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(formerly known as Cambridge Silicon Radio Ltd.)

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Introduction to Bluetooth Smart

CSR

2Confidential © Cambridge Silicon Radio Limited 2015

• Technology Overview

− Features of the radio interface

− Data transmission principles

• Bluetooth Smart Connections

− Operating modes and roles

− Connection events

− Slave latency

• Communication protocol overview

− ATT and GATT protocol

• Bluetooth Smart profiles

This Session

Introduction to Bluetooth Smart


Dual-mode and Single-mode Radios

• Dual-mode Radio

− Can support Bluetooth classic connections and Bluetooth low energy connections

− Typically for Master devices - Phones, PC, Tablet, PMP, TV

− Does not deliver power savings of Bluetooth Smart

• Single-mode Radio

− Only supports Bluetooth low energy devices (cannot communicate with Bluetooth classic radios)

− Typically for sensors and peripherals (can act as master to a small number of sensors)

− Much lower power than Bluetooth Classic or dual mode radio

Basic Concepts


CSR1010

HID

CSR1011

HID

CSR1011

HID

Heart Rate

CSR1010

Cycle Speed

CSR1010

Insulin

pump

CSR1010

Weight scale

CSR1010

Glucose

meter

CSR1010

Bluetooth Smart ecosystem


What is Bluetooth Smart?


Optimized for low power consumption

• Low data rates

− Optimally less than 64kbps (up to 300kbps theoretical limit)

− Packets are short and the radio is off more

• Simple profile structure – attributes

− Peripheral operates like a database

− Host devices can read or write attributes e.g. battery level

− Peripherals can inform host devices of a change e.g. “key pressed”

Basic concepts


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

Spectrum usage

Direct Radio waves Visible X-rays

Current 100 kHz – 300 GHz light

Extremely Ultraviolet Gamma

low frequency FM radio radiation rays

(ELF) 88-108 MHz

Very

low frequency Microwaves

(VLF) 300 MHz – 300 GHz

medium wave radio

550-1600 kHz

Infrared

long wave radio radiation

150-350kHz

Frequency in hertz (Hz)

kHz MHz GHz

0 102 104 106 108 1010 1012 1014 1016 1018 1020 1022

Bluetooth

• The 2.4GHz ISM Band is

also used by:

• Microwave Ovens

• Digital Cordless

Phones

• 802.11b/g


• Bluetooth Low Energy (Bluetooth Smart)

− Designed to run from Coin Cell Battery

− Optimised for low power, low cost

− Global Standard

− Interoperable

− Robust

− Duty Cycle is low

− Maximum length of packets is very short

• Radio is off for longer periods

− Efficient Protocols

− Fast / Lazy acknowledgement both possible

− Very low latency from wake-up to communication complete (< 10 ms)

− Low data rates

Bluetooth Smart

Slave

Master


Topology

Advertiser

Slave

Master

Slave

Slave

Slave

Advertiser

Scanner

Advertiser

Advertisement


• Transmit output power

− -20dBm to +10dBm

− No concept of Class 1 / 2 / 3

• Receive sensitivity

− -70dBm (-92dBm is expected performance)

• Modulation Index

− 0.5 (compared to 0.25 for Bluetooth BR/EDR)

− Easier to distinguish “1” from “0”

− Frequency hopping not required by regulatory agencies

• No frequency hopping in advertising/scanning

• Frequency hopping only in connections

− Frequency changes every packet (vs. every bit in Bluetooth classic)

Transmitter and Receiver Characteristics


• Data is transmitted using Gaussian Frequency Shift Keying (GFSK)

• FSK uses two different frequencies to transmit a binary ‘1’ or ‘0’

• For Bluetooth low energy the two frequencies are:

− fc + for ‘1’

− fc - for ‘0’

where fc = frequency of current hop and = >185kHz

Modulation Scheme


• For channel 0 (Frequency 2.402GHz)

• During one time slot the data can change value every 1µs, so the transmit frequency oscillates back and forth around the centre channel frequency.

