Method and device for announcing authorized data rates for control and management frames in a Wi-Fi network

Abstract

Method and device for announcing allowed bit rates for control and management frames in a Wi-Fi network. Method for announcing lists of allowed bit rates for control frames in a Wi-Fi network comprising an access point (AP) and a station (STA), implemented by the access point and comprising: Transmission (E006) of a first beacon message (B01) containing a first list of allowed bit rates; Measurement of at least one parameter representative of the quality of a radio link between the access point and the station; Modification of the first list into a second list of allowed bit rates, based on the at least one measured parameter; Transmission (E013) of a second beacon message (B02) containing the second list of allowed bit rates. Figure for the abstract: Figure 1b

Description

Title of the invention: Method and device for announcing authorized data rates for control and management frames in a Wi-Fi network 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 the authorized rates for control frames or management frames exchanged between a station (STA) and an access point (AP). 2. Prior art

[0002] Current Wi-Fi access points (APs) send beacon messages that, among other things, announce the permitted physical data rates for control and management frames (collectively referred to as "control frames" hereafter), as well as for other types of frames in specific situations. Physical data rates depend on the frequencies used by the AP, and this announcement aims to indicate once and for all, among all possible data rates for the frequency band, which ones are permitted, and consequently, to prohibit those not announced in a beacon message. The speeds are announced in ascending order, for example on an interface of the 2.4GHz frequency band the list of announced physical speeds is "1; 2; 5.5; 11; 18; 24; 36; 54" which indicates that 8 speeds are allowed, the lowest being 1Mbps and the highest being 54Mpbs.In practice, control frames are transmitted at the lowest rate, i.e., 1Mbps. Also, the rates in the list are not only used for control frames, but are also used for data frames (Data and QoS_Data) when radio conditions are poor (distance, retransmission).

[0003] Since the lowest data rate is used for a large number of control frames, including those sent by the AP, and in particular beacon messages, the transmission channel occupancy can be significant, especially if an AP uses several logical interfaces (also called VAP, LVAP, or vBSS...). This has the disadvantage of increasing the transmission channel occupancy time between the AP and stations, and reducing radio coverage on the AP in general (i.e., on all virtual interfaces).

[0004] One of the aims of the invention is to remedy these drawbacks of the prior art. 3. Description of the invention

[0005] The invention improves the situation by means of a method for announcing lists of authorized bit rates for control frames in a Wi-Fi network comprising an access point and a station, implemented by the access point and comprising: • Transmission of an initial beacon message including a first list of authorized flow rates, • Measurement of at least one parameter representative of the quality of a radio link between the access point and the station, • Modification of the first list into a second list of authorized flow rates, based on at least one measured parameter, • Issuance of a second beacon message including the second list of authorized flow rates.

[0006] By measuring the quality of the radio link between the access point and the station, the access point can deduce a data rate at which the station is capable of transmitting and receiving control frames. Thus, the access point can adapt the list of authorized data rates that it periodically announces in a beacon message when the measured parameter changes, instead of constantly transmitting the same list as in the prior art, regardless of the situation. A parameter representative of the quality of the radio link is understood to be any parameter that allows the state of the transmission channel between an access point and a station to be quantified. Such parameters include, for example, the frame rate, the Received Signal Strength Indicator (RSSI), the Signal-to-Noise Ratio (SNR), the Channel State Information (CSI), etc.

[0007] According to one aspect of the announcement method, the modification is an addition of at least one flow rate lower than the lowest of the flow rates in the first list.

[0008] According to one aspect of the announcement process, the modification is a removal of at least one of the lowest rates from the first list.

[0009] Thus, modifying the list implemented by the access point has a direct and immediate effect on the data rate used by the control messages exchanged between the station and the access point. Indeed, it should be noted that stations and access points transmit control messages preferably using the lowest data rate from the list transmitted in a beacon message.

[0010] According to one aspect of the announcement method, a flow rate is added or removed based on a comparison between a representative value of at least one measured parameter and an addition or removal threshold specific to the added or removed flow rate and the parameter.

