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Hands-free infotainment demands good software

Posted: 01 Nov 2006 ?? ?Print Version ?Bookmark and Share

Keywords:hands-free automotive technology? Bluetooth in car? wireless car? automotive infotainment system? software for automotive infotainment?

Modern cars are electronics-packed technology marvels. With their development cycle measured in years, however, they remain on the trailing edge of CE developmentsa market where product cycles can be only a few months. These cycle times, along with comparable product lifetimes, are not necessarily a bad thing. After all, who would want a cellphone that was 10 years old or a car that was obsolete after a year or so?

Any new technology, like wireless, takes a couple of years to implement in automotive applications. This allows the technology to mature, making a more reliable and robust product that consumers demand much from, given the vehicle's big ticket price compared with everyday purchases.

While technological maturity is desirable, the same product cycle disparity means it's difficult for car electronics developers to chart the road ahead. Consumer preferences and demands fashioned by personal electronics technology choices or the technologies themselves are not always easy to predict. Thus, designers have to come up with systems flexible enough to allow the car to accommodate as many developments as possible down the road.

Mandates, Bluetooth
Besides consumer market pressures, safety legislation and regulations influence automotive electronics developments. Thus, the availability of Bluetooth wireless technology has spurred automotive developers to adopt it as today's key enabler in wireless communication between consumer cellphones and infotainment systems in cars. But going about this integration requires attention to detail.

Bluetooth cellphones are integrated into cars today with aftermarket hands-free kits or by means of systems developed as original equipment on later-model vehicles. While aftermarket kits allow current car owners to update them for Bluetooth-equipped phones, developers agreed that for connection with either type of system, software quality is vital. System algorithms also perform acoustic echo cancellation, noise reduction and voice recognition.

Such functionality is necessary in a hands-free kit, said John Dixon, world-wide low-power market manager at Texas Instruments, because these functions in a car are based on using a different set of speakers (either the car's audio system or one in the kit head unit) rather than the small device in the phone. Any software in the phone is thus irrelevant for use with the car's system.

Like any product for automotive applications, hands-free kits have to balance cost with performancewhich in this case, Dixon notes, is a balancing act trying to provide "horses for courses."

"To enhance sound most efficiently, you have to balance processing speed vs. on-board memory (which costs money), so that you don't have to go off-chip for information, which takes time," Dixon summarized. "And too much processing at too high a speed can also cost too much power." In short, silicon and software have to be balanced.

Bluetooth kit shares time with automotive infotainment functions.

Unique problems
Dixon said that good software leads to a quality audio experience with the hands-free phone I the car, with conversation approaching that of a face-to-face meeting. Smart software also conserves cellphone power and is vital in allowing designers to solve unique problems.

"Information has to get from the phone to the kit on time," Dixon said. "Algorithms running on DSPs come into play with gain/loss scenarios and data taken from a number of points to quickly perform an error correctionbut all this may only be needed for a short time."

Dixon cautioned that memory must fit the processor to accommodate adequate software. Thus, the highest-performing processor without balanced memory would not be an optimum choice.

"You can't just go with the hottest hardware, but have to get involved with the platform and the software," Jack Morgan, senior director of automotive at NXP, agreed. "The challenge is more in the software. It's subtle in implementation and you need to pay attention to software from suppliers, looking for those who have been successful."

Bottom line: Software may be too complex for customers to attempt with fixed resources and limited staff skills.

Can you hear me?
Software utility goes beyond signal integrity by ensuring the voice quality riding on that signal. "Except for a factory floor, the car cabin is the harshest environment around, from a noise perspective," said Tom Houy, VP at Cambridge Silicon Radio. His company has its Clear Voice Capture software for its Bluetooth cores.

Houy said the algorithms divide the audio stream into 64 frequency bands and check those for speech timing patterns. These are then processed, "throwing away the noise without even trying to cancel it." The Clear Voice Capture software will also prevent the car speaker system, if used for voice output, from overwhelming any aftermarket hands-free kit's microphone.

The car noise environment is characterized by low-level frequencies that change over time and with vehicle velocity, said Greg Eslinger, VP of engineering at Acoustic Technologies. Acoustic Tech's SoundClear algorithms adapt to speech and cancel noise, he said.

The software also looks for both noise and speech characteristics to ensure that processing the noise does not remove some of the voice.

Acoustic Tech also consults with the designers of aftermarket hands-free kits about acoustic design. For these add-on kits, Eslinger said, "proper plastic design is essential." He was referring to potential acoustic coupling between a kit's speakers (if not using the car's system) and its microphone through the device's plastic housing. In such cases, the distance between the two and the flexibility of the housing material have to be compatible with vibration modes.

Such hurdles for automotive infotainment engineers integrating wireless hands-free technologies into today's and tomorrow's cars certainly allow them to say they live in interesting times. The uncertainty of where developments may be heading may be made up for by the interesting challenges of bringing consumers' personal electronics devices, whatever they may turn out to be, into those vehicles.

- Rick DeMeis
EE Times




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