Alvarion Technologies Ltd. BMAX-BA36 Manuale Utente

274

BreezeMAX Modular Base Station System Manual

Appendix B - Defining Service Profiles for Generic VoIP Gateways

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 = 87.2Kbps

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: