Live Chat Software by Kayako |
Knowledgebase: Digital Phone Services
|
What is the bandwidth usage for GSM?
Posted by Nicky Smith on 28 June 2010 08:24 PM
|
|
|
GSM codec is indeed 13.2 kb/s (kilobits per
second). However when you want to
send the codec data across an IP network, it's going to increase the
used
bandwith. When dealing with voice you don't want to introduce too much latency. That's why the default latency choice, for example, is to send voice frames every 20 ms. Now that means that we have to send 50 frames a second. When you divide 13.2 kb/s by 50 it'll give 33 bytes. That is sending 33 bytes of voice data per one frame. But that's not it yet. You have to add IP header (20 bytes a packet), UDP header (8 bytes a packet) plus if you're using RTP protocol (with SIP/H323)(12 bytes a packet) or IAX (4 bytes a packet). So, if you add all the overhead you end up with 29.2 kb/s (with RTP protocol) or 26 kb/s (IAX protocol). Now if you're using Ethernet you have to add Ethernet header. | |
 (146 votes) This article was helpful This article was not helpful |
|
Comments (0)