FR3067210A1 - METHOD OF DIRECT COMMUNICATION BETWEEN TERMINALS - Google Patents

Abstract

The invention relates to a method of direct communication between at least two terminals of a mobile network, on a set of radio resource blocks defined in one or more dimensions, organized in a frame, the method being implemented by a transmitting terminal and comprising the following steps: - transmission test (40), at least one receiving terminal, at least one signaling message according to a first subset of radio resource blocks; and - according to at least one acknowledgment message received in response to the transmission test, transmission (44), to the at least one receiving terminal, data on the first subset of blocks.

Description

FIELD OF THE INVENTION

The invention is in the field of telecommunications. It relates in particular to direct communications between terminals, standardized by the LTE standard (for Long Term Evolution) from release 12 under the name of "Sidelink communications".

BACKGROUND OF THE INVENTION

In general, a mobile telephone network allows the simultaneous use of mobile equipment (eg mobile phones and digital tablets equipped with SIM cards) to communicate by radio with a terrestrial infrastructure comprising in particular base stations (typically comprising antennas) covering a specific geographic area (cell), as well as a core network responsible for managing the routing of mobile communications.

These elements (including antennas, SIM cards and mobile equipment) can come from various manufacturers. It is therefore necessary to comply with certain technical specifications, and to apply the same rules to allow these elements of various origins to be able to interact, for example for the establishment and routing of communications.

It is to address this problem that ETSI (for European Telecommunications Standards Institute) has been cooperating since the late 1990s, notably with its American and Asian equivalents on a partnership project called 3GPP (for 3rd Generation Partnership Project). This cooperation led to the development and publication of technical specifications for mobile networks from the 3 ^rd generation (3G).

To meet growing needs in speed due in particular to the democratization of video streaming and mobile applications, 4G was born with the

LTE (for Long Term Evolution), optimized for transporting data.

The 3GPP working groups are also developing 5G which aims to address the increased needs of complex applications requiring very high speed and high reliability, for example cloud computing and big data, home automation or even communications involving vehicles. autonomous (without driver).

In addition to uplink (from mobile equipment to the network) and downlink (from the network to mobile equipment) communications standard in mobile networks, the LTE standard (from release 12) provides for the establishment of communications sidelink (SL) direct between neighboring mobile devices, i.e. without going through the network infrastructure. D2D (for Device to Device) communications between terminals are known, for example, but also V2V (for Vehicle to Vehicle) communications between intelligent, for example autonomous (driverless) vehicles.

This new type of communication is possible in particular thanks to a specific PC5 radio interface which makes it possible to create a WLAN network (for Wireless Local Area Network) between neighboring mobile devices.

Regarding the allocation of resources for SL communications, two modes are provided in the LTE standard (Release 13). In the first mode called "scheduled mode", the allocation of resources is managed by the base station and indicated to the terminals via a signaling message. In the second mode called "autonomous mode", the allocation of resources is managed by the terminals themselves (that is to say the terminals communicating directly), by choosing the resources of their choice from a set of preconfigured resources.

The second mode allows greater autonomy of the terminals and better use of resources. Indeed, each terminal is free to choose the resources it wishes whether or not it is within the range of a base station and it is thus possible to satisfy the needs of different services, in particular in terms of speed.

In order to make data transmissions more reliable and reduce the number of collisions due to the fact that the terminals do not know which resources will be chosen by other neighboring terminals for their own data transmissions, repetition and frequency hopping mechanisms are put in place. implemented.

However, these mechanisms do not make it possible to achieve good spectral efficiency (that is to say a good orthogonal distribution of frequencies and more generally of radio resources, between neighboring terminals) or to offer guarantees of quality of service .

In general, the LTE standard, in particular the specification

ETSI TS 136 213 V14.2.0 (2017-04), does not provide an effective mechanism to reduce the risk of collisions without affecting spectral efficiency or quality of service. There is therefore a need to propose such a mechanism.

SUMMARY OF THE INVENTION

The present invention thus aims to overcome at least one of these drawbacks.

In this context, a first aspect of the invention relates to a method of direct communication between at least two terminals of a mobile network, over a set of blocks of radio resources defined according to one or more dimensions, organized in a frame, the method being implemented by a transmitting terminal and comprising the following steps:

- test transmission, to at least one receiving terminal, of at least one signaling message based on a first subset of radio resource blocks; and

- as a function of at least one acknowledgment message received in response to the test transmission, transmission, to at least one receiving terminal, of data on the first subset of blocks.

Advantageously, the risks of collision are drastically reduced since the data transmission is not really carried out or completed until after a test phase allowing to confirm that the chosen resources are not in conflict.

In addition, spectral efficiency is improved since repetition is not necessary.

Correlatively, a second aspect of the invention relates to a communication device conforming to the LTE standard and implementing the above-mentioned method.

The advantages, aims and particular characteristics of this device are similar to those of the above method.

Other characteristics of the method and of the device according to embodiments of the invention are described in the dependent claims.

The acknowledgment message can be a function of the radio quality of reception by the receiving terminal and / or of the modulation and coding scheme (MCS) used for the test transmission. So for example, when the quality is too bad, the receiving terminal can decide not to send an acknowledgment, or else indicate in this acknowledgment that the reception quality is bad. In another example, the acknowledgment may indicate the new MCS to be used for data transmission on the first subset of blocks.

In particular embodiments, the frame comprises a plurality of predefined configurations of radio resource blocks and the first subset is a predefined configuration of radio resource blocks.

In particular embodiments, the frame comprises at least one control part and the at least one signaling message is transmitted on a block of radio resources of the at least one control part associated with the predefined configuration corresponding to the first sub- set of blocks, thus allowing the identification of the first subset of blocks.

This signaling message indicates for example that the data will be transmitted on the first subset of blocks.

The frame can also include one or more parts reserved for data transmission.

When the frame is organized into configurations, in certain embodiments, there may be a unique correspondence between resources of the control part and each configuration of the data part. This facilitates the identification of the configuration or configurations of the data part concerned by the signaling messages sent on the control part.

In particular embodiments, the test transmission comprises a transmission of test data over a second subset of radio resource blocks representative of the first subset of radio resource blocks.

In this case, the acknowledgment message may indicate that the test data has been received on the second subset.

Typically, this test data can consist of a sample of the data to be transmitted on the first subset of blocks.

Depending on the modes, the test data can be transmitted in the control part of the frame or in the data part.

In particular embodiments, the test transmission is carried out on a first frame while the data transmission is carried out on a second frame comprising the first subset of radio resource blocks, the second frame being different from the first frame.

In particular embodiments, the radio resource blocks located between the radio resource blocks used for the test transmission and the reception of the acknowledgment message (s) are reserved for transmitting short direct data DSSL and / or transmitting or receiving d other acknowledgment or acknowledgment request messages.

In particular embodiments, the frame may include a plurality of control parts.

In particular embodiments, the test transmission and the reception of the at least one acknowledgment message in response to the test transmission are carried out on the same control part of the frame.

In particular embodiments, the radio resource blocks used for the test transmission are also used by the transmitting terminal for the transmission of data, whether it is spread over one or more frames.

In particular embodiments, the method comprises receiving another acknowledgment message on predefined control parts of the frame, in response to the data transmitted on the first subset of blocks, the other acknowledgment message notifying the sending terminal of a change in an MCS modulation and coding scheme used by the at least one receiving terminal and / or acknowledging the data received until then.

In particular embodiments, the method comprises receiving a reservation message for a third subset of radio resource blocks of the current frame or of a future frame.

In particular embodiments, the method comprises the transmission of another signaling message to the at least one receiving terminal, indicating at least one block of radio resources in use on the current frame by the transmitting terminal.

In particular embodiments, the method comprises receiving connection quality measurements between the transmitting terminal and each receiving terminal of a plurality of receiving terminals, the method further comprising a step of selecting at least one relay terminal among the plurality of receiving terminals according to the quality measures, an identifier of the at least one relay terminal being indicated in a header message transmitted with the data on the first subset of blocks.

In particular embodiments, the method comprises receiving quality measurements of the connection between the two terminals of a plurality of pairs of terminals, the method further comprising a step of calculating a multicast broadcast graph from quality measurements received.

In particular embodiments, the method further comprises the following steps:

- reception of a reservation message from a subset of radio resource blocks sent by a terminal of the mobile network to another terminal different from the transmitter;

- measurement of the quality of reception of the reservation message; and

- as a function of the result of the comparison of the reception quality measured with a threshold value, reservation or not of said subset of blocks of radio resources.

In particular embodiments, the reservation message indicates a level of quality of reception of messages by said terminal of the mobile network.

In particular embodiments, the reservation of the subset of radio resource blocks is also a function of the result of the comparison of the reception quality indicated in the reservation message with a threshold value.

In particular embodiments, the future frame is separated from the current frame by a predefined duration function of at least one block of radio resources dedicated to the reservation message and / or signaled in the reservation message.

