FR2921532A1 - Node i.e. wireless active speaker, synchronizing method for e.g. 7.1 type wireless synchronous home cinema network, involves synchronizing node from determined orientation information of receiving aerial of node to be synchronized - Google Patents

Abstract

The method involves obtaining two orientation information that represent an arrival direction of a signal on two nodes i.e. wireless active speakers, respectively, where the signal is emitted by third node that has to be synchronized i.e. wireless active speaker. Third orientation information representing an arrival direction of a signal emitted by one of two nodes on the third node, is obtained. Fourth orientation information of a receiving aerial of the third node is determined from three orientation information. The third node is synchronized from the fourth orientation information. Independent claims are also included for the following: (1) a computer program product comprising instructions to perform a method for synchronizing a node (2) a storage unit comprising instructions to perform a method for synchronizing a node (3) a node comprising an aerial.

Description

A method of synchronizing a node to be synchronized in a first synchronous wireless communication channel of a communication network, corresponding computer program product and node to be synchronized. FIELD OF THE DISCLOSURE The field of the invention is that of wireless synchronous communication networks for example of the mesh type (or MESH in English), comprising a plurality of nodes each having, for example, an antenna. receiving and transmitting antenna. The invention relates in particular but not exclusively to such networks that use the radio-frequency waveband (or RF for Radio-Frequency in English) millimeter and a multiplexed access medium in a given sequence (TDM sequence). 2. Solutions of the Prior Art Wireless applications are today more and more numerous. There appear wireless communication systems comprising a plurality of nodes, and this in multiple application areas such as that of packet data communications or that of streaming or streaming applications (e.g. audio and / or video content, voice over IP, ...).

In order to respond to the increase in the bit rate required by the applications (for example of the audio and / or video type), the bandwidth of the radio frequency spectrum must be increased. Because of the physical, normative and legal limits, the frequency spectrum can not be increased indefinitely, and therefore it must be limited to a bandwidth around the carrier frequency corresponding, for example, to a percentage of the carrier. If we take the example of a bandwidth of 1%, in the authorized band for Wi-Fi around the 2.4 GHz carrier, we will have a bandwidth of 24 MHz, while in the band 60 GHz, the bandwidth would be 600 MHz. As a result, communication systems using higher frequency carriers have greater bandwidth.

Thus, the wireless technology using the millimeter RF waveband, that is to say around 60 GHz, achieves a very high rate of data transmission. However, the physical characteristics of a millimeter RF wave link are: high directivity, little reflection on obstacles (eg walls, furniture, living things, ...), limited power and therefore limited signal range . Thus, the wireless communication links operating in the millimetric waveband are directional, and a line of sight (or LOS for Line Of Sight in English) is necessary to establish a communication between a transmitting node and a receiving node. such a link.

Practically, this imposes to ensure a good transmission of the data without loss, the direct sight of the communicating nodes antennas, in other words a millimeter RF wave connection without obstacle except the air. However, the air attenuating the millimeter RF waves (according to physical laws well known to those skilled in the art) to maintain a good level of quality of the wireless communication link and have a sufficient radio range without having to transmit to powers unauthorized directional antennas with positive gain can be used. The use of these antennas requires, for example, the receiving node to properly orient its antenna reception at the right angle and at the right time to the transmitting antenna of the transmitter node. In a home-wide, room-wide application, this technology can be used for a high-bit rate application up to a distance of about 10m. Thus, the 60GHz radio transmission systems are particularly well suited for transmitting very high data rates in a limited radius, for example as a connectivity means that is particularly well suited to the various elements of a home cinema system. Indeed, for this use case, the range is limited to about ten meters, by cons the speeds put into play are very high (beyond the gigabit per second) by nature, both audio and video, and the very high resolution of the information transmitted.

In home theater systems, the transmission system requires perfect synchronism between the sending node (s) and the receiving nodes, especially in the case of a multi-channel audio system, comprising up to 10 (or more) loudspeakers, and known as the English surround sound system. Indeed in this case, a transmitting node (also including an audio decoder) perfectly synchronously transmits different audio channels from a single source to a subset of receiver nodes, each comprising a speaker, all of these receiver nodes to restore overall perfectly synchronized multi-spatial sound. Moreover, given the particularly random nature of this type of transmission medium (particularly very sensitive to masking caused for example by an individual crossing the transmission field), it is necessary to perform multiple transmissions of the data symbols in order to ensure good reception beyond a predefined residual error rate. The following is set forth in the context of a wireless synchronous home cinema communication network for example of the mesh type comprising a plurality of nodes each having, for example a receiving antenna and a transmitting antenna. The nodes operate in the millimetric waveband. To enable each node of the network to transmit information in regularly spaced time intervals, time division multiplexing (TDM) may be implemented, hereinafter referred to as TDM multiplexing. , according to which the time domain is divided into a plurality of fixed length recursive time intervals called TDM sequence. TDM multiplexing makes it possible to make certain parameters such as latency, the bit rate of the data invariant, also makes it possible to obtain a very good level of quality and makes it possible to maintain this level of constant quality. In a wireless network using TDM multiplexing, each node transmits and receives in determined time intervals and must therefore orient its antenna in reception at each of these time slots (or Time slot in English).

In order to transmit to several receiving nodes simultaneously, the transmitting antenna of a transmitting node of the network may be an omnidirectional antenna which has a gain close to zero. However, it is evoked omnidirectional antenna, an almost omnidirectional antenna with an emission angle of 220 ° for example, since the realization of an antenna emitting perfectly in all directions is very difficult to design. Thus, the RF power emitted by the transmitting node is dispersed in all directions. The success of a transmission between a transmitting node and a receiving node is conditioned by the power at transmission, by the distance between the transmitting antenna of the transmitting node and the receiving antenna of the receiving node, by the gain of antennas and noise on the side of the receiving node. The received power which is equal to the product of the transmit power due to propagation channel attenuation shall have a signal to noise ratio sufficient for the transmission channel to have a bit error rate ( or bit error rate in English) around 10-6. The gain of the antenna can improve the communication. This is why a directional antenna having a gain of 15 dB, for example, can be used as antenna in reception by the nodes of the network. Thus, since a transmitting node transmits with an omnidirectional antenna to reach each receiving node of the network, the receiving nodes must orient their receiving antenna which is directional in the direction of the transmitting node. For example, to ensure good reception of data by each of the nodes, a retransmission of these data is performed by each of the nodes of the network. That is, after transmission of the data by the transmitting node during an ITO time interval and reception by the receiving nodes by means of their directional antenna, a first receiving node retransmits the data by means of its omnidirectional transmission antenna during a time interval IT1, then the other nodes receive the data by means of their directional antenna previously oriented. Then, a second receiving node retransmits the data for a time interval IT2 and so on.

In the context of a normal use of such a synchronous wireless communication network implementing a TDM sequence and comprising a plurality of nodes operating in the millimetric waveband, a given receiving node of the network, also called node moved or node to synchronize, may lose the radio link (and therefore data) in case eg of displacement of the node or misdirection thereof during transmission. The quality of the transmitted signal can then be very strongly degraded which can become very uncomfortable (for example in the case of a high-fidelity audio signal). Indeed, while in normal operation the antennas of the various nodes of the network are perfectly aligned at the right time, during an involuntary or voluntary movement of a node causing a change in its orientation and therefore the proper alignment of its antenna, a loss of the radio signal may be caused. Since the antenna of the receiving node to be synchronized is no longer oriented correctly towards the antenna of the transmitting node, the latter can no longer receive a radio signal and consequently can no longer decode data. Also, to maintain the quality level of the data transmission, it is better to restore the radio link very quickly by realigning correctly the antenna of the node to be synchronized. Thus, the moved node can spend a long time trying to synchronize in the network, that is to say find the sending node and / or its position in the TDM sequence and / or the network clock synchronization. To realign the antenna of the node to be synchronized, a first conventional technique consists of performing a complete antenna scan (or antenna scan in English) of all the antenna sector angles for all the nodes of the network as in the phase of the antenna. discovery and configuration of the system. A disadvantage of this first conventional technique is that it requires a significant amount of time to implement (for example, several TDM sequences since the scanning must be repeated for each node transmitting the network) and can therefore cause a damaging data loss for audio and / or video signals. The quality of the signal is greatly degraded (eg appearance of a hole in the audio signal and therefore a blank in the sound signal, or noise in the sound signal). Moreover, to resynchronize the node to synchronize in order to reintroduce it into the communication network as quickly as possible, other conventional techniques (called in English Angle Of Arrival or AOA, or Direction Of Arrival or DOA, respectively for Angle d Arrival and Direction of arrival in French) propose to estimate the direction of arrival of millimeter RF waves. Thus, according to a second conventional technique of DOA type, for example as described in patent document US20020039912A1, a base station of a communication network receives RF waves from a mobile node on the different elements of an antenna. wide beam. The signal received by the various elements of the antenna is then directed to a DSP (for Digital Signal Processor in English or Digital Signal Processor in French) processor. The DSP processor then applies on this received signal a digital processing algorithm (for example of the MUSIC type) to determine the direction of arrival of the millimeter RF waves received. When the arrival direction has been obtained, the communication network determines the narrowband antenna most suitable for retransmitting the data to the mobile node via a narrow data beam. A disadvantage of this technique is that it requires significant digital data processing and many signal conversion steps (eg digital / analog) which therefore requires a significant time.

In addition, in the context where each node of the network is allocated a time slot for data transmission, the determination of the arrival direction of the waves must be repeated for each of the nodes, which makes the realignment of the antenna of the node to synchronize very slow. 3. OBJECTIVES OF THE INVENTION The object of the invention is notably to overcome these disadvantages of the prior art.

