Download presentation
Presentation is loading. Please wait.
Published byThomas Smith Modified over 9 years ago
1
Juan J. Ramos-Muñoz, Angel M. Gómez, Juan M. Lopez-Soler Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver Signal Theory, Telematics and Communications Department
2
2 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. Outline Introduction Basic and Multi-flow Block Interleavers Algorithms Intelligibility Estimation Experimental Results Conclusion
3
3 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. 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
4 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. 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
5 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. 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
6 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. 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(n f ) and propose TypeII(n f,s) where n f is the number of available flows and s is the maximum expected burst length Round-robin interleaver (TypeII(n f )) is suited for n f ≥ s it requires one (n f 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 n f < s, TypeII(n f ) interleaver does not isolate all the packet losses
7
7 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. Basic and Multi-flow Block Interleavers Algorithms The proposed TypeII(n f,s) assures the isolation of losses for a given (n f,s) pair of values, even when n f < s, with tolerable (bounded) delay Memory requirements If s is a multiple of n f then one (s x s) matrix is required. Otherwise, n f squared (s x s) matrices are needed.
8
8 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. Basic and Multi-flow Block Interleavers Algorithms Let us define R i j 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(n f,s) matrix writing procedure First matrix: R i 1 = int(s/n f ), for i = { 1, 2, …, n f - rem(s,n f )}. R j 1 = int(s/n f ) + 1 for j = { n f -rem(s,n f ), n f -rem(s,n f )+1, …, n f } Next j = 2, …, n f matrices and flows i = 2, …, n f If R i (j-1) = int(s/n f )+1 and R (i-1) (j-1) = int(s/n f ) then R i j = int(s/n f ) and R (i-1) j = int(s/n f )+1 Type II(n f,s) matrix reading procedure Packets are read by columns, from bottom to top and from left to right.
9
9 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. Basic and Multi-flow Block Interleavers Algorithms TypeII(n f,s) maximum delay D max is given by D max =º where r = rem(s,n f ) d = int((s-r) / n f ) For typical VoIP values and for the best case TypeII(n f,s) interleaver scatters bursts up to s < 15 favorably compared to TypeI(s) limited to s < 5 s·(r·(d +1)-1-(r - 1)·d) if r (n f - r) s·(r·(d +1)-1-((r - 1)·d+2·r - n f -1))if r > (n f - r)
10
10 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. 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
11 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. Experimental Results Experimental results were obtained by simulation. We adopt a single error model based on a Markov chain (Yajnik et al [9]).
12
12 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. 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
13 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. Experimental Results WER and D max (seconds) obtained values
14
14 Juan J. Ramos-Muñoz, Ángel M. Gómez, Juan M. Lopez-Soler University of Granada Intelligibility Evaluation of a VoIP Multi-flow Block Interleaver. IWAN 2005. 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
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.