FR2781955A1 - Network communication procedure - Google Patents

Abstract

The procedure includes a communication station functioning initially in base station mode. It involves an operation of determination of the presence of a station functioning in mobile station mode. When during the course of the presence determination operation, it is determined that any station is not functioning in the mobile station mode, a switching operation in the mobile station mode is initiated during which this station changes to a mobile station mode.

Description

The present invention relates to a method and a device for

  communication over a network. It applies, in particular, to wireless local area networks with centralized architecture, for which each communication is organized between a communication station called base, also called "fixed part" and a mobile communication station, also called "part

portable".

  An example of such a communication network is given by telephones using the European standard DECT (initials of the English words "Digital Enhanced Cordless Telecommunication", which mean

  "improved digital wireless telecommunications").

  In such a local network, a base station provides a signal

  synchronization to all mobile stations present in the network.

  All the stations (the base station and one or more mobile stations) which

  thus synchronize with each other, constitute a cell.

  A particular problem with these networks is that in the absence of a base station, there is no possible communication between the stations

  mobile because they are not synchronized.

  Document US-A-5,598,407 is known, which describes a wireless local area network using the European DECT standard. The network consists of a fixed base station and mobile stations. In the absence of a central station, no communication is possible between the mobile stations

present in the network.

  We also know the document US-A-5,551,066, which describes a wireless local area network, in which it is possible to change the master node dynamically. In this system, all nodes are equal and the master node

  definitively remains the master once he has been chosen.

  The present invention aims to remedy this drawback by making it possible, in the absence of a base station, for a mobile station to perform the role of base station. Thus, a network can be established even in the absence

a permanent base station.

  Another object of the invention is to make it possible to establish, so

  dynamic, a wireless local area network in the absence of a base station.

  To this end, the present invention aims, according to a first aspect, a method of communication between communication stations adapted to communicate with each other when at least one of said communication stations provides a control signal, said station then operating in "base station" mode and the stations not providing a control signal then operating in "mobile station" mode, characterized in that it comprises, carried out by at least one communication station initially operating in base station mode: - an operation for determining the presence of a station operating in mobile station mode, and - when during the operation for determining presence, it is determined that no station is operating in mobile station mode, a switching operation in mobile station mode, during which said

  station goes into mobile station mode.

  Thanks to these provisions, when a communication station which operates in base station mode cannot communicate with any mobile station, it switches to mobile station mode, which allows it: on the one hand, to save energy and , - on the other hand, to allow a base station to enter

communication with her.

  According to particular characteristics, in the communication method as succinctly set out above, for at least one communication station operating in mobile station mode: an operation for determining the presence of a station operating in base station mode, and - When during the presence determination operation, it is determined that no station is operating in base station mode, a switching operation in base station mode, during which said

  station goes into base station mode.

  Thanks to these provisions, this station can take the role of base station to determine whether at least one communication station

  operating in mobile station mode is able to communicate with it.

  According to particular characteristics, following the switching operation in mobile station mode, said communication station 1 5 performs: - an operation for determining the presence of a station operating in base station mode, and - when at during the presence determination operation, it is determined that no station is operating in base station mode, a switching operation in base station mode, during which said

  station goes into base station mode.

  According to other particular characteristics, between two successive operations for determining the presence of a station operating in base station mode, said station performs an operation

  waiting, during which it does not change its operating mode.

  Thanks to each of these provisions, said station successively takes on the role of base station and mobile station, which allows it to come into contact with any communication station, whether the latter

  works in mobile station mode or in base station mode.

  According to a second aspect, the present invention relates to a communication device between communication stations adapted to communicate with each other when at least one of said communication stations provides a control signal, said station then operating in "station mode". base "and the stations not supplying a control signal then operating in" mobile station "mode, characterized in that it comprises, in at least one communication station initially operating in base station mode, a processing means adapted to : determine the possible presence of a station operating in mobile station mode, and - when it has determined that no station is operating in mobile mode

  mobile station, to switch to mobile station mode.

  The invention also relates to a network, a computer, a camera, a fax machine, a camera, a television set, a printer, a scanner and an audio / video player, characterized in that they include a

  device as succinctly set out above.

  The invention also relates to: - a means of storing information readable by a computer or a microprocessor retaining instructions of a computer program characterized in that it allows the implementation of the method of the invention as briefly described above, and - a removable information storage means, partially or totally, and readable by a computer or a microprocessor keeping instructions of a computer program characterized in that it allows the setting

  using the process of the invention as succinctly described above.

  The preferential or particular characteristics, and the advantages of this device, this computer, this camera, this fax machine, this photographic device, this television set, this printer, this scanner, this audio / video player and these information storage means being identical to those of the method such as

  succinctly explained above, these advantages are not recalled here.

  Other advantages, purposes and features of this

  invention will emerge from the following description, made with reference to the drawings

  attached, in which: - Figure 1 shows, schematically, a flowchart of operation of a mobile station, with a view to its insertion into a network, in accordance with the prior art, - Figure 2 shows, schematically , a network comprising communication devices according to the present invention, adapted to implement the communication method of the present invention, - Figure 3 schematically shows the architecture of an electronic circuit incorporated in a communication device communication in accordance with the present invention, - Figure 4 shows, schematically, a flowchart of operation of a communication device in accordance with the present invention, with a view to its insertion into a network, - Figure 5 details a part of the flow diagram illustrated in FIG. 4, FIG. 6 represents, schematically, the organization of information transmitted by a communication device unification in accordance with the present invention, with a view to informing a base station of the capacities of this device linked to operation in base station mode, - FIGS. 7, 8A and 8B schematically represent information exchanges taking place between communication devices in accordance with the present invention, when a mobile station joins or leaves a cell, FIGS. 9, 10, 11 and 12 show, diagrammatically, flowcharts of operation of communication devices in accordance with the present invention, for a change of base station, - Figure 13 is a schematic time representation of the messages exchanged between communication devices according to the flowcharts of Figures 9 to 12, - Figures 14A and 14B show, schematically, the organization of information transmitted by communication devices according to the present invention, in order to glue cter information concerning the capacity of mobile stations to operate in base station mode, - Figures 15 and 16 show, schematically, messages exchanged between communication devices according to the present invention, with a view to collecting information concerning the capacity of mobile stations to operate in base station mode, - FIG. 17 schematically represents a physical frame structure known in the state of the art, - FIG. 18A schematically represents an internal communication to a cell according to the state of the art, - Figures 18B and 18C show, schematically, a cell split implemented by the device object of the present invention, - Figures 19 and 20 show, schematically , flowcharts of operation of communication devices in accordance with the present invention, with a view to dividing the cell during the duration of an internal communication, - Figures 21A, 21B and 22 show, schematically, exchanges of information occurring between communication devices in accordance with the present invention, with a view to dividing the cell for the duration of 'an internal communication, - Figure 23 shows, schematically, a flowchart of classification of mobile stations according to criteria

  defining their ability to operate as a base station.

  In the following description, the term "

  communication "designates a communication station capable of behaving, in a communication network, as a base station or as a mobile station, in accordance, on the one hand, with the DECT standard and, on the other hand, with the different operating modes described next to the drawings

attached.

