Source: https://patents.google.com/patent/WO2002037257A1/en
Timestamp: 2018-07-18 15:25:40
Document Index: 437495731

Matched Legal Cases: ['art 180', 'art 0', 'art 0', 'art 180', 'art 0', 'art 180']

WO2002037257A1 - Method and device for transmission of data in an electronic shelf labeling system - Google Patents
Method and device for transmission of data in an electronic shelf labeling system
WO2002037257A1
WO2002037257A1 PCT/SE2001/002396 SE0102396W WO2002037257A1 WO 2002037257 A1 WO2002037257 A1 WO 2002037257A1 SE 0102396 W SE0102396 W SE 0102396W WO 2002037257 A1 WO2002037257 A1 WO 2002037257A1
PCT/SE2001/002396
A method for creating synchronized transmission of messages in a wireless electronic shelf labeling system comprising at least two transmitters, a plurality of receiving label-units and a central processing unit capable of issuing messages to be transmitted via said transmitters. Wherein a first step involves determining, for each transmitter, the signal delay between issuing of a message at the central processing unit and transmission of the message from the transmitter. Wherein a second step involves actively delaying, in response to said determined signal delay, transmission from the individual transmitters such that synchronized transmission from all transmitters is achieved. The present invention further relates to a wireless electronic shelf labeling system and a transmitter for such a system.
Method and device for transmission of data in an electronic shelf labeling system.
The present invention relates to a novel method for creating synchronized transmission of messages in a wireless electronic shelf labeling system and a novel transmitter for such systems.
Today, systems, in which the price indicating items of information are stored in a central system computer, are introduced in greater retail stores, which computer, in turn, provides the cash-point locations with price indicating items of information related to various articles. The cashier normally reads, usually by means of an optical reading device, a unique bar code, the so-called EAN code, which is present on each article. Through this code the cash register thereby obtains the current price information of the article in question from the central system computer.
Common to such systems is that the transmission of information should be achieved wireless in order to obtain a flexible price-marking system. Such transmission is suitably performed by means of radio or light waves. Preferred radio waves are within the short wave range, mainly due to bandwidth regulations. Preferred light waves are within the range of non- visible light, e.g. IR-light as used in prior art for various remote control devices to control electronic or electrical apparatuses, such as TV-sets etc.
Electronic Shelf Labelling (ESL) systems in retail environments using -wireless transmission of data from transmitters to electronic labels (EL) commonly comprise a Base Station (BS) to which a number of transceivers are connected, which BS is capable of issuing messages to be transmitted via said transmitters. The BS is in turn connected to and controlled by a central processing unit, and in special embodiments the BS may even be integrated in the central processing unit. Large systems may further comprise several BS, all connected to the central processing unit. With Transciever (TRX) is meant a combined transmitter and receiver device for electromagnetic radiation (like radio, IR etc) or sound waves or other physical means of distributing signals.
Pig. 1 shows a schematic view of a typical ESL system 10 wherein eight TRX 20 are connected to a BS 30. The TRX 20 is typically connected to the BS 30 by a signal distribution line 40, such as a twisted pair-cable, a coaxial-cable or the like. The coverage area 50 from a single TRX 20 is shown by the solid line, but to obtain maximum coverage, the TRXes are arranged such that constructive interference of signals is used to obtain the required signal-level in the intermediate regions 60 between the coverage areas 50 of two adjacent TRX 20. Fig. 2a shows the principle of constructive interference of signals from two spaced apart TRX 20. The required signal level is shown by LI.
However, as communication frequencies are getting higher, due to a demand for higher transmission capacities and other factors, problems associated with destructive interference or pulse-broadening often arise in the intermediate regions 60. This phenomenon is illustrated in fig. 2b wherein the part of the resulting pulse that exceeds LI cannot be detected as a pulse at the receiving end.
The main reason for destructive interference in such system is non-synchronous transmission from transmitters with adjacent coverage areas. One main contributor to non-synchronous transmission is delay in distribution lines 40 of different lengths.
The object of the invention is to provide a new method for providing synchronized transmission of messages in a wireless electronic shelf labelling system, which overcomes the drawbacks of the prior art. This is achieved by the method for creating synchronized transmission of messages in a wireless electronic shelf labelling system as defined in claim 1 , and the transmitter for a wireless electronic shelf labelling system as defined in claim 4.
Embodiments of the invention are defined in the dependent claims. Brief description of the figures
Fig. 1 shows a schematic view of a typical ESL system.
Figs. 2a and 2b show the principle of constructive and destructive interference of signals from two transmitters respectively.
