Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
45~MR-68
10832:23
Our invention relates to function control apparatus,
and particularly to function control apparatus for producing
an improved synchronizing code for binary messages uqed in
conlrolling radio communication systems,
Radio communication systems, particularly those having
a command or a base station and one or more controlled
stations, such as mobile stations, are expected to provide
many functions over and above the simple call and answer
voice communication, and are also expected to establish
voice communication quickly and reliably on one of several
radio frequencies or channels, An example of a provided
function is where a base station needs to determine the
status or condition of a particularly mobile station in a
system, An example of establishing voice communication is '`
where one of several radio frequencies or channels is used
for voice communication between two stations in a system.
The functions to be provided are indicated by binary bits or
pulses whose sequence of values indicate the desired function.
In order that the stations may synchronize themselves with
the binary message bits being tramsmitted, reliable synch-
ronizing codes are needed for inclusion in the function
messages transmitted by the stations.
Accordingly, a primary object of our invention is
to provide new and improved function control apparatus for
producing outbound and inbound binary messages having a
synchxonizing code that permits rapid and reliable message
synchronization between radio stations transmitting such
binary messages,
Another object of our invention is to provide new and
improved function control apparatus that transmits messages
~ .
- . - ., , , .:.. , , ,. .. :
1~)83Z23
45-MR-68
Another object of our invention i9 to provide new
and improved function control apparatus that transmits
messages in binary form with a synchronizing code that is
relatively free from error, despite the effects of inter-
ference, noise, and fading of messages transmitted at the
radio frequencies.
Another object of our invention is to provide apparatus
for producing binary messages having a new and improved
message synchronizing code that improves the speed and
reliability of control apparatus for radio communication
systems
Briefly, these and other objects are achieved in
accordance with our invention by function control apparatus
provided at each station in a radio communication system.
The stations effect control and response by transmitting
binary messages including a plurality of synchronizing
words, address words, and command or response words. The
synchronizing words are spaced in a message, and include a
first synchronizing word having nine bit values 011100100
in sequence, a secGnd synchronizing word having nine bit
values 100011011 in sequence, and a third synchronizing
word having the bit values 100011011 in sequence. Or, the
three synchronizing words may have the values 001001110,
110110001, and 110110001 respectively. This improved code
produced by our apparatus enables radio receiving stations
to achieve message synchronization quickly and reliably.
~.
1083Z23 45-MR- 68
Brief DescriPtion of the Drawin~
The subject matter which we regard as our invention
is particularly pointed out and distinctly claimed in the
claims. m e structure and operation of our invention, to-
gether with furthet object~ and advantages, may be better
understood from the following description given in connection
with the accompanying drawing, in which:
FIGURE 1 shows a diagram illustrating an example
of a radio communication sy~tem utilizing function control
apparatus in accordance with our invention;
FIGURE 2 shows a schematic block diagram of a
base station function control apparatus in accordance with
our invention7
FIGURE 3 shows a schematic block diagram of a mobile
lS station function control apparatus in accordance with our
invention;
FIGURE 4 shows the outbound message format used
in the function control apparatus in accordance with our
in~ention;
FIGURE 5 shows the inbound message format used
in the function control apparatus in accordance with our
invention:
FIGU ~ 6a through 6d show wave forms illustrating
certain pulses and their manipulation in the operation of
function control apparatus in accordance with our invention;
FIGURE 7 shows a more detailed schematic block
diagram of the transmit modem of our function control
apparatus of FIGURE 2;
FIGURE 8 shows a more detailed schematic block
diagram of the receive modem of our function control
. ~ . .
'~ :
45-MII- 68
~83Z23
app,aratus of FIGURE 2;
FIGVRE 9 shows a more detailed schematic block
diagram of the transmit and receive modem of our function
control apparatus of FIGURE 3;
FIGURE 10 shows a more detailed schematic block
diagram of a diphase to binary converter in accordance with
our invention that can be used in the modems of FIGURES 8
and 9;
FIGURES lla through llf show wave forms for illus-
trating the operation of the converter of FIGURE 10;
FIGURE 12 shows a more detailed schematic block
diagram of the encoder of our function control apparatus of
FIGURES 2 and 3; and
FIGURE 13 shows a more detailed schematic block
diagram of the decoder of our function control apparatus of
FIGURES 2 and 3.
Description of Preferred Embodiments
Introduction
In the following description, we will first give
a general description of a radio communication system having
function control apparatus utilizing our invention. Then,
we will give a more detailed description of the function
control apparatus and our inventions in that appaxatus.
