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What can Bluetooth do besides make calls? (ABCs of Car Tech)

These days Bluetooth-enabled cars can do much more than just take calls. In this week's ABCs of Car Tech, I explain the advanced features of Bluetooth in the car and explain why not all systems are created equally.

Bluetooth audio streaming, on the other hand, is not standard, but included as part of the Technology package.
Josh Miller/CNET

Most of us can agree now that Bluetooth connectivity is something that every tech car should have, but why is it important? Is it enough for a car to simply support Bluetooth or is there something more that you should be looking for?

In this week's ABCs of Car Tech, I'll do my best to answer those questions and explain the ins and outs of Bluetooth wireless technology.

Bluetooth SIG

What is Bluetooth?
When most people hear the word "Bluetooth," they immediately think about speakerphones and wireless headsets for hands-free calling. That's partially correct in that these devices often use Bluetooth technology to connect with your phone, but hands-free calling is only part of the whole picture.

At the top level, Bluetooth is a wireless short-range communication technology that lets devices share data with each other -- for example, your phone communicates audio data with your car's built-in speakerphone and vice versa. More specifically, Bluetooth is a collection of dozens of profiles, which are basically communication modules that define how a particular feature operates or how the paired devices communicate with each other.

What are these profiles and why should I care?
For purposes of this article, I'll be sticking to the profiles and features that apply to cars.

HFP is the most commonly used Bluetooth profile, allowing users to make hands-free calls. Josh Miller/CNET

HandsFree Profile (HFP)
This is the Bluetooth profile that is most commonly used and with which most users are familiar. This profile is what enables your phone to send its voice data to your car's hands-free system, a visor-mounted speakerphone, or a wireless headset, and receive input from a microphone. You can thank HFP for some people's annoying tendency to refer to all wireless headsets generically as "Bluetooth"; however, this profile's ubiquity means that you never have to worry about compatibility.

Phone Book Access Profile (PBAP)
You don't want to be fiddling with your phone when behind the wheel, so you need some way to get the names and numbers of your contacts from the phone and into your car's infotainment system where they can be safely browsed or used in voice commands. PBAP gives your car's hands-free system access to your phone's address book for syncing.

Advanced Audio Distribution Profile (A2DP)
A2DP is sometimes referred to as Bluetooth audio streaming. This profile transforms your Bluetooth connection into an invisible auxiliary audio cable, enabling wireless transmission of digital audio to your car's audio system. Audio quality varies from case to case with a dynamic bit pool (or range of bit rates) being negotiated by the transmitting the device (your phone) and the receiver (your car) at the time of pairing. Generally speaking, we've found the quality to be good enough for compressed MP3s with only a few isolated examples of a noticeable quality drop.

The most recent version of AVRCP supports the display of song metadata. Josh Miller/CNET

Audio/Video Remote Control Profile (AVRCP)
AVRCP often goes hand in hand with A2DP -- in fact, you'll often hear us Car Tech guys refer to the two profiles as one feature. What AVRCP does is add transport controls to A2DP's audio streaming. Users are able to skip tracks forward and backward and pause and resume playback. The most current implementation of AVRCP also includes the communication of metadata (artist name, album, song title, and so on) and playback state (playing, paused, or stopped). In the future, we may eventually be able to browse media on the connected phone and perform simple searches.

Serial Port Profile (SPP), Dial-up Networking Profile (DUN), Personal Area Networking Profile (PAN)
These profiles allow an external device, in this case your car, to connect to the Internet using your smartphone's data connection. Why would you want to connect your car to the Internet? Possible reasons include downloading traffic data, using online search engines to find destinations, and connecting to telematics services. Different cars work in different ways, using one or more of these three profiles. For example, Toyota Entune uses SPP to communicate with the Web through your phone. Ford Sync AppLink also uses SPP to connect with supported apps, but the Ford Sync Services function actually uses HFP to make voice calls to its automated call center.

Message Access Profile (MAP)
Texting while driving is bad, mmkay. However, many drivers have a hard time resisting the siren song of their notification beep. MAP allows incoming messages (usually SMS) to be relayed to your car's infotainment system where they can be displayed or read aloud by a text-to-speech system. No longer will you need to wonder whether that incoming message is an important message from your boss or spouse that requires immediate attention or an unimportant message that can be attended to later. MAP is a bidirectional communicator, so certain cars can be set to automatically respond with a "Do not disturb" message. In the future, we may even be able to reply to the important messages via voice recognition.

Secure Simple Pairing (SSP)
This one's not so much a profile as it is a pairing mechanism. If you've ever paired a phone with a Bluetooth speakerphone or headset, you're familiar with the four-digit PIN input of Bluetooth's legacy pairing system. If you've done it more than once, you'll notice that most devices default to "0000" or "1234" for simplicity -- not the most secure solution. SPP replaces the PIN input with a six-digit key that is generated at the time of pairing and displayed on both devices. The user simply confirms the match and the pairing is done. This pairing approach is both simpler because it doesn't require inputting a PIN (just matching the keys) and safer because there are way more numbers between 0 and 999,999 than just 0 and 1234.

What's the catch?
All of these profiles (and many, many more) are supported by Bluetooth, but that doesn't mean that your phone or your car supports them all. Hardware and software makers can pick and choose the profiles they want and simply leave off the rest. Sometimes, that's a good thing; you don't really have a need to connect a Bluetooth keyboard to your car with the Human Interface Device Profile (HID), so why bother with the overhead required to load it.

Most Bluetooth-enabled cars support HFP, PBAP, and A2DP, but don't support features like MAP or SPP. Josh Miller/CNET

Sometimes, however, it's not so good. For example, some car audio systems that support Bluetooth HFP leave A2DP audio streaming out of their feature set. Additionally, both devices need to support a profile before the user can access the feature associated with it. So if your car supports MAP, but your phone doesn't, you can forget about hearing those text messages read aloud.

Some profiles are more widely supported than others. For example, while every car that touts Bluetooth supports HFP and most with voice command support PBAP, A2DP is sometimes left out. A2DP implementation is rare, but only the techiest of cars support AVRCP's ability to display metadata. SPP is so new that most of the automotive world hasn't had time to catch up to it; and I've never once found myself in a car that supported MAP with a phone that did the same.

But it's getting better. This time last year, A2DP streaming was a rarely spotted bonus feature tacked on to a system bought for the HFP. This year, A2DP/AVRCP are almost a requirement for any car audio system worth its salt. We should be seeing more widespread implementation of MAP and Bluetooth's Web connectivity features in the future. You can count on CNET's Car Tech to point out the best implementations of this tech in our reviews.

Hopefully, by now you have a good idea of what Bluetooth is, what it's composed of, and how it can be useful in the car. If still you have questions about Bluetooth wireless technology in the car, leave them in the comments below.