FR3134272A1 - Method and device for announcing authorized flow rates for control and management frames in a Wi-Fi network - Google Patents

Abstract

Method and device for announcing authorized flow rates for control and management frames in a Wi-Fi network Method for announcing lists of authorized flow 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) comprising 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 rates, depending on the at least one measured parameter, Emission (E013) of a second beacon message (B02) comprising the second list of authorized rates. Figure for abstract: Figure 1b

Description

Method and device for announcing authorized flow rates for control and management frames in a Wi-Fi network 1. Field of the invention

The invention is located in the field of so-called Wi-Fi networks (IEEE 802.11 standards, Institute of Electrical and Electronics Engineers, or in French Institute of Electrical and Electronic Engineers), and more particularly that of authorized flow rates for control frames or management frames exchanged between a station (STA) and an access point (AP).

2. State of the prior art

Current Wi-Fi access points (APs) send beacon messages which, among other things, announce the authorized physical flow rates for control and management frames (collectively called "control frames" in the following), as well as for other types of frames in particular situations. The physical rates depend on the frequencies used by the AP, and this announcement aims to indicate once and for all, among all the possible rates depending on the frequency band, which ones are authorized, and therefore, to prohibit those which are not announced in a beacon message. The speeds are announced in ascending order, for example on an interface in the 2.4GHz frequency band the list of physical speeds announced is "1; 2; 5.5; 11; 18; 24; 36; 54" which indicates that 8 Bitrates are allowed, the lowest being 1Mbps and the highest being 54Mpbs. In fact, control frames are transmitted at the lowest bit 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).

As the lowest 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, even more so if an AP uses several logical interfaces (also called VAP, LVAP, or vBSS, etc.). This has the disadvantage of increasing the occupation time of the transmission channel between AP and stations, and of reducing radio coverage on the AP in general (i.e. on all virtual interfaces).

One of the aims of the invention is to remedy these drawbacks of the state of the art.

3. Presentation of the invention

The invention improves the situation using a process for announcing lists of authorized 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 a first beacon message including 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 flow rates, depending on the at least one measured parameter,
• Transmission of a second beacon message including the second list of authorized rates.

By measuring the quality of the radio link between the access point and the station, the access point can deduce a rate at which the station is capable of transmitting and receiving control frames. Thus, the access point can adapt the list of authorized flow 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, whatever the situation. By parameter representative of the quality of the radio link, we mean any parameter making it possible to quantify the state of the transmission channel between an access point and a station. Such parameters are for example the rate of a frame, the signal power (RSSI, Received Signal Strength Indicator), the signal to noise ratio (SNR, Signal to Noise Ratio), the channel state information (CSI , Channel State Information), etc.

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

According to one aspect of the announcement process, the modification is a withdrawal of at least one of the lowest flow rates from the first list.

Thus, the modification of the list implemented by the access point has a direct and immediate effect on the rate used by the control messages exchanged between the station and the access point. Indeed, it is recalled that stations and access points transmit control messages preferably using the lowest rate from the list transmitted in a beacon message.

According to one aspect of the announcement method, 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 setting.

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

According to one aspect of the announcement method, the measurement of the at least one parameter is repeated several times, and the modification is triggered if the representative values remain several times in a row on the same side of the addition or modification threshold. withdrawal.

Thus, the list is only modified if a trend is confirmed in the measured flow, and we avoid modifying the list too frequently.

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

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

In the case where the virtual access point is dedicated to a single station, this allows management of announcements which is specific to the quality of the radio link between the virtual access point and this station only.

According to one aspect of the announcement method, 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:

• Throughput when receiving a frame from the station;
• Signal strength received by the station;
• Noise level ;
• Number of identical frames retransmitted by the station.

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 quality of the radio link can make it possible to adapt to each type of station, for example when the reception rate of a frame is not reliable or easy to measure. In this case the RSSI (signal power received by the station) allows the access point to deduce the attenuation between the station and the access point, without it knowing a priori the power emitted by the station. By subtracting the noise level, the SNR (signal to noise ratio) is obtained. Based on this SNR the rate of transmitted frames can be estimated. If this rate is low, certain unreceived frames are not acknowledged and this causes frame retransmissions. We understand that these 4 parameters, taken into account alone or in combination, are relevant for the decision to modify or not the list of authorized flow rates.

According to one aspect of the announcement method, the frame used to measure the throughput on reception of a frame coming from the station is a QoS_DATA type frame.

QoS_DATA type frames are the most used in the prior art to measure the reception rate of a Wi-Fi frame. Thus, infrastructural modifications compared to the prior art are minimized. In some implementations DATA type frames are also used.