More specifically, an objective of the invention, in at least one of its embodiments, is to provide a technique for synchronizing a node to be synchronized in a synchronous wireless communication network comprising a plurality of nodes that are faster than existing techniques. Another object of the invention, in at least one of its embodiments, is to provide a technique for rapidly reintroducing a node to be synchronized in a wireless communication channel after it has been moved and has therefore lost synchronization on the wireless communication channel. Yet another object of the invention, in at least one of its embodiments, is to implement such a technique which makes it possible to avoid the loss of data by the nodes of the network. The invention, in at least one of its embodiments, still aims to provide such a technique that is simple to implement and for a low cost. 4. DESCRIPTION OF THE INVENTION In accordance with a particular embodiment, the invention relates to a method of synchronizing a node to be synchronized having a directional receiving antenna for receiving a signal from a first channel communication method in a wireless communication network comprising a plurality of nodes, said method being implemented by the node to be synchronized. According to the invention, such a method comprises the following steps: obtaining a first and a second orientation information representative of the direction of arrival of a signal transmitted by the node to be synchronized, respectively, on a first and a second node of the wireless communication network; obtaining at least a third orientation information representative of the direction of arrival of a signal transmitted by at least one of said first and second nodes, on the node to be synchronized; determining antenna orientation information on reception of the node to be synchronized from said first, second and third orientation information; and synchronization of the node to be synchronized from said orientation information of the determined reception antenna.

Thus, the general principle of the invention is based on the determination of an orientation information of the receiving antenna (for example an angle) of the node to be synchronized in the first communication channel from orientation information. of antenna in reception of several nodes of the network. Thus, the aforementioned synchronization method makes it possible to synchronize quickly (and therefore without loss of data) a node to be synchronized (for example a node moved) from the antenna orientation information in reception of the node to be synchronized. Preferably, the first and second nodes use a directional antenna in reception and the first and second orientation information are obtained by scanning the directional antennas of said first and second nodes respectively. Advantageously, the step of obtaining said first and second orientation information comprises the following steps: transmission on a second communication channel of an alert message representative of a loss of synchronization of said node to be synchronized relative to the first communication channel; receiving, through the second communication channel, said first and second orientation information. Thus, a second RF communication channel is implemented to enable a node to be synchronized to inform the other nodes of the network that it has lost synchronization in the first communication channel, but also to receive data (for example). example of antenna information). Preferably, the step of determining said guidance information of the antenna in directional reception of the node to be synchronized comprises the following steps: determining at least one displacement parameter of the node to be synchronized from said first, second and third orientation information; calculating said antenna orientation information in directional reception of the node to be synchronized from the parameter (s) of displacement. Advantageously, each of the nodes able to transmit data on said first communication channel in a predetermined sequence, the first node is the node following the node to be synchronized in the predetermined sequence, and the second node is the node following said first node in the sequence. predetermined. Thus, the antenna orientation information of the node to be synchronized can be determined as soon as the first and second nodes have finished sending, the node to be synchronized then finds the radio link without loss of data in a minimum of time .

According to a preferred embodiment in accordance with the invention, the node to be synchronized uses a synchronization table comprising, for each node of the network, orientation information of the antenna in directional reception of the node to be synchronized, said antenna being adapted for receiving data transmitted by said node.

Such a synchronization table includes all the useful information (including antenna orientation information) to the node to synchronize to synchronize in the first communication channel. Preferably, the synchronization method comprises a step of updating said synchronization table as a function of said orientation directional antenna orientation information of the node to be synchronized obtained. Thus, once the antenna orientation information has been determined, the synchronization table is updated to allow the node to synchronize to orient its directional antenna correctly and thereby restore synchronization.

According to an advantageous characteristic of the invention, the method further comprises a step of detecting a loss of synchronization of the node to be synchronized in the first communication channel, and the loss of synchronization of the node to be synchronized results from a displacement. of the node to be synchronized. Thus, the present invention makes it possible to quickly reintroduce a node to be synchronized in a wireless communication channel after this node has been moved and thus lost synchronization on the wireless communication channel. Advantageously, the loss of synchronization is detected thanks to a displacement sensor provided in the node to be synchronized. The displacement sensor may for example be a pressure sensor disposed under the node to be synchronized which indicates where appropriate that the node has been moved. Advantageously, the synchronization loss is detected by means of a measurement of an indicator of the level of reception of a signal by the node to be synchronized. The indicator of the level of reception of a signal is for example an indicator of RSSI (for English Received Signal Strength Indication). Preferentially, a step of determining whether the node to be synchronized has lost synchronization in the first communication channel is implemented at regular intervals, and said synchronization method is triggered in the case of a positive determination. Advantageously, the process is triggered at regular intervals. The invention also relates to a computer program product downloadable from a communication network and / or recorded on a computer readable medium and / or executable by a processor, the program comprising program code instructions for the execution of steps of the synchronization method as previously described, when said program is run on a computer.

The invention also relates to a storage medium, possibly totally or partially removable, readable by a computer, storing a set of instructions executable by said computer to implement the synchronization method as previously described.

The invention also relates to a node to be synchronized having a directional receiving antenna for receiving a signal from a first communication channel in a wireless communication network comprising a plurality of nodes. According to the invention, the node to be synchronized also comprises synchronization means comprising the following means: means for obtaining a first and a second orientation information representative of the direction of arrival of a signal transmitted by said node to be synchronized, respectively, on a first and a second node of the wireless communication network; Means for obtaining at least a third orientation information representative of the direction of arrival of a signal transmitted by at least one of said first and second nodes, on said node to be synchronized; means for determining an orientation information of the antenna 20 receiving the node to be synchronized from said first, second and third orientation information; and synchronization means of said node to be synchronized from said orientation information of the determined reception antenna. Advantageously, the first and second nodes use a directional antenna 25 in reception and in that said means for obtaining the first and second orientation information comprise means for implementing a scanning by the directional antennas of said first and second signals. nodes respectively. Preferably, said means for obtaining said first and second orientation information comprise the following means: transmission means on a second communication channel, an alert message representative of a loss of synchronization of said node to synchronize with respect to the first communication channel; means for receiving, through the second communication channel, said first and second orientation information.

According to an advantageous characteristic of the invention, said means for determining said guidance information of the antenna in directional reception of the node to be synchronized comprise the following means: means for determining at least one parameter for moving the node synchronizing from said first, second and third orientation information; means for calculating said antenna orientation information in directional reception of the node to be synchronized from the parameter (s) of displacement. Advantageously, each node can transmit data on said first communication channel in a predetermined sequence, the first node is the node following the node to be synchronized in the predetermined sequence, and said second node is the node following said first node in the predetermined sequence. Preferably, said synchronization means comprise means for using a synchronization table comprising, for each node of the network, orientation information of the antenna in directional reception of the node to be synchronized, said antenna being adapted for reception data transmitted by said node. Advantageously, said synchronization means comprise means for updating said synchronization table as a function of said orientation directional antenna information of the node to be synchronized obtained. Preferably, the node to be synchronized further comprises means for detecting a loss of synchronization of the node to be synchronized in the first communication channel, and the loss of synchronization of the node to be synchronized results from a displacement of the node to synchronize. According to an advantageous characteristic of the invention, said means for detecting synchronization loss of the node to be synchronized comprise a displacement sensor of the node to be synchronized. Advantageously, said means for detecting synchronization loss of the node to be synchronized comprise means for measuring an indicator of the level of reception of a signal by the node to be synchronized. Preferably, the node to be synchronized comprises means for determining whether it has lost synchronization in the first communication channel activated at regular intervals, and that said synchronization means are triggered in the case of a positive determination. Advantageously, said synchronization means are triggered at regular intervals. 5. List of Figures Other features and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment, given as a simple illustrative and nonlimiting example, and the accompanying drawings. among which: FIGS. 1A to 1E illustrate the configuration of the radiation patterns of the antennas of the nodes of a wireless synchronous home cinema network of type 7.1 according to a particular embodiment of the invention respectively during the time interval No. 0 of a super frame (FIG. 1A), during the time slot No. 1 of the super frame (FIG. 1B), during the time interval No. 2 of the super frame (FIG. 1C), during the time interval No. 3 of the super frame (Figure 1D), and during the time slot No. 4 of the super frame (Figure 1E); FIG. 2 illustrates the configuration of the radiation patterns of the antennas of the nodes of the wireless synchronous home cinema network of type 7.1 according to a particular embodiment of the invention during the time slot No. 1 of the superframe ( FIG. 1B) when a node has been moved; FIG. 3 shows diagrams of WAS nodes 100 to 800 according to the particular embodiment of the invention; FIG. 4 shows time diagrams of super frames n and n + 1 of a conventional 60 GHz RF transmission channel; FIG. 5 illustrates the discovery phase of the nodes of the network on a time diagram of the super frames n and n + 1 of the first and second RF transmission channels according to the particular embodiment of the invention; FIG. 6 presents the main steps of the algorithm implemented as part of the discovery phase of the nodes of the network according to the particular embodiment of the invention; FIG. 7 illustrates a timing diagram of the n and n + 1 superframes of the first and second RF transmission channels according to the particular embodiment of the invention; FIG. 8 presents the main steps of an algorithm for determining the parameters (angles, inter-node distances, orientation, etc.) modified after moving a node according to the particular embodiment according to the invention; FIG. 9 shows the Cartesian references associated with each of the nodes of the synchronous home cinema network of FIG. 1A according to the particular embodiment of the invention; FIG. 10 shows a schematic representation of the antenna sector angles associated with certain nodes of the communication network before and after displacement of the displaced node, when they are in omnidirectional transmission on the first RF communication channel according to the embodiment. particular according to the invention; FIG. 11 shows a schematic representation in the reference Cartesian reference of the antenna sector angles associated with the nodes and before and after displacement of the displaced node, when this node transmits omnidirectionally on the first RF communication channel according to the mode. particular embodiment according to the invention; FIG. 12 illustrates a schematic representation of the antenna sector angles associated with two nodes of the network in the Cartesian coordinate system of the moved node before and after displacement of the latter, when it transmits omnidirectionally on the first RF communication channel according to FIG. the particular embodiment according to the invention; FIG. 13 illustrates a geometric representation of the rotation associated with the displacement of the displaced node in the communication network according to the particular embodiment of the invention; FIG. 14 describes the main steps of the general algorithm for recovering a lost RF radio link according to the particular embodiment of the invention. FIG. 15 presents the main steps of a data transmission algorithm on the second RF communication channel according to the particular embodiment of the invention; FIG. 16 describes the main steps of an algorithm for receiving data on the second RF communication channel of the communication network according to the particular embodiment of the invention; and FIG. 17 shows an exemplary frame (or time slot) of a super frame of the second RF transmission channel according to the particular embodiment of the invention. 6. DESCRIPTION OF AN EMBODIMENT OF THE INVENTION According to a particular application of the synchronization method according to a particular embodiment of the invention, one places oneself in the sequel as part of a home cinema network (or home). type 7.1 synchronous wireless audio system comprising a first RF transmission or communication channel 10 (implementing a first timing which defines a first cycle, based on a TDM sequence, for the transmission of data on this first channel) of the network as illustrated by Figures IA to 1E. Of course, the invention also applies in the context of any home theater wireless network such as 5.1 home theater network.

