Bluetooth Low Energy (BLE) is a wireless personal area network technology designed for applications in healthcare, fitness, security, and home entertainment, offering low power consumption and long battery life. It operates in the 2.4 GHz ISM band with various channel and advertising mechanisms to facilitate device discovery and connections. The protocol encompasses roles for devices, security mechanisms, and profiles tailored to specific domains such as healthcare and fitness.

1. Bluetooth Low Energy
Overview

2. What is BLE
• Wireless Personal Area Network technology
• Target for healthcare, fitness, beacons, security
and home entertainment
• Provides considerably reduced power
consumption
• Low Energy requirements, operating for “months
or years” on a button cell
• Small size and low cost
• Compatibility with large installed base
• Starting point of automation in nearly all domain

3. Architecture
BLE Radio
Link Layer
L2CAP
Application / Profiles
APIs
Generic Attribute Profile ( GATT )
Attribute Protocol ( ATT )
Security
Manager
( SM )
Generic
Access
Profile
( GAP )

4. BLE Radio Layer
• Operates in 2.4 GHz ISM ( Industrial Scientific
Medical ) band 2402 MHz – 2480 MHz
• 40 RF Channels with 2 MHz Spacing
• 3 out of 40 channels are advertising
– Used for device discovery
– connection establishment
– broadcast
• Advertising channel frequencies are selected
to minimize the interference

5. BLE Radio Layer …
• All physical channels use GFSK
– Gaussian Frequency Shift Keying modulation
– Allows reduced peak power consumption
– Physical layer data rate is 1 Mbps
• Range is typically 0 – 50 meters from smart
phone

6. BLE Link Layer
• First level of control & data structure over raw
radio operations
• Bit stream transmission & Reception
• State machine & state transitions
• Data & Advertisement Packet formating
• Link Layer operations
• Connections, packet timings, retransmission
• Link Layer level security

7. BLE - PDU

8. BLE L2CAP
• Advertisement
• Scanning
• Connection Establishment

9. BLE L2CAP - Advertisement
• Provides a way for devices to broadcast their
presence
• Allows connection to be established
• Broadcast data like the list of supported
services, device name and TX Power Level
• Device will send advertising broadcast packets
to one or multiple advertisement channels,
which remote devices will pick up.

10. BLE L2CAP – Advertisement
Passive Scanning

11. BLE L2CAP – Active Scanning

12. BLE Advertising Parameters
Parameter Values Description
Advertisement
Interval
20 mSec to 10240 mSec Interval between
advertisement packets
Advertisement
channels
37, 38 & 39 RF Channel used to
transmit
Discoverability Mode Not Discoverable
Generic Discoverable
Limited Discoverable
Broadcast
How the advertiser visible
to other devices
Connect ability mode Not connectable
Directly connectable
Undirected connectable
Defines if advertiser can be
connected or not
Payload 0 – 31 Byte Data byte can be included
in advertisement packet

13. BLE L2CAP – Connection

14. BLE L2CAP – Network Topology
• Advertiser
– Broadcasts advertisement packets
• Scanner
– Only listen for advertisements, can connect to advertiser
• Slave
– Device connected to master
• Master
– Device connected with one or more slaves
– Master can connect upto 4 – 8 slaves at a time
• Hybrid
– Device advertise and scan at the same time
– Connected to a master and advertise or scan
simultaneously

15. BLE L2CAP – Connection

16. BLE L2CAP – Topology Change

17. BLE Generic Attribute Profile
• Provides access to the link layer operations
related to
– Device discovery
– Connection establishment & termination
– Connection timing control
• GAP defines roles
– Broadcaster : Sends advertising & broadcast data
– Observer : Listens for advertising events
– Peripheral : Always slave, is connectable & advertising
– Central : Always master, never advertise
– Device can have more than one role, only one role can
be adopted at a given time

18. BLE GAP Modes
• Connectable
– Can make a connection.
– Not connectable, connectable
• Discoverable
– Can be discovered ( is advertising )
– None, limited, general
• Bondable
– If connectable, will pair with connected device for a
long term connection
– Bondable, Non Bondable

19. BLE GAP Procedures
• Name Discovery
– Find the name of other device
• Device Discovery
– Find address and name of devices
– Define device role
• Link Establishment
– Instruct link layer to send a CONNECT_REQ
– Service discovery, device authentication
• Service Discovery
– Find services available on the peer devices

20. BLE Attribute Protocol
• Defines communication between two devices
playing the roles of server & client
• ATT Protocol defines two roles
– Server : device that stores the data as one or more
attributes
– Client : Collects the information for one or more
servers

21. BLE ATT Data Transfer

22. BLE GATT
• Built on top of Attribute Protocol
• Establishes common framework for data
transported & stored
• GATT defines two roles
– Server
– Client

23. BLE GATT
• Attributes
– Transported by Attribute protocol
– Formatted as services & characteristics
• Service
– Contain collection of characteristics
• Characteristics
– Contain single value and any number of
descriptors

24. BLE GATT Data Structure

25. BLE GATT Characteristics
• Value used in a service
– Expose and / or exchange the data
– Control information
• Well defined, known format
• Information about how the value can be
passed and security achievement
• Contain descriptors describe the value or
permit configuration or characteristics data
indication

26. BLE Security Manager ( SM )
• Ensure the trust, integrity, privacy and
encryption of data
• Security Manager responsible for
– Pairing
– Key distribution
– Generating hashes and short term keys

27. BLE Security Model
• Pairing
– Process of creating shared keys
• Bonding
– Storing the keys created during pairing for later usage
• Device authentication
– Verification of stored keys
• Encryption
– Data confidentiality
• Message Integrity
– Protection against data alteration

28. Profiles – Health Care
• BLP – Blood Pressure Profile
• HTP – Health Thermometer Profile
• GLP – Glucose Profile
• CGMP – Continuous Glucose Monitor Profile

29. Profiles – Sports & Fitness
• BCS – Body Composition Service
• CSCP – Cycling Speed and Cadence Profile
• CPP – Cycling Power Profile
• HRP – Heart Rate Profile
• LNP – Location and Negotiation Profile
• RSCP – Running Speed and Cadence Profile
• WSP – Weight Scale Profile

30. Profiles …
• IPSP – Internet Protocol Support Suite
• ESP – Environmental Sensing Profile
• UDS – User Data Service
• HOGP – HID over GATT Profile