1. G.711 Codec: It uses Pulse Code Modulation (PCM) to create its digital audio signal. This codec provides the highest call quality but also uses more bandwidth than other codecs. It uses a bit rate of 64 Kbps (kilobits per second), but if you include Ethernet, IP, UDP, and RTP headers, a typical G.711 codec will use approximately 87.2 Kbps of bandwidth per call.
2. G.729 Codec: This lower-bandwidth codec compresses data much more aggressively. It uses a bit rate of 8 Kbps, equating to much less bandwidth. However, the call quality is not as high as G.711. Considering the overhead caused by headers, a G.729 codec will use approximately 31.2 Kbps of bandwidth per call.
Keep in mind that these are per-call numbers. So if you have multiple concurrent calls, you must multiply these figures by the number of concurrent calls to get your total bandwidth requirement.
Also note that these numbers might vary slightly depending on the specific VoIP system and network infrastructure you’re using, including whether any header compression or silence suppression is in place.
G711 = 87.2 Kbps
G729 = 31.2 Kbps
Example 1: 1500 Phones
1. Using G.711:
If you have 1500 concurrent calls, each using about 87.2 Kbps, then the total bandwidth required would be around 130,800 Kbps, or about 130.8 Mbps.
1500 x 87.2Kbps = 130,800Kbps or 138.8Mbps
2. Using G.729:
If you have 1500 concurrent calls, each using about 31.2 Kbps, then the total bandwidth required would be around 46,800 Kbps, or about 46.8 Mbps.
1500 x 31.2Kbps = 46,800Kbps or 46.8Mbps
Example 2: 7000 Phones
1. Using G.711:
If you have 7000 concurrent calls, each using about 87.2 Kbps, then the total bandwidth required would be around 609,400 Kbps, or about 609.4 Mbps.
7000 x 87.2Kbps = 609,400Kbps or 609.4Mbps
2. Using G.729:
If you have 7000 concurrent calls, each using about 31.2 Kbps, then the total bandwidth required would be around 218,400 Kbps, or about 218.4 Mbps.
7000 x 31.2Kbps = 218,400Kbps or 218.4Mbps
Remember, these numbers are for concurrent calls – if not all phones are used at the same time, the required bandwidth would be less. Plus, these calculations don’t account for other network traffic that may be present. It’s also essential to have a network infrastructure capable of managing such loads, with adequate Quality of Service (QoS) mechanisms in place to ensure voice traffic gets priority.