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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 phone service. Yes with cordless phones we have this already, well kind of.
You still need to have the base connected to the VoIP ATA. Yes the
technology up until now has definitely been of the wired variety.
VoWLAN gives you additional freedom. Here your WiFi enabled Broadband phone will talk directly do your WiFi router wirelessly.
Many providers are now releasing such digital phone sets 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 used with VoIP (often referred to as Internet Phone, Broadband Phone or Digital Phone service) tend to be significantly smaller.
Often these digital packets are 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 digital 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 digital 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 digital 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 digital 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 digital 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 digital 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 digital 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 digital 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 digital voice and data network.
I hope this has given you some insight into the world of VoWLAN.
Interested in buying a WiFi VoIP phone?
Looking for a VoIP provider?
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