Method for managing a wireless access point, method for transmitting data from a station to a wireless access point, corresponding access point, station and computer program

Abstract

The present invention relates to a method for managing a wireless access point, comprising: - broadcasting (21) a downlink frame to one or more stations present in the coverage area of ​​the access point, the downlink frame carrying an indicator requesting the station receiving the downlink frame to transmit the power level of the access point received; - in response to the downlink frame, receiving (26) at least one uplink frame from at least one of the stations, the uplink frame transmitted by the station carrying information indicating the power level of the access point received by the station; - determining (27) at least one power level of the access point received by the at least one station based on the information indicating the power level carried by the one or more uplink frames.

Description

Technical Field

[0001] The field of this invention is wireless communication.

[0002] More specifically, the present invention relates to wireless communication networks in an infrastructure mode that implement at least one access point and at least one site, and proposes a solution for specifically managing the transmission power of the access point(s).

[0003] This invention particularly relates to wireless communication networks compatible with the IEEE 802.11 standard, according to different current or future versions, more commonly referred to as Wi-Fi networks for “Wireless Fidelity”. Specifically, this invention relates to Wi-Fi networks according to the IEEE 802.11ax or IEEE 802.11be standards. Background Technology

[0004] like Figure 1 As shown, the Wi-Fi network in infrastructure mode includes at least one access point 11 (AP) and at least one site located in the coverage area of ​​the access point.

[0005] Access point 11 and the sites (STA1 121, STA2 122, STA3 123, and STA4 124) within its coverage area form the basic service set (BSS) associated with the communication cell. In the infrastructure model, access point 11 can be considered the central point of the cell because, except for some special purposes, communication with the sites within its coverage area passes through this access point. Therefore, the coverage area of ​​the access point defines the size of the cell and thus the range of the network.

[0006] Therefore, to achieve a large cell size, or to ensure that sites expected to be added to the network are within range of the access point, the transmission power of the access point can be quite high. For example, in Europe, the maximum equivalent isotropic radiated power (EIRP) in the low 5 GHz Wi-Fi band (i.e., 5150-5350 MHz) is 23 dBm. Therefore, the transmission power of the access point can approach this value.

[0007] Using high transmission power for downlink communication (i.e., from the access point to the site) also allows for improved signal-to-noise ratio at sites not in coverage-limited areas, which in particular allows for the use of higher-order modulation for communication.

[0008] Correspondingly, the power consumption of access points becomes non-negligible in the long run. Furthermore, especially in home Wi-Fi networks, sites are typically located near the access point (e.g., in the same room or adjacent rooms).

[0009] Therefore, using high transmission power for access points does not always seem appropriate, especially in home Wi-Fi networks.

[0010] Solutions have been proposed, but these solutions are expensive in terms of channel access and / or sensitive to collisions.

[0011] Therefore, a new technology is needed that allows for the management of transmission power and other parameters of wireless access points. Summary of the Invention

[0012] This invention is based on a novel method for managing wireless access points, comprising:

[0013] - Broadcasts a downlink frame to one or more stations within the coverage area of ​​the access point. The downlink frame carries an indicator that requests the stations receiving the downlink frame to transmit the power level received by the access point.

[0014] - In response to the downlink frame, at least one uplink frame is received from at least one of the stations, wherein the uplink frame sent by the station carries information representing the power level of the access point received by the station;

[0015] - Based on the information representing the power level carried by the uplink frame, determine at least one power level of the access point received by at least one of the stations.

[0016] This process, implemented by the access point, specifically allows for the estimation of the power received by the access point from the site and the feedback of that information to the access point.

[0017] More specifically, according to this embodiment, the access point broadcasts a specific frame to stations present in its coverage area. The station's reception of such a downlink frame specifically allows for the triggering of an estimation of the power of the received downlink frame, and thus an estimation of the access point's power level. Information representing this power level can then be fed back from the station to the access point for processing.

[0018] It should also be noted that several power levels, or power ranges, can be defined, each power level being associated with information representing the power level. Therefore, several power values ​​can be associated with the same power level and thus encoded by the same information representing the power level.

[0019] Specifically, the access point can receive several uplink frames from different sites simultaneously or with slight offset, and determine the power level associated with each different site based on information representing the power level carried by each uplink frame.

[0020] According to one embodiment, the method includes updating the transmission power of the access point by taking the determination into account.

[0021] In this way, the access point can adjust its transmission power. Specifically, the access point can reduce its transmission power without affecting the performance of the network site, which allows for reduced power consumption of the access point. Adjusting the transmission power also allows for reduced interference between neighboring networks.

[0022] According to a specific embodiment, the downlink frame is a dedicated frame that triggers information feedback in the uplink frame when received by the station.

[0023] In this case, the indicator is, for example, a specific frame type or format.

[0024] According to another embodiment, the downlink frame is an uplink resource allocation frame.

[0025] These resource allocation frames (also known as control frames) are typically broadcast by the access point to indicate to different sites in the network the resources (e.g., preambles) used to feed back information in uplink frames. In particular, they can carry scheduling information that allows for the simultaneous feedback of information from different sites (resources allocated to the sites, modulation schemes to be used by each site, and decoding, etc.).

[0026] For example, such an uplink resource allocation frame is a "trigger" frame, as defined in the IEEE 802.11ax standard.

[0027] According to a first exemplary embodiment, the indicator is inserted into the “trigger type” field of the uplink resource allocation frame.

[0028] In this case, the access point sends variations of the "trigger" frame. For example, the values ​​of the indicator inserted in the "trigger type" field are between 8 and 15, and values ​​0 to 7 have been reserved to identify the basic "trigger" frame and other variations.

[0029] According to the second exemplary embodiment, the indicator is inserted into the “Association ID” field of the uplink resource allocation frame.

[0030] In this scenario, the access point sends a specific identifier, such as a value or a set of values.

[0031] This second example specifically allows for maintaining the structure of a “trigger” frame as currently defined in the IEEE 802.11ax standard.

