What is path loss in RF?
Path loss, or path attenuation, is the reduction in power density (attenuation) of an electromagnetic wave as it propagates through space. This term is commonly used in wireless communications and signal propagation.
How is path loss measured?
The path loss is measured by the method of directly measuring the frequency transfer function by scanning the specified frequency band using Vector Network Analysis (VNA). And in the process of measurement, the same VNA is the transmitting end and the receiving end, in [4]–[6].
What is signal propagation in data communication?
In addition to receiving these signals from the sites, user devices transmit similar types of signals back to the sites. This creates two-way communication. Wireless signal propagation is the movement of these radio waves (which move at the speed of light) to and from these sites and devices.
What are the main problems of signal propagation?
Transmission Limitations
- Attenuation. The strength of signal falls with distance over transmission medium.
- Distortion.
- Dispersion.
- Noise.
- Fading.
- Multipath propagation.
- Delay spread.
- Doppler spread.
What are the means to mitigate narrowband interference?
What are the means to mitigate narrowband interference? Frequency hopping:Slow frequency hopping (several symbols per frequency) may avoid frequencies with interference most of the time with a certain probability. This scheme may be used in GSM.
What are the three basic propagation mechanisms?
Reflection, diffraction, and scattering are the three basic propagation mechanisms which impact propagation in a mobile communication system. Reflection occurs when a propagating electromagnetic wave impinges upon an object which has very large dimensions when compared to the wavelength of the propagating wave.
What is basic radio propagation mechanism?
Radio waves can propagate from transmitter to receiver in four ways: through ground waves, sky waves, free space waves, and open field waves. Ground waves exist only for vertical polarization, produced by vertical antennas, when the transmitting and receiving antennas are close to the surface of the earth.
What are the modes of propagation?
Radio Wave Propagation
- Line of sight (LOS) propagation.
- Ground wave propagation.
- Sky wave propagation.
What are the factors influencing small scale multipath propagation?
The factors which influence small scale fading are: Multipath propagation, Speed of the mobile, Speed of surrounding objects and the transmission bandwidth of the signal.
What are the consequences of small scale fading?
Small-Scale Multipath Propagation • The three most important effects – Rapid changes in signal strength over a small travel distance or time interval – Random frequency modulation due to varying Doppler shifts on different multipath signals – Time dispersion caused by multipath propagation delays • Factors influencing …
What are the different types of fading?
Examples of fading models for the distribution of the attenuation are:
- Dispersive fading models, with several echoes, each exposed to different delay, gain and phase shift, often constant.
- Nakagami fading.
- Log-normal shadow fading.
- Rayleigh fading.
- Rician fading.
- Two-wave with diffuse power (TWDP) fading.
- Weibull fading.
Which of the following factor does not influence small scale fading?
Which of the following factor does not influence small scale fading? Explanation: Many physical factors in radio channel influence small scale fading. Multipath propagation, speed of mobile, speed of surrounding objects, transmission bandwidth of the signal influences small scale fading in a large way.
Which is more effective and commonly preferred technique?
4. Which is more effective and commonly preferred technique? Explanation: Most commonly used and more effective diversity technique is spatial diversity technique. Explanation: Diversity technique does not require training overhead at the transmitter and also provides significant link performance.
Which of the following is not channel parameters?
1. Which of the following is not a channel parameter? Explanation: Channel parameters are coherence bandwidth, rms delay spread and Doppler spread. Signal parameters are bandwidth and symbol period.
Why does small scale fading occur?
Small-scale fading: Due to the constructive and destructive interference of the multiple signal paths between the transmitter and receiver. This occurs at the scale of the order of the carrier wavelength, and is frequency dependent. The fading characteristics vary over different spaces, frequencies, and times.
How do you overcome Multipathy fading?
Our research shows that destructive interference and multipath fading can be eliminated by using reference phase to control LOS beam phase.
What is slow fading channel?
In slow fading channels, the coherence time of the channel is long and encoding can be performed only over a single or a few fading states (e.g., time diversity). While encoding still averages out the randomness of the noise, it may not be possible to fully average out the randomness of the channel.
What is fading in LTE?
In wireless communication environment, many copies of the signals get combined at the reciever side and some of them constructively combines and some of them destructively combines. This kind of process of signal deterioration by the multiple propogation path of a signal is called ‘Fading’.
What causes fast fading?
Fast Fading: It occurs mainly due to reflections for surfaces and movement of transmitter or receiver. High doppler spread is observed in the fast fading with Doppler bandwidth comparable to or greater than the bandwidth of the signal and the channel variations are as fast or faster than the signal variations.
What is the difference between Rayleigh and Rician fading?
Rayleigh fading is most applicable when there is no dominant line-of-sight propagation between the transmitter and receiver. Rician model considers that the dominant wave can be a phasor sum of two or more dominant signals, e.g. the line-of-sight, plus a ground reflection.
Why does fading occur?
Ultraviolet rays are one of the causes of fading because they can break down chemical bonds and fade the color in an object. Other major contributors to fading include visible light and solar heat. Other objects may reflect the light more, which makes them less prone to fade. Sunlight causes some foods to fade.
Which color fades the fastest?
red
Where does selective fading occur?
Frequency selective fading occurs when the symbol length is shorter than the delay spread, or equivalently when signal bandwidth is larger than the channel bandwidth.
How can slow fading be minimized?
Explanation: Slow fading can be minimized by using error correcting codes and also by using diversity technique to get additional uncorrelated estimates of a signal.
Which of the following is a drawback of zero forcing algorithm?
Explanation: The zero forcing algorithm has the disadvantage that the inverse filter may excessively amplify noise at frequencies where the folded channel spectrum has high attenuation. 8.
How does CDMA minimize fading?
CDMA systems use a signal fast chip rate for spreading the spectrum. It has a high time resolution, due to which it receives a different signal from each path separately. The RAKE receiver prevents signal degradation by summing all the signals.
What is the condition of handoff?
Explanation: Handoff occurs when a mobile moves into a different cell while a conversation is in progress. The MSC automatically transfers the call to a new channel belonging to the new base station. 2. Handoff does not require voice and control channel to be allocated to channels associated with the new base station.