Patent Publication Number: US-2021195516-A1

Title: Method for switching off a communication network

Description:
TECHNICAL FIELD 
     The present invention relates to a method for switching off at least part of a wide-area communication network, the wide-area communication network comprising a plurality of wireless networks referred to as fronthaul networks. 
     PRIOR ART 
     In a communication network such as a home network, the use of extenders can extend the range of the home network to remote areas such as various rooms in a house. An extender is an access point of the communication network that manages a wireless network referred to as a fronthaul network with which terminals or stations can be associated and which is moreover connected to a so-called backhaul network. The backhaul network makes it possible to interconnect together the access points of the communication network, whether by cable and/or by wireless. 
     By disposing, in various rooms in a house, a plurality of access points each emitting a fronthaul network, it is thus possible to provide wireless access to the communication network in various zones. In this way, stations such as a printer, a connected socket, a connected bulb or a television can be connected to the communication network even if they are situated remote from each other. In addition, a mobile station such as a telephone or a tablet can easily remain connected to the communication network while moving in the various rooms in a house. 
     However, the improvement in coverage of a wireless network permitted by the use of a plurality of extenders broadcasting fronthaul networks gives rise to additional energy consumption and additional emission of electromagnetic radiation that are often unnecessary. This is because a user is not continuously at home. Consequently it is not necessary to continuously maintain all the coverage of the wireless network in an optimum manner. 
     It is possible to switch off fronthaul networks according to defined time ranges, but this solution may prove to be constraining in a multiuser environment or in cases of use of connected objects requiring connectivity that is not easily predictable. 
     It is desirable to overcome these drawbacks of the prior art. It is in particular desirable to provide a solution that makes it possible to limit energy consumption and emission of electromagnetic radiation while providing a service affording optimum use according to the user requirements. 
     DISCLOSURE OF THE INVENTION 
     One object of the present invention is to propose a method for switching off at least part of a communication network, the communication network comprising a plurality of access points coordinated in a centralised fashion by a master device, the access points and the master device being interconnected with each other by a backhaul network, each access point managing a wireless network known as a fronthaul network, a station being able to be associated with a fronthaul network of the communication network. The method is implemented by the master device and comprises:
         obtaining, from each access point, at least one item of information relating to each station in the communication network associated with said access point or which is dissociated from said access point, said at least one item of information obtained comprising association information indicating with which fronthaul network the station is associated or from which fronthaul network the station is dissociated,   determining, for each station in the communication network, whether the station is present or absent according to the association information,   initiating a phase of switching off at least one fronthaul network when all the stations are ab sent.       

     According to a particular embodiment, said at least one item of information obtained further comprising information representing a signal level received by the access point coming from the station, said method further comprises:
         determining, for each station in the communication network, whether the station is mobile or fixed according to a variation in the received signal level coming from the station,   determining, for each absent mobile station, the last fronthaul network with which the station was associated according to the association information, said last fronthaul network being said to be critical,       

     and wherein initiating a phase of switching off at least one fronthaul network when all the stations are absent comprises initiating a phase of switching off at least one non-critical fronthaul network when all the mobile stations are absent. Thus the reassociation of the mobile stations is facilitated in zones where the probability of reassociation is the highest. 
     According to a particular embodiment, the step of the method for determining, for each station in the communication network, whether the station is mobile or fixed according to a variation in the received signal level comprises: comparing a standard deviation of a set of a plurality of averages of the received signal level with a predefined threshold, each average being calculated over a period with a duration different from the other periods, and determining that the station is mobile in the case where the standard deviation of all the averages is higher than said threshold and that the station being fixed otherwise. 
     According to a particular embodiment, determining, for each station in the communication network, whether the station is mobile or fixed according to a variation in the received signal level comprises: comparing an instantaneous value of the received signal level at a given instant with an average value of the received signal level calculated over a period of time preceding said given instant and determining that the station is mobile in the case where the instantaneous value of the received signal level is lower than a difference of the average value minus a first predefined threshold or in the case where the instantaneous value of the received signal level is higher than a sum of the average value and a predefined second threshold. 
     According to a particular embodiment, the phase of switching off at least one non-critical fronthaul network comprises switching off a non-critical fronthaul network if no station is associated with said non-critical fronthaul network. 
     Thus the switching off of the fronthaul networks is adapted to the temporary requirements of the associated stations. The power consumption of the communication network and the emission of electromagnetic waves can then be limited while guaranteeing optimum use adapted to the requirements of a user. 
