Method for operating several RFID readers, and control and monitoring unit for RFID readers

Abstract

The invention relates to a method for operating several RFID readers, to each of which several antennas are connected. The RFID readers (R1-R3) are time-synchronised via a communication network (NET). Antennas (A11-A14, A21-A24, A31-A34) allocated to different RFID readers or the same RFID reader are determined, the detection ranges of said antennas at least partially overlapping. On a graphical user interface of a control and monitoring unit (CFG) connected to the RFID readers via the communication network, the determined antennas with the at least partially overlapping detection ranges are flagged as being in conflict with one another. For the use of each antenna on the respective RFID reader for selecting or writing into RFID transponders, at least one cyclically repeating time window (T1-T4), which is allocated to the respective antenna, is reserved in each case. An allocation of the antennas which are in conflict with one another for the same time window is blocked.

Description

[0001] Description

[0002] Method for operating multiple RFID readers and control and monitoring unit for RFID readers

[0003] The present invention relates to a method for operating several RFID readers, in particular UHF RFID readers, and a control and monitoring unit for RFID readers for carrying out such a method

[0004] Radio transponders can be, for example, RFID tags (radio frequency identification), which are attached to objects to identify or locate them. RFID tags contain a memory unit whose contents can be read or modified using an RFID reader. RFID tags usually contain at least one identifier. To read information stored in RFID tags, RFID readers send out a request signal by generating an alternating electromagnetic field. This alternating electromagnetic field can be used to supply energy, particularly to passively operated RFID tags that do not have their own energy source. The alternating electromagnetic field can also be modulated by RFID tags to transmit a response signal, for example by load modulation or varying their antenna impedance.

[0005] Radio transponder systems for industrial automation systems must meet special requirements regarding reliable data transmission, authenticity of transmitted data, and immunity to interference. Since industrial automation systems are used to monitor, control, and regulate technical processes, particularly in the areas of manufacturing, process, and building automation, disrupted or tampered with radio transponder systems can have serious consequences, in the worst case scenario, even leading to the shutdown of an automation system.

[0006] EP 3 291 488 B1 discloses a method for configuring a communication module of at least one RFID reader, which is connected to a communication network via the communication module. The at least one RFID reader is connected to the communication module via a serial interface. Configuration information comprising at least communication network address information and device type information is stored in a configuration memory unit of the communication module. The configuration information stored in the configuration memory unit of the communication module is transmitted via the serial interface to the at least one RFID reader and stored there in a predetermined configuration memory area.The configuration information stored in the specified configuration memory area of ​​the RFID reader is loaded to configure the replacement communication device when a replacement communication module used instead of the communication module is started after a successful validity check.

[0007] EP 3 290 948 B1 describes a position detection sensor of a position detection system, comprising a first and a second radio transponder, each having a transmitting and receiving unit connected to an antenna and a memory unit for persistent data storage. The first radio transponder has a power supply source and can be placed selectively into a sleep state with reduced energy consumption and into an active operating state with full functionality. In the active operating state, at least one radio connection for position detection is established to at least one first radio transponder reader.The second radio transponder, which can be supplied with energy inductively by a radio transponder reader, is designed and configured to switch the first radio transponder from the idle state to the active operating state upon entry into a detection range of a second radio transponder reader or to transmit position information assigned to the second radio transponder to a server of the position detection system via the second radio transponder reader.

[0008] US 2006 / 022800 A1 and US 2009 / 256683 A1 each disclose a method for operating multiple RFID readers, in which the RFID readers are time-synchronized via a communications network (NET). This involves identifying RFID readers whose detection ranges at least partially overlap.

[0009] UHF RFID systems, which operate in the frequency range from 865 MHz to 928 MHz, have a larger coverage area than HF RFID systems, which operate at 13.56 MHz. If several RFID readers or several RFID reader antennas are located in close proximity to one another, both the positioning and alignment of the antennas must be planned even more carefully to avoid mutual interference, particularly during simultaneous reading processes. This problem can be solved by synchronizing the reading processes of RFID readers, for example by means of a programmable logic controller that controls the RFID readers or by means of a master RFID reader. In this case, synchronization only takes place at the device level, and not per antenna.Furthermore, synchronization is only guaranteed as long as the respective programmable logic controller or the respective master RFID reader is available without interruption. As an alternative to synchronization, RFID readers can generally use the CSMA method to check whether a radio channel is already occupied by other participants before using it. However, this method can only detect collisions when accessing a radio channel, not prevent them. Furthermore, an additional check for existing radio channel occupancy regularly results in performance losses.

[0010] The present invention is therefore based on the object of creating a reliable and high-performance method for operating a plurality of RFID readers, each of which is connected to a plurality of antennas, and of specifying a suitable implementation of the method.

