Prof. Jong-Won Yu

KAIST

WSN (Wireless Sensor Network)

WSN(Wireless Sensor Network)

Environmentalmonitoring

Health Care

Mood-base services

•Tom’s ceremony•Tom’s friends•Danger’s warning•Personal coaching•Mental counseling•Daily travel

Entertainment

Positioning and animals tracking

Logistics

Transportation

Homes and office

Industrialapplications

q WSN : A network of (possibly low-size and low –complex) devices denoted as nodes that can sense the environment and communicate the information gathered from the monitored field through wireless links.

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UWB

802.11(WLAN/Wi-Fi)

Bluetooth

ZigBee

RFID

Short-range, high-speed networking solution

Long-range networking solution

Short-range networking solution

Networking solution for home/industrial automation

Active/Passive tags for inventory trackingCost/Complexity

q UWB (Ultra-Wideband, IEEE 802.15.3a, IEEE 802.15.4a)- 500 Mbps ( < 2m), 110Mpbps (> 10m)- low power, high speed

q Wi-Fi(IEEE 802.11)- 11 Mbps(2.4GHz), 54Mbps(5GHz)- Range : < 150m- high power (<1W, multi-hours)

q Bluetooth (IEEE 802.15.1)- 1 Mbps- Range : 10 ~ 100m- medium power (multi-days)

q ZigBee (IEEE 802.15.4)- 250 kbps@2.4 GHz, 40 kbps@915 MHz, 20 kbps@868 MHz

- Range : 10 ~ 100 m- low power (multi-month ~ years)

q RFID (140 different ISO standards)- < 200 kbps @ 2.4 GHz- Range : < 1m (passive tag)- unpowered tag (passive tag)

Wireless Sensor System

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IEEE 802.11(Wi-Fi)

q Wireless Local Area Network (WLAN)q 2.4 GHz ISM band (2.4GHz ~ 2.4835GHz) : IEEE 802.11b/g

- DSSS (Direct Sequence Spread Spectrum)- 1Mbps(DBPSK), 2Mbps(DQPSK), 5.5Mbps(CCK), 11Mbps(PBCC)

q 5GHz band(5.15GHz ~ 5.825 GHz) : IEEE 802.11a- OFDM (orthogonal frequency-division multiplexing)- 6 Mbps (BPSK) ~ 54 Mbps(64QAM)

q Operation Range of 100mq 10-5 bit error @ -80dBm

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IEEE 802.11b/g – Radio Block Diagram

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q Direct Conversion

IEEE 802.11a – Radio Block Diagram

q Superheterodyne Conversion q OFDM (Orthogonal Frequency Division Multiplexing)

OFDM Symbol Assembly for N = 8 Subcarriers

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IEEE 802.11(Wi-Fi) – Frequency vs. Channel Allocation

q IEEE 802.11b/g(2.4GHz band)

q IEEE 802.11a(5GHz band)

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Personal Ad-hoc ConnectivityCable ReplacementData/Voice Access Points

Bluetooth

• A Short Range Wireless Communication Technology– Intended to create Personal Area Network (PAN)– Operating Range : 100m (class 1, 100mW), 10m (class 2, 2.5mW), 10 cm (class 3, 1mW)

• Operates in ISM Band (1MHz 79 channel, 2.402 GHz to 2.408 GHz)• Frequency Hopping• Gaussian Minimum Shift Keying (GMSK)• 0.1% bit error rate @ -70dBm• Targeted at all types of Devices

– Wireless Telephones (Cellular, Portables, Satellite, etc.)– Computers, PDAs, Peripherals, etc.– Set-top Boxes, Audio Systems, Cameras and Camcorders, etc.– Consumer Electronics, Headsets, Remote controls, etc.

Bluetooth Transceiver

FLASHBasebandProcessor

RFTransceiver

q GMSK modulation

• 0 : phase no change• 1 : phase change 0 to p

• reducing sideband power(continuous phase)

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Bluetooth Frequency Hopping

2.402 2.480freq

time

slave

master

•Frequency Hopping : 1600hops/sec

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Comparison of Wi-Fi and Bluetooth

Wi-Fi (2.4 GHz band) Bluetooth

DSSS( Direct Sequence Spread Spectrum) FHSS (Frequency Hopping Spread Spectrum)

Use only 22MHz X 3 (channel) = 66 MHz Use 1MHz X 79 (channel) = 79 MHzThe hop rate is 1600 hops/sec

Max data rate 56 Mbps at close range,5.9 Mbps < 175 ft, 5.5 Mbps at 250 ft Max data rate 550 kbps at 250 ft.

