Wireless Access

Hello.

Here is a simple scenario.

 

There is a room 4*8 meters (one AP fits it) with 30 devices.

Let's think all devices have 1 antenna 5GHz adapters 802.11n. No dual band.
Bandwidth for every user must be at least 20 mbps (real TCP speed), not slower.

How many IAP's should I have for this room?
What IAP's?
Why?

 

Here is what I think.
30 users * 20mpbs TCP = 600 mbps TCP
600 mbps TCP * 2 = 1200 mbps channel layer speed (marketing speed).

 

IAP-103 has 2x2:2 antennas.

1 antenna is 150mbps. So the speed is 300mbps per IAP.

 

1200 / 300mbps per AP = 4 AP

4 APs in a room for 20mbps speed per user.
Is it right?

What application is being deployed?

What are the capabilities of your clients?

 

How many users can be on an access point is dependent on the application, not necessarily the speed. Applications like web and email can easily share bandwidth and are fairly tolerant of congested areas.  You can fit many of those users on an access point (30 or even more) comfortably if it is deployed correctly.  Wireless VOIP, on the other hand is very delay sensitive, and you can only have about 12 to 15 users on an AP maximum.

 

WLAN traffic is very bursty, so most users will get on the network, get their traffic and then remain idle; the traffic is normally not sustained, so your math should not really include the total traffic for all those users, because rarely does everyone transmit at the same time.

 

In addition, due to the half duplex nature of wireless, a client that associates at 600 megs rarely gets 300 megabits in throughput if that is the only client on the access point.  As more users get on, it is divided up from there.

 

Again, what is your application that you are deploying with dictate how many users you can host.

cjoseph, thanks for the reply.

> What application is being deployed?

1. The most important is skype video-conferencing. It is not used all the time but when it is used, it must be good. It is business critical app.

2. HD video watching. It is not used all the time but when it is used, it must be good.

3. Most of the time it is web-based apps like office365, dropbox-sync, etc.

 

> What are the capabilities of your clients?

About 10 vaio notebooks support 2.4 GHz, AR9285-like adapter

About 10 notebooks are mac air or pro. Support 5GHz MIMO.

The other 10 are mobile devices like iphone or ipad.

 

The goal is to design a really stable wifi-infrastructure. Without any excuses. Is it possible? The people are tired of unstable wifi. They want their 20 mbps (when they need) and stable video and audio conferencing.

Okay.  I would honestly say 2 access points in that space.  3 tops.

 

Regardless of how many people are in the room, they will be ultimately limited by your internet bandwidth.   What is your ISP speed?

 

 

Thanks, cjoseph.

 

1. The ISP speed is 100 mbps.

2. The other question is - what APs should I use and why? 103? 110-series?

HI Ilmik,

 

Honestly speaking, avg datarate rate can not be constant ( 20mbps) all the time. it depends on various factors. but you can achieve a decent speed if you plan and deploy WiFi by choosing suitable APs. in your scenario AP110 (High-performance 802.11n) AP is suitable but need to be careful on location and position of deployment.

 

Is your ISP speed static or dynamic, if it is static you should be able to chive your targeted speed.

Thanks, dhanraj_puduchery

>  in your scenario AP110 (High-performance 802.11n) AP is suitable

But why 110 and not 103? - the client will ask.

What the high-performance is? Is it processor speed or just 1 more antenna?

How to calculate the right performance?

If the customer is mainly concerned about speed, they should get the 892.11ac AP 225. It will handle speed as well as density without compromise. If they get an 802.11n AC, they cannot be guaranteed the highest speed now or in the future. Their needs could change or increase.

cjoseph, thanks

But if the client devices have only 1 antenna without MIMO, what IAP is better?

Does this 3x3:3 radios really matter?

I would also weigh in that the customer probably won´t have only 1 stream 802.11n clients 3+ years from now. I would pitch the client 802.11ac and motivate it with future proofing their infrastructure better than 802.11n.

 

Due to your 100Mbit internet connection you will hardly see any use of drawing 600Mbit TCP through it. Although you motivate putting 2x IAP-205 in there to cover two different channel pairs and gain hardware redundancy and torelate higher client density.

 

Is this only a one room deployment or are there many more rooms like this that will also need wifi?

Christoffer, thanks.

As I mentioned before, they have about 10 VAIO notebooks with AR2985 adapters.

As i know it supports only 1 stream.

Specifications: http://www.qca.qualcomm.com/wp-content/uploads/2013/11/AR9285.pdf