SELECTION PROCEDURE FOR A COMMUNICATION CHANNEL

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for selecting a communication channel in a wireless communication network. More particularly, the present invention finds its application in radio coverage extension systems. STATE OF PRIOR ART

[0002] In Local Area Networks (LANs), radio coverage extension systems can be used to increase the range of these LANs by coordinating several APs (Access Points) distributed in space. These different APs are integrated into communication node devices, also called extendeurs ("extenders" in English), interconnected through a backhaul network and all provide the same WLAN ("Wireless Local Area Network" in English). All these AP access points therefore use the same network identifier, called identifiant de jeu de services SSID ("Service Set IDentifier" in English) in the terminology of the IEEE 802.11 family of standards on which Wi-Fi technology is based (registered trademark), for example "my_home", and the same password (also called clef de sécurité). We can then speak of a fronthaul network, to which user equipment is intended to connect. Thus, the radio coverage extension is transparent for these user equipment connected to the WLAN. Note that in some implementations (for example "easyMesh"), the fronthaul network can be used as a routing network.

[0003] In residential environments, a residential gateway provides access to a Wide Area Network (WAN), such as the Internet, for terminals connected to it directly via wired (e.g., Ethernet) or wireless (e.g., Wi-Fi (registered trademark)) LAN interfaces embedded in the residential gateway, or indirectly via a radio coverage extension system as mentioned above. Thus, the residential gateway embeds one or more AP access points that typically operate on frequency bands at 2.4 GHz and 5 GHz, and soon at 6 GHz. These AP access points are operated by radio interfaces, each radio interface being dedicated to one of said frequency bands and capable of containing one or more AP access points. Each radio interface chooses at least one predefined position communication channel on the frequency band concerned.Typically, a first communication channel, called . canal primaire, is chosen in order to broadcast beacons from all AP access points that the radio interface contains, and one or more complementary communication channels (usually adjacent to the primary channel), called canaux secondaires, are chosen to allow an increase in communication throughput by aggregating communication capacities. Each AP access point is identified in the tags that concern it by a unique identifier, called identifiant de jeu de services de base BSSID (“Basic Service Set IDentifier”) in the terminology of the IEEE 802.11 family of standards.

[0004] When the routing network is in place, a node device (called "parent") sets up a first access point AP (for the routing network) via at least one of its radio interfaces and one or more other node devices (called "children") connect to it using a station functionality, as a user equipment would do with respect to a conventional access point AP. A child node device uses a radio interface in line with the radio interface that implements the first access point AP of the parent node device. This radio interface of the child node device can itself embed a second access point AP to extend the coverage of the routing network, so that other node devices of the routing network can connect to it in turn.Then, the second AP (belonging to the routing network) uses the same communication channel, namely the same primary channel, as the one imposed by the first AP on the station functionality of the radio interface that carries the second AP. If another AP is also set up by the same radio interface for the front-end network, then the same communication channel, namely the same primary channel, is also used by this other AP (because it belongs to the same radio interface).

[0005] The routing network is coordinated by a communication node device, called dispositif noeud maître. In residential environments, the role of master node device is generally provided by the residential gateway, which has a strategic position for concentrating data flows with respect to access to the WAN and, in particular, has more processing capacity than simple extenders (the residential gateway can also be considered, from the point of view of the routing network, as an extender).

[0006] Thus, when the master node device chooses a communication channel, this is reflected in the entire routing network so that all APs forming the routing network use this communication channel. Typically, all these APs have the same primary channel, since the same type of radio interface (e.g., at 5 GHz) is used to support the routing network.

[0007] However, the master node device chooses this communication channel based on the information available to it locally (scan of its own radio environment, noise level, interference, etc.), generally called an automatic channel selection mechanism (ACS), and since this choice does not take into account the radio environments specific to the other node devices of the routing network, this choice of communication channel may not be satisfactory from the point of view of at least one other node device of the routing network, which may harm the performance (throughput, retransmissions, etc.) of the WLAN wireless local area network whose coverage is extensive.

[0008] Patents US2020 / 119836 and EP2907334 disclose a method for selecting a communication channel in a wireless communication network.

[0009] It is then desirable to overcome these drawbacks of the state of the art. It is particularly desirable to provide a solution that makes it possible to improve the performance (throughput, retransmissions, etc.) of a WLAN wireless local area network comprising a routing network, as mentioned above, which is intended to extend the radio coverage of said WLAN wireless local area network. STATEMENT OF THE INVENTION

[0010] The invention is defined by the independent claims. The embodiments are defined by the dependent claims.

[0011] A first method is proposed for selecting a communication channel in a wireless communication network comprising a routing network interconnecting node devices and intended to extend a radio coverage of a wireless front-end network by implementing a plurality of access points of the wireless front-end network. A same first communication channel, selected by a master node device of the routing network, is used in the routing network to interconnect said node devices. The method comprises the following steps carried out by each node device of the routing network: carrying out an evaluation of transmission conditions of its radio environment; calculating, for each communication channel available to said node device, a score representative of a transmission quality via said communication channel based on the evaluation carried out.In addition, when, from the point of view of a said node device of the routing network, at least one second communication channel shows a better score than the first communication channel, the method further comprises the following steps performed by the master node device: obtaining, from each node device of the routing network, the score of the first communication channel and the score of at least one said second communication channel, to perform an evaluation of communication channel change; deciding whether or not to change the communication channel used in the routing network, depending on the scores obtained. Thus, the performance (throughput, retransmissions, etc.) of a wireless communication network whose radio coverage is extended by such a routing network is improved by taking into account, via the scores, the radio environments of the different node devices of the routing network.Additionally, by using score calculations, the volume of information / data exchanged in the routing network to enable communication channel selection is limited.

