Tuesday, March 27, 2007

Who's ready for VoWLAN?

A cheery hello from the warming North (so now Leo can stop bragging about Florida). As the weather has turned more conducive to outdoor activities, I have noticed more and more mesh customers are starting to ask about voice over wireless. Similar to its Voice over IP sibling, voice over wireless has been plagued by misinformation, bandwidth issues, and usability concerns. However, VoWLAN is around the corner and several handset makers are already making 802.11 or dual-mode handsets. Cisco has two 802.11 phones. The first one, the 7920 suffered from design and performance issues, but those problems were corrected with the 7921. It would behoove us to understand what the early problems were and why I believe that VoWLAN will soon be a reality.

First off, I am not talking about Skype, Vonage or any of those types of service if used on your computer. They do fall under the category of VoIP and subsequently VoWLAN, but I want to deal with the more impending issue of talking AND walking. Currently, you can open your computer at any wireless hotspot, fire up skype and talk to your friends- it's not that big a deal. As long as there is enough bandwidth and some measure of Quality of Service (don't worry, there usually is), you'll be fine.

Since people like to use their cellphones so much, there is going to be a booming market (unless the cell carriers try to block it) of VoWLAN phones. However, the issue is not how to do the call and be able to talk to someone, but instead, how do you walk around the city while staying on that same call? Remember, for people to consider this a success and have widespread adoption, the call quality and reliability must rival that of cell phones (which, even with all the dropped calls and static have come a long way in the last few years).

In mesh deployments, Cisco currently does not support VoWLAN, because we have no way of guaranting the level of service. However, as dual-mode phones and phones with a/b/g radios become more prevelant, we are going to see consistent levels of service. Most of these phones are going to play in the 802.11a radio spectrum, and with the enhanced abilities of fast roaming (a topic which must be discussed in the future), we can have clients roam from AP to AP and not drop packets. With the 1500 AP, we have tested it on courses with cars in excess of 100mph staying connected to the network and easily hopping from AP to AP. The issue of roaming has been the one thing holding back VoWLAN. We have been able to do it in office buildings for some time because there are few areas without coverage and people did not need to roam off one AP to another. Outdoors it is a different matter entirely

In addition to roaming, great strides have been made in offering quality of service through wireless. Similar to the wired network, we can tag frames and give them special priority through the controller. So while it is true that all packets and frames are competing for the same space, some of those frames are getting more help.

In conclusion, it is not a crazy idea that you will be talking on a phone outside that will not be linked up to a cell tower but instead to the coffee shop network. Phones that are both cell phones and wi-fi phones are already hitting the market, but are going to take off once wireless mesh networks really start to take off. We shall be covering mesh networks in a later segment- but for now, allow your thoughts to entertain VoWLAN..

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