Practical Limitations of Wideband Terminals Workshop on Wideband
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 n wideband was standardized in the 90 s by ETSI for ISDN terminals n becomes more popular with the proliferation of PC based IP telephony (Skype) n finds it‘s way into conventional telephony systems (Siemens opti. Point 410) Introduction Standards Response Masks § Handset sending § Handset receiving § Hands free sending § Hands free receiving § Discussion Artificial Ear Conventional Transducers § Receiver § Speaker mobile terminals Conclusion n high quality wideband codecs G. 722, G. 722. 1, G. 722. 2, i. LBC. . . are available ETSI Wideband Workshop, C. Sydow, 11/1/2020 2 © Siemens, 2003
Wideband Standards n applicable standards (list not complete) operating mode country narrowband wideband handset Europe TBR 8 I-ETS 300 245 -5 USA TIA 810 A TIA 920 hands free Europe USA I-ETS 300 245 -3 I-ETS 300 245 -6 TIA 810 A TIA 920 Introduction Standards Response Masks § Handset sending § Handset receiving § Hands free sending § Hands free receiving § Discussion Artificial Ear Conventional Transducers § Receiver § Speaker mobile terminals Conclusion n main differences between wideband narrowband standards § frequency response mask § type of artificial ear for handset measurements n minor differences § distortion and noise requirements ETSI Wideband Workshop, C. Sydow, 11/1/2020 3 © Siemens, 2003
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 mobile terminals Conclusion ETSI Wideband Workshop, C. Sydow, 11/1/2020 4 © Siemens, 2003
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 mobile terminals Conclusion ETSI Wideband Workshop, C. Sydow, 11/1/2020 5 © Siemens, 2003
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 mobile terminals Conclusion ETSI Wideband Workshop, C. Sydow, 11/1/2020 6 © Siemens, 2003
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 mobile terminals Conclusion ETSI Wideband Workshop, C. Sydow, 11/1/2020 7 © Siemens, 2003
Frequency Response Masks: Discussion n main differnce: extension of frequency range from 300 Hz 3400 Hz to 160 Hz to 6300 Hz Introduction Standards Response Masks n practical problem lies in the low frequency extension § Handset sending § Handset receiving § Hands free sending § Hands free receiving § Discussion n significant differences between European and US standards § Europe: higher bandwidth Artificial Ear Conventional Transducers § Receiver § Speaker mobile terminals Conclusion ETSI Wideband Workshop, C. Sydow, 11/1/2020 8 © Siemens, 2003
Artificial Ear for Wideband Measurements n TBR 8: type 1 (optional type 3. 2 ll) Introduction Standards Response Masks n TIA 810 A: „suitable“ ear n I-ETS 300 245 -5: 3. 2 ll or 3. 3 (depending on handset geometry) § Handset sending § Handset receiving § Hands free sending § Hands free receiving § Discussion n TIA 920: not type 1 n leakage effect: Artificial Ear Conventional Transducers § Receiver § Speaker mobile terminals Conclusion ETSI Wideband Workshop, C. Sydow, 11/1/2020 9 © Siemens, 2003
Suitability of conventional transducers: Receiver n typical handset receiver response Introduction Standards Response Masks § Handset sending § Handset receiving § Hands free sending § Hands free receiving § Discussion Artificial Ear Conventional Transducers § Receiver § Speaker mobile terminals Conclusion n frequency response tuned to meet narrowband requirements ( 3 resonances ) n closed back volume n high mechanical impedance n side conditions: cost, robustness, HAC, weight receiver cannot be easily modified to meet the wideband requirements ETSI Wideband Workshop, C. Sydow, 11/1/2020 10 © Siemens, 2003
Suitability of conventional transducers: Speaker n typical 50 mm speaker response Introduction Standards Response Masks § Handset sending § Handset receiving § Hands free sending § Hands free receiving § Discussion Artificial Ear Conventional Transducers § Receiver § Speaker mobile terminals n resonance frequency > 300 Hz Conclusion n stiff membrane suspension, small size (small wight), small magnet ETSI Wideband Workshop, C. Sydow, 11/1/2020 11 © Siemens, 2003
Suitability of conventional transducers: Speaker for Mobile Terminal n 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 mobile terminals Conclusion ETSI Wideband Workshop, C. Sydow, 11/1/2020 12 © Siemens, 2003
Conclusion n conventional receivers and speakers cannot transmit the whole „wideband“ frequency range Introduction Standards Response Masks n even small extension of the narrowband frequency range lead to significant improvements in speech quality ad intelligibility § Handset sending § Handset receiving § Hands free sending § Hands free receiving § Discussion n wideband telephony will only get into the market if additional cost is low § Receiver § Speaker mobile terminals à several degrees of wideband (1, 2, 3) à take care of spectral balance !!! Conclusion à take care of leakage sensitivity à E-model and objective quality measurements have to rate frequency range, spectral balance and leakage sensitivity ETSI Wideband Workshop, C. Sydow, 11/1/2020 Artificial Ear Conventional Transducers 13 © Siemens, 2003
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