FR2781958A1 - System for network communication for a wireless local network with centralized architecture, has facility for switching from one station to another in the base station mode - Google Patents

Abstract

The system includes an operation of determination of the capacity of the station functioning in base station mode, and an operation of determination of the capacity of this station functioning in base station mode for continuing this role, and when during the capacity determination operation, it is determined that this capacity is reduced, a request operation during which a first communication station transmits to a second communication station, a message representative of the demand for station change functioning in base 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 so-called base communication station, 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").

  Document US-A-5,691,980 describes how a master node of a network can detect a low battery level and choose a new master node from among slave nodes. It chooses the slave node with the best battery level. According to this document, it is the initial master node which determines its replacement. This document does not take into account a system comprising heterogeneous portable terminals, as in a DECT network. Furthermore, according to this document, a slave node cannot

  take the initiative to become a master node.

  When the base station is no longer able to perform this role correctly or when the quality of the transmission is not sufficient, no prior art is known which allows switching

  automatic from a mobile station to a base station.

  To this end, according to a first aspect, the present invention relates to 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 supplying a control signal then operating in "mobile station" mode, characterized in that it comprises, carried out by a station operating in base station mode: - an operation for determining capacity of said station operating in base station mode to continue this role, and - when, during the capacity determination operation, it is determined that said capacity is reduced, a request operation during which a first station of communication transmits to a second communication station, a message representative of request for

  change of station operating in base station mode.

  Thanks to these provisions, the cell can be reconfigured automatically when the base station leaves the cell or when a mobile station which may have better capacities to operate in the station

  base that the current base station enters the cell.

  According to particular characteristics, during said request operation, the change request message includes information representative of a mobile station identity envisaged as

new base station.

  Thanks to these provisions, the first station, which requires the change of base station, can determine and transmit the identity of the

  station envisaged as a new base station.

  According to particular characteristics, the first communication station is the communication station operating in station mode

  basic, preliminary to the request operation.

  According to other particular characteristics, the second communication station is a communication station envisaged for

  operate in base station mode following the request operation.

  Thanks to these arrangements, the two communication partners are the two communication stations which plan to exchange their role in the cell. This simplifies communication and avoids

  disturb other communication stations.

  According to particular characteristics, the request operation is carried out by the communication station operating in base station mode prior to the request operation and the second communication station performs, following the reception of the message representing the request for change of station operating in base station mode: - an operation for determining whether or not to operate in base station mode, and - a response operation at the base station, during which the second station communication transmits a message

  representative of the agreement, or not to operate in base station mode.

  Thanks to these provisions, it is the station envisaged as future base station which determines whether it accepts this role or not. Thus, if the initial base station is only partially informed of the effective capacity of the mobile station to take on the role of base station, it cannot impose this

  change of role at the second communication station.

  According to particular characteristics, the communication station operating in base station mode determines said capacity by

  depending on the amount of energy it has.

  According to other particular characteristics, said communication station operating in base station mode performs a switching operation in mobile station mode when the amount of energy which it

  disposes is less than a predetermined value.

  Thanks to these provisions, it reduces its energy consumption by switching from a base station operating mode, which involves high energy consumption, to a mobile station operating mode for which the energy is mainly consumed in communication course. According to other particular characteristics, the communication station operating in base station mode determines said capacity by

  depending on the quality of transmission between it and mobile stations.

  Thanks to these provisions, when the initial base station moves away from the other communication stations of the cell, and, more generally when it no longer ensures a sufficient quality of transmission, another communication station is called upon to take the role of base station. According to particular characteristics, the first communication station is the communication station operating preliminary to

  the request operation in base station mode.

  According to other particular characteristics, the second communication station is a communication station envisaged for

  operate in base station mode following the request operation.

  Thanks to these arrangements, the two communication partners are the two communication stations which plan to exchange their role in the cell. This simplifies communication and avoids

  disturb other communication stations.

  According to particular characteristics, in the absence of a response from the second communication station, the first station

  considers that the proposed change of base station has failed.

  Thanks to these provisions, the method of the invention works as well with devices according to the present invention as with

  devices known in the state of the art prior to the present invention.

  According to particular characteristics, following the request operation, carried out by the first communication station: - an operation for determining acceptance of change of station operating in base station mode, and - when it is determined that the envisaged change is not accepted, a new request operation during which a new message representing the request for a change of base station is

  addressed to another communication station.

  Thanks to these provisions, the station which requires a change of base station, can make several successive attempts to reach

this goal.

  According to particular characteristics, each request operation includes an operation for selecting the destination station of the station change request message operating in station mode.

basic.

  According to other particular characteristics: - the selection operation comprises an operation of reading a destination station identity from a list of communication stations, - the selection operation comprises an operation of determining the mobile station having better capacities to become the new base station, - the selection operation comprises an operation of determining a mobile station having a need to transmit, - the selection operation comprises an operation of determination

  of a mobile station having already operated in base station mode.

  Thanks to each of these provisions, the stations which are envisaged to operate in base station mode can, in a preferential order which depends on the characteristics of the selection operation, be recipients of messages representative of request for change of

  station operating 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 stations not supplying a control signal then operating in" mobile station "mode, characterized in that it includes suitable processing means: - determining a capacity of a communication station operating in station mode base to continue this role, and - when it has determined that said capacity is reduced, to have transmitted by a first communication station to a second communication station, a message representative of request for change of

  station operating in base 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.

  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 shows, schematically, 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 flowchart illustrated in FIG. 4, FIG. 6 represents, schematically, the organization of information transmitted by a communication device munication 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, - Figures 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, with a view to coll ect information concerning the capacity of mobile stations to operate in base station mode, - Figures 15 and 16 schematically represent messages exchanged between communication devices in accordance with 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 for classifying mobile stations according to criteria defining their capacity to operate as a base station, - Figure 24 shows, schematically, a flowchart set up work by a communication station operating, initially in mobile station mode, for communication, in the absence of a base station, - Figure 25 shows, schematically, a flowchart implemented by a station communication initially operating in mobile station mode, upon receipt of a base station change request message conforming to the illustrated message in Figure 6, - Figure 26 shows, schematically, a flowchart implemented by a communication station connected to an external network, - Figure 27 shows, schematically, a flowchart implemented by a communication station operating, initially, in base station mode, when its ability to continue this operating mode decreases, - FIG. 28 diagrammatically represents a flow diagram implemented by a communication station operating, initially, in mobile station mode, on receipt of a base station change request message, - Figure 29 schematically shows a flow diagram implemented by a communication station, operating in base station mode, to determine a radio transmission quality , and FIG. 30 schematically represents a flow diagram implemented by a communication station operating, initially in mobile station mode, but having already operated in base station mode, when its capacities to operate in base station mode

have been restored.

  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 Figure 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 receives on the next channel (there are ten) the allocated frequency band for communications conforming to the DECT standard (1880 to 1900 MHz), looking for a signal transmitted by a base station that suits it. During the first iteration of operation 102, the first channel is chosen. before performing the operation ion 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

  through 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 according to the present invention, 201, 204 or 205, comprises, connected to each other by a bus 301: - a controller 306, - a DECT baseband unit 302, - a unit radio 303, itself connected, moreover, to a transmitting-receiving 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), - an input / output interface 311, and

  - a communication quality controller 312.

  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 recognize the type of electrical supply (mains or battery), in a known manner, and to evaluate the level of energy available for the communication device, in order to determine: - timer values (see below), and

  - an ability to become or remain a base station.

  The communication quality controller 312 is adapted to assess the quality of the radio signal and to supply a QR value representative of

this quality.

  The main memory 304 stores, in registers which, for convenience, each bear the same name as the data it contains: - temporary variables I and k, - a "QR" value representative of the quality of the radio signal measured by the controller 312, - a "NB" value representative of an amount of available energy, - a "DB" value representative of the past operation of the station, in base station mode, - a "MO" variable representative of the mode operational in progress, 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 MDN2, is between the two predetermined values or is greater than the two predetermined values, - a memory area" T x / Rx "reserved for receiving or transmitting data, - a" TableSMA 'table containing a list of the identities of the mobile stations (including the devices in accordance with the present invention) declared to the base station, and the information associated with 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 identities of mobile stations likely to change operating mode, by intervention of their user (for example station 201), and - a" ListSMdirecft "list containing a list of identities of mobile stations likely to communicate directly with each other, without

base station.

