空白频段变身超级Wi-Fi (ZT) 阿方2012-01-02 22:38:47
【展望2012——美国宽带】微软公司已开始试验性地仅用两根空白频段的天线，取代几千个Wi-Fi基站，覆盖它在华盛顿州雷蒙德市的园区。超市、商场、 甚至市政部门都可以用它将互联网服务提供给当地居民，人们将通过它上网，或在智能手机及其他设备上使用Skype、Google+打免费电话
White-space puts Wi-Fi on steroids
空白频段变身超级Wi-Fi
A second wireless revolution is starting, thanks to television’s switch to digital
托电视数字化的福，第二次无线革命开始了
Who needs TV?
谁还需要电视机？
引语：“空白频段”一直被人们称作“超级Wi-Fi”(WiFi on steroids)。微软和谷歌等公司一直支持这个技术。
http://tech.ifeng.com/telecom/detail_2011_12/23/11523876_0.shtml
Think of how Wi-Fi has made computing so much more convenient. It has untethered users from pesky cable connections to the internet, allowing them to wander around the home or office with laptop or tablet in hand, surfing the web, making free phone calls, sending files wirelessly to printers, video to television sets, and many more things. But what if Wi-Fi radio beams travelled not just a few hundred feet but stretched for several miles—and were unimpeded by trees, terrain and walls so that they could penetrate all the nooks and crannies within buildings? That is the promise of “white-space” wireless.
想一想无线网络是如何使运算变得快捷方便的吧？它将用户从麻烦的网线连接中解放出来，使他们可以手持笔记本或平板电脑在家庭、办公室里转悠，上网冲浪，打 免费电话，无线传输资料给打印者，收看电视信号的视频，或做其他事情。但是假若无线网络信号不只是投射在几百英尺以内，而是能延长至若干英里——而且不受 树木、岩层、墙壁的阻碍，畅通无阻地到达建筑物里的所有角落呢？这正是“空白频段”无线网络的前景所在。
“White-space” is technical slang for television channels that were left vacant in one city so as not to interfere with TV stations broadcasting on adjacent channels in a neighbouring city. In the early days of television, America’s broadcasting authorities reserved 50 or so channels for TV stations. But because of worries about interference, no metropolitan area has ever come close to using all 50 channels at its disposal. In rural areas, vacant channels (ie, white-space) have frequently amounted to 70% or more of the total bandwidth available for television broadcasting.
“空白频段”是技术领域的行话，指一个城市里为防止干扰邻市电视信号而被留作空白的电视频道。在电视出现的早期，美国的电视部门为电视台保留了50个频 道。但因为担忧干扰，大都市地区从未计划使用全部。在乡村地区，未使用的频道（比如空白频段）经常占到全部电视机可用带宽的百分之七十，甚至更多。
With the recent switch from analogue to digital television, much of this protective white-space is no longer needed. Unlike analogue broadcasting, digital signals do not “bleed” into one another—and can therefore be packed closer together. All told, the television networks now require little more than half the frequency spectrum they sprawled across previously.
近来，随着模拟信号向数字信号的转变，很多保护性的空白频段不再需要。数字信号不像模拟信号那样会“流”进另一个频道——因此它可以更近地集中在一起用。总的来说，电视机信号现在需要的频谱长度很少超过从前的一半。
The attraction of white-space is that the frequencies used for television broadcasting (54MHz to 806MHz) were chosen in the first place for the distance they could travel and their ability to penetrate obstacles. They were also good at transmitting information quickly. Where Wi-Fi can shuttle data at 160-300 megabits per second, white-space can do so at 400-800 megabits per second.
空白频段的诱人之处在于，其用于电视播放的频率（54兆赫~806兆赫），因为传输距离远、能穿透障碍物，而为人们所青睐。它们还能高速输送信息。无线网络可以每秒传输160~300兆比特的地方，空白频段能每秒传400~800兆比特。
In America the best frequencies for doing all this—the 700MHz band covering channels 52 to 69 on the old television dial—were auctioned off in 2008 to mobile-phone companies. Between them, Verizon, AT&T and others paid close to $20 billion for this “beachfront property” of the wireless spectrum. The white-space freed below 700MHz is to be made available for unlicensed use by the public.
