Note: Descriptions are shown in the official language in which they were submitted.
CA 02505890 2005-04-29
MULTI-MODULATION REMOTE CONTROL COMMUNICATION SYSTEM
BACKGROUND OF THE INVENTION
[0001] I. Field of the Invention
[0002] This invention relates in general to a multi-modulation remote control
communication system and more particularly to an AM/FM remote control
communication system for range optimization of remote control systems
including for
vehicle applications.
[0003] II. Description of the Prior Art
[0004] Radio frequency remote control systems are used in a number of vehicle
applications, such as various combinations of convenience and security
systems. For
example, remote starter and security systems feature a transmitter carried by
a user and
a receiver mounted in the vehicle to receive the transmitted signal in order
to remotely
start the vehicle. The skilled person will appreciate that some of the
combinations of
vehicle applications to be remotely controlled, while not exhaustively listed,
could
comprise for example a convenience system alone, a security system alone, or a
combined convenience and security system.
[0005] Historically the radio frequency remote control systems have been using
amplitude modulation (AM) schemes due to their lower manufacturing costs,
compactness, and ease of implementation.
[0006] Radio frequency remote control systems for vehicle applications may
have
unidirectional or bidirectional communications capability. In a unidirectional
system, the
user can send wireless signals to the vehicle. In a bidirectional system, the
user can
send wireless signals to the vehicle, and the vehicle can respond with for
example
feedback signals to indicate changes of state in the vehicle's security
status, or a
confirmation that a particular command has been carried out. In a
bidirectional system
the vehicle can autonomously send signals to the user, for example to warn the
user that
the vehicle is being tampered with.
[0007] In a vehicle environment there are many potential sources of electrical
interference (RF noise). The sources of RF noise can be from the vehicle
itself or from
external sources, especially in an urban environment. Furthermore, the
characteristics
of on-vehicle RF noise may change during the service life of a particular
vehicle. For
CA 02505890 2005-04-29
example, the electric motor that drives the heater blower emits electrical
interference at
a certain frequency in a new vehicle. As the blower ages and wears, the
frequency of
the electrical interterence may change, thus placing an additional technical
challenge on
the remote control system to provide the expected range.
[0008] RF noise will reduce the range of an AM remote control system because
the
signal is encoded in the amplitude. The RF noise tends to affect the amplitude
of an AM
signal and will therefore change the information being carried, resulting in
"interference".
So, while many radio frequency remote control systems for vehicle applications
have
been designed using AM receivers and transmitters, the AM solution is less
resistant to
interference.
[0009] Prior art remote control communications devices have been devised to
attempt to
address the problems cited above but the disadvantages remain.
[0010] For example, US2004/0037365: Remote transmitter system and method. An
AM
carrier signal of selectable frequency is applied, but still an AM signal with
attendant
drawbacks.
[0011] US 4,660,192: Simultaneous AM and FM transmitter and receiver. This
patent
teaches simultaneous modulation of a carrier in AM and FM.
[0012] FM is more resistant to RF noise, however requires a more complex
oscillator
and receiver design. The reason why an FM signal is less affected by RF noise
is
because the FM signal has constant amplitude but varying frequency. The data
is
encoded by varying the frequency and thus RF noise does not affect FM as much.
[0013] It is an object of the present invention to provide a wireless remote
control
system with improved range and resistance to RF noise, for vehicle
applications.
Furthermore, the same solution could be applied to equivalent wireless remote
control
systems, regardless of the application, for stationary as well as mobile
systems.
[0014] It is a further object of the present invention to carry out mode
optimization when
data is exchanged between a remote and a mobile.
[0015] It is another object of the present invention to carry out mode
synchronization so
a remote control system is continuously ready for service.
[0016] It is yet another object of the present invention to notify the user if
the remote unit
is out of range of the mobile unit.
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SUMMARY OF THE INVENTION
[0017] In carrying out the above objects, a radio frequency multiple-
modulation remote
control system for vehicle applications is provided. The system comprises a
remote unit
for carrying by the user and a mobile unit for mounting on a vehicle. The
remote unit
comprises controllable RF circuitry such as transceiver, receiver,
transmitter, and the
like, as well as control circuitry such as a microprocessor, microcontroller,
or other
baseband processor circuitry. The mobile unit comprises controllable RF
circuitry such
as transceiver, receiver, transmitter, and the like, as well as control
circuitry such as a
microprocessor, microcontroller, or other baseband processor circuitry, and
furthermore
links to a vehicle application controller for the vehicle applications. The
remote circuitry
is operative to transmit a communications signal at a plurality of different
radio
modulation modes and to select a modulation mode for transmission. The mobile
circuitry is operative to receive a communications signal from the remote
unit. The
remote circuitry is also configured to sequentially scan for a communications
signal in
two or more radio modulation modes. The mobile circuitry is further operative
for a
receive state, wherein the mobile will select a modulation mode from the
remote that
provides error-free transmission of data to the microprocessor,
microcontroller, or other
baseband processor circuitry. The mobile circuitry is further operative to
send
instructions to the remote transceiver to continue transmitting data in that
particular
modulation mode, until data is no longer being successfully received. At that
point the
mobile and remote would repeat the process to negotiate another modulation
mode for
data transmission.
(0018] In accordance with one aspect of the present invention there is
provided a
vehicle application wireless remote control communications system comprising:
a
remote unit comprising transceiver, receiver and/or transmission circuitry,
for carrying by
a user, the remote unit being operative to exchange data in a plurality of
modulation
modes and to select a modulation mode for such purpose, the remote unit
further being
operative to contain and transmit one or more user-selected vehicle
application
functions, the remote unit further being operative to receive and optionally
indicate
vehicle-selected vehicle application functions; a mobile unit comprising
transceiver,
receiver and/or transmission circuitry, for mounting on a vehicle and
exchanging data
with the remote unit, and operative to transmit and receive data in the
plurality of
modulation modes and to select a modulation mode for such purpose, the mobile
unit
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further being operative to contain and transmit one or more vehicle-selected
vehicle
application functions; a means for the communications system to select the
modulation
mode from among the plurality of modulation modes for exchange of data between
said
remote and mobile units; and a means of optionally bidirectionally interfacing
the mobile
unit to a vehicle application controller so that the user-selected vehicle
application
function can be implemented whereby the user-selected vehicle application
function is
transmitted from said remote unit to said mobile unit by said selected
modulation mode,
wherein the user-selected vehicle application function is sent via the
optionally
bidirectional interface to the vehicle application controller for execution.
[0019] In accordance with another aspect of the present invention there is
provided a
vehicle application wireless remote control communications system comprising:
a
remote unit comprising transceiver, receiver and/or transmission circuitry,
for carrying by
a user, the remote unit being operative to transmit data in a plurality of
modulation
modes, the remote unit further being operative to contain and transmit one or
more user-
selected vehicle application functions; a mobile unit comprising transceiver,
receiver
and/or transmission circuitry, for mounting on a vehicle and receiving data
from the
remote transmitter, and operative to receive data in the plurality of
modulation modes; a
means for the communications system to select the modulation mode from among
the
plurality of modulation modes for receipt of data from said remote unit; and a
means of
optionally bidirectionally interfacing the mobile unit to a vehicle
application controller so
that the user-selected vehicle application function can be implemented whereby
the
user-selected vehicle application function is transmitted from said remote
unit to said
mobile unit by a selected mode from said plurality of modulation modes,
wherein the
user-selected vehicle application function is sent via the optionally
bidirectional interface
to the vehicle application controller for execution.
[0020] In accordance with yet another aspect of the present invention there is
provided
a vehicle application wireless remote control communications system
comprising: a
remote unit comprising transceiver, receiver and/or transmission circuitry,
for carrying by
a user, the remote unit being operative to exchange data in a plurality of
modulation
modes, the remote unit further being operative to contain and transmit one or
more user-
selected vehicle application functions, the remote unit further being
operative to receive
and optionally indicate vehicle-selected vehicle application functions; a
mobile unit
comprising transceiver, receiver and/or transmission circuitry, for mounting
on a vehicle
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and exchanging data with the remote unit, and operative to transmit and
receive data in
the plurality of modulation modes, the mobile unit further being operative to
contain and
transmit one or more vehicle-selected vehicle application functions; the
remote unit
further being operative to determine the received signal strength of each of
the
modulation modes; the mobile unit further being operative to determine the
received
signal strength of each of the modulation modes; a means for the
communications
system to select the modulation modes having the highest received signal
strengths
from among the plurality of modulation modes for exchange of data between said
remote
and mobile units; and a means of optionally bidirectionally intertacing the
mobile unit to a
vehicle application controller so that the user-selected vehicle application
function can
be implemented whereby the user-selected vehicle application function is
transmitted
from said remote unit to said mobile unit by said plurality of modulation
modes, wherein
the user-selected vehicle application function is sent via the optionally
bidirectional
interface to the vehicle application controller for execution.
[0021] In accordance with yet another aspect of the present invention there is
provided
a wireless remote control communications system comprising: a first
communication
means for exchanging data in a plurality of modulation modes; a second
communication
means for exchanging data in a plurality of modulation modes; a first signal-
processing
means operatively coupled to the said first communications means, the first
signal-
processing means programmed to perform the following functions: a) contain and
transmit one or more application functions; b) receive and analyse signals
indicative of
criteria for modulation selection; c) receive and indicate one or more
application
functions originating from a second signal-processing means; and d) select the
modulation mode from among the plurality of modulation modes based on the
criteria for
modulation selection; a second signal-processing means operatively coupled to
the
second communications means and interfaced with an application controller, the
second
signal-processing means programmed to perform the following functions: a)
contain and
transmit one or more application functions; b) receive and analyse signals
indicative of
criteria for modulation selection; c) receive and implement one or more
application
functions originating from the first signal-processing means by sending a
command
signal to the application controller; and d) select the modulation mode from
among the
plurality of modulation modes based on the criteria for modulation selection.
CA 02505890 2005-04-29
(0022] In accordance with one method aspect of the present invention there is
provided
a method for operating a vehicle application wireless remote control
communications
system comprising a remote unit comprising transceiver, receiver and/or
transmission
circuitry, for carrying by a user, the remote unit being operative to exchange
data in a
plurality of modulation modes, the remote unit further being operative to
contain and
transmit one or more user-selected vehicle application functions, the remote
unit further
being operative to receive and optionally indicate vehicle-selected vehicle
application
functions, and a mobile unit comprising transceiver, receiver and/or
transmission
circuitry, for mounting on a vehicle and exchanging data with the remote unit,
the mobile
unit being operative to transmit and receive data in the plurality of
modulation modes,
the mobile unit further being operative to contain and transmit one or more
vehicle-
selected vehicle application functions, and a means for the communications
system to
select the modulation mode from among the plurality of modulation modes for
exchange
of data between said remote and mobile units, and a means of optionally
bidirectionally
interfacing the mobile unit to a vehicle application controller so that the
user-selected
vehicle application function can be implemented whereby the user-selected
vehicle
application function is transmitted from said remote unit to said mobile unit
by said
selected modulation mode, wherein the user-selected vehicle application
function is sent
via the optionally bidirectional interface to the vehicle application
controller for execution,
the method comprising the steps of: exchanging data between the remote unit
and the
mobile unit in one or more of the plurality of modulation modes; selecting the
modulation
mode from among the plurality of modulation modes; transmitting the user-
selected
vehicle application function from said remote unit to said mobile unit by said
selected
modulation mode; and interfacing the mobile unit to a vehicle application
controller so
that the user-selected vehicle application function is implemented.
(0023] In accordance with another method aspect of the present invention there
is
provided a method for operating a vehicle application wireless remote control
communications system comprising a remote unit comprising transceiver,
receiver
and/or transmission circuitry, for carrying by a user, the remote unit being
operative to
exchange data in a plurality of modulation modes, the remote unit further
being operative
to contain and transmit one or more user-selected vehicle application
functions, the
remote unit further being operative to receive and optionally indicate vehicle-
selected
vehicle application functions, and a mobile unit for mounting on a vehicle and
exchanging data with the remote, the mobile unit being operative to transmit
and receive
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CA 02505890 2005-04-29
data in the plurality of modulation modes, the mobile unit further being
operative to
contain and transmit one or more vehicle-selected vehicle application
functions, and a
means for the communications system to select the modulation mode from among
the
plurality of modulation modes for exchange of data between said remote and
mobile
units, and a means of optionally bidirectionally interfacing the mobile unit
to a vehicle
application controller so that the user-selected vehicle application function
can be
implemented whereby the user-selected vehicle application function is
transmitted from
said remote unit to said mobile unit by said selected modulation mode, wherein
the user-
selected vehicle application function is sent via the optionally bidirectional
interface to
the vehicle application controller for execution, the method comprising the
steps of:
transmitting the user-selected vehicle application function from the remote
unit to the
mobile unit in the plurality of modulation modes; selecting the modulation
mode from
among the plurality of modulation modes; receiving the user-selected vehicle
application
function at said mobile unit in said selected modulation mode; and interfacing
the mobile
unit to a vehicle application controller so that the user-selected vehicle
application
function is implemented.
[0024] In a preferred embodiment, the modulation modes are on-off keying
(00K),
amplitude shift keying (ASK) and frequency shift keying (FSK), and digital
data is
modulated onto an RF carrier using these modulation modes to produce the
communications signals.
[0025] Conveniently, the present invention carries out mode synchronization on
a
periodic basis.
[0026] Preferably, the user is notified if the remote transceiver is out of
range of the
mobile.
[0027] In another embodiment of the invention the invention is implemented in
a
unidirectional system. A remote transmitter transmits AM data as well as FM
data. The
mobile receiver will scan both AM and FM, and will receive the data in the
modulation
type that provides the best reception.
[0028] These and other objects of the present invention will be more readily
described
by reference to the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0029] An embodiment of the invention will now be described by way of example
only
with reference to the accompanying drawings, in which like numbers refer to
like
elements. The drawings are:
[0030] FIG. 1, in a block diagram, illustrates a basic remote starter system
for vehicles
in accordance with the prefer-ed embodiment of the present invention;
[0031] FIG. 2, in a block diagram, illustrates the mobile transceiver of FIG.
1.
[0032] FIG. 3, in a block diagram, illustrates the remote transceiver of FIG.
1.
[0033] FIG. 4, in a diagram, illustrates the basic data element.
[0034] FIG. 5, in a diagram, illustrates the general data structure.
[0035] FIG. 6, in a flow chart, illustrates an AM-default AM/FM modulation
scheme.
(0036] FIG. 7, in a flow chart, illustrates an AM/FM transmit AM/FM modulation
scheme.
[0037] FIG. 8, in a flow chart, illustrates a signal-strength analysed AM/FM
modulation
scheme.
[0038] FIG. 9, in a flow chart, illustrates a unidirectional AM/FM modulation
scheme.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(0039 Referring now to FIG. 1, a radio frequency multiple-modulation remote
control
system for vehicle applications of the present invention comprises a remote
unit (TX) 40
for carrying by a user and a mobile unit (RX) 20 for mounting on a vehicle 10.
Through a
vehicle application controller 30, the RX interfaces with the on-board systems
that are to
be controlled by the TX.
(0040) Referring to FIGS. 2 and 3 the RX and the TX comprise an RF transceiver
circuit
50 and 60 controlled by baseband processor circuitry 52 and 62. The term
"baseband
processor circuitry" is intended to indicate the use of circuitry such as a
microprocessor,
a microcontroller, or an application-specific integrated circuit. The baseband
processor
circuitry has at least the following functionality: it controls the RF
transceiver circuitry,
decodes and encodes data, and operates a control program which includes the
vehicle
operating functions and instructions for multiple modulation mode operation,
selection
and data exchange. For use in both the RX and the TX, a transceiver circuit
TRF6903
manufactured by Texas Instruments has been found satisfactory, as has the
TH7122 by
Melexis, the XE1202 by XEMICS, the CC1000 by Chipcon, and the AT86RF211 by
Atmel. The skilled person will appreciate that other circuitry will be
satisfactory for use in
the RX and the TX. The term "transceiver" is used to represent circuitry
capable of
transmitting as well as receiving. It is further understood that whenever the
capability to
transmit and receive is indicated by the use of the term "transceiver", any
circuitry or
collection of circuitries that have these capabilities can be used to practice
the invention.
All devices or collections of devices that are able to receive and/or transmit
either
successively or simultaneously can be used to practice the invention and are
understood
to be represented by the term "transceiver". All devices or collections of
devices that, as
a subset of their capabilities, are able to receive and/or transmit either
successively or
simultaneously can be used to practice the invention and are understood to be
represented by the term "transceiver'.
(0041 Describing now the RX in more detail, FIG. 2 depicts the RF transceiver
circuitry
50, the baseband processor circuity 52, an antenna 54 and the interface 56 to
the
vehicle application controller 30. The RX transceiver circuitry 50 may be
reconfigured
under the control of the baseband processor circuitry 52 to function in the
required AM or
FM mode. The skilled person will appreciate that the mobile 20 could be
integrated with
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CA 02505890 2005-04-29
the vehicle application controller 30 and still be within the scope and spirit
of the present
invention.
[0042] Referring now to FIG. 3 the TX 40 is operative to transmit data to and
receive
data from the mobile transceiver RX unit 20. The TX 40 comprises RF
transceiver
circuitry 60 controlled by the baseband processor circuitry 62, a user
interface 64 which
for example may include a keyboard 66 and display 68, an antenna 72 and a
battery 70.
Upon receiving the appropriate selection signal from the baseband processor
circuitry
62, the transceiver circuitry 60 will function in the required AM or FM mode.
[0043] As aforesaid, both the TX and the RX have the capability to communicate
in AM
or FM modes. They will change the active mode in the transceiver chip upon
receipt of a
signal from the baseband processor circuitry. Variants of the AM modes can be
amplitude shift keying (ASK) and on-off keying (00K). The FM mode can be
frequency
shift keying (FSK). The RX and TX transceivers also comprise received signal
strength
indicator (RSSI) circuitry.
[0044] The skilled person will appreciate that other arrangements of circuitry
can be
used to obtain multiple modulation mode capability. For example, by
selectively
controlling a single-mode transceiver, emulated output signals can be obtained
that have
the characteristics of additional modulation modes. Thus the skilled person
will
appreciate that ASK, OOK and FSK signals can be prepared, transmitted,
received and
processed by numerous arrangements of circuitry, and the resulting plurality
of
modulation modes are within the spirit and scope of the invention, whether one
or more
of the modulation modes are obtained in an emulated manner or not. The
terminology
"a plurality of modulation modes" is thus understood to comprise emulated
modulation
modes as well.
[0045] Prior to describing the process to establish data communications, the
data
structure will be described. FIG. 4 illustrates an example of a fundamental
structure of
the basic data element, a logical data bit. Each logical data bit 80 or 90,
when
transmitted, is a set of two tones or periods, a high state 82 or 92 followed
by a low state
84 or 94. The logical 1 bit 80 is distinguished from the logical 0 bit 90 by
the length of
the tones or periods. Thus the period for a logical 1 bit 80 can be for
example in a range
from 50 milliseconds to 1 millisecond, while the period for the logical 0 bit
90 would be
50% longer. The skilled person will appreciate that other fundamental data bit
structures
and time periods will be satisfactory for use in the invention.
CA 02505890 2005-04-29
[0046]The logical data bits are grouped into data frames, which form the
general data
structure. FIG. 5 illustrates an example of a general structure of a data
frame 100.
Thus, when a frame 100 is transmitted, a certain number of bits representing
one piece
of information are transmitted. In one embodiment, a frame contains
approximately 50
bits. Generally, a frame comprises a set of start bits 102, a set of data bits
or commands
104, a set of checksum bits 106, and a set of bits representing a device
identification
number 108. The skilled person will appreciate that other data frame
structures will be
satisfactory for use in the invention.
[0047] In order to carry out a vehicle application function, the user
initiates a command
using the keyboard 66 of the remote unit (TX) 40. The signal from the keyboard
66 is
picked up by the baseband processor circuitry 62 at an appropriate input,
which then
initiates a communications algorithm, which is contained in the control
program. The
purpose of the communications algorithm is to enable the transmission of a
collection of
logical data bits (a frame) representing the desired function of the keyboard
selection.
The RX is programmed to wait for commands from the TX. The default state of
the RX
is a continuous receive mode. Since the RX is vehicle-mounted, the vehicle's
on-board
electrical system will provide adequate power to allow the RX to remain in
continuous
receive mode.
[0048] On initiating data communications between the remote and the mobile,
the data
frames will be repeatedly transmitted sufficiently often to facilitate
reception by the
remote, ensuring that the transmit and receive cycles converge sufficiently
quickly to
permit timely activation of the user-selected command, while making
appropriate use of
system resources such as battery capacity. It will be appreciated that all
processes
described herein as being initiated by the remote to establish communications
and mode
synchronization with the mobile can analogously be initiated by the mobile in
order to
establish communications with the remote. For example, an alarm signal can be
generated by the vehicle application controller for autonomous transmission
back to the
user, to warn the user that the vehicle is being tampered with.
[0049] When initiating data communications using a bidirectional system, if
the user is
too far away from the RX, or environmental conditions are such that data
communications cannot take place, the TX, having completed the data
transmission
without receiving a confirmation signal will indicate to the user that data
communications
could not be established.
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CA 02505890 2005-04-29
[0050] FIG. 6 illustrates an embodiment of the method of the present invention
using an
AM default scheme to accomplish dual-mode data communications. In this
embodiment,
the mobile is programmed to continuously scan for data transmissions from the
remote.
The scanning is done alternately in AM and FM. The mobile is programmed to
return a
feedback message in the same type of modulation it received. The remote
transmits a
sequence, with sufficient repetitions, of identical data frames representing a
command in
AM mode at block 130 and then is placed in receive mode by the baseband
processor
circuitry to wait for feedback from the mobile. If the remote gets AM feedback
at block
132, then an appropriate icon is displayed at block 138, confirming that the
mobile has
received data communications representing a command and has carried it out. If
after a
time period the remote gets no AM feedback, the remote then transmits the data
in FM
at block 134 and listens for feedback from the mobile. The mobile has in the
meantime
been scanning alternately in AM and FM, and if range and RF noise conditions
are
appropriate the mobile will receive at least one of the AM commands sent by
the remote.
The mobile then transmits a confirmatory feedback command back to the remote.
If the
remote receives FM feedback from the mobile at block 136, then the appropriate
icon is
displayed at block 138, as a confirmation that the mobile has received data
communications representing a command and has carried it out. If the remote
does not
receive an FM feedback signal from the remote at block 136, an out of range
icon is
displayed at block 140.
[0051] FIG. 7 illustrates an embodiment of the method of the present invention
using an
AM/FM scheme to accomplish data communications. The mobile in this embodiment
is
programmed to alternately scan AM and FM. The remote is actuated by the user
and
alternately transmits a sequence of AM and FM data frames at block 150. Once
the
remote has finished transmitting, it turns on the receiver and alternately
scans AM and
FM, awaiting data from the mobile at block 180. Meanwhile, if the mobile has
received
either AM at block 152 or FM data at block 154 from the remote, it will carry
out the
command contained in the data and will transmit the appropriate feedback to
the remote
at blocks 156 and 158, which upon receiving the AM or FM data respectively at
blocks
162 and 164 will display the appropriate confirmation icon.