  The read-only memory 305 stores, in registers which, for convenience, each bear the same name as the data it contains: - information "CAr of memory capacity of the device, - information" CP "of processor capacity of the device, - a minimum value of communication quality QRmin, - a maximum value of communication quality QR_max, - a minimum value of quantity of energy available NB_min, - a maximum value of quantity of energy available NB_max, - an indicator 'IP "representative of the DECT standard profiles supported by the device (in fact by its DECT 302 baseband unit), - an energy coefficient" CE "which represents the energy source of the station considered, according to three values: "CE_HIGI-", being worth "2", for a printer, a copier, a fax machine or a desktop computer, and more generally for any equipment which is generally connected to the sector or which includes a means of detection of the connection to the sector which indicates that the station is connected to the sector, "CE_MID", worth "1", for a portable computer and more generally for a communication station which can operate either on the sector, or on battery and "CELOW", worth "0" n, for a pocket organizer or a mobile phone, and more generally for a communication station which operates almost exclusively on battery, - a coefficient of fixity "CF" which represents the usual mobility of the station considered, according to three values: "CFHIGH ', worth" 2 ", for a printer, copier, fax machine or desktop computer, and more generally for any equipment that is generally fixed," CFMID ", worth" 1 ", for a computer portable and more generally for a communication station which can be moved but which is generally not moving during its operation and "CF_LOW ', being worth" 0 ", for a pocket organizer or a tel mobile phone, and more generally to a communication station that can be moved during use - network interface information "I '? which represents the types of network that can be accessed by the station, equal to "0" when no other network can be accessed and being non-zero when another network can be accessed, the positions of the bits equal to "1" in the binary representation " I? ' indicating which types of network can be accessed: xxxx xxxl PSTN (switched telephone network) (PSTN, in English) xxxx xxlx ISDN (integrated service digital network) xxxx x1xx LAN (local area network) xxxx lxxx ATM (asynchronous transfer mode) , - a network interface coefficient "CIR" which represents the number of accessible external networks, "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, "SB / SM_manuef': the device can change of operational mode by intervention of its user, "SB / SM_auto" 'the device can automatically change operational mode, 30. "SM / SM_direct"': the device can communicate directly with another mobile whose information "CO" takes the value "SM / SM_direct", 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), we place ourselves, with reference to 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 the test 501 is positive, the result of the test 409 is negative, operation 502. When the result of the test 501 is negative, during an operation 503, a temporary variable I which is initialized to the value '0' serves as an identifier on said list. Then, during an operation 504, the communication device sends, to the network, a response request message to the device identified by the I-th identifier of the list. the communication device allows a predetermined duration T4, operation 505, to pass before performing a test 506, during which it determines whether or not a response message has been sent by a communication device. 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 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-proprietary" which means, word for word "output to owner". According to the invention, the 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 bit rate supported by the device (byte 710).

  - "CF" fixity coefficient (byte 712), - "CE" energy coefficient (byte 713), - "IR" network interface (byte 714), Position bit 8 (left) of the bytes information 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 "accessrightsrequest" message which contains in particular the capacities of the mobile station in the "terminal capability" field (which means word for word (terminal capacity). according to the invention, the profile indicator parameters ("profile indicato? ') are used and

  slot type capability (see below).

  The additional information necessary for the operation of the device according to the present invention is transmitted in the "escape to proprietar / 'field of the" accessrightsrequest "message.

(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, information about the mobile station that issued the "accessrightsrequest" message. The information thus collected is stored in table_SM, from RAM 304, and organized as follows: N Identity CO CM RM CP IP TS DM CE CF IR When a mobile station is added to table_SM, the following information concerning are 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 bit rate (DM), - its energy coefficient (CE), - its fixity coefficient (CF), - its network interface information (IR),

  and, possibly, other information characterizing it.

  The IP and TS parameters are read in the "Terminal Capability 'field of the" accessrightsrequest "message, while the CO, CM, RM, CP, DM, CF, CE and IR parameters are read in the" escape to proprietary /' field described in FIG. 6. When a mobile station wishes to close its access rights to a base station, it sends a message 803 "accessrights_terminaterequest" (which means, word for word, request for the end of access rights). The base station then erases the information concerning this mobile station in its table_SM and returns a message "accessrights_terminate_accept" 804. The mobile station can then 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 message "Locaterequest '811 which contains information concerning in particular the identity and capabilities of the communication station and the possibility of sending non-standardized information. With the message "Locate.request '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 right of access procedure, it can use the 'escape to proprietary' 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 table SM, 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 / SMauto, Liste_SM_manuel if its operational capacity CO is equal to SB / SMmanual or Liste_SMdirect 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_infosuggest' 821 whose field "infotype" 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 liste_SM_auto 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

  table_SM_auto (CM, RM, CP, IP, TS, DM, CF, CE, IR, ...).

  The list_SM_manuel is sorted in the same way as the list_SM_auto. 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 list. If the SMauto list is empty, or if none of the stations in the auto SM_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_base_requesf '(which means, word for word" request for new base ") at 1-

  th mobile station of the list_SM_auto. 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 it has received from the mobile station under consideration a

message "new_base_accept", or not.

