Single communication channel between a contactless frontend device and a transceiver device

FIELD OF THE INVENTION

The invention relates to a method and a device for exchanging data between a contactless frontend device and a transceiver device.

BACKGROUND OF THE INVENTION Nowadays, many smart cards according to the standard ISO/IEC 14443 and

ISO/IEC 18092 are used. These smart cards can e.g. be formed as a SIM (Subscriber Identity Module) with integrated mobile phone functionality. Furthermore, the smart cards can also be formed as a SAM (Secure Access Module) which is a dedicated microprocessing unit for authenticating procedures. In standard applications, the smart cards are directly connected with an antenna via analog signal lines. However, for additional applications of smart cards, particularly when they are employed in SIM modules, it would also be desirable to directly connect existing types of smart cards with near field communication (NFC) devices without the need to provide separate antennas for both the smart card and the NFC device. In order to connect smart cards and NFC devices with each other, a communication channel is foreseen for such purpose.

From standard ECMA-373 a near field communication wired interface (NFC-WI) with two wires is known. Furthermore, from ETSI document SCPt060577 there is known a single wire interface between a smart card and an NFC frontend device.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved single communication channel between a contactless frontend device and a smart card acting as a secure transceiver device. According to the invention there is provided a method for exchanging data between a contactless frontend device and a transceiver device via a single communication channel, comprising the steps: extracting a clock for the data exchange on the communication channel from an external RF-field, and coding of the data via symbols, wherein the symbols comprise status information relating to simultaneous accesses of

contactless card functionalities on the transceiver to the single communication channel.

In this way, simultaneous accesses of contactless card functionalities on the smart card are supported by the inventive method. Due to the fact that a clock period for an "internal" data communication between the contactless frontend device and the smart card is extracted from the external RF field, a well defined real-time inventory procedure being initiated by the external reader is thus supported. In a preferred embodiment of the method according to the invention, a framing of the data on the single communication channel is bit- oriented. Thus, the method is well suited to support real time and anticollision requirements of ISO/IEC 14443 Type A and B, ISO/IEC 18092 or ISO/IEC 15693. According to the invention, there is further provided a single communication channel for an exchange of data between a contactless frontend device and a transceiver device, wherein the data are coded via symbols, wherein the symbols comprise status information relating to simultaneous accesses of contactless card functionalities on the transceiver device to the single communication channel. By means of the inventive single communication channel, advantageously, a multiplicity of contactless card functionalities can simultaneously access the single communication channel without disturbing a well defined information flow between the external reader and a dedicated one out of the emulated card functionalities.

The aspects defined above and further aspects of the invention are apparent from an exemplary embodiment to be described and explained with reference to this exemplary embodiment hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained now in greater detail with reference to the following figures:

Fig. 1 shows in principle a block diagram of an RFID communication system with a contactless frontend device, a transceiver device and a single communication channel arranged in between.

Fig. 2 shows in principle a framing of data and status information being exchanged on the single communication channel.

DESCRIPTION OF EMBODIMENTS

Figure 1 shows in principle a block diagram of an RFID communication system 100 with a contactless frontend device 10. The contactless frontend device 10 can e.g.

be formed as a near field communication (NFC) frontend device being galvanically connected to a contactless terminal, e.g. an antenna 40. By means of the antenna 40, the RFID communication system 100 is able to communicate with an external reader (not shown) via an external RF-fϊeld 50. Via the antenna 40 the contactless frontend device 10 supports a wireless communication being compliant with ISO/IEC 14443 or ISO/IEC 15693 or ISO/IEC 18092. The contactless frontend device 10 is connected to a smart card 20 (e.g. formed as a SIM card) via a single communication channel 30. Preferably, the single communication channel 30 is formed by a single wire. However, in principle it is also possible that the single communication channel 30 is formed as a wireless communication channel between the contactless frontend device 10 and the smart card 20. The smart card 20 acts preferably as a secure transceiving unit, which means that it sends and transmits data to the contactless frontend device 10 via the single commumnication channel 30 in a secure manner with authenticating functionality. Inside the smart card 20 there are arrangeable and executeable a muliplicity of secure emulated contactless card functionalities 21, 22, 23. These functionalities 21, 22, 23 can e.g. be formed as reader and/or payment and/or authenticating functionalities. However, though not explicitely shown, also additional contactless card functionalities are possible to be arrangeable and executeable on the smart card 20. Furthermore, the smart card 20 can also be formed as a secure access module (SAM) with integrated authenticating functionalities. A high speed data connection 60 (e.g. via the USB protocol) is arranged between the smart card 20 and a baseband IC (not shown) of the RFID communication system 100 and is foreseen to exchange high speed data between the smart card 20 and the baseband IC. Due to hardware requirements of said high speed connection 60, an availability of hardware resources on the smart card 20 for the connection to the contactless frontend device 10 may be limited. Therefore, it is desirable to provide an improved single communication channel between the contactless frontend device 10 and the smart card 20.

