chapter 3: overview 802 standard - universität bremen 3: overview 802 standard - 2 - tzi – fb 1...

TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2012

Chapter 3: Overview 802 Standard

- 2 - TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014

IEEE - Institute of Electrical and Electronics Engineers

What is the IEEE?• international non-profit, professional organization for the advancement

of technology related to electricity. • largest technical professional organization in the world (in number of

members), with more than 360,000 members in around 175 countries (2005)

What does the IEEE do?• produces 30 percent of the world's literature in the electrical and

electronics engineering and computer science field, • sponsors or cosponsors more than 300 international technical

conferences each year. • publishes an extensive range of peer-reviewed journals, • major international standards body (nearly 900 active standards with

700 under development).


Notable IEEE Committees and Formats• IEEE 754 floating point arithmetic specifications• IEEE 802 LAN/MAN• IEEE 802.11 Wireless Networking• IEEE 829 Software Test Documentation• IEEE 896 Futurebus• IEEE 1003 POSIX• IEEE 1076 VHDL VHSIC Hardware Description Language• IEEE 1149.1 JTAG• IEEE 1275 Open Firmware• IEEE 1284 Parallel port• IEEE P1363 Public key cryptography• IEEE 1394 Serial Bus ("FireWire")• IEEE 12207 Information Technology


IEEE 802• Family of IEEE standards on

– metropolitan area networks– local area networks– personal area networks

restricted to non-isochrononous networks carrying variable-size packets.

• By contrast: in cell-based networks data is transmitted in short, uniformly sized units called cells.

• Isochronous networks, where data is transmitted as a steady stream of octets, or groups of octets, at regular time intervals (example: mobile phone networks).

Source: IEEE


IEEE 802 OverviewIEEE 802.1 Higher layer LAN protocols IEEE 802.2 Logical link control IEEE 802.3 Ethernet IEEE 802.4 Token bus IEEE 802.5 Token Ring IEEE 802.6 Metropolitan Area Networks IEEE 802.7 Broadband TAG IEEE 802.8 Fiber Optic TAG IEEE 802.9 Integrated Services LAN IEEE 802.10 Interoperable LAN SecurityIEEE 802.11 Wireless LAN

Grey entries: working group ishibernated ordisbanded

IEEE 802.12 demand priority IEEE 802.13 (not used) IEEE 802.14 Cable modems IEEE 802.15 Wireless PAN IEEE 802.16 Broadband wireless access IEEE 802.17 Resilient packet ring IEEE 802.18 Radio Regulatory TAG IEEE 802.19 Coexistence TAG IEEE 802.20 Mobile Broadband Wireless

Access IEEE 802.21 Media Independent Handoff IEEE 802.22 Wireless Regional Area

NetworksIEEE 802.23 Emergency ServicesIEEE 802.24 Smart Grid TAG

www.ieee802.org


Network Differentiation by Range• Body Area Networks (BAN)• Personal Area Network (PAN)

– wireless PAN (IEEE 802.15)

• 802.15.1/Bluetooth• 802.15.3/UWB• 802.15.4/ZigBee

• Local Area Network (LAN) – Ethernet (IEEE 802.3)– Wireless LAN (IEEE

802.11)– HomePNA (ITU-T G.hn) – Power line communication

(IEEE 1901)

• Metropolitan Area Network (MAN) – IEEE 802.16

• Regional Area Network (RAN)– IEEE 802.22

www.ieee802.orgwww.homepna.orgwww.homeplug.org


OSI Layers and IEEE 802Services and protocols specified in IEEE 802 address the lower two layers (Data Link and Physical) of the seven-layer OSI networking reference model

802.11802.15802.16802.20

{


Chapter 4: Wireless LANs IEEE 802.11

These slides are to a great extent based on slides of Jochen Schiller,

“Mobilkommunikation”, Chapter7


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Overview Chapter 44.1 Characteristics of WLANs4.2 Overview on IEEE 802.114.3 IEEE 802.11 Physical Layer

