Q4- A 128 Kbps point-to-point link is set up between Earth and the Spirit Rover
ID: 3730639 • Letter: Q
Question
Q4- A 128 Kbps point-to-point link is set up between Earth and the Spirit Rover on Mars. The distance from Earth to Mars (when they are closest together) is approximately 55x10 km, and data travels over the link at the speed of 3x103 km/s. If a camera on the Spirit Rover takes pictures of its surroundings and sends these to Earth, how quickly after a picture is taken can it reach Mission Control on Earth? Assume the following: the link uses a stop-and-wait protocol frame size of 1 KB; picture size of 1 MB; frame and ACK creation time of 0 seconds; and negligible ACK transmission time.Explanation / Answer
Transmission time = 1 KB/128Kbps
= 2^10B/2^17Bps
= 2^-7 s
total Transmission time for picture = (1MB/1KB)*2^ -7 s
= 2^20/2^10)* 2^-7 s
= 2^3 sec
= 8 s
Propagation time = 55*10^6 / 3*10^5
= 183.3333 s
time taken to receive picture in earth = 8 + 183.3333
= 193.3333 s
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