topic Re: open area Coverage in Wireless

open area Coverage

eng_elshreef — Sun, 04 Jul 2021 04:17:07 GMT

I need to get wireless coverage for outdoor open area , the distance between AP and location needs to have wireless coverage is 250m.

I put the design to use AIR-ANT2410 antenna .

I found in another post that the client can see the signal but the laptop or the mobile can’t send enough power to reach the AP .

https://supportforums.cisco.com/thread/2107854

So please help if I shall concern about this issue or not .

Re: open area Coverage

Scott Fella — Thu, 22 Dec 2011 13:24:47 GMT

The reason the other post mentions that is because of the client. You have to take a look at the wireless client.... if they TX and RX is 50mW and antenna is 2dbi for example, how far could this device send its information. Using a yagi on one end and having a client with an external yagi would work, but not an internal wireless card in a laptop.

Re: open area Coverage

Kayle Miller — Thu, 29 Dec 2011 14:13:24 GMT

A rough calculation says that a completely open space, no obstructions, no vegitation, means that over the 250m distance you would lose approx 88db of signal power as a result of Free Space Path Loss. so as Scott stated the issue is not on the AP side but on the client side. Many portable client devices today have a maximum transmit power of 25 to 50 mw and many now have a 0dbi antenna at best it would be a 2.2dbi antenna.

So for a quick look lets determine the EIRP of the client device in both scenarios

50mw = 17dbm

17dbm + 2.2dbi = 19.2dbm

17dbm + 0dbi = 17dbm

so over the distance of 250m this device would yield an RSSI of roughly

19.2dbm - 88db = -68.8

17dbm - 88db = -71

25mw = 14dbm

14dbm + 2.2dbi = 16.2dbm

14dbm + 0dbi = 14dbm

so over the distance of 250m this device would yield an RSSI of roughly

16.2dbm - 88db = -71.8

14dbm - 88db = -74

So depending on the receive sensitivity and no other obstructions you maybe able to get a low data rate connection; but if you start to add in other obstructions, climate, and things like that you may find that you can't make the link work since obstructions can add as much as 12db of additional loss. which would make the numbers look like this

19.2dbm - 88db -12db = -80.8

17dbm - 88db -12db = -83

16.2dbm - 88db -12db = -83.8

14dbm - 88db -12db = -86

Hope this helps explain it.

Re: open area Coverage

dschlicht — Fri, 30 Dec 2011 05:38:41 GMT

I have an outdoor deployment using that antenna that covers distances you require. Yes clients will extend coverage or decrease ultimately. Only way to determine properly is to do a survey.

Thinking more, the deployment I speak of isn't a single ap. it is 2- 1300's, one with the antenna acting as ap, and another at the property line on the far side that is bridge/ap which covers that area. This is deployed at a landscaping company where their property is covered with small/mid sizes trees/bushes/etc. the clients are all handheld devices for staff to take real time orders from customer.

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