CA2722926C

CA2722926C - Method and device for relaying a radio-frequency communication between communication apparatuses situated in different environments

Info

Publication number: CA2722926C
Application number: CA2722926A
Authority: CA
Inventors: Christophe Brevalle; Patrice Courtet; Yves Bard
Original assignee: Sagem Defense Securite SA
Current assignee: Safran Electronics and Defense SAS
Priority date: 2008-06-13
Filing date: 2009-06-11
Publication date: 2017-02-28
Anticipated expiration: 2029-06-11
Also published as: BRPI0915162B1; FR2932626B1; CA2722926A1; FR2932626A1; BRPI0915162A2; ATE551848T1; AU2009259435B2; EP2308181B1; WO2009153210A1; EP2308181A1; RU2520975C2; AU2009259435A1; RU2010147883A

Abstract

The invention relates to a method and a device for relaying a beacon signal or a traffic signal of a radiofrequency communication established between communication apparatuses located in environments to be relayed. An antenna is located in each environment, the method being characterised in that it comprises a step (100) of at least one antenna receiving the beacon signal or traffic signal, a step (200) of generating a so-called relayed signal from the received signal, and the step of simultaneously transmitting (300) the relayed signal from each antenna, wherein the power level of the relayed signal transmitted by each antenna is equal to a percentage of the total power level of the relayed signal.

Description

2 METHOD AND DEVICE FOR RELAYING A RADIO-FREQUENCY
COMMUNICATON BETWEEN COMMUNICATION APPARATUSES SITUATED IN
DIFFERENT ENVIRONMENTS

The present invention concerns a method and device for relaying a beacon signal or a traffic signal in a radio-frequency communication established between communication apparatuses situated in different environments that do not enable the radio-frequency waves relating to this communication to propagate from one environment to the other without being attenuated.
The said environments are hereinafter referred to as environments to be relayed in order to express the fact that they do not enable the radio-frequency waves carrying a beacon signal or a traffic signal to propagate from one environment to the other without being attenuated.

A radio-frequency communication is used to deploy in an environment a service of the audio and/or data transfer type in which apparatuses communicate with each other the data that are either voice data or other, such as for example images, data files, etc.

A radio-frequency communication consists of transporting these data by radio-frequency waves that propagate in an environment so that the signal carrying these data is routed from a sending apparatus to either a receiving apparatus in the case of communication or several receiving apparatuses in the case of a broadcast.

In some communication networks, such as for example a DECT (Digital Enhanced Cordless Telecommunications) network, one of the communication apparatuses, referred to as the base hereinafter, broadcasts a beacon signal that any other communication apparatus must receive in order to be able to synchronise in time and frequency with this base. Thus, once an apparatus is synchronised in time and frequency with the base, this apparatus can establish radio-frequency communications with this base according to a protocol. On the other hand, when an apparatus is no longer receiving the beacon signal, this apparatus can no longer

3 establish new communications. It should be noted that, if apparatuses are already in communication when the beacon signal is lost, the communication is maintained since the synchronisation is directly made by the communication slots, that is to say the slots that are dedicated to the traffic signals.
So that a radio-frequency communication on such networks is of acceptable quality, it is consequently necessary for the radio-frequency waves relating to the signals exchanged, beacon or traffic signals, not to be excessively attenuated between the apparatus transmitting these waves and a receiving apparatus with which it is in communication. This because it is necessary for the power level of these radio-frequency waves to be sufficient so that, in particular, an apparatus remains synchronised with the beacon signal when this apparatus is not in communication.

The attenuation of a radio-frequency wave is due to the distance that separates the transmitting apparatus from a receiving apparatus but is also due to the reflection of these waves on obstacles situated on the path connecting these two apparatuses. To mitigate this phenomenon of reflections, the DECT standard has defined an antenna diversity mechanism, defined by the ETSI standard EN 300 175-6 vl.4.2 (1999-06) Part 3: Medium Access Control (MAC) layer, which is activated as soon as an apparatus is in communication with another.
The antenna diversity mechanism is implemented by a communication apparatus by means for measuring the power level of a signal received by each antenna of this apparatus and means for selecting one of these antenna as a reception antenna by comparison of the power levels thus measured with each other. Thus, whenever a signal is received by a communication apparatus, including the base, the antenna diversity mechanism makes it possible to determine which is the antenna that makes it possible to receive the signal in an optimum manner.

We should consider hereinafter that each communication apparatus, including the base, is equipped with means that enable it to implement an antenna diversity mechanism.

4 The antenna diversity mechanism does not make it possible to overcome all causes of attenuation of a radio-frequency wave. In particular, it is does not make it possible to solve the attenuation of a radio-frequency wave that is due to an obstacle separating two environments to be relayed. Thus an apparatus receiving a radio-frequency wave that was up until then situated in the same environment as an apparatus transmitting this wave and that changes environment in order to go into a new environment that does not enable this radio-frequency wave to propagate in this new environment without being highly attenuated, no longer receives the wave at a sufficient power level, thus causing interruption of the communication with the transmitting apparatus and in particular stoppage of the reception of the beacon signal necessary to this receiving apparatus to synchronise with the apparatus transmitting this beacon signal.

The problem that is posed is therefore that of the continuity of the reception of a beacon signal or of a traffic signal of a radio-frequency communication established between communication apparatuses situated in environments to be relayed when these apparatuses change environment.
Figures la-b show an illustration of this problem of continuity of reception of a beacon signal or of a traffic signal of a communication established between a transmitting apparatus and a receiving apparatus in the case of a military application.

Figures la shows an armoured vehicle V in which there are two mobile communication apparatuses referenced C and Fl. The apparatus C is the base that broadcasts a beacon signal that the apparatus F1 receives. The apparatus F1 is then synchronised with this beacon signal and these two apparatuses can establish communication since the two apparatuses are situated in the same environment E2, in this case the inside of the vehicle V.

Outside the vehicle V, that is to say in an environment El, there are two other items of mobile communication equipment F2 and F3 that are designed to receive the beacon signal transmitted by the base C and thus establish communications with the other communication apparatuses synchronised on the beacon signal. However, since the armouring of the vehicle B consists of materials that very greatly attenuate the radio-frequency waves transmitted inside

5 the vehicle, the apparatuses F2 and F3 do not receive the beacon signal and cannot therefore come into communication either with each other or with the base C or the apparatus Fl.

In a similar manner, figure lb shows the case where the base C is situated outside the vehicle V. This time, the apparatuses F2 and F3 that are situated in the same environment E1 as the base C receive the beacon signal and can therefore communicate with each other and/or with the base C. On the other hand, the apparatus F1 situated inside the vehicle V
no longer receives the beacon signal and cannot therefore come into communication with the apparatuses C, F2 or F3.

Thus moments occur, in particular during phases when a group of persons each equipped with a mobile communication apparatus get on board or disembark from the vehicle, when certain members of the group are not in the same environment as the person who is equipped with the base. For example, when these members leave the vehicle V and the person carrying the base remains in the vehicle V, these members are no longer in communication with the members who have remained inside the vehicle. In addition, when all the members in the group, including the one who is carrying the base, have left the vehicle, the members of this group can establish communications with each other. On the other hand, this group is no longer in communication with other persons who have remained on board the vehicle because the armouring of the vehicle very greatly attenuates the external radio-frequency waves, which cannot propagate inside the vehicle V.

To solve this problem of continuity of reception of a signal between different environments to be relayed when an apparatus changes environment, a device is known for relaying a signal between two environments. The device comprises two antennas, one antenna being positioned

6 in each environment, and a radio-frequency relay used for relaying the signal received by one of these two antennas to the other antenna.

However, the inventor has observed that such a device does not solve the problem of continuity of reception of a signal since breaks in reception of this signal occur all the same when an apparatus changes environment.

Let us consider such a device shown in figure lc. The device comprises an antenna AE2 positioned inside the vehicle V, another antenna AE1 positioned outside the vehicle V and a radio-frequency relay R, positioned for example inside the vehicle V, which is used for relaying the signals received by the antenna AE1 to the antenna AE2 and the signals received by the antenna AE2 to the antenna AE1.

The radio-frequency relay R consists of two radio parts independent of each other in terms of radio frequency. Each of these parts is connected to a port of the relay and each of these relay ports is connected to one of the two antennas AE 1 or AE2. One of the radio parts of the relay is synchronised with a beacon signal broadcast by a base, a signal that is received via one of its two ports, and uses this beacon signal to give a time reference to the other radio part. Thus the two radio parts of the relay are synchronised in time and frequency with the beacon signal broadcast by this base. It is then said that the relay is synchronised.

An example of a radio-frequency communication relay is given by the ETSI DECT
standard EN 300 700, which also defines a protocol, of the TDMA (Time Division Multiple Access) type. In substance, once the relay is synchronised, a beacon or traffic signal is transmitted by an apparatus on a slot/frequency pair S 1. Once received on one of the ports of the relay, referred to as the reception port, for example the one relating to the antenna AE1, this signal is relayed, that is to say a new beacon or traffic signal is created on a slot/frequency pair S2 different from the slot/frequency pair Si. This relayed signal is then sent via the other relay port, referred to as the transmission port of the relay, relating to the antenna AE2 according to

7 this example.

Les us consider, with reference to figure lc, that the apparatus F1 is inside the vehicle V and the base Cis outside. The base C transmits the beacon signal over the slot/frequency pair S1 and this signal is received by the relay R via the antenna AE1. The relayed beacon signal, that is to say the beacon signal transmitted over the slot/frequency pair S2, is then broadcast via the antenna AE2. The apparatus F1 is then synchronised on this relayed beacon signal, that is to say on a signal transmitted over the slot/frequency pair S2.

Let us consider now that the apparatus F1 leaves the vehicle. The apparatus Fl then loses the relayed beacon signal transmitted over the slot/frequency pair S2 that it was receiving up until then from the antenna AE2 since this signal is very highly attenuated by the armouring of the vehicle V. The apparatus Fl, no longer receiving the beacon signal, then goes into search mode in order to find a new beacon signal, in this case the beacon signal that is transmitted by the base C over the slot/frequency pair S 1.

As long as the apparatus 171 has not found this beacon signal again, it cannot synchronise with the base C and cannot therefore establish new communications. There is therefore a break in reception of the beacon signal during this search time.
The problem is posed in a similar manner for the continuity of the traffic signals, the break in reception of which causes loss of synchronisation of the apparatus F1 with the base C and therefore a break in the current communication.

In order to enable an apparatus to change environment without a break in reception of the beacon signal or reception of a traffic signal of an established communication, the inventor has observed that the same beacon or traffic signal should be transmitted simultaneously in all the environments, whatever the environment in which the base C is situated.

8 To this end, the invention concerns a device for relaying a beacon signal or a traffic signal of a radio-frequency communication established between communication apparatuses liable to move from one environment to another, the said environments not enabling the radio-frequency waves relating to this communication to propagate from one environment to the other without being highly attenuated, each communication apparatus being designed to use an antenna diversity mechanism, the said device comprising a plurality of antennas intended to receive a signal and a radio-frequency relay intended to relay a signal received by an antenna positioned in one of the said environments to another antenna positioned in another environment. The device is characterised in that it comprises an apparatus, referred to as a radio-frequency switching apparatus, which comprises - at least one port, referred to as the relay reception port, which is connected to a reception port of the radio-frequency relay and functions in reception mode, - a port, referred to as the relay transmission port, which is connected to a transmission port of the radio-frequency relay and functions in transmission mode, and - as many ports, referred to as antenna ports, as there are environments to be relayed, each antenna port being connected to an antenna of an environment and being connected with at least one relay reception port.

The said radio-frequency switching apparatus is designed so that a signal received on one of the antenna ports is entirely routed to a relay reception port, and so that, when a relayed signal is received on the relay transmission port, the said signal is simultaneously routed to each antenna port, the power level of the signal relayed on each antenna port being equal to a percentage of the total power level of the relayed signal.

The radio-frequency switching apparatus enables a beacon signal or a traffic signal of an established communication that is transmitted by the base to be received by the relay whatever

9 the environment in which this apparatus is situated. In addition, the radio-frequency switching apparatus enables a signal received on one of its antenna ports to be relayed by the radio-frequency relay and the relayed signal is transmitted simultaneously in the various environments. The radio-frequency switching apparatus is also advantageous since each percentage of the power level of the relayed signal can be adjusted according to the environment, by means of its internal structure.

In addition, in reception mode, the radio-frequency switching apparatus does not attenuate a signal received on one of its antenna ports but switches this signal to one of the reception ports of the radio-frequency relay.

According to one embodiment, the radio-frequency switching apparatus is designed so that the percentage of the power level of the relayed signal that is routed to an antenna port is higher than the percentages of the power level of the relayed signal that is routed to each other antenna port.

According to variant of this embodiment, the radio-frequency switching apparatus is designed so that the proportions of the power level of the relayed signal that is routed to said other antenna ports are all equal to the same value.
According to one embodiment, the relay transmission port, during a transmission, is connected to all the other antenna ports with transmission levels adapted to each of the environments, whereas in reception mode each relay reception mode is connected directly to a single antenna port.
Thus the relay transmission port is also a relay reception port.