Modulation example

2.402

Frequency,

GHz

>185kHz

To transmit ‘1’

2.402

Frequency,

GHz

>185kHz

To transmit ‘0’


• Frequency hopping occurs while in a connection

− Advertisements are transmitted on 1, 2 or 3 channels at the same time (configurable)

• The frequency hops follow a hop-length that is pseudo-random per connection

− Communicated in the “Connection Request”

− Provides instant adaptive frequency hopping capability

− Can be updated using a channel update message

Frequency Hopping Spread Spectrum -FHSS

2.400

0

Frequency,

GHz

2.402

0

2.480

0

2.483

5

Guard

Band

Guard

Band

Bluetooth Smart connections


Operating States and Roles

State State Description

StandbyDoes not transmit or receive

packets

AdvertisingBroadcasts advertisements in

advertising channels

Scanning Looks for advertisers

Initiating Initiates connection to advertiser

Co

nn

ectio

n

Maste

r Communicates with device in the

Slave role, defines timings of

transmissions

Sla

ve Communicates with device in

Master Role

StandbyAdvertising

Scanning

Initiating

Connection


Establishing BLE Connection

Slave

Master

Slave

Slave

Slave

Advertiser

Advertisement

11

11

11

11

11

11

11

11

11

6

6

6

6

6

6

6

6

6

1

1

1

1

1

1

1

1

1

WiFi

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Data

39

38

37

Advertising

2480

2478

2476

2474

2472

2470

2468

2466

2464

2462

2460

2458

2456

2454

2452

2450

2448

2446

2444

2442

2440

2438

2436

2434

2432

2430

2428

2426

2424

2422

2420

2418

2416

2414

2412

2410

2408

2406

2404

2402

MHz

BLE Channels: An unconnected device decides it wants to be connected....

This device (e.g. data gatherer) needs to “advertise” its presence

• 3 channels for connectable and discoverable

compromise for low power and robustness

• Time when connectable & discoverable = 1.3 ms

(22.5 ms minimum for BR Bluetooth)

• Duty cycle 10x to 20x better than BR Bluetooth


Establishing BLE Connection – Advertising

• Slave device broadcasts its presence when it is ready to communicate.

• Advertising is broadcast on between 1, 2 or 3 available channels (user configurable)

Advertising Event:

Send Advert

PDU on

channel 37

2402 MHz

Send Advert

PDU on

channel 38

2426 MHz

Send Advert

PDU on

channel 39

2480 MHz

Advertising Interval delay Advertising Interval delay

time

Advertising Interval delay

Advertising Interval is configurable by the

host.

Min = 20ms

Max = 10.24s

Pseudo-random delay of 10ms added by

stack to improve coexistence between

devices


Establishing BLE Connection – Scanning

Scanning Interval

Scanning Window

time

Scanning Window and Scanning

Interval are configurable by the host

Min = 2.5ms

Max = 10.24s

If both are the same, scanning is

continuous

time

Scanning interval coincides with advertising event.

Master is aware that the advertiser is present


Establishing BLE Connection

Extract from the Bluetooth Core Specification

Important Parameters for Low Energy Operation

Connection Interval - How much time elapses between connections

Connection Latency – How many intervals a slave device may sleep for


Anchor Points and Latency

time

ConnInterval (e.g. 100ms)

Connection Event

Anchor Point

Master PDUSlave

PDU

time

time

Conn_Latency = 3 (400ms)

Conn_Latency = 0

..........


Anchor Points and Latency

time


time



Frequency Usage

37 0 1 2 3 4 5 6 7 8 9 10 38 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 39

BLE Channel Map

CONNECTION REQUEST

PACKET DATA PAYLOAD

(from core spec)

Channel Map

Bitfield containing information on

which channels are available for use

Min number of channels “enabled”

per connection = 2.

Unused channels are automatically

remapped to used channels

Hop Increment

Channel Hop between

consecutive connection

events.

Bluetooth Smart protocol


Bluetooth Smart stack

FIRMWARE

GATT

ATT SMP GAP

L2CAP

APPLICATION

GA

P S

ERV

ICE

GA

TT

SER

VIC

E

AP

PLI

CA

TIO

N

PR

OFI

LE

AP

PLI

CA

TIO

N

PR

OFI

LE

...

HCI

HARDWARE

LINK LAYER

PHYSICAL LAYER


• All current BLE profiles use ATT for transport

• Client-server architecture

• ATT defines protocol for client to discover and access server data

• Client and server roles do not depend on the link establishment roles –connection initiator can be ATT server or both client and server at the same time

• Server data is arranged in table of attributes

• Each row in the server table is indexed by attribute handle

Attribute protocol

FIRMWARE

GATT

ATT SMP GAP

L2CAP

APPLICATION

GA

P S

ERV

ICE

GA

TT

SER

VIC

E

AP

PLI

CA

TIO

N

PR

OFI

LE

AP

PLI

CA

TIO

N

PR

OFI

LE

...

