Low-Complexity
Network Echo Canceller
by D2 Technologies, Inc.

Software Overview

D2's Low-Complexity Network Echo Canceller (LCNEC) algorithm module is an ITU-T G.165-compliant 
network echo canceller that is designed for echo tails of 16 msec and under.
Designed to the VP Open interface, the LCNEC module easily integrates with other VP Open modules, 
runs in real-time concurrently with other VP Open modules, and handles any number of voice ports 
assigned to the DSP. Like all of D2's algorithm modules, the LCNEC consists of robust software that 
is rigorously tested.

Features and Benefits

•	Meets or exceeds G.165 requirements;  non-linear processing (NLP) and tone disable options 
available via other VP Open modules
•	Low complexity for echo tails of 16 msec and under
•	Operates in fast adapt, slow adapt, and fixed modes;  integrates with D2's tone detector to 
achieve best talk-down performance in the industry
•	Programmable minimum Echo Return Loss (ERL) of 0 and 6 dB

Processor and System Specifications

•	Devices supported: TMS320C2xx, TMS320C5x
•	Processor resource required:
•	Algorithm category: Telecommunications
TMS320C2xx (Est.)
TMS320C5x
Program memory
1 kwords
0.8 kwords
Data memory/voice port
0.3 kwords (tails 16 msec or under)
0.3 kwords (tails 16 msec or under)
Processor loading
worst case
1.7 MIPS (tails of 16 msec and under)
1.5 MIPS (tails of 16 msec and under)

Usage Limitations or Performance Considerations

•	The host, voice data input and output, memory allocation, and module to module communication 
interfaces must conform to VP Open as described in the VP Open Software Interface Specification.

Algorithm Verification

D2's Low-Complexity Network Echo Canceller algorithm module is validated through the following 
suite of tests:
•	Standard G.165 test suite for tails of 8–16 msec and ERL of 6 dB: steady state residual echo 
test, convergence test, convergence in the presence of near end noise, halting of convergence by 
double-talk, halting of convergence by large continuous background noise, leak rate test, infinite 
return loss convergence test, and tone-stability test
•	Voice application tests - single talker, double-talker (far-end first and near-end first), 
reflector change, live two-way conversation, tone-detection (talk down) tests
•	VP Open interface validation – the Network Echo Canceller module is integrated with other VP Open 
modules and tested concurrently in real-time on the D2 VDS50 system for multiple voice ports

Availability

Currently available for the TMS320C5x. A demonstration package is also available for the TI EVM50 
DSP board. The TMS320C2xx implementation will be available 2Q 1996.

Company Background and Contact Information

Contact:	D2 Technologies, Inc.
		Attn:  Product Sales
		104 West Anapamu Street
		Suite J
		Santa Barbara,  CA 93101
		(805) 564-3424
		Fax:  (805) 966-2144
		e-mail:  sales@d2tech.com