WO2000056086A1 - Targeted frequency selection for two-way wireless communication system - Google Patents

Targeted frequency selection for two-way wireless communication system Download PDF

Info

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
Authority
WO
WIPO (PCT)
Prior art keywords
frequency
carrier frequency
successful
frequencies
esl
Prior art date
Application number
PCT/US2000/006976
Other languages
French (fr)
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/en

Links

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W88/00Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02Terminal devices
    • H04W88/022Selective call receivers
    • H04W88/023Selective 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

Abstract

Multiple previously successful frequencies (33) for a single electronic shelf label (ESL) are stored (35), and then this stored information in used to help select each frequency that may be attempted for communication with that ESL (10). Thus, the invention increases the probability of success for the second, third, fourth, etc. frequencies (34) that might be selected when attempting to communicate with an ESL (10). The host computer (1) is disposed to save multiple previously successful frequencies only for ESLs that have been difficult to communicate with (45). This optimization avoids unnecessarily storing multiple data items about previously successful frequencies (43) for ESLs with which it is easy to communicate.

Description

TARGETED FREQUENCY SELECTION FOR TWO-WAY WIRELESS COMMUNICATION SYSTEM
This application claims priority from US application number 60/125,001, filed March 18, 1999, which application is hereby incorporated herein by reference.
BACKGROUND
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
(Cell Antennas) connected to transceivers that permit two-way communication between the host computer and the ESLs. Prior art systems for accomplishing this include, but are not limited to, those disclosed in World Intellectual Property Organization International Publication Number WO 96/27957, for International Application No. PCT/US96/03065 (the '"957 Publication"), entitled "LOW POWER TWO-WAY WIRELESS COMMUNICATION
SYSTEM FOR ELECTRONIC SHELF LABELS", which is hereby incorporated herein by reference.
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.
In 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. For example, and not by way of limitation, 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.
In a second case, 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. For example, and not by way of limitation, moving objects in the store might create or destroy reflected propagation paths.
Prior art systems deal with multipath and other propagation problems in various different ways. A first general approach is to decrease cell size so that each ESL is reachable by more than one Cell Antenna. 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).
Unfortunately, these prior art examples of the frequency agile approach can result in various inefficiencies. 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. However, with 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.
SUMMARY OF THE INVENTION
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. Thus, 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.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described with respect to a drawing in several figures, of which
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; and
Fig. 4 shows a flowchart for selecting a next frequency in accordance with the invention.
Where possible, like elements have been denoted with like reference numerals.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Fig. 1 provides context for the invention by showing a general overview of a typical store electronic shelf label system. In the embodiment shown in Fig. 1, 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.
For purposes of this Application, the phrase "carrier frequency" in the context of a spread spectrum signal, means the frequency of the RF oscillator whose output is being spread. For example, and not by way of limitation, 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. In an exemplary embodiment, store central computer 1 selects
31 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. Next, 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.
If cell controller 7 receives a response from ESL 10. then 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.
(Note that different frequencies might work differently for different cell controllers even when communicating with the same ESL.) 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. For example, and not by way of limitation, 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.
If cell controller 7 does not receive a response from ESL 10, then 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. In an alternative embodiment of the invention, 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.
First, 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.
If ESL 10 has been marked as a Targeted RF ESL, then central computer 1 selects 42 a next frequency to try based upon previously successful frequencies stored in central computer 1. For example, and not by way of limitation, 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. For example, and not by way of limitation, 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.
If ESL 10 has not been marked as a Targeted RF ESL. then 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.
If the communication success rate is sufficiently high, then central computer 1 selects 44 the next frequency using a normal sequence of frequencies.
If the communication success rate is not sufficiently high, then 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. In an alternate embodiment of the invention, the next frequency is always selected based upon previously stored successful frequencies for the applicable cell controller 7 and
ESL 10, and steps 41, 43, 44 and 45 are eliminated.
Those skilled in the art will appreciate that numerous obvious modifications and variations could be made to the invention without departing from it in any way. All these obvious modifications and variations are intended to be encompassed within the scope of the claims.