  When the result of test 906 is positive, during an operation 907, the information stored in the table_SM table, and in the auto SM list, manual SM list and direct SM list, are transferred to the station's RAM. mobile considered. 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 l-th station of the list liste_SM_auto. Then, during an operation 910, the value of the variable is incremented by 1. Then, during a test 911, the initial base station determines whether the value of the variable / is greater than or equal to the number of mobile stations represented in the SM_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 all communications to be suspended, operation 913. According to a variant, not shown, when, during the test 911, it is determined that the list listeSMauto has been entirely traversed, operations and tests 905 to 912 are repeated by traversing the list listeSMmanuel. Operation 912 is then only performed after the mobile station which sent the "new-base-acceptf't" 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 message "new_baserequesf '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_manual, or not, by determining whether the value of the information "BA" is "true / i" or not. When the result of test 1002 is negative, during an operation 1004, a message "new_base reject" is transmitted by the mobile station considered bound for the base station to notify him of the refusal to assign the role of base station. 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 test 1003 is negative, during an operation 1005, the mobile station sends a base station role acceptance message "new_base_accepf ', bound 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 all of the information kept in the lists list_SM_auto, list_SM_manuel 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 SB / SMmanuel operating code, 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 the test 1103 is positive, during an operation 1104, the mobile station sends a message "chg base request" which means change of base required, to the initial base station, then lets pass a sufficient time so that the base station can, if it conforms to the communication device of the present invention, transmit 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_accep't", 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 message uchgbaserequest ", from a mobile station which is locked, it performs a test 1202 during from 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 test 1202 is negative, during an operation 1203, the initial base station sends, to the mobile station in question, a message "chg_base_reject '. Then the procedure is completed. When the result of test 1202 is positive, during an operation 1204, the initial base station sends, to the mobile station considered, a message "chg_baseaccept". Then, during a test 1205, 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 table table_SM, and in the lists liste_SM auto, listeSMmanuel 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 FIGS. 11 and 12. To collect information concerning the capacity of the stations mobiles 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, - The 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 criteria fixed 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 station 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, 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 CM, - its energy coefficient CE, - its fixity coefficient CF, - its network interface information IR, - 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 "broadcastSB_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 information relating 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

  CR 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 CR response field 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 USB / SM_manuel ', or not, and, if so, whether its

  available memory capacity is greater than the predetermined value MD_N1.

  In FIG. 16, the broadcast message 1401B is a message 1401 of the type with delay (CT = I) 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 is a function of the value of their operational capacity: the first mobile stations which respond have an operational capacity equal to "SB / SMauto" (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 + CE.tcE + CF. tcF + CIR. tCIR, formula in which: - CCO is the operational capacity coefficient (which is worth "0" if the operational capacity is "SB / SMauto", "5" if the operational capacity is "SB / SM_manuef '," 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 worth" 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 profile coefficient supported, - tcMD is the duration assigned to the coefficient of available memory, - tcE is the duration assigned to the energy coefficient, - tCF is the duration assigned to the coefficient of fixity,

  - tCIR is the duration assigned to the network interface coefficient.

  For example, the six durations above are equal to 10 milliseconds (the duration of a DECT frame for the response duration to be

  always a multiple of 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 communication, a fixed allocation is made

  or more time intervals in each cycle.

  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 implementation is implemented.

  direct communication from mobile stations.

  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 21 B).

  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 message "switch-mode-reques't" 2101 (FIG. 21A) to indicate to it that it must switch to base station mode and send 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 from the mobile station 1805 to the base station fails (for example if it rejects the switching), a test 1909 is carried out (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_SMauto, 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_SM_auto, 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

  listeSM_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 SM_auto list, 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 message “switch-mode-request”, 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_manuel" 'instead of the list "liste_SM_auto".

  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-requesf't" 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 "switch-mode-acceptf' 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-reques't "2201 indicating the required mode of communication, base station mode and the two mobile stations 1805 and 1806 to which access rights must be opened. Upon receipt, from mobile station 1810, d 'a "switch-mode-accept" message 2202, the base station 1804 transmits, to

  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" messages 2210 and 2211, from mobile stations 1805 and 1806, base station 1810

switches to mobile station mode.

  We will now describe how, when a station has determined that it has better capabilities as a base station than the current station, it sends it a "chg-base-request" message which includes information representative of its fixity coefficient CF, from her

  CE energy coefficient and its CIR network interface coefficient.

  On receipt of this message, the initial base station then successively compares these coefficients, in decreasing order of their importance (communication coefficient of importance greater than that of the fixity coefficient, itself of importance greater than that of the coefficient of energy): for each coefficient successively processed: if the initial base station has a better coefficient than the mobile station, it rejects the change of base, via a message "chg-base-reject ', - if the initial base station has a lower coefficient than the mobile station, it accepts the change of base, by means of a "chg-base-acceptf 'message, and - in the latter case (equality for the coefficient considered ) she

go to the next coefficient.