  FIG. 1 describes the procedure for locking a mobile station to a signal transmitted by a base station, in a manner known in the prior art. When a mobile station is powered up, it goes into an internal initialization state 101. Then, during an operation 102, the mobile station starts receiving on the next channel (there are ten) of the frequency band allocated for communications conforming to the DECT standard (ie 1880 to 1900 MHz), in search of a signal transmitted by a base station which is suitable for it. During the first iteration of operation 102, the first channel is chosen. When, before carrying out operation 102, the last channel was considered, it is the first channel which is chosen, during

operation 102.

  Then, during a test 103, the mobile station listens to the radio channel considered, for a predetermined duration, in order to detect a synchronization pulse originating from a base station. The mobile station thus determines whether a base station uses the channel considered for

  send a synchronization signal, or not.

  When the result of test 103 is negative, during a test 104, the mobile station determines whether the channel considered is the last, or not. When the result of test 104 is negative, operation 102 is repeated. When the result of test 104 is positive, during an operation 105, the mobile station goes into standby mode, then, during an operation 107, it waits for a predetermined duration TO (which can be a decreasing function of

  energy resources of the mobile station), before repeating operation 102.

  When the result of the test 103 is positive, during a test 108, the mobile station determines whether it has an access right to the base station

  which transmits the synchronization signal, or not.

  To this end, when the result of test 103 is positive, the mobile station can obtain the information broadcast by the base station, all the multi-frames (each multi-frame being composed of sixteen frames with a duration of ten milliseconds) . Among the information broadcast by the base station, there is in particular the parameter called "ARI" (initials of the English words "Access Rights Identity", which mean "identity of access rights") and which define access rights at the base station in question. Each mobile station having at least one identity called "PARK" (initials of the English words "portable Access Rights Key" which mean "portable access right key"), it is the correspondence between at least one of the identities " PARK "and the parameter

  "ARI" which is tested during test 108.

  When the result of test 108 is negative, test 104 is carried out.

  When the result of the test 108 is positive, during an operation 109, the mobile station is locked on the base station which transmits the signal

  synchronization detected on the channel in question.

  At the end of operation 109, the mobile station can obtain the information broadcast by the base station whose ARI parameter corresponds

  with at least one of his "PARK" identities.

  The mobile station can then initiate or accept a connection by

  The intermediary of the base station to which the mobile station is locked.

  The mobile station can then communicate with the other mobile stations which are also locked on the same base station and with the base station itself, in particular when the latter provides an access point to a

  other network, for example telephone.

  It is observed here that if there is no base station which transmits a synchronization signal, no communication is possible between the

  mobile stations, in accordance with the prior art.

  FIG. 2 represents, in the same local area 200, different communication devices in accordance with the present invention: - the communication devices 202 and 203 are telephones of known type, responding, for example, to the DECT GAP standard (initials of the English words "Generic Access Profile" which mean, in French "generic access profile") and which is dedicated to the transmission of voice in mobile telephony, - the communication devices 201, 204 and 205 are multimedia terminals capable of being include, in cell 200,

  as a base station or as a mobile station.

  In the embodiment described and shown, the communication devices 201, 204 and 205 support the DECT GAP standard, comply with the "A" type data profile, relating to data transfers up to a speed of 24 kilobits per second. . The communication device 201 also complies with the “AB” type data profile, relating to the transfer of data up to a speed of 552 kilobits per second, but cannot switch to station mode.

  as a result of manual user operation.

  Each device according to the present invention, 201, 204 and

  205, works, by default, as described in FIG. 1, that is

  that is, at the time of initialization, it goes into the operating mode of

mobile station.

  In FIG. 3, it can be seen that each communication device in accordance with the present invention, 201, 204 or 205, comprises, interconnected by a bus 301 - a controller 306, - a DECT baseband unit 302, - a radio unit DECT 303, itself connected, moreover, to a transmitter-receiver antenna 307, - a random access memory 304, - a read-only memory 305, - a keyboard 307, - a display 308, - an energy level controller 309 , itself connected, moreover, to a power supply 310 (battery, battery, or mains), and

  - an input / output interface 311.

  The controllers 306 and 309 and the DECT baseband unit 302 are, in fact, made up of a processor and an operating program

kept in read-only memory 305.

  The DECT 302 baseband unit is of known type and is adapted to exploit all the capacities of the DECT standard known from before.

the present invention.

  The controller 306 is suitable for implementing the method of the invention and, in particular, the flowcharts illustrated in the figures. The energy level controller 309 is intended to evaluate the available energy level, in a known manner, in order to determine timeout values (see infra). The random access memory 304 stores, in registers which, for convenience, each bear the same name as the data it contains: - temporary variables / and k, - a variable "MO" representative of the current operational mode, mobile station or base station, - a variable "MD" representative of the available RAM, a variable "CMD" representative of a coefficient of value of the available memory which takes one of the three values "0", "1" or "2" depending on whether the available memory area has a capacity less than two predetermined values MD_N1 and MD_N2, is between the two predetermined values or is greater than the two predetermined values, - a "Tx / Rx" memory area reserved for reception or when transmitting data, a "TableSM" table containing a list of the identities of the mobile stations (including the devices in accordance with the present invention) declared at the base station, and the associated information at these mobile stations, a "ListSMauto" list containing a list of the identities of the devices in accordance with the present invention, that is to say capable of automatically changing operational mode (for example, stations 204 and 205), - a "ListSMmanual" list containing a list of the identities of the mobile stations likely to change operational mode, by intervention of their user (for example, station 201), and - a "ListSMdirect" list containing a list of the identities of the mobile stations likely to communicate directly with each other, without

base station.

  Read-only memory 305 stores, in registers which, for convenience, each have the same name as the data it contains: - "CM" information on the memory capacity of the device, - "CF" information on the capacity of the processor of the device, - an "IP" indicator representative of the DECT standard profiles supported by the device (in fact by its DECT 302 baseband unit), - "TS" information representative of the types of intervals of

  time (called "slots" in the following description, and in particular in the figure

  17, designation conforming to the customs of the communications person) DECT supported (single, double or half-slot), - "DM" information representative of a maximum data rate supported by the device (for example between 24 and 552 kilobits per second), - the memory zone capacity values MD_N1 and MD_N2, - information representative of its identity, - a "CPR" coefficient representative of the number of DECT profiles supported, - "CO" information representative of the operational capacity of the device. This information can take the following values: "SB": the device can only operate in base station mode, "SM": the device can only operate in mobile station mode, 25. "SB / SMmanuer ': the device can change operational mode by intervention of its user, "SB / SM_auto" 'the device can automatically change operational mode, "SM / SMdirect": the device can communicate directly with another mobile whose information "CO" takes the value "SM / SMdirect", and - information "BA" representative of the automatic or manual switching capacity from an operating mode in the base station to an operating mode in the mobile station and vice versa ("BA"

  being "true" when this capacity exists and "false", otherwise).

