WiFi遠傳紀錄

看來這個話題會持續延燒下去，在此開個檔案做個紀錄。

話說上次WiFi遠傳100km的新聞沒有實作數據，沒想到後來還真有人持續此實驗，將WiFi遠傳距離的紀錄不斷更新。

1. 原文：The old record was 310 kilometers. Swedish scientists made a link between a balloon and an Earth-bound station. We say "apparently" on Pietrosemoli's record, in case someone out there has set a better record about which we are unaware. [3]
[Justin's note]
第一個紀錄是由瑞典科學家締造，遠傳310公里。工法是利用熱氣球將WiFi的設備架在熱氣球上與地面站通訊，這是一個很聰明的作法，熱氣球在高空很容易對準地面站，或者由地面站使用天線追蹤技術來鎖定，而且短時間的相對移動不會太快。

如此說來，那下次建議太空人不妨將WiFi帶上太空梭，與地面站試連，可能可以輕易打破400公里以上的遠傳紀錄。:)

2. 原文：Researcher Ermanno Pietrosemoli has set what appears to be a new record for the longest communication link with Wi-Fi.

Pietrosemoli, president of the Escuela Latinoamerica de Redes (which means networking school of Latin America) established a Wi-Fi link between two computers located in El Aguila and Platillon Mountain, Venezuela. That's a distance of 382 kilometers, or 238 miles. He used technology from Intel, which is concocting its own long-range Wi-Fi equipment, and some off-the-shelf parts. Pietrosemoli gets about 3 megabits per second in each direction on his long-range connections.[3]

[Justin's note]
- 根據筆者的計算(方法與無線電波50公里連線的挑戰相同)，El Aguila與Platillon Mountain的高度必須都在2860公尺以上，這點日後查證。

- "Pietrosemoli gets about 3 megabits per second in each direction on his long-range connections."這句話中的"各個方向"實在耐人尋味，382公里是一個比台灣南北還長的距離，LOS連線後隨時可能因為天線的小小偏移而失連，因此兩點間只可能一個方向而已，筆者實在不知道文中所指"各個方向"是什麼意思。

- 無論310km或382km，傳輸頻寬都是3Mbps,這是很值得留心的數據。不知純粹與信號強度有關，或者delay也會成為頻寬的理論限制？

- 文中不斷提到使用Intel增強型WiFi技術，筆者實在很好奇，"Intel增強型WiFi技術"的實際內容到底是什麼呢？最遠傳輸的理論限制又是多少呢？

(老實說，這樣無止境地WiFi遠傳競賽，實在有點無聊呢。sorry, Intel.)

Ref:
[1] 癮科技Engadget; Posted Jun 19th 2007 10:00PM by Atticus Wu
[2] Engadget英文網站,Posted Jun 19th 2007 7:01AM by Nilay Patel
[3] CNET: New Wi-Fi distance record: 382 kilometers, June 18, 2007,Posted by Michael Kanellos.
[-] 感謝Kun-yi的提醒。

070716r2版本