• Legacy 802.11, 802.11b, a, g, n• Future developments: 802.11ac,ad

4.4 IEEE 802.11 MAC Layer4.5 Security in 802.11


4.1 Characteristics andDesign Goals


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Characteristics of wireless LANs• Advantages

– very flexible within the reception area – ad-hoc networks without previous planning possible– (almost) no wiring difficulties (e.g. historic buildings, firewalls)– more robust against disasters like, e.g., earthquakes, fire - or users pulling

a plug... • Disadvantages

– typically lower data rate compared to wired networks (600 Mbit/s vs. 10 Gbit/s), higher error rates (10-4 instead of 10-12)

– many proprietary solutions, especially for higher bit-rates, standards take time (e.g. 802.11n)

– products have to follow many national restrictions if working wireless, it takes a very long time to establish global solutions like, e.g., IMT-2000

– heavy interference on ISM band, no service guarantees


- 12 -

Design goals for wireless LANs● global, seamless operation● low power for battery use ● no special permissions or licenses needed to use the WLAN ● robust transmission technology● simplified spontaneous cooperation at meetings ● easy to use for everyone, simple management ● protection of investment in wired networks ● security (no one should be able to read my data), privacy (no one

should be able to collect user profiles), safety (low radiation)● transparency concerning applications and higher layer protocols, but

also location awareness if necessary


4.2 Overview on IEEE 802.11


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The IEEE 802.11 Standard802.11 Working Group for Wireless LANs• “over-the-air” interface

– between wireless client and base station– among wireless clients

• comparable to the IEEE 802.3 standard for Ethernet for wired LANs

• addresses both the Physical (PHY) and Media Access Control (MAC) layers

• resolve compatibility issues between manufacturers of Wireless LAN equipment.

[http://standards.ieee.org/wireless/overview.html]


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Infrastructure vs. Ad-hoc Networksinfrastructure network

ad-hoc network

APAP

AP

wired network

AP: Access Point


- 16 -

802.11 - Architecture of an infrastructure network• Station (STA)

– terminal with access mechanismsto the wireless medium and radiocontact to the access point

• Basic Service Set (BSS)– group of stations (incl. AP) using

the same radio frequency• Access Point

– station integrated into the wireless LAN and the distribution system

• Portal– bridge to other (wired) networks

• Distribution System– interconnection network to form one

logical network (ESS: Extended Service Set) based on several BSS

Distribution System

Portal

802.x LAN

Access Point

802.11 LAN

BSS2

802.11 LAN

BSS1

Access Point

STA1

STA2 STA3

ESS


- 17 -

802.11 - Architecture of an ad-hoc network

• Direct communication within a limited range– Station (STA):

terminal with access mechanisms to the wireless medium

– Independent Basic Service Set (IBSS):group of stations using the same radio frequency

802.11 LAN

IBSS2

802.11 LAN

IBSS1

STA1

STA4

STA5

STA2

STA3


- 18 -

Legacy IEEE 802.11

• Original version released in 1997• 1 and 2 Mbit/s via infrared (IR) and ISM band (2.4 Ghz)

– IR was never implemented in commercial products• Media access method: Carrier Sense Multiple Access with Collision

Avoidance (CSMA/CA)• 5 different, somewhat-interoperable, commercial products appeared

using the original specification, e.g. – Alvarion PRO.11 and BreezeAccess-II), Netwave Technologies (AirSurfer

Plus and AirSurfer Pro) and Proxim (OpenAir).

• Weakness of original spec.: too many choices, interoperability = challenge ⇒ rapidly supplemented by 802.11b.