  The read-only memory 305 constitutes a means of storing information readable by a computer or a microprocessor, retaining instructions of a computer program characterized in that it allows the implementation of the method of the invention. According to a variant, the read-only memory 305 is removable, partially or totally, and comprises, for example, a magnetic tape, a flash memory, a floppy disk or a compact memory disk

frozen ("CD-ROM" in English).

  The procedure followed by controller 306 to determine the mode

  operating station (base station or mobile station) is detailed in Figure 4.

  When a communication device according to the present invention is powered up, it goes into an internal initialization state 401. Then, during an operation 402, the communication device goes into reception mode on the next frequency band channel allocated for DECT compliant communications, as shown opposite

of operation 102 (Figure 1).

  Then, during a test 403, the communication device listens to the radio channel considered, for a predetermined duration, in order to detect a synchronization pulse originating from a base station (including the case of another communication device communication behaving as a base station). The communication device thus determines whether a base station

  uses the channel in question to send a synchronization signal, or not.

  When the result of test 403 is negative, during a test 404, the communication device determines whether the channel considered is the last, or

  no. When the result of test 404 is negative, operation 402 is repeated.

  When the result of test 403 is positive, during a test 405, the communication device determines whether it has an access right to the base station which transmits the synchronization signal, or not, in the manner

  described next to operation 108 (Figure 1).

  When the result of test 405 is negative, the communication device performs test 404. When the result of test 405 is positive, during an operation 406, identical to operation 109 (FIG. 1), the communication device locks on the base station which transmits the synchronization signal detected on the channel in question. At the end of operation 406, the communication device can obtain the information broadcast by the base station whose ARI parameter corresponds with at least one of its "PARK" identities. The communication device can also initiate or accept a connection via the base station to which the device is locked. The communication device can then communicate, on the one hand, with the other mobile stations and the communication devices according to the present invention which behave as mobile stations, and which are also locked on the same base station and, on the other hand with the base station itself or with the

  communication device which behaves as a base station.

  When the result of the test 404 is positive, during an operation 407, the controller 306 of the communication device switches this

  communication device in base station mode.

  In this base station operating mode, it transmits, at regular time intervals, a duration less than the predetermined duration of test 403, a synchronization signal, on one of the DECT channels. The duration of

  the regular time interval is, according to the DECT standard, 160 milliseconds.

  Then, the communication device lets pass a duration T1 (for example one minute), operation 408, while continuing to operate as a base station, before carrying out a test 409, during which it determines whether mobile stations have synchronized with him (see

detail of test 409 in FIG. 5).

  When the result of test 409 is negative, during an operation 411, the controller 306 switches the operating mode to a mobile station, then the communication device lets a predetermined duration T2 pass (for example in decreasing function of the available energy evaluated by the energy level controller 309), operation 412, before

repeat operation 402.

  When the result of the test 409 is positive, during an operation 413, the communication device allows a predetermined duration T3 to pass (for example as an increasing function of the available energy evaluated by the energy level controller 309), while continuing to operate in base station mode, before performing a test 414, during which the communication device determines whether at least one communication with a mobile station is active or not. When the result of test 414 is positive, it is repeated. When the result of the test 414 is negative, during an operation 415, the controller 306 switches the communication device from the base station mode to the mobile station mode. Then the device

  communication repeats operation 402.

  It is understood that, in accordance with the flow diagram of FIG. 4, two operating criteria are used: - when, in the mobile station operating mode, the communication device does not detect any base station, it goes into operating mode base station, and - when, in base station operating mode, the communication device does not detect any mobile station, it is placed in

  mobile station operating mode.

  Furthermore, when, in the base station operating mode, the communication device detects no communication with a mobile station, it switches to the mobile station operating mode. The purpose of these latter provisions is to return the base station to a mobile station in order to search, again, if another base station can be detected. To detect the presence of mobile stations (including the case of communication devices according to the present invention which behave as mobile stations), one places oneself, opposite FIG. 5, in the case where each communication device capable of operate in base station mode is informed of the identity of each communication device

  and each mobile station likely to communicate with it.

  In this case, the communication device first performs a test 501 (FIG. 5), during which the controller 306 determines whether the list of mobile stations capable of communicating with the communication device is empty or not. When the result of test 501 is positive, the result of test 409 is negative, operation 502. When the result of test 501 is negative, during an operation 503, a temporary variable / which is initialized to the value "0" serves as an identifier on the said list. Then, during an operation 504, the communication device sends, to the network, a response request message to the device identified by the l-th identifier of the list. Then, the communication device lets a predetermined duration T4, operation 505, pass before carrying out a test 506, during which it determines whether or not a response message has been sent by a communication device. When the result of test 506 is positive, during a test 507, the device determines whether the identity of the device which sent the response message corresponds to the identity of the device which had been called during the operation 504. When the result of test 507 is positive, the result of test 409 is positive, operation 510. When the result of test 507 is negative, or when the result of test 506 is negative, during an operation 508, the

  value of variable I is incremented.

  Then, during a test 509, the communication device determines whether the value of the variable I is less than or equal to the dimension of the list, or not. When the result of test 509 is positive, operation 504 is repeated. When the test result 509 is negative, the test result 409 is

negative, operation 502.

  Alternatively, to detect the presence of mobile stations, the following procedure is used: when a mobile station detects a base station, and locks on this base station, the mobile station sends the base station a message representative of his identity and his abilities (see below). The base station can then update a list of mobiles present in the cell. Conversely, when a mobile station leaves the cell (that is to say the coverage area of the base station) or before switching off, it sends a message to the base station signifying that it is closing its access rights. It is observed here that the procedure for detecting that a mobile station leaves a cell is known from the prior art, by analysis of the

signal reception power.

  FIG. 6 represents the structure of the information concerning the operational mode capacity of a station of the network. This information can be transmitted in DECT protocol messages using a field reserved for the transfer of non-standardized information, called, in the standard "escape-to-proprietar / 'which means, word for word" output to owner ". According to the invention, non-standardized information is used only in the following messages of the standard: "access-rights-request" which signifies word for word "access right request", and - "locate-request", which word for word means "location request"

  and which includes an attachment request.

  The first byte 701 of the field described in FIG. 6 indicates that the information elements which follow are non-standardized information items to be sent inside a DECT protocol message. The second byte 702 contains the number of information bytes to be transmitted. The third byte 703 indicates that bytes 704 and 705 contain an EMC ("Equipment Manufacturer Code") parameter which stands for word for word "equipment manufacturer code" which is used to identify the manufacturer using this proprietary information. Thus, if a device whose EMC parameter is different from that indicated by the

  bytes 704 and 705, it does not process the following information.

  Of course, if the present invention were to be the subject of standardization between different manufacturers, bytes 701, 704 and 705 do not

  would be used more in the same way.

  The byte 706, is representative of the operational capacity CO (identical to its value, in the embodiment described and shown) of the device which acts as a mobile station. The following bytes, 707 to 711, the number of which is equal to the number of information bytes to be transmitted (number represented by byte 702) minus four, are used to transmit more precise information about the capabilities of the device, to operate as a base station. For example, the following parameters can be transmitted: - device memory capacity (byte 707), - device memory filling rate (byte 708), - power, processor speed of the device (byte 709), and

  - maximum data rate supported by the device (byte 710).

