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Practical Limitations of Wideband Terminals

This workshop discusses the practical limitations of wideband terminals in terms of standards, response masks, artificial ear measurements, and conventional transducers. It focuses on the differences between narrowband and wideband standards, frequency response masks for handset sending, receiving, hands-free sending, and hands-free receiving, and the suitability of conventional transducers for wideband applications.

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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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