[0012] According to a particular embodiment, following the evaluation of transmission conditions of its radio environment, when a node device other than the master node device evaluates that at least one second communication channel shows a better score than the first communication channel, the node device in question transmits to said master node device a communication channel change request message including, at least, an identifier of said at least one second communication channel having obtained the best score and its score, as well as the score obtained by the first communication channel. Then, the master node device probes each of the node devices of the routing network other than the one having transmitted said communication channel change request message to obtain the score of each communication channel to which the communication channel change request message refers.Thus, the master node device can evaluate switching to any other communication channel that would be perceived as better from the point of view of the node device that transmitted the communication channel change request message.

[0013] According to a particular embodiment, the score S i assigned to each communication channel i is a weighted sum of grades n i,j attributed to different metrics j following the evaluation of the transmission conditions of the radio environment with respect to said communication channel i , using predetermined weights α i,j used to favor one metric over another for the communication channel i , so that: S i = ∑ j α i , j . n i , j with ∀ i , ∀ j , ∑ j α i , j = 1

[0014] Thus, the score is easily calculated.

[0015] According to a particular embodiment, when a metric is not observable for the communication channel i , a maximum score is assigned to said metric, or said metric is output from the score calculation without adjusting the weights of the other metrics, or said metric is output from the score calculation by proportionally adjusting the weights of the other metrics to ensure that their sum is equal to 1. Thus, different metrics are easily taken into account for different communication channels and / or for different node devices.

[0016] According to a particular embodiment, the metrics are chosen from: an ambient noise level for the communication channel i ; a quantity of access points detected on the communication channel i , excluding access points of the routing network; a proportion of the time where the communication channel iis seen as free; a rate of retransmitted packets; a quantity of access points, excluding access points in the routing network, using a communication channel adjacent to the communication channel i ; a quantity of access points, excluding access points in the routing network, detected with a power greater than a predetermined threshold. Thus, the range of possible metrics is vast.

[0017] According to a particular embodiment, the master node device determines the gain or loss δ c → t ( k ), for each node device k, to switch from the first communication channel c to a second target communication channel t as follows: δ c → t k = s t k − s c k Or s t ( k ) is the score for the first communication channel c And s t ( k ) is the score for the second target communication channel t .

[0018] According to a particular embodiment, the master node device estimates the gain or loss of using the second target communication channel. t instead of the first communication channel c for the entire routing network, using a cost function as follows: Δ c → t = ∑ k γ k δ c → t k = ∑ k γ k s t k − s c k Or γ k are weighting coefficients defined in order to take into account the type of traffic in progress on the first communication channel c, as reported by each node device k of the routing network. Thus, it is possible to easily prioritize the selection of the appropriate communication channel depending on the traffic concerned.

[0019] According to a particular embodiment, when the master node device has decided whether or not to change the communication channel for the routing network, the node device having initiated the communication channel change evaluation triggers a timeout, during which it is not authorized to initiate a new communication channel change evaluation. Thus, untimely requests for communication channel change are avoided.

[0020] According to a particular embodiment, the master node device performs the following steps: exchange with the other node devices of the routing network to collect information on the capacities to measure such or such metric; select the applicable metrics for the score calculations according to said information; inform the other node devices of the routing network on the metrics to be used for the score calculations. Thus, the metrics to be used can be dynamically defined.

[0021] According to a particular embodiment, the front-end network and the routing network use Wi-Fi type radio interfaces.

[0022] A second method is also provided for selecting a communication channel in a wireless communication network comprising a routing network interconnecting node devices and intended to extend a radio coverage of a wireless front-end network by implementing a plurality of access points of the wireless front-end network. A same first communication channel, selected by a master node device of the routing network, is used in the routing network to interconnect said node devices.The method comprises the following steps performed by a node device of the routing network other than the master node device: performing an evaluation of transmission conditions of its radio environment; calculating, for each communication channel available to said node device, a score representative of a quality of transmission via said communication channel based on the evaluation performed; when at least one second communication channel shows a better score than the first communication channel, initiating with said master node device an evaluation of a change of communication channel in favor of a said second communication channel; waiting for a decision from the master node device to change, or not, the communication channel used in the routing network.

[0023] A third method is also proposed for selecting a communication channel in a wireless communication network comprising a routing network interconnecting node devices and intended to extend a radio coverage of a wireless front-end network by implementing a plurality of access points of the wireless front-end network. A same first communication channel, selected by a master node device of the routing network, is used in the routing network to interconnect said node devices. The method comprises the following steps carried out by the master node device: carrying out an evaluation of transmission conditions of its radio environment; calculating, for each communication channel available to said master node device, a score representative of a transmission quality via said communication channel based on the evaluation carried out.Furthermore, when, from the point of view of the master node device or another node device of the routing network, at least one second communication channel shows a better score than the first communication channel, the third method further comprises the following steps performed by the master node device: obtaining, from each other node device of the routing network, the score of the first communication channel and the score of at least one said second communication channel, to perform a communication channel change evaluation; deciding whether or not to change the communication channel used in the routing network based on the scores obtained.

[0024] Also provided is a computer program product comprising instructions for implementing, by a processor, the second method or the third method, when said program is executed by said processor. Also provided is an information storage medium storing such a computer program product.

[0025] There is also provided a node device for use in a wireless communication network comprising a routing network interconnecting said node device with other node devices and for extending a radio coverage of a wireless front-end network by implementing a plurality of access points of the wireless front-end network. A same first communication channel, selected by a master node device of the routing network, is used in the routing network to interconnect said node devices.The node device in question comprises: means for carrying out an evaluation of transmission conditions of its radio environment; means for calculating, for each communication channel available to said node device, a score representative of a quality of transmission via said communication channel according to the evaluation carried out; when at least one second communication channel shows a better score than the first communication channel, means for initiating with said master node device an evaluation of a change of communication channel in favor of a said second communication channel; means for waiting for a decision from the master node device to change, or not, the communication channel used in the routing network.

