Large Scale Fading

• Large scale fading occurs when an obstacle comes in between transmitter and receiver. This interference type causes significant amount of signal strength reduction. This is because EM wave is shadowed or blocked by the obstacle. It is related to large fluctuations of the signal over distance.
• Large-scale fading is called “large-scale” because the variations occur over long distances, typically several kilometers.
• Unlike small-scale fading, which affects individual symbols or bits, large-scale fading affects the entire signal.
• Large-scale fading is a slow-varying phenomenon, meaning that it changes over time scales of seconds to minutes.
• Mitigation techniques for large-scale fading include power control, antenna placement, repeaters, and site diversity.
• Overall, large-scale fading is an important factor to consider in wireless communication system design, as it can significantly impact the quality of the received signal.

Path Loss

• Path loss is the reduction in signal power as the signal travels from the transmitter to the receiver.
• Path loss is caused by a variety of factors, including distance, the frequency of the signal, obstacles in the path of the signal, and the characteristics of the environment.
• The path loss is generally modeled using an attenuation equation that takes into account these factors.
• Path loss is generally a slow-varying phenomenon and affects the overall received signal power.
• Path loss can be mitigated by increasing the transmitted power, using directional antennas, or reducing the distance between the transmitter and the receiver.

The free space path loss formula can be expressed as :
Pt/Pr = {(4 π d)2/ Gt Gr λ2} = (4 π f d)2/ Gt Gr c2
Where,
Pt = Transmit power 
Pr = Receive power 
c = speed of light i.e. 3 x 108
d = distance between transmitting and receiving antenna
λ = wavelength
Gt = is the transmit antenna gain
Gr = is the receive antenna gain

Shadowing

• Shadowing is a type of large-scale fading that occurs due to the presence of obstacles or obstructions in the path of the signal.
• Shadowing causes the signal power to vary as the receiver moves in the environment
• Shadowing is generally modeled as a log-normal distribution, with a mean and standard deviation that depend on the characteristics of the environment.
• Shadowing is a slow-varying phenomenon and affects the overall received signal power.
• Shadowing can be mitigated by using techniques such as diversity, where multiple antennas are used to combine multiple signal paths, or by using signal processing techniques to estimate the shadowing effects and compensate for them.

To battle the impacts of blurring, remote correspondence frameworks utilize different strategies, including:

• 1. Variety strategies: This includes the utilization of different radio wires or channels to give numerous variants of a similar transmission, which can be joined at the recipient to diminish the impacts of blurring.
• 2.Balance procedures: This includes the utilization of computerized signal handling calculations to make up for the bending brought about by blurring.
• 3.Power control strategies: This includes changing the sending ability to keep a specific degree of sign quality, even within the sight of blurring.
• 4.Tweak procedures: This includes the utilization of more strong balance plans, for example, QPSK or 16-QAM, that can endure a more elevated level of clamor and twisting.

Comparison between Small Scale fading and Large Scale fading:

Note that while small-scale fading is mainly caused by multipath propagation, it can also be affected by Doppler spread, while large-scale fading is mainly caused by path loss and shadowing. Small-scale fading is a fast-varying phenomenon that affects individual symbols or bits, while large-scale fading is a slow-varying phenomenon that affects the overall signal power.

In wireless communication, fading is a phenomenon in which the strength and quality of a radio signal fluctuate over time and distance. Fading is caused by a variety of factors, including multipath propagation, atmospheric conditions, and the movement of objects in the transmission path. Fading can have a significant impact on the performance of wireless communication systems, particularly those that operate in high-frequency bands.