Adaptive time scale modification of speech for graceful degrading voice quality in congested networks for VoIP applications

Ilk H., Guler S.

SIGNAL PROCESSING, vol.86, no.1, pp.127-139, 2006 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 86 Issue: 1
  • Publication Date: 2006
  • Doi Number: 10.1016/j.sigpro.2005.05.006
  • Journal Name: SIGNAL PROCESSING
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.127-139
  • Keywords: quality of service, adaptive time scale modification, adaptive voice communication, wired and wireless access
  • Ankara University Affiliated: No

Abstract

This paper proposes an alternative scheme to variable bit rate (VBR) speech coding for voice over Internet protocol (VoIP) during network congestion in Internet. The proposed scheme is called "adaptive bit rate switching" and ensures that the available bandwidth is most efficiently used. When congestion is signaled, a time scale modification algorithm called WSOLA (waveform similarity overlap and add) with time-dependent compression rate, determined according to the severity of the network congestion, is employed in order to reduce the bit rate required to transmit speech adaptively. This approach is different from VBR speech coding and novel in the sense that the coder operates at any desired bit rate for any desired duration. This is particularly useful in network environments because load may be different at each direction.