WO2009098631A1

WO2009098631A1 - Adaptive capacitive coupling for body-coupled communication

Info

Publication number: WO2009098631A1
Application number: PCT/IB2009/050411
Authority: WO
Inventors: Karin Klabunde; Wolfgang Stiller; Heribert Baldus; Steven Corroy
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N.V.
Priority date: 2008-02-05
Filing date: 2009-02-02
Publication date: 2009-08-13

Abstract

In summary, the present invention relates to a device, a method, a system and a computer program, wherein the device (100) comprises a coupling unit (110) configured to capacitively couple a body-coupled communication signal onto a human or animal body, and an adapting unit (120) configuredto adapt the device (100) to a current usage context. The adaptation can be performed by changing settings of variable-capacitance diodes forming part of an oscillating unit (150). In this way, the capacitance of the oscillating unit (150) may be adjustedso as to compensate for capacitance changes at the coupling unit (110) due to factors such as temperature, humidity, state of body etc.

Description

Adaptive capacitive coupling for body-coupled communication

FIELD OF THE INVENTION

The present invention generally relates to a device, a system, a method and a computer program for adapting a capacitive coupling of a body-coupled communication.

BACKGROUND OF THE INVENTION

Body-coupled communication (BCC) allows exchange of information between devices that are located at or in close proximity of a human or animal body. BCC signals are conveyed over the body instead of through the air. The body is utilized as a communication channel, so that communication can take place with much lower power consumption than in standard radio frequency (RF) communication systems commonly used for body area networks (BANs), e.g. Zigbee or Bluetooth systems. Further, a communication based on BCC signals is confined to an area close to the body. This is in contrast to RF communications, where a much larger area is covered. Thus, when using BCC signals, a communication is only possible between devices situated on, connected to or placed close to the same body. This enables the creation of a secure BAN. For these and other reasons, BCC has been proposed as one candidate for the physical layer technology of BANs (IEEE 802.15.6 BAN standardization).

Since BCC is usually applied in close proximity to the body, it can be used to realize an easy and intuitive interaction between users and wireless devices at/close to the body. BCC can be used for automatic identification, personalization, authentication, verification or data communication applications. In general, the goal of BCC consists in enabling a communication between devices that can be placed somewhere at the body, so that the communication range for these devices is the whole body.

BCC is technically realized by a capacitive coupling of low-energy electrical fields onto the body surface. That is, BCC is accomplished by electric fields that are generated by a small body-worn tag being e.g. integrated into a credit card or another suitable device attached to or worn in close proximity to the body. Such tag capacitively couples a low-power signal to the body of a user. A signal is modulated with a digital code that uniquely identifies e.g. a credit card of the user and is transmitted to a reader integrated in e.g. the user's mobile phone. The credit card, i.e. the tag integrated in the same, is only readable close to the user's body (up to about 15 cm).

A detailed description of the basic underlying communication principle is given by Thomas Guthrie Zimmerman, "Personal Area Networks (PAN): Near-Field Intra- Body Communication", MASTER OF SCIENCE IN MEDIA ARTS AND SCIENCES at the Massachusetts Institute of Technology, September 1995. In this thesis, the term "near-field intra-body communication" is used when describing a body-coupled or body-based communication. Near-field intra-body communication is a wireless technology that allows electronic devices on and near a human body to exchange digital information through near- field electrostatic coupling. Information is transmitted by modulating electric fields and electrostatically (capacitively) coupling small currents into the body. The body conducts a tiny current such as a picoamp current (e.g. 50 pA) to body mounted receivers. The environment (the air and/or earth ground) provides a return path for a transmitted signal.

In Zimmerman's thesis a transmitter-receiver model of a near- field intra-body communication is described. Both the transmitter and the receiver are electronic battery powered devices, electrically isolated and having a pair of electrodes A, B. The transmitter and receiver electrodes A, B can be modeled as capacitor plates. Such intra-body communication can be used for a data exchange between devices in so-called personal area networks (PANs). A PAN prototype working at 330 kHz was developed to demonstrate the digital exchange of data through the body.

The system described by Zimmerman does not adapt to a current usage situation or context and does not take into account factors such as temperature, humidity, state of human body etc.

The performance of BCC systems and other kinds of capacitive coupling systems is strongly influenced by factors such as body contact, position of a transmitting/receiving device at the body, temperature, humidity of the air, humidity of the skin, current state of the body at which the system is used, and further conditions of the environment and other conditions. If a system is not adapted to a current usage situation, sending and receiving circuits are not optimally tuned, which lowers the communication performance. Existing systems using capacitive coupling for communication do not take into account these factors.