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

The invention also relates to a device 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 , a transmitter, a processor and a memory coupled to the processor with instructions intended to be executed by the processor for:

• 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 flow rates, depending on the at least one measured parameter,
• transmit a second beacon message including the second list of authorized rates.

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

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 for announcing lists of authorized debits, which has just been describe.

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

The above-mentioned program 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 partially compiled form, or in n any other desirable shape.

The information carrier mentioned above can be any entity or device capable of storing the program. For example, a medium may comprise a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or even a magnetic recording means.

Such a storage means can for example be a hard disk, flash memory, etc.
On the other hand, an information carrier may be a transmissible medium such as an electrical or optical signal, which may be carried 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.

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 executing the method in question.

4. Presentation of the figures

Other advantages and characteristics of the invention will appear more clearly on reading the following description of a particular embodiment of the invention, given by way of simple illustrative and non-limiting example, and the appended drawings, among which :

there presents an example of Wi-Fi frame exchanges between station and access point before moving away from the station, according to one aspect of the invention,

there 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,

there presents an example of exchanges of Wi-Fi frames between station and access point before bringing the station closer, according to one aspect of the invention,

there presents an example of exchanges of Wi-Fi frames between station and access point after bringing the station closer, according to one aspect of the invention,

there presents an example of the structure of a device in a Wi-Fi access point, implementing the method for announcing a list of authorized speeds, according to one aspect of the invention.

5. Detailed description of at least one embodiment of the invention

In the remainder of the description, it is understood that the invention applies to all variations of the IEEE 802.11 standards.

The diagrams in Figures 1a to 2b illustrate the steps of the flow rate announcement method according to the invention, in an example of configuration where the Wi-Fi network complies with the 802.11n standard and uses the 2.4GHz 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 the movement away or closer of a STA in relation to an AP, but the invention applies to any scenario of change of condition affecting the quality of the radio link between the AP and the STA, whatever the cause.

In the 2.4GHz frequency band, the complete list of speeds that can be authorized, denoted PRL, is, in megabits per second (Mbps):

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

There presents 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.

According to the invention, the beacon messages include a dynamic list of authorized rates. For illustration purposes, the presentation of exchanges between STA and AP begins with a current list of authorized debits PRL01, which is a sub-list of PRL.

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

PRL01 = [24; 36; 54]

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

Whether on the side of the AP which transmits the beacon signal, or on the side of the STA which receives it, the control frames, including the beacon signal, are transmitted at one of the rates indicated in the PRL01 list of the beacon signal B01.

In our example, the control frames are sent at the lowest rate in the current list, that is to say 24Mbps at the time of this step E001.

During a step E002 , the STA transmits a frame T01, for example a QoS_DATA type frame, at a rate of 155Mbps, which is received by the AP. This T01 frame is not a control frame. During this step, the AP measures the quality of the radio link with the STA, for example by measuring the reception rate of frame T01. The measurement, 155Mbps, is kept for the moment when a new beacon message must be sent, which will possibly be an opportunity to modify the current PRL01 list of authorized speeds. This measurement can also be used in the choice of the rate of the current list which will be used to transmit a control frame. In fact, this flow must be lower than the measurement. At the time of step E002, all the speeds in the PRL01 list can therefore theoretically be used because they are all less than 155Mbps.

During a step E003 , the AP acknowledges the T01 frame received during step E002, by sending an ACK frame at a rate of 24Mbps. ACK frames are control frames, and must therefore be sent at one of the rates in the current list, which is PRL01. The ACK frame is therefore sent at the lowest rate in the current list, that is to say 24Mbps at the time of step E003.

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

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

There presents an example of Wi-Fi frame exchanges between an STA station and an AP access point, after moving away from the station, according to one aspect of the invention. This distance induces a reduction in the quality of the radio link between AP and STA.

Following step E005, during a step E006 , the AP transmits a beacon signal. In order to determine whether the list should be modified, the AP must take into account the last measurement it made of the quality of the radio link with the STA. In this case, this measurement was made during step E002, when the AP received for the last time a frame of the type used for the measurement, for example a frame of the QoS_DATA type. The measured speed was 155Mbps, which does not trigger a modification of the PRL01 list. The beacon message that is sent remains B01, with the PRL01 list, still at a rate of 24Mbps.

During a step E007 , the STA transmits a T03 frame, for example a QoS_DATA type frame, at a rate of 36Mbps, which is received by the AP. This T03 frame is not a control frame. Its throughput has significantly decreased compared to a frame of the same type received during step E002, which is for example the result of the distance of the STA from the AP. During this step, the AP measures the quality of the radio link with the STA, for example by measuring the reception rate of the T03 frame. The measurement, 36Mbps, is kept for the moment when a new beacon message must be sent, which will possibly be an opportunity to modify the PRL01 list of authorized speeds.