[0011] Thus, the access point can easily automate the adjustment of the flow rate list, with simple operations of comparison between numerical values.

[0012] According to one aspect of the announcement method, the measurement of at least one parameter is repeated several times, and the modification is triggered if the representative values ​​remain several times in succession on the same side of the addition or subtraction threshold.

[0013] Thus, the list is only modified if a trend is confirmed in the measured flow rate, and the list is not modified too frequently.

[0014] According to one aspect of the announcement method, the access point is a virtual access point.

[0015] Thus, it is possible to separate the different virtual access points (VAP, Virtual Access Point, or LVAP, Light Virtual Access Point) of the same physical access point in their respective management of the announcements of authorized rates for control frames.

[0016] In the case where the virtual access point is dedicated to a single station, this allows for announcement management that is specific to the quality of the radio link between the virtual access point and that station only.

[0017] According to one aspect of the announcement method, at least one parameter representative of the quality of a radio link between the access point and the station belongs to a group comprising: • Throughput when receiving a frame from the station; • Signal strength received by the station; • Noise level; • Number of identical frames retransmitted by the station.

[0018] A Wi-Fi network can accommodate a large number of stations. These stations may have different physical characteristics. Taking into account more than one parameter representative of the radio link quality can allow adaptation to each type of station, for example, when the received frame rate is unreliable or easy to measure. In this case, the RSSI (received signal strength) allows the access point to deduce the attenuation between the station and the access point, without knowing a priori the power transmitted by the station. By subtracting the noise level, the SNR (signal-to-noise ratio) is obtained. Based on this SNR, the transmitted frame rate can be estimated. If this rate is low, some unreceived frames are not acknowledged, resulting in frame retransmissions.It is understood that these four parameters, taken into account alone or in combination, are relevant to the decision of whether or not to modify the list of authorized flow rates.

[0019] According to one aspect of the announcement process, the frame used to measure the receiving rate of a frame from the station is a QoS_DATA type frame.

[0020] QoS_DATA frames are the most commonly used in prior art techniques for measuring the receive throughput of a frame in Wi-Fi. This minimizes infrastructure changes compared to the prior art. In some implementations, DATA frames are also used.

[0021] The different aspects of the announcement process that have just been described can be implemented independently of each other or in combination with each other.

[0022] The invention further relates to a device for announcing lists of authorized bit rates for control frames in a Wi-Fi network comprising an access point and a station, the device being contained within the access point and comprising a receiver, a transmitter, a processor, and memory coupled to the processor with instructions intended to be executed by the processor for: • transmit an initial beacon message including an initial list of authorized flow rates, • measure at least one parameter representative of the quality of a radio link between the access point and the station, • modify the first list into a second list of authorized flow rates, based on at least one measured parameter, • send a second beacon message including the second list of authorized flow rates.

[0023] This device, capable of implementing in all its embodiments the announcement process which has just been described, is intended to be implemented in a Wi-Fi access point.

[0024] The invention also relates to a computer program comprising instructions which, when these instructions are executed by a processor, lead the latter to implement the steps of the method of announcing lists of authorized flow rates, which has just been described.

[0025] 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.

[0026] The program mentioned above may use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form.

[0027] The information 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.

[0028] Such a means of storage can, for example, be a hard drive, a flash memory, etc. On the other hand, an information medium can 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 onto an Internet-type network.

[0029] 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

[0030] 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:

[0031] [Fig. 1a] [Fig. 1a] presents an example of Wi-Fi frame exchanges between station and access point before the station moves away, according to one aspect of the invention,

[0032] [Fig. 1b] [Fig. 1b] presents an example of Wi-Fi frame exchanges between station and access point after moving away from the station, according to one aspect of the invention,

[0033] [Fig.2a] [Fig.2a] presents an example of Wi-Fi frame exchanges between station and access point before the station approaches, according to one aspect of the invention,

[0034] [Fig.2b] [Fig.2b] presents an example of Wi-Fi frame exchanges between station and access point after the station has moved closer, according to one aspect of the invention,

[0035] [Fig.3] [Fig.3] presents an example of the structure of a device in a Wi-Fi access point, implementing the method of announcing the list of authorized rates, according to one aspect of the invention.

[0036] 5. Detailed description of at least one embodiment of the invention

[0037] In the following description, it is understood that the invention applies to all variations of the IEEE 802.11 standards.

[0038] The diagrams in Figures 1a to 2b illustrate the steps of the data rate announcement method according to the invention, in an example configuration where the Wi-Fi network conforms to the 802.11 standard and uses the 2.4 GHz frequency band. This is only an example, and it is understood that the invention applies to other configurations, in particular to other frequency bands and other standards. The example scenarios adopted are those of moving a STA (Single Terminal Access) away from or towards an AP (Access Point), but the invention applies to any scenario of changing conditions affecting the quality of the radio link between the AP and the STA, whatever the cause.

[0039] In the 2.4GHz frequency band, the complete list of permitted data rates, denoted PRL, is, in megabits per second (Mbps):

[0040] PRL = [1; 2; 5.5; 11; 18; 24; 36; 54]

[0041] Figure 1a shows an example of Wi-Fi frame exchanges between an STA station and an AP access point, before moving away from the station, according to one aspect of the invention.

[0042] According to the invention, the beacon messages include a dynamic list of authorized rates. For illustrative purposes, the presentation of the exchanges between STA and AP begins with a running list of authorized rates PRL01, which is a sublist of PRL.

[0043] During an E001 step, the AP transmits a beacon signal B01, at a rate of 24 Mbps, which is received by the STA. B01 includes the PRL01 rate list, which is shorter than PRL:

[0044] PRL01 = [24; 36; 54]

[0045] PRL01 does not include the 5 lowest PRL rates for example because the quality of the radio link at the time of step E001 allows the use of higher rates for the control frames.

[0046] Whether on the side of the AP that transmits the beacon signal, or on the side of the STA that receives it, the control frames, including the beacon signal, are transmitted at one of the rates indicated in the PRL01 list of the BOL beacon signal

[0047] In our example, the control frames are transmitted at the lowest rate in the current list, i.e. 24Mbps at the time of this step E001.

[0048] During step E002, the STA transmits a TOI frame, for example, a QoS_DATA frame, at a rate of 155 Mbps, which is received by the AP. This TOI frame is not a control frame. During this step, the AP measures the radio link quality with the STA, for example, by measuring the received rate of the TOI frame. The measurement, 155 Mbps, is retained for when a new beacon message needs to be transmitted, which may be an opportunity to modify the current PRL01 list of allowed rates. This measurement can also be used in choosing the rate from the current list that will be used to transmit a control frame. Indeed, this rate must be lower than the measurement. At the time of step E002, all the rates in the PRL01 list can therefore theoretically be used because they are all lower than 155 Mbps.

[0049] During step E003, the AP acknowledges the TOI frame received during step E002 by transmitting an ACK frame at a rate of 24 Mbps. ACK frames are control frames and must therefore be transmitted at one of the rates in the current list, which is PRL01. The ACK frame is thus transmitted at the lowest rate in the current list, i.e., 24 Mbps at the time of step E003.

[0050] During step E004, the AP transmits a T02 frame, for example a QoS_DATA type frame, at a rate of 155 Mbps, which is received by the STA. This T02 frame is not a control frame and can therefore be transmitted at a rate that is not limited by the PRL01 list.

[0051] During an E005 step, the STA acknowledges the T02 frame received during the E004 step, by transmitting an ACK frame, always at a rate of 24Mbps.

[0052] Figure 1b shows an example of Wi-Fi frame exchanges between a station STA and an access point AP, after the station has moved away, according to one aspect of the invention. This movement leads to a decrease in the quality of the radio link between AP and STA.