Since the publication of Zimmerman's thesis, a lot of research on wireless communication systems using the human body as a communication medium has been done. For example, experiments regarding the size of capacitor plates, the position of transmitting/receiving devices at the body and different operating frequencies have been conducted. However, none of the previously proposed body-based communication systems is adaptable to a current usage situation. All the existing solutions describe only static systems that do not adjust to environment conditions and other factors having an impact on the communication performance.

If a BCC system or other body-based communication system is not adjusted to the above described influencing factors, the sending and receiving capabilities of the system decrease substantially, so that the possible distance between devices at the body is limited, not allowing to place the devices far away from each other at the body. The receiving and/or sending performance is not optimal, because resonance frequencies of oscillating circuits of the BCC devices are detuned. The contact of a BCC device with a human or animal body always influences the oscillating circuit of a BCC board. Different bodies influence the system differently, so that it is not possible to set the optimal system parameters without considering the current usage context.

SUMMARY OF THE INVENTION

It is desirable to provide a BCC system or other capacitive coupling system that is able to adapt to the current usage context in order to achieve a maximal possible communication performance. This can be achieved by a device according to claim 1 , a system according to claim 11, a method according to claim 14 and a computer program according to claim 15. Accordingly, in a first aspect of the present invention a device is presented. The device comprises a coupling unit configured to capacitively couple a body-coupled communication signal onto a human or animal body, and an adapting unit configured to adapt the device to a current usage context. The device may take into account different working conditions with respect to temperature, humidity, state of body etc. It can achieve an optimal performance for sending and receiving. As a result, the energy efficiency and reliability may be increased due to optimal device settings, as e.g. less retransmission is necessary.

In a second aspect of the present invention the adapting unit is configured to adapt a carrier frequency and/or amplitude of the body-coupled communication signal. Adapting the carrier frequency and/or amplitude allows compensating for capacitance changes at the coupling unit.

In a third aspect of the present invention the adapting unit comprises a measuring unit configured to measure a value indicative of the carrier frequency and/or amplitude, wherein the adapting unit is configured to adapt the carrier frequency and/or amplitude based on a measurement result of the measuring unit. Measuring a value indicative of the carrier frequency and/or amplitude of the body-coupled communication signal, e.g. the amplitude of a carrier frequency signal forming a basis for the body-coupled communication signal, and influencing the carrier frequency and/or amplitude by adapting the same enables a precise setting of the carrier frequency and/or amplitude due to the feedback by the measurement result.

In a fourth aspect of the present invention the measuring unit is configured to perform a received signal strength indication (RSSI) measurement. The RSSI function measures the amplitude of a voltage at the coupling unit, e.g. capacitive plates. Thus, it allows an easy determination of the amplitude of the body-coupled communication signal or carrier frequency signal.

In a fifth aspect of the present invention the adapting unit comprises an oscillating unit configured to supply the body-coupled communication signal to the coupling unit, wherein the adapting unit is configured to adapt a resonance frequency of the oscillating unit. By adapting the resonance frequency of the oscillating unit, sending and receiving capabilities of the device can be held stable on a maximal level. The fifth aspect may be combined with any one of the preceding aspects.

In a sixth aspect of the present invention the oscillating unit comprises at least one variable-capacitance diode, and the adapting unit is configured to change a setting of the at least one variable-capacitance diode. Variable-capacitance diodes allow an easy modification of the oscillating unit's capacitance by just changing a voltage supplied to the variable-capacitance diodes.

In a seventh aspect of the present invention the adapting unit comprises a controlling unit configured to control an adaptation performed by the adapting unit, a digital- to-analog converter configured to convert a control signal supplied by the controlling unit into a voltage, and a step-up regulator and amplifier unit configured to increase the voltage, wherein the increased voltage is used for the adaptation. The controlling unit can be provided with software that may easily be modified to change a characteristic of the adapting unit without hardware modifications. The digital-to-analog converter and the step-up regulator and amplifier enable processing of a digital output of the controlling unit and provision of a higher voltage needed for the oscillating unit without increasing a supply voltage of the device. The seventh aspect can be combined with any one of the preceding aspects. In an eighth aspect of the present invention the adapting unit is configured to perform an iterative adaptation. The iterative adaptation allows finding an optimal setting to achieve a maximal communication performance. The eighth aspect may be combined with any one of the preceding aspects. In a ninth aspect of the present invention the adapting unit is configured to regularly perform an adaptation. By the regular adaptation it can be ensured that a deviation from a desired value remains small enough. The ninth aspect may be combined with any one of the preceding aspects.

