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ECHO CANCELLATION IN VOICE OVER IP

 

TITLE ECHO CANCELLATION IN VOICE OVER IP
AUTHOR ITTIPON RASSAMEEROJ
DEGREE MASTER OF SCIENCE PROGRAMME IN COMPUTER SCIENCE
FACULTY FACULTY OF SCIENCE
ADVISOR SUPACHAI TANGWONGSAN
CO-ADVISOR VASAKA VISOOTTIVISETH
CHOMTIP PORNPANOMCHAI
 
ABSTRACT
The emerging technology called Voice over IP (VoIP) has been widely recognized as a rival system against the public switched telephone network (PSTN) in voice communication. Nonetheless, the quality of signal transmission over IP is still a major concern because of echo. Echo is one of the serious types of noise commonly found in VoIP communication. In general, there are two types of echo problems in VoIP, hybrid/network echo and acoustic echo. In this research, an approach to echo cancellation in VoIP based on the packetbased echo cancellation model was employed. In addition, analyze and perform comparative validation specifically in the state of echo canceller as adaptive filtering was done by using two class measurements: mean square error (MSE) and least square (LS) methods. For experimentation, normalized least mean square (NLMS), recursive least square (RLS), least square lattice (LSL) algorithms were applied in the echo canceller. Communication environments, near-end speech, far-end speech, and three difference echo strength levels were simulated. Perform and present nine experiments for each adaptive filter approach with various strength levels of echo, 20%, 50%, and 70% of far-end speech were done. ERLE value was measured for accuracy of echo canceller output. The experimental results showed that the ERLE of the RLS and the LSL gave better figures than the NLMS, but the RLS took more time in processing than LSL. Accordingly, it was concluded that the LSL algorithm is the best of those tried.
KEYWORD VOICE OVER IP / ECHO CANCELLATION / ADAPTIVE FILTER/ LEAST SQUARE LATTICE

 

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