Patent Description:
The management frames in Wi-Fi networks (IEEE <NUM>) are frames used to establish a successful association between the access points and the stations (or client devices) of the Wi-Fi network. The management frames may be, among others, a Beacon frame, a Probe Request frame, a Probe Response frame, an Association Request frame, an Association Response frame, an Authentication Request frame and an Authentication Response frame. Given their importance, they are transmitted at a minimum rate (normally <NUM> Mbps), maximum power and great redundancy at the physical level (<NUM> out of every <NUM> bits is redundant in case data is lost). For instance, the Beacon frame is constantly transmitted every <NUM> seconds as long as the access point is powered on. Document <CIT> discloses: in response to receiving a beacon-poll frame, a wireless AP transmits a unicast beacon frame to an STA, thereby eliminating the need for the STA to periodically wake up to receive broadcast beacon frames from the AP.

The redundancy and minimum transmission rate of the management frames poses a problem, since a significant portion of airtime (or transmission time) is wasted on management frames, which reduces the quality of service (QoS) and generates interferences or collisions in Wi-Fi networks. The present invention aims to solve this problem.

The present invention refers to a system and method for increasing available airtime in Wi-Fi networks.

The method aims to improve the quality of service (QoS) and reduce collisions in Wi-Fi networks, by improving airtime availability in the Wi-Fi network. The method is based on compression and decompression of the management frames (such as Beacon frames or Probe Request frames) to reduce the airtime occupied by these frames. For instance, access points emit several Beacon frames every <NUM> seconds continuously, and the airtime dedicated to these frames cannot be used to transmit other important data.

The method for increasing available airtime in Wi-Fi networks comprises the following steps:.

According to another aspect of the present invention, a system for increasing available airtime in Wi-Fi networks is herein provided. The system comprises one or more first Wi-Fi devices and one or more second Wi-Fi devices. Each first Wi-Fi device comprises a data processing unit configured to generate a management frame and compress the management frame to obtain a compressed management frame, and a radio transmitter unit configured to broadcast the compressed management frame. Each second Wi-Fi device comprises a radio receiver unit configured to receive the compressed management frame and a data processing unit configured to decompress the compressed management frame to obtain the management frame generated by the first Wi-Fi device.

Another aspect of the present invention refers to a Wi-Fi transmitter device for increasing available airtime in Wi-Fi networks. The Wi-Fi transmitter device comprises a data processing unit configured to generate an IEEE <NUM> management frame and compress the management frame to obtain a compressed management frame, and a radio transmitter unit configured to transmit the compressed management frame to a Wi-Fi receiver device.

Another aspect of the present invention refers to a Wi-Fi receiver device for increasing available airtime in Wi-Fi networks. The Wi-Fi receiver device comprises a radio receiver unit configured to receive a compressed management frame from a Wi-Fi transmitter device, and a data processing unit configured to decompress the compressed management frame to obtain an IEEE <NUM> management frame.

The present invention also refers to a computer program product comprising instructions which, when the program is executed by a first processor, cause the first processor to generate an IEEE <NUM> management frame, compress the management frame to obtain a compressed management frame, and transmit the compressed management frame to a second processor.

The present invention also refers to a computer program product comprising instructions which, when the program is executed by a second processor, cause the second processor to receive a compressed management frame from a first processor and decompress the compressed management frame to obtain an IEEE <NUM> management frame.

A series of drawings which aid in better understanding the invention and which are expressly related with an embodiment of the said invention, presented as a non-limiting example thereof, are very briefly described below.

The present invention refers to a method for increasing available airtime in Wi-Fi networks. A flow diagram with the steps of the method <NUM> is depicted in <FIG>. The method comprises the following steps: generating <NUM>, by a first Wi-Fi device, a management frame <NUM>; compressing <NUM>, by the first Wi-Fi device, the management frame <NUM> to obtain a compressed management frame <NUM>; wirelessly broadcasting <NUM>, by the first Wi-Fi device, the compressed management frame <NUM>; receiving <NUM>, at a second Wi-Fi device, the compressed management frame <NUM>; and decompressing <NUM>, by the second Wi-Fi device, the compressed management frame to obtain the management frame <NUM> which was initially generated by the first Wi-Fi device.

The method is preferably applied to IEEE <NUM> management frames that are long and more frequently broadcast.

In an embodiment, the management frame is a Beacon frame, the first Wi-Fi device is an access point, and the second Wi-Fi device is a station (i.e. a client device, such as a smartphone, that connects to the Wi-Fi network created by an access point). Beacon frames are long messages that are constantly broadcast (normally at a rate of ten or more times per second).

The vast majority of the weight of the management frame is contained in the frame body, which has a fixed part (which is normally small) and a variable part (which includes the so-called "Information Elements" or "Tagged Parameters"). <FIG> illustrates the structure of a Beacon frame <NUM>, which consists of a MAC header <NUM>, a frame body <NUM> and a frame check sequence (FCS) <NUM>. The frame body <NUM> comprises a plurality of fixed parameters <NUM> and tagged parameters <NUM> (or information elements). The fixed parameters <NUM> include the following fields: a timestamp <NUM>, a beacon interval <NUM> (time interval between beacon transmissions) and capability information <NUM> of the device/network. The extension of the tagged parameters <NUM> is variable and may include different optional fields, such as SSID <NUM>, supported rates <NUM>, other information elements <NUM> and vendor-specific fields <NUM>. The number of bytes that each field may contain are shown above the field.

<FIG> is an example of a captured Beacon frame showing the different fields of <FIG>. The extension of the beacon frame <NUM> is mostly determined by the extension of the tagged parameters <NUM>, which may occupy up to <NUM>% of the beacon frame size.

Each access point (AP) periodically transmits, for each SSID (Service Set IDentifier), a Beacon frame with multiple parameters that describe the network, the supported rates, the capabilities of the access point, the security options, etc. Each SSID is a network name to which each a station or client device (smartphone, tablet, laptop, etc.) can connect. <FIG> depicts the percentage of total airtime occupied by all the beacon frames transmitted on a channel depending on the number of SSIDs that each AP advertises per channel and the number of access points that share the same channel. As can be seen in the figure, the amount of wasted airtime increases enormously for each SSID that the AP advertises (columns), and for each AP in the collision domain (rows) given by the channel used and the coverage area.

For a Wi-Fi network to work properly it is recommended that the saturation of airtime is not higher than <NUM>% of the total airtime. For instance, when three access points share a channel and each access point advertises only one SSID per channel, the beacon frames occupy <NUM>% of the total airtime. However, a typical situation in Wi-Fi networks occurs when three access points share the same channel and each access point advertises two SSIDs on said channel. It is also frequent that two access points share a channel and announce three SSIDs each. In both cases, highlighted in <FIG>, almost <NUM>% of the total airtime is consumed by Beacon frames that are being continuously transmitted by the APs over the channel. This saturation of the airtime generates the following negative effects:.

To minimize these negative effects (network performance reduction and higher probability of collisions), it is advisable to reduce the saturation of airtime so that the highest amount of airtime is available for the data transmissions between stations and access points. The method <NUM> of <FIG> achieves a reduction in the airtime saturation by compressing management frames <NUM> that are being transmitted over the Wi-Fi network. The method requires modifying the software of Wi-Fi transmitters and receivers (both access points and client devices) to carry out the compression and decompression of the frames in real time, with the aim of occupying the minimum airtime possible. These modifications may be carried out at low level (driver or firmware).

<FIG> shows the compression <NUM> of management frames <NUM> at a first Wi-Fi device, the transmission <NUM> of the compressed management frames <NUM> by a radio transmitter <NUM> of the first Wi-Fi device, the reception <NUM> of the compressed management frames <NUM> at a radio receiver <NUM> of a second Wi-Fi device, and the decompression <NUM> of the compressed management frames <NUM> at the second Wi-Fi device. The radio transmitter <NUM> of the first Wi-Fi device also receives and transmits other frames <NUM> that are not compressed (e.g. data frames, control frames, or other management frames). When the radio receiver <NUM> of the second Wi-Fi device receives these other uncompressed frames, the data is directly obtained by the second Wi-Fi device (it does not require decompression <NUM>). When receiving data, the second Wi-Fi device only needs to check whether the received data is compressed or not to determine whether decompression <NUM> is to be applied or not.