     According to a particular embodiment, said at least one item of information obtained also comprising information representing a bit rate of data exchanged by said station with an access point and/or information representing a quality of service of the data exchanged by said station with an access point and/or information representing a connection request intended for the station, the method comprises:
         determining, for each fixed station in the communication network, whether said station is managing critical or non-critical traffic, according to said information representing a data rate and/or a quality of service and/or said information representing a connection request,       

     and wherein the switching-off phase comprises:
         for each non-critical fronthaul network with which only one or more fixed stations managing non-critical traffic are associated, making an attempt at switching said fixed stations in order to transfer them from their original fronthaul network to another not switched-off fronthaul network.       

     It is thus possible to reduce the power consumption and the transmission of electromagnetic waves of the communication network without this impairing a quality of service provided to the user by switching off fronthaul networks with which stations are associated when said fronthaul networks are easily replaceable. Furthermore, a station that manages high-rate traffic (i.e. above a given threshold) and/or for which an incoming connection has been identified will remain associated with its original fronthaul network, which has a high probability of providing better conditions for access to said station. 
     According to a particular embodiment, determining, for each fixed station in the communication network, whether the station is managing critical or non-critical traffic comprises determining that said fixed station is managing critical traffic in the case where at least one following criterion is met: said station is managing traffic having voice and/or video as a quality of service; the number of packets sent and/or received by said station is above a given threshold; connection requests are transmitted to said station. 
     According to a particular embodiment, the attempt at switching the stations is made, for the stations associated with the non-critical fronthaul networks with which only one or more fixed stations managing non-critical traffic are associated, successively in an order of said fronthaul networks that increases with the number of stations associated with said fronthaul networks, so that switching attempts are first of all made for the stations associated with the fronthaul network the number of associated stations of which is smaller before being made for the stations associated with a fronthaul network the number of associated stations of which is greater. 
     Thus the switching off of the fronthaul networks with which stations are associated is done gradually and makes it possible to optimise the coverage of the communication network according to the requirements of the stations while minimising the number of fronthaul networks switched on. 
     According to a particular embodiment, the master device initiates the switching-off phase after a time-delay period commencing as soon as the last station determined as being mobile is determined as being absent. 
     According to a particular embodiment, the method further comprises, after at least one non-critical fronthaul network has been switched off, switching on the fronthaul networks if a station in the communication network is determined as being mobile and present, a station that connects for the first time to the communication network while associating with a fronthaul network being considered to be mobile by default. 
     Thus the use of a mobile station is privileged. 
     According to a particular embodiment, the switching-off phase further comprises attributing a movement indicator to a fixed station transferred during an attempt at switching from their original fronthaul network to another fronthaul network that is not switched off, and wherein the master device, after at least one non-critical fronthaul network has been switched off: switches on all the fronthaul networks in the case where the traffic managed by a station passes from non-critical to critical and if a transfer indicator is attributed to said station. 
     In a particular embodiment, only the original fronthaul network of said station is switched on in the case where the traffic managed by said station passes from non-critical to critical and if a transfer indicator is attributed to said station. 
     Thus the switching on of the fronthaul networks is adapted to the change in the traffic of the stations. In addition, it is possible to avoid switching on all the fronthaul networks when a station has remained associated with the fronthaul network in question as providing the best conditions for connection to said station. 
     According to a particular embodiment, the method comprises sending a listening instruction to an access point managing a switched-off fronthaul network so as to switch on said fronthaul network in listening mode only, and, in the case where at least one association request coming from a non-associated station is received by said access point, switching on said fronthaul network. 
     Thus a fixed station that was absent at the time of the switching-off phase can reassociate with the communication network even when only switched-off fronthaul networks are potentially accessible to it. 
     The invention also relates to a master device in a communication network, the communication network comprising a plurality of access points coordinated in a centralised manner by the master device, the access points and the master device being interconnected with each other by a backhaul network, each access point managing a wireless network known as a fronthaul network, a station being able to associate itself with a fronthaul network of the communication network. The master device comprises:
         means for obtaining, from each access point, at least one item of information relating to each station in the communication network associated with said access point or which dissociates itself from said access point, said at least one item of information obtained comprising association information indicating with which fronthaul network the station is associated or from which fronthaul network the station is disassociating itself,   means for determining, for each station in the communication network, whether the station is present or absent according to the association information,   means for initiating a phase of switching off at least one fronthaul network when all the stations are absent.       

     According to a particular embodiment, said at least one item of information obtained further comprising information representing a signal level received by the access point coming from the station, said master device further comprises:
         means for determining, for each station in the communication network, whether the station is mobile or fixed according to a variation in the received signal level coming from the station,   means for determining, for each absent mobile station, the last fronthaul network with which the station was associated according to the association information, said last fronthaul network being said to be critical,       

     and wherein said means for initiating a phase of switching off at least one fronthaul network when all the stations are absent are configured to initiate a phase of switching off at least one non-critical fronthaul network when all the mobile stations are absent. 
