Bluetooth 101. Training for Plantronics презентация

Contact Info Roger Garvert Field Application Engineer   2445 Flambeau Drive Naperville, IL  60564

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

What is Bluetooth? Robust unlicensed short range wireless standard It is an open and license free standard for anyone who signs up to be an adopter The standard is presided over by the Special Interest Group (SIG)

What does Bluetooth provide? Provides point-to-point connections Provides ad-hoc networking capabilities Bluetooth specification details how the technology works Bluetooth Profiles detail how specific applications work to ensure interoperability

Point-to-point Two devices locate each other Form a connection and transfer data “Wireless cable replacement” scenario The device that initiates the connection is called the Master Any other devices the Master is connected to are referred to as Slaves

Point-to-multipoint – the Piconet Two devices create a point-to-point connection A third device comes into range

Identifying Bluetooth Devices Each Bluetooth device is assigned a unique 48-bit MAC address by the Bluetooth SIG This is enough addresses for 281,474,976,710,656 Bluetooth units, this should last a few years even with the optimistic predictions of the analysts! The address is split into three parts: LAP: Lower Address Part - used to generate frequency hop pattern and header sync word UAP: Upper Address Part - used to initialize the HEC and CRC engines NAP: Non-significant Address Part - used to seed the encryption engine

Bluetooth Channels A master can create two types of logical channel with a slave device: Asynchronous Connection Less (ACL): Packet Switched System provides a reliable data connection with a best effort bandwidth; depends on radio performance and number of devices in the piconet Synchronous Connection Oriented (SCO): Circuit Switched System provides real time unreliable connection with a guaranteed bandwidth; usually used for voice based applications The Bluetooth connections are limited to 1Mbps across the air (without EDR) This gives a theoretical maximum of ~723kbps of useable data

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

Spectrum Usage The 2.4GHz ISM band is a free for all for anyone who wants to use it

Frequency Hopping Spread Spectrum - FHSS Bluetooth splits the spectrum up into 79 1MHz wide channels The Bluetooth radio changes transmission frequency 1600 times a second for a 1 slot packet type The frequency hops follow a pseudo-random sequence that meets the power density requirements for the FCC and other regulatory bodies

Benefits of FHSS Reliability - If a packet is not correctly received on one channel due to interference it is unlikely that there will be interference on the next channel used to re-transmit the data Low Interference - Conversely, if Bluetooth is interfering with another system that uses a set of channels, Bluetooth will only use those channels a small proportion of the time Security - Since the hop pattern is pseudo random it is very difficult for anyone to eavesdrop on the Bluetooth link

Hop Selection and Synchronization One frequency hop lasts 625µs, this increment is called a time slot Each Bluetooth device has a clock circuit that counts frequency hops The address of the master of the piconet is used to seed a frequency hop calculation algorithm The phase of the hop sequence is defined by the Bluetooth clock of the master Device address and clock phase information is exchanged during connection negotiation The slave synchronizes its own clock to the master’s during connection so that both devices change frequency at the same time

Adaptive Frequency Hopping Introduced in Bluetooth v1.2 Bluetooth shares the 2.4GHz ISM band with: 802.11b/g Wi-Fi Systems 2.4GHz cordless phones Microwave ovens More devices = More interference. 802.11b/g does not work well with BT interferers. AFH allows BT to avoid known ‘bad’ channels. Increased bandwidth, reduced lost data.

Adaptive Frequency Hopping Three steps

Adaptive Frequency Hopping Three steps Identify Bad Channels by monitoring RSSI, BER and/or PER

Adaptive Frequency Hopping Three steps Identify Bad Channels by monitoring RSSI, BER and/or PER Receive reserved channel usage from host

Adaptive Frequency Hopping Three steps Identify Bad Channels by monitoring RSSI, BER and/or PER Receive reserved channel usage from host Agree with other devices on Bad Channels

Adaptive Frequency Hopping Three steps Identify Bad Channels, monitor RSSI, BER & PER Receive reserved channel usage from host Agree with other devices on Bad Channels

Adaptive Frequency Hopping Three steps Identify Bad Channels, monitor RSSI, BER & PER Receive reserved channel usage from host Agree with other devices on Bad Channels Use alternative channels

Adaptive Frequency Hopping Benefits: Fewer lost packets = better audio quality Less degradation to Bluetooth and 802.11b/g networks Greater bandwidth efficiency Not backward compatible with v1.1 systems

Modulation Scheme During each hop, data is transmitted using Gaussian Frequency Shift Keying, G-FSK. FSK uses two different frequencies to transmit a binary ‘1’ or ‘0’ For Bluetooth the two frequencies are: fc +  for ‘1’ fc -  for ‘0’ where fc = frequency of current hop and  = ~157kHz