Of course, the method according to at least one other embodiment of the invention can also be implemented in any synchronous wireless communication network implementing a TDM sequence and comprising a plurality of nodes operating in the band of millimeter waves.

For example, the wireless home theater network 7.1 is arranged in a room of a dwelling and includes an audio-video source terminal, for example a DVD player (not shown), a television screen (not shown), a control panel, wireless environment 1000 hereinafter referred to as WSC node (for Wireless Surround Controller) to which are connected, via a wireless network, the first 100, second 200, third 300, fourth 400, fifth 500, sixth 600, seventh 700 and eighth 800 active wireless speakers, hereafter referred to as WAS (Wireless Active Speaker) nodes. The circle 35 represents the placement of the speakers around the listener, recommended by the Dolby laboratories, given here by way of example, the invention being able to work for any other configuration (THX, ...). In the room, a listener is located at a location 30. For example, each WAS node (100 to 800) includes (or is associated with) a speaker that broadcasts an audio channel, these audio channels are respectively the FR channels ( for Front Right or Front Right) for WAS node 400, SR (for Surround Right or Surround-right) for WAS node 300, RR (for Rear Right or right-rear) for WAS node 700, RL (for Rear Left or Left) for WAS 600, SL (for Surround Left or Surround-Left) for WAS 200, FL (for Front Left or Front Left), C (for Center or Center) also called FC ( for Front Center or Front Center) for the WAS node 100, and SW (for SubWoofer or subwoofer) for the WAS 800 node. Thus, the source terminal sends the digital audio data of each audio channel to the WSC node 1000 via a audio-video interface (or only audio) digital that can be e conforms for example to one of the standards SPDIF, IEEE-1394 or HDMI.

For example, the first RF transmission channel 10 of the wireless network enables the WSC node 1000 to transmit to each of the WAS nodes the data of the audio channels to be rendered. To perform these reception and transmission operations, each node of the network has respectively a transmitting antenna and an antenna receiving RF signals (these antennas are described below). The data of the audio channels to be rendered arranged in the form of frames are modulated and delivered to a front-end RF module for transmission to the first RF transmission channel 10 of the network. The front-end RF module performs digital-to-analog conversion on the frames, performs amplification on the frames and transmits the frames on the first RF transmission channel 10 by means of a transmitting antenna (hereinafter described). The node WSC 1000 comprises a microcontroller on which is implemented one or more software (s) implementing the invention. The microcontroller is suitable for communicating with and controlling multichannel audio decoders, baseband RF module and front RF module. The RAM can be used by the microcontroller to store the temporary data needed to perform its various tasks. An EEPROM (or FLASH) memory stores various information such as a hardware identifier (or serial number) of the WSC node 1000, user data, the total number of WAS nodes and their respective identifiers, the audio channel assigned to each WAS, antenna angle tables (hereinafter described), ... FIG. 1A is an illustration of the configuration of the network in the spatial domain and at the time interval # 0 corresponding to the frame no. 0 of a super frame n. The node WSC 1000 transmits for the entire duration of the time slot No. 0 on its omnidirectional transmission antenna represented here by the lobe formed by its emission radiation pattern 1052 to all the other nodes WAS 100 to 800 of the network. Thus, during this time interval No. 0 each of the other 30 nodes WAS 100 to 800 of the network must orient the lobe 151, 251,... 851 formed by the radiation pattern in reception of its directional receiving antenna in the direction of the Figure 1B (respectively Figure 1C, Figure ID, Figure 1E) is an illustration of the configuration of the network in the spatial domain and at the time interval No. 1 (respectively No. 2, No. 3; ° 4) corresponding to the frame No. 1 (respectively No. 2, No. 3, No. 4) of the super frame n. The WAS node 100 (respectively WAS 200, WAS 300, WAS 400) transmits the entire duration of the time slot No. 1 (No. 2, No. 3, No. 4) on its omnidirectional transmission antenna shown here. by the lobe formed by its emission radiation pattern 152 (respectively 252; 352; 452) to all the other nodes WSC 1000 and WAS (200 to 800) of the network (respectively WAS (100, 300 to 800); WAS (100 , 200 and 400 to 800), WAS (100 to 300 and 500 to 800). Thus, during this time interval No. 1 (No. 2, No. 3, No. 4), each of the other nodes WSC 1000 and WAS (200 to 800) of the network (respectively WAS (100, 300 to 800); WAS (100, 200, and 400 to 800), WAS (100 to 300, and 500 to 800) should orient the lobe 251 to 851 (respectively lobe 151 and 351 to 851, lobe 151, 251, and 451 to 851; lobe 151 to 351 and 551 to 851) formed by the radiation pattern in reception of its directional receiving antenna in the direction of the WAS node 100 (respectively WAS 200, WAS 300, WAS 400). FIG. 2 illustrates the configuration of the radiation patterns of the antennas of the nodes of the wireless synchronous home cinema network type 7.1 according to the particular embodiment of the invention during the time interval No. 1. a super frame when a node has been moved; FIG. 2 is identical to FIG. 1B with the difference that a node has been displaced during the time interval n ° 1 of a super frame n, for example the node WAS 200 (or node 2), the moving the WAS node 200 being indicated by the arrow 255. In the remainder of the description, it is considered, by way of example, that the WAS node 2 has been moved. As a result of the displacement of the WAS node 200, the reception radiation pattern 251 of its directional receiving antenna is no longer oriented correctly towards the WAS node 100, which causes the breaking of the radio link, and therefore the interruption of the transmission. data transmission. The breaking of the radio link lasts for all the time intervals of the current superframe n and the following superframes which results in a loss of data, the WAS node 200 no longer receiving nor sending more data correctly. With reference to FIG. 3, diagrams of WAS nodes 100 to 800 are presented according to a particular embodiment of the invention. The WAS node 200 is hereinafter described in detail, the WAS nodes 100 and 300 to 800 are not described because they are similar to the WAS node 200. Hereinafter described a first RF equipment of the dedicated node WAS 200 to the first RF transmission channel 10. For example, the WAS node 200 receives, through a receiving antenna 202, frames from the network. The frames received by the receiving antenna 202 are transmitted to a first front-end RF module 203 of the WAS node 200. The first front-end RF module 203 receives these frames from the first RF transmission channel 10 and then amplifies (by means of an amplifier low noise said LNA (low noise amplifier) not shown) these frames. Then the first frontal RF module 203 transmits these frames to a first baseband RF module 204 (adapted to the millimeter RF waves for example by the 802.15.3C standard) which performs an analog / digital conversion on these received frames and a filtering these frames. Then, the first baseband RF module 204, equipped with a modem, error correction means and means for adjusting the antenna angle in reception according to the RSSI parameter (for Received Signal Strength Indication) of the received signal and of a suitable protocol, carries out the processed frames which it then sends to a first data buffer 205 which can send them to a first baseband output 215. Then the converter Digital / Analogue performs digital-to-analog conversion on the audio data and delivers an analog audio signal to an audio amplifier. The frequency spectrum of this analog audio signal is typically between 100Hz and 20kHz. After amplification in the amplifier, the amplified analog audio signal is delivered to the speaker of the WAS node 200 via a filter. The speaker converts the analog audio signal into an acoustic signal.

The WAS node 200 is also adapted to send RF data to the network by means of a transmitting antenna 201. In this case, the first frontal RF module 203 amplifies the data to be transmitted by means of a power amplifier (or PA for Power amplifier). A second RF equipment of the WAS node 200 dedicated to a second RF transmission channel 20 (implementing a second timing which defines a second cycle for the transmission of data on this second channel) which is a bidirectional channel is described below. This second RF equipment is for example a wireless communication link compliant with the IEEE 802.11 protocol, a BLUETOOTH (registered trademark) link or even any other wireless communication link (such as DECT links or PHS links). The second RF equipment comprises, in the context of this preferred embodiment, a single antenna 206 (which is preferably omnidirectional in a frequency band around 2.4GHz to guard against masking phenomena) to make more robust the connection of the second RF equipment.

The second RF equipment comprises a second frontal RF module 207 and a second baseband module 208. Two outputs of this second baseband module 208 are respectively connected to a first register 212 for storing the identifier of the transmitting node. transmitting data on the first RF transmission channel 10 and a second register 213 for storing the frame scheduling of the TDM sequence on the first RF transmission channel 10. A third output of the second RF band 10 base 208 delivers, at the first baseband module 204, a second clock synchronization signal 214 of the following explained. The WAS node 200 also comprises a microcontroller 209 connected to a RAM 210 (which can be used to store the temporary data necessary to perform its various tasks) and to a ROM (or EEPROM, or Flash, ...) 211 ( adapted to store different information such as a hardware identifier, or serial number, WAS node 200, user data, the total number of WAS and their respective identifier, the audio channel assigned to each WAS, ...).

