EP1941683A2

EP1941683A2 - Method, program and system for transferring data between a number of terminals that communicate via a common communications channel in a wireless network, and wireless terminal

Info

Publication number: EP1941683A2
Application number: EP06831283A
Authority: EP
Inventors: André Gautier; Christian Bouissou
Original assignee: France Telecom SA
Current assignee: Orange SA
Priority date: 2005-10-24
Filing date: 2006-10-23
Publication date: 2008-07-09
Also published as: FR2892539A1; US8203945B2; WO2007048968A3; WO2007048968A2; US20090135719A1

Abstract

According to this method, each terminal (T1, T2, T3, T4) is capable of covering a coverage area. The method comprises a step (22) of sending a signal for requesting data (RTS) to be sent from a first terminal (T1) to a second terminal (T2) located in its coverage area, provided for notifying the second terminal (T2) of the fact that the first terminal (T1) requests it to send the data (D1), and a step (24) for sending an availability signal (CTS) to the first terminal (T1) serving to notify the first terminal (T1 of the fact that the second terminal (T2) is available to receive the data (D1). The method also comprises a step (26) for sending a signal for requesting the reception of the data (RTR) from a third terminal (T3) having received the availability signal (CTS) but not having received the sending request signal (RTS) serving to notify the fact that it is available to receive data (D2).

Description

Method, program and system for transferring data between a plurality of terminals that communicate via a common communication channel in a wireless network, and wireless terminal

The present invention relates to a method, a program and a system for transferring data between a plurality of terminals that communicate via a common communication channel in a wireless network, and a wireless terminal.

In such a wireless network with a single communication channel, each terminal can receive data from any other terminal of the network. Note that each terminal is able to transmit data to a coverage area of its own and that each other terminal in this coverage area is likely to receive the transmitted data, even if this other terminal is not the recipient of these data.

Thus, in some cases, a terminal may be in coverage areas of several other terminals, and can therefore simultaneously receive data transmitted by at least two other terminals.

These data being transmitted on the same channel, the data receiving terminal is not able to distinguish them from each other. We then say that there is data collision. In order to avoid certain collisions, each terminal in the coverage area of another terminal being transmitted must not transmit data while the channel is busy. This avoids collisions with the data transmitted by the other terminal being transmitted.

However, the case where a terminal simultaneously receives data transmitted by two other terminals being transmitted is not resolved in this way. Indeed, any terminal can start transmitting data without knowing that a terminal in its coverage area is already receiving data from another terminal.

In order to limit the inconvenience of the collisions thus generated, it is conventional to use a collision detection method called CSMA / CA (Carrier Sense Multiple Access Protocol with Collision Avoidance). This method comprises in particular an acknowledgment step during which a receiving terminal acknowledges the good reception of the data by sending an acknowledgment signal. Thus, if a transmitting terminal does not receive an acknowledgment signal after sending data to a receiving terminal, it is because there has been a collision and this data has not been received correctly. In this case, the transmitting terminal transmits the data again, usually after a random time. This collision detection method does not, however, prevent these collisions in a systematic manner.

Also known in the state of the art is a method for transferring data between a plurality of terminals that communicate via a common communication channel in a wireless network, each terminal being able to cover a coverage area, the method comprising:

a step of sending a request signal for sending data, from a first terminal to a second terminal located in its coverage area, intended to warn the second terminal that the first terminal requests from it send data;

a step of sending an availability signal to the first terminal, intended to warn the first terminal that the second terminal is available to receive the data.

Such a method, in accordance with the MAC 802.11 protocol, is generally called RTS / CTS (Request To Send / Clear To Send).

FIG. 1 shows a system for transferring data between wireless terminals according to such a method of the state of the art.

In this FIG. 1, each terminal T1, T2, T2 ', T3, T3', T4, T4 ', T is in the coverage area of the two terminals which are adjacent thereto. The data transfer takes place from the first terminal T1 to the second terminal T2.

According to this method, a terminal T3 located in the coverage area of the second terminal T2 should not transmit data, in order to avoid collisions with the data received by this second terminal T2. In particular, the terminal T3 will not have to send an availability signal if another terminal T4 sends this terminal T3 a request signal for sending data. Thus, no other terminal will be able to send data to the terminal T3 during the transfer of data from the first terminal T1 to the second terminal T2, since no terminal will be able to receive an availability signal from this terminal T3.

Thus, a disadvantage of this state of the art is that none of the terminals T3 in the coverage area of the second terminal T2 can receive data during data transfer between the first T1 and the second terminal T2.

The invention aims in particular to overcome this drawback by providing a data transfer method reducing the blocking of certain terminals of the coverage area of the second terminal. For this purpose, the subject of the invention is a method for transferring data of the aforementioned type, characterized in that the method further comprises a step of sending a a request signal for receiving data from a third terminal having received the availability signal and not having received the send request signal, intended to warn that the third terminal is available to receive data.

Thus, a third terminal located in the coverage area of the second terminal, but not in the coverage area of the first terminal, is able to warn the terminals of its coverage area, upon receipt of the availability signal broadcast by the second terminal, that it can receive data.

Therefore, if another terminal plans to send data to it, this other terminal can do it without the need to send a request signal to send data, or require to receive an availability signal, since it will already have received a signal that the third terminal can receive data.

There is therefore no risk that the third terminal sends an availability signal during the transfer of data from the first terminal to the second terminal. The third terminal is no longer fully blocked since it can freely receive data from another terminal.

Note that the third terminal may be any terminal in the coverage area of the second terminal and not in the coverage area of the first terminal. Since the system can include many such terminals, the invention has the advantage of allowing all these terminals to be able to receive data during the transfer of data from the first terminal to the second terminal.

A data transfer method according to the invention may further include one or more of the following features. The data transfer method comprises, after the step of sending the data sending request signal and before a data transfer step, a waiting step for a predefined duration sufficient for the steps of sending of the signal of availability and sending of the data reception request signal are completed before the step of transferring the data. Thus, the first terminal transmits the data only when all the signals of availability and request for receiving data have been sent, in order to avoid possible collisions of the data transmitted with these signals.

At least one of the data sending request signal and the data reception request signal comprises an identifier of the terminal transmitting this signal. Thus, the terminals receiving this signal know the identifier of the terminal requesting to send or receive data.

At least one of the data request request signal and the availability signal comprises an identifier of the destination terminal of this signal. Thus, the terminals receiving this signal can know if this signal is intended for them or not.

At least one of the data request request signal, the availability signal and the data reception request signal includes information concerning the duration of the data transfer between the first and second terminals. With this information, the terminals receiving the signal know the data transfer time and can, if necessary, be configured not to emit signals during this transfer time to avoid collisions.

- At least one terminal is associated with a temporal parameter, decrementing over time, the terminal can not emit any signal until this parameter is non-zero. Thus, this parameter allows the blocking of the terminal, for example during the duration of the data transfer between the first and second terminals.

- When a terminal receives a data request request signal or an availability signal of which it is not the recipient, its time parameter is incremented by a value corresponding to the information concerning the duration of the data transfer. , so as to be non-zero until the data is transmitted in their entirety from the first terminal to the second terminal. The first terminal sends the request signal for sending data only if the data to be transferred have a size greater than a predetermined threshold, for example greater than 500 bytes. Thus, in the case of small data, which can be transmitted quickly, we can use another method of transfer less time to implement, the risk of collision during the transfer being less.

The invention also relates to a data transfer program for wireless, comprising software instructions for:

send a data request request signal intended to warn another terminal of the fact that it is planned to send data to it, sending an availability signal intended to warn another terminal, having sent it a request signal for sending data, since it is available to receive the data, characterized in that the program also comprises a software instruction. for: - when the wireless terminal has received an availability signal and has not received a send request signal, send a data request request signal to warn that the terminal is available to receive data. data.

The invention further relates to a wireless terminal capable of communicating with other wireless terminals via a common communication channel in a wireless network, characterized in that it is provided with a data transfer program such that previously defined.

The invention finally relates to a system for transferring data between wireless terminals communicating via a common communication channel in a wireless network, characterized in that it comprises at least one wireless terminal as defined above.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the appended drawings in which: FIG. 1 represents a system for transferring data between wireless terminals according to a method of the state of the art as described above.

