问题 问答题

【说明】
某学校欲构建校园网,根据实际情况,计划在校园总部采用有线网络和无线网络相结合的接入方式,校园分部通过Internet采用VPN技术与校园总部互联,该校园网采用了分层设计结构,其网络拓扑结构如图2-5所示。


1.【问题1】
该校园网的部分区域部署了无线网络(WLAN),采用符合IEEE 802.11g标准的无线网络设备,该校园网无线网络部分的最大数据传输速率为 (1)

  • A.11Mb/s
  • B.54Mb/s
  • C.100Mb/s
  • D.108Mb/s

答案

参考答案:(1)B,或54Mb/s

解析:[要点解析]
这是一道要求读者掌握无线局域网技术的基本常识题。本题所涉及的知识点如下。
IEEE 802.11g采用效率较高的OFDM调制技术,最高数据传输速率可提升至54Mb/s,它工作在2.4GHz的ISM频段,与现有IEEE 802.11b标准兼容。对于IEEE 802.11a、IEEE 802.11b和IEEE 802.11g等3种标准的异同点见表2-10。
                              表2-10 IEEE 802.11的3个子标准异同点对比表

比较项目
阅读理解

阅读理解。

                         UK students get more morrung rest

    You  get lost in the forest, and  then  you walk  forward  and  fall  over.

Opening  your eyes, you find yoursclfin a swimming pool full of chocolate.

Just when you're about to enjoy the chocolate,a voice shouls,“CET UP!!"

    This isn't some boot camp(新兵训练营).It's the wake-up call that

every teenager in the UK goes through each morning.  Sleeping late is their

dream, but they have to get up and go to school early in themorning.

    Now,one  school  finally  understands  that asking teenagers to amve at

school at  9:00  a.m. is not just unfair but can also hurt both kids and their

studies.

    The Monkseaton High School in England recently decided to see whether

there was any diffrence  they started their school day one hour later, at 10:00 am instead of'9:00 am.

    The results have been  surprising. Since  the later start, 28 percent fewer

students  have been absent,seven percent fewer have  been late. Best of all,

students get higher test scores. One stude.nt, Emelye Hood, 13, said, "When

I get more sleep,I can focus(集中精力)more on my lessons.”

    In  trying the experiment(试验),the  school  used studies by Oxford

scientist Russell Foster,a neuroscientist(神经系统学专家).He says

that teenagers have different sleep cycles(周期)than adults.Adults are

active and ready for the day at 8:00 am, while teenagers aren't fully awake

until 10:00 am.

    Ryan Thompson, 13, also welcomes the later start. He says, "Now I get

to sleep and don't rush breakfast. It makes me much happier to go to

school.”

根据短文内容,判断下列句子的正误,正确的用“A,错误的用“B。

( )1. The teenagers in the UK usually don't have enough time to sleep.

(     )2. One school in the UK has realized that it's good for kids to get more

sleep.

(     )3. The students can pay more attention to their studies if they get enough sleep.

(     )4. The teenagers can get ready for the day earlier than the adults.

(     )5.Many teenagers feel happy about the later start because they don't need to go to school in a hurry.