WhichVoIP Blog

Voice over Wireless LAN, or VoWLAN as it is referred to, has been getting a lot of publicity recently.

What is VoWLAN?  In simplistic terms this is VoIP but over WiFi or Wireless IP.  Many households have WiFi these days just due to the convenience of accessing the Internet, especially those with laptops.  Sit in the living room watching the basketball game on the TV and surfing the web and with no CAT5 Ethernet cable or the likes getting tangled up with your bottle of beer.

How nice would it be if you had the same flexibility with your telephone.  Yes with cordless phones we have this already….well kind of.  You still need to have the base connected to the VoIP ATA or the POTS line if you have the old fashioned form of telephony   Yes the technology up until now has definitely been of the wired variety.

VoWLAN gives you additional freedom.  Here your WiFi enabled VoIP phone will talk directly do your WiFi router wirelessly.  Many providers are now releasing such phones in the marketplace or frantically designing one to release imminently as this is likely to be a huge market over the next year.

However, there are some technical drawbacks with this technology that should be brought to your attention.  All of these can be overcome but may be of interest to you.

The fundamental problem is the way that the packets are handled.  The beauty of Internet Protocol is that the packets sent over the Internet backbone can be voice, video or data.  It does not matter, they are made up of packets of digital bits and sent across the Internet to their destination.  However, all packets are not the same.  Data packets such as web browsing tend to be large packets often over 1000 bytes at a time.  Voice packets tend to be significantly smaller, often as small as 30 bytes depending on the codec used for the voice compression.

Now with the various OSI stack layers used to send data and voice over the Internet, each layer adds overhead packets that define protocols, source and destination addressing, checksums for error correction and the likes.  When the actual voice packets are so small to begin with this ends up making the data transmission very inefficient due to the extra overhead, often as bad as 30% (e.g. 100 byte packet but only 30 bytes of actual voice information). 

Why is this such a bad thing?  Well, the WiFi Media Access layer tries to give each station on the network equal access and gives no consideration to the time each station has during its access time.  Therefore, because the voice packets are so small compared to the data packets a lot of time is spent by the VoWLAN phones backing off and waiting to transmit the next voice packet.  Now VoIP is very much reliant on low latency and low jitter.  This environment does not suit it well at all especially when many Data nodes are trying to access the WLAN at the same time.  The result, if not managed properly, is reduced system capacity and poor voice quality.

Another issue is the distance from the WiFi access point.  The further away you are the lower the signal strength and the lower the transmission rate needs to be otherwise the signal to noise ratio takes a serious hit and some of the voice packets can be lost.  The lower the transmission rate the longer it takes to send the packet and the more hold-offs required by the stations on the WLAN.  Again the voice quality can suffer and of course the system capacity.

It’s not all bad news.  The VoWLAN providers have worked hard at resolving these issues or at least limiting their effects.  The upside is the lack of wires and equipment needed in your home and the portability of your voice and data network.

I hope this has given you some insight into the world of VoWLAN. 

Interested in buying a WiFi VoIP phone, check out our hardware section for more details:

http://www.whichvoip.com/voip/voip_business_hardware.htm

Any of you using this technology at home or at work now - we would love to hear about your experiences, please add a comment below?

Andy

Technorati Tags: VoWLAN, Wireless IP, Wireless VoIP, VoIP

This entry was posted on Tuesday, February 27th, 2007 at 10:25 pm and is filed under VoIP Residential, VoIP Business, Broadband, General, Techie Corner. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.