1. NOISE IN RADIO WAVES Mr. Husnain Sherazi @leads.edu.pk Lecture 3

2. Electromagnetic Waves Waves can travel through space without any need of medium. Light and Heat waves are example of these waves which can travel through space without any medium. These waves are called electromagnetic waves. These waves can travel freely through space in all the direction at the speed of light.

3. Radio Waves

4. Limitations of Electromagnetic Waves Electromagnetic waves have great speed but they have certain limitations Light waves cannot penetrate through materials like wood etc. Heat waves cannot penetrate certain objects. Heat waves are absorbed by the surrounding objects. Because of these limitations, Light and Heat waves have limited range. Similarly, intensity of these waves are also limited.

5. Radio Waves Besides Light and Heat, there are some other types of waves called Radio Waves. Electric current passing through the wires generates magnetic field which can be spread out in the space. Using these Radio waves, information can be transferred from one place to another. Radio waves also spread in all directions in space.

6. Characteristics Radio Waves Radio waves can travel through long distances unlike Light and Heat waves. Radio waves can penetrate through materials unlike Light and Heat waves. Radio waves are invisible. Radio waves are normally not felt. Because of all these characteristics, radio waves are superior means of communication in Computer Networks.

7. Comparison of Waves

8. Noise in Wireless Communication Various definitions are available. Noise is an unwanted disturbance in the wireless signal. It is also defined as radio interference in radio frequency of a wireless communication. Undesired signal interfering in a desired signal.

9. Effect of Noise Effect of noise can vary from minor to major. Noise affecting the wireless signal can cause errors in wireless communication. It can break a wireless communication. It can be misread by the receiver. Information, energy and cost can be wasted if large amount of noise is present in a wireless communication.

11. Types of Noise In a wireless communication, there are various types of noises that can affect the wireless signal. Normally noise is categorized as: Thermal Noise Intermodulation CrossTalk Impulse Noise

12. Types of Noise Thermal Noise The noise created when heat generated by an electronic device is called a Thermal Noise Every electronic device is affected by Thermal Noise. Thermal noise is related to heat and is also called White Noise If temperature of any device or transmission medium is raised to an extent that heat is generated, thermal noise will be produced.

13. Types of Noise Intermodulation Noise This type of noise occurs when two different frequencies enter a non-linear device. The mix of frequencies will create fake or improper results causing the devices to malfunction. Mixers and power amplifiers normally cause this type of noise. These kind of noises can be reduced by aligning the frequencies and increasing the linearity of device.

14. Types of Noise CrossTalk Noise The noise created by electrical coupling is called CrossTalk. Electrical coupling is referred to as, the transfer of electric current from one circuit segment to another. CrossTalk can also be created by poor control of frequency between different circuit segments during transmission of signal.

15. Types of Noise Impulse Noise It is a series of non-continuous, irregular impulses for a short duration. The amplitude of these impulses is normally very high. It degrades the signal to a small extent, however, the data is corrupted and might be meaningless when received at the receiver. They are normally caused by corrupted media.

16. Terminologies in Radio Waves Gain It is the positive difference in amplitude of two signals. It is sometimes also called Amplification. Gain can occur intentionally from some external power source. Gain can occur unintentionally, when a wave strikes some hurdle.

17. Terminologies in Radio Waves Gain

18. Terminologies in Radio Waves Loss It is the negative difference in amplitude of two signals. Loss can also be intentional or unintentional. Intentional loss can occur to meet the standards so that signals do not interfere with other RF signals. Unintentional loss can occur because of Absorption Reflection Scattering Refraction Diffraction

19. Terminologies in Radio Waves Loss

20. Terminologies in Radio Waves Loss due to Absorption Some materials can absorb RF signals. These can be wood, concrete etc.

21. Terminologies in Radio Waves Loss due to Reflection Sometimes signals are reflected from surfaces like metal surfaces with large areas.

22. Terminologies in Radio Waves Loss due to Scattering Sometimes signals are scattered because of rough surfaces like trees and rocks.

23. Terminologies in Radio Waves Loss due to Refraction RF signal sometimes bend when enters from clear medium to a dense medium e.g. from bright weather to a rainy weather.

24. Terminologies in Radio Waves Loss due to Diffraction Diffraction is caused when an object comes in the way of the signal.