The automotive and mobile phone industries meet when drivers communicate via their vehicles’ hands-free systems. Speech quality tests for vehicle-mounted hands-free systems are defined in Recommendations ITU-T P.1100 “Narrow-band hands-free communication in motor vehicles” and ITU-T P.1110 “Wideband hands-free communication in motor vehicles”.
In the most common use case for hands-free communication, a driver’s mobile phone is linked via wireless communication to the vehicle’s hands-free system which provides for mobile network access. Here the mobile phone acts as an “audio gateway” and should provide fully transparent voice transmission in uplink and downlink. The relevant signal processing is performed solely by the vehicle’s hands-free system; therefore mandating that the signal-processing functionality of a mobile phone be disabled while the phone is mounted on a hands-free system.
Experience has shown, however, that the internal signal-processing in mobile phones is often not disabled – despite the hands-free unit sending the appropriate control command (AT command) to the mobile phone. In this situation, the mobile phone may significantly degrade the quality of the whole system, and car manufacturers have received complaints from customers having experienced speech quality shortfalls. The automotive industry is very concerned and is demanding stronger focus on standardization, especially as the wideband telephony now being deployed should increase speech quality as compared to narrowband telephony.
Corresponding tests to verify the performance of mobile phone in vehicle-mounted Hands-free Terminal are described in Chapter 12 (“Verification of the transmission performance of short-range wireless (SRW) transmission enabled phones”) of Recommendations ITU-T P.1100 and ITU-T P.1110.
A possible reason for some mobile handset manufacturers not configuring their handsets correctly for use in vehicles’ hands-free systems may be a lack emphasis on the “Chapter 12 tests” of ITU-T P.1100 and ITU-T P.1110. Increasing the visibility of these important tests, and thus the extent to which they are employed, will work to improve the quality of the hands-free services that customers receive from the automotive and mobile phone industries.
