Attenuation Results in path loss Received signal strength is a function of the distance d between sender and transmitter Friis free-space model Signal strength at distance d relative to some reference distance do<d for which strength is known -do is far-field distance, depends on antenna technology CS5602: Principles and Techniques for Sensors and Information Perception
Attenuation ▪ Results in path loss ▪ Received signal strength is a function of the distance d between sender and transmitter ▪ Friis free-space model ▪Signal strength at distance d relative to some reference distance d0 < d for which strength is known ▪d0 is far-field distance, depends on antenna technology CS5602: Principles and Techniques for Sensors and Information Perception 16
Attenuation Friis free-space model t Gt·G·入 t recv (4π)2·d2.L Gt·G·入 2 t O O (4π)2·d recv(ao) CS5602: Principles and Techniques for Sensors and Information Perception
Attenuation ▪ Friis free-space model CS5602: Principles and Techniques for Sensors and Information Perception 17
Non-line-of-sight Because of reflection, scattering,. radio communication is not limited to direct line of sight communication Effects depend strongly on frequency, thus different behavior at higher frequencies Non-line-of-sight path sight path Do Line -of CS5602: Principles and Techniques for Sensors and Information Perception
Non-line-of-sight ▪ Because of reflection, scattering, …, radio communication is not limited to direct line of sight communication ▪Effects depend strongly on frequency, thus different behavior at higher frequencies CS5602: Principles and Techniques for Sensors and Information Perception 18 Line-ofsight path Non-line-of-sight path
Non-line-of-sight Different paths have different lengths propagation time Results in delay spread of the wireless channel multipath LOs pulses pul signal aT receiver CS5602: Principles and Techniques for Sensors and Information Perception
Non-line-of-sight ▪ Different paths have different lengths = propagation time ▪Results in delay spread of the wireless channel CS5602: Principles and Techniques for Sensors and Information Perception 19 signal at receiver LOS pulses multipath pulses