[0026] There is also provided a master node device intended to be used in a wireless communication network comprising a routing network interconnecting node devices and intended to extend a radio coverage of a wireless front-end network by implementing a plurality of access points of the wireless front-end network. A same communication channel, selected by the master node device, is used in the routing network to interconnect said node devices. The master node device comprises: means for carrying out an evaluation of transmission conditions of its radio environment; means for calculating, for each communication channel available to said master node device, a score representative of a quality of transmission via said communication channel according to the evaluation carried out.Furthermore, when, from the point of view of the master node device or another node device of the routing network, at least one second communication channel shows a better score than the first communication channel, the master node device further comprises: means for obtaining, from each other node device of the routing network, the score of the first communication channel and the score of at least one said second communication channel, to carry out an evaluation of change of communication channel; means for deciding whether or not to change the communication channel used in the routing network according to the scores obtained.

[0027] According to a particular embodiment, the master node device is a residential gateway.

[0028] Also provided is a wireless communication network comprising a routing network interconnecting a master node device and node devices as discussed above, for extending a radio coverage of a wireless front-end network by implementing a plurality of access points of the wireless front-end network. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above-mentioned features of the invention, as well as others, will appear more clearly on reading the following description of at least one exemplary embodiment, said description being made in relation to the attached drawings, among which: [ Fig. 1 ] schematically illustrates a wireless communication network arrangement, in which the present invention can be implemented; [ Fig. 2 ] schematically illustrates an example of a hardware arrangement of a node device usable within the framework of the wireless communication network of the Fig. 1 ; [ Fig. 3A ] schematically illustrates a first example of exchanges within the framework of a selection of communication channel in the wireless communication network of the Fig. 1 ; [ Fig. 3B ] schematically illustrates a second example of exchanges within the framework of a selection of communication channel in the wireless communication network of the Fig. 1 ; And [ Fig. 4 ] schematically illustrates a third example of exchanges within the framework of a selection of communication channel in the wireless communication network of the Fig. 1 . DETAILED PRESENTATION OF IMPLEMENTATION METHODS

[0030] There Fig. 1 schematically illustrates a wireless communication network arrangement, in which the present invention can be implemented. Preferably, the wireless communication network is a WLAN 100 wireless local area network. The WLAN forms a radio coverage extension system built around a backhaul network (as already indicated) comprising a set of node devices. In the illustrative arrangement of the Fig. 1 , a first node device is included in a residential gateway RGW 110 and a set of second node devices are included in extenders EXT1, EXT2, EXT3 120. The set of extenders EXT1, EXT2, EXT3 120 makes it possible to extend the radio coverage of the WLAN 100 wireless local area network compared to the sole installation of the residential gateway RGW 110. In one embodiment, the residential gateway RGW 110 and the extenders EXT1, EXT2, EXT3 are arranged to create a mesh WLAN wireless local area network.

[0031] The residential gateway RGW 110 comprises a WIF connection interface 113 designed to connect the residential gateway RGW 110 to a wide area network WAN 101, such as the Internet. The WIF connection interface 113 is, for example, an ADSL (Asynchronous Digital Subscriber Line) type interface, a VDSL (Very-high-bit-rate Digital Subscriber Line) type interface or an FTTH (Fiber To The Home) type interface.

[0032] The RGW 110 residential gateway acts as the master node device in the routing network, but any other node device in the routing network can alternatively act as the master node device. As detailed later, the master node device selects the communication channel to be used in the routing network.

[0033] The residential gateway RGW 110 has a first radio interface WLAN_IF1 111 carrying an access point AP1.1 forming part of a fronthaul network setup (as already indicated) identified by an identifier SSID1 and using a communication channel Ch_a. The residential gateway RGW 110 has a second radio interface WLAN_IF2 112 carrying an access point AP2.1 and an access point AP2.2. The access point AP2.1 of the second radio interface WLAN_IF2 112 of the residential gateway RGW 110 is part of the fronthaul network setup identified by the identifier SSID1, and uses a communication channel Ch_b. The AP2.2 access point of the second radio interface WLAN_IF2 112 of the residential gateway RGW 110 is part of the routing network setup, identified by an SSID2 identifier, and also uses the communication channel Ch_b. The AP2.1 and AP2 access points.2 use the same communication channel Ch_b since they are both embedded in the same radio interface WLAN_IF2 112 of the residential gateway RGW 110.

[0034] The EXT1 120 extender has a first radio interface WLAN_IF1 111 carrying an AP1.1 access point forming part of the setup of the front-end network identified by the identifier SSID1 using the communication channel Ch_a. The EXT1 120 extender has a second radio interface WLAN_IF2 112 carrying a bSTA2.1 station functionality connected via the communication channel Ch_b to the AP2.2 access point of the second radio interface WLAN_IF2 112 of the residential gateway RGW 110 for the setup of the routing network. The second radio interface WLAN_IF2 112 of the EXT1 120 extender also carries an AP2.1 access point and an AP2.2 access point. The AP2.1 access point of the second radio interface WLAN_IF2 112 of the EXT1 120 extender is part of the front-end network setup identified by the SSID1 identifier, and uses the communication channel Ch_b. The AP2.1 access point.2 of the second radio interface WLAN_IF2 112 of the extender EXT1 120 is also part of the routing network setup, identified by the identifier SSID2, and also uses the communication channel Ch_b. The station bSTA2.1 and the access points AP2.1 and AP2.2 use the same communication channel Ch_b since they are all three embedded in the same radio interface WLAN_IF2 112 of the extender EXT1 120.

