题型：阅读理解 题类：常考题 难易度：普通
山西省实验中学2020届高三上学期英语阶段性测评试卷
You're probably used to the regular upgrades in our cell-phone networks. There was 2G, which came along in 199l, replaced with 3G in 2001, followed by 4G in 2009. Now we're hearing about the coming of 5G.
But 5G is a much bigger leap than before. 5G, of course, is much faster than 4G in the real world and a 5G phone in a 5G city will enjoy Internet speeds between 9 and 20 times as fast. The arrival of 5G also means enormous leaps forward in capacity－so much that every cell-phone plan will offer cheap, truly unlimited Internet access. "The consequences of that are huge," says Sherif Hanna, Qualcomm's director of 5G marketing. For example, apps will no longer degrade (降低) your video quality or postpone downloading when you're out of Wi-Fi range. In fact, you'll probably prefer to do your downloads when you're on cellular (使用流量) because 5G will be much faster than whatever service you've got at home or work.
"However, not everyone is excited by the 5G development. The new standard gets its speed partly by using existing transmission(传输) frequencies more efficiently and partly by using the millimeter wave range. That's a big, juicy line of radio frequencies that are currently underused because millimeter wave is really hard to use," Hanna says.
These frequencies are much higher than anything we've used for the cellular, which means they can offer unbelievable speed－but at the cost of range. Millimeter wave cellular towers have to be about 500 feet apart. Cell carriers not only will have to upgrade all their cell transceivers (called small cells) but will install(安装) a lot more of them as well.
That's why the millimeter wave flavor of 5G, the superfast coverage, will be available only in densely populated cities such as New York and San Francisco. In suburban and rural areas, 5G will bring a speedup of "only" nine times faster.
试题篮