[0011] This object is achieved according to the invention by a method having the features specified in claim 1 and by a control and monitoring unit for RFID readers having the features specified in claim 9. Advantageous developments of the present invention are specified in the dependent claims.

[0012] According to the method according to the invention for operating a plurality of RFID readers, to each of which a plurality of antennas are connected, the RFID readers, in particular UHF RFID readers, are time-synchronized via a communications network. A time-division multiplexing method, in particular Time Division Multiple Access (TDMA), is preferably used in the communications network. The RFID readers advantageously each comprise a communications module which is synchronized by a time synchronization server provided in the communications network, in particular in accordance with Network Time Protocol (NTP) or Precision Time Protocol (PTP). According to the invention, antennas assigned to different RFID readers or to the same RFID reader, whose detection ranges at least partially overlap, are determined.A partial overlap of the detection ranges of multiple antennas occurs particularly when signals from different antennas are received at at least one position, each with a reception field strength above a specified threshold. The antennas with at least partially overlapping detection ranges are identified during a listen-before-talk operating mode of the antennas or RFID readers.

[0013] According to the invention, the identified antennas with at least partially overlapping detection ranges are identified as conflicting with each other on a graphical user interface of a control and monitoring unit connected to the RFID readers via the communications network. A configuration tool for the RFID readers is advantageously provided by the control and monitoring unit.

[0014] For the use of each antenna on the respective RFID reader for reading or writing RFID transponders, at least one cyclically repeating time slot is reserved, which is assigned to the respective antenna. The cyclically repeating time slots are reserved for the antennas of the RFID readers, preferably by means of the control and monitoring unit.

[0015] According to the invention, the time windows are synchronized with time information, in particular NTP or PTP time stamps, within the communications network. Furthermore, assignment of conflicting antennas to the same time window is blocked. In this way, reliable and high-performance synchronization of the RFID readers and avoidance of access conflicts at the antenna level can be realized. In particular, the present invention is completely robust against the failure of a previously conventional programmable logic controller or a master RFID reader used as an alternative for synchronization. In contrast, redundant time synchronization servers are regularly used in communications networks anyway.

[0016] According to a particularly preferred embodiment of the present invention, the antennas of the RFID readers are visualized in a conflict matrix on the graphical user interface of the control and monitoring unit, grouped according to the respective RFID reader. Each antenna is assigned a column and a row within the conflict matrix. The conflicting antennas are advantageously highlighted graphically within the conflict matrix. This enables particularly simple and effective monitoring of potential conflicts.

[0017] Analogously, the assignment of the cyclically repeating time windows to the antennas of the RFID readers is preferably visualized on the graphical user interface of the control and monitoring unit, grouped according to the respective RFID reader, in a time window antenna matrix. Each time window is assigned a column or row within the time window antenna matrix, while each antenna is correspondingly assigned a row or column within the time window antenna matrix. Conflicting antennas can thus be graphically highlighted within the time window antenna matrix, enabling easy monitoring of critical time window assignments.

[0018] The control and monitoring unit for RFID readers according to the invention is provided for carrying out a method according to the preceding embodiments and comprises a graphical user interface. Furthermore, the control and monitoring unit is configured to identify antennas assigned to different RFID readers or to the same RFID reader whose detection ranges at least partially overlap, and to mark the identified antennas with the at least partially overlapping detection ranges as conflicting with one another on the graphical user interface.

[0019] Furthermore, the control and monitoring unit is configured to reserve at least one cyclically repeating time slot for each antenna on the respective RFID reader for reading or writing RFID transponders and to assign it to the respective antenna. Finally, the control and monitoring unit is configured to block the assignment of conflicting antennas to the same time slot.

[0020] The present invention will be explained in more detail below using an exemplary embodiment with reference to the drawing. It shows

[0021] Figure 1 shows an arrangement with several RFID readers, each of which is connected to several antennas, and a control and monitoring unit connected to the RFID readers via a communication network, Figure 2 shows a conflict matrix visualised on a graphical user interface of the control and monitoring unit to represent potentially mutually interfering antennas,

[0022] Figure 3 shows a time window antenna matrix visualized on the graphical user interface of the control and monitoring unit for controlling the allocation of time windows for the use of the antennas.

[0023] The arrangement shown in Figure 1 comprises a plurality of RFID readers R1-R3 which are interconnected via a communications network NET and to which a plurality of antennas A11-A14, A21-A24, A31-A34 are each connected. In the communications network NET, a time-division multiplexing method, for example Time Division Multiple Access (TDMA), is used, with the RFID readers R1-R3 each comprising a communications module which is synchronized by a time synchronization server NTP provided in the communications network NET. In this way, the RFID readers are time-synchronized. This can be done in particular according to the Network Time Protocol (NTP) or the Precision Time Protocol (PTP).