FIG. 2 represents a system for transferring data between wireless terminals according to an exemplary embodiment of the invention; FIG. 3 represents steps of a method of transferring data between wireless terminals of the system of FIG. 2;

FIG. 4 diagrammatically represents the content of request signals for sending data, availability and request for receiving data exchanged between the wireless terminals of the system of FIG. 2; FIG. 5 diagrammatically represents information contained respectively by the data sending request, the availability and the data receiving request signals, concerning time periods between the sending of these respective signals and the end of the transfer. of data ; FIG. 6 diagrammatically represents the activities of the terminals of FIG. 2 during the implementation of the method of FIG. 3. FIG. 2 shows a wireless network 10 comprising a plurality of wireless terminals T, T ₁ , T ₂ , T ₃ , T ₃ ', T ₄ , T ₄ ', Ti and T _j which communicate together via a wireless network. common communication channel in the wireless network 10. In the example described, the communication channel is a radio channel. In this example, two terminals are said to transmit on the same channel when they use the same transmission frequency.

Each wireless terminal T, T ₁ , T ₂ , T ₃ , T ₃ ', T ₄ , T ₄ ', T 1 and T _j is, depending on the case, a mobile terminal or an access point, for example a terminal fixed.

The wireless network 10 comprises a first terminal T ₁ , provided with data to be sent to a second terminal T ₂ located in a first coverage area Z ₁ covered by the first terminal T ₁ .

It will be noted that terminals T ₁ and T _j are also in the first coverage area Z ₁ .

The second terminal T ₂ covers a second coverage area Z ₂ , in which there are third terminals T ₃ , T ₃ 'of the wireless network 10. Note that the terminal T _j is also in the second coverage area Z ₂ .

The third terminals T ₃ , T ₃ 'also cover respective coverage areas in which there are other terminals respectively labeled T ₄ and T ₄ '.

Note that in the example described, all terminals cover coverage areas of substantially identical sizes. Each wireless terminal of the network 10 is provided with a data transfer program.

This data transfer program includes a software instruction for sending a request signal for sending RTS data when the wireless terminal plans to send data to another terminal. This RTS data sending request signal is intended to warn this other terminal that the wireless terminal plans to send data to it.

The data transfer program also comprises a software instruction for sending a CTS availability signal when the wireless terminal receives an RTS data sending request signal intended for it and this wireless terminal is available to receive the data. that is, it is not in the process of transmitting or receiving other data. The availability signal CTS is intended to warn another terminal having sent the request signal sending RTS data to the wireless terminal that this wireless terminal is available to receive the data.

The data transfer program further comprises a software instruction for sending a RTR data reception request signal when the wireless terminal has received a CTS availability signal and has not received a request signal. RTS sending. This RTR data reception request signal is intended to warn other terminals that the wireless terminal is available to receive data.

The data transfer program finally comprises a software instruction for sending an acknowledgment signal ACK when the wireless terminal has received data transmitted in their entirety. This acknowledgment signal ACK is intended to warn another terminal that has sent data to the wireless terminal that these data have been received in their entirety.

Moreover, so that no terminal emits a signal during a data transmission, each terminal is associated with a temporal parameter, decrementing over time, corresponding to a period during which this terminal must not emit a signal. For example, each terminal is configured not to emit a signal until the time parameter associated with it is non-zero.

Finally, note that each wireless terminal is configured to be blocked for a short time interval, generally noted SIFS (Short InterFrame Space), after each sending or receiving a signal. This short time interval represents a margin of safety intended to ensure that there will be no collision between two signals transmitted or received in succession.

FIG. 3 shows a method for transferring data between the terminals of the network 10. FIG. 6 represents the activities of the terminals T1, T2, T3 and T4 during the implementation of this method.

During a first initialization step 20, the first terminal T ₁ initializes the data transfer D1 to the second terminal T ₂ , being in its coverage area Z ₁ . Preferably, during this step, the size of the data to be sent is checked. If the size of these data is less than a predetermined threshold, for example 500 bytes, it is considered that it is not useful to use the data transfer method according to the invention and the data is then sent using only a conventional CSMA / CA collision detection method. If the size of the data is greater than the predetermined threshold, it proceeds to a step 22 of sending a data sending request signal RTS, from the first terminal T ₁ to the second terminal T ₂ . This RTS data sending request signal is intended to warn the second terminal T ₂ that the first terminal T ₁ requests to transfer data D1 to it. It will be noted that the first terminal T ₁ sends this signal RTS over all the first zone Z ₁ that it covers. Thus, all the terminals T ₂ , T ₁ , T _j being in the first coverage area Z ₁ also receive the request signal for sending RTS data.

So that each terminal T ₂ , J ₁ , J ₁ of the first coverage area Z ₁ can know which are the transmitters and recipients of the request signal for sending data RTS, this signal carries information I ₁ identifying the transmitting terminal signal and information I ₂ identifying the destination terminal of this signal (see Figure 3). This information I ₁ and I ₂ generally comprise MAC (Medium Access Control) addresses of the transmitter and receiver terminals respectively.

