Site-general models indicate power loss coefficients ranging approximately from ង to ᡖ where walls and obstacles are taken into account. These values for frequencies from 900 MHz to 60 GHz. (n.b. ង for open space, ᡖ for crowded offices).
Floor penetration depending on type of building (residential, office, commercial), and construction material (concrete floor, influence of air-conditioning units and lighting fixtures).
Radio channel varies in time, frequency and with spatial displacement. Many propagation paths between TX and RX. Time delay associated with each path.
since radio channel is linear, it is fully described by its impulse response, and once impulse response is known, can determine the response of channel to any input.
impulse response usually described by power delay profile (power density as function of excess delay)
“Delay spread” is one parameter by which power delay profiles are characterised.
BER dependent on ratio of delay spread to symbol duration (but also ratio of wanted/unwanted amplitude depending on modulation scheme used).
Statistical models based on representation of channel by a few multipath components; site specific models might employ ray-tracing techniques requiring detailed knowledge of indoor environment.
