PART I
1) Wireless Spectrum
2) Frequency
3) Amplitude
4) Free Path Loss Model
5) Absorption
6) Reflection
7) MultiPath
2) Frequency
3) Amplitude
4) Free Path Loss Model
5) Absorption
6) Reflection
7) MultiPath
1) WIRELESS SPECTRUM
RF Bandwidth:-
* Bandwidth is what we get is accomplished by emitting data as electronic signals, and we place data on these RF signals by using Modulation Techniques. Modulation is the process of adding data to the carries signal.
* Spread Spectrum is method for modulation. It is used by ISM BANDS.
ISM BANDS :- Unlicensed Industrial, Scientific and Medical Bands (900MHz-2.4GHz)
* Spread Spectrum is method for modulation. It is used by ISM BANDS.
ISM BANDS :- Unlicensed Industrial, Scientific and Medical Bands (900MHz-2.4GHz)
(5GHz - Unlicensed National Information Infratructure [UNII BAND])
* B/W means of acutal DATA RATE or [Width of RF Channel] --> For us
* B/W is measured in Hertz = Cycles per sec
* Radio Waves :- Are used to send infiormation in a wide variety of fashion (eg. AM, FM).
It is elctromagnetic field that radiates from the sender, and propogates to the reciever
that revieves the energy.
* Hz expreses how often a wave happenes. Cycles per second
Wave Category :- Lowest -> Sonic
* B/W means of acutal DATA RATE or [Width of RF Channel] --> For us
* B/W is measured in Hertz = Cycles per sec
* Radio Waves :- Are used to send infiormation in a wide variety of fashion (eg. AM, FM).
It is elctromagnetic field that radiates from the sender, and propogates to the reciever
that revieves the energy.
* Hz expreses how often a wave happenes. Cycles per second
Wave Category :- Lowest -> Sonic
Higest -> Gamma Ray
900MHz - 5Ghz -> Wireless
2) FREQUENCY - How often a signal is seen ?
900MHz - 5Ghz -> Wireless
2) FREQUENCY - How often a signal is seen ?
* Wavelength - The distance the signal travels in a single cycle
Shorter wavelength signal has more freqency, since it travels more times in a second than signal with longer wavelength.
Eg:- 6 cycles/sec = 6Hz
Lower freq signals travels farther than higher freq.
RF signals are generated by Transmitter, sent through a cable to an antenna,
where it is radiated in the form of electromagnetic wireless signals.
Impact of obstacle on a signal depends wavelength and also the obstacle.
3) AMPLITUDE
This is the strength of the signal. Level of energy injected into 1 cycle. More energy -> Higher Amplitude
Height or vertical distance between the crest of signal. Y -> Gamma
Active -> Increasing the amplitude
/
i) Amplification
-------------
\
Passive -> done by focusing the energy into a single direction by a special antenna
ii) Attenuation --> Decreasing the amplitude
-----------
Amplitide Modulation (AM) - Amplitude that is modified dynamically by transmitter
Frequncy Modulation (FM) - Modifying the frequency of signal to encode the information
4) FREE PATH LOSS
Amount of energy is going to decrease as the distance increases for the signal.
Quantity of energy available at each point is going to be less the farther out you get.
This wave propogation attenuation.
The loss of energy is simply due to the distance (since energy is dispersed), and not because of any obstacle blocking the signal.
5) ABSORPTION
Shorter wavelength signal has more freqency, since it travels more times in a second than signal with longer wavelength.
Eg:- 6 cycles/sec = 6Hz
Lower freq signals travels farther than higher freq.
RF signals are generated by Transmitter, sent through a cable to an antenna,
where it is radiated in the form of electromagnetic wireless signals.
Impact of obstacle on a signal depends wavelength and also the obstacle.
3) AMPLITUDE
This is the strength of the signal. Level of energy injected into 1 cycle. More energy -> Higher Amplitude
Height or vertical distance between the crest of signal. Y -> Gamma
Active -> Increasing the amplitude
/
i) Amplification
-------------
\
Passive -> done by focusing the energy into a single direction by a special antenna
ii) Attenuation --> Decreasing the amplitude
-----------
Amplitide Modulation (AM) - Amplitude that is modified dynamically by transmitter
Frequncy Modulation (FM) - Modifying the frequency of signal to encode the information
4) FREE PATH LOSS
Amount of energy is going to decrease as the distance increases for the signal.