Range up to 100 m, depends on power and environment Power range; 100 m (class 1), 10 m (class 2), 10 cm (class 3)

Each Wi-Fi network uses 1 channel, max 3 non-overlapping networks

FCC requires BT devices to hop > 75 channels up to max 79 channels

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WiFi and Bluetooth can Coexist

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ZigBee

q IEEE 802.15.4 LR-WPAN (Wireless Personal Aria Network)q Data Rates : 250 kbps @ 2.4 GHz, 40 kbps @ 915 MHz, 20 kbps @ 868 MHz ( < 1mW)q 255 devices per networkq Low Power Consumption (Battery life multi-month to nearly infinity)q Range : 10m nominal(1~100m)q DSSS (Direct Sequence Spread Spectrum), O-QPSK (2.4GHz Band)

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2.4GHz ZigBee Transceiver

• Direct Conversion• DSSS• O-QPSK

q O-QPSK (Offset quadrature phase-shift keying)

• Offset Ts/2 at Q data• Phase Shift lower than 90o (QPSK 180o)

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Comparision of Zigbee and Bluetooth

Bluetooth Zigbee

Transmission Scheme

FHSS (Frequency Hopping Spread Spectrum)

DSSS (Direct Sequence Spread Spectrum)

Modulation GFSK (Gaussian Frequency Shift Keying)

QPSF (Quadrature Phase Shift Keying) or BPSK (Binary Phase Shift Keying)

Frequency Band 2.4 GHz 2.4GHz, 915MHz, 868 MHz

Raw Data Bit Rate 1 Mbps 250 kbps, 40 kbps, 20 kbps(depends on frequency band)

Power Output Maximum 100mW, 2.5mW, or 1mW(depending on class)

Maximum capability 0.5 mW;Maximum as allowed by local regulation

Minimum Sensitivity -70 dBm for 0.1% BER-85 dBm (2.4 GHz) or -92 dBm(915/868 MHz) for packet error rate < 1%

Network topology Master-Slave 8 active nodes Star or Peer-Peer 255 active nodes

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UWB (Ultrawideband)

q DS-UWB, MB-UWB : IEEE 802.15.3a(PAN) , IR-UWB : IEEE 802.15.4a(WSN)q Data Rates : > 100 Mbps ~ 400 Mbps (BW > 500 MHz) q 3.1~10.6GHz indoor power limit < -41.3 dBm/MHz (noise floor)

* DS-UWB (direct sequence UWB), MB-UWB (multiband UWB), IR-UWB (impulse radio-UWB)

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MB-OFDM UWB & DS-UWB

q MB-OFDM UWB

q DS-UWB

• OFDM(128FFT)/QPSK• 55 ~ 480 Mbps

• CDMA/MBOK(M-ary biorthogonal keying) or BPSK• 28.5 Mbps ~ 1.2Gbps

• 4-ary biorthogonal symbols

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MB-OFDM UWB & DS-UWB Transceiver

q MB-OFDM UWB q DS-UWB transceiver

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Impulse Radio UWB

q Pulse Shape & spectrum (pulse width = 0.192 ns)

q Pulse Position Modulation UWB Radio

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RFID : Radio-Frequency Identification

• The lowest cost of identifying an object• The fastest growing sector of the radio technology industry.

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Range & Operating Frequency of RFID System

q Operating Frequency q Interrogation zones

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Binary Code Signal, subcarrier freq. (fs)

Transponder

Magnetic field H

Inductive Coupling

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Electric field backscattering

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Passive, Semi-passive, and Active RFID

u Passive RFID- no independent source of electricalpower to drive the circuitry in tag- no radio transmitter of their own- Reading range is limited

u Semi-passive RFID- Incorporating a battery to power thepassive tag (battery assisted passive tag)- Long reading range (~ 100m)- wake-up signal from reader

u Active RFID- Synthesizes a carrier signal using a local oscillator and crystal reference- communicate by using different frequency channel

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• Transponder, which is located on the object to be identified• Interrogator or reader, which may be a read or write/read device

Components of RFID System

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UHF RFID Transmitter & Receiver

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Elements of a Passive UHF Tag

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