  When all the coefficients have been processed, the base station returns a base change acceptance, in the form of a

"chg-base-accept" message.

  For the implementation of this procedure, the mobile station follows the flow diagram illustrated in FIG. 11, only the operation 1104 being modified to transmit, in the message "chg-base-request ', information

  representative of the coefficients CF, CE and CIR.

  The base station then performs the operations illustrated in FIG. 25. First of all, during an operation 2501, the base station receives a "chg-base-requesf" message. Then, during a test 2502, the base station determines whether, at the same time, its operating mode is the base station mode (MO = SB) and if it has the capacity to change operating mode (BA = true ), or not. When the result of test 2502 is negative, the controller 306 of the base station performs an operation 2505, during which it sends a message "chg-base- rejectf 'to the mobile station which sent the message

  "chg-base-request". The procedure is then completed (on failure).

  When the test result 2502 is positive, during a test

  2503, the controller 306 determines whether the CIR coefficient received is zero, or not.

  When the result of the test 2503 is positive, during a test 2512, the controller 306 determines whether the coefficient CIR retained in read-only memory 305 is zero, or not. When the result of test 2512 is negative, operation 2505 is carried out. When the result of test 2512 is positive, during a test 2504, the controller 306 determines whether, at the same time, the coefficient CF received is less than or equal to the coefficient CF kept in read-only memory 305, and if the coefficient CE received is less than or equal to the CE coefficient stored in ROM 305, or

no.

  When the result of test 2504 is positive, operation 2505 is carried out. When the test result 2504 is negative, an operation 2507,

described below, is performed.

  When the result of test 2503 is negative, during a test 2506, the controller 306 determines whether, at the same time, the coefficient CIR received is different from the coefficient CIR retained in read-only memory and the coefficient CIR

  kept in read only memory is different from "2", or not.

  When the result of test 2506 is negative, test 2504 is carried out. When the result of test 2506 is positive, during operation 2507, the initial base station transmits, to the mobile station having transmitted the message "chg-base-reques't", a message "chg-base - accept't ". Then, during a test 2508, the controller 306 determines whether the coefficient CIR

  retained in read-only memory is zero, or not.

  When the test result 2508 is negative, the procedure is completed and the initial base station remains in base station mode. When the result of test 2508 is positive, during a test 2509, the controller 306 determines whether a connection is active or not. When the result of test 2509 is positive, it is repeated. When the test result 2509 is negative, during an operation 2510, the initial base station switches to station mode

mobile.

  In the case where the communication station is combined with access to an external network, the device illustrated in FIG. 3 further comprises: an external communication means 314 accessing an external line 315 from an external network, and

- a line controller 313.

  The line controller 313 is adapted to detect the seizure of the external line 315 by the external communication means 314. In this case, it operates by implementing the flowchart illustrated in FIG. 26. It can be observed that initially, a such a device operates in base station mode, operation 2601. It then performs a test 2602, during which it determines whether the external line is taken or not, by making use of the

line controller 313.

  When the result of test 2602 is negative, it is repeated. When the result of test 2602 is positive, during a test 2603, it determines whether access to the external line is carried out by a mobile station, or not. When the result of test 2603 is positive, test 2602 is repeated. When the result of the test 2603 is negative, during an operation 2604, the controller 306 switches the operating mode to mobile station mode. Then, during a test 2605, the controller 306 determines whether the external line is busy or not, by making use of the line controller 313. When the result of the test 2605 is negative, it is repeated. When the result of test 2605 is positive, during a

  operation 2606, the operating mode is switched to base station mode.

  The procedure followed by the base station to request a new base station when its communication quality is too low,

is illustrated in figure 27.

  The station considered operating in base station mode, operation 2301, its controller 306 performs a test 2302 during which it determines whether: - if the quantity of NB power available is less than the quantity NB_min, or - if the signal quality radio QR is less than the QR_min value,

or not.

  When the result of test 2302 is negative, during an operation 2310, the controller 306 waits for a period of time T7, then test 2302 is repeated. When the result of test 2302 is positive, during one; ': r 2781958 I I operation 2303 the controller 306 performs a search procedure for a

new base station.

  Following operation 2303, during a test 2304, the

  controller 306 determines whether or not a new base station has been found.

