Abstract: Disclosed are combination radio frequency identification (RFID) and electronic article surveillance (EAS) tags and methods of producing such tags. The claimed method is characterized by feeding a first plurality of first type inlays and a second plurality of second type inlays into a laminating machine, wherein each of the first and second type inlays are formed on first and second substrates, respectively; laminating the first type inlays to the second type inlays, thereby forming a plurality of pairs of the first and second type inlays, each of the pairs comprising an RFID inlay and an EAS inlay, wherein the RFID inlay and the EAS inlay of each pair are functionally independent.

Abstract: Various electronic credentials comprising signal activation are disclosed. An electronic credential core comprises a controller configured to maintain an off-state until activated by a received signal during a personalization process. The electronic credential core further comprises an antenna configured to receive a first signal. The energy in the first signal is harvested by a signal interface. The signal interface generates a second signal using the harvested energy of the first signal. The second signal is provided to the controller. The controller transitions to an active state and continuously performs one or more functions until an onboard battery is depleted. By maintaining an off-state until personalization, the electronic credential can be stored without draining power from the battery, extending the shelf life of the electronic credential.

Abstract: A system for remotely monitoring communications equipment is provided that includes at least one communications remote monitoring panel (CRMP) operatively coupled to a plurality of radios. The CRMP is configured for communicating messages that includes queries for information relating to radio functionality to and information responsive to the queries for information from the plurality of radios using one of a plurality of communication specifications. A first of the plurality of radios is configured to communicate using a first communication specification and a second of the plurality of radios is configured to communicate using a second communication specification, and the CRMP is further configured to determine, for each of at least the first radio and the second radio, an applicable communication specification and communicate with the first radio and second radio using the applicable communication specification.

Abstract: The present disclosure provides a RFID terminal and a method of using the same. The RFID terminal includes: a directional antenna module configured to directionally receive a signal transmitted by an electronic tag on an item in a region to be read; a camera configured to collect an image of the region to be read; and a control unit configured to screen information of a target item according to the image of the region to be read captured by the camera.

Abstract: Disclosed is a product anti-theft system having a product anti-theft device configured to be attached to a product to be secured, the anti-theft device having a housing with a connecting portion designed to be connected to the product to be secured and a locking mechanism associated with the connecting portion and having a secured state and a released state. The anti-theft system further includes a release device for transmitting a release signal that triggers transferring of the locking mechanism from the secured state to the released state. Also disclosed is a method of operating an anti-theft device.

Abstract: A tag assignment system, comprising a processing circuitry and being communicatively connected to a data repository comprising records, each of which (i) being associated with a respective distinct animal of a plurality of animals, and (ii) including a Unique Animal Identifier (UAI) associated with the respective distinct animal; the processing circuitry is configured to: substantially simultaneously: (i) obtain an ID reading of an animal identification tag attached to a given animal of the animals from a first tag reading device, wherein the ID reading including the UAI uniquely identifying the given animal, and (ii) obtain a tag reading of a second tag attached to the given animal from a second tag reading device, the tag reading including tag identification information uniquely identifying the second tag; and cause update of the data repository to assign the tag identification information to a given record of the records associated with the UAI.

Abstract: Exemplary embodiments are directed to a method and apparatus for storing data for a batch of manufactured items. The method comprises defining in a processor, using a lower limit identifier and an upper limit identifier, a range of unique item identifiers for the batch, wherein each manufactured item in the batch is allocated a unique item identifier falling within the range. The item identifiers are stored in allocated storage space. If an upper limit identifier is specified for each time interval, an amount of storage specified for all manufactured items during a production time period is calculated as a sum of a first product and a second product, the first product being a product of a production time and a size allocated to each upper limit identifier, and the second product being a product of the production time, a total number of manufactured items, and a percentage of unused identifiers.

Abstract: A terminal device sleep state control method includes: monitoring a wake up signal; and determining, on the basis of a monitoring result of the wake up signal, whether to enter a sleep state from an activated state.

Abstract: In an example, a method comprises communicating with a radio frequency (RF)-enabled asset tag within a space, tracking a location of the RF-enabled asset tag within the space, determining location estimates of the asset tag as the asset tag moves within the space, and accepting identifying information from or about a selected user. The method additionally comprises determining, based on a predetermined correspondence criteria, a correspondence between the asset tag location and a position estimate of an electronic hardware device within the space. Further, in response to determining the correspondence between the asset tag and the electronic hardware device and based at least in part on the identifying information accepted via the electronic hardware device, the method includes associating tracked asset tag location information corresponding to the location estimates of the asset tag as the asset tag moved within the space to identification of the selected user.