[0053] Following step E005, during step E006, the AP transmits a beacon signal. To determine whether the list should be modified, the AP must consider the last measurement it performed of the radio link quality with the STA. In this case, this measurement was taken during step E002, when the AP last received a frame of the type used for measurement, for example, a QoS_DATA frame. The measured data rate was 155 Mbps, which does not trigger a modification of the PRL01 list. The beacon message that is transmitted remains B01, with the PRL01 list still at a data rate of 24 Mbps.

[0054] During step E007, the STA transmits a T03 frame, for example a QoS_DATA frame, at a bit rate of 36 Mbps, which is received by the AP. This T03 frame is not a control frame. Its bit rate has decreased significantly compared to a frame of the same type received during step E002, which is, for example, a result of the STA's distance from the AP. During this step, the AP measures the radio link quality with the STA, for example by measuring the received bit rate of the T03 frame. The measurement, 36 Mbps, is retained for when a new beacon message needs to be transmitted, which will potentially be an opportunity to modify the PRL01 list of allowed bit rates.

[0055] During step E008, the AP acknowledges the T03 frame received during step E007 by transmitting an ACK frame at a rate of 24 Mbps. It should be noted that the other two rates in the current list, 36 Mbps and 54 Mbps, cannot be used, as both are greater than or equal to the measurement retained during step E007, which is 36 Mbps.

[0056] During step E009, the AP transmits a T04 frame, for example a QoS_DATA type frame, at a rate of 72 Mbps, which is received by the STA. This T04 frame is not a control frame and can therefore be transmitted at a rate not limited by the PRL01 list. However, it is observed that the rate of 72 Mbps has decreased compared to a frame of the same type transmitted during step E004, which can be explained, for example, by the distance between the STA and the AP.

[0057] During an E010 step, the STA acknowledges the T04 frame received during the E009 step, by transmitting an ACK frame, still at a rate of 24Mbps.

[0058] During step E011, the STA transmits a T05 frame, for example a QoS_DATA frame, at a rate of 36 Mbps, which is received by the AP. This T05 frame is not a control frame. Its rate is the same as that of a frame of the same type received during step E007, which could indicate that the STA remained stationary after moving away from the AP. During this step, the AP measures the radio link quality with the STA, for example by measuring the receive rate of the T05 frame. The measurement, 36Mbps, is kept for when a new beacon message needs to be issued, which will eventually be an opportunity to modify the PRL01 list of allowed speeds.

[0059] During an E012 step, the AP acknowledges the T05 frame received during the E011 step, by transmitting an ACK frame, still at a rate of 24Mbps.

[0060] During step E013, the AP transmits a beacon signal that is received by the STA. Before transmission, the AP must determine whether the list needs to be modified, and to do so must take into account the last measurement it performed of the radio link quality with the STA. In this case, this measurement was taken during step E011, when the AP last received a frame of the type used for measurement, for example, a QoS_DATA frame. The measured rate was 36 Mbps, which triggers a modification of the PRL01 list to a PRL02 list containing more low rates than the PRL01 list, in order to take into account the decrease in the radio link quality between the AP and the STA, as reflected by the measured rate of the T05 frame received during step E011. The PRL02 list is also a sublist of PRLs:

[0061] PRL02 = [ll, 18, 24; 36; 54]

[0062] The low data rates of 1 Mbps and 18 Mbps have been added to the current list. During this step E013, the AP sends a B02 beacon message containing the PRL02 list, which becomes the current list in place of PRL01.

[0063] The AP transmits B02 at a rate of 1 Mbps, instead of 24 Mbps, because that is now the lowest rate in the current list.

[0064] During step E014, the AP transmits a T06 frame, for example a QoS_DATA type frame, at a rate of 36 Mbps, which is received by the STA. This T06 frame is not a control frame and can therefore be transmitted at a rate not limited by the PRL02 list. However, it is observed that the rate of 36 Mbps has decreased compared to a frame of the same type transmitted during step E009, which is explained by the distance between the STA and the AP.

[0065] During an E015 step, the STA acknowledges the T06 frame received during the E014 step, by transmitting an ACK frame, at a rate of 1 IMbps, because this is now the lowest of the rates in the current PRL02 list that the STA received during the E013 step.

[0066] Figure 2a shows an example of Wi-Fi frame exchanges between an STA station and an AP access point, before approaching the station, according to one aspect of the invention.

[0067] According to the invention, the beacon messages include a dynamic list of authorized rates. For illustrative purposes, the presentation of the exchanges between STA and AP begins with a running list of authorized rates PRL11, which is the complete list of rates from the PRL list.

[0068] During an E101 step, the AP transmits a B11 beacon signal, at a rate of IMbps, which is received by the STA. B11 includes the PRL11 rate list, which is identical to PRL:

[0069] PRL11 = [1; 2; 5.5; 11; 18; 24; 36; 54]

[0070] PRL11 includes the lowest PRL rates for example because the quality of the radio link at the time of step E101 does not allow the use of higher rates for the control frames.

[0071] Whether on the side of the AP that transmits the beacon signal, or on the side of the ST A that receives it, the control frames, including the beacon signal, are transmitted at one of the rates indicated in the PRL11 list of the beacon signal B11. In our example, the control frames are transmitted at the lowest rate of the current list, i.e. IMbps at the time of step E101.

[0072] During an E102 step, the STA transmits a Tl 1 frame, for example a QoS_DATA type frame, at a rate of 7.2 Mbps, which is received by the AP. This Tl 1 frame is not a control frame. During this step, the AP measures the radio link quality with the STA, for example by measuring the received rate of the Tl 1 frame. The measurement, 7.2 Mbps, is retained for when a new beacon message needs to be transmitted, which will eventually be an opportunity to modify the current PRL11 list of allowed rates.

[0073] During an E103 step, the AP acknowledges the Tl 1 frame received during the E102 step, by transmitting an ACK frame, at a rate of IMbps because ACK frames are control frames, and IMbps is the lowest rate in the current list, which is PRL11.

[0074] During an E104 step, the AP transmits a T12 frame, for example a QoS_DATA type frame, at a rate of 14.4 Mbps, which is received by the STA. This T12 frame is not a control frame and can therefore be transmitted at a rate that is not limited by the PRL IL list.

[0075] During an E105 step, the STA acknowledges the T12 frame received during the E104 step, by transmitting an ACK frame, at a rate of IMbps which is the lowest rate in the current list, PRL11.

[0076] Figure 2b shows an example of Wi-Fi frame exchanges between a station STA and an access point AP, after the station has been brought closer, according to one aspect of the invention. This closer proximity results in an increase in the quality of the radio link between AP and STA.

[0077] Following step E105, during step E106, the AP transmits a beacon signal. To determine whether the list should be modified, the AP must consider the last measurement it performed of the radio link quality with the STA. In this case, this measurement was taken during step E102, when the AP last received a frame of the type used for measurement, for example, a QoS_DATA frame. The measured data rate was 7.2 Mbps, which does not trigger a modification of the PRL11 list. The beacon message that is transmitted remains B11, with the PRL11 list, at a data rate of I Mbps because this is the lowest data rate in the current PRL11 list.

[0078] During step E107, the STA transmits a T13 frame, for example a QoS_DATA frame, at a bit rate of 21.7 Mbps, which is received by the AP. This T13 frame is not a control frame. Its bit rate has increased significantly compared to a frame of the same type received during step E102, which is the normal result of the STA moving closer to the AP. During this step, the AP measures the radio link quality with the STA, for example by measuring the received bit rate of the T13 frame. The measurement, 21.7 Mbps, is retained for when a new beacon message needs to be transmitted, which will eventually be an opportunity to modify the PRL11 list of allowed bit rates.

[0079] During an E108 step, the AP acknowledges the T13 frame received during the E107 step, by transmitting an ACK frame, always at the rate of IMbps.

