Cognitive body coupled communication

FIELD OF THE INVENTION

The present invention generally relates to a device, a system, a method and a computer program for reducing an interference sensitivity of a body coupled communication (BCC).

BACKGROUND OF THE INVENTION

BCC is a viable alternative for radio frequency (RF) based communications as a basis for personal-area networks (PANs) and body-area networks (BANs). BCC signals are conveyed over a human or animal body instead of through the air. Therefore, a communication based on such signals is confined to an area close to the body, contrary to RF communications covering a much larger area. 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 and creates possibilities for many applications in the fields of e.g. identification and security. Since lower frequencies than those typically applied in RF-based low range communications can be used, BCC further enables low-cost and low-power implementations of BANs/PANs. Possible application areas of BCC include medical sensor networks, e.g. for wireless patient monitoring, and identification applications, e.g. for access to medical IT systems. Moreover, BCC is currently considered as one candidate for the physical layer technology of BANs in the IEEE 802.15.6 BAN standardization.

BCC signals are transmitted via couplers such as e.g. electrodes, which are placed near or on the body. These couplers transfer a data signal to the body, wherein the transfer can be galvanic or capacitive. An example of a coupler configuration is sketched in Fig. 7 showing a schematic diagram of a BCC system 700. A body communication system setup is illustrated, where a "transmitter" (TX) 705 transmits BCC signals to a "receiver"

(RX) 710 via a person's forearm. Generally though every node of a BCC system acts as both a transmitter and receiver, i.e. as a transceiver (TRX), and communication can take place from everywhere on the body.

The BCC system 700 shown in Fig. 7 comprises the transmitter 705 and the receiver 710 as well as electrodes 715, 720, 725 and 730 for reference or ground (GND) and signal (S) levels. The transmitter 705 is connected to the electrodes 715 and 720, and the receiver 710 is connected to the electrodes 725 and 730. Each of the electrodes 715, 720, 725 and 730 is illustrated as a flat plate in Fig. 7. The transmitter 705 is coupled to the receiver 710 through the part of the forearm extending between them, so as to transmit BCC signals from the former to the latter. Actually, the transmitter 705 is a BCC transceiver acting as a transmitter, and the receiver 710 is a BCC transceiver acting as a receiver.

Fig. 8 shows a schematic diagram of a BCC transceiver 800. The depicted BCC transceiver 800 is a possible implementation of the transmitter 705 and receiver 710 as shown in Fig. 7. It comprises a receiver part 805 and a transmitter part 810. The receiver part 805 includes a reception (RX) front-end unit 815 and a BCC reception (RX) signal detection unit 820. The transmitter part 810 includes a transmission (TX) data generation unit 825, a BCC transmission (TX) signal generation unit 830 and a transmission (TX) front-end unit 835. In addition to these components, the BCC transceiver 800 comprises a switch 840. If the BCC transceiver 800 is acting as a receiver, i.e. is in a reception mode, a BCC signal picked up by couplers 845 and 850 is conditioned using the RX front-end unit 815. The BCC RX signal detection unit 820 applies a detection to the conditioned BCC signal. Data resulting from the detection are output. If the BCC transceiver 800 is acting as a transmitter, i.e. is in a transmission mode, the TX data generation unit 825 generates TX data from incoming data. The BCC TX signal generation unit 830 transforms the TX data into a BCC transmission signal, i.e. generates a BCC TX signal. This signal is passed through the TX front-end unit 835, which could include amplification and filtering, and then transmitted via the couplers 845 and 850. Switching from the transmission mode to the reception mode and vice versa can be effected by the switch 840.

In the BCC technology the human or animal body is used as a transmission medium. It has been shown that the body channel provides a good transfer for frequencies from about 100 kHz up to about 100 MHz, i.e. the optimal transmission frequency band for BCC is between about 100 kHz and 100 MHz. Frequencies below 100 kHz are severely suppressed by the body channel and, therefore, not optimal for transmission. At frequencies above approximately 100 MHz the wavelength is below approximately 3 m. That is, it comes into the range of the length of the human or animal body or parts thereof. Consequently, the body starts to act as an antenna. Thus, there is a possibility that BCC nodes located on different bodies can communicate with each other, using the "body antenna". For higher

frequencies, even the couplers of a BCC system start acting as antennas. Hence, communications can also take place when the human or animal body is not present as a communication medium. Both effects are unwanted, since only devices placed on or near the same body are supposed to communicate. Since BCC is confined to the human or animal body, a BCC system on one body does not create interference for other BCC systems near or attached to other bodies or systems based on different communication technology. However, other communication systems such as e.g. RF wireless systems also use the frequency band from 100 kHz to 100 MHz for communications. Frequency bands in this span are licensed to various wireless systems, including e.g. amplitude modulation (AM) radio, television (TV) broadcasting, amateur radio and different mobile applications. These systems can create some interference for BCC transceivers. Moreover, other electrical devices such as e.g. personal computers and microwave devices might also output electromagnetic radiation in this frequency range and create interference for BCC systems. Thus, it is a drawback of BCC that it is susceptible to interference from RF solutions and other systems using the frequency band of 100 kHz to 100 MHz.

Fig. 9 shows a schematic diagram of an interference scenario 900. The interference scenario 900 illustrates the interference problem in BCC systems. A transceiver 905 is connected to couplers 910 and 915. An antenna 920 emits an interfering signal. Although the couplers 910 and 915 are not tuned to a frequency of the interfering signal, the transceiver 905 can still receive a considerable signal contribution from an interference source such as e.g. a broadcasting system generating the interfering signal transmitted via the antenna 920. That is the case since interference sources like e.g. broadcasting systems generally work at higher transmit power levels than BCC systems. The interference caused in this way results in unreliable BCC communications. Since one of the possible applications of BCC is in the medical domain, where wireless BCC enabled medical sensors are used for monitoring purposes, this is not acceptable.

In more detail, communication systems such as e.g. RF systems can create interference at several places in a BCC system: 1) In a BCC transmitter or BCC transceiver acting as a transmitter: by impinging on transmitter electronics/boards. An interference signal is then transmitted together with a wanted BCC signal.

2) At transmitter couplers, i.e. couplers connected to a BCC transmitter or BCC transceiver acting as a transmitter: these act as "low-gain antennas" and couple the

interference signal together with the wanted BCC signal onto a human or animal body used as a communication medium.

3) At the body: the body is most suitable as an antenna, since its length is closest to wavelengths used by interfering systems such as e.g. broadcasting systems. Further, other objects such as e.g. door frames, metal cabinets, cables, metallic structures etc. in the proximity of the body can also pick up interference signals and couple it to the body.

4) At receiver couplers, i.e. couplers connected to a BCC receiver or BCC transceiver acting as a receiver: these act as "low-gain antennas" and receive the interference signal together with the wanted BCC signal. 5) In a BCC receiver or BCC transceiver acting as a receiver: by impinging on receiver electronics/boards. Since this is close to an actual digital receiver, even a small interference signal can have a serious impact.

That is, the interference can be picked up via a human or animal body, body couplers or transceiver boards/electronics. In general, it can be expected that the most severe sources of interference in the BCC system are those described above under items 3) to 5). The way the inference is generated in the BCC system will likely result in similar interference signals/levels for different BCC nodes on one body.

Fig. 10 shows a schematic diagram of a measurement setup 1000. Two symmetrical couplers 1005 and 1010 illustrated as flat plates are placed parallel and close to a person's forearm, i.e. a human body. They are connected to a probe 1015 with high input impedance, e.g. a HP 1142 A differential probe with the following input impedance: 1 MOhm, 7 pF. The probe 1015 is connected to a spectrum analyzer 1020. A voltage difference between the couplers 1005 and 1010 can be measured by means of the probe 1015 and the spectrum analyzer 1020. Fig. 11 shows a graph 1100 depicting measurement results obtained by the measurement setup 1000 shown in Fig. 10, i.e. a measured spectral characterization of the interference. The x-axis indicates a frequency, and the y-axis indicates a power level. A curve 1105 illustrates the measurement results without the arm. It shows that a noise floor is observable and, hence, there is almost no interference. This is due to the fact that there is symmetry between the couplers 1005 and 1010. A curve 1110 illustrates the measurement results with the arm. It shows that a considerable interference occurs if the arm is placed at or close to the couplers 1005 and 1010. This is caused by the lost symmetry between the couplers, which is used for BCC transmissions. Thus, the human body picks up a

considerable amount of interference in the band of interest, which has to be dealt with in the receiver processing.

It is apparent from the experimental interference characterization as described above with respect to Fig. 10 and Fig. 11 that it would be desirable to reduce the occurring interference. It might be taken into account to characterize the interference on average and design countermeasures based on that. However, this is not very beneficial for the following reason. The use of frequency bands by wireless systems such as e.g. RF systems is very dependent on location and time. Therefore, the experienced interference caused by such systems will not have a similar behavior under different conditions. As a result, countermeasures on the basis of the interference characterized on average will not be sufficient. Thus, it is desired to have a BCC system that can deal with a locally experienced interference.

WO 2007/123343 Al discloses a human body communication method enabling a stable communication when users are exposed to strong RF interference generated at other electronic devices. The stable communication is achieved by determining whether an interference signal exists in a bandwidth of sub-channels and determining a modulation method for modulating the sub-channels, based on the determination whether the interference signal exists. That is, a dynamic allocation method is used, which automatically regulates a number of bits per symbol in a sub-channel.

SUMMARY OF THE INVENTION

It is an object of the present invention to reduce the impact of interference on the performance of a BCC system.

This object can be achieved by a device according to claim 1 and a method according to claim 14.