Fig. 3 shows si schematic view of an active delay unit in the form of a shift register.
Figs. 4a and 4b show another aspect of the invention.
Figs. 8a and 8b show another aspect of the invention.
Figs. 9a and 9b show another aspect of the invention.
Referring again to fig. 1, the physical distance between the BS 30 and different TRX 20 differ over a wide range and hence the length of the distribution lines 40 used to connect each TRX 20 with the BS 30 varies over a wide range. As is shown in fig. 1 the TRX 20 may be connected by a direct line to the BS 30 or in series with one or more other TRX 20.
For example, if the distribution line is represented by a conventional twisted pair cable actual delay times are in the order of 50 ns for a difference in cable length of 10 m. For transmissions with pulse-rates above 1MHz each pulse have a duration that is less than 500 ns. Hence, a difference in cable length in the order of 50 m between two adjacent TRX will result in a delay of 250 ns in the intermediate region 60, which is not tolerated by many receiving units.
More precise a method for creating synchronized transmission of messages in a wireless electronic shelf labelling system comprise the following steps:
• determining, for each transmitter, the signal delay between issuing of a message at the central processing unit and transmission of the message from the transmitter; • actively delaying, in response to said determined signal delay, transmission from the individual transmitters such that synchronized transmission from all transmitters is achieved.
As is clear from above the step of actively delaying the transmission is preferably performed at the TRX 20 by an active signal delay unit, but other embodiments may give the same result, such as delaying the transmission for each TRX 20 already in the BS 30. For systems wherein all TRX 20 are connected directly to the BS 30 similar active signal delay units may be arranged at the outputs from the BS 30.
The active delay unit may be in the form of a shift register or a commercially available delay circuit. Fig. 2 shows one exemplary embodiment of an active delay unit, in the form of a shift register. In this embodiment the input signal from the BS 30 is connected to a shift register 70 which length determines the delay range. The shift register has a serial input 80, a clock input 90 and a number of parallel outputs 100. For each clock pulse, the input data is shifted one step in the shift register 70. For each step in the shift register 70 the signal is delayed a predefined amount of time. The active signal delay parameter is set in a multiplexer 110, and it defines from which parallel output 100 the signal is be read and thereafter provided as an output from the multiplexer 110.
To achieve reliable communication between the BS 30 and the TRX 20 a system for error detection is proposed. The distribution line between a BS and a TRX (in general; between to units) may in some cases be a Front End LAN (FEL) cable, which is a cable that use balanced pairs for signal transmission. A balanced pair is a pair A and B of conductors that always have opposite level. A > B is interpreted as a logical one and A < B is interpreted as a logical zero. There is one pair A/B for transmit and one pair A/B for receive between the units.
To detect errors in the FEL cable the remote driver forces A > B in idle state. A local line termination in the receiver end forces A < B. The line termination is weaker than the driver. Then, if cables A and B are connected, A > B is measured at the receiver end indicating a proper cable. If cable A and/or B is broken A < B or A = B will be measured at the receiver end indicating a cable error.
At the transmitter end a remote strong termination forces A > B. A local weak termination forces A < B. The local driver is switched off. Then, if cables A and B are connected, A > B is measured at the transmitter end indicating a proper cable. If cable A and/or B is broken A < B or A = B will be measured at the transmitter end indicating a cable error.
Fig. 4a shows one embodiment of the transmitter end of the error detection system of the invention, wherein the resistors Rl are smaller than R2 (for example Rl=lk, R2=10k) and hence the pullup /pulldown in the TRX (Transceiver) is weaker than the pullup /pulldown in the BS (Base station). When a line is at potential VCC it is regarded to have digital value l,if line is grounded it have digital value 0.
If "TX enable" signal in the TRX is off, then the RX part in the TRX can listen at the lines 1 and 2 and measuring digital values A and B. A logical signal "result" is defined by below described possible values this signal can be used to see that the FEL cable is working properly.
• If the FEL cable connecting the TRX to the BS is completely functional A=l, B=0, i.e. A>B and this measurement will give a result of OK (FEL cable OK).
• If the line 1 is broken in the FEL cable A=0, B=0, i.e. A=B and the result will be NOT OK (FEL cable faulty).
• If the line 2 is broken in the FEL cable A=l, B=l, i.e. A=B and the result will be NOT OK (FEL cable faulty).
• If both the lines is broken in the FEL cable A=0, B=l, i.e. A<B and the result will be NOT OK (FEL cable faulty).
Fig. 4b shows one embodiment of the reciever end of the error detection system of the invention. The Remote driver is stronger than the local termination (R2 resistors) and in idle state the local driver forces A>B.
