Patent Description:
IEEE <NUM> wireless local area networks (WLANs, also referred to herein as Wi-Fi) are typically multiple access networks. User devices may access the network via a randomized Medium Access Control (MAC) protocol, namely the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol, and the enhanced distributed channel access (EDCA) scheme according to a distributed coordination function (DCF). The specific MAC protocol employed by Wi-Fi networks is standardized in the IEEE <NUM> protocol.

<CIT> and <CIT>, which discuss the time interval of the transmitted beacons, are considered to be relevant prior art for the following disclosure.

Further embodiments are set out in the dependent claims.

Both mobile wireless devices and fixed wireless devices may employ one or more wireless ("Wi-Fi") chips to access the Internet through a Wireless Local Area Network (WLAN). With the introduction of Voice over Wi-Fi (VoWiFi), even telephone calls are being carried over Wi-Fi networks. Although the number of devices using Wi-Fi is increasing at an exponential pace, the available bandwidth allocated for Wi-Fi communication, namely the <NUM> band and the <NUM> band, has remained the same. In an effort to keep up with the increasing demand for Wi-Fi bandwidth, new IEEE <NUM> protocols with additional physical layer capabilities are being developed and introduced.

Whereas the physical layer and the data link control layer of the protocol has evolved significantly since the protocol's introduction (e.g., the protocols IEEE <NUM> a/b/g/n/ac/ax), the basic operation of the MAC layer has not changed much. As the number of Wi-Fi users in the same vicinity and in the same channel increases, airtime overhead created by the management frames may become so significant that the overall system performance (e.g., in terms of throughput, delay) may be degraded dramatically.

The following description includes methods, systems, and apparatuses to minimize management frame overhead in Wi-Fi networks. The examples described herein may be applied in any wireless network by a person skilled in the art.

Referring now to <FIG>, a diagram illustrating components of a communication device <NUM> is shown. The communication device <NUM> may be a station (STA) or may be an access point (AP) as described in further detail below. The communication device <NUM> may include a processor <NUM>, a transceiver <NUM>, a transmit/receive element <NUM>, a speaker/microphone <NUM>, a keypad <NUM>, a display/touchpad <NUM>, non-removable memory <NUM>, removable memory <NUM>, a power source <NUM>, a global positioning system (GPS) chipset <NUM>, and/or other peripherals <NUM>, among others. It should be noted that the STA and the AP described below may include any subcombination of the foregoing elements while remaining consistent with the description.

The processor <NUM> may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the communication device <NUM> to operate in a wireless environment.

The transmit/receive element <NUM> may be configured to transmit signals to, or receive signals from other communication devices over an air interface <NUM>.

Although the transmit/receive element <NUM> is depicted as a single element, the communication device <NUM> may include any number of transmit/receive elements <NUM>. More specifically, communication device <NUM> may employ MIMO technology. In an example, the communication device <NUM> may include two or more transmit/receive elements <NUM> (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface <NUM>.

As noted above, the communication device <NUM> may have multimode capabilities. Thus, the transceiver <NUM> may include multiple transceivers for enabling the communication device <NUM> to communicate via multiple air interfaces <NUM>.

The processor <NUM> of the communication device <NUM> may be coupled to, and may receive user input data from, the speaker/microphone <NUM>, the keypad <NUM>, and/or the display/touchpad <NUM> (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). In other embodiments, the processor <NUM> may access information from, and store data in, memory that is not physically located on the communication device <NUM>, such as on a server or a home computer (not shown).

The processor <NUM> may receive power from the power source <NUM>, and may be configured to distribute and/or control the power to the other components in the communication device <NUM>. The power source <NUM> may be any suitable device for powering the communication device <NUM>.

The processor <NUM> may also be coupled to the GPS chipset <NUM>, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of communication device <NUM>. In addition to, or in lieu of, the information from the GPS chipset <NUM>, the communication device <NUM> may receive location information over the air interface <NUM> from a base station (e.g., base stations 114a, 114b) and/or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the communication device <NUM> may acquire location information by way of any suitable location-determination method.

The communication device <NUM> may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the uplink (e.g., for transmission) and downlink (e.g., for reception) may be concurrent and/or simultaneous. In an embodiment, the communication device <NUM> may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the uplink (e.g., for transmission) or the downlink (e.g., for reception)).

A source of management overhead may be a probe request and probe response message exchange that occurs between a STA and one or more APs. The probe request may be a management frame that a STA may make use of to gather information about the APs in its vicinity when it is in Active Scanning mode. The STA may send a probe request message to a broadcast address, meaning that the message is intended for multiple recipients. The probe request may include identifying information about the STA, such as, for example, a Medium Access Control (MAC) address. The one or more APs that receive the probe request message may respond to the message by sending a probe response message. The probe response message may include information about the AP's capabilities, such as channel capabilities, supported IEEE <NUM> protocols, supported bandwidths, supported number of spatial streams, and various other physical layer capabilities. Probe response frames may include the same content as a beacon frame. Accordingly, the STA may be provided with the technical capabilities supported by the AP before it initiates association with the AP. The probe response message may be sent in unicast mode. In other words, the probe response frames may be intended only for one receiver STA (i.e., the transmitter of the probe request frame).