General Description
FIGURE 1 shows an example of a radio communication
system having function control apparatus utilizing our
invention. In the example of FIGURE 1, it is desirable that
relatively efficient use be made of the radio spectrum when
~ ' communicating between a fixed command or base station and
one or more controlled or mobile stations, or when communi-
45-MR- 68
1083ZZ3
cating between mobile stations. The base station may be
connected by telephone lines to other user locations in
order to permit those other locations to connect with the
radio transmitter and receiver at the base ~tation for communi-
cation with the mobile stations. While only one base station,
two mobile stations, and three user telephones are shown,
our apparatus can be used with more or less such stations or
users. ~ecause the mobile station transmitters are, usually,
of lower power than the base station transmitter, satellite
radio receivers may be strategically located so a~ to pick
up transmitted signals from the mobile station transmitters
and supply those signals over telephone lines to the base
station. In order that communication can be established
and completed more efficiently between a base station and
one or more mobile stations or between mobile stations, we
have provided function control apparatus for use with the
radio communication system. Our function control apparatus
utilizes relatively high speed binary or digital signals
to establish the desired communication, or to obtain inform-
ation, or to indicate a status condition. Where there are
a relatively large number of radio frequency channels avail-
able for communication, we prefer that a single channel be
dedicated for the transmission of this binary or digital
information. However, it is to be understood that the binary
or digital information can be transmitted and received on the
same radio frequencies used for the voice communication. The
base station is shown with a data transmitter and several
voice transmitters. The receivers must be able to receive
on the dedicated channel, if used, and the voice channels.
The binary or digital information transmitted is used to
45-MR- 68
1~83ZZ3
provide a control function, such as the establishment of
desired communication betweenthe base station and a mobile
station, or between two mobile stations, or to obtain informa- ;
tion.
An example of the establishment of communication
between the base station and a mobile station is where a
person at a fixed location connected to the base station by
a telephone line desires to communicate with a mobile station.
That person can dial an appropriate number to the base station.
m e base station computer than processes (including recording
if desired) the information represented by the dialed number,
provides switching, and transmits appropriate binary or
digital information over either the dedicated channel or the
voice channel to the desired mobile station. If the mobile
station receives the transmission and i9 available, the mobile
station transmits a response using binary or digital informa-
tion. The base station then directs the mobile station to
begin communication with the person at the fixed location
either on the frequency used to establish the communication,
or on some frequency directed by the base station. In a
similar manner, the base station can receive a response from
a mobile station and establish communication between that
mobile station and some other station, either mobile or a
user through the base station.
An example of indicating status or other condition
is where a person at the base station wishes to know
whether a mobile station is in operation, or is in some
other condition. Such applications are common in police
forces where a central dispatcher wishes to know the status
or condition of one or more of his moblle police stations.
4 5--MR- 68
~083ZZ3
In such a case, the dispatcher can send out an appropriate
inquiry identifying the particular mobile station, and the
mob:ile 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 the mobile station
is in some other condition, such as off duty or unavailable.
The two relatively specific examples given above
will suggest many other uses and applications. Generally,
the function control apparatus of our invention can be used
in many different types of radio communication ystems and
for many different purposes in such systems, such purposes
including without Iimitation the establishment of communica-
tion between two stations on a radio frequency, or the inquiry
as to the situation or condition in a distant station.
FIGURE 2 shows a block diagram of function control
apparatus in accordance with our invention for use in a base
station of a radio communication system. Functions and voice
signals from either the base station or a telephone line are
applied to a computer and audio switcher 10. If the base
station utilizes a separate frequency for the function signals
and a separate frequency for the voice signals, the computer
10 switches the function signals to an interface and encoder
circuit 11. The interface portion makes whatever conversion
may be needed to provide the proper electrical relations
between the computer 10 and the encoder 11. The encoder 11
converts the function instructions received from the computer
10 to the desired format in accordance with our invention,
and then supplies this format to a modem 12 for transmission
by the base station data transmitter. After communication
is established, if voice communication is provided, then
45-MR- 68
1083ZZ3
the audio switcher 10 connects the voice input to the voice
tran~3mitter. Signals from ~he data receiver are applied to
a modem 13 which converts the received signals to binary signals
for application to an interface and decoder circuit 14. The
decoder circuit 14 with the interface circuit converts the
binary information into the proper language for the computer
10. The indicated functions are supplied, and after communi-
ca~ion is established, if voice communication i8 provided, the
voice receiver is connected to the appropriate lines for a
voice output signal. A frequency stable clock or oscillator
circuit 15 provides timing signals for the various components
at the base station.
FIGURE 3 shows a block diagram of function control
apparatus in accordance with our invention for use in a
mobile station of a radio communication system. The diagram
of FIGURE 3 is similar to that of FIGURE 2. However, because
a mobile station typically has only one transmitter and one
receiver, the data information mu~t be transmitted and received
by the same transmitter and receiver used for voice communi-
cation. Typically, a mobile station does not transmit when
it is receiving, ar.d does not receive when it is trans-
mitting, so that a single modem 16 can be used. Received
data signals are applied to the modem 16, and then decoded
by a decoder 14 which may be similar to the decoder 14 for
the base station. Signals from the decoder 14 are applied
to a control 10 which generally provides the same functions
as the computer and audio switcher 10 in FIGURE 2. The
data signals so received are utilized at the mobile station
in any way desired, such as establishing a communication
channel, or requesting information from the mobile station.
--8--
. . - . . .