  Position bit 8 (left) of information bytes 707 to 710 takes one of the values: - "1", when the information element is transmitted in this message, or - "0", when the value of the following bits of the byte has no

  meaning (the information element is not transmitted in the message).

  Figure 7 describes how a mobile station obtains access rights to a base station and how it terminates its access rights. The access rights procedure allows a base station and a mobile station to exchange their respective identities and information regarding the capabilities of the mobile station. The mobile station initiates the procedure by sending the base station an "access rightsrequest" message which contains in particular the capacities of the mobile station in the "terminal capabilit / 'field (which means word for word (terminal capacity). field, according to the invention, the profile indicator parameters ("profile indicator") are used and

  slot type capability (see below).

  Additional information necessary for the operation of the device according to the present invention is transmitted in the "escape to proprietary" field of the message "accessrightsrequest '

(figure 6).

  When a base station receives an "accessrightsrequest" message, if the mobile station is authorized to access the resources of the base station, the latter returns an "accessrightsaccept" message, and adds, in the table of declared mobile stations, the information concerning the mobile station which emitted the message "accessrightsrequest '. The information thus collected is stored in the table_SM, of the RAM 304, and organized as follows

  N Identity CO CM RM CP IP TS DM ...

  When a mobile station is added to table_SM, the following information concerning it is stored there: - its mobile identity, - its operational capacity (CO), - its memory capacity (CM), - its memory filling rate (RM) , - its processor capacity (CP), - its profile indicator (IP), - its slot type capacity (TS), - its maximum throughput (DM), and possibly others

information characterizing it.

  The IP and TS parameters are read in the "Terminal Capability 'field of the" access rights request "message, while the CO, CM, RM, CP and DM parameters are read in the" escape to proprietary "field described in Figure 6 When a mobile station wishes to close its access rights to a base station, it sends an 803 message "access rightsterminaterequest '(which means, word for word, request to end access rights). The base station then erases the information concerning this mobile station in its tableSM and returns a message "accessrights_terminateaccept" 804. The station

  mobile can no longer use the resources of the base station.

  Figure 8A illustrates how a mobile station attaches to or detaches from a base station. When a mobile station enters the cell of a base station, on which the mobile station has obtained access rights, it must initiate an attachment procedure on the base station. By this procedure, the mobile station indicates to the base station that it is ready to receive calls. To attach, the mobile station sends the base station a "Locaterequest" message 811 which contains information concerning in particular the identity and the capabilities of the communication station and the possibility of sending non-standardized information. With the message "Locaterequest" 811, the same information can be transferred to the base station as with the message "accessrightsrequest '. If a mobile station has significant modifications to its parameters (eg memory space still available) compared to the at the time of the access right procedure, she can use the "escape to proprietar / 'field as defined in

  Figure 6, to inform the base station.

  When a base station receives a "Locaterequest '811 message, it verifies that the mobile station is identified in its table_SM and, if so, returns a" Locate_accept "812 message. The base station then uses the information contained in its tableSM, the table of declared mobile stations, to insert the mobile station considered in the appropriate list, Liste_SM_auto, if its operational capacity CO is equal to SB / SM_auto, Liste_SM_manuel if its operational capacity CO is equal to SB / SM_manuel or ListeSMdirect if its operational capacity is equal to SM / SMdirect.

  The reverse procedure of attachment is detachment.

  When a mobile station leaves the cell or when it is switched off, it sends a "detach" message 813 to the base station which then removes the station

  mobile from the list corresponding to its operational capacity.

  However, the detachment procedure cannot always be initiated by the mobile station which leaves the cell (due to a breakdown or too fast speed, for example). The last part, in FIG. 8B, illustrates how the base station can periodically check the validity of the information which it keeps in the lists stored in its random access memory 304. The base station then periodically sends a request for procedure for update of its location (or its attachment), via a message "MM_info_suggest" 821 whose "infotype" field is equal to "locate suggest". The procedure for updating the location of a mobile station is identical to the attachment procedure, messages 822 and

  823 being identical to messages 811 and 812 respectively.

  Thanks to the arrangements illustrated in FIGS. 7, 8A and 8B, the list listeSMauto contains all the mobile stations present in the cell and having the capacity to switch automatically between the base station mode.

and mobile station mode.

  As explained with regard to figure 23, the list_SM_auto is classified according to the decreasing capacity of the mobile stations to become a base station: the first element of the list concerns the mobile station which has the best capacity to become a base station. To classify this list, after each attachment, detachment or update procedure, the base station takes into account all the parameters stored in the

  tableSMauto (CM, RM, CP, IP, TS, DM, ...).

  The SM_manual list is sorted in the same way as the SM_list. These lists can be used in the following situations: - the base station becomes inactive following a power off or a switch to mobile station mode and it searches for a replacement base station among the mobile stations having a capacity to become a base station, - the base station is overused (memory full, number of simultaneous calls greater than a predetermined value) and it is looking for a second base station to take over part of the traffic. The base station then chooses the first mobile station from the auto SM list. If the auto SM list is empty or if none of the stations in the SM_auto list is suitable, the base station can use the first mobile station represented in the SM_manual list. It must then transmit a message which triggers the display or emission of a signal on the chosen mobile station in order to warn the user that a change in the mode of

  operation of the mobile station considered is required.

  The base station uses the list SM_direct so that the communications internal to the cell and implying, each, at least one station represented in this list, are directly organized by this station. FIGS. 9 and 10 illustrate how an active base station (called "initial") finds a replacement base station (called "final"), for example when the initial base station can no longer fulfill its role as base station (power off or automatic or manual switching

to mobile station mode).

  The procedure described in FIG. 9 can only be implemented when there is no active connection. In addition, any new request for

  connection is refused during this procedure.

  As illustrated in FIG. 9, the initial base station begins with a test 902 during which it determines whether another base station is present or not (as illustrated in FIG. 1). When the result of test 902 is positive, the procedure is successfully completed, since the mobile stations which communicate with the initial base station will be able to replace the latter, for their communications and the initial base station changes from

  operating mode and becomes mobile station, operation 912.

  When the result of test 902 is negative, during a test 903,

  the initial base station determines whether the auto_SM_list is empty or not.

  When the result of test 903 is positive, the procedure is terminated, having failed, since no mobile station can take the role of base station. The user is then informed that if the base station stops operating,

  all communications will be suspended, operation 913.

  When the result of test 903 is negative, during an operation 904, the variable I is initialized to the value "0". Then, during an operation 905, the initial base station sends a message

  "new_baserequest" (which means, word for word "new base request") at 1-

  th mobile station in the SMauto_list. During operation 905, the initial base station waits sufficient time to allow a mobile station in accordance with the device which is the subject of the present invention, to respond, before carrying out a test 906. Then, during this test 906, the initial base station determines whether or not it has received a "new_base_accept" message from the considered mobile station. When the result of the test 906 is positive, during an operation 907, the information stored in the table table_SM, and in the lists listeSM_auto, liste_SMmanuel and liste_SM_direct, are transferred into the random access memory of the considered mobile station. Then, during a test 908, the initial base station determines whether it has received from the mobile station

  considered, a message of acknowledgment of the data transfer, or not.

  When the result of test 908 is negative, it is repeated. When the result of test 908 is positive, the initial base station changes operating mode, operation 912 and the operation of changing base station is completed, from

  side of the initial base station, successfully.

  When the result of test 906 is negative, the initial base station considers that the assignment of the role of base station has been refused by the I-th station of the list liste_SM_auto. Then, during an operation 910, the value of the variable I is incremented by 1. Then, during a test 911, the initial base station determines whether the value of the variable I is greater than or equal to the number of mobile stations represented in the Auto list, or not. When the result of the 911 test is negative, operation 905 is repeated. When the result of the 911 test is positive, the procedure for changing the base station is completed, having failed and the user is warned that the cessation of the activity of the initial base station will cause the suspension of

  all communications, operation 913.

  According to a variant, not shown, when, during the test 911, it is determined that the list liste_SM_auto has been entirely traversed, the operations and tests 905 to 912 are repeated by browsing the list liste_SM_manuel. Operation 912 is then performed only after the mobile station which sent the "new-base-accept" message (test 906) has sent a

  operating mode change confirmation message.

  When the procedure has been successfully completed, by detection of another base station during test 902 or by acknowledgment of an information transfer by a mobile station during test 908, the base station has thus changed its operating mode and became a mobile station, unless the procedure illustrated in FIG. 9 had been caused by a power off

  from the initial base station, in which case it ceases to operate.

  FIG. 10 illustrates the procedure for changing the base station on the side of a mobile station, when during a test 1001, it determines that a "new_baserequest" message has been received from the base station and is intended for the mobile station considered. Then, during a test 1002, the mobile station determines whether its operating capacity CO has one of the values SB / SM_auto or SB / SM_manuel, or not, by determining whether the value of the information "BA" is " true ', or not. When the result of test 1002 is negative, during an operation 1004, a message "new_basereject" is transmitted by the mobile station considered bound for the base station to notify it of the refusal of the assignment of the base station role. Then the procedure is completed, without the mobile station having switched

  in base station operating mode.

  When the result of test 1002 is positive, during a test 1003, the mobile station determines whether its available memory capacity MD is

  strictly lower than the value MDN1 kept in read-only memory 305.

  This MD_N1 value corresponds, in effect, to a memory capacity

  minimum available to fulfill the role of base station.

  When the result of test 1003 is positive, operation 1004 is carried out. When the result of the test 1003 is negative, during an operation 1005, the mobile station sends a base station role acceptance message "new_base_accept", intended for the initial base station. Then, during a test 1006, the mobile station determines whether it has received from the initial base station the information necessary to assume the role of base station, that is to say the set information kept in the lists list- SMauto, listeSMmanuel and liste-SM direct, and in the table

tableSM.

  When the result of test 1006 is negative, it is repeated. When the result of the test 1006 is positive, during an operation 1007, the mobile station sends, to the base station, an acknowledgment of receipt of the information. Then, during an operation 1008, the mobile station changes

  of operating mode and becomes base station. The procedure is then completed.

  In the case where the mobile station has a value of operating code SB / SM_manuel, the test 1003 is completed by: - triggering of an alert signal intended to warn the user that he must manually switch the operating mode of the station communication concerned, - a wait of sufficient time for the user to have time to perform manual switching, and - a test of change of operating mode by the user (not shown) and in the case where the the user has not made the change of operating mode during a predetermined period following the test 1003,

operation 1004 is carried out.

  It is observed that, in accordance with the operating mode illustrated in FIGS. 9 and 10, the initial base station uses static criteria, that is to say that does not immediately change in value depending on the evolution of the network or of the stations mobile, to choose a replacement base station, while the mobile station envisaged as future base station can accept or refuse the role of new base station, based on dynamic criteria, that is to say taking into account immediately any change in the state of the mobile station which would prevent its activity as

base station.

  FIGS. 11 and 12 illustrate how, on the initiative of a station which is initially a mobile station, a change of base station can be carried out. For example, when such a mobile station has locked onto the initial base station, following its power-up and this mobile station is intended to be a base station (for example because it supports all the variants and the most extensive modes of the DECT standard), a test 1101 is positive. Otherwise, this procedure is completed. When the result of the test 1101 is positive, during an operation 1102, the mobile station listens to the known channel, in the DECT standard under the name of "Q". On this channel, in fact, the initial base station regularly broadcasts information which may be useful to mobile stations, and, in particular, information relating to

the DECT profiles it supports.

  Then, during a test 1103, the mobile station determines whether it has better capabilities to be a base station than the initial base station, or not. When the result of test 1103 is negative, the procedure is completed. When the result of test 1103 is positive, during an operation 1104, the mobile station sends a message "chg_baserequesr 'which means change of base required, to the initial base station, then lets pass a sufficient time for the station basic can, if it conforms to the communication device of the present invention, emit a

reply message.

  Then, during a test 1105, the mobile station determines whether it has received, in return, from the base station, a message "chg_base_accept ', which signifies acceptance of change of base, or not. When the result of test 1105 is negative, the mobile station considers that it has received a refusal to change the base from the initial base station and the procedure for

base change is complete.

  When the result of test 1105 is positive, operations 1106, 1107 and 1108 are respectively identical to operations 1006, 1007 and

  1008. Then, the procedure for changing the base station is completed.

  On the side of the initial base station, when, during a test 1201, it determines that it has received a "chg_base request" message, from a mobile station which is locked, it performs a test 1202 during which it determines whether, at the same time, the information "BA" representative of its switching capacity is worth "true" and its operating mode MO corresponds to

  that of a base station, or not.

  When the result of the test 1202 is negative, during an operation 1203, the initial base station sends, to the mobile station considered, a message "chg_basereject". Then the procedure is completed. When the result of the test 1202 is positive, during an operation 1204, the initial base station sends, to the mobile station considered, a message "chg_base_accept". Then, during a 1205 test, the

  initial base station determines whether there is an active connection or not.

  When the result of test 1205 is positive, it is repeated. When the result of the test 1205 is negative, during an operation 1206, the base station sends to the mobile station considered the information kept in the tableSM table, and in the lists auto_list, manual_list and

direct SM list.

  Then, during a test 1207, the initial base station determines whether or not it has received a data transfer acknowledgment message from the mobile station considered. When the result of test 1207 is negative, it is repeated. When the result of the test 1207 is positive, during an operation 1208, the initial base station changes operating mode and starts to operate in mobile station mode, and the operation of

  base station change is successfully completed.

  FIG. 13 represents: - in the form of messages 1301 to 1304, the messages exchanged between the initial base station, on the left, and the mobile station which will become base station, on the right, within the framework of the procedure illustrated in FIGS. 9 and, and - in the form of messages 1305 and 1306, the messages exchanged between a mobile station, on the left, and the base station, within the framework of the

  procedure illustrated in Figures 11 and 12.