- 19 -

IEEE 802.11b/a• IEEE 802.11 b

– Higher Speed Physical Layer Extension in the 2.4 GHz Band (1999)– 2 additional modulation schemes: CCK, PBCC 5.5 or 11 Mbit/s→

– Uses DSSS, downward compatible to 802.11 1 Mbit/s

• IEEE 802.11 a– High Speed Physical Layer in the 5 GHz Band, (1999)– OFDM with BPSK, QPSK, 16-QAM and 64-QAM, coding rates 1/2,

3/4 leading to data rates of 6 – 54 Mbit/s


- 20 -

IEEE 802.11g/n• IEEE 802.11 g

– Further Higher Data Rate Extension for the 2.4 GHz Band (2003)– OFDM within 2.4 GHz band– Data rates up to 54 Mbit/s as in 802.11a– Downwards compatible to 802.11

• IEEE 802.11 n– Enhancements for Higher Throughput (2009)– Multiple Input Multiple Output, Frame Aggregation– Gross data rates up to 600 Mbit/s


- 21 -

IEEE 802.11 c-rIEEE 802.11c (included in 802.1D) (2001)• Bridging functionaliy for data exchange

between wireless and wired networks (MAC layer)

IEEE 802.11d (2001)• Specification for operation in additional

regulatory domainsIEEE 802.11e (2005)• Quality-of-Service support (ongoing work)• Different service classes, traffic types…IEEE 802.11F (withdrawn 2006)• Specification of an Inter-Access Point

Protocol (IAPP)• Seamless handover on link-layer; support

of different vendors in larger WLANsIEEE 802.11h (2004)• Spectrum Management in Europe for 5

GHz band (802.11a)• Dynamic Frequency Selection/Transmit

Power ControlIEEE 802.11i (2004)• Enhancing Security and Authentication • Extension of basic WEP (Wired Equivalent

Privacy)

IEEE 802.11j (2004)• 4.9-5 GHz adaptation for JapanIEEE 802.11k (2008)• Enhancements for Radio Resource

Measurements IEEE 802.11p (2010)• For vehicular usage, speeds up to 200km/h• 1 km range, 5 GHz frequency band• WAVE – Wireless Access for the Vehicular

EnvironmentIEEE 802.11r (2008) • Improves L2 handover, Fast RoamingIEEE 802.11s (2011)• Wireless Distribution Systems and

Extended Service Set Mesh Networking• Self-configuring multi-hop topologies to

improve ad-hoc capabilities of 802.11IEEE 802.11T• Wireless Performance Prediction (WPP) -

test methods and metrics


- 22 -

IEEE 802.11u (2011)• Interworking with non-802.11 networksIEEE 802.11v (2011)• Wireless Network ManagementIEEE 802.11w (2009)• Protected Management FramesIEEE 802.11y (2008)• 3650-3700 MHz operation in the U.S.IEEE 802.11z (2010)

Extensions to Direct Link Setup (DLS)IEEE 802.11aa (2012)

robust streaming of audio video transport streams

IEEE 802.11ac (ongoing)very high throughput < 6 Ghz

IEEE 802.11ad (2012)very high throughput at 60 GHz

IEEE 802.11ae (2012)QoS Management

IEEE 802.11af (ongoing)WLAN in TV Whitespace

IEEE 802.11ah (ongoing)Sub 1 GHz

IEEE 802.11ai (ongoing)Fast Initial Link Setup

IEEE 802.11aj (onging)Chinese millimeter-wave freq. bands

IEEE 802.11ak (onging)Enhancements For Transit Links Within Bridged Networks

IEEE 802.11aq (ongoing)Pre-association discovery

IEEE 802.11.2• Def. of Performance metrics,

measurement methodologies and test conditions

IEEE 802.11 s-aq, 802.11.2

802.11a to z now included in 802.11-2012


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IEEE Standard 802.11

mobile terminal

access point

fixedterminal

application

TCP

802.11 PHY

802.11 MAC

IP

802.3 MAC

802.3 PHY

application

TCP

802.3 PHY

802.3 MAC

IP

802.11 MAC

802.11 PHY

LLC

infrastructurenetwork

LLC LLC


- 24 -

802.11 - Layers and functions• PLCP (Physical Layer

Convergence Protocol)– clear channel assessment

signal (carrier sense)• PMD (Physical Medium

Dependent)– modulation, coding

• PHY Management– channel selection, MIB

• Station Management– coordination of all

management functionsPMD

PLCP

MAC

LLC

MAC Management

PHY Management

• MAC– access mechanisms,

fragmentation, encryption

• MAC Management– synchronization, roaming,

MIB, power management

PHY

DLC

Sta

tion M

anag

emen

t


4.3 IEEE 802.11 Physical Layer

4.3.1 IEEE 802.114.3.2 IEEE 802.11b4.3.3 IEEE 802.11a4.3.4 IEEE 802.11g4.3.5 IEEE 802.11n4.3.6 IEEE 802.11ac4.3.7 IEEE 802.11ad


