Junseok Kim

Wireless Networking Lab (WINLAB)

Konkuk University, South Korea

http://usn.konkuk.ac.kr/~jskim

1

IEEE 802.x Standards 802.11 for Wireless Local Area Network

802.15 for Wireless Personal Area Network

802.16 for Broadband Wireless Metropolitan Area Network

2

1997 1999 2003 2005 2007 2009

802.11 legacyreleased

802.11 legacyclarified

802.11a&breleased

802.11greleased

Amendmentscombined

802.11nreleased

802.11ereleased

IEEE 802.x Standards 802.11 for Wireless Local Area Network

802.15 for Wireless Personal Area Network

Task Group (TG) 1 (WPAN / Bluetooth)

Released in 2002 Revised in 2005 / max. 1Mbps / 2.4GHz / freq. hopping (Bluetooth 2.0+EDR supports 3Mbps)

TG 2 (Coexistence)

TG 3 (high rate WPAN)

Released in 2003 / max. 55Mbps / 2.4GHz / no spreading code

TG 4 (low rate WPAN / ZigBee)

Released in 2003 / max. 250kbps / 2.4GHz / DSSS

3

Home Network with IEEE Standards

4

802.11 802.11

802.15.4

802.15.1

Not determined

802.15.1

CSMA-CA Carrier Sense Multiple Access – Collision Avoidance

5

DATA

ACK

silent...

silent...

S

R

DATA

R S

R

S1

S2

DATA

DATA

ACK

ACK ACK

CSMA-CA (Cont.) Collision Avoidance

6

DATA

collision

DATA

RS1 S2

collisionR

S1

S2

DATA

DATA

DATA

silent...

No ACK

CSMA-CA (Cont.) RTS-CTS handshaking

7

collisionR

S1

S2

DATA

DATA

DATA

silent...

collisionR

S1

S2

DATA

silent...

No ACK

RTS

RTS

No CTS

RTS

CTS ACK

CSMA-CA (Cont.) Hidden node

8

DATADATA DATA

collision

RTSCTS

CTSsilent

0 1 2 3

0 1 2 3

Hidden node

NAV

CSMA-CA (Cont.) Random back-off (BO)

9

DIFS

BO 8 slot

BO 3 slot

BO 10 slot

BO 6 slot

BO 5 slot

BO 7 slot

BO 3 slot

0

1

2

3

RTS

CTS

DATA

ACK

NAV

NAV

RTS

CTS

DATA

NAV

BO = uniform(0, CW) * slotTime

3slots

CSMA-CA (Cont.) Contention Window (CW)

1015

3163

127

255

511

1023

CW

*Window: An interval of time during which an activity can or must take place

802.11e enhanced distributed channel access (EDCA)

Enhancement of distributed contention function (DCF) in 802.11 legacy

11

DATADATA SIFS

PIFS

DIFS

AIFS[i]

Contention Window

Access Class CWmin CWmax AIFSN TXOP limit

BACKGROUND aCWmin (=15) aCWmax (=1023) 7 0

BEST EFFORT aCWmin aCWmax 3 0

VIDEO (aCWmin+1)/2-1 aCWmin 2 3.008ms

VOICE (aCWmin+1)/4-1 (aCWmin+1)/2-1 2 1.504ms

802.11e (Cont.) Block ACK

12

AD

DB

A R

equ

est

AC

K

AD

DB

A R

espo

nse

AC

K

Qo

S D

ata MP

DU

Qo

S D

ata MP

DU

Qo

S D

ata MP

DU

Qo

S D

ata MP

DU

...B

lock

Ack

Req

uest

AC

K

Blo

ckA

ck R

espo

nse

AC

K

DE

LB

A R

equ

est

AC

K

NAV

Originator

time

time

Recipient

Other STAs

Setup Data & Block ACK Tear Down

802.11n Data rate is up to 600Mbps

802.11g’s max. data rate is 54Mbps

13

time

freq

802.11g 802.11 n

802.11g vs. 802.11n 802.11g

64QAM: 6bits (=log264) per one symbol

OFDM: 48 sub-carriers * 6 = 288bits

3/4FEC: 288 * 3/4 = 216bits

4us symbol duration: 216/4 = 54Mbps

802.11n 64QAM: 6bits

OFDM: 108 sub-carriers * 6 = 648bits

5/6FEC: 648 * 5/6 = 540bits

4 sets of TX/RX antennas: 540 * 4 = 2160bits

3.6us symbol duration: 2160/3.6 = 600Mbps

14

MANLAN

Do not Confuse Wireless Sensor Network (WSN) is neither Bluetooth,

ZigBee, WiFi, or any IEEE Standard.

