如何使用Signal Strength来计算Wifi路由器的距离？ [英] How to calculate distance from Wifi router using Signal Strength?

问题描述

我想计算建筑物内移动设备的确切位置（所以没有GPS接入）我想用信号强度（in dBm）至少3个固定的wifi信号（我知道这个位置的3个固定路由器）

Google已经这么做了，我想知道他们是怎么弄出来的确切的位置基于这些数据

查看这篇文章的更多细节： http://www.codeproject.com/Articles/63747/Exploring-GoogleGears-Wi-Fi-Geo-Locator-Secrets

解决方案

FSPL取决于两个参数：一是无线电信号的频率;二是无线传输距离。

  FSPL（dB）= 20log10（d）+20log10（f）+ K 
 
d =距离
f =频率
 K =常数，取决于用于d和f 
的单位如果d用公里表示，f用MHz表示，公式是：
 
 FSPL（dB）= 20log10（d）+20log10（f）+ 32.44 
  

从Fade Margin方程中，可以用下式计算自由空间路径损耗。

自由空间路径损耗= Tx Power-Tx电缆损耗+ Tx天线增益+ Rx天线增益 - Rx电缆损耗 - Rx灵敏度 - 衰落余量

利用上述两个自由空间路径损耗方程，我们可以找出距离。

 距离（km）= 10（自由空间路径损失 -  32.44  -  20log10（f））/ 20 
  

菲涅耳区是无线电波离开天线后传播到视线周围的区域。你需要清晰的视线来保持强度，尤其是对于2.4GHz无线系统。这是因为2.4GHz的波浪被水吸收，就像树木中的水一样。经验法则是，60％的菲涅耳区必须避开障碍物。通常情况下，20％的菲涅耳区阻塞对链路造成很小的信号损失。在40％以上的阻塞情况下，信号损失将变得显着。

  FSPLr = 17.32 *√（d / 4f）
 
d =距离[km] 
f =频率[GHz] 
r =半径[m] 
  

资料来源： http://www.tp-link.com/en/support/calculator/

I would like to calculate the exact location of a mobile device inside a building ( so no GPS access)

I want to do this using the signal strength(in dBm) of at least 3 fixed wifi signals(3 fixed routers of which I know the position)

Google already does that and I would like to know how they figure out the exact location based on the this data

Check this article for more details : http://www.codeproject.com/Articles/63747/Exploring-GoogleGears-Wi-Fi-Geo-Locator-Secrets

解决方案

FSPL depends on two parameters: First is the frequency of radio signals；Second is the wireless transmission distance. The following formula can reflect the relationship between them.

FSPL (dB) = 20log10(d) + 20log10(f) + K

d = distance
f = frequency
K= constant that depends on the units used for d and f
If d is measured in kilometers, f in MHz, the formula is:

FSPL (dB) = 20log10(d)+ 20log10(f) + 32.44

From the Fade Margin equation, Free Space Path Loss can be computed with the following equation.

Free Space Path Loss=Tx Power-Tx Cable Loss+Tx Antenna Gain+Rx Antenna Gain - Rx Cable Loss - Rx Sensitivity - Fade Margin

With the above two Free Space Path Loss equations, we can find out the Distance in km.

Distance (km) = 10(Free Space Path Loss – 32.44 – 20log10(f))/20

The Fresnel Zone is the area around the visual line-of-sight that radio waves spread out into after they leave the antenna. You want a clear line of sight to maintain strength, especially for 2.4GHz wireless systems. This is because 2.4GHz waves are absorbed by water, like the water found in trees. The rule of thumb is that 60% of Fresnel Zone must be clear of obstacles. Typically, 20% Fresnel Zone blockage introduces little signal loss to the link. Beyond 40% blockage the signal loss will become significant.

FSPLr=17.32*√(d/4f)

d = distance [km]
f = frequency [GHz]
r = radius [m]

Source : http://www.tp-link.com/en/support/calculator/

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