Zigbee

Giuseppe Iannaccone

WPAN

Wireless Personal Area Network

• < 10 m omnidirectional

• Low cost, low power, small range, small size

• IEEE 802.15 Working Group

– High Data Rate WPAN (11-55 Mbps)

• 802.15.3

– Medium Data Rate WPAN (Bluetooth v 1.2 MAC & PHY)

• 802.15.1

– Low Data Rate WPAN (MAC & PHY)

• 802.15.4

• Industrial, Home, Medical Applications

• Low cost, Low QoS requirementsGiuseppe Iannaccone

Zigbee and IEEE 802.15.4

• The Zigbee protocol

– Low data rate, low power, low cost

– For automation and remote control

– from the Zigbee Alliance (www.zigbee.org)

• Zigbee Alliance and IEEE joined forces for the development of

the Zigbee protocol

– PHY and MAC of Zigbee are provided by IEEE 802.15.4.

Includes links for star, tree, mesh topologies

• Zigbee 1.0: Dec. 2004

• Zigbee 2007: Oct. 2007

Giuseppe Iannaccone

Zigbee Bluetooth

• Range: 10-75 m

• Datarate:

– 250 Kbps @ 2.45 GHz

– 40 Kbps @ 916 MHz

– 20 kbps @ 868 MHz

• Simple network nodes: 254

• Wake up and receive time:

– 15 ms

• Redundant to remove

“Single point of failure”

• Transmitted power: 1-4 mW

• Range: 10 m (1dBm)

• Datarate:

– 1 Mbps @ 2.45 GHz

• Simple network nodes : 8

• Wake up and receive time:

– 3 s

• Transmitted power: 1 mWGiuseppe Iannaccone

Channels

• Receiver sensitivity (packet error rate<1%):

– -85 dBm @ 2.45 GHz, -92 dBm @ 868 MHz

868MHz / 915MHz

PHY

2.4 GHz

868.3 MHz

Channel 0 Channels 1-10

Channels 11-26

2.4835 GHz

928 MHz902 MHz

5 MHz

2 MHz

2.4 GHz

PHY

Giuseppe Iannaccone

IEEE 802.15.4 (PHY)

• 2 services:

– PHY DATA SERVICES

– PHY Management SERVICES

Phy (MHz) Frequency

band (MHz)

Spreading Parameters Data Parameters

Chip rate

(kchip/s)

Mod. Bit rate

(kbps)

Symbol Rate

(ksymb/s)

Symbols

868/915 868-868.6 300 BPSK 20 20 Binary

902-928 600 BPSK 40 40 Binary

2450 2400-2483 2000 O-QPSK 250 62.5 16-

orthogonal

Giuseppe Iannaccone

IEEE 802.15.4 (PHY)2.4 GHz PHY

• 250 kb/s (4 bits/symbol,

62.5 kBaud)

• Modulation: 16-ary

orthogonal modulation

• The 16 symbols are a set of

(quasi)-orthogonal 32-chip

codes

– MSK 2.0 Mchips/s

868MHz/915MHz PHY

• 868 MHz : 20 kb/s (1

bit/symbol, 20 kBaud)

• 915 MHz : 40 kb/s (1

bit/symbol, 40 kBaud)

• Modulation: BPSK with

differential encoding

• Spreading code: 15-chip

sequence

– 868 MHz Band: 300 kchips/s

– 915 MHz Band: 600 kchips/s

Giuseppe Iannaccone

Trame PHY e MAC

• 4 types of MAC Frame• Data Frame

• Beacon Frame

• Acknowledgment Frame

• MAC Command Frame

Payload

PHY

Header

(PHR)

Synch.

Header

(SHR) PHY Service Data Unit (PSDU)PH

Y L

ayer

MAC

Layer MAC

Header

(MHR)

MAC

Footer

(MFR)

MAC Protocol Data Unit (MPDU)

MAC Service Data

Unit

(MSDU)

Giuseppe Iannaccone

5 bytes 1 byte

Data link

• Without Beacon

– CSMA/CA without slot (asynchronous) with optional

acknowledgment

• With Beacon

– Slotted CSMA/CA (9 slot in the Contention Access Period)

– 7 Guaranteed Time Slots in the Contention Free Period,

assigned by the coordinator to the applications that need a

guaranted band

– Enables energy saving (Zigbee devices can go on standby

between a superframe and the beacon of the following one)

Giuseppe Iannaccone

GTS 1

MAC: Superframe with Beacon

(optional)

15ms * 2n

where 0 ≥ n ≥ 14

Network beacon Transmitted by network coordinator. Contains network information,

frame structure and notification of pending node messages.