• If the line 1 and line 2 are without failure the local receiver will register A>B.
• If line 1 is broken it will register A=B
• If line 2 is broken it will register A=B
• If both lines 1 and 2 are broken it will register A<B
The error detection system of the invention may further be summarized as a cable malfunction detection system, said cable comprising a balanced pair (A, B) of conductors for signal transmission between a base station (BS) and a peripheral unit (TRX), the system comprising
• a first driver unit at one end of said cable for forcing one line (A) to a HIGH level, and the other line (B) to a LOW level, such that A>B; • a second driver unit at the other end of said cable capable of setting B>A, but being weaker than the first driver unit, such that the first driver unit, if operative, always takes precedence over the second driver unit;
• means for measuring the actual levels of A and B in the peripheral unit; and
• means for comparing A and B, and output means for presenting the result of the comparison.
The cable malfunction detection system may further comprise means for issuing a malfunction message if the relation A>B does not hold.
• a non- volatile memory unit within said hardware, the contents of which is readable by the new software, and in which hardware version identification information is stored.
A method for enabling software operation modification according to hardware version, by new software installed on said hardware, may be summarized as to comprise the steps of • storing hardware version identification information in a nonvolatile memory in the hardware in question; and
• reading said information by said new software when new software is installed and modifying the operation of new software in accordance with the information read
During the production process of a hardware unit a number of production tests are done to verify unit operation. It can be of interest to log that these different test steps are performed and optionally also log details about the different tests.
• Results of first production test [Test A] is stored in subpart A
• Results of second production test [Test B] is stored in subpart B
• Results of third production test [Test C] is stored in subpart C
• Results of final production test [Test N] is stored in subpart N
This method of hardware test logging, may be summarized as to comprise the steps of
• performing at least one test of said hardware during production;
• storing information relating to said test(s) in a non-volatile memory in said hardware.
Such a device may be summarized as to comprise a non-volatile memory, having a number of partitions, each containing information relating to a different production test that said device was subjected to during production thereof. IR transmitters are based on one or several IR diodes. The IR diodes can be connected in serial in one or several chains. When current flows through a diode or chain of diodes IR light is emitted. One type of error that may occur in the transmitter is that a diode or chain of diodes is broken so no current can flow. To be able to detect such a malfunction a control circuit may be connected to each diode or chain of diodes. The control circuit gives one logical output when current flows and another logical output when no current flows. If the output is read when the IR transmitter is active, the circuit indicates if a diode or chain of diodes is broken or not.
One example of how to implement this function for a three-diode chain is shown in fig 6. When I_l is zero the potential on Sense is zero, if the current I_l is larger than zero the potential on sense is also larger than zero, by measuring potential on sense signal one can determine if a current is larger than zero. In fact one also could set a voltage limit for sense to determine that a predefined amount of current is flowing in this diode / diode chain.
The intention of this invention is to see to that the PCB layout is made in such a manner that the Magnetic and Electric field emitted from the diode chain is minimised. Two currents in different directions will minimise the fields, and by also change position (above the diode or below the diode in the figure) of the two current directions one gets a wire "twisted in two dimensions" and that will further decrease the Electro-magnetic interference (EMI).
IR diodes are sensitive to high current during long time. At operation the current may be high but the operation is pulsed in a way not degenerating the diodes. Operation is controlled by a micro controller. During power up of an IR transmitter there is a start up time of the micro controller (and optionally other integrated circuits) during which the outputs are uncontrolled; outputs are in high impedance state. Hence, there is a risk for high current during long time at power up. Therefore a passive, weak, deactivation circuit (for example a pullup or pulldown resistor) is proposed to be connected between the controller and the IR driver. During power up the deactivation circuit will ensure that the IR driver is switched off. When the controller become operational, the outputs will take their appropriate values and since the outputs are stronger than the deactivation circuit the controller can control the IR driver.
• providing a control by a weak deactivation circuit such that no current is passed through said device (IR LED) during power up;
• providing outputs from said controller at full power that take precedence over said control by said weak deactivation circuit, to render said device operative.
To detect I/Q offsets for unbalanced hardware a quadrature detector is proposed. The quadrature detector is effective when to detect a signal of known frequency but unknown phase. The signal to be detected is split into two parts; 0° part and 180° part. (Part 180° is the inverse of part 0°.) The detector generates four clocks of same frequency as the signal but all four clocks are separated 90°. The clocks are called CO, C90, C180 and C270. The detector has two integrators. The first integrator I integrates the sum of signal part 0° sampled with CO and signal part 180° sampled with C180. The second integrator Q integrates the sum of signal part 0° sampled with C90 and signal part 180° sampled with C270. By this method the contents of the integrators can be viewed as an I/Q diagram where I integrator represents the I vector and Q integrator represents the Q vector. The vectors will always be perpendicular. The resultant vector of I- and Q-vectors will represent the signal. The length of the resultant is the signal strength and the angle of the resultant is the phase of the signal with reference to the detector clocks.