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

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

During a step E010 , the STA acknowledges the frame T04 received during step E009, by sending an ACK frame, always at a rate of 24Mbps.

During a step E011 , the STA transmits a frame T05, for example a QoS_DATA type frame, at a rate of 36Mbps, which is received by the AP. This T05 frame is not a control frame. Its rate is the same compared to 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 quality of the radio link with the STA, for example by measuring the reception rate of the T05 frame. The measurement, 36Mbps, is kept for the moment when a new beacon message must be sent, which will possibly be an opportunity to modify the PRL01 list of authorized speeds.

During a step E012 , the AP acknowledges the T05 frame received during step E011, by sending an ACK frame, always at a rate of 24Mbps.

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

PRL02 = [11, 18, 24; 36; 54]

Low speeds 11Mbps and 18Mbps have been added to the current list. During this step E013, the AP transmits a beacon message B02 including the list PRL02, which becomes the current list in place of PRL01.

The AP transmits B02 at a rate of 11Mbps, instead of 24Mbps, because it is now the lowest rate in the current list.

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

During a step E015 , the STA acknowledges the frame T06 received during step E014, by sending an ACK frame, at the rate of 11Mbps, because it is now the lowest of the rates in the current list PRL02 that the STA received during step E013.

There presents an example of Wi-Fi frame exchanges between an STA station and an AP access point, before bringing the station closer, according to one aspect of the invention.

According to the invention, the beacon messages include a dynamic list of authorized rates. For illustration purposes, the presentation of the exchanges between STA and AP begins with a current list of authorized debits PRL11, which is the complete list of debits from the PRL list.

During a step E101 , the AP transmits a beacon signal B11, at a rate of 1Mbps, which is received by the STA. B11 includes the list of debits PRL11 which is identical to PRL:

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

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

Whether on the side of the AP which transmits the beacon signal, or on the side of the STA which 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 sent at the lowest rate in the current list, that is to say 1Mbps at step E101.

During a step E102 , the STA transmits a T11 frame, for example a QoS_DATA type frame, at a rate of 7.2Mbps, which is received by the AP. This T11 frame is not a control frame. During this step, the AP measures the quality of the radio link with the STA, for example by measuring the reception rate of the T11 frame. The measurement, 7.2Mbps, is kept for the moment when a new beacon message must be sent, which will possibly be an opportunity to modify the current PRL11 list of authorized speeds.

During a step E103 , the AP acknowledges the T11 frame received during step E102, by sending an ACK frame, at a rate of 1Mbps because the ACK frames are control frames, and 1Mbps is the lowest rate from the current list, which is PRL11.

During a step E104 , the AP transmits a T12 frame, for example a QoS_DATA type frame, at a rate of 14.4Mbps, which is received by the STA. This T12 frame is not a control frame and can therefore be transmitted at a rate which is not limited by the PRL11 list.

During a step E105 , the STA acknowledges the frame T12 received during step E104, by sending an ACK frame, at the rate of 1Mbps which is the lowest rate in the current list, PRL11.

There presents an example of exchanges of Wi-Fi frames between an STA station and an AP access point, after bringing the station closer, according to one aspect of the invention. This rapprochement induces an increase in the quality of the radio link between AP and STA.

Following step E105, during a step E106 , the AP transmits a beacon signal. In order to determine whether the list should be modified, the AP must take into account the last measurement it made of the quality of the radio link with the STA. In this case, this measurement was made during step E102, when the AP last received a type frame used for the measurement, for example a QoS_DATA type frame. The measured speed was 7.2Mbps, which does not trigger a modification of the PRL11 list. The beacon message that is sent remains B11, with the PRL11 list, at a rate of 1Mbps because it is the lowest rate of the current PRL11 list.

During a step E107 , the STA transmits a T13 frame, for example a QoS_DATA type frame, at a rate of 21.7Mbps, which is received by the AP. This T13 frame is not a control frame. Its throughput has significantly increased compared to a frame of the same type received during step E102, which is the normal result of bringing the STA closer to the AP. During this step, the AP measures the quality of the radio link with the STA, for example by measuring the reception rate of the T13 frame. The measurement, 21.7Mbps, is kept for the moment when a new beacon message must be sent, which will possibly be an opportunity to modify the PRL11 list of authorized speeds.