[0024] In addition, a control and monitoring unit (CFG) is provided for the RFID readers R1-R3, which is connected to the RFID readers R1-R3 via the NET communication network. The control and monitoring unit (CFG) provides, in particular, a configuration tool for the RFID readers R1-R3.

[0025] To avoid mutual interference between the antennas A11-A14, A21-A24, A31-A34 that could cause malfunctions or lead to interference when reading or writing to RFID transponders, antennas A11-A14, A21-A24, A31-A34 assigned to different RFID readers R1-R3 or to the same RFID reader R1-R3 are identified, the detection ranges of which at least partially overlap. Such adverse interference is exacerbated when the RFID readers R1-R3 are UHF RFID readers. Partial overlap of the detection ranges of several antennas occurs in particular when signals from different antennas A11-A14, A21-A24, A31-A34 are received at at least one position with a reception field strength threshold value above a predetermined value.

[0026] As indicated in Figure 1 by dashed or dotted lines around pairs of antennas that adversely affect each other, in the present embodiment, the detection ranges of antennas A13 and A22 overlap. Further overlaps exist between antennas A14 and A21, between antennas A23 and A32, and between antennas A24 and A31. Such overlaps can lead to RFID transponders not being read correctly using the affected antennas A13 / A22, A14 / A21, A23 / A32, and A24 / A31. The antennas A13 / A22, A14 / A21, A23 / A32, A24 / A31 with the at least partially overlapping detection ranges can be detected, for example, during a listen-before-talk operating mode of the antennas A11-A14, A21-A24, A31-A34 or the RFID readers R1-R3.

[0027] According to Figure 2, the identified antennas A13 / A22, A14 / A21, A23 / A32, A24 / A31 with at least partially overlapping detection ranges are marked as conflicting with each other on a graphical user interface of the control and monitoring unit CFG. For this purpose, the antennas A11-A14, A21-A24, A31-A34 of the RFID readers R1-R3 are visualized in a conflict matrix M1 on the graphical user interface of the control and monitoring unit CFG, grouped according to the respective RFID reader R1-R3. Each antenna A11-A14, A21-A24, A31-A34 is assigned a column and a row within the conflict matrix M1. The conflicting antennas A13 / A22, A14 / A21, A23 / A32, A24 / A31 are graphically highlighted within the conflict matrix Ml, for example with a different color or brightness or with additional symbols to indicate overlaps.

[0028] For the use of each antenna A11-A14, A21-A24, A31-A34 on the respective RFID reader R1-R3 for reading or writing RFID transponders, at least one cyclically repeating time slot T1-T4 is reserved, as shown in Figure 3, which is assigned to the respective antenna A11-A14, A21-A24, A31-A34. The time slots T1-T4 are synchronized with time information, in particular NTP or PTP time stamps, within the communication network NET. This is preferably done periodically by the RFID readers R1-R3, for example, once every several minutes or hours. In the present exemplary embodiment, the cyclically repeating time windows T1-T4 for the antennas A11-A14, A21-A24, A31-A34 of the RFID readers R1-R3 are reserved by means of the control and monitoring unit CFG.In addition, the control and monitoring unit CFG blocks the assignment of the conflicting antennas A13 / A22, A14 / A21, A23 / A32, A24 / A31 to the same time slot T1-T4.

[0029] The assignment of the cyclically repeating time windows T1-T4 to the antennas A11-A14, A21-A24, A31-A34 of the RFID readers R1-R3 is visualized in a time window-antenna matrix M2 on the graphical user interface of the control and monitoring unit CFG, grouped according to the respective RFID reader R1-R3, as shown in Figure 3. In the present exemplary embodiment, each time window T1-T4 is assigned a column within the time window-antenna matrix M2, while each antenna A11-A14, A21-A24, A31-A34 is assigned a row within the time window-antenna matrix M2. Analogous to the previous explanations, the conflicting antennas A13 / A22, A14 / A21, A23 / A32, A24 / A31 are graphically highlighted within the time window antenna matrix M2.As an alternative to the embodiment shown in Figure 3, each time window T1-T4 can be assigned a row within the time window antenna matrix M2, while each antenna A11-A14, A21-A24, A31-A34 can be assigned a column within the time window antenna matrix M2.