According to a variant of this embodiment, at least one relay reception port is connected to more than one antenna port.

This variant of this embodiment is advantageous when several environments require the same percentage of the power level of the relayed signal.

5 According to one embodiment, the device comprises means for determining in which environment an apparatus at the origin of the transmission of a signal received by at least one of the antenna ports is situated.

This embodiment is advantageous since, whenever a signal transmitted by a communication

10 apparatus is received, the device determines in which environment this apparatus is situated.
This is advantageous for applications in which the support carrying this communication apparatus moves frequently and rapidly.

According to a variant of this embodiment, the device comprises means for displaying the environment in which each apparatus is situated.

According to a variant of this embodiment, the device comprises means for detecting the change in environment of a communication apparatus at the origin of the transmission of a signal received on at least one of the antenna ports.
The inventor has observed that a radio-frequency communication system comprising one of the above devices in which the switching apparatus is associated with the antenna diversity mechanism used by the relay does not ensure continuity of synchronisation when the communication apparatuses are synchronised directly on the base. This is because, when the said base changes environment, the communication apparatuses lose its beacon signal.

To avoid this, according to one embodiment of such a system, the device comprises means for ordering the base to trigger means for preventing the communication apparatuses that are synchronised from the beacon signal that it is transmitting from synchronising on the beacon

11 signal relayed by the device. The base then comprises means for preventing the communication apparatuses that are synchronised from the beacon signal that it is transmitting to synchronise on the beacon signal relayed by the device, means that are activated following the reception by the base of the triggering instruction.
The inventor has also observed that the multiple and simultaneous broadcasting of a relayed signal in the different environments gives rise to problems such as combinations destroying the radio-frequency waves relayed among them. This case occurs, according to the example in figure lc, when the door of the vehicle V is open for example. The inventor has then observed that, by adapting the power level of the signals transmitted by the communication apparatuses according to the environments in which these communication apparatuses are situated, the interference between the relayed signals decreases considerably.

To this end, according to one embodiment of the system, the device comprises means for instructing a communication apparatus detected as having changed environment to adapt its transmission power level according to the new environment in which it is situated. Each communication apparatus of the system then comprises means for adapting its power level following the receipt of this instruction.

Such a system is advantageous since it makes it possible to adapt the power level of the signals that are transmitted in environments that may be very different particularly in terms of volume or in environments that comprise electronic circuits liable to be sensitive to the broadcasting of radio-frequency signals such as those that are on board a vehicle.

According to another of its aspects, the invention concerns a method for relaying a beacon signal or a traffic signal of a radio-frequency communication established between communication apparatuses liable to move from one environment to another, the said environments not enabling the radio-frequency waves relating to this communication to propagate from one environment to another without being highly attenuated, each

12 communication apparatus being designed to use an antenna diversity mechanism, and an antenna being positioned in each environment. The method is characterised in that it comprises a step of reception of the beacon or traffic signal by at least one antenna, a step for generating a signal, referred to as the relayed signal, from the signal received, and a step of simultaneous transmission by each antenna of the relayed signal, the power level of the relayed signal that is transmitted per antenna being equal to a percentage of the total power level of the relayed signal.

According to one embodiment, the percentage of the power level of the relayed signal that is transmitted by an antenna is higher than the percentages of the power level of the relayed signal that are transmitted by the other antennas.

According to a variant of this embodiment, the percentages of the power level of the relayed signal that are transmitted by the said other antennas are all equal to the same value.
According to one embodiment, the method comprises a step of determining the environment in which an apparatus at the origin of the transmission of a signal received by at least one of the antennas is situated.

Advantageously, the method comprises a display step during which the environment in which a communication apparatus is situated is displayed.

According to a variant of this embodiment, the method comprises a step of detecting a change in environment of a communication apparatus.
Advantageously, following the detection of a change in environment of a communication apparatus, the method comprises a step of adapting the transmission power level of the said communication apparatus during which the highest power level among those measured of a received signal is compared with a predetermined value in order to adapt the transmission

13 power level of the said communication apparatus at the origin of the transmission of the received signal to the environment in which this apparatus is situated.

Preferably, during the step of adapting the transmission power level of the said communication apparatus, a signal, referred to as the transmission power level adaptation signal, preferentially of a CLMS service, is received on the reception antenna of this communication apparatus so that this communication apparatus adapts its transmission power level to the new environment in which it is situated.

Advantageously, following the detection of change in environment of a base, the method comprises a step for warning the communication apparatuses that are synchronised from the beacon transmitted by this base to synchronise onto the relayed beacon signal.

According to another of its aspects, the invention concerns a computer program stored on an information carrier of a device for relaying a beacon signal or a traffic signal of a radio-frequency communication established between communication apparatuses situated in different environments, the said program containing instructions for implementing one of the above methods, when it is loaded onto and executed by one of the above devices.

The features of the invention mentioned above, as well others, will emerge more clearly from a reading of the following description of an example embodiment, the said description being given in relation to the accompanying drawings, among which:

figures la-b show an illustration of the problem of continuity of reception of a beacon signal or of a traffic signal of a communication established between a transmitting apparatus and a receiving apparatus situated in environments to be relayed when these apparatuses change environment, figure lc show schematically a device for relaying a beacon signal or a traffic signal of a

14 communication established between communication apparatuses of the prior art, figure 2 shows schematically an embodiment of a device for relaying a beacon signal or a traffic signal of a communication established between communication apparatuses according to the invention, figures 3a-c show schematically the internal structure of the radio-frequency switching apparatus, figure 4 shows schematically embodiments and variants of a device for relaying a beacon signal or a traffic signal of a communication established between communication apparatuses situated in environments to be relayed when these apparatuses change environment according to the invention, figure 5 shows the steps of the method for relaying a beacon signal or a traffic signal of a communication established between communication apparatuses situated in environments to be relayed when these apparatuses change environment, figure 6 shows schematically an example of use of the device according to the invention for relaying two environments, figure 7 shows schematically an example of use of the device according to the invention for relaying three environments.

The invention concerns a method and device for relaying a beacon signal or a traffic signal of a radio-frequency communication established between communication apparatuses situated in environments to be relayed.

Although this device is presented in the context of an application of the military type, the field of application of the invention extends to any application that requires continuity of a radio-frequency communication between mobile apparatuses situated in environments to be relayed as soon as one of these apparatuses changes environment, that is to say in any application having recourse to a radio-frequency relay intended to relay the radio-frequency waves 5 relating to a communication that propagate in one environment so that these waves can also propagate in another environment, whatever these environments may be, such as the inside of a room in a building, the inside of a mobile or static vehicle, open air, etc.

