AUTOMOTIVE BLUETOOTH TELEPHONY.

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AUTOMOTIVE BLUETOOTH TELEPHONY.

COMBINING BlueZ AND THE MODERN VEHICLE.

Timo Müller, Mikel Astiz

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Building Open Source IVI Stack for Bluetooth Use Cases using BlueZ, oFono and PulseAudio

feeding back APIs and architectural decisions into the GENIVI Alliance

AUTOMOTIVE BLUETOOTH TELEPHONY.

WHY ARE WE DOING THIS?

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BLUETOOTH BASICS.

DATA TRANSPORT ARCHITECTURE.

L2CAP Channels

Logical Links

Logical Transports

Physical Links

Physical Channel

(cf. [1] Architecture &Terminology Overview, p. 39)

L2CAP Layer

Logical Layer

Physical Layer

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BLUETOOTH BASICS.

PHYSICAL LAYER.

Physical Channel

• Frequency Hopping Sequence

• Access Code

• Packet Timing

Physical Link

represents a connection between Bluetooth devices

L2CAP Channels Logical Links Logical Transports

Physical Links Physical Channel L2CAP Layer

Logical Layer

Physical Layer

Master Slave

(see. [2] Core System Package, p. 71ff and 96ff)

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BLUETOOTH BASICS.

LOGICAL LAYER.

Logical Transport

defines a communication channel with a set of characteristics:

• Flow control

• Acknowledgment and repeat mechanisms

• Sequence numbering

• Scheduling behaviour

Logical Link

associated with a logical transport supports applications with

different transport requirements

Logical Layer

Physical Layer

(see. [1] Architecture & Terminology Overview, p. 61)

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Automotive Bluetooth Telephony, BMW Car IT GmbH

BLUETOOTH BASICS.

LOGICAL TRANSPORTS.

ACL (Asynchronous Connection-Oriented) Packet-switched communication

SCO (Synchronous Connection-Oriented) Circuit-switched communication

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Logical Layer

Physical Layer

Master Slave

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BLUETOOTH BASICS.

LOGICAL LINK CONTROL AND ADAPTATION PROTOCOL LAYER.

L2CAP Channel

used for connection-oriented and connectionless data services offers

• Segmentation and reassembly of packets

• Flow Control

• Error Control and retransmission

Logical Layer

Physical Layer

(see. [3] Core System Package, p. 30ff)

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HANDS-FREE PROFILE (HFP).

ROLES.

Cellular Network

(cf. [4] Hands-Free Profile 1.6, p. 14)

Hands-Free Unit (HF) Audio Gateway (AG) Headset

Hands-free car kit

Cellular connection Bluetooth

connection

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SCO and eSCO (Audio)

HANDS-FREE PROFILE (HFP).

STRUCTURE.

Hands-Free Profile (HFP)

Controller(s)

Host Controller Interface (HCI) RFCOMM

Generic Access Profile

(GAP)

Logical Link and Adaption Layer (L2CAP)

Service Discovery Profile (SDP) Serial Port Profile (SPP)

AT CMD

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HANDS-FREE PROFILE (HFP).

STRUCTURE.

Controller(s)

Host Controller Interface (HCI) Generic

Access Profile (GAP)

AT CMD

L2CAP Socket SCO Socket

RFCOMM RFCOMM Socket

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HANDS-FREE PROFILE (HFP).

STRUCTURE.

Controller(s)

Host Controller Interface (HCI) RFCOMM

Generic Access Profile

(GAP)

AT CMD

L2CAP Socket SCO Socket

RFCOMM Socket

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ARCHITECTURE.

CORE COMPONENTS AND APIs.

oFono BlueZ D-Bus API Pulseaudio

Kernel

Bluetooth Hardware

Host Controller Interface (HCI) D-Bus API

Management Socket SCO Socket

RFCOMM Socket

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ARCHITECTURE.

CORE COMPONENTS AND APIs.