Claims

CLAIMS We claim
1. A method comprising
(a) for each of one or more successful frequencies (i) transmitting a message addressed to a first address using such successful frequency as a carrier frequency,
(ii) receiving a reply to such message using such successful frequency as a carrier frequency, and
(iii) storing such successful frequency; (b) selecting a first carrier frequency;
(c) transmitting a first message addressed to the first object using the first carrier frequency;
(d) listening for a reply to the first message using the first carrier frequency;
(e) not receiving a reply to the first message using the first carrier frequency; (f) selecting a second carrier frequency based upon the successful frequencies.
2. The method of claim 1, wherein the second carrier frequency is one of the successful frequencies.
3. The method of claim 1, wherein the second carrier frequency differs by no more than a predetermined amount from at least one of the successful frequencies.
4. The method of claim 1. wherein the second carrier frequency is selected based upon more than one of the successful frequencies.
5. A method comprising
(a) for each of one or more successful frequencies
(i) transmitting a message addressed to a first address using such successful frequency as a earner frequency.
(ii) receiving a reply to such message using such successful frequency as a carrier frequency, and (iii) storing such successful frequency; (b) after step a, selecting a next carrier frequency based upon the successful frequencies, where the next carrier frequency is not equal to a last carrier frequency used to receive a reply to a transmitted message addressed to the first address.
6. The method of claim 5, wherein the next earner frequency is one of the successful frequencies.
7. The method of claim 5, wherein the next carrier frequency differs by no more than a predetermined amount from at least one of the successful frequencies.
8. The method of claim 5, wherein the next carrier frequency is selected based upon more than one of the successful frequencies.
9. A system comprising a transmitter; a receiver; one or more storage elements, each of which contains information that identifies a frequency for which both
(i) the transmitter transmitted a message addressed to a first address using such frequency as a carrier frequency and
(ii) the receiver received a reply to such message using such frequency as a carrier frequency; a control means, communicatively coupled to the transmitter, the receiver and the storage elements, for
(i) causing the transmitter to transmit a first message addressed to a first address using a first carrier frequency;
(ii) causing the receiver to listen for a reply to the first message using the first carrier frequency;
(iii) if no reply to the first message is received within a predetermined time interval after the first message is transmitted, causing the transmitter to transmit a second message addressed to the first address using a second carrier frequency that is selected based upon the contents of the storage elements.
10. The system of claim 9, wherein the second carrier frequency is a frequency identified by information contained in one of the storage elements.
11. The system of claim 9, wherein the second carrier frequency differs by no more than a predetermined amount from a frequency identified by information contained in at least one of the storage elements.
12. The system of claim 9, wherein the second carrier frequency is selected based upon the contents of more than one of the storage elements.
13. A system comprising a transmitter; a receiver; one or more storage elements, each of which contains information that identifies a frequency for which both (i) the transmitter transmitted a message addressed to a first address using such frequency as a carrier frequency and
(ii) the receiver received a reply to such message using such frequency as a carrier frequency: a control means, communicatively coupled to the transmitter and the storage elements, for causing the transmitter to transmit a message addressed to the first address using a next carrier frequency that both (i) is selected based upon the contents of the storage elements and (ii) is not equal to a last carrier frequency used by the receiver to receive successfully a response to a message addressed to the first address that was transmitted by the transmitter.
14. The system of claim 13. wherein the next carrier frequency is a frequency identified by information contained in one of the storage elements.
15. The system of claim 13, wherein the next carrier frequency differs by no more than a predetermined amount from a frequency identified by information contained in at least one of the storage elements.
16. The system of claim 13, wherein the next carrier frequency is selected based upon the contents of more than one of the storage elements.
PCT/US2000/006976 1999-03-18 2000-03-18 Targeted frequency selection for two-way wireless communication system WO2000056086A1 (en)

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 (en) 2000-09-21

Family

ID=22417784

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2000/006976 WO2000056086A1 (en) 1999-03-18 2000-03-18 Targeted frequency selection for two-way wireless communication system

Country Status (2)

Country Link
AU (1) AU3890500A (en)
WO (1) WO2000056086A1 (en)

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

Similar Documents

Publication Publication Date Title
CN100527858C (en) Pulsed power method for increased read range for a radio frequency identification reader
US5521601A (en) Power-efficient technique for multiple tag discrimination
US6351630B2 (en) Wireless communication system, radio frequency communications system, wireless communications method, radio frequency communications method, and backscatter radio frequency communications system
US5841365A (en) Method and apparatus for communicating with a product label
US5704049A (en) Subglobal area addressing for electronic price displays
US5940006A (en) Enhanced uplink modulated backscatter system
EP1146455B1 (en) Electronic shelf label system
US6046682A (en) Electronic price label including noisemaker and method of locating electronic price labels
EP0790596B1 (en) Method of locating electronic price labels in transaction establishments
JP2010518485A (en) Article-level inventory management using a radio frequency identification (RFID) system
JPH0894746A (en) Protocol for identifying tags for plurality of item radio frequencies
US6429775B1 (en) Apparatus for transporting radio frequency power to energize radio frequency identification transponders
US20080165007A1 (en) Queued Operations in HF/UHF RFID Applications
EP1072128A1 (en) Method of identifying wireless units
KR20110039340A (en) A display system
US20070279228A1 (en) Media access control and signaling protocol for low power, large-scale wireless networks
NZ280545A (en) Remote electronic display: acknowledgement depends on signal to noise ratio
JPH10173680A (en) Method and device for low power communication between mobile computing devices
US20140313012A1 (en) System and method for updating electronic shelf labels and updating apparatus and method of an electronic shelf label
CN106550313A (en) A kind of automatic identifying method of goods
US10489619B2 (en) Inventory system for objects contained in a space bounded by an enclosure as well as an inventory method implemented by such an inventory system
US20070187497A1 (en) Channel search method and communication apparatus using the same
Wang et al. Effective anti-collision algorithms for RFID robots system
CA2208884C (en) Subglobal area addressing for electronic price displays
WO2000056086A1 (en) Targeted frequency selection for two-way wireless communication system

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY CA CH CN CR CU CZ DE DK DM DZ EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT TZ UA UG US UZ VN YU ZA ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH GM KE LS MW SD SL SZ TZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase