Internet of Things ( IoT )

Session2 - Protocols

Protocols – IoT Device• Bluetooth Low Energy• Zigbee• Z-Wave• 6LowPAN• Thread• WiFi• Cellular• NFC• SigFox• Neul• LoRaWAN

Bluetooth Low Energy

• Short Range communication technology• Key for wearable IoT products• Not designed for file transfer, more suitable

for small chunks of data• Range : 50 – 150 meters• Offer significantly reduced power

consumption• Access internet via 6LowPAN directly

HCI

BLE Architecture

PHY

Link Layer

L2CAP

GATT/ATT

Profile

Application

BLE – Physical Layer• 2.4 GHz Industrial Scientific Medical Band• 40 Radio channels with 2 MHz spacing• Channel Types– Advertising Channel

• Device discovery, connection establishment and broadcast transmission

• Three channels assigned with center frequencies– Data channel

• Bi directional communication between connected devices• Adaptive Frequency hopping to avoid face interferences and

wireless propagation issues.• 37 data channels available for communication.

BLE – Link Layer• To broadcast data, it transmits data in advertising

channel through advertising channels• Advertiser– Device that transmits the advertising packets– Advertising event : Transmission takes place in intervals.– Sequentially uses each advertising channel

• Scanner– Device only aim at receiving data through advertising

channel• Data communication– Requires them to connect to each other

BLE – Link Layer …

Standby InitiatingAdvertising(Advertiser)

Scanning( Scanner )

Connected

Conn Failed

Initiate

SuccessMaster

SuccessSlave

Conn LostDisconnection

BLE – L2CAP Layer

• Optimized, simplified protocol based on classic bluetooth

• Data services handled in best approach without retransmission and flow control

• Multiplex the data of higher three layers protocols, ATT, SMP and Link Layer Signaling

• Segmentation and reassembly are not used• Upper layer protocol data fits into max L2CAP

payload size – 23 bytes.

BLE – ATT Layer• Defines communication between two devices, which are server & client• Server contains set of attributes• Attribute is a data structure that stores information managed by GATT.• Client or Server will be decided by GATT, is independent of master &

slave in link layer• Client will access server attributes• Server will also send two types of messages

– Notifications – Indications

• Request / response and Indication / Confirmation follow blocked communication

BLE – GATT Layer• A framework uses ATT for device discovery• Exchanges the characteristics from one device to another• Characteristics

– Set of data includes value and properties• Data related to services and characteristics stored in

attributes.• For ex: server with temperature sensor

– Attributes of the sensor– Attributes of temperature measurement– Attributes of measurement units

BLE – Security Layer• Protects information exchange between two

connected devices• Security Modes– LE Security Mode 1– LE Security Mode 2

• Provides security functionality at Link Layer and ATT• Link Layer– Supports encryption & authentication using Cipher Block

Chain Message Code ( CCM ).– 4 Byte Message Integrity Check ( MIC )

• Encryption will be applied to PDU & MIC

BLE - GAP• Highest level of BLE Stack• Specifies

– device roles, modes– Procedures for discovery of devices and services

• Roles– Broadcaster, Observer, Peripheral and Central

• Broadcaster– Only broadcast data– Does not support connections

• Observer– Complimentary of the Broadcaster

• Central– In charge for initiating & managing multiple connections

• Peripheral– Uses a Single connection with a device in central role.

• Device Support multiple roles, but only one at a given time.

BLE – Application Profiles• Blood Pressure• Proximity• Heart Rate• Phone Alert• Alert Notification• Fine Me• Humidity• iBeacon• Health Thermometer• Glucose meter• Temperature• Time • Pressure

BLE – Performance Points

• Power Consumption• Latency• Maximum Pico Net Size• Data Throughput

Some BLE Chips / Modules

• NXP KW4x• TI CC254x, CC26xx• Nordic nRF518xx• BT832 – Bluetooth 5.0• Microchip RN4020• Silabs Bluetooth Smart

Zigbee• Based on 802.15.4 specification• Creates Personal Area Networks with small, low power

digital radios• Simpler & less expensive than wireless PANs like

Bluetooth or WiFi• Transmission distance of 10 – 100 meters• Used in short range low range wireless data transfer

applications• Transmits data over long distance by using mesh networks• Secured with Symmetric Encryption Key

Zigbee Network Architecture

ZC ZR

ZR

ZEDZED

ZED

ZEDExternalNetwork

Zigbee Co Ordinator

• Forms root of network tree and bridge to other networks

• One specific ZC in each network since it the device started

• Stores information about the network• Acts as Trust center & repository for security

keys

Zigbee Router ( ZR )

• Acts as a intermediate router• Passes data from other devices• Can also capable to running application along

with routing.

Zigbee End Device

• Contains limited to functionality to talk with parent node like Co Ordinator or Router.

• Cannot relay data from other devices• This makes the device asleep for a significant

amount of time• Device will consume less power, thereby

giving long battery life.• Requires least processing power & memory.

Zigbee Architecture

Physical Layer

Media Access Control Layer

Network Layer

Application Support Sublayer

Application Framework

Zigbee Device Control ( ZDO )

Zigbee PHY / MAC Layer

• PHY Layer– IEEE 802.15.4 for low rate WPANs– Frequency : 2.40 GHz– Data rate : 250 Kbps– Channels : 11 - 26

• Mac Layer– Uses Carrier Sense Multiple Access / Collision Avoidance

( CSMA / CA )– Transmits beacons for synchronization– Provides reliable communication

Zigbee Network Layer• Supports both star and tree networks and generic mesh

networking• Assigns 16 bit network addresses

• Provides the following functions,– Network initialization– Manages ZED joining or leaving the network– Routes the network packets– Route Discovery of one hop neighbors– Receives and send network data packets– Neighbor discovery

Application Support Sublayer• Provides needed services for application objects ( endpoints )

and ZDO– Binding tables– Message forwarding between devices– Group address and management– Address mapping between 64 bit addresses and 16 bit network

address– Fragmentation and reassembly

• Provides interface with network layer for data transfer like request, confirm and response

• Provides communication for application by defining a unified communication structure like a profile, cluster or endpoint

• Application Support Data Entity• Application Support Management Entity

Zigbee Device Object ( ZDO )• Does the overall device management• Initializes APS Sub layer and Network layer• Configures the operating mode ( Co Ordinator,

Router or Device )• Device and its application services discovery• Handles the binding requests• Supports security management

Zigbee Application

• Home Automation / Smart Home• Smart Building automation• PC & Peripherals• Personal & Healthcare• Industrial Automation• Toys & Gaming Terminal

Some Zigbee Chips / Modules

• Xbee module• NXP KW2x , MC1323x• TI Simple Link• Silabs EFR32xx