Accordingly, in a first aspect of the present invention a device is presented. The device comprises a communication portion configured to communicate a body coupled communication signal via a body coupled communication channel, and a sensing portion configured to sense the body coupled communication channel, to adapt a reception mode of the sensing portion based on a sensing result, and to set a communication mode of the communication portion based on the adapted reception mode of the sensing portion. The device implements a cognitive communication technique. It can determine an impact of interference on different reception modes. Based on resulting observations, the device may select a most appropriate communication mode for following data transmissions, which is

optimal for the experienced interference. Thus, a reliability and robustness of the device against interference caused by wireless systems such as e.g. RF systems can be increased. Hence, an improved communication with a reduced error rate may be achieved.

In a second aspect of the present invention the communication portion is configured to transmit a body coupled communication message indicating the communication mode to another device. A communication mode may be determined by one device of a communication system. At least one other device of the communication system can be informed on this communication mode. In this way, all devices communicating with each other may be adjusted to the same communication mode, so that a smooth communication can be achieved.

In a third aspect of the present invention the communication portion is configured to transmit the body coupled communication message in a predefined communication mode ensuring an extra stable communication. A reliable notification of a newly set communication mode to other devices is enabled. Thus, it can be ensured that all devices communicating with each other use the same communication mode.

In a fourth aspect of the present invention the sensing portion is configured to set the communication mode by selecting at least one frequency band of a frequency multiplexing scheme, adjusting a hopping sequence of a frequency hopping scheme, or selecting at least one spreading code of a code spreading scheme. When using a frequency multiplexing scheme, frequency bands experiencing interference above a certain level may be avoided. In case of a frequency hopping scheme, frequencies for which considerable interference occurs can be used less often or omitted in a hopping sequence. When using a code spreading scheme, a longer spreading code can be used if a higher level of interference occurs, or a code out of a codebook can be used that has a minimal spectral correlation with the interference signal. Any of these measures may reduce the impact of the interference. The fourth aspect can be combined with any one of the preceding aspects.

In a fifth aspect of the present invention the sensing portion is configured to repeatedly carry out the sensing and the adaptation until the sensing result is below a target value. Thus, the sensing adaptation may be iterated until appropriate reception settings providing a sufficient reduction of the influence of noise and interference have been found. Hence, an appropriate communication mode can be determined. The fifth aspect may be combined with any one of the preceding aspects.

In a sixth aspect of the present invention the sensing portion is configured to set a communication mode providing a highest data rate from among communication modes

available when the sensing result is below a target value. This enables to obtain a highest data rate possible subject to the condition that a certain interference level can be sustained or a certain level of interference suppression can be achieved. The sixth aspect may be combined with any one of the preceding aspects. In a seventh aspect of the present invention the sensing portion is configured to sense the body coupled communication channel by means of a reception section of the device, the reception section is configured to output an error signal as the sensing result, and the sensing portion is configured to repeatedly carry out the sensing and the adaptation until the error signal has a minimal value. Thus, reception settings enabling a minimization of the error caused by noise and interference may be found. Hence, an optimal communication mode can be determined. The seventh aspect may be combined with any one of the preceding aspects.

In an eighth aspect of the present invention the communication portion comprises a reception section configured to receive the body coupled communication signal and a transmission section configured to transmit the body coupled communication signal, and the communication mode comprises a reception mode of the reception section and a transmission mode of the transmission section. As the communication mode includes a reception mode of the reception section as well as a transmission mode of the transmission section, each of these sections can adjust its settings to the communication mode. The eighth aspect may be combined with any one of the preceding aspects.

In a ninth aspect of the present invention the reception section comprises a reception front-end unit and a reception signal detection unit, the transmission section comprises a transmission signal generation unit and a transmission front-end unit, the reception mode of the reception section indicates settings of at least one of the reception front-end unit and the reception signal detection unit, and the transmission mode of the transmission section indicates settings of at least one of the transmission signal generation unit and the transmission front-end unit. Providing settings of the reception front-end unit and the transmission front-end unit in addition to those of the reception signal detection unit and the transmission signal generation unit enables to adjust all of these components to an appropriate communication mode. This can result in an improved reduction of the impact of interference as compared to the case where only settings of the reception signal detection unit and the transmission signal generation unit are adjusted.

In a tenth aspect of the present invention the sensing portion is configured to carry out the sensing when no body coupled communication signal is communicated via the

body coupled communication channel. This enables to determine the impact of noise and interference on the BCC channel. An appropriate communication mode can be found based on resulting observations. The tenth aspect may be combined with any one of the preceding aspects. In an eleventh aspect of the present invention the sensing portion is configured to carry out the sensing and the adaptation on a regular schedule, when the device is switched on, or when the device or another device cannot perform reliable body coupled communications. In this way, the sensing and adaptation can be performed at an appropriate point in time. The eleventh aspect may be combined with any one of the preceding aspects. In a twelfth aspect of the present invention the communication portion comprises a reception section configured to receive the body coupled communication signal, and the sensing portion is configured to sense the body coupled communication channel by means of the reception section or a further reception section of the sensing portion. Sensing the BCC channel by means of a shared reception section enables to commonly use the same hardware for sensing and reception tasks. As a result, the size, the complexity and the costs of the device can be reduced. The twelfth aspect may be combined with any one of the preceding aspects.

In a thirteenth aspect of the present invention a system is presented. The system comprises a plurality of devices configured to perform body coupled communications, wherein at least one device of the plurality of devices is a device according to the second aspect or third aspect, and wherein at least one other device of the plurality of devices is configured to receive the body coupled communication message indicating the communication mode, and to adjust its communication settings to the communication mode indicated by the body coupled communication message. Devices of the system that communicate with each other can be informed on a newly set communication mode and adjust their settings to the same. Therefore, all of them may use the same communication mode. This enables a smooth communication between the devices.

In a fourteenth aspect of the present invention a method is presented. The method comprises sensing a body coupled communication channel by means of a sensing portion, adapting a reception mode of the sensing portion based on a sensing result, setting a communication mode of a communication portion based on the adapted reception mode of the sensing portion, and communicating a body coupled communication signal via the body coupled communication channel by means of the communication portion. The method implements a cognitive communication technique. It can determine an impact of interference

on different reception modes. Based on resulting observations, a most appropriate communication mode for following data transmissions may be determined, which is optimal for the experienced interference. Thus, a reliability and robustness against interference caused by wireless systems such as e.g. RF systems can be increased. Hence, an improved communication with a reduced error rate may be achieved.

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 can 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 embodiments described hereinafter, by way of example, with reference to the accompanying drawings, in which:

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

Fig. 2 shows a diagram illustrating an example of different communication modes in a frequency multiplexing scheme;

Fig. 3 shows a schematic block diagram illustrating a possible implementation of a mode selection according to the first embodiment;

Fig. 4 shows a schematic block diagram illustrating a basic arrangement of an exemplary device according to a second embodiment; Fig. 5 shows a flowchart illustrating basic steps of an exemplary method according to the first and second embodiments;

Fig. 6 shows an example of a software-based implementation of the first and second embodiments;

Fig. 7 shows a schematic diagram of a BCC system; Fig. 8 shows a schematic diagram of a BCC transceiver;

Fig. 9 shows a schematic diagram of an interference scenario; Fig. 10 shows a schematic diagram of a measurement setup; and Fig. 11 shows a graph depicting measurement results obtained by the measurement setup shown in Fig. 10.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 shows a schematic block diagram illustrating a basic arrangement of an exemplary device 100 according to a first embodiment. The device 100 can comprise a communication part or communication portion 105 and a cognitive part, cognitive portion or sensing portion 110, which may overlap at least partially. The communication portion 105 may include a receiver part or reception section 115 and a transmitter part or transmission section 120. The reception section 115 can comprise a reception front-end unit 125 and a reception signal detection unit 130 such as e.g. a body coupled communication (BCC) reception signal detection unit. The transmission section 120 may comprise a transmission data generation unit 135, a transmission signal generation unit 140 such as e.g. a BCC transmission signal generation unit, and a transmission front-end unit 145. The sensing portion 110 can include a mode selection unit or mode adaptation and setting unit 150. It may also comprise the reception front-end unit 125 and the reception signal detection unit 130. In addition to these components, the device 100 can include a switch or switching unit 155 such as e.g. a transistor.

The device 100 can transmit a BCC signal to at least one other device not depicted in Fig. 1 and receive a BCC signal from such device. That is, the communication portion 105 may communicate a BCC signal via a BCC channel. Such BCC channel can extend from the device 100 to another device and via at least a part of a human or animal body between them. That is, the human or animal body can be used as a communication medium. A BCC signal may be transmitted by transferring it onto the body by means of couplers or coupling units 160 and 165 such as e.g. electrodes, which are placed near or on the body or connected to the same. That is, the coupling units 160 and 165 can be placed on or close to the human or animal body or connected thereto. This may also apply to the device 100. The coupling units 160 and 165 for reference or ground (GND) and signal (S) levels are illustrated as ideal flat plates in Fig. 1 but can also have other forms. For example, they may be circular.

Fig. 1 shows a coupling setup where either the signal level or the reference or ground level is coupled to the human or animal body, while the respective other level is coupled to the "air", "surrounding" or "earth ground". Two isolated coupling electrodes can be situated on, connected to or placed close to the body, where one is directed towards the body and the other one is stacked parallel to it. This kind of coupling setup may provide a vertical field orientation and is often used for capacitive coupling. The coupling setup shown

in Fig. 1 is merely exemplary. Other coupling setups can also be applied. For example, a coupling setup may be used where a coupling unit for the signal level and a coupling unit for the reference or ground level are placed side by side and situated on, connected to or located close to the body. This kind of coupling setup enables coupling of both levels to the body. It can provide a horizontal field orientation and is commonly used for galvanic coupling. Moreover, a coupling setup may be applied where one coupling unit for the signal level is connected to or placed on or close to the body, and a ground plate of e.g. a printed circuit board (PCB) of the device 100 acts as a coupling unit for the reference or ground level. This kind of coupling setup is frequently utilized for capacitive BCC. When a communication takes place, the reception section 115 and the transmission section 120 can perform operations similar to those of the receiver part 805 and the transmitter part 810 of the BCC transceiver 800 depicted in Fig. 8. That is, in a reception operation a BCC signal transmitted by another device via the BCC channel may be received or picked up by the coupling units 160 and 165. This signal can then be processed or conditioned using the reception front-end unit 125. For example, it may be amplified, filtered, down-converted to baseband and converted from an analog signal into a digital signal. The reception signal detection unit 130 may apply a detection to the conditioned BCC signal supplied by the reception front-end unit 125. Data resulting from the detection, i.e. a detected signal, can be output by the reception signal detection unit 130 for usage by a subsequent unit not depicted in Fig. 1, such as e.g. a processing unit.

On the other hand, in a transmission operation the transmission data generation unit 135 may generate transmission data from incoming data supplied by a preceding unit not illustrated in Fig. 1, such as e.g. a processing unit. The transmission signal generation unit 140 can transform the transmission data into a BCC transmission signal, i.e. generate a BCC transmission signal. This signal may be passed through the transmission front-end unit 145 and processed by the same. For example, it can be converted from a digital signal into an analog signal, up-converted from baseband as well as amplified and filtered. A resulting BCC signal may then be transmitted via the coupling units 160 and 165, i.e. coupled onto the human or animal body and transmitted via the BCC channel to another device. Switching from the reception operation to the transmission operation and vice versa can be effected by the switching unit 155. In Fig. 1 a setting of the switching unit 155 for the reception operation and a cognitive or sensing operation described below is illustrated. That is, there is a signal path from the coupling unit 165 to the reception front-end unit 125, i.e. the reception section 115 of the communication portion 105. For the transmission

operation, the switching unit 155 would be set such that there is a signal path from the transmission front-end unit 145, i.e. the transmission section 120 of the communication portion 105, to the coupling unit 165.

The cognitive portion or sensing portion 110 enables a cognitive communication technique that can improve the reliability and robustness of BCC communications against an interference caused by other communication systems such as e.g. (broadcasting) RF systems and other electrical equipment/devices. The challenges of transmitting and receiving data using BCC signals in varying interference environments is different from the typical cognitive radio problem addressed up to now. In cognitive radio systems, a transmitter has to abandon a band when it detects a primary user in the band, in order to prevent usage of the same band by a secondary user causing an interference for the primary user. In the regarded BCC scenario, the purpose is to choose a transmission mode for the transmission operation, and settings of a reception mode for the reception operation that is matched to this transmission mode, which is optimal for an experienced interference. This is enabled by the fact that the available bandwidth is relatively wide compared to the bandwidth needed for the typical low data rate applications in body-based communication systems.

In a cognitive BCC system, a transceiver or BCC node may schematically look like the device 100 depicted in Fig. 1 and operate as follows. First, the cognitive part or sensing portion 110 can be used to sense the communication medium in a cognitive phase. In other words, it may be used to sense the BCC channel. The sensing can be performed when there is no data transmission on the communication medium. A signal picked up by the coupling units 160 and 165 at this time can be due to noise and/or an interference caused by other communication systems such as e.g. (broadcasting) RF wireless systems. It is called interference signal in the following.

The interference signal may be passed through the reception front-end unit 125, which can process or condition it by e.g. filtering, amplifying, down-converting to baseband and converting from an analog signal into a digital signal. The conditioned interference signal may be input to the reception signal detection unit 130, which can output an error signal e as a sensing result. The error signal e may be supplied to the mode selection unit or mode adaptation and setting unit 150, which can be used to select or determine an appropriate or optimal communication mode comprising transmission and reception modes, based on the received interference signal. Possible implementations of the mode determination are discussed in the following.

Alternatively, the communication mode may be determined by another device such as e.g. a BCC node, and the device 100 may receive a message indicating the communication mode from the other device in the cognitive phase and apply the communication mode based on this message, i.e. the one determined by the other device. Subsequently, the sensing portion 110 can communicate the determined communication mode comprising reception and transmission modes to the reception section 115 and transmission section 120, which may use it in a following BCC data transmission and reception. That is, a communication mode of the communication portion 105 can be set. In the reception section 115 parameters of the reception signal detection unit 130, which may be a (digital) baseband receiver, can be adjusted or set based on the determined reception mode. For some transmission schemes it may also be beneficial to adjust the reception front- end unit 125, e.g. by adjusting filters thereof or switching between them. In this case, solely the reception front-end unit 125 or both of the reception front-end unit 125 and the reception signal detection unit 130 can be adjusted. In the transmission section 120 parameters of the transmission signal generation unit 140, which may be a baseband transmitter, can be adjusted or set based on the determined transmission mode. For some transmission schemes it may also be beneficial to adjust the transmission front-end unit 145, e.g. by adjusting filters thereof or switching between them. In this case, solely the transmission front-end unit 145 or both of the transmission front-end unit 145 and the transmission signal generation unit 140 can be adjusted.

As described above, the mode adaptation and setting unit 150 of the sensing portion 110 can be used to select or determine a communication mode comprising reception and transmission modes for the communication portion 105. Different transmission modes, where the sensing portion 110 may choose from, can be achieved in various ways. A first one is frequency multiplexing.

Fig. 2 shows a diagram illustrating an example of different communication modes in a frequency multiplexing scheme, where the BCC channel spanning the frequency band from 100 kHz to 100 MHz is subdivided in 10 parallel (non-overlapping) frequency bands. One communication mode now consists of using one out of these 10 bands, wherein this sub-band may be the one with least interference. This can for example be implemented by using one out of a set of 10 different carriers both for up-conversion in the transmission section 120 and for down-conversion in the reception section 115. To reduce the impact of noise and interference, also filters in the transmission front-end unit 145 and the reception front-end unit 125 can be adjusted to the chosen mode.

Data can also be transmitted in different bands simultaneously, to increase robustness by using redundancy. For example, bands 1, 3, 8 and 10 may simultaneously be used to transmit the same data, while other bands are not selected since they receive interference above a certain level. Alternatively, the data rate can be scaled based on the (number of) selected bands. That is, the more bands experience an interference level below a given threshold, the higher the data rate. In such a configuration every band may be used to transmit independent data.

A second way to create different transmission modes applicable in this context is frequency hopping. Different transmission modes can be achieved in a frequency hopping scheme by adjusting a hopping sequence by using the sensing portion 110. Frequencies where there is considerable interference may for instance be used less often in the hopping sequence or be omitted from the same. That is, frequencies or frequency bands with a high level of interference can be avoided.

A third way to create different transmission modes is code spreading. In the code spreading scheme, the spreading codes can effectively shape the transmission spectrum on the transmission side. Similarly, at the reception side correlation with the spreading codes may achieve a suppression of frequency components not related to the transmitted code. Thus, spreading codes least affected by an interference can be selected in order to reduce the influence of the interference. In contrast to the frequency multiplexing scheme illustrated in Fig. 2, the spectra achieved by the spreading codes may generally be overlapping.

The sensing portion 110 can select the code out of the spreading codebook that is least affected by the interference. That is, the code that is the most orthogonal to the interference may be chosen.

The data rate can also be scaled in such a solution by applying n codes that are most orthogonal to the interference, where these codes are preferably orthogonal to each other. The data rate may further be scaled by using spreading codes with different code lengths. That is, when the level of interference is low, a short spreading code can be used, and when it is high, a longer spreading code may be used. The advantage of longer spreading codes consist in that they provide a better spectral shaping and, thus, yield a better noise and interference suppression at the receiver. However, this is achieved at the cost of a reduced data rate.

Fig. 3 shows a schematic block diagram illustrating a possible implementation of a mode selection according to the first embodiment. It depicts the cognitive part of the device 100 in more detail. A cognitive portion or sensing portion 300 corresponds to the

sensing portion 110 of the device 100 shown in Fig. 1. The sensing portion 300 can comprise a reception front-end unit 305, a reception signal detection unit 310 such as e.g. a baseband BCC reception unit, and a mode selection unit or mode adaptation and setting unit 315, respectively, which correspond to the reception front-end unit 125, the reception signal detection unit 130, and the mode adaptation and setting unit 150 of the sensing portion 110, respectively. The sensing portion 300 is the part of the cognitive BCC system that may determine a transmission/reception mode to be applied, i.e. the mode selection algorithm.

The mode selection can be effected in the following way. An input interference signal may be fed into the reception front-end unit 305, which can process or condition the interference signal by e.g. filtering, amplifying, down-converting it to baseband and converting it from an analog signal into a digital signal. The reception signal detection unit 310 may be an adaptive receiver, which can change its reception mode based on an output of the mode adaptation and setting unit 315 and output an error signal e as a sensing result. Since the mode selection is applied when no BCC transmissions are occurring, ideally e equals zero. However, actually there is a non-zero error signal due to noise and interference. The power of e, denoted by P _e , may be a measure of the level of noise and interference experienced by the cognitive BCC system. The power P _e can depend on a configuration of the used receiver. Consequently, when the receiver is optimally configured, P _e and the influence of the noise and interference may be minimized. The mode adaptation and setting unit 315 can select or set a new reception mode for the reception signal detection unit 310, i.e. adapt the same, based on the power of the error signal e. In some schemes also the reception front-end unit 305 may be adapted based on P _e . Subsequently, again the power of the error signal e can be measured and a new reception mode set. This may be iterated until appropriate or optimal reception settings have been found, which can be the case if the error signal e or the power P _e thereof is below a target value such as e.g. a certain threshold. That is, the sensing of the BCC channel and the adaptation of the reception mode can be repeatedly carried out until the sensing result is below the target value. In this way, an appropriate reception mode may be determined.

Every reception mode relates to a corresponding transmission mode. Thus, a transmission mode can be chosen if an appropriate reception mode has been determined as described above. For example, for a code spreading setup the receiver is a correlator-based receiver. The adaptation of the baseband receiver consists of choosing another spreading code to correlate with. For example, all codes out of a codebook can be applied for correlation, and the one yielding the smallest P _e may be chosen as an optimal reception

setting or reception mode. That is, a code out of a codebook can be selected that has a minimal spectral correlation with the interference signal. When there is a tradeoff between data rate and interference robustness, and codes of different lengths can be applied, one would not choose the code yielding the smallest P _e , but the shortest spreading code yielding a P _e smaller than a target error signal power level. This enables to obtain a highest data rate possible subject to the condition that a certain interference level may be sustained or a certain level of interference suppression may be achieved. Thus, a higher data rate can be achieved while still reducing the interference sensitivity to an acceptable level. Once a code has been chosen, the appropriate transmission mode may be known. In other words, the transmission mode can be selected based on a determined appropriate reception mode. That is, an appropriate communication mode comprising reception and transmission modes may be set based on an adapted reception mode providing sufficient interference robustness, which can be the case if the power P _e is below a target value.

After this has been carried out, the device 100 may adjust its communication settings, i.e. transmission and reception settings, to the chosen transmission mode and use it for following data transmissions. In the code spreading setup this means that the selected spreading code for the reception processing can also be used to spread the data in the transmission processing.

The device 100 applying the sensing may be adjusted as a result of the above- described procedure. Thus, it can use a suitable communication mode. However, other devices of a BCC system or body-area network on a human or animal body may not be aware of the adjustment. Anyway, all the devices should use suitable communication modes in order to be able to communicate with each other. That is, all the devices should use the same communication mode or at least communication modes compatible with each other. A first approach may be that all devices of the body-area network use the same sensing mechanism and independently make their decisions as to a communication mode to be utilized. That is, all the devices can use the sensing mechanism as described above for the device 100 and respectively set a communication mode based on a sensing result. However, the reliability of this approach may be low. At least one of the devices can choose a different communication mode, since several communication modes may yield a similar P _e . Thus, there is a certain probability that at least one of the devices is set to a communication mode that is not compatible with the communication modes of the other devices. For example, two devices may perform the above-described procedure. If a first device selects a first reception mode yielding a first power P _e j, and a second device selects a different second reception

mode yielding a second power P _e2 similar to P _e j, both of P _e j and P _e2 can be below a given threshold in spite of the different reception modes. As a result, the first and second devices may be set to different communication modes not compatible with each other.

A second approach can be to communicate a communication mode determined by a single device to all other devices in the body-area network. Hence, one device such as e.g. the device 100 shown in Fig. 1 may determine a new communication mode, i.e. new communication settings, and then communicate it to the other devices. This can be achieved by transmitting a message such as e.g. a BCC message indicating the new communication mode to the other devices. Subsequently, all devices may adjust their settings to the new communication mode. This approach may be more reliable than the first one. For an increased reliability, it is quite important that all the other devices receive the message indicating the new communication mode. This can be achieved by transmitting the message in a very reliable communication mode, i.e. a communication mode ensuring an extra stable communication. One option may be to use a fixed or predefined communication mode providing the highest reliability. For example, for a code spreading setup a very long spreading code can be applied, which may provide a low data rate, but at least high reliability.

Another point is when the sensing/adaptation should take place. There are several possibilities. A first option can be to carry out the sensing and adaptation on a regular schedule, e.g. once every 5 minutes. This may for instance be scheduled in a communication protocol, to make sure that no device is transmitting in the same body-based network. That is, the sensing and adaptation can be triggered at a time where none of devices in one body-area network or BCC system performs a transmission. A second option may be to perform the sensing and adaptation when at least one of the devices in the body-area network or BCC system cannot perform reliable BCC communications any more, which can e.g. be indicated by missed acknowledgements. In this case also e.g. a communication protocol can be used to ensure that no device in the same body-based network is transmitting when the sensing and adaptation are effected. A third option may be to carry out the sensing and adaptation when the system is switched on, i.e. when the devices are switched on. By means of the above-described adaptation protocol all devices of a body- area network or BCC system can respectively be set to a suitable communication mode at an appropriate point in time. In this way, an improved communication with a reduced error rate can be achieved.

Fig. 4 shows a schematic block diagram illustrating a basic arrangement of an exemplary device 400 according to a second embodiment. The device 400 may comprise a communication part or communication portion 405 and a cognitive part, cognitive portion or sensing portion 410. The communication portion 405 can include a receiver part or reception section 415 and a transmitter part or transmission section 420. The reception section 415 may comprise a reception front-end unit 425 and a reception signal detection unit 430 such as e.g. a BCC reception signal detection unit. The transmission section 420 can comprise a transmission data generation unit 435, a transmission signal generation unit 440 such as e.g. a BCC transmission signal generation unit, and a transmission front-end unit 445. The sensing portion 410 may include a further reception section 470 comprising a further reception front- end unit 475 and a further reception signal detection unit 480, and a mode selection unit or mode adaptation and setting unit 450. In addition to these components, the device 400 can comprise a switch or switching unit 455.

The reception front-end unit 425, the reception signal detection unit 430, the transmission data generation unit 435, the transmission signal generation unit 440, the transmission front-end unit 445, and the mode adaptation and setting unit 450, respectively, basically correspond to the reception front-end unit 125, the reception signal detection unit 130, the transmission data generation unit 135, the transmission signal generation unit 140, the transmission front-end unit 145, and the mode adaptation and setting unit 150, respectively, of the device 100 shown in Fig. 1. This also applies to couplers or coupling units 460 and 465 that correspond to the coupling units 160 and 165 shown in Fig. 1. Therefore, these components and their functionality are not discussed in detail again. Rather, merely differences are described in the following.

The device 400 according to the second embodiment differs from the device 100 according to the first embodiment in that the sensing portion 410 can have its own reception section 470 rather than sharing the reception section 415 with the communication portion 405. That is, the communication portion 105 and the sensing portion 110 of the device 100 may commonly use the reception front-end unit 125 and the reception signal detection unit 130 of the reception section 115 for both of receiving a BCC data signal and sensing the BCC channel. On the other hand, the communication portion 405 of the device

400 can use the reception front-end unit 425 and the reception signal detection unit 430 of the reception section 415 for receiving a BCC data signal, and the sensing portion 410 of the device 400 may use the further reception front-end unit 475 and the further reception signal detection unit 480 of the further reception section 470 for sensing the BCC channel.

The switching unit 455 can have three different switching positions for the reception operation, the transmission operation and the sensing operation. Switching between these operations or operation modes may be effected by the switching unit 455. In Fig. 4 a setting of the switching unit 455 for the reception operation is illustrated. That is, there is a signal path from the coupling unit 465 to the reception front-end unit 425, i.e. the reception section 415 of the communication portion 405. For the transmission operation, the switching unit 455 would be set such that there is a signal path from the transmission front-end unit 445, i.e. the transmission section 420 of the communication portion 405, to the coupling unit 465. For the sensing operation, the switching unit 455 would be set such that there is a signal path from the coupling unit 465 to the further reception front-end unit 475, i.e. the sensing portion 410.

In the sensing operation, an interference signal picked up by the coupling units 460 and 465 can be passed through the further reception front-end unit 475, which may process or condition it by e.g. filtering, amplifying, down-converting to baseband and converting from an analog signal into a digital signal. The conditioned interference signal can be input to the further reception signal detection unit 480, which may output an error signal e as a sensing result. The error signal e can be supplied to the mode adaptation and setting unit 450. The latter may be used to select or determine an appropriate or optimal communication mode comprising transmission and reception modes, based on the interference signal. This can be achieved in the same manner as described above with reference to Fig. 3. However, now the front-end unit 305, the reception signal detection unit 310, and the mode adaptation and setting unit 315, respectively, correspond to the further reception front-end unit 475, the further reception signal detection unit 480, and the mode adaptation and setting unit 450, respectively. Fig. 5 shows a flowchart 500 illustrating basic steps of an exemplary method according to the first and second embodiments. The method comprises a step S505 of sensing a body coupled communication channel by means of a sensing portion, a step S510 of adapting a reception mode of the sensing portion based on a sensing result, a step S515 of setting a communication mode of a communication portion based on the adapted reception mode of the sensing portion, and a step S520 of communicating a body coupled communication signal via the body coupled communication channel by means of the communication portion.

Fig. 6 shows an example of a software-based implementation of the first and second embodiments. Here, a device 600 comprises a processing unit (PU) 605, which may

be provided on a single chip or a chip module and which may 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 (MEM) 610. Program code instructions are fetched from the MEM 610 and loaded into the control unit of the PU 605 in order to perform processing steps such as those described in connection with Fig. 5. The processing steps of the blocks S505 to S520 may be performed on the basis of input data DI and may generate output data DO, wherein the input data DI may correspond to e.g. a sensed interference signal, and the output data DO can correspond to e.g. a set communication mode.

Applications of the above-described cognitive BCC solution are e.g. in the field of identification, security and medical body-area networks. Thus, the application domain may be in healthcare and lifestyle. Other application areas like consumer electronics, the automotive field, sports, military, wellness etc. are possible. In the healthcare field, it can be used e.g. for patient monitoring, where it allows for

- automatic recognition of patients during medical examinations; - safe and automatic association of devices, sensors and wireless measurements to individual patients;

- automatic pairing of wireless sensors on one patient;

- continuous verification of body- worn devices;

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

In summary, the present invention relates to a body coupled communication (BCC) cognitive solution, where a BCC device can be used to sense a BCC medium e.g. when no data transmissions are taking place. Based on resulting observations about an influence of occurring noise and interference on different reception modes, the BCC device may decide on an optimal transmission mode. Subsequently, this transmission mode can be applied during following BCC data communications. Further, the chosen transmission and reception modes may be shared between different BCC devices in a body-area network. Thus, the reliability of communications in the body-area network can be increased.

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 embodiments.

Variations to the disclosed embodiments 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. 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 capable of controlling a processor to perform the claimed features can 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. A computer program product for a computer can comprise software code portions for performing e.g. processing steps such as those described in connection with Fig. 5 when the computer program product is run on the computer. The computer program product may further comprise a computer-readable medium on which the software code portions are stored, such as e.g. an optical storage medium or a solid-state medium.

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