  To collect information concerning the capacity of the mobile stations present in the network to operate in base station mode, the base station according to the present invention uses a broadcast type message illustrated in FIG. 14A. The base station thus interrogates all the mobile stations to obtain the following information - the list of mobile stations which can automatically switch to base station mode, - this same list sorted according to one or more parameters chosen by the base station, - I identity of the mobile station having the best overall capacity to operate in base station mode, at a given time, - the identity of the mobile station having the best capacity to operate in base station mode, according to one or more fixed criteria by the base station. A first type of message 1401 (in FIG. 14A) is a request from the broadcast base station intended for all mobile stations, which includes the following fields: a message code field 1402 "broadcast_SB_req", which roughly means " request broadcast by the database ", - a type field 1403 CT, defining the type of the request concerned, - a length field 1404 CL which defines the number of parameters of the request, and - parameter fields 1405 CP (O) to 1406 CP (CL-1) which

  contain the criteria against which the response is expected.

  Fields type 1403 CT and length 1404 CL can take different values, enabling the different mobile stations to be specified how to respond to the request and according to what criteria, the latter being

  specified by fields 1405 to 1406.

  When the information transmitted in field 1403 CT is equal to '0 ", each mobile station must immediately return its capacity to act as a base station and, if the value contained in field 1404 CL is not zero, each

  mobile station must return the value of the parameters specified in the request.

  When the information transmitted in the 1403 CT field equals "1", each mobile query must return its capacity to act as a base station after a period of time whose value is representative of the value of the capacity of the mobile station to become a base station , and, if the value contained in the 1404 CL field is not zero, each mobile station must return the value

  parameters specified in the request.

  Measuring the ability of the mobile station to become a

  base is determined in accordance with the response time described below.

  The parameters represented by fields 1405 to 1406 include: - the operational capacity CO, - the available memory capacity, - the DECT profiles supported, - the type of DECT slot supported (single, double or half slot), and

  - the computing power of the central unit.

  The message 1411 "broadcast_SB_ans" (in FIG. 14B) which roughly means "response to the message broadcast by the base station", relates to the response of the various mobile stations to the base station. This message 1411 is sent using the oriented connection mode. It includes the following fields: - a message code field 1412, - an identity field 1413, in which the mobile station specifies its identity, - a response field 1414 CR, making it possible to specify the response of the mobile station, - a length field 1415 CL ', representing the number of response data, - data fields 1416 to 1417, containing the data

required by the base station.

  The response field 1414 CR can take the following values - "accept" ("acceptance"), meaning that the communication station has the capacity to act as a base station, the data fields, if the length field 1415 indicates a length not zero, then give indications concerning the parameters required by the base station, - "reject", meaning that, temporarily, the mobile station cannot act as a base station or does not have relative information to the parameters required by the base station. Data fields, if the length field 1415 indicates a non-zero length, can

  then give an explanation for the rejection.

  A lack of response to message 1401 from a mobile station is considered to be a response whose response field

  OR would be "reject" when a predetermined time has elapsed.

  By default, if in the 1401 message, operational capacity is not required, only mobile stations having the capacity to switch automatically from one operating mode to another, can respond to

Using a 1411 message.

  FIG. 15 represents an exchange of messages between the base station and each mobile station having the capacity to become a base station. Message 1401 is broadcast by the base station at regular time intervals,

for example every minute.

  In FIG. 15, the message 1401A is a message 1401 of the type without delay (CT = O) and the length field CL is also "0". Each of the mobile stations in accordance with the present invention then responds by return (that is to say without waiting), in the form of messages 1411A, 1411B or 1411C. In the example described, the mobile stations 204, 205 and 201 respond, the first two with a response field CR of type "accept" and the last

* with a response field CR of type "reject".

  To determine the response field, each mobile station in accordance with the present invention determines whether its operating code is one of the codes "SB / SM_auto" or "SB / SM_manuel ', or not, and, if so, whether its

  available memory capacity is greater than the predetermined value MDN1.

  In FIG. 16, the broadcast message 1401B is a message 1401 of the type with delay (CT = 1) and with parameters (CL = 1), the only parameter retained being the operational capacity. Mobile stations having the capacity to operate as a base station respond while waiting for a delay which depends on the value of their operational capacity: the first mobile stations which respond have an operational capacity equal to "SB / SM_auto" (message 1411 D and 1411E ), while the last responding mobile station has a

  operational capacity equal to 'SB / SMmanuer' (message 1411 F).

  Generally, in the embodiment of the present invention, the waiting time before the response is determined from the moment of reception of the message 1401B. This duration takes the value: Tréponse = CCO.tco + CPR.tCPR + CMD.tcMD, formula in which: - CCO is the coefficient of operational capacity (which is worth "0" if the operational capacity is "SB / SM_auto", " 5 "if the operational capacity is" SB / SM_manuel ', "5" if the operational capacity is "SM / SM_direct' and infinite if the operational capacity is worth" SM "), - CPR is the coefficient of supported profiles (which is" 0 "if the supported profiles are B, MMAP and GAP," 1 "if the supported profiles are A and GAP and" 2 "if the only supported profile is GAP), - CMD is the available memory coefficient, - tcco is the duration assigned to the operational capacity coefficient, tCPR is the duration assigned to the supported profile coefficient,

  - tCMD is the duration assigned to the available memory coefficient.

  For example the three durations are equal to 10 milliseconds (the duration of a DECT frame so that the response duration is always a multiple

the duration of a DECT frame).

  In Figure 16, the response time calculation formula is limited to Tréponse - CCO.tco, since the only parameter represented in message 1601 is

  the operational capacity parameter.

  In FIG. 17, it can be seen that the messages are transmitted according to a predetermined timing. Each communication cycle 1701, 1702 or 1703 lasts 10 milliseconds and is divided into twelve equal time slots. For a communication, one or more time intervals of each cycle are fixedly allocated. FIG. 18A represents the state of the art for establishing an internal connection to a cell. In FIG. 18A is represented the path of an internal communication between a mobile station 1802 and a mobile station 1803. This communication passes through a base station 1801. The information which passes at the instant t on the link between the mobile station 1802 and the base station 1801, then transit on the link between the base station 1801 and the mobile station 1803. There is therefore a duplication of information and a double occupation of the communication medium of the

  cell for two transmissions of the same information.

  This double occupation of the communication medium is not critical when the information transmitted is voice information. In the case of a data communication, the duplication of links, information and the occupation of the communication medium risks saturating the cell and

  block a connection request outside the cell.

  In FIGS. 18B and 18C, the operation of the device which is the subject of the present invention is observed, operation intended to avoid such duplication. In this operation: - when at least one of the mobile stations to communicate, referenced 1805 and 1806, is capable of operating in base station mode, or when the mobile stations 1805 and 1806 are both capable of communicating directly, the cell is organized so that the communication between the two mobile stations is direct, without passing through another station, - and, otherwise, a mobile station 1810 capable of operating as a base station, takes this role vis-à-vis vis the two mobile stations 1805 and 1806 which must communicate and constitute with them a new cell, to free the initial base station 1804 from the traffic concerning

  communication between mobile stations 1805 and 1806.

