Calculation of the path loss is usually called prediction. Exact prediction is

possible only for simpler cases, such as the free space propagation or the flatearth

model, which is called deterministic methods. They based on the physical

laws of wave propagation are also used ray tracing is one such method. These

methods are expected to produce more accurate and reliable predictions of the

path loss than the empirical methods however, they are significantly more

expensive in computational effort and depend on the detailed and accurate

descr iption of all objects in the propagation space, such as buildings, roofs,

windows, doors, and walls.-Calculation of the path loss is usually called prediction. Exact prediction is

possible only for simpler cases, such as the free space propagation or the flatearth

model, which is called deterministic methods. They based on the physical

laws of wave propagation are also used　ray tracing is one such method. These

methods are expected to produce more accurate and reliable predictions of the

path loss than the empirical methods　however, they are significantly more

expensive in computational effort and depend on the detailed and accurate

descr iption of all objects in the propagation space, such as buildings, roofs,

windows, doors, and walls.