Many fields of the Beacon frame have low entropy, that is, they contain little information. Entropy marks the theoretical limit from which the information contained in a data set (such as a sequence of bits) can no longer be compressed. <FIG> shows an example of the sequence of bits ('<NUM>') that form the capability information <NUM> field of a Beacon frame <NUM>. This sequence of bits contains very little information since there is little uncertainty in the data (it is very likely that a random bit is <NUM>). The Shannon entropy of this sequence is <NUM> bit/byte. The size of the sequence is <NUM> bytes, but it can be compressed to as little as <NUM> bytes. Therefore, the compressed sequence of bits could occupy <NUM>% of its original size, so that <NUM>% of the airtime could be saved with good compression.

<FIG> depicts an example of the sequence of bytes (represented in hexadecimal format) that form a complete Beacon frame. The size of a Beacon frame is normally between <NUM> and <NUM> bytes. In the example, the Beacon frame is formed by <NUM> bytes and many sections of the frame have redundancy (for example, there are many consecutive '<NUM>' bytes). The Shannon entropy of this example is <NUM> bits/byte. This Beacon frame could be compressed down to <NUM> bytes, which is only <NUM>% of the original size of <NUM> bytes. Therefore, <NUM>% of the airtime originally occupied by the Beacon frame could be saved and used for other frames. In general, considering the compression capacity applied to Beacon frames, between <NUM>% and <NUM>% of the airtime could be saved as an average for most cases. Therefore, with the method of the present invention the airtime occupied by the beacon frames may be practically reduced by half. This means that in the table of <FIG> the airtime occupied by the Beacon frames would move towards optimal areas (highlighted in <FIG>) around <NUM>% of the total airtime, where there is hardly any QoS degradation and the probability of collision is much lower.

The management frame may be fully compressed (i.e. the whole content of the frame) or partially compressed (only part of the frame, e.g. some particular fields of the frame, such as the tagged parameters) by the first Wi-Fi device.

In some cases, certain fields of the management frame may be not compressed. In an embodiment, the MAC header of the management frame is not compressed and the frame body of the management frame is partially or fully compressed. For example, the first Wi-Fi device may compress only the tagged parameters <NUM> of the Beacon frame <NUM>, highlighted in <FIG>, which occupy the vast majority of the length of the Beacon frame. In this case, the radio receiver <NUM> of the second Wi-Fi device would advantageously process the received Beacon frame <NUM> faster, since the MAC header <NUM> is not compressed and thus it would take less time to decode the MAC header <NUM> to determine the type of the frame received (e.g. that the data received is a Beacon frame) or to determine whether the frame is addressed or not to the device.

In another embodiment, the management frame is a Probe Request frame, the first Wi-Fi device is a station and the second Wi-Fi device is an access point. Probe Request frames are long messages sent by the stations when they are searching for Wi-Fi networks. Probe Request frames are sent from time to time by the stations. When there is a great deal of stations grouped around a certain area, such as a shopping center or a football stadium, there may be thousands of Probe Request frames sent per second by the multiple stations (e.g. smartphones), and these frames would occupy a significant percentage of the total airtime on the different Wi-Fi channels.

A Probe Request frame is somewhat smaller than a Beacon frame, with a size comprised between <NUM> and <NUM> bytes. In the Probe Request frame the device advertises its capabilities and everything the device can support, including many parameters such as the manufacturer of the chip, the device type, the driver, the operating system, etc. In the example of <FIG>, the Probe Request frame <NUM> has a size of <NUM> bytes which can be compressed down to as little as <NUM> bytes. In the image, the <NUM> bytes of the tagged parameters <NUM> of the frame body are marked, the tagged parameters <NUM> including a SSID field, a supported rates field, capabilities fields (HT capabilities, extended capabilities, VHT capabilities) and vendor-specific fields. The bytes above that are not highlighted correspond to the MAC header of the Probe Request frame and the fixed parameters.

The exemplary Probe Request frame <NUM> illustrated in <FIG> has only <NUM>% efficiency, with <NUM>% of the airtime being wasted. The Shannon entropy in this case is <NUM> bits/byte. When the Probe Request frame is compressed, <NUM>% of the airtime originally occupied by the frame is left free for other transmissions. In general, when compressing Probe Request frames, the observed percentage of airtime save is similar to that of the Beacon frame, between <NUM>% and <NUM>%.

In an environment with a high density of users, such as a concert, a football stadium or a demonstration, the Probe Request frames are flooding the Wi-Fi channels, with hundreds or thousands of these frames being transmitted per second. Although the Probe Request frames are normally not as long as the Beacon frames, due to the high number of Probe Request frames transmitted (especially when the Wi-Fi network is highly populated) they may have similar or even more negative impact in terms of QoS and collisions in the Wi-Fi networks.

Although the method may be applied to any management frame, the invention is especially useful when applied to either Beacon frames or Probe Request frames. The rest of the management frames are more sporadic and therefore the gain in airtime, when they are compressed, would be more marginal.

The management frame may be compressed (and later decompressed) using any known compression algorithm. However, to achieve higher efficiency for the type of sequences of bits used in these particular frames (Beacon or Probe Requests), the Huffman algorithm or the Lempel-Ziv-Welch compression algorithms are preferably selected, although other compression algorithms (e.g. Fano, Shannon, double-pass Huffman, etc) may also be used.

Another aspect of the present invention refers to a system for increasing available airtime in Wi-Fi networks. <FIG> depicts an embodiment of the system <NUM>, comprising a first Wi-Fi device <NUM> and a second Wi-Fi device <NUM>, although the system <NUM> may comprise a plurality of first Wi-Fi devices <NUM> and/or a plurality of second Wi-Fi devices <NUM>.

Each first Wi-Fi device <NUM> comprises a data processing unit <NUM> and a radio transmitter unit <NUM> (Wi-Fi interface). The data processing unit <NUM> is configured to generate a management frame and compress the management frame. The radio transmitter unit <NUM> is configured to transmit or broadcast the compressed management frame.

Each second Wi-Fi device <NUM> comprises a radio receiver unit <NUM> configured to receive the compressed management frame, and a data processing unit <NUM> configured to decompress the compressed management frame to obtain the original management frame generated by the first Wi-Fi device <NUM>.

In an embodiment, each first Wi-Fi device <NUM> is an access point, each second Wi-Fi device <NUM> is a station (or client device, such as a smartphone, able to connect to a Wi-Fi network generated by an access point), and the management frame <NUM> is a Beacon frame.

According to another embodiment, each first Wi-Fi device <NUM> is a station, each second Wi-Fi device <NUM> is an access point, and the management frame <NUM> is a Probe Request frame.

The radio transmitter unit <NUM> of the first Wi-Fi device <NUM> may be a transceiver (i.e. an electronic unit that is both transmitter and receiver). Similarly, the radio receiver unit <NUM> of the second Wi-Fi device <NUM> may also be a transceiver.

Claim 1:
A method for increasing available airtime in Wi-Fi networks, the method (<NUM>) comprising:
generating (<NUM>), by a first Wi-Fi device (<NUM>), a management frame (<NUM>), wherein the management frame (<NUM>) is an IEEE <NUM> Beacon frame (<NUM>) or an IEEE <NUM> Probe Request frame (<NUM>);
compressing (<NUM>), by the first Wi-Fi device (<NUM>), the management frame (<NUM>) to obtain a compressed management frame (<NUM>);
wirelessly broadcasting (<NUM>), by the first Wi-Fi device (<NUM>), the compressed management frame (<NUM>);
receiving (<NUM>), at a second Wi-Fi device (<NUM>), the compressed management frame (<NUM>); and
decompressing (<NUM>), by the second Wi-Fi device (<NUM>), the compressed management frame (<NUM>) to obtain the management frame (<NUM>) generated by the first Wi-Fi device (<NUM>).