Wireless LANs/data networks - EIT, Electrical and Information

RADIO SYSTEMS - ETIN15
Lecture no:
12
Wireless LANs/data networks
Ove Edfors, Department of Electrical and Information Technology
Ove.Edfors@eit.lth.se
2016-05-03
Ove Edfors - ETIN15
1
Centralized and AdHoc networks
2016-05-03
Ove Edfors - ETIN15
2
Centralized and AdHoc Networks
Centralized
CentralizedNetwork
Network
AdHoc
AdHocNetwork
Network
Wired network
AP
AP
MS
MS
MS
MS
MS
2016-05-03
MS
MS
Ove Edfors - ETIN15
3
Infrastructure and AdHoc Networks
• Some issues to consider:
– Centralized networks
•
•
•
•
•
•
Integration with wired LAN
Network planning (access points)
Interoperability
Roaming and handover between access points
Security / authentication
Power management
– AdHoc networks
•
•
•
•
•
2016-05-03
Multi-hop and routing
Quality of service
Interoperability
Security / authentication
Power management
Ove Edfors - ETIN15
4
Error control and ARQ
2016-05-03
Ove Edfors - ETIN15
5
Error-correcting and Error-detecting
Codes
• In wireless systems we need error-correcting and errordetecting codes
• The quality of the wireless channel changes with time and
we need to safeguard our data.
– Data transmitted during a fading dip can (if the coding scheme is
properly designed) be recovered by an error-correcting code.
• To reach very low error rates we need error detection to
trap incorrectly decoded data.
2016-05-03
Ove Edfors - ETIN15
6
Automatic Repeat Request (ARQ)
• Using error-detection codes we can reduce the error rate by
applying an ARQ scheme.
• ARQ is usually not an option for time critical data over ‘slow’
channels, such as real-time audio and video.
• For high efficiency, ARQ schemes for wireless channels
need to be more intricate than the ones used on wired
channels
– This is due to the fading nature of wireless channels
2016-05-03
Ove Edfors - ETIN15
7
Digital transmission
in WLANs
2016-05-03
Ove Edfors - ETIN15
8
Some WLANs
Data rate [Mbit/sec]
1000
100
Increasing
equalization
complexity IEEE 802.11a
Hiperlan/2
IEEE 802.11b
10
2000
IEEE 802.11n
IEEE 802.11g
Recent
RecentWLAN
WLANstandards
standardsand
and
specifications
specifications
The
Thelatest
lateststandards,
standards,with
withthe
thehighest
highest
data
rates
are
based
on
OFDM
data rates are based on OFDM
(in
(incombination
combinationwith
withMIMO).
MIMO).
0.1
1998 1999
OFDM
Bluetooth 2.0
IEEE 802.11
1
Bluetooth 1.0
1997
IEEE 802.11ac
2001
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
Year
2016-05-03
Ove Edfors - ETIN15
9
Wireless LAN standards and specifications
2016-05-03
Ove Edfors - ETIN15
10
Wireless LAN Standards and
Specifications
• Some of the available standards and specifications
– ETSI
• HIPERLAN/2 (not used, but of historical importance)
– IEEE
• 802.11
• 802.11a
• 802.11b
• 802.11g
• 802.11n
• 802.11ac
• etc ..
– BlueTooth SIG
• BlueTooth
2016-05-03
Ove Edfors - ETIN15
11
ETSI - HIPERLAN/2
www.etsi.fr
HIPERLINK
HIPERACCESS
Part
Partofofthe
theETSI
ETSI
BRAN
BRANfamily
family
HIPERLAN
2016-05-03
Ove Edfors - ETIN15
12
ETSI - HIPERLAN/2
• Digital transmission
– OFDM (multicarrier) with sampling rate 20 MHz
– 5.150-5.350 GHz & 5.470-5.725 GHz
– 48 data carriers + 4 pilot carriers
– Carrier spacing 0.3125 MHz
– Symbol length 4 us (0.8 us cyclic prefix)
– Range < 150 m.
– TDMA/TDD
• Syncronization
– Broadcast (base => all). Preamble 16 us.
