如何使用信号强度计算与 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(因此无法访问 GPS)

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

我想使用至少 3 个固定 wifi 信号(我知道位置的 3 个固定路由器)的信号强度(以 dBm 为单位)

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 已经这样做了，我想知道他们如何根据这些数据找出确切的位置

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

查看这篇文章了解更多详情:http://www.codeproject.com/Articles/63747/Exploring-GoogleGears-Wi-Fi-Geo-Locator-Secrets

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

推荐答案

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.下面的公式可以反映它们之间的关系.

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

根据 Fade Margin 方程，可以使用以下方程计算自由空间路径损耗.

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

自由空间路径损耗=Tx 功率-Tx 电缆损耗+Tx 天线增益+Rx 天线增益 - Rx 电缆损耗 - Rx 灵敏度 - 衰减余量

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

通过以上两个自由空间路径损失方程，我们可以找出距离，单位为公里.

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

菲涅耳区是无线电波在离开天线后扩散到的视线周围的区域.您需要清晰的视线以保持强度，尤其是对于 2.4GHz 无线系统.这是因为 2.4GHz 波被水吸收，就像树木中的水一样.经验法则是 60% 的菲涅耳区必须没有障碍物.通常，20% 的菲涅耳区阻塞对链路几乎没有信号损失.超过 40% 的阻塞，信号损失将变得显着.

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]

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

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