     The invention also relates to a computer program that comprises instructions for implementing, by a processor, the method mentioned above in any one of the embodiments thereof, when said program is executed by said processor. 
     The invention also relates to an information storage medium storing such a computer program. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the invention mentioned above, as well as others, will emerge more clearly from the reading of the following description of at least one example embodiment, said description being made in relation to the accompanying drawings, among which: 
       [ FIG. 1A ] illustrates schematically a communication network comprising so-called fronthaul networks; 
       [ FIG. 1B ] illustrates schematically the communication network comprising fronthaul networks wherein a part of the fronthaul networks is switched off; 
       [ FIG. 2A ] illustrates schematically a method for switching off at least part of the communication network according to a first embodiment, the switching-off method being performed by a master device of the communication network; 
       [ FIG. 2B ] illustrates schematically a method for switching off at least part of the communication network according to various embodiments, the switching-off method being performed by a master device of the communication network; 
       [ FIG. 3A ] illustrates schematically steps of a switching-off phase of the switching-off method according to a first embodiment; 
       [ FIG. 3B ] illustrates schematically steps of the switching-off phase of the switching-off method according to a second embodiment; 
       [ FIG. 4 ] illustrates schematically steps of the switching-off method subsequent to the switching-off phase; and 
       [ FIG. 5 ] illustrates schematically the hardware architecture of the master device. 
     
    
    
     DETAILED DISCLOSURE OF EMBODIMENTS 
       FIG. 1A  thus illustrates schematically a communication network  100  wherein a method for switching off at least part of said communication network  100  is implemented. 
     The communication network  100  comprises a plurality of access points AP  130 , each access point AP  130  managing at least one wireless network referred to as a fronthaul network  140 . Each fronthaul network  140  can thus cover a geographical zone distinct from the other fronthaul networks  140 , which makes it possible to extend the communication network, for example by covering a plurality of rooms in a house. A plurality of access points AP  130  may be co-located in the same item of equipment, each access point AP  130  managing a fronthaul network in a different frequency band (e.g. 2.4 GHz and 5 GHz). 
     The access points AP  130  are interconnected with each other and interconnected with a master device  110  by a backhaul network  120 . The master device  110  coordinates all the access points AP  130 . The master device  110  can thus collect data exchanged between any access point AP  130  in the backhaul network  120  and a station  150 . The master device  110  can furthermore send, to each access point AP  130 , instructions to switch off or switch on a fronthaul network via the backhaul network  120 . The master device  110  may or may not itself manage one or more fronthaul networks  140 . 
     A station  150  connects to the communication network  100  by associating itself with a fronthaul network  140  managed by one of the access points AP  130 . The station  150  is associated with a fronthaul network  140  after having exchanged messages with the access point AP  130  that manages the fronthaul network  140  according to a conventional association procedure and after having received an association authorisation from said access point AP  130 . Each station  150  that is authorised to associate with one of the fronthaul networks  140  of the communication network is identified uniquely in the communication network  100 , for example by means of its MAC (media access control) address. The master device  110  can thus recognise a station  150  that is associated with a first fronthaul network  140  and then which, by transferring, associates itself with an adjoining fronthaul network  140 . The master device  110  can furthermore recognise a station  150  which, after having disconnected from the communication network by dissociating itself from a fronthaul network  140 , reassociates with said fronthaul network  140  or reassociates with another fronthaul network  140 . 
       FIG. 1B  illustrates schematically the communication network  100  wherein the method for switching off at least part of said communication network  100  is implemented and wherein a part of the fronthaul networks  140  is switched off. 
     Identically to  FIG. 1A , the master device  110  and all the access points AP  130  are interconnected by the backhaul network  120 . 
     However, at least one fronthaul network  140  is switched off. The corresponding access point AP  130  normally managing the fronthaul network  140  switched off thus does not send any corresponding beacon to said fronthaul network  140 . 
     The stations  150  identified in the communication network  100  are associated with the fronthaul networks  140  that have remained switched on. 
       FIG. 2A  illustrates schematically the method for switching off at least part of the communication network  100 , implemented by the master device  110 , according to a first embodiment. 
     In a first step  200 , the master device  110  obtains from the access points AP  130  one or more items of information relating to the stations  150  identified in the communication network  100 . For each station, the information relating to the stations  150  identified in the communication network  100  comprise an identification of the station  150  and association information for the station  150 . The association information for the station  150  comprises an identification of the fronthaul network  140  with which said station  150  has just associated itself or an identification of the fronthaul network  140  from which the station  150  has just disassociated itself. 
