CCNA 2 - Capitulo 12.5

CCNA 2 - Capitulo 12.5

1. WLAN CONCEPTS

   • CHANNEL MANAGEMENT
     • CHANNEL SELECTION
       • FREQUENCY 2.4 GHz
         • USE CHANNELS - 2,4 GHZ
           • 1,6 E 11
         • 11 CHANNELS (NORTH AMERICA)
           • EACH CHANNEL IS ALLOTED 22 MHZ BANDWIDTH
             • FROM THE NEXT CHANNEL BY
               • 5 MHZ
           • CAUTION : EUROPE AND JAPAN IS 13 CHANNELS
         • WHEN INTERFERENCE OCCURS ?
           • WHEN ONE SIGNAL OVERLAPS A CHANNEL RESERVED FOR ANOTHER SIGNAL , CAUSING DISTORTION
         • EX : 802.11 N / G / N
       • FRQUENCY 5GHz
         • THERE ARE 24 CHANNELS
         • BAND IS DIVIDED IN THREE SECTIONS
           • EACH CHANNEL IS SEPARATED FROM NEXT CHANNEL
             • 20MHZ
         • EX : 802.11 A / N / AC
         • CAN PROVIDE FASTER DATA BEACAUSE LARGER AMOUNT FO NON OVERLAPPING WIRELESS CHANNELS
         • SHOULD BE USED IN AREA PRONE TO INTERFERENCE
       • BEST PRACTICE FOR WLAN WITH MULTIPLS APS ?
         • USE NON OVERLAPPING CHANNELS
     • WHAS IS INTERFERENCE ?
       • SIGNAL OVERLAPS A CHANNEL ANOTHER SIGNAL
     • FREQUENCY CHANNEL SATURATION
       • WHATS IS OVERSATURATED ?
         • DEMAND SPECIFIC CHANNEL IS HIGH
         • DEGRADES THE QUALITY COMMUNICATION
       • WLAN HAVE TRANSMITTERS AND RECEIVERS TUNED TO
         • SPECIFIC FREQUENCIES OF RADIOS
       • FREQUENCIES ALLOCATED SMALLER RANGE ?
         • THIS RANGE IS CALLED CHANNELS
       • TECHNIQUE MODULATION
         • DIRECT-SEQUENCE SPREAD SPECTRUM (DSSS)
           • MODULATION TECHNIQUE THAT SPREADS.
             • A SIGNAL OVER A WIDER FREQUENCY BAND
           • DEVELOPED TO REDUCE INTERCEPTION AND JAMMING
             • HIDES THE DISCERNIBLE PEAK OF THE SIGNAL
               • RECEIVER CAN REVERSE MODULATION AND RECONSTRUCT SIGNAL
           • USES SPREAD SPECTRUM PRINCIPLES
           • USED IN 802.11B (2.4 GHZ)
           