  In FIG. 19, we observe, in the form of a flowchart, how the creation of a new cell or the direct communication of the mobile stations is implemented. When, during a 1901 operation, the base station 1804 receives a call request internal to the cell, from a mobile station 1806 and bound for a mobile station 1805, it performs a test 1902 during which it determines: - if the requested connection requires a number of slots greater than a predetermined value (for example 4 slots, value beyond which the communication is necessarily other than a voice communication), or if the number of slots required is greater than the number of

slots available.

  When the result of the test 1902 is negative, during an operation 1903, the connection between the mobile stations 1805 and 1806 is established via the base station, in a manner known in the state of the

  technique prior to the present invention.

  When the result of the test 1902 is positive, during a test 1904, the base station determines whether at least one of the mobile stations 1805

  or 1806 has a connection in progress, or not.

  When the result of test 1904 is positive, operation 1903 is carried out. When the result of the test 1904 is negative, during a test 1905, the base station determines whether the mobile stations 1805 and 1806 are both in the list SM_direct, or not. When the result of the 1905 test is positive, during an operation 1906, the base station sends, to destination

  from each of the mobile stations 1805 and 1806, a message "switch-mode-

  request "to tell them to switch to direct communication mode, and tell them the identity of the mobile station that constitutes their contact (see

Figure 21B).

  If the implementation of direct communication between mobile stations 1805 and 1806 has failed (for example if one of the mobile stations rejects switching to direct communication mode), a test 1907

is performed (see below).

  If the direct communication between the mobile stations 1805 and 1806 is successful, at the end of their direct communication, the two mobile stations are synchronized again with the base station 1804. When the result of the test 1905 is negative, during a test 1907, the base station 1804 determines whether the mobile station 1805 is in the list_SM_auto, or not. When the result of the test 1907 is positive, during an operation 1908, the base station 1804 sends to the mobile station 1805 a "switch-mode-request" message 2101 (FIG. 21A) to indicate to it that it must switch in base station mode and sends it the identity of the station

  mobile 1806 so that mobile station 1805 assigns it access rights.

  In addition, on receipt of a "switch-mode-accept" message 2102 from the mobile station 1805, the base station 1804 sends the mobile station 1806 a "switch-base-request" message 2103 containing the identity of the base station 1805, to signify to the mobile station 1806 that it must

  synchronize with the new base station 1805 (see Figure 21A).

  If the switching of the mobile station 1805 to the base station fails (for example if it rejects the switching), a test 1909 is

performed (see below).

  When the result of the test 1907 is negative, during a test 1909, the base station 1804 determines whether the mobile station 1806 is in the list_SM_auto, or not. When the result of the test 1909 is positive, during an operation 1910, the base station 1804 sends to the mobile station 1806 a "switch-mode-request" message 2101 to indicate to it that it must switch to station mode. base and sends him the identity of mobile station 1805 for

  that the mobile station 1806 assigns it access rights.

  In addition, on receipt of a "switch-mode-accept" message 2102 from the mobile station 1806, the base station 1804 sends the mobile station 1805 a "switch-base-request" message 2103 containing the identity of the base station 1806, to signify to the mobile station 1805 that it must

  synchronize with the new base station 1806.

  It is observed, with reference to FIG. 21A, that for that of the mobile stations which switches to base station mode, as soon as the data communication 2104 between the stations 1805 and 1806 is completed,

  it returns to mobile station mode after sending a message "switch-

  base-request "2105 to the mobile station with which it communicated data. The mobile station which receives this message 2105 then synchronizes, at

  new, with base station 1804.

  If the switching of the mobile station 1806 to the base station fails (for example if it rejects the switching), a 1911 operation

is performed (see below).

  When the 1909 test result is negative, during a 1911 operation (figure 20), the base station determines whether the number of slots that remain available is strictly less than the number of slots required

  to the requested communication, or not.

  When the result of the 1911 test is negative, operation 1903 is carried out. When the result of the 1911 test is positive, during an operation 1912, the temporary variable k is initialized to the value "0". Then, during a 1913 test, the base station determines whether the value of the variable k is strictly less than the size of the list liste_SMauto, or not. When the result of the 1913 test is negative, operation 1903 is carried out. It is observed here that the execution of the operation 1903 does not guarantee the establishment of the communication, rejection procedures being provided, in accordance with the known state of the art. When the result of the 1913 test is positive, during a 1914 test, the base station determines whether the k-th station in the list

  liste_SM_auto has a connection in progress, or not.

  When the result of the 1914 test is positive, during an operation 1915, the value of the variable k is incremented by 1. Then the test 1913 is repeated. When the result of the 1914 test is negative, during an operation 1916, the base station 1804 sends to the mobile station identified at the k-th position of the list liste_SM_auto, here the mobile station 1810, a message "switch- mode-request ", then, if the mobile station considered 1810 accepts to take on the role of new base station, the initial base station 1804 transmits to each of the mobile stations 1805 and 1806, a message" switch-base-request "by indicating the identity of the new base station 1810 so that each of the mobile stations 1805 and 1806 synchronizes with the

  new base station 1810 (see Figure 22).

  At the end of the communication between the mobile stations 1805 and 1806, the new base station 1810 switches again to the

mobile station operation.

  If, on receipt of the "switch-mode-request" message, the mobile station 1810 refuses to change the communication mode, by transmitting a

  message "switch-mode-reject", or by not responding to the message "switch-

  mode-request ", operation 1915 is performed by base station 1804.

  According to a variant not shown, when the result of the 1913 test is negative, the part of the flow chart illustrated in FIGS. 19 and 20, from the 1907 test, is again implemented, but considering the list

  "liste_SM_manuef 'instead of the list" listeSMauto ".

  In FIG. 21A, it is observed that, in order for the mobile station 1805 to switch to the base station and for the mobile station 1806 to be linked to the base station 1805, the initial base station 1804 transmits first, bound for the station mobile 1805, a "switch-mode-request" message 2101, and waits, in return, for a "switch-mode-accept" message 2102. Then the initial base station 1804 transmits, to the mobile station 1806, a message

  "switch-base-request" 2103, and waits, in return, for a message "switchbase-

accept "2106.

  When the communication between stations 1805 and 1806 is completed, the message "switch-base-request" 2105 is followed, in return, by

message "switch-base-accept" 2107.

  In FIG. 21B, it can be seen that, in order to establish direct communication between the mobile stations 1805 and 1806, during the operation 1906, the base station 1804 transmits, first, to one of the mobile stations involved in the communication to be set up (for example the station 1805), a message 2111 "switch-mode-request" indicating the requested communication mode (direct communication mode) and indicating

  the identity of the other mobile station. On receipt of a message "switchmode-

  accept "2112 from the mobile station for which the message (station 1805 in our example) was intended" switch-mode-request "2111, the base station 1804 transmits, bound for the other mobile station involved in the

  communication (station 1806 in our example), a message "switch-mode-

  request "2113 by indicating the requested communication mode (direct communication mode) and by indicating the identity of the other mobile station. Upon receipt of a" switch-mode-accept "message 2114 from the mobile station for whom the message (station 1806 in our example) "switch-mode-request" 2113 was intended, the two mobile stations switch to direct communication mode. At the end of the communication, station 1805 transmits, bound for the station 1806, a message "switch-mode-request" 2116 and receives, in return a message "switchmode-accept" 2117 and the two stations

  1805 and 1806 then switch to mobile station mode.