     In a step  203 , the master device  110  determines, for each station  150 , whether the station  150  is present or absent. In other words, the master device  110  determines, from the association information, whether at an instant in question a station  150  is associated with a fronthaul network  140  or disassociated from any fronthaul network  140 . 
     In a step  208 , the master device  110  identifies whether all the stations  150  are absent. If at least one station  150  is present, the master device  110  reiterates steps  200  to  203 . If there is no longer any station  150  present, the master device  110  performs a step  214 . 
     In the step  214 , the master device  110  initiates a phase of switching off at least one fronthaul network  140 . 
       FIG. 2B  illustrates schematically the method for switching off at least part of the communication network  100 , implemented by the master device  110 , according to various embodiments. 
     In a first step  200 , the master device  110  obtains, from the access points AP  130 , information relating to the stations  150  identified in the communication network  100 . For each station, the information relating to the stations  150  identified in the communication network  100  comprises an identification of the station  150  and association information for the station  150 . The association information for the station  150  comprises an identification of the fronthaul network  140  with which said station  150  has thus associated itself or an identification of the fronthaul network  140  from which said station  150  has just disassociated itself. In the case where the station  150  is dissociated from any fronthaul network  140 , the association information enables the master device  110  to identify the last fronthaul network  140  with which the station  150  was associated. The information relating to the stations  150  identified in the communication network  100  and associated with a fronthaul network  140  further comprises a received signal level, coming from each station  150 , through the access point AP  130 , such as an RSSI (received signal strength indicator) and information representing a flow rate of data exchanged between the station  150  and the communication network  100  such as for example a number of packets sent and/or received by the station  150 , a quality of service marker indicating whether the station  150  is managing traffic having a voice and/or video quality of service. The master device  110  can furthermore obtain information indicating whether incoming connection requests are transmitted to the station  150 . This may for example be the case for a camera that a user is seeking to control remotely. For each station  150  associated with a fronthaul network  140 , the master device  110  periodically, and throughout the duration of association of the station  150 , obtains the received signal level information, the information representing a flow rate of data exchanged and the information indicating whether incoming connection requests are transmitted to the station  150 . 
     In a following step  202 , the master device  110  determines, for each station  150 , whether said station  150  is fixed or mobile. A station  150  is considered to be mobile if a variation in its signal level or RSSI is above a threshold, and fixed otherwise. 
     According to one embodiment, the variation in the signal level is determined by calculating the standard deviation of a set of averages of the signal level, each average being calculated over a period of predefined duration and distinct from the other periods. For example, the signal level is averaged over a plurality of periods of time the durations of which may be one minute, five minutes, ten minutes, fifteen minutes, thirty minutes and one hour. The standard deviation of all these averages is then compared with a threshold, for example with the threshold of 3%. The corresponding station  150  is considered to be mobile if the standard deviation of the averages is higher than said threshold and fixed otherwise. 
     According to an alternative embodiment, the time is divided up as from the moment when the station  150  associates itself with a fronthaul network into periods equal to a predefined duration. An average value M of the signal level is calculated for each of said periods. An instantaneous value of the signal level denoted RSSI_c, received at each period end, is compared with the average value M calculated over the period preceding said given instant. If the instantaneous value of the signal level is lower than a difference consisting of the average value M minus a first threshold S 1  or if the instantaneous value of the signal level is higher than a sum of the average value M and of a second threshold S 2 , then the station  150  is considered to be mobile. Otherwise the station  150  is considered to be fixed. 
     In other words, a station  150  is considered to be mobile if at least one of the following conditions is met: RSSI_c&lt;M−S 1 , or RSSI_c&gt;M+S 2 . 
     At the moment when a station  150  associates itself with a fronthaul network  140  and until an analysis of the variation in the signal level makes it possible to determine whether said station  150  is fixed or mobile, the station  150  is considered to be fixed if it was fixed at the moment of its previous disassociation from one of the fronthaul networks  140  and considered to be mobile if it was mobile at the moment of its previous disassociation from one of the fronthaul networks  140 . If the station  150  connects for the first time to the communication network  100  and has therefore never been identified in the communication network  100 , said station  150  is considered to be mobile by default. This is the case for example with a new station introduced into the network by a user. 
     In a step  203 , the master device  110  determines, for each station  150 , whether the station  150  is present or absent. In other words, the master device  110  determines, from the association information, whether at a particular instant a station  150  is associated with a fronthaul network  140  or dissociated from any fronthaul network  140 . 
