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© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-1
Wireless Fundamentals
Introducing Wireless Regulation Bodies, Standards, and Certifications
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-2
The IEEE
The IEEE develops communication standards in electrical and computer sciences, engineering, and related disciplines.
There are more than 1300 protocols.
The 802.11 committee analyzes the applications and environments in which wireless networks are used and develops standards for them.
The 802.11 family has more than 26 subprotocols.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-3
The Wi-Fi Alliance
Wi-Fi Alliance certifies interoperability between products WLAN products.
Products include 802.11a, 802.11b, 802.11g, 802.11n draft v2.0, dual-band products, and security testing.
The organization provides assurance to customers of migration and integration options.
Cisco is a founding member of Wi-Fi Alliance.
Certified products can be found at http://www.wi-fi.com.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-4
Regulatory Bodies
Each country or region defines its rules about the use of the RF space, including the following rules:
Which frequencies are allowed (spectrums and channels)
Which transmit powers are possible (transmitters and antennae gain and EIRP)
How a wave can be sent in each frequency (modulation and encoding techniques)
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-5
FCC Part 15 Antenna Requirements
Antennas Antennas must use a unique or proprietary connector.
Cisco Aironet products typically use RP-TNC connectors.
Some Cisco products designed for professional installation can use nonproprietary connectors such as a Type N connector.
FCC Part 15 Standards Approved antenna may exceed the regulations of other countries.
Exceeding the regulations may lead to interference problems.
Penalties could result in fines.
FCC standards apply to Part 15 users in the United States.
Different countries will have similar standards.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-6
Point-to-multipoint Maximum of 36 dBm EIRP 30-dBm maximum transmitter power with 6-dBi maximum gain of antenna
and cable combination A 1:1 ratio between the maximum power and maximum gain Reduce transmit power below maximum of 30 dBm by 1 dBm and
increase maximum antenna and cable system gain by 1dBi
Point-to-point Maximum of 36 dBm EIRP 30-dBm maximum transmitter power with 6-dBi in gain of antenna and
cable combination FCC allows exceeding the 36 dBm EIRP in point-to-point installations
using the 3:1 ratio rule Reduce transmit power below maximum of 30 dBm by 1 dBm and
increase maximum antenna and cable system gain by 3 dBi
2.4-GHz EIRP Output Rules—FCC Example
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-7
2.4-GHz EIRP Output Rules—FCC Example (Cont.)
Transmitter Power - dBm Maximum Gain EIRP
FCC Maximum 30 dBm 6 dBm 36 dBm
Cisco Maximum 20 dBm 16 dBm 36 dBm
Point-to-Multipoint
Transmitter Power - dBm Maximum Gain EIRP
FCC Maximum 30 dBm 6 dBm 36 dBm
Cisco Maximum 20 dBm 36 dBm 56 dBm
Point-to-Point
The above values reflect the 3:1 rule.
The above values reflect the 1:1 rule.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-8
2.4-GHz EIRP Output Rules—ETSI Example
Currently ETSI stipulates a maximum of 20 dBm EIRP on point-to-multipoint and point-to-point installations; it also stipulates 17-dBm maximum transmitter power with 3-dBi in gain attributed to antenna and cable combination.
Professional installers are allowed to increase the gain of an antenna and cable system if the transmitter power is reduced below 17 dBm in a 1:1 ratio.
Reduce transmit power below maximum of 17 dBm by 1 dBm and increase antenna and cable system gain by 1 dBi.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-9
2.4-GHz EIRP Output Rules—ETSIExample (Cont.)
Governing bodies with 20-dBm ceiling on EIRP:ETSI, France/Singapore, Israel, Mexico
Point-to-Multipoint and Point-to-Point
Transmitter Power-dBm
Maximum Gain EIRP
Gov. Body Maximum 17 dBm 3 dBi 20 dBm
Cisco dipole Antennae 17 dBm 2.2 dBi 19.2 dBm
Reduced Tx* Power 15 dBm 5 dBi 20 dBm
Reduced Tx Power 13 dBm 7 dBi 20 dBm
Reduced Tx Power 7 dBm 13 dBi 20 dBm
Reduced Tx Power 0 dBm 20 dBi 20 dBm
The above values reflect the 1:1 rule.*Tx = transmission
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-10
Wireless Spectrum
The 2.4-GHz ISM band ranges from 2.4 to 2.4835 GHz (2.4970 GHz in Japan). In this range 11 channels are allowed in the United State, 13 in Europe, and 14 in Japan.
The 5-GHz ISM band ranges from 5.725 to 5.875 GHz.
The 5-GHz ISM band overlaps with the Unlicensed National Information Infrastructure (UNII) bands:
– UNII-1 ranges from 5.15 to 5.25 GHz (4 channels).
– UNII-2 ranges from 5.25 to 5.35 GHz (4 channels).
– UNII-2 extended ranges from 5.470 to 5.725 GHz (up to 11 channels).
– UNII-3 ranges from 5.725 GHz to 5.825 GHz (4 channels).
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-11
Current State of 5-GHz 802.11a Spectrum
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-12
Some IEEE 802.11 Standard Activities
802.11a — 5GHz, 54 Mb/s; ratified in 1999
802.11b — 2.4 GHz, 11 Mb/s; ratified in 1999
802.11d — World Mode; ratified in 2001
802.11e — QoS; ratified in 2005
802.11g — 2.4GHz, 54 Mb/s; ratified in 2003
802.11h — DFS and TPC mechanisms; ratified in 2004
802.11i — Authentication and security; ratified in 2004
802.11k — Radio resource measurement enhancements (under development)
802.11n — Higher throughput improvements using MIMO antennas(under development)
802.11t — WPP; test methods and metrics recommendation (under development)
802.11w — Protected management frames (under development)
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-13
802.11 Standards for Spectrums and Speeds
802.11 802.11b 802.11a 802.11g 802.11n
Ratified 1997 1999 1999 2003Not
Ratified
Frequency Band
2.4 GHz 2.4 GHz 5 GHz 2.4 GHz2.4 GHz,
5 GHz
No of Channels
3 3 Up to 23 3 varies
TransmissionIR,
FHSS, DSSS
DSSS OFDM DSSS OFDMDSSS, CCK,
OFDM
Data Rates (Mb/s)
1, 21, 2, 5.5,
11
6, 9, 12, 18, 24, 36, 48,
54
1, 2, 5.5, 11
6, 9, 12, 18, 24, 36,
48, 54100+
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-14
802.11
802.11 became a standard in July 1997, the first standard for wireless.
Two RF technologies were defined: FHSS and DSSS.
The standard allows 1 Mb/s and 2 Mb/s.
It defined specifications for Layer 1 and Layer 2, and basic security.
802.11 is defined in the 2.4-GHz ISM band.
Three nonoverlapping channels is the most common deployment.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-15
802.11b
11 Mb/s, 2.4 GHz, DSSS Ratified as standard in September 1999
11 U.S. channels
13 ETSI channels
14 Japanese channels
Power levels:
– 36 dBm Effective Isotropic Radiated Power (EIRP); FCC
– 20 dBm EIRP; ETSI
Approved for use nearly worldwide
Not recommended for new deployments
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-16
802.11b Speed Coverage
Two different encodings:
− Barker 11
− CCK
Two different modulations:
− DBPSK
− DQPSK
Four different speeds:
− 1 Mb/s (Barker + DBPSK)
− 2 Mb/s (Barker + DQPSK)
− 5.5 Mb/s (CCK-16 + DQPSK)
− 11 Mb/s (CCK-128 + DQPSK)
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-17
802.11g
Standard for higher-rate extensionin the 2.4-GHz ISM spectrum
Speed up to 54 Mb/s
OFDM added to DSSS
Backward-compatible with 802.11b
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-18
802.11b/g Cell Speeds
802.11g speeds:
– 54 Mb/s, 48 Mb/s
– 36 Mb/s, 24 Mb/s
– 18 Mb/s, 12 Mb/s
– 9 Mb/s, 6 Mb/s
– Include 802.11b data rates
Client looks for the best speed
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-19
802.11b/g Encoding and ModulationsModulation with
SubchannelsEncoding Total Data Rate (Mb/s)
BPSK Barker 1
QPSK Barker 2
QPSK CCK-16 5.5
BPSK OFDM 6
BPSK OFDM 9
QPSK CCK-128 11
QPSK OFDM 12
QPSK OFDM 18
16-QAM OFDM 24
16-QAM OFDM 36
64-QAM OFDM 48
128-QAM OFDM 54
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-20
802.11b and 802.11g Coexistence
802.11b presence triggers protection mode:
− RTS/CTS
− “CTS to self” protection
“Non-ERP present” wave spreads throughout the network.
Throughput can drop from 22 Mb/s to 8 Mb/s.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-21
802.11a
Ratified as standard in September 1999
54 Mb/s 5 GHz (OFDM)
23 U.S. channels
− Dynamic Frequency Control (DFS)*
− Transmitter Power Control (TPC)*
19 ETSI channels (many countries)
− DFS
− TPC
*Required by July 20th, 2007
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-22
802.11a Spectrum
Twenty-eight different channels available: 23 United States, 19 Europe Three different bands Channels have 30 MHz of protection in the lower band, 20 MHz in the
others
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-23
802.11a Speeds
Same speeds as 802.11g
No 802.11b interoperability
Higher frequency, which implies lower range but also less scattering
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-24
Comparing the Technologies802.11a Data Rates
Modulation with Subchannels
Data Rate Per Subchannel (kb/s)
Total Data Rate (Mb/s)
BPSK 125 6
BPSK 187.5 9
QPSK 250 12
QPSK 375 18
16-QAM 500 24
16-QAM 750 36
64-QAM 1000 48
128-QAM 1125 54
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-25
802.11n: State of the Protocol
IEEE is developing 802.11n standard features and attributes.
Wi-Fi Alliance is using 802.11n Draft 2.0 in an interim baseline.
Goal is for software upgrades to meet standard compliance and minimize hardware upgrades.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-26
Greater Reliability and Predictability
Primary 802.11n Components
40-MHz Channels Improved MAC Efficiency
Multiple-Input, Multiple-Output (MIMO)
Two adjacent 20-MHz channels are combined to create a single 40-MHz channel.
MAC aggregation packs smaller packets into a single unit.
Block acknowledgment improves throughput.
Maximal Ratio Combining (MRC)
Beam forming
Spatial multiplexing
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-27
802.11n Channel Aggregation
802.11g and 802.11a use 20-Mhz channels.
Tones on the side arenot used to protectthe main carrier (11 Mb/s unused).
802.11n aggregatestwp carriers to doublethe speed from54 Mb/s to 108+11 = 119 Mb/s
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-28
Block Acknowledgment
802.11 requires acknowledgment of each frame.
802.11n uses block acknowledgment for constituent frames.
802.11Header Packet
802.11ACK
802.11nACK
802.11nHeader
Packet 802.11nHeader
Packet 802.11nHeader
Packet
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-29
Spatial Multiplexing
Several frames are sent by several antennae over several paths and are recombined by several antennae to optimize throughput and multipath resistance.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-30
Transmit Beamforming
Coordinates the signal sent from each antenna so that the signal at the receiver is dramatically improved
Generally used when the receiver has only a single antenna
Magnitude and phase dynamically adjusted at each transmitter with client feedback if client is 802.11n
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-31
Maximal Ratio Combining
MRC is used by the receiver with multiple antennas to optimally combine energies from multiple receive chains. An algorithm eliminates out-of-phase signal degradation.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-32
MIMO Benefits
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-33
Summary
The IEEE defines the 802.11 family of protocols.
The Wi-Fi Alliance ensures the interoperability of wireless devices.
The local or regional regulatory bodies define what is allowed in which spectrum.
The 802.11 family has more than 26 protocols.
The original 802.11 protocol defined 1- and 2-Mb/s speeds with FHSS and DSSS.
802.11b increased the speed to 11 Mb/s.
802.11g increased the speed to 54 Mb/s, but still in the ISM band.
802.11b devices degrade the performances of 802.11g cells.
802.11a uses the same modulation and speed as 802.11g, but in the 5-GHz band.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-34
Summary (Cont.)
802.11n tries to increase speed and throughput in the ISM and UNII bands.
892.11n provides several new features to increase speed.
Channels can be aggregated from 20 to 40 MHz.
MAC layer behavior is enhanced.
Spatial multiplexing is used over several antennae.
Several antennae can be used to send to one single antennae.
Several antennae can be combined to receive the signal of one emitter.
802.11n enhances range and throughput for both 802.11n clients and non-802.11n clients.
© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—1-35
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