[0032] According to at least one embodiment, the downlink frame carries at least one information item belonging to the group consisting of:

[0033] If the power level is below the maximum power, the station must report the received power level back to the access point.

[0034] - A family of at least one sequence used by the station to feedback power levels.

[0035] - The number of cyclic shifts authorized by the station for the sequence used to feed back power levels.

[0036] - A set of at least one location-value pairs used by the station to provide feedback on power levels.

[0037] Therefore, according to the first example, a station that only receives downlink frames with power below a determined threshold (maximum power) may have to report the received power level.

[0038] According to the second example, the access point can transmit a family comprising at least one sequence in a downlink frame, each sequence being associated with a different power level. Specifically, different sequences of the family can be obtained by applying a cyclic shift to a reference sequence from the family of sequences. In this case, different cyclic shifts of the reference sequence are associated with different power levels.

[0039] According to another example, an access point may send multiple authorized cyclic shifts for a reference sequence in a downlink frame, which may be known to the site or sent in a sequence family of downlink frames.

[0040] According to another example, the access point can transmit in a downlink frame a set of location-value pairs to be used by the station to report power levels, each location-value pair being associated with a different power level. For example, the location of the location-value pair corresponds to (or allows identification of) the index of the subcarrier to which the station will use to report power levels, and the value of the location-value pair corresponds to the value associated with the constellation point to be transmitted on such identified subcarriers.

[0041] In particular, as already noted, several power values ​​of the access point estimated by the site can be associated with the same power level and therefore encoded by the same information representing the power level. Thus, a limited number of sequences or position-value pairs (or even a limited number of cyclic shifts) to be used can be broadcast in downlink frames, where each sequence or position-value pair encodes a wider range of power values, allowing for a reduction in the granularity of information feedback.

[0042] A limited number of sequence or position-value pairs (or even a limited number of cyclic shifts) to be used can also be broadcast in downlink frames, where each sequence or position-value pair encodes a range of power values ​​whose maximum value is less than a defined threshold (maximum power). Thus, the list can be restricted to encode sequences or position-value pairs with the lowest power (that is, typically, the sites farthest from the access point and therefore most affected by a reduction in the access point's transmission power).

[0043] Furthermore, the number of sequences or pairs that need to be identified on the access point side can be reduced, for example, by retaining only sequences or pairs that encode low power levels for the determination steps implemented by the access point. This allows for, for example, improvements in responsiveness, complexity, and / or power consumption.

[0044] In other embodiments, this information (e.g., maximum power type, sequence family, number of authorized cyclic shifts, set of position-value pairs, etc.) is not transmitted in the downlink frame, but is known to the access point and site. For example, this information is defined in a standard.

[0045] According to a particular embodiment, downlink frames are broadcast periodically or after triggering events belonging to a group including:

[0046] At least one beacon is sent from the access point.

[0047] Associate at least one new site with the access point.

[0048] Detect nearby access points.

[0049] Detect mobility at at least one site.

[0050] The repeated broadcasting of this downlink frame specifically allows for ensuring that the maximum number of sites receive information from the access point with sufficient power.

[0051] According to a specific embodiment of an embodiment known as a family of sequences, the determination of at least one sequence in a family of at least one sequence known for the access point implements the correlation between the sequence and the at least one upstream frame.

[0052] According to this embodiment, the information representing the power level is a sequence selected from a family of sequences known to the access point. Therefore, a correlation is performed between the access point's sequence and the received uplink frames to identify the sequence carried by each uplink frame. In other words, a correlation is performed between the power level information carried by the uplink frames and different sequences from the family known to the access point.

[0053] For example, when the family of sequences includes a reference sequence and a shifted version of that reference sequence, the determination step implements sliding correlation.

[0054] The detection of correlated peaks allows for the identification of sequences transmitted in uplink frames and the determination of associated power levels.

[0055] Note that an access point can receive multiple uplink frames simultaneously, or receive multiple uplink frames with shifts within a few microseconds. In this case, the combination of sequences associated with each received uplink frame can be associated with at least one sequence from a family of sequences known to the access point.

[0056] According to another embodiment (referred to as the embodiment with a bitmap), determining at least one location-value pair from a set of at least one location-value pairs known for the access point achieves the following:

[0057] - Obtain the value associated with the position of the location-value pair in the at least one uplink frame.

[0058] - Compare the obtained value with the determined threshold.

[0059] According to this embodiment, the information representing the power level is a location-value pair selected from a set of known location-values ​​of the access point.

[0060] Upon receiving an uplink frame, the access point obtains the value of the uplink frame associated with the position of the position-value pair known to the access point (e.g., the value associated with a constellation point transmitted on a subcarrier whose index corresponds to the position of that pair (position, value)), and if this value is greater than a determined threshold, the power level associated with that position-value pair can be obtained. In particular, such a threshold can be determined based on the value of the position-value pair.

[0061] Similarly, an access point can receive several uplink frames simultaneously, or receive several uplink frames with a shift within a few microseconds.

[0062] In another embodiment, the present invention relates to a corresponding access point.

[0063] Such an access point is particularly suitable for implementing the management method described above. This is, for example, a set-top box or a home gateway. Such an access point may specifically include different features related to the management method according to the invention; these features may be combined or used individually. Therefore, the features and advantages of this access point are the same as those of the management method, and will not be described in further detail.

[0064] The present invention also relates to a method for transmitting data from a site to a wireless access point, comprising:

[0065] - The station receives downlink frames from the access point.

[0066] - Detect an indicator in the downlink frame that requests the transmission of the power level of the access point received by the station;

[0067] - Estimate the power of the downlink frames received by the site;

[0068] - Send an uplink frame to the access point carrying information representing the power level associated with the estimated power.

[0069] This approach, implemented by one or more sites within the coverage area of ​​the access point, particularly allows information from the sites to the access point about the power of downlink frames received by the sites.

[0070] In other words, receiving such a downlink frame at the site specifically allows for the triggering of an estimation of the power of the received downlink frame, and thus an estimation of the access point's power level. Information representing this power level can then be fed back from the site to the access point.

[0071] In particular, access points can use this information to adjust their transmission power.

[0072] Note that such sites may or may not be associated with an access point.

[0073] According to a first embodiment of an embodiment referred to as a family of sequences, the information representing the power level is a sequence in a family of at least one sequence known to the access point, each sequence in the family being associated with a different power level.

[0074] For example, a family could be selected that includes different sequences with good cross-correlation and / or autocorrelation properties, or that includes a reference sequence and shifted versions of that reference sequence. For instance, a family of sequences could include the Zadoff-Chu sequence.

[0075] Specifically, the complex symbols forming the sequence are mapped to points in a constellation associated with the modulation used for the transmission of the uplink frame.

[0076] The transmission of sequences in the frequency domain, rather than the time domain, allows for simplified detection of sequences in uplink frames received by the access point by performing simple correlations. Furthermore, modules typically implemented in the transmit and receive chains can therefore be used.

[0077] In another specific embodiment, referred to as the embodiment with a bitmap, the information representing the power level is a set of at least one location-value pair known to the access point, each location-value pair in the set being associated with a different power level.

[0078] Specifically, the values ​​of the position-value pairs are mapped to points of a constellation associated with the modulation used for the transmission of the uplink frame, the constellation points being transmitted on subcarriers identified from the positions of the position-value pairs.

[0079] For example, position-value pairs can be represented by vectors that encode power levels. Such vectors carry a component equal to the value of the position-value pair (e.g., "1") at the position identified by the position of the position pair, and a zero component at other positions. For transmission, the zero component can be mapped to a constellation point with a low-amplitude negative in-phase component, and the non-zero component can be mapped to a constellation point with a high-amplitude positive in-phase component, and then each constellation point can be transmitted on a separate subcarrier.

[0080] Specifically, in OFDM symbols, a set of subcarriers can be reserved for the transmission of such vectors. Therefore, different components of the vector can be mapped to different constellation points, each of which is transmitted on a subcarrier derived from the reserved subcarriers. For example, the first component of the vector is transmitted on the first reserved subcarrier (i.e., the subcarrier with the smallest index), the second component of the vector is transmitted on the second reserved subcarrier (i.e., the subcarrier with the second smallest index), and so on.

[0081] The reserved subcarriers can be known or identified in the uplink frame. In particular, these subcarriers are distributed across OFDM symbols in order to preserve the properties of the OFDM symbols and limit the crest factor (“peak-to-average power ratio” or PAPR).

[0082] Similarly, transmission in the frequency domain allows for simplified detection of position-value pairs in uplink frames received by the access point. Furthermore, modules typically implemented in the transmit and receive chains can therefore be used.

[0083] According to another specific embodiment, power level information is repeatedly represented on several consecutive OFDM symbols.

[0084] This repetition of sequences or location-value pairs allows for an increase in the probability of detecting sequences or location-value pairs in (multiple) uplink frames received by the access point.

[0085] According to a particular embodiment, the uplink frame is transmitted on a resource shared by at least one other station that transmits the same information representing the power level.

[0086] According to another embodiment, the uplink frame is transmitted on resources shared by at least one other site associated with the access point.

[0087] In other words, groups can be formed by frequency bands (or resource elements, RUs) instead of allocating the entire frequency band to all sites. For example, each power level defines a group, and each site determines which group it belongs to based on its estimated power. According to another example, groups can be defined that have sites associated with access points, and groups that have sites not associated with access points.

[0088] According to a particular embodiment, a method for sending data from a site to an access point includes receiving an uplink frame from at least one other site and retransmitting the uplink frame to the access point.

[0089] In other words, a site can be used as a relay for another site.

[0090] In another embodiment, the present invention relates to a corresponding site.

[0091] Such a site is particularly suitable for implementing the transmission method described above. It is, for example, a sensor, printer, smartphone, computer, etc., or more generally, a client terminal. Such a site may specifically include different features related to the transmission method according to the invention, which may be combined or used individually. Therefore, the features and advantages of this site are the same as those of the transmission method, and will not be repeated here.

[0092] In another embodiment, the present invention relates to one or more computer programs including instructions which, when executed by a processor, are used to implement methods for managing access points and / or methods for sending data from a site to an access point according to at least one embodiment of the present invention.

[0093] In yet another embodiment, the present invention relates to one or more information carriers that are non-removable, or partially or fully removable, and computer-readable, and according to at least one embodiment of the invention, includes instructions for performing steps of one or more computer programs for methods of managing access points and / or methods of sending data from a site to an access point.

[0094] Therefore, the method according to the invention can be implemented in different ways, particularly in wired and / or software form. Attached Figure Description

[0095] Other features and advantages of the invention will become more apparent when reading the following description and accompanying drawings of specific embodiments given by way of simple illustrative and non-limiting examples, in which:

[0096] Figure 1 An example of a wireless network implementing an access point and several stations is shown;

[0097] Figure 2 The main steps of a method for managing a wireless access point and a method for sending data from a site to the access point according to at least one embodiment of the present invention are shown.

[0098] Figure 3 This illustrates mapping Zadoff-Chu type sequences to constellation points associated with 64-QAM modulation;

[0099] Figure 4 An example of frames exchanged between an access point and a site is shown;

[0100] Figure 5 A simplified structure of an access point for implementing a method for managing wireless access points according to an embodiment of the present invention is shown;

[0101] Figure 6 A simplified structure of a site is shown, illustrating a method for implementing data transmission between a site and an access point according to an embodiment of the present invention. Detailed Implementation

[0102] General principles

[0103] The general principle of this invention is based on the broadcast of downlink frames from the access point to stations in the coverage area of ​​the access point, triggering feedback on information about the power of the downlink frames received by each station.

[0104] In this way, access points can establish a mapping of received power (e.g., the number of stations per power level) and adjust their transmission power.

[0105] about Figure 2 The following describes the main steps implemented by an access point and at least one site existing in the coverage area of ​​the access point, according to a specific embodiment.