Quantity of energy available at each point is going to be less the farther out you get.
This wave propogation attenuation.
The loss of energy is simply due to the distance (since energy is dispersed), and not because of any obstacle blocking the signal.
5) ABSORPTION
Absorption is going to take energy from this wave.
Energy is dissipited as heat from the object. Frequency stays same
6) REFLECTION
Wave bounces uniformly out of a regular flat surface, paritally reflect and absorb the signal
Reflection depends on the frequncy and the angle of signal.
7) Multi-Path
Energy is dissipited as heat from the object. Frequency stays same
6) REFLECTION
Wave bounces uniformly out of a regular flat surface, paritally reflect and absorb the signal
Reflection depends on the frequncy and the angle of signal.
7) Multi-Path
Multi-path happens when a signal is going to reflect off of surfaces.
So, delayed multiple copies of the same signal is hitting the reciever.
This makes the signal weak.
PART II
1) Scattering
2) Refraction
3) Line of Sight (LOS)
4) Fresnel zone
5) RSSI
6) SNR
1) Scattering
So, delayed multiple copies of the same signal is hitting the reciever.
This makes the signal weak.
PART II
1) Scattering
2) Refraction
3) Line of Sight (LOS)
4) Fresnel zone
5) RSSI
6) SNR
1) Scattering
Scattering will have an effect on the signal quality, coz the recieved result of the signal is going to be weaker,
coz some of it was send in other directions along the path, and also because of the attenuation.
Caused by :- dust, humidity (water), surface, humans, leaves etc
Its effect depends on frequency.
Two major effects are :-
i) Degradtion of wave strength and quality of the signal
coz some of it was send in other directions along the path, and also because of the attenuation.
Caused by :- dust, humidity (water), surface, humans, leaves etc
Its effect depends on frequency.
Two major effects are :-
i) Degradtion of wave strength and quality of the signal
ii) Uneven signal quality
2) Refraction
2) Refraction
Mostly occurs outdoors (not much indoor).
Refraction happens when wave changes direction (from one medium to another).
3) Line of Sight (LOS)
A building or wall might cause absorption hence attenuation, that may prevent the comm.
At 6 feet the horizon appears at 10KMs.
4) Fresnel zone
Augustine Fresnel was a physicist.
60% of the 1st zone of the Fresnel Zone should be interference free (80% recommended).
Mainly for outdoors.
5) RSSI
Recieved Signal Strength Indicator (Unit -> dBm)
We express RSSI as a relative value determined by the recieving LAN Card.
It is a grade value between 0-255
It is used to compare the signal to itself in different locations.
Typically expressed as a -ve value. The closer to zero, the better.
6) SNR
Signal to Noise Ratio.
It tells us how much stronger the signal is than the noise.
Refraction happens when wave changes direction (from one medium to another).
3) Line of Sight (LOS)
A building or wall might cause absorption hence attenuation, that may prevent the comm.
At 6 feet the horizon appears at 10KMs.
4) Fresnel zone
Augustine Fresnel was a physicist.
60% of the 1st zone of the Fresnel Zone should be interference free (80% recommended).
Mainly for outdoors.
5) RSSI
Recieved Signal Strength Indicator (Unit -> dBm)
We express RSSI as a relative value determined by the recieving LAN Card.
It is a grade value between 0-255
It is used to compare the signal to itself in different locations.
Typically expressed as a -ve value. The closer to zero, the better.
6) SNR
Signal to Noise Ratio.
It tells us how much stronger the signal is than the noise.
The more the better.
* LINK BUDGET
* LINK BUDGET
The accumulation of all of the losses from the sender to the recievers transmitter.
It tells us how much power we need to send for the reciever to interpret it.
Applied only for outdoor networks.
It tells us how much power we need to send for the reciever to interpret it.
Applied only for outdoor networks.
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