Rise of Connected Car Service – IVI Speech Test Verification

Technological development is changing the auto/driving experience and creating an ecosystem that supports connectivity between automobile and mobile applications. According to China Industrial Development Research Network report, the global car network terminals can reach 66.95 million units. China’s car network terminal was only 1 million units in 2013, expected to grow to around 10 million units in 2018. The “mobile phone-car mode” network terminal increased from 19% in 2013 and will increase to nearly 50% in 2018.

Automobile connectivity will improve traffic safety and make traffic more efficient. The concept of car network connectivity is changed by “V2X (Vehicle-to-Everything)”, divided into: Vehicle to Vehicle (V2V), Vehicle to Infrastructure (V2I), Vehicle to People (V2P), and Vehicle to Network (V2N). For V2X, the car is like a large mobile intelligence device that can be linked to the Internet, navigation and driving system, traffic monitoring, and even unmanned applications for “safe,” “convenient,” and “comfortable” demands.

The car network application for information and entertainment (in-vehicle infotainment systems, IVI system) has a large market potential for its applications. Infotainment systems could grow in demand with more smartphones and compatibility as “Apple Carplay,” “Android Auto,” “MirrorLink,” “Microsoft’s SYNC AppLink,” and similar technologies connected to vehicle’s in-built functions, allowing drivers and passengers to take control of all kinds of information and data transmission between the car and the mobile device.

Technological improvements in cable and wireless related technologies change how interaction between people and vehicles take place. Car manufacturers also have to adjust to these developments and get through its challenges. Prediction of voice control technology and its spread in vehicle application makes voice / speech testing necessary. Manufacturers will have to adapt with the trend for better future potential.

In-vehicle hands-free voice test – ITU-T standards

The ITU-T P.1100 and ITU-T P.1110 standards are developed by the International Telecommunication Union (ITU), based on real-life vehicle applications. The “P” series deal with features relating to telephone transmission quality, telephone installation, local line network, etc. The main differences with these two telephony standards are in the frequency range. P.1100 is designed for narrowband hands-free calling but P.1110 is the standard specification for free hands-free calling.

Standard Name
ITU-T P.1100 Narrow-band hands-free communication in motor vehicles
ITU-T P.1110 Wideband hands-free communication in motor vehicles


The test items for both the ITU-T P.1100 and P.1110 specifications are similar. At Allion, we take on the recommended ITU-T specifications for vehicles according to the requested test requirements of the car manufacturers for the best hands-free call quality test. Each of the tests performed is aligned with the nine test items within the IVI system development process for verification of voice performance.

  1. Delay

The delay test measures call delay between the device and the hands-free interface to ensure the call delay time is within the specified range. Any delay level outside the specified range is not allowed.

  1. Loudness Ratings

The loudness rating test verifies that the voice quality of the call is within the specified range and is not suddenly loud or soft. Loudness rating more than the allowed specification limit is not allowed. The required detection ranges for optimal sound rating is:

Transmitter loudness detection value (Sending Loudness Rating): 9dB ~ 17dB

Receiver loudness detection value (Receive Loudness Rating): – 2dB ~ 6dB

  1. Sensitivity Frequency Response

The sensitivity frequency response test measures the different frequency ranges and whether change in frequency will affect the call quality from either receiving or sending calls.

Figure: Green line is the actual test results. Accepted range is between the upper and lower limit of the measured curve

  1. Speech Quality During Single Talk

Through this voice call evaluation, the sound quality will not be affected by background noise, or sound outside the tested interface. This test evaluation is based on TOSQA (Telecommunications Objective Speech Quality Assessment) measurement technique. The speech quality is rated between 1 and 5. Higher rating score show better sound quality.

  1. Listening Speech Quality Stability

Listening Speech Quality Stability focuses on the sounds’ qualities of both caller and receiver. By variating the environments’ conditions, callers’ different positions, and the transmission characteristics, this test aims to ensure positive user experiences during a call (or several calls).

  1. Idle Channel Noise

When there is no signal present to the channel, this test evaluates the noise on the receiving and sending side. There should be no additional sound when there is no signal present and the sound measured should not exceed the upper limit.

  1. Out-of-band signals

The narrow band and wide band call band signal test verifies frequency range for different electrical reference points and checks that the transmitting frequency signal is within the acceptable in-band level measurement. This out of band signal test ensures detection of non-voice band signals and is able to distinguish between such non-voice signals and voice signals.

  1. Echo Performance Without Background Noise

This echo suppression measurement test checks the echo loss scale based on the predicted delay time of the communication systems. Generally, a lower echo loss index below 50dB is preferred.

  1. Double Talk Performance

During separate ongoing voice call from the caller and receiver, this test checks the sound interference between both sides. Performing this test ensures there is no interference on the receiver using the same channel band. The test results are divided into five grades, namely 1,2a, 2b, 2c, 3 (please refer to the figure below).

  1. Background Noise Transmission

This item measures different background noise conditions, actual call quality and noise suppression capacity under simulated actual driving condition. Background noise record is first measured before testing and measured again as the vehicle engages in idling speed mode between 80 km/h per hour and 130 km/h.

All nine tests above are designed to test actual call quality such as the delay time between the two sides of the call, the sound quality is suddenly loud and soft, poor sound quality of the call, different call frequency  on sound quality, sound quality under echo suppression, and different background noise suppression capabilities and so on.

In addition to the car hands-free audio test, some vehicles still require USB connection between the IVI vehicle interface and the phone, so the wired connection test is also very important. Many manufacturers find it difficult to self-validate the connection feature. Allion is a USB-IF authorized test center that supports manufacturers implement USB signal integrity (USB SI) test to obtain the relevant certification.

In-Vehicle Interoperability Applications Testing

The interoperability between mobile devices and vehicles is a very important part. The recent developments in smart devices, such as smart phones, smart watches and other application provides interoperability challenges.

Allion is the world’s largest interoperability testing laboratory, based on years of testing experience, we have acquired three kinds of vehicle-mounted interoperability test focus: Connectivity and real-time communication software and user scenarios.

In general, connection technologies of vehicle-mounted devices, such as Bluetooth, USB, Wi-Fi, etc. all have standard certification mechanism but the actual application will have interoperability problems. So customers need different device connectivity test to ensure quality of operation. Some real time communication software, such as Wechat, Whatsapp, LINE, and so on have VoIP call functions. Some devices with these VoIP functions do not work correctly when connected to the car. User scenario testing simulates real-life use case such as taking the mobile phone out and then returning back to the car, or call interruption while listening to music, to confirm the devices and applications are working correctly.

In-vehicle network and connectivity provides huge opportunities. Therefore, automobile equipment cannot be unrecognized. Certifications such as Wi-Fi, USB, Bluetooth, DLNA, MirrorLink, MHL, and others are the technical threshold. Validation provides the most comprehensive test environment to ensure devices can work with other software and hardware features. This is an important aspect of future in-vehicle systems.