4.3.1. IEEE 802.11

● FHSS (Frequency Hopping Spread Spectrum)– spreading, despreading, signal strength, typ. 1 Mbit/s

– min. 2.5 frequency hops/s (USA), two-level GFSK modulation● DSSS (Direct Sequence Spread Spectrum)

– DBPSK modulation for 1 Mbit/s (Differential Binary Phase Shift Keying), DQPSK for 2 Mbit/s (Differential Quadrature PSK)

– preamble and header of a frame is always transmitted with 1 Mbit/s, rest of transmission 1 or 2 Mbit/s

– max. radiated power 1 W (USA), 100 mW (EU), min. 1mW● Infrared

– 850-950 nm, diffuse light, typ. 10 m range

– carrier detection, energy detection, synchonization

DSSS was most commonly used in the market

- 26 -


- 27 -

Recap from Chapter 2: DSSS• XOR of the signal with pseudo-random number (chipping sequence)

– many chips per bit (e.g., 128) result in higher bandwidth of the signal

• Advantages– reduces frequency selective

fading– in cellular networks

• base stations can use the same frequency range

• several base stations can detect and recover the signal

• soft handover

• Disadvantages– precise power control necessary

user data

chipping sequence

resultingsignal

0 1

0 1 1 0 1 0 1 01 0 0 1 11

XOR

0 1 1 0 0 1 0 11 0 1 0 01

=

tb

tc

tb: bit periodtc: chip period


- 28 -

DSSS• Similar to CDMA, but only one Spreading Sequence used for all users

⇒ not possible for several users to operate in same frequency at same time• Spreading to increase robustness

– 11-chip Barker Code(+1, –1, +1, +1, –1, +1, +1, +1, –1, –1, –1)

• US 11 Channels, EU 13 channels are available; 5 MHz apart from each other, each 22 MHz wide ⇒ co-channel interference

• DBPSK modulation for 1 Mbit/s (Differential Binary Phase Shift Keying), DQPSK for 2 Mbit/s (Differential Quadrature PSK)

• Scrambling with s(z)=z7+z4+1, to eliminate DC components• preamble and header of a frame is always transmitted with 1 Mbit/s,

rest of transmission 1 or 2 Mbit/s• max. radiated power 1 W (USA), 100 mW (EU), min. 1mW


- 29 -

Physical Layer

0 0 1User data

transmit receive

1

00110011011 01100100 11001100100 00110011011

Symbols, comprising of chips

1 0 0 1 0 0 1 1

00110011011

11001100100

transmit receive

1 Mbit/s

2 Mbit/s

DSSS (Direct Sequence Spread Spectrum)

01100100

10011011

00110011011

00110011011

11001100100

11001100100

0

1

11

00

DQPSK

011

DBPSK


- 30 -

DSSS PHY packet format

synchronization SFD signal service HEC payload

PLCP preamble PLCP header

128 16 8 8 16 variable bits

length

16

• Synchronization– synch., gain setting, energy detection, frequency offset compensation

• SFD (Start Frame Delimiter)– 1111001110100000

• Signal– data rate of the payload coded in steps of 100 kbit/s;

0A: 1 Mbit/s DBPSK; 14: 2 Mbit/s DQPSK• Service • Length

– future use, 00: 802.11 compliant – of the payload• HEC (Header Error Check)

