Wireless Access

I'm working on a new-construction sports arena at the moment, and looking at Wi-Fi AP placement options. See attached floor plan and section of the arena, with our current AP locations. Seating is 100% retractable, so both the pull-out seats and the floor require fairly high density Wi-Fi coverage.

Would it be possible to provide a very rough estimate for the maximum number of simultaneous users that could be supported using our current AP layout? (We’re assuming 802.11ac AP’s). Any help here would be greatly appreciated.

Also, currently we have the AP’s located on the surrounding walls of the arena facing inward. Doing some research I’ve noticed some arenas mount AP’s from the catwalks above the floor seating, so each AP is facing downward above the seats. Do you think that could have any advantage for this installation?

Attachment(s)

Floor Plan.pdf   822 KB 1 version

Section.pdf   398 KB 1 version

This is where you need to start. 

https://community.arubanetworks.com/t5/Validated-Reference-Design/Very-High-Density-802-11ac-Networks-Validated-Reference-Design/ta-p/230891

It likely has everything you need and anything over and above this would likely require a professional services engagement with one of our LPV partners. 

Rough client per AP counts should be in the 75-100 clients per AP neighborhood, but the VRD goes in to this as well. Not knowing how many seats (maybe this is 10-15k seats?), you would need around 100-150 APs. But ballpark, for rough BOM'ing you shoudl scope 75 clients per AP, divide your seating capacity by 75 and round up to the nearest 10-25 (so if you have a 23,500 seat capacity, I would say 325 APs)

All APs firing inwards is a bad idea, that will 100% assure you that you will have to deal with a significant amount of ACI and CCI. Best cases  are under seat AP deployments to allow the human bodies to help in attenuating the RF (creating small cells of RF), or APs above, down firing with narrow antennas, creating smaller cells of RF with a minimal amount of reflectivity. From your floor plan drawing, though, if those are the only APs you have, your WLAN will likely be over-loaded and perform very poorly.

Thanks. Total capacity is only around 5,000 actually, but the seating is all retractable so we can mount beneath the seats. 

The guideline you posted a link to mentions that only venues with seating above ~10,000 typically need external antennas. But given that we can't mount beneath the seats, do we likely need external antennas to control the signal overlap firing downward from the catwalks? (That appears to be our only mounting location without overlap issues)

That drawing looks much bigger, but 5k users, assuming 50% uptake, is 2500 concurrent, and at 75 users per AP you are at 35 APs. If you want the best possible design since under seat is not an option, for the sake of optimal RF, overhead  firing down is your next best bet. Behind users firing inwards means that APs have to hear and listen to every AP in front of them, which even at a 300-400m distance, will be enough to cause issues.

Couple follow questions when calculating capacity per AP, the guide mentions connections per radio of 150 max or 300 max per AP (dual radio). 

1. Can both radios on an AP (e.g. 330 series) handle 5 GHz devices simultaneously on 2 separate channels? (Since there's fewer channels and less overlap at 5 GHz, I assume a few AP's in an high density design will be 5 GHz only to reduce 2.4 GHz interference)

2. Alternatively, is 100 devices per AP assume 50 devices per radio at 5 GHz, or 50 devices at 5 GHz + 50 devices at 2.4 GHz)

3. So with 24 (5 GHz) + 3 (2.4 GHz) non-overlapping 20 MHz channels, the system would max out at 27 radios, or 14 AP's before channel re-use is required in one or both bands. At 75 devices per AP, that's 1,050 devices. 

1) No, is not possible

2) 100 devices per AP, regardless of radio

3) You'll have channel re-use in 2.4GHz on fourth AP, unless counting some 5GHz-only AP's. For 5GHz, depends on what is available for region/country, but going by your example: 25th AP will result in channel re-use. 

Some of those numbers are older and will likely be revised downwards based on the last few years of experience, but if there are pockets where it need to go beyond 100 users, they can, it's just not recommended for optimal performance. 

Ok, so for 100% iPhone users (no MIMO), that's 86 Mbps throughput on 20 MHz channel width. Assume ~40 Mbps TCP/IP goodput seen by each devices.

40 Mbps x 80% max airtime / 75 users = 427 kbps per device.

Is that roughly correct for estimating purposes?

Thos VRDs go deep into estimating per client throughput. Those numbers are generated on the amount of channel reuse as much as it is uptake, interference, numbers of users per AP, etc. Without checking the tables or doing the math, that number looks high though.