FR2844952A1 - Process/mechanism subscription network digital enhanced cordless telecommunications having capacitor electrical conductor surfaces with second terminal presence detected measuring two wire electrical capacitance. - Google Patents

Abstract

The subscription process between a first and second terminal positions the terminals to reconstitute electrical capacitors each carrying electrical conductor surfaces (110,120). The second terminal presence is detected by effecting and measuring the electrical capacitance between two wires connected to the surfaces of the first terminal.

Description

The present invention relates to a subscription method and

  subscription devices in a telecommunications network.

  The invention finds a preferred but non-limiting application for the implementation of a subscription method between a mobile terminal and

  a base station in a wireless telecommunications network.

  In known manner, the subscription of a mobile terminal with

  of a base station is a step enabling the mobile terminal to acquire access rights to the wireless telecommunications network managed by the base station. This subscription step notably makes it possible to secure the wireless telecommunications network by limiting access to this network to predetermined mobile terminals.

  In the particular case of wireless networks using the DECT standard ("Digital Enhanced Cordless Telecommunications", advanced wireless digital telecommunications, ETSI, EN 300 175) this subscription step includes in particular a step of communicating an authentication key 20 by the base station to the mobile terminal, this authentication key being used subsequently during an authentication phase, itself prior to the use by the mobile terminal of the resources managed by the

base station.

  Different methods of distributing such an authentication key during a subscription process are known from

the skilled person.

  A first known method consists in manually entering, during the subscription step, the authentication key via a keyboard. This method has the disadvantage of requiring a user input operation.

  A second known method consists in preconfiguring in the factory each mobile terminal with an authentication key allowing it to

  communicate with a predetermined base station.

  This solution has the drawback of requiring the intervention of an operator to change the authentication key when the mobile terminal wishes to access the resources managed by another base station, by

  example in case of failure of the first base station.

  In order to solve these problems, it is preferable and known to those skilled in the art that the data necessary for the subscription is transmitted by the base station to the mobile terminal.

  For obvious security reasons, it is nevertheless essential that this data transmitted by the base station be accessible only to mobile terminals located near the base station.

  A method described in document WO 00/51293 describes such a method of transmitting subscription information by means of a radio link under certain proximity conditions, these conditions being verified.

  by measuring the strength of the signal received by the mobile terminal.

  The level of security obtained by the implementation of this method is however not satisfactory, the proximity criterion being simply evaluated by measuring the radio signal received. In particular, it is difficult to ensure that subscription information is not

  intercepted by an unauthorized mobile terminal.

  The present invention solves the above problems. More precisely and according to a first aspect, the present invention relates to a method of subscription between a first terminal and a second terminal in a telecommunications network, the subscription method comprising the following steps: positioning of the terminals one with respect to the other so as to reconstitute at least two electrical capacities each comprising two electrically conductive surfaces facing each other, the surfaces belonging respectively to the first and to the second terminal and - detection, by the first terminal, the presence of the second terminal, this detection being carried out by measuring the electrical capacity

  between two terminals connected to surfaces of the first terminal.

  This subscription method is, from the point of view of a user, particularly simple to implement since it suffices to position the terminals adequately relative to each other so that the first terminal

  detects the presence of the second terminal.

  According to a preferred embodiment, the subscription method according to the invention further comprises, following the detection step, the sending of a subscription invitation message by the first terminal to the second terminal, the sending being effected by capacitive effect through the

electrical capacities.

  Thus, the invitation message is sent by capacitive link, an example of which, known to a person skilled in the art, is described in US Pat. No. 6,211,999.

  In one embodiment, the invitation message transmitted by capacitive effect comprises an authentication key.

  The authentication key is thus transmitted between the base station and the mobile terminal in a highly secure manner since this key 20 cannot be intercepted by a third-party terminal, as was the case for the

  subscription method of the aforementioned prior art using radio technology.

  According to a second aspect, the invention relates to a first subscription device adapted to be incorporated in a first data transmission terminal comprising at least two electrically conductive surfaces, means for positioning a second terminal in a predetermined position with respect to to the first device, and means for detecting the presence of the second terminal in the predetermined position, by measurement

  of the electrical capacity between two terminals connected to these surfaces.

