主题：【IT新闻】下一代Wi-Fi无线网络什么样 -- 802.11n简介 -- Highway
家园 【IT新闻】下一代Wi-Fi无线网络什么样 -- 802.11n简介 现在的Wi-Fi无线网络够快吗？108MB的Wireless设备现在已经非常普遍了。虽然在实际应用中Wi-Fi并没有这么快，但是对于广大用户来说，802.11a/b/g都已经More than enough了！
外链图片需谨慎，可能会被源头改但是Wi-Fi的厂商并不这么想，这不，下一代的802.11n正在酝酿之中，可能在2006年就会正式出台。
802.11n将使用4G Hz左右的频率，比现在的2.4G快一倍。理论传输率为250MB，实际可用传输率也高达175MB(现在的802.11g实际可用传输率大概是25MB左右)。怎么样，够快吗？
我过，我倒是对这越来越快的Wireless有一点疑问：这种辐射对人体有害吗？大家都知道长时间使用手机会对大脑有损害，那么成天沐浴在这种高强的Digital信号中，我们的身体会受到损害吗?
[SIZE=4]802.11n: Next-Generation Wi-Fi[/SIZE]
Tired of pokey 802.11g wireless performance? September is slated to bring the first comprehensive look at what is likely to be the future of Wi-Fi: 802.11n. On the 13th, in Berlin, the Institute of Electrical and Electronics Engineers' (IEEE) 802.11n Task Group (TGn) will consider official proposals from numerous companies on what the specifications should be for the next-generation proposed standard, which promises speeds fast enough for an influx of new wireless applications. Although a ratified standard isn't expected until late 2006, the first wave of 802.11n products could arrive in the first quarter of 2005. "There's a good chance you'll see products by then that will be software upgradable to the 'n' standard," says Mary Cramer, strategic marketing manager at Agere Systems. In the past, users―and consumers with home networks in particular―have purchased early products well in advance of ratification of Wi-Fi standards. Agere Systems founded TGn Sync, one of the most powerful consortiums scheduled to deliver a proposal in Berlin. Cisco, Intel, Nokia, Nortel, Philips, Sony, and many more companies are members. TGn Sync's proposal gives a glimpse of how much impact the 802.11n standard may have on everything from digital homes to wireless offices. "We're focusing on 40-MHz channel bandwidth [double the current 20-MHz bandwidth], backward compatibility with 'a,' 'b' and 'g,' and shooting for a data rate of 250 Mbps with actual throughput of around 175 Mbps," says Cramer. To put that in perspective, 802.11g has a quoted data rate of 54 Mbps, but actual data rates are about half that. "Many of our member companies said we need speeds at least four times faster than current Wi-Fi performance to get people to upgrade," Cramer adds. Multiple-input, multiple-output (MIMO) antenna technology is key to how TGn Sync intends to boost speeds. "Many of the highest hopes for the standard rest on getting that in there," says Mike Wolf, senior analyst at Instat/MDR. Cramer adds that increased range may make it feasible for an 802.11n-based home to have just one inexpensive access point. So what applications might go on in an 'n' home? Cramer and Wolf point to multiple wireless video streams, many kinds of analog connections giving way to digital ones, and lickety-split large file downloads. It's not too early to keep an eye out for the next generation of Wi-Fi.
家园 Wi-Fi的辐射应该没有手机厉害 手机发送的无线电波一般需要能够到达机站（Basestation），而机站一般在几公里到几十公里以外，因此辐射会比较强，（但是是否真的有损健康，我仍然持怀疑态度）。
而Wi-Fi则一般是工作在局域网上，信号只需要传送几米到几百米的范围，因此Wi-Fi设备发射的无线信号功率比手机应该小很多，就对健康的影响也应该小很多。
家园 我不是EE出身，所以是外行。但我觉得辐射强度和功率关系更近，而不是 传输距离。比如微波炉发射距离并不远，但由于功率很大，所以它的危害是最大的。所以人们建议离微波炉远一些，因为泄露出来的些许辐射都是比较危险的。
手机功率很小，所以它的危害我认为不是由于传输距离远造成的，主要是由于紧贴大脑，距离太近照成的。
Wi-Fi的辐射又多大，我没看到过专门的介绍，只是隐约有些担心！
家园 恩，怪我没有讲清楚 辐射强度当然是和发送功率有直接关系. 但是发送功率又和需要传送的距离有直接关系。
由于空间的衰减，无线电波传送到距离发射点距离D的位置以后，接受点的信号功率P1与距离D的关系是
P1 正比于 1/ (D^k) （1）
k是一个常数， 一般为2-4之间的一个数字，具体大小取决于空间传输特性，比如是在乡村，还是城市，是陆地还是水面，遮挡物体的多少，天晴还是下雨等等。
如果忽略接收端设备的灵敏性的话，若需要传送的距离是R, 要在接受点有同样的信号功率，发送者的功率和距离R的关系是：
P2 正比于 R^k （2）
其中P2 是发送功率，R是需要传送的距离
手机因为靠近脑部，所以如果造成影响，也比离开脑部较远的设备大得多，其原理就是公式（1），同样原因，离微波炉远一些， 可以减少受到的辐射。