A channel has a data rate of 4 kbps and a propagation delay of 20 ms. For what range of frame sizes does stop-and-wait give an efficiency of at least 50%?
Q1. A channel has a data rate of 4 kbps and a propagation delay of 20 ms. For what range of frame sizes does stop-and-wait give an efficiency of at least 50%?
Answer: Greater than 160 bits
Explanation: For 50% efficiency, frame size / (bandwidth * (transmission time + 2*propagation time)) = 0.5. Simplifying, we get frame size > bandwidth * 2 * propagation time. So, frame size > 4 * 10³ * 2 * 20 * 10^-3 = 160 bits.