在美国，最适合承担（远程信息传输）这一任务的频率——覆盖传统电视拨号52台至69台的700兆赫——已经于2008年拍卖给了几家移动电话公司。其中，Verizon，AT&T和其他几家为了“滨海产业”出资近200亿美元收购了无线频段。700兆赫以下的空白频段免费，向无认证的公众开放。
Do you want to play in my bandwidth?
用用我的带宽如何？
White-space should help to solve the bandwidth problem that has begun to plague wireless networks in general—as more consumers download films, television episodes and other video offerings wirelessly from the internet, instead of receiving such fare from their traditional cable, satellite or over-the-air TV broadcasters.
空白频段应该用来解决大众使用无线网络时的带宽问题——越发庞大的消费群体通过无线方式，在互联网上下载电影、电视剧和其他视频文件，而不再以传统的网线、卫星信号或电视直播的方式得到这些资源。
A decade ago the biggest bandwidth hogs were computer users downloading music tracks from Napster and other peer-to-peer websites. Nowadays media seekers are more likely to be downloading whole television episodes from Amazon, iTunes or Hulu (which typically gobble up 14 times the bandwidth of music tracks) or streaming films from Netflix (110 times). Blame the current bandwidth crunch on the growing popularity of the iPhone and Android smartphones as well as media tablets like the iPad.
十年前，占用带宽最大的是从Napster和其他对等式网站下载音乐链接的电脑用户。而如今，用户更倾向于通过亚马逊、iTunes和Hulu下载整集电视剧（通常挤占音乐带宽达14倍），从Netflix下载排名靠前的电影（挤占音乐带宽110倍）。对于这个用户规模膨胀挤占带宽的局面，无论苹果、安卓智能手机还是平板电脑（如iPad），都难辞其咎。
What if Wi-Fi radio beams stretched for several miles?
一旦Wi-Fi信号辐射到几英里以外呢？
Apart from easing bandwidth problems, white-space could lead to a wireless revolution even bigger than the wave of innovation unleashed over a decade ago when Wi-Fi, Bluetooth and other wireless technologies embraced the unlicensed 2.4GHz band previously reserved for microwave ovens and garage-door openers. Some insiders even talk about white-space offering a “third pipe” that will rival cable and telephone broadband for access to the internet. Others see it as a cheaper alternative to today’s mobile-phone system.
除了能解决带宽方面的问题，空白频段还可能掀起一场无线革命，规模比十年前那次突破性的创新狂潮还要大得多。那时，Wi-Fi、蓝牙和其他无线技术都使用无认证的2.4千兆赫带宽，这个带宽以前都是留给微波炉和车库遥控器用的。一些内部人士甚至谈论用空白频段提供“第三管道”，以在互联网领域同有线信号和电视信号展开竞争。
Microsoft has been using just two experimental white-space antennae, instead of thousands of Wi-Fi access points, to blanket its 500-acre (200-hectare) campus in Redmond, Washington. With white-space hotspots capable of covering such wide areas, supermarkets, shopping malls, even local municipalities could use it to offer free (advertising-supported) internet services to their customers and local residents, to search the web and make free telephone calls using Skype, Google+, or something similar on their smartphones and other devices.
微软公司已开始试验性地仅用两根空白频段的天线，取代几千个Wi-Fi基站，覆盖它在华盛顿州雷蒙德市的园区。有了可以覆盖如此大范围的空白频段，超市、 商场、甚至地方市政部门都可以用它将互联网服务免费地（含广告赞助）提供给消费者和当地居民，人们将通过它上网，或在智能手机及其他设备上使用 Skype、Google+（或别的什么）打免费电话。
Pipe-dreams? Far from it. Technical hurdles remain, but the first “enterprise-level” pieces of white-space equipment are about to go into service, with commercial trials of various applications expected throughout 2012. How soon before individuals can buy $100 white-space routers for the home? The consensus view is 2015 at the very latest.
这是幻想吗？绝对不是。尽管还存在技术瓶颈，但空白频段装备的“企业水平”部分已开始运作，不同应用方式的商业试验将贯穿2012全年。人们过多久会去购买100美元的空白频段家用路由器？较主流的观点是最迟不过2015年。
Nick Valéry: Difference Engine columnist, The Economist