 12 l:~its, in order tha~ a logic correction circuit 75 can consider the eight message bits in relation to the four ~, , -3~-~76'~

parity bits, and do whatever bit correction may be necessary.
After this correction is made, the four parity bits may be stripped off or eliminated, and the eight message bits can be provided either in parallel or in series to the computer or control 10. If the correct address is received by the computer or control 10, then the computer or control 10 provides the necessary function, whatever it may be as determined by the comn~and portion of the message. At the mobile station, this may include transmi-tting back the given mobile station's address along with the response to the command. However, other features or functions may be provided if desiredO
As mentioned, the shift register 73 actually need not store 36 bits, but may only store 24 bits, in which case the first and thirteenth bi~s are compared and voted on along with the incomin~ bit which would be the twenty-fifth bit. This would eliminate one set of 12 bit registers.
However, this is a matter that is obvious to a person of ordinary skill, so that various arrangements may be utilized.
Conclusion It will thus be seen that we have provided a new and improved function control apparatus which is parti-cularly useful and adaptable to radio communication systems.
Our apparatus provides all of the speed and versatility of modern binary digital techniques, but is also reliable and accurate, even th~ugh ik is used in the relatively noisy and harsh radio communication environment. While we have shown specific embodiments, persons skilled in the digital ~-and logic art will appreciate that modifications may be made to various combinations or all of our invention.
;i., . :~;

45~R-Sy8t@m n !~ i ~L~7 6Z~

Th~refore, it is to be under~tood that mod~flcation~ ~aay be made to the embodiment~ shown without de~?artin51 from the spirit of the invention or from the scope of the claims .
~- .

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Claims (3)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. For use in a radio communication system having a command station transmitter for transmitting outbound messages, each outbound message being formed by a sequence of binary bits at a first rate and comprising a first synchronizing word of nine bits, a first address word of eight message bits and four parity bits and produced at least three times, a second synchroniz-ing word of nine bits that are the binary inversion of said nine bits of said first synchronizing word, a second address word of eight message bits and four parity bits and produced at least three times, a third synchronizing word of nine bits that are the binary inversion of said nine bits of said first synchronizing word, and a command word of eight message bits and four parity bits and produced at least three times; a command station receiver; a controlled station transmitter;
and a controlled station receiver for receiving outbound messages from said command station transmitter, a message generator comprising:
(a) first means for connection to said controlled station receiver for deriving a received outbound message transmitted by said command station transmitter, and received by said controlled station receiver;
(b) second means connected to said first means for producing an inbound message only in response to a predetermined outbound message, said inbound message being formed by a sequence of binary bits at a second rate that is one and one half times said first rate and comprising a synchronizing preamble having a plurality of different binary bits, said first synchronizing word, said first address word produced at least three times, said second synchronizing word, said second address word produced at least three times, said third synchronizing word, and a response word of eight message bits and four parity bits and produced at least three times; and (c) third means connected to said second means for applying said produced inbound message to said controlled station transmitter.

2. The message generator of claim 1, wherein said first synchronizing word comprises nine bits having the binary values 011100100.

3. The message generator of claim 1, wherein said first synchronizing word comprises nine bits having the binary values 001001110.