Patent Description:
As quality of experience becomes a more stringent requirement on modern wireless local area networks (WLANs), it becomes rapidly clear that a single wireless access point (AP) is not able to deliver the full service set that is required by an end user. As a response, many WLANs are migrating to a multi-access point architecture. As a direct result of this trend, the industry started with the development of either WLAN repeater devices or simple access point nodes called extenders. Hence, WLAN is being reshaped from a strongly centralized architecture to a decentralized architecture where the combination of access point nodes form a backbone to ensure the high quality of experience level required. While the poor coverage issue might be handled that way, there is a wide variety of further issues with a decentralized architecture, which do not relate to signal strength or the lack thereof.

As more access points are installed in the home or professional environment, a new problem emerges that did not exist before. The new decentralized network architecture must now guarantee that each end user terminal device or WLAN client and, therefore, a station (STA), which is a device that has the capability to use the <NUM> protocol, receives the best quality of experience or user experience as a whole. Such a "function to ensure quality" does not exist in any current WLAN standard (IEEE (Institute of Electrical and Electronics Engineers) <NUM> or WFA (Wi-Fi™ Alliance)) and hence resides in vendor proprietary solutions.

On the professional side, the networks are generally managed based on a mix of internet protocol (IP) layer (L3) metrics (e.g. round trip delay, average throughput) and L2 metrics (e.g. packet loss, amount of users). An important aspect to be noted is that all management techniques are AP centric and roaming from one AP to another can still be independently controlled by the individual STAs without the AP interfering in that decision. As the "control"-function only uses L3/L2 metrics in combination with some simple WLAN metrics such as received signal strength indicator (RSSI) and/or physical layer (PHY) rate it is not able to detect specific WLAN anomalies such as hidden nodes or rogue radio frequency (RF) interference.

On the residential side, there is no quality control at all. STAs are roaming based on the simple implementation, which is currently embedded in the (open source) WLAN management code - "Wi-Fi™ protected access (WPA) supplicant" - namely an RSSI level based trigger to rescan the environment for a more "powerful" AP.

Sheer reception power (RSSI) is not a decent benchmark for signal quality, as will be acknowledged by persons skilled in the art of WLAN, the trigger condition to roam is wrong to say the least. This in combination with the inability for end users to modify the roaming behavior to a more clever mechanism leads currently to a more or less "best effort" approach of user experience control. Prior art is disclosed in <CIT>.

The patent application publication <CIT> provides coordinating user equipment handover in a heterogeneous network cell that includes a plurality of overlaying cell layers. An access controller of a network core receives a first parameter relating to signal quality for the user equipment with a serving cell of a cell layer of the plurality of overlaying cell layers, and receives a second parameter based upon a velocity estimation of user equipment within the heterogeneous network cell. When the first parameter indicates a cell boundary, the access controller forms a handoff decision to a cell base station of a cell layer of the plurality of overlaying cell layers based upon the second parameter, and initiates a handoff to the cell base station based upon the handoff decision.

The patent application publication <CIT> provides a method of managing Wi-Fi™ access points using a Wi-Fi™ network manager is disclosed. Measurement data is received from a plurality of Wi-Fi™ access points via a control interface. Optimized adjustments to one or more Wi-Fi™ parameters associated with one or more of the plurality of access points are searched based at least in part on a set of network optimization goals and the measurement data received from the plurality of access points. At least some of the optimized adjustments to the one or more Wi-Fi™ parameters are transmitted to the one or more of the plurality of access points using the control interface.

Current roaming decisions in multi-access point (AP) IEEE802. <NUM> networks (Wi-Fi™) are made by each mobile device (STA) without knowledge of the infrastructure. The roaming decisions may result in poor roaming experience w/ poor connection quality. A mechanism or method that controls the user experience or quality of service for each of the connected STAs individually is currently not available.

The invention relates to methods according to claims <NUM>, <NUM> and <NUM> and corresponding apparatuses according to claims <NUM>, <NUM> and <NUM>, respectively.

