Consider an access point and two base stations A and B as shown in figure. Base stations can communicate with the access point, if they are within the communication range. Initially base station A is not within communication range. After sometimes, A starts moving and comes within the range and starts transmitting packets to the access point.

Base station A does not know the presence of another base station B (hidden node) and vice versa. Both the hidden nodes start transmitting at the same time and collision occurs. To overcome this RTS and CTS frames are used.

The flash video on the right hand side shows

• Base station can transmit packets to access point , it they are in communication range
• Collision occurs if both the hidden node starts transmission at the same time
• To avoid hidden node problem, RTS/CTS are used