METHOD AND DEVICE FOR SWITCHING A WI-FI CONNECTION

Description

1. Scope of the invention

[0001] The invention is in the field of so-called Wi-Fi networks (IEEE 802.11 standards, Institute of Electrical and Electronics Engineers, or, in French, Institut des ingénieurs électriciens et électroniqueiciens), and more particularly that of guiding the switchover of a station (STA) between several access points (AP). 2. Prior art

[0002] In a location equipped with the same home local area network (or LAN), it is common to find several Wi-Fi access points (APs) in order to improve radio coverage for client stations (STAs) moving around the location.

[0003] When these access points (APs) are jointly managed, as is the case, for example, with a set of virtual access points (LVAPs) sharing the same BSS identifier, a mechanism called "Wi-Fi steering" allows a mobile STA to be forced to connect to the "best" AP based on its proximity. To determine the most suitable AP for an STA, it is essential to estimate this proximity relative to the different APs. For this purpose, the signal strength level (RSSI) of the signal emitted by the STA and received by the AP is used to estimate the distance between the STA and the AP. This method is not very precise and can lead to failover decision errors.

[0004] US patent application US2010 / 069070(A1) describes a mobile radio communications system in which access point selection is based on location, with transmission triggered when the distance to an access point exceeds a certain threshold. CN patent application CN106792954(A) discloses a Bluetooth / Wi-Fi station, an environmental detection module for acquiring environmental parameters from the Bluetooth device, predicting the transmission rate, and transmitting these parameters and the rate to a switching decision module. This decision module then selects between a Bluetooth device and a Wi-Fi device for data transmission.

[0005] One of the aims of the invention is to remedy some of the drawbacks of the prior art. 3. Description of the invention

[0006] The present invention is defined by the attached claims. The following embodiments, aspects, examples, and implementation clauses are provided in this section to better understand the invention, which is exclusively defined by the attached claims. The invention improves the situation by means of a method for switching a connection of a mobile Wi-Fi station, from a first access point of a plurality of Wi-Fi access points, to a second access point of the plurality, the method comprising: an establishment of a logical link between the station and a station carrier, based on a comparison between a first position of the carrier and at least one value relative to a signal emitted by the station; a switchover decision based on a second position of the carrier, the first and second positions of the carrier being determined by at least one access point of the plurality, based on a signal reflected by the carrier, called a Wi-Fi radar signal.

[0007] According to the earlier technique called Wi-Fi steering, the failover of a mobile station between several access points within the same BSS—for example, virtual access points hosted by several physical access points under the same controller—is decided based on parameter values, such as the RSSI parameter, which the access point measures on a signal emitted by the station. The RSSI value represents the strength of the signal received by one device from another and can be likened to an estimate of the distance between the two devices.

[0008] According to the invention, a logical link is established between the station and its carrier, for example between a smartphone and the person using it, and the carrier's position can thus trigger or contribute to triggering the station's switch from one access point to another. This offers, among other advantages, greater precision compared to the value of parameters determined or measured by the access point using prior art, such as RSSI.

[0009] The process can be implemented by a controller of the plurality of access points, or by one of the access points of the plurality.

[0010] The carrier's position is determined by a technique analogous to radar and is more accurate than an RSSI value, thus improving the station failover process.

[0011] A person's body is large enough to reflect radio waves emitted by a Wi-Fi access point. This access point can therefore receive a portion of the reflected waves, measure them, and calculate the body's position, much like a monostatic radar (where the transmission and reception points are combined into a single location). This geolocation technique is referred to as "Wi-Fi sensing" in the remainder of this document.

[0012] According to one aspect of the process, Wi-Fi radar signals are beacon signals.

[0013] Thanks to this feature, the station's carrier position can be calculated by Wi-Fi sensing at a frequency equal to that of a Wi-Fi beacon signal, for example, every 100ms. Other types of frames emitted by the access point can also be used as Wi-Fi radar signals, but beacon frames have the advantage of a regular transmission frequency, which increases the reliability and accuracy of geolocation.

[0014] Furthermore, by reusing existing beacon signals, there is no need to create a specific Wi-Fi signal for Wi-Fi sensing, and the AP's operation in transmit mode is not impacted.

[0015] According to one aspect of the process, at least one value relating to a signal emitted by the station is translated into a distance of the station from an access point that emitted the signal received by the station, according to a predetermined correspondence grid.

[0016] Thus, it is easy to determine if the station and the carrier are in the same location. Indeed, if the carrier's position is at a distance from the access point that is equal to or close to the distance, given by the mapping grid, between the station and the access point, there is a high probability that the carrier and the station are in the same location.

[0017] According to one aspect, the process includes at least one update of the logical link after establishment, based on a comparison between a new position of the carrier and at least one new value relative to a signal emitted by the station.

[0018] It is important that the station be matched with its carrier, and not with the body of another person not carrying the station. This prevents the station's carrier from being mistaken for another body reflecting Wi-Fi radar signals.

[0019] This check, which can be repeated after the logical link is established, verifies that the station is still being transported by the carrier. If this is no longer the case, it generally means that the carrier has unloaded the station, which then becomes immobile.

[0020] If the station is not stationary but the position determined by the radar Wi-Fi signals and the signal emitted by the station no longer correspond, it is possible to repeat the step of establishing a correspondence with another moving body detected using the radar Wi-Fi signals, or to use another monitoring method to decide on a possible switchover, for example by the Wi-Fi steering method.

[0021] In one aspect, the process includes memorizing the logical link before the update.

[0022] Thanks to this feature, the previous value of a logical link can be used to differentiate between several possible new values ​​when the carrier moves away from the station and then closer again—for example, when someone places their smartphone on a table, moves away, and then returns later to retrieve it. Indeed, there can be several possible values ​​for updating the logical link when multiple carriers and stations are located within the area covered by the plurality of Wi-Fi access points.

[0023] According to one aspect of the process, the logical link is established using at least two values ​​relating to a signal emitted by the station, measured by at least two access points of the plurality.

[0024] This feature facilitates establishing a logical link. The strength of a signal emitted by the station allows an access point measuring it to estimate the radius of a circle around the access point, where the station is located. With estimates from two separate access points, the intersection of the two distance circles around each of them allows for triangulation to estimate the station's position, rather than its distance. It is more accurate to compare this station position with the carrier's position determined using the Wi-Fi radar signal.

[0025] According to one aspect of the process, at least one value relating to a signal emitted by the station is the value of an RSSI parameter.

[0026] Thanks to this feature, a parameter already used for Wi-Fi steering is employed to establish and monitor the connection between station and carrier. Other parameters can also be used, such as the SNR (signal-to-noise ratio).

[0027] According to one aspect of the process, the switchover decision is also made based on the value of an RSSI parameter.

[0028] Thanks to this feature, the failover decision depends both on a geographical location criterion for the station's carrier, calculated using Wi-Fi sensing with Wi-Fi radar signals, and on a criterion used by Wi-Fi steering. Thus, the match between the station and its carrier is verified up to the moment of failover, and priority can be given to one of the two criteria in case of disagreement.

[0029] According to one aspect of the process, the establishment of the logical link is carried out on the basis of several values ​​relating to a signal emitted by the station, received respectively by several access points.

[0030] This feature allows the distance between the station and multiple access points to be calculated. Furthermore, triangulation can be used to determine the station's position, increasing the reliability of the comparison with the carrier's position.

[0031] The different aspects of the switching process that have just been described can be implemented independently of each other or in combination with each other.

[0032] The invention also relates to a device for switching a connection from a mobile Wi-Fi station, from a first access point of a plurality of Wi-Fi access points, to a second access point of the plurality, the device comprising a receiver, a transmitter, a processor and memory coupled to the processor with instructions intended to be executed by the processor for: establish a logical link between the station and a station carrier, based on a comparison between a first position of the carrier and at least one value relative to a signal emitted by the station; decide on a switchover based on a second position of the carrier, the first and second position of the carrier being determined by at least one access point of the plurality of Wi-Fi access points, on the basis of a signal reflected by the carrier, called the Wi-Fi radar signal.

[0033] This device is capable of implementing the failover process described above in all its embodiments. It can be integrated into one of the access points of a plurality of access points, which is, for example, a set of virtual access points (LVAPs) sharing the same BSS or SSID identifier. It can also be separate from the access points and integrated into separate equipment controlling the plurality of access points, such as a controller, as used in Wi-Fi steering. If the failover process according to the invention is used in combination with the Wi-Fi steering method, the device is preferably integrated into the equipment housing the Wi-Fi steering controller.