It is preferentially placed in the case where the communications between the nodes WAS and WSC of the network are made via the first RF transmission channel 10 which is a 60GHz channel because such a channel has the following advantages: - minimization of reflections on the walls the room in which the network is located; - high flow. However, such a channel has the disadvantage of limiting the distances on which the information is transmitted. To solve this problem of reduced transmission distance, it is preferentially chosen that the radiation pattern of the antenna in reception of each of the nodes WSC 1000 and WAS 100 to 800 is narrow (directional antenna) and orientable. Thus, the receiving antenna of each of the nodes WSC 1000 and WAS 100 to 800 is directional and the orientation of the direction of the radiation pattern of this antenna can be tuned (steerable). Receiving antennas use a conventional technique of beam forming (or technical beam forming in English) to form its radiation pattern receiving 1051, 151, 251, 351, 451, 551, 651, 751, 851 which is narrow ( directional antenna) and steerable (directional orientation of the radiation pattern can be tuned). For example, the above-mentioned receiving antennas are electromagnetic antennas consisting of an array of radiating elements which are controlled in phase and amplitude so as to form a directional antenna whose orientation is controlled. Such receiving antennas have a narrow radiation pattern and gain. The transmitting antenna of each of the nodes of the network is an omnidirectional antenna with a broad pattern of radiation (1052, 152, 252, ...) in transmission in order to be able to reach a maximum number of nodes (WAS and WSC) of the network.

Upon initialization of the wireless home theater network 7.1, it is necessary for each WSC node 1000, WAS 100 to 800 of the network to know the angle of orientation of its receiving antenna when each of the other nodes of the network transmits data. (This makes it possible to fill a table of angles and distances, also called synchronization table, dedicated to this node) on the first RF transmission channel 10. To do this, a discovery phase is implemented (hereinafter described in connection with FIGS. 5 and 6) of the WSC, WAS 100 to 800 nodes implemented in the network just after the initialization of the wireless home cinema network 7.1.

We put ourselves in the following in the case where the network is operational, that is to say that the discovery phase has taken place, and the angle tables described below in connection with FIGS. 5 and 6 are up to date. In addition, one places oneself in the case where each node receives at least twice the useful data. All the nodes of the network are synchronized on a predetermined TDM sequence. Synchronization can be maintained for a sufficiently long time compared to the phenomena that can be achieved within the scope of the present invention, this existing in many systems well known to those skilled in the art. The following is placed in the context of the distribution (or transmission) in the first RF channel 10 of the 7.1 wireless home cinema network, via the node WSC (current transmitter node), a data content current which is for example an audio content c0 and in the case where the node 200 has lost the synchronization following a voluntary or involuntary displacement (hereinafter called node 200 displaced or to be synchronized) on the first RF transmission channel 10 of the network. The synchronization method according to the invention is implemented in the form of software and / or a plurality of sub-software (comprising a plurality of algorithms described below) which is (are) executed in several machines of the home cinema network type 7.1, for example in the node WSC 1000 and in the nodes WAS 100 to 800. In the following, we consider the following indices: - t: number of the time interval; i: number of any node (for example i = 1, i = 3, ...); - j: number of the moved node (in our example j = 2); - n: total number of nodes; m: number of antenna sector angles; - k: index variable; with t, i, j, k, n, m being integers. In addition, the directions of the directional receiving antennas of the WSC and WAS nodes of the network are defined by means of the following parameters: angle α which corresponds to the angle of the sector of the antenna in directional reception by which a node j (before move) senses the 60GHz radio signal of a node i transmitting during the time interval t = i on the first RF communication channel 10; angle α 'i which corresponds to the new angle of the sector of the antenna by which the node j captures the 60GHz radio signal of the node i transmitting during the time interval t = i, after the node j has been moved; - Angle 13 i which corresponds to the angle of the antenna sector by which a node i has captured the 60GHz radio signal of the node moved j (before displacement) emitting during the time interval t = j. The angle i is transmitted to the node j by means of the second communication channel. The angle 13 i is a temporary variable which makes it possible in particular to determine the parameters of the translation associated with the displacement of the displaced node (the WAS node 200 in our example) in the Cartesian frame associated with the displaced node j. The parameters of the translation are then corrected for the orientation b i of the node i relative to the Cartesian reference system reference (detailed below); angle 13 'i which corresponds to the new angle of the antenna sector by which the node i captures the 60GHz radio signal of the displaced node j transmitting during the time interval t = j, this angle being transmitted to the node j moved by means of the second communication channel, after a move. The angle 13 i is a temporary variable which makes it possible in particular to determine the parameters of the translation associated with the displacement of the displaced node (the WAS node 200 in our example) in the reference associated with the displaced node j. The parameters of the translation are then corrected for the orientation b i of the node i with respect to the Cartesian reference frame of the system; parameter T which corresponds to the translation of coordinates (xt, yt) in the Cartesian coordinate system of the node j displaced, this translation being associated with the displacement of the node j; angle O which corresponds to the angle of rotation associated with displacement of the displaced node j; angle b i which corresponds to the angle between the reference Cartesian reference of the communication network and the Cartesian coordinate system of the node i. In relation to FIG. 4, time diagrams of the n and n + 1 superframes of a conventional 60GHz RF transmission channel are presented. The RF transmission channel 20 is a high bit rate data channel. A synchronous wireless communication network whose configuration is similar to that previously described in relation with FIGS. 1A to 1E is considered. Preferably, the 60GHz RF transmission channel is organized into 25 superframes, each comprising time slots (or frames) No. 0, No. 1, No. 2, No. 3, No. 4, No. 5, No. 6, No. 7 and No. 8 respectively dedicated to the nodes WSC 1000a (also referenced node 0), WAS 100a (also referenced node 1 and similar to WAS100), WAS 200a (also referenced node 2), WAS 300a (also referenced node 3), WAS 400a (also referenced node 4), WAS 500a (also referenced node 5), WAS 600a (also referenced node 6), WAS 700a (also referenced node 7) and WAS 800a (also referenced node 8).

At moment 4001, a loss of the radio link of the node 200a is detected following a movement thereof and a movement of its angle marker system. The moved node 200a starts a scan of the different antenna sector angles. Between times 4001 and 4002, the moved node 200a scans different antenna sector angles. At time 4002, a radio link detection module belonging to the moved node 200a (for example a signal reception quality level detector or RSSI parameter detects the node 100a again.) At this precise moment 4002, the node moved 200a can record the antenna angle a '1 corresponding to the transmission of the node 100a in its table of angles and distances, and then the moved node 200a starts again from the beginning of the time slot n ° 3 (instant 4003 ) the operation of scanning and detecting the data transmitted by the node 300a.

At the instant 4004, the displaced node 200a can record the antenna angle a'3 corresponding to the transmission of the node 300a in its table of angles and distances. This operation of scanning and detecting the transmitter nodes can be repeated for all the nodes of the network during the time equivalent of a super frame n between times 4005 and 4006. At the moment 4007, from the information obtained between moment 4005 and instant 4006, the displaced node 200a is able to orient its directional receiving antenna in the right direction (to the current transmitting node broadcasting data) and at the right time to again recover the data. useful data transmitted by the current transmitter node (here the node 100a).

Thus, from time 4007, the displaced node 200a, having correctly oriented its antenna in reception, receives and decodes the data (from the network) of the frame No. 1, then the frame No. 2,. .. of the n + 1 super frame of the 60GHz RF transmission channel.

However, this method of data recovery (or synchronization phase) requires a relatively high implementation time. Indeed, if the loss of the radio link takes place during the super frame n, the data can only be overlaid with the super frame n + 1, or even the super frame n + 2. In addition, when the displacement of the moved node 200a extends over several super frames, the moved node 200a does not recover any data during this time interval, generally causing a loss of data, and a serious degradation of the audio signal (and / or video) . FIG. 5 illustrates the discovery phase of the nodes WSC 1000, WAS 100 to 800 on a timing diagram of the superframes n and n + 1 of the first 10 and second 20 RF transmission channels according to the embodiment particular of the invention. The first RF transmission channel 10 is a high bit rate data channel and the second RF transmission channel 20 is a low bit rate data channel that is robust in terms of fading (English fading) and masking .

Preferably, the two RF transmission channels 10, 20 are synchronized and are organized in super frames as described in FIG. 4. This phase of discovering the nodes WSC 1000, WAS 100 to 800 is implemented in the network just after the Initialization of the wireless home cinema network 7.1.

In relation to FIG. 6, the main steps of the algorithm implemented in the context of the discovery phase of the WSC 1000, WAS 100 to 800 nodes according to a particular embodiment of the invention are presented. This algorithm, given by way of example, is based on n + 1 nodes (WSC 1000 and WAS 100 to 800), each node WSC 1000 and WAS 100 to 800 being respectively identified by the integers 0 to n = 8. The purpose of this discovery phase is for the microcontroller of each node to establish a table of angles and distances including the values of the angle formed by its receiving antenna with respect to a reference frame (which is for example the reference plane of the direction of emission of the sound waves coming from the loudspeaker associated with the considered node, that is to say the front face of the loudspeakers) when this antenna is oriented so as to receive the data transmitted by each of the other nodes of the network (by describing the TDM sequence) on the first RF transmission channel 10. It also includes the inter-node distances and the coordinates of the node with which it is associated in the reference Cartesian reference frame. This table of angles and distances is stored by the microcontroller in the RAM memory of the considered node. Each node of the network includes a table of angles and distances different from the fact that it has a position in the different network. This phase involves each of the nodes WSC 1000 (corresponding to a value of a node counter equal to 0), WAS 100 to 800 (respectively corresponding to node counter values of 1 to 8) one after the another according to the TDM sequence of a super frame of the first RF transmission channel 10. Thus, the nodes WSC 1000, WAS 100 to 800 will successively transmit in the network according to a scheduling defined by the TDM sequence. Before the instant 5001 of FIG. 5, the nodes of the network do not have a table of angles and distances in their RAM memory. In a step 500, it is implemented to start the discovery phase with a node counter i which is initialized to 0 which corresponds to the node WSC 1000 (which is the first in the TDM sequence) which therefore initiates the phase of discovered in the instant 5001. To do this, in steps 50 and 60, the node WSC 1000 (node 0) is placed in a transmission mode Tx (it is therefore a transmitting node) while the other nodes (nodes WAS 100 to WAS 800 or nodes 1 to 8) are placed in a reception mode Rx (they are therefore receiver nodes) either at the level of the first RF transmission channel 10 (step 51) or at the second transmission channel RF transmission 20 (step 60).