With many WLANs migrating to a multi-access point architecture, a unified control function for all stations (STAs) rather than allowing each STA to make the roaming decision individually is becoming a key feature for solving above stated problems of the prior art. This unified control function should be based on link quality assessment rather than packet/frame counter based in combination with some uncorrelated physical layer (PHY) statistics to address current problems. In order to ensure a uniformly controlled quality of experience the individual access points should assess the environment and actual link quality in a first stage and communicate that information with a control entity and other access points in a second stage.

In order to ensure good quality of service/user experience in a multi-access point Wi-Fi™ setup in which a user roams with a mobile device (STA) the access points (APs) continuously or at intervals assess the wireless environment's quality (for example, noise, interference from other APs, traffic concentrated on individual APs, APs on the same channel) and report to a control entity. The control entity determines, from the assessment data, alternative "candidate" APs that could be used in case the link quality of a current connection between an AP and a STA falls below a predefined value. Assessment is done on Open Systems Interconnection (OSI) layers <NUM> and <NUM>. The control entity then "primes" "candidate" APs to accept or reject a STA's connection request, e.g. by accordingly setting MAC filters (white listing or blacklisting). This effectively establishes a controlled roaming in multi-AP Wi-Fi™ networks that is fully compatible with legacy mobile devices and does not require any update of deployed mobile devices.

It is an advantage of embodiments of the invention that the real potential of a link is evaluated, rather than only the signal strength. Based on the real potential of the link and, thus the link quality or quality of user experience, respectively, roaming decisions may be forced compared to pure RSSI roaming to ensure that all stations (STAs) roam equally.

Accordingly, embodiments of the invention facilitate a satisfying WLAN experience to a user by forcing the station to connect with the best possible access point, based upon WLAN link quality measurements per station per access point. This experience is an improvement over the generally used best effort based mechanisms.

It is an advantage of embodiments of the invention that a relatively simple method for controlling the WLAN quality of service in a multi-access point environment is provided that gives handoff control to a control entity and is compatible with existing stations. No standard update for the stations is required. Embodiments of the invention will enable fast handoffs of about <NUM> to <NUM>.

According to embodiments of the present invention, a method for controlling wireless local area network (WLAN) user quality in a multi-access point environment is disclosed. The method comprises: establishing a wireless local area network system including a first access point (AP), a second access point, a control entity, and a station (STA), wherein a communication channel is established between the first access point and the second access point; connecting the station to the first access point; generating and publishing link quality reports to the control entity and to the second access point using the first access point; generating and publishing environment quality reports to the control entity and to the first access point using the second access point; blacklisting a media access control (MAC) address of the station via an access control list (MAC ACL) upon receiving consecutive unacceptable link quality reports and a quality alarm from the first access point with the control entity; instructing the first access point with the control entity to actively disconnect the station; determining a new target access point with the control entity based on the received environment quality reports; and connecting the station to the new target access point.

According to embodiments of the present invention, the method further includes forcing the station to roam for another access point by actively disconnecting the station from the first access point.

According to embodiments of the present invention, the method further includes calculating link quality scores with the control entity based on the link quality reports and environment quality reports.

According to embodiments of the present invention, the method further includes calculating the link quality scores based on values of a maximum physical layer (PHY) rate, a physical limits PHY rate, a trained TX PHY rate, a medium busy indicator, a total available throughput (power saving mode (PS) off), and available throughput (power saving mode (PS) on).

According to embodiments of the present invention, the method further includes comparing the link quality scores with a threshold that separates an acceptable link from an unacceptable link using the control entity, wherein the threshold is a configurable integer number threshold.

According to embodiments of the present invention, the method further includes integrating additional access points into the wireless local area network system; and instructing all non-eligible access points with the blacklisted a media access control (MAC) address using the control entity.

According to embodiments of the present invention, the method further includes instructing all access points eligible as the new target access point using the control entity to white list a media access control address; and enabling the station to be connected with one of these access points.

According to embodiments of the present invention, the method further includes holding the blacklist for at least a given time period; preventing a too frequent access point switch over; and removing the media access control (MAC) address of the station from the blacklist after expiration of the time period.