Before a signal is to be detected the integrators are reset. Each integrator output is connected to input of a sample and hold circuit. During signal sampling the sample and hold circuits are set in mode sample. At end of signal sampling the sample and hold circuits are set in mode hold and the I- and Q vectors can be read out and the resultant vector calculated. The detector clocks can be switched off when no signal is expected to reduce system noise and current consumption.
Due to non-linearity in the detector circuits the origo of the I/Q diagram may not be centred. By taking multiple noise samples as described above the effective centre of the I/Q diagram can be calculated as an I/Q offset and this offset can be used in later calculations of the resultant vector for a signal sampled to compensate for any non-linearity.
The I and Q values can be expressed as imaginary and real part of a complex number (Mathematics) and to illustrate I and Q one can draw two perpendicular axes I and Q like in fig. 8a. In the I/Q diagram of fig 8a the noise have been sampled and the I and Q values result is according to the figure not centred around the origin, but when the vector I/Q offset is subtracted from all the values result shown in fig 8b is achieved, and the received signal is also written in this graph, now centred around the origin:
• taking a plurality of noise samples represented as I/Q vectors, and calculating an average I/Q vector representing an offset from origo in said I/Q diagram; and
• using said average offset I/Q vector for compensating subsequent sampled signals to obtain a corrected I/Q diagram.
Product marking on chassis is an easy way to identify type of unit. At service, one or several units may be disassembled. When reassembling again, there is a risk that the part with the unit identifier is mounted on the wrong unit. Description: Product marking is placed on a part of the unit that not is subject for removal at service. Hence, there is no risk that part with unit identifier is mounted on wrong unit.
In ESL systems there are receivers for reception of wireless data from ESLs to Master Computer (MC; an item controlling the ESL system). Data can be acknowledge of data sent to the ESL or other data. In the environment there is noise interfering with the data. To prevent the noise to disturb the receiver a threshold can be defined. All signals of strength below this threshold are ignored and all signals of strength above this threshold are interpret as valid signals.
To achieve this a calibration mechanism is used to find an appropriate threshold level. The threshold is based on a calibration result and a threshold multiplier. The calibration result is obtained by the receiver sampling the noise a number of times (the number is configurable with 400 samples as default) and then calculate the mean value of the strongest fraction of the noise samples. This mean value is the calibration result. The calibration result is then multiplied with an adjustable value called threshold multiplier. By changing threshold multiplier, the Signal to Noise Ratio (SNR) can be changed. SNR gives the probability for not detecting a valid signal and the probability to interpret noise as signal. The threshold multiplier is set once to get required SNR and calibration is done on a regular basis based on a configurable time-out to handle the fact that environment noise may vary over time. If the time-out has expired when the receiver is expected to receive data, a re-calibration is done. If noise now has changed compared to previous calibration the threshold will be changed preserving the selected SNR.
The strongest fraction can be described by using a histogram like in fig. 9a showing a statistical distribution (not the actual statistical distribution but an example of a statistic distribution). The calibration result is the mean value of the strongest fraction.
The Threshold that defines what value of the signal that is regarded as noise and that is regarded as signal. The threshold is defined as the calibration result multiplied by the wanted S/N ratio (S/N ratio is also called Threshold multiplier in this text), as shown in fig. 9b.
Such a method of setting a threshold for accepting a received signal as a valid signal in a transceiver system exposed to varying environmental noise levels, may comprise the steps of:
• sampling noise data a selected number of times;
• calculating a mean value of a fraction of sampled noise data representing the strongest noise signals;
• multiplying said mean value with a selectable and adjustable threshold multiplier representing a desired S/N ratio to obtain a desired threshold; • storing said threshold in the transceiver system.
The noise level could further be monitored during operation, and if said noise level is changed, the threshold setting procedure is repeated, so as to change the threshold in order to maintain the desired S/N ratio. The method could further comprise the step of waiting a predetermined maximum time during which no valid signal is detected before repeating the threshold setting procedure.
Of many reasons it is of interest to assign a unique identity the each hardware unit. The identity may be used for tracking or addressing purposes.