Thus, any terminal J ₁ , J ₁ receiving the request signal for sending RTS data without being the recipient blocks during the total duration of the data transfer, so as not to risk sending signals that can collide with the signals emitted by the first terminal T ₁ .

In order to determine the period during which each of these terminals J ₁ , J ₁ must be blocked, the RTS data sending request signal carries information I ₃ concerning the total planned duration until the data D1 is transmitted. in their entirety from the first terminal T ₁ to the second terminal T ₂ .

This total duration, represented in FIG. 5, comprises:

the duration of a first short time interval SIFS,

the duration of sending a CTS availability signal, the duration of a second short SIFS time interval,

the duration of sending a RTR data reception request signal,

- the duration of a third short time interval SIFS,

the duration of the transfer of the data D1,

the duration of a fourth short time interval SIFS, and the duration of sending of an acknowledgment signal ACK.

Thus, when a terminal T ₁ , T _j receives the RTS data sending request signal, its time parameter is incremented by a value calculated from this total duration, so as to be non-zero until that the data D1 are transmitted in their entirety from the first terminal T ₁ to the second terminal T ₂ . Finally, it will be noted that the RTS data sending request signal comprises control information I ₄ and I ₅ , sent respectively at the beginning and at the end of this RTS data sending request signal, making it possible to control that this signal has been received in its entirety.

After the first terminal T ₁ has sent the request signal for sending data RTS, we go to a step 23 during which the terminal T ₁ goes into waiting for a predefined duration A1 sufficient for a CTS availability signal and a RTR data reception request signal to be sent. This predefined duration A1 therefore comprises:

the duration of a first short time interval SIFS; the duration of sending of a CTS availability signal;

- the duration of a second short time interval SIFS,

the duration of sending a RTR data reception request signal, and

- the duration of a third short time interval SIFS.

The terminal T ₁ will be able to send the data D1 to the terminal T ₂ only when this waiting time is over, in order to avoid any collisions of the data with a CTS availability signal sent by the second terminal T ₂ or a request signal from receiving RTR data received by this second terminal T ₂ .

If the second terminal T ₂ is available to receive the data D1, that is to say that it is not in the process of sending or receiving other data, then it goes to a step 24 during of which the second terminal T ₂ sends a CTS availability signal to the first terminal T ₁ . This availability signal CTS is intended to warn the first terminal T ₁ that the second terminal T ₂ is available to receive the data D1.

This availability signal CTS is also received by the third terminals T ₃ , T ₃ 'and the terminal T _j being in the coverage area Z ₂ of the second terminal T ₂ . Thus, the terminals T ₃ , T ₃ ', T _j know that a terminal in their coverage area will receive data and therefore they must not send signals that can collide with the data received by this terminal.

It will be noted that the availability signal CTS includes information I ₆ concerning the time remaining before the data transfer is completed. This information I ₆ makes it possible to update the time parameters associated with the terminals T ₃ , T ₃ 'so that these terminals can not send data until the data are transmitted in their entirety from the first terminal T ₁ to the terminal. second terminal T ₂ , that is to say for a predefined duration, represented in FIG. 5, comprising: the duration of a first short period of time SIFS,

the duration of sending a RTR data reception request signal,

- the duration of a second short time interval SIFS,

the duration of the transfer of the data D1,

the duration of a third short time interval SIFS; and the duration of sending of an acknowledgment signal ACK. Furthermore, the availability signal CTS includes information I ₇ concerning the destination terminal of this signal, that is to say the first terminal T ₁ . This information I ₇ makes it possible to warn the first terminal T ₁ that this availability signal CTS is intended for it, and therefore that the second terminal T ₂ is available to receive the data D1 that it wishes to transmit to it and not not the data that another terminal would like to transmit to it.