45-MR- 68
1083223
If ~le data signals are used to establish voice communication,
a swLtch 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 control 10 and encoded
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 signals. If information has been
requested from the mobile station, these data signals indicate
the status or desired information. If the function control
0 i9 used to establish communication, the control 10 operates
the switch 18 to connect voice signals to the mobile station
transmitter. And as in the base of the base station, a
frequency stable clock or oscillator circuit 15 provides the
necessary timing signals for the mobile station.
In order that our function control apparatus can
be used in various applications such as establishing communi-
cation channels or requesting information, and in order that
our function control apparatus can be used in the relatively
noisy and sometimes unreliable radlo frequency environment,
we developed a function message control format to meet those
requirements and still give reliable transmission of data
at a relatively rapid rate. FIGURE 4 shows the format of
the function control messages used for transmission from a
base station to a mobile station. The base station may
and preferably does transmit messages continuously and
sequentially, BO that message 2 is shown immediately
following message 1. Subsequent outbound messages would
follow immediately, each outbound message having the same
format but having unique or particular address and command
woras depending on the station to which the message is
45-MR-68
1083ZZ3
addressed and the function or inquiry desired. If the function
conl:rol apparatus is to provide communication between the
stations in a radio communication system, the base station
may send a message addressed to each mobile station in a
sequence, the message inquiring whether the mobile station
desires to communicate. The sequence can, of course, be
repeated continuously. Or, the base statlon can send an address
to all mobile stations. When its addressed message is received,
a mobile station can respond to the inquiry by sending a message
(to be described) indicating that the mobile station does
or does not desire to communicate. If the function control
apparatus i9 to obtain information, the base station may send
a message addressed to a mobile station, the message inquiring
as to information about or status of the mobile station. When
its addressed message is received, the mobile station can
respond to the inqUiTy by sending a message (to be described)
that answers the inquiry. The messages comprise binary or
digital bits in a train or sequence. Message 1 is representa-
tive of the format of all outbound messages, and comprises,
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 time~, a logic inverted
synchronizing word (abbreviated ~Y~n, a second address word
(abbreviated ADD.l') which is produced a total of three times,
a second inverted synchronizing word (abbreviated SYN), and
a command word (abbreviated COM.l) which is produced a total
of three times. The binary or digital makeup of each address
and command word comprises 8 message and 4 parity bits as
indicated by the arrows leading from the words. It will be
seen that each message has a total of 135 binary bits. The
--10--
45-MR~8
~083ZZ3
SYN word comprises nine binary bits 011100100, which will be
recognized as a seven bit Barker code having a prefix 0 and
a suffix 0. The SYN word is, of course, the logic inversion
of this. The Barker code also includes the reverse sequence
which, with the added prefix 0 and suffix 0, is 001001110.
m is sequence may serve as the SYN word, and the SYN Word is
the logic inversion of this. Hence, as used in this applica-
tion, the ~arker code with prefix and suffix zeros may be
011100100 or 001001110. And of course, persons skilled in
the art will appreciate that logic ones and zeros may be
interchanged, since they refer to two binary levels, and not
to a rigid voltage polarity or magnitude. Each of the
address and command words comprises eight message bits and
four parity bits whose generator polynomial is X4 + X + 1.
m e generator matrix is:
1 o o O O O O 0 1 1 1 0 :
O 10 0 0 0 0 0 0 1 11
G = 0 0 1 0 0 0 0 0 1 0 1 0
O O 0 1 0 0 0 0 0 1 0 1
O O O 0 1 0 0 0 1 0 1 1
O O O O 0 1 0 0 1 1 0 0
O O O O O O 1 0 0 1 10
o 0 0 0 0 0 0 1 0 0 1
The parity check matrix is:
10101100 1000
H - 1 1 0 1 0 1 1 0 0 1 0 0
1 1 1 0 1 0 1 1 0 0 1 0
0 1 0 1 1 0 0 1 0 0 0
~5 We have selected a bit rate of approximately 1111 bits per
second, so that each message requires approximately 121.5
milliseconds. While other message formats and other bit
rates are possible, we prefer those described above and
shown in FIGURE 4.
Since a typical application of our function control
45-MR- 68
1083223
apparatus transmits outbound messages continuously, it is
relaltively easy for the function control in a mobile receiver
to synchronize with the transmitted outbound message even
though the message is not addressed to that receiver. On
inbound messages, however, a mobile station generally does
not transmit continuously, so that the base station has less
opportunity to synchronize with an inbound message. Accord-
ingly, as shown in FIGURE 5, we provide our inbound mRssage
format with a binary preamble ahead of the 135 binary bits
that provide synchronization, 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 as 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.l and ADD.l' words,
and that the response word RESP.l (produced three times) be
partly similar to the command word, and partly different to
indicate the response to that comma~d or question. However,
this is a matter of choice and preference, depending upon the
application and environment. Since the mobile station transmits
a longer message and requires some time to respond to an address
and command, we provide a time interval between mobile inbound
message~. ~ccordingly, 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 95.2 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
~12-
45-MR- 68
~0832Z3
stations.
