Wireless TechnologyWireless Technology

A T T H E E N D O F T H I S S E C T I O N , Y O U S H O U L D H A V E A N U N D E R S T A N D I N G O F T H E

U N D E R L Y I N G W I R E L E S S T E C H N O L O G I E S U N D E R L Y I N G W I R E L E S S T E C H N O L O G I E S .

References…2

The physical layer…p y y3

“ id h i l l t i l f ti l d “…provides mechanical, electrical, functional, and procedural characteristics to establish, maintain, and release physical connections (e g data circuits) release physical connections (e.g., data circuits) between data link entities.”WSN t i ll i l ff th h lf (COTS) WSNs typically use commercial-off-the-shelf (COTS) wireless communications and infrastructures:

Bl h/Wi l P l A N k (WPAN )Bluetooth/Wireless Personal Area Networks (WPANs)ZigBee/IEEE 802.15.4

Radio technology primer…gy p4

Electromagnetic spectrum provides an unguided Electromagnetic spectrum provides an unguided medium for point-to-point and/or broadcast radio transmissiontransmissionRadio transmission is usually frequency-band limitedtedThe analog bandwidth of the channel determines how much information (analog and digital) can be ( g g )transmittedA transmission channel is subjected to internal and jexternal noise sources; thus degrade, disrupt, or affect the quality of the signal

Propagation….p g5

Th t b i d l f di ti i The most basic model of radio-wave propagation in WSN environments is “direct or free-space wave”

h i ff i di iMechanisms affecting radio propagation:Reflection

A i l i i bj l h i lfA signal impinges upon an object larger than itselfDiffraction

The radio path is obstructedThe radio path is obstructedScattering

Impingement by smaller objectsp g y jSignal strength fluctuations

Multipath, large- and small-scale effects

Modulation…6

i th l f “i t lli t” i l …is the overlay of an “intelligent” signal over an underlying carrying signal, which is then transmitted over the mediumover the mediumTypes:

AM (ASK), FM (FSK), PM (PSK)Combination of ASK and PSK is QAM

Spread spectrumSpread spectrumDSSS (used by WLANs, including ZigBee)FHSS (used by Bluetooth PANs)FHSS (used by Bluetooth PANs)

Typical frequency bands…yp q y7

I d t i l i tifi di l (ISM) b d t GH Industrial, scientific, medical (ISM) band at 2.4GHz (2.412–2.484)

li d k f i f (Unlicensed Network Information Infrastructure (U-NII) band at 5GHzUltra wide band (UWB) at 3.1–10.6GHz

UWB…8

IEEE 802 wireless space…p9

WWAN IEEE 802.22

nge WMAN

WiMax

IEEE 802.20

Ran

WLAN WiFi

IEEE 802.16

ZigBee802.15.415.4c

802.15.3802.15.3cWPAN

802.11Bluetooth802 15 1 802.15.3c

0.01 0.1 1 10 100 1000

802.15.1

Source: ZigBee Alliance Tutorial Data Rate (Mbps)

ZigBee…g10

A technological standard based on the IEEE 802 15 4 A technological standard based on the IEEE 802.15.4 specification for low data rates in the Industrial, Scientific, and Medical (ISM) radio bandsScientific, and Medical (ISM) radio bandsThe technology

allows for devices to communicate with one another with very allows for devices to communicate with one another with very low power consumption, allowing the devices to run on simple batteries for several yearsis targeting various forms of automation as the low data rate is targeting various forms of automation, as the low data rate communication is ideal for sensors, monitors, and the like Home automation is one of the key market areas for Zigbee, y gwith an example of a simple network shown next

Sources: ZigBee Alliance Tutorial; presentation slides by C DiamondSources: ZigBee Alliance Tutorial; presentation slides by C. Diamond

ZigBee: Home automation…g11

ZigBee: and IEEE 802.15.4…g 5 412

Group 15 works more specifically with wirelessGroup 15 works more specifically with wirelessnetworkingTask Group 4 drafted the 802.15.4 standard for a low Task Group 4 drafted the 802.15.4 standard for a low data rate wireless personal area network (WPAN).

The standard for this WPAN specifies not only a low data rate but l l ti d l l it th also low power consumption and low complexity, among other

things.The data rate is limited to 250 kbps in the global 2.4 GHz Industrial, S i ifi M di l (ISM) b d kb i h 868 MH b d d Scientific, Medical (ISM) band, 20 kbps in the 868 MHz band used in Europe, and 40 kbps in the 915 MHz band used in North America and Australia.The ZigBee standard is built on top of this IEEE standard, addressing remote monitoring and control for sensory network applications.

ZigBee: and IEEE 802.15.4…2g 5 413

Application

API

Customer

– “the software”

– Network, Security & Security32- / 64- / 128-bit encryption

API

ZigBeeApplication layers

– Brand managementNetwork

Star / Mesh / Cluster-Tree

32 / 64 / 128 bit encryption ZigBeeAlliance

IEEE 802.15.4– “the hardware” PHY

MACIEEE

802 15 4– Physical & Media Access

Control layers

PHY868MHz / 915MHz / 2.4GHz

802.15.4

Silicon Stack App

ZigBee: Topologies…g p g14

Mesh

Star

ZigBee CoordinatorZigBee CoordinatorZigBee RouterZigBee End Device

Cluster Tree

ZigBee: Device types…g yp15

ZigBee Coordinator (ZC)ZigBee Coordinator (ZC)One required for each ZB networkI i i k f iInitiates network formation

ZigBee Router (ZR)Participates in multihop routing of messages

ZigBee End Device (ZED)gDoes not allow association or routingEnables very low cost solutionsEnables very low cost solutions

ZigBee: Stack architecture…g16

I i i d j i k

ApplicationInitiate and join networkManage networkDetermine device relationshipsSend and receive messages

Application ZDO

App Support (APS)S it f ti

Device managementD i di

NWK

pp pp ( )SSPSecurity functions

Network organizationR t di

Device binding

Device discoveryService discovery

Physical Radio (PHY)

Medium Access (MAC)Route discoveryMessage relaying

e ce b d gMessaging

ZigBee: Applications…g pp

securityTVVCRDVD/CD

t

securityHVACAMR

lighting controlt l ZigBee

Wireless Control that Simply Works

CONSUMER ELECTRONICS

remoteBUILDING AUTOMATION

access control

p y

PC &PERSONAL

mousekeyboardjoystick

patient monitoring

fitness monitoring

TELECOM SERVICES

it

PC & PERIPHERALS

asset mgt

PERSONAL HEALTH CARE

j ymonitoring

m-commerceinfo servicesobject interaction HOME

CONTROL

securityHVAClighting controlaccess controlINDUSTRIAL

CONTROL

asset mgtprocess control

environmental j(Internet of Things)

CONTROL access controlirrigation

CONTROLenergy mgt

Bluetooth…18

Named after a Danish Viking and King Harald BlåtandNamed after a Danish Viking and King, Harald BlåtandConceived initially by Ericsson (1994) and later became an industry standard, Bluetooth is a standard for a

ll h di hi b l d dsmall, cheap radio chip to be plugged into devices, such as computers, printers, and mobile phonesIt is a cable-replacement technology: new It is a cable-replacement technology: new technology using short-range radio links, intended to replace the cable(s) connecting portable and/or fixed

l t i d ielectronic devicesData rates:

Version 1.1 up to 720 KbpsVersion 1.1 up to 720 KbpsVersion 1.2 up to 1 MbpsVersion 2.1 (current) with enhanced data rate (EDR), up to 3 Mbps

Bluetooth: Specs…p19

Th ifi ti id f diff t l f The specification provides for different classes of radio that allow transmission ranges of up to 100 meters by boosting the radio power meters by boosting the radio power. The technology isn't limited to line of sight t i i i it di ti l th t transmission since it uses directional waves that are capable of transmitting through many obstructions.

h ifi i d fi di dThe specification defines a radio system and a "stack" of protocol layers and profiles.

Bluetooth: Technology…gy20

U d ti f h i (AFH) bilit t Uses adaptive frequency hopping (AFH) capability to reduce interference between wireless technologies sharing the 2 4 GHz spectrumsharing the 2.4 GHz spectrum.The operating range depends on the device class:

l d h f fClass 3 radios —have a range of up to 1 meter or 3 feet Class 2 radios—most commonly found in mobile devices —have a range of 10 meters or 30 feet (most commonly used)have a range of 10 meters or 30 feet (most commonly used)Class 1 radios —used primarily in industrial use cases —have a range of 100 meters or 300 feetg 3

Bluetooth: Protocol stack…21

Th t i t f RF t i The core system consists of an RF transceiver, baseband, and protocol stack.

Bluetooth: Core layers…y22

HCI: The Host Controller Interface layer provides a standard HCI: The Host Controller Interface layer provides a standard communications protocol between the stack and the Bluetooth module. HCI communication packets can be transmitted using UART RS232 or USB interfaceUART, RS232 or USB interface.L2CAP The Logical Link Control and Adaptation Protocol layer allows multiple channels to share a single Bluetooth link. It also handles segmentation and assembly of long messages group handles segmentation and assembly of long messages, group management and quality of service functionalities.RFCOMM: The RFCOMM layer implements the functionalities of a virtual RS232 link Most of the application Profiles uses of a virtual RS232 link. Most of the application Profiles uses RFCOMM as a means of transmitting and receiving data.SDP The Service Discovery Protocol layer provides functionalities to publish supported Bluetooth functionalities functionalities to publish supported Bluetooth functionalities (SDP server), as well as for querying remote Bluetooth devices for supported functionalities (SDP client).

Bluetooth: Higher layers…g y23

Th hi h l i l t “Bl t th The higher layers implement one or more “Bluetooth profiles” with specific APIs:

Bluetooth audioBluetooth audioBluetooth printingData access profiles (incl. TCP/IP over Bluetooth)Information transfer profiles (calendar, contacts sync.)Human Interface device profiles (mouse, keyboard,…)