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Apple’s CarPlay in the Volvo XC90.

There are many ways to integrate a smartphone with a vehicle, although a lack of industry standardization has led auto makers and the aftermarket to experiment with different inputs.

The simplest method, and most pervasive, has been to use a 3.5-mm headphone cable to connect the phone into the vehicle's Aux-In for audio playback, a method that still exists in almost every model coming off an assembly line.

But it was Apple's proprietary 30-pin connector found in the iPod that became the most popular, in part because the iPhone, up until the 4S, was using the same port. Certain original equipment and aftermarket car stereos could interface directly with apps on the phone, making it possible to display mapping and navigation apps onto the head unit's screen, for example.

Apple's subsequent move to the eight-pin digital, or "Lightning" connector, rendered obsolete the analog video output of its predecessor, forcing users to spend $35 for the company's adapter, which couldn't do video out, either.

"While we could easily handle the audio, consumers took a while to understand that video output was available only via an HDMI adapter and required an HDMI input on the deck itself," says Francisco Lacey, assistant marketing manager at Kenwood Electronics Canada. "There were no workarounds for video output from Lightning devices, so we had to develop product with HDMI on the next development cycle, which we achieved and introduced in early 2014."

The irony is that Lightning is one of the only proprietary connectors left. In the past four years, smartphone and accessories manufacturers all adopted microUSB as the charging port. Doing so meant that competing standards, such as MirrorLink and MHL, could be used in the vehicle as well.

MirrorLink, an open and non-proprietary protocol, was founded by Nokia but is now managed by the Car Connectivity Consortium (CCC) – a group of auto and electronic manufacturers that are trying to establish an industry standard for apps and devices. It uses the microUSB port to essentially mirror the phone's display onto an infotainment screen, allowing drivers to access all apps using the vehicle's controls.

MHL, or Mobile High-Definition Link, was primarily focused on beaming content from a phone or tablet to a television, but has since been adopted to a limited degree by aftermarket vendors Kenwood, Sony, Pioneer, JVC and Panasonic. It, too, is non-proprietary and run by a consortium that includes some of the same companies in the CCC.

Like Lightning for Apple devices, MirrorLink and MHL utilize the microUSB port to charge connected devices. Android handsets make up the overwhelming majority of compatible phones, though MirrorLink recently added Windows Phone to its device support. Both are also able to use Bluetooth or WiFi as a complement to USB to increase functionality.

"MirrorLink has a very steep hill to climb because it's open-sourced, crowdsourced and the CCC has to work with each individual device-maker in order to get their standard approved. We think there's still life for it, but their battle will be getting and continuing to keep up device support," says Mark Boyadjis, senior analyst of infotainment and HMI at IHS Automotive Technology Solutions. "MHL could find its way into the car in a more consistent manner, only because we're seeing the device support be pretty significant there."

Boyadjis believes there will be less reliance on wired standards going forward if in-car WiFi and WiFi Direct emerge quickly. WiFi Direct is essentially an ad hoc WiFi connection between devices that omits the need for an access point to bridge the two. In a vehicle, it could mean a phone beaming content to a WiFi-enabled car stereo directly, with neither needing a data connection from a service provider, unless one was streaming said content from a cloud service.

A recent IHS report projected that as many as 25 million vehicles will have WiFi by the end of the decade, with the highest usage in North America. Bluetooth and USB already have high attach rates in cars because users are familiar with the technology through work or home use.

"People are integrating their phones through a cable more for charging than they are for content, and that trend will likely continue to evolve," Boyadjis says. "These are connectivity mediums, not necessarily experience platforms, like Apple's CarPlay and Google's Android Auto.

"Still, you're going to need to integrate the connectivity standard – be it Bluetooth, USB, WiFi, MirrorLink, MHL, Android Auto or CarPlay – and then work to integrate that into the car, which auto makers are trying to make easier. It's only one step to discuss the connection medium, the next step is to discuss human-machine interface integration."

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