  The invention also relates to a second subscription device 30 adapted to be incorporated in a second data transmission terminal comprising means for positioning a first terminal incorporating a first subscription device in a predetermined position relative to the second device and to the at least two electrically conductive surfaces adapted, in the predetermined position, to reconstitute two by two of the electrical capacities with the electrically conductive surfaces of the first device. Thus, the first subscription device is adapted to detect the presence of the second data transmission terminal comprising the second subscription device according to the invention, by implementing

  the step of detecting the subscription process described briefly above.

  In a preferred embodiment, the first subscription device comprises means for sending a subscription invitation message to the second terminal, the sending being effected by capacitive effect through at least two electrical capacities, each of them being partly constituted by one of the surfaces and by an electrically surface

  conductor of the second terminal in the predetermined position.

  In this preferred embodiment, the second device

  subscription includes means for receiving a subscription invitation message from the first terminal, and means for sending a subscription confirmation message to the first terminal, reception and sending being carried out by capacitive effect through the electrical capacitors.

  Thus, the first subscription device can securely send the subscription invitation message to the second subscription device. The main advantages of the first and second subscription devices are the same as those set out above regarding the

  underwriting method according to the invention.

  In particular, the first and second subscription devices can automatically trigger the subscription process as soon as the

  terminals are suitably positioned relative to each other.

  On the other hand, the first and second subscription devices implement a highly secure subscription process, the information necessary for the subscription contained in the subscription invitation message cannot be intercepted by a third-party terminal.

unauthorized.

  According to a first preferred embodiment, the means for positioning the first subscription device comprise at least one protruding element from a housing of the first terminal, the protruding element being adapted to fit into a corresponding recessed element of the housing of the second terminal, In this first preferred embodiment, the positioning means of the second subscription device comprise at least one element recessed from the housing of the second terminal, the recessed element being adapted to receive a corresponding element in projection of the housing of the first terminal. In a second preferred embodiment, the means for positioning the first subscription device comprise at least one element recessed from the housing of the first terminal, this recessed element being adapted to receive a corresponding element projecting from the housing of the second terminal. In this second preferred embodiment, the positioning means of the second subscription device comprise an element 20 projecting from the housing of the second terminal adapted to fit into the element in

  removal of the housing from the first terminal.

  In the two preferred embodiments described above, the positioning means of the first and second subscription devices in accordance with the present invention make it possible to obtain a precise positioning of the terminals relative to each other, which helps to make the

  subscription process between these terminals.

  In a preferred embodiment, the recessed and projecting elements are of substantially cylindrical shape.

  The invention also relates to a base station in a telecommunications network comprising a first subscription device such as

described above above.

  The invention also relates to a mobile terminal in a telecommunications network comprising a second subscription device such as

briefly described above.

  The invention also relates to a telecommunications network 5 comprising at least one base station and at least one mobile terminal as described briefly above.

  The characteristics and advantages specific to the base station, to the mobile terminal, and to the telecommunications network being the same as those described above concerning the subscription method, the first and second subscription devices according to the invention, they do not will not be recalled here,

  Other aspects and advantages of the present invention will appear more clearly on reading the description of a particular embodiment which follows, this description being given solely by way of nonlimiting example and made with reference to the accompanying drawings in

  which: - Figure 1 schematically shows a telecommunications network according to the present invention in a particular embodiment; - Figure 2 shows schematically a base station according to the present invention in a particular embodiment; - Figure 3 shows a mobile terminal according to the invention in a particular embodiment; FIGS. 4a and 4b respectively show diagrammatically parts cut away from a first and second subscription device in a preferred embodiment in accordance with the present invention; - Figure 5 shows schematically in section a first and second subscription devices according to the present invention in a preferred embodiment during a subscription phase; - Figure 6 shows the electrical diagram equivalent to the capacitive link according to the invention; - Figure 7 shows a frequency transposition block of a first subscription device according to the present invention, in a preferred embodiment; FIG. 8 represents a base band transposition block of a second subscription device in accordance with the present invention in a particular embodiment; and FIG. 9 represents the main steps of a subscription method in accordance with the present invention in a particular embodiment.

  FIG. 1 represents a telecommunications network R in accordance with the present invention in a preferred embodiment.

  The network R comprises a base station SB and a plurality of 15 mobile terminals TM.

  In the example described here, each mobile terminal TM is connected by means of an Ethernet link 10 to a data processing equipment PC. This example is of course not limiting. The invention can in particular be implemented for the subscription of an independent mobile terminal TM, that is to say not connected to a processing equipment for

external digital data.