According to embodiments of the present invention, the method further includes generating and publishing link quality reports to the control entity and to the first access point using the second access point after connecting the station to the new target access point; and generating and publishing environment quality reports to the control entity and to the second access point using the first access point after connecting the station to the new target access point.

According to embodiments of the present invention, the method further includes using an active style link assessment to generate the link quality reports; launching a forced data connection with the access point the station is connected to; and sending layer <NUM> metrics data to the control entity.

According to embodiments of the present invention, the method further includes using a medium availability threshold set by the control entity on a link under test to trigger a more accurate diagnosis; forcing the link under test to be stressed; obtaining an overview of the losses due to interference, signal strength, and PHY layer anomalies; and linking real observed throughput to physical layer parameters using the control entity.

According to embodiments of the present invention, a wireless local area network (WLAN) system for controlling wireless local area network user quality in a multi-access point environment is disclosed. The system comprises a first access point (AP); a second access point, wherein a communication channel is established between the first access point and the second access point; a control entity in communication with the first access point and the second access point; wherein the first access point and the second access point generate and publish link quality reports or environment quality reports; and wherein the control entity calculates link quality scores based on the link quality reports and environment quality reports.

According to embodiments of the present invention, the system further includes a station (STA) in communication with the first access point and the second access point; wherein the first access point actively disconnects the station if the access point has a link quality score below a preset threshold and forces the station to roam for another access point having a link quality score above the threshold.

According to embodiments of the present invention, an access point otherwise compliant with the IEEE <NUM> standard additionally comprises software code to generate and publish link quality reports or environment quality reports to a control entity, to actively disconnect the station based on a command from the control entity.

According to embodiments of the present invention, a control entity otherwise compliant with the IEEE <NUM> standard comprises software code to calculate link quality scores based on the link quality reports and environment quality reports and to blacklist a media access control (MAC) address of a station via an access control list (MAC ACL) upon receiving consecutive unacceptable link quality reports and a quality alarm from an access point.

According to one or more embodiments of the present invention the control entity is integrated in a Wi-Fi ™ router or access point.

Embodiments of the invention are discussed in more detail below by way of example with reference to the drawings, in which.

Similar or same elements are referenced with the same reference numbers.

It will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of illustrative system components and/or circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable storage media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

Referring to <FIG>, a wireless local area network (WLAN) system <NUM> is illustrated according to an embodiment of the present invention. The WLAN system <NUM> may be a network that may include at least a first access point (AP) <NUM> and a second access point (AP) <NUM>, a control entity <NUM>, such as a WLAN controller unit, at least one station (STA) <NUM>, such as an end user terminal device or WLAN client device, and a communication channel <NUM> between the first access point <NUM> and the second access point <NUM>. Each of the access points <NUM> and <NUM> is capable of performing a link quality assessment. The control entity <NUM> may be integrated in one of the access points, for example the first access point <NUM> or the second access point <NUM>. Each access point may be an access point according to the IEEE <NUM> standard. Each of the access points <NUM> and <NUM> could also be a home automation gateway (GWY). A unidirectional link may be established between each of the access points <NUM> and <NUM> and the station (STA) <NUM>.

Referring to <FIG>, a link quality assessment method <NUM> is illustrated in accordance with an embodiment of the present invention. In order to ensure a uniformly controlled quality of experience the individual access points <NUM> and <NUM> should access the environment and actual link quality in a first stage and communicate that information with other the access points in a second stage.

Environment quality assessment does not require the presence of a client device, such as station (STA) <NUM> (as shown in <FIG>) and is generally well understood. Each of the access points <NUM> and <NUM> can easily monitor various items including, for example, background noise level, medium availability due to "other WLAN devices", medium availability in general, medium availability due to traffic concentrated at the access point <NUM> or <NUM>, and amount of other access points in the same channel. The environment quality assessment is a task that each access point, the first access point <NUM> and the second access point <NUM> as shown in <FIG>, must execute in background and periodically report to the control entity <NUM>. The control entity <NUM> then uses the environment quality assessment as "bias" to estimate which access points can be eligible to serve as "alternative" access point once a specific AP-STA link is determined to be bad.