– Downlink (base => terminal). Preamble 8 us.
– Uplink (teminal => base). Short preamble 12 us and long preamble
16 us.
2016-05-03
Ove Edfors - ETIN15
13
ETSI - HIPERLAN/2
BURST
BURSTSTRUCTURES
STRUCTURES
Broadcast
Down link
Preamble
Data
16 us
4 us
Preamble
Data
Data
...
Data
Data
Data
...
Data
Data
8 us
Up link (short preamble)
Preamble
...
Data
12 us
Up link (long preamble)
Preamble
Data
Data
...
Data
16 us
2016-05-03
Ove Edfors - ETIN15
14
ETSI - HIPERLAN/2
SIGNAL
SIGNALCONSTELLATIONS
CONSTELLATIONS
BPSK
1 bit/symbol
2016-05-03
QPSK
2 bit/symbol
16-QAM
4 bit/symbol
Ove Edfors - ETIN15
(OPTION)
64-QAM
6 bit/symbol
15
ETSI - HIPERLAN/2
TRANSMISSION
TRANSMISSIONMODES
MODES
Sig.const Code Databit/symbol Data rate
BPSK
1/2
24
6 Mbit/s
BPSK
3/4
36
9 Mbit/s
QPSK
1/2
48
12 Mbit/s
QPSK
3/4
72
18 Mbit/s
16QAM 9/16
108
27 Mbit/s
16QAM 3/4
144
36 Mbit/s
64QAM 3/4
216
54 Mbit/s
2016-05-03
Ove Edfors - ETIN15
16
IEEE - 802.11
• 802.11-1997
– PHY layer
• diffused infrared - in baseband
www.ieee.org
• DSSS and FHSS (50 hops/sec) in 2.4 GHz ISM band
• 1 and 2 Mbps data rate
– MAC layer
• Two network architectures: Infrastructure Network and Ad-Hoc Network
• Primary services: Data transfer, Association, Reassociation,
Authentication, Privacy, and Power Management
– MISSING
• AP-to-AP coordination for roaming, Data frame mapping, Confomance
test
2016-05-03
Ove Edfors - ETIN15
17
IEEE - 802.11
• 802.11a-1999 (supplement to 802.11-1997)
– New PHY (and MAC) layer for 802.11
– 5 GHz band
– Essentially the same physical layer (OFDM) as HIPERLAN/2
– 6-54 Mbps data rate
• 802.11b-1999 (supplement to 802.11-1997)
– New PHY (and MAC) layer for 802.11
– 2.4 GHz band
– DSSS based physical layer
– 11 Mbps data rate
2016-05-03
Ove Edfors - ETIN15
18
IEEE - 802.11
• 802.11g-2003 (supplement to 802.11-1997)
– Same PHY layer as 802.11a
– 2.4 GHz band
– New MAC layer
– 6-54 Mbps data rate
• 802.11n-2009
– Up to 500 Mbit/sec
– Proposal based on MIMO technology
– Developed beyond 500 Mbit/sec in 802.11ac
2016-05-03
Ove Edfors - ETIN15
19
IEEE 802.11 – a bigger family
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
IEEE 802.11 - The original 1 Mbit/s and 2 Mbit/s, 2.4 GHz RF and IR standard
IEEE 802.11a - 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001)
IEEE 802.11b - Enhancements to 802.11 to support 5.5 and 11 Mbit/s (1999)
IEEE 802.11d - international (country-to-country) roaming extensionsNew countries
IEEE 802.11e - Enhancements: QoS, including packet bursting
IEEE 802.11F - Inter-Access Point Protocol (IAPP)
IEEE 802.11g - 54 Mbit/s, 2.4 GHz standard (backwards compatible with b) (2003)
IEEE 802.11h - 5 GHz spectrum, Dynamic Channel/Frequency Selection (DCS/DFS) and Transmit
Power Control (TPC) for European compatibility
IEEE 802.11i (ratified 24 June 2004) - Enhanced security
IEEE 802.11j - Extensions for Japan
IEEE 802.11k - Radio resource measurements
IEEE 802.11n - Higher throughput improvements
IEEE 802.11p - WAVE - Wireless Access for the Vehicular Environment (such as ambulances and
passenger cars)
IEEE 802.11r - Fast roaming
IEEE 802.11s - Wireless mesh networking
IEEE 802.11T - Wireless Performance Prediction (WPP) - test methods and metrics
IEEE 802.11u - Interworking with non-802 networks (e.g., cellular)
IEEE 802.11v - Wireless network management
… and more!