According to the invention, there is foreseen a single communication channel 30 with improved features over conventional single communication channels. For example, a handling of a conventional RF-communication protocol (which handles, amongst others, a coding and framing of data on the RF field 50, a handling of synchronization-bits, an amount of data bits inside data frames, cyclic-redundancy- checks (CRC) and so on) between the external reader and the transceiver 20 is exclusively and completely handled by the smart card 20, preferably inside the smart card 20. Hence, security relevant portions of the RF- communication protocol are handled inside the smart card 20, thus hampering any harmful

spy-attacks to the RFID communication system 100. In this way, it is advantageously impossible to decouple a handling of the inventory procedure between the contactless frontend device 10 and the smart card 20. An additional protocol according to the invention handles the data exchange on the single communication channel 30 and is performed both by the contactless frontend device 10 and the transceicer 20. For the sake of unambiguousness, said protocol is referenced with CP-protocol ("Common protocol") hereinafter. The CP- protocol has a transparent behaviour for the data of the RF-protocol and has two main challenges. Firstly, it hands over data from the RF-protocol for a data transmission on the single communication channel 30 in a transparent or mirroring behaviour. Furthermore, the CP-protocol handles an exchange of status information between the contactless frontend device 10 and the smart card 20.

Preferably, the single communciation channel 30 offers half duplex performance. Advantageously, said half duplex performance accommodates requirements of the contactless frontend devide 10 and reduces hardware complexities. Therefore, it supports a cost-saving realization of the single communication channel 30. Furthermore, data on the single communication channel 30 are coded via electrical voltage levels. To this end, the contactless frontend device 10 is able to pull an electrical signal level of the single communication channel 30 up to a logical "HIGH" level. In equivalence thereto, the smart card 20 is able to pull a signal condition on the commmunication channel to a logical "LOW" level. In other words, the logical "HIGH" level is always driven by the contactless frontend device 10, whereas the logical "LOW" level is always driven by the smart card 20.

In more detail, during sending clock/direction information and/or data to the contactless frontend device 10, the contactless frontend device 10 drives both the logical "HIGH" and the logical "LOW" level strong. During reception of data from the smart card 20, the frontend device 10 drives a weak "HIGH" level. In correspondence thereto, the smart card 20 drives the "LOW" level strong. Moreover, the "HIGH" level is never driven by the smart card 20. Thus, advantageously, a multiplicity of card functionalities 21, 22, 23 on the smart cards 20 can simultaneously access the single communication channel 30 by maintaining well defined physical and logical conditions on the single communication channel 30. Due to the fact that signal conditions on the single communication channel 30 are represented by electrical voltages, advantageously, standard digital I/O pads may be used on the smart card 20 for a galvanical connection to the single communication channel 30.

Figure 2 shows in principle an exemplary implementation of a data frame FR being transmitted on the single communication channel 30 by means of the CP-protocol. A

fundamental time base tβ of the data frame FR is extracted from the external RF field 50 by the contactless frontend device 10. To this end, the contactless frontend device 10 calculates the time base tβ from received signals from the external reader (not shown) via calculation algorithms. The time base tβ has preferably a length between 60 nanoseconds and 2400 nanoseconds. Thus, a data rate on the single communication channel 30 is in accordance with a data rate on the external RF field 50. Resulting therefrom, advantageously, any kind of data buffering inside the contactless frontend device 10 or inside the smart card 20 is superfluous, as there is no difference between the mentioned data rates. Furthermore, a clock oscillator 25 can be arranged on the smart card 20 and is foreseen to calculate the data rate from the time base tβ on the single communication channel 30. For this calculation, technical requirements to the clock oscillator 25 can be low, so that no high-qualitative clock oscillators 25 are necessary to be implemented in the smart card 20.

A clock period CLK, on which the data transmissison rate inside the data frame FR is based, has a length of 3 x tβ (duty cycle 2/3). The length of the time base tβ is extracted from the external RF field 50, as mentioned above. Furthermore, the data frame FR comprises a direction bit DIR, which defines a direction of a data transmission between the contactless frontend device 10 and the smart card 20. In a case, that the direction bit DIR is "LOW", data are transmitted from the contactless frontend device 10 to the smart card 20. In a case, that the direction bit DIR is "HIGH", data are transmitted from the smart card 20 to the contactless frontend device 10. Due to the fact, that the clock CLK for the single communication channel 30 is extracted from the external RF field 50, a separate clock oscillator inside the contactless frontend device 10 is advantageously superfluous. However, it should be mentioned, that nevertheless any kind of clock oscillator may be foreseen to be implemented in the contactless frontend device 10. The date frame FR further comprises six so called "code units" CU. The code units have a numbering from 1 to 6 (CUl to CU6). As can be seen from Fig. 2, CU6 operates as a most significant bit (MSB) and CUl operates as a least significant bit (LSB) inside a data portion DATA of the data frame FR. The direction bit DIR and each of the code units CUl to CU6 have preferably a length of 3 x tβ.

