7. Radio Channel Intro

 

7. Radio Channel Intro



17.12.2018

Radio Channel Intro – Video: Register for Course


Selected issues:

Reflection ‐ occurs when a propagating wave impinges upon an object that which has large dimension when compared to the wavelength of the propagating wave. Part of propagating wave energy may be absorbed or propagating through reflecting medium. It can be occurred from the surface of the earth and buildings and walls.

Diffraction  ‐  Propagating radio waves bend or deviate due to the obstacle that has sharp edges. At high frequencies, diffraction depends upon geometry of object, amplitude and phase at point of diffraction.

Scattering  ‐  happens when a propagating signal hits a rough surface whose size is much smaller than that of the signal wavelength. At receiver it can be seen as another radio wave source.    Street sign, lamps, foliage, etc can induce scattering in mobile communication system.

Multipath – is when all the copies of the signal coming from different diffraciton, reflections and scattering reach the signal. They can create constructive or destructive versions of the transmitted symbols

Thermal noise – comes from the non-ideality of the electric elements (with the highest influence is on the resistance element – that „noises” with the temperaturę – the hihger the temperaturę – the higher the noise).

Interference – is a distortion of the received signal by other sources like other signals from other wifi APs or other systems – e.g. bluetooth or microwaves

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