During a step E108 , the AP acknowledges the T13 frame received during step E107, by sending an ACK frame, always at a rate of 1Mbps.

During a step E109 , the AP transmits a T14 frame, for example a QoS_DATA type frame, at a rate of 21.7Mbps, which is received by the STA. This T14 frame is not a control frame and can therefore be transmitted at a rate which is not limited by the PRL11 list. On the other hand, it is observed that the throughput of 72Mbps has increased compared to a frame of the same type transmitted during step E104, which can be explained for example by the rapprochement of the STA in relation to the AP.

During a step E110 , the STA acknowledges the T14 frame received during step E109, by sending an ACK frame, always at a rate of 1Mbps.

During a step E111 , the STA transmits a T15 frame, for example a QoS_DATA type frame, at a rate of 57.8Mbps, which is received by the AP. This T15 frame is not a control frame. Its throughput has further increased 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 quality of the radio link with the STA, for example by measuring the reception rate of the T15 frame. The measurement, 57.8Mbps, is kept for the moment when a new beacon message must be sent, which will possibly be an opportunity to modify the PRL11 list of authorized speeds.

During a step E112 , the AP acknowledges the T15 frame received during step E111, by sending an ACK frame, always at a rate of 1Mbps.

During a step E113 , the AP transmits a beacon signal which is received by the STA. Before transmission, the AP must determine whether the list must be modified, and to do this must take into account the last measurement it made of the quality of the radio link with the STA. In this case, this measurement was made during step E111, when the AP last received a type frame used for the measurement, for example a QoS_DATA type frame. The measured rate was 57.8Mbps, which triggers a modification of the PRL11 list into a PRL12 list including fewer low rates than the PRL11 list, in order to take into account the increase in the quality of the radio link between the AP and the STA, as reflected by the measured rate of the T15 frame received during step E111. The PRL12 list is also a sublist of PRL:

PRL12 = [24; 36; 54]

The low speeds 11Mbps and 18Mbps have been removed from the current list. During this step E113, the AP transmits a beacon message B12 including the list PRL12, which becomes the current list in place of PRL11.

The AP transmits B12 at a rate of 24Mbps, instead of 1Mbps, because it is now the lowest rate in the current list.

During a step E114 , the AP transmits a T16 frame, for example a QoS_DATA type frame, at a rate of 43.3Mbps, which is received by the STA. This T16 frame is not a control frame and can therefore be sent at a rate which is not limited by the PRL12 list. It is observed, however, that the throughput of 43.3Mbps has increased compared to a frame of the same type transmitted during step E109, which is explained by the rapprochement of the STA in relation to the AP.

During a step E115 , the STA acknowledges the T16 frame received during step E114, by sending an ACK frame, at the rate of 24Mbps because it is now the lowest of the rates in the current list PRL12 that the STA has received during step E113.

During steps E013 or E113, one or more flow rates are respectively added or removed from the current list based on a comparison between an addition threshold or a removal threshold, respectively, and the measured parameter.

The following table gives an example of such thresholds when the parameter measured the rate on reception of a QoS_DATA type frame when receiving the STA, for the rates of the PRL list specific to the 2.4GHz frequency band. In this table each threshold is specific to one of these flow rates, and a flow rate is added to the current list (resp. removed from the current list) if the measured parameter is lower than the addition threshold (resp. higher than the removal threshold ) specific to this flow rate. Throughput (Mbps) Add Threshold (Mbps) Withdrawal 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

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

PRL01 = [24; 36; 54]

The method for managing the list of authorized rates first takes the lowest rate from the current list PRL01, that is to say 24Mbps, and the last measurement taken of the quality of the radio link with the STA , that is to say the rate of the QoS_DATA type frame received during step E011, which was 36Mbps. The process performs the following steps:

• 36Mbps is less than 144.4Mbps which is the threshold for adding 24Mbps throughput, so 24Mbps is kept in the list, and the next lower PRL01 list throughput, 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 next lower PRL01 list rate, 11Mbps, is examined:
• 36Mbps is less than 39Mbps which is the threshold for adding the 11Mbps rate, so 11Mbps is added to the list, and the next lower PRL01 list rate, 5.5Mbps, is examined:
• 36Mbps is not less than 28.9Mbps which is the threshold for adding 5.5Mbps throughput, so 5.5Mbps is not added to the list, and the list editing stops.