[0034] Radar Wi-Fi signals are emitted by at least one, some, or all of the access points in the plurality, which perform measurements on the reflected signals and communicate them to the device.

[0035] The invention further relates to a Wi-Fi access point comprising a failover device as described above. The invention also relates to a Wi-Fi network comprising a plurality of geolocated access points, and a controller for the plurality comprising a failover device as described above.

[0036] The invention also relates to a computer program comprising instructions which, when executed by a processor, cause the processor to implement the steps of the switching process, which has just been described.

[0037] The invention also relates to an information carrier readable by a Wi-Fi access point, and comprising instructions for a computer program as mentioned above.

[0038] The program mentioned above may use any programming language, and be in the form of source code, object code, or code intermediate between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0039] The information storage medium mentioned above can be any entity or device capable of storing the program. For example, a medium can include a storage means, such as a ROM, for example a CD-ROM or a microelectronic circuit ROM, or a magnetic recording means.

[0040] Such a storage medium could be, for example, a hard drive, flash memory, etc. Furthermore, an information carrier could be a transmissible medium such as an electrical or optical signal, which can be transmitted via an electrical or optical cable, by radio, or by other means. A program according to the invention can, in particular, be downloaded from a network such as the Internet.

[0041] Alternatively, an information carrier may be an integrated circuit in which a program is incorporated, the circuit being adapted to execute or to be used in the execution of the process in question. 4. Presentation of the figures

[0042] Other advantages and features of the invention will become more apparent upon reading the following description of a particular embodiment of the invention, given by way of simple illustrative and non-limiting example, and the accompanying drawings, among which: [ Fig 1a ] there figure 1a presents an example of implementing the method for switching a Wi-Fi station between Wi-Fi access points, according to an embodiment of the invention (first part of the implementation), [ Fig 1b ] there figure 1b presents an example of implementing the method for switching a Wi-Fi station between two Wi-Fi access points, according to an embodiment of the invention (second part of the implementation), [ Fig 1c ] there figure 1c presents an example of implementing the method for switching a Wi-Fi station between two Wi-Fi access points, according to an embodiment of the invention (third part of the implementation), [ Fig 1d ] there figure 1d presents an example of implementing the method for switching a Wi-Fi station between two Wi-Fi access points, according to an embodiment of the invention (fourth part of the implementation), [ Fig 1 e ] there figure 1epresents an example of implementing the method for switching a Wi-Fi station between two Wi-Fi access points, according to an embodiment of the invention (fifth part of the implementation), [ Fig 2 ] there figure 2 presents an example of the correlation between the attenuation of the signal received by a Wi-Fi station and the distance between that station and two Wi-Fi access points, according to one aspect of the invention, [ Fig 3 ] there figure 3 presents an example of the sequence of steps in the switching process according to one aspect of the invention, [ Fig 4 ] there figure 4 presents an example of the structure of a device implementing the method of switching a Wi-Fi station between Wi-Fi access points, according to one aspect of the invention. 5. Detailed description of at least one embodiment of the invention

[0043] In the following description, it is understood that the invention applies to all variations of the IEEE 802.11 standards. Wi-Fi access points, in particular, can be physical or virtual (LVAP). The terms "connection" and "connect" are to be understood in the Wi-Fi context and are respectively synonymous with "association" and "associate" in this document.

[0044] THE figures 1a , 1b , 1c , 1d And 1e present an example of implementation of the method of switching a Wi-Fi station between Wi-Fi access points, according to an embodiment of the invention (first part of the implementation) where 3 people with 2 Wi-Fi stations enter and disperse in a room L equipped with 2 separate Wi-Fi access points.

[0045] Stations STA1 and STA2 are, for example, "smartphones" equipped with Wi-Fi. Station STA1 is carried by its user, person U1, also referred to as carrier U1 in this document. Station STA2 is carried by its user, person U2, also referred to as carrier U2 in this document. Person U3 does not carry any Wi-Fi station, but for convenience is also referred to as carrier in this document (in theory, they can start carrying a Wi-Fi station at any time). Access point AP1 is in a home access gateway, for example, a Livebox (the commercial name of the gateway from the operator Orange, an internet service provider for individuals in France). Access point AP2 is in a Wi-Fi repeater that provides internet access from the Livebox to rooms in room L that are too far from access point AP1 to receive its Wi-Fi signal adequately.Access points AP1 and AP2 can form a Wi-Fi network in room L.

