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Practical Limitations of Wideband Terminals

Practical Limitations of Wideband Terminals. Workshop on Wideband Speech Quality in Terminals and Networks: Assessment and Prediction 8 th and 9 th June 2004 – Mainz Germany Dr.-Ing. Carsten Sydow Siemens AG. Introduction. wideband was standardized in the 90s by ETSI for ISDN terminals

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Practical Limitations of Wideband Terminals

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  1. Practical Limitations of Wideband Terminals Workshop on Wideband Speech Quality in Terminals and Networks: Assessment and Prediction 8th and 9th June 2004 – Mainz Germany Dr.-Ing. Carsten Sydow Siemens AG

  2. Introduction • wideband was standardized in the 90s by ETSI for ISDN terminals • becomes more popular with the proliferation of PC based IP telephony (Skype) • finds it‘s way into conventional telephony systems (Siemens optiPoint 410) • high quality wideband codecs G.722, G.722.1, G.722.2, iLBC ... are available Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  3. Wideband Standards operating mode country narrowband wideband handset Europe TBR8 I-ETS 300 245-5 USA TIA 810A TIA 920 hands free Europe I-ETS 300 245-3 I-ETS 300 245-6 USA TIA 810A TIA 920 • applicable standards (list not complete) • main differences between wideband and narrowband standards • frequency response mask • type of artificial ear for handset measurements • minor differences • distortion and noise requirements Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  4. Frequency Response Mask: Handset Sending Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  5. Frequency Response Mask: Handset Receiving Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  6. Frequency Response Mask: Hands-Free Sending Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  7. Frequency Response Mask: Hands-Free Receiving Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  8. Frequency Response Masks: Discussion • main differnce: extension of frequency range from 300 Hz 3400 Hz to 160 Hz to 6300 Hz • practical problem lies in the low frequency extension • significant differences between European and US standards • Europe: higher bandwidth Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  9. Artificial Ear for Wideband Measurements • TBR8: type 1 (optional type 3.2 ll) • TIA 810A: „suitable“ ear • I-ETS 300 245-5: 3.2 ll or 3.3 (depending on handset geometry) • TIA 920: not type 1 • leakage effect: Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  10. Suitability of conventional transducers: Receiver • typical handset receiver response • frequency response tuned to meet narrowband requirements ( 3 resonances ) • closed back volume • high mechanical impedance • side conditions: cost, robustness, HAC, weight •  receiver cannot be easily modified to meet the wideband requirements Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  11. Suitability of conventional transducers: Speaker • typical 50 mm speaker response • resonance frequency > 300 Hz • stiff membrane suspension, small size (small wight), small magnet Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  12. Suitability of conventional transducers: Speaker for Mobile Terminal • response of a 36 mm diameter speaker Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

  13. Conclusion • conventional receivers and speakers cannot transmit the whole „wideband“ frequency range • even small extension of the narrowband frequency range lead to significant improvements in speech quality ad intelligibility • wideband telephony will only get into the market if additional cost is low • several degrees of wideband (1, 2, 3) • take care of spectral balance !!! • take care of leakage sensitivity • E-model and objective quality measurements have to rate frequency range, spectral balance and leakage sensitivity Introduction Standards Response Masks • Handset sending • Handset receiving • Hands free sending • Hands free receiving • Discussion Artificial Ear Conventional Transducers • Receiver • Speaker • Speaker mobile terminals Conclusion ETSI Wideband Workshop, C.Sydow, 2004-06-01

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