V.8 Signal Analysis Support

The SBC Core includes an option of enabling the “V.8” detector on each DSP channel for V.34 fax.  The V.8 detector is responsible for detecting the early signaling protocol used for setting up high speed modem and high speed fax sessions.This allows the SBC to determine if a call is modem or fax, and then process the call accordingly.

To enable V.8 detector, set T.38 protocol version to “3”. The CLI syntax is shown below . Refer to Packet Service Profile - CLI  and Media Profiles - Packet Service Profile (EMA)).

% set profiles media packetServiceProfile <unique_profile_name> t38 protocolVersion 3

The V.8-capable calling fax machine or a calling data modem, starts the V.8 signalling by sending a CM (Call Menu) signal in response to an ANSAm signal (amplitude modulated 2100 Hz with phase reversals) from anwering fax machine. Physical layer for CM is ITU-T V.21 FSK modulation using lower channel (980 Hz for mark and 1180 Hz for space). ANSAm signal is generated by answering fax as well as modem telephony terminals, as a result SBX cannot determine precise intent of this call merely by analyzing ANSAm. This is possible by analysis of CM because CM contains an information field called "call function" which clarifies capability and intent of the calling terminal.

V.8 signal analysis module in DSP demodulates the CM and decodes the demodulated bits to learn about calling machine capability and intent. When enabled, V.8 module, determines if the CM is from a V.34 data modem, a Super G3 (V.34) fax machine or a group 3 fax machine and passes this information to call processing layer software so that call processing software then can take appropriate actions such as initiate a transition to T.38 protocol to support fax or initiate a transition to G.711 codec to support modem, based on packet service profile configurations.

V.8 Detector for SPS100 Card

The table below list the number of voice channels with and without V.8 on SPS100 per card:

V.8 Detector for DSP20 Card

The table below lists the number of voice channels with and without V.8 on DSP20 per card:

V.8 Detector for DSP25 Card

The table below lists the number of voice channels with and without V.8 on DSP25 per card:

V.8 Detector for DSP-LC Card

The table below lists the number of voice channels with and without V.8 on DSP-LC per card: