Note: Descriptions are shown in the official language in which they were submitted.
CA 02335527 2000-12-19
Method for communication between contactless-type
data carriers and terminals
This invention relates to a method for bidirectional com-
munication between contactless-type data carriers and termi-
nals which are provided with devices for radiating electro-
magnetic waves for nongalvanic, electromagnetic coupling with
the data carriers. It also relates to a data carrier and a
terminal for carrying out the method.
The devices of the terminals for radiating electromag-
netic waves are coils and capacitors, resonant circuits, op-
tocouplers and the like. The data carriers, which are formed
as transponders, likewise have devices such as coils, capaci-
tors, resonant circuits, optocouplers, for nongalvanic energy
and/or data transfer so that the data carriers transfer en-
ergy and/or data with the terminals, such as read/write ter-
minals.
Contactless-type data carriers, for example contactless
smart cards, are used for a great variety of applications,
for example in the utilization of public transport systems,
as electronic purses, health insurance ID cards and the like.
Since the number of smart cards carried by a person is gener-
ally increasing constantly, a multifunctional data carrier is
desirable which can be used for as many applications as pos-
sible, preferably a single personal data carrier which can be
used virtually for all services utilized by a person.
Contactless-type data carriers are classified depending
on the possible data transfer distance as "close coupling"
data carriers with a data transfer distance between 0 and 2
millimeters and "remote coupling" data carriers, the latter
being further classified as "proximity" data carriers with a
data transfer distance up to 100 millimeters and "vicinity"
or "hands free" data carriers with a data transfer distance
of more than 100 millimeters. While close coupling or proxim-
ity data carriers can be used without any problem for some
applications, there are other applications for which only vi-
CA 02335527 2000-12-19
- 2
(corresponding to p. 3 of German)
cinity data carriers are suitable. For example, an electroni-
cally rechargeable Subway ticket can be readily designed for
data transfer to the terminal according to the "touch and go"
principle, i.e. as a close coupling or proximity data car-
rier, while such data carriers are unsuitable, or in any case
extremely awkward, for access control systems at ski lifts,
for example, since the lift card can be e.g. fastened to the
clothing or the data carrier integrated into a wristwatch.
The carrier frequency for data transfer, the permissible
frequency bandwidth and the transmitting energy emitted by
the terminal for contactless data transfer between data car-
riers and terminals are governed by regulations. For example,
an ISO standard stipulates a carrier frequency of 13.56 MHz,
whereby only a low given frequency bandwidth is permissible.
In order to solve the problem of different data transfer
distances for multifunctional data carriers, one might con-
sider increasing the emitted transmitting energy so that the
vicinity data transfer distance holds for all applications.
However, the maximum transmitting energy is likewise limited
officially for physiological and other reasons. Also, data
protection provisions oppose a vicinity data transfer dis-
tance in some applications of such a multifunctional data
carrier.
WO 98/10364 discloses a method for identifying smart
cards in order to let only one certain smart card from a
group of similar cards communicate with a terminal. It is
also known to operate terminals with lower power in economy
operation (e. g. WO 98/01816).
US-A-4 41I 004 discloses, iii a transmitter connected with
a plurality of receivers via a cable, performing data trans-
fer at different transfer rates, i.e. using a higher data
transfer rate for a receiver at a small distance from the
transmitter than for a receiver at a large distance there-
from.
CA 02335527 2000-12-19
- 2a
(corresponding to p. 3a of German)
The problem of the invention is to provide a method which
permits one and the same data carrier to be used for applica-
tions with both small and large data transfer distances.
This is obtained according to the invention by the method
stated in claim 1.
According to the invention the rate of data transfer is
varied in accordance with the distance of data transfer to be
bridged.
The higher the data transfer distance is, the higher the
transmitting energy emitted by the terminal must be. As
CA 02335527 2000-12-19
- 3 -
stated above, however, the maximum permissible emitted trans-
mitting energy is limited by administrative provisions. The
higher the data transfer rate used, and the shorter the
transaction time is thus selected for the processing opera-
tion in the device, the higher the frequency bandwidth re-
quired by the data transfer process is. Depending on the car-
rier frequency used, however, the frequency bandwidth is also
limited by corresponding regulations.
