WO2000056086A1 - Selection de frequence ciblee pour systeme de communication bidirectionnel sans fil - Google Patents

Selection de frequence ciblee pour systeme de communication bidirectionnel sans fil Download PDF

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Publication number
WO2000056086A1
WO2000056086A1 PCT/US2000/006976 US0006976W WO0056086A1 WO 2000056086 A1 WO2000056086 A1 WO 2000056086A1 US 0006976 W US0006976 W US 0006976W WO 0056086 A1 WO0056086 A1 WO 0056086A1
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WO
WIPO (PCT)
Prior art keywords
frequency
carrier frequency
successful
frequencies
esl
Prior art date
Application number
PCT/US2000/006976
Other languages
English (en)
Inventor
Lawrence A. Cardani
Ted Kelley
Original Assignee
Electronic Retailing Systems Int'l Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Electronic Retailing Systems Int'l Inc. filed Critical Electronic Retailing Systems Int'l Inc.
Priority to AU38905/00A priority Critical patent/AU3890500A/en
Publication of WO2000056086A1 publication Critical patent/WO2000056086A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H04W88/022—Selective call receivers
    • H04W88/023—Selective call receivers with message or information receiving capability

Definitions

  • the invention relates generally to store price display systems controlled by a host computer that communicates pricing information to individually addressable price display devices through a low-power, wireless, two-way communication system, and relates more particularly to reducing communications problems by varying the frequency of signals used to communicate with ESLs.
  • An electronic shelf label (ESL) system comprises many individual, addressable ESLs in a store, typically 15,000 or more. ESLs might be located almost anywhere in a store, including, but not limited to, shelf edges, peghook displays, produce areas, free-standing display tables, display cases, wire bins, and other merchandising displays and fixtures.
  • a wireless ESL system typically comprises one or more ceiling mounted antennas
  • the propagation of wireless signals inside a store using a wireless ESL system can be affected by factors that can change over time, including, but not limited to the relative positions of Cell Antennas and ESLs; the type, quantity and location of merchandise in the store; the types and locations of merchandising displays and fixtures; the numbers and locations of customers; and the presence and locations of carts, baskets and other mobile objects.
  • the communications frequencies used in a wireless ESL system can strongly influence the propagation of wireless signals inside a store.
  • a first case at a first time, it might be difficult to communicate with a particular ESL using a first communications frequency but easy to communicate with the same ESL using a second communications frequency.
  • destructive interference arising from multipath propagation might interfere with transmissions to or from the ESL at the first frequency but not at the second frequency.
  • a communications frequency that permits reliable communication with a particular ESL at one time might not permit reliable communication with the same ESL at a different time.
  • moving objects in the store might create or destroy reflected propagation paths.
  • a first general approach is to decrease cell size so that each ESL is reachable by more than one Cell Antenna.
  • the system When a label is unresponsive in such a system (which may be due to multipath or other causes), the system then tries a different cell antenna. The assumption is that the physical objects giving rise to the multipath (or other) effect will be unlikely to give rise to a multipath node (or to have the same effect) for the different antenna.
  • a second general approach, the "frequency agile" approach is to establish several different frequencies to be used for the downlink and/or uplink and to change communications frequencies when problems are encountered. For example, the '957 Publication suggests two different methods for selecting a communications frequency
  • Method 1 a store's central computer could always try a particular frequency first for all ESLs. and then shift to a second frequency for any labels that failed to respond to the first frequency, and so on (See '957 Publication at page 30 lines 9-12); or
  • Method 2 a store's central computer could keep note, for each ESL, of the frequency that worked the last time that ESL was communicated with and each subsequent attempt to reach that ESL could start with the stored frequency (See '957 Publication at page 29 lines 1 1-18).
  • Method 1 always trying the same frequency first, can waste time (thereby reducing the effective bandwidth of the wireless system) if an ESL rarely or never is able to communicate using that first frequency (or perhaps even the first several frequencies tried for each message).
  • Method 2 improves upon Method 1, because Method 2 avoids repeatedly starting with a frequency that rarely or never works for a particular ESL.
  • Method 2 if the first frequency tried for a message does not work, then the second and subsequent attempts are no more likely to be successful than would be the second and subsequent attempts of Method 1. That is, Method 2 offers no suggestion of what frequency to try next if the first attempt fails. Consequently, while Method 2 improves the probability that the first frequency selected will be successful, it does not improve the probability that the second or subsequent frequency will be successful.
  • the invention improves upon the prior art Method 2 for the frequency agile approach by storing multiple previously successful frequencies for a single ESL and then using this stored information to help select each frequency that may be attempted for communication with that ESL.
  • the invention increases the probability of success for the second, third, fourth, etc. frequencies that might be selected when attempting to communicate with an ESL.
  • the invention also improves upon the prior art by requiring the host computer to save multiple previously successful frequencies only for ESLs that have been difficult to communicate with. This optimization avoids unnecessarily storing multiple data items about previously successful frequencies for ESLs with which it is easy to communicate.
  • Fig. 1 shows in block diagram form exemplary components of the store electronic shelf label system
  • Fig. 2 shows in perspective view an exemplary electronic shelf label
  • Fig. 3 shows a flowchart for frequency-agile communication with an electronic shelf label in accordance with the invention.
  • Fig. 4 shows a flowchart for selecting a next frequency in accordance with the invention.
  • Fig. 1 provides context for the invention by showing a general overview of a typical store electronic shelf label system.
  • a multiplicity of electronic shelf labels 10, 10' etc. are dispersed throughout the store.
  • the ESLs are controlled by a store central computer 1.
