空白頻段變身超級Wi-Fi (ZT)

來源: 阿方於 2012-01-02 14:38:47 [檔案] [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次 (10013 bytes)

【展望2012——美國寬帶】微軟公司已開始試驗性地僅用兩根空白頻段的天線，取代幾千個Wi-Fi基站，覆蓋它在華盛頓州雷蒙德市的園區。超市、商場、甚至市政部門都可以用它將互聯網服務提供給當地居民，人們將通過它上網，或在智能手機及其他設備上使用Skype、Google+打免費電話

White-space puts Wi-Fi on steroids
空白頻段變身超級Wi-Fi

A second wireless revolution is starting, thanks to television’s switch to digital
托電視數字化的福，第二次無線革命開始了

Who needs TV?
誰還需要電視機？

引語：“空白頻段”一直被人們稱作“超級Wi-Fi”(WiFi on steroids)。微軟和穀歌等公司一直支持這個技術。
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.

想一想無線網絡是如何使運算變得快捷方便的吧？它將用戶從麻煩的網線連接中解放出來，使他們可以手持筆記本或平板電腦在家庭、辦公室裏轉悠，上網衝浪，打免費電話，無線傳輸資料給打印者，收看電視信號的視頻，或做其他事情。但是假若無線網絡信號不隻是投射在幾百英尺以內，而是能延長至若幹英裏——而且不受樹木、岩層、牆壁的阻礙，暢通無阻地到達建築物裏的所有角落呢？這正是“空白頻段”無線網絡的前景所在。

“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.

“空白頻段”是技術領域的行話，指一個城市裏為防止幹擾鄰市電視信號而被留作空白的電視頻道。在電視出現的早期，美國的電視部門為電視台保留了50個頻道。但因為擔憂幹擾，大都市地區從未計劃使用全部。在鄉村地區，未使用的頻道（比如空白頻段）經常占到全部電視機可用帶寬的百分之七十，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.

近來，隨著模擬信號向數字信號的轉變，很多保護性的空白頻段不再需要。數字信號不像模擬信號那樣會“流”進另一個頻道——因此它可以更近地集中在一起用。總的來說，電視機信號現在需要的頻譜長度很少超過從前的一半。

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.

空白頻段的誘人之處在於，其用於電視播放的頻率（54兆赫~806兆赫），因為傳輸距離遠、能穿透障礙物，而為人們所青睞。它們還能高速輸送信息。無線網絡可以每秒傳輸160~300兆比特的地方，空白頻段能每秒傳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.

在美國，最適合承擔（遠程信息傳輸）這一任務的頻率——覆蓋傳統電視撥號52台至69台的700兆赫——已經於2008年拍賣給了幾家移動電話公司。其中，Verizon，AT&T和其他幾家為了“濱海產業”出資近200億美元收購了無線頻段。700兆赫以下的空白頻段免費，向無認證的公眾開放。

Do you want to play in my bandwidth?
用用我的帶寬如何？
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.

空白頻段應該用來解決大眾使用無線網絡時的帶寬問題——越發龐大的消費群體通過無線方式，在互聯網上下載電影、電視劇和其他視頻文件，而不再以傳統的網線、衛星信號或電視直播的方式得到這些資源。

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，占用帶寬最大的是從Napster和其他對等式網站下載音樂鏈接的電腦用戶。而如今，用戶更傾向於通過亞馬遜、iTunes和Hulu下載整集電視劇（通常擠占音樂帶寬達14倍），從Netflix下載排名靠前的電影（擠占音樂帶寬110倍）。對於這個用戶規模膨脹擠占帶寬的局麵，無論蘋果、安卓智能手機還是平板電腦（如iPad），都難辭其咎。

What if Wi-Fi radio beams stretched for several miles?
一旦Wi-Fi信號輻射到幾英裏以外呢？
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.

除了能解決帶寬方麵的問題，空白頻段還可能掀起一場無線革命，規模比十年前那次突破性的創新狂潮還要大得多。那時，Wi-Fi、藍牙和其他無線技術都使用無認證的2.4千兆赫帶寬，這個帶寬以前都是留給微波爐和車庫遙控器用的。一些內部人士甚至談論用空白頻段提供“第三管道”，以在互聯網領域同有線信號和電視信號展開競爭。

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.

微軟公司已開始試驗性地僅用兩根空白頻段的天線，取代幾千個Wi-Fi基站，覆蓋它在華盛頓州雷蒙德市的園區。有了可以覆蓋如此大範圍的空白頻段，超市、商場、甚至地方市政部門都可以用它將互聯網服務免費地（含廣告讚助）提供給消費者和當地居民，人們將通過它上網，或在智能手機及其他設備上使用 Skype、Google+（或別的什麽）打免費電話。

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.

這是幻想嗎？絕對不是。盡管還存在技術瓶頸，但空白頻段裝備的“企業水平”部分已開始運作，不同應用方式的商業試驗將貫穿2012全年。人們過多久會去購買100美元的空白頻段家用路由器？較主流的觀點是最遲不過2015年。

Nick Valéry: Difference Engine columnist, The Economist