[0035] The EXT2 120 extender has a first radio interface WLAN_IF1 111 carrying an access point AP1.1 forming part of the setup of the front-end network identified by the identifier SSID1 using a communication channel Ch_c. The EXT2 120 extender has a second radio interface WLAN_IF2 112 carrying a bSTA2.1 station functionality connected via the communication channel Ch_b to the access point AP2.2 of the second radio interface WLAN_IF2 112 of the residential gateway RGW 110 for the setup of the routing network. The second radio interface WLAN_IF2 112 of the EXT2 120 extender also carries an access point AP2.1 and an access point AP2.2. The AP2.1 access point of the second radio interface WLAN_IF2 112 of the EXT2 120 extender is part of the front-end network setup identified by the SSID1 identifier, and uses the communication channel Ch_b. The AP2.1 access point.2 of the second radio interface WLAN_IF2 112 of the extender EXT2 120 is also part of the routing network setup, identified by the identifier SSID2, and also uses the communication channel Ch_b. The station bSTA2.1 and the access points AP2.1 and AP2.2 use the same communication channel Ch_b because they are all three embedded in the same radio interface WLAN_IF2 112 of the extender EXT2 120.

[0036] The EXT3 120 extender has a first radio interface WLAN_IF1 111 carrying an AP1.1 access point forming part of the setup of the front-end network identified by the identifier SSID1 using a communication channel Ch_d. The EXT3 120 extender has a second radio interface WLAN_IF2 112 carrying a bSTA2.1 station functionality connected via the communication channel Ch_b to the AP2.2 access point of the second radio interface WLAN_IF2 112 of the EXT1 120 extender for the setup of the routing network. The second radio interface WLAN_IF2 112 of the EXT3 120 extender also carries an AP2.1 access point and an AP2.2 access point. The AP2.1 access point of the second radio interface WLAN_IF2 112 of the EXT3 120 extender is part of the front-end network setup identified by the SSID1 identifier, and uses the communication channel Ch_b. The AP2.1 access point.2 of the second radio interface WLAN_IF2 112 of the EXT3 120 extender is also part of the routing network setup, identified by the SSID2 identifier, and also uses the communication channel Ch_b. The bSTA2.1 station and the AP2.1 and AP2.2 access points use the same communication channel Ch_b because they are all three embedded in the same radio interface WLAN_IF2 112 of the EXT3 120 extender.

[0037] The WLAN_IF1 111 radio interfaces are, for example, of the Wi-Fi (registered trademark) type operating in the 2.4 GHz band and the WLAN_IF2 112 radio interfaces are, for example, of the Wi-Fi (registered trademark) type operating in the 5 GHz band. In certain embodiments, the WLAN_IF1 111 and WLAN_IF2 112 radio interfaces are respectively compatible with certain amendments to the IEEE 802.11 family of standards. These amendments are, for example, and without limitation, IEEE 802.11n, IEEE 802.11ac, IEEE 802.11ax, IEEE 802.1 1be.

[0038] The choice of the communication channel Ch_b to support the routing network is made by the master node device. This choice is then imposed on all the AP access points embedded in the WLAN_IF2 radio interfaces 112, as already explained. The master node device adapts this choice according to exchanges with the other node devices of the routing network, as explained below in relation to the Figs. 3A And 3B .

[0039] There Fig. 2 schematically illustrates an example of hardware arrangement of a node device 200 usable within the framework of the WLAN 100 wireless local area network. The first node device can be implemented according to the example arrangement of the Fig. 2 . Each of the second node devices can be made according to the arrangement example of the Fig. 2 .

[0040] The node device 200 comprises, connected by a communication bus 210: a CPU processor 201; a RAM (Random Access Memory) 202; a ROM (Read Only Memory) 203 or a Flash memory; a storage unit or a storage media reader, such as an SD (Secure Digital) card reader 204 or a HDD (Hard Disk Drive); and at least one COM communication interface 205 (eg, as illustrated in the Fig. 1 ) which includes the aforementioned radio interfaces.

[0041] The CPU processor 201 is capable of executing instructions loaded into the RAM memory 202 from the ROM memory 203 or Flash memory, from an external memory (such as an SD card), from a storage medium (such as a hard disk drive HDD), or from a communication network. When the node device 200 is powered on, the CPU processor 201 is capable of reading instructions from the RAM memory 202 and executing them. These instructions form a computer program causing the CPU processor 201 to execute some or all of the behaviors, algorithms, and steps described herein.

[0042] Thus, all or part of the behaviors, algorithms and steps described herein may be implemented in software form by executing a set of instructions by a programmable machine, such as a DSP (Digital Signal Processor) or a microcontroller or a processor. All or part of the behaviors, algorithms and steps described herein may also be implemented in hardware form by a machine or a component (chip), such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit). Thus, the node device 200 comprises electronic circuitry adapted and configured to implement the behaviors, algorithms and steps described herein.

[0043] There Fig. 3A schematically illustrates an example of exchanges within the framework of a selection of communication channel in the wireless local area network WLAN 100. More particularly, the exchanges of the Fig. 3A operate within the framework of a selection of communication channel to be used to support the routing network, when a node device of the routing network other than the master node device assesses that another communication channel would be, from its point of view, more suitable to support the routing network and / or a front network operating on the same channel as said routing network in view of the transmission conditions (transmission and / or reception) of its radio environment.

[0044] Before the exchanges of the Fig. 3A , a communication channel has been selected by the master node device. This communication channel may have been preconfigured, for example at the factory, within the master node device, or selected at startup of the master node device.

[0045] Based on the illustration of the Fig. 1 , when the AP2.2 access point of the RGW 110 residential gateway is activated, the communication channel Ch_b is used to set up the backhaul network identified by the SSID2 identifier. The bSTA2.1 station functionality of the EXT1 120 extender, which is within radio range of the RGW 110 residential gateway, recognizes the SSID2 identifier broadcast in the beacons emitted by the AP2.2 access point of the RGW 110 residential gateway and connects to the AP2.2 access point of the RGW 110 residential gateway via the communication channel Ch_b. The same applies to the bSTA2.1 station functionality of the EXT2 120 extender. After exchanging the information necessary for setting up the routing network (such as the SSID2 identifier and potential security data), the AP2.2 access points of the EXT1 and EXT2 120 extenders are activated, which enables the bSTA2 station functionality.1 of the EXT3 120 extender, which is within radio range of the EXT1 120 extender, to connect to the AP2.2 access point of the EXT1 120 extender via the communication channel Ch_b. For illustration purposes, consider that the communication channel Ch_b is the communication channel “36”.