Finally, the availability signal CTS comprises control information I ₈ and Ig, sent respectively at the beginning and at the end of this availability signal CTS, making it possible to verify that this signal has been received in its entirety. Note that if the second terminal T ₂ is not available to receive the data, it goes to a step 25 end of the process. Indeed, the second terminal T ₂ does not send an availability signal CTS, and the first terminal T ₁ will not send him the data D1. In this case, the terminal T ₁ will generally be put on hold for a random time before trying again to send the data. In the case where the third terminals T ₃ , T ₃ 'receive the availability signal CTS of the second terminal T ₂ , proceed to a step 26 during which each third terminal T ₃ , T ₃ ' has not received the send request signal RTS sends, in its coverage area, a request signal for receiving RTR data. The RTR data reception request signal is intended to warn other terminals T ₄ , respectively T ₄ ', located in the coverage area of the third terminal T ₃ , respectively T ₃ ', because this third terminal T ₃ , respectively T ₃ ', is available to receive D2 data.

It will be noted that the terminal T _j , which receives the availability signal CTS of the second terminal T ₂ , but which has also received the send request signal RTS of the first terminal T ₁ , does not send a reception request signal. RTR data. Indeed, since it is in the coverage area Z ₁ , in which the communication channel is occupied by the transfer of data from the first terminal T ₁ to the second terminal T ₂ , it will not be able to receive data during this period. data transfer. Thanks to the RTR data reception request signal, it is not necessary for another terminal T ₄ , respectively T ₄ ', to send a request signal for sending RTS data or to receive an availability signal. CTS when it wishes to send data D2 to the third terminal T ₃ , respectively T ₃ ', during the data transfer from the first terminal T ₁ to the second terminal T ₂ . Indeed, this other terminal T ₄ , respectively T ₄ ', is already informed that the third terminal T ₃ , respectively T ₃ ', is available to receive its data D2. Thus, the third terminals T ₃ , T ₃ 'are not likely to send CTS availability signal during the transfer of data from the first terminal T ₁ to the second terminal T ₂ , which avoids possible collisions between such an availability signal CTS and the data D1 received by the second terminal T ₂ . Note that each data reception request signal RTR carries information I ₁₀ concerning the terminal identification transmitter of this signal, i.e. the third terminal T _3, T ₃ respectively. Thus, the other terminals T ₄ , respectively T ₄ ', are informed of the identity of the terminal T ₃ , respectively T ₃ ', which is able to receive data D2. Preferably, the RTR data reception request signal comprises information ₁₁ relating to the time remaining until the data D1 is transmitted integrally between the first terminal T ₁ and the second terminal T ₂ . Thus, the terminal T ₄ , T ₄ 'can send data D 2 to the corresponding terminal T ₃ , T ₃ ' only for a predefined duration, represented in FIG. 5, comprising: the duration of a first short period of time SIFS ,

the duration of the transfer of the data D1,

the duration of a second short time interval SIFS, and

the duration of sending of an acknowledgment signal ACK.

Finally, the RTR data reception request signal comprises information I ₁₂ and I ₁₃ respectively sent at the beginning and at the end of this RTR data reception request signal, intended to verify that this signal has been received in the receiver. its entirety.

After the waiting time of the first terminal T ₁ is over, that is to say that the second terminal T ₂ can begin to receive the data D1 without risk of collision, we go to a step 28 of data transmission D1.

When the data D1 has been sent in their entirety, a step 30 is taken, during which the second terminal T ₂ sends an acknowledgment signal ACK to the first terminal T _{1 in} order to confirm the good reception of the data D1. It will be noted that the transfer of the data D2 from the terminal T ₄ , T ₄ 'to the terminal

Corresponding T ₃ , T ₃ 'is interrupted at the same time as the transfer of data D1 from the first terminal T ₁ to the second terminal T ₂ . Thus, in step 30, each third terminal T ₃ , T ₃ 'also sends an acknowledgment signal ACK to the corresponding terminal T ₄ , T ₄ ' in order to confirm the good reception of the data D 2. It is generally after this step 30 that the terminals Tj, T _j blocked can emit again, their time parameter having decremented during the transmission of data until it became zero.

It is understood that the embodiment which has just been described is not limiting in nature and may receive any desirable modification without departing from the scope of the invention.

Claims

A method of transferring data between a plurality of terminals (T, T ₁ , T ₂ , T ₃ , T ₃ ', T ₄ , T ₄ ', T 1, T _j ) communicating via a common communication channel in a wireless network (10), each terminal (T, T ₁ , T ₂ , T ₃ , T ₃ , T ₄ , T ₄ , T ₁ , T _j ) being capable of covering a coverage area (Z ₁ , Z ₂ ), the method comprising:

a step (22) of sending a data sending request signal (RTS) from a first terminal (T ₁ ) to a second terminal (T ₂ ) lying in its coverage area (Z ₁ ), intended to warn the second terminal (T ₂ ) that the first terminal (T ₁ ) requests to send data to it (D 1),

a step (24) of sending an availability signal (CTS) to the first terminal (T ₁ ), intended to warn the first terminal (T ₁ ) that the second terminal (T ₂ ) is available for receiving the data (D1), characterized in that the method further comprises: - a step (26) of sending a data request request signal

(RTR) of a third terminal (T ₃ , T ₃ ) having received the availability signal (CTS) and not having received the request for sending signal (RTS), intended to warn that this third terminal (T ₃ , T ₃ ) is available to receive data.