2016-05-03
Ove Edfors - ETIN15
20
Bluetooth Special Interest Group Bluetooth
• FHSS in the 2.4 GHz band
www.bluetooth.com
– max 1600 hops/sec (much faster than IEEE 802.11 FHSS)
– 1 MHz channels
– 79 frequency channels
• Modulation
– Version 1.x
• GFSK (BT=0.5)
• 1 Mbps (raw)
– Version 2.x
• Additionally differential 4PSK and 8PSK
• 2 & 3 Mbps
• Range
– 10 cm -- 10 m (for Class 2)
2016-05-03
Ove Edfors - ETIN15
21
Bluetooth Special Interest Group Bluetooth
PICONET
Slave 2
Master
Slave 3
Slave 1
2016-05-03
Ove Edfors - ETIN15
22
Bluetooth Special Interest Group Bluetooth
SCATTERNET
Master
2016-05-03
Master
Ove Edfors - ETIN15
23
Bluetooth Special Interest Group Bluetooth
SLAVE
MASTER
same
Mater
internal
clock
(hop sequence
timing)
Frequency
hop
generator
Hop
freq.
clock
Slave
internal
clock
Frequency
hop
generator
Hop
freq.
Offset
Master unit
BlueTooth Device
Address
Master unit
BlueTooth Device
Address
(selection of hop sequence)
2016-05-03
Ove Edfors - ETIN15
24
Bluetooth Special Interest Group Bluetooth
FH
FH/ /TDD
TDD
Frequency:
f(2k)
f(2k+1)
f(2k+2)
f(2k+3)
MASTER
t
SLAVE
t
625 us
2016-05-03
Ove Edfors - ETIN15
25
Bluetooth Special Interest Group Bluetooth
625 us
f(k)
Packet
Packetlengths
lengths1,1,33and
and55
f(k+1)
f(k+2)
f(k+3)
f(k+4)
f(k+5)
t
f(k)
f(k+3)
f(k+4)
f(k+5)
t
f(k)
f(k+5)
t
2016-05-03
Ove Edfors - ETIN15
26
Bluetooth Special Interest Group Bluetooth
Modulation
Gaussian-filtered Frequency Shift Keying (GFSK) [c.f. GMSK]
BTb = 0.5
B = 500 kHz
Mod.index = 0.32 (+/-3%)
fd = 320/2 kHz = 160 kHz (+/-3%)
Bitrate 1 Mbit/sec (+/-1ppm)
f
FT + fd
Transmit
center
frequency
1
1
FT
t
FT - fd
0
0
Tb = 1 us
2016-05-03
Ove Edfors - ETIN15
27
Bluetooth Special Interest Group Bluetooth
• Synchronous connection oriented (SCO)
– Synchronous transmission
– Symmetric data rate
– Reserved time slots
– Intended for voice
– No retransmission
• Asymmetric connection less (ACL)
– Asynchronous transmission
– Used for asymmetric communication
– Retransmission used (Go-back-1 ARQ)
These are the basic packet types.
2016-05-03
Ove Edfors - ETIN15
28
Bluetooth evolution
• Bluetooth has evolved to newer versions, e.g.
– Version 2.0 + EDR
• Main feature: (optional) higher data rate (3 Mbit/sec)
– Version 2.1 + EDR
• Main feature: secure simple pairing of devices
– Version 3.0 + HS
• Main feature: up to 24 Mbit/sec by using 802.11 MAC/PHY
– Version 4.0 (Smart)
• Includes classic Bluetooth, Bluetooth high speed and Bluetooth low
energy (previously Wibree)
2016-05-03
Ove Edfors - ETIN15
29
Download PDF