[0046] There is also a control device C, or controller, not shown, which can be housed in the Livebox with the access point AP1, or be physically separated from the access points in separate equipment, inside or outside the premises L. A communication link is established between the controller and each of the access points AP1 and AP2, for example by Wi-Fi, or by any other means, wired or wireless.

[0047] At time T0, carriers U1, U2, and U3, and stations STA1 and STA2, are too far from room L to be within range of access points AP1 and AP2. For controller C, no link yet exists between carriers and Wi-Fi stations.

[0048] At time T0+5 ( figure 1aThe three carriers U1, U2, and U3 enter room L at the same time as stations STA1 and STA2. Since access point AP1 is the closest to the entrance, stations STA1 and STA2 connect to this access point. Because the three carriers and the two stations are still grouped in the same location near the entrance, according to the Wi-Fi sensing technique detailed later, controller C determines that carriers U1, U2, and U3 are 8 meters from access point AP1. Controller C also determines that stations STA1 and STA2 are connected to access point AP1 at -55 dBm attenuation, which corresponds to a distance of 8 meters. Controller C deduces that all carriers and stations are in the same location and establishes the following logical links: logical link LL 1 = U 1 + STA 1 , STA 2 meaning that carrier U1 is linked to both station STA1 and station STA2, a logical link LL 2 = U 2 + STA 1 , STA 2 meaning that carrier U2 is linked to both station STA1 and station STA2, a logical link LL 3 = U 3 + STA 1 , STA 2 meaning that the U3 carrier is linked to both station STA1 and station STA2.

[0049] At time T0+1 0 ( figure 1b The carriers disperse throughout room L. Controller C determines that station STA1 is connected to access point AP1 at -30dBm attenuation, corresponding to a distance of 1m, and that station STA2 is connected to access point AP2 at -52dBm attenuation, corresponding to a distance of 7m. For simplicity, the possible ways in which station STA2 switched from access point AP1 to access point AP2 are not detailed here. This could be according to a prior art technique, initiated by the station (by "handover") or the controller (by steering), or by the same method as that detailed here, i.e., according to the invention.

[0050] Controller C also determines via Wi-Fi sensing that: one carrier is 1m from access point AP1 and 14m from access point AP2, one carrier is 16m from access point AP1 and 7m from access point AP2, one carrier is 14m from access point AP1 and 13m from access point AP2.

[0051] Controller C deduces that: The transporter that is 1m from access point AP1 is in the same location as station STA1, the transporter that is 7m from access point AP2 is in the same location as station STA2, the transporter that is 14m from access point AP1 and 13m from access point AP2 is not in a location where there is also a station.

[0052] Controller C therefore updates the logical links it determined at time T0+5: logical link LL 1 = U 1 + STA 1 meaning that carrier U1 is linked to station STA1, a logical link LL 2 = U 2 + STA 2 meaning that the U2 carrier is linked to the STA2 station, a logical link LL 3 = U 3 meaning that the U3 carrier is not linked to any station.

[0053] Furthermore, the C controller remembers the previous links as they were before the update: logical link LL 1 _ANT = U 1 + STA 1 , STA 2 logical link LL 2 _ANT = U 2 + STA 1 , STA 2 logical link LL3_ANT=U3+STA1,STA2

[0054] Note that the order and numbering of the links and carriers were determined randomly when the logical links were created at time T0+5, and are retained thereafter.

[0055] At time T0+15 ( figure 1c), the carrier U1 moves, with the station STA1. Carriers U2 and U3 do not move. The controller C determines that the station STA1 is connected to the access point AP1 at -50dBm attenuation, which corresponds to a distance of 6m (new situation compared to time T0+10), and that the station STA2 is connected to the access point AP2 at -52dBm attenuation, which corresponds to a distance of 7m (unchanged situation compared to time T0+10).

[0056] Controller C also determines via Wi-Fi sensing that: a carrier is 6m from access point AP1 and 4m from access point AP2 (new situation compared to time T0+10), a carrier is 16m from access point AP1 and 7m from access point AP2 (unchanged situation compared to time T0+10), a carrier is 14m from access point AP1 and 13m from access point AP2 (unchanged situation compared to time T0+10).

[0057] Controller C deduces that: The transporter that is 6m from access point AP1 is in the same location as station STA1, the transporter that is 7m from access point AP2 is in the same location as station STA2, the transporter that is 14m from access point AP1 and 13m from access point AP2 is not in a location where there is also a station.

[0058] Therefore, controller C does not modify the logical links that it updated at time T0+10, which remain: logical link LL 1 = U 1 + STA 1 logical link LL 2 = U 2 + STA 2 logical link LL 3 = U 3

[0059] The C controller also does not modify previously stored links, which remain: logical link LL 1 _ANT = U 1 + STA 1 , STA 2 logical link LL 2 _ANT = U 2 + STA 1 , STA 2 logical link LL 3 _ANT = U 3 + STA 1 , STA 2

[0060] However, what has changed is that, thanks to the LL1 logical link, controller C detects that the position of station STA1, accurately determined by Wi-Fi sensing because it is that of carrier U1, is now closer to access point AP2 than to access point AP1. Consequently, controller C decides to switch STA1's connection from access point AP1 to access point AP2. Controller C issues a switchover command to access point AP1, for example, using a method known as EasyMesh, defined by the Wi-Fi Alliance standards body. Access point AP1 can then, for example, send STA1 a list of access points to which the station is invited to connect, containing only access point AP2 (for example, a BTM Request message).

[0061] At time T0+20 ( figure 1d), carrier U2 moves, without station STA2. Carriers U1 and U3 do not move. Controller C determines that station STA1 is connected to access point AP1 at -50dBm attenuation, which corresponds to a distance of 6m (unchanged situation compared to time T0+15), and that station STA2 is connected to access point AP2 at -52dBm attenuation, which corresponds to a distance of 7m (unchanged situation compared to time T0+15).

[0062] Controller C also determines via Wi-Fi sensing that: a carrier is 6m from access point AP1 and 4m from access point AP2 (situation unchanged from time T0+15), a carrier is 7m from access point AP1 and 14m from access point AP2 (new situation compared to time T0+15), a carrier is 14m from access point AP1 and 13m from access point AP2 (situation unchanged from time T0+15).

[0063] Controller C deduces that: The transporter that is 6m from access point AP1 is in the same place as station STA1, the transporter that is 14m from access point AP2 is no longer in the same place as station STA2, and is not in the same place as station STA1 either, the transporter that is 14m from access point AP1 and 13m from access point AP2 is not in a place where there is also a station.

[0064] Controller C therefore updates the logical links as follows: logical link LL 1 = U 1 + STA 1 (as before), logical link LL 2 = U 2 meaning that the U2 carrier is now not linked to any station, logical link LL 3 = U 3 (as before).

[0065] The C controller also updates previously stored logical links, as follows: logical link LL 1 _ANT = U 1 + STA 1 , STA 2 (unchanged), logical link LL 2 _ANT = U 2 + STA 2 (new, meaning that the U2 carrier was previously linked to the STA2 station), logical link LL 3 _ANT = U 3 + STA 1 , STA 2 (unchanged).

[0066] At time T0+30 ( figure 1eCarrier U2 moves again, this time to station STA2, which it then takes control of. Carrier U1 moves to the same location as U2, but without the station STA1 it dropped. Using the mechanisms described above, Controller C determines that U1, U2, and STA2 are in the same location. This could pose a challenge for Controller C in determining how to update the existing logical links. Indeed, two new logical links are possible: either Carrier U2 is linked to station STA2, or Carrier U1 is linked to station STA2. By consulting the stored previous logical links, Controller C observes that a previous link, LL2_ANT, linked carrier U2 to station STA2 one-to-one, and that no previous link linked carrier U1 to station STA2 one-to-one. The stored previous links allow Controller C to prioritize the one most likely to occur, which is the LL2_ANT link.

[0067] Controller C therefore updates the logical links as follows: logical link LL 1 = U 1 updated; meaning that carrier U1 is now not linked to any station, logical link LL 2 = U 2 , STA 2 updated; meaning that carrier U2 is linked to station STA2, logical link LL 3 = U 3 (unchanged).

[0068] Storing previous links prevents the controller C from having to distinguish between different carriers. It should be noted that in this embodiment, a logical link connects a single carrier to any number of stations (0, 1, or more). Another possible embodiment is one in which a logical link connects a single station to any number of carriers.

[0069] There figure 2presents an example of the correspondence between the attenuation of the signal received by a Wi-Fi station and the distance between that station and two Wi-Fi access points, according to one aspect of the invention.

[0070] In this example, access point AP1 receives a signal from station STA1 with an RSSI parameter value of -50dBm. Access point AP2, on the other hand, receives a signal from station STA2 with an RSSI parameter value of -45dBm. Based on predetermined charts depending on the type of Wi-Fi station (Wi-Fi 4, Wi-Fi 5, or Wi-Fi 6), and possibly other parameters such as the environmental configuration (indoors with specific types of partitions, etc.), a correlation can be established between the RSSI parameter value and the distance between the station and the access point to which it is connected.

[0071] In the example of the figure 2Where such a nomogram is illustrated, the access point controller can determine, based solely on the RSSI parameters, that station STA1 is 6m (RSSI = -50dBm) from access point AP1, and that station STA2 is 4m (RSSI = -45dBm) from access point AP2. In theory, if the controller can also retrieve the RSSI parameters of access point AP2 measured on a signal from station STA1 even if that station is not connected to access point AP2, the controller can then further determine that station STA1 is 8m (RSSI = -55dBm) from access point AP2, and can, through triangulation, estimate the position of station STA1 more precisely.

[0072] This is not possible for station STA2, which is connected to access point AP2 but out of range of access point AP1.

[0073] Thanks to its radar mechanism, Wi-Fi sensing allows for the geolocation of any station carrier from a single access point with greater accuracy than the estimation made using the RSSI parameter, without resorting to triangulation. However, it is necessary to be able to link the carrier to the correct station, as described above.

[0074] Wi-Fi sensing uses existing Wi-Fi signals emitted by an access point to detect events and changes, such as the movement of bodies or objects around the access point. The access point processes the received signals by reflection, similar to radar, and sends information about these reflected signals to a control device (such as the C controller) which performs the calculations necessary to determine the position of the body or object.

[0075] In practice, this means that Wi-Fi networks can be used to identify and measure distances, linear or angular speeds, detect movements (even simple gestures or breathing), presences, proximity, for objects, people or animals, in a room, a house, a car or a building.

[0076] In one embodiment, beacon frames emitted by access points are used as "Wi-Fi radar" signals. Since these frames are emitted every 100ms, a person's position can be updated every 100ms. This frequency is significantly higher than that achievable with Wi-Fi steering.

[0077] Wi-Fi sensing, that is, determining the position of an object using existing Wi-Fi signals as radar signals, is possible as long as an access point is functional. Wi-Fi sensing can be performed on all frequency bands used by a physical access point, and more generally, on all frequency bands of all physical access points, provided these bands are operational.

[0078] In the simple case of use on a single frequency band, since the access points are not time-synchronized, they transmit their beacon frames in an uncoordinated manner but all at the same frequency (every 100ms). It is therefore possible to send information to the controller every 100ms to locate people.

[0079] This represents a large amount of information to send, and it's not necessary for all access points to do so constantly. Indeed, after a logical connection is established between the person (the carrier) and a station using the method described above, if the station is connected, for example, to access point AP1, Wi-Fi sensing will only be triggered on access points other than AP1 if the person moves beyond a certain distance from AP1, and / or moves closer to another access point below a certain distance. It's also possible to trigger Wi-Fi sensing only on the access point that has become closest to the person, and not on the other access points.

[0080] The controller can then instruct this access point to monitor: the station using the mechanisms of the Wi-Fi steering method (based on RSSI), and / or the person linked to the station using Wi-Fi sensing, In order to trigger a failover of the station's connection to this access point, as soon as predetermined failover conditions are met. These conditions can, for example, be the same as those of Wi-Fi steering, i.e., RSSI values ​​reported by the station with the new access point that are higher than those reported with the old one.

[0081] There figure 3 presents an example of the sequence of steps of the switching process according to an aspect of the invention.

[0082] The process steps can be divided into three groups. The first group represents the Wi-Fi sensing operating mode and consists of steps E1u to E4u. The second group represents part of the Wi-Fi steering operating mode (without the failover decision) and consists of steps E1sta to E4sta. The last group is the failover decision step E5.

[0083] During the E1u step, the controller C commands the access point AP1 to switch to Wi-Fi sensing mode, that is, to monitor a moving body around it.

[0084] In response, during step E2u, access point AP1 transmits a Wi-Fi frame, for example a beacon frame, known as a Wi-Fi radar signal. This signal bounces off carrier U1 and returns to the access point, which receives it degraded during step E3u.

[0085] During step E4u, access point AP1 transmits information about this signal to controller C. This information is, for example, a Fast Fourier Transform (FFT) of the signal received by the access point. Such information allows for the calculation of a position relative to the access point, using a technique such as that described, for example, in the article "Multi-Person Localization via RF Body Reflections" by Fadel Adib et al., NSDI'15: Proceedings of the 12th USENIX Conference on Networked Systems Design and Implementation, May 2015. This calculation can be performed by the controller or by the access point. In the latter case, the signal information transmitted by the access point is a set of coordinates, such as a distance and an angle.

[0086] Steps E2u and E3u can be repeated at the same frequency as the beacon frames, i.e., every 100ms. Step E4u can be repeated at a lower frequency to avoid overloading the C controller.

[0087] During the E1sta step, the controller C commands the access point AP1 to switch to partial Wi-Fi steering mode, that is to say to monitor the station STA1 which is connected to it by monitoring its RSSI parameter, but without deciding on a possible switchover of the connection.

[0088] During the E3sta step, possibly in response to a Wi-Fi frame emitted during an E2sta step calling for a response from station STA1, this station sends to access point AP1 a Wi-Fi frame constituting a signal from which access point AP1 extracts, for example, a value of the RSSI parameter, representative of the strength of the signal emitted by the station, upon its reception by the access point.

[0089] During step E4sta, access point AP1 sends the value of the RSSI parameter to controller C.

[0090] Step E3sta can be repeated each time station STA1 transmits a Wi-Fi frame to access point AP1. Step E4sta can be repeated at a lower frequency to avoid overloading controller C.

[0091] During step E5, controller C processes the information it received from access point AP1 and calculates the position of carrier U1, the distance between U1 and access point AP1, and / or the distance between station STA1 and access point AP1. During this step, controller C can create a logical link between carrier U1 and station STA1 if no link already exists between them, and if the position of carrier U1 corresponds to a possible position of station STA1 given its distance from access point AP1. Otherwise, during this step E5, if this position and distance no longer match, and the logical link already exists, the controller can update it.

[0092] Finally, if the link exists, and the position of carrier U1 has changed to move closer to an access point other than AP1, for example access point AP2, the controller can decide to switch station STA1 to access point AP2. Alternatively, for example if this proximity is insufficient (predefined threshold not reached), it can anticipate such a switchover by instructing access point AP2 to switch to Wi-Fi sensing mode (step E1u applied to AP2), or to partial steering mode (step E1sta applied to AP2), which is possible even without station STA1 being connected to access point AP2.

[0093] The frequency of step E5 is independent of those of the other steps.

[0094] There figure 4 presents an example of the structure of a device implementing the method of switching a Wi-Fi station between Wi-Fi access points, according to one aspect of the invention.

[0095] Device 100 implements the tipping process, various embodiments of which have just been described.

[0096] Such a device can be implemented in equipment controlling multiple Wi-Fi access points. This equipment, for example, controller C, can be separate from the controlled access points or integrated into one of them. This Wi-Fi access point, for example, access point AP1, can be a home or business gateway, or a home or business router, providing access to the Internet.

[0097] For example, the device 100 comprises a receiver 101, a transmitter 102, a processing unit 130, equipped, for example, with a microprocessor µP, and controlled by a computer program 110, stored in a memory 120 and implementing the switching method according to the invention. At initialization, the code instructions of the computer program 110 are, for example, loaded into RAM before being executed by the processor of the processing unit 130.

[0098] Such a memory 120, such a processor of the processing unit 130, such a receiver 101 and such a transmitter 102 are capable of, and configured to: establish a logical link between the station and a carrier of the station, based on a comparison between a first position of the carrier and at least one value relative to a signal emitted by the station, and decide a switchover based on a second position of the carrier.

[0099] Advantageously, they are also capable of, and configured to: update the logical link after establishment, based on a comparison between a new position of the carrier and at least one new value relative to a signal emitted by the station, store the logical link before the update, issue an i-E1u command to an access point ordering it to switch to Wi-Fi sensing mode, i.e. to monitor a body around it, receive in response an i-E4u information allowing to obtain or calculate a position of the body relative to the access point, issue an i-E1sta command to an access point ordering it to switch to partial Wi-Fi steering mode, i.e. to monitor a station by monitoring the station's RSSI parameter, but without deciding a possible switchover of the connection, receive in response an i-E4sta information including a value of the RSSI parameter.

[0100] The entities described and included in the devices described in relation to the figure 4 They can be hardware or software. The figure 4This illustrates only one particular way, among several possible ways, of implementing the process detailed above, in relation to the preceding figures. Indeed, the technique of the invention can be implemented equally well on a reprogrammable computing machine (a PC, a DSP processor, or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example, a set of logic gates such as an FPGA or an ASIC, or any other hardware module). If the invention is implemented on a reprogrammable computing machine, the corresponding program (i.e., the sequence of instructions) may or may not be stored on a removable storage medium (such as, for example, a USB flash drive, a floppy disk, a CD-ROM, or a DVD-ROM), this storage medium being partially or fully readable by a computer or a processor.

Claims

1. Method for switching a connection of a mobile Wi-Fi station (STA1) from a first access point (AP1) of a plurality of Wi-Fi access points to a second access point (AP2) of the plurality of Wi-Fi access points, the method comprising: • establishment of a logic link between the station and a carrier (U1) of the station, on the basis of a comparison between a first position of the carrier and at least one value in relation to a signal transmitted by the station; • a switching decision (E5) on the basis of a second position of the carrier, wherein the first position and the second position of the carrier are determined by at least one access point of the plurality of Wi-Fi access points, on the basis of a signal reflected by the carrier, called Wi-Fi radar signal.

2. Method according to Claim 1, wherein the Wi-Fi radar signal is a beacon signal.

3. Method according to either of the preceding claims, wherein the at least one value in relation to a signal transmitted by the station is translated into a distance of the station from an access point that transmitted the signal received by the station, in accordance with a predetermined correspondence table.

4. Method according to one of the preceding claims, comprising at least one update to the logic link after the establishment, on the basis of a comparison between a new position of the carrier and at least one new value in relation to a signal transmitted by the station.

5. Method according to Claim 4, comprising storing the logic link before the update.

6. Method according to one of the preceding claims, wherein the logic link is established using at least two values in relation to a signal transmitted by the station, measured by at least two access points of the plurality of Wi-Fi access points.

7. Method according to one of the preceding claims, wherein the at least one value in relation to a signal transmitted by the station is the value of an RSSI parameter.

8. Method according to one of the preceding claims, wherein the switching decision is also made on the basis of a value of an RSSI parameter.

9. Method according to one of the preceding claims, wherein the logic link is established on the basis of multiple values in relation to a signal transmitted by the station, received respectively by multiple access points.

10. Device (100) for switching a connection of a mobile Wi-Fi station (STA1) from a first access point (AP1) of a plurality of Wi-Fi access points to a second access point (AP2) of the plurality of Wi-Fi access points, the device comprising a receiver (101), a transmitter (102), a processor (130) and a memory (120) coupled to the processor with instructions intended to be executed by the processor in order to: • establish a logic link between the station and a carrier of the station (U1), on the basis of a comparison between a first position of the carrier and at least one value in relation to a signal transmitted by the station; • decide whether to switch on the basis of a second position of the carrier, the first position and the second position of the carrier being determined by at least one access point of the plurality of Wi-Fi access points, on the basis of a signal reflected by the carrier, called Wi-Fi radar signal.

11. Wi-Fi access point comprising a device according to Claim 10.

12. Wi-Fi network comprising a plurality of geolocated access points and a controller able to control the plurality of geolocated access points, the controller comprising a device according to Claim 10.

13. Computer program (110) comprising instructions that, when these instructions are executed by a processor, prompt said processor to implement the steps of the switching method according to Claim 1.

14. Information medium able to be read by a computer of a Wi-Fi access point and comprising instructions of a computer program (110) according to Claim 13.