Because the probe request and probe response message exchange occurs in broadcast and unicast mode, respectively, a STA that sends a probe request message may trigger a probe response transmission by all the APs within the transmission range of the STA. For example, if there are four APs within the range of the STA, the probe request may trigger four probe response messages.

According to the IEEE <NUM> standards, broadcast messages may be transmitted using a basic rate, which is one of the possible slowest transmission rates available in the standards. It should be noted that slow transmissions occupy the wireless medium longer than fast transmissions. Accordingly, as the number of probe requests in the wireless medium increases, a considerable amount of airtime may be consumed by these frames.

Referring now to <FIG>, a diagram illustrating a first wireless network 200A having an AP 202A and one or more STAs is shown. The one or more STAs described below may include any combination of internet-connected devices, such as mobile devices, computers, televisions, wearables, smart devices, thermostats, cameras, and Internet of Things (IoT) devices. The wireless network 200A may include a first STA 204A, a second STA 206A, a third STA 208A, and a fourth STA 210A. As shown in <FIG>, the wireless network 200A may be in a proximity to one or more neighbor wireless networks. For example, the wireless network 200A may be in proximity with a second wireless network 200B and a third wireless network 200C. The second wireless network 200B may have its own AP 202B and one or more STAs such as a first STA 204B, a second STA 206B, a third STA 208B, and a fourth STA 210B. The third wireless network 200C may have its own AP 202C and one or more STAs such as a first STA 204C, a second STA 206C, and a third STA 208C.

As described above, the probe request and probe response message exchange occurs in broadcast and unicast mode, respectively. A STA that sends a probe request message triggers probe response transmission by all the APs within the transmission range of the STA. As shown in <FIG>, STAs from the second wireless network 200B and the third wireless network 200C may send broadcast probe request messages that are received by the AP 202A. The AP 202A may then send individual unicast probe response messages to the STAs in the second wireless network 200B and the third wireless network 200C. The probe response messages may be sent by the AP <NUM> using the basic rate. Since they are unicast, they may be repeatedly transmitted until the recipient STA acknowledges successful reception of the frame or the packet is dropped due to reaching retry count.

If there are many APs and STAs in the vicinity (e.g., in public spaces, office buildings, and multi dwelling units (MDUs)), then probe response frames originating from different APs may collide with each other. This may cause retransmissions and may contribute considerably to airtime overhead.

Referring now to <FIG>, a histogram illustrating a number of probe requests (y-axis) with respect to observed received signal strength indicator (RSSI) levels (x-axis) is shown. The information presented may be collected by a sniffer collocated with an AP in residential or public environment, such as the AP 202A of <FIG>. As shown in <FIG>, most of the probe requests received by the AP 202A may have very low RSSI levels (e.g., approximately -<NUM> dBm to -<NUM> dBm). These probe requests may be sent by STAs that belong to other networks, such as the second wireless network 200B and the third wireless network 200C. These STAs may not have any intention to associate with the AP 202A. This may be an expected result, as probe requests transmitted by STAs that belong to neighboring wireless networks may reach the AP 202A at very low signal levels.

It should be noted that setting the AP 202A, the AP 202B, and the AP 202C to different operating channels may not solve this problem, because the STAs from the second wireless network 200B and the third wireless network 200C may send probe request messages in all channels. Thus, even though the AP 202A, the AP 202B and the AP 202C may operate in different channels, the STAs that belong to the second wireless network 200B and the third wireless network 200C may send probe requests in the channels the AP 202A is operating in.

The examples described herein may mitigate or prevent responses from the AP 202A to these probe request messages.

Referring now to <FIG>, a histogram illustrating a number of probe response frames (y-axis) with respect to observed RSSI levels (x-axis) is shown. The information presented may be collected by a sniffer collocated with an AP in residential or public environment, such as the AP 202A of <FIG>. It should be noted that there may be a significant difference in the number of probe requests (<FIG>) and probe response frames (<FIG>). The number of probe response frames (<FIG>) may be almost an order of magnitude more than the number of probe request frames (<FIG>).

The description herein includes methods by which the AP 102A may reduce the overhead caused by the probe request and probe response messaging. In one example, the methods may not require any modifications to STA devices. The overhead minimization (i.e., the improvement in performance) may be realized by modifying the AP 102A firmware.