In a tenth aspect of the present invention the adapting unit is configured to adapt an adaptation interval dynamically. When adapting the adaptation interval dynamically, only a minimum number of adaptations has to be performed in a certain situation. Therefore, the number of adaptations can be decreased. Thus, a required processing power may be reduced. The tenth aspect can be combined with any one of the first to eighth aspects.

In an eleventh aspect of the present invention a system is presented. The system comprises a plurality of devices according to any one of the preceding aspects, wherein at least two devices of the plurality of devices are configured to communicate with each other. The sending and receiving capabilities of such system can be stable on a maximal level, due to the adaptation mechanism included which ensures that the system is not influenced by temperature, humidity, current body characteristics etc. A transmitter and receiver may be distributed all over the body. A complete coverage of the human or animal body can be achieved. The overall power consumption of the system may be minimized and reliability can be increased, because less retransmissions may be needed due to having an optimal communication success probability.

In a twelfth aspect of the present invention at least one device of the plurality of devices is configured to control an adaptation of at least one other device. If not every single device has to be provided with all elements used for adapting purposes, at least some of the devices can be less complex. Therefore, the size, the costs and the power consumption of the devices may be reduced.

In a thirteenth aspect of the present invention the system is a body area network. A system of such type can easily be employed for a plurality of applications including e.g. medical applications.

In a fourteenth aspect of the present invention a method is presented. The method comprises capacitively coupling a body-coupled communication signal onto a human or animal body by means of a device, and adapting the device to a current usage context. With the method, different working conditions with respect to temperature, humidity, state of body etc. may be taken into account. An optimal performance for sending and receiving can be achieved. As a result, the energy efficiency and transmission reliability may be increased due to optimal device settings. In a fifteenth aspect of the present invention a computer program is presented.

The computer program comprises program code means for causing a computer to carry out the steps of a method according to the fourteenth aspect when the computer program is carried out on a computer. Thus, the same advantages as with the method according to the fourteenth aspect may be achieved. Further advantageous modifications are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will be apparent from and elucidated by an embodiment described hereinafter with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic block diagram illustrating an exemplary arrangement of a device according to the embodiment;

Fig. 2 shows a flowchart illustrating steps of an exemplary adaptation procedure 200 according to the embodiment; Fig. 3 shows a flowchart illustrating steps of an exemplary determination procedure 300 as carried out in step S240 of Fig. 2;

Fig. 4 shows a diagram illustrating a first exemplary arrangement of a system according to the embodiment;

Fig. 5 shows a diagram illustrating a second exemplary arrangement of a system according to the embodiment;

Fig. 6 shows a diagram illustrating a third exemplary arrangement of a system according to the embodiment; and

Fig. 7 shows a diagram illustrating a fourth exemplary arrangement of a system according to the embodiment.

DETAILED DESCRIPTION OF AN EMBODIMENT

Fig. 1 shows a schematic block diagram illustrating an exemplary arrangement of a device according to the embodiment. A device 100 can comprise a coupling unit 110, an adapting unit 120, a modulator and gate unit 130 and an oscillator 140. The adapting unit 120 may include an oscillating unit 150, a step-up regulator and amplifier unit 160, a digital-to- analog (D/ A) converter 170 and a processing unit 180. The device 100 can be provided with a supply voltage of e.g. 3 V supplied by a power supply unit such as e.g. a battery.

The device 100 may be a body-coupled communication (BCC) module or other kind of transmitting/receiving module based on capacitive coupling. The device 100 or at least the coupling unit 110 thereof can be placed at or close to a human or animal body to use the body as a communication medium for communicating a BCC signal. Such placement allows a good capacitive coupling and, therefore, a stable communication with low power consumption. The BCC signal may be intended for a body area network (BAN), and the device 100 can be configured to be part of such network. This enables an easy integration of the device 100 into a BAN without additional adaptation effort.

The oscillator 140 may generate an oscillator frequency of e.g. 125 kHz and supply an oscillator frequency signal to the modulator and gate unit 130 that can be controlled by a modulation and gate signal supplied by the processing unit 180. The modulator and gate unit 130 may connect the oscillator frequency signal to the oscillating unit 150 such as e.g. an oscillating circuit. In other words, the oscillator 140 can be switched on and off. The modulator and gate unit 130 may either perform a modulation of the oscillator frequency signal or simply pass this signal through. In the former case, e.g. an amplitude-shift keying (ASK) modulation or a Manchester encoding can be performed. In the latter case, no modulation is effected. Depending on whether or not a modulation is carried out, either a modulated signal or just the oscillator frequency signal is supplied by the modulator and gate unit 130 to the oscillating unit 150. The latter applies e.g. in case that an adaptation procedure such as described below is performed. The oscillating unit 150 may be operated in a sending mode (serial connection) and a receiving mode (parallel connection), i.e. act as a sending and receiving circuit. Switching between these modes can be controlled by the modulator and gate unit 130.

