Nera WiLink-I 3000, System Manual

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204 WiLink-I Modular Base Station System Manual
Appendix -
B.5 1 POTS Advanced VoIP G.711 Service
Profile
B.5.1 Service Characteristics
¢ G.729 codec, 20msec sample interval
¢ 1 POTS
¢ T.38 Fax
¢ DSCP priority marking behind the SU is used, with the following values:
¯ 63: RTP traffic
¯
26: RTCP and VoIP traffic
¯
0: Data traffic
¢
Single media stream to support Call-Waiting
B.5.2 Voice RTP BW Calculation
The required bandwidth for a G.711 call (64 Kbps codec bit rate) with RTP and
160 bytes of voice payload is:
Total packet size (bytes) = (Ethernet of 18 bytes) + (IP/UDP/RTP header of 40
bytes) + (voice payload of 160 bytes) = 218 bytes
Total packet size (bits) = (218 bytes) * 8 bits per byte = 1744 bits
PPS = (64 Kbps codec bit rate) / (1280 bits) = 50 pps
Note: 1280 bits = 160 bytes (voice payload) * 8 bits per byte
Bandwidth per call = total packet size (1744 bits) * 50 pps = 87.2 Kbps
B.5.3 Voice RTCP BW Calculation
RTCP BW is 10% of RTP: 10 % of 87.2 Kbps is 8.72 Kbps.
B.5.4 T.38 14,400 Kbps Fax RTP BW Calculation
The required bandwidth with a 20 msec sample interval is as follows: