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I know this is basic but...

/* referring to a device with integrated features */

Let modem be:
a modem/router/access point device

We have a cheap modem from our ISP with an internal antenna. Unfortunately, it's weak (the signal seems to be directed upward the gadget). We are planning on getting a strong modem (or at least an AP). After giving it some thought, if the modem wasn't able to reach the laptop, how likely is it that the laptop can not reach the modem either? So replacing the modem with a stronger one isn't really a solution because only the new modem will be able to reach the laptop but the laptop won't be able to communicate back?

If so, what would be a better solution?

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migrated from serverfault.com Dec 24 '12 at 16:41

This question came from our site for system and network administrators.

3 Answers 3

You've said the solution in your question, if the current AP device is inferior, you need a new, proper AP.

While asymmetric device communication is theoretically a problem with wireless (think of when your cellphone gets full bars, but the tower can't hear your phone... no connection), I don't think I've ever seen that problem with WiFi. The AP's antenna should be sufficient to receive signals from at least as far as it can transmit them. I'd imagine a design that didn't take that into consideration would be pretty crappy.

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Exactly. A router with better transmitting antennas will have better receiving antennas as well. –  David Schwartz Dec 24 '12 at 23:58
    
hmm....good point. But how did "stronger" external wireless adapters get into the market? –  WikiWitz Dec 25 '12 at 4:03
    
Bigger/better/more antennas. –  Bigbio2002 Dec 25 '12 at 4:36

Wifi is nothing more than radio carrying data rather than voice, It should behave like any two way radio, if you want it to hear and talk better more power can help yes but higher gain antennas boost the transmit as well as receive, get some bigger antennas.

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You can calculate it by Friss formula

enter image description here [1]

  • Pr is the received power
  • Pt is the transmitted power
  • Gt and Gr are the antenna gains
  • the last part is the free space path loss where you can calculate the distance, lambda is the wave length and R is the distance

If you check the datasheet of the equipment that you are using, you can find the all these values then you can decide how if your devices are good enough and how far you need to place them. Also note that the formula uses free space path loss, you should consider there might be signal attenuation due to the obstacles (wall ,etc.) and multipath effects.

Here is a friss calculator: http://www.daycounter.com/Calculators/Friis-Calculator.phtml

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