Then, at the first RF transmission channel 10, the WSC node transmits an RF test signal (e.g., random data) for the duration of a current time interval (which is sufficient for each of the other nodes (nodes WAS 100 to WAS 800) can perform the step of tuning the angle of their radiation pattern in reception described below). At the first RF transmission channel 10, between the instant 5001 and a time 5002 (during the step 51), during this transmission of the RF test signal, each of the other nodes (nodes WAS 100 to WAS 800) is in a reception mode according to which it gives the angle of its radiation pattern on reception in order to find the best antenna angle so that its receiving antenna is adapted to the reception of data transmitted by the node WSC 1000.

Thus, at the end of this agreement, in a step 52, each of the other nodes (nodes WAS 100 to WAS 800) finds the best antenna angle for its receiving antenna to be adapted to the reception of data transmitted by the WSC node. 1000 on the first RF transmission channel 10. In parallel, at the second RF transmission channel 20, the WSC node 1000 transmits a signal in which its current transmitter node identifier is transported. Then, in a step 61, each of the other nodes (nodes WAS 100 to WAS 800) receives the signal from the second RF transmission channel 20 from which, in a step 62, it decodes the: - second synchronization signal of clock ; - identifier of the current transmitter node broadcasting data on the first RF transmission channel 10; and - scheduling the frames of the TDM sequence on the first RF transmission channel 10. As soon as they have found the best angle, at time 5002, in a step 53, each of the other nodes (nodes WAS 100 to WAS 800 ) stores this angle, associated with the identifier of the transmitter node of the test signal (the node WSC 1000 in this case), in a table of angles and distances 40 of its own. Then, at the end of the current time interval, at the first RF transmission channel 10, the WSC node is no longer in transmission mode Tx and the other nodes (WAS nodes 100 to WAS 800 or nodes 1 to 8) are no longer in a reception mode Rx, and this, either at the first RF transmission channel 10 (step 54) or at the second RF transmission channel 20 (step 63). Then, in a step 55, it is checked whether the node counter i is equal to n (n = 8), if it is not the case then in a step 56, the node counter i is incremented by one. unit and the aforementioned steps 50 to 55 and 60 to 63 are repeated with the next node corresponding to the new value of the node counter. Thus, from a moment 5003, thanks to the incrementation of the node counter, each of the other nodes WAS 100 to 800 in turn transmits an RF test signal in the network according to the pseudo-random sequence so that the other nodes WAS can get and store the value of their best angle when the WAS node transmits. If the node counter i is equal to n, in a step 57, we reach the end of the discovery phase. In this case, from time 5004, each node WSC 1000, WAS 100 to 800 has constructed and stored its table of angles and distances 40 and can thus function normally on the first RF transmission channel 10 of the network. This discovery phase corresponds to a duration of at least one superframe of the first RF transmission channel 10, that is to say at least 9 frames of this first RF channel 10. The identifier of each node of the network can be fixed by example, during manufacture (by means of a serial number or a usage number), or can be written in the node later, for example by a network user or by the node WSC 1000 during initialization network. On the other hand, during this discovery phase, the distances between the different nodes of the network are determined and recorded in the table of angles and distances. Several methods can be implemented to determine the distances during the discovery phase. Thus, according to a first method, a user can manually enter distances via an interface, for each node, with distance values that he has previously measured.

According to a second method described in US Patent 3,076,519 (Alsabrook et al., Ultrasonic surveyor distance measuring instrument) and US 4,055,830 (Wilson et al .: Sonic measurement system), inter-node distances are obtained and recorded automatically. The nodes of the network transmit in turn an audio signal (in the sound or ultrasonic domain) by means of an electroacoustic transducer. Time synchronization and the commands for transmitting and receiving the audio signals are sent this time using radio waves whose propagation time is negligible. Each audio signal is then picked up by the other nodes with a delay equivalent to the propagation time of the sound (about 300 meters per second). This delay is measured by each node, which allows the node in question to determine, by calculation, the distance separating it from the transmitting node. Moreover, the table of angles and distances associated with a node i considered also comprises: the orientation θi of the Cartesian coordinate system of the node i with respect to the reference cartesian reference of the communication network which is determined from the following formula : 8i = 180 ° -ai-Ri - the Cartesian coordinates (xi, yi) of the node i in the reference Cartesian reference. They are the result of the transformation of the polar coordinates (angle a and distance d relative to reference Cartesian reference associated with node 100). FIG. 7 illustrates a time diagram of the n and n + 1 superframes of the first 10 and second 20 RF transmission channels according to the particular embodiment of the invention. The first RF transmission channel 10 is a high bit rate data channel and the second RF transmission channel 20 is a low bit rate data channel that is robust in terms of fading (English fading) and masking . Advantageously, the two RF communication channels 10, 20 are synchronized and are organized in super frames on the same model as that presented in relation to FIG. 6 previously described.

Unlike the synchronization method previously described in relation with FIG. 4, FIG. 7 illustrates in the time domain the synchronization method of the invention according to the particular embodiment of the invention.

At the instant 7001, a loss of the radio link is detected following a displacement of the node 200 (or node 2) and a movement of its angle marker system, the node 200 now being called the moved node 200. At the instant 7002, the moved node 200 transmits, in the time slot No. 2 assigned to it on the second RF transmission channel 20, an antenna sector angle loss warning signal to inform the assembly. nodes of the communication network. Simultaneously, the displaced node 200 transmits on the first RF communication channel 10 a signal which may be the repetition of the data that it has transmitted during the time slot allocated to it in the superframe (n-1). Since the detection of the alert signal transmitted by the displaced node 200 on the second RF transmission channel 20, all the nodes of the network scan the different antenna sector angles to find the signal transmitted on the first RF transmission channel 10. by the displaced node 200, and record the new angle a 'j in their table of angles and distances. Preferably, the nodes 300 and 400 which are the sending nodes following the displaced node 200 in the predetermined TDM sequence transmit, on the second RF communication channel 20, the angles '3 (first antenna orientation information) and' 4 (second antenna orientation information) (respectively at the intervals No. 3 (reference 21) and No. 4 (reference 22) of the super frame n) to the node 200 as well as to the other nodes of the network (the transmission being omnidirectional). In parallel with the first communication channel, at time 7003, when the node 300 starts transmitting a radio signal, the node 200 starts scanning the antenna sector angles to retrieve the radio signal from the node 300. at time 7004, when the moved node 200 detects the radio signal from the node 300, it records the corresponding angle a '3 (third antenna orientation information), associated with the direction of its directional receiving antenna, in his new table of angles and distances to the line dedicated to node 300. Similarly, at time 7005, when node 400 begins transmitting a radio signal, node 200 starts scanning antenna sector angles to retrieve the radio signal from node 400. At the instant 7006, when the moved node 200 detects the radio signal from the node 400, it records the corresponding angle a '4, associated with the direction of its antenna in directional reception, in its new table of angles and distances to the dedicated line at node 400. Then, between times 7007 and 7008, the moved node 200 determines the translation and rotation parameters corresponding to its displacement. At time 7009, the node 200 is again able to correctly orient its directional receiving antenna according to the transmitting node in the predetermined TDM sequence to be able to receive the data of the super frame n. Advantageously, at time 24, the node 200 transmits on the second transmission channel (when it is its turn to transmit in the TDM sequence), its new coordinates in the cartesian reference reference network (x'2, y'2), and its orientation b '2 with respect to this reference Cartesian reference to allow the other nodes to calculate the new distance separating them from the displaced node 200. This distance being useful in the case of a new displacement of any node of the network.

It is understood that, according to a variant of the particular embodiment, the moved node can detect the new angles a 'i of other nodes (different from the nodes 300 and 400) of the network. In relation to FIG. 8, the main steps of an algorithm for determining the parameters (angles, inter-node distances, orientation,

.) modified after the displacement of a node (in our example the node 200) according to the particular embodiment according to the invention. The initial table (before displacement) of the angles and distances 40 associated with the displaced node 200, an RSSI indicator 41, a clock signal 42, a node identifier 43, and the signal from a motion sensor 44 are the input data of the algorithm for determining the parameters. The initial table 40 of the angles and distances of the displaced node 200 contains the angles ai and (3i and the inter-node distance di associated with each of the nodes of the network, the orientation 82 of the node 200 and the coordinates (x2, y2) of the The RSSI indicator 41 corresponds to the level of the RSSI signal which determines the strength of the received radio signal, the clock signal 42 of the first timing indicates the beginning, the end and the number of the signal. time interval of the predetermined TDM sequence ... DTD: The identifier 43 of the current transmitter node is obtained from the information provided by the TDM sequence synchronized with the clock signal 42 of the first RF communication channel 10. This identifier The current transmitter node may be available on the second RF transmission channel 20. The motion sensor 44 determines whether the loss of the radio signal is due to movement or masking of the receiving antenna. Advantageously, the motion sensor 44 may be a simple pressure switch located below the displaced node 200 which, when it is raised, closes and indicates by a logic level (0 or 1) the state of movement of the 'object. Of course, one can also consider a more sophisticated sensor type optical sensor or any other sensor. In a step E1, the moved node 200 (again according to our example) transmits with its omnidirectional antenna on the first RF communication channel 10 during the time slot No. 2 reserved for it. During the step E1, each of the nodes of the network (other than the moved node 200) performs a scan of the various antenna sector seek or antenna scan angles to determine the angle of the antenna. antenna sector which allows the best reception of the 60GHz RF signal transmitted by the moved node 200. This scanning is active as soon as a displacement is detected. The scanning can for example be a very simple incremental type scanning, that is to say that the RSSI measurement is made for each angle of the antenna sector starting with 0 °, then 5 °, then 10 °, etc. The angle of the selected antenna sector is the sector for which the RSSI value is the highest. This angle value (corresponding to the highest RSSI value) is stored in a register. Each node of the network saves this value and corrects the line of their table of angles and distances corresponding to the moved node. As previously illustrated in connection with FIG. 7, during step E1, the nodes 300 and 400 which, in our example, follow the displaced node 200 in the predetermined TDM sequence, respectively determine the angles 13'3 and f3 ' 4. Of course, according to a variant of the particular embodiment of the invention, other nodes i of the network (other than the nodes 300 and 400) can respectively determine angles (3'i useful for the determination of the parameters of the displacement of the The angles 13'3 and 13'4 are then saved in registers referenced respectively 45 and 46 so that each of the nodes 300 and 400 can then transmit them, when their turn has come to transmit, in a frame on the second RF communication channel 20, in particular at the displaced node 200.

Advantageously, the measurement of the angles 13'3 and 13'4 makes it possible to measure one of the parameters of the displacement of the displaced node 200: the translation. Indeed, the displaced node 200 emitting on its omnidirectional antenna, the rotation associated with its displacement is canceled which allows the determination of the translation. In a step E2 (respectively E3), the node 300 (respectively 400) transmits during the time slot No. 3 (respectively No. 4), and the moved node 200 is in reception mode. The nodes 300 and 400 conventionally transmit on the first RF communication channel 10 the useful data, and on the second RF communication channel 20 the angle data respectively 13'3 and 13'4, and other data (for example their identifier 43). During steps E2 and E3, the displaced node 200 triggers a scan of the different antenna sector angles in the same manner as previously described. The antenna sector angles chosen are those giving the best reception, that is to say obtaining the highest level of RSSI. The displaced node 200 then determines in step E2 (respectively E3) the angle a'3 (respectively a'4) associated with the node 300 (respectively at the node 400). The angles a'3 and a'4 are then saved in registers referenced 47 and 48.

Advantageously, the link represented by the arrow 49 makes it possible to update the angles a'3 and a'4 in the table of angles and distances 40 for the nodes 300 and 400. From the measurements of the angles a'3, 13 3, a'4, and 13'4, a calculation module 50 can determine, in a step E4, the translation and the rotation (T and 0) constituting the displacement of the displaced node 200. The result of the calculation is stored in a register 51. The two parameters T and 0 determined during the step E4 make it possible, in a step E5, to calculate the angles and distances associated with each node of the network and then to update the table of angles and distances. 40. Thus, in step E5, the angles ai and (3i and the distance di associated with each node of the network, the coordinates (xj, yj) of the displaced node 200, and the orientation 8j of the Cartesian coordinate system of the node j (in our example the node 200) with respect to the reference frame of the system of nodes are corrected in the Table 40. Then, in a step E6, during the following time slot No. 5 (t = 5), the antennas of the different nodes of the network can be oriented towards the transmitting node (in our example the node 500). The steps E4 and E5, the link 49 and the registers (40, 45, 46, 47, 48, 51) may be performed by a microcontroller (also noted as C) or processor integrated with the other components of the system (for example an FPGA ( for Field Programmable Gate Array in English) and / or an ASIC (for Application 10 Specific Integrated Circuit in English) with a microcontroller). Similarly, the steps E1, E2, E3 (scanning of antenna sector angles and antenna alignment) can be performed by sequential and / or combinatorial type logic (for example of the FPGA and / or ASIC type), driven by the same processor mentioned above. These embodiments are applicable to each node of the network. With reference to FIG. 9, the Cartesian references associated with each of the nodes of the synchronous home cinema network of FIG. 1A according to the particular embodiment of the invention are presented. Advantageously, all the nodes of the communication network 20 can be located in the spatial domain by a reference Cartesian reference system associated with the node 100 (or node 1). Thus, after the discovery phase previously described in connection with FIGS. 5 and 6, each node has its own coordinates (xi, yi) in the Cartesian reference frame of the system, as well as an orientation corresponding to FIG. angle between its own Cartesian coordinate system and that of reference system (in our example that associated with node 100). From these data, each node i of the network constructs a table of angles and distances 40 in which is shown the polar coordinates (a i, di) of all the other nodes brought back to its own Cartesian coordinate system.

The table of angles and distances 40 also includes the angle 13 j by which the other nodes see the node j transmitting on its omnidirectional antenna. This angle 13 j can in particular be used to determine the displacement parameters of a node as previously described.

Moreover, the two components of a displacement: the rotation 34 and the translation 33 are also represented in FIG. 9. The symbol 31 is a hardware representation of the node, the arrow indicating its orientation and the origin of the sector angles. 'antenna. A node may be represented by a point (for example reference 32) when it does not use its directional antenna, that is to say when it uses its omnidirectional antenna in transmission for example. FIG. 10 shows a schematic representation of the antenna sector angles associated with the nodes 300 and 400 of the communication network before and after the displacement of the node 200, when they are in omnidirectional transmission on the first channel of the antenna. RF communication 10 according to the particular embodiment according to the invention. Thus, if we consider the reference defined by the origin of the displaced node 200 and the axes referenced x and y, it is possible to obtain the polar coordinates of all the nodes of the network in this reference associated with the moved node. 200.

As illustrated by FIG. 10, the angles a3 and a4 and the distances d3 and d4 are respectively associated with the nodes 300 and 400 during the discovery phase of the network as previously described in relation with FIGS. 5 and 6. Moreover, FIG. 10 illustrates the angles a'3 and a'4 which correspond to the antenna sector angles by which the node 200 sees, after displacement, respectively the node 300 and the node 400 when they transmit radio signals at the same time. during the time intervals Nos. 3 and 4 on the first RF communication channel 10. It should be noted that the two angles a'3 and a'4, although representative of translation and rotation, are insufficient for calculate these two unknowns. Indeed, new inter-node distances are missing in order to solve the equation. It is thus necessary to implement a new measurement step as described below in relation with FIG. 11. A schematic representation in the reference Cartesian reference frame of the antenna sector angles associated with the nodes 300 and 400 before and after displacement of the node 200, when the node 200 transmits omnidirectionally on the first RF communication channel 10 according to the particular embodiment according to the invention. The displaced node 200 (in our example) transmits, during the time interval, which is reserved for it with its omnidirectional antenna. This makes it possible to cancel the rotational component 34, only the translation 33 is then taken into account. The displaced node 200 may be represented by a dot, meaning that any notion of direction has disappeared. The nodes 300 and 400 scan all the antenna sector angles to retrieve the radio signal transmitted by the displaced node 200 on the first RF communication channel 10. When the radio signal of the node 200 has been retrieved by the nodes 300 and 400 the latter save the angle values respectively 13'3 and 13'4 to transmit them by means of the second RF communication channel 20 previously described. With reference to FIG. 12, a schematic representation of the antenna sector angles associated with the nodes 300 and 400 in the Cartesian coordinate system of the moved node before and after displacement of the latter, when it transmits omnidirectionally on the first RF communication channel 10 according to the particular embodiment according to the invention. After measuring the angles 13'3 and 13'4 as illustrated by FIG. 11, since only the translation is taken into account here, the displaced node 200 (represented by its reference (x, y)) sees the other nodes of the network move T 33 translation with an inverted direction (that is, ûÉ) in its Cartesian coordinate system.

Advantageously, the passage in the Cartesian coordinate system of the displaced node 200 makes it possible to simplify the calculation of the parameters of the translation.

The displaced node 200 retrieves the measured angles 13'3 and 13'4 via the second RF communication channel 20 according to a simplified protocol described later. Thus, the calculation of the parameters of the translation T identified in the Cartesian coordinate system of the displaced node 200 by the coordinates (Xt, Yt) implements the system with two equations and two unknowns according to: Yt û tan (3'3.Xt = (tan (3'3 û tanin) X3 Yt û tan (3'4.Xt = (tan 13'4 û tan (34) X4 where (X3, Y3) and (X4, Y4) are the coordinates of the nodes 300 and 400 in the Cartesian coordinate system of the displaced node 200, and 13'3 and J3'4 the angles measured previously.

The resolution of this system makes it possible to obtain the parameters of the translation T: (Xt, Yt). The polar coordinates of the angle and distance table 40 can be used indifferently Cartesian coordinates for writing facilities, then the reverse operation for the update of this table 40 after calculations. These operations are not more fully described because they present no particular difficulty and will be obvious to the skilled person. FIG. 13 illustrates a geometric representation of the rotation associated with the displacement of the displaced node 200 in the communication network according to the particular embodiment of the invention.

As for the determination of the parameters of the translation T described above in relation to FIG. 13, the rotation associated with the displacement of the node 200 can be considered, by placing itself in the Cartesian frame (x, y) of the displaced node 200. as a rotation of angle 0 of all the other nodes around the origin of the displaced node 200. Thus, as illustrated in FIG. 13, we have: 0 = a "4-a '4 where a" 4 is defined by tana "4 = (x4 + xt) / (y4 + yt) Advantageously, the angle a '4 associated with the node 400 has been used to determine 0. Of course, the calculation can also be performed with the angle a 3 of node 3, or any other angle a 'i associated with a node of the network Thus, using a' 3, we have: 0 = a "3-a '3 where a" 3 is defined by tan a "3 = (x3 + xt) / (y3 + yt) Optionally, in order to improve the accuracy of the measurement of the angle θ, it is conceivable to average the two determined angles associated with the rotation: e = ( e3 + e4) / 2 where 0 3 was determined using a '3, and 0 4 using a' 4. With reference to FIG. 14, the main steps of the general algorithm for recovering a lost RF radio link according to the particular embodiment of the invention are described.

