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802.11n & Voice

Nearpoints
Nearpoints
Nearpoints
8/31/2007

3:00 PM -- Sure, faster/better/cheaper drives high tech. Improving price/performance is the jacks-or-better to get into (or stay in) the game. 802.11n is faster and better and cheaper, and those are the obvious reasons why it’s going to be so successful. 11n improves every dimension of the WLAN experience -- or does it?

One thing that is sometimes forgotten in networking and communications is that real-time media doesn’t really need “faster,” assuming that the sustained bit rate achieved yields acceptable performance in terms of audio and/or video/visual quality. Faster, of course, has a beneficial effect on capacity, but making an individual stream faster doesn’t buy anything for that stream.

In addition, real-time media suffers from the relatively large amount of overhead associated with individual IP packets and .11 frames. Generally, media involves fairly small packets, meaning the packet and frame header overhead is proportionally greater here. Given the additional overhead in setting up each transfer, and the guard interval involved in cleaning up afterwards, .11n may not contribute as much additional capacity as one might think. This is not to say that .11n won’t become dominant in voice-over-WiFi and other media applications; it will. But this will primarily be due to the broad availability of components and the commonality in infrastructure and clients that otherwise contribute to better bandwidth utilization.

— Craig Mathias is Principal Analyst at the Farpoint Group , an advisory firm specializing in wireless communications and mobile computing. Special to Unstrung

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wap545
wap545
12/5/2012 | 3:03:21 PM
re: 802.11n & Voice
As a service provider we look very favorably on deploying 802.11n based products in our customers Enterprise markets as well as in our Mesh Networks. Initially in the backhaul (5Ghz) space (QoS and low Latency) and eventually in and for Access using both the 2.4 & 5Ghz based 802.11n systems.
VoiceIP and P2P type demands on our Public & private Mesh Networks will require the 100+Mbps capability of these new radios.

Jim
wirelessfreak
wirelessfreak
12/5/2012 | 3:03:21 PM
re: 802.11n & Voice
Craig,

I think there are definitely issues with 802.11n and voice. Of course, many things can change as .11n becomes more common, but looking at it today - what about:
1) battery life and 802.11n if it is incorporated into a handset (similar to Apple's argument against 3G for the 1st gen iphones)
2) impact of 802.11n used in 2.4GHz since handsets most commonly supporting b/g only - whether it is you or your neighbor taking up two channels in 2.4GHz there isn't much space in this band
Net Worthy
Net Worthy
12/5/2012 | 3:03:15 PM
re: 802.11n & Voice
In a controlled indoor environment, where there is little interference from outside sources (other Wi-Fi systems, microwave ovens, wireless security cameras), VoWLAN works fine. SpectraLink's proprietary voice solution, for example, works well when there are no other sources of voice-priority WLAN traffic. SIP-based handsets are now starting to support call admission control, which is vital for good voice quality.

Move that same VoWLAN system into a less controlled environment, such as an urban multi-tenant office building, and there is too much interference for voice to work reliably. Move the system outdoors to a metro Wi-Fi network and the interference problem gets even worse. No amount of admission control and QoS can help when your VoWLAN system is competing with other VoWLAN systems for the same spectrum.

802.11n improves throughput for high bit rate traffic and for multiple consecutive packets sent between a source/destination pair. Neither of those apply to voice.

If Wi-Fi (802.11a/b/g/n) is used over licensed spectrum then scheduled channel access in the form of HCCA can be used. But licensed spectrum ain't cheap, and cheap is the main reason to use Wi-Fi.
farpoint
farpoint
12/5/2012 | 3:03:01 PM
re: 802.11n & Voice
I don't think power will be that big an issue because most .11n voice handsets won't initially use MIMO. They'll get by with space-time block coding (STBC). And they'll work in 20 MHz. channels, so 2.4 GHz. is OK, especially if you're willing to support n and g is the same channel simultaneously.

Thx. Craig.
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