In particular embodiments, at least a first block of radio resources is dedicated to the at least one signaling message and at least a second block of radio resources is dedicated to the at least one acknowledgment message, the at least a first block and the at least a second block being spaced by a predefined duration at least equal to the time necessary for the decoding of the at least one acknowledgment message.

In particular embodiments, at least a third block of radio resources is dedicated to the reservation message, the at least one first block and the at least one third block being spaced by a predefined duration at least equal to the time required when decoding the reservation message.

In particular embodiments, the third subset of reserved radio resource blocks corresponds to the first subset of blocks.

In particular embodiments, the at least one signaling message indicates reservation information, this reservation information comprising all of the radio resources and identifying at least one future frame than at least one terminal of the mobile network other than the sending terminal has reserved.

In particular embodiments, the reservation information is associated with a period of validity limited in time starting with the emission of the at least one signaling message.

In particular embodiments, the method further comprises the following steps:

- calculation of a probability of success of the test transmission as a function of a number of signaling messages received from other terminals of the mobile network and indicating the first set of blocks of radio resources and of a total number of signaling messages received from other mobile network terminals from the test transmission; and

- depending on the probability of success calculated, whether or not to transmit data on the first subset of blocks.

In practice, the total number of signaling messages also includes signaling messages received which do not indicate the first set of radio resource blocks.

In particular embodiments, the at least one signaling message indicates a priority index associated with each future transmission and the calculation step takes this priority index into account.

In particular embodiments, blocks of radio resources dedicated to signaling and / or acknowledgment messages are of reduced size compared to the other radio resource blocks of the frame or have different dimensions compared to the other resource blocks. frame radio.

In particular embodiments, the different steps of the aforementioned methods are determined by instructions from computer programs.

Consequently, the invention also relates to a computer program on an information medium, this program being capable of being implemented by a microprocessor, this program comprising instructions adapted to the implementation of the steps of the method such than mentioned above.

This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form.

The aforementioned information carrier and computer program have characteristics and advantages analogous to the process that they implement.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the invention will become apparent in the description below, illustrated by the attached figures which illustrate exemplary embodiments thereof without any limiting character. In the figures:

- Figure 1 illustrates the direction of downlink and uplink communications between a terminal and the mobile network as well as sidelink communications between two terminals;

- Figure 2 illustrates a resource block;

- Figure 3 illustrates an example frame format for managing sidelink communications;

- Figure 4 shows, in the form of a flowchart, the main steps of a direct communication method between terminals according to embodiments of the invention;

- Figure 5 illustrates a first example of SL transmission in accordance with the implementation of the method of Figure 4;

- Figure 6 illustrates a second example of SL transmission in accordance with the implementation of the method of Figure 4;

- Figure 7 illustrates a third example of SL transmission in accordance with the implementation of the method of Figure 4;

- Figure 8 illustrates an example of unicast SL transmission spread over several frames with free choice of DP resources (Open DSP);

- Figures 9a and 9b illustrate an example of the distribution of resources dedicated to DCH (Figure 9a) and signaling messages (Figure 9b) of a SCPeriod SL;

- Figure 9c illustrates an example of unicast SL transmission spread over several frames whose resources are organized in accordance with Figures 9a and 9b (Closed DSP);

- Figure 10 illustrates an example of unicast SL transmission on a single frame with free choice of DP resources (Open DSP);

- Figure 11 illustrates an example of unicast SL transmission on a single frame with a choice limited to the configurations of DP (Closed DSP);

FIG. 12 illustrates an example of a unicast SL transmission spread over several frames with a choice limited to the configurations of DP (Closed DSP) without test data;

- Figure 13 illustrates an example of transmission SL on a frame comprising several control parts SP;

- Figure 14 shows an example of a multicast communication link in a multicast group;

FIG. 15 illustrates an example of establishment of SL multicast communication on frames composed of a certain number of control parts SP.

DETAILED DESCRIPTION OF THE INVENTION

In general, the present invention makes it possible to control access to a set of blocks of radio resources of a sidelink communications management frame. Typically, the method is implemented by a transmitting node and comprises a first phase comprising a test transmission of the quality of the radio link during which a signaling message depends on a first subset of blocks of radio resources of the frame and optionally test data is transmitted to at least one receiving node. In practice, the test data constitute a sample (a first part) of the data that the sending node wishes to send.

Then, the sending node waits to receive one or more acknowledgment messages indicating that the test transmission went well or not.

Once this acknowledgment message has been received, a second phase starts, during which a conventional data transmission takes place to the receiving node on the first subset of radio resource blocks. In the case where a sample of this data (test data) has already been sent during the test phase, conventional transmission consists in sending the rest of the data.

This second phase takes place only on condition that the first (test) phase has ended with the receipt of one (or more) acknowledgment message (s) attesting to the good progress of the test.

Thus, the risks of collisions due to the fact that transmitting nodes have chosen the same blocks of radio resources are avoided.

Examples will now be described.

FIG. 1 illustrates the direction of downlink and uplink communications between a terminal 10 and the mobile network (antenna 12) as well as sidelink communications between two terminals 10 and 14.

Such terminals are typically mobile phones or tablets equipped with a USIM card, or any other user equipment UE within the meaning of the LTE standard. The present invention is not limited to this standard and can be applied in other contexts.

FIG. 2 illustrates a resource block RB (for Resource Block).

The basic transmission unit is the RB. An RB has a certain duration corresponding to a certain number Nsym of transmission symbols and it is defined on a number Nsc of subcarriers. An RB (or a set of RB) carries either signaling messages (SIG) or data packets (DATA). The size of the information transported by a set of RB is defined according to the modulation and coding scheme (MCS) used (e.g. SC-FDMA, RSMA).

In this example, the radio resources are represented in RB with two time / frequency dimensions. However, a different number of dimensions and / or dimensions of a different nature than time and frequency can be considered. For example, BR could be three-dimensional (e.g. time, frequency and code) or one-dimensional (time).

Also, in the following description, the BRs considered will be of the same size and identical in nature. However, the invention is not limited to this and the BRs can also be of different sizes (eg small BRs for signaling and larger for data) or even of different nature (eg transmission of data by SC-FDMA on Time / frequency RB and transmission of signaling by RSMA on time / frequency / code RB).

Figure 3 illustrates an example frame format for managing sidelink communications.

The LTE standard has defined a frame for SL communications management, called SC-Period. A SC-Period is composed of a ^part 1 of control or signaling SP (Signaling for Pool) followed by a 2 ^nd DP data portion (Data for Pool). The SP is used for the transmission of the SCI0 signaling message also called SA (Scheduling Assignment). This message is sent by a transmitting terminal subsequently called “source node”, “transmitting node” or “transmitter” to one or more receiving terminals subsequently called “recipient nodes”, “receiving nodes” or “receivers”. This message carries the information necessary to allow the recipient (s) to identify themselves and the source, and to decode the data transmission that takes place in the DP. The DP and the SP are composed of RB, as shown in the figure.

As will be seen later, in certain embodiments of the present invention, the SC-Period frame is used as it is known from the standard.

LTE, that is to say with a temporal separation between the control parts SP and data DP (see for example Figures 5 to 12). In other embodiments, a modified SC-Period frame is used, in which the parts control SP and data

DPs are not separated in time so that communications can be initiated at different locations in the frame (see for example Figure 13).

In both cases (SP and DP separated temporally or not), it is proposed here to partition the DP data part of each frame into several subparties denoted DSP (for Data Sub-Pool). A DSP sub-part differs from the T-RPT provided by the LTE standard in that the repetition of data on several DSPs is not necessary. In addition, the resources chosen for a transmission can be identical on all the DSPs in the frame (no frequency hopping between several DSPs).

FIG. 4 illustrates the general principle of access control carried out during direct communication between terminals in accordance with embodiments of the invention.

During a step 40, a test transmission is carried out by a transmitter to one or more receivers. According to the invention, this test transmission is a function of a first subset of radio resource blocks on which data will be transmitted subsequently.

Thus, this test transmission consists notably in transmitting a signaling message SCI0 also called SA (for Scheduling Assignment) on a block of the control part SP of the frame. This SA message typically indicates the identity of the intended receiver (s). It also indicates the first subset of resource blocks on which it intends to transmit data.

For example, this first subset of resource blocks is a set of RB chosen freely (situation called "Open DSP") by the transmitter in a DSP.

As a variant, the radio resource blocks of the data part DP of the frame can be organized into a plurality of predefined resource configurations denoted DCH (for Data CHannel). In this case, the first subset of resource blocks is a DCH chosen from the set of available configurations (situation called "Closed DSP"). In this case, it may suffice to indicate the identifier of the DCH in the SA message.

According to a particular embodiment, the control part SP of the frame can include resources dedicated to messages SA by DCH. In other words, a unique correspondence is provided between each DCH and each resource block dedicated to SA messages. In this case, it is not necessary to indicate the identifier of the DCH in the SA message because the receiver will be able to identify the corresponding DCH according to the resource used to send the SA message.

In embodiments, the test transmission also includes the transmission of test data which typically consists of a sample (i.e. a first part) of the data that would be sent during a conventional transmission. This test data is typically transmitted over a second subset (T-DSP) of radio resource blocks representative of the first subset of blocks.

