AN2834 Freescale Semiconductor / Motorola, AN2834 Datasheet - Page 10

• Manufacturer Part Number: AN2834
• Description: AN2834, Packet Telephony Automatic Level Control on the StarCore SC140 Core
• Manufacturer: Freescale Semiconductor / Motorola

Conclusion
Table 3 summarizes the test results, along with the corresponding test controls and test conditions. A sinusoid
wave with a frequency of 1004 Hz was selected as the test signal. The tests indicate that selecting different signal
types does not affect the results.
5
ALC is an important application in packet telephony systems for monitoring and adjusting the transmit signal level
to improve voice quality over the communications network. The ITU-T G.169-compliant ALC design described in
this application note takes into account all the current ALC requirements and provides a clear mathematical
formulation of the problem for a successful implementation on fixed-point architectures. The ALC design was
efficiently implemented and extensively tested in real-time on the Freescale StarCore-based MSC8101 DSP,
requiring less than 0.3 million cycles per second (MCPS) on average. The ALC device was validated in
conjunction with a carrier-class network echo canceller. The tests were based on standard ALC testing equipment
and included both objective and subjective assessments. No apparent speech quality degradation was identified
during real-time tests, and no interference was observed on such signaling tones as DTMF, TTY, and facsimile
communication, which demonstrates that the proposed ALC device is adequate for standard ALC digital telephony
applications and can be used as a foundation for future extensions of the ALC specification.
6
[1] G. A. Hellwarth and G. D Jones, “Automatic Conditioning of Speech Signals,” IEEE Transactions on Audio
[2] ITU-T Recommendation G.160, “Voice Enhancement Devices,” SG15, TD13 (WP 2/15) draft 9.1., 2003.
[3] R. A. Dyba, P. P. He, and L. F. C. Pessoa, Network Echo Cancellers and Freescale Solutions using the StarCore
[4] I. Cotanis, “Speech in the VQE Device Environment,” IEEE Conference on Wireless Communications and
[5] ITU-T Recommendation P.82, Method for Evaluation of Service from the Standpoint of Speech Transmission
[6] ITU-T Recommendation G.169, Automatic Level Control Devices, 1999.
[7] MSC8101 Application Development System (MSC8101ADS) User’s Manual, Metrowerks, Inc., 2001.
10
Number
NOTE: X:Y:Z to be read as X for the lower/upper bound, Y for the incremental size, and Z for the upper/lower bound.
1
2
3
4
5
6
and Electroacoustics, vol. AU-16, no. 2, June 1968, pp. 169–179.
SC140 Core, Freescale Application Note AN2598/D, 2004.
Networking, 2003, pp. 1102–1106.
Quality, 1988.
Conclusion
References
7.1.2C
7.1.2A
7.1.2B
7.2B
7.3A
7.3B
Test
Packet Telephony Automatic Level Control on the StarCore SC140 Core, Rev. 1
ECAN
OFF
OFF
ON
ON
ON
ON
–13 dBm0
–13 dBm0
–13 dBm0
–13 dBm0
–13 dBm0
–13 dBm0
Target
Level
Table 3. G.169 Test Results Summary
–29: –5: –39;
Test Conditions
(S
gen
–20: 2: 0;
default;
in dBm0; A
–2.0;
–5.0;
–5.0;
echo
6:6:30;
in dB; T
—;
—;
—;
—;
—;
d
0:10:60
in ms)
—
—
—
—
—
Number
of Tests
11
18
35
9
5
5
Freescale Semiconductor
Number
Passes
11
18
35
of
9
5
5
Rate (%)
Passing
100
100
100
100
100
100