A meaning of a coding of the code units CUl to CU6, bits bitl, bit2, bit3 of the data frame FR and status information which are all handled by the inventive CP-protocol are illustrated in more detail with respect to the following table:

Table 1

Table 1 shows an exemplary mapping of bits (code units, respectively) inside the data frame FR to digital symbols. As can be seen, bits inside the data frame FR are named as bit 1, bit 2, bit 3 and are formed as a combination two code units. A mapping between the digital symbols and the bits 1, 2 and 3 is as follows: CU6 is the most significant single bit (MSB), CUl is the least significant bit (LSB) inside a data portion DATA of the data frame FR. CU6 (MSB) and CU5 together form bit 1 , CU4 and CU3 together form bit 2 and CU2 and CUl (LSB) together form bit 3.

In case, that for bit 1 the digital symbol "11" is transmitted on the single communication channel 30, this means that no data are to be transmitted in the subsequent data frame FR. Instead, in this case there may be sent numerous status information which are formed of the bits 2 and 3. For example, an initiation of a speed change on the single communication channel 30 can be implemented in this way. Furthermore, also activation/deactivation or idle commands can be transmitted from the contactless frontend device 10 to the smart card 20 or vice versa. In this way, a total amount of 16 different status messages are implementable by the possible 16 states of a combination of bits 2 and 3. Furthermore, in case that for any of the bits 1, 2, or 3 the digital symbol "10" is assigned, this means a transmission of digital data "0". Furthermore, in case that to any of the bits 1, 2, or 3 the digital symbol "01" is assigned, this means a transmission of digital data "1". In a case that the external reader starts an inventory procedure of the contactless card functionalities 21, 22, 23 on the smart card 20, at least two or more of the contactless card funtionalities may respond simultaneously to the inventory procedure. This results in an assignment of the digital symbol "00" to any of the bits 1, 2 or 3 and a transmission of this digital symbol on the single communication channel 30. If any of the bits 1, 2 or 3 shows a content of digital "00", this fact indicates to the external reader, that at least two contactless

card functionalities on the smart card 20 had tried to access the single communication channel 30 simultaneously.

Hence, a state of "collision" is transmitted on the single communication channel 30. From this information, advantageously, the external reader may repeat or cancel its inventory procedure, thus obtaining a timely well defined response behaviour of all of the inventoried secure emulated contactless card functionalities 21, 22, 23 on the smart card 20. Therefore, by means of the single communication channel 30 according to the invention, a response behaviour of numerous contactless card functionalities to an inventory procedure of an external reader can be well structured. Summarizing, the method according to the present invention allows an emulation of more than one contactless card functionality 21, 22, 23 on the smart card 20. Further, also more than a single smart card 20 may be connected to the single communication channel 30, thus also allowing an emulation of more than one contactless card functionality.

As can be easily seen from Figure 2 and table 1, the arrangement of bits to be exchanged on the single communication channel 30 is bit oriented. Resulting therefrom, together with the fact that the data rate on the single communication channel 30 matches exactly the data rate in the external RF field 50, the method according to the invention supports real time- and/or anticollision requirements of ISO/IEC 14443. Further, the single communication channel 30 according to the invention provides a simultaneous transmission of clock, data and control information between the contactless frontend device 10 and the smart card 20. This provides the quality that the clock CLK is extracted from the external RF field 50, thus supporting an avoidance of any kind of data congestion in the RFID communication system 100. Furthermore, by use of the invention any conversions between the conventional RF-protocol and the CP-protocol are superfluous. This saves an overhead of protocol handling and thus further supports the fulfilment of the above mentioned real time- and anticollision requirements. As a result, the external reader, advantageously, does not realize an existence of the contactless frontend device 10 and is able to perform a "direct" communication procedure with the smart card 20.

It should further be observed, that, although the present invention has been illustrated by an embodiment which is an implementation according to ISO/IEC 14443 or ISO/IEC 18092 or ISO/IEC 15693 , the present invention is not limited to these standards, but is also applicable to any RFID communication systems with comparable timing requirements.

Finally, it should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parentheses shall not be construed as limiting the claims. The word "comprising" and "comprises", and the like, does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice-versa. In a device claim enumerating several means, several of these means may be embodied by one and the same item of software or hardware. 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.