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New Contributor
Posts: 1
Registered: ‎07-26-2012

Voice over WiFi improvement

[ Edited ]

I am a Grad student at the University of Texas, McCombs School of Business, Master of Science in Technology Commercialization. I am researching the use of voice over WiFi in an attempt to determine if a new technology will be useful in the wifi market and was hoping that you experts would be able to help. This new technology is a software only optimization solution that has to be deployed at the access-point and the mobile client and can significantly improve the VoIP call capacity. Using both simulations and real-life prototypes they have validated their solution and include frame aggregation, block acknowledgements, and intelligent rate adaptation. My team is trying to determine if there is a need for such a technology and would this technology be useful to hardware manufactures of access points and mobile clients. Below are a few questions to get us started and I’m sure I’ll have more as we discuss this topic.

1. What are the maximum amounts of calls that can be sent over one access point?
2. Is there a pain in the market with the amount of calls that currently can be sent over one access point?
3. Would the market accept a technology that would allow more calls to be sent over one access point?
4. If an access point could provide more calls can the network handle the additional users?

Aruba
Posts: 105
Registered: ‎04-09-2007

Re: Voice over WiFi improvement

Hello Chris, this is certainly an interesting area you are looking at.  One reason is that there are at least two application areas for multi-media over Wi-Fi today.  In hospitals, retail, manufacturing and schools,  we still see a lot of embedded single-mode voice over Wi-Fi handsets such as Polycom/Spectralink (I refer to these as 'conventional' voice over Wi-Fi).  Newer applications are emerging, including UC offerings with variable-rate (wideband) codecs, video calling and PC/tablet/smartphone endpoints, and this is a more varied environment.  I'll respond to your questions:

 

1. What are the maximum amounts of calls that can be sent over one access point?

- You will find disagreement even on something as basic as this.  If you are talking conventional G.711 or G.729 voice, I would use design rules of thumb of ~12 calls on 802.11b, ~24 on 802.11a/g and maybe 25-30 on 802.11n.  The model assumes the phones are connecting at the best rate (e.g. 54Mbps for 802.11a) and there's not much noise or interference.  This is a call-count rather than a user-count, the latter would be a multiple of these figures.  

- For UC applications, where codecs can use hundreds of kbps per call, the figures are obviously lower.  But of course, these are variable rate codecs, so if they see poor conditions they will reduce rates.  Add in different usage scenarios and It's complicated: you need to make reasonable assumptions based on the situation.

 

2. Is there a pain in the market with the amount of calls that currently can be sent over one access point?

- I would say that the conventional applications are well-understood and there is not a pressing need for more calls per AP.  Enterprise WLANs typically have an AP spacing of 20 - 25 metres for good coverage, and you don't normally get enough people in one place and making calls to approach the limits.  Where you do get isolated traffic peaks, there are various load balancing and call admission control mechanisms that take care of it. 

- However, some of the UC applications will be more interesting because of higher bandwidths per-call and situations where a large number of people may want to make calls simultaneously over a single access point.  I haven't come across a scenario where our existing technology is inadequate, but I would not be surprised if one came up.

 

3. Would the market accept a technology that would allow more calls to be sent over one access point?

- If you need software on the AP and software on the client, you will need to interest two different groups of vendors.  This is typically done through the standards bodies, depending on what the software is doing.  If you can find a group of vendors who are convinced there's a need, and that this is a good solution, you will probably find the conversation leads in that direction.  And our industry has a good record of adopting new technologies to respond to market needs.

 

4. If an access point could provide more calls can the network handle the additional users?

- I don't see why not.

 

These answers are my opinions only, and I suspect you will find a divergence of views if you ask around.

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