In this case we can use an optical link, where a signal is aimed at a reflector attached to the ceiling - often called satellite. The signal is reflected from the walls etc., but problems caused by multipath propagation are diminished, because there is one reflector that is clearly better than the others. If we are speaking of a large hall divided into many cubicles, it may be better to use directed optical links. It is also possible to use short range radio networks as long as we are not disturbing the network in the neighbouring room.

b) a larger office that has several small rooms

Now we have to use a radio network. There are two kinds of these: some have base stations supported by a wired network (these are called infrastructure wireless LANs) while others  (called ad-hoc wireless LANs) rely on direct communication between portable stations. The range (as long as there are not several base stations) is in tens of meters. The radio frequencies used (a few GHz) do not pass massive stone walls easily. Besides extending the range, this may be another reason to rely on base stations.

c) a large factory hall (a metal factory)

There are good reasons to use a wireless network, because it may be difficult to install wires: cranes move about above and if the cables are on the floor, they must tolerate being driven over by a forklift with a heavy load. A radio network must have base stations and there may be some heavy disturbance caused by big motors, electrical welding machines etc. Directed optical links are perhaps the safest.

d) a largish campus area (such as Otaniemi)

We must ask separately, whether to have a wired or wireless network to connect the buildings to each others and what kind of a network is best within each building. All combinations of wired and wireless networks are basically possible. A wireless network connecting the buildings might consist of directed optical or radio links.

It is also possible to have just one base station with which the stations communicate as in the cellular telephone network. The limits for this solution are set by the range of the base station and by its traffic capacity. Moreover, we are not willing to pay to an external network operator for calls within the campus area. Since calls within the internal telephone network are free this points at the direction of cordless telephones (such as DECT) as an alternative.