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Table 21.12 Major components of IEEE 802.11n
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Bog'liq garg2007Table 21.12 Major components of IEEE 802.11n.
Feature
Defi nition
Status
Better OFDM
Supports wider bandwidth and higher code
rate to bring maximum data rate to 65 Mbps
Mandatory
Space-Division
Multiplexing (SDM)
Improve performance by parsing data into
multiple streams transmitted through mul-
tiple antennas
Optional for up to four
antennas
Diversity
Exploits the existence of multiple antennas
to improve range and reliability. Typically
employed when the number of antennas on
the receiving end is higher than the number
of streams being transmitted.
Optional for up to four
antennas
MIMO Power Save
Limits power consumption penalty of
MIMO by utilizing multiple antennas only
on as-needed basis.
Required
40 MHz Channels
Effectively doubles data rates by doubling
channel width from 20 MHz to 40 MHz
Optional
Aggregation
Improves effi ciency by allowing transmis-
sion bursts of multiple data packets between
overhead communication
Required
Reduced Inter-frame
Spacing (RIFS)
Designed to improve effi ciency by providing
a shorter delay between OFDM transmis-
sions than in 802.11a or g.
Required
Greenfi eld Mode
Improves effi ciency by eliminating support for
802.11a/b/g devices in an all 802.11n network
Optional
21.10 IEEE
802.11n
751
Table 21.13 Primary IEEE 802.11 specifi cations and their comparisons.
802.11a
802.11b
802.11g
802.11n
Approval date
July 1999
July 1999
June 2003
August 2006
Maximum data
rate
54 Mbps
11 Mbps
54 Mbps
600 Mbps
Modulation
OFDM
DSSS or CCK
DSSS or CCK
or OFDM
DSSS or CCK
or OFDM
RF band
5 GHz
2.4 GHz
2.4 GHz
2.4 GHz or 5 GHz
Number of spa-
tial streams
1
1
1
1, 2, 3, or 4
Channel width
20 MHz
20 MHz
20 MHz
20 MHz or
40 MHz
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