In a step 70, a loss of 60GHz RF radio connection is detected when the RSSI falls below a minimum threshold called Th mini and when a displacement detector indicates a displacement (the sensor variable associated with the detector is equal to 1 ). According to a variant of the particular embodiment of the invention, the detection of a loss of connection can be made solely from the analysis of the RSSI level. According to another variant of the particular embodiment, the step of detecting a loss of synchronization is implemented at regular intervals. In the remainder of the description, the index j is that of the moved node 25 (in our example the node 200).

Thus, when the node j detects a displacement (RSSI <THmini and sensor = 1), it sets an alert bit named flag to 1, in a step 71. The node j can then transmit, during its reserved time interval, a motion alert signal on the second RF communication channel 20 (the transmission of the alert signal is detailed below in connection with FIG. 15). In a step 72, the node j verifies whether the current time interval is the time interval j + 1 (i.e., the node j + 1 is transmitting). The node j is then in a waiting state. Of course, according to a variant of the particular embodiment, this verification of the current time interval may relate to any other time interval associated with a node of the network other than the node j + 1. In case of negative verification of step 72 (node j + 1 does not transmit), node j repeats step 72.

In case of positive verification of step 72 (the node j + 1 transmits), the node j scans, in a step 73, the different antenna sector angles to find the RF signal transmitted by the node j + 1 on the first RF communication channel 10. When the node ja found the RF signal transmitted by the node j + 1, it records the angle of the sector a'j + 1 giving the best reception. Simultaneously, on the second RF transmission channel 20, the node j retrieves, in a step 76, the identifier of the node j + 1 and the angle 13 'j + 1 measured by the node j + 1 during the time interval j. In a step 77, the node j records the angle 13 'j + 1.

At the end of steps 75 and 77, the node j verifies, in a step 80, that the current time interval is the time interval j + 2 (i.e., the node j + 2 is in process to issue). The node j is then in a waiting state. In case of negative verification of step 80 (node j + 2 does not transmit), node j repeats step 80.

In case of positive verification of step 80 (the node j + 2 transmits), the node j scans, in a step 81, the different antenna sector angles to find the RF signal transmitted by the node j + 2 on the first RF communication channel 10.

When the node j has found the RF signal transmitted by the node j + 2, it records the angle of the sector a'j + 2 giving the best reception. Simultaneously, on the second RF transmission channel 20, the node j retrieves, in a step 84, the identifier of the node j + 2 as well as the angle 13 'j + 2 measured by the node j + 2 during the time interval j.

In a step 85, the node j records the angle 13 'j + 2. At the end of steps 83 and 85, in a step 86, the node j calculates the parameters of the translation and of the rotation associated with its displacement from the angles previously obtained. In a step 87, the node j can correct all the angles and distances of its table of angles and distances to then orient, in a step 88, its directional reception antenna for the next time intervals of the predetermined TDM sequence. In a step 89, the node j computes its new coordinates (x'j, y'j) in the Cartesian reference frame and its new orientation (b 'j) with respect to this same reference frame. The main steps of a data transmission algorithm on the second RF communication channel 20 according to the particular embodiment of the invention are now presented in relation to FIG. In a step 901, a node j belonging to the communication network is in a waiting state during the transmission of a super frame n comprising a predetermined TDM sequence. In a step 902, it is verified, by means of the second timing, that the current time interval is the time interval j in order to determine the time from which the node j will be able to transmit data on the second RF transmission channel 20 In case of negative verification of step 902 (the current time interval is not the time interval j), steps 901 and 902 are repeated.

In case of positive verification of step 902 (the current time interval is the time interval j), the node j verifies, in a step 903, that a displacement alert is to be sent on the second communication channel. In case of negative verification of step 903, a Flag Alert variable is set to 0 in a step 904. The node j then inserts, in a step 905, the value 0 in the field Moving the frame j of the super frame n (described later in connection with FIG. 17) that it will transmit on the second RF communication channel 20. In a step 906 (the node j is not concerned with a displacement), it is verified that a new angle 13 'is to be transmitted.

In case of positive verification of step 906 (a new angle 13 'is to be transmitted), the node j insert, in a step 907, the angle 13' j in the field Angle of the frame j which it transmits in a step 908. In case of negative verification of step 906 (no new angle is to be transmitted), the node j transmits the frame j of the super frame n in a step 909 on the second channel. RF communication 10. At the end of steps 908 and 909, the node j returns to step 901 in a waiting state when transmitting the super frame n + 1. In case of a positive verification of step 903 (a movement alert is to be sent), the Flag Alert variable is set to 1 in a step 910. The node j then insert, in a step 911, the value 1 in the field Diplacement Flag of the frame j it will transmit on the second RF communication channel 20. Then, in a step 912, the node j transmits the frame j on the second RF communication channel 20.

Then, in a step 913, after transmission of the frame j belonging to the super frame n, the node j returns to a waiting state, and verifies that the current time interval of the super frame n + 1 is the time interval j. In case of negative verification of step 913, the node j remains in a waiting state, step 913 being repeated. In case of positive verification of step 913 (the current time interval is the time interval j), the node j transmits, in a step 914, the frame j of the super frame n + 1 containing the new coordinates (x 'j, y'j) and the new orientation of the node j relative to the reference Cartesian reference.

At the end of step 914, node j returns to step 901 in a wait state upon transmission of the n + 2 superframe. With reference to FIG. 16, the main steps of an algorithm for receiving data on the second RF communication channel 20 of the communication network according to the particular embodiment of the invention are described. In a step 60, from the second timing, a node i can know its position in the predetermined TDM sequence of a super frame n. Then, in a step 61, the node i verifies that it does not transmit data on the second communication channel, that is to say that the current time interval is not the time interval i ( the current time interval being used by another node of the network to transmit). In case of negative verification of step 61 (the node i is transmitting), the algorithm returns to step 60. In the case of positive verification (the node i is in reception), the node i reads, in a step 62, the data transmitted by the other nodes of the network that it has received. In a step 63, the node i verifies that there is a displacement warning message in the received data. In case of negative verification of step 63 (no alert message has been received), node i records the coordinates (x, y) of the transmitting node in the reference Cartesian frame.

Then in a step 72, the node i verifies whether the coordinates of the transmitter node received are new. In the event of negative verification of step 72 (the transmitting node coordinates received are not new), the algorithm returns to step 60.

In the case of a positive verification of step 72 (the coordinates of the transmitter node received are new), node i calculates, in a step 73, the new distance separating it from this transmitting node in the Cartesian reference frame, then the records in its table angles and distances during a step 74. The algorithm then returns to step 60.

In case of positive verification of step 63 (an alert message from a node ja has been received), the node i checks, in a step 64, that the RSSI reception level of the radio signal on the first channel of RF communication 10 is less than a first threshold noted THminimuml. In the positive case of step 64 (RSSI <THminimum1), the node i starts, in a step 65, a scan of the different antenna sector angles to find the node j transmitter. In a step 66, when the node i has found the radio signal of the node j, it checks that the RSSI level is greater than a second threshold noted THminimum2. In case of negative verification of step 66 (RSSI <THminimum2), the node j continues scanning the antenna sector angles (steps 65 and 66 are repeated). In case of positive verification of step 66 (RSSI> THminimum2), the node j records, in a step 67, the new reception angle a 'j measured by the node i on the first RF communication channel 10 in the table angles and distances from node i to line j. Then, in a step 68, the node i checks whether it is one of the two transmitting nodes that follow the moved node j in the predetermined TDM sequence (i.e. i j + 1 or i = j + 2). In case of negative verification of step 69 (i ≠ j + 1 and i ≠ j + 2), then the algorithm returns to step 60.

