It’s the Throughput, Stupid!

In the real world, wireless networks (and wired networks for that matter) don’t perform anywhere near their raw theoretical speed or maximum data rate touted in product marketing because Wi-Fi is (as the name suggests) wireless. Networks are affected by all kinds of limiting factors because of the physics of wireless transmissions. Such factors include: network overhead, user congestion, distance, obstacles (such as walls), interference, and more.

The real numbers that matter are throughput. Why? Because throughput measures the real-world capabilities of a wireless network with a more accurate measurement of Wi-Fi network speeds that takes into account all the bits eaten up by network overhead and environmental factors. Although the touted data rate speeds don’t happen in the real world, they still serve as a useful benchmark. In general, the higher the data rate speeds, the higher the corresponding throughput.

Throughput

Maintaining the dependable operation and security of a wireless network can reduce a product’s raw speed by 30 to 50 percent. Environmental factors (such as walls, floors, and other barriers) also affect wireless signals, as does the distance from the Access Point (AP) and the number of clients using the Wi-Fi network. One of the great things about Wi-Fi is its capability to share Internet connections across devices in a hotspot. However, all these devices compete for access through the same Wi-Fi network, so the more devices that people connect to a Wi-Fi hotspot, the more traffic they create and the slower the speed for everyone.

Throughput helps you get a grasp of how the raw speeds touted for a Wi-Fi product translate to the type of performance you may actually get at home with multiple users and devices. Here’s the basic formula:

Max throughput = (max data rate ÷ 2) ÷ number of clients

The underlying assumption is that both your Wi-Fi AP (i.e. wireless router) and your client (i.e. device, like a laptop) are using the same Wi-Fi standard and configuration. For example, the maximum data rate for 802.11ac 2×2 is 867 Mbps.
The “max data rate ÷ by 2” part of the equation broadly estimates actual throughput by taking into account network overhead and environmental factors explained earlier; that number is then divided by the number of clients sharing the bandwidth to arrive at the maximum throughput. It’s important to keep in mind that the throughput formula doesn’t take into account that data rate and throughput decrease as clients move away from the AP.

The following shows how the throughput for an 802.11ac 2×2 Wi-Fi device decreases as you add clients:

    (867 Mbps ÷ 2) ÷ 1 client = ~433 Mbps per client
    (867 Mbps ÷ 2) ÷ 2 clients = ~216 Mbps per client
    (867 Mbps ÷ 2) ÷ 3 clients = ~144 Mbps per client
    (867 Mbps ÷ 2) ÷ 6 clients = ~72 Mbps per client

Now compare 802.11ac throughput with 802.11bgn 1×1 Wi-Fi commonly found in devices today:

    (150 Mbps ÷ 2) ÷ 1 client = ~75 Mbps per client
    (150 Mbps ÷ 2) ÷ 2 clients = ~38 Mbps per client
    (150 Mbps ÷ 2) ÷ 3 clients = ~25 Mbps per client
    (150 Mbps ÷ 2) ÷ 6 clients = ~13 Mbps per client

What seemed like more speed than you might need quickly shrinks to speeds that you do need, especially in a modern home setting where multiple members of a family are streaming video, playing online games, or downloading files across multiple devices. In essence: the higher the maximum data rate, the more throughput.

For a more detailed explanation of throughput, be sure to download the Next-Gen 802.11ac Wi-Fi Guide for Dummies, and check out intel.com/wireless for examples of devices that come equipped with the new wireless standard. If you have any questions about the future of Wi-Fi, don’t hesitate to reach out on Twitter at @IntelWireless.

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