If a base station sends a message 1 to a given
mobile station, its outbound message format will comprise
the synchronizing word 011100100, followed by an address word
for the mobile station transmitted a total of three times.
men the inverted synchronizing code word 100011011 is ænt,
followed by a second address word for the mobile station trans-
mitted a total of three times. Then, the inverted synchronizing
word 100011011 is sent followed by the command word transmitted
a total of three times. The given mobile station responds to
its add'ress words and command word by sending its inbound
message having a preamble (preferably having 24 bits of alter-
nate zeros and ones) to enable the base station to bit synchron-
ize with the inbound message. This is necessary because an
inbound message will not be repeated until a subsequent out-
bound message addressed for the given mobile is'received.
After the preamble, the inbound message has the synchronizing
word 011100100 followed by an address word transmitted a
total of three times, the inverted synchronizing word, the
second'address word transmitted a total of three times, the
inverted synchronizing word, and finally the response trans-
mitted a total of three times. And as mentioned earlier, this
inbound message bit rate is 1~ times faster than the outbound
message bit rate, namely 1666 bits per second. Thus, the
inbound message only requires 95.2 milliseconds, leaving a
26.3 milliseconds space for the next message from a mobile
station. Of course, while the given mobile station is trans- -
mitting its message 1, the base station may be transmitting ' '
its message 2 to another mobile station. However, the given
mobile station generally will have its receiver disconnected
i . ,, ~ .
4 5-MF<- 68
~083ZZ3
from the antenna when its transmitter is operating. Hence,
message 2 should not be addressed to the same given mobile
station, but should be for a different mobile station.
The triple transmission of each address word ADD.l,
S each address word ADD.l', and each command word COM.l or
response word RESP.l was provided because of the nature of
radio communication. Such communication is subject to impulse
noise and fading because of bridges, buildings, and other
objects. Hence, the triple transmission provides added
assurance that the message will be received. When a message
is received, and the receiving station iain synchronization
with the message, corresponding bits of each repeated word are
stored, and the majority of similar bits (that is 2 or more
of the 3 corresponding bits) is selected by a digital or logic
voting process. Thus, if the first bit of the first and
second words of ADD.l are a logic 1 but the first bit of the
third word of ADD.l is a logic 0, then our system selects the
majority and decides that the first bit of ADD.l is properly
a logic 1. The remainder of the bits of each word arè
correspondingly selected, and after such selection, the selected
bits are combined and utilized as the proper logic sequence of
bits. As for synchronization, we assume that if, in a given
message, the synchronizing word SYN and 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
to remain in synchronization until five sequential synchronizing
words are incorrectly received. This is possible because the
mobile station is constantly receiving messages from the base
station. At the base station, however, a mobile only transmits
-14-
45-MR- 68
1083ZZ3
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 pos~ible. Hence, we have
provided the inbound message preamble which aids bit
synchronization, and alerts the base sta~ion to an inbound
message. The base stati~n then ~t~empts to messags synchron-
ize on the remainder of the inbound message, and considers a
message properly recelved if it receives the first synchron-
izing word SYN properly.
From this general description of our function
control apparatus, it will be seen that we prefer that only a
- base or central station transmit addressed messages inquiring
from or directing mobile stations in a communication system.
Each mobile station in the system responds only to messages
addressed to that mobile station ~or to an all-station message),
such response being any desired function such as switching to
a communication frequency or indicating a status or condition~
However, we contemplate that other stations (base or mobile)
in a communications system may have the ability to send the
inquiring or directing messages if desired.
Detailed Descri~tion - Computer and Audio Switching; Control
We ha~e not shown a more detailed diagram of the
computer and audio switcher 10 of FIGURE 2 or the control
10 of FIGURE 3 since such devices are known and may take many
different forms, depending upon the features and arrangements
desired in the function control apparatus. It-is for this
reason that the computer and control have been given the same
reference numeral 10. In the base station, the designated
block 10 has been called a computer because it may have to
hold more information and perform more functions than it would
~ .
-15-
45-MR- 68
1083ZZ3
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 unique address, so
that only one mobile station acts on a particular message.
However, a unlque address for all mobile stations may be
provided to call all mobile stations simultaneously. 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 perform es~entially~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-
-16-
45-MR-- 68
1083Z23
going base station transmitters and receivers such as shown
in Fi[GUR~ 1.
The computer or control 10 is the element where
functions and commands are initiated and manifested. This
includes an inquiry from the base station to the mobile
station; comparisons of addresses and commands; establi~h-
ment of a communication channel, on either the data designated
channel or on another channel, between the base station and
a mobile station or between mobile stations; and any other
functions which might be desired in a customer-subscriber
arrangement. Hence the number of functions desired determine
the capabilities which the computer or control 10 must provide.
It is for this reason that we have simply designated the input
and outputs to the computer or control as a function in or a
function out. Such functions can be of almost any type,
depending upon the application or purpose of the radio com-
munication system. Such techniques are well known to persons
skilled in the art, and need not be described.
