1. Voice Quality Evaluation for Wireless Transmission with ROHC S. Rein and F.H.P. Fitzek and M. Reisslein Voice Quality Evaluation for Wireless Transmission with ROHC. 2003. in International Conference on Internet and Multimedia Systems and Applications (IMSA 2003), pages 461-466. Honolulu, USA.

2. Center for TeleInFrastructure 2 GSM Encoder RTP UDP IP ROHC link GSM Decoder RTP UDP IP ROHC link IPRTPGSMUDP ROHCGSM Original voiceTransmitted voice Communication System UMTS link error simulation Protocol suite with ROHC

3. Center for TeleInFrastructure 3 Methodology for ROHC evaluation Communication System with ROHC Communication System without ROHC Original speechDistorted speech Predict ROHC speech quality Predict speech quality Calculate gain for ROHC

4. Center for TeleInFrastructure 4 Voice quality evaluation framework  Usually expensive software required (state of the art PESQ software available for 10.000 U.S.$)  Alternative methodology: used a set of elementary objective metrics to predict the subjective voice quality  Metrics represent sensible engineering trade off to networking studies  Performance of the metrics is usually verified by a correlation analysis

5. Center for TeleInFrastructure 5 Voice quality metrics: Correlations to subjective quality Segmental SNR0.77 Inverse linear spectral distance0.63 Delta form spectral distance0.61 Log area ratio0.62 Energy ratio0.59 Log likelihood0.49 Cepstral distance0.93

6. Center for TeleInFrastructure 6 Combined Metric  Every metric covers different distortion types  Coding and noise distortions in the time and frequency domain  Good reliability by including metrics verified by different authors

7. Center for TeleInFrastructure 7 Segmental Cross Correlation  Varying delay with IP packet voice  Reference and transmitted voice file have to be synchronized  Developed segmental cross correlation (SCC) algorithm in the time domain  SCC makes elementary metrics usable for modern communication systems

8. Center for TeleInFrastructure 8 missing samples wrongly inserted Segmental Synchronization

9. Center for TeleInFrastructure 9 Results: Delay jitter measurements

10. Center for TeleInFrastructure 10 Results: SNR measurements

11. Center for TeleInFrastructure 11 Results: voice quality

12. Center for TeleInFrastructure 12 Results: voice quality

13. Center for TeleInFrastructure 13 Results: Mean Opinion Score

14. Center for TeleInFrastructure 14  On top of bandwidth savings: Voice quality is improved  ROHC roughly cuts bandwidth for voice transmission in half  ROHC is a very useful complement to third generation mobile systems Conclusion