[0030] Based on the time window antenna matrix M2 shown in Figure 3, it can be seen that the conflicting antennas A13 / A22, A14 / A21, A23 / A32, A24 / A31 are each assigned different time windows T1-T4 due to the blocking described above. For example, the antenna A13 is assigned the time windows TI and T3, while the antenna A22 is assigned the complementary time windows T2 and T4. Analogously, the antenna A14 is assigned the time windows TI and T3, while the antenna A21 is assigned the complementary time windows T2 and T4. In addition, the antenna A23 is assigned the time windows T2 and T4, while the antenna A32 is assigned the complementary time windows TI and T3. Accordingly, the antenna A24 is assigned the time slots T2 and T3, while the antenna A31 is assigned the complementary time slots TI and T4.Since antennas A11-A12 and A33-A34 do not conflict with other antennas as shown in Figure 2, all time slots T1-T4 can be assigned to them. The assignments shown in Figure 3 are merely examples to avoid the conflicts shown in Figure 2.

[0031] Therefore, numerous other assignments than those shown in Figure 3 are possible.

Claims

Patent claims 1 . Method for operating several RFID readers, each of which has several antennas connected to it, in which - the RFID readers (R1-R3 ) are time synchronized via a communication network (NET ), - antennas (A11-A14, A21-A24, A31-A34) assigned to different RFID readers and / or to the same RFID reader are determined, the detection ranges of which overlap at least partially, characterized in that - the antennas (A11-A14, A21-A24, A31-A34) with the at least partially overlapping detection areas are determined during a listen-before-talk operating mode of the antennas and / or the RFID readers (R1-R3), - the identified antennas with at least partially overlapping detection ranges are marked as conflicting with each other on a graphical user interface of a control and monitoring unit (CFG) connected to the RFID readers via the communication network, - for the use of each antenna on the respective RFID reader for reading and / or writing RFID transponders, at least one cyclically repeating time window (T1-T4) is reserved, which is assigned to the respective antenna, - the time windows are synchronized with time information within the communication network, - the assignment of conflicting antennas to the same time slot is blocked.

2. Method according to claim 1, wherein there is a partial overlap of the detection ranges of a plurality of antennas (A11-A14, A21-A24, A31-A34) when signals from different antennas are received at at least one position, each with a reception field strength above a predetermined threshold value.

3. Method according to one of claims 1 or 2, wherein the RFID readers (R1-R3) are UHF RFID readers.

4. Method according to one of claims 1 to 3, in which the antennas (A11-A14, A21-A24, A31-A34) of the RFID readers (R1-R3) are visualized on the graphical user interface of the control and monitoring unit (CFG) grouped according to the respective RFID reader in a conflict matrix (M1), wherein each antenna is assigned a column and a row within the conflict matrix, and in which the conflicting antennas are graphically highlighted within the conflict matrix.

5. The method according to claim 4, wherein the assignment of the cyclically repeating time windows (T1-T4) to the antennas (A11-A14, A21-A24, A31-A34) of the RFID readers (R1-R3) is visualized on the graphical user interface of the control and monitoring unit (CFG) grouped according to the respective RFID reader in a time window antenna matrix (M2), wherein each time window is assigned a column or row within the time window antenna matrix and each antenna is assigned a row or column within the time window antenna matrix, and wherein the conflicting antennas within the time window antenna matrix are graphically highlighted.

6. Method according to one of claims 1 to 5, wherein the cyclically repeating time windows (T1-T4) for the antennas (A11-A14, A21-A24, A31-A34) of the RFID readers (R1-R3) are reserved by means of the control and monitoring unit (CFG).

7. Method according to one of claims 1 to 6, wherein a configuration tool for the RFID readers (R1-R3) is provided by means of the control and monitoring unit (CFG).

8. Method according to one of claims 1 to 7, in which a time-division multiplexing method, in particular Time Division Multiple Access, is used in the communication network (NET) and in which the RFID readers (R1-R3) each comprise a communication module which is synchronized by a time synchronization server (NTP) provided in the communication network, in particular in accordance with Network Time Protocol or Precision Time Protocol.

9. Control and monitoring unit for RFID readers for carrying out a method according to one of claims 1 to 8, wherein the control and monitoring unit comprises a graphical user interface and is configured to - to determine antennas (A11-A14, A21-A24, A31-A34) assigned to different RFID readers (R1-R3) and / or to the same RFID reader, the detection ranges of which at least partially overlap, wherein the antennas (A11-A14, A21-A24, A31-A34) with the at least partially overlapping detection ranges are determined during a listen-before-talk operating mode of the antennas and / or the RFID readers (R1-R3), - to mark the identified antennas with at least partially overlapping detection areas as conflicting with each other on the graphical user interface, - for the use of each antenna on the respective RFID Reading device for reading and / or writing RFID transponders to reserve at least one cyclically repeating time window (T1-T3) and to assign it to the respective antenna, - to block the assignment of the conflicting antennas to the same time window.

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