VOIP Over Wide-Area Wireless: A Tricky Proposition
Sprint Corp. (NYSE: S) and Verizon Wireless will be deploying EVDO Rev A in the 2007 time frame. Rev A primarily features a faster uplink, but it also includes provisions such as QOS that will enable VOIP. However, that doesn’t mean that the operators will roll out VOIP right away. That will take another year or two as there are a lot of additional items required to make VOIP work.
What Qualcomm aptly showed was that to deliver high-quality, low-latency voice in IP at the equivalent (or slightly higher) spectral efficiency of current circuit-switched approaches is going to require extremely sophisticated communications protocols and voice processing. First there is packet header compression, as otherwise you’re sending 20 bytes of IP header information for every 22 bytes of VOIP payload. Robust Header compression knocks this down to 4 bytes. Then there is the elimination of PPP framing overhead, QOS implementation, de-jitter mechanisms, and items called smart blanking and time warping to recover from low-level bit loss.
Qualcomm and other vendors are actively working on these areas. Until all these capabilities are baked into the broadband wireless technology itself, any VOIP usage will be of significantly lower quality, and will consume far more bandwidth than existing voice services. Similar efforts will be required to make VOIP a reality for technologies such as UMTS and WiMax. It’s going to be the end of the decade before you see widespread VOIP over wide-area wireless networks.
— Peter Rysavy is President of Rysavy Research . Special to Unstrung