More level headed analysis of VoIP over 3G
I’ve been saying for years that 3G is not suitable or scalable for VoIP communications, but it’s great to see Gigaom being level headed about the lack of VoIP services over 3G and going beyond the usual conspiracy theories. There were some things in Om’s article that needs to be clarified. Skype’s VoIP payload is 6 to 40 Kbps (depending on quality), but we need to add another 23 Kbps of packet header overhead so it’s more like 29 to 63 Kbps. That doesn’t sound like very much and one would think that we could fit a lot of Skype calls on a 3G network.
The problem is that the 3G data network isn’t really suitable for VoIP because of the latency and jitter, and the scheduling might not be optimum for handling concurrent VoIP or Skype usage. Even on a really fast 802.11g Wi-Fi network with 24 Mbps of usable payload throughput which should theoretically handle 250+ calls, it only handles about 8 simultaneous VoIP calls in reality because the number of random collisions between the VoIP streams become unbearable once there are more than 8 active VoIP users. Standards like 802.11e which is the QoS standard for Wi-Fi can help double or triple the caller capacity, but it’s still nowhere near as efficient as the wireless networks designed for cell phones.
I don’t understand the desire to want to use VoIP on 3G networks. That seems to me like wanting to use a network to stream TV over IP when a digital coax connection that is already in place will do.
They want to bypass the minute charge on the voice circuit. Skype wants this because then they’d be racking up the minute charges using the Telco’s wireless infrastructure.
I didnt know that it was even possible (except for sip applications on the iphone). interesting read…
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