Hidden and Exposed Station Problems

We referred to hidden and exposed station problems in the previous section. It is time now to dicuss these problems and their effects.

Hidden Station Problem
Figure 14.10 shows an example of the hidden station problem.

Station B has a transmission range shown by the left oval (sphere in space);
every station in this range can hear any signal transmitted by station B. Station C has a transmission range shown by the right oval (sphere in space); every station located in this range can hear any signal transmitted by C. Station C is outside the transmission range of B; likewise, station B is outside the transmission range of C. Station A,however, is in the area covered by both B and C; it can hear any signal transmitted by B or C.

Assume that station B is sending data to station A. In the middle of this transmission,station C also has data to send to station A. However, station C is out of B’s range and transmissions from B cannot reach C. Therefore C thinks the medium is free.