Detailed Description - Modem
At this point, it is appropriate to describe the
binary bits or pulses which we prefer to be used in our function
control apparatus. The pulses are shown in the waveforms of
FIGURE 6 which are plotted along a common time axis. In
FIGURE 6(a), we have shown what we consider binary pulses,
that is pulses which alternate between two values designated
, a logic 0 and a logic 1. It is immaterial whether the upper
- value is considered a logic 1 and the lower values a logic 0,
or whether the upper value is considared a logic 0 and the
lower value is considered a logic 1. We have as~umed that
~he upper value is a binary logic 1, and tha lower value is a
--17-- :
, :
4 5-MR- 68
1083223
binary logic 0. The pulses shown in FIGURE 6(a)represent a
typical train of binary pulses which would be produced by the
computer or control 10 and the encoder 11. Such pulses are ~ -
not desirable when they have to be transmitted over a radio or
other paths which cannot easily transmit direct current.
Accordingly, the binary pulses of FIGURE 6(a) are converted to ~ ~ -what we call diphase pulses as shown in FIGURE 6(b). Corres-
ponding binary and diphase pulses are respectively above and
below each other. The diphase pulses carry the same informa-
tion, but have a voltage transition at the end of each binary
pulse, and a voltage transition in the middle of either a
binary logic 0 or a binary logic 1. In FIGURE 6(b), we have
assumed that the middle transition is provided for a binary
logic 1. Hence, it will be seen that the diphase pulses have
a transition, either up or down, at the end of each binary
pulse, and also have a transition, either up or down, at approxi-
mately the middle of each logic 1 binary pulse. These added
transitions provide more alternating current components, and
are readily adaptable to being transmitted by radio paths or
communication paths which are intended to carry alternating
current signals. Conversion from binary to diphase pulses
and from diphase to binary pulses is a known technique.
FIGURES 6(c) and 6(d) will be discussed subsequently.
With respect to FIGURE 2, we have assumed that
the base station is constantly transmitting outbound messages
and is or may be constantly receiving inbound messages. -
Accordingly, the base station of FIGURE 2 has a transmitting
modem 12 and a receiving modem 13. On the other hand, we
have assumed that the mobile station is either transmitting
or receiving, so that the common modem 16 may be provided
-18-
1083223 45-MR- 68
for the mobile station as shown in FIGURE 3. The following
descrip~ion 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 diagra~ of the transmit
modem 12 used in the base station. m is 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 tran~forma-
tion is made by any of the known converter circuits, utili~ing
clock pulseæ 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.
Thus, 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 pulses.
FIGURE 8 shows a block diagram of the receive
modem 13 for the base station. FIGURE 8 includes more
bIocks 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
pul~es 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
.
--19--
' ' ~
1 0 8 32Z3 45-MR-68
vot:ing on the pulses in the SYN word to provide an indication
that the base station apparatus i9 synchronized with the in-
bound message from the mobile station.
A primary requisite for this synchronization i8 that
a stable frequency having the same bit rate and phase as
the incoming diphase pulses be supplied to the base station
function control apparatus This frequency is achieved by
means of the clock 15 which supplies the C400~000 pulses.
These pulses are divided and converted to two sets of pulses
preferably having a 180 degree phase relation, by means of
a divide by six divider 37 which provides C66666~1 and
c66666~ pulses, where ~1 and ~2 may indicate 0 and 180
degree phases respectively. These 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 signal produced by the
phase comparator 40. The C66666~1 and c66666~2 pulses
passed by the gates 38, 39 are combined sequentially in an
adder 41 and then divided by a divide by 10 divider 42 to
produce a sequence of c6666 pulses. These pulses are further
divided by dividers 43, 44 to supply adjusted alock pulses
Cl666 These adjusted clock 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 rate converter 45 which
may take a number of known forms. The converter 45 senses
the data rate of the diphase pulses of FIGURE 6 ~b), and omit
the intermediate logic 1 transistions. The output of the
_ 20 -
45-MR-- 68
1083223
converter 45 for the applied diphase pulses is shown in
FIGURE 6(c). This output is applied to the other input of
the p~lase comparator 40 which compares the phase of the
adjusted clock pulses C1666 with the phase of the received
data rate pulses. If the phase of the adjusted clock pulses
C1666 lags the phase of the data xate pulses, as shown in
the left portion of FIGURE 6(d), then the phase comparator
40 produces a lag signal that opens the gate 39 to add some
C66666~2 pulses to the pulse train. These added pulses, when
divided, result in the adjusted clock signal coinciding in
phase with the data rate pulses as indicated at the time Tl
in FIGURES 6(b), 6(c), and 6(d). Conversely, if the phase of
the adjusted clock pulses leads the phase of the data rate
pulses, as shown at the right portion of FIGURE 6(d), the phase
comparator 40 produces a lead signal which closes the normally
open gate 38 to block some C66666~1 pulses. m is reduces the
number of pulses in the train. After these pulses are divided,
the phase of the adjusted clock pulses coincides with the phase
of the data rate pulses as indicated at the time T2 in FIGURES
6(b), 6(c), and 6(d). Thus, the reliable and stable pul~es
supplied by the clock 15 have their leading edge or phase
adjusted so that they coincide with the inc~ming diphase pulses
from the receiver. These adjusted clock pulseR are utilized
in various parts of the apparatus, particularly the decoder 14
and an apparatus signal generator 47.