1. A method for creating synchronized transmission of messages in a wireless electronic shelf labeling system comprising at least two transmitters, a plurality of receiving label-units and a central processing unit capable of issuing messages to be transmitted via said transmitters, the method comprising
deterrriining, for each transmitter, the signal delay between issuing of a message at the central processing unit and transmission of the message from the transmitter;
actively delaying, in response to said determined signal delay, transmission from the individual transmitters such that synchronized transmission from all transmitters is achieved.
2. Method according to claim 1 characterized in that the active delay of the transmission from the transmitters is performed by an active signal delay unit associated with each transmitter.
3. Method according to claim 1 or 2 characterized in that the step of determining the signal delay comprises setting the transmitters in a mirror- mode so that they automatically mirror all received pulses back to the central processing unit and measuring the time-difference between sending and receiving the same pulse.
4. Method according to any of the claims 1 to 3 characterized in that the active delay for each transmitter is set to the difference between the delay to that particular transmitter and a predefined maximum delay value.
5. Method according to any of the claims 1 to 3 characterized in that the active delay for each transmitter is set to the difference between the delay to that particular transmitter and the highest determined signal delay to any transmitter in the system.
6. A transmitter for a wireless electronic shelf labelling system, characterised in that it comprises an active signal delay unit that is arranged to delay transmission from said transmitter, and is adjustable in correspondence with an active signal delay parameter.
7. A transmitter for a wireless electronic shelf labelling system according to claim 6 characterised in that the active signal delay unit comprises a shift- register.
8. A wireless electronic shelf labelling system comprising at least two transmitters, a plurality of receiving label-units and a central processing unit capable of issuing messages to be transmitted via said transmitters, characterised in that it comprises one or more active signal delay units that are arranged to delay transmission from said transmitters, and adjustable in correspondence with an active signal delay parameter.
9. A wireless electronic shelf labelling system according to claim 8, characterised in that each active signal delay unit is arranged in a transmitter and arranged to delay transmission from said transmitter.
10. A -wireless electronic shelf labelling system according to claim 8, characterised in that the active signal delay units are arranged at the central processing unit and arranged to delay issuing of messages their associated transmitters.
1 l.A wireless electronic shelf labelling system according to any of the claims 8 to 10, characterised in that the transmitters communicates with the central processing unit by means of distribution lines in the form of cables.
12. A wireless electronic shelf labelling system according to any of the claims 8 to 10, characterised in that the transmitters communicates with the central processing unit by means of wireless connections.
PCT/SE2001/002396 2000-10-31 2001-10-31 Method and device for transmission of data in an electronic shelf labeling system WO2002037257A1 (en)
US24464000 true 2000-10-31 2000-10-31
US60/244,640 2000-10-31
US10415464 US7213751B2 (en) 2000-10-31 2001-10-31 Method and device for transmission of data in an electronic shelf labeling system
JP2002539942A JP2004513424A (en) 2000-10-31 2001-10-31 Method and apparatus for transmitting data in an electronic shelf label system
EP20010981245 EP1336138B1 (en) 2000-10-31 2001-10-31 Method and device for transmission of data in an electronic shelf labeling system
DE2001637640 DE60137640D1 (en) 2000-10-31 2001-10-31 Method and apparatus for transmitting data in an electronic shelf labeling system
WO2002037257A1 true true WO2002037257A1 (en) 2002-05-10
ID=22923558
PCT/SE2001/002396 WO2002037257A1 (en) 2000-10-31 2001-10-31 Method and device for transmission of data in an electronic shelf labeling system
US (1) US7213751B2 (en)
EP (1) EP1336138B1 (en)
JP (1) JP2004513424A (en)
DE (1) DE60137640D1 (en)
ES (1) ES2322333T3 (en)
WO (1) WO2002037257A1 (en)
US9141841B2 (en) * 2012-12-20 2015-09-22 Ebay, Inc. Methods, system and apparatus for conducting a point of sale transaction
EP0042144A1 (en) * 1980-06-14 1981-12-23 Licentia Patent-Verwaltungs-GmbH Method and arrangement for the simultaneous transmission of information by several common-wave transmitters
CA2175032A1 (en) * 1995-10-05 1997-04-06 John C. Goodwin, Iii System for determining location of electronic price labels for merchand-ise in store shelves
EP0887757A2 (en) * 1997-06-25 1998-12-30 Ncr International Inc. Method of controlling price changes in epls
JP2004513424A (en) 2004-04-30 application
ES2322333T3 (en) 2009-06-19 grant
US20040011868A1 (en) 2004-01-22 application
US7213751B2 (en) 2007-05-08 grant
EP1336138A1 (en) 2003-08-20 application
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