Eli5 What really limits speeds of communication technologies ? Don’t they all depend on electromagnetic waves ?

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Edit : I meant bandwidth not really the speed , like why can I send more data per second with WIFI than Bluetooth .

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The speed of communication technologies depends on the electromagnetic waves that they use, as well as other factors such as the distance between the sender and receiver, and the amount of interference in the environment. However, the speed of electromagnetic waves is limited by the speed of light. This means that the fastest communication technologies can only transmit information at the speed of light.

Communication devices are limited to transmitting data at the speed of light. Maybe if quantum entanglement gets up and going that could solve it. But for now, data is transferred over wire, optically, or wirelessly, which all are limited to the speed of light.
Processing power too can limit speed.

>Eli5 What really limits speeds of communication technologies ? Don’t they all depend on electromagnetic waves?

The only hard limit for a single signal is the speed of light. That’s why you’ll never have a 10ms latency with a connection from Singapore to Madrid, no matter the technology.
In practice it’s the speed of light within copper wire or fiber optics cable, to be specific, not the “usual” vacuum speed.

I have the feeling you might be asking about *bandwidth* though, since folk often use that synonymously with “speed”?!

The *speed*, literally, is limited by how fast your message can travel.

If our technology was hand signals, then the speed would be determined by the time it takes for light to travel from my hand to your eyes, and the time it takes for your brain to recognize what it’s looking at.

Because of this, hand signals are faster than sound.

For modern data transmission, this speed ranges from light speed to about a third of light speed.

But usually, when people refer to “speed”, they’re really talking about throughput. Hand signals have good speed compared to sound, but the throughput is very bad. You can’t really communicate things very fast with hand signals, compared to speech. Especially at longer distances.

Throughput is more complicated, and involves how quickly you can move from one signal to the next, as well as how much information you can send in each signal. It’s usually limited by the hardware involved, but is also more fundamentally limited by the frequency of your system. This is why 5g is expected to be a huge step up in speed – it uses higher frequencies.

While the speed of the wave carrying the signal is a hard limit, the practical limit is based on noise and attenuation.

Noise is random elements that the signal picks up as it travels through space that make it harder to extract information. The more such uncertainty a signal gains, the less we’re able to transform the signal into communications.

In mechanical waves (such as sound), attenuation can occur because the signal loses energy to the medium. With any waves, attenuation occurs because the wavefront expands spherically, causing the energy of the signal to be spread over a larger and larger area.

We have a variety of strategies for dealing with these problems. Think of being in a noisy bar. If you’re close to someone, you can probably communicate with them. If you’re farther away, you may need to shout (putting more energy into the signal). If they still can’t hear you, you may need to repeat yourself (encoding the signal to overcome noise). If they still can’t hear you, you may need to cup your hands around your mouth (focusing the energy on a smaller expanding wavefront to prevent signal attenuation).