The resulting current list, PRL02, is therefore:

PRL02 = [11, 18, 24; 36; 54]

As an additional example, applied in step E113, this table is used as follows. In step E113, the current list of authorized flow rates is:

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

The method for managing the list of authorized rates first takes the lowest rate from the current list PRL11, that is to say 1Mbps, and the last measurement taken of the quality of the radio link with the STA , that is to say the rate of the QoS_DATA type frame received during step E111, which was 57.8Mbps. The process performs the following steps:

• 57.8Mbps is not less than 13Mbps which is the threshold for adding 1Mbps speed, then the comparison is made with the withdrawal threshold:
• 57.8Mbps is greater than 13Mbps which is the 1Mbps rate removal threshold, so 1Mbps is removed from the list, and the next higher PRL11 list rate, 2Mbps, is examined:
• 57.8Mbps is greater than 21.7Mbps which is the 2Mbps rate removal threshold, so 2Mbps is removed from the list, and the next higher PRL11 list rate, 5.5Mbps, is examined:
• 57.8Mbps is greater than 28.9Mbps which is the 5.5Mbps rate removal threshold, so 5.5Mbps is removed from the list, and the next higher PRL11 list rate, 11Mbps, is examined:
• 57.8Mbps is greater than 39Mbps which is the 11Mbps rate removal threshold, so 11Mbps is removed from the list, and the next higher PRL11 list rate, 18Mbps, is examined:
• 57.8Mbps is greater than 52Mbps which is the 18Mbps rate removal threshold, so 181Mbps is removed from the list, and the next higher PRL11 list rate, 24Mbps, is examined:
• 57.8Mbps is not higher than 144.4Mbps which is the threshold for removing 24Mbps speed, so 24Mbps is not removed from the list, and the list modification stops.

The resulting current list, PRL12, is therefore:

PRL12 = [24; 36; 54]

In the table above, the addition and removal thresholds are the same for convenience of demonstration, but they may be different. Likewise, if the parameter measured to determine the quality of the radio link between AP and STA is other than the reception rate of a QoS_DATA frame, for example the power of the RSSI received signal, a similar table but adapted to the RSSI must be used .

In a variant, it is not the last parameter measured which 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.

In another variant, it is checked whether the current list must 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 including the new current list.

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

The above variants can be combined and make it possible to modulate the process between very rapid adaptation of the current list to a slight change in radio condition, and, on the contrary, stabilization of the list in the face of very unstable radio conditions.

There presents an example of the structure of a device in a Wi-Fi access point, implementing the method for announcing a list of authorized speeds, according to one aspect of the invention.

The device 100 implements the announcement method, different embodiments of which have just been described.

Such a device 100 can be implemented in a Wi-Fi access point, such as for example the AP access point, which can be a domestic or professional gateway, or a domestic or professional router, for access to Internet

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 announcement method according to the invention. Upon 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.

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 for:

• 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 flow rates, depending on the at least one measured parameter,
• transmit a second beacon message including the second list of authorized rates.

The entities described and included in the devices described in relation to the can be hardware or software. There illustrates only one particular way, among several possible, of carrying out the process detailed above, in relation to the previous figures. Indeed, the technique of the invention is carried out indifferently on a reprogrammable calculation machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated calculation machine (for example a set of logic gates like an FPGA or an ASIC, or any other hardware module).

In the case where the invention is implemented on a reprogrammable calculation machine, the corresponding program (that is to say the sequence of instructions) can 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 partially or totally readable by a computer or a processor.

Claims (11)

Processfor 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 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, depending on the at least one measured parameter,
• Transmission (E013, E113) of a second beacon message (B02, B12) comprising the second list of authorized rates.

Announcement method according to claim 1, where the modification is an addition of at least one flow rate lower than the lowest flow rate in the first list. Announcement method according to claim 1, where the modification is a removal of at least one of the lowest flow rates from the first list. Announcement method according to one of claims 2 or 3, where a flow rate is added or removed as a function of a comparison between a value representative of the at least one measured parameter and an addition or removal threshold specific to the flow added or removed and to the parameter. 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 are maintained several times in a row on the same side of the threshold addition or removal. Announcement method according to one of the preceding claims, where the access point is a virtual access point. Processannouncement 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:

• Throughput when receiving a frame from the station;
• Signal strength received by the station;
• Noise level ;
• Number of identical frames retransmitted by the station.

Announcement method according to claim 7, where the frame used to measure the throughput on reception of a frame coming from the station is a QoS_DATA type frame. 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 for:

• 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 flow rates, depending on the at least one measured parameter,
• transmit a second beacon message including the second list of authorized rates.

Computer program (110) , comprising instructions which, when these instructions are executed by a processor, lead the latter to implement the steps of the method for announcing lists of authorized debits, according to claim 1. Information medium readable by a Wi-Fi access point, and comprising instructions for a computer program (110) according to claim 10.