Wireless Access

Is there a simple formula for calculating cell size for client access?  IE AP-xx with ant-xx and client radio xx in  flat open environment with negligible non-rf energy would be a xx db signal at xx feet?  

 

I have a <another vendor> guy who tells me always use a 150' cell size for client access in a mesh environment using a ~max 25 dbm ap signal going to a ~4 db 2.4 ghz omni antenna.  Since that s roughly the same as a ap-175 and an ant-2005, wouldn't that be the same?

 

*Insert discaimer that nothing is ever 100% the same even using identical equipment in the same environment except on opposite sides of a building and there never is a cookie-cutter solution...yadda..

 

The design "guides" and VRDs don't exactly spell this out, and when clients need to install poles for APs I'd like to not completely WAG a solution, and have it operate poorly.  My customer uses the normal-ish laptop clients, and baar code scanners, and would like to implement RFID at some point, which I believe means many more APs.

Signup for the Outdoor planner here:  https://outdoorplanner.arubanetworks.com/index.cfm?

I have used it.  It isn't very predictive.  I have a situation where I need to place AP 175s on the exterior of a building with 2005 antennas for 2.4 ghz client access, and accurately place additional APs on poles where a 2.4 ghz client (laptop, motorolla barcode scanner, etc.) can actually use them.   I know the distances and ranges and estimated signal strengths for point to point mesh wireless, but clients have such lower powered antennas, and useable client cell size shrinks and I don't know what that size needs to be.

The solution has modeling for both point to point and client radio applications. You can even specify the client power.

Yup, I understand that.  Thanks.  I'm still confused on how to illustrate the usable client area?  If I limit it to only...say -70 db signal strength at client, that circle is too large to be realistic.  The client might be able to see a -75 signal at 800 feet away, but the AP will never hear back from the client at that range.

 

I tried checking only the through-put upstream @ 15 mb.  This is a smaller circle but still 355 feet.  355 feet seems too big to be an  accurate client coverage cell?

The Global Client Parameters will allow you to define the types of clients that will be connecting:

 

In open space, and with directional antennas, it is possible to connect at that distance.  You can uncheck the rates you do not want to connect at in Google Earth and your radius will diminish accordingly.

 

Yes, I did that part.  The client manual says 100 mW which is a 20 db antenna.  I wanted to be conservative, so I left it at the 802.11g default of 15 db.  I did not select antenna gain.  For the radios on the APs, I deactivated the A radios (current AP 175 APs are already mounted on buildings).  I enabled the G radios as ant-2005 (Omni antennas).  

 

When you say "uncheck the rates you do not want to connect at in Google Earth" do you mean for example the "through-put upstream @ 15 mb"?

 

Thank you for your assistance by the way!

The outdoor planner, with regard to mesh link AND client modeling is indeed accurate, as we base the coverages and antenna patterns on real-world range testing. I would suggest you snag the outdoor planner user guide and look through the sections on design margin. The deisgn margin section pertains to setting a 'headroom' based on the environment type. If you are not changing those values from the default, the planner is assuming complete and clear line of sign from the client to the AP, which in that case can go pretty far. 

 

For client coverage, I usually use design margins of 9-12dB average, 15 if I know there will be lots of obstructions. From the same page you set your client type models, 15dB for HT20 should be fine for laptops. If you are modeling for phones and tablets I would go lower. After that, you set your AP, bands, antennas, headings and downtilts, etc and usually assume max power of the AP, but you can change this as well. After that is where you select your client data rate and mesh link SNR and Data Rates. I think the default SNR starts with -55 and steps up in 5dB increments, which is really unrealistic. I usually us -75 or -78dB and do 3dB step down increments (-78, -75, -73,-70, -67) which is a more realistic client SNR for larger range outdoor deployments. Same for data rates, the default start with 60Mbps for HT20, which is useful only in close range. I like to do 5Mbps, and step up in 5Mbps increments up to max of 25Mbps.

 

Note that the planner takes in to account the AP power output and the client power output and figures out bidirectional rates and SNRs based on the link budget you design above. So you will see in many cases the downlink speeds are faster than the uplink speeds since usually the APs are 'louder' than the clients. 

 

If you just want to build a flat-rate assumption of client range versus throughput, you can model that yourself with the planning tool, and use multiple placemarks to represent different AP and antenna configurations. But the planner is as realistic and accurate as the data put in to it. If you want to send out the KMZ you are working with, I can look at it and offer any suggestions.

As a separate note, we do real-world range testing with clients (laptops, tablets, and phones) using real-world devices (Intel 6300, iPhone 5s, Galaxy 3, etc) out to 400m (1200ft) usually. See attached graphs showing some testing on the MSR2K using the 2005 and 5005 antennas on an Intel 5300, iPad2, and iPhone 4 in both 2.4Ghz and 5Ghz, showing 10Mbps or faster at 400m. We find that most clients past 400m start to really drop in performance, mostly due to ACK timeouts...

 

Edit - Clear Line-of-Sight between client and AP

To add further if you really want to improve the range of your outdoor clients AND make installations easier, faster, and cheaper, you would use our AP-275 mounted on the sides of the buildings with the integrated omnis. Mesh support will come around August time frame within AOS 6.4.

 

50Mbps down and 20Mbps up at 600 meters (1800ft) using nothing more than a 11ac macbook pro!

Is there a way I can email you the kmz file?  I am pretty sure the customer would not want it out on the forum.

You can PM me the file...or email to jhoward -at- arubanetworks -dot- com.

Thanks so much for assisting.  This is a lot of fun, albeit stressful to get right.  

 

For my latest model I set the client design margin to 10, disabled the A radio (only using this test as 802.11g client cell size calculation anyway), the client snr values to 78-67.  This left me a circle for 15 mb upstream at 300'.  This sounds much more reasonable.  This is for a "lay-down yard" at a manufacturing facilty and there will be some stuff stacked outside.  

 

How much does the fact that the client want to possibly equip passive RFID tags out in this "lay-down yard" change the design scope?

Note that passive RFID for RTLS outdoors is notoriously inaccurate. Far far better to use GPS tags outdoors. The only time RFID outdoors is OK is if thei don't mind wide ranging accuracy ranges.

Are there any published studies showing RTLS/RFID usage outside is not quite ready for prime time?

I cannot speak to slides, but RTLS depends on high access point density to work well.  Outdoors is the complete opposite of that.