Abstract: A modulation scheme conversion device includes: a backscattering tag to which a tag signal is provided; and a tag signal forming unit for forming a tag signal. The modulation scheme conversion device multiplies a radio signal, which has been modulated in a first modulation scheme, and a tag signal, and reconfigures the multiplied signal by using a second modulation scheme, so as to backscatter the reconfigured signal, wherein the reconfiguration is performed in a physical (PHY) layer.

Abstract: The present invention relates to an RFID tagged and identified cookware in robotic or automated cooking system for identification of each one of the cooking vessels throughout the variety of stages of the cooking processes or meal preparation processes in automated or robotic cooking apparatus through an integrated RFID tag.

Abstract: A method of manufacturing an electrical circuit from bulk materials includes the steps of machining a first bulk dielectric material, forming a conductive element, and placing the conductive element on a first side the first bulk dielectric material. The method further includes the step of machining a second bulk dielectric material and placing the second bulk dielectric material on the first side of the first bulk dielectric material and over the conductive element. The first bulk dielectric material and the second bulk dielectric material may be laminated together.

Abstract: A method and apparatus for handling packet duplication based on congestion level of frequency in a wireless communication system is provided. A wireless device configures at least two lower entities associated with an upper entity. A wireless device activates packet duplication in the upper entity for multiple frequencies. A wireless device submits a data unit to at least one lower entity among the at least two lower entities based on a congestion level of at least one frequency among the multiple frequencies. A wireless device performs transmission of the data unit.

Abstract: A tag communication device includes a communication device and one or more control processors configured to cause the communication device to transmit a first command for notifying selection of a wireless tag including an identification code including a mask pattern that is a part of the common portion of identification codes. The one or more control processors are configured to cause the communication device to transmit a second command for requesting a response to the selected wireless tag and to cause the communication device to transmit a third command for requesting rewriting to the wireless tag that transmits data in response to receiving the data transmitted from one wireless tag. The one or more control processors are configured to cause a repeat of transmission of the second command if a third command is transmitted until the third commands are transmitted to each of a predetermined number of the wireless tags.

Abstract: User access to a physical location (e.g., a homes, businesses, or other locations) may be granted for certain limited tasks based on one or more access procedures stored in a registry and associated with an identity of the user. Such access may be given without including an interaction with an owner, administrator, or manager of the location. User individuals may self-identify themselves to an access server or registry after arriving at the premises and receive corresponding access privileges via one or more devices within the premises based on access procedures stored in the access registry. The access procedures may be executed by the access server through communications with access devices within or about the premises and may be tailored based on the type of user individual or type of access requested.

Abstract: A rollable antenna mat for sports timing comprises one or more planar antenna structures connected to one or more transmission lines for conveying signals to and/or from the one or more planar antenna structures. Each of the one or more planar antenna structures comprises a conductive plate positioned above a conductive ground plane. A spacer element is positioned between the conductive ground plane and the conductive plate. The planar antenna structure is configured to generate a radiation field having a main axis that is substantially perpendicular to the conductive plate. The planar antenna structure and a transmission line is embedded in a flexible elongated sheet structure of one or more elastomeric materials, and comprises the embedded one or more planar antenna structures being suitable to be rolled up in a roll, the axis of the roll being substantially perpendicular to the longitudinal axis of the flexible elongated sheet structure.

Abstract: A radio frequency identification integrated circuit for reducing pin counts and an RFID providing method thereof are provided in the present invention. The radio frequency identification integrated circuit includes a first IO pin, a second IO pin and a third IO pin. The method includes determining whether the coil is coupled to the first IO pin, the second IO pin and the third IO pin when the RFID IC is enabled; and determining the identification according to the voltage status of the non-coupled pin and the pins coupled to the coil.

Abstract: According to one embodiment, a wireless tag reading apparatus includes a first communication interface configured to communicate with a first external device, a second communication interface configured to communicate with a second external device, an antenna configured to emit a radio wave to read a wireless tag, and a controller. The controller is configured to identify either (a) the first communication interface as being in communication with the first external device or (b) the second communication interface as being in communication with the second external device. The controller is configured to change a power level of the radio wave emitted by the antenna based on which of the first communication interface or the second communication interface is identified. The controller is configured to read the wireless tag by controlling the antenna to emit the radio wave with the changed power level.