  When the result of the test 2304 is positive, during an operation 2305, the value DB is set to the value "1" then, during an operation 2306, the operating mode of the base station considered is switched to mobile station mode. When the result of test 2304 is negative, during a test 2307, the controller 306 determines whether the quantity of available energy NB is

  ! 1I I 1 lower than the NB_min value, or not.

  When the result of test 2307 is positive, operation 2306 is carried out. When the result of test 2307 is negative, during an operation

  - ^ 5 2309, the central unit waits for a period of time T8, then test 2302 is repeated.

  Of course, the procedure illustrated in FIG. 27 can be followed only when no connection is active. Otherwise, add a

  connection deactivation operation, before operation 2306.

  iHall For a mobile station (see Figure 28), when it receives a "new-base-requesf 'message which designates it, operation 2801, its controller 306 first performs a test 2802, during which it determines if at the same time, on the one hand, the quantity of NB power available is greater than the quantity NB_max, and, on the other hand, the quality of the radio signal QR is greater than the

QR_max value, or not.

  When the result of the test 2802 is negative, during an operation 2807, the controller 306 sends a "new-base-rejec't" message to the base station, and thus completes the procedure for changing its operating mode. When the result of test 2802 is positive, during an operation

  2803, the central unit 306 sends to the base station a message "newbase-

  accept ". Following operation 2803, the controller 306 determines, during a test 2804, whether it has received the information necessary for its

  operating in base station mode, or not.

  yi When the result of test 2804 is negative, it is repeated. When the result of the test 2804 is positive, during an operation 2805, the controller 306 of the mobile station considered, sends an acknowledgment message "ack", to the initial base station. Then, during an operation 2806, the controller 306 switches to base station operating mode. The procedure switching procedure due to failure of the

initial base is then completed.

  To assess the quality of communication, a first method

  is to determine a transmission error rate.

  A second method is illustrated in Figure 29. It is intended to be executed at regular time intervals. First of all, during an operation 2901, the controller 306 of the base station initializes the variables which are used in the flowchart of FIG. 29. Then, at

  during operation 2902, the controller 306 sends a message "signal-

  strength-request ", to all mobile stations in the cell.

  Each mobile station then returns a message representative of the strength of the "signal-strength-request" message it received (see, for this purpose,

  in the DECT standard, the use of the primitive "PL_ME_SIGSTRreq").

  So that all the responses have time to reach it, the base station waits for a duration T9, operation 2903, before performing an operation 2904, during which the variable QR is determined as being the average of the values of the responses obtained during operation 2903. FIG. 30 illustrates a procedure followed by a mobile station which was previously a base station and which has recovered the capacities of

  operate correctly in base station mode.

  This station being in mobile station operating mode, operation 3101, its controller 306 performs a test 3102, during which it determines whether, at the same time: - the quantity of NB power available is greater than the quantity NBmax, - the quality of the radio signal QR is greater than the QRmax value, and - the value of the variable DB is equal to "1",

or not.

  When the result of test 3102 is negative, the controller 306 performs an operation 3110, during which it waits for a period of time.

  T10. Then it repeats test 3102.

  When the result of the test 3102 is positive, during an operation 3103, the controller 306 gives the variable DB, the value "0". Then, during an operation 3104, the controller 306 listens to the Q channel. Then, during a test 3105, the controller 306 determines whether its capacities to be a base station are better than those of the station basic in

activity course.

  When the result of test 3105 is negative, the procedure is terminated (by a failure). When the result of the test 3105 is positive, during an operation 3106, the controller 306 sends a "chgbase-reques't" message to the active base station. During operation 3106, the mobile station considered waits for a sufficient time to allow a communication station in accordance with the present invention and operating in mode

  base station, to respond, before performing a 3107 test.

  Then, during test 3107, the controller 306 determines whether it has received a "chg-base-accept 'message from the active base station or not. When the result of test 3107 is negative, the controller 306 considers that the request to change the base station has failed and the procedure is completed (on a failure) When the result of test 3107 is positive, during operation 3108, the controller 306 switches the operating mode to

  base station mode. Then the procedure is completed (successfully).

  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 I is greater than or equal to the size of the list liste_SM_auto, or not. When the result of test 3202 is positive, during an operation 3207, the identity of the mobile station SMk is inserted at position I of the list list_SM_auto and the classification procedure is finished When the result of 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 l-th station in the list

list_SM_auto, 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 -th station in the list

list_SM_auto, 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 AutoS List list, 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

auto SM 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.

  In Figure 24, there is a second mode of operation of a communication device according to the present invention. When such a communication device has not detected any base station (in accordance with the prior art or after having carried out all the operations and tests illustrated in FIG. 4, including one of operations 411 or 415, but without reproducing operation 402), and that it has an information transmission to perform, it assumes the role of base station for the duration of

the transmission.

  To this end, during an operation 601, the station considered determines that it has an information transmission to be carried out. It then reproduces operations 401 to 403 of FIG. 4, and - if a base station which provides it with access rights is detected, it locks on this base station, but - if no base station is detected, it performs operation 602 during which the controller 306 switches the operational mode

  of the device in base station mode.

  Then, during an operation 603, the device waits for a predetermined duration T5, while regularly transmitting synchronization signals. This duration is intended to allow time for the mobile station with which the device wants to communicate, to lock onto it. Then, during an operation 604, the device sends an identification request to the mobile station with which it wants to communicate. Then, during an operation 605, it lets a predetermined duration T6 pass which must

  be sufficient for the called mobile station to respond.

  Then, during a test 606, the device determines whether it has received, from at least one mobile station, a response to the identification request, or not. When the result of test 606 is negative, during an operation 610, the controller 306 switches the operating mode of the device to mobile station mode. When the result of test 606 is positive, during a test 607, the device determines whether the identity of one of the mobile stations

  corresponds to the identity of the station with which it must communicate, or not.

  When the result of test 607 is negative, operation 610 is carried out. When the result of test 607 is positive during an operation 608, the transmission that the device must perform is. Then, at the end of the transmission, during an operation 609, the transmission is completed. Finally,

Operation 610 is carried out.

  According to a first variant, all the communication requests originating from the other mobile stations are refused, the base station testing the identity of each mobile station requesting the communication and only accepting communications originating from the mobile station with which it has communicated during operation 608 and which are intended for it. According to this first variant, the other mobile stations therefore do not therefore benefit from the device's ability to change operational mode. According to a second variant, if, while the device acts as a base station, a mobile station locks onto it and attempts to establish a communication, the device behaves like a base station, until the attempt is aborted or, if the attempt succeeds, until the end of the call, or until another base station replaces it (see Figures 9 to 13). To implement this second variant, after operation 609 and before carrying out operation 610, the controller 306 of the communication station determines, during a test (not shown) whether a connection with it is active , or not, and if so, repeat this test, at regular time intervals. If this test determines that no connection is

  active, operation 610 is carried out.

Claims (44)

