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Required channel bandwidth reference

Frame size
20 msec 30 msec 40 msec 60 msec 80 msec
transfer cost
(EasyChannel protocol)
12000 Bit/sec 8000 Bit/sec 6000 Bit/sec 4000 Bit/sec 3000 Bit/sec
transfer cost
(H.323 protocol)
16000 Bit/sec 10656 Bit/sec 8000 Bit/sec 5328 Bit/sec 4000 Bit/sec
bandwidth
(GSM6.10 codec)
(13000)**
25000 Bit/sec
(29000 Bit/sec)*
19000 Bit/sec
(24000 Bit/sec)*
16000 Bit/sec
(17000 Bit/sec)*
bandwidth
(G.723.1 codec)
(6400)**
14400 Bit/sec
(17056 Bit/sec)*
10400 Bit/sec
(11728 Bit/sec)*

* - stands for H.323 protocol (unparenthesed values refer to AMSD EasyChannel)

** - nominal bandwidth (without TCP/IP expenditures and like).

Transfer costs commonly include:

  • 20 bytes of IP header;
  • 8 bytes of UDP information;
  • Voice transmission protocol header (2 bytes for AMSD EasyChannel and 12 bytes for H.323).

Bandwidth is shown unadjusted by VOX (silence suppression). Echo cancellation and silence suppression may reduce voice traffic by 15 to 20% without any QoS penalty (speech fragmentation).

For instance, GSM6.10 codec and AMSD EasyChannel protocol with 40 msec frame size yield 19000 - 19000*1/5 = 15200 bit/sec bandwidth.