• Handle Connections

• Handover RFCOMM

oFono Pulseaudio

User Interface (Human Machine Interface)

• Handle audio streams

• Suspend and resume

• Echo cancellation and noise reduction

BlueZ

Handsfree API Media API

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ARCHITECTURE.

CORE COMPONENTS AND APIs.

oFono BlueZ Pulseaudio

Audio Control

• Microphone Mute

• Echo Cancellation / Noise Reduction

• Policy Handling

Bluetooth Device Control

• Device Inquiry

• Device Pairing

• Profile Activation

• Priority Handling

Telephony Control

• Dialing

• Call Handling

(Accept, Reject, Hold)

• Multiparty Call Handling

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ARCHITECTURE.

HUMAN MACHINE INTERFACE.

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BLUETOOTH BASICS.

OTHER RELEVANT AUDIO PROFILES.

A2DP (Advanced Audio Distribution Profile)

• Setup, Control and manipulate streaming of compressed audio

• Stream high-quality Audio over ACL-Link AVRCP (Audio/Video Remote Control Profile)

• Control a media player and retrieve current status

• Browse and Search library of a media player HSP (Headset Profile)

• Full-duplex audio connection over SCO-Link

• Minimal device control

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SINGLE PHONE USE CASES.

PUTTING CALLS ON HOLD.

Hold call Put call on hold

Activate held call

Activate call

Bluetooth connection Call active

Audio connection (HFP) Call on hold

Active call

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SINGLE PHONE USE CASES.

PRIVATE MODE (ACTIVE CALL).

Disconnect Audio

Connect Audio

Enter private mode

Leave private mode

Active call

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SINGLE PHONE USE CASES.

PRIVATE MODE (INCOMING CALL).

Answer call

Ringing

Connect Audio Leave private mode

Active call

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SINGLE PHONE USE CASES.

AUDIO PRIORITIES.

Answer call

Hang up call

Audio stream (A2DP)

Ringing Active call

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SINGLE PHONE USE CASES.

AUDIO PRIORITIES.

Answer call

Hang up call

Audio stream (A2DP)

Ringing Active call

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SINGLE PHONE USE CASES.

AUDIO PRIORITIES – UNDER THE HOOD.

Audio stream (A2DP)

Stop audio

Acquire()

PropertyChanged() SCO Socket

call_answer()

PropertyChanged(call active)

UI

+CIEV

new_call()

Answer SCO connect

Ringing ATA

OK

OK Notify

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DEMO.

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MULTI-PHONE USE CASES.

HOLD AND ANSWER.

1 2

Ringing Active call

Put call on hold

Hold and Answer

Answer call

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MULTI-PHONE USE CASES.

SWAPPING CALLS.

Activate held call

1 2

Swap calls

Put call on hold Call on hold

Active call

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MULTI-PHONE USE CASES.

AUTOMATIC REJECT.

1 2

Active call Call on hold

Ringing Reject Ringing

Reject

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THE ROAD AHEAD.

• Wide band speech

• Transition to BlueZ 5.0

• Audio Routing

• IOP Testing

Used Versions:

BlueZ:

dbd9c3109e77088de3d7e35dec78524ba73d1ad4

oFono:

ce79121d27555dc8ad43b5db49a35db83a01a0b8

PulseAudio:

a423ee0f3d36b98baff64cc31558632e738b402d

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THANK YOU VERY MUCH FOR YOUR INTEREST.

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RESOURCES.

www.bluetooth.org www.bluez.org

www.genivi.org www.ofono.org

www.press.bmwgroup.com www.pulseaudio.org

[1] Bluetooth SIG, Specification of Bluetooth System, Core, v4.0, Volume 1: Architecture & Terminology Overview

[2] Bluetooth SIG, Specification of Bluetooth System, Core, v4.0, Volume 2: Core System Package [BR/DER Controller Volume]

[3] Bluetooth SIG, Specification of Bluetooth System, Core, v4.0, Volume 3: Core System Package [Host Volume]

[4] Bluetooth SIG, Specification of Bluetooth System, Profiles, Version 1.6, Hands-Free Profile