As mentioned previously, the base station function
control apparatus must synchronize with an inbound message
very quickly, as typically the inbound message may not be
repeated u~til a considerable number of intervening inbound
messages have been sent to the base station by other mobile
-21-
'.
'~' .
45-MR- 68
~o83ZZ3
stations. It is for this reason that we have provided the 24
bit preamble to each inbound message as shown in FIG~RE 5 to
assist the base station in achieving bit synchronization.
Generally, the base station will have some internal timing circuit
or device that alerts the base station to the time it should be
receiving a preamble from a given mobile station in response
to the predetermined outbound message to the given mobile station.
At the proper time, the base station begins looking for this
pream~le from the given mobile station. When received, the
preamble and message bits of an inbound message are passed
through the nine bit shift register 36. Each first bit output,
each inverted fourth bit output, and each inverted seventh
bit output of the shift register 36 are applied to a voter
circuit 48. Thus, the voter circuit 48 determines the binary
value of each bit in each group of three equally spaced bits,
and produces a binary value representing the majority binary
value of those bits. For example, if two or more of the three
bits in a group are a logic 1, the voter circuit 48 applies a
logic 1 to a three bit shift register 49. If two or more of
the three bits in a group are a logic zero, the voter circuit
4~ applies a logic zero to the three bit shift register 49.
The following table and explanation will explain how the base
station operates on the first synchronizing word SYN to put the
base station function control apparatus in synchronization
with the inbound message: TABLE 1
,,
.j . _ S~l1C ~: ~7.i ng r de Ri ~
~J(1 2 __ ~ ~ fi 7 a q Ma~or;tv vote
'.,i, (1) O 1 L~ 1 o o 1 o o
INV. INV.
(23) I 1 1 1 X 0
(4) _ _ = INV. _ - INV. _ = 1
(6) 1 1 0 INV 1 0 INV. X 1 _ ¦
-22- .
45-MR- 68
1083223
As the sequence of bits from the converter 35 passes through
the shift register 36 at the C1666 pulse rate, the first,
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 nine bi~ synchronizing code 011100100 is completely
entered in the shit register 36. In this condition, the first
bit of the synchronizing code is at the first shift register
output, the fourth bit of the synchronizing code is at the
fourth shift register output, and the seventh bit of the
synchronizing code is at the seventh shift register output.
After the fourth and seventh bits are inverted, line 2 shows
the logic on which the voter 48 votes. As indicated, all
three bits are at a logic 0 so that the voter produces a logic
0. In line 3, another bit X has been received by the register
so that the first bit (a 0) of the code is shifted out. At
this time, the second, fifth, and eighth bits of the code
word are at the first, fourth, and seventh shift register
outputs, so that these outputs are at logic 1, 0 and 0
respectively. After inversion, the voter 48 sees the bits
shown in line 4, all of which are a logic 1 so that the voter
48 produces a logic 1. In line 5, another bit Y is received
and the second bit (a 1) of the code is shifted out. At this
time, the third, sixth, and ninth bits of the code word are at
the shift register output, so that after inversion, as shown
in line 6, the voter 48 sees three logic l's so that the
voter 48 produces a logic 1. The right hand column of
Table 1 shows that the majority vote is 011, based on the best
two out of three bits for each vote. In summary, we provide
an IN SYNC signal if a majority voted sequence of 011 is
received after the preamble. This sequence is highly unique,
-23-
. .
.
45-MR- 68
iO83~Z3
so that the chances of an error are reduced considerably by
our ~ne bit synchronizing word 011100100. Voting of the
first, fourth, and seventh bit outputs is a continuous opera-
tion~ but ~e uniqueness of the synchronizing word and the
majority voting insure synchronizing on almost all inbound
messages. The voted bits are applied to a three bit shift
register 49. When the three bit shift register 49 shows an
011 at its outputs, an 011 detector 50 produces an appropriate
in-synchronization signal, designated IN SYNC in FIGURE 8.
o mis synchronizing signal indicates that a command word will
begin ~ith the next bit received after the synchronizing 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.
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
majority voted sequence would be 001 for an inverted seventh
register output or would be 110 for inverted first and fourth
register outputs. In the above description, we refer to one
or more of the first, fourth, and seventh shift register 36
outputs being inverted. The net result of this is that the
first, second, and third code bits appear inverted if the
- first shift register output is inverted, and the fourth through
ninth code bits appear inverted if the fourth and seventh shift
register outputs are inverted. And in this and other discussions,
the use of logic 1 and logic 0 simply means any two binary
levels, such as plus and zero voltages, zero and minus voltages,
-24-
4 5--MR- 68
~083Z;z3
or plus and minus voltages.
From the message in-synchronization signal, and with
refere!nce to the format of FIGURE 5, the generator 47 produces
a function word signal at the beginning of each of the address
words and the response word, a bit voter signal to indicate
to the decoder 14 that three corresponding bits of a repeated
word are present and should be voted on, a parity signal to
indicate that the four parity bits in a 12 bit word have been
received and corrections should be made, and a first word
signal to indicate the firs~ of the three repeated address or
response words.