     In an optional step  204 , the master device  110  determines, for each fixed station  150 , whether said station  150  is managing critical or non-critical traffic according to a data flow rate or according to connection requests intended for said station  150 . A fixed station  150  is managing critical traffic if it fulfils at least one of the following criteria. A first criterion is that the station  150  is managing traffic having voice and/or video as its quality of service, this quality of service being identified either at the MAC layer, or at the IP layer, or at the application originating this traffic in the case of use of the Deep Inspection algorithm. This is because a voice and/or video quality of service requires less latency and/or more flow rate than an exchange of information with an email server intended to check the presence of new messages. A second criterion is that the station  150  sends or receives a number of packets above a given threshold, such as for example a threshold of ten packets sent or received per second. A third criterion is that the connection requests are transmitted to the station  150 . The third criterion may be verified by the master device  110  by analysing a table of incoming and outgoing connections underway in the communication network  100 , also referred to as a conntrack table. A conntrack table may be transmitted by each access point AP  130  to the master device  110 . In an alternative embodiment, a conntrack table may be communicated to the master device  110  by an entity responsible for connections such as a gateway external to the communication network  100 . The master device  110  may determine over time whether the traffic of a station  150  is critical or non-critical according to the data received. This information is in particular used by the method described in relation to  FIGS. 3B and 4 . 
     In a step  206 , the master device  110  determines, for each mobile and absent station  150 , the last fronthaul network  140  visited by said station  150 . Each fronthaul network  150  of the communication network  100  can be identified by a unique indicator, such as for example the BSSID (basic service set identifier) for the Wi-Fi/IEEE 802.11 wireless network technology. Such a last fronthaul network  140  visited by a station  150  is said to be a critical fronthaul network  140 . It should be noted that, when a mobile station  150  associates itself with a fronthaul network  140 , for example when a mobile station  150  is determined as being present at the step  203 , the master device  110  deletes, from said station  150 , the last fronthaul network  140  visited that was determined previously, if there was one. The fronthaul network  140  in question is then no longer considered to be critical, unless it is determined as being the last fronthaul network  140  visited by another station  150 . The critical fronthaul networks  140  correspond, at a given moment, to all the last fronthaul networks  140  visited determined for all the mobile and absent stations  150  of the communication network  100 . 
     In a particular embodiment, the master device  110  undertakes a permanent monitoring of the stations  150  and thus determines, as it collects information coming from access points AP  130 , whether a station  150  is fixed or mobile, present or absent, optionally whether it is managing critical or non-critical traffic and furthermore determines the last fronthaul network  140  visited by an absent mobile station. The master device  110  may furthermore identify a change in status, for example if a mobile station  150  becomes fixed or vice versa, if critical traffic managed by a station  150  becomes non-critical, or if a station  150  present becomes absent. In an alternative embodiment, the master device  110  undertakes a periodic monitoring of the stations  150 , for example every ten seconds. 
     In the step  208 , the master device  110  identifies whether all the mobile stations  150  are absent. If at least one mobile station  150  is present, the master device  110  reiterates the steps  200  to  206 . If there is no longer any station  150  present or if only fixed stations  150  are present, the master device  110  performs a step  214 . 
     In a step  214 , the master device  110  initiates a phase of switching off at least one non-critical fronthaul network  140 . As stated in relation to the step  206 , a fronthaul network  140  is considered to be critical at a given moment if it forms part of the last fronthaul networks  140  visited determined for all the mobile stations  150  absent from the communication network  100 . 
     In a particular embodiment, the master device  110  initiates the switching-off phase  214  after a time-delay period, in a step  210 , commencing as soon as the last mobile station  150  present disassociates itself from a fronthaul network  140 . At the end of the time-delay period, the master device  110  checks, in a step  212 , that every station  150  associated with a fronthaul network  140  of the communication network  100  is fixed. If such is the case, the master device  110  initiates the switching-off phase. In the contrary case, for example if a station  150  that is absent and considered to be mobile before the previous disassociation thereof sends a request for association with a fronthaul network  140  of the communication network  100  or if a station  150  that is fixed and present has become mobile, the master device  110  does not initiate the switching-off phase and the steps  200  to  206  are reiterated. Thus the power consumption of the communication network  100  and the sending of electromagnetic waves can be limited while guaranteeing optimum use adapted to the requirements of a user. 
       FIG. 3A  illustrates schematically steps of the switching-off phase of the switching-off method according to a first embodiment. Said steps are performed by the master device  110  when the switching off of at least one fronthaul network  140  is initiated, or in other words during the step  214  described above in relation to  FIG. 2B . 
     During the switching-off phase, the master device  110  identifies, for each fronthaul network  140  of the communication network  100 , whether or not it must be switched off. In a step  302 , the master device  110  identifies, for each fronthaul network  140 , whether said fronthaul network  140  is critical. If such is the case, a step  304  is performed and the fronthaul network  140  is not switched off. Otherwise a step  306  is performed. 
