DE102010021656A1 - Method for reading out radio frequency identification tags, involves providing transponder within operating distance of reader, where transponder emits set of data, where data are received by reader - Google Patents

Abstract

The method involves sending a carrier signal in a frequency range of two transponders (1, 2) by an antenna. One of the transponders is provided outside operating distance of a reader, where the transponder obtains energy from the carrier signal and transmits a set of data. The other transponder is provided within the operating distance of the reader, where the latter transponder receives the data directly from the former transponder and emits another set of data including the former set of data. The latter set of data is received by the reader. An independent claim is also included for a transponder comprising a microprocessor.

Description

Transponders, today mainly RFID transponders in the form of RFID tags, are frequently used to track goods along a supply chain, as anti-theft protection in department stores or in production. To read out the individual RFID labels, a reader is required in the vicinity of the read RFID tag.

Passive RFID tags are usually powered from outside via an electromagnetic field to respond. The communication is initiated by the reader. Depending on the technology and frequency used, the maximum distance between the RFID tag and the reader varies, in which the RFID tag can still be supplied with energy from the outside and read out. Therefore, at least one reader must be within read range of the RFID tag so that the RFID tag can be read out.

The invention has for its object to provide a transponder and a method for reading transponders, which provide an alternative to the known from the prior art transponders and methods for reading transponders.

This object is achieved in that an antenna emits a carrier signal in a frequency range of a first transponder and a second transponder. The first transponder, which is out of the range of a reader, gains energy from the carrier signal and sends out first data. The second transponder, which is within range of the reader, receives the first data directly from the first transponder and transmits second data including the first data. The reader receives the second data.

The transponder has a transponder antenna, which is set up to receive a carrier signal and to obtain energy from the carrier signal. Furthermore, the transponder has a microprocessor which is programmed to receive first data directly from a first transponder and to send out second data containing the first data.

The transponders may in particular be RFID tags.

The method and the transponder make it possible to efficiently read with a single reader a plurality of RFID tags that are out of range of the reader. For this purpose, the RFID labels are networked with each other similar to a meshed network or ad-hoc network by simple power antennas that do not require read / write logic and no connection to a computer network, the passive RFID labels , For this purpose, the respective antenna only needs to emit a suitable carrier signal in the frequency range of the RFID tag. The transponders gain energy from the carrier signal for processing and, if appropriate, for forwarding the data.

The process and the transponder make use of the fact that passive RFID tags can not only read but also write information. Furthermore, the method and the transponder are based on the knowledge that the energy supply can not necessarily take place via a reading device but also via a simple antenna.

The method and the transponder save costs because it is possible to dispense with additional readers which are more expensive than simple antennas. Depending on the application scenario, many readers may be saved and replaced by simple antennas.

Furthermore, every RFID tag communicates chaotically with every other RFID tag within its reach. To collision avoidance standard methods such. ALOHA, Slotted ALOHA or Slotted Terminal Adaptive Collection (STAC). As a result, a redundancy is generated, which allows a check of the consistency of the read data. For this purpose, only at different times or data received from different readers data to be compared.

In the method and the transponder, the individual transponders operate as repeaters.

According to a development of the method, the antenna transmits the carrier signal alternately for a first time interval and not for a second time interval. This offers the advantage that when storing the data in a volatile memory in the RFID tags all information is reset regularly, so that a current status is always transmitted to the reader. This is suitable, for example, for an application in which objects provided with RFID tags are transported by a conveyor belt and pass the reader.

Further advantageous embodiments of the invention are characterized by the features of the subclaims.

In the following, embodiments of the invention will be explained in more detail with reference to figures. Show it:

1 a flowchart according to an embodiment of the method

2 a time-ordered flowchart according to an embodiment of the method

3 a diagram with components according to an embodiment of the method

4 the transponder and its components.

1 shows a flowchart for an embodiment of the method. A first transponder 1 For example, an RFID tag starts with a first step 41 by generating a local list from its own record, which contains, for example, an EPC number, a product name or a product category. In principle, the local list can contain a large number of own and foreign data records, but in this case it initially only consists of its own data record. Subsequently, the first transponder transmits 1 his local list in a second step 42 out. The energy for the steps 41 and 42 the first transponder gets 1 from an antenna, which is not connected to any reader, but only designed to the first transponder 1 to provide energy. The first transponder 1 sent out local list is from a second transponder 2 , a third transponder 3 and a fourth transponder 4 receive. These check in a third step 43 whether the records are in the local list of the first transponder 1 already included in their own local lists. If so, go directly to a fourth step 44 about, which consists of not reusing the respective data record. Otherwise, go to a fifth step 45 As a result, the respective data record is transferred to the local list of the respective transponder. Finally, send the second transponder 2 , the third transponder 3 as well as the fourth transponder 4 their respective local list on their part.

2 shows a further aspect of the method in the embodiment. In 2 is shown from top to bottom a time course. An antenna 10 sends during a first time interval 51 a carrier signal 7 out. The carrier signal 7 is from a first transponder 1 which is out of range of a reader 5 located. Because the antenna 10 their carrier signal 7 in the frequency range of the first transponder 1 This can be transmitted from the carrier signal 7 Gain energy and first data 21 send out. These are the ones at 1 described local list, consisting of at least one record of the first transponder 1 , The antenna 10 supplied with its carrier signal 7 also a second transponder 2 , which is the first data 21 directly from the first transponder 1 receives. Alternatively, the second transponder 2 also by a carrier signal of the reader 5 be energized. The second transponder 2 is the same as the first data 21 as in 1 described with the records in his local list, which he uses as second data 22 sending out. The second data 22 in turn are from the reader 5 read.

The antenna 10 is provided with a timer, which the carrier signal 7 at the end of the first time interval 51 off. There follows a second time interval 52 with a carrier signal interruption 8th , The carrier signal interruption 8th leads in the first transponder 1 as well as in the second transponder 2 to an interruption of the power supply. Because the first transponder 1 and the second transponder 2 store their local lists in a volatile memory, the interruption of the power supply leads to a data erasure 9 , This has the advantage that obsolete information is discarded at regular intervals, which makes the method particularly suitable for scenarios with frequent transponder changes in the examined area, for example on an assembly line. The reader 5 always receives an up-to-date picture of all transponders in the transmission range of the antenna available in the examined area 10 , On the second time interval 52 follows again the first time interval 51 by the antenna 10 the carrier signal 7 sending out. The first transponder 1 sends new first data 31 out, which from the second transponder 2 received and new second data 32 further processed and forwarded.

In summary shows 2 that the antenna 10 repeated for the first time interval 51 the carrier signal 7 emits and thus supplies the transponder with energy, which in turn the in 1 Run shown.

3 shows a first antenna 11 , a second antenna 12 , a third antenna 13 and a fourth antenna 14 , The fourth antenna 14 Here is the antenna of a reader 5 , The antennas shown are placed in different locations, for example in a room or in a hall, so that a transponder can be supplied with energy anywhere in the room. The reader 5 is to an infrastructure 6 connected, which for further processing of the reader 5 read information serves. The first transponder 1 The EPC number 123 (EPC stands for "Electronic Product Code") has been stored as a separate data record in a fixed memory. This own record he wears according to the in 1 shown first step 41 in his local list. He sends the local list as the first data 21 according to the second step 42 out 1 to all other transponders ("broadcast"). The second transponder 2 receives the first data 21 and add them, according to the steps 43 - 46 out 1 to his own local list. He then sends these as second data 22 , The third transponder 3 receives the second data 22 , but possibly also the first dates 21 additionally. According to the flowchart 1 It merges all the information into a local list, removing redundant records. He also sends the result as third data 23 again to all transponders in his environment. The fourth transponder 4 receives as the first all records of the surrounding transponder. Its local list, which it extracts from the received records according to the flowchart in 1 is complete and is called fourth data 24 again to all transponders in the vicinity of the fourth transponder 4 sent out. So also receives the reader 5 the fourth data 24 which represent a complete image of all the transponders in the room. The reader 5 receives all information, although it only with the nearest third transponder 3 can establish a radio connection.

As soon as the antennas are switched on, all transponders, as described above, send their local lists to all other transponders in range. The transponders send at random times or at fixed intervals to ensure that all transponders can receive the required information. To collision avoidance standard methods such. ALOHA, Slotted ALOHA or Slotted Terminal Adaptive Collection (STAC).

4 shows a transponder which is suitable for the previously described transponder-to-transponder transmission. The transponder consists of a transponder antenna 61 a microprocessor 62 , a solid store 63 as well as a volatile memory 64 , The transponder's own data record, for example an EPC number, is located in the fixed memory 63 , For example, records that the transponder receives from other transponders are stored in the volatile memory as a local list 64 from. If the transponder is supplied with energy via a carrier signal, it sends out all stored data records. As soon as the energy supply of the transponder breaks off due to the carrier signal, all data records are stored in volatile memory 64 the transponder is deleted automatically.

In the following, a development of the embodiment described above will be explained. The transponders can store their own records in their fixed memory 63 stored secure. As a backup in particular a digital signature is eligible. Accordingly, the transponders collect data records in their local lists, all of which are digitally signed. Here, a transponder can check the signature of received records before accepting them and transferring them to its local list. This requires the microprocessor 62 of the transponder have a corresponding programming and the transponder antenna 61 be supplied with sufficient energy.

According to one development of the exemplary embodiment, the transmitted data and / or the data stored in each transponder are encrypted with a group-based key. Preferably, the data sets are not processed by the microprocessor 62 the transponder decrypted during reception or encrypted when sending, as this would entail a complex programming and a high energy demand. Instead, the records are encrypted, encrypted and sent encrypted.