While a low data transfer rate involves a low frequency
bandwidth, thus permitting high transmitting power of the
terminal, i.e. a large data transfer distance, a high data
transfer rate involves a considerably greater frequency band-
width, so that the transmitting power and thus the data
transfer distance are reduced according to the invention in
order to meet the governing regulations.
That .is, according to the invention, data transfer is ef-
fected at a low rate in remote coupling and in particular vi-
cinity applications for example, while a high data transfer
rate is provided in proximity and in particular close cou-
pling applications for example.
Thus, one and the same data carrier can be used for
bridging small and large data transfer distances according to
the invention, while heeding the relevant limiting values for
frequency bandwidth and emitted electromagnetic energy.
According to the invention, the terminals and data carri-
ers are thus so designed that the data carriers for example
are suitable for use as vicinity data carriers, proximity
data carriers and close coupling data carriers. Therefore, a
data transfer rate as high as possible adapted to the data
transfer distance to be bridged can be used for the particu-
lar application of the data carrier.
For carrying out the inventive method one preferably uses
terminals having control means for varying their transmitting
power in accordance with the data transfer rate. This at the
same time permits use according to the invention of conven-
tional data carriers, i.e. data carriers communicating at
CA 02335527 2000-12-19
- 4 -
only one data transfer rate, without disturbing the function
and while heeding the stated relevant regulations.
Further, according to the invention the data carrier is
preferably designed for carrying out the inventive method so
as to communicate at different data transfer rates in accor-
dance with the data transfer distance. This permits use ac-
cording to the invention of conventional terminals, i.e. ter-
minals whose transmitting power is not controllable in accor-
dance with the data transfer rate, without disturbing the
function and while heeding the relevant regulations.
In other words, the inventive method providing low trans-
mitting power of the terminal and thus a small data transfer
distance at a high data transfer rate, and high transmitting
power of the terminal and thus a large data transfer distance
at a low data transfer rate, can be realized by a data car-
rier communicating at different data transfer rates in accor-
dance with the data transfer distance, and/or a terminal
whose transmitting power is controllable in accordance with
the data transfer rate.
The data transfer rate corresponding to the data transfer
distance to be bridged is preferably varied by an additional
communication step at the onset of data transfer.
In said additional communication step the relevant regu-
lations for emitted energy, required transmission frequency
band and physiological safety are heeded, whereby both inven-
tive data carriers on conventional terminals can be used
without disturbing the function and while heeding the stated
relevant regulations, and inventive terminals in order to be
able to read and write conventional data carriers without
disturbing the function and while heeding the relevant regu-
lations.
Said additional communication step can be constructed
such that the inventive terminal emits a signal pattern to
the data carriers before the onset of communication as an
identification code for the data transfer rate to be se-
lected. So that conventional data carriers can also be used
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- 5 -
for this terminal, said signal pattern must not be misinter-
pretable by conventional data carriers so as to disturb and
influence the subsequent data transfer.
Emission of such a signal pattern before the onset of
communication as an identification code for the data transfer
rate to be selected applies to those systems in which data
carriers, after approaching the electromagnetic field radi-
ated by the terminal, wait for a command from the terminal
before beginning with transfer of data to the terminal.
Such a terminal used for access control at a ski lift for
example thus emits a signal pattern blindly for the vicinity
application, i.e. a signal pattern identifying a low data
transfer rate, whereby a data carrier brought into the elec-
tromagnetic field radiated by said terminal sends back to the
terminal at the slow data transfer rate intended for said
terminal, without the transmitting power of the terminal be-
ing varied.
As are alternative to the abovementioned system there are
methods wherein data carriers begin spontaneously with trans-
fer of data after approaching the electromagnetic field radi-
ated by the terminal. With an inventive terminal and an in-
ventive data carrier which work according to the latter
method, the inventive terminal can emit a signal pattern as
an identification code for the data transfer rate to be se-
lected for further data transfer after the inventive data
carriers have spontaneously begun with data transfer at a
given data transfer rate after approaching the electromag-
netic field radiated by the terminal. The signal pattern used
is one which cannot be misinterpreted by conventional data
carriers, i.e. data carriers not capable of the inventive
method, and therefore leads to no disturbance or influence of
subsequent data transfer.