[0046] The node devices of the routing network regularly perform evaluations of the transmission conditions (transmission and / or reception) of their radio environment. Thus, in a step 301, the extender EXT1 120 preferably performs a scan of its radio environment. This scan comprises operations of scanning different communication channels available to the radio interface WLAN_IF2 112 and of evaluating the quality of transmission via these different communication channels using one or more predefined metrics. Such metrics are, for example, a level of ambient noise perceptible on the communication channel in question, a quantity of access points AP which do not belong to the routing network and which are detected via their beacons transmitted as using the communication channel in question, an vacancy or occupancy rate of the communication channel in question.Other metrics can be used regarding the currently used communication channel (Ch_b in our example), such as a transmission error rate or a retransmission rate. A history of events relating to these metrics can be built, with timestamps and relevance duration management of said events, in order to enrich or refine these metrics. Still other metrics can be used, such as the quantity of AP access points (excluding AP access points of the routing network) using a communication channel adjacent to the communication channel considered, in order to take into account aggregation possibilities, or the quantity of AP access points (excluding AP access points of the routing network) detected with a power greater than a predetermined threshold, in order to estimate the quantity of very close neighboring AP access points (and therefore affecting transmissions more than the others).

[0047] At the end of these evaluations of transmission conditions of their radio environment, the node device in question constructs a descriptor, for example a list or a table, where each communication channel is associated with a score representative of a transmission quality via the communication channel in question. A timestamp information, i.e., indicating when this communication channel was evaluated, is preferentially added to it. For example, the higher the score, the more adequate the communication channel is considered.

[0048] The score S i assigned to each communication channel i can be a weighted sum of grades n i,j attributed to the different metrics j by evaluating transmission conditions via said communication channel i, the notes n i,j having the same possible amplitude (eg, from 0 to 100), using predetermined weights α i,j used to favor one metric over another for the communication channel i in question, so that: S i = ∑ j α i , j . n i , j with ∀ i , ∀ j , ∑ j α i , j = 1

[0049] It is also possible to apply predefined weights α j to each metric, regardless of the communication channel i evaluated, which gives: S i = ∑ j α j . n i , j with ∀ j , ∑ j α j = 1

[0050] In a particular embodiment, when a metric is not observable for a communication channel i , the node device in question may assign it the maximum score, or remove the metric in question from the score calculation without adjusting the weights of the other metrics, or remove the metric in question from the score calculation by proportionally adjusting the weights of the other metrics to ensure that their sum is equal to 1.

[0051] For example, the following metrics can be considered (with their rating from 0 to 5): Table 1 Ambient noise level measured in dBm µ Note -65dBm ≤ µ 0 -70 dBm ≤ µ < -65dBm 1 -75 dBm ≤ µ < -70 dBm 2 -80dBm ≤ µ < -75 dBm 3 -85 dBm ≤ µ < -80 dBm 4 µ < -85dBm 5 Table 2 Number of AP access points detected v (excluding routing network access points) Note 15 < v 0 12 ≤ v < 15 1 9 ≤ v < 12 2 6 ≤ v < 9 3 3 ≤ v < 6 4 v < 3 5 Table 3 Proportion of time the communication channel is seen as free, in percentage TXOP Note TXOP < 5 0 5 ≤ TXOP < 25 1 25 ≤ µ < 45 2 45 ≤ v < 65 3 65 ≤ v < 85 4 85 < TXOP 5 Table 4 Rate of packets retransmitted per 100 packets transmitted as a percentage r tx Note 30 < r tx 0 25 ≤ r tx < 30 1 20 ≤ r tx < 25 2 15 ≤ r tx < 20 3 10 ≤ r tx < 15 4 r tx < 10 5

[0052] Considering, still for illustrative purposes, the following values ​​of the metrics observed on the communication channels “36”, “48”, “100” (which are not numerical references of the attached drawings), the communication channel “36” being, at the time when the transmission conditions evaluation is carried out, the communication channel Ch_b configured for the WLAN_IF2 radio interface 112 considered: Table 5 Canal de communication µ v TXOP r tx 36 -88 dBm 16 40% 33% 48 -90 dBm 1 2% 100 -84 dBm 4 80%

[0053] So, if the same weight is given to these metrics for all communication channels (∀ i , ∀ j , α i,j = 0.25), and a maximum score is assigned to an unknown metric, then the following scores and grades are obtained: Table 6 Canal de communication note ( µ ) note ( v ) note ( TXOP ) note ( r tx ) score s i 36 5 0 2 0 1,75 48 5 5 0 5 3,75 100 4 4 4 5 4,25

[0054] On the Fig. 3A , in a step 301, the EXT1 extender 120 performs the aforementioned transmission condition evaluation (eg, scan operation) and calculates the score S i assigned to each communication channel i available to its WLAN_IF2 112 radio interface. If the communication channel "36" shows a score higher than or equal to that of each of the other communication channels, the EXT1 120 extender waits to have to repeat the transmission condition evaluations (e.g., scan operation). In the meantime, the EXT1 120 extender maintains any information necessary for the metrics used for the score calculation S i (rate of packets retransmitted on the communication channel "36"...). Consider that, as illustrated in the tables above, the communication channel "36" shows a score lower than that of at least one other communication channel, here the communication channel "100". Then, in a step 302, the EXT1 extender 120 transmits to the residential gateway RGW 110, as master node device, a CHG_REQ message requesting the change of the communication channel used by the routing network. Thus, the EXT1 extender 120 does not decide by itself to change the configuration of the AP access points of its WLAN_IF2 radio interface 112 to use a better communication channel. It refers to the master node device.

[0055] The CHG_REQ message includes at least information indicating which communication channel has the best score (target communication channel) for the EXT1 extender 120, what its score is, and what the score of the currently used communication channel is. Optionally, the CHG_REQ message includes timestamp information, indicating when each communication channel was evaluated. In a preferred embodiment, the CHG_REQ message lists all the communication channels that obtained a better score than the currently used communication channel, as well as their respective scores, and does not give the score obtained by each of the communication channels for which this score is worse than that of the currently used communication channel.