The required group-based key can be sent directly as identification. However, this is uncertain because it can be eavesdropped. Alternatively, the group-based key can be linked to the data records to be sent via a logical, exclusive or. However, the group-based key can also be hashed into a hash value that is sent out with the records. This is a safe variant. This ensures that only approved transponders in possession of the group-based key can participate in the communication.

The exemplary embodiments described apply equally to different frequency ranges, different form factors and different RFID technologies (for example backscatter and inductive coupling). Furthermore, the variants described can be freely combined with different technological platforms and also with each other. The reader only needs to match the entirety of the received lists and records for duplicates.

Claims (13)

Method for reading out transponders, - in which an antenna ( 10 ) a carrier signal ( 7 ) in a frequency range of a first transponder ( 1 ) and a second transponder ( 2 ), - in which the first transponder ( 1 ), which is out of range of a reader ( 5 ) from the carrier signal ( 7 ) Energy wins and first data ( 21 ), - in which the second transponder ( 2 ), which is within the range of the reader ( 5 ), the first data ( 21 ) directly from the first transponder ( 1 ) and second data ( 22 ), which the first data ( 21 ), and - in which the reader ( 5 ) the second data ( 22 ) receives. Method according to Claim 1, - in which the antenna ( 10 ) the carrier signal ( 7 ) alternately for a first time interval ( 51 ) and for a second time interval ( 52 ) does not send out. Method according to one of the preceding claims, - in which a plurality of antennas ( 11 . 12 . 13 ), including the antenna ( 10 ), the carrier signal ( 7 ), which completely covers an area, so that each transponder ( 1 . 2 . 3 . 4 ) in the area, including the first transponder ( 1 ) and the second transponder ( 2 ), Energy from the carrier signal ( 7 ) be able to win. Method according to Claims 2 and 3, - in which each transponder ( 1 . 2 . 3 . 4 ) in the area own data in a fixed memory ( 63 ) and foreign data which he has received from other transponders ( 1 . 2 . 3 . 4 ), in a volatile memory ( 64 ), - in which each transponder ( 1 . 2 . 3 . 4 ) its own data from its fixed memory ( 63 ) and the foreign data from its volatile memory ( 64 ), while being removed from the carrier signal ( 7 ) Gains energy, and - in which the foreign data in the volatile memory ( 64 ) as soon as the respective transponder ( 1 . 2 . 3 . 4 ) no carrier signal ( 7 ) receives more. Method according to Claim 4, - in which each transponder ( 1 . 2 . 3 . 4 ) its own data in its fixed memory ( 63 ), in particular digitally signed, has been available. Method according to Claim 5, - in which each transponder ( 1 . 2 . 3 . 4 ) Data, which he receives from another transponder ( 1 . 2 . 3 . 4 ), only in its volatile memory ( 64 ) if it is not yet in its fixed memory ( 63 ) or its volatile memory ( 64 ) and verification of a digital signature of the data is successful. Method according to one of Claims 4 to 6, - in which each transponder ( 1 . 2 . 3 . 4 ) only emits data encrypted with a group-based key, whereby the group-based key is sent out with, is linked with the data to be sent via a logical exclusive OR, or is converted into a hash value with a hash function, which is sent out with the data. Transponder, - with a transponder antenna ( 61 ) arranged to receive a carrier signal ( 7 ) and to obtain energy from the carrier signal ( 7 ), and - with a microprocessor ( 62 ) programmed to receive first data ( 21 ) directly from a first transponder ( 1 ) and sending out second data ( 22 ), which contains the first data ( 21 ). Transponder according to claim 8, - with a fixed memory ( 63 ), in which own data can be stored, - with a volatile memory ( 64 ), in which foreign data, which the transponder of other transponders ( 1 . 2 . 3 . 4 ), are storable, - in which the microprocessor ( 62 ) is programmed to send its own data from the fixed memory ( 63 ) and the foreign data from the volatile memory ( 64 ), while the transponder antenna from the carrier signal ( 7 ) Energy gains, and - where the volatile memory ( 64 ) is automatically erasable when no carrier signal ( 7 ) is received more. Transponder according to Claim 9, - in which the microprocessor ( 62 ) is programmed to store its own data in the fixed memory ( 63 ) secured, in particular digitally signed, store. Transponder according to claim 10, - in which the microprocessor ( 62 ) is programmed to receive data from another transponder ( 1 . 2 . 3 . 4 ), only in the volatile memory ( 64 ), if they are not yet in the fixed memory ( 63 ) or the volatile memory ( 64 ) and verification of a digital signature of the data is successful. Transponder according to one of Claims 9 to 11, - in which the microprocessor ( 62 ) is programmed to send only data encrypted with a group-based key, and to send out the group-based key -, - to associate with the data to be sent via a logical exclusive OR, or - to hash it into a hash value and send it with the data. Transponder according to one of claims 8 to 12, - designed as an RFID tag.

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