  In the example described here, a mobile terminal TM wishing to access the telecommunications network R must authenticate itself with the base station SB.

  At the end of this authentication phase, the mobile terminals can access the network resources R managed by the base station SB; PC data processing equipment connected to these terminals

  mobiles can then exchange data.

  Before this authentication step, each terminal

  mobile must subscribe with the base station SB.

  We will now describe with reference to FIG. 2 a base station SB in accordance with the present invention in a preferred embodiment. The base station SB comprises a CPU controller conventionally associated with ROM, RAM and EEPROM memories. The base station SB also comprises a radio unit 30 adapted to receive and transmit digital data by radio link via

its antenna 40.

  In accordance with the present invention, the base station SB 10 also comprises a first subscription device 100 which will be described

  later with reference to Figures 4a and 7.

  FIG. 3 schematically represents a mobile terminal TM according to the present invention.

  The mobile terminal TM comprises a CPU controller associated with ROM, RAM, EEPROM memories, a radio controller 30 and an antenna 40

  identical to those described above with reference to FIG. 2.

  The mobile terminal TM also includes an Ethernet controller 20 for connection to a data processing equipment PC.

  In a known manner, after the authentication phase, the processor 20 CPU is adapted to read the data received by the network unit 20, write this digital data in a port of the radio unit 30 for transmission on the

radio link.

  The CPU controller is also suitable for reading the digital data received by the radio unit 30, and writing this data to a port 25 of the Ethernet controller 20 for transmission to the processing equipment.

PC data.

  In accordance with the present invention, the mobile terminal TM also includes a second subscription device 200 which will be described

  later with reference to Figures 4b and 8.

  Figure 4a shows schematically a part

  torn from a first subscription device 100.

  The first subscription device 100 notably comprises means for positioning a terminal, for example a mobile terminal TM, these positioning means being constituted in the example described here by

electrodes 110 and 120.

  In a preferred embodiment, the electrodes 110 and 120

are the same.

  The electrode 110 is shown in section in FIG. 5 during a subscription phase in accordance with the present invention.

  In the embodiment described here, and represented in FIG. 5, the armature of the electrode 110 of the first subscription device 100 is constituted by a metallic deposit 112 on the surface of a cylindrical element

  114 projecting from the housing 105 of the base station SB.

  In the preferred embodiment described here, and in order to avoid oxidation of the metal deposit 112, the electrode 110 comprises an insulating protective layer 116.

  We will now describe with reference to FIG. 4b a part cut away from a second subscription device 200.

  The second subscription device 200 comprises means for positioning a first terminal, for example a base station SB, these positioning means being constituted here by electrodes 210, 220.

  In the preferred embodiment described here the electrodes 210 and 220 are similar.

  The electrode 210 is also shown in section in FIG. 5, during a subscription phase according to the invention.

  In the example described here, the electrode 210 of the second subscription device 200 comprises a metal deposit 212 on the surface of a hole 214

  set back from the housing 205 of the mobile terminal TM.

  Preferably, the metal deposit 212 of the electrode 210 of the second subscription device 200 is covered with an insulating layer 30 216.

  In the underwriting phase, the electrodes 110 of the first underwriting device 100 and 210 of the second underwriting device 200 thus constitute cylindrical armatures of diameter dl and

d2 with an electrical capacity Cl.

  The diameter d2 of the electrode 210 of the second subscription device 200 is very slightly greater than the diameter dl of the electrode 110 of the first subscription device 100.

  Preferably, and so as to allow precise fitting of the electrode 110 of the first subscription device 100 into the electrode 210 of the second subscription device 200, the end 118 of the electrode 110 and the end 218 of the the electrode 210 of the second underwriting device 200 10 are conical in shape, as shown in FIG. 5.

  In the example shown in FIG. 5, the positioning means 110, 120 of the first subscription device 100 and 210, 220 of the second subscription device 200 are respectively projecting and in

removal of housings 105 and 205.

  In another embodiment not described here, the means for positioning the first subscription device 100 comprise a part set back from the housing 105, capable of receiving a projecting part from the housing 205

  means for positioning the second subscription device 200.

  With reference to FIG. 6, we will now describe the electrical model equivalent to the capacitive link between the base station SB

  and the mobile terminal TM in accordance with the present invention.