That is, if for example a large data transfer distance,
i.e. low data transfer rate, is to be used and the data car-
rier has spontaneously begun to transmit at a high data
transfer rate upon approaching the electromagnetic field of
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- b -
the terminal, it receives from the terminal for further data
transfer a signal pattern giving it the command to now switch
to the low data transfer rate.
The signal pattern as an identification code for the par-
ticular data transfer rate can for example be amplitude-
modulated according to a certain pattern. For example, a
"single side band" or SSB modulation is possible, or a phase
modulation.
The signal pattern as an identification code for the data
transfer rate to be selected for further data transfer can
also be a telegram used during the customary following commu-
nication, which is transmitted to the data carriers at the
data transfer rate used for further data transfer. That is,
if the terminal transmits at a low data transfer rate for ex-
ample, the data carriers only send back data at a low rate.
As an identification code for the data transfer rate to
be selected for data transfer one can further use a corre-
sponding data bit signal or corresponding protocol. The iden-
tification can also be effected by a corresponding data sig-
nal before the protocol.
Adaptation of data transfer rate refers according to the
invention to data transfer from the terminal to the data car-
rier. However, in particular if the terminal has such low re-
ception sensitivity that data sent by the data carrier at a
high data transfer rate can no longer be read, adaptation of
data transfer rate can also refer to data transfer from the
data carrier to the terminal or to both transfer directions.
Communication is effected according to the inventive
method between contactless-type data carriers and contact-
less-type terminals, whereby one or more data carriers de-
signed as transponders, i.e. having coils and other suitable
devices for data reception and data transfer, are brought
into the electromagnetic field emitted by the terminal for
the purpose of contactless, nongalvanic, electromagnetic cou-
pling and bidirectional data transfer.
CA 02335527 2000-12-19
(corresponding to p.10 of German)
With the use of the inventive data carrier, i.e. data
carriers communicating at different data transfer rates in
accordance with the data transfer distance, and with the use
of the inventive terminal, i.e. a terminal which is control-
lable for varying its transmitting power in accordance with
the data transfer rate, the inventive method permits adapta-
tion of the data transfer rate to the data transfer distance
to be bridged so that the highest possible data transfer rate
can be obtained at a given data transfer distance while heed-
ing the relevant regulations.
The transmitting power of the terminal corresponding to
the data transfer rate is varied in steps. It is possible for
example to switch over the transmitting power of the terminal
in only two steps, i.e. for a small, for example proximity,
data transfer distance and for a large, for example vicinity,
data transfer distance.
The data carrier can be designed in different ways, for
example as a card, wristwatch, bracelet or key pendant.
The invention will be explained in more detail by way of
example below with reference to the enclosed drawings, in
which:
Fig. 1 shows a diagram rendering maximum transmitting
power of the terminal as a function of frequency bandwidth,
Fig. 2 shows schematically the representation of the com-
bination consisting of the inventive data carrier and inven-
tive terminal.
Fig. 1 shows the maximum permissible transmitting power
of the terminal and the maximum permissible frequency band-
width at a certain carrier frequency by curve A rendered with
unbroken lines. While a low frequency bandwidth occurs at a
low data transfer rate according to dashed line B and thus
the maximum permissible transmitting power of the terminal,
i.e. a large data transfer distance, is possible, the fre-
quency bandwidth is considerably greater at a high data
transfer rate according to dotted line C and thus only low
CA 02335527 2000-12-19
_ g -
transmitting power or a low data transfer distance is possi-
ble.
Fig. 2 shows as le an inventive terminal, i.e. a terminal
whose transmitting power is controllable in accordance with
the data transfer rate, as lk a conventional terminal without
such control of the transmitting power, as 2e an inventive
data carrier communicating at different data transfer rates
in accordance with the data transfer distance, and as 2k a
conventional data carrier whose communication ability is re-
stricted to a single data transfer rate. According to vari-
ants A and B the inventive method can also be performed when
conventional data carriers 2k communicate with inventive ter-
minals (A) or conventional terminals lk with inventive data
carriers (B). According to variant C using an inventive ter-
minal and an inventive data carrier, the maximum possible
data transfer rate can be attained both at a large data
transfer distance (a) and at a small data transfer distance
(b) .