Modulation Example For channel 0 (Frequency 2.402GHz)

EDR Modulation Schemes π/4-DQPSK – 2Mbps 1MSps => 2Mbps

EDR Packets v1.2 Packets: v2.0 EDR Packets:

Transmission timing A slave can only send data to the master after it has received a valid packet from the master Masters transmit in even numbered slots and slaves respond in the next odd numbered slot Single slot packets are less then 366µs long to allow the synthesizer to retune to the next frequency hop

Multi-slot packets To increase the throughput of the Bluetooth link longer packets are available. These result in less time spent re-tuning the synthesizer and therefore more time spent transferring data 1, 3 and 5 slot packets are available for use in a dynamic fashion

Packet Types There are 14 basic rate packet types defined, split into 4 segments: Common Packets (both ACL & SCO) Single slot packets ACL 3 slot packets ACL 5 slot packets Each packet type has a different level of error correction and protection and different size payloads

Forward Error Correction Bluetooth defines three levels of forward error correction No Error Correction: There is no error correction! Data is just put in the payload and sent 1/3 FEC: Each bit is repeated 3 times Majority voting decides bit value 2/3 FEC: The data is encoded using a (15,10) shortened hamming code Every 10 bits of data are encoded into 15 bits of data Can correct single bit errors and detect double bit errors

Common Packet Types

SCO Packets

ACL Packets

Mixing ACL and HV3 SCO packets

Mixing ACL and HV2 SCO packets

Mixing ACL and HV1 SCO Packets

Enhanced SCO (eSCO) Bluetooth v1.1 SCO connections have serious impact on air interface usage. Limited to 64kbps audio with CVSD encoding CVSD highly susceptible to packet loss No packet re-transmission Bluetooth v1.2 added multi-slot SCO packet types allows variable data rates Larger duty cycle allows additional connections, scans, etc Also added CRC, FEC and data re-transmission

Bluetooth 1.2 eSCO Packets

Enhanced SCO (eSCO)

Bluetooth 2.0 EDR ACL Packets

Bluetooth 2.0 EDR eSCO Packets

Power Classes Bluetooth defines 3 power classes for devices: Class 1: 0dBm to +20dBm (1mW to 100mW) Class 2: -6dBm to +4dBm (250µW to 2.5mW) Class 3: <0dBm ( <1mW) These power classes translate into approximate distances often used when discussing Bluetooth: Class 1: 100 Meters Class 2: 10 Meters Class 3: <10 Meters

Discovering and Connecting to Other Devices For a Bluetooth device to discover new devices that are in range it must perform an inquiry A device that wants to be found by another device must be in inquiry scan mode Once a device has been found it must be paged to initiate a connection A device that wants to be connected to must be in Page Scan Mode. A device that wants to connect to a particular device must be in Page Mode

Discovering a Bluetooth Device

Establishing a baseband connection

Secure Simple Pairing (SSP) Feature of Bluetooth 2.1 Enables easier connectivity between devices and better use of security features

Input/Output Capabilities Four I/O capabilities defined Display Only Display Yes/No Keyboard Only No Input No Output The I/O capabilities are used to determine which association model is used

“Just Works” User chooses to “add a device”

“Just Works”

Numeric Comparison Step 1 – User enables technology on PC and activates connection from phone Step 2 – User selects “ADD” Step 3 – Phone displays ‘laptop’ and asks user if he/she wishes to connect Step 4 – Phone displays 6-digit number and asks user to confirm Same for mobile phone to car kit and mobile to stereo headset

Passkey Entry Step 1 – User powers on keyboard and activates connection from phone Step 2 – User selects “ADD” on the phone Step 3 – Phone displays ‘keyboard’ Step 4 – User is asked to enter 6-digit number on the keyboard and press “Enter”

Extended Inquiry Response Feature of Bluetooth 2.1 Problem: Takes a long time to find devices, work out what they are called, and what you can do with them… Solution: Include information in the inquiry response Name of Device Profiles supported Etc. Side effects Task oriented actions quicker as devices can get filtered quickly Can transmit other information: time, location, etc.

Low Power Modes To help reduce power consumption, there are three Bluetooth low power modes Sniff Mode (The most used) Hold Mode Park Mode Slaves can request to be placed in any of these modes Masters can ask a slave to enter one of these modes Masters can also force a slave into one of these modes if it has previously accepted the mode

Sniff Subrating Feature of Bluetooth 2.1 Problem: HID devices want low power and low latency Solution: Laptop transmits packets at required latency to mouse to give low latency Mouse ignores laptop most of the time Side effects Better scatternet support Mouse has 2-3 times better battery life Keyboard has 10x better battery life

Sniff Mode Devices agree upon a time delay during which no communication will occur During the silent periods the slave can sleep or perform other functions After the silent period the slave wakes up and ‘sniffs’ for a number of slots for its AM_ADR. If there is no data it goes back to sleep Any active SCO connections between the devices must still be supported Difference between sniff and hold mode: Hold mode is a one shot deal during which no communication occurs Sniff mode defines a repeating period during which no communication occurs

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

Bluetooth Protocol Stack Bluetooth stack is loosely based around the OSI model HCI layer is not a real layer, it is a hardware interface Audio data bypasses the upper layers and is sent straight to the application

The Link Manager (LM)

The Link Manager (LM) Manages link set-up Manages security Manages piconet connections Provides test modes for simplified testing Link manager messages have higher priority than user data LMP messages are not specifically acknowledged LM assumes LC provides error free link But, LC cannot supply 100% error free link!

The Link Manager (LM) cont Link Set-up Procedures: Processes results of Inquiry and Page “Non-connection” oriented commands Device Name, Class of Device, etc. Security Procedures: Authentication, Authorization, Encryption Safer+ algorithm up to 128-bit encryption key Remember there are regional encryption laws to abide by! Pairing and Bonding

The Link Manager (LM) cont. Piconet Connection Management: Packet type adjustment based on channel quality Switch between 1,3 and 5 slot packets Master-Slave role switching Low Power Modes Sniff, Park and Hold Quality of Service contracts Transmit power control

The Host Controller Interface (HCI)

Host Controller Interface (HCI) The HCI interface defines a physical connection between a host (e.g. PC) and a host controller (e.g. Bluetooth module) The specification defines three interfaces: USB v1.1 RS-232 UART It also defines messages that are passed across the HCI interface

HCI - Not really a layer!

HCI cont. Independent of hardware implementation Standard interface to Link Manager and Link Controller HCI Command groups: Link Control (Inquiry, Paging, Encryption, etc.) Link Policy (Hold, Sniff, Park, QoS) Host Controller and Baseband Commands (PINs, event masks, timeouts, etc.) Informational Parameters (Device address, country code, buffers) Status (Link Quality, RSSI, Failed connections) Testing (Test mode commands) Vendor specific commands

Logical Link Control and Adaptation Protocol (L2CAP)

Logical Link Control and Adaptation Protocol (L2CAP) Logical Link Control Multiplexing: many logical links onto one physical link Adaptation Segmentation & reassembly: adapts large packets to baseband size Protocol A well defined set of signaling rules understood by all devices

L2CAP Multiplexing L2CAP adds a Destination Channel ID to every packet The DCID is used to identify and direct packets to the appropriate handler

L2CAP Segmentation and Reassembly

L2CAP Quality of Service No Traffic This level indicates that no traffic will be sent out. Traffic will be incoming only Best Effort Default level of service for all links All values included in the QoS request should be viewed as hints and may be entirely ignored Guaranteed Remote device will attempt to honor the service level Cannot overcome radio level interference Not likely to be able to be maintained under poor radio conditions. Best level of QoS for adding multiple connections

Service Discovery Protocol (SDP)

Service Discovery Protocol (SDP) SDP servers maintain a database on services offered Made up of service records. Servers maintain their own database, there is no central registry. SDP allows clients to search for services. based on attributes and service classes. SDP uses connections set up via the usual Inquiry and Paging operations.

SDP Example

RFCOMM

RFCOMM Serial cable replacement Up to 60 emulated serial port connections per RFCOMM session Depending on implementation, multiple RFCOMM sessions are possible Large base of legacy applications using serial communications Uses GSM TS 07.10 standard Credit Based Flow Control Negotiated credit tokens determine data flow RS-232 control signal emulation RS-232 flow control emulation Software (Xon/Xoff) Hardware (CTS/RTS)

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

Bluetooth Profiles Basic set of standards for common usage models. Reduces set of requirements for each usage model. Ensures interoperability Radio Level – ensures devices can contact each other. Protocol Level – ensures devices can communicate. User/usage Level: Ensures application can interoperate. Ensures user can interact with the device.