Figure 2 shows schematically the device Dl for relaying a beacon signal or a traffic signal of a 10 communication established between communication apparatuses according to the invention.
The device D1 comprises a radio-frequency relay R, a plurality of antennas AEi each positioned in an environment Ei to be relayed, and a radio-frequency switching apparatus AG.

15 The radio-frequency relay R comprises at least one so-called reception port Rrk, that is to say a port intended to receive a signal to be relayed, and a so-called transmission port Re, that is to say a port intended to transmit a relayed signal. It should be noted that a port of the relay R
may be both a transmission port Re and a reception port Rrk.

When a signal is received on a reception port Rrk, a signal transmitted on a particular slot/frequency pair, a new signal, said to be relayed, is generated and transmitted on another slot/frequency pair as explained in the introductory part, and this new relayed signal is then transmitted on the transmission port Re.

For the purpose of increasing the quantity of information circulating per frame, some of the TDMA slots are allocated to the communications of one of the two radio parts of the relay R
while the rest of the TDMA frame slots are allocated to the other radio part.
Thus there are no unoccupied slots and the entire frame can be used for transmitting data. One of the radio parts will use only the slots, for example even, of a TDMA frame and the other radio part will use

16 only the odd slots of this frame. French patent FR 2,869,495 describes such a system.

The radio-frequency switching apparatus AG comprises as many ports PAi, referred to as antenna ports, as there are environments to be relayed, in this case N, at least one port Prj, referred to as the relay reception port, and a port Pe referred to as the relay transmission port.
It should be noted that a port of the switching apparatus AG may be both a relay transmission port Pe and a relay reception port Prj.

Each antenna port PAi is connected to another antenna AEi that is intended to transmit the radio-frequency waves carrying a beacon or traffic signal in the environment Ei in which it is situated. In addition, each antenna port PAi is in relationship with a relay reception port N.
Thus a signal received by an antenna PAi is routed to a relay reception port Prj.

Each relay reception port Prj is connected to a reception port Rrk of the radio-frequency relay R and the relay transmission port Pe is connected to the transmission port Re of the relay R.
The radio-frequency switching apparatus AG is designed so that a signal received on one of the antenna ports PAi is routed with a power level equal to that of the signal received to the relay reception port corresponding to this antenna port and so that, following the reception of a signal on the relay transmission port Pe, this signal is routed to each antenna port PAi, the power level of the signal on each antenna port PAi being equal to a percentage of the total power level of the signal received on the relay transmission Pe.

The radio-frequency switching apparatus AG is preferentially a printed circuit on which an RF
circuit is etched and this circuit is installed in a housing placed close to the relay. The RF
circuit is either a passive circuit or an active circuit that amplifies the signals received and/or transmitted.

17 Figures 3a-c show schematically the internal structure of the radio-frequency switching apparatus AG.

With reference to figure 3a, during transmission, a signal Se is received on the relay transmission port Pe, and this signal is routed to each antenna port PAi. Thus the signal Se is broadcast simultaneously in all the environments Ei to be relayed.

The power level of the relayed signal Psei on each antenna port PAi is a percentage of the total power level Pse of the of the signal Se, that is to say the sum of the power levels Psei is equal to that of the signal Se. In mathematical terns, the power level Psei is given by Psei = a; *Pse with a; a non-zero positive real value strictly less than 1 for any i and subject to the constraint N
that 7'a;=1.

According to one embodiment of the radio-frequency switching apparatus AG, the percentage, for example al, of the power level Psel of the signal Se that is routed to an antenna port is higher than the percentages al i ~ 1 of the power level of the signal that is routed to each other N
antenna port, that is to say a, =1- a;

Preferentially, the percentages a; i : 1 of the power level of the signal Se that is routed to the said other antenna ports are all equal to the same value b, that is to say a;
= b b'; t- 1 with b a non-zero positive real value strictly less than 1. For example b = 0.01 forN
<10.

The radio-frequency switching apparatus AG is also designed so that a signal received on one

18 of the antenna ports PAi is routed entirely to a relay reception port Prj, that is say the power level of the signal received on the antenna port PAi is equal to that of the signal once routed to the relayed reception port Prj.

Figure 3b shows an embodiment of the radio-frequency switching apparatus AG in reception mode.

According to this mode, each relay reception port Prj is connected to a single antenna port PAi and the relay transmission port Pe is connected to a single antenna port, in this case PA1.
Thus a signal received on an antenna port PAi is routed with a power level equal to that of the received signal Sri to the corresponding relay reception port PRi and a signal received on the antenna port PA 1 is routed with a power level equal to that of the signal received to the relay transmission port Pe.

It should be noted that, according to this embodiment, the relay transmission port Pe is also a relay reception port Rrk.

Figure 3c shows a variant of the embodiment of the radio-frequency switching apparatus of figure 3b.
According to this embodiment, a relay reception port Prj is connected to more than one antenna port, in this case the relay reception port PR1 is connected to the antenna ports PAN-1 and PAN. Thus a signal received either by the antenna port PAN-1 or PAN is routed with a power level equal to that of the received signal to the relay reception port PR 1.
Figure 4 shows schematically embodiments and variants of a device for relaying a beacon signal or a traffic signal of a communication established between communication apparatuses according to the invention.

19 The device D2 comprises a plurality of antennas AEi each positioned in an environment Ei to be relayed, a radio-frequency switching apparatus AG the internal structure of which is in accordance with figure 3b (as shown in figure 4) or according to the variant thereof described in relation to figure 3c, and each relay port Prj is connected to a reception port Rrk of the relay R.

According to one embodiment, the device D2 also comprises means DETER for determining in which environment Ei an apparatus at the origin of the transmission of a signal received on at least one of the antenna ports PAi is situated.
Preferably, the means DETER are composed of means MES for measuring per antenna the power level of a signal received, means COMP for comparing with each other the power levels thus measured and means SEL for selecting as the reception antenna for the apparatus the antenna on which the highest power level was measured. The environment in which the apparatus is situated is then determined as being that in which the said reception antenna thus selected is situated. The means MES are widely known in the prior art. Such means enable a power level measurement that is known by the measurement name RSSI (Received Signal Strength Indication).

Thus the means MES, COMP and SEL use an antenna diversity mechanism, that is to say a mechanism that enables the device, each time a signal is received, to choose the reception antenna that enables it to receive optimally any signal transmitted by a communication apparatus.

According to a variant of this embodiment, the device D2 comprises means VISU
for displaying the environment in which each communication apparatus is situated.
For example, the means VISU comprise a display screen on which there is displayed, for each communication apparatus, an indicator for designating one of the environments Ei. The means VISU are in communication with the means DETER by a cabled or radio-frequency connection.

