Why is Bluetooth so slow if it uses the same frequency as WiFi?

Why is Bluetooth so slow if it uses the same frequency as WiFi?

The Bluetooth and Wi-Fi They share the same frequency. Both wireless standards operate on the 2.4 GHz band, although WiFi also does so at 5 GHz and soon 6 GHz. However, WiFi reaches speeds of tens and even hundreds of Mbps on 2.4 GHz, but not Bluetooth. Why?

There are two important factors that make WiFi and Bluetooth differ in range and speed. The first aspect to take into account is the power used to broadcast each signal, and the second is the bandwidth used in each broadcast to send content.

Bluetooth power is usually less than WiFi

Starting with the power, the higher the power with which a signal is emitted, the greater its range. In the case of Wi-Fi, the maximum power is 0.1W (or 100 mW) for 2.4 GHz networks, and up to 0.2 W (or 200 mW) for 5 GHz networks. In contrast, in the case of Bluetooth, the speed varies depending on the class. The Bluetooth classes are:

  • Class 1: range of up to 100 meters, with an average power of 100 mW
  • Class 2: range of up to 20 meters, with an average power of 2.5 mW
  • Class 3: range of up to 1 meter, with an average power of 1 mW
  • Class 4: range of up to 0.5 meters, with an average power of 0.5 mW

As we see, a basic sign of Class 1 Bluetooth It has a range of 100 meters with a power of 100mW. That distance is similar to what a 2.4 GHz WiFi signal can reach, since it operates using the same 100 mW power. 5 GHz WiFi, having a more limited range due to having a higher frequency, uses twice the power.

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The problem for Bluetooth is that it does not always operate at 100 mW of power, since in those cases it would use up a lot of battery. Since Bluetooth 4.0 the mode was integrated low-energy, which enables Bluetooth reduce power used in the event that, for example, the device is close. In these cases, the power used drops considerably, and with it the range, as we see in the different classes. In return, the battery life increases.

Bandwidth, another Bluetooth problem

However, if at maximum power it consumes the same as WiFi and has the same range, why is it slower? This is where the bandwidth of the channels used comes into play. With WiFi 4, we find channels with 20 MHz of bandwidth, while with WiFi 5 there are channels of up to 80 and 160 MHz. With WiFi 6E the option of having up to 320MHz. Thus, in addition to being much wider channels, in the future it will even be possible to use several at the same time.

In the case of Bluetooth, the bandwidth is quite limited by the use of 1 or 2 MHz channels. The latest standards have been improving the speed, where 4.0 reaches figures of up to 32 Mbps, and 5.0 and later reach figures of up to 50Mbps. For this reason, Bluetooth has a very difficult time reaching high transfer speeds like those of WiFi.