问题
单项选择题
用户A与用户B通过卫星链路通信时，传播延迟为540ms，假设数据速率是64Kbit/s，帧长4000bit，若采用停等控制协议通信，则最大链路利用率为 (1) ；若采用后退N帧 ARQ协议通信，发送窗口为8，则最大链路利用率可以达到 (2) 。
1（）
A．0.058
B．0.116
C．0.188
D．0.231
答案
参考答案：A
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用户A与用户B通过卫星链路通信时，传播延迟为540ms，假设数据速率是64Kbit/s，帧长4000bit，若采用停等控制协议通信，则最大链路利用率为 (1) ；若采用后退N帧 ARQ协议通信，发送窗口为8，则最大链路利用率可以达到 (2) 。
1（）
A．0.058
B．0.116
C．0.188
D．0.231
参考答案：A
第二节摘录信息 （共5小题；每小题1分，满分5分） 阅读下面短文，根据所读内容在文后第65至第69小题的空格里填上适当的单词或短语，并将答案转写到答题卡上。 注意：每空不超过3个单词。 FOR many young people, Halloween is the best day of the year. The holiday has a very interesting history. It was first celebrated in Ireland and Scotland as a festival of the dead. Families invited their ancestors (祖先) into their homes but tried to keep bad spirits (精灵) out by wearing scary costumes (服装). Now the holiday is a time for fun and excitement. Families carve (雕刻) scary or funny faces into pumpkins and put candles inside to make them into lanterns (灯笼). These are called jack-o''-lanterns. Children dress up in costumes and walk around their neighborhoods collecting candy. They knock on doors and when a person opens the door, the children shout, “Trick or treat!” Once, this meant that if the person at the door did not give the children a treat, they would play a mean (坏的) trick. But today, children usually do not play tricks. They are too busy getting as much candy as they can!
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