BLUETOOTH LOW ENERGY
Operates in 2.4GHz-2.48GHz ISM band
1Mbps over the air data exchange speed (theoretical)
7.5ms – 4 S connection interval
Max 6 packets per connection interval
Max packet size 20 Bytes (increased to 256 in 4.2)
133 * 7.5 = 1000ms
Max bytes per sec = 133 conn. intervals*6 packets*20 bytes =
15960Bps = 125Kbps
Range up to 100meter – 2m-5m optimal
Bluetooth 4.0+ to support LE mode
Bluetooth smart and smart ready support (dual mode)
Low power consumption
Fast connection time
PAIRING, CHANNEL ENCRYPTION AND LINK KEYS
AES-128 with encryption engine
Identity Resolving Key: for privacy
Signing Resolving Key: authentication without
LTK: used for encryption
Paring encrypts the link using a temporary key
Temporary key is derived key: pass key, nfc pair,
Central initiates/terminates connection
Connection is nothing but periodic exchange of data
at regular intervals
Data exchange can be bidirectional, when connected
FHSS – Frequency Hopping Spread Spectrum
Channel = (current_channel+hop) mod 37
Hop value will be communicated on successful connection.
GFSK: Gaussian Frequency Shift Keying used to
encode bit stream over the air.
Link layer manages the preamble, access address,
CRC, encryption, data whitening,
PROFILES VS PROTOCOLS
Protocol is the set of rules followed by different layers
Protocol defines packets format, muxing, encoding and
Protocols are the building blocks to assure device
conformant to bluetooth.org standard
Profiles defines the basic modes of operation to be
supported by all devices conformant to bluetooth.org
These are the set of rules, which essentially define how to
Defines usage model for low level radio
Define roles & procedure to broadcast, discover, establish
connection and manage security etc.
Top most control layer
Entry point for the application to interact with protocol layer
Enables discover, read, write and push data.
Use case specific (GATT based):
SERVICES AND CHARACTERISTICS (CONTD…)
Break data into small logical entities
Collection of characteristic entities
Smallest data units of a service
This is a encapsulated single data point
Entities where actual exchange of data happens
UNIVERSAL UNIQUE IDENTIFIER:
16-bit UUID are generally assigned by the
128-bit UUID are custom ID’s.
BLE FOR IOT RECAP
Why BLE is popular in IoT world?
Why it consumes lesser power than classic BT?
MITM: Man In The Middle attack
Resolvable –private address
Non resolvable private address
BEACONS FOR BETTER USER EXPERIENCE
Proximity based applications
Passenger navigation in airports
Initial setup time
FUTURE OF IOT
Smart consumer goods
Technology that could influence politics
Potential opportunities and global trends
Imagination is the limit
Is BLE PHY layer is full duplex?
What is the difference between GAT/GAP/ATT?
ATT defines the fundamental storage unit for data in BLE.
GATT defines server and client models
GAP provides device information and service listing.
Enables device features like discovery, scan,
What is the server client vs. master slave?
Link layer defines - master/slave
GATT defines - server/client
GAP defines - Central/Pheripheral
What is the MTU size limits?
Can slave and Master transmit on same channel?
Yes ! On every connection it does so.
Works on the basis of electro magnetic radio fields
13.54MHz operating band – same as RFID
Active and Passive modes of operation
No requirement for an additional battery (passive
Short range technology – 10cm
Highly secure compare to any other competing
technologies - (rfid/ble)
Smart card protocol support (contact less smart