     At the step  306 , the master device  110  identifies, for each remaining fronthaul network  140 , whether at least one fixed station  150  is associated with said fronthaul network  140 . If such is the case, the step  304  is performed and the fronthaul network  140  is not switched off. Otherwise a step  308  is performed and the fronthaul network  140  is switched off. In the step  308 , the master device sends a switching-off instruction to the access point AP  130  that manages the fronthaul network  140  in question so that said access point AP  130  switches off said fronthaul network  140 , typically by stopping sending beacons from said fronthaul network  140  or completely stopping the radio chipset responsible for said fronthaul network  140  if it is the only fronthaul network  140  present in said radio chipset. 
     At the step  304 , the master device  110  may furthermore identify each fronthaul network  140  that is not switched off and must remain switched on. 
     Thus the switching off of the fronthaul networks  140  is adapted according to the temporary requirements of the associated stations  150 . In addition, the reassociation of mobile stations  150  is facilitated in zones where said mobile stations  150  have disassociated themselves for the last time, which correspond to the zones where the probability of reassociation is the highest, as is the case for example for a fronthaul network  140  that is close to the entrance to a dwelling. 
       FIG. 3B  illustrates schematically steps of the switching-off phase of the switching-off method according to a second embodiment. 
     In the step  302  presented above in relation to  FIG. 3A , the master device  110  identifies whether a fronthaul network  140  is a critical fronthaul network  140 . If such is the case, the step  304  is performed and the fronthaul network  140  in question is not switched off. In the contrary case, the step  306  is performed. 
     At the step  306 , previously described in relation to  FIG. 3A , the master device  110  identifies, for each non-critical fronthaul network  140 , whether at least one station  150  is associated with said fronthaul network  140 . If no station  150  is associated, the step  308  is performed and the fronthaul network  140  in question is switched off If at least one station  150  is associated with said fronthaul network  140 , a step  310  is performed. 
     In the step  310 , the master device  110  identifies, for each non-critical fronthaul network  140 , whether, among the associated station or stations  150 , at least one station  150  is managing critical traffic. If at least one station  150  associated with a fronthaul network  140  is managing critical traffic, the step  304  is performed and said fronthaul network  140  is not switched off. Thus a station  150  that is managing traffic at a high rate, such as for example a camera that is exchanging video data, can remain associated with the fronthaul network  140  with which the station  150  has preferentially associated itself, and therefore which has a high probability of providing the best conditions for access to said station  150 . 
     In the contrary case, if, for a fronthaul network  140 , no station  150  that is associated therewith is managing critical traffic, a step  312  is performed. 
     At the step  312 , the master device  110  makes an attempt at switching stations  150  that are associated with the fronthaul networks  140  concerned, i.e. the fronthaul networks  140  that are not switched off, which are not considered to be critical at the step  302  and with which only stations  150  managing non-critical traffic are associated. The switching attempt made by the master device  110  aims to transfer the stations  150  associated with said fronthaul networks  140  concerned to another fronthaul network  140  that is not switched off. 
     In order to make the switching attempt, the master device  110  sends a transfer instruction to the access point AP  130  managing the fronthaul network  140  concerned. On reception of the transfer instruction, said access point AP  130  can use a disassociation frame intended for the station  150  in order to force the station  150  to disassociate itself from the fronthaul network  140 , and then identify the station  150  as being forbidden access to said fronthaul network  140 , for example by entering it in a blacklist. A join request sent by the station  150  to said fronthaul network  140  will be refused or ignored by said fronthaul network  140 . Consequently the station  150  will seek to join another fronthaul network  140  within range of said station  150 . The master device  110  can furthermore check that each station  150  forced to disassociate itself has reassociated with another fronthaul network  140 . If such is not the case, for example when a station  150  does not manage to reassociate itself with another fronthaul network  140 , said station  150  is deleted from the blacklist. Alternatively, the access point AP  130  can use an environment measurement frame in accordance with IEEE 802.11k (Measurement Request/Report) making it possible to identify a fronthaul network  140  that is not switched off within range of said station  150  and/or a transition frame specific to IEEE 802.11v (BSS Transition Management Request/Report) making it possible to request a station  150  to transfer to such a fronthaul network  140 . 
     Alternatively, in order to make the switching attempt, the master device  110  counts the number of stations  150  to be transferred and then sends a switching-off instruction to the access point AP  130 . The master device  110  next checks that each station  150  previously associated with the fronthaul network  140  that has been switched off has associated itself with another fronthaul network  140  that is not switched off in the communication network  100  and, if such is not the case, then the master device  110  sends a switching-on instruction to the access point AP  130 . 