In the description of the receive modem 13 of FIGURE
8, we have used terminology and designations which, we feel,
aid in understanding the modem 13. Persons skilled in the
art will appreciate that other logic or operating functions
can be substituted. For example, the shift regi6ter 36
actually only needs to be able to store six bits, as the
seventh bit can be voted on as it is received from the
converter 35. Similarly, other divide circuits could be used
in order to achieve the desired bit rate. And, of course,
other bit rates may be utilized.
In the mobile station, the modem is generally
similar except for the fact that a mobile station is usually
receiving outbound messages constantly one after another,
whether they are designated for that given mobile station or
not. These outbound messages provide more opportunities for
the mobile station to synchronize its function control apparatus
with the base station pulses or bits and messages. Another
difference is the fact that the mobile station receives pulses
at the outbound message rate of 1111 bits per second, and
-~; ~,. .
.
`
~o83223 45-MR-68
transmits pulses back at the inbound message rate of 1666
bits per second, which is 1~ times as fast. Finally, the
modem for the mobile station may combine the transmitting
and receiving portions, since generally the mobile station
is either transmitting or receiving, but not both transmitting
and receiving as in the case of a base station.
FIGURE 9 shows a block diagram of the modem 16
for a 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
register 36. The binary 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
synchronizing and inverted synchronizing word sensor 55 looks
at each nine bits in the register 36. If the proper synchron-
izing word 011100100 is received followed by the proper inverted
synchronizing word 100011011, the sen~or 55 produces an in-
synchronization (IN SYNC) signal for use in the function
control apparatus and in the apparatus 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
nature of the communication medium. It is quite possible
-26-
45-MR- 68
iO83223
that several synchronizing errors could be received without
the f~mction control apparatus getting out of synchronization.
If a correct synchronizing word or a correct inverted
synchronizing word is received before five consecutive errors
are counted, the sensor 55 produces a recount signal which
sets the counter 56 back to zero so that the error count is
started over again. However, if the counter 56 does count
five consecutive ~ynchronizing errors, it provides a reset
signal to the sensor 5S, which causes the sensor 55 to
produce an out-of-synchronization signal (or remove the in-
synchronization signal) until a correct synchronizing word
followed by a correct inverted synchronizing word are received.
As mentioned before, the synchronizing code may have the bit
values OOlOOlllO and inverted bit values llOllOOOl.
In the transmitting direction, the binary pulses
from the encoder ll at the l~ t1mes or 1666 bits per second
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 the mobile station clock is adjusted
in accordance with outbound messages. These pulses are
derived from the divide by lO divider 42 and applied to a
divide by 4 divider 57 to produce C1666 clock pulses for the
converter 30.
Detailed Descri~tion - Modem Diphase to Binary Converter
While there are known diphase to binary converters
which can be used for the converters 35 in FIGURE 8 and
FIGURE 9, we have provided a converter which,we believe, improves
the message acceptance rate when a data format such as previously
described is used. When binary or digital pulses a~e trans-
mitted over radio paths, resultant errors are primarily due
-27-
~ `
1083~Z3 45-MR- 68
to multipath ~ading of the radio frequency signal. When, as
in our function control apparatus, majority voting of repeated
pulses is used to improve the accuracy of such received pulses,
any arrangement which produces a negative or zero correlation
of errors will enhance the accuracy of the voted bits. ~ormally
the occurrence of multipath fades is predictable; therefore
the errors foll~w a predictable or correlated pattern. Our
diphase to binary converter will produce either zero or two
binary errors for each diphase error. The probability that a
double binary error will occur when a diphase error oCcur-C
is 0.5. Hence, the total number of bit errors due to multi-
path fading is the same as a diphase to binary converter with
a one-to-one error correspondence, but the number of voted
errors is less since the errors are not correlated. The
converter shown in FIGURE 10 produces a negative or zero
correlation of errors and thus improves the voted bit prob-
ability. In FIGURE 10 we have provided three D type flip-
flops FFl, FF2, FF3. These flip-flops are of the bistable
type and are triggered or clocked at their clock input C by
pulses which have a rate twice the binary pulse rate. m e
diphase pulses from the receiver are applied to the D input
of the first flip-flop FFl. The Q output of the first flip-
flop FFl is applied to the D input of the second flip-flop
FF2, and the Q output of the second flip-flop FF2 is applied to
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 FIGURE 9. As known in the
art, an exclusive OR gate produces a logic 0 when its inputs
-28-
45-MR- 68
10832Z3
have the same logic level, that is all inputs are at logic 0
or all inputs are at a logic 1. An exclusive OR gate produces
a logic 1 output when its inputs are at different logic levels.
The combination of the exclusive OR gate EOR and the inverter
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 inputs to the exclusive OR
gate EOR are at different logic levels.