  The base station SB comprises means 150 for measuring the electric capacity measured at terminals A and B connected respectively to the cylindrical armatures of the electrodes 110 and 120 of the first subscription device 100.

  When the positioning means constituted by the electrodes 110 and 120 of the first subscription device 100 are not fitted into the projecting positioning means 210 and 220 of the second subscription device 200, the capacity measured by the measurement means 150 aux terminals A and B is a stray capacitance C3.

  On the other hand, when the first subscription device 100 is fitted into the second subscription device 200, this positioning of the terminals relative to each other makes it possible to reconstitute two electrical capacities made up, Cl, C2 on the one hand by the electrically conductive surfaces 110 and 210 (Cl), and on the other hand the electrically

conductors 120 and 220 (C2).

  The electrical capacity measured by the measuring means 150 at terminals A and B is then equivalent to the capacity resulting from the parallel connection of the above-mentioned parasitic capacity C3 with the dipole consisting of the placing in series of the following 3 components - the capacity Cl constituted by the armatures of a first electrode 110 of the first device 100 and of a second electrode 210 of the second subscription device 200; a component consisting of the paralleling of the stray capacitance C4 (created in particular by the various components of the mobile terminal TM) and of the input impedance Rload of the near-field reception system 15 of the mobile terminal TM; and a capacitor C2 constituted by the armatures of a second electrode 120 of the first subscription device 100 and of a second

  electrode 220 of the second subscription device 200.

  In practice, the resistance Rload being low, the capacity C4 is negligible in the capacity CAB measured by the measuring means 150 aux

  terminals A and B of the first subscription device 100.

  In a known manner, the capacity CAB is then approximately equal to CAB = C3 + (C1.C2) / (C1 + C2) In an exemplary embodiment, in which the height of the electrode 110 is 8 mm, and the diameters dl and d2 are respectively

  of the order of 8mm and 12mm, the capacities Cl and C2 are of the order of 10 pF.

  In this preferred embodiment the parasitic capacities C3 and C4 are of the order of 0.5 pF.

  Thus, when the capacities C1 and C2 are not formed, that is to say in the absence of subscription, the capacity CAB measured by the means of

measure 150 is CAB = C3 = 0.5 pF.

  In the embodiment described here, the capacities C1, C2, C3 and C4 are respectively of the order of 10 pF, 10 pF, 0.5 pF and 0.5 pF.

  Thus, during the course of the subscription, the measurement means 150 measure the electrical capacity CAB at terminals A and B approximately equal to 5.5 pF.

  The measurement of the capacity CAB by the measurement means 150 between the terminals A and B therefore makes it possible to detect the presence of the mobile terminal TM by comparing this value with a predetermined threshold. We can for example choose in the embodiment described here the value of the threshold equal to 3 10 pF.

  In the preferred embodiment described here, the first subscription device 100 also includes means for sending a subscription invitation message to the mobile terminal TM, this sending being effected by capacitive effect through the electrical capacities Cl and C2 described

1 5 previously.

  This subscription invitation message includes, for example, an authentication key required during an authentication phase.

  the mobile terminal TM at the base station SB.

  Anyway, in this preferred embodiment, the subscription invitation message is received by the second device.

  subscription 200 of the TM mobile terminal.

  In FIG. 6, the source of data to be transmitted is represented diagrammatically by the digital data generator 170. In the preferred embodiment described here, the second subscription device also includes means for sending a message of confirmation of subscription to the base station SB

also by capacitive effect.

  For the sake of simplification of FIG. 6, the generator of digital data to be transmitted by the second subscription device

is not shown.

  We will now describe, with reference to FIG. 7, a TX near field transmission system of the first subscription device

  1 00 for sending digital data by capacitive effect.

  In the preferred embodiment described here, the TX near field transmission system 5 is implemented by frequency transposition.

  In practice, the carrier frequency Fc is chosen so that the capacity created has a constant range around this frequency, over a bandwidth at least equal to the bandwidth of the transmitted signal. In the preferred embodiment described here , the digital data to be transmitted is first coded according to the NRZI coding (No

  Return to Zero) known to those skilled in the art.

  The data coded in NRZI format are first amplified by a first stage 208 then filtered using a low pass filter 201, the

  cut-off frequency is around 150 Mhz.