[0106] As an example, Wi-Fi networks are considered to be like... Figure 1 As shown, it includes access point AP 11 and four sites STA1 121, STA2 122, STA3 123 and STA4 124.

[0107] Access point 11 broadcasts (21) a downlink frame carrying an indicator that requests the site receiving the downlink frame to transmit the power level received by the access point.

[0108] Such downlink frames can be received by all stations within the coverage area of ​​the access point, regardless of whether they are associated with the access point, such as stations STA1 121, STA2 122, STA3 123, and STA4 124.

[0109] The steps implemented by the first station STA1 121 are shown below. Similar steps can be implemented by the other stations STA2 122, STA3 123 and STA4 124.

[0110] The first station STA1 121 receives (22) a downlink frame broadcast by the access point and detects (23) an indicator requesting the transmission of the access point's power level received by the station. Such an indicator may be the frame format, frame type, specific identifier, etc.

[0111] The first station STA1 121 estimates (24) the power of the downlink frames received by the station in a conventional manner, and thus estimates the power of the access point. The first station thus obtains, for example, a Received Signal Strength Indicator (RSSI).

[0112] The estimated power can then be fed back to access point 11.

[0113] For example, the first station STA1 121 identifies the power level to which the estimated power belongs and sends (25) an uplink frame to access point 11 carrying information indicating the power level associated with the estimated power.

[0114] Different "granularities" of power levels can be defined: for example, power levels can be defined by power or by power range. For example:

[0115] - The first power level is associated with the power included in the interval [Smax; -30dBm].

[0116] - The second power level is associated with the power within the range [-30dBm; -60dBm], and

[0117] - The third power level is associated with the power within the range [-60dBm; Smin].

[0118] Here, Smax and Smin are the maximum and minimum sensitivity levels of the site receiver. For example, Smax equals 0 dBm and Smin equals -110 dBm.

[0119] Therefore, information representing the power level associated with the estimated power allows the power level to be “encoded.” The correspondence between the power level and the information representing the power level can be, in particular, previously known to the access point and site (e.g., defined in a standard), or transmitted by the access point in a downlink frame or another frame.

[0120] Therefore, access point 11 receives (26) an uplink frame in response to a downlink frame previously broadcast by the access point from the first site STA1 121, and may receive other uplink frames in response to a downlink frame previously broadcast by the access point from other sites STA2 122, STA3 123 and STA4 124.

[0121] Then, the access point can determine (27) the power level received by the first site STA1 121 and possibly other sites STA2 122, STA3 123 and STA4 124 based on information representing the power level carried by each uplink frame.

[0122] Access point 11 can use the obtained power level to create a power level mapping, adjust its transmission power, etc.

[0123] In particular, it should be noted that using information representing power levels in uplink frames allows for the "encoding" of the power level associated with each station (the power level received by the access point from each station). Therefore, when several stations simultaneously report the power levels received by the access point, the access point can potentially find the power level associated with each station, regardless of uplink frame collisions. Furthermore, both associated and unassociated stations can participate in this information feedback.

[0124] Example of downlink frame generation

[0125] As described above, access point 11 broadcasts (21) a downlink frame carrying an indicator that requests the site receiving the downlink frame to transmit the power level received by the access point.

[0126] According to the first embodiment, such a downlink frame is a frame dedicated to triggering information feedback.

[0127] According to the second embodiment, such a downlink frame is an uplink resource allocation frame, such as a "trigger" frame according to the IEEE 802.11ax standard or a variant thereof.

[0128] In this case, the indicator requesting the power level received by the access point can be the frame type. If we consider a "Trigger" frame, such an indicator can be inserted into the "Trigger Type" field of the common information field of the "Trigger" frame to define a specific variant of the "Trigger" frame.

[0129] As an example, Table 9-31b of the IEEE 802.11ax / D6.0 standard of November 2019 defines several variations of the “trigger” frame: a regular “trigger” frame if the “trigger type” field equals 0 (“basic”), a variation of the “BFRP” type “trigger” frame if the “trigger type” field equals 1 (“beamforming report polling”), a variation of the “MU-BAR” type “trigger” frame if the “trigger type” field equals 2 (“multi-user block acknowledgment (ack) request”), and so on.

[0130] Therefore, a new type of uplink resource allocation frame can be defined to trigger feedback of power information received at the site side.

[0131] Alternatively, a specific identifier that can be assigned in the downlink frame to a site within the coverage area of ​​the access point that can respond.

[0132] For example, if we consider a “trigger” frame, the indicator of the power level received by the sending access point can be an identifier in the form of a value or set of values ​​inserted into the “Associated ID” (or AID) field of the user information field in the “trigger” frame.

[0133] Note that the use of a "trigger" frame specifically allows for the implementation of OFDMA ("Orthogonal Frequency Division Multiple Access") type multiple access techniques in the uplink, also referred to as UL OFDMA. In this way, by using this multiple access technique, different stations receiving downlink frames can simultaneously (or substantially simultaneously) feed back the received power information. Therefore, this ensures a limited channel occupancy footprint during the power information feedback phase, which allows for implementation, for example, at higher frequencies.

[0134] Example of uplink frame generation

[0135] As described above, according to the present invention, the reception of a downlink frame by at least one station triggers a power estimation (24) of the downlink frame received by that station, and then feeds back (25) an uplink frame carrying information about the power level associated with the estimated power to the access point.

[0136] The following presents two types of information representing power levels, which can be used to encode power levels associated with, for example, the first station STA1121. Similar encoding can be performed to encode power levels associated with other stations STA2 122, STA3 123, and STA4 124.

[0137] According to a first embodiment of an embodiment referred to as a family with sequences, the information representing the power level is a sequence. Thus, a family of at least one sequence previously known to the access point and the site, or sent from the access point to the site (e.g., in a downlink frame or in another frame), is considered, and the power level is associated with each sequence in that family, for example in a known correspondence table of access points and sites, or sent from the access point to the site (e.g., in a downlink frame or in another frame).