     In a particular embodiment, when an attempt at switching a station  150  results in the transfer of said station  150  from a fronthaul network  140  referred to as the original fronthaul network  140  to another fronthaul network  140 , the master device  110  assigns to said station  150  a transfer indicator comprising the identification of the original fronthaul network. Thus it is possible to keep a track of a transfer of a station  150  made during the switching-off phase. 
     When the attempt at switching each station  150  from a fronthaul network  140  has been made, the method continues at a step  314 . In the step  314 , the master device  110  identifies whether at least one station  150  is associated with said fronthaul network  140 . If such is the case, this means that the switching attempt has failed for at least one station  150  and the step  304  is performed, said fronthaul network  140  not being switched off. In the contrary case, if no station  150  is associated with the fronthaul network  140 , the step  308  is performed and the fronthaul network  140  is switched off. In the contrary case, if no station  150  is associated with the fronthaul network  140 , the step  308  is performed and the fronthaul network  140  is switched off. In this way, it is possible to reduce the power consumption of the communication network  100  by maximising the number of fronthaul networks  140  switched off while keeping sufficient access and service for the user. It is thus possible to switch off a fronthaul network  140  normally used by a station  150  if said fronthaul network  140  can easily be replaced by another fronthaul network  140  without this impairing the quality of service provided to the user. 
     According to a particular embodiment, the master device  110  determines an order of switching off that defines in what order the switching attempts are made and in what order the fronthaul networks  140  are switched off. For this purpose, the master device  110  determines an order of the non-critical fronthaul networks  140  with which only stations  150  managing non-critical traffic are associated. The order of said fronthaul networks  140  is determined according to the number of stations  150  associated with each of said fronthaul networks  140  and in an increasing order. In other words, an order that increases with the number of associated stations  150  is attributed to each of said fronthaul networks  140 . In the order determined, the first fronthaul network  140  thus presents the smallest number of associated stations  150  and the last fronthaul network  140  presents the greatest number of associated stations. If two fronthaul networks  140  present the same number of associated stations  150 , an arbitrary classification may be made. 
     The master device  110  then makes the attempts at switching the stations  150  in the order of the fronthaul networks  140  with which they are associated. Thus the master device  110  first of all makes an attempt at switching the stations  150  associated with the first fronthaul network  140 . If all the stations  150  associated with said first fronthaul network  140  are transferred, the first fronthaul network  140  is switched off. Otherwise the fronthaul network  140  is left switched on. The master device then proceeds in the same way for the second fronthaul network  140  and then successively for each fronthaul network  140  in the order determined. 
       FIG. 4  illustrates schematically steps of the switching-off method that are implemented by the master device  110  subsequently to the switching-off phase. Said steps are therefore performed after the steps described in relation to  FIGS. 3A or 3B  have been performed and when at least one of the fronthaul networks  140  is switched off. 
     The master device  110  firstly performs the steps  400 ,  402 ,  403  and  404  similar to the respective steps  200 ,  202 ,  203  and  204  previously described in relation to  FIG. 2B . Thus the master device  110  obtains information from the access points AP  130  and, from said information, determines for each station  150  whether it is mobile or fixed, whether it is present or absent and, for each fixed station  150 , determines whether it is managing critical or non-critical traffic. 
     In a step  406 , the master device  110  detects whether at least one station  150  is mobile and present. The switching-off phase being initiated when all the mobile stations  150  are absent, a station  150  that is mobile and present can be detected at the step  406  in the following cases: either a station  150  previously considered to be mobile sends a join request to a fronthaul network  140 , or a fixed station  150  present becomes mobile or a station  150  associates itself for the first time with a fronthaul network  140  of the communication network  100  and is therefore considered to be mobile by default. If at least one mobile station  150  is detected, a step  408  is performed. 
     In the step  408 , the master device  110  sends a switching-on instruction to all the access points AP  130  no longer emitting a fronthaul network  140  requesting switching on all the fronthaul networks  140  switched off. 
     If no mobile station  150  is detected at the step  406 , a step  410  is performed. 
     In the step  410 , the master device  110  detects, for each station  150  managing non-critical traffic at the moment when the extension phase is initiated, if the traffic managed by said station  150  becomes critical. In other words, the master device identifies a change to the traffic managed by each station  150  and if said traffic changes from a non-critical to a critical status. If no change is detected, a step  412  is performed. 
     In the step  412 , no fronthaul network  140  is switched on and the master device reiterates the steps  400  to  406 . 