HCI

HARDWARE

LINK LAYER

PHYSICAL LAYER


• Data is arranged as table of attributes

• Each attribute consists of

− Handle

− Attribute type (UUID)

− Permissions

− Attribute value

Attributes

0001 ATTRIBUTE

0002

FFFE

FFFF

HANDLE

...

ATTRIBUTE

ATTRIBUTE

ATTRIBUTE

HANDLE UUID PERMISSIONS VALUE


• Client-initiated access

− Find information

− Read attributes

− Write attributes

− Queued attribute write

ATT: client-initiated data access


• Server-initiated access

− Notifications

− Indications (acknowledged by client)

ATT: server-initiated data access


• All current BLE profiles are based on GATT

• Reuses ATT data structure and client-server architecture

• Similar to ATT, GATT server and client roles do not depend on the link establishment role

• GATT server data is arranged in services with characteristics

• Defines access protocol to discover and access services and their characteristics

Generic attribute protocol

FIRMWARE

ATT

GATT

SMP GAP

L2CAP

APPLICATION

GA

P S

ERV

ICE

GA

TT

SER

VIC

E

AP

PLI

CA

TIO

N

PR

OFI

LE

AP

PLI

CA

TIO

N

PR

OFI

LE

...

HCI

HARDWARE

LINK LAYER

PHYSICAL LAYER


• GATT server data is conceptually arranged into services, e.g. Battery Service

• The actual data (e.g. battery level in percent or battery state) is represented by characteristics of the service and their values, e.g. Battery Level

GATT database

SERVICE

CHARACTERISTIC

VALUE

DESCRIPTOR

CHARACTERISTIC

VALUE

DESCRIPTOR

CHARACTERISTIC

VALUE

SERVICE

CHARACTERISTIC

VALUE

...

...

...


• The characteristic may be further described by characteristic descriptor, for example:

• Appearance

• Client configuration

• The services, characteristics and descriptors are mapped on top of the ATT table structure

• Services and characteristics are identified by UUID

GATT database

SERVICE

CHARACTERISTIC

VALUE

DESCRIPTOR

CHARACTERISTIC

VALUE

DESCRIPTOR

CHARACTERISTIC

VALUE

SERVICE

CHARACTERISTIC

VALUE

...

...

...


0010 SERVICE DECLARATION

0011

0012

0013

...

CHARACTERISTIC DECLARATION

CHARACTERISTIC VALUE

CHARACTERISTIC DESCRIPTOR DECLARATION

0015

0016



0017

0018



0019 SERVICE DECLARATION

...

SERVICE

0014 CHARACTERISTIC DESCRIPTOR DECLARATION

SERVICE

GATT database mapped to the ATT attributes table


• Client-initiated access

− Services, characteristics and descriptors discovery

− Read characteristic and descriptor value

− Write characteristic and descriptor value

GATT: client-initiated data access


• Server-initiated access

− Characteristic value notification

− Characteristic value indication

• Server has to be configured first by setting the “Client configuration” descriptor of the characteristic

GATT: server-initiated data access


• Defines profile roles

− Broadcaster – optimised for transmitter only applications

− Observer – optimised for receiver only applications

− Peripheral – optimised for low power, slave devices (e.g. sensors, input devices)

− Central – initiates and maintains connections (e.g. smartphone)

Generic Access Profile - GAP

FIRMWARE

ATT SMP GAP

L2CAP

APPLICATION

GA

P S

ERV

ICE

GA

TT

SER

VIC

E

AP

PLI

CA

TIO

N

PR

OFI

LE

AP

PLI

CA

TIO

N

PR

OFI

LE

...

HCI

HARDWARE

LINK LAYER

PHYSICAL LAYER

GATT


• Defines procedures for:

− Discovering identities, names, and basic capabilities

− Creating bonds

− Exchange of security information

− Establishing connections

− Resolvable Private addresses

• Defines Advertising and Scan Response Data formats

• All profiles are built upon GAP

Generic Access Profile - GAP

FIRMWARE

ATT SMP GAP

L2CAP

APPLICATION

GA

P S

ERV

ICE

GA

TT

SER

VIC

E

AP

PLI

CA

TIO

N

PR

OFI

LE

AP

PLI

CA

TIO

N

PR

OFI

LE

...

HCI

HARDWARE

LINK LAYER

PHYSICAL LAYER

GATT


• All current Bluetooth Smart application have to use GATT and GAP

• Mandatory support for GAP service in GAP Central and Peripheral applications

• Mandatory support for GATT service in GATT Client applications

• Bluetooth Smart profiles define requirements to GATT services, security aspects and GAP roles

Application layer

FIRMWARE

ATT SMP GAP

L2CAP

APPLICATION

GA

P S

ERV

ICE

GA

TT

SER

VIC

E

AP

PLI

CA

TIO

N

PR

OFI

LE

AP

PLI

CA

TIO

N

PR

OFI

LE

...

HCI

HARDWARE

LINK LAYER

PHYSICAL LAYER

GATT

Bluetooth Smart profiles


CSR1010

HID

CSR1011

HID

CSR1011

HID

Heart Rate

CSR1010

Cycle Speed

CSR1010

Insulin

pump

CSR1010

Weight scale

CSR1010

Glucose

meter

CSR1010

Bluetooth Smart ecosystem


• The Bluetooth SIG publishes a number ofdocuments that describe Profiles andServices which form the basis of industrywide interoperability:https://www.bluetooth.org/en-us/specification/adopted-specifications


Profiles

Services

Define required functions and features of each layer

Specify inter–layer communication formats

Specify connection, scanning and advertising parameters

Specify collections and format of required characteristics

https://www.bluetooth.org/en-us/specification/adopted-specifications


• Bluetooth Smart profiles and services – as of Q2’14


ANP Alert Notification Profile

ANS Alert Notification Service

BAS Battery Service

BCS Body Composition Service

BLP Blood Pressure Profile

BLS Blood Pressure Service

BMS Bond Management Service

CGMP Continuous Glucose Monitoring Profile

CGMS Continuous Glucose Monitoring Service

CPP Cycling Power Profile

CPS Cycling Power Service

CSCP Cycling Speed and Cadence Profile

CSCS Cycling Speed and Cadence Service

CTS Current Time Service

DIS Device Information Service

ESP Environmental Sensing Profile

ESS Environmental Sensing Service

FMP Find Me Profile

GLP Glucose Profile

GLS Glucose Service

HIDS HID Service

HOGP HID over GATT Profile

HRP Heart Rate Profile

HRS Heart Rate Service

HTP Health Thermometer Profile

HTS Health Thermometer Service

IAS Immediate Alert Service

IPSP Internet Protocol Support Profile

LLS Link Loss Service

LNP Location and Navigation Profile

LNS Location and Navigation Service

NDCS Next DST Change Service

PASP Phone Alert Status Profile

PASS Phone Alert Status Service

PXP Proximity Profile

RSCP Running Speed and Cadence Profile

RSCS Running Speed and Cadence Service

RTUS Reference Time Update Service

ScPP Scan Parameters Profile

ScPS Scan Parameters Service

TIP Time Profile

TPS Tx Power Service

UDS User Data Service

WSP Weight Scale Profile

WSS Weight Scale Service


• CSR µEnergy SDK includes exampleimplementation for the most of the ratifiedBluetooth Smart profiles

− Full source code is available with detaileddocumentation and customisation guidelines

− Example applications are qualified and listed onBluetooth SIG website

− Designed for the final products – significantly reduces product time-to-market, for example:

• Mouse and keyboard applications are designed for real keyboards and mice – available as CSR µEnergy HID Evaluation Kit

• Health and Fitness applications – like heart rate meter, health thermometer, cycling sensor – are designed to run both in simulation mode and on the real hardware

CSR µEnergy SDK example applications


Example applications

• Heart Rate

• Glucose Meter

• Blood Pressure

• Thermometer

• Proximity Tag

• Phone Alert Status

• Mouse

• Keyboard

• GATT Client

• GATT Server

• Apple Notification Center Service

CSR µEnergy SDK 2.4 Applications and Profiles

• Watch

• Cycling Speed and Cadence

• Running Speed and Cadence

• Environmental Sensor

• Beacon

• Weight Scale

• SPP-over-GATT

• Automotive-related

−Temperature and Pressure Sensor

−Keyless Entry System

−Multi-FunctionSteering Wheel

Automotive-related development boards

will be available later in this year

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