  • the central computer 1 contains records indicative of the information (e.g. price) that is to be displayed by each ESL.
  • the central computer 1 is communicatively coupled with the multicell controller 3 by a bidirectional link 2.
  • the multicell controller 3 is connected via multiple bidirectional data lines 4 to multiple cable interfaces 5.
  • Each cable interface 5 is connected to a cell controller 7 by a bidirectional cable 6.
  • Each cell controller controls a transmitting antenna 8 and a receiving antenna 12.
  • the multiple pairs of antennas 8, 12 effectively divide the store into "cells".
  • Each cell is served by one pair of antennas 8, 12. Transmitting antenna 8 sends wireless signals 9 to ESLs 10, 10', etc.
  • Dotted lines 9 denote RF energy coupled through the air between the store transmit antenna 8 and an antenna within the ESLs 10. 10'.
  • ESLs 10, 10', etc. receive wireless signals 9, process them, and transmit wireless signals 11 to receiving antenna 12.
  • Dotted lines 11 denote RF energy coupled through the air between ESLs 10, 10' and store receiving antenna 12.
  • Each cell controller 7. each antenna 8. 12. and each ESL 10, 10'. etc.. is capable of communicating using multiple different carrier frequencies. In a preferred embodiment, such communication is performed using a spread spectrum signal based upon a carrier frequency selected by central computer 1.
  • the phrase “carrier frequency” in the context of a spread spectrum signal means the frequency of the RF oscillator whose output is being spread.
  • the phrase “carrier frequency” as used in this Application would mean the frequency of oscillator 10 in Fig. 1 of the '957 Publication.
  • Fig. 2 shows an electronic shelf label 10 with a liquid crystal display 21 suitable for displaying the price of an item offered for sale in a store.
  • Each ESL 10 may be mounted next to a relatively unpredictable variety of metal and plastic store shelves, and may be attached directly to a metal or plastic rail on the shelf edge.
  • Each ESL 10 also contains a processor, a battery, an antenna, and analog circuitry relating to sending and receiving information via an antenna.
  • Fig. 3 shows a flowchart for frequency-agile communication with an ESL in accordance with the invention.
  • store central computer 1 selects
  • a first frequency This selection could be done in any way, including, but not limited to, always selecting the same first frequency for all attempted communications or always selecting the last frequency that was successful in communicating between the applicable cell controller 7 and ESL 10.
  • cell controller 7 attempts to communicate with ESL 10 by transmitting a message addressed to ESL 10 using the first frequency and then listening for a response from ESL 10.
  • central computer 1 determines 33 that the communication was successful and stores 35 information which indicates that cell controller 7 successfully communicated with ESL 10 using that frequency.
  • This information could be stored in any way that will later allow central computer 1 to recall what frequencies have been successful for communicating between cell controller 7 and ESL 10.
  • this information could be stored as (i) a list, where each element of the list identifies at least a cell controller, an ESL and a successful frequency or (ii) a three dimensional array in which (a) the first dimension identifies a cell controller, the second identifies an ESL and the third identifies a frequency and (b) each cell in the array contains at least one element that is set to a specified value if communication between the applicable cell controller and the applicable ESL is successful at the applicable frequency. What is important is that central computer 1 is able to recall frequencies that have been successful for communicating between a particular cell controller and a particular ESL.
  • central computer 1 determines 33 that the communication was not successful and selects 34 a next frequency to try. (Fig. 4, discussed below, shows a flowchart for one method of making such a selection.)
  • Cell controller 7 then attempts 32 to communicate with ESL 10 using the new frequency. This process can be repeated as many times as necessary until cell controller 7 successfully communicates with ESL 10. Once the communication is successful, then, as described above, central computer 1 stores 35 information which indicates that cell controller 7 successfully communicated with ESL 10 using the last frequency tried.
  • the first frequency is selected using the method illustrated in Fig. 4. In another alternative embodiment, the first frequency is always selected based upon previously stored successful frequencies
  • Fig. 4 shows a flowchart for selecting a next frequency to use for communicating between a cell controller 7 and an ESL 10 in accordance with one embodiment of the invention.
  • central computer 1 examines information stored in its memory to determine 41 whether ESL 10 has previously been "marked” as a "Targeted RF ESL". For purposes of this application, an ESL is marked as a Targeted RF ESL if information stored in the system will cause the central computer 1 to determine that the ESL is so marked. For example, and not by way of limitation, central computer 1 might mark ESL 10 as a Targeted RF ESL by setting a bit in a binary array or by adding it to a list of ESLs. Note that if multiple cell controllers are able to communicate with a particular ESL, then that ESL might be a Targeted RF ESL with respect to one such cell controller but not the other.
  • central computer 1 selects 42 a next frequency to try based upon previously successful frequencies stored in central computer 1.
  • the central computer could be programmed to select only frequencies that match predetermined selection criteria given the saved set of successful frequencies for ESL 10.
  • the predetermined selection criteria could be limited to an exact match with a previously successful frequency or could be extended to include frequencies that are within a particular range of one of the saved successful frequencies.
  • central computer 1 determines 43 whether the communication success rate between cell controller 7 and ESL 10 is sufficiently high. This determination could, for example, and not by way of limitation, be based upon an automated algorithm or user selection. For example, and not by way of limitation, a communications success rate could be deemed insufficient if some predetermined percentage of attempted communications failed during some predetermined interval or if some predetermined number of attempted communications failed during some predetermined interval.
  • central computer 1 selects 44 the next frequency using a normal sequence of frequencies.
  • central computer 1 marks 45 ESL 10 as a Targeted RF ESL and selects 42 a next frequency based upon previously successful frequencies stored in central computer 1 as described above.
  • the next frequency is always selected based upon previously stored successful frequencies for the applicable cell controller 7 and

