A Survey of Bandwidth Optimization Techniques and Patterns in VoIP Services and Applications <s> Parameters Value <s> We discuss techniques for voice activity detection (VAD) for voice over Internet Protocol (VoIP). VAD aids in reducing the bandwidth requirement of a voice session, thereby using bandwidth efficiently. Such a scheme would be implemented in the application layer. Thus the VAD is independent of the lower layers in the network stack (see Flood, J.E., "Telecommunications Switching - Traffic and Networks", Prentice Hall India). We compare four time-domain VAD algorithms in terms of speech quality, compression level and computational complexity. A comparison of the relative merits and demerits along with the subjective quality of speech after the pruning of silence periods is presented for all the algorithms. A quantitative measurement of speech quality for different algorithms is also presented. <s> BIB001 </s> A Survey of Bandwidth Optimization Techniques and Patterns in VoIP Services and Applications <s> Parameters Value <s> We discuss techniques for voice activity detection (VAD) for voice over Internet Protocol (VoIP). VAD aids in saving the bandwidth requirement of a voice session, thereby increasing the bandwidth efficiently. We compare the quality of speech, level of compression and computational complexity for three time-domain and three frequency-domain VAD algorithms. Implementation of time-domain algorithms is computationally simple. However, better speech quality is obtained with the frequency-domain algorithms. A comparison of the merits and demerits along with the subjective quality of speech after removal of silence periods is presented for all the algorithms. A quantitative measurement of speech quality for different algorithms is also presented. <s> BIB002 </s> A Survey of Bandwidth Optimization Techniques and Patterns in VoIP Services and Applications <s> Parameters Value <s> In packet voice communication systems, silence suppression algorithms are employed to achieve bandwidth efficiency by suppressing the inactive part of the speech. In this paper, we consider a Nortel fixed-point silence suppression algorithm to investigate means of reducing the computational complexity with a little or no loss in the performance. In view of the compact structure and superior performance of the existing Nortel algorithm, certain modifications are introduced without altering the structure of the original design. Based on these modifications, two algorithms are proposed. Results from objective and subjective quality tests show that the performance of each of the two modified algorithms is comparable to that of the Nortel algorithm. As for the average computational complexity, simulation tests based on TMS320C5402 DSK show that reduction of about 40% and 22% can be achieved for the two modified algorithms. <s> BIB003
Mean Duration of ON-Period (1/α) 352ms Mean Duration of ON-Period (1/β) 650ms With the adoption of ITU-T G.729A and B, numerous silence suppression algorithms have advanced with the objective reducing substantially the load on communication channel, by decreasing to a large extent (40-60%) the number of voice blocks generated by the codec  ,  thereby enhancing performance. Conversely, performance is not only the crucial issue, implementation complexity is a much an issue. The probable solution of which is; provisioning lowcomplexity silence suppression algorithms among other needs BIB003 . Consequently, appropriate features of VAD that makes better silence suppression schemes include; Good Decision Rule, A physical property of speech which when exploited yields stable and precise decision in categorizing fragments of the signal into silence or otherwise. Adaptability to Background Noise, this improves sturdiness, particularly in wireless mobile telephony. Low Computational Complexity, required for efficiency in real-time applications by BIB001 and BIB002 . One potential solution is presented in BIB001 , comparing VAD algorithms for VoIP applications. The submission is based on efficient VAD scheme used for VoIP systems. The time domain VAD algorithms were seen to be computationally less composite, despite speech quality deterioration in comparison to frequency domain algorithms. The frequency domain algorithm is observed to sustain better immunity to low SNR compared to time domain algorithms. These outcomes informed the proposition of some VAD algorithms whose test outputs demonstrates the unfailing superiority of Comprehensive VAD scheme above all other schemes. Its lead over others is seen in better speech detection and noise immunity, although their still exist performance degradation under low SNR conditions, it is yet a better option for real-time applications BIB001 .