Wireless enterprise-grade phones have existed for many years. Just about every company that makes regular PBXs or digital phones manufactures a wireless phone, but for some reason, wireless phones never gained the popularity in the enterprise space that they enjoy in the residential space. After all, who doesn't have a wireless phone in their house? Perhaps it's because of cost, or a technical issue like the number of users in an office or maybe users just prefer to use their cellular phones when mobility is desired. In any case, I find it interesting that so many new companies are making wireless VoIP phones now.
Justification and popularity aside, if you're considering one of these new phones, there are a number of technical issues you may want to address before deploying them. Foremost is that there really isn't a standard for QoS on the shared airwaves. This creates a lot of problems because it seems every vendor has their own proprietary system, and with some, voice tends to dramatically decrease the bandwidth available to data applications. In most wired environments, your data traffic can use all of the bandwidth that isn't being used by voice. i.e. dataBW == totalBW – voipBW. Apparently, in many 802.11 environments, that presence of a VoIP call, can reduce available bandwidth by as much as 2/3rds. That's pretty scary. Again, know what you're getting into.
One thing you might want to consider, if your environment isn't too large, or if
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you have extra money lying about, is overlapping networks. That is, have data flow across one set of WAPs on one frequency, and have your VoIP devices on a separate network of WAPs using a different frequency. This would work similar to the popular "voice VLANs" and may potentially get around the performance issues encountered when they're mixed. Of course, at this point, you may ask, "why not just use legacy non-VoIP wireless phones?" Why not, indeed.Thomas Alexander Lancaster IV is a consultant and author with over 10 years experience in the networking industry, focused on Internet infrastructure.
This was first published in January 2004