According to a variant of this embodiment, the device D2 comprises means DETEC
for detecting that a communication apparatus at the origin of the transmission of a signal received 5 on at least one of the antenna ports PAi changes environment.

The means DETEC preferably also comprises a memory MEM designed to store an environment EiM previously determined by the means DETER, an environment in which the said apparatus was situated, and means COMPA for comparing the said environment EiM thus 10 stored with the environment Em newly determined by the means DETER, the environment in which the said apparatus is henceforth situated. The apparatus is then detected as having changed environment if the previously stored environment EIM and the newly determined environment Em are different.

15 As illustrated in figure 4, the means DETER and DETEC are connected to each port PAi of the switching apparatus AG and the means DETER and DETEC communicate with each other.

The means DETER and DETEC and in particular the means COMP, COMPA and SEL are

20 preferably software means, that is to say a set of instructions in a program preferably used by a programmable electronic component associated with the device D2.

A radio-frequency communication system comprising one of the devices described above, in which the switching apparatus is associated with the antenna diversity mechanism used by the relay, makes it possible to relay the beacon and traffic signals between the communication apparatuses of this system. It should be stated that at least one of these communication apparatuses sends a beacon signal continuously so that the other communication apparatuses are synchronised in terms of time and frequency on this beacon signal or on this beacon signal once relayed by the device.

21 According to one embodiment of this system, the device D2 comprises means ORD
for ordering the base to trigger means for warning the communication apparatuses that are synchronised from the beacon signal that it is transmitting, to synchronise on the beacon signal relayed by the device D2. The base then comprises means for warning the communication apparatuses that are synchronised from the beacon signal that it is transmitting to synchronise on the beacon signal relayed by the device D2. These means internal to the base are activated following the reception by the base of this triggering order. In addition, these means also use a list of the communication apparatuses synchronised on the beacon signal transmitted by the base. Such a list, widely known in the prior art, is kept up to date by the base.

The means ORD are preferably software means, that is to say a set of instructions of a program preferably used by a programmable electronic component associated with the device D2.
According to one embodiment of the system, the device D2 comprises means ANP
for ordering a communication apparatus that has been detected as having a change of environment to adapt its transmission power level according to the new environment in which it is situated.
Each communication apparatus of the system then comprises means for adapting its power level following this order emanating from the device D2.

The means ANP are preferably software means, that is to say a set of instructions of a program preferably used by a programmable electronic component associated with the device.

According to one embodiment of the ANP means, a signal SA, referred to as the signal for adapting the transmission power level, preferentially of a CLMS (Connection Less Message System) service, is transmitted by the device D2 and received on the reception antenna of the communication apparatus so that this communication apparatus corrects its transmission power level in the case where the power level of the signal measured by this apparatus is

22 greater than or less than a predetermined value.

According to a variant of this embodiment of the means ANP, the adaptation signal SA bears the value of the transmission power level that the communication apparatus must now use in the new environment in which it is situated.

According to another variant of this embodiment of the means ANP, the adaptation signal SA
carries information indicating to this communication apparatus that it must correct its transmission power level without for all that specifying this new power level.
In this case, the communication apparatus knows in advance, for each environment in which it is liable to move, the transmission power level that it must use. These transmission power levels are for example stored in an internal memory.

According to one embodiment of the system, at least one communication apparatus internally comprises means for detecting that it is changing environment.

Preferably, the said means internal to a communication apparatus for detecting that it is changing environment comprise means for regularly measuring the power level of the beacon signal and means for comparing the variation in the said power level measured with a predetermined high or low threshold. The apparatus then detects that it has changed environment if it determines that the variation is lower than the low threshold or higher than the high threshold.

Figure 5 shows the steps of the method for relaying a beacon signal or a traffic signal of a communication established between communication apparatuses.

The method is, according to one embodiment, a set of instructions of a program that is used by the software means of one of the devices D2 as described in relation to figure 4.

23 The method comprises a step 100 of reception by at least one antenna AEi of a beacon or traffic signal, a step 200 for generating a so-called relayed signal, from the received signal, and a step 300 of transmission by each antenna AEi of the signal thus relayed.
The power level of the relayed signal Psei that is transmitted by each antenna AEi is equal to a percentage of the total power level Pse of the relayed signal.

According to one embodiment, the percentage of the power level of the relayed signal that is sent by an antenna is higher than the percentages of the power level of the relayed signal that are sent by the other antennas.
According to a variant of this embodiment, the percentages of the power level of the relay signal that are sent by the said other antennas are all equal to the same value b, as will be seen later.

According to one embodiment, the method comprises a step 400 of determining the environment Ei in which an apparatus at the origin of the transmission of a signal received by at least one of the antennas AEi is situated.

Preferably, during the said step 400, the power level of the received signal Pse is measured per antenna by the means MES of the device D2 and the power levels thus measured are compared with each other by the means COMP. A reception antenna is then selected by the means SEL, for example the antenna AEi of the device D2, on which the highest power level was measured. The environment Ei in which the apparatus is situated is the one that relates to the reception antenna thus selected, in this case the antenna AEi.
Preferably, step 400 is performed at each reception of a signal on at least one of the antennas AEi.

Advantageously, the method comprises a display step 500 during which the environment in

24 which a communication apparatus is situated is displayed.

According to a variant of this embodiment, the method comprises a step 600 of detecting a change in environment of a communication apparatus.
Preferably, during the step 600, the means DETER are used in order to determine the new environment Em in which this apparatus is situated. It should be noted that, for this purpose, step 400 is implemented and that, at the end of this step, the reception antenna AEm relating to this new environment Em has been selected. The new environment Em is then compared with the environment EiM in which the communication apparatus was situated up until then. This environment EiM was stored during a previous step 600. In the case where the environments EiM and Em are different, the apparatus is then detected as having changed environment.
Advantageously, following the detection of change in environment of a communication apparatus, the method comprises a step 700 of adapting the transmission power level of the apparatus thus detected as having changed environment. During step 700, the power level of the signal measured on the reception antenna AEm, that is to say the one on which the power level measured is the highest, is compared with a predetermined value Th in order to adapt the transmission power level Pe of the communication apparatus at the origin of the transmission of the signal received on the antenna AEm to the new environment in which this apparatus is situated.

Preferably, during step 700, a so-called transmission power level indication signal, preferably of a CLMS service, is transmitted on the reception antenna of this communication apparatus so that this communication apparatus adapts its transmission power level to the new environment Em.

According to a variant, the power level indication signal carries the value of the transmission power level that the communication apparatus should now use in the environment Em and, according to another variant, the power level indication signal carries information indicating to this communication apparatus that it should adapt its transmission power level without for all that specifying this new power level. This new power level is for example stored by the apparatus:

Advantageously, following the detection of change in environment of a base, the method comprises a step 800 for warning the communication apparatuses that are synchronised from the beacon signal transmitted by the said base to synchronise on this beacon signal once relayed.
In other words, a base C situated in the environment El transmits a beacon signal (not relayed) that is received by the other communication apparatuses situated also in the environment El.
When the base C changes environment in order to into the environment E2, the base C
indicates to the other communication apparatuses situated in the environment E1 and that are synchronised with this non-relayed beacon signal that they should receive the beacon signal relayed via the antenna AEi rather than the non-relayed beacon signal. For this purpose, the base C knows the communication apparatuses that are synchronised on the beacon signal that it is transmitting since the base C keeps up to date a list of these communication apparatuses as explained previously.
For the purpose of illustrating the method used by one of the devices D2, lets us consider the case of a DECT network used for radio-frequency communication between communication apparatuses situated in different environments Ei to be relayed.

Figure 6 shows schematically an example of use of the device D2 for relaying two environments El and E2, which are for example the outside and inside of the vehicle V.
The device D2 is in conformity with one of those described in relation to figure 4. It comprises, according to this example, two antennas AE1 and AE2 each positioned in an environment to be relayed, in this case the environments E1 and E2, a radio-frequency switching apparatus AG the internal structure of which in transmission is in accordance with figure 3a and in reception is in accordance with figure 3b. The switching apparatus AG
comprises, according to this example, an antenna port PAl connected to the antenna AE1, an antenna port PA2 connected to the antenna AE2, a relay reception port PRl and a relay transmission port PE.

The device D2 also comprises a relay R in accordance with figure 2 designed to receive a beacon or traffic signal on a slot/frequency pair, for example on two even slots of a TDMA
frame, and to generate a signal relayed on another slot/frequency pair, for example on odd slots. In addition, the relay R comprises a reception port Rrl connected to the reception port PR1 and a transmission port Re connected to the relay transmission port Pe.

Let us consider first of all the case where the base C is situated in the environment E2 and a communication apparatus Fl is situated in the environment El. The base C, which is designed to fulfil the functions of a DECT base, transmits on an even slot a TDMA
frame, a beacon signal SB that is received by the antenna AE2 (step 100) and therefore on the antenna port PA2 of the radio-frequency switching apparatus AG. The beacon signal Sb is then routed to the port PR1 of the radio-frequency switching apparatus AG and then to the port Rrl of the relay R, which is synchronised with this beacon signal Sb. It should be noted that the beacon signal Sb received by the radio-frequency switching apparatus AG is completely routed to the relay R. In addition, the beacon signal Sb being received solely by the antenna AE2, the power level measured on the antenna AE2 is the highest. The base C is consequently considered to be inside the vehicle V (step 400).
The relay R relays the signal Sb, which is then transmitted on odd slots of TDMA frames via the port Re. The beacon signal Sb relayed is then received by the port Pe of the switching apparatus AG. The beacon signal Sb relayed is then routed to the antenna ports PAl and PA2 by means of the internal structure of the radio-frequency switching apparatus AG in transmission mode (step 300). For example, the power level of the beacon signal Sb relayed which is routed to the antenna port PA2 is equal to 1% of the total power level of the beacon signal relayed Sb and the power level of the beacon signal Sb relayed that is routed to the antenna port PA1 is equal to 99% of the total power level of the beacon signal relayed Sb.
Thus the beacon signal Sb relayed is transmitted over the odd slots of a TDMA
frame simultaneously by the antenna AE1 and by the antenna AE2. It should be noted that, according to this example of use, the power level of the beacon signal Sb relayed that is routed to the antenna port PA1 is very much greater than that of the relayed beacon signal Sb that is routed to the antenna port PA2 in order to limit the destructive combinations of the waves transmitted simultaneously by the two antennas. This configuration is possible since the cabin of the vehicle is a very small space and it requires only a small transmission power.

It will be understood that a traffic signal transmitted on an even slot is relayed in a similar manner by the device.
Let us look now at how the device according to the invention enables the beacon signal to be received continuously by the apparatus F1 in the case where either the apparatus F1 or the base C changes environment.

Let us take the case where the apparatus F1 and the base C are not situated in the same environment as illustrated in figure 6. The base C transmits the beacon signal Sb on which the relay R is synchronised. The apparatus F1 is then synchronised on the relayed beacon signal.
Let us assume that the base C changes environment in order to go into the environment E1.
The device D2, which measures the power level of the signal received by each antenna port, will then note that the signal is stronger on the antenna AE1 and select this antenna port as the port for receiving the beacon signal Sb. As each of the antennas is dedicated to an environment, the device D2 makes it possible to determine the new environment in which the base C is not situated, in this case the outside of the vehicle V (step 400), in order to be displayed (step 500) and stored. The base C is then detected as having changed environment (step 600).

Following this change, the device D2 informs the base C that it should adapt its transmission power level of the beacon signal to the environment E l (step 700).

The change in environment of the base C is transparent for the apparatus Fl, which continues to receive the beacon signal relayed via the antenna AE2. It should be noted that the apparatus F1 can also choose to receive the beacon signal Sb transmitted directly by the base C if this signal is stronger than the one received via the antenna AE2. At this time, the apparatus F1 performs a handover in order to receive the non-relayed beacon signal Sb (step 800).

Let us take the case where the apparatus F1 and the base C are not situated in the same environment, as illustrated in figure 6. The base C transmits the beacon signal Sb on which the relay R is synchronised. The apparatus F1 is then synchronised on the relayed beacon signal Sr.

Let us suppose that the apparatus F1 changes environment. The device D2 detects that the communication apparatus F1 has changed environment when, following the reception of a message from the apparatus F1, preferably CLMS, by the device D2, the said message is received on the antenna corresponding to the environment in which the communication apparatus F1 is situated. The device D2 the requests the apparatus F1 to adapt its transmission power level to the environment E2 (step 700). During the change in environment, the communication apparatus F1 does not suffer any break in reception of the relayed beacon signal Sr by virtue of the fact that the said beacon signal is transmitted simultaneously on the antennas AE1 and AE2.

Let us take the case where the apparatus F1 and the base C are situated in the same environment E2. The base C transmits the beacon signal Sb on which the relay R
and the apparatus F1 are synchronised.

Let us assume that the base has been detected as having changed environment (step 600).

The device D2 then transmits a signal to the base C requesting it to warn the apparatus F1 to synchronise on the relayed beacon signal Sr and the apparatus Fl then performs a handover in order to receive the relayed beacon signal Sr (step 800). The fact that the relay R and the apparatus Fl are synchronised on the same beacon signal Sb enables the apparatus F1 to perform a "jump" (handover) of the non-relayed beacon signal Sb to the relayed beacon signal Sr without breaking reception of the beacon signal by the apparatus F1.