15

PAN

802.15

802.11

802.16

802.15.1 IEEE Standard for Wireless Personal Area Network (WPAN)

For wireless connectivity with fixed, portable, and moving devices within a personal operating space.

1600 hops/sec across 79 frequencies Class 1: +20 dBm (100 mW), 50-100 meters Class 2: +4 dBm (2.5 mW), 20 meters Class 3: 0 dBm (1 mW), 10 meters

.

16

625us

3-slot packet 5-slot packet

fk fk+1 fk+2 fk+3 fk+4 fk+5 fk+6 fk+7 fk+8 fk+9 fk+10 fk+11 fk+12 fk+13 fk+14 fk+15 fk+27-1

…

max. length

802.15.1 (Cont.) Master establishes a piconet with up-to 7 slaves

Master determines piconet’s frequency hopping pattern

17

M

S1 S1 S6 S7….

M

S1 S1 S6 S7….either

PICONETSCATTERNET

802.15.4 IEEE Standard for Low-Rate Wireless Personal Area

Network (LR-WPAN) For communication devices using low data rate

low power

low complicate

short range radio

Do not Confuse 802.15.4 is not ZigBee

ZigBee is not WSN

18

802.15.4 - Low Power Most LR-WPAN devices operates with small batteries

Turn off the radio periodically to save the energy

19

S

RPower On

Power On

DATA

ACK

S

RPower On

Power On

DATA

ACK

Power Off

Power Off

Energy Efficiency

<

802.15.4 – Super-frame Structure Most LR-WPAN devices operates with small batteries

20

CONTENTION ACCESSPERIOD

CONTENTIONFREE PERIOD

INACTIVE

Super-frame

active

beacon beacon

802.15.4 – ZigBee vs. Bluetooth ZigBee defines network, security, application layers

21

PHY

MAC

Application Support Sublayer Zig

Bee

80

2.15.4 RF (Radio transceiver)

Baseband Controller (timing, framing, flow control . . .)

Link Manager (managing slaves, connections, power . . .)

Host Controller Interface

Logical Link Control and Adaptation Protocol

Profiles

Applications

RFCOMMTCP/IP

Audio

Service Discovery ProtocolReflectorManagement

APS MessageBroker

APS SecurityManagement

Network Layer

SecurityManage.

NWK Message

RoutingManage.

NetworkManage.

ApplicationFramework

ZigBee Device Object

Blu

etoo

th

Home Network with IEEE Standards

22

802.11 802.11

802.15.4

802.15.1

Not determined

802.15.1

Wireless Sensor Network (WSN) Large Ad-hoc Network consists of numerous sensors

(which have RF transmitter)

23

WSN applications But, very few commercial success. Why?

In addition, research interests on WSN decline.

24

Home Networking Structure Health Monitoring Disaster Monitoring

low power MCU

low capacity Memory

low power low rate Transceiver

Maybe. It’s Future direction A few leading research centers started these kinds of

projects

25

Future WSN device?

Integrated & Cognitive Wireless Connection

More features (e.g. camera, GPS)

Pedestrian navigationLocation-based servicesIntelligent Transportation Systems Smart shopping assistantEntertainment integrationEnvironment Monitoring in City by iPhones

Powerful MCU

Research topics on WPAN and WSN

Application

Transport

Network

MAC

PHY

Topology control

Routing

Localization

Coverage

Transmit power control

Duty cycle

Channel Modeling

Multi rate / multi channel

Energy-aware routing

Traffic-aware routing

Data aggregation

Geographical routing

Network connectivity

Reduce energy consumption

Traffic-aware duty cycle

Power-aware duty cycle

RSSI based localization

GPS-free localization

TOA based localizationMonitoring system

Increase network capacity

Interference impact

Link quality estimation

Congestion control

Fast recovery

27