Explain the hidden node problem and how RTS/CTS helps.

Explain the hidden node problem and how RTS/CTS helps.

• A. Hidden node occurs when two devices can hear each other but the AP cannot hear them.
• B. Hidden node occurs when there are multiple APs; RTS/CTS prevents handoffs.
• C. Hidden node occurs when two devices can’t hear each other but both hear the AP.
• D. Hidden node scenario occurs when two devices can’t hear each other but both hear the AP.

Answer: (D)

The hidden node problem happens when two devices can’t hear each other but both can hear the access point. Because they can’t hear each other, they may both think the channel is idle and start transmitting to the AP, causing their signals to collide at the AP and waste airtime. RTS/CTS helps by adding a brief handshake before data is sent. The transmitting device sends a Request-To-Send to the AP, and the AP replies with a Clear-To-Send. The CTS is heard by all devices within range, including the hidden node, so they realize the channel is about to be used and pause their own transmissions. This coordination prevents two hidden devices from transmitting at once to the AP, reducing collisions. Overhead from RTS/CTS is the trade-off, but it’s particularly valuable in networks where hidden nodes are likely or when transmitting larger frames.

The hidden node problem happens when two devices can’t hear each other but both can hear the access point. Because they can’t hear each other, they may both think the channel is idle and start transmitting to the AP, causing their signals to collide at the AP and waste airtime.

RTS/CTS helps by adding a brief handshake before data is sent. The transmitting device sends a Request-To-Send to the AP, and the AP replies with a Clear-To-Send. The CTS is heard by all devices within range, including the hidden node, so they realize the channel is about to be used and pause their own transmissions. This coordination prevents two hidden devices from transmitting at once to the AP, reducing collisions.

Overhead from RTS/CTS is the trade-off, but it’s particularly valuable in networks where hidden nodes are likely or when transmitting larger frames.