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Seminar - An Overview of Communications Technologies


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Module 7 - LAN, WAN, VPN, WLAN, MAN, FDDI and Optical MANS                                                      Slide 26 of 45 _________________                                                                                  __________

                                                 Summary of IEEE WLAN Standards

  802.11 802.11a 802.11b 802.11g
Standard Approved July 1997 September 1999 September 1999 Approval Expected in 2003
Available b/w 83.5 M Hz 300 M Hz 83.5 M Hz 83.5 M Hz
Unlicensed Frequencies of operation 2.4 - 2.4835 G Hz 5.15 - 5.35 G Hz
5.725-5.825 G Hz		 2.4-2.4835 G Hz 2.4-2.4835 G Hz
Technology used Direct Sequence Spread Spectrum
(DSSS) and Frequency Hopping Spread Spectrum (FHSS)		 Orthogonal Frequency Division Multiplexing (OFDM)  DSSS DSSS, OFDM
# of non-overlapping Channels (indoor/outdoor) 3 4 3 3
Data Rate per Channel 2,1 M bps 54, 48, 36, 24, 18, 12, 9, 6 M bps 11, 5.5, 2, 1 M bps 54, 36, 33, 24, 22, 12, 11, 9, 6, 5.5, 2, 1 M bps
Modulation Type DQPSK - (2 M bps DSSS); DBPSK (1 M bps - DSSS); 4GFSK (2 M bps - FHSS); 2GFSK (1 M bps - FHSS) BPSK (6,9 M bps)
QPSK (12, 18 M bps)
16-QAM (24, 36 M bps)
64-QAM (48, 54 M bps)		 DQPSK/CCK (11, 5.5 M bps)
DQPSK (2 Mbps)
DBPSK (1 M bps)		 OFDM (6, 9, 12, 18, 24, 36, 48, 54)
DQPSK/CCK (22, 33, 11, 5.5 M bps)
DQPSK (2 M bps)
DBPSK (1 M bps)

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Many different type of modulation techniques are used to obtain high speeds.802.11g products are backward compatible with 802.11b products.