The oscillating unit 150 such as e.g. an oscillating sending and receiving circuit can comprise at least one adaptable capacitive diode, for example two variable- capacitance diodes such as e.g. varactor diodes. The at least one adaptable capacitive diode may be used in place of one or more conventional capacitors as contained in a usual oscillating circuit and to vary a capacitance of the oscillating unit 150, wherein this capacitance can include a coupling capacitance of the coupling unit 110. Thus, specific hardware may be used that allows tuning an oscillating circuit or unit of communication boards. Further elements like e.g. a coil, a capacitor and a resistor can be included in the oscillating unit 150. A sending signal provided by the oscillating unit 150 may be coupled onto the human or animal body by the coupling unit 110 in order to communicate it to a receiving end. In this case, the oscillating unit 150 can act as a serial oscillating circuit. If the oscillating unit 150 is used to receive a signal picked up by the coupling unit 110, it may act as a parallel oscillating circuit. The coupling unit 110 can be comprised of, for example, electrodes such as e.g. capacitive plates acting as antennas. That is, the coupling unit 110 may be formed by antenna plates or other kinds of electrodes.

A resonance frequency of the oscillating unit 150 may be detuned due to factors such as e.g. body contact, position of the coupling unit 110 at the body, temperature, humidity of the air, humidity of the skin, current state of the body at which the device 100 is used, and further conditions of the environment and other conditions. As a result, the communication performance of the device 100 can be strongly influenced by such factors. To compensate for this, the following adaptation procedure based on measuring and influencing a carrier frequency and/or amplitude of a BCC signal at the coupling unit 110, e.g. capacitive plates thereof, may be performed. In other words, the frequency and/or the amplitude of a carrier frequency signal forming a basis for the BCC signal can be adapted, wherein the carrier frequency may be identical with the oscillator frequency generated by the oscillator 140 or at least dependent on the same.

The processing unit 180 can measure a value indicative of the carrier frequency signal, e.g. a value indicating the amplitude of the carrier frequency signal. For example, a received signal strength indication (RSSI) measurement may be performed, as the RSSI function measures the amplitude of a voltage at the coupling unit 110, e.g. capacitive plates, of a current board, which is determined from a received signal at an input of the processing unit 180. In other words, the RSSI function can measure a voltage at the oscillating unit 150. The processing unit 180 such as e.g. a microcontroller may determine whether or not a measured value is optimal. The measured value can be considered to be optimal if it is substantially maximal, since in this case the oscillating unit 150 is in resonance. In case the measured value is not optimal, an adaptation may be performed. Such adaptation can be achieved by influencing capacitive diodes of the oscillating unit 150 accordingly, i.e. by increasing or decreasing the capacitance of the capacitive diodes until the amplitude of the voltage at the oscillating unit 150 is at its maximum. Thus, the processing unit 180 may determine the setting for the capacitive diodes and send a signal indicative of the setting, for example a 12-bit signal, via a serial output of the processing unit 180 to the D/A converter 170. The D/A converter 170 can transform this signal into a corresponding voltage within a voltage range of e.g. 0...3 V. The step-up regulator and amplifier unit 160 may increase the value accordingly, wherein a step-up regulator provides a supply voltage for a direct current (DC) amplifier, and the DC amplifier increases the voltage, e.g. from 3 V to 50 V. An output voltage to be achieved by the DC amplifier depends on a voltage at the coupling unit 110. For example, if a peak-to-peak antenna voltage between antenna plates of the coupling unit 110 amounts to more than 50 V, the output voltage of the DC amplifier also amounts to more than 50 V.

As a result, a DC voltage in a range of e.g. 0...50 V can be supplied by the step-up regulator and amplifier unit 160 to the oscillating unit 150 in order to set the capacitive diodes thereof to a desired value corresponding to the setting determined by the processing unit 180. That is, this voltage acts as a control voltage of the capacitive diodes. In this way, the capacitive diodes may be set such that their changed capacitance, i.e. the changed capacitance of the oscillating unit 150, results in a compensation of capacitance changes at the coupling unit 110, e.g. antenna plates, that are caused by external factors such as those described above. For example, capacitance changes at the coupling unit 110 due to factors like body contact, temperature, humidity etc. can be compensated by changing the setting of the capacitive diodes such as variable-capacitance diodes. In other words, the oscillating unit 150 may be tuned to compensate for such capacity changes. This can be achieved by changing the capacitance of the oscillating unit 150, whereby the resonance frequency thereof may be optimized as described in more detail below.

The above described arrangement of a device 100 according to the embodiment is merely exemplary and can be varied in a plurality of ways. For instance, one or more constituent elements of the adapting unit 120 may be commonly provided for a plurality of devices and shared by these devices. For example, a processing unit 180 of one of the devices can determine a current device from a received signal at an input of the processing unit 180 and perform the adaptation procedure for the current device. Further, the processing unit 180 may comprise a measuring unit 190 such as e.g. a RSSI measuring unit, a controlling unit and other units, even if only the measuring unit 190 is explicitly depicted in Fig. 1. As an alternative, the processing unit 180 can provide the functionality of a measuring unit, a controlling unit and other units.

Further, the device 100 may be an adaptive capacitive coupling BCC module. The realization of the device 100 and an adaptive capacitive coupling BCC system described below covers both software and hardware. Protocols for reliable, secure communication and identification, that provide functionality for device discovery and secure data transfer and allow easy integration of BCC modules into other devices, have been developed. Protocol software can be loaded as firmware into the processing unit 180.

In the following, the adaptation procedure will be explained in more detail. Fig. 2 shows a flowchart illustrating steps of an exemplary adaptation procedure 200 according to the embodiment. In a step S210, the oscillator 140 may be switched on, and the oscillator frequency of e.g. 125 kHz generated by the same can be connected to the oscillating unit 150 using the modulator and gate unit 130. This may occur e.g. every 100 ms. In a step S220, the processing unit 180 may perform a RSSI measurement to measure the amplitude of the carrier frequency signal at the coupling unit 110. In other words, an antenna voltage at the coupling unit 110 can be measured. The measurement may be carried out by a dedicated RSSI measuring unit 190 included in the processing unit 180, or can be effected by means of RSSI measuring functionality provided by the processing unit 180. A measured value may be buffered at the processing unit 180. In a step S230, it can be determined whether or not a measured RSSI value is OK. In case the measured value is not optimal, i.e. a result of the determination in the step S230 is "no", an adaptation may be performed. If an adaptation is to be performed, an optimal setting of the oscillating unit 150 can be determined in a step S240. Then, the oscillator 140 may be switched off in a step S250. In case the measured value is optimal, i.e. a result of the determination in the step S230 is "yes", no adaptation is required. A measured value can be considered to be optimal if it is maximal. In this case, the oscillator may be switched off in the step S250 after determining that the RSSI value is OK. In a step S260, the adaptation procedure can sleep for X ms. Then, the steps S210 to S260 may be carried out again. These steps can be performed regularly, e.g. each 0.1 s or 0.5 s. The interval for performing them may also be adapted dynamically, e.g. depending on the history or current usage scenario. Fig. 3 shows a flowchart illustrating steps of an exemplary determination procedure 300 as carried out in step S240 of Fig. 2. That is, the steps of determining an optimal setting are depicted. In a step S310, a value for setting can be determined. The processing unit 180 may determine the setting for capacitive diodes of the oscillating unit 150, e.g. by means of a microprogram. A signal indicating the value for setting, e.g. a 12-bit signal, can be sent via the serial output of the processing unit 180 to the D/A converter 170. The D/A converter 170 may transform the signal into a corresponding voltage and supply the same to the step-up regulator and amplifier unit 160. The step-up regulator and amplifier unit 160 can increase the voltage accordingly. Based on the increased voltage supplied by the step-up regulator and amplifier unit 160, the capacitive diodes of the oscillating unit 150 may be set to a corresponding value, i.e. in accordance with the value for setting determined in the step S310. That is, in a step S320 the setting of the capacitive diodes of the oscillating unit 150 can be influenced by varying a control voltage thereof. In more detail, either a control voltage of the DC amplifier in the step-up regulator and amplifier unit 160 may be increased to increase a control voltage of the oscillating unit 150, decrease the capacitance of the capacitive diodes and increase the resonance frequency of the oscillating unit 150, or the control voltage of the DC amplifier can be decreased to decrease the control voltage of the oscillating unit 150, increase the capacitance of the capacitive diodes and decrease the resonance frequency of the oscillating unit 150. In a step S330, an RSSI measurement may be performed, and a result thereof can be buffered at the processing unit 180. That is, the RSSI measurement can be repeated to check whether the situation has improved. In a step S340, it may be determined whether or not a result of the RSSI measurement performed in the step S330 is better than a result of a previous RSSI measurement and, thus, a local optimum has been found. In case the result of the RSSI measurement performed in the step S330 is better, i.e. a result of the determination in the step S340 is "yes", the steps S310 to S340 can be carried out again in order to increase/decrease the capacitance of the capacitive diodes of the oscillating unit 150 again so as to find out whether the optimal value thereof has already been found. This may be repeated until it is discovered that the measurement becomes worse, i.e. a current optimum was already detected in a previous setting which then has to be restored. That is, if a result of the determination in the step S340 is "no", an optimal setting determined in a previous pass of the steps S310 to S340 can be restored in a step S350. Then, the determination procedure may be exited or terminated in a step S360. In this way, the capacitance of the oscillating unit 150 can be increased or decreased by influencing the capacitive diodes thereof accordingly. In other words, the determination procedure 300 may repeatedly measure the antenna voltage at the oscillating unit 150 and respectively compare a new measurement result with a buffered previous measurement result. If the new measurement result is greater than the previous measurement result after increasing the control voltage of the DC amplifier in the step-up regulator and amplifier unit 160, this control voltage can be further increased until the antenna voltage has reached its maximum. If the new measurement result is less than the previous measurement result after increasing the control voltage of the DC amplifier in the step-up regulator and amplifier unit 160, the control voltage may be decreased in the following until the antenna voltage has reached its maximum. The oscillating unit 150 is in resonance if the antenna voltage is maximal. Thus, the oscillating unit 150 can be automatically and dynamically adjusted to the optimal setting, so that the current usage context has no influence on the communication performance. This may be achieved by regularly measuring the amplitude of the carrier frequency signal at the coupling unit 110, e.g. capacitive plates, and by readjusting the resonance frequency of the oscillating unit 150 by means of an iterative procedure that determines the optimal setting for the device 100. Hence, the communication performance can be optimized by an automatic adaptation. In other words, the device 100 for BCC using capacitive coupling is able to adapt to the current usage environment, tuning communication to a maximal possible performance. The above described adaptation and determination procedures can be realized by software. Thus, a computer program may be used to implement the embodiment, wherein the computer program comprises program code means for causing a computer to carry out the steps of a method according to the embodiment when the computer program is carried out on a computer. The computer program can be stored on a machine-readable medium like e.g. a digital versatile disk (DVD), a floppy disk etc. A computer program product may comprise the machine-readable medium storing the computer program. A computer can comprise a processing unit, which may be provided on a single chip or a chip module and which can be any processor or computer device with a control unit that performs control based on software routines of a control program stored in a memory. Program code instructions may be fetched from the memory and loaded into the control unit of the processing unit in order to perform the processing steps described in connection with Fig. 2 and Fig. 3 or a subset thereof.

Fig. 4 shows a diagram illustrating a first exemplary arrangement of a system according to the embodiment. A system 400 such as e.g. an adaptive capacitive coupling BCC system can comprise two devices 405 and 410 according to the embodiment. The devices 405 and 410 may be capable of communicating with each other and can e.g. be adaptive BCC interfaces.

The system 400 is an example of a static system. Both of the adaptive BCC interfaces 405 and 410 are respectively integrated into another static device. When a user touches both static devices, the adaptive BCC interfaces 405 and 410 can e.g. be used to connect these two devices or for configuration purposes.

Fig. 5 shows a diagram illustrating a second exemplary arrangement of a system according to the embodiment. A system 500 such as e.g. an adaptive capacitive coupling BCC system may comprise two devices 505 and 510 according to the embodiment. The devices 505 and 510 can be capable of communicating with each other and may e.g. be adaptive BCC interfaces.

The system 500 is an example of a semi-mobile system. One adaptive BCC interface may be integrated into a static device, while the other one can be included in a mobile device worn by a user as a wrist watch, a badge or a similar device. In the exemplary system 500 depicted in Fig. 5, the adaptive BCC interface 505 is included in such a mobile device, while the adaptive BCC interface 510 is integrated in a static device. This may e.g. be used for identification of the user, configuration or personalization of the device.

Fig. 6 shows a diagram illustrating a third exemplary arrangement of a system according to the embodiment. A system 600 such as e.g. an adaptive capacitive coupling

BCC system can comprise three devices 605, 610 and 615 according to the embodiment. The devices 605, 610 and 615 may be capable of communicating with each other and can e.g. be adaptive BCC interfaces.

The system 600 is an example of a mobile system such as e.g. a BAN. The adaptive BCC interfaces 605, 610 and 615 may be integrated into mobile devices in contact with a user's body or worn at the body as an identifier. This can e.g. be used for identification of the user, verification of the presence of devices, configuration or personalization of devices.

Fig. 7 shows a diagram illustrating a fourth exemplary arrangement of a system according to the embodiment. A system 700 such as e.g. an adaptive capacitive coupling BCC system may comprise two devices 705 and 710 according to the embodiment. The devices 705 and 710 can be capable of communicating with each other and may e.g. be adaptive BCC interfaces.

Fig. 7 illustrates an example of a handshake situation, where two users shake hands with each other. The adaptive BCC interface 705 may be integrated into a mobile device in contact with a first user's body or worn at the body as an identifier. The adaptive BCC interface 710 can be integrated into a mobile device in contact with a second user's body or worn at the body as an identifier. If the users shake hands or touch each other in a different way, the adaptive BCC interfaces 705 and 710 can communicate with each other. For example, business card data of the users may be exchanged when they shake hands, or the first user can authorize the second user to access a certain area of premises, a hospital etc. by simply touching the second user. There may be more than two users, which can touch each other simultaneously or one after the other. The above described adaptation procedure 200 may ensure that all devices of a system such as one of the systems depicted in Fig. 4 to Fig. 7 are in an optimal state for sending and receiving for BCC. This can be achieved by a regular adaptation of the resonance frequency of the oscillating unit 150. This adaptation may be based on the measurement of the amplitude of the carrier frequency signal at the coupling unit 110, e.g. capacitive plates.

Fig. 4 to Fig. 7 illustrate four basic usage scenarios for adaptive capacitive coupling BCC. Each of the above described first to fourth exemplary arrangements has a system set-up for an adaptive capacitive coupling BCC solution consisting of two or more devices according to the embodiment (405 and 410 in Fig. 4, 505 and 510 in Fig. 5, 605, 610 and 615 in Fig. 6, and 705 and 710 in Fig. 7). While each of the exemplary arrangements depicted in Fig. 4 to Fig. 7 includes a certain number of devices, these arrangements can respectively comprise a different number of devices. For example, one of the users shown in Fig. 7 or both of them may have two or more devices. The devices can be adaptive BCC modules or may have another form. The adaptive BCC modules may either be used as a single board, e.g. as an identifier, or can be integrated into a device. This allows realizing BCC for all kinds of wireless devices as well as for static devices with integrated adaptive BCC interfaces.

Adaptive capacitive coupling BCC systems such as the system according to the embodiment have possible applications in many domains. In the following, examples in some of the most promising technology fields where these systems could be applied for improving people's life and creating simple and useful digital applications are described.

In the field of consumer electronics, an easy set-up of wireless connections may be enabled by using a BCC system. As the number of available electronic devices increases (home computer, laptop, pocket pc, mobile phone, etc.), the interaction between these devices becomes more and more arduous to set up for common users. Used as a facilitating tool, BCC systems can help to connect several different devices using heterogeneous platforms and protocols. For example, with BCC a Bluetooth connection between a laptop and a mobile phone may be set up by simply touching the two devices, allowing e.g. a photo exchange application.

Another example of applying a BCC system in the field of consumer electronics is theft protection. The fact that people wear more and more expensive mobile devices leads to a strong need of protection against robbery. BCC capable mobile devices can form a BCC network where mobile devices check the presence of other devices in order to instantaneously detect the theft of one of them.

In the automotive field, BCC may be used to realize applications which provide more convenience in the automotive area. Examples in this field are: - car entry, where a car can be opened by just touching it

- theft protection, which allows only specified users, wearing an identification tag, to operate the car

- car configuration/personalization, which takes off the burden from the user to adjust car settings to his/her personal preferences, wherein the user is immediately recognized when entering the car

- intelligent switches inside a car, which recognize whether they are operated by a driver or co-driver.

In the medical field, automatic identification is increasingly required to improve both patient safety and workflow efficiency. Examples of medical applications are access control and patient identification. One application area being very important is secure access to medical devices and hospital information systems. Clinicians frequently access medical systems, for reporting, for patient information retrieval, to change settings of devices or to check vital patient data at the bedside with handheld medical devices. It must be ensured that only authorized personnel have access to patient data and that the data of the correct patient is accessed. Using a BCC system for clinician identification may give clinicians direct authenticated access whenever they approach a monitor, use a mobile device or use other medical equipment that requires authentication before usage. Using BCC for access control requires no extra action of the clinician to authenticate. Using patient identifiers based on BCC allows for: - automatic recognition of patients during medical examinations

- safe and automatic association of devices, sensors and wireless measurements to individual patients

- continuous verification of body-worn devices

- support of medical spot measurements with data collection and automatic inclusion of patient identity.

As a matter of course, a BCC system can also be used in the personal healthcare domain for easy set-up of the network, support for multi-user systems or authentication and security. Other application areas like sports, military, security, wellness etc. are possible. In the above description, the abbreviation "BCC" is used to denote a body- coupled communication. However, usage of this abbreviation is not to be interpreted in any restrictive way, for example such that a specific standard is to be employed. By contrast, any kind of body-coupled communication or other body-based communication can be meant. In summary, the present invention relates to a device, a method, a system and a computer program, wherein the device 100 comprises a coupling unit 110 configured to capacitively couple a body-coupled communication signal onto a human or animal body, and an adapting unit 120 configured to adapt the device 100 to a current usage context. The adaptation can be performed by changing settings of variable-capacitance diodes forming part of an oscillating unit 150. In this way, the capacitance of the oscillating unit 150 may be adjusted so as to compensate for capacitance changes at the coupling unit 110 due to factors such as temperature, humidity, state of body etc.

While the present invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiment.

Variations to the disclosed embodiment can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. For example, the functions of a measuring unit and a control unit can be performed by a single processing unit such as e.g. a microcontroller. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. In this case, the embodiment can be implemented by a computer program product.

Any reference signs in the claims should not be construed as limiting the scope thereof.

Claims

CLAIMS:

1. Device (100; 405, 410; 505, 510; 605, 610, 615) comprising: a coupling unit (110) configured to capacitively couple a body-coupled communication signal onto a human or animal body; and an adapting unit (120) configured to adapt said device (100; 405, 410; 505, 510; 605, 610, 615) to a current usage context.

2. Device (100; 405, 410; 505, 510; 605, 610, 615) according to claim 1, wherein said adapting unit (120) is configured to adapt a carrier frequency and/or amplitude of said body-coupled communication signal.

3. Device (100; 405, 410; 505, 510; 605, 610, 615) according to claim 2, wherein said adapting unit (120) comprises a measuring unit (190) configured to measure a value indicative of said carrier frequency and/or amplitude, and wherein said adapting unit (120) is configured to adapt said carrier frequency and/or amplitude based on a measurement result of said measuring unit (190).

4. Device (100; 405, 410; 505, 510; 605, 610, 615) according to claim 3, wherein said measuring unit (190) is configured to perform a received signal strength indication measurement.

5. Device (100; 405, 410; 505, 510; 605, 610, 615) according to claim 1, wherein said adapting unit (120) comprises an oscillating unit (150) configured to supply said body- coupled communication signal to said coupling unit (110), and wherein said adapting unit (120) is configured to adapt a resonance frequency of said oscillating unit (150).

6. Device (100; 405, 410; 505, 510; 605, 610, 615) according to claim 5, wherein said oscillating unit (150) comprises at least one variable-capacitance diode, and said adapting unit (120) is configured to change a setting of said at least one variable-capacitance diode.

7. Device (100; 405, 410; 505, 510; 605, 610, 615) according to claim 1, wherein said adapting unit (120) comprises a controlling unit (180) configured to control an adaptation performed by said adapting unit (120), a digital-to-analog converter (170) configured to convert a control signal supplied by said controlling unit (180) into a voltage, and a step-up regulator and amplifier unit (160) configured to increase said voltage, wherein said increased voltage is used for said adaptation.

8. Device (100; 405, 410; 505, 510; 605, 610, 615) according to claim 1, wherein said adapting unit (120) is configured to perform an iterative adaptation.

9. Device (100; 405, 410; 505, 510; 605, 610, 615) according to claim 1, wherein said adapting unit (120) is configured to regularly perform an adaptation.

10. Device (100; 405, 410; 505, 510; 605, 610, 615) according to claim 1, wherein said adapting unit (120) is configured to adapt an adaptation interval dynamically.

11. System (400; 500; 600) comprising: a plurality of devices (100; 405, 410; 505, 510; 605, 610, 615) according to any one of the preceding claims, wherein at least two devices of said plurality of devices (100; 405, 410; 505, 510; 605, 610, 615) are configured to communicate with each other.

12. System (400; 500; 600) according to claim 11, wherein at least one device of said plurality of devices (100; 405, 410; 505, 510; 605, 610, 615) is configured to control an adaptation of at least one other device.

13. System (400; 500; 600) according to claim 11, wherein said system is a body area network.

14. Method comprising: capacitively coupling a body-coupled communication signal onto a human or animal body by means of a device (100; 405, 410; 505, 510; 605, 610, 615); and adapting (200) said device (100; 405, 410; 505, 510; 605, 610, 615) to a current usage context.

15. Computer program comprising program code means for causing a computer to carry out the steps of a method according to claim 14 when said computer program is carried out on a computer.