Wednesday, October 8, 2008

VOIP per call bandwidth

Voice Over IP - Per Call Bandwidth Consumption

for VOIP CALCULATOR click Here

Codec Information

Bandwidth Calculations

Codec & Bit Rate (Kbps)

Codec Sample Size (Bytes)

Codec Sample Interval (ms)

Mean Opinion Score (MOS)

Voice Payload Size (Bytes)

Voice Payload Size (ms)

Packets Per Second (PPS)

Bandwidth MP or FRF.12 (Kbps)

Bandwidth w/cRTP MP or FRF.12 (Kbps)

Bandwidth Ethernet (Kbps)

G.711 (64 Kbps)

80 Bytes

10 ms

4.1

160 Bytes

20 ms

50

82.8 Kbps

67.6 Kbps

87.2 Kbps

G.729 (8 Kbps)

10 Bytes

10 ms

3.92

20 Bytes

20 ms

50

26.8 Kbps

11.6 Kbps

31.2 Kbps

G.723.1 (6.3 Kbps)

24 Bytes

30 ms

3.9

24 Bytes

30 ms

34

18.9 Kbps

8.8 Kbps

21.9 Kbps

G.723.1 (5.3 Kbps)

20 Bytes

30 ms

3.8

20 Bytes

30 ms

34

17.9 Kbps

7.7 Kbps

20.8 Kbps

G.726 (32 Kbps)

20 Bytes

5 ms

3.85

80 Bytes

20 ms

50

50.8 Kbps

35.6 Kbps

55.2 Kbps

G.726 (24 Kbps)

15 Bytes

5 ms


60 Bytes

20 ms

50

42.8 Kbps

27.6 Kbps

47.2 Kbps

G.728 (16 Kbps)

10 Bytes

5 ms

3.61

60 Bytes

30 ms

34

28.5 Kbps

18.4 Kbps

31.5 Kbps

Explanation of Terms

Codec Bit Rate (Kbps)

Based on the codec, this is the number of bits per second that need to be transmitted to deliver a voice call. (codec bit rate = codec sample size / codec sample interval).

Codec Sample Size (Bytes)

Based on the codec, this is the number of bytes captured by the Digital Signal Processor (DSP) at each codec sample interval. For example, the G.729 coder operates on sample intervals of 10 ms, corresponding to 10 bytes (80 bits) per sample at a bit rate of 8 Kbps. (codec bit rate = codec sample size / codec sample interval).

Codec Sample Interval (ms)

This is the sample interval at which the codec operates. For example, the G.729 coder operates on sample intervals of 10 ms, corresponding to 10 bytes (80 bits) per sample at a bit rate of 8 Kbps. (codec bit rate = codec sample size / codec sample interval).

MOS

MOS is a system of grading the voice quality of telephone connections. With MOS, a wide range of listeners judge the quality of a voice sample on a scale of one (bad) to five (excellent). The scores are averaged to provide the MOS for the codec.

Voice Payload Size (Bytes)

The voice payload size represents the number of bytes (or bits) that are filled into a packet. The voice payload size must be a multiple of the codec sample size. For example, G.729 packets can use 10, 20, 30, 40, 50, or 60 bytes of voice payload size.

Voice Payload Size (ms)

The voice payload size can also be represented in terms of the codec samples. For example, a G.729 voice payload size of 20 ms (two 10 ms codec samples) represents a voice payload of 20 bytes [ (20 bytes * 8) / (20 ms) = 8 Kbps ]

PPS

PPS represents the number of packets that need to be transmitted every second in order to deliver the codec bit rate. For example, for a G.729 call with voice payload size per packet of 20 bytes (160 bits), 50 packets need to be transmitted every second [50 pps = (8 Kbps) / (160 bits per packet) ]

Bandwidth Calculation Formulas

The following calculations are used:

  • Total packet size = (L2 header: MP or FRF.12 or Ethernet) + (IP/UDP/RTP header) + (voice payload size)
  • PPS = (codec bit rate) / (voice payload size)
  • Bandwidth = total packet size * PPS