According to particular embodiments, this second subset is located in the control part SP of the frame.

According to other particular embodiments, the test data are sent in the DP data part of a first frame, thus reserved for the test. These embodiments are particularly advantageous when the transmission is spread over several frames

During a step 42, the transmitter monitors the reception of an acknowledgment message of the test transmission. This acknowledgment message confirms that the test transmission was successful or not.

According to embodiments, the acknowledgment message can be received on the control part SP of the same frame on which the test transmission was carried out. In this case, this acknowledgment message is for example noted SAA (for Scheduling Assignment Acknowledgment).

As a variant, the acknowledgment message can be received on the control part SP of a following frame. In this case, this acknowledgment message is for example noted ARM (for Acknowledgment Reservation MCS).

The acknowledgment message also indicates the modulation and coding scheme (MCS) to be used later for data transmission.

Other acknowledgment messages fulfilling additional functions could be used.

Returning to our example, if an acknowledgment message is received and this message attests to the success of the test transmission, the real data transmission can take place on the first subset of radio resource blocks during a step 44.

If an acknowledgment message is received but it indicates a test transmission problem or if an acknowledgment message is not received at the level of resources dedicated to acknowledgment messages, the transmission is interrupted during a step 46 and the data is not sent.

The example described can be adapted to the multicast or multicast case (multiple receivers forming a group). In this particular case, a positive acknowledgment can be expected from each member of the multicast group, without which the test transmission cannot be successful. Thus, for example, if the transmitter receives only a given number of positive acknowledgments while the SA message was aimed at a multicast group comprising more receivers, these acknowledgments may not be sufficient to validate the test transmission and the communication may be abandoned.

Thus, in general, depending on the number of acknowledgments received and their nature (positive or negative acknowledgments), the issuer can conclude that a test transmission was successful or not, and decide whether or not to continue transmitting the data accordingly. .

Advantageously, the proposed solution makes it possible to manage both unicast communications and multicast communications.

Examples of an SC-Period frame will now be described with reference to FIGS. 5, 6 and 7. FIGS. 5 and 6 relate to examples in which the test transmission is carried out on the control part SP of a frame and the data transmission which follows is performed on the DP data part of the same frame. FIG. 7 relates to a variant in which the test transmission is carried out on a first frame and the acknowledgment as well as the data transmission are carried out on another frame.

In the next figures, the data (test or not) is denoted DATA, as opposed to signaling messages.

In FIG. 5, a signaling message SA is transmitted on the control part SP of the frame. In this example, the sending node is free to choose the resources on which it wishes to transmit the data, among the resources of the DSP sub-parts (situation called "Open DSP").

After a sufficient time for the SA message to be decoded by the receiving nodes concerned, test data (here constituting a first part of the data to be transmitted) are transmitted to the receiver (s) targeted by the SA message, on a dedicated resource sub-block (second subset) denoted TDSP (for Test Data Sub-Pool). After a sufficient period of time for the test data to be decoded by the receiving nodes concerned, an SAA acknowledgment message is received by the sending node. It is assumed in this example that this SAA acknowledgment is positive in that it attests to the good reception of the test data on the T-DSP. The transmission of the rest of the data can therefore take place on the DP data part of the frame. In this example, we note that the time-frequency pattern used for the test data in the T-DSP is identical to the pattern used for the data transmission on the DSP sub-parts of the DP.

In FIG. 6, a signaling message SA is transmitted on the control part SP of the frame.

In this example, DCH (for Data Channel) resource configurations are predefined in each DSP. The sending node is free to choose the configuration of its choice on which it wishes to transmit the data (situation called "Closed DSP"). In this case, it is assumed that there is a unique correspondence between the resource used to send the message. SA and a given configuration of the DP part.

Thus, sending the SA message on this dedicated resource allows the receiver (s) to identify the configuration (DCH) chosen by the transmitter for future data transmission. In this example, the test transmission consists mainly of the sending of the SA signaling message.

After a sufficient time for the SA message to be decoded by the receiving nodes concerned, an SAA acknowledgment message is received by the sending node.

It is assumed in this example that this SAA acknowledgment is positive in that it attests to the good reception of the SA message. Data transmission can therefore take place on the DP data part of the frame, in particular on the DCH configuration corresponding to the SA message.

In FIG. 7, the data transmission is spread over several frames.

A signaling message SA is transmitted on the control part SP of a first SC-Period frame.

After a sufficient time for the SA message to be decoded by the receiving nodes concerned, test data are transmitted to the receiver (s) targeted by the SA message, on a resource sub-block of the DP part. .

This test data consists of a first part of the data that the transmitter wants to transmit to the receiver (s).

In a future SC-Period frame, for example the next frame, an ARM acknowledgment message is received by the sending node. It is assumed in this example that this ARM acknowledgment is positive in that it attests to the good reception of the test data sent on the previous frame. The transmission of the rest of the data can therefore take place on the DP data part of the new frame. Thus, the transmission of the first part of the data carried out on the previous frame serves as test transmission for the future frame. In this example, the time-frequency pattern used for the test data in the first frame is identical to the pattern used for the transmission of the data on the DSP sub-blocks of the next frame.

These three examples described with reference to Figures 5, 6 and 7 are only simplified examples intended to illustrate the principle underlying the invention.

More detailed examples will now be described with reference to the following figures.

Figure 8 illustrates an example of SL transmission spread over several SC-Period frames with free choice of DP resources (Open DP).

In FIG. 8, only a few frames are shown, in particular the first two and the last frame. However, the invention is not limited to this representation. In some embodiments, transmissions are implemented over several consecutive frames or alternatively spaced in time.

In general, the transmission is spread over several frames when the volume of data to be sent is large and / or in the event of real-time or periodic traffic.

In this example, the transmitter transmits a signaling message SA in the control part SP of a first frame.

The transmitter chooses the radio resources on which it transmits the SA message. In practice, this selection can be random (after or without a Backoff mechanism) among the resources dedicated to SA messages. Alternatively, SA resources can be pre-allocated to the nodes.

If a Backoff mechanism is used then the Backoff counter is stopped or decremented upon detection or not of an acknowledgment message (for example ARM message).

In this example, the choice of resources for data transmission in the DSP is free (Open-DSP). In other words, the transmitter can choose the resources it will use to transmit the data.

Thus, in the signaling message SA, the transmitter explicitly signals the resources chosen in the DSP as well as the information necessary for their decoding. This is called a "reservation" of resources.

If the transmission is to continue on a future frame then the transmitter signals the identifier of this future frame either in the SA message or jointly with the data. As will be seen below, according to embodiments of the invention, this reservation can be accepted or refused by the receiver (s) of the message SA, according to conflicts existing with other resource reservations or according to the quality of the radio link or other criteria.

Then, the transmitter transmits data on the resources chosen in the DP data part of this first frame. This transmission serves as a test of the quality of the radio link between the transmitter and the receiver (s).

In response to the test transmission, the transmitter receives an ARM acknowledgment message in the control part SP of the following frame.

In practice, the receiver chooses the radio resources on which it transmits the ARM message to the sender of the SA message. This selection can be random among resources dedicated to ARM messages or signaled by the sender in its SA message. The latter solution is useful in the case of a multicast transmission (multiple receivers) because the transmitter can indicate separate resources for the different receivers. Another possible solution is to provide a predefined correspondence between the resources used for the transmission of the message SA and the resources to be used for the transmission of the ARM message. Alternatively, the dedicated resources for ARM messages are pre-allocated to the nodes.

Returning to our example, the ARM message attests to the good reception of the test data by the receiver (s) referred to in the SA message. This acknowledgment allows the transmitter to know the state of the previous transmission.

If the transmission is not successful, the ARM message indicates a negative response or it is not sent and the transmitter abandons the transmission of the data it intended to follow after the reception of the ARM message (case not shown in the figure 8).

Otherwise (shown in Figure 8), the ARM message can identify the frame where the future transmission will take place and indicates the MCS modulation and coding scheme that the transmitter could use during this future transmission.

Advantageously, the transmitter has every interest in using the MCS indicated in the ARM message because it is representative of the quality of the current radio link between the transmitter and the receiver. Indeed, the MCS indicated is based on a recent measurement of the quality of the radio link between the transmitter and the receiver, which will be noted as RLQI (for Radio Link Quality Indication).

For example, this measurement takes into account the RSRP (for Reference signal Receive Power) which makes it possible to obtain an average value of the power received from a reference signal per resource block, the RSSI (for Reference Signal Strength Indicator) which provides an average value of the power received from a reference signal over the entire frequency band and / or SI NR (for Signal-toInterference-plus-Noise Ratio).

In a particular embodiment, the signaling message SA indicates a threshold MCS below which the transmission cannot take place. When the MCS measured by the receiver and which should be used for the transmission of data by the transmitter is lower than the MCS threshold indicated in the SA message, the receiver sends a negative ARM acknowledgment so that the transmission stops.

