A 50 kbps satellite channel is used to transmit 1000-bit frames between Sophie in Moscow and Richard in New York. Assume that the distance between Richard and the satellite and the distance between the satellite and Sophie are the same, which is approximately 36; 000 km. The satellite acts as a transponder (a repeater). Assume that the processing time at transmitter, satellite and receiver, and the transmission time for the acknowledgment frame are all negligible. Due to the good error correction code in the frame, you could assume that the channel error rate is negligible. We de ne channel efficiency as:

(x frame transmission times)/ (total time spent for transmitting x frames) ,

where x can be any positive integer. The speed of light is 3x 10^8 meter per second.

a. If the Stop and Wait ARQ Protocol is used, what is the channel efficiency?
b. If the sliding window ARQ protocol is used with receiving window size equal to 1, the sequence number field in the frame is 3 bits long, what is the channel efficiency if the maximum sending window size is used?
c. If the sliding window ARQ protocol is used with receiving window size equal to sending window size, the sequence number field in the frame is 3 bits long, what is the channel efficiency if the maximum sending window size is used?
d. If the sequence number field in the frame is 8 bits long, answer (b) and (c).