  The filtered signal is then multiplied using a mixer 205 which can for example be a mixer sold by the Hititte Company under the

  reference HMC296MS8 with the carrier from the local oscillator OL (203).

  The oscillator 203 can be produced with a frequency synthesizer MC145202 from the Motorola company with a voltage controlled oscillator, for example from JTOS 1750 from the Mini-Circuits company.

  The mixed signal is then filtered by a bandpass filter 202 whose central frequency is of the order of 1.3 GHz. The filtered signal is amplified

  then buffered by a buffer amplifier 204.

  The signal thus filtered and amplified is transmitted to the electrode 110. The electrode 120 is connected to ground.

  We will now describe with reference to FIG. 8 a near field reception system RX of the second device

subscription 200.

  This system is here produced by means of a frequency transposition 30 opposite to that carried out in the TX near field transmission system of the first subscription device 100 described previously in

reference to figure 7.

  The signal received from electrodes 210 and 220 is buffered using an amplifier 301 and then filtered using a bandpass filter 302.

  The filtered signal is then amplified using a gain-controlled amplifier 303.

  This gain adjustment circuit is here adjusted during installation on the power of the pure carrier frequency received as long as the band signal

base is not shown.

  This gain control circuit is conventional and known to those skilled in the art.

  The amplifier can be an ERA-3Sm from the company Mini-Circuits,

  the programmable attenuator an HMC 273 from Hititte.

  Then the always transposed signal enters a mixer 304 to carry out the conversion by multiplication with a frequency from the local oscillator 308, while a replica of itself enters a second but identical mixer 304 to be mixed with a replica remodulated by the signal from the voltage controlled oscillator 308 offset by 90 by a

coupler 307.

  The mixer output is then filtered by a low-pass filter 306 having a cut-off frequency of 150 MHz and this filtered signal 20 controls the voltage-controlled oscillator 308.

  The signal 310 from the low pass filter is formed by the circuit 310. This circuit produces a phase-locked block called by remodulation.

  This circuit has the advantage of being applicable to numerous forms of transposed signals.

  The mass of the second subscription device 210 is connected to the electrode 220.

  FIG. 9 represents the main steps of a subscription method in accordance with the present invention.

  When a user wishes to proceed with the subscription of a mobile terminal TM with a base station SB, the latter positions the base station SB and the mobile terminal and the mobile terminal with respect to one another. so as to reconstitute two electrical capacities C1, C2 each comprising two surfaces (110, 120 and 210, 220) electrically conductive opposite one another, these surfaces belonging respectively to the station

  base SB and the mobile terminal TM.

  In the preferred embodiment described here, the positioning is carried out by fitting the positioning means 110, 120 of the first subscription device 100 of the base station SB into the positioning means 210, 220 of the second subscription device 200 of the terminal

mobile TM.

  The subscription method according to the invention comprises a step E90 during which the base station SB detects the presence of the mobile terminal TM by measuring the electrical capacity between the terminals A and B of the

SB base station.

  As long as the base station and the mobile terminal are not positioned relative to one another as described above, the presence of the mobile terminal by the base station is not detected by the

measuring means 150.

  Once the presence of the mobile terminal has been detected, the result of the E90 test is positive. This test is then followed by step E92 of sending by the base station a subscription invitation message to the mobile terminal.

  The sending of this subscription message is carried out by capacitive effect through the electrical capacitors Cl, C2 by means of the frequency transposition block TX of the first subscription device 100 described.

  previously with reference to FIG. 7.

  This subscription invitation message is received by the baseband transposition block RX of the second subscription device 200

  of the mobile terminal TM as described above with reference to FIG. 8.

  In the preferred embodiment, the subscription invitation message includes for example the identification key necessary for an authentication phase of the mobile terminal TM with the base station SB.

