Unguided media | unbounded transmission media with examples?

Unguided media | unbounded transmission media with examples?


Unguided media | unbounded transmission media

Radio waves


Infrared waves


Unguided media


Unguided media | unbounded transmission media:

The Unguided media transmits the electromagnetic waves without using any of the physical media. That is why it is also called wireless communication. Unguided media is also called unbounded transmission media.

Through this media, signals are broadcast via free space .So these signals are available to anyone who has a device and the device is capable of receiving them.

These signals can move to a destination using propagation like Ground propagation, Sky propagation, and Line-of-sight propagation.
The Unbounded media is divided into three broad groups:

  • Radio waves
  • Microwaves
  • Infrared waves


Radio waves:

Radio waves are the electromagnetic waves that range in frequencies between 3 kHz and 1 GHz. These are omnidirectional waves. In this, The sending and receiving antennas do not have to be aligned.

It is because when an antenna transmits radio waves, these waves are propagated in all directions.

So, The sending antenna sends the waves and they can be received by the receiving antenna very easily due to the omnidirectional property. But this property has disadvantages too and that is when radio waves are transmitted by one antenna.

They are susceptible to interference by another antenna that is may send signals using the same frequency or band. Low medium frequency radio waves can penetrate walls.



The microwaves have frequencies between 1 and 300 GHz. These are unidirectional waves. The microwaves are narrowly focused when an antenna transmits them. This means that the sending and the receiving antennas have to be aligned.

Here, a unidirectional property gives an advantage. A pair of antennas can be aligned without interfering with the pair of another aligned antenna.

The microwaves with very high frequency cannot penetrate walls. But if the recievers are inside a building then this can be a disadvantage. The band of microwaves is wide, almost 299GHz.

That is why wider sub-bands can be assigned and the high data rate is made possible.


Infrared waves:

The frequency of infrared waves is from 300GHz to 400THz. Infrared waves are normally used for short-range communication. High-frequency infrared waves cannot penetrate walls. This prevents interference between two different systems.

For example:

The short-range communication in one room cannot be affected by another short-range communication in another room. Another example can be a TV remote. We can not interfere with the use of the remote by our neighbor.

But it also has a disadvantage and that is infrared signals are useless for long-range communication. Infrared waves also can not be used outside the building.

It is because the sun rays contain infrared waves that will interfere with the communication. Infrared communication can provide much better security with very few interferences.

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