[0080] During step E109, the AP transmits a T14 frame, for example a QoS_DATA type frame, at a rate of 21.7 Mbps, which is received by the STA. This T14 frame is not a control frame and can therefore be transmitted at a rate not limited by the PRL11 list. However, it is observed that the rate of 72 Mbps has increased compared to a frame of the same type transmitted during step E104, which can be explained, for example, by the STA moving closer to the AP.

[0081] During an E110 step, the STA acknowledges the T14 frame received during the E109 step, by transmitting an ACK frame, always at the rate of IMbps.

[0082] During step E11, the STA transmits a T15 frame, for example, a QoS_DATA frame, at a bit rate of 57.8 Mbps, which is received by the AP. This T15 frame is not a control frame. Its bit rate has increased further compared to a frame of the same type received during step E107, which could indicate that the STA has moved even closer to the AP. During this step, the AP measures the radio link quality with the STA, for example, by measuring the received bit rate of the T15 frame. The measurement, 57.8 Mbps, is retained for when a new beacon message needs to be transmitted, which will eventually be an opportunity to modify the PRL11 list of allowed bit rates.

[0083] During an E112 step, the AP acknowledges the T15 frame received during the El 11 step, by transmitting an ACK frame, always at the rate of IMbps.

[0084] During step E113, the AP transmits a beacon signal that is received by the STA. Before transmission, the AP must determine whether the list needs to be modified, and to do so must take into account the last measurement it performed of the radio link quality with the STA. In this case, this measurement was taken during step E11, when the AP last received a frame of the type used for measurement, for example, a QoS_DATA frame. The measured rate was 57.8 Mbps, which triggers a modification of the PRL11 list to a PRL12 list containing fewer low rates than the PRL11 list, in order to take into account the increase in radio link quality. between the AP and the STA, as reflected by the measured rate of the T15 frame received during step El 11. The PRL 12 list is also a sublist of PRLs:

[0085] PRL12 = [24 ; 36 ; 54]

[0086] The low data rates of 1 Mbps and 18 Mbps have been removed from the current list. During this step El 13, the AP sends a B12 beacon message containing the PRL12 list, which becomes the current list in place of PRL11.

[0087] The AP transmits B12 at a rate of 24Mbps, instead of IMbps, because that is now the lowest rate in the current list.

[0088] During step E114, the AP transmits a T16 frame, for example a QoS_DATA type frame, at a rate of 43.3 Mbps, which is received by the STA. This T16 frame is not a control frame and can therefore be transmitted at a rate not limited by the PRL12 list. However, it is observed that the rate of 43.3 Mbps has increased compared to a frame of the same type transmitted during step E109, which is explained by the STA moving closer to the AP.

[0089] During an E115 step, the STA acknowledges the T16 frame received during the El 14 step, by transmitting an ACK frame, at a rate of 24Mbps because this is now the lowest of the rates in the current PRL 12 list that the STA received during the El 13 step.

[0090] During steps E013 or El 13, one or more flow rates are respectively added or removed from the current list based on a comparison between respectively an addition threshold or a removal threshold, and the measured parameter.

[0091] The following table gives an example of such thresholds when the measured parameter is the receive rate of a QoS_DATA type frame received from the STA, for the PRL rates specific to the 2.4 GHz frequency band. In this table, each threshold is specific to one of these rates, and a rate is added to the current list (or removed from the current list) if the measured parameter is less than the addition threshold (or greater than the removal threshold) specific to that rate. Data rate (Mbps) Add threshold (Mbps) Withdraw threshold (Mbps) 1 13 13 2 21.7 21.7 5.5 28.9 28.9 11 39 39 18 52 52 24 144.4 144.4 36 240 240 54 300 300

[0092] For example, applied to step E013, this table is used as follows. In step E013, the current list of permitted flow rates is:

[0093] PRL01 = [24 ; 36 ; 54]

