Design of high-density WiFi terminal occupied air interface resources calculation method

In places where high-density WI-FI terminals are used, the more terminals that share air interface resources, the less air interface resources each terminal will occupy, thus affecting the overall throughput. So how do we calculate the air interface resources occupied by terminals in a Wi-Fi network environment? In this issue, we will discuss this issue.

[[198211]]

First let's take a simple example:

If there is only one AP in a room and only one laptop connected (see the figure below)

The maximum TCP/IP transmission rate of the laptop is 220Mbps. Since there are no other devices connected to the AP, the laptop can monopolize 100% of the air interface resources. Therefore, it should be no problem to achieve a TCP/IP transmission rate of 220Mbps.

Now we have another iPad connected to the AP

The TCP/IP transmission rate of iPad is 70Mbps. Now that there are two terminal devices connected to the AP, each terminal device needs to share the air interface resources (50% each). As a result, the original TCP/IP transmission rate will be halved - the laptop's TCP/IP transmission rate will be reduced from 220Mbps to 110Mbps; the iPad's TCP/IP transmission rate will be reduced from the original 70Mbps to 35Mbps. The overall Wi-Fi network throughput will also be reduced from 220 Mbps when only the laptop is connected to 145Mbps.

This shows the impact of the increase in the number of terminals on the Wi-Fi network throughput.

In the above examples, we assume that the channel utilization rate can reach 100%, but in reality the channel utilization rate can generally only reach about 80%.

So if we want to estimate how many APs are needed in a certain environment to ensure that users can obtain a transmission rate that meets their applications, what parameters do we need?

1. The TCP/IP bandwidth required by each terminal (Min. Bandwidth required by client) – This mainly depends on what application the terminal is running (web browsing, video streaming, voice...)

2. Maximum TCP/IP transmission rate of each terminal (Raw Bandwidth of client)

3. Number of clients

Many people may be confused at this point. How to obtain these parameters? Don't worry, we will give the calculation formula below.

1. (Bandwidth required by the terminal / Maximum TCP/IP transmission rate of the terminal) x 100% = Air port percentage

2. (Air interface percentage x number of terminals) / 0.8 = Number of radios required

The number of radios required is not equal to the number of APs required, because one AP can support multiple radios.