1 / 14

Juan J. Ramos-Muñoz, Angel M. Gómez, Juan M. Lopez-Soler

Signal Theory, Telematics and Communications Department. Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. Juan J. Ramos-Muñoz, Angel M. Gómez, Juan M. Lopez-Soler. Outline. Introduction Basic and Multi-flow Block Interleavers Algorithms Intelligibility Estimation

iona
Download Presentation

Juan J. Ramos-Muñoz, Angel M. Gómez, Juan M. Lopez-Soler

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Signal Theory, Telematics and Communications Department Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver Juan J. Ramos-Muñoz, Angel M. Gómez,Juan M. Lopez-Soler

  2. Outline • Introduction • Basic and Multi-flow Block Interleavers Algorithms • Intelligibility Estimation • Experimental Results • Conclusion

  3. Introduction • Background • Bursts degrade the perceived quality in Voice over IP • VoIP services are extremely delay concerned • Enhanced VoIP services must be subjectively evaluated

  4. Introduction • In this work • We contribute to demonstrate some perceptual benefits that can be obtained by using active routers in VoIP • We propose a new delay-aware interleaver to mitigate the bursty-error-prone nature of IP • We evaluate the service performance by using Automatic Speech Recognition

  5. Basic and Multi-flow Block Interleavers Algorithms • Given and an interleaver is defined by • Basic TypeI(s): to face bursts of length equal to s packets, with the minimum incurred delay, an (s x s) matrix is required • Packets are written by rows, from left to right and from top to bottom. • Packets are read by columns, from bottom to top and from left to right. • Type I(s) maximum interleaver delay is given by • Type I(s) is limited to such that • For typical VoIP values and TypeI(s) is restricted to bursts with length s < 5

  6. Basic and Multi-flow Block Interleavers Algorithms • We interleave packets from different flows to face consecutive losses by introducing a tolerable delay • We use the reference TypeII(nf) and propose TypeII(nf,s) where • nf is the number of available flows and • s is the maximum expected burst length • Round-robin interleaver (TypeII(nf)) is suited for nf≥ s • it requires one (nf x 1) interleaver matrix • to write the matrix each row will be assigned to a single flow. • the matrix will be read from bottom to top • if no switching delay is assumed then • Drawback: when nf < s, TypeII(nf) interleaver does not isolate all the packet losses

  7. Basic and Multi-flow Block Interleavers Algorithms • The proposed TypeII(nf,s) assures the isolation of losses for a given (nf ,s) pair of values, even when nf< s, with tolerable (bounded) delay • Memory requirements • If s is a multiple of nf then one (s x s) matrix is required. • Otherwise, nf squared (s x s) matrices are needed.

  8. Basic and Multi-flow Block Interleavers Algorithms • Let us define Rij as the number of consecutive rows that the flow i will be assigned for matrix j. rem(a,b) as the remainder of the integer division a/b. int(a) largest integral value not greater than a. • TypeII(nf,s) matrix writing procedure • First matrix: • Ri1 = int(s/nf), for i = { 1, 2, …, nf - rem(s,nf)}. • Rj1 = int(s/nf) + 1 for j = { n f -rem(s,nf), nf -rem(s,nf)+1, …, nf} • Next j = 2, …, nf matrices and flows i = 2, …, nf • If Ri(j-1) = int(s/nf)+1 and R(i-1)(j-1) = int(s/nf) then Rij = int(s/nf) and R(i-1)j = int(s/nf)+1 • Type II(nf,s) matrix reading procedure • Packets are read by columns, from bottom to top and from left to right.

  9. s·(r·(d +1)-1-(r - 1)·d) if r  (nf - r) s·(r·(d +1)-1-((r - 1)·d+2·r - nf -1)) if r > (nf - r) Basic and Multi-flow Block Interleavers Algorithms • TypeII(nf ,s) maximum delay Dmax is given by Dmax =º where r = rem(s,nf ) d = int((s-r) / nf ) • For typical VoIP values and for the best case TypeII(nf ,s) interleaver scatters bursts up to s < 15 favorably compared to TypeI(s) limited to s < 5

  10. Intelligibility Estimation • For performance evaluation, we propose to use a high level end-user intelligibility estimation: ASR rate • Compared to MOS, ASR has lower cost and is more reproducible • For end-user intelligibility estimation ASR rate can be more suitable than other measures like PESQ (P.862) or the E-model • The Word Error Rate is defined by

  11. Experimental Results • Experimental results were obtained by simulation. • We adopt a single error model based on a Markov chain (Yajnik et al [9]).

  12. Experimental Results • For ASR evaluation we use the connected digit Project Aurora 2 database • The speech recognizer is based on eleven 16-state continuous Hidden Markov Models (HMM) • The HMM models are trained from a set of 8440 noise-free sentences, while the out-of-train-test set comprises 4004 noise-free sentences • More details are explained in the printed version of the paper

  13. Experimental Results • WER and Dmax (seconds) obtained values

  14. Conclusion • Compared to a single-flow approach, our proposed interleaver reduces the packet delay and makes it applicable under conditions where the reference scheme is unfeasible. • Compared to the round-robin multi-flow interleaver, our proposed scheme increases the perceived end-user intelligibility (WER) • With a slight penalty on the introduced delay • We propose to consider ASR as a tool to measure VoIP services enhancements. • Future work: by setting up mapping functions • for ASR rate to human intelligibility • for ASR rate to MOS score and using it together with AN technology, enhanced VoIP services can be envisaged. Thank you for your attention

More Related