  On receipt of the subscription invitation message from the base station SB, the mobile terminal TM sends a subscription confirmation message to the base station SB, the reception and sending of this confirmation message being carried out by capacitive effect through the electrical capacitors Cl and C2 as described above. For the sake of simplification, the frequency transposition block of the second subscription device 200 and the baseband transposition block of the first subscription device 100 for sending and receiving the confirmation message have not been shown. They are similar to the TX and RX blocks described above. 10

Claims (17)

  1. Subscription method between a first terminal (SB) and a second terminal (TM) in a telecommunications network (R), characterized in that it comprises the following steps: - positioning of the terminals (SB, TM) one relative to the other so as to reconstitute at least two electrical capacitors (Cl, 02) each comprising two electrically conductive surfaces ((110, 120), (210, 220)) opposite one of the another, said surfaces belonging respectively to the first (SB) and to the second (TM) terminal; and - detection (E90), by the first terminal (SB), of the presence of the second terminal (TM), said detection being carried out by measuring the electrical capacity (CAB) between two terminals (A, B) connected to said surfaces (110 , 120) of the first terminal (SB),   2. Subscription method according to claim 1, characterized in that it further comprises, following said detection step (E90), the sending (E92) of a subscription invitation message by the first terminal ( SB) to the second terminal (TM), said sending being effected by capacitive effect through said electrical capacitors (C1, C2).   3. First subscription device (100) adapted to be incorporated in a first data transmission terminal (SB), characterized in that it comprises at least two electrically conductive surfaces (112), positioning means (110, 120) a second terminal (TM) in a predetermined position relative to said first device, and means for detecting the presence of said second terminal in said predetermined position, by measuring the electrical capacity (CAB) between two terminals (A , B) connected to said surfaces. 30 4. First subscription device (100) according to claim 3 characterized in that it further comprises means for sending a subscription invitation message to said second terminal (TM), said sending being effected. capacitive through at least two electrical capacitors (Cl, C2) each of which being partly constituted by one of said surfaces (112) and by an electrically conductive surface (212) of said second terminal (TM) in said predetermined position . 5. First subscription device (100) according to claim 3 or 4, characterized in that said positioning means (110, 120) comprise at least one element (110, 120) projecting from a housing (105) of said 10 first terminal (SB), said projecting element (110, 120) being adapted to fit into a corresponding element (210, 220) set back from the housing (205) said second terminal (TM).   6. First subscription device (100) according to any one of claims 3 to 5, characterized in that said means for   positioning comprise at least one element set back from a housing (105) of said first terminal (SB), this recessed element being adapted to receive a corresponding element projecting from a housing (205) of said second terminal (TM). 7. First subscription device (100) according to claim 5, characterized in that said element (110, 120) projecting from the housing (105) of the   first terminal is of substantially cylindrical shape.   8 First subscription device (100) according to claim 6, characterized in that said element set back from the housing (105) of the first   terminal is of substantially cylindrical shape.   9. Second subscription device (200) adapted to be incorporated in a second data transmission terminal (TM) and characterized in that it comprises positioning means (210, 220) of a first terminal (SB) incorporating a first subscription device (100)   according to any one of claims 5 to 7 in a predetermined position relative to said second device (200) and at least two electrically conductive surfaces (212) adapted, in said predetermined position, to reconstitute two by two of the electrical capacities (Cl, C2) 5 with the electrically conductive surfaces (112) of said first device (100).   10. Second subscription device (200) according to claim 9, characterized in that it comprises means for receiving a subscription invitation message from said first terminal (SB), and sending means a subscription confirmation message to the first terminal (SB), said reception and said sending being   performed by capacitive effect through said electrical capacitors.   11. Second subscription device (200) according to one   any one of claims 9 or 10, characterized in that said positioning means comprise at least one element recessed from a housing (205) of said second terminal (TM), said recessed element being adapted to receive a   corresponding element projecting from a housing (105) of said first terminal (SB). 20   12. Second subscription device (200) according to claim 9 to 11, characterized in that said positioning means comprise at least one protruding element from a housing (205) of said second terminal (TM), said protruding element being adapted to fit into a corresponding element set back from a housing (105) of said first terminal (SB).   13. Second subscription device (200) according to claim 11, characterized in that said element set back from the housing (205) of the second terminal is of substantially cylindrical shape. 30 14. Second subscription device (200) according to claim 12, characterized in that said protruding element of the housing (205)   of the second terminal is of substantially cylindrical shape.   15. Base station (SB) in a telecommunications network, characterized in that it comprises a first subscription device (100)   according to any one of claims 3 to 8.   16. Mobile terminal (TM) in a telecommunications network, characterized in that it comprises a second subscription device (200)   according to any one of claims 9 to 14.   17. Telecommunication network (R) characterized in that it comprises at least a base station (SB) according to claim 14 and at least 15 a mobile terminal (TM) according to claim 15.