Space reserved for beacon growth due to pending node messages

Access by any node using CSMA-CA

GTS 2

GuaranteedTime Slot

Reserved for nodes requiring guaranteed bandwidth [n = 0].

Contention

Access PeriodContention Free

Period

Giuseppe Iannaccone

Data transmission with beacon

From Coordinator to device From Device to Coordinator

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Data transmission without beacon

From Coordinator to Device From Device to Coordinator

Giuseppe Iannaccone

Device types

Full Function Device (FFD)

• Can perform packet routing

• Can communicate with

other FFDs o RFDs

• Can act as PAN coordinator

Reduced Function Device (RFD)

• Cannot perform packet

routing

• Can only communicate with

an FFD

• Can only perform very

simple functions

Giuseppe Iannaccone

(MAC) Star Topology

Full function device

Reduced function device

Communications flow

Master/slave

PAN

Coordinator

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(MAC) peer-to-peer topology

Full function device Communications flow

Point to point Cluster tree

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(MAC) Mixed topology

Full function device

Reduced function device

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(MAC) PAN Formation• Association

– Each device periodically scans the channel to find a local

PAN

– The application chooses whether to associate the device to

a PAN

• De-association

– The coordinator releases a device from a PAN by sending a

de-association notification

– The device can ask to be de-associated by sending a

notification command to the coordinator.

– After the de-association coordinator and device can remove

any reference to the other.

• Note that more than one PAN can coexist in the same channel

Giuseppe Iannaccone

Architettura Zigbee

Giuseppe Iannaccone

Zigbee Nodes

• Zigbee Coordinator

– Forms the network,

– Routes the packets,

– Is a security trust center

– Allows nodes to join the network

• Zigbee Router

– Joins the network, routes the packets, allows other nodes

to join the network

• Zigbee End Device

– Joins the network, operates on batteries, can go in sleep

mode

Giuseppe Iannaccone

Routing Layer – Zigbee (1)

Two hierarchical routing strategies

1) AODV: Ad-hoc On-demand

Distance Vector

• Defines the path of a message

from source to destination. The

nodes on the active path maintain

routing information

• If the source does not know the

path to reach the destination it

sends a discovery packet (RREQ)

with arguments: sender address,

destination address, hop count

Giuseppe Iannaccone

Routing Layer – Zigbee (2)• Those nodes that receive RREQ and

are not the destination, re-send RREQ

with increased hop count. Plus, they

remember from whom they have

received RREQ and hop count

• When RREQ reaches destination, its

sends back a reply command RREP to

the sender of the received RREQ.

• Every node receiving RREP forwards it

to the sender of RREQ and stores the

path in its own routing table

(src,dst,hop count, next hop)

Giuseppe Iannaccone

Zigbee addresses

• The address of every application in a node is an Endpoint (1-

240).

– The endpoint allows the coexistence of multiple

applications and of multiple devices (sensors, actuators)

on the same node.

• Application profiles (16bit): group and define a set of devices

and applications

– Home Automation

– Industrial Plant Monitoring

– Personal Home and Hospital Care, etc.

• Device ID (it identifies the device type)

Giuseppe Iannaccone

APS

Application Support Sublayer

• Generates end-to-end acknowledgments

• Maintains local tables for

– Binding (unidirectional connections between endpoints of

different nodes)

– Groups

– Addresses

• AES 128 bit Security

– 128 bit shared key in the PAN

– Crypted payload of the network layer

– Every frame is authenticated

Giuseppe Iannaccone

ZDO and ZCL services

• Zigbee Device Object

– Is the application running on endpoint 0 of each node

– Maintains the Zigbee network

• Zigbee Cluster Library

– Is a library of functions used to build Zigbee applications

– It is organized in functional domains (e.g. air conditioning,

switches, lighting, …)

Giuseppe Iannaccone

Radio Zigbee/802.15.4 producers• Atmel

• Ember

• Freescale

• Integration Associates

• Jennic

• Microchip

• NEC

• Oki

• Radio pulse

• Renesas

• ST

• TI

Zigbee Platform =

Radio +

MCU +

Zigbee Stack

2 typical solutions

• Radio + MCU in a single

package (SOP)

• Radio module + MCU

connected via SPI

Giuseppe Iannaccone

Freescale MC13224V• Platform-in-Package

• IEEE 802.15.4 standard compliant on-chip transceiver/modem

– 2.4 GHz ISM Band operation

– 16 selectable channels

– Programmable transmitter output power (-30 dBm to +4 dBm typical)

