Panasonic KX-NS500 - Page 319

Required Bandwidth for Each IP Extension Card
To allow
all IP telephones to make calls simultaneously, it is necessary to keep available the bandwidth required
by an IP extension card with the maximum number of IP telephones connected.
Provided below is the formula to calculate the amount of bandwidth required for each IP extension card.
When using the V-IPEXT/V-SIPEXT card:
Required Bandwidth = (Required Bandwidth per IP telephone ´
32)
Bandwidth Assessment for V-IPGW Card
Required Bandwidth for One VoIP Channel
The required bandwidth depends on what combination of codecs and packet sending intervals is used. Keep
in mind
the following points about the type of codec and packet sending interval, in terms of the speech quality:
• The speech quality of the G.711 codec is higher than that of the G.729A codec.
• The shorter the packet sending interval, the higher the speech quality.
• The higher the speech quality the V-IPGW card provides, the more bandwidth the card requires.
Via LAN
Codec
Packet Sending Interval
20 ms 30 ms 40 ms 60 ms 90 ms
G.711 87.2 kbps 79.5 kbps 75.6 kbps 71.7 kbps —
G.729A 31.2 kbps 23.5 kbps 19.6 kbps 15.7 kbps —
Via WAN (PPP: Point-to-Point Protocol)
Codec
Packet Sending Interval
20 ms 30 ms 40 ms 60 ms 90 ms
G.711 84 kbps 77.3 kbps 74 kbps 70.7 kbps —
G.729A 28 kbps 21 kbps 18 kbps 14.7 kbps —
Bandwidth Calculation
Provided below is the formula to find out the amount of bandwidth required for VoIP communications:
Required Bandwidth
= (No. of Fax Machines ´ Required Bandwidth for the G.711 codec) +
[(16 - No. of Fax Machines) ´ Required Bandwidth for Voice Communication]
Example
Consider the following case as an example:
• Communication: via LAN
• No. of Fax Machines: 2
• G.711 Packet Sending Interval: 20 ms (requiring 87.2 kbps per channel)
• G.729A Packet Sending Interval for Voice Communication: 20 ms (requiring 31.2 kbps per channel)
In this case, the required bandwidth will be as follows:
Required Bandwidth
= (2
´ 87.2) + [(16 - 2) ´ 31.2]
= 611.2 (kbps)
Installation Manual 319
8.3.3 Bandwidth Assessment