– protection of signal, service and length, x16+x12+x5+1


- 31 -

4.3.2 IEEE 802.11b• Data rate

– 1, 2, 5.5, 11 Mbit/s, depending on SNR – User data rate max. approx. 6 Mbit/s

• Transmission range– 300m outdoor, 30m indoor– Max. data rate ~10m indoor

• Frequency– Free 2.4 GHz ISM band

• Only compatible to DSSS of legacy 802.11, not to FHSS● Meanwhile superseded by faster standard extensions

− However downward compatibility still provided


- 32 -

802.11b PHY: Modulation Schemes• DBPSK (1 Mbit/s)• DQPSK (2 Mbit/s)• Complementary Coded Keying (CCK)

– Complex spreading codes– Chip Rate 11 Mchip/s– Symbol: sequence of 4 chips (5.5 Mbit/s) or 8 chips (11 Mbit/s) – 5.5 Mbit/s: 4 bits per symbol, 2 chips per bit– 11 Mbit/s: 8 bits per symbol, 1 chip per bit– Low-level modulation scheme: DQSK


- 33 -

Physical Layer: 5.5 Mbit/s

1 0 1 0 1 1 0 1

2 bit 2 bit

0 1 j -1 -j 1 -1 j -j 1 j 1 -1 j 1 j -1 -j 2 -j 1 j -1 j -j -1 1 3 1 -1 j -j 1 j -1 -j

A value

user data byte

1

j

-1

-j

B1

B times

A1

QPSK

CCK (Complementary Coded Keying)

j -1 -j 1 -j j 1 -1

complementary sequencesphase rotationof CCK symbol

A2 B2


- 34 -

Physical Layer: 11 Mbit/s

0 1 1 0 1 0 1 0

6 bit 2 bit

0 1 j -1 -j 1 -1 j -j 1 j 1 -1 j 1 j -1 -j 2 -j 1 j -1 j -j -1 1

A value

User data byte

1

j

-1

-j

B

B times

A

QPSK

CCK (Complementary Coded Keying)

22

63

1 -1 j -j 1 j -1 -j

-1 j 1 -j j -j -1 1

j -1 j 1 -j j 1 -1

complementary sequences

phase rotation ofCCK symbol


- 35 -

PHY Transmission Modes: OverviewBit rateMbit/s

Modula-tionscheme

Chips/bit

Chip rateMchips/s

SymbolRate

MSyms/s

Bits/Sym-bol

RF BWMHz

1 DBPSK 11 real 11 1 1 22

2 DQPSK 5.5 complex

11 1 2 22

5.5 CCK 2 complex 11 1.375 4 22

11 CCK 1 complex 11 1.375 8 22

sensitivityagainst

interference

Transmit power: min. 1 mW; max. 100 mW EIRP (Europe); 1000mW (US); 200 mW (Japan)


- 36 -

Channel selection (non-overlapping)

2400MHz

2412 2483.52442 2472

channel 1 channel 7 channel 13

Europe (ETSI)

US (FCC)/Canada (IC)

2400MHz

2412 2483.52437 2462

channel 1 channel 6 channel 11

22 MHz

22 MHz


- 37 -

Spectrum of DSSS signal

http://www-sop.inria.fr/intech/reseau_ss_fil_presentations/aad.pdf


- 38 -

IEEE 802.11b – PHY frame formats

synchronization SFD signal service HEC payload

PLCP preamble PLCP header


length

16

192 µs at 1 Mbit/s DBPSK 1, 2, 5.5 or 11 Mbit/s

short synch. SFD signal service HEC payload

PLCP preamble(1 Mbit/s, DBPSK)

PLCP header(2 Mbit/s, DQPSK)


length

16

96 µs 2, 5.5 or 11 Mbit/s

Long PLCP PPDU format

Short PLCP PPDU format (optional)


- 39 -

802.11b PHY Frame Format• Long Frame: Mandatory Frame Format, backwards compatible to

802.11• Optional Short Frame half the length of Long Frame and further

differences:– Short sync field: scrambled 0s instead of scrambled 1s– SFD of short is mirrored SFD of long frame– Receiver not able to decode short frames can only detect activity

on channel

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