六级模拟试题2文档格式.docx

1、 swifter, higher, stronger. The Path to 4GBeijing has the good fortune of looking at previous generations of wireless networks and avoiding the same mistakes as it prepares for 2008. First generation （1G） wireless telecommunications-the brick-like analog phones that are now collectors items-introduc

2、ed the cellular architecture that is still being offered by most wireless companies today. Second generation （2G） wireless supported more users within a cell by using digital technology, which allowed many callers to use the same multiplexed channel. But 2G was still primarily meant for voice commun

3、ications, not data, except some very low data-rate features, like short messaging service （SMS）. So-called 2. 5G allowed carriers to increase data rates with a software upgrade at the base transceivers stations （BTS）, as long as consumers purchased new phones too. Third generation （3G） wireless offe

4、rs the promise of greater bandwidth, basically bigger data pipes to users, which will allow them to send and receive more information.All of these architectures, however, are still cellular. Cellular architecture is sometimes referred to as a star architecture, because users within that cell access

5、a common, centralized base station. The advantage is that given enough time and money, carriers can build nationwide networks, which most of the big carriers have done. Some of the disadvantages include a singular point of failure, no load balancing, and spectral inefficiencies. The single biggest d

6、isadvantage to cellular networks going forward is that as data rates increase, output power will have to increase-or the size of the cells will have to decreaseto support those higher data rates. Since significant increases in output power scare both consumers and regulators, it is far more likely t

7、hat we will see significantly smaller cells. This will further reduce the return on investment in already fragile 3G business plans.Fourth generation （4G） wireless was originally conceived by the Defense Advanced Research Projects Agency （DARPA）, the same organization that developed the wired Intern

8、et. It is not surprising, then, that DARPA chose the same distributed architecture for the wireless Internet that had proven so successful in the wired Internet. Although experts and policymakers have yet to agree on all the aspects of 4G wireless, two characteristics have emerged as all but certain

9、 components of 4G: end-to-end Internet Protocol （IP）, and peer-to-peer （点对点） networking. An all IP network makes sense because consumers will want to use the same data applications they are used to in wired networks. Peer-to-peer networks, where every device is both a transceiver（收发器） and a router（路

10、由器） for other devices in the network, eliminates the weakness of cellular architectures, because the elimination of a single node does not disable the network. The final definition of 4G will have to include something as simple as this: if a consumer can do it at home or in the office while wired to

11、 the Internet, that consumer must be able to do it wirelessly in a fully mobile environment.Lets define as wireless collaborated peer-to-peer networking. 4G technology is significant because users joining the network add mobile routers to the network infrastructure. Because users carry much of the n

12、etwork with them, network capacity and coverage is dynamically shifted to accommodate changing user patterns. As people congregate and create pockets of high demand, they also create additional routes for each other, thus enabling additional access to network capacity. Users will automatically hop a

13、way from congested routes to less congested routes. This permits the network to dynamically and automatically self-balance capacity, and increase network utilization.What could 4G mean for Beijing and its Olympics?There is a statistic （without any known attribution） that estimates that the first pho

14、ne call made by a majority of Chinese alive today was with a cell phone. This would mean that most Chinese skipped a whole generation of telephony （copper twisted pair） and jumped into the world of wireless telephony. So too might the Chinese skip a generation of wireless and deploy a 4G network bef

15、ore 2008. Following are a few applications that could further enhance the Olympic experience, both for the visitors during the Games, and for the residents of Beijing long afterwards.SecurityBeijing has already deployed cameras throughout the city and sends those images back to a central command cen

16、ter. This is generally done using fiber, which limits where the cameras can be hung, i. e. , no fiber, no camera. 4G networks allow Beijing to deploy cameras and backhaul（回传） them wirelessly. And instead of having to backhaul every camera, cities can backhaul every third or fifth or tenth camera, us

17、ing the other cameras as router/repeaters.Traffic ControlBeijing is a challenging city for drivers, with or without an Olympics going on. The growing middle class, and their new-found ability to purchase automobiles, is increasing the number of passenger vehicles on the road at a staggering annual r

18、ate of 30%. 4G networks can connect traffic control boxes to intelligent transportation management systems wirelessly. This would create a traffic grid that could change light cycle times on demand, e. g., keeping some lights green longer temporarily to improve traffic flow. It also could make vehic

19、le based on demand all green routes for emergency vehicles responding to traffic accidents, reducing the likelihood that those vehicles will themselves be involved in an accident route.Hot SpotsBeijing could deploy information kiosks（亭） around the city to allow visitors to the Olympics to get real-t

20、ime information on results, venue updates, and traffic conditions. They could be backhauled to the Internet via existing cable or DSL. But they could also be home to 802. 11 access points, providing free information to anyone with an 802. 11 card. And with 4Gs peer-to-peer capabilities, the city cou

21、ld deploy access points even where there is no fiber, by having those remote access points hop through backhauled access points.Mobile Hot SpotsTo exploit the real power of 4G, Beijing could create mobile hot spots. This would allow users in the subways. trains, and buses to connect to the Internet

22、via standard 802. 11 cards talking to standard 802. 11 access points. But since those access points obviously cannot be wired to the network, they are connected via 4G wireless networks.ConclusionHosting an Olympic Games is, well, an Olympian task. Modern China is more than up to the challenge and i

23、t is safe to predict that Beijing 2008 will be one of the most impressive Games of all times. But one other way to measure the success of the Games is the impact it has on the host city after the torch is extinguished. By deploying a 4G mobile broadband network for the Games, Beijing will ensure tha

24、t its residents will enjoy profound and lasting benefits.1. Which of the following is NOT one of the words of the Beijing Olympic motto?A） swifter B） higher C） bigger D） stronger2. Which one introduced the cellular architecture that is still being offered by most wireless companies today?A） First ge

25、neration （1G） wireless telecommunications.B） The so-called 2. 5G.C） Second generation （2G） wireless.D） Third generation （3G） wireless.3. Which one of the following quality CANNOT be used in the definition of ?A） collaborated B） peer-to-peer C） wired D） networking4. If many people have demand for the

26、 network at the same time, the network will_. A） be difficult in the data communicationB） break down completelyC） keep dynamically and automatically self-balance capacityD） give no information5. 4G wireless communication can take the place of_to send images back to central command center.A） screen B

27、） cell phone C） television D） fiber6. The growing middle class in Beijing is increasing the number of passenger vehicles on the road at an annual rate of_. A） 20% B） 25% C） 30% D） 35%7. 4G networks can keep some lights_longer temporarily to improve traffic flow.A） green B） yellow C） red D） blue8. Du

28、ring Beijing Olympics, tourists can easily obtain the information about game results and traffic conditions in time from _. 9. Even on their way to destinations, travelers can easily surf internet by 802.11 cards if there are_. 10. Whether Beijing 2008 is successful or not can be ascertained by_on B

29、eijing after it is over.Part IV. Reading Passage 1Can you walk a straight line? The question is much more difficult to answer than you think. A recent experiment held in Japan shows that it is almost _1_ for people to walk exactly straight for 60 meters. Each man had to wear socks soaked with red in

30、k and walk on white paper fixed _2_ to the floor. The _3_ showed that all walked in a winding rather than a straight line. Researchers found that people _4_ their direction of walking regularly. However, the range differed from subject to subject. This suggests that none of us can walk in a _5_ straight line. Rather, we meander （散步）, mainly due to a slight structural of functional _6_ of our legs. So steps by the left and right legs of a person are _7_.As a result, although we may start walking in