It will be seen that the flip-flops FFl through
FF3 provide a way to shift ~e phase or time delay diphase
pulses so that two signals identical to the diphase input can
be produced that have a 360 (or one binary bit) phase relation.
m e exclusive OR gate EOR provides a way to produce one binary -
logic output when the two inputs are different, and to produce
the other binary logic output when the two inputs are the
same. This can be shown by the following truth table:
FFl FF3 I
Q Q OUTPUT
O O .~ .,
_ 01 0
O --1 '-O .'
The following explanation of our converter of FIGURE 10 is
given with the waveforms shown in FIGURE 11. FIGURE ll(a)
shows the binary pulse rate, and this can be any rate, such
as 1111 bits per second or 1666 bits per second, as mentioned
earlier. The outputs of the three flip-flops FFl, FF2, FF3
are shown Ln FIGURES ll(b), ll(c), and ll(d), and it will be
seen that each flip-flop introduces a 180 time delay
between its input and output pulses. Thus, the output of the
-29-
~083Z23 45-MR- ~8
flip-flop FF3 is 360 or one binary time period delayed with
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 exclusive OR gate EOR are
derived from the outputs of the first and third flip-flops FFl,
FF3. Just before the time Tl, it will be seen that both these
outputs are at a logic 1, so that the exclusive OR gate EOR
produces a logic 0 which is inverted by the inverter to a
logic l. This logic l is a binary pulse and is shown in
FIGURE ll(f) prior to the time Tl. Immediately after the
time Tl, the fIip-flop FFl is still producing a logic l but
the flip-flop FF3 is producing a logic 0, so that the exclusive
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-flop FFl is producing a logic 0 but the flip-flop FF3
is producing a logic l so that the inverted output remains a
logic 0. Immediately after the time T3, the flip-flop FFl
is producing a logic l and the flip-flop FF3 is producing a
logic l. 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 1. Subsequent changes in the binary pulses are
produced in a similar manner. Thus, the diphase input, such
as represented in the waveform of FIGURE ll(b), is converted to
binary pulses as represented in the waveform of FIGURE ll(f).
~lthough the converter circuit of FIGURE 10 is
relatively simple, we have found that when this converter is
used in a voting arrangement such as we utilize in our function
control apparatus, the accuracy of transmitted binary or
-30-
. ' , '
4 5-MR- 68
~083223
digit:al data is greatly increased, particularly where the
transmission path is noisy or is subject to fading, such as in
the ]and mobile radio frequency spectrum.
Detailed Descri tion - Encoder
P _ :
The encoder 11 for the base station is intended to
receive commands from the computer 10 and generate an out-
bound message format such as shown in EIGURE 4. Similarly,
the encoder 11 for the mobile station receives commands from
the control 10 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. Commands
from the computer or control 10 are applied to a suitable
storage device 65 which retains the command for the needed
length of time. A parity generator 66 is connected to the
storage device 65 and generates, on the basis of the stored
function, the necessary sequence of four parity bits to be
supplied after the eight message bits. The storage device 65
also causes a function generator 67 to produce the necessary
sequence of eight message bits. Last, a preamble-synchronizing
generator 68 generates the preamble bits for inbound messages,
and generates the synchronizing and inverted synchronizing
bits for both 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 which is absolute or under
control of the mobile station clock which is corrected in
accordance with outbound messages. Of course, the time
-31-
,, ,. . . ~ : ,. :
., ~
. . ~ ' ' ' ' ::
45-MR- ~8
1083223
control provides the proper rate, namely 1111 pulses per
secc,nd for outbound messages, and 1666 bits per second for
inbc,und messages. The sequencing circuit 69 also provides
the necessary repetition of the function words, namely address
S 1, address 1', and command or response 1. The pulse sequence
so produced is applied to the modem for transmissioh.
Detailed Description - Decoder
A diagram of a decoder 14 which can be used with
the base station of FI~URE 8 or the mobile station of FIGURE
9 is shown in FIG~RE 13. This decoder receives the binary
pulses from the modem shift register 36 at a function word
gate 72 which permits only the function 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. Pulses passed by the gate 72-are applied
to a 36 bit shift register 73. The shift register 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 each 12 bit word of a function address or
command are voted on by a voting circuit 74. This voting is
provided by deriving bits 1, 13 and 25 from the shift register
73, so that as the bits are shifted into and through the register
73, the corresponding bits (separated by 12 intermediate
bits) are voted on. The voter 74 votes the majority, namely
2 out of 3, of the bits present at the 1, 13 and 25 outputs
of the register 73, and supplies the majority voted bit to
another 12 bit shift register 75. The register 75 stores the
voted 12 bits, in order that a logic correction circuit 76
can consider the eight message bits in relation to the four
-32-
45-MR- 68
10832Z3
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 command portion of the message. At the mobile station,
this may include transmitting back the given mobile station's
address along with the response to the command. However,
other features or functions may be provided if desired.
As mentioned, the shift register 73 actually need
not store 36 bits, by may only restore 24 bits, in which
case the first and thirteenth bits are compared and voted
on along with the incoming 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 i9 also reliable and
accurate, even though it 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.
-33-
1~83223 45-MR- 68
Therefore, it is to be understood that modifications may
be made to the embodiments shown without departing from
the spirit of the invention or from the scope of the
claims.