     If, for a station  150 , the traffic managed by said station  150  changes from non-critical to critical, the step  408  is performed and all the fronthaul networks  140  switched off are switched on again. 
     According to an alternative embodiment, if the traffic of a station  150  changes from non-critical to critical, a step  414  is performed prior to the step  408 . In the step  414 , the master device  110  identifies, for each station  150  the traffic of which has changed from non-critical to critical, whether a transfer indicator is attributed to said station  150 . As described above in relation to the step  312  of  FIG. 3 , a transfer indicator is attributed to a station  150  when said station  150  is transferred from its original fronthaul network  140  to another fronthaul network  140  following a switching attempt. If no transfer indicator is attributed, the step  412  is performed and the fronthaul networks  140  switched off are not switched on again. If a transfer indicator is attributed to the station  150 , the step  408  is performed and all the fronthaul networks  140  switched off are switched on again. Thus it is possible to adapt the switching-on of the fronthaul networks  140  according to the change in the traffic of a station  150 . In addition, it is possible to avoid switching on all the fronthaul networks  140  if a station  150  has remained associated with its original fronthaul network  140  during the switching-off phase, the original fronthaul network  140  being considered to provide the best conditions for connection, from a point of view of transfer rate for example, to a station  150 . 
     Alternatively, if at step  414  a transfer indicator is identified for a fixed station  150  the traffic of which changes from non-critical to critical, the master device  110  sends a switching-on instruction solely to the access point AP  130  that manages the original fronthaul network  140  of the station  150  in question. Then, if fronthaul networks  140  are still switched off, the step  400  is reiterated. Thus it is possible to limit the switching-on of the fronthaul networks  140  solely to the fronthaul networks  140  that are useful to the user. 
     When the step  408  is performed, the master device  110  deletes all the transfer indicators that have been able to be attributed. 
     Following the step  408 , the master device  110  can reiterate the step  200  described previously. 
     According to a particular embodiment (not shown in the figures), the master device  110 , subsequently to the switching-off phase, performs a step of listening to the stations  150 . The listening step may be performed when at least one fronthaul network  140  is switched off, for example following the step  412  periodically. In the listening step, the master device  110  sends a listening instruction to at least one access point AP  130  managing a switched-off fronthaul network  140 . On reception of the listening instruction, the access point AP  130  switches on the fronthaul network  140  in a listening mode only, or in other words the access point AP  130  switches on only a reception chain and not a transmission chain, enabling the access point AP  130  to receive messages but not to send any. The access point AP  130  can thus detect whether any join requests are sent coming from stations  150  that are not associated but are authorised to access the communication network, or in other words stations  150  that do not manage to associate with the fronthaul networks  150  left switched on. If such is the case, the step  408  is performed and the fronthaul networks  140  are switched on. Alternatively, only the fronthaul network  140  managed by said access point AP  130  is switched on. 
     Thus it is possible to enable a fixed station  150  that was absent at the time of the switching-off phase to reassociate with the communication network  100  if only switched-off fronthaul networks  140  are potentially accessible to it. 
       FIG. 5  illustrates schematically the hardware architecture of the master device  110 . The master device  110  then comprises, connected by a communication bus  510 ; a processor or CPU (central processing unit)  501 ; a random access memory RAM  502 ; a read only memory ROM  503 ; a storage unit  504 , such as a hard disk HDD (hard disk drive), or a storage medium reader, such as an SD (Secure Digital) card reader; and an interface COM  505  for communicating with the access points AP  130 . 
     The processor CPU  501  is capable of executing instructions loaded in the RAM  502  from the ROM  503 , from an external memory (such as an SD card), from a storage medium, or from a communication network. When the master device  110  is powered up, the processor CPU  501  is capable of reading instructions from the RAM  502  and executing them. These instructions form a computer program causing the implementation, by the processor CPU  501 , of all or some of the steps described here in relation to the master device  110 . 
     All or some of said steps can thus be implemented in software form by the execution of a set of instructions by a programmable machine, such as a DSP (digital signal processor) or a microcontroller, or be implemented in hardware form by a machine or a dedicated component, such as an FPGA (field-programmable gate array) or an ASIC (application-specific integrated circuit). In general terms, the master device  110  thus comprises electronic circuitry configured to implement all or some of the steps described here in relation to the master device  110 . 
     Thus all or some of the algorithms and steps described here in relation to the master device  110  can be implemented in software form by the execution of a set of instructions by a programmable machine, such as a DSP (digital signal processor) or a microcontroller, or be implemented in hardware form by a machine or a dedicated component, such as an FPGA (field-programmable gate array) or an ASIC (application-specific integrated circuit). It should be noted that each access point AP  130  can follow the same hardware architecture.