In a particular embodiment, the ARM message can also indicate commands for PC power control (for Power Control), TA time advance (for Timing Advance) provided for in the LTE standard or any other useful information.

In practice, the frame and the resources to be reserved for the future transmission of the data are indicated by the transmitter in its SA message or jointly with the data. When the receiver detects that this frame (to be reserved) or these resources are in conflict with its own reservations, the latter can refuse the reservation, for example by negatively acknowledging the test transmission (negative ARM message).

In fact, in a particular embodiment, the receiver can also reserve resources to protect its reception, for example by using the ARM acknowledgment message. To do this, it can indicate in the ARM message the identifier of the future frame as well as the radio resources to reserve in this future frame. In this case, another terminal, different from the transmitter, located in the vicinity of the receiver, can manage to decode the ARM message transmitted by the receiver. This neighboring terminal can then measure the quality of the reception of this ARM message, denoted RLQIrx. When the quality of the RLQIrx reception is sufficiently good (this criterion being evaluated according to the implementation), this means that the neighboring terminal cannot use the reserved resources without interfering with the communication between the receiver and the transmitter. Consequently, this neighboring terminal refrains from using the radio resources reserved during the future frame indicated in the ARM message. This avoids access conflicts between terminals neighboring the receiver.

In a variant of this particular embodiment, the ARM message can also indicate a measurement of the quality of the radio link with the transmitter denoted RLQIsig, based on the reception of test data (ie the data transmitted in the previous frame here) and / or the SA message. In this case, the aforementioned neighboring terminal takes this measure into account to determine whether it can use the reserved resources without interfering with the communication between the receiver and the transmitter or whether, on the contrary, it must refrain from using the radio resources. reserved during the future frame indicated in the ARM message.

In the event of a reservation by the receiver to protect the reception of data, the ARM message must be able to be decoded before the occurrence of a resource dedicated to SA messages of the reserved frame. In practice, this is the organization of resources dedicated to signaling messages in the frame. This gives the receiver's neighbors time to take the reservation into account before trying to access the frame resources.

In practice, following a reservation by ARM message, a communication can be established on the reserved frame either by transmitting a new message SA on the control part SP of the reserved frame, or by proceeding directly to the transmission of the data on the part DP data of the reserved frame.

In this example, the ARM message used to acknowledge the test transmission is used as the reservation message. However, the invention is not limited to this and another reservation message, for example independent of acknowledgment, could be used.

Back to our example, after a certain period of time necessary for decoding the ARM message here positive, the transmitter transmits a signaling message SA in the control part SP of the second frame then starts the transmission of the other data in the data part DP of this frame.

In this example, this transmission is carried out on the same RB radio resources as the previous one, that is to say on the resources having been used for the test transmission in the first frame. Indeed, the test transmission was made successfully on these resources and the ARM message made it possible to warn the neighbors of the receiver of the future use of these resources.

Sending an SA message on each reserved frame can be useful, for example, to change the MCS to take into account a change in radio conditions. Typically, such a change in radio conditions can be observed following a modification of the network topology (for example displacement of the nodes). In this case, the sending node can directly transmit the data in the DP with the new MCS.

Also, sending an SA message on each reserved frame can be useful in the case of point-to-multipoint transmission, that is to say from one transmitter to a plurality of receivers in a group. given called "multicast group", where the members of the multicast group change during the communication. Indeed, the message SA indicates the identity of the targeted receivers.

Returning to our example, the transmitter receives after the last transmission an ACK acknowledgment message signifying the good reception of all the data (from the first to the last frame).

As with the ARM message, the receiver chooses the radio resources over which it transmits the ACK message to the sender of the SA message. This selection can be random among resources dedicated to ARM / ACK messages or signaled by the sender in its SA message. The latter solution is useful in the case of a multicast transmission (multiple receivers forming a group) because the transmitter can indicate separate resources for the different receivers. Another possible solution is to provide a predefined correspondence between the resources used for the transmission of the SA message and the resources to be used for the transmission of the ARM / ACK messages. Alternatively, dedicated resources for ARM / ACK messages are pre-allocated to the nodes.

Thus, while the ARM acknowledgment message concerns the test data, the ACK acknowledgment message concerns all the data transmitted during the communication.

Alternatively, the ARM message can also play the role of an ACK message.

In this case, it is sent without indication of future reservation or MCS.

Advantageously, the acknowledgment mechanisms for test data according to the invention make it possible to activate FEC error control schemes (for

Forward Error Correction) fast at the various layers (in particular

RLC / MAC / PHY) terminals and thus make communications more reliable.

In certain embodiments, the control part SP of the frames can be used to introduce any type of signaling messages (SA, ARM, ACK ...) or even of short data service without signaling such as for example discovery messages of neighborhood, routing signaling or application signaling messages, or for broadcasting traffic.

In the SP control part, resources can be dedicated to each type of signaling message. Alternatively, several types of signaling messages can share the same resources.

In practice, the different signaling messages can be transmitted over resources of different dimensions. Also or alternatively, the dimension of the resources to which the signaling messages are sent and the dimension of the resources dedicated to the data may be different. As an illustration, ARM messages can be transmitted on small RBs in subcarrier or on 3 time / frequency / code dimensions.

In a particular embodiment, the resources of the control part SP can be used for sending ACKREQ acknowledgment request messages and receiving the corresponding ACK-RSP response messages.

The ACK-REQ acknowledgment request message is typically sent by the transmitter following one or more data transmissions already carried out but for which it has not received ACK messages, either because the system does not provide a message ACK either because it did not succeed in decoding it correctly (radio loss). The ACK-REQ acknowledgment request message can be intended for a single receiver and correspond to one or more data transmissions. As a variant, it may be intended for several receivers and correspond to one or more common data transmissions (multicast) or separate data (unicast).

In practice, the transmitter chooses the radio resources on which it transmits the ACK-REQ acknowledgment request message. This selection can be random among resources dedicated to ACK-REQ messages or depend on the selection of resources for sending the SA message.

The ACK-RSP response message is typically sent by a receiver in response to an ACK-REQ acknowledgment request message. It can therefore correspond to one or more data transmissions already carried out. Alternatively, a receiver can respond to multiple ACK-REQ messages from the same transmitter or from multiple different transmitters in the same ACK-RSP message.

In practice, the receiver chooses the radio resources on which it transmits the ACK-RSP response message. This selection can be random among the resources dedicated to ACK-RSP messages or signaled by the sender in its acknowledgment request message ACK-REQ, or even be dependent on the selection of resources dedicated to ARM or ACK or ACK messages. REQ.

The resources of the control part SP can also be used for direct short data transmission DSSL (for Direct Short Side Link) with prior sending of SA message. Resources dedicated to this type of transmission are denoted DSSLP (for DSSL Pool).

Generally, the organization of the resources of the control parts SP and data DP, that is to say the resources dedicated to the different types of messages, is either signaled by the network (RRC message for example within the framework of the standard LTE) is preconfigured in the terminals.

FIG. 9a illustrates an example of distribution of the resources dedicated to the different DCH configurations (Closed DSP) in the DP part for a unicast SL transmission spread over several frames.

Thus, unlike the example described with reference to Figure 8, the choice of resources for data transmission in the DP is not free here but is limited to a finite number of predefined DCH configurations.

In this example, each DSP of the DP part is organized into two configurations denoted DCH # 1 and DCH # 2.

Thus, the transmitter can only choose the predefined configuration that it will use to transmit the data, but not the resources that compose it.

In practice, a DCH can be shared between the terminals or alternatively be pre-allocated to a subset of terminals.

FIG. 9b illustrates an example of the distribution of resources dedicated to the different types of signaling messages (and possibly to DSSL data) in the SP part of the frame.

In this example, the SP part contains resources dedicated by DCH (DCH # 1 and DCH # 2 in FIG. 9a) to ARM messages, to ACK acknowledgments and to SA messages. It also contains resources dedicated to short direct DSSL data.

Advantageously, when there is a unique correspondence between the resources dedicated to the SA, ARM and ACK messages and the different DCHs, the resource chosen for the transmission of one of these messages allows the receiver to identify the DCH concerned. It is therefore not necessary to indicate the identifier of the

DCH chosen in the SA, ARM or ACK message.

As a variant (not shown), the resources dedicated to the different types of signaling messages, in particular the SA, ARM and ACK messages, could be shared between several DCHs. In this case, the message should explicitly indicate the identifier of the DCH concerned in order to allow the receiver of the message to identify the DCH concerned.

Obviously, all the resources dedicated to these messages / data are not necessarily effectively used during a transmission. For example, even if there are two RB dedicated to SA messages relating to DCH # 1 and two RB dedicated to SA messages relating to DCH # 2, only one dedicated RB can actually be used to send an SA message for a given DCH , as will be seen in the transmission example of FIG. 9c.

FIG. 9c illustrates an example of a SL unicast transmission spread over several frames with a choice limited to the configurations of the DSP (Closed DSP).

In this example, each frame is organized as illustrated in Figures 9a and 9b.