– World-class receiver sensitivity

• < -96 dBm typical receiver sensitivity using Differential Chip

Detection mode (<1% PER, 20-byte packets)

• < -100 dBm typical receiver sensitivity using Non Coherent

Detection mode (<1% PER, 20-byte packets)

– Hardware acceleration for IEEE 802.15.4 applications

– MAC accelerator (sequencer and DMA interfaces

– Advanced encryption/decryption hardware engine (AES 128-bit)

Giuseppe Iannaccone

MC 13224V• 2-bit ARM7TDMI-S CPU core with programmable performance up to 26

MHz (24 MHz typical)

• Extensive on-board memory resources

– 128 Kbyte serial FLASH memory

– 96 Kbyte SRAM

– 80 Kbyte ROM

• Best-in-class power dissipation

– 22 mA typical RX current draw (DCD mode) with radio and MCU active

– 29 mA typical TX current draw with radio and MCU active (coin cell

capable)

– 3.3 mA typical current draw with MCU active (radio off)

– 0.8 mA typical current with MCU idle (radio off)

– 0.85 μA typical Hibernate current (retain 8 Kbyte SRAM contents)

– 0.4 μA maximum Off current (device in reset)

Giuseppe Iannaccone

MC13224V• Extensive sleep mode control and variation

– Hibernate and Doze low power modes

– Programmable degree of power down

– Clock management

– Onboard 2 kHz oscillator for wake-up timer.

– Optional 32.768 kHz crystal oscillator for accurate real-time sleep

mode timing and wake-up with a possible sleep period greater than

36.4 hours

– Wake-up through programmable timer, external real-time interrupts,

or ADC timer

• Extensive MCU peripherals set

– Dedicated NVM SPI interface for managing FLASH memory

– Two dedicated UART modules capable of 2 Mbps with CTS/RTS

support

– SPI port with programmable master and slave operation

Giuseppe Iannaccone

MC13224V

• Two 12-bit analog-to-digital converters (ADCs) share 8 input channels

• Four independent 16-bit timers with PWM capability. These can cascade in

combinations up to

– 64-bit operation

– Inter-integrated circuit (I2C) interface

– Synchronous Serial Interface (SSI) with IS and SPI capability and FIFO

data buffering

– Up to 64 programmable I/O shared by peripherals and GPIO

• Powerful In-circuit debug and FLASH programming available via on-chip

debug ports

— JTAG debug port

— Nexus extended feature debug port

Giuseppe Iannaccone

MC13224V• Low external component count

— Only antenna needed for single-ended 50-Ω RF interface (balun in package)

— Only a single crystal is required for the main oscillator; programmable

crystal load capacitors

— All bypass capacitors in package

• Supports single crystal reference clock source (typical 24 MHz crystal with

13 - 26 MHz usable)

– with on-chip programmable crystal load capacitance or external

frequency source. Also provides

– onboard 2 kHz oscillator for wake-up timing or an optional 32.768 kHz

crystal for accurate low

– power timing.

• 2.0 V to 3.6 V operating voltage with on-chip voltage regulators.

• Optional buck converter for better battery life.

Giuseppe Iannaccone

Data acquisition and localization

infrastructure for an energy plant

Data security: AES 128 bit (link radio) – AES 256 (su filo) – HTTPS (web)

Data acquisition and localization

infrastructure

ICT infrastructure in a plant

• Localization and acquisition infrastructure

– Automatic acquisition of plant operating parameters and

transfer to the information system (retrofit of present

instrumentation with Zigbee radios)

– Localization of workers in plant recognition tour

• Maintenance:

– Plant data acquisition and validation through handset

devices

– Interactivity and decision support

• Analysis of plant operating parameters:

– Anticipation of possible failures and preemptive

maintenance actions

Localization and data acquisition

• Zigbee coordinator and routers: fixed position and connected

to an AC power supply

• Zigbee coordinators on the company intranet (WAN/LAN)

• Retrofit of present instrumentation to ad hoc interfacing to

Zigbee nodes � parameters can be automatically transferred

to company ERP systems

• Wearable zigbee nodes for worker localization (e.g. helmet)

• Headset/Smart Phone for decision support

Localizzazione: varying transmission

powerAltra opzione (trilaterazione)

�Anchor nodes in fixed and known position

� Trilateration

Zigbee transceiver with

dedicated hardware

� Jennic JN5148

� Texas CC2431

�Options: integration with

plant map

Unipi spinoff company on IoT Demo: WSN with Zigbee nodes

Sensori zigbee

Coordinatore/

Gateway

Demo: human/computer interfaceAccesso sicuro https

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