[0052] The previous two embodiments require data modulation synchronization
every
time a command has been sent from the remote to the mobile, or every time the
mobile
has sent a message to the remote. Embodiments wherein modulation
synchronization is
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CA 02505890 2005-04-29
carried out periodically, to maintain the remote and mobile at a state of
readiness for a
given period of time, are also within the scope and spirit of the present
invention.
[0053] FIG. 8 illustrates an embodiment of a method of the present invention
using a
modulation synchronization request command. Using this method, the remote is
programmed to transmit in one mode and receive feedback from the mobile in an
alternate mode. The remote sends a modulation synchronization request command
to
the mobile at block 170. The transmit sequence alternately comprises AM and FM
data
frames representing the modulation synchronization request command. The remote
transmits the same modulation synchronization request command data frame with
sufficient repetitions to ensure reception by the mobile if range and RF noise
conditions
are acceptable. The mobile by default alternately scans for AM and FM signals.
If the
mobile detects either AM or FM data or both at block 172, the mobile tests the
signal-
strength of the detected data at block 178 by using the RSSI circuitry and
then transmits
an AM/FM feedback requesting either AM or FM modulation, whichever has the
stronger
signal, from the remote at blocks 178 and 180, respectively. The mobile then
switches
to receive mode at block 182 and waits for a mode confirmation from the TX;
the mobile
alternately scans for AM and FM signals. If at block 184 the mobile has
obtained
confirmation from the remote, then the mobile's microprocessor will set the
mobile to
receive in that particular modulation at block 186. However, if confirmation
has not been
received, the mobile at block 188 will continue to wait for confirmation by
operating the
receiver alternately in AM and FM.
[0054] Continuing to refer to FIG. 8, having transmitted data to the mobile,
the remote
tests for feedback from the mobile at block 190, by alternately being set to
receive in AM
and FM. On detecting data from the mobile at block 192, the remote will test
the
strength of the signals at block 196 using the RSSI circuitry and will be set
to receive
whichever modulation is stronger. The mobile will be sent a confirmation, from
either of
blocks 198 or 200, notifying it which modulation the remote will continue to
use for the
duration of the synchronization period, in order to receive feedback signals
from the
mobile. By using the method of FIG. 10, the remote and the mobile can be
synchronized
to transmit and receive in different modulation modes, in order to have
improved range
for the remote and the mobile. For example, the remote could transmit in AM
but
receive feedback from the mobile in FM. The mobile would set to receive and
transmit
accordingly.
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[0055] In yet another embodiment of the method of the present invention using
a
modulation synchronization request command, the modulation types to be used by
the
remote and the mobile are selected manually by the user. The manual
synchronization
is implemented by sending an AM communication command from the remote
transceiver
to the mobile transceiver to test the communication. On receiving a feedback
signal the
remote will indicate the AM signal strength to the user. If the AM signal
strength is
insufficient, the user can then select FM modulation on the TX.
[0056] FIG. 9 illustrates another embodiment of the method of the present
invention,
AM/FM modulation for a unidirectional system. In such a unidirectional system,
the TX
comprises a transmitter instead of a transceiver, and the RX is equipped with
a receiver
instead of a transceiver. Thus the TX can transmit to the RX, which can
receive, at
block 210; the TX cannot receive, and the RX cannot transmit. The TX will
transmit both
AM and FM data. The mobile RX receiver will scan both modulation types at
blocks 212
and 214 and pick up the data in the mode that provides the best reception,
wherein it will
execute the function command that it has received (block 216).
[0057] An embodiment of the present invention is used to solve a range and
interference problem for a general wireless remote control communication
system, which
may for example be an industrial stationary application such as a remote gate
control, or
an industrial mobile application such as the remote control of a warehouse
trolley. If a
wireless remote control system as applied to any of such general remote
control
systems has reception problems such as limited range or apparent
susceptibility to
interference, those skilled in the art will understand that any of the
solutions described
above are appropriate to solve such reception problems, while remaining within
the spirit
and scope of the present invention.
[0058] While the present invention has been described with reference to one or
more
preferred embodiments, those skilled in the art will recognize that many
changes may be
made thereto without departing from the spirit and scope of the present
invention which
is set forth in the following claims.
14