Referring now to <FIG>, a diagram illustrating a STA information table <NUM> is shown. The AP 202A may keep track of the clients (e.g., STAs) that have associated with it, in the STA information table <NUM>. The STA information table <NUM> may be stored in one or more of the non-removable memory <NUM> and the removable memory <NUM> described above with reference to <FIG>. The STA information table <NUM> may include first column <NUM> identifying STA MAC addresses and a second column <NUM> identifying a timestamp of last association. It should be noted that currently unassociated STAs, which have associated with the AP 202A at some time in the past, may also be stored in the STA information table <NUM>. After a predetermined but configurable amount of time has passed since the last association of a STA, that STA may be removed from the list. In an example, this predetermined amount of time may be <NUM> days, but it may be set to be a longer or shorter time period in other implementations.

The AP 202A may determine the address of a STA from the probe request message and may not respond to probe requests sent by the STAs that are not listed in the STA information table if the measured signal strength (e.g., in terms of RSSI) falls below a predetermined but configurable RSSI threshold. In an example, the RSSI threshold may be approximately -<NUM> dBm. The RSSI threshold may vary depending on a transmitting STA's physical layer capabilities, which may be specified in the probe request message. For example, if a STA is using the IEEE <NUM> protocol, the RSSI threshold may be -70dBm. If a STA is using the IEEE <NUM>. 11ac protocol, the RSSI threshold may be -75dBm. The RSSI threshold may be set lower or higher than this value in other implementations.

The AP 202A may be allowed to respond to probe request messages sent by STAs that are listed in the STA information table, regardless of the RSSI of the received probe request. This way, a STA belonging to the first wireless network <NUM> may initiate association from far corners of the first wireless network <NUM>. In this example, a STA that is new to the first wireless network <NUM> that is to be associated with the AP 202A may be brought relatively close, depending on the RSSI threshold used for preventing probe response transmission to the AP <NUM>. This may ensure that the STA may receive a response to its probe request message.

It should be noted that not all STAs may depend on probe request and probe response message exchange to initiate association. For example, STAs may make use of passive scanning of beacon frames transmitted by the AP 202A to learn of its supported capabilities and to initiate association.

Applying these methods to the deployment scenario illustrated in <FIG>, the AP 202A may only respond to probe request messages sent by the STAs in the first wireless network 200A, the AP 202B may only respond to probe request messages sent by the STAs in the second wireless network 200B, and the AP 202C would only respond to the probe request messages sent by STAs in the third wireless network 200C. The airtime overhead due to the probe request and probe response exchange may be significantly reduced.

If only the AP 202A employs the above method, but the AP 202B and the AP 202C do not employ the method, then only the AP 202A may stop sending probe responses to the STAs that belong to the other wireless networks 200B and 200C. The AP 202B and the AP 202C may still continue responding to probe requests sent by the STAs that belong to the first wireless network 200A. In order to minimize the probe response overhead caused by the neighboring legacy networks, the AP 202A may adjust its operating channel such that it does not overlap with the operating channels of neighboring APs. For example, if the AP 202B is operating in channel <NUM>, and the AP 202C is operating in channel <NUM>, then the AP 202A may operate in channel <NUM>. Accordingly, the AP 202A may avoid probe responses sent by the AP 202B and the AP 202C. In an example, the AP 202A may choose its operation channel by making use of a channel selection scheme that takes into account the interference caused by the other networks in the vicinity. Examples of this scheme may be found in in <CIT> and PCT Application Serial No. <CIT>, the contents of which are hereby incorporated by reference. Moreover, the AP 202A may keep track of its neighbor wireless networks by carrying out periodic off-channel scans, and it may identify the channels in which its close neighbors are operating.

Referring now to <FIG>, a flowchart illustrating a method of reducing overhead in the probe request and probe response message exchange is shown. In step <NUM>, the AP 202A may receive a probe request message from a STA. In step <NUM>, the AP 202A may determine the identity of the STA using the probe request message. In step <NUM>, the AP 202A may determine if the identity of the STA is stored in the STA information table <NUM>. If yes, the method proceeds to step <NUM>. If no, the method proceeds to step <NUM>.

In step <NUM>, the AP 202A may determine if the STA is currently associated with the AP 202A or has been recently associated with the AP 202A within a predetermined time. If yes, the method proceeds to step <NUM>. If no, the method proceeds to step <NUM>.

In step <NUM>, the AP 202A may determine if the RSSI of the probe request message is above the predetermined threshold. If no, the method proceeds to step <NUM> and the AP 202A does not send a probe response message. If yes, the method proceeds to step <NUM> and the AP 202A sends a probe response message to the STA.

Referring now to <FIG>, a flowchart illustrating another method of reducing overhead in the probe request and probe response message exchange is shown. In step <NUM>, the AP 202A may receive a probe request message from a STA. In step <NUM>, the AP 202A may determine the identity of the STA using the probe request message. In step <NUM>, the AP 202A may determine if the identity of the STA is stored in the STA information table <NUM>. If yes, the method proceeds to step <NUM>. If no, the method proceeds to step <NUM>.

