Wi-Fi “Secrets” Part 3— Wired is Faster Than Wireless Networking

 

In my past couple of articles looking at the differences between wired and wireless networking, we’ve looked at the fact that Wi-Fi is a half duplex medium and that it is also a contended medium. Although Wi-Fi is a fabulously convenient network access method, understanding some of its technical limitations will help you get the best out of your Wi-Fi network.

There is another nuance of Wi-Fi networking, which is related to the contended nature of access to the RF medium. As devices using Wi-Fi have to take turns to send their data, there is an additional effect caused by the varying capabilities of the devices using network.

Different Wi-Fi devices have varying capabilities depending on when they were manufactured and the components used to construct them. Some may have the “latest and greatest” super-fast wireless cards, whereas others may be a few years older and may not have speed capabilities of newer equipment. Even the “latest and greatest” Wi-Fi equipment may have different performance characteristics dues to differences in numbers of antennas, antenna size, power availability and chip-set capabilities.

The best analogy to understand this subtlety of Wi-Fi networking is to think back to our example of a single lane highway from part one of this series. We discussed how only one vehicle can travel in each direction at any time, in the same way that half-duplex Wi-Fi connections operate.

We can extend this analogy a little further and consider the impact if we have a mix of vehicle types. Instead of having only fast vehicles using our road, we may have a mix of sports cars, family saloons, trucks, farm tractors and bicycles.

When sports cars are using the highway, they use the road at high speed and quickly complete their journey to make it available for other vehicles to use. But, when a bicycle decides to use the highway, it takes a lot longer to travel along its length. This means that all of the other vehicles (even the fast ones) are waiting longer to use the highway again.

Everyone has to wait, even the fast cars…

 

We have exactly the same issue with Wi-Fi networks. Devices which are “less capable” and connect at lower speeds will have an impact on faster devices that need to use the network. When a slower device sends its data, as it uses a slower connection speed, it will take longer to send its data than a faster device. As we add more slower devices that need to send data, then the more impact they will have on the faster devices that have to wait longer for their turn to use the RF medium and send their data.

What can we do about this?

The best solution is to ensure that our Wi-Fi is correctly designed to be as efficient as possible. If we ensure that all devices can operate at their highest possible speeds, we will at least ensure that we gain the maximum possible throughput available from all devices. This will maximize the air-time (i.e. throughout) available to all clients. A good RF design for your Wi-Fi network is critical — get an expert to design your Wi-Fi RF environment.

Another approach is to consider upgrading the devices that use the Wi-Fi network. This is a particularly important consideration if your wireless network is mission critical and provides the primary access method to your wired network. If you have any 802.11b, 802.11g or 802.11a devices on your network, seriously consider replacing them with 802.11n or 802.11ac devices.

Another useful approach is to relegate slower, legacy devices to the less-desirable 2.4Ghz band. By creating an SSID that is specific to only 2.4GHz and getting slower devices to use only that SSID, you can keep the higher performance 5GHz band for your higher-spec, mission critical devices. This approach obviously depends on the requirements of your particular network, but can be useful in some scenarios.

References:

(image attribution: Hans Deragon — hans@deragon.biz)

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