Wireless Optimisation


When providing Wireless network connectivity either for guest Internet access or a working environment, ensuring that it is fast and reliable is essential. The speed and reliability of wireless can often be limited by interference caused by nearby wireless networks or when there are many clients connecting to the same Access Point.

To improve the user experience of the wireless network, DrayTek Vigor Access Points incorporate features designed to optimise the utilisation of the wireless network and improve its effectiveness, by more intelligently handling connections to single and multiple access points at both the wireless radio level and network level.

These features can help your wireless network achieve the best possible speeds with legacy 802.11b/g/n clients connecting to the 2.4GHz frequency band and faster 5GHz capable 802.11n (up to 300mbps) and 802.11ac (up to 1300mbps) clients using the 5GHz band.

Airtime Fairness Aims to maximise the total wireless throughput by improving how time is shared between wireless clients to prevent slower clients from negatively affecting other users and to enable faster clients to obtain higher speeds that they're capable of.
Band Steering
(Dual Band VigorAPs only)
Increases capacity for Vigor Access Points by directing wireless clients, that are capable of connecting to 5GHz wireless networks, to the less congested and faster 5GHz (802.11n and 802.11ac) band. The aim is to more evenly distribute wireless clients between the AP's wireless radios.
AP Assisted Mobility Allows VigorAP access points on the network to improve how clients handle moving between VigorAPs. It intelligently allows VigorAPs to disassociate clients from a VigorAP, when the client could get a better connection with a nearer VigorAP access point.
Mobile Device Management Control which type of devices connect to your VigorAP access points, for instance, to stop desktop and laptop computers connecting to a network intended for guest's mobile phones and tablets.


Airtime Fairness

What is Airtime Fairness?

Wireless networks transmit and receive on a single channel; if multiple wireless clients are downloading files or watching videos at the same time, the access point must share the airtime (the duration that the channel is used for) between these clients by transmitting data packets to one client, then another and repeats this for all clients connected to the wireless network.

Ideally, all of the wireless clients operate at the same speed and are at the same distance from the access point and have optimally performing drivers, however, in any wireless network, there will usually be a mix of faster and slower clients. This can cause issues once there are enough clients on the network in that the amount of airtime / throughput available to each device can become significantly limited, which would result in downloads stalling and videos buffering constantly.

One significant cause of this is that slower devices, either through interference, distance or older wireless standards, require more time to receive the same amount of data as a faster client, which results in less airtime available to the other, faster clients.

Airtime Fairness is designed to give all wireless clients equal access to the airtime of the access point so that faster clients and slower clients each have equal access to the overall air-time of the access point.

How Airtime Fairness works

Without Airtime Fairness, the access point will serve each client equally, as defined by the mechanism in the 802.11 standard of providing equal probability to each client that it can access the wireless channel. When all clients operate at the same speed, they would have the same airtime because they're transmitting at a similar rate.

When there are mixed clients, such as an 802.11g 54mbps client and an 802.11n 300mbps client (or two 802.11n clients that are using different datalink rates due to their relative position from the access point or interference), there is a significant difference in the speed of transmission for each packet, which results in the slower clients taking a longer time period to complete the transmission of it's packet. The end result would be that a significantly higher proportion of the access point's time is used when sending packets to these slower clients.

This results in disproportionately slow throughput for faster clients when slower clients are receiving data because the airtime available becomes limited by the transmission time for the slowest clients.

Without Airtime Fairness

In this example, Station A is an 802.11g client capable of 54mbps throughput at most and Station B is an 802.11n client capable of up to 300mbps throughput. Sending a single packet to Station A takes longer than Station B, but the access point shares packet transmissions equally between the two.
Station B is only able to achieve a low throughput when the access point is sending packets to Station A:

With Airtime Fairness

Airtime Fairness improves this by controlling the rate at which packets are sent to slower clients, which allows the access point to send more packets to the faster clients in between the points where it sends data to the slower clients.

In this example, Station A is still receiving packets but the access point puts a longer delay between when those packets are sent, allowing it to send many more packets to Station B, which results in higher throughput for Station B. If Station B is downloading a file or loading a webpage, that could complete much more quickly, leaving the channel free for Station A to use, resulting in a better throughput and usage experience for each station:

With Airtime Fairness, instead of speeds being limited solely by the speed of the slowest clients, speeds are more representative of the speeds possible with each wireless client, resulting in higher throughput to faster clients and less interruptions to downloads by each client, giving a better overall throughput and experience to clients of a DrayTek Vigor access point with Airtime Fairness enabled.

In many cases the total combined throughput (sum of the all the wireless client's throughput) achieved across on the wireless network is increased with airtime fairness enabled because the faster clients are given more opportunity to fulfill their potential.