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saenito
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receive sensitivity for metal 2

Thu Jan 03, 2019 12:36 am

Hello, how can i know the receive sensitivity for metal 2 at 1mbps? mikrotik webpage only shows at 6mbps
 
mistry7
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Re: receive sensitivity for metal 2

Thu Jan 03, 2019 4:47 am

please explain for what you need this.
With signals weaker then -90 you would not be able to transport anything serious
 
saenito
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Re: receive sensitivity for metal 2

Thu Jan 10, 2019 11:58 pm

please explain for what you need this.
With signals weaker then -90 you would not be able to transport anything serious
128kbps using a mobile device would be serious?

so why basebox 2 has a receive sensitivity of -100 at 1mbps while metal 52 ac has a receive of -97 if weaker than -90 is useless? Then the receive sensitivity is not a factor to choose between basebox 2 (tx 30dbm) , metal 52 ac (tx 31dbm) and metal 2 (tx 32dbm) regarding distance achieved using a mobile device?

disregarding the cpu mhgz of these devices for this question of course.
Sorry for the dumb question, im still begginer on this topics
 
mistry7
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Re: receive sensitivity for metal 2

Fri Jan 11, 2019 11:50 am

please explain for what you need this.
With signals weaker then -90 you would not be able to transport anything serious
128kbps using a mobile device would be serious?

so why basebox 2 has a receive sensitivity of -100 at 1mbps while metal 52 ac has a receive of -97 if weaker than -90 is useless? Then the receive sensitivity is not a factor to choose between basebox 2 (tx 30dbm) , metal 52 ac (tx 31dbm) and metal 2 (tx 32dbm) regarding distance achieved using a mobile device?

disregarding the cpu mhgz of these devices for this question of course.
Sorry for the dumb question, im still begginer on this topics
If you calculate with these values, you will end up with nothing working.
WiFi is not a protocol type with works fine at low end, if we need small Bandwidth link, eg for Sensor Info, we only deploy with minimum signals -80
 
mkx
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Re: receive sensitivity for metal 2

Fri Jan 11, 2019 4:03 pm

There are a few things to consider:
  • there's receiver's receive sensitivity. I suspect it somehow has something to do with own noise figure (i.e. self-inducted noise) and if signal strength is lower than this figure, receiver won't be able to pick it up.
  • there's noise floor ... the overall noise present at receiver's location. Could be only thermal noise (at something like -110dBm @ 20MHz channel width, related to Boltzmann's constant and absolute temperature) or it could be much higher if there's some (mostly man-made) interference in the air
  • there's signal strength ... of the signal that actually makes the connection between AP and client

and then there's

  • SNR ... signal to noise ratio, which actually defines achievable data rate. It is defined as ratio between signal strength and (interference + noise + anything else disturbing signal).

    Let's say that for decent service needed SNR is 20 or better.
    Now, if receiver is "in the middle of nowhere" with only thermal noise around, the base for SNR will be receiver's sensitivity. If receiver's sensitivity is -87dBm, then decent signal strength will be -67dBm. If receiver's sensitivity is -91dBm, then decent signal strength will be -71dBm.
    If, on the other hand, the receiver is in the middle of wifi-infested street with noise floor of -80dBm, then decent signal strength will be -60dBm.

    I somehow suspect that stated receiver sensitivity figures for RB devices already include the necessary SNR, but then I also suspect that used noise figure of receivers is slightly optimistic.

For even better service one needs higher SNR, hence higher signal strength.

In some cases communication is possible even with negative values of SNR (e.g. in CDMA or even in LTE), but the service is less than decent by consumer-grade standards. Military-grade standards define usable service slightly differently :wink:.
BR,
Metod
 
saenito
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Re: receive sensitivity for metal 2

Sun Jan 13, 2019 5:29 am

Thanks to all

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