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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).
- 3 - TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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
- 4 - TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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
- 5 - TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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
- 6 - TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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
- 7 - TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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
{
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2012
Chapter 4: Wireless LANs IEEE 802.11
These slides are to a great extent based on slides of Jochen Schiller,
“Mobilkommunikation”, Chapter7
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2012
4.1 Characteristics andDesign Goals
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2012
4.2 Overview on IEEE 802.11
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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]
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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Infrastructure vs. Ad-hoc Networksinfrastructure network
ad-hoc network
APAP
AP
wired network
AP: Access Point
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
- 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.
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
- 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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2012
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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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 -
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
- 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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
- 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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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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)
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
- 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
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
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Spectrum of DSSS signal
http://www-sop.inria.fr/intech/reseau_ss_fil_presentations/aad.pdf
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
- 38 -
IEEE 802.11b – PHY frame formats
synchronization SFD signal service HEC payload
PLCP preamble PLCP header
128 16 8 8 16 variable bits
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)
56 16 8 8 16 variable bits
length
16
96 µs 2, 5.5 or 11 Mbit/s
Long PLCP PPDU format
Short PLCP PPDU format (optional)
TZI – FB 1 – Communication Networks Andreas Könsgen – Summer Term 2014
- 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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