[0138] Such a family of sequences can consist of different sequences, each associated with a different power level. Alternatively, the family of sequences can consist of a sequence called a reference sequence and shifted versions of that reference sequence (i.e., shifted versions of the reference sequence with applied cyclic shifts), each shifted version associated with a different power level. According to this variant, the reference sequence is considered to be known to the access point and the station, or transmitted from the access point to the station (e.g., in a downlink frame or in another frame). Similarly, the number of authorized cyclic shifts can be known to the access point and the station, or transmitted from the access point to the station (e.g., in a downlink frame or in another frame).

[0139] According to this first example, different sequences within a family (different sequences or reference sequences and shifted versions) exhibit good autocorrelation and / or cross-correlation properties. For example, a family sequence is a Zadoff-Chu sequence with a cyclic shift large enough to guarantee very low cross-correlation.

[0140] Therefore, when an access point receives one or more uplink frames from one or more sites, it does not attempt to decode each signal to extract information (a solution susceptible to collisions). Instead, it identifies the presence of at least one sequence for each power level by performing a correlation between the signals it receives and the different sequences it knows. Thus, the detection of correlation peaks for a given sequence allows identification of the power level received by the access point from the site. In other words, the correlation property of a family of sequences allows distinguishing the presence of each sequence, and therefore the presence of the corresponding power level.

[0141] Potential collisions between uplink frames sent from different stations are not a problem because the cross-correlation and / or autocorrelation properties of the families of sequences used allow one sequence to be distinguished from another.

[0142] For each uplink frame, a sequence of power levels associated with the station can be transmitted in the time domain.

[0143] Alternatively, sequences encoding the power levels associated with a station can be transmitted in the frequency domain. In this way, correlation can be performed in the baseband, and thus utilize the access point processor.

[0144] For example, a sequence encoding the power level associated with a station can be transmitted on the selection of constellation points in a constellation diagram associated with the modulation (e.g., 16-QAM, 64-QAM, etc.) used for uplink frame transmission.

[0145] Therefore, if we consider a Zadoff-Chu sequence of length Nzc = 242 and index u = 25, then in relation to... Figure 3The complex symbols forming the sequence, represented by "x" on the constellation diagram associated with the 64-QAM modulation shown (where each point in the constellation is represented by "+"), are mapped to the constellation point closest to the complex symbol. For example, if the complex symbols and constellation points are represented as 2D vectors with in-phase and quadrature phase components, the complex symbols from the sequence are mapped to points in the constellation that minimize the Euclidean distance to that symbol.

[0146] The chosen constellation points are in relation to Figure 3 The constellation diagram associated with the 64-QAM modulation is circled.

[0147] The selected constellation point can then be transmitted on different subcarriers, for example, one selected constellation point per subcarrier.

[0148] Specifically, the maximum length of the sequence is equal to the number of subcarriers of the OFDM symbol. Advantageously, the maximum length of the sequence is equal to the number of useful subcarriers of the OFDM symbol.

[0149] According to a particular embodiment, in particular, the sequence can be repeated over several QFDM symbols (preferably consecutive) to increase the probability of good detection at the access point.

[0150] Note that, based on the example above, a Zadoff-Chu sequence of length Nzc = 242 and index u = 25 is used to encode a given power level. Therefore, it can be fed back by all stations associated with the same power level.

[0151] In particular, the step of selecting the sequence to map complex symbols to constellation points can be implemented in the mapping / interleaving module of the transmission chain of a multi-carrier signal of, for example, OFDM type.

[0152] On the access point side, the reverse operation can be achieved through, for example, a demapping / deinterleaving module in the receiver chain of OFDM-type multicarrier signals.

[0153] In this way, a portion of the conventional OFDM processing chain can be reused (e.g., on the transmission side, channel decoding type module, frequency-time conversion, guard interval insertion, carrier shaping, etc., and on the reception side, guard interval suppression type module, time-frequency conversion, channel decoding, etc.).

[0154] According to the second embodiment (referred to as the embodiment with a “bitmap”), the information representing the power level is a position-value pair (“bitmap”). The presence of a specific value at a given position in an uplink frame is associated with the power level. For example, the position-value pair is represented by a binary vector of size N, which has a single component equal to 1 and (N-1) components equal to 0, and different vectors are associated with each power level. Therefore, if as Figure 1 Considering three power levels, the first power level can be encoded by vector (100), the second power level by vector (010), and the third power level by vector (001). The correspondence table between the different vectors and the different power levels can be known to the access point and the site, or sent from the access point to the site (e.g., in a downlink frame or in another frame).

[0155] For each uplink frame, location-value pairs that encode the power level associated with the station can be transmitted in the time domain. For example, the location of the location-value pair indicates the location in the uplink frame, and the value of the location-value pair indicates the value carried by the field at that location in the uplink frame.

[0156] Alternatively, position-value pairs encoding the power level associated with the site can be transmitted in the frequency domain. The power level-value pairs then can be transmitted with respect to the selection of constellation points in a constellation diagram associated with the modulation used to transmit uplink frames (e.g., 16-QAM, 64-QAM, etc.).

[0157] Considering the binary vector example above, the component equal to "0" can be mapped to a constellation point with a low-amplitude negative in-phase component, and the component equal to "1" can be mapped to a constellation point with a high-amplitude positive in-phase component.

[0158] Each constellation point can be transmitted on a different subcarrier.

[0159] For example, the position of the component in the vector that is equal to "1" gives the index of the subcarrier of the constellation point to which the component of the transmitted binary vector that is equal to "1" is mapped.

[0160] Therefore, some useful subcarriers of a uniformly distributed OFDM symbol can be reserved to transmit the components of a vector representing a position-value pair mapped onto constellation points. Using the binary vector example above, a single subcarrier among the reserved subcarriers can be assigned a "1" (corresponding to the subcarrier with the desired power level), and all other subcarriers can be assigned a "0".

[0161] Using an example of a vector with length N equal to 3, N subcarriers evenly distributed in an OFDM symbol can be reserved for transmitting different components. For example, if considering an OFDM symbol formed by 242 useful carriers, carriers at indices 48, 96, and 144 can be reserved for the transmission of the first, second, and third components of the binary vector, respectively.

[0162] Therefore, for the first power level encoded by the vector (100) corresponding to the position-value pair (1, 1), the component "1" can be mapped to the constellation point transmitted on the subcarrier at index 48, and the component "0" can be mapped to the constellation point transmitted on the subcarriers at indices 96 and 144.

[0163] For the second power level encoded by the vector (010) corresponding to the position-value pair (2, 1), the component "1" can be mapped to the constellation point transmitted on the subcarrier at index 96, and the component "0" is mapped to the constellation point transmitted on the subcarriers at indices 48 and 144.

[0164] For the third power level encoded by vector (001) corresponding to the position-value pair (3, 1), the component "1" can be mapped to the constellation point transmitted on the subcarrier at index 144, and the component "0" is mapped to the constellation point transmitted on the subcarriers at indices 48 and 96.

[0165] Other subcarriers of the OFDM symbol can also be used to transmit random values ​​in order to preserve the properties of the OFDM symbol.

[0166] In particular, the maximum length of the vector (N) is small relative to the number of useful subcarriers of an OFDM symbol.

[0167] Similarly, the step of mapping vector components to constellation point selection can be implemented in the mapping / interleaving module of a transmission chain for OFDM-type multicarrier signals, for example. On the access point side, the reverse operation can be achieved through the demapping / deinterleaving module of a receiver chain for OFDM-type multicarrier signals, for example. In this way, a portion of a conventional OFDM processing chain can be reused.

[0168] In addition, position-value pairs or vectors representing those pairs can be repeated on several (preferably consecutive) OFDM symbols to increase the probability of good detection at the access point.

[0169] It should also be noted that the use of higher-order modulation allows for more robust uplink frame pairs to collisions, as constellation points associated with component "0" can have low amplitudes.

[0170] Therefore, when an access point receives one or more uplink frames from one or more sites, it can compare the values ​​received on different subcarriers with a given threshold. Recall that the location of the component equal to "1" in the vector allows the subcarriers to identify the transmitting constellation point, and the component of the binary vector equal to "1" is mapped to that constellation point. Therefore, the access point can determine the presence of a power level by comparing the values ​​received on the corresponding subcarriers with a given threshold.

[0171] In particular, such a threshold can be determined by considering the value of the position-value pair. For example, for a value equal to 1, the threshold could be 0.8 (to account for a loss in the range of 20%).

[0172] Regardless of the embodiment considered, information indicating the power level can be sent in the "preamble" portion of the uplink frame. In this way, the access point obtains power information very quickly. Recall for this purpose that if the downlink frame is a "trigger" frame, the station sends the uplink frame within a fixed time after receiving the "trigger" frame, for example, within a range of 16 μs.

[0173] The drawback of this implementation is that the site must use the inter-carrier spacing (i.e., 312.5 kHz) defined in versions prior to the IEEE 802.11ax standard. This reduces the number of subcarriers per OFDM symbol and thus the length of the sequence or bitmap. Furthermore, this implementation makes it impossible to use uplink OFDMA-type access technologies, as such technologies are only defined for the IEEE 802.11ax standard or future versions.

[0174] Alternatively, regardless of the embodiment under consideration, information representing the power level can be sent in the "data" portion of the uplink frame. This information representing the power level is then considered as physical layer (PHY) ("payload") data.

[0175] This implementation allows for feedback of power level information using the IEEE 802.11ax frame format (or any newer version). This particularly allows for the use of 78.125 kHz inter-carrier spacing and uplink OFDMA-type access technologies.

[0176] In particular, a power control mechanism on the OFDMA uplink, as defined in the IEEE 802.11ax standard, can be implemented, which allows ensuring that uplink frames sent by different sites in response to downlink frames (e.g., “trigger” frames) arrive at the access point with substantially equal power.

[0177] For illustrative purposes only, Figure 4 It shows in Figure 1 The image shows an example of frames exchanged between access point 11 of the network and stations STA1 121, STA2 122, STA3 123 and STA4 124.

[0178] As already described, access point AP 11 broadcasts downlink frames to (multiple) stations present in the coverage area of ​​the access point. For example, the downlink frame is a "trigger" frame that requests all stations receiving the "trigger" frame to transmit the power level received by the access point.

[0179] Upon receiving an uplink frame, the first station STA1 121 estimates the power of the downlink frame received by the first station, obtains a Received Signal Strength Indicator (RSSI) 1, and feeds back the representative information of RSSI 1 to access point 11. The second station STA2 122 also estimates the power of the downlink frame received by the second station, obtains an RSSI 1, and feeds back the information representing RSSI 1 to access point 11. The third station STA3 123 estimates the power of the downlink frame received by the third station, obtains an RSSI 2, and feeds back the information representing RSSI 2 to access point 11. Finally, the fourth station STA4 124 estimates the power of the downlink frame received by the fourth station, obtains an RSSI 4, and feeds back the information representing RSSI 4 to access point 11.

[0180] As shown in the example, the first station STA1 121 and the second station STA2 122 use the same information representing the power level, such as the same sequence or the same bitmap, because they are located at the same distance from access point 11.

[0181] Example of implementation

[0182] The following examples illustrate an implementation of the invention based on a family of sequences that include a reference sequence and a shifted version of the reference sequence to encode power levels, and based on the use of “trigger” frames with specific identifiers for downlink frames.

[0183] Access points send “trigger” frames by placing a specific identifier in the AID field and by providing power control information to be sent back by the site to the uplink frame according to OFDMA access technology (according to the conventional method described in the IEEE 802.11ax standard).

[0184] The “trigger” frame is received by every station within the range of the access point (i.e., within the coverage area of ​​the access point):

[0185] - Decode the "trigger" frame.

[0186] - Due to the presence of the identifier in the "trigger" frame, detecting it requires feedback of its received power level.

[0187] - Use the power received from the "trigger" frame to determine the shift to be applied to the reference sequence (assuming the access point and site are known or have been previously communicated) based on a mapping table (assuming the access point and site are known or their attributes have been previously signaled).

[0188] - Constellation points associated with the modulation used for transmission may be selected to transmit the shifted sequence (e.g., 64-QAM, assuming it is pre-configured, signaled, or selected during operation based on the link budget), and the shifted sequence may be repeated over several consecutive OFDM symbols (repetition also assuming signaled notification).

[0189] - After transmitting the preamble according to the IEEE 802.11ax standard, and according to the upstream transmission procedure (UL: uplink) OFDMA, at a fixed time (e.g., within 16 μs) after receiving the "trigger" frame, the selected constellation point is transmitted via frequency-time conversion, etc.

[0190] The data symbols constructed from this (the data symbols).

[0191] Therefore, the access point receives uplink frames from different sites existing in its coverage area, and different uplink frames can be superimposed.

[0192] After the standard steps of receiving the preamble, the access point:

[0193] - Obtain the sign corresponding to the shifted sequence at the output of the time-frequency conversion module.

[0194] - Apply sliding correlation with a known reference sequence of access points

[0195] - Identify relevant peaks around the expected shift and compare them to a threshold.

[0196] - Establish a mapping of power levels received via a correspondence table.

[0197] Then, due to this mapping, the access point can adjust its transmission power level. It can also take other standards into account to adjust its power level.

[0198] variants

[0199] Different variations or options can be implemented.

[0200] For example, possible optimizations include reducing the number of power levels to be identified in order to achieve responsiveness, complexity, and / or power consumption. Therefore, the list of sequences or bitmaps can be limited to the lowest power (i.e., the furthest stations, and thus most affected by the reduced transmission power at the access points).

[0201] Another optimization involves providing a restricted list of sequences or bitmaps to be used in downlink frames (that is, reducing the granularity of the return).

[0202] Possible variations include forming groups per frequency band (or per resource element RU), instead of allocating the entire frequency band to all sites (a single virtual user). In fact, the UL OFDMA access technology specifically allows for group-based site scheduling. Sites that can be grouped can be identified in a “trigger” frame sent by the access point to notify allocation and used as a synchronization frame. Sites belonging to the same group can then simultaneously feed back information in resource elements indicating their RSSI. This group-based information feedback particularly allows for compressed feedback time.

[0203] This variant is based on the grouping of sites. For example, each site determines which group it belongs to based on its estimated power. According to another example, sites associated with access points belong to the first group, and sites not yet associated with access points belong to the second group.

[0204] In particular, certain variations, such as reserving subbands for certain sites or limiting the number of power levels, may require additional information to be transmitted in the downlink frame for use in generating the uplink frame.

[0205] Furthermore, different embodiments have been described, according to which each power level uses a sequence or a bitmap without distinction of BS. In the presence of multiple access points, each access point is associated with a BSS, and a family of sequences or a set of vectors can be assigned to each BSS. Therefore, the risk of conflicts between processes initiated by different access points is reduced.

[0206] For example, sequence families can be defined using BSS colors. Short range (up to 64 different colors for the IEEE 802.11ax standard) and existing mechanisms for managing color conflicts provide good selection criteria for sequence families. Furthermore, if sequence families are orthogonal, the state of close neighborhoods (especially in terms of power) can be obtained from access points that have already received uplink frames for neighboring access points.

[0207] Note that since the BSS color information is already present in the header of the "trigger" frame, this variant is less relevant to implementations according to the IEEE 802.11ax standard. Therefore, the same family can be used without the risk of confusing the BSS, and different sequence families are not required.

[0208] According to another variant, a station can be used to relay uplink frames it receives from at least one other station. Specifically, if information representing power levels is transmitted in the frequency domain, the station receiving the uplink frame can demodulate it and relay the corresponding bits / symbols (if it manages to identify the frame type). The access point receiving the relayed uplink frame can then post-process these bits / symbols by performing a reverse path.

[0209] According to another variant, the access point can periodically transmit downlink frames at nominal power (without reduction), so that dormant sites do not eventually lose coverage, or even sites within the nominal range of the BSS can be included.

[0210] Access points can also transmit downlink frames with reduced power, especially after analyzing the environment generated by the previous collection phase (transmitting downlink frames and receiving associated uplink frames).

[0211] Specifically, downlink frames can be broadcast periodically or after triggering events such as an access point sending a beacon, the association of at least one new site with the access point, the detection of neighboring access points, the detection of mobility of at least one site, etc. In practice, because sites are mobile and the environment changes over time (e.g., a new site may enter the access point's coverage area and wish to be associated), it is desirable to collect power information periodically. In particular, the fact that certain occurrences of this process immediately after beacon transmission allow for ensuring that a maximum number of sites are active. In practice, standby sites are periodically woken up, particularly to listen for basic information transmitted in certain beacons.

[0212] equipment

[0213] Finally, regarding Figure 5 and Figure 6 This illustrates a simplified structure of access points and sites according to at least one of the above embodiments.

[0214] like Figure 5 As shown, the access point includes at least one memory 51 and at least one processing unit 52. The memory includes a buffer memory, and the processing unit is equipped with, for example, a programmable calculator or a dedicated calculator, such as a processor P, and is driven by a computer program 53 to implement the steps of a method for managing a wireless access point according to at least one embodiment of the present invention.

[0215] During initialization, the code instructions of computer program 53 are loaded into RAM memory, for example, before being executed by the processor of processing unit 52.

[0216] The processor of processing unit 52 implements the steps of the aforementioned management method according to the instructions of computer program 53, in order to:

[0217] - Broadcasts a downlink frame to (multiple) stations within the coverage area of ​​the access point, the downlink frame carrying an indicator requesting the station receiving the downlink frame to transmit the power level of the access point it has received.

[0218] - In response to the downlink frame, at least one uplink frame is received from at least one of the stations, wherein the uplink frame sent by the station carries information indicating the power level of the access point received by the station.

[0219] - Based on information representing the power level carried by (a plurality of) the uplink frames, determine at least one power level of the access point received by at least one station.

[0220] like Figure 6 As shown, the station includes at least one memory 61 and at least one processing unit 62, the memory including a buffer memory, the processing unit being equipped with, for example, a programmable calculator or a dedicated calculator, such as a processor P, and driven by a computer program 63 to implement the steps of a method for sending data from the station to an access point according to at least one embodiment of the present invention.

[0221] During initialization, the code instructions of computer program 63 are loaded into RAM memory, for example, before being executed by the processor of processing unit 62.

[0222] The processor of processing unit 62 implements the steps of the aforementioned data transmission method according to the instructions of computer program 63, in order to:

[0223] - Receive downlink frames from the access point

[0224] - Detect an indicator in the downlink frame that requests the transmission of the access point's power level received by the station;

[0225] - Estimate the power of the downlink frames received by the site;

[0226] - Send an uplink frame to the access point carrying information representing the power level associated with the estimated power.

Claims

1. A method for managing wireless access points, comprising: - Broadcast (21) a downlink frame to stations within the coverage area of ​​the access point, the downlink frame carrying an indicator requesting the stations receiving the downlink frame to transmit the power level received by the access point. - In response to the downlink frame, simultaneously or slightly offset, at least two uplink frames are received from at least two stations (26), wherein each uplink frame transmitted by one of the at least two stations carries information representing the power level of the access point received by that station, and - Based on the information representing the power level carried by the at least two uplink frames, determine (27) at least one power level of the access point received by the at least two stations, wherein the information representing the power level of the access point is encoded by each of the at least two stations such that the access point can still determine the power level of the access point received by each of the at least two stations even if the at least two uplink frames are received simultaneously or slightly offset.

2. The method according to claim 1, characterized in that, The downlink frame is an uplink resource allocation frame.

3. The method according to any one of claims 1 and 2, characterized in that, The determination (27) is to determine at least one sequence in a family of at least one sequence known to the access point, and to establish a correlation between the sequence and the at least two uplink frames.

4. The method according to any one of claims 1 and 2, characterized in that, The determination (27) for at least one location-value pair in the set of at least one known location-value pairs of the access point is implemented as follows: - Obtain the value associated with the position of the location-value pair in the at least two uplink frames. - Compare the obtained value with the determined threshold.

5. The method according to claim 1, characterized in that, The downlink frame carries at least one information item belonging to the group consisting of: - Maximum power; if the power level is below this maximum, the site must report the received power level to the access point. - A family of at least one sequence used by the station to feedback power levels. - The number of authorized cyclic shifts of the sequence used by the station to feedback power levels. - A set of at least one location-value pairs used by the station to provide feedback on power levels.

6. The method according to claim 1, characterized in that, The method includes updating the transmission power of the access point by taking the determination into account.

7. The method according to claim 1, characterized in that, The downlink frame is broadcast periodically or after a triggering event, the triggering event being a group including the following: -At least one beacon is emitted by the access point. Associate at least one new site with the access point. -Detect nearby access points, - Detect mobility at at least one site.

8. A method for transmitting data from a site to a wireless access point, comprising: - The station receives (22) downlink frames from the access point. - Detect (23) in the downlink frame an indicator requesting the transmission of the power level of the access point received by the station. - Estimate (24) the power of the downlink frames received by the station, - Simultaneously or slightly offset from the transmission of a second uplink frame by another station carrying information indicating a power level associated with an estimated power of the downlink frame received by the other station, the access point sends (25) a first uplink frame carrying information indicating a power level associated with the estimated power, wherein the information indicating the power level is encoded by each station such that the access point can still determine the power level associated with each station even if the first uplink frame and the second uplink frame are received simultaneously or slightly offset.

9. The method according to claim 8, characterized in that, The information representing the power level is a sequence in a family of at least one sequence known to the access point, each sequence in the family being associated with a different power level.

10. The method according to claim 8, characterized in that, The information representing the power level is a set of at least one location-value pair known to the access point, each location-value pair in the set being associated with a different power level.

11. The method according to any one of claims 8 to 10, characterized in that, The information representing the power level is repeated over several consecutive OFDM symbols.

12. The method according to claim 8, characterized in that, The first uplink frame is transmitted on resources shared by the other station that transmits the same information representing the power level.

13. A wireless access point capable of communicating with at least one site, comprising at least one processing unit, said at least one processing unit being configured to: - Broadcast (21) a downlink frame to stations within the coverage area of ​​the access point, the downlink frame carrying an indicator requesting the stations receiving the downlink frame to transmit the power level received by the access point. - In response to the downlink frame, simultaneously or slightly offset, at least one uplink frame (26) is received from at least two stations, wherein, Each uplink frame sent by one of the at least two stations carries information representing the power level of the access point received by that station, and - Based on the information representing the power level carried by the at least two uplink frames, determine (27) at least one power level of the access point received by the at least two stations, wherein the information representing the power level of the access point is encoded by each of the at least two stations such that the access point can still determine the power level received by each of the at least two stations even if the at least two uplink frames are received simultaneously or at a slight offset.

14. A station capable of communicating with a wireless access point, the station comprising at least one processing unit configured to: - Receive (22) downlink frames from the access point, - Detect (23) in the downlink frame an indicator requesting the transmission of the access point's power level received by the station. - Estimate (24) the power of the downlink frames received by the station, - Simultaneously or slightly offset from the transmission of a second uplink frame by another station carrying information indicating a power level associated with an estimated power of the downlink frame received by the other station, the access point sends (25) a first uplink frame carrying information indicating a power level associated with the estimated power, wherein the information indicating the power level is encoded by each station such that the access point can still determine the power level associated with each station even if the first uplink frame and the second uplink frame are received simultaneously or slightly offset.

15. A computer-readable storage medium comprising program instructions that, when executed by a processor, are used to implement the method according to any one of claims 1 to 7 or 8 to 12.

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