50 Android smartphones + ASUS RT-AC5300

[niemion]

I am working on a project where 10-50 Android smartphones are going to connect to a ASUS RT-AC5300 and live stream video from a server also connected to the router. The bitrate per phone is 6 Mbps.

50 x 6 Mbps = 300 Mbps
The room is 150 m2 - full line of sight

Is there a tool that can help us simulate up to 50 Android devices (lower class 1x1 radios) connected to the ASUS RT-AC5300, at a particular bitrate?

When do you expect the number of connected Android devices to become the limiting factor at 6 Mbps each?

 

[System Error Message]

android sdk, you can have as many virtual android devices running as you like.

its not a question of when but more of how little interference there is, how much computing power you have. The android virtual device can use quite a bit of CPU so it is unlikely a single quad core PC is fast enough to have 50 devices on it.

using android virtual devices, simulates having a client but not the radio. You would have a single wireless radio that would be connected to a virtual switch. This is different from having 50 1x1 wireless cards as despite emulating more cards it still counts as 1 physical card so in terms of performance with the AP it is the same as 1 physical card. You will need to get 50 cards/android phones instead. However using virtualisation and with many many cards you can pull it off especially if you fill up all your usb ports with usb wifi cards.

when you reach past a certain number of NICs and have sufficient compute power, it becomes a question of how the AP handles clients. Some APs dont use the CPU rather the micro controller in the NIC to handle clients while some use software and CPU instead. APs like the netgear r7000 and mikrotik routerboards have been known to handle more than 100 clients at a time, not sure about asus though however the typical hardware limit is 32 clients per chip, that means that the AC5300 can handle 96 clients using all 3 radios.

 

[wouterv]

Do the Android devices support 802.11n or 802.11ac (that gives a major difference in throughput)?

 

[niemion]

They are Samsung Galaxy S7, so yes, they should support ac:

Wi-Fi 802.11 a/b/g/n/ac, dual-band, Wi-Fi Direct, hotspot

 

[sfx2000]

Might run into some problems with airtime with 50 clients... and if I recall, there is a hard limit on the number of IP's that will be shared out via the dhcp processes...

Try it and see - you'll know if you hit hard limits when adding clients and older clients start getting dropped.

 

[drabisan]

I have no experience with AC5300, but I have some (lots of) experience with enterprise class APs. From both most important vendors plus a couple of small ones.
50 concurrent streams will fail even if all clients are AC with good/excellent signal.
It's simply too much air time usage! At best you may expect some clients to be dropped randomly because they can get to confirm the control packets in time.
The channel will very likely get busy all they way to 100% and at that moment anything that can happen wrong will happen!
You can get into the math and calculate/estimate channel usage if you know the average packet size of the video stream, add beacons and confirmations (you can approximate one confirmation per client per each packet), or you can run some tests. If the stream is a multicast one, that would be a different story, you don't have to count one airframe per client, but you still have to count the ack.

We've done some presos in the past and it was reliable all the way to 12-15 clients, all laptops running on AC not battery and each one doing a 1080p unicast streaming. But even that pushed the channel utilization up to 100% so there was little/no space for more clients. And having an absolutely clean wireless environment, even in 5GHz, is far from trivial, but it can be done.

 

[wouterv]

With RT-AC5300 you can (shall) divide the 50 phones over the two 5 GHz channels, 25 on each.
Regarding the previous reply: I don't think Multicast will save airframes, I believe the router will still handle every client individual and sequential.

 

[niemion]

Thanks everyone.

sfx2000 and drabisan, you both mention airtime / channel utilization. How do I best monitor airtime utilization on the RT-AC5300 while adding Android devices one at a time?

Let's say that I hit a limit at 12 clients (as suggested by drabisan's findings), would adding four or five AP's solve that issue? And which AP's would you pick in this case for live video streaming?

 

[drabisan]

You'll need a spectrum analyzer and a considerable experience to measure and optimize channel usage. And it's not a very expensive investment, but worth doing only if you're going to pursuit a career in wifi.

If you can afford time, you can do some testing to find the limits - an AP in as clean as possible environment, keep adding clients until things start going south. If you don't see any SSID on or near the frequency you choose, you can consider it's a clean environment. That in 5GHz. In 2.4 there's no way not to have large number of neighbor SSIDs.

If you need more clients than one AP can support, you just find another clean channel and add a new AP. Maybe a different SSID so it will be easier to allocate the clients.

 

[niemion]

keep adding clients until things start going south...

There is no monitoring software that can help analyze channel utilization? And no readings in the router itself?

just find another clean channel and add a new AP...

Can you recommend an AP for live video streaming?

 

[drabisan]

1. It's not only about software, you need a device to "understand" radio waves better than a normal wireless adapter can. That's why there's no build-in solution on any ordinary router/AP.
2. Live streaming is not a huge deal actually. It's only about bandwidth and less about roaming. And bandwidth is a combination of AP and client capabilities. For ex: if you have the best possible MIMO AP with 2x5GHz radio but 1:1 clients with aggressive power management, you will have far less useful bandwidth than with 2:2 clients that don't care about battery life.

There's no one place shop for what you're looking for. You need to measure and run tests for your requirements and decide what's best for your demo.

 

[sfx2000]

One of the nice things that Asus has done is to enable the QBSS load stanza in the beacon frame - this shows number of client stations associated, and the channel utilization... this can help with determining overall loading (it's not the only indication, but it's good for a quick glance)

Depending on what tools are on hand (screenshot below is from WiFi Explorer on Mac) - Wireshark can show this as well from a wireless PCAP file...

 

[drabisan]

Wireshark on Windows with a disclaimer - you can't capture by default wireless frames in Windows. You need some 3rd party ndis drivers that may or may not function properly on every possible wireless adapter.
Or a Linux or a Mac - either are capable of this with no complicated additional steps.

Good point with channel utilization in beacon! I didn't knew that!

 

[sfx2000]

The other thing to consider in this application/use case is that spreading loss is a 10LogR function - it's not linear...

Consider it is like a hockey stick - high rates close to the AP, and the fringe will be very low rates - and depending on the transport, if you need to ack frames sent, this takes up time (the airtime concerns I mentioned earlier).

While the AP might have decent Tx power (25 to 30 dBM), most mobiles are down in the weeds with 16 to 20 dBM Tx power, and antennas that are not conducive to long range compared to a laptop... Most handsets are focused on near range performance (think bluetooth as an example, as this is shared with WiFi in both bands), so antenna gain on the phones tends to be -3 or worse...

 

[sfx2000]

Wireshark on Windows with a disclaimer - you can't capture by default wireless frames in Windows. You need some 3rd party ndis drivers that may or may not function properly on every possible wireless adapter.
Or a Linux or a Mac - either are capable of this with no complicated additional steps.

Good point with channel utilization in beacon! I didn't knew that!

Certain Broadcom NIC's with Acrylic WiFi (and the bundled driver) will support Wireshark pcaps for post processing...

 

[sfx2000]

Good point with channel utilization in beacon! I didn't knew that!

WiFi Explorer does this in real-time, which is quite nice...

 

[drabisan]

WiFi Explorer does this in real-time, which is quite nice...

Just it's Mac only, while I'm a Ubuntu user.
So
sudo iw dev wlan0 interface add mon0 type monitor flags otherbss
sudo ifconfig mon0 up promisc
sudo iw dev mon0 set channel

are my good friends

 

[RMerlin]

One of the nice things that Asus has done is to enable the QBSS load stanza in the beacon frame - this shows number of client stations associated, and the channel utilization... this can help with determining overall loading (it's not the only indication, but it's good for a quick glance)

Depending on what tools are on hand (screenshot below is from WiFi Explorer on Mac) - Wireshark can show this as well from a wireless PCAP file...

View attachment 8747

I wish I had the BCM documentation, cause I bet this could be queried by the router itself through ioctl. Would be a nice information to display on the webui.

 

[hotsauce2007]

well, I dont know if it´s gonna help you but I did some extreme tests over here:

Lan Party Internet Test:

ASUS AC68 x 3 in 5Ghz Media Bridge
35 Devices / 8 PCS / 12 CELLPHONES / 3 TABLETS / CONSOLES AND MORE...
400MB / 200MB ISP SPEED

LAN SPEED 1GIGABIT / CAT6A FURUKAWA

 

[sfx2000]

I wish I had the BCM documentation, cause I bet this could be queried by the router itself through ioctl. Would be a nice information to display on the webui.

Not sure if it would percolate up the stack back to Linux - might be worthwhile reviewing the header files and see what's there in the broadcom driver...