System and method for wireless communication between several transceivers, arranged respectively in several delimited spaces, and portable electronic units

• US 6,588,661 B2
• Filed: 02/28/2002
• Issued: 07/08/2003
• Est. Priority Date: 03/23/2001
• Status: Expired due to Term

• Current Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Original Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Inventors: Desjeux, Olivier, Degrauwe, Marc
• Primary Examiner(s): Frech, Karl D.
• Assistant Examiner(s): Labaze, Edwyn
• Application Number:
  US10/084,058
• Publication Number:
  US 20020134833A1
• Time in Patent Office: 495 Days
• Field of Search: 235/375, 235/382, 235/384, 340/928, 340/825, 340/933, 701/117, 342/42
• US Class Current: 235/382
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10069 the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other frequency hopping or spread spectrum techniques H04B7/00
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas

Abstract

System for communication between a plurality of transceivers, transmitting in particular at a high frequency and arranged respectively in a plurality of delimited spaces each having at least one entrance, and portable electronic units fitted with means for radio-communication with the plurality of transceivers, in particular with a view to detecting each of them penetrating one of the delimited spaces. The communication between the transceivers and the portable electronic units for neighboring delimited spaces is effected at different exclusive frequencies or frequencies of sub-sets of frequencies associated with the exclusive frequencies. In order to do this, devices for occupying an exclusive frequency are provided which include listening circuits (30, 32, 34, 36, 38, 46, 48) for determining whether an occupied signal is present on any frequency of a set of exclusive frequencies able to be selected and/or whether a determined amplitude threshold is received for this frequency, and transmission circuits (30, 52, 54, 56, 58) arranged to transmit an occupied signal in a selected exclusive frequency. This system thus prevents disturbances or interference between portable units located in a delimited space and a transceiver arranged in a neighboring delimited space.

Claims

1. A system for communication between a plurality of transceivers, arranged respectively in a plurality of delimited spaces each having at least one entrance, and portable electronic units fitted with means for radio-communication with said plurality of transceivers, in particular with a view to detecting each of these electronic units which penetrates one of said delimited spaces, wherein said transceivers and said electronic units are arranged to be able to communicate, among a set of given frequencies and/or frequency sub-sets respectively associated with said frequencies, at any frequency and/or frequencies of an associated sub-set of frequencies, each of said transceivers being associated with means for occupying a frequency exclusive thereto, said transceivers including:

listening means arranged to determine whether an occupied signal is present on any frequency among said set of frequencies and/or whether a given amplitude threshold is exceeded upon reception of said frequency;

transmission means arranged to transmit at any frequency of said set of frequencies; and

means for selecting, in a period prior to a period of communication with electronic units, an exclusive frequency among said set of frequencies which does not contain an occupied signal or whose received amplitude level is less than said threshold;

said transmission means transmitting at the selected exclusive frequency an occupied signal for said exclusive frequency at least periodically during at least said communication period, this system having means for communicating information relative to said exclusive frequency to the portable units entering and/or exiting and/or located in the delimited space inside which the transceiver being considered is arranged.

2. The system according to claim 1, wherein said exclusive frequency selection means include control means for alternately activating said listening means and said transmission means at any frequency of said set of frequencies and means for passing to another frequency of said set as soon as said occupied signal for this frequency is received by said listening means or the power level received on this frequency is greater than said threshold.

3. The system according to claim 2, wherein the selection of an exclusive frequency only occurs after said listening means and transmitting means have been activated alternately several times, without said frequency being received by said listening means.

4. The system according to claim 2, wherein the period of activation of said listening means is different for each transceiver of said system.

5. The system according to claim 1, wherein said set of frequencies is in the high frequencies, said exclusive frequency selected for a transceiver being communicated to the low frequency electronic units by one or more transmitters placed respectively at said entrance or at the entrances to the delimited space of said transceiver.

6. The system according to claim 1, wherein during said preliminary phase, said listening means are activated firstly at a frequency which was used for a previous communication.

7. The system according to claim 1, wherein each frequency of said frequency set is associated with a sub-set of frequencies which are different from the other sub-sets of frequencies and also different from the frequencies of said frequency set, so as to allow a collision-avoidance protocol to be implemented which distributes the communication frequencies with said electronic units on frequencies of a sub-set of frequencies associated with said exclusive frequency.

8. A method of communication between transceivers, arranged respectively in delimited spaces next to each other or capable of being at least temporarily and portable electronic units fitted with radio-communication means and capable of penetrating these delimited spaces, said transceivers and said electronic units being arranged to allow high frequency communication, among a set of given frequencies and/or sub-sets of frequencies respectively associated with said frequencies, at any frequency and/or frequencies of an associated sub-set of frequencies, this method having, for each transceiver, the following steps in a period prior to a high frequency communication period:

listening at a first frequency of said set of frequencies to determine whether an occupied signal is present on this first frequency and/or whether a given amplitude threshold is exceeded for this first frequency;

changing channel to listen at another frequency of said set of frequencies to determine whether an occupied signal is received on said first frequency or whether the amplitude level received for this first frequency is greater than said threshold;

until a frequency is available, which is then selected as the exclusive frequency, this method further including the following steps;

sending an occupied signal for said selected exclusive frequency, so that it is not subsequently taken by transceivers arranged in neighboring delimited spaces, at least during a subsequent period of communication at the selected exclusive frequency and/or at a frequency of said sub-set of frequencies associated with this exclusive frequency;

communicating, to the electronic units entering and/or exiting and/or located in the delimited space being considered, information relative to the exclusive frequency selected for a high frequency communication.

9. The communication method according to claim 8, wherein the communication of information relative to said selected exclusive frequency is effected at a low frequency by transmitters located at the entrances to said delimited spaces.

10. The method according to claim 8, wherein during said preliminary period, a signal is transmitted alternately with listening at a same frequency of said set of frequencies, said selection of said exclusive frequency occurring only after a certain number of listening-transmitting alternations.

11. The method according to claim 10, wherein the period of listening-transmitting alternations is different for each delimited space.

12. The method according to claim 10, wherein as soon as an exclusive frequency is selected, said transmitting means continue to transmit said signal at said exclusive frequency without interruption, periodically or continuously, until the start of said communication period and during the latter, this signal forming said occupied signal.

13. The method according to claims 10 wherein said listening means are deactivated during said communication period.

14. The method according to claims 8, wherein said listening means are deactivated during said communication period.