Abstract: In accordance with a first aspect of the present disclosure, a radio frequency identification (RFID) transponder is provided, comprising: a receiver configured to receive a command from an external RFID reader, wherein the command is a first command transmitted by the RFID reader during a communication session and wherein said command comprises a at least one parameter indicative of one or more modifiable settings of the RFID transponder; and a controller configured to modify the settings of the RFID transponder in accordance with a value of said parameter. In accordance with a second aspect of the present disclosure, a corresponding method of operating a radio frequency identification (RFID) transponder is conceived.

Abstract: A noncontact communication medium includes a processing circuit mounted on a substrate having a coil to induce power by action of an external magnetic field applied from an outside, and processing circuit having an internal capacitor; and an external capacitor externally attached to the processing circuit. The external capacitor, the internal capacitor, and the coil constitute a resonance circuit resonating at a predetermined resonance frequency by the action of the external magnetic field. The external capacitor is connected in parallel with the internal capacitor, and the resonance circuit has a Q-value determined in accordance with a characteristic of the external capacitor.

Abstract: RFID tag ICs in a population can adjust the impedance values used to backscatter-modulate reply signals to increase the distribution or spread of backscattered signal parameters, thereby facilitating the recovery of collided tag replies. An RFID tag IC may adjust its impedance value(s) based on a reader command or independently.

Abstract: A device and method are configured to provide a notification of an occurrence of a vehicle accident when an airbag is deployed. The device acquires an intensity of a signal received from a server for at least one communication medium, transmits a notification including information on an occurrence of an accident to the server when an airbag of a vehicle is deployed, and retransmits the notification based on the intensity of the received signal when the transmission of the notification has failed. When the transmission of the notification including the information on the occurrence of the accident has failed because a wireless network communication is not operating correctly, wireless communication connection may be reattempted the appropriate number of times to increase a success rate.

Abstract: A magnetic field induction coupled RFID system for scanning and reading at least one object having an RFID tag or inlay label device attached or embedded therein to impart a unique identity to each of the objects. The RFID tag has two distinct modes of air interface protocol operation, such that the tag is capable of being read at close proximity range by a device utilizing a command-and-control protocol, such as an NFC-protocol compatible smartphone or similarly functioning device, and alternatively by an RFID reader utilizing a different protocol capable of supporting efficient high-speed anti-collision features for enabling fast inventorying at item level of retail store items, warehousing, customs and logistics operations over considerably greater interrogation distances, where both protocols utilize substantially the same carrier frequency.

Abstract: A method includes detecting, by a first near-field communication device, the presence of a second near-field communication device. In a case where the second device is intended to be charged in near-field by the first device, the method further includes adjusting, by a control device, an impedance of an impedance matching circuit forming part of a near-field communication circuit of the first device.

Abstract: A system for processing barcode information provided by the user, which may be used to print and encode RFID-enabled product labels. The system may include a bar code scanner or may include a manual bar code entry interface such as a keyboard and mouse, and may be configured to output a label corresponding to a barcode once the barcode has been scanned, optionally with user customization by an operator and optionally including variable data provided through a variable data module. This system may allow for the calculation of EPC values, the tracking of serial values used in the printing process, exporting of the printing history, and printing and encoding of tag.

Abstract: A load control system may include devices for performing communications for controlling an amount of power provided to an electrical load. The devices may include load control devices that may communicate by transmitting digital messages. A user device having an adjustable wireless communication range may be used for discovering devices, configuring devices, and/or diagnosing devices in the load control system. The user device may detect whether devices are within an established wireless communication range of one another for performing communications. The user device may detect digital messages transmitted from a device and/or digital messages received at a device to determine whether the digital messages are correctly communicated in the load control system. The user device may provide an indication to a user indicating whether a digital message is correctly transmitted or received by a device in the load control system.

Abstract: Aspects of the present invention disclose a method for routing one or more autonomous vehicles to minimize a density of autonomous vehicles and passengers passing through network areas with oversubscribed bandwidth. The method includes one or more processors determining a bandwidth requirement of a first autonomous vehicle. The method further includes determining respective bandwidth requirement for one or more additional autonomous vehicles utilizing a wireless network. The method further includes determining a total bandwidth capacity of one or more nodes of the wireless network. The method further includes determining routing instructions from a current location of the first autonomous vehicle to a destination of the first autonomous vehicle based at least in part on the bandwidth requirement of the first autonomous vehicle and the total bandwidth capacity of the one or more nodes of the wireless network.

Abstract: There are disclosed devices, systems and methods for keyless courier entry into a safe using a courier mobile computing device for receiving and authenticating a courier login and a selection for keyless courier entry into the safe. The safe has a computing device for receiving and authenticating a selection for keyless courier entry into the safe. Upon receiving the authenticated selection for keyless entry, the safe computing device generates and displays a factor code based on a safe's serial number. The courier inputs the factor code into the mobile device. In response to receiving and authenticating of the factor code, the mobile computing device generates and displays a security check code. The courier enters the security check code into the safe computing device, which in response to the entry and upon authenticating the security check code, unlocks the safe.

Abstract: An emitting method, by an emitting device to at least one receiving station, of UWB messages, the emitting device including a simplex communication module for the emitting of UWB messages, a module for receiving wireless electrical energy suitable for receiving emitted electrical energy and for storing the electrical energy received in an electric accumulator, the method including a charging of the electric accumulator by the module for receiving wireless electrical energy, an evaluation of a criterion of sufficient electrical energy for the emitting of a UWB message, when the criterion of sufficient electrical energy for the emitting of a UWB message is satisfied, a selecting of a random emission delay and an emitting of the UWB message, by the simplex communication module, after the expiration of the random emission delay selected.

Abstract: A mobile computing device including a modal antenna is disclosed. The mobile computing device may include a radio frequency circuit and a modal antenna mechanically coupled to a portion of the mobile computing at a location that is remote from the radio frequency circuit. The modal antenna may include a driven element and a parasitic element positioned proximate to the driven element. The modal antenna may be operable in a plurality of different modes. Each mode may be associated with a different radiation pattern. The mobile computing device may include a transmission line coupling the radio frequency circuit to the modal antenna. The radio frequency circuit may be configured to transmit an RF signal over the transmission line to the modal antenna and configured to communicate a control signal to adjust the mode of the modal antenna over the transmission line.

Abstract: Embodiments relate to a method, an apparatus, a computer program, a base station and a vehicle for providing information related to an approaching vehicle. The method comprises Receiving (110) information related to a velocity of a plurality of vehicles. The method further comprises Determining (120) the information related to the approaching vehicle based on the information related to the velocity of the plurality of vehicles. The information related to the approaching vehicle indicates a presence of a vehicle of the plurality of vehicles having a velocity higher than an average velocity of the plurality of vehicles. The method further comprises Providing (130) the information related to the approaching vehicle to at least a subset of vehicles of the plurality of vehicles.

Abstract: A method for providing identification and access with respect to a passive radio-frequency tag in a tag population, including, receiving a command for initiating an inventory round or a command for initiating a tag access, the command including, as a parameter, a number including an identifier of a reader, generating a 16-bit value referred to as first or second binding handle, the first or second binding handle including N juxtaposed bits forming the reader identifier, backscattering the first or second binding handle, receiving an ACK command, analyzing the identification parameter of the ACK command, and in a case where the identification parameter includes the reader identifier then ignoring the ACK command, only tags having the selected inventoried flag value for the session number are inventoried, the first initiating command only including the same inventoried flag for every inventoried tags during a session and wherein the at least other inventoried flag value is never used during the session.

Abstract: A transceiver may wirelessly transmit a communication signal at a first frequency and a sensing signal at a second frequency. The communication signal may include a command that causes a backscatter node to modulate impedance of an antenna, and thereby modulate reflectivity of the backscatter node. The communication signal may also deliver wireless power to the backscatter node. While the impedance is being modulated in response to the command, the transceiver may transmit the sensing signal and measure wireless reflections. The power of the sensing signal may be much lower than that of the communication signal. The transceiver may frequency hop the sensing signal in a wide band of frequencies and take measurements at each frequency in the hopping. Based on the measurements, a computer may determine time-of-flight or phase of a reflected signal from the backscatter node and may estimate location of the backscatter node with sub-centimeter precision.

Abstract: Systems, methods, and computer-executable instructions for reducing network traffic from a beacon reader including detecting a plurality of beacon information from the beacon during a read delay period of time. A distance between the beacon reader and the beacon for each of the two of more beacon information is determined. A combined distance based on the determined distances between the beacon reader and the beacon for each of the plurality of beacon information is determined. A distance moved from the combined distance and the previous distance of the beacon is determined. The distance moved is greater than a predetermined distance threshold. A beacon identifier is transmitted to a remote server based on the distance moved being greater than the predetermined distance threshold.

Abstract: A configuration that achieves stable wireless communication. In this configuration, electrical power according to transmission waves is reliably supplied to a wireless tag serving as a target of wireless communication. A first wireless communication device and a second wireless communication device are provided. Both the wireless communication devices substantially simultaneously transmit transmission waves on different channels separated from each other by a predetermined frequency or more on a frequency band in the frequency axis, when performing wireless communication processing to wirelessly communicate with a wireless tag in a predetermined communication area.

Abstract: Systems, methods, and apparatuses for receiving wireless power using a wireless power receiver client architecture are disclosed. A simplified wireless power receiver apparatus includes an energy storage device and a radio frequency (RF) transceiver including an antenna. Energy harvester circuitry is coupled to the energy storage device and the RF transceiver, and control circuitry is coupled to the energy storage device, the RF transceiver, and the energy harvester. The control circuitry causes the RF transceiver to: establish a connection with a wireless power transmitter (WPT), transmit a beacon signal to the WPT, and receive a wireless power signal from the WPT. The control circuitry causes the energy harvester to deliver at least a portion of energy of the wireless power signal to the energy storage device for storage therein. In some embodiments, a single antenna is utilized both for transmitting the beacon signal and for receiving the wireless power signal.

Abstract: An access control system includes a plurality of physical access control readers that form a reader network which utilizes a first communication protocol. The system includes a plurality of mobile communication devices each having a first communication interface and a second communication interface. The first communication interface enables the mobile communication devices to access a mobile communication network which utilizes a second communication protocol, and the second communication interface enables the mobile communication devices to communicate with the access control readers. The plurality of physical access control readers exchange status information for the plurality of physical access control readers and for the plurality of mobile communication devices over the reader network.

Abstract: A gradient sensing probe system, and method of using same, including a sensing segment which includes a plurality of sensors, a support structure, and an electrical interface having first and second faces. The system further includes a housing, a power source, and an electronics package including a controller and disposed within the housing. The sensing segment is configured to measure external gradients and to exchange data with the controller. The power source is connected energetically to provide power to the sensing segment and the electronics package, and is controlled by the controller.

Abstract: The present application generally relates to battery powered door unlock mechanisms. More specifically, the application teaches an unlock system including a door unlock mechanism, a capacitive circuit having a first time response, a resistive-capacitive circuit having a second time response wherein the second time response is longer than the first time response, a battery for coupling a battery charge to the capacitive circuit and the resistive capacitive circuit in response to a door unlock authentication signal, and a relay for coupling a first charge from the capacitive circuit to the door unlock mechanism in response to the relay being activated by a second charge from the resistive-capacitive circuit after the second time response.

Abstract: A method for operating an access control comprises creating a plurality of wake-up schedules for a wireless transceiver. Each of the plurality of wake-up schedules may be configured to control how frequently the wireless transceiver wakes up to transmit or receive information. Each of the plurality of wake-up schedules for the wireless transceiver may be different from another one or the plurality of wake-up schedules for the wireless transceiver. The method may further comprise automatically switching between the plurality of wake-up schedules for the wireless transceiver such that a duration of time between wake-ups for the wireless transceiver radio is shorter during some predefined times and longer during other predefined times. The duration of time between wake-ups for the wireless transceiver may be configurable by an administrative user via an interface.

Abstract: When a received message is found to be corrupted in 5G or 6G, the receiver can request a retransmission. If only one message element is faulted, retransmitting the whole message may be a waste. Procedures are disclosed for the receiver to determine which message elements are likely faulted by measuring the modulation quality, based on how far each message element's modulation deviates from the states of the modulation scheme. The receiver can then indicate, in an acknowledgement for example, which portion of the message needs to be retransmitted. After receiving that retransmitted portion, the receiver can then produce a merged version by substituting the retransmitted portion in the as-received message, or can select the best-quality elements from the two versions for the merged copy, and thereby eliminate most or all of the faults.