In addition, the base C is informed that it should adapt its transmission power level of the beacon signal to the environment E1 (step 700).

Let us now take the case where the apparatus Fland the base C are situated in the same environment E2. The base C transmits the beacon signal Sb on which the relay R
and the apparatus F1 are synchronised.

Let us assume that the apparatus F1 changes environment, that is to say it leaves the vehicle V.
The power level of the beacon signal Sb received by the apparatus Fl will then change abruptly and the variation in this power level then becomes lower than a predetermined threshold, referred to as the low threshold. Likewise, it will be understood that, if the apparatus F1 enters the vehicle, the variation in the power level of the signal Sb then becomes greater than a predetermined threshold, referred to as the high threshold. The apparatus F1 will then detect that it is leaving the vehicle and stores this new environment. Consequently it performs a handover on the signal Sr.

The apparatus F1 that up until then received the non-relayed beacon signal Sb via the antenna AE2 now receives the relayed beacon signal Sr via the antenna AE1. There is no break in reception of the beacon signal Sb since the beacon Sb and the relayed beacon signal Sr are synchronised with each other.

The apparatus Fl, having detected that it has changed environment, adapts its transmission 5 power level to the environment El (step 700).

Figure 7 shows schematically an example of use of the device D2 for relaying three environments El, E2 and E3, which are respectively the outside of the vehicle V, the troop transport compartment and the driving cab of the vehicle V. The troop transport compartment 10 and the driving cab are separated by armouring that does not enable the radio-frequency waves to propagate from one environment to another without being highly attenuated.

The reference signs of the elements in figure 7 that are identical to the reference signs of figure 6 designate the same elements.
The device D2 is in accordance with one of those described in relation to figure 4. It comprises, according to this example, three antennas AE1, AE2 and AE3 each positioned in an environment to be relayed, in this case the environments El, E2 and E3, a radio-frequency switching apparatus AG the internal structure of which in transmission mode is in accordance with figure 3a and is accordance with figure 3b in reception mode. The switching apparatus AG comprises, according to this example, an antenna port PA1 connected to the antenna AE1, an antenna port PA2 connected to the antenna AE2, antenna port PA3 connected to the antenna AE3, two relay reception ports PRl and PR2 and a relay transmission port PE.

The device D2 also comprises a relay R according to figure 2 designed to receive a beacon or traffic signal on a slot/frequency pair, for example on even slots of a TDMA
frame, and to generate a relayed signal on another slot/frequency pair, for example on odd slots. In addition, the relay R comprises a reception port Rrl connected to the reception port PR1, a reception port Rr2 connected to the reception port PR2 and a transmission port Re connected to the relay transmission port PE.

Let us consider first of all the case where the base C is situated in the environment E2 and where a communication apparatus Fl is situated in the environment El and a communication apparatus is situated in the environment E3. The base C transmits, on an even slot of a TDMA
frame, a beacon signal Sb that is received by the antenna AE2 (step 100) and therefore on the antenna port PA2 of the radio-frequency switching apparatus AG. The beacon signal Sb is then routed as far as the port PR2 of the radio-frequency switching apparatus AG and then to the port Rr2 of the relay R, which is synchronised with this beacon signal Sb.
It should be noted that the beacon signal Sb received by the radio-frequency switching apparatus AG is entirely routed to the relay R. In addition, the beacon signal Sb being received solely by the antenna AE2, the power level measured on the antenna AE2 is the highest. The base C is consequently considered to be in the troop transport compartment of the vehicle V (step 400).

The relay R relays the signal Sb, which is then transmitted over odd slots of TDMA frames via the port Re. The relayed beacon signal Sb is then received by the port Pe of the switching apparatus AG. The relayed beacon signal Sb is then routed to the antenna ports PA1, PA2 and PA3 by means of the internal structure of the radio-frequency switching apparatus AG (step 300). For example, the power level of the relayed beacon signal Sb that is routed to the antenna ports PA2 and PA3 is equal to 1% of the total power level of the relayed beacon signal Sb and the power level of the relayed beacon signal Sb that is routed to the antenna port PA1 is equal to 98% of the total power level of the relayed beacon signal SB.
Thus the relayed beacon signal Sb is transmitted over the odd slots of a TDMA frame simultaneously by the antenna SE I, the antenna AE2 and the antenna AE3.
It will be understood that a traffic signal transmitted over an even slot is relayed in a similar manner by the device and that the cases of change in environment of a communication apparatus described in relation to figure 6 apply whatever the number of environments to be relayed.

Claims

What is claimed is:

1. A device for relaying one of: a beacon signal, and a traffic signal of a radio-frequency communication established between communication apparatuses liable to move from one environment to another environment, the environments not enabling the radio-frequency waves relating to this communication to propagate from one environment to the other environment without being highly attenuated, each communication apparatus being designed to use an antenna diversity mechanism, the device comprising a plurality of antennas (AEi) intended to receive a signal and a radio-frequency relay (R) intended to relay a signal received by an antenna positioned in one of the environments to another antenna positioned in a further environment, wherein the device comprises an apparatus (AG), referred to as a radio-frequency switching apparatus, which comprises - at least one port (PRj), referred to as the relay reception port, which is connected to a reception port (Rrk) of the radio-frequency relay (R) and functions in reception mode, - a port (Pe), referred to as the relay transmission port, which is connected to a transmission port (Re) of the radio-frequency relay (R) and functions in transmission mode, - as many ports (PAi), referred to as antenna ports, as there are environments to be relayed, each antenna port (PAi) being connected to an antenna of an environment and being connected with at least one relay reception port (PRj), the radio-frequency switching apparatus (AG) being designed so that a signal received on one of the antenna ports (PAi) is entirely routed to a relay reception port (PRj), and so that, when a relayed signal is received on the relay transmission port (Pe), the relayed signal (PSei) is simultaneously routed to each antenna port (PAi), the power level of the signal relayed on each antenna port being equal to a percentage (ai) of the total power level of the relayed signal (Pse).

2. The device according to claim 1, wherein the radio-frequency switching apparatus is designed so that the percentage of the power level of the relayed signal that is routed to an antenna port is higher than the proportions of the power level of the relayed signal that is routed to each other antenna port.

3. The device according to claim 2, wherein the radio-frequency switching apparatus is designed so that the percentages of the power level of the relayed signal that is routed to the other antenna ports are all equal to the same value (b).

4. The device according to any one of claims 1 to 3, wherein the relay transmission port (Pe), during a transmission, is connected to all the antenna ports (PAi) with transmission levels adapted to each of the environments, whereas in reception mode each relay reception port (PRj) is connected directly to a single antenna port.

5. The device according to any one of claims 1 to 3, wherein, during a transmission, the relay transmission port (Pe) is connected to all the antenna ports (PAi) with transmission levels adapted to each of the environments, whereas in reception mode at least one relay reception port (PRj) is connected more than one antenna port (PAi).

6. The device according to any one of claims 1 to 5, wherein the device comprises a means (DETER) for determining in which environment an apparatus at the origin of the transmission of a signal received by at least one of the antenna ports (PAi) is situated.

7. The device according to claim 6, wherein the means (DETER) for determining in which environment an apparatus is situated is composed of a means (MES) for measuring per antenna the power level of the received signal, a means (COMP) for comparing with each other the power levels thus measured and a means (SEL) for selecting as the reception antenna for the apparatus the antenna on which the highest power level was measured, the environment in which the apparatus is situated being determined as being the one in which the reception antenna thus selected is situated.

8. The device according to any one of claims 6 and 7, wherein the device comprises a means (VISU) for displaying the environment in which each communication apparatus is situated.

9. The device according to any one of claims 6 to 8, wherein the device comprises a means (DETEC) for detecting that the apparatus at the origin of the transmission of the received signal is changing environment.

10. The device according to claim 9, wherein the device comprises a memory (MEM) designed to store the previously determined environment in which the apparatus is situated and a means (COMPA) for comparing the environment thus stored with the newly determined environment in which the apparatus is situated, the apparatus being detected as having changed environment if the previously stored environment and the newly determined environment are different.

11. The device according to any one of claims 9 and 10, the communication apparatus being thus detected as having changed environment and transmitting a beacon signal, characterised in that it comprises means (ORD) for ordering the communication apparatus to trigger means for warning the communication apparatuses that are synchronised from the beacon signal transmitted by the communication apparatus to synchronise on the beacon signal relayed by the device.

12. The device according to any one of claims 9 and 11, wherein the device comprises means (ANP) for ordering the communication apparatus thus detected as having changed environment to adapt its transmission power level according to the new environment in which it is situated.

13. A communication system comprising a plurality of communication apparatuses liable to move from one environment to another, the environments not enabling the radio-frequency waves relating to a communication between the plurality of communication apparatuses to propagate from one environment to another without being highly attenuated, each communication apparatus being designed to use an antenna diversity mechanism, wherein the antenna diversity mechanism comprises a device according to any one of claims 1 to 12 for relaying the radio-frequency communication from one environment to another.

14. The communication system according to claim 13, wherein at least one of the plurality of communication apparatuses broadcasts a beacon signal, wherein the at least one of the plurality of communication apparatuses comprises a means for warning the communication apparatuses synchronised on the beacon signal to synchronise on the beacon signal once relayed by the device.

15. The communication system according to any one of claims 13 and 14, wherein each communication apparatus comprises a means for adapting a transmission power level according to the environment in which it is situated.

16. The communication system according to any one of claims 13 to 15, wherein at least one communication apparatus comprises a means for detecting that the at least one communication apparatus is changing environment.

17. The communication system according to claim 16, wherein the means internal to the at least one communication apparatus for detecting that the at least one communication apparatus is changing environment comprises a means for regularly measuring the power level of the beacon signal and a means for comparing the variation in the measured power level with a predetermined high or low threshold.

18. A method for relaying one of: a beacon signal and a traffic signal of a radio-frequency communication established between communication apparatuses liable to move from one environment to another, the environments not enabling the radio-frequency waves relating to the radio-frequency communication to propagate from one environment to another without being highly attenuated, each communication apparatus being designed to use an antenna diversity mechanism, and an antenna being positioned in each environment, wherein the method comprises a step (100) of reception by at least one antenna of the beacon or traffic signal, a step (200) for generating a signal, referred to as the relayed signal, from the signal received, and a step (300) of simultaneous transmission of the relayed signal by each antenna, the power level of the relayed signal that is transmitted per antenna being equal to a percentage of the total power level of the relayed signal.

19. The method according to claim 18, wherein the percentage of the power level of the relayed signal that is transmitted by an antenna is higher than the percentages of the power level of the relayed signal that are transmitted by the other antennas.

20. The method according to claim 19, wherein the percentages of the power level of the relayed signal that are transmitted by the other antennas are all equal to the same value (b).

21. The method according to any one of claims 18 to 20, wherein the method comprises a step (400) of determining the environment in which an apparatus at the origin of the transmission of a signal received by at least one of the antennas is situated.

22. The method according to claim 22, wherein, during the step (400) of determining the environment, the power level of the received signal is measured per antenna, the power levels thus measured are compared with each other and the environment in which the apparatus is situated is the one that relates to the antenna the power level of which is the highest.

23. The method according to any one of claims 21 and 22, wherein the method comprises a display step (500) during which the environment in which each communication apparatus is situated is displayed.

24. The method according to any one of claims 21 to 23, wherein the method comprises a step (600) of detecting a change in environment of a communication apparatus.

25. The method according to claim 24, wherein, during the step of detecting a change in environment of a communication apparatus, the new environment in which the apparatus is situated is determined and then compared with the previously determined environment in which the apparatus was situated, the apparatus being determined as having changed environment if the previously stored environment and the newly determined environment are different.

26. The method according to any one of claims 24 to 25, wherein the method comprises a step (700) of adapting the transmission power level of the apparatus thus determined as having changed environment during which the power level of a highest measured signal is compared with a predetermined value (Th) in order to adapt the transmission power level of the communication apparatus at the origin of the transmission of the received signal to the new environment in which this apparatus is situated.

27. The method according to claim 26, wherein, during the step (700) of adapting the transmission power level of the communication apparatus, a signal, referred to as the signal for adapting the transmission power level, preferentially of a Connection Less Message System (CLMS) service, is received on the reception antenna of this communication apparatus so that this communication apparatus adapts its transmission power level to the new environment in which it is situated.

28. The method according to claim 27, wherein the signal for adapting the transmission power level bears the value of the transmission power level that the communication apparatus must henceforth use in the environment in which it is situated.

29. The method according to claim 27, wherein the signal for adapting the transmission power level bears information indicating to this communication apparatus that it must adapt its transmission power level without specifying this new power level.

30. The method according to any one of claims 24 to 29, wherein at least one of the communication apparatuses, referred to as the base, broadcasting a beacon signal, characterised in that the method comprises a step (800) for warning the communication apparatuses synchronised on the beacon signal transmitted by the base to synchronise on the beacon signal once relayed, once the base has been determined as having changed environment.

31. A computer readable medium having stored thereon computer executable instructions which, when executed by the device according to any one of claims 1 to 12, implement the method according to any one of claims 18 to 30.