  In FIG. 22, it is observed that, to establish communication between the mobile stations 1805 and 1806 via a new base station 1810, during operation 1916, the base station 1804

  first transmits to the mobile station 1810 a message "switch-

  mode-request "2201 by indicating the required mode of communication, base station mode and the two mobile stations 1805 and 1806 to which access rights will have to be opened. Upon receipt, from mobile station 1810, of a message "switch-mode-accept" 2202, the base station 1804 transmits, at

  destination of mobile station 1806, a "switch-base-request" message 2203.

  On receipt of a "switch-base-accept" 2208 return message, the base station 1804 transmits, to the mobile station 1805, a "switch-base-request" message 2204. Each of the messages 2203 and 2204 indicates , at each mobile station, that the new base station which concerns them

is station 1810.

  After the mobile station 1805 has sent a message "switch-

  base-accept "2209 at base station 1804, mobile stations 1805 and 1806

  attached to the new base station 1810.

  Via communications 2205 and 2206, the mobile stations 1806 and 1805 then communicate data to each other, via the new base station 1810. At the end of the communication of the data, the new base station 1810 transmits , to the mobile station 1806, a "switch-base-request" message 2207 and, to the mobile station 1805, a "switch-base-request 'message 2208, indicating to each of the

  mobile stations that the new base station is station 1804.

  On reception, in return, of "switch-base-accept '2210 and 2211 messages, from mobile stations 1805 and 1806, base station 1810

switches to mobile station mode.

  In FIG. 23 is described a flowchart allowing the classification of the mobile stations having a capacity to automatically switch to base station mode, according to criteria defining this capacity to

become a base station.

  Of course, a similar procedure can be followed to classify the list of mobile stations having an ability to switch

  manually in base station mode.

  The procedure illustrated in FIG. 23 is executed by a base station when a new mobile station (hereinafter referred to as SMk) joins

  a cell and sends a message illustrated in Figure 6.

  When this event occurs, during an operation 3201, the controller 306 of the base station initializes the temporary variable /, to the value "0". Then, during a test 3202, the controller 306 determines whether the value of the temporary variable / is greater than or equal to the size of the list liste_SMauto, or not. When the result of the test 3202 is positive, during an operation 3207, the identity of the mobile station SMk is inserted at the position / of the list SM_auto list and the classification procedure is finished When the result of the test 3202 is negative , during a test 3203, the controller 306 determines whether the maximum bit rate of the station SMk is strictly greater than the maximum bit rate of the / -th station in the list

auto_list, or not.

  When the result of test 3203 is positive, operation 3207 is carried out. When the result of test 3203 is negative, during a test 3204, the controller 306 determines whether the maximum bit rate of the station SMk is strictly less than the maximum bit rate of the I-th station in the list

auto SM list, or not.

  When the result of test 3204 is positive, during an operation 3208, the value of the temporary variable I is incremented by 1 and test 3202 is repeated. When the result of test 3204 is negative, during a test 3205, the controller 306 determines whether the memory capacity of the station SMk is strictly greater than the memory capacity of the l-th station of

the list liste_SMauto, or not.

  When the result of test 3205 is positive, operation 3207 is carried out. When the result of test 3205 is negative, during a test 3206, the controller 306 determines whether the memory capacity of the station SMk is strictly less than the memory capacity of the ith station in the list

autoS list, or not.

  When the result of test 3206 is positive, operation 3208 is carried out. When the result of test 3206 is negative, a new parameter of capacity to become a base station is considered and tests similar to tests 3203 and 3204, or 3205 and 3206 are carried out by considering this new parameter in place of the maximum throughput (tests 3203 and 3204) or memory capacity (tests 3205 and 3206). Of course, the parameters tested are in decreasing order of importance. When the last parameter has been considered with a negative result again in the two tests concerning it, the operation

3207 is performed.

Claims (18)

  1. Method of communication between communication stations adapted to communicate with each other when at least one of said communication stations provides a control signal, said station then operating in "base station" mode and the stations not providing control signal then operating in "mobile station" mode, characterized in that it comprises, performed by at least one communication station initially operating in base station mode: - an operation for determining the presence of a station operating in mobile station mode, and - when during the presence determination operation, it is determined that no station is operating in mobile station mode, a switching operation in mobile station mode, during which said   station goes into mobile station mode.   2. Communication method according to claim 1, characterized in that it comprises, for at least one communication station operating in mobile station mode: - an operation for determining the presence of a station operating in base station mode, and - When during the presence determination operation, it is determined that no station is operating in base station mode, a switching operation in base station mode, during which said   station goes into base station mode.   3. Communication method according to claim 1, characterized in that, following the switching operation in mobile station mode, said communication station performs: - an operation for determining the presence of a station operating in station mode base, and when during the presence determination operation, it is determined that no station is operating in base station mode, a switching operation in base station mode, during which said   station goes into base station mode.   4. Communication method according to any one of   Claims 2 and 3, characterized in that, between two successive operations   determining the presence of a station operating in base station mode, said station performs a standby operation, during which it does not   not change the operating mode.   5. Communication device between communication stations adapted to communicate with each other when at least one of said communication stations provides a control signal, said station then operating in "base station" mode and the stations not providing control signal then operating in "mobile station" mode, characterized in that it comprises, in at least one communication station initially operating in base station mode, a processing means suitable for: - determining the possible presence of '' a station operating in mobile station mode, and - when it has determined that no station is operating in mobile station mode   mobile station, to switch to mobile station mode.   6. Communication device according to claim 5, characterized in that its processing means is adapted, when it operates in mobile station mode: - to determine the possible presence of a station operating in base station mode, and - when it has determined that no station is operating in mode   base station, to switch to base station mode.   7. Communication device according to claim 5, characterized in that the processing means is adapted, after having switched to mobile station mode: - to determine the possible presence of a station operating in base station mode, and - when '' determined that no station is operating in mode   base station, to switch to base station mode.   8. Communication device according to any one of   claims 6 and 7, characterized in that the processing means is suitable,   wait for a predetermined period of time without changing the   operation, between two switches.   9. Network, characterized in that it comprises at least two   devices according to any one of claims 5 to 8.   10. Telephone, characterized in that it comprises a device according to   any one of claims 5 to 8.   11. Photographic camera, characterized in that it comprises a   device according to any one of claims 5 to 8.   12. Printer, characterized in that it includes a device   according to any one of claims 5 to 8.   13. Scanner, characterized in that it comprises a device according to   any one of claims 5 to 8.   14. Camera, characterized in that it comprises a device   according to any one of claims 5 to 8.   15. Computer, characterized in that it comprises a device according to   any one of claims 5 to 8.   16. Fax machine, characterized in that it includes a device   according to any one of claims 5 to 8.   17. Television, characterized in that it comprises a device according to   any one of claims 5 to 8.   18. Audio / video player, characterized in that it includes a   device according to any one of claims 5 to 8.