Link quality assessment is a key component for validating the quality of a WLAN link. Link quality assessment can be implemented in several forms. An access point, such as access point <NUM> or access point <NUM>, can evaluate the link quality either in a passive way or in an active way. While the active evaluation of the link quality results in the most accurate analysis, passive assessment serves the purpose to detect "trend line" error conditions, such as hidden nodes, non-WLAN noise, or WLAN medium sharing overload. The link quality assessment may be based on the performance of the actual link rather than the physical parameters such as signal strength or packet loss.

Based on the link quality assessment various link quality metric that may be expressed as a link quality score can be derived as visualized in <FIG> The link quality metric may be based on values of, for example, a maximum physical layer (PHY) rate <NUM>, a physical limits PHY rate <NUM>, a trained TX PHY rate <NUM>, a medium busy indicator <NUM>, a total available throughput (power saving mode (PS) off) <NUM>, and available throughput (power saving mode (PS) on) <NUM>. A total achieved throughput may be reflected in the link quality score.

The maximum PHY rate <NUM> is the PHY rate negotiated at association and, thus, the maximum achievable link speed. The physical limits PHY rate <NUM> is the maximum target PHY rate for a given amount received signal strength. The physical limits PHY rate <NUM> is thus the expected PHY rate based on a received signal strength indicator (RSSI) and may depend on the number of spatial streams. The trained TX PHY rate <NUM> is the PHY rate at which the transmission takes place, with TX referring to the physical medium that carries the signal. The medium busy indicator <NUM> refers to the amount of airtime that is lost due to sharing of the medium with other networks. The total available throughput (PS off) <NUM> is the maximum amount of available throughput based on the available airtime. The available throughput (PS on) <NUM> is the maximum available throughput based on the available airtime reduced with the recorded amount of time that the STA <NUM> is in a sleep mode due to power save. The total achieved throughput is the throughput that is generally achieved when using the active link.

Passive style link assessment can be combined with the environment quality assessment, as it will generally deliver similar statistics. The main difference is that the actual data traffic counters, which may include valid packets transmitted and the trained TX PHY rate <NUM>, will be recorded based on the random data traffic that exists between the STA <NUM> and the AP <NUM> or <NUM> with which the STA <NUM> is connected. With this approach the determination of the total achieved throughput may be inaccurate as the active link is likely not to be used at its maximum throughput, additionally the trained TX PHY rate <NUM> can be off due to the fact that power saving techniques are pushing the PHY rate down as the STA <NUM> is not utilizing the WLAN link to its full potential. Passive monitoring data may be useful to build a "quality degradation alarm", which can trigger the control logic of the control entity <NUM> indicating that there might be a need to take action.

Active style link assessment is to some extend identical to the passive style link assessment but instead of calculating link metrics based on "random" data flows between the access point <NUM> or <NUM> and STA <NUM>, the access point <NUM> or <NUM>, to which the STA <NUM> is connected, will launch a forced data connection via which the access point <NUM> or <NUM> will try to send as much layer <NUM> (L2) metrics data (e.g. packet loss, amount of users) as possible. By doing so, the access point <NUM> or <NUM> will be able to determine an exact value for the trained TX PHY rate <NUM> and will further be able to determine the exact percentage of available throughput, trained TX PHY rate <NUM> and all other metrics listed previously and illustrated in Fig. <NUM>. A medium availability threshold may be used on the active link to trigger a more accurate diagnosis, which forces the interface under test to be stressed. The outcome of this test is an overview of the losses due to interference, signal strength, PHY layer anomalies (e.g. fading). This way real observed throughput (and the lack thereof) is linked to PHY layer parameters.

For instance, if the signal strength is very high and there is a zero packet loss, the signal-to-interference-plus-noise ratio (SINR) is still acceptable and yet the link performance is nearly zero. This occurs due to a specific type of interference that cannot be represented by PHY layer counters as this a natural cause of the CSMA-CA (carrier sense multiple access with collision avoidance) protocol. By diagnosing an active link, useful parameters may be derived and used to decide whether or not to remove a client (STA) from a given access point (AP). Accordingly, a parameter that is related to a link quality or a metric based on quality of user experience, respectively, is used.

Each access point, such as the first access point <NUM> and the second access point <NUM>, reports a link quality report periodically. When there is no STA <NUM> connected to the access point <NUM> or <NUM>, the link quality report will be an environment quality report. The access point <NUM> or <NUM> should in any case report the full set of parameters <NUM> to <NUM> listed earlier.

Once a monitor period completes, the access point <NUM> or <NUM> sends the report, time stamped with an indication of an access point identifier (based on the basic service set identifier (BSSID) of the access point <NUM> or <NUM>) to the control entity <NUM>. The control entity <NUM>, such as, for example, a WLAN controller, will then calculate a link score based on the obtained report and store the link score per access point <NUM> or <NUM> with a time stamp in its monitor table.

The described concept may not be limited to access points transmitting the full measurement report only. If an access point to access point link, such as a link between access point <NUM> and access point <NUM>, is used, it can be beneficial to send an "alarm" signal only in case the access points are calculating the link score directly. In this case, the access points should report the failing link score only to the corresponding device that triggers it.

The control entity <NUM>, for example a WLAN controller, may calculate a link quality metric expressed as a link quality score based on at least the following parameters: the maximum physical layer (PHY) rate <NUM>, the trained TX PHY rate <NUM>, the medium busy indicator <NUM>, and a TZ time fraction. The link quality metric reflects the amount of performance that is lost due to loss of medium availability. The link quality metric is essentially equal to the environment quality assessment report, which is generated in case no connections with a STA <NUM> are present at the access point <NUM> or <NUM> performing the assessment. The link quality metric represents a scaled performance result. As such, the link quality metric and, thus, the link quality score, takes into account the actual obtained performance and the potential for improvement. The link quality score may be given as a number between <NUM>% and <NUM>%.

A threshold that separates a good/acceptable link from a bad/unacceptable link may be modeled as a configurable integer number threshold so that it can be easily adjusted to adapt the aggressiveness of the decision. For example, a good/acceptable link may have a link quality and, thus, a link score, of > <NUM>% and a bad/unacceptable link may have a link quality and, thus, a link score, of < <NUM>%. This way the control entity <NUM> can determine if an access point, such as access point <NUM> or access point <NUM>, reports an acceptable or an unacceptable link quality.

Based on the periodical data that the control entity <NUM>, such as a WLAN controller, receives from the access points <NUM> and <NUM>, the control entity <NUM> can react on the time varying nature of WLAN quality or experience.

Referring now to <FIG>, a WLAN user quality control algorithm <NUM> for a multi-access point environment is illustrated in accordance with an embodiment of the present invention.

The station (STA) <NUM> may be connected to the first access point <NUM> in a step <NUM>. The access point <NUM> publishes link quality reports to the control entity <NUM> and to the second access point <NUM>, to which the access point <NUM> is connected via the communication channel <NUM>, in a step <NUM>. Since no STA <NUM> is connected with the second access point <NUM>, the second access point <NUM> publishes environment quality reports to the control entity <NUM> and to the first access point <NUM> in a step <NUM>. The control entity <NUM> may use the link quality reports to calculate a link quality score and may compare the link quality score with a threshold that separates a good/acceptable link from a bad/unacceptable link, which may be modeled as a configurable integer number threshold, in a step <NUM>. While only the first access point <NUM> and the second access point <NUM> are used as an example in <FIG>, more than two access points may be present. Also more than the one station (STA) <NUM> may be present.

When the control entity <NUM> receives consecutive bad/unacceptable link quality reports and a quality alarm from the access point <NUM>, the control entity <NUM> instructs the access point <NUM> to remove the STA <NUM> by blacklisting the STA MAC (media access control) address on the access point <NUM> via a simple access control list (MAC ACL), which may be an layer <NUM> active control list. The term consecutive may be modeled as an integer threshold to allow configuration of the aggressiveness of the controller's reaction.

Accordingly, the blacklist may be published by the control entity <NUM> in a step <NUM> to be received by the first access point <NUM> and the second access point <NUM>. By publishing the black list, the access point <NUM> is instructed by the control entity <NUM> to actively disconnect the STA <NUM>, for which the alarm was reported.

As a result, the STA <NUM> is immediately disconnected from the first access point <NUM> and forced to roam to find another access point in a step <NUM>. The control entity <NUM> however does not allow the STA <NUM> to pick just any other access point. Instead, the control entity uses the environment quality reports and, thus, link quality scores, of the other access points to determine which access point would be the ideal candidate to host the new STA connection. In the case illustrated in <FIG>, this is the second access point <NUM> and, thus, the STA <NUM> is connected with the second access point <NUM> in a step <NUM>. Accordingly, the new target access point, here the second access point <NUM>, will be determined based on an assessment of the operational environment of the individual access point, the access point <NUM>.

All non-eligible access points may be instructed by the control entity <NUM> to apply the same STA MAC blacklist. A white list strategy may be applied on the new target access point, here the second access point <NUM> while all other access points, here the first access point <NUM>, blacklist the STA MAC. The control entity <NUM> may instruct the new target access point <NUM> to whitelist the client MAC address and thus enable the STA <NUM> to be connected with the access point <NUM>. This way the STA <NUM> cannot associate anywhere else but with the ideal target access point. This may be enabled by embedding pass/fail logic not only into the control entity <NUM> but also in the individual access points <NUM> and <NUM>.

There may be requirement for the blacklist to be held for at least a given time period (e.g. <NUM>) to prevent too frequent access point switch over as the STA's own roaming could trigger frequent jumps to other access points. However if the blacklists are held, the STA <NUM> learns that it cannot establish a connection and will stop trying.

After the STA <NUM> switched over from the first access point <NUM> to the second access point <NUM>, the first access point <NUM> now publishes environment quality reports to the control entity <NUM> and to the second access point <NUM> in a step <NUM>. The access point <NUM> publishes now link quality reports to the control entity <NUM> and to the first access point <NUM> in a step <NUM>. Once the blacklist timeout expires, the control entity <NUM> will remove the blacklist state in a step <NUM>. In a following step <NUM>, the blacklist will be unpublished by the control entity <NUM>.

As mentioned earlier, the basic system can utilize passive link quality assessment techniques. The overall architecture however allows a much broader application such as service based load balancing.

For example, the alarm conditions for the algorithm illustrated in <FIG> may have been configured to raise an alarm when the link quality score (or the link quality metric) drops below <NUM>% for instance to raise frequent triggers. At this point, the control entity <NUM> can request the target access point <NUM> to perform an active style link assessment to figure out if the situation is unacceptable or if the target service (e.g. voice call or video streaming) can still be met. The access point <NUM> will then perform the active style link assessment and report the exact total achieved throughput to the control entity <NUM>, which can then use this input to either remove other stations from the access point or move the target station, STA <NUM>, to an access point, here the second access point <NUM>, that is reporting <NUM>% environment quality.

Various other applications can be built in a similar way due to the qualitative assessment in combination with the inter-access point communication mechanism that allows instructing access points to execute tests or take actions.

Claim 1:
A method (<NUM>) of controlling user quality of experience in a multi-access point wireless local area network, the method comprising:
- a control entity (<NUM>) receiving link quality reports generated by a first access point (<NUM>), wherein a station (<NUM>) is associated with the first access point (<NUM>);
- the control entity (<NUM>) receiving environment quality reports generated by one or more access points (<NUM>);
- after receiving an alarm from the first access point (<NUM>), the control entity (<NUM>) sending a first message to the first access point (<NUM>), the first message including information (i) indicating a media access control, MAC, address of the station (<NUM>) to add in a list, wherein the list is used to reject a connection request from a listed station, and (ii) instructing the first access point (<NUM>) to actively disconnect the station (<NUM>);
- the control entity (<NUM>) sending a second message to a target access point (<NUM>), selected from the one or more access points based on the received environment quality reports, the second message indicating the MAC address of the station (<NUM>), wherein the indication is used to instruct the target access point (<NUM>) to accept a connection request from the station (<NUM>).