Hidden Terminal Problem

Overview

• Hidden Terminal Problem occurs in wireless networks when two devices cannot hear each other’s transmissions but can hear a common third device.
• This situation leads to potential collisions when both devices attempt to communicate with the third device simultaneously, unaware of each other’s presence.

Example Scenario

• Devices A and C are within range of Device B but not each other.
• Device A and Device C might both attempt to send data to Device B at the same time, causing a collision at Device B.

Solution: RTS/CTS Mechanism

RTS/CTS

Request to Send (RTS) / Clear to Send (CTS)

• RTS/CTS is a protocol used to address the hidden terminal problem.
• It involves a two-step handshake to manage access to the shared medium and reduce the risk of collisions.

How It Works

1. Request to Send (RTS):

   • When a device wants to transmit data, it first sends an RTS frame to the intended recipient.
   • The RTS frame includes information about the duration of the transmission.

2. Clear to Send (CTS):

   • The recipient of the RTS frame responds with a CTS frame if the medium is clear.
   • The CTS frame notifies all other devices in the range of the recipient that the channel is reserved for the transmission.

3. Transmission:

   • Once the RTS/CTS exchange is complete, the sender transmits its data.

4. Network Awareness:

   • Other devices that receive the CTS frame will defer their transmissions to avoid collisions.

Benefits

• Collision Avoidance: Helps prevent collisions by ensuring that all devices are aware of ongoing transmissions.
• Efficient Use of Medium: Improves overall network efficiency by managing access to the shared medium.

Summary

• The Hidden Terminal Problem can cause collisions in wireless networks when devices cannot detect each other’s transmissions.
• The RTS/CTS Mechanism is a solution that helps manage access to the medium and prevent such collisions through a handshake process.