Referring now to <FIG>, a diagram illustrating a wireless mesh network <NUM> is shown. Mesh networks may also be affected significantly by management frame overhead. The mesh network <NUM> may include one or more mesh APs and one or more STAs. For example, the mesh network <NUM> may include a first AP <NUM>, a second AP <NUM>, and a third AP <NUM>. The first AP <NUM> may be connected to the Internet <NUM>. The mesh network <NUM> may also include a first STA <NUM>, a second STA <NUM>, and a third STA <NUM>. The first AP <NUM>, the second AP <NUM>, and the third AP <NUM> may be subject to probe request messages sent from STAs that belong to other networks in the vicinity of the mesh network <NUM>. For example, broadcast probe request messages sent by a fourth STA <NUM> associated with a fourth AP <NUM>, a fifth STA <NUM> associated with a fifth AP <NUM>, and/or a sixth STA <NUM> associated with a sixth AP <NUM> may be received by the APs in the mesh network <NUM>. As described above, the APs in the mesh network <NUM> may not respond to these probe request messages unless the probe request message is received with an RSSI level above a determined threshold.

The APs in the mesh network <NUM> may each have a Station Information Table <NUM> as described above. These APs may exchange their Station Information Tables <NUM> so that each AP in the mesh network <NUM> has the same set of information about which STAs belong to the network and their last association time.

In an example, the APs in the mesh network <NUM> may be equipped with client steering functionality as disclosed in PCT Patent Application Serial No. <CIT>, <CIT>, and PCT Patent Application Serial No. <CIT>, the contents of which are hereby incorporated by reference. When equipped with client steering functionality, only one AP in the mesh network <NUM> may respond to probe request messages sent by a STA. The other APs in the mesh network <NUM> may not respond to probe request messages irrespective of the RSSI level of the probe request frame. The responding AP may be determined by client steering logic implemented in the client steering functionality. For example, if the first STA <NUM> is being steered to the second AP <NUM> while it is connected to the first AP <NUM>, only the second AP <NUM> may respond to probe request messages from the first STA <NUM>. The first AP <NUM> and the third AP <NUM> may not respond. If a STA is not being steered to any other AP, then the associated AP may respond to probe requests sent by the STA.

Another type of management frames that may cause significant airtime overhead are periodic beacon frames sent by APs. These beacon frames may be used for the announcement of an AP's capabilities to other nodes, sleep-awake scheduling in power save mode, channel switch synchronization (e.g., in Channel Switch Announcement (CSA) and Extended-CSA standards), and other functions that require time synchronization among the nodes in the network.

Since the mesh network <NUM> employs more than one mesh AP, each may transmit its own beacon frames. For example, if each AP in the mesh network <NUM> sends beacon messages every <NUM>, it makes <NUM> beacon frame transmissions per second. If there are three APs in the mesh network, then the network may transmit <NUM> beacon frames per second. Beacon messages may be broadcast using the basic rate. The amount of airtime overhead due to beacon frame transmission may become significant as the number of nodes in the same vicinity increases.

In order to reduce the airtime overhead caused by beacon frame transmissions, the APs in the mesh network <NUM> may employ a beacon period adjustment. If there are no STAs associated with an AP in the mesh network <NUM>, for example the first AP <NUM>, the first AP <NUM> may increase the beacon transmission period. In other words, the first AP <NUM> may send beacon frames less frequently. This may be achieved by adjusting the target beacon transmission time (TBTT) parameter.

However, if there are STAs associated with the first AP <NUM>, the first AP <NUM> may adjust its beacon frame period by considering the minimum timing synchronization required by the associated STAs and the connected APs. The first AP <NUM> may go back to a default beacon frame period if it has an associated STA. In an example, the default beacon period may be approximately <NUM>. If the first AP <NUM> does not have any connected STAs, it may increase its beacon frame period to <NUM>. The other APs in the mesh network <NUM> may use a beacon period of approximately <NUM> if they have associated STAs.

Claim 1:
A method implemented by a wireless local area network, WLAN, wireless access point (<NUM>) in a mesh network (<NUM>), the method comprising:
determining a new transmission time period for an access point beacon that differs from a default transmission time period for the access point beacon, wherein the new transmission time period is based on a number of clients associated with the wireless access point, wherein the access point beacon includes technical capabilities of the wireless access point, wherein the new transmission time period is higher than the default transmission time period on a condition that there are no clients associated with the wireless access point, wherein the new transmission time period is determined further based on the minimum timing synchronization required by the clients associated with the wireless access point; and
transmitting, from the wireless access point, the access point beacon periodically using the new transmission time period.