Data transfer method according to claim 1, comprising, after the step (22) of sending the data sending request signal (RTS) and before a step (28) for transferring the data (D1). , a waiting step (23) for a predefined duration (A1) sufficient for the steps (24, 26) for sending the availability signal (CTS) and for sending the data reception request signal (RTR) ) are completed before the data transfer step (28).

A data transfer method according to claim 1 or 2, wherein at least one of the data request request signal (RTS) and the data request request signal (RTR) comprises an identifier (I ₁ , I ₁₀ ) of the terminal transmitting this signal

A method of data transfer according to any one of claims 1 to 3, wherein at least one of the data request request signal and the availability signal comprises an identifier (I ₂ , I ₇ ) of the receiving terminal of this signal.

A data transfer method according to any one of claims 1 to 4, wherein at least one of the data request request signal (RTS), the availability signal (CTS) and the request signal receipt of data (RTR) comprises information (I ₃ , I ₆ , I ₁₁ ) concerning the duration of the data transfer between the first (T ₁ ) and the second (T ₂ ) terminal.

Data transfer method according to any one of claims 1 to 5, wherein at least one terminal (T, T ₁ , T ₂ , T ₃ , T ₃ , T ₄ , T ₄ , T 1, T _j ). is associated with a temporal parameter, decrementing over time, the terminal (T, T ₁ , T ₂ , T ₃ , T ₃ ', T ₄ , T ₄ ', T 1, T _j ) can not emit any signal so much that this parameter is not zero.

7. A method of data transfer according to claims 4 and 6 taken together, wherein, when a terminal (T, T ₁ , T ₂ , T ₃ , T ₃ -, T ₄ , T ₄ , T ₁ , T _j ) receives a data sending request signal (RTS) or an availability signal (CTS) of which it is not the recipient, its time parameter is incremented by a value corresponding to the information (I ₃ , I ₆ , I ₁₁ ) relating to the duration of the data transfer, so as to be non-zero until the data are transmitted in their entirety from the first terminal (T ₁ ) to the second terminal (T ₂ ).

A data transfer method according to any one of claims 1 to 7, wherein the first terminal (T ₁ ) sends the data request request signal (RTS) only if the data to be transferred has a larger size. at a predetermined threshold, for example greater than 500 bytes.

9. Data transfer program for a wireless terminal (T, T ₁ , T ₂ , T ₃ , T ₃ , T ₄ , T ₄ , T 1, T _j ), comprising software instructions for:

sending a request signal for sending data (RTS) intended to warn another terminal that it is planned to send data to it (D1),

sending an availability signal (CTS) intended to warn another terminal, having sent it a data sending request signal (RTS), because it is available to receive the data, characterized in that the program further comprises a software instruction for:

when the wireless terminal (T, T ₁ , T ₂ , T ₃ , T ₃ , T ₄ , T ₄ , T 1, T _j ) has received an availability signal (CTS) and has not received a signal of send request (RTS), send a request data reception signal (RTR) to warn that the terminal is available to receive data.

10. Wireless terminal (T, T ₁ , T ₂ , T ₃ , T ₃ , T ₄ , T ₄ , T 1, T _j ) capable of communicating with other wireless terminals (T, T ₁ , T ₂ , T ₃ , T ₃ -, T ₄ , T ₄ , T ₁ , T _j ) via a common communication channel in a wireless network (10), characterized in that it is provided with a data transfer program according to claim 9.

11. System for transferring data between wireless terminals (T, T ₁ , T ₂ ,

T ₃ , T ₃ ', T ₄ , T ₄ , T 1, T _j ) communicating via a common communication channel in a wireless network (10), characterized in that it comprises at least one terminal (T, T ₁ , T ₂ , T ₃ , T ₃ ', T ₄ , T ₄ ', T 1, T _j ) according to claim 10 .