[0094] The method for managing the announcement of the authorized bitrate list first takes the lowest bitrate from the current list PRL01, i.e., 24 Mbps, and the last measurement taken of the radio link quality with the STA, i.e., the bitrate of the QoS_DATA frame received during step E011, which was 36 Mbps. The method performs the following steps: • 36Mbps is less than 144.4Mbps, which is the threshold for adding the 24Mbps rate, so 24Mbps is kept in the list, and the immediately lower rate from the PRL01 list, 18Mbps, is examined: • 36Mbps is less than 52Mbps, which is the threshold for adding the 18Mbps rate, so 18Mbps is added to the list, and the immediately lower rate from the PRL01 list, UMbps, is examined: • 36Mbps is less than 39Mbps, which is the threshold for adding the 1 IMbps rate, so 1 IMbps is added to the list, and the next lowest rate in the PRL01 list, 5.5Mbps, is examined: • 36Mbps is not less than 28.9Mbps, which is the threshold for adding the 5.5Mbps throughput, so 5.5Mbps is not added to the list, and the modification of the list stops.

[0095] The resulting current list, PRL02, is therefore:

[0096] PRL02 = [ll, 18, 24; 36; 54]

[0097] As a further example, applied to step El 13, this table is used as follows. In step El 13, the current list of permitted flow rates is:

[0098] PRL11 = [1; 2; 5.5; 11; 18; 24; 36; 54]

[0099] The method for managing the announcement of the authorized bitrate list first takes the lowest bitrate from the current PRL11 list, i.e., IMbps, and the last measurement taken of the radio link quality with the STA, i.e., the bitrate of the QoS_DATA frame received during step El 11, which was 57.8Mbps. The method performs the following steps: • 57.8Mbps is not less than 13Mbps, which is the threshold for adding the 1Mbps throughput, so the comparison is made with the subtraction threshold: • 57.8Mbps is greater than 13Mbps, which is the threshold for removing the IMbps rate, therefore IMbps is removed from the list, and the next highest rate in the PRL11 list, 2Mbps, is examined: • 57.8Mbps is greater than 21.7Mbps, which is the threshold for removing the 2Mbps rate, therefore 2Mbps is removed from the list, and the next highest rate in the PRL11 list, 5.5Mbps, is examined: • 57.8Mbps is greater than 28.9Mbps, which is the threshold for removing the 5.5Mbps rate, therefore 5.5Mbps is removed from the list, and the next highest rate in the PRL11 list, UMbps, is examined: • 57.8Mbps is greater than 39Mbps, which is the threshold for removing the 1 IMbps rate, therefore 1 IMbps is removed from the list, and the next highest rate in the PRL11 list, 18Mbps, is examined: • 57.8Mbps is greater than 52Mbps, which is the threshold for removing the 18Mbps rate, therefore 181Mbps is removed from the list, and the next higher rate on the PRL11 list, 24Mbps, is examined: • 57.8Mbps is not greater than 144.4Mbps, which is the threshold for removing the 24Mbps speed, therefore 24Mbps is not removed from the list, and the modification of the list stops.

[0100] The resulting current list, PRL 12, is therefore:

[0101] PRL12 = [24 ; 36 ; 54]

[0102] In the table above, the addition and removal thresholds are identical for demonstration purposes, but they may be different. Similarly, if the parameter measured to determine the radio link quality between AP and STA is other than the receive rate of a QoS_DATA frame, for example the received signal strength RSSI, a similar table adapted for RSSI should be used.

[0103] In one variant, it is not the last measured parameter that is retained, but a parameter representative of several measurements distributed over time. This representative parameter is, for example, an average of the measurements between two beacon messages.

[0104] In another variant, it is checked whether the current list should be modified after each measurement, for example without waiting for the transmission of a beacon message. In this case, the AP uses the new current list, but the STA continues to use the old one until it has received the beacon message containing the new current list.

[0105] In one variant, a flow rate is added to or removed from the current list only if the result of the comparison with its addition or removal threshold gives the same result several times in a row.

[0106] The above variants can be combined and allow the process to be modulated between a very rapid adaptation of the current list to a small change in radio conditions, and, on the contrary, a stabilization of the list in the face of very unstable radio conditions.

