Agilent Technologies N2620A - Manual (Page 125)

Voice Testing with the FrameScope Pro 3
N2620A User’s Guide 107
Core Services
Audio input and output
The Megaco/H.248 Voice Test captures the environment sound
or speech as well as the playback network audio data received.
The supported audio format is 8 kHz-16 bits-Mono.
Call setup and call control
The Megaco/H.248 IP Phone MG implementation supports two
operating modes.
• Active mode - acts as an IP phone MG and initiates calls to
other phone via the MGC on demand
• Passive mode - acts as an IP phone MG and answers incoming
calls from other MGC
Data transmission and receiving
The Megaco/H.248 uses the RTP stack (RFC 1889 or RFC 3550)
to transmit and receive audio (speech) data over UDP only.
Voice quality measurement
During the VoIP transactions, RTCP (RFC 1889 or RFC 3550) is
used to exchange QoS information among the senders and
receivers. Some of the information, such as the total packet
sent, inter-arrival jitter, packet loss ratio, and network
round-trip delay, will be displayed as the reference of the voice
quality.
R-Factor or MOS calculation
During the VoIP transactions, the R-Factor (Network-based) and
MOS (CQE) values are periodically calculated based on the
RTP/RTCP and audio codec information collected (such as the
packet loss ratio, inter-arrival jitter, round trip delay, and used
audio codec). The result is displayed to indicate voice quality.