[0056] Optionally, the CHG_REQ message includes information about the type of traffic currently being used for each indicated communication channel and the associated quality of service. For example, one possible implementation is a bitmap where each bit is associated with a quality of service (type Best Effort (BE) / Background (BK) / Video (VI) / Voice (VO)) and is set to 1 if traffic associated with this quality of service has recently occurred (within a predetermined observation window, the observation duration of which may also be indicated in the CHG_REQ message) and / or is currently being used, or to 0 otherwise.Instead of one bit per quality of service, the CHG_REQ message may include a counter incremented each time a flow associated with that quality of service is opened and decremented each time a flow associated with that quality of service is closed or each time a group acknowledgment ("Block Ack agreement" in the terminology of the IEEE 802.11 family of standards) is negotiated for that quality of service.

[0057] Following the sending of the CHG_REQ message, the EXT1 extender 120 waits for a decision from the master node device to change, or not, the communication channel used in the routing network (and consequently on the front network operated by the same radio interface).

[0058] In a step 303, the residential gateway RGW 110 probes the other node devices to determine whether a change of communication channel would be appropriate. To do this, the residential gateway RGW 110 transmits an SC_RQ message to them. The SC_RQ message instructs each node device receiving it to perform transmission condition assessments of its radio environment and to return the score of the communication channels concerned. In a particular embodiment, the SC_RG message identifies each communication channel indicated in the CHG_REQ message. The transmission condition assessments are thus limited to the communication channels that can provide a benefit to the extender EXT1 120 and to the communication channel currently in use.In another particular embodiment, each node device receiving the SC_RG message must perform transmission condition evaluations for all the communication channels available to its WLAN_IF2 radio interface 112. In yet another particular embodiment, if the node device receiving the SC_RQ message has already performed transmission condition evaluations for each of the communication channels indicated in the SC_RQ message at a time t0 prior to the time t1 of reception of the SC_RQ message and if the difference t1 - t0 is less than a threshold ΔT preferably included in the SC RQ message, then the node device in question returns the score of the communication channels concerned without having to re-evaluate the transmission conditions via said communication channels.

[0059] In a step 304, the residential gateway RGW 110 also performs the evaluations of transmission conditions (e.g., scan operation) of its radio environment and performs the corresponding score calculations. The extenders EXT2 and EXT3 120 do the same in respective steps 305 and 307. In steps 306 and 308, the extenders EXT2 and EXT3 120 respectively transmit to the residential gateway RGW 110 SC_RSP responses including the scores for the communication channels concerned. The SC_RSP responses preferably include the same information with respect to said communication channels as the CHG_REQ message (but from the point of view of the extenders EXT2 and EXT3 120).

[0060] If the communication channel c is the currently used communication channel (current communication channel) and the communication channel t is the target communication channel, then the master node device has, at least, for each node devicek, of the score s c ( k ) for the communication channel c and the score s t ( k ) for the communication channel t.

[0061] The master node device determines the gain or loss for all node devices k to switch from communication channel c to communication channel t as follows: δ c → t k = s t k − s c k

[0062] If δ c → t ( k ) is positive, then it is advantageous for the node device k to change the communication channel used in the WLAN_IF2 112 radio interface. On the contrary, if δ c → t ( k ) is negative, then it is disadvantageous for the node device k to change the communication channel used in the WLAN_IF2 112 radio interface.

[0063] Therefore, the master node device estimates the gain of using communication channel t instead of communication channel c for the entire routing network. For example, the following cost function can be evaluated: Δ c → t = ∑ k γ k δ c → t k = ∑ k γ k s t k − s c k where weighting coefficients γ k are defined to take into account the type of traffic currently taking place on the communication channel c, as reported by each node device k. For example: if no traffic γ k =0, if BK traffic γ k =1, if BE traffic γ k =2, if traffic VI γ k =3, and if used traffic γ k =4.

[0064] Other cost functions can of course be applied, for example by excluding the node device that transmitted the CHG_REQ message from its calculation.

[0065] If the cost function Δ c → t is negative, then switch to the communication channel tinstead of the communication channel c would not benefit the routing network.

[0066] In which case, in a step 309, the master node device decides not to grant the request to change the communication channel. In a step 310, the residential gateway RGW 110 then transmits to the extender EXT1 120 a CHG_RSP message representing a negative response to the CHG_RQ message.

[0067] Optionally, in a step 311, the EXT1 extender 120 triggers a timeout, during which the EXT1 extender 120 is not authorized to transmit a CHG_RQ message again to the master node device. The EXT1 extender 120 is thus prevented from making a new request for a change of communication channel until the timeout expires. The timeout may have a predefined duration or a duration set by the master node device in the CHG_RSP message. The master node device may further indicate in the CHG_RSP message whether it instructs the EXT1 extender 120 to trigger said timeout or not.

[0068] Note that the cost function Δ c → tcan be applied for each communication channel indicated in the CHG_RQ message as having obtained, from the EXT1 extender 120, a better score than the communication channel c. If the master node device does not have the scores corresponding to another target communication channel to be checked (because this other target communication channel was not concerned by the SC_RQ messages transmitted in step 303), the master node device repeats sendings of SC_RQ messages at least for this other target communication channel. The master node device can proceed in this way until it finds, or not, a target communication channel which gives a positive result of the cost function Δ c → t. If the master node device fails to find a target communication channel among those listed in the CHG_RQ message that gives a positive result of the cost function Δ c → t, then the master node device decides not to grant the communication channel change request and transmits to the EXT1 extender 120 a CHG_RSP message representative of a negative response to the CHG_RQ message, as shown in the Fig. 3A .

[0069] Unlike the exchanges of the Fig. 3A , the exchanges of the Fig. 3B present a scenario in which the master node device decides to change the communication channel intended to support the routing network. The Fig. 3B repeats steps 301 to 308 as described above. In step 309, the master node device has determined that the target communication channel t indicated in the CHG_RQ message would benefit the routing network (or one of the target communication channels indicated in the CHG_RQ message) instead of the communication channel c. Then, the master node device decides to grant the request to change the communication channel. In a step 350, the residential gateway RGW 110 then transmits to each other node device of the routing network a CHG_INS message instructing it to change the communication channel and to switch to the target communication channel that said master node device has selected. In a step 351, the residential gateway RGW 110 configures its WLAN_IF2 radio interface 112 to communicate via said selected target communication channel instead of the communication channel c.The extenders EXT1, EXT2 and EXT3 120 do the same in respective steps 352, 353 and 354.

[0070] Prior to transmitting the CHG_INS message, the master node device may transmit to the EXT1 extender 120 a CHG_RSP message representing a positive response to the CHG_RQ message. Step 311 is optionally performed by the EXT1 extender after switching the communication channel.

[0071] Preferably, the master node device verifies that all the node devices of the routing network have correctly applied the change of communication channel for their respective WLAN_IF2 112 radio interfaces. The attachments of the node devices to each other may have changed following this change of communication channel, i.e. the routing network has changed topology. If at least one node device is missing following the change of communication channel, then the master node device can either instruct to return to the previously used communication channel to give each node device a chance to re-enter the routing network, or the master node device can either decide to continue operating on the newly configured communication channel.

[0072] There Fig. 4 schematically illustrates another example of exchanges within the framework of a selection of communication channel in the wireless local area network WLAN 100. More particularly, the exchanges of the Fig. 4 operate within the framework of a selection of communication channel to be used to support the routing network, when the master node device evaluates that another communication channel would be, from its point of view, more suitable to support the routing network and / or a front network operating on the same channel as said routing network in view of the transmission conditions (transmission and / or reception) of its radio environment.

[0073] Like the other node devices of the routing network, the master node device regularly performs evaluations of the transmission conditions (transmission and / or reception) of its radio environment. Thus, in a step 401, the residential gateway RGW 110 preferentially performs a scan of its radio environment, as already described. Then, the residential gateway RGW 110 calculates the score S i assigned to each communication channel i available to its WLAN_IF2 radio interface 112. If the communication channel Ch_b currently used for the routing network shows a score higher than or equal to that of each of the other communication channels evaluated, the residential gateway RGW 110 waits to have to repeat the transmission condition evaluations (eg, scan operation). Consider that, as in the context of the Figs. 3A And 3B, at least one other communication channel shows a score higher than the communication channel currently in use to support the routing network. Then, in a step 402, the residential gateway RGW 110 queries the other node devices of the routing network to evaluate the relevance of a change in the communication channel used by the routing network. To do this, the residential gateway RGW 110 transmits the SC_RQ message to them, as already described. Then, the extenders EXT1, EXT2 and EXT3 120 carry out the transmission condition evaluations (eg, scan operation) of their radio environment and carry out the corresponding score calculations in respective steps 403, 405 and 407. In steps 404, 406 and 408, the extenders EXT1, EXT2 and EXT3 120 respectively transmit to the residential gateway RGW 110 the SC_RSP responses including the scores for the communication channels concerned, as already described.

[0074] In a step 409, the master node device decides, based on the scores obtained, whether or not to change the communication channel used to support the routing network. If the master node device decides not to change the communication channel, the exchanges are interrupted here, until any node device of the routing network detects that another communication channel is more suitable than the one currently in use to support the routing network. The master node device may apply a time delay (step 415) during which the residential gateway RGW 110 refrains from initiating a new evaluation of a change of communication channel used to support the routing network.If the master node device decides to change communication channel, the residential gateway RGW 110 then transmits to each other node device of the routing network, in a step 410, the message CHG_INS instructing to change communication channel and to switch to the target communication channel that said master node device has retained. In a step 411, the residential gateway RGW 110 configures its radio interface WLAN_IF2 112 to communicate via said retained target communication channel. The extenders EXT1, EXT2 and EXT3 120 do the same in respective steps 412, 413 and 414. The master node device can then apply, or not, the time delay of step 415.

[0075] An alternative to the Fig. 4 is that the master node device internally transmits a CHG_REQ message, when it wishes to initiate an evaluation of a communication channel change to support the routing network. The resulting sequence of steps is then easily derivable from the description of the Figs. 3A And 3B .

[0076] In a particular embodiment, the master node device communicates with the other node devices of the routing network to collect information on the capabilities of measuring a particular metric. The master node device can thus select the applicable metrics for the score calculations based on this information. The master node device then informs the other node devices of the routing network about the metrics to be used for the score calculations. This makes it possible to dynamically define which metrics to use in a context where the node devices of the routing network are of various designs.

[0077] In a particular embodiment, conversion tables for scaling are used by the master node device. When the master node device examines a score calculated by a node device in the routing network, the master node device performs, using the conversion tables, a scaling of the score to ensure that all scores are calculated on the same reference frame. In this case, each node device that transmits a score to the master node device indicates, in association with said score, a minimum value and a maximum possible value for said score. This allows the use of radio interfaces that track their metrics and perform score calculations in various ways.

Claims

1. Method for selecting a communication channel in a wireless communication network comprising a backhaul network interconnecting node devices and intended to extend a radio coverage of a wireless fronthaul network by using a plurality of access points of the wireless fronthaul network, wherein one and the same first communication channel, selected by a master node device of the backhaul network, is used in the backhaul network to interconnect said node devices, characterised in that the method comprises the following steps performed by each node device of the backhaul network: - making (301) an evaluation of transmission conditions of its radio environment, - calculating (301), for each communication channel available to said node device, a score representing a quality of transmission via said communication device according to the evaluation made, and in that when, from the point of view of a said node device of the backhaul network, at least one second communication channel shows a better score than the first communication channel, the method further comprises the following steps performed by the master node device: - obtaining (309), from each node device of the backhaul network, the score of the first communication channel and the score of at least one said second communication channel, to make an evaluation of change of communication channel; - deciding to change (309), or not, communication channel used in the backhaul network, according to the scores obtained.

2. Method according to claim 1, wherein, following the evaluation of transmission conditions of its radio environment, when a node device other than the master node device assesses that at least one second communication channel shows a better score than the first communication channel, the node device in question transmits to said master node device a message requesting change of communication channel including at least an identifier of said at least one second communication channel that obtained the better score and its score, as well as the score obtained by the first communication channel, and wherein the master node device sounds each of the node devices of the backhaul network other than the one that transmitted said message requesting change of communication channel in order to obtain the score of each communication channel to which the message requesting change of communication channel refers.

3. Method according to claim 1 or 2, wherein the score Si attributed to each communication channel i is a weighted sum of marks ni,j attributed to various metrics j following the evaluation of the transmission conditions of the radio environment with respect to said communication channel i, using predetermined weights αi,j serving to privilege one metric rather than another for the communication channel i, so that: S i = ∑ j α i , j . n i , j with ∀ i , ∀ j , ∑ j α i , j = 1 4. Method according to claim 3, wherein, when a metric is not observable for the communication channel i, a maximum mark is attributed to said metric, or said metric is taken out of the score calculation without adjusting the weight of the other metrics, or said metric is taken out of the score calculation while proportionally adjusting the weights of the other metrics in order to ensure that the sum thereof is equal to 1.

5. Method according to claim 3 or 4, wherein the metrics are selected from: - an ambient noise level for the communication channel i, - a quantity of access points detected on the communication channel i, apart from access points of the backhaul network, - a proportion of the time where the communication channel i is seen as free, - a proportion of packets retransmitted, - a quantity of access points, apart from access points of the backhaul network, using a communication channel adjacent to the communication channel i, - a quantity of access points, apart from access points of the backhaul network, detected with a power above a predetermined threshold.

6. Method according to any one of claims 1 to 5, wherein the master node device determines the gain or loss δc→t(k), for each node device k, in switching from the first communication channel c to a target second communication channel t in the following manner: δ c → t k = s t k − s c k where st(k) is the score for the first communication channel c and st(k) is the score for the target second communication channel t.

7. Method according to claim 6, wherein the master node device estimates the gain or the loss in using the target second communication channel t in place of the first communication channel c for the whole of the backhaul network, by means of a cost function as follows: Δ c → t = ∑ k γ k δ c → t k = ∑ k γ k s t k − s c k where γk are weighting coefficients defined in order to take into account the type of traffic taking place on the first communication channel c, as reported by each node device k of the backhaul network.

8. Method according to any one of claims 1 to 7, wherein, when the master node device has decided to change, or not, communication channel for the backhaul network, the node device that initiated the evaluation of change of communication channel triggers a time delay, during which it is not enabled to initiate a new evaluation of change of communication channel.

9. Method for selecting a communication channel in a wireless communication network comprising a backhaul network interconnecting node devices and intended to extend a radio coverage of a wireless fronthaul network by using a plurality of access points of the wireless fronthaul network, wherein the same first communication channel, selected by a master node device of the backhaul network, is used in the backhaul network to interconnect said node devices, characterised in that the method comprises the following steps performed by a node device of the backhaul network other than the master node device: - making (301) an evaluation of transmission conditions of its radio environment, - calculating (301), for each communication channel available to said node device, a score representing a quality of transmission via said communication channel according to the evaluation made, - when at least one second communication channel shows a better score than the first communication channel, initiating, with said master node device, an evaluation of change of communication channel in favour of a said second communication channel; - awaiting a decision of the master node device to change, or not, communication channel used in the backhaul network.

10. Computer program product comprising instructions for implementing, by a processor, the method according to claim 9, when said program is executed by said processor.

11. Information storage medium storing a computer program comprising instructions for implementing, by a processor, the method according to claim 9, when said program is read and executed by said processor.

12. Node device intended to be used in a wireless communication network comprising a backhaul network interconnecting said node device with other node devices and intended to extend a radio coverage of a wireless fronthaul network by using a plurality of access points of the wireless fronthaul network, wherein the same communication channel, selected by a master node device of the backhaul network, is used in the backhaul network for interconnecting said node devices, characterised in that it comprises: - means for making an evaluation of transmission conditions of its radio environment, - means for calculating, for each communication channel available to said node device, a score representing a quality of transmission via said communication channel according to the evaluation made, - when at least one second communication channel shows a better score than the first communication channel, means for initiating, with said master node device, an evaluation of change of communication channel in favour of a said second communication channel; - means for awaiting a decision of said master node to change, or not, communication channel used in the backhaul network.

13. Master node device intended to be used in a wireless communication network comprising a backhaul network interconnecting node devices and intended to extend a radio coverage of a wireless fronthaul network by using a plurality of access points of the wireless fronthaul network, wherein one and the same first communication channel, selected by the master node device, is used in the backhaul network for interconnecting said node devices, characterised in that it comprises: - means (301) for making an evaluation of transmission conditions of its radio environment; - means (301) for calculating, for each communication channel available to said master node device, a score representing a quality of transmission via said communication channel according to the evaluation made, and in that when, from the point of view of the master node device or of another node device of the backhaul network, at least one second communication channel shows a better score than the first communication channel, the master node device further comprises: - means (309) for obtaining, from each other node device of the backhaul network, the score of the first communication channel and the score of at least one said second communication channel, for making an evaluation of change of communication channel; - means (309) for deciding to change, or not, communication channel used in the backhaul network according to the scores obtained.

14. Wireless communication network comprising a backhaul network interconnecting node devices according to claim 12 and a master node device according to claim 13, for extending a radio coverage of a wireless fronthaul network by using a plurality of access points of the wireless fronthaul network.