In case of positive verification of step 69 (i j + 1 or i = j + 2), the node i reads the new reception angle a j previously saved (step 67) in its table of angles and distances. Then in a step 70, the node i prepares the angle information a 'j corrected of the bi orientation of the node i relative to the reference reference, so that the angle 13' i corrected (13 'i being equal corrected by bi) is transmitted to the moved node Once the frame i of the super-frame n is transmitted on the second transmission channel, the algorithm returns to step 60. It is presented, in connection with FIG. 17, an example of a frame (or time interval) 2300 of a super frame of the second RF transmission channel 20 according to the particular embodiment of the invention Preferably, the first 10 and second 20 RF transmission channels have the In the same frame synchronization 24, however, the frames of the second RF transmission channel 20 may also be shifted from those of the first RF transmission channel 10 by a constant time difference.The first 10 and second 20 RF transmission channels are organized in accordance with FIG. super frames each and time intervals (or frames) No. 0, No. 1, No. 2, No. 3, No. 4, No. 5, No. 6, No. 7 and No. 8 respectively dedicated to the WSC 1000 nodes ( also referenced node 0), WAS 100 (also referenced node 1), WAS 20 200 (also referenced node 2), WAS 300 (also referenced node 3), WAS 400 (also referenced node 4), WAS 500 (also referenced node 5) ), WAS 600 (also referenced node 6), WAS 700 (also referenced node 7) and WAS 800 (also referenced node 8). The frame 23 comprises: a preamble 26 (of a length which may be equal to 32 bits or even more) for transmitting (via the second clock synchronization signal 514) the clock synchronization of the first channel of RF transmission to the first baseband RF modules of the nodes receiving the frame 23; a data zone 2300 (for example, of a length of 60 bits) comprising; a header 2301 (for example, of a length of 10 bits) which makes it possible to identify the current transmitter node broadcasting data on the first RF transmission channel 10; a displacement field (for example, of a length of 2 bits) making it possible to indicate that a displacement of the node has taken place; a field 2302 TDM sequence which comprises the scheduling of the frames of the predetermined TDM sequence (for example, of a length of 16 bits) which makes it possible to obtain the chronological order of the frames in the current super-frame the order of the TDM sequence of the first RF communication channel 10; a field 28 Angle (for example, of an 8-bit length) which may comprise the value of a new measured angle; a coordinate field 2303 (for example, of a length of 24 bits) which makes it possible to transmit the new coordinates of the displaced node and its orientation with respect to the Cartesian reference reference. This Coordinates field can be divided into three subfields 29: Abscisse X'j, Y'j ordinate, Orientation b 'j (for example, each of a length of 8 bits); an end-of-frame field gathering error correction information, for example a CRC (for Cyclic Redundancy Code in English or a code with a Cyclic Redundancy Code in French) (for example, a length of 8 bits). By way of example, the formats of the essential fields of the invention and constituting the previously described frame of the second RF communication channel 20 are described below: 8-bit angle field: b7, b6, b5, b4, b3 , b2, bl, b0. The bits can be used as follows: • b7 = 1 indicates that a new angle has been measured by node j + 1 or node j + 2; • b7 = 0 indicates that there is no change; B6, b5, b4, b3, b2, b1, b0 are data bits: from 000 0000 to 111 1000: values of the angle in degrees per sector of 3 degrees; - from 111 1001 to 111 1111: unused values. - 8-bit Abscisse Xj field belonging to the Coordinates field: b7, b6, b5, b4, b3, b2, b1, b0. The bits can be used as follows: • b7 is sign bit; • b6, b5, b4, b3, b2, b1, b0 are data bits: - from 000 0000 to 110 0011: values of the abscissa in steps of 10 cm, from 0 to 10 m; - from 110 0100 to 111 1111: unused values. - Yd Yield field in 8 bits: b7, b6, b5, b4, b3, b2, bl, b0. The bits can be used as follows: • b7 is a sign bit; • b6, b5, b4, b3, b2, b1, b0 are data bits: - from 000 0000 to 110 0011: values of the abscissa in steps of 10 cm, from 0 to 10m; - from 110 0100 to 111 1111: unused values. 8-bit Orientation field 8j: b7, b6, b5, b4, b3, b2, bl, b0. The bits can be used as follows: • b7 is an unused bit; • b6, b5, b4, b3, b2, bl, b0 are data bits: - from 000 0000 to 111 1000: values of the angle in degree by sector of 3 degrees, - from 111 1001 to 111 1111: values not used The synchronization method of the invention can operate up to 140km / hr movement speed values for near nodes (0.5m) and much more for distant nodes. This is because, for example, for antenna sector angles of 9 ° aperture, a 2 ms super-frame duration and a node close to a distance of 0.5 m, there is a maximum displacement speed which is equal to: V = (2 * ft) * (9 ° / 360 °) * (0.5) / (2e-6) = l4lkm / h The values presented throughout this description are as follows: non-limiting example.

The synchronization method of the invention described above makes it possible in particular to reduce the antenna realignment time following a loss of radio link and therefore the reintroduction of a node moved in the network without loss of data by rapidly adjusting the antennas. directional nodes network at the right angle.

Moreover, thanks to the synchronization method of the invention, a moved node finds the radio link and a table of angles and distances updated without loss of data and in a minimum of time which can be at most equivalent to 3 time intervals. 20

Claims (26)

A method of synchronizing a synchronizing node (200) having a directional receiving antenna for receiving a signal from a first communication channel (10) in a wireless communication network comprising a plurality of nodes (100, 200, 300, 400, 500, 600, 700, 800, 1000), said method being implemented by the node to be synchronized (200) and is characterized in that it comprises the following steps: - obtaining (7003, 7005) first and second orientation information representative of the arrival direction of a signal transmitted by the node to be synchronized, respectively, on a first (300) and a second (400) node of the wireless communication network; obtaining (7004; 7006) at least one third orientation information representative of the direction of arrival of a signal transmitted by at least one of said first (300) and second (400) nodes, on the node to synchronize (200); determining (86) an orientation information of the antenna on reception of the node to be synchronized (200) from said first, second and third orientation information; and synchronizing (88) the node to be synchronized (200) from said orientation information of the determined receiving antenna. 2. A synchronization method according to claim 1, characterized in that the first (300) and second (400) nodes use a directional antenna in reception and in that the first and second orientation information are obtained by performing a scan ( E2, E3) by the directional antennas of said first (300) and second (400) nodes respectively. 3. synchronization method according to any one of claims 1 and 2, characterized in that the step of obtaining said first and second orientation information comprises the following steps: -mission (7002) on a second communication channel (20), an alert message representative of a loss of synchronization of said node to be synchronized (200) relative to the first communication channel (10); receiving (70, 76, 84), through the second communication channel (20), said first and second orientation information. 4. synchronization method according to any one of claims 1 to 3, characterized in that the step of determining (86) said orientation information of the directional receiving antenna of the node to be synchronized (200) comprises the following steps: - determining at least one displacement parameter of the node to be synchronized (200) from said first, second and third orientation information; calculating said antenna orientation information in directional reception of the node to be synchronized (200) from the parameter (s) of displacement. A synchronization method according to any one of claims 1 to 4, each of the nodes being able to transmit data on said first communication channel (10) according to a predetermined sequence, characterized in that the first node (300) is the node following the node to be synchronized (200) in the predetermined sequence, and in that said second node (400) is the node following said first node (300) in the predetermined sequence. 6. synchronization method according to any one of claims 1 to 5, characterized in that the node to be synchronized (200) uses a synchronization table (40) comprising, for each node of the network, information of orientation of the directional receiving antenna of the node to be synchronized (200), said antenna being adapted for reception of data transmitted by said node. 7. synchronization method according to claim 6, characterized in that it comprises a step of updating (ES) of said synchronization table (40) according to said antenna orientation information directional reception of the node to synchronize (200) obtained. 8. Synchronization method according to any one of claims 1 to 7, characterized in that it further comprises a step (70) for detecting synchronization loss of the node to be synchronized (200) in the first communication channel (10), and in that the synchronization loss of the node to be synchronized (200) results from a displacement of the node to be synchronized. 9. Synchronization method according to claim 8, characterized in that the loss of synchronization is detected by means of a displacement sensor provided in the node to be synchronized (200). The synchronization method according to claim 8, characterized in that the loss of synchronization is detected by means of a measurement of an indicator of the level of reception of a signal by the node to be synchronized (200). 11. synchronization method according to any one of claims 1 to 10, characterized in that a step of determining whether the node to be synchronized (200) has lost synchronization in the first communication channel (10) is implemented at regular intervals, and in that said synchronization method is triggered in the case of a positive determination. 12. A method of synchronization according to any one of claims 1 to 10, characterized in that it is triggered at regular intervals. 13. Computer program product downloadable from a communication network and / or recorded on a computer readable medium and / or executable by a processor, characterized in that it comprises program code instructions for the execution of synchronization method steps according to at least one of claims 1 to 12, when said program is executed on a computer. 14. A computer-readable, possibly totally or partially removable storage medium, storing a set of instructions executable by said computer for carrying out the synchronization method according to at least one of claims 1 to 12. A node to be synchronized having a directional receiving antenna for receiving a signal from a first communication channel (10) in a wireless communication network comprising a plurality of nodes (100, 200, 300, 400, 500, 600, 700, 800, 1000), characterized in that it also comprises synchronization means comprising the following means: means for obtaining a first and a second orientation information representative of the direction of arrival of a signal transmitted by said node to be synchronized (200), respectively, to a first (300) and a second (400) node of the wireless communication network; means for obtaining at least a third orientation information representative of the direction of arrival of a signal transmitted by at least one of said first and second nodes, on said node to be synchronized; means for determining an orientation information of the antenna in reception of the node to be synchronized from said first, second and third orientation information; and means for synchronizing said node to be synchronized from said orientation information of the determined reception antenna. 16. Node to be synchronized according to claim 15, characterized in that the first and second nodes use a directional antenna in reception and in that said means for obtaining the first and second orientation information comprise means for implementing scanning by the directional antennas of said first and second nodes respectively. 17. Node to synchronize according to any one of claims 15 and 16, characterized in that said means for obtaining said first and second orientation information comprise the following means: - transmission means on a second communication channel (20), an alert message representative of a loss of synchronization of said node to be synchronized relative to the first communication channel (10); means for receiving, through the second communication channel, said first and second orientation information. 18. Node to be synchronized according to any one of claims 15 to 17, characterized in that said means for determining said orientation information of the directional receiving antenna of the node to be synchronized comprise the following means: determining at least one displacement parameter of the node to be synchronized from said first, second and third orientation information; means for calculating said antenna orientation information in directional reception of the node to be synchronized from the parameter (s) of displacement. 19. Node to be synchronized according to any one of claims 15 to 18, each of the nodes can transmit data on said first communication channel in a predetermined sequence, characterized in that the first node is the node following the node to be synchronized in the predetermined sequence, and in that said second node is the node following said first node in the predetermined sequence. 20. Node to be synchronized according to any one of claims 15 to 19, characterized in that said synchronization means comprise means for using a synchronization table comprising, for each node of the network, orientation information of the directional receiving antenna of the node to be synchronized, said antenna being adapted for receiving data transmitted by said node. 21. A node to be synchronized according to claim 20, characterized in that said synchronization means comprise means for updating said synchronization table according to said antenna orientation directional reception information of the node to be synchronized obtained. 22. Node to synchronize according to any one of claims 15 to 21, characterized in that it further comprises means for detecting a loss of synchronization of the node to be synchronized in the first communication channel, and in that the synchronization loss of the node to be synchronized results from a displacement of the node to be synchronized. 23. Node to be synchronized according to claim 22, characterized in that said means for detecting synchronization loss of the node to be synchronized comprise a displacement sensor of the node to be synchronized. Node to be synchronized according to claim 22, characterized in that said means for detecting a loss of synchronization of the node to be synchronized comprise means for measuring an indicator of the level of reception of a signal by the node to be synchronized. 25. Node to synchronize according to any one of claims 15 to 24, characterized in that it comprises means for determining whether it has lost synchronization in the first communication channel activated at regular intervals, and in that said synchronization means are triggered in the case of a positive determination. 26. Node to synchronize according to any one of claims 15 to 24, characterized in that said synchronization means are triggered at regular intervals.