In this example, the transmitter transmits a signaling message SA in the control part SP of a first frame.

Then, the transmitter transmits a first part of the data which serves as a radio link test on the DCH configuration chosen in the DP data part of this first frame.

In response to the transmission of the test data, the transmitter receives an ARM acknowledgment message in the control part SP of the following frame.

As in the previous example, this ARM message attests to the good reception of the test data by a receiver referred to in the SA message. This acknowledgment allows the transmitter to know the status of the transmission.

If the transmission is not successful, the ARM message is not sent by the receiver or otherwise it indicates a negative response and the transmitter abandons the transmission of the data it intended to follow following the reception of the ARM message (case not shown in Figure 9c).

Otherwise (shown in FIG. 9c), the ARM message identifies the frame where the future transmission will take place and the MCS modulation and coding scheme that the transmitter could use during this future transmission.

In a particular embodiment, the receiver can also reserve the resources to protect its future reception, for example by using the ARM acknowledgment message.

In this case, as for the resources dedicated to SA messages, if the resources dedicated to ARM messages are shared between the different DCHs, the receiver must indicate the identifier of the DCH reserved in the ARM message.

On the other hand, if there is a correspondence between the resources dedicated to ARM messages and the DCHs, the resource chosen for the transmission of the ARM message makes it possible to identify the DCH reserved. It is therefore not necessary to indicate the identifier of the DCH chosen in the ARM message.

Advantageously, thanks to the unique correspondence between the resources dedicated to ARM messages and the DCHs, even if the ARM message is not correctly decoded by a terminal neighboring the receiver other than the transmitter, this neighboring terminal can measure the quality of the reception RLQIrx of the ARM message and determine if it can use the identified DCH (thanks to the resource on which the ARM message is transmitted) without interfering with the communication between the receiver and the transmitter. If necessary, the neighboring terminal refrains from using the DCH reserved during the future frame. This avoids reservation conflicts between neighboring terminals.

In practice, in order to allow a terminal neighboring the receiver to determine the future frame reserved by an ARM message without necessarily decoding it correctly in order to extract the content, each set of resources dedicated to ARM messages and corresponding to a DCH can be divided into a number of subsets of resources. Each subset of resources thus constituted makes it possible to transport one or more ARM messages and corresponds to a reservation request on a future frame distant by a certain predefined time from the frame where the ARM message was sent. As mentioned previously, an ARM message can possibly make it possible to reserve the corresponding DCH in a future frame. However, this is not always the case as an ARM message can simply be used to acknowledge good data reception.

Preferably, in a half-duplex (HD) transmission / reception mode, a node which is transmitting on a slot containing resources dedicated to messages

ARM refrains from accessing any DCH that may be reserved by message

ARM on this slot during the future frames that these ARM messages could reserve. One possible solution to overcome this constraint is to group the resources dedicated to ARM messages of different DCHs corresponding to the same future frame on the same slot or slots.

The examples described with reference to FIGS. 8 and 9 relate more particularly to transmissions spread over several frames. As mentioned, conflicts over access to resources in such situations are avoided by using transmission over a previous frame as a means of testing whether or not the selected radio resources will conflict over the next frame. The ARM message reservation mechanism avoids new conflicts during future transmissions.

The examples described with reference to FIGS. 10, 11 and 12 more particularly make it possible to avoid conflicts before even accessing the DP data part of a frame for the first time.

To do this, it is proposed to carry out a test transmission directly in the SP control part of the frame and to provide resources dedicated to acknowledgment messages (such as the SAA message for Scheduling Assignment Acknowledgment). In a first embodiment, specific resources denoted T-DSP (for Test DSP) are dedicated to sending a first part of the data serving as test data (FIGS. 10 and 11). In a second embodiment, resources dedicated to the SA signaling messages by DCH are provided (FIG. 12).

FIG. 10 illustrates an example of unicast SL transmission on a single frame with free choice of DSP resources (Open DSP).

This example differs from that described with reference to FIG. 8 in that the test transmission and the acknowledgment are carried out in the SP part of the frame and the data transmission which follows is carried out in the same frame.

In this example, the transmitter transmits a signaling message SA in the control part SP of the frame.

The transmitter chooses the radio resources on which it transmits the SA message. In practice, this selection can be random (after or without a Backoff mechanism) among the resources dedicated to SA messages.

Alternatively, SA resources can be pre-allocated to the nodes.

If a Backoff mechanism is used then the Backoff counter is stopped or decremented upon detection or not of an acknowledgment message (for example SAA message).

In this example, the choice of resources for data transmission in the DSPs is free (Open-DSP). In other words, the transmitter can choose the resources it will use to transmit the data in the event of a positive test.

Thus, in the signaling message SA, the transmitter explicitly signals the chosen resources as well as the information necessary for their decoding.

The transmitter then transmits test data to dedicated T-DSP resources.

The receiver decodes the SA message intended for it, decodes the test data transmitted in the T-DSP and sends an SAA acknowledgment message to the transmitter on the dedicated resource in the control part SP of the frame.

In practice, the receiver chooses the radio resources on which it transmits the SAA message. This selection can be random among the resources dedicated to SAA messages or signaled by the transmitter in its SA message. Another possible solution is that there is a predefined correspondence between the resources used for the transmission of the SA message and the resources to be used for the transmission of the SAA message. As a variant, the resources dedicated to SAA messages are pre-allocated to the nodes.

In general, the resources dedicated to SAA messages are separated from those of the T-DSP by a time "Tp" allowing on the one hand the decoding of the test data sent on the T-DSP and on the other hand the coding of the message SAA by the receiver. As an illustration, in the current LTE standard, "Tp" corresponds to 4ms.

This SAA message attests to the good reception of the test data by the receiver (s) referred to in the SA message. This acknowledgment allows the transmitter to know the status of the transmission.

If the test transmission is not successful, the SAA message is not sent or otherwise it indicates a negative response and the transmitter abandons the transmission of the data it intended to follow upon receipt of the SAA message (case not shown in Figure 10).

Otherwise (shown in FIG. 10), after a certain period of time necessary for decoding the SAA message here positive, the transmitter starts transmitting data in the DP part of this frame.

In this example, the time-frequency pattern of the RB resources used to send data to the DSPs is identical to the time-frequency pattern of the resources that are used to send the test data to the T-DSP.

Finally, at the start of the next frame, the transmitter receives an ACK acknowledgment message signifying that all the data has been received.

FIG. 11 illustrates another example of unicast SL transmission on a single frame with choice of DSP configurations (Closed DSP).

This example differs from that described with reference to FIG. 9 in that the test transmission and the acknowledgment are carried out in the SP part of the frame and the data transmission which follows is carried out in the same frame.

In addition, unlike the example described with reference to FIG. 10, the choice of resources for data transmission in the DSPs is not free here (Closed-DSP) but is limited to a finite number of predefined DCH configurations. . Each DSP is for example organized as illustrated in FIG. 9a. In general, a DCH can have different resource configurations in each DSP in the frame.

Thus, the transmitter can only choose the predefined configuration that it will use to transmit the data in the event of a positive test, but not the resources that compose it.

In this example, the transmitter transmits a signaling message SA in the control part SP of the frame.

The transmitter then transmits test data to dedicated T-DSP resources. It is recalled that this test data constitutes part of the "useful" data that the transmitter wishes to transmit to the receiver (s) indicated in the SA message.

In this Closed-DSP scheme, the size of the T-DSP can be reduced compared to the Open-DSP. Indeed, it suffices that each DCH is represented in the T-DSP by at least one RB.

The receiver decodes the SA message intended for it, decodes the test data transmitted in the T-DSP and sends an SAA acknowledgment message to the transmitter on the dedicated resource in the control part SP of the frame.

If the test transmission is not successful, the SAA message indicates a negative response or is not sent and the sender abandons the transmission of the other data that he intended following the reception of the SAA message (case not shown on Figure 11).

Otherwise (shown in FIG. 11), after a certain period of time necessary for decoding the SAA message here positive, the transmitter starts transmitting data in the DP part of this frame.

In this example, the time-frequency pattern of the RB resources used for sending data in the DSPs corresponds to the configurations of the DCH in these DSPs and may be different from the time-frequency pattern of the resources that are used to send the test data. in the T-DSP. This is because it is sufficient that each DCH is represented by at least one RB in the T-DSP.

In this example, the transmitter receives an ARM acknowledgment message at the start of the next frame, acknowledging on the one hand the reception of all the data on the previous frame and on the other hand being the reservation message for a frame future, as previously explained with reference to Figure 9.

In this example, following the ARM message, a new test transmission takes place on the reserved future frame. The various messages and data mentioned in this example (SA, test data on the T-DSP, SAA, data) are exchanged again on the frame reserved by the ARM message.

FIG. 12 illustrates an example of a unicast SL transmission spread over several frames with a choice limited to the configurations of DSP (Closed DSP).

In this example, the transmitter transmits a signaling message SA in the control part SP of the frame. This transmission constitutes the test transmission. Indeed, in this example, there is a unique correspondence between the resources dedicated to SA messages and DCH, and the SA message is used to both report and test the quality of the radio link between the transmitter and the receiver on the DCH chosen. Thus, unlike the example described with reference to FIG. 11, during the test transmission, no data is sent in addition to the message SA.

It is important to note that the SA message must be transmitted on all SA resources dedicated to the DCH in question. In this case, in this example, only one RB is dedicated by DCH so only one SA message is necessary. However, if two (or more) RBs were dedicated to SA messages, as many SA messages should be sent.

Advantageously, it is not necessary to indicate the identifier of the DCH in the SA message because the receiver will be able to identify the corresponding DCH according to the resource used to send the SA message.

The receiver decodes the SA message intended for it and sends an SAA acknowledgment message to the transmitter on the dedicated resource in the control part SP of the frame to indicate that it has correctly received the SA message.

The SAA message can indicate the MCS to be used later in data transmission, a power control or time advance command or any other useful information.

If the sender receives the SAA message correctly, data transmission can take place on the DCH corresponding to the resource on which the SA message was received. A transmitter that does not receive an SAA message does not transmit data.

In this example, the transmitter receives an ARM acknowledgment message at the start of the next frame, acknowledging on the one hand the reception of all the data on the previous frame and on the other hand being the reservation message for a frame future, as previously explained.

In this example, following the ARM message, a new test transmission takes place on the reserved future frame. In practice, this test transmission includes the sending of an SA message on the reserved frame. The different messages and data mentioned in this example (SA, SAA, data) are exchanged again on the frame reserved by the ARM message.

In embodiments, a frame may contain DSPs of different sizes. In case of Open-DSP, a T-DSP corresponding to each type of DSP can be provided in the SP section. In the case of Closed-DSP, a T-DSP where each DCH is represented or a resource dedicated to the SA message corresponding to each DCH can be provided in the SP part.

The resources dedicated to signaling messages can be shared between different types of DSP or be divided into fixed configurations where each is dedicated to a type of DSP. If the resources dedicated to SA messages are shared between different types of DSP, the SA message explicitly identifies the DSP used.

FIG. 13 illustrates an example of transmission SL on a frame comprising several control parts SP so that communications can be initiated and terminated at different locations in the frame. Such a configuration allows several terminals to access the radio resources of the same SCPeriod frame successively and while avoiding conflicts. Indeed, thanks to the plurality of parts SP, a communication can be initiated at several places in the frame.

An SP section can contain resources dedicated to signaling but also to data (Open-DSP or Closed-DSP). In some cases, the same BR can be shared between signaling and data.

Preferably, a part SP which contains resources dedicated to the SA messages contains resources dedicated to the corresponding SAA messages. In this case, the SP part must be long enough in time to allow the establishment of a communication, that is to say to allow the sending by a transmitter of a SA message and possibly test data. (generally consisting of part of the "useful" data to be sent), the reception of the SAA response and the decoding of this response.

The frame may possibly include a DP part solely dedicated to data, composed of DSPs and / or DCHs.

In general, the resources dedicated to SA messages, to test data if necessary and to SAA messages, can be placed anywhere in the SP parts. However, the resources dedicated to the SA and SAA messages used for the establishment of a communication must be sufficiently spaced in time to allow the decoding of the SA message, the decoding of any test data and the decoding of the SAA message before the occurrence of a new resource dedicated to SA messages.

In the example illustrated in FIG. 13, the frame consists of three parts SP and there is no part DP. Each part SP consists of a slot dedicated to SA messages (first column of RB) then a first DSP followed by a T-DSP then a second DSP, then a slot dedicated to acknowledgment messages (SAA / ACK) then a final DSP. The resources for data transmission are at the free choice of the transmitter (Open-DSP).

As visible in FIG. 13, in a first part SP, a terminal A transmits to a terminal B a message SA then test data on a first part of the resources dedicated in the T-DSP. Terminal B decodes the SA message from terminal A as well as the test data and transmits an SAA acknowledgment to the terminal

A to authorize the transmission of data. This data transmission takes place on the corresponding resources of the DSPs and T-DSPs of the following SPs of the frame. It is noted that the time-frequency pattern is identical on the DSP and T-DSP of the following SP and on the T-DSP of the first part SP where the test transmission was carried out from A to B.

In this example, a terminal C close to terminal B also receives the SAA acknowledgment transmitted by terminal B and thus detects that it is too close to it to use the same resources for its own transmissions.

Thus, in the second part SP, the terminal C transmits to a terminal D a message SA indicating resources different from those used by B to receive data from A.

The terminal C also transmits test data on a second part of the dedicated resources in the T-DSP. Terminal D decodes the SA message from terminal C as well as the test data and sends an SAA acknowledgment to terminal C in order to authorize the transmission of data on the corresponding resources. This data transmission takes place on the corresponding resources of the DSP and T-DSP of the following SP part. It is noted that the time-frequency pattern is identical on the DSP and T-DSP of the next SP part and on the T-DSP of the second SP part where the test transmission from C to D.

These embodiments thus make it possible to reduce conflicts between neighboring terminals, while allowing optimal use of radio resources.

Although the example described with reference to FIG. 13 relates to an Open-DSP case, those skilled in the art can easily transpose the lessons to the Closed-DSP case where data configurations are predefined so that the transmitter does not is not able to individually choose RB resources.

In general, embodiments allow a communication initiated in an SP part to continue after the reception of the SAA acknowledgment on all the following DSP / DCHs of the frame, whether they are in SP parts or in DP parties.

Thus, when the transmitter can choose the resources (Open-DSP) when establishing a communication to a certain SP #i of the frame, the T-DSPs of the following SPs are used as regular data DSPs. This allows the communications which will be established at the following SPs to take into account the presence of the communications already established on the resources of the frame.

When there is a unique correspondence between the resources dedicated to SA messages and the DCHs (Closed-DSP), the SA message must be transmitted on the resources corresponding to the DCH chosen for data transmission. Once a communication is established, the resources dedicated to SA messages and

DCH are used by this communication. This also allows neighboring terminals to take into account the communications already established on the DCHs of the frame.

In a particular embodiment, the SAA acknowledgment message can indicate the resources or the DCH reserved by the SA message. Another terminal, different from the transmitter, located in the vicinity of the receiver, can manage to decode this SAA acknowledgment message and can then measure the quality of RLQIrx reception of this message. When the quality of the RLQIrx reception is sufficiently good (this criterion being evaluated according to the implementation), this means that the neighboring terminal cannot use the resources or the DCH reserved without interfering with the communication between the receiver and the transmitter. Consequently, this neighboring terminal abstains from using the radio resources / DCH reserved by the message SA. This avoids reservation conflicts between neighboring terminals.

In a variant of this particular embodiment, the SAA message can also indicate a measurement of the quality of the radio link with the transmitter, noted RLQIsig, based on the reception of the SA message and / or test data if there is any. at. In this case, the aforementioned neighboring terminal takes this measure into account to determine whether it can use the resources or the DCH reserved without interfering with the communication between the receiver and the transmitter or whether it must on the contrary refrain from using radio resources / DCH reserved by the SA message.

Advantageously, in the event of a single correspondence between the resources dedicated to the PAC messages and the DCHs, even if the SAA message is not correctly decoded to extract the content thereof by a terminal neighboring the receiver other than the transmitter, this neighboring terminal can measure the quality of reception RLQIrx of the SAA message and determine if it can use the identified DCH (thanks to the resource on which the SAA message is transmitted) without interfering with the communication between the receiver and the transmitter. If necessary, the neighboring terminal refrains from using the DCH reserved during the rest of the frame.

Thus, the SAA message makes it possible to protect a communication established on a frame and to avoid that neighboring terminals themselves establish a communication on the resources used.

Preferably, in a half-duplex (HD) transmission / reception mode, a node which is transmitting on a slot containing resources dedicated to messages

SAA refrains from accessing any resources / DCH that may be reserved by SAA messages on this slot during the current frame.

Prohibiting the neighbors of a receiver, through the SAA message, from accessing the resources used by this receiver solves the well-known problem of the hidden terminal.

It is recalled that the problem of the hidden terminal arises when a terminal A is in the vicinity of a terminal B itself in the vicinity of a terminal C, the terminals A and C not being in the vicinity l of each other. Thus, terminal A is a hidden terminal for terminal C and vice versa. The consequence of this problem is that if terminal A transmits to terminal B, terminal C does not see it and can therefore decide to transmit to terminal B, in which case there will be a collision (and terminal A will not will not report).

The embodiments in which the resources dedicated to SAA messages are not shared with other signaling messages or with data also make it possible to solve the well-known problems of the hidden terminal and of the exposed terminal, which allows spatial reuse. radio resources.

It is recalled that the problem of the hidden terminal arises when a terminal A transmits to a terminal B close to a terminal C and that a terminal D close to the terminal C is already in transmission to a terminal E. The terminal C is a masked terminal for B because the signaling messages sent by the B are masked by the transmission of D. This situation is frequent in topologies with several radio hops and degrades performance in terms of bit rate.

It is also recalled that the problem of the terminal exposed arises when a terminal B transmits to a terminal A and that the terminal B is close to a terminal C that the terminal A does not see. Terminal C refrains from transmitting to another neighboring terminal D because it hears that B is in transmission (towards terminal A), it is therefore exposed to B, whereas it could quite well transmit to terminal D without interfering with the communication from B to A.

It is pointed out that the problem of the hidden terminal is solved even in case of non reception of the SAA message when there is correspondence between the resource used to send the SAA and a DCH (Closed-DSP) since the detection of a transmission on a resource dedicated to SAA messages alone can protect reception on the DCH in question until the end of the frame.

In general, the fact of providing resources dedicated to SA messages on several SPs allows, with a minimum of resources, several communication links which are not mutually in conflict to be established throughout the frame. The solution thus presented makes it possible to achieve maximum spatial reuse of radio resources with a minimum of resources dedicated to SA messages.

According to particular embodiments, the SAA message could be sent after the establishment of the call. This is optional and could be advantageous in various situations, for example when changing the MCS.

In a particular embodiment, the receiver sends several SAA messages, for example at regular intervals, over several predefined parts SP of the frame. This allows for example to update the MCS used and to acknowledge the data previously received.

Indeed, the fact that communications can be initiated and terminated at any SP part of a frame can cause changes in the radio quality of established communications. A change in the MCS used is desirable in this case to adapt to possible changes in the quality of the radio link.

Advantageously, a new SAA message being sent during communication (that is to say after the test phase), it makes it possible to use fast FEC error control schemes, for example of the H-ARQ type ( for Hybrid Automatic Repeat reQuest) at the level of the different layers (in particular RLC / MAC / PHY).

According to a particular embodiment, the new SAA message can also be used to protect the radio resources in reception on a frame. In this case, the new SAA message protects the receiving resources until the next occurrence after a predefined interval of a resource dedicated to SAA messages in the frame where forwarding is planned or, if necessary, until the end of the frame. .

This scheme has the advantage of freeing nodes which could not access protected resources (that is to say in use) during transmission following changes in their quality of radio link to the receiver .

If a reservation scheme by SAA message is used and a receiver wishes to make a reservation of the same resources for a future frame then the SAA message is sent to each resource dedicated to the SAA messages of the frame where the forwarding is planned even if the data transmission stops before the end of the frame.

In a half-duplex transmission / reception mode, a node in transmission on a slot containing resources dedicated to SAA messages (or any other reservation message) is prohibited from accessing any data resources other than SAA messages. (or any other reservation message) from this slot could reserve until the occurrence of the next resources dedicated to SAA messages in the frame where forwarding is planned or, if necessary, until the end of the frame.

In particular embodiments, it may be advantageous to establish bidirectional SL communication on the same frame.

In this case, the transmitter which initiates bidirectional communication (hereinafter called "first transmitter" or "second receiver") indicates in its SA message the radio resources / DCH on which it is already transmitting or receiving in the current frame. It then indicates, jointly with the data, any change in resources / DCH that it uses while waiting for the receiver (hereinafter called "first receiver" or "second transmitter") to establish communication in the other direction .

In the case of bidirectional Half-Duplex transmission / reception, the first receiver establishes communication with the first transmitter by choosing resources for the transmission of the SA message and the data which are not on slots on which the first transmitter is in transmission and which are not already used in reception by this first transmitter.

To allow the establishment of a bidirectional SL communication, the 1 ^st control part SP of the frame containing SA / SAA signaling must contain resources for the transport of two SA messages on two separate slots, as well as for the transport of two SAA messages on two separate slots. If a future frame is reserved by ARM message, the first control part SP of this frame must also contain resources for two messages SA and SAA.

Similarly, the frame must contain resources for the transport of two ACK and ARM messages on two separate slots, if these are used.

In practice, the first receiver (i.e. the second transmitter) can indicate in its SA message the resources it will use for the transmission of ACK and ARM messages. Similarly, the transmitter (i.e. the second receiver) can indicate in its SAA message the resources it will use for the transmission of ACK and ARM messages. Also, the first transmitter and the first receiver can indicate in their ARM messages the resources that they will use in the future frame reserved for the transmission of their SA and SAA messages.

It should be noted that for fast bidirectional traffic or exhibiting an asymmetry in the volume of data exchanged in the different directions (SIP signaling, TCP session, HTTP, etc.), it is preferable to establish bidirectional SL communication in the same frame.

In particular embodiments, it may be advantageous to establish communication between two terminals by using a multiplicity of SL communications established between relays located between these terminals.

In this case the communication is relayed by one or more relay terminals on one or more radio hops. The choice of relays is made on the basis of a certain knowledge of the state of the links between terminals, but generally without relation taking into account existing communications which can lead to conflicts at the level of access to the resource.

In order to solve this problem, it is proposed to use the test transmission to obtain quality measurements of the paths between the remote terminals (called source node and destination node) passing through different relays.

To do this, it is proposed to send the SA message to the various possible relays. A source node having the choice between a number k of potential relays to its final destination which is at a radio hop number B sends a message SA containing the identification information of these relays and the identifier of the destination node.

Each relay k decodes the message SA and measures the quality of reception RLQIrx of the message SA and / or of the test data if there is any. It then calculates an indication of the quality of the paths between the source node and the destination node passing through it, denoted PQlE2N (k) (for Path Quality Indication). This indication can for example be an average of the hoped-for flows on all or a selection of the possible paths between the source node and destination node passing through the relay. Relay k subsequently sends an SAA response message. This SAA message contains, among other information, the MCS between the relay and the source node and the PQlE2N (k).

The transmitting node can thus, from the SAA messages and in particular from the different PQlE2N (k) received, choose one of the relays. It indicates the identifier of this relay in a header message (J-leader) transmitted with the data.

Then, a relay which correctly decodes this header and which is designated as relay continues to receive the data. If the decoding of the header fails or if the source node does not select it, the relay will stop receiving data.

In some cases, it is possible that the speed between the source node and the destination node is lower than the cumulative speed between the source node and the relay on the one hand and on the other hand between the relay and the destination node.

In this case, it may be advantageous to go through this relay even if the source node and the destination node are within the range of each other and can communicate directly.

In a particular embodiment, the source node can indicate in the message SA a threshold THpqi such that when a relay k responds with a message SAA only if the indication of quality of the paths PQlE2N (k) is greater than this threshold .

Also, the source node can indicate in the SA message the maximum number of radio hops that the calculation of the quality indication of the paths PQlE2N <k) must take into account.

The source node can indicate in the SA message a threshold RLQImin on the RLQI such that only the paths having an RLQI greater than this threshold are taken into account in the calculation of the indication PQI e2n by the relays.

In particular embodiments, point-to-multipoint transmission, that is to say from one transmitter to a plurality of receivers of a given group called "multicast group", can be established. Such transmissions are used for example in the context of public security services.

In this example, we consider a multicast group made up of N (N> 2) nodes of which K (1 <k <N) are potential transmitters PT (for Potential Transmitters). Several multicast groups denoted MG (for Multicast Group) share radio resources of the system and a node can belong to several MG.

The SA message sent during the test transmission identifies the target MG and the MCS that the sender intends to use for data transmission.

In order to be able to adapt the MCS used to the radio conditions between the transmitter and the receivers, the MCS indicated in the SA message is only used on the first slots containing resources chosen by the transmitter.

Based on the number of SAA messages received and the information they contain, the issuer can decide whether to transmit the data or not.

In the first case, it sends a header message, transmitted exclusively or jointly with the data, to the first slots containing the resources it has chosen, indicating the MCS which will be used for the rest of the transmission. The first slots must be in sufficient number to allow the transport of the header message and give the receivers the time necessary to decode it. This number can be reported in the SA message or be preconfigured in the system.

The nodes of a MG may not all be within radio range of each other. A node can indicate in its SAA message the RLQIs of its radio links with all or a selection of MG nodes. A selection can be made by a threshold on the RLQI for example signaled in the SA message or preconfigured. On the basis of the information received in the SAA messages, the transmitter decides which MCS to use for the transmission, calculates a distribution graph in the group and designates a list of relays as well as a list of nodes to which each relay must relay. transmission, directly and possibly via other relays.

This information is also transmitted in the data header message. A relay k with a transmission to be relayed to a part of the nodes of the MG proceeds in the same way as the source node with the exception of the identity of the destination nodes and of the following relays. A transmitter can also indicate in the header message on which frame and which radio resources (for signaling and data) its relays can establish communications for data relaying.

A relay can inform the relay preceding it or the source node of the state of its own transmission (establishment or not, identity of its effective receivers, resources used, MCS employed, ...) via SAA, ARM messages, or ACK.

A transmitter can indicate during a multicast communication on several frames the change of information relating to the destination nodes and relaying. This indication can be made via the SA message or jointly with the data via a header message. A change can take place in the event of mobility of the nodes for example.

A node which receives several SA messages to join the same multicast communication can decide to join the best in terms of radio quality or distance from the source node in terms of number of radio hops.

