Wireless Access

Hi all,

I'm in the process upgrading our campus with the following:

305 IAPs for offices, classrooms, and corridor areas

335 IAPs for large performance theatres

275 Outdoor APs 

So far I have tested the 305 and 335 model of APs with Ekahau and from the survey results I am perplexed to see that the range of 2.4GHz is "worse" than 5GHz? 2.4Ghz fails to penetrate most walls, but 5GHz seems to do a bit better. I have made sure the APs are well spaced apart and also made sure the old Trapeze APs (which will be taken down once the upgrade is complete) is on a different channel or out of range.

I have checked that radio assignment is set to single-band and not multi-band, i'm presuming this is correct?

Is it just a case that these APs are optimized for 5GHz only?

Has anyone had a similar experience?

Thanks

Must be an issue with the Ekahau models or config.

These APs deliver similar (conducted, per chain) max power in both bands, although regulatory limits may result in different restrictions per band. Antenna gain will be a bit higher in 5GHz (+2dB max), but not enough to overcome the inherent ~7dB "link budget advantage" of 5GHz.

However, be aware that the AP-305 has a 2x2 radio for 2.4GHz, versus 3x3 on 5GHz. That delivers another 2dB. Still not enough to result in more coverage in 5GHz.

In most cases "wall attenuation" is more pronounced in 5GHz than in 2.4GHz, which would againm lead you to expect to see better coverage in 2.4GHz.

What are the RF power settings used by Ekahau?

Hmmm... not sure, i'll check the settings of Ekahau tomorrow morning.

But just to clarify, i'm looking at pure survey results and not the radio planning feature. 

That's an interesting point that 2.4GHz is on 2x2 txpower as opposed to 3x3 on 5GHz. The walls in the building are very thick and dense solid stone and brick so I was anticipating a good amount attenuation and was starting to wonder if these APs were designed for an environment such as ours.

What is your transmit power on each AP?

So on 2.4GHz the EIRP value is set at 9.0 out of a maximum of 19.6 for each AP

On 5GHz it's 18.0 out of a max. of 23.0

And yes I did already try increasing the TxPower on a single test AP to the maximum of 19.6 on the 2.4GHz and as a result the RSSI limit (which I set to -65dBm) increased by about 1.5m to 2.5m at various points in the test location. This is all according to Ekahau survey data, where a thorough survey was carried out allowing me to view results at "super" accuracy and a contour spacing of 1. I surveyed the surrounding areas and some areas outside the building to determine the cell boundary so I'm not relying on any "predicted" results.

In other words there wasn't a significant enough increase of range by boosting the TxPower to the max.

I checked through the settings of Ekahau and couldn't see anything where I can tweak the RF power settings, so I'm assuming you were referring to the radio planner rather than taking survey measurements, but do correct me if anyone knows any better.

You mentioned:

"So on 2.4GHz the EIRP value is set at 9.0 out of a maximum of 19.6 for each AP.  On 5GHz it's 18.0 out of a max. of 23.0"

and

"So far I have tested the 305 and 335 model of APs with Ekahau and from the survey results I am perplexed to see that the range of 2.4GHz is "worse" than 5GHz? 2.4Ghz fails to penetrate most walls, but 5GHz seems to do a bit better"

Are you expecting the EIRP at 9.0 at 2.4ghz to propagate better than an EIRP of 18.0 at 5ghz?

From what I know about Wi-Fi, 2.4GHz should have a longer range and be better at penetrating through obstructions than 5GHz. So yes, even though the EIRP is ~half for 2.4ghz and the 5ghz value is closer to its max EIRP with a value of 18 I would still expect a decent propagation on 2.4ghz.

However, knowing the "difficult to predict" nature of RF as well as varying specs of APs, I didn't want to rely on my expectations only which is why I carried that test on one of the APs. Sorry I should have mentioned that I carried out that test in my initial post.

I think the '2.4 is better at walls' thing is pushed a bit too hard in trainings.

Sure it's true but as you are noticing, results vary in the real world due to a multitude of factors. I have noticed the same.

Not to disparage your design but I would add that if your client and AP are separated by a wall, perhaps that deisgn is not ideal. I suppose you could increase the power levels on 2.4 but the client would still struggle to talk back.

Hi,

Having the min and max EIRP in the 2,4 GHz band with lower values than those in the 5 GHz band is a known strategy to "gracefully" steer the clients towards the 5 GHz band.

My question is: are you desingning the networks to work on both bands or just in one of them ?

/Kevin

Thanks for all your input and thoughts.

So the design is not mine, a consultancy company was hired to carry out the design before I started in my job in this place and am carrying out my own independant checks of their design. It looks to me not much considaration was given to the nature of the buildings we are rolling out in. The Trapeze APs that are being phased out provide a significantly better inter-floor and wall bleed-through on both radios (not to disparage Aruba products).

Out of curiosity, what Aruba AP models would anyone say are best at propagation and penetrating walls, would it be a solution that would require external antennas or are there any decent internal antenna APs?

AP model is irrelevant in terms of RF propagation, once the RF leaves the AP, the RF propagates and is attenuated the same regardless of AP type, vendor, etc.

Also, in response to a previous comment, the 2.4Ghz radio at 9dB and the 5Ghz radio at 18dB will NOT be the same. Every 3dB increase is 2x the power (radio power in dB is logrithmic). As such, even in clear space, the 2.4Ghz radio at 9dB will not propagate farther than 5Ghz at 18dBm. There is more FSPL with 2.4Ghz at 9dB than 5Ghz at 18dB. Couple that with the higher noise floor in 2.4Ghz and it will be worse.