  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 a station operating in base station mode: - an operation of determining the capacity of said station operating in base station mode to be continued this role, and - when, during the capacity determination operation, it is determined that said capacity is reduced, a request operation during which a first communication station transmits to a second communication station, a message request representative of   change of station operating in base station mode.   2. Communication method according to claim 1, characterized in that, during said request operation, the change request message comprises information representative of a station identity   mobile planned as a new base station.   3. Communication method according to any one of   claims 1 or 2, characterized in that the first station   communication is the communication station operating in station mode   basic, preliminary to the request operation.   4. Communication method according to any one of   Claims 1 to 3, characterized in that the second station   communication is a communication station planned to operate   in base station mode following the request operation.   5. Communication method according to claim 4, characterized in that the request operation is carried out by the communication station operating in base station mode prior to the request operation and in that the second communication station performs, following the reception of the message representing the request for a change of station operating in base station mode: - an operation for determining whether or not to operate in base station mode, and - a response operation to the base station, during which the second communication station transmits a message   representative of the agreement, or not to operate in base station mode.   6. Communication method according to any one of   claims 1 to 5, characterized in that the communication station operating   in base station mode determines said capacity according to the quantity the energy it has.   7. A communication method according to claim 6, characterized in that said communication station operating in base station mode performs a switching operation in mobile station mode when the   amount of energy it has is less than a predetermined value.   8. Communication method according to any one of   Claims 1 to 7, characterized in that the communication station operating   in base station mode determines said capacity according to the quality of   transmission between it and mobile stations.   9. Communication method according to any one of   claims 1 or 2, characterized in that the first station   communication is the communication station envisaged to operate in   base station mode following the request operation.   10. Communication method according to any one of   Claims 1, 2 or 9, characterized in that the second station   communication is a communication station operating in station mode   basic preliminary to the request operation.   11. Communication method according to any one of   Claims 1 to 10, characterized in that, in the absence of a response from the   from the second communication station, the first station considers   that the proposed change to base station has failed.   12. Communication method according to any one of   Claims 1 to 11, characterized in that it comprises, following the operation   request, carried out by the first communication station: - an operation for determining acceptance of station change operating in base station mode, and - when it is determined that the envisaged change is not accepted, a new operation request during which a new message representing the request for a change of base station is sent   to another communication station.   13. The communication method as claimed in claim 12, characterized in that each request operation comprises an operation of selecting the destination station of the message requesting a change of   station operating in base station mode.   14. The communication method according to claim 13,   characterized in that said selection operation comprises an operation of reading a destination station identity from a list of communication stations. 15. Communication method according to any one of   Claims 13 or 14, characterized in that the selection operation   includes an operation of determining the mobile station having   better capabilities to become the new base station.   16. Communication method according to any one of   Claims 13 to 15, characterized in that the selection operation comprises   an operation of determining a mobile station having a need to transmit.   17. Communication method according to any one of   Claims 13 to 16, characterized in that the selection operation comprises   a determination operation of a mobile station having already operated in mode base station.   18. 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 includes suitable processing means: determining a capacity of a communication station operating in base station mode to continue this role, and - when '' he determined that said capacity is reduced, to have transmitted by a first communication station to a second communication station, a message representative of request for change of   station operating in base station mode.   19. Communication device according to claim 18, characterized in that the processing means is adapted so that the change request message includes information representative of a   mobile station identity envisaged as a new base station.   20. Communication device according to any one of   claims 18 or 19, characterized in that the processing means is   adapted so that the first communication station is the communication station operating in base station mode, preliminary to the query operation.   21. Communication device according to any one of   Claims 18 to 20, characterized in that the processing means is   adapted so that the second communication station is a communication station envisaged to operate in base station mode as a result of the request operation.   22. Communication device according to claim 21, characterized in that the processing means is suitable for when the transmission of said request message is carried out by the communication station operating in base station mode prior to the request operation, reception of the message representing the request for a change of station operating in base station mode: - to determine an agreement, or not, to operate in base station mode, and - to respond to the base station by transmitting a message   representative of the agreement, or not, to operate in base station mode.   23. Communication device according to any one of   Claims 18 to 22, characterized in that the processing means is   suitable for the communication station operating in base station mode   determines said capacity based on the amount of energy it has.   24. Communication device according to claim 23, characterized in that the processing means is adapted so that said communication station operating in base station mode switches to mobile station mode when the amount of energy available to it is less than a predetermined value.   25. Communication device according to any one of   Claims 18 to 24, characterized in that the processing means is   adapted to determine said capacity as a function of transmission quality between it and mobile stations.   26. Communication device according to any one of   claims 18 or 19, characterized in that the processing means is   adapted so that the first communication station is the communication station operating prior to the request operation in mode base station.   27. Communication device according to any one of   claims 18, 19 or 26, characterized in that the processing means is   adapted so that the second communication station is a communication station envisaged to operate in base station mode as a result of the request operation.   28. Communication device according to any one of   Claims 18 to 27, characterized in that the processing means is   adapted, in the absence of a response from the second communication station, to consider that the envisaged change of base station has failed. 29. Communication device according to any one of   Claims 18 to 28, characterized in that the processing means is   adapted after the transmission of said request for change of base station, to - determine, for the first communication station, an acceptance of change of station operating in base station mode, and - when it has determined that the envisaged change n is not accepted, to transmit a new message representative of request for   change of base station to another communication station.   30. Communication device according to claim 29, characterized in that the processing means is adapted to select the destination station of each station change request message operating in base station mode.   31. Communication device according to claims 30,   characterized in that the processing means is adapted to select the second communication station by reading a station identity   recipient in a list of communication stations.   32. Communication device according to any one of   claims 30 or 31, characterized in that the processing means is   adapted to select the mobile station having better capacities to   become the new base station.   33. Communication device according to any one of   claims 30 to 32, characterized in that the processing means is   adapted to select a mobile station having a need to transmit.   34. Communication device according to any one of   Claims 30 to 33, characterized in that the processing means is   suitable for selecting a mobile station which has already operated in base station mode. 35. Network, characterized in that it comprises at least two   devices according to any one of claims 18 to 34.   36. Telephone, characterized in that it comprises a device according to   Any of claims 18 to 34.   37. Photographic camera, characterized in that it comprises a   device according to any one of claims 18 to 34.   38. Printer, characterized in that it includes a device   according to any one of claims 18 to 34.   39. Scanner, characterized in that it includes a device according to   any one of claims 18 to 34.   40. Camera, characterized in that it includes a device   according to any one of claims 18 to 34.   41. Computer, characterized in that it comprises a device according to   any one of claims 18 to 34.   42. Fax machine, characterized in that it includes a device   according to any one of claims 18 to 34.   43. Television, characterized in that it includes a device according to   Any of claims 18 to 34.   44. Audio / video player, characterized in that it includes a   device according to any one of claims 18 to 34.