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un procédé consistant à mémoriser une pluralité de fréquences (33) qui se sont préalablement avérées valables pour une étiquette électronique de rayon (EER), et à utiliser cette information mémorisée pour contribuer à sélectionner chaque fréquence pouvant être essayée afin d'établir une communication avec cette étiquette (10) électronique de rayon. Cette invention permet ainsi d'accroître la probabilité de succès pour la seconde, troisième, quatrième fréquence (34) etc. pouvant être sélectionnée lors d'une tentative de communication avec une (10) électronique de rayon. L'ordinateur (1) hôte est conçu pour mémoriser une pluralité de fréquences préalablement valables uniquement pour les étiquettes électroniques pour lesquelles la communication a été difficile à établir (45). Cette optimisation permet d'éviter la mémorisation inutile de données multiples concernant des fréquences (43) préalablement valables pour les étiquettes électroniques avec lesquelles la communication est facile à établir.
PCT/US2000/006976 1999-03-18 2000-03-18 Selection de frequence ciblee pour systeme de communication bidirectionnel sans fil WO2000056086A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU38905/00A AU3890500A (en) 1999-03-18 2000-03-18 Targeted frequency selection for two-way wireless communication system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US12500199P 1999-03-18 1999-03-18
US60/125,001 1999-03-18

Publications (1)

Publication Number Publication Date
WO2000056086A1 true WO2000056086A1 (fr) 2000-09-21

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Application Number Title Priority Date Filing Date
PCT/US2000/006976 WO2000056086A1 (fr) 1999-03-18 2000-03-18 Selection de frequence ciblee pour systeme de communication bidirectionnel sans fil

Country Status (2)

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AU (1) AU3890500A (fr)
WO (1) WO2000056086A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5418839A (en) * 1990-04-13 1995-05-23 Phonemate, Inc. Environmental adaptive mechanism for channel utilization in cordless telephones
US5475868A (en) * 1992-08-04 1995-12-12 U.S. Philips Corporation Cellular radio system having channel evaluation and optimal channel selection via trial use of non-assigned channels
US5694418A (en) * 1995-06-13 1997-12-02 Ncr Corporation System and method for determining EPL message transmission retries
US5710976A (en) * 1996-01-18 1998-01-20 Motorola, Inc. Method and apparatus for reducing noise interference to improve outbound message reliability in a two-way messaging system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5418839A (en) * 1990-04-13 1995-05-23 Phonemate, Inc. Environmental adaptive mechanism for channel utilization in cordless telephones
US5475868A (en) * 1992-08-04 1995-12-12 U.S. Philips Corporation Cellular radio system having channel evaluation and optimal channel selection via trial use of non-assigned channels
US5694418A (en) * 1995-06-13 1997-12-02 Ncr Corporation System and method for determining EPL message transmission retries
US5710976A (en) * 1996-01-18 1998-01-20 Motorola, Inc. Method and apparatus for reducing noise interference to improve outbound message reliability in a two-way messaging system

Also Published As

Publication number Publication date
AU3890500A (en) 2000-10-04

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