Indoor Propagation Models
Introduction: PCS service help users to communicate within a building. Propagation within buildings is strongly influenced by specific features such as the layout of the building, the construction materials, and the building type. Indoor propagation models also works on same mechanism like diffraction, reflection and scattering. But conditions are much more variable. The signal levels vary greatly depending on whether interior doors are open or closed inside a building. Antenna position also affects the indoor propagation. Indoor channels may be classified either as line-of-sight (LOS) or obstructed (OBS), with varying degrees of clutter
Some of the key models which have recently emerged are now
1. Partition Losses (same floor)
2. Partition Losses between Floors
3. Log-distance Path Loss Model
4. Ericsson Multiple Breakpoint Model
5. Attenuation Factor Model
Partition Losses (same floor):
- Buildings have a wide variety of partitions and obstacles which form the internal and external structure
- Partitions that are formed as part of the building structure are called hard partitions, and partitions that may be moved and which do not span to the ceiling are called soft partitions
- Partitions vary widely in their physical and electrical characteristics, making it difficult to apply general models to specific indoor installations
Partition Losses between Floors:
- The losses between floors of a building are determined by the external dimensions and materials of the building, as well as the type of construction used to create the floors and the external surroundings.
- Even the number of windows in a building and the presence of tinting (which attenuates radio energy) can impact the loss between floors
Table 1 illustrates values for floor attenuation factors (FAF) in three buildings
- It can be seen that for all three buildings, the attenuation between one floor of the building is greater than the incremental attenuation caused by each additionalfloor in table 1
- Table 2 illustrates very similar tendencies. After about five or six floor separations, very little additional path loss is experienced
Log-distance Path Loss Model:
- Indoor path loss has been shown by many researchers to obey the distance power law in equation 1 ― (1)
Where the value of n depends on the surroundings and building type, and Xσrepresents a normal random variable indB having a standard deviation of σ dB