Bluetooth foundation profiles

Generic Access Profile

Profile building blocks

Serial Port Profiles

Profile Building blocks

OBEX Profiles File Transfer Object Push Synchronisation

Profiles A2DP- Advanced Audio Distribution Profile AVRCP - A/V Remote Control Profile BIP - Basic Imaging Profile BPP - Basic Printing Profile CTP - Cordless Telephony Profile DID - Device ID Profile DUN - Dial-Up Networking Profile FAX - Fax Profile FTP - File Transfer Profile GAVDP - Generic A/V Distribution Profile GOEP - Generic Object Exchange Profile HCRP - Hardcopy Cable Replacement Profile HDP - Health Device Profile

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

HFP Profile Dependency

Configuration and Roles Audio Gateway (AG) gateway for the audio input/output typically a cell phone Hands-Free Unit (HF) AG’s remote audio input/output means of remote control

Feature Requirements Must support CVSD Only one audio connection per service level connection (SLC) Can have an SLC without an audio connection Must have an SLC with an audio connection

Establishing a Service Level Connection

Transferring Status Information

Answering a call - in-band ring tone

Answer/end call – no in-band ring tone

Three-way call – hold active/accept waiting

Call Control Audio connection setup Audio connection release Answer incoming call from AG Change in-band ring tone setting Reject incoming call from HF Reject incoming call from AG Audio connection transfer toward HF Audio connection transfer toward AG Place call with phone number supplied by HF

Common AT Command and Result Codes

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

A2DP Profile Dependency

Configuration and Roles Source (SRC) Source of digital audio stream that is delivered to the sink of the piconet Media player, phone, PC Sink (SNK) Acts as a sink of the digital audio stream that is delivered by the source Stereo headset, wireless speakers, car audio system

Audio Codec Interoperability Requirements Must support SBC Optional support for MP3, AAC, ATRAC Support can be extended to non-A2DP codecs

Codec Specific Information Elements AVDTP signaling procedure negotiates codec parameters Parameters part of Codec Specific Information Elements Sampling frequencies Channel modes (mono, dual channel, stereo, joint stereo) Bit rates Other information specific to selected codecs

AVDTP Signaling Procedures

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

AVRCP Profile Dependency

Configuration and Roles Controller (CT) Initiates transaction by sending command to target Headsets, remote controls Target (TG) Receives command and generates a response frame Media player, TV, tuner

Feature Requirements

Procedure of AV/C Command

AV/C Command Types UNIT INFO 1394 Trade Association AV/C Digital Interface Command Set SUBUNIT INFO 1394 Trade Association AV/C Digital Interface Command Set VENDOR DEPENDENT Allows own set of AV/C commands PASS THROUGH Used to transfer user operation information from CT to Panel subunit of TG

A/V Categories A/V categories specified to ensure interoperability Four Categories Player/Recorder Monitor/Amplifier Tuner Menu Each category has operations which are: Mandatory for the TG Optional Not supported It is mandatory for CT to support At least one category At least one operation

Supported Operations in TG

Newer AVRCP Versions AVRCP 1.3 - adds support for metadata Query capabilities Query application settings Attributes for currently selected media track Event notifications Continuation (i.e. segmentation/re-assembly) Group navigation AVRCP 1.4 Media player selection Browsing Searching Advanced volume control

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

PBAP Profile Dependencies

PBAP Overview Client-server interaction model Tailored for hands-free usage case Read only – cannot alter content More feature-rich than OPP

Configuration and Roles Phone book Server Equipment (PSE) Contains source phonebook objects Phone Phone book client equipment (PCE) Retrieves phone book objects from server Accessory in automobile, car kit, headset

Phone Book Objects and Representations Based upon IR Mobile Communications specification Five types of phone book objects Main phone book – entries are vCard 2.1 or 3.0 in XML format Incoming call history Outgoing call history Missed call history Combined call history Object representations File representation Folder representation

PBAP Features and Functions

Phone Book Download Sequence Example

Phone Book Browsing Sequence Example

Agenda Bluetooth Overview Bluetooth Air Interface & Baseband Bluetooth Protocol Stack Bluetooth Profiles HFP A2DP AVRCP PBAP New Bluetooth Standards

Bluetooth 3.0+HS Alternate MAC/PHY (AMP) Enables high speed using other radio technologies (e.g. 802.11) Bluetooth Basic Rate acts as control channel Can use 802.11 as high speed bearer channel when needed Enhanced Power Control Faster and more responsive power control

Bluetooth 4.0 (BTle) Used to transfer simple data sets between compact devices Opens up whole new classes of Bluetooth applications watches, sneakers, TV remote controls, medical sensors, etc. Takes less time to make a connection than conventional Bluetooth. Consumes approximately 98% less power than Bluetooth Basic Rate

Why is Bluetooth low energy low power? Bluetooth Listens frequently Listens for a longer time On 1% Bluetooth low energy Transmits quickly Listens quickly Turned off 99.9% of the time

Why is Bluetooth low energy low power?