In practice, sufficient resources are provided for PAC messages. In particular, the SAA resources can be on RBs of reduced size (in time and / or in frequency for example) compared to the other RBs of the frame. They can also be on RB having an additional dimension compared to the other RB of the frame.

Figure 14 shows an example of a multicast communication link in an MG multicast group. Other MGs can share radio resources with this MG but are not represented. In this example, the MG is composed of nodes (A, B, C, D, E, F, G and H). The transmission from node A to the group requires relaying from node E to nodes F, G and H.

FIG. 15 illustrates an example of establishment of SL multicast communication on frames composed of a certain number of SPs.

The resources dedicated to SAA signaling are pre-allocated to each MG node or signaled by the sending node in the SA message. The resources dedicated to SAA signaling are on reduced BR corresponding to half the size of a regular BR in terms of subcarrier. During a first frame, node A has passed the test transmission to B, C, D, and E. On the following frame, node E, designated by A, relays this transmission to F, G and H.

In particular embodiments, it may be advantageous to establish a communication of broadcast type, between a transmitter and any receiver being within the range of the transmitter. In this case, the target receivers do not belong to a given group as for multicast.

A difficulty which then arises is that the transmitter does not know the number of acknowledgments that it is supposed to receive following the test transmission since it does not target a precise receiver during this test transmission.

To overcome this difficulty, it is possible to provide for an implicit acknowledgment, in particular when the broadcast communication is spread over several frames.

In practice, the transmitter signals the future frame on which it wishes to transmit data in its SA message sent during the test transmission. In this embodiment, the test transmission is carried out for example on the same set of resources as that desired for the data transmission.

Each node receiving the SA message and decoding its content can identify and then store all of the radio resources that will be used in future frames. Thus, when it wishes to establish a communication itself, the node can indicate this information (ie the list of resources which will be used by the transmitter, and other transmitters if there are any) in its own message HER. For example, the information may be associated with a limited time period of validity.

When the time comes for the data transmission desired by the initial transmitter, that can calculate a ratio between the number of SA messages indicating the resources that he himself has reserved and the total number of SA messages received since the test transmission. (also including SA messages which do not indicate the resources it has reserved). The initial sender may decide to make the desired transmission based on the calculated ratio. The closer it is to 1, the higher the probability that the test transmission was successful for all the nodes in range.

Thus, each transmission serves as a test for the next transmission and the SA messages sent by the nodes located in its vicinity and indicating the 5 resources reserved by the initial transmitter allow the latter to know that the test transmission went well at least for a certain proportion of the nodes. In this sense, these SA messages constitute (implicit) acknowledgments of the test transmission.

This mechanism can also be applied to cases of unicast or multicast communications where resources dedicated to acknowledgment messages (SAA, ARM) are not available in the frame.

In a particular embodiment, the message SA also signals a priority index associated with each future transmission and the calculated report takes this priority index into account.

The foregoing examples are only embodiments of the invention which is not limited thereto.

Claims (27)

1. A method of direct communication between at least two terminals of a mobile network, over a set of blocks of radio resources defined according to one or more dimensions, organized in a frame (SC-Period), the method being implemented by a terminal transmitter and comprising the following steps: - test transmission (40), to at least one receiving terminal, of at least one signaling message (SA) function of a first subset (DSP; DCH) of radio resource blocks; and - as a function of at least one acknowledgment message (SAA; ARM) received in response to the test transmission, transmission (44), to said at least one receiving terminal, of data on said first subset of blocks. 2. The method of claim 1, wherein the frame comprises a plurality of predefined configurations of radio resource blocks (DCH) and said first subset is a predefined configuration of radio resource blocks. 3. Method according to claim 2, in which said frame comprises at least one control part (SP) and the at least one signaling message (SA) is transmitted on a block of radio resources of said at least one control part (SP) ) associated with the predefined configuration corresponding to the first subset of blocks, thus allowing the identification of the first subset of blocks. 4. Method according to claim 1 or 2, in which the test transmission comprises a transmission of test data on a second subset (TDSP) of radio resource blocks representative of the first subset of radio resource blocks. 5. Method according to any one of claims 1 to 4, in which the test transmission is carried out on a first frame while the data transmission is carried out on a second frame comprising said first subset (DSP; DCH) of blocks of radio resources, the second frame being different from the first frame. 6. Method according to any one of claims 1 to 5, in which the radio resource blocks situated between the radio resource blocks used for the test transmission and the reception of the acknowledgment message (s) are reserved for transmitting direct data. short (DSSL) and / or transmit or receive other acknowledgment (ACK / ACK-RSP) or acknowledgment request (ACK-REQ) messages. 7. Method according to any one of claims 1 to 6, wherein said frame comprises a plurality of control parts (SP). 8. The method of claim 7, wherein the test transmission and the reception of said at least one acknowledgment message in response to the test transmission are carried out on the same control part (SP) of the frame. 9. Method according to any one of claims 1 to 8, in which the radio resource blocks used for the test transmission are also used by the transmitting terminal for said data transmission, whether it is spread over one or more frames. 10. Method according to any one of claims 1 to 9, comprising the reception of another acknowledgment message (SAA) on predefined control parts (SP) of the frame, in response to the data transmitted on said first sub- set of blocks, said other acknowledgment message (SAA) notifying the sending terminal of a change in a modulation and coding scheme (MCS) used by said at least one receiving terminal and / or acknowledging the data received up to the. 11. Method according to any one of claims 1 to 10, comprising receiving a reservation message (SAA, ARM) from a third subset of radio resource blocks of the current frame or of a future frame. . 12. Method according to any one of claims 1 to 11, comprising the transmission of another signaling message (SA) to said at least one receiving terminal, indicating at least one block of radio resources in use on the frame. current by the transmitting terminal. 13. Method according to any one of claims 1 to 12, comprising the reception of connection quality measurements between the transmitting terminal and each receiving terminal of a plurality of receiving terminals, the method further comprising a step of selecting at least one relay terminal among the receiving terminals of said plurality as a function of the quality measurements, an identifier of said at least one relay terminal being indicated in a header message transmitted with said data on said first subset of blocks. 14. Method according to any one of claims 1 to 13, comprising receiving quality measurements of the connection between the two terminals of a plurality of pairs of terminals, the method further comprising a step of calculating a graph multicast broadcast from the quality measurements received. 15. Method according to any one of claims 1 to 14, further comprising the following steps: - reception of a reservation message from a subset of radio resource blocks sent by a terminal of the mobile network to another terminal different from the transmitter; - measurement of the quality of reception of said reservation message (RLQIrx); and - as a function of the result of the comparison of the reception quality measured with a threshold value, reservation or not of said subset of blocks of radio resources. 16. The method of claim 15, wherein said reservation message indicates a level of quality of reception of messages (RLQIsig) by said terminal of the mobile network. 17. The method of claim 16, wherein said reservation of said subset of radio resource blocks is also a function of the result of the comparison of the reception quality indicated in the reservation message (RLQIsig) with a threshold value. 18. The method of claim 11, wherein said future frame is separated from the current frame by a predefined duration function of at least one block of radio resources dedicated to said reservation message and / or signaled in said reservation message. 19. Method according to any one of claims 1 to 18, in which at least a first block of radio resources is dedicated to said at least one signaling message (SA) and at least a second block of radio resources is dedicated to said at least an acknowledgment message (SAA; ARM), said at least a first block and at least a second block being spaced by a predefined duration at least equal to the time necessary for the decoding of said at least one acknowledgment message (SAA; ARM ). 20. The method of claims 11 and 19, wherein at least a third block of radio resources is dedicated to said reservation message (SAA; ARM), said at least a first block and at least a third block being spaced by a duration predefined at least equal to the time necessary for decoding said reservation message. 21. The method of claim 11, wherein said third subset of reserved radio resource blocks corresponds to said first subset of blocks. 22. The method of claim 1 or 2, wherein said at least one signaling message (SA) indicates reservation information, said reservation information comprising all of the radio resources and identifying at least one future frame that at least a network terminal has reserved. 23. The method of claim 22, wherein said reservation information is associated with a period of validity limited in time starting with the issuance of said at least one signaling message. 24. The method of claim 1, 2, 22 or 23, further comprising the following steps: calculation of a probability of success of the test transmission as a function of a number of signaling messages (SA) received from other terminals of the mobile network and indicating said first set of blocks of radio resources and of a total number of signaling messages (SA) received from other terminals of the mobile network since the test transmission; and - depending on the probability of success calculated, transmission or not of said data on said first subset of blocks. 25. The method of claim 24, wherein said at least one signaling message (SA) indicates a priority index associated with each future transmission and said calculation step takes into account said priority index. 26. Method according to any one of claims 1 to 25, in which blocks of radio resources dedicated to signaling (SA) and / or acknowledgment (SAA; ACK; ARM) messages are of reduced size compared to the others. blocks of radio resources in the frame or have different dimensions compared to other blocks of radio resources in the frame. 27. Communication device implementing a method according to any one of claims 1 to 26 for communicating with another communication device.