Abstract: A tag enhances vehicle radar visibility of objects by increasing the effective radar cross-section of the object, allowing detection at longer ranges and providing the vehicle/driver with more time to avoid a collision. The tag may include a receive antenna and a bandpass filter configured to receive a signal from the receive antenna and to allow a portion of the frequency range of the signal from the receive antenna through. The tag may also include an amplifier configured to receive and amplify the signal with the portion of the frequency range from the bandpass filter. The tag may further include a transmit antenna configured to transmit the amplified signal. The receive antenna, the transmit antenna, and the amplifier may be configured such that antenna-to-antenna isolation between the receive antenna and the transmit antenna is greater than a gain of the amplifier.

Abstract: A user equipment (UE) comprises a processor configured to execute executable instructions to receive configuration information associated with at least two uplink carriers from a base station, the at least two uplink carriers including a supplementary uplink carrier and a normal uplink carrier, select one of the at least two uplink carriers of the base station if a power of a first downlink reference signal from the base station and measured by the UE is below a first threshold value, select a contention-free random access (CFRA) resource associated with a second downlink reference signal on the selected uplink carrier of the base station if a power of the second downlink reference signal from the base station and measured by the UE is above a second threshold value, and perform a random access procedure with the base station by using the selected CFRA resource over the selected uplink carrier.

Abstract: A computer-implemented method is provided for picking a 16-bit random sequence (RN16) and generating an acknowledgement packet in a tag reading session. The method includes decoding RN16s from signals received by a plurality of antennas by treating signal interference as noise. The method further includes selecting the RN16 from the decoded RN16s based on properties of the decoded RN16s and the signals from which they are decoded in the tag reading session. The method also includes generating the acknowledgement packet based on the selected RN16.

Abstract: A method for employing cycle counting is presented. The method includes interrogating, by an RFID reader, RFID tags by using a plurality of antenna ports, determining, by an activation sequencer, an activation sequence of the plurality of antenna ports that have been enabled, collecting RFID tag responses from each of the RFID tags, and matching one or more of the RFID tag responses to a particular antenna port of the plurality of antenna ports in an activation cycle.

Abstract: A method of handling communication for a communication device of a wireless communication system, wherein the communication device is configured with a plurality of frequency bands, includes the step of: receiving a downlink (DL) control signal from a network of the wireless communication system via a first frequency band among the plurality of frequency bands, wherein the DL control signal indicates whether at least one of the plurality of frequency bands is available or not available.

Abstract: A system including a first device with a surface and an identification feature that includes or encodes machine-readable data related to the surface, and a second device including a sensor and one or more processors coupled to the sensor that are configured to determine a relative displacement of the second device as it is moved along the surface of the first device. The second device receives the machine-readable data related to the surface from the identification features from the first device and configures the second device to determine the relative displacement along the surface differently (e.g., improves displacement tracking) based on the machine-readable data related to the surface.

Abstract: A tracking system uses a mobile reader or scanner that scans, for example through a barcode reader, a passive tag reader, a probe, input, camera, or an active RF tag communication reader, and records item (asset or inventory) data. After being recorded, this item data and other relevant data is sent by radio transmission to a receiver network in the tracking system. The receiver network has at least two receivers (or at least two receiver antennae). The scanner location data, calculated by comparing the signal information at each receiver antenna receiving the radio transmission, is then used to register and record the location data of the scanned item.

Abstract: The present application provides a computer system which allows a user to make available a dataset for analysis by others whilst hiding the contents of the dataset.

Abstract: A monitoring system 22 for a distributed antenna system (DAS) 10 is provided. The DAS comprises central transmitter 12 which is connected by a signal transmission network 14 to a plurality of distributed antenna devices (DAD) 16.1 to 16.n. The network comprises physical branches. Each of the DAD's is connected to a respective sub-branch 14.11 and comprises at least one antenna 18. The antenna is associated with a frequency band having a center frequency fc and an associated wavelength Ac. The monitoring system comprises a central monitoring unit (CMU) 24 which is coupled to the network 14. A monitoring device 28.1 is associated with at least one of the DAD's and permanently mounted a distance d<2?c away from the antenna of the DAD. The monitoring device comprises a controller 30, a transceiver 32 and an antenna 34.