[0107] Figure 3 presents an example of the structure of a device in a Wi-Fi access point, implementing the method of announcing a list of authorized rates, according to one aspect of the invention.

[0108] Device 100 implements the announcement process, various embodiments of which have just been described.

[0109] Such a device 100 can be implemented in a Wi-Fi access point, such as, for example, an AP access point, which can be a home or business gateway, or a home or business router, providing access to the Internet

[0110] For example, the device 100 comprises a receiver 101, a transmitter 102, a processing unit 130, equipped, for example, with a pP microprocessor, and controlled by a computer program 110, stored in a memory 120 and implementing the announcement method according to the invention. At initialization, the code instructions of the computer program 110 are, for example, loaded into a RAM memory before being executed by the processor of the processing unit 130.

[0111] 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: • transmit an initial beacon message including an initial list of authorized flow rates, • measure at least one parameter representative of the quality of a radio link between the access point and the station, • modify the first list into a second list of authorized flow rates, based on at least one measured parameter, • send a second beacon message including the second list of authorized flow rates.

[0112] The entities described and included in the devices described in relation to [Fig. 3] may be hardware or software. [Fig. 3] illustrates only one particular way, among several possible ways, of carrying out the process detailed above, in relation to the preceding figures. Indeed, the technique of the invention can be carried out 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).

[0113] In the case where the invention is implemented on a reprogrammable computing machine, the corresponding program (i.e. the sequence of instructions) may be stored in a removable storage medium (such as, for example, a USB key, a floppy disk, a CD-ROM or a DVD-ROM) or not, this storage medium being readable partially or totally by a computer or a processor.

Claims

Claims

1. Method for announcing lists of authorized rates for control frames in a Wi-Fi network comprising an access point (AP) and a station (STA), implemented by the access point and comprising: • Transmission (E001, E006, E101, E106) of a first beacon message (B01, B11) comprising a first list of authorized rates, • Measurement of at least one parameter representative of the quality of a radio link between the access point and the station, • Modification of the first list into a second list of authorized rates, as a function of the at least one measured parameter, • Transmission (E013, E113) of a second beacon message (B02, B12) comprising the second list of authorized rates, the method being characterized in that the access point is a virtual access point dedicated to the station.

2. An advertising method according to claim 1, wherein the modification is an addition of at least one rate lower than the lowest of the rates in the first list.

3. An advertising method according to claim 1, wherein the modification is a removal of at least one of the lowest rates from the first list.

4. Announcement method according to one of claims 2 or 3, where a flow rate is added or removed based on a comparison between a value representative of the at least one measured parameter and an addition or removal threshold specific to the added or removed flow rate and to the parameter.

5. Announcement method according to one of the preceding claims, where the measurement of the at least one parameter is repeated several times, and where the modification is triggered if the representative values ​​remain several times in a row on the same side of the addition or removal threshold.

6. Announcement method according to one of the preceding claims, where the at least one parameter representative of the quality of a radio link between the access point and the station is part of a group comprising: • Rate of reception of a frame from the station; • Signal strength received by the station; • Noise level; • Number of identical frames retransmitted by the station.

7. An announcement method according to claim 6, wherein the frame used to measure the throughput when receiving a frame from the station is a QoS_DATA type frame.

8. Device (100) for announcing lists of authorized rates for control frames in a Wi-Fi network comprising an access point and a station, the device being included in the access point and 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 to: • transmit a first beacon message comprising a first list of authorized rates, • measure at least one parameter representative of the quality of a radio link between the access point and the station, • modify the first list into a second list of authorized rates, as a function of the at least one measured parameter, • transmit a second beacon message comprising the second list of authorized rates. the device being characterized in that the access point is a virtual access point dedicated to the station.

9. Computer program (110), comprising instructions which, when these instructions are executed by a processor, cause the latter to implement the steps of the method of announcing lists of authorized debits, according to claim 1.

10. Information medium readable by a Wi-Fi access point, and comprising instructions of a computer program (110) according to claim 9.

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