Overview a Frequency bands Modulation Signal Distortion- Wireless Channel Errors From waves to bits Channel models Transceiver design CS5602: Principles and Techniques for Sensors and Information Perception
Overview ▪ Frequency bands ▪ Modulation ▪ Signal Distortion – Wireless Channel Errors ▪ From waves to bits ▪ Channel models ▪ Transceiver design CS5602: Principles and Techniques for Sensors and Information Perception 11
Wireless channel propagation Attenuation: As the signal wave propagates through air, the signal strength is attenuated Proportional to the distance traveled over the air Results in path loss for radio waves Reflection and refraction When a signal wave is incident at a boundary between two different Reflected rays types of material a certain fraction of the wave bounces off the surface, reflection a certain fraction of the wave propagates through the boundary, refraction. x===:. Refracted rays CS5602: Principles and Techniques for Sensors and Information Perception
Wireless channel propagation ▪ Attenuation: As the signal wave propagates through air, the signal strength is attenuated. ▪ Proportional to the distance traveled over the air ▪ Results in path loss for radio waves ▪ Reflection and refraction: When a signal wave is incident at a boundary between two different types of material ▪ a certain fraction of the wave bounces off the surface, reflection. ▪ a certain fraction of the wave propagates through the boundary, refraction. CS5602: Principles and Techniques for Sensors and Information Perception 12
Wireless channel propagation Diffraction: When signal wave propagates through sharp edges such as the tip of a mountain or a building the sharp edge acts as a source, New waves are generated Signal strength is distributed to the new generated waves Scattering: In reality, no perfect boundaries. When a signal wave is incident at a rough surface, it scatters in different directions CS5602: Principles and Techniques for Sensors and Information Perception
Wireless channel propagation ▪ Diffraction: When signal wave propagates through sharp edges such as the tip of a mountain or a building, the sharp edge acts as a source, ▪ New waves are generated ▪ Signal strength is distributed to the new generated waves. ▪ Scattering: In reality, no perfect boundaries. When a signal wave is incident at a rough surface, it scatters in different directions CS5602: Principles and Techniques for Sensors and Information Perception 13
Wireless channel model Path-Joss Multi-path effects Channel errors Signals-to-bits Bits-to-packets CS5602: Principles and Techniques for Sensors and Information Perception
Wireless Channel Model ▪ Path-loss ▪ Multi-path effects ▪ Channel errors ▪ Signals-to-bits ▪ Bits-to-packets CS5602: Principles and Techniques for Sensors and Information Perception 14
Wireless channel Wireless transmission distorts any transmitted signal Wireless channe describes these distortion effects Sources of distortion Attenuation- Signal strength decreases with increasing distance Reflection/refraction- Signal bounces of a surface; enter material Diffraction-start"new wave"from a sharp edge Scattering- multiple reflections at rough surfaces CS5602: Principles and Techniques for Sensors and Information Perception
Wireless Channel ▪ Wireless transmission distorts any transmitted signal ▪ Wireless channel describes these distortion effects ▪ Sources of distortion ▪ Attenuation – Signal strength decreases with increasing distance ▪ Reflection/refraction – Signal bounces of a surface; enter material ▪ Diffraction – start “new wave” from a sharp edge ▪ Scattering – multiple reflections at rough surfaces CS5602: Principles and Techniques for Sensors and Information Perception 15