Nera WiLink-I 3000, System Manual

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202 WiLink-I Modular Base Station System Manual
Appendix -
B.4 1 POTS Basic VoIP G.711 Service Profile
B.4.1 Service Characteristics
¢ G.711 codec, 20msec sample interval
¢ 1 POTS
¢ No Fax
¢ Priority marking behind the SU is not used: All VoIP related traffic is classified
onto a single Continuous Grant (CG) connection.
¢
Multiple media streams to support Call-Waiting: If the traffic exceeds the BW
allocated to the CG connection, the SU may request to double the allocated
BW.
B.4.2 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 = 87.2Kbps
B.4.3 RTCP BW Calculation
RTCP BW is 10% of RTP: 10 % of 87.2 Kbps approximately 8.7 Kbps.
B.4.4 QoS Profile
The calculated bandwidth required for RTP traffic is approximately 88 Kbps. To
accommodate for other traffic types, such as RTCP (up to 8.7 Kbps), Voice
Signaling (up to 2 Kbps) and Data (Device Management), we allocate to it a total
bandwidth of 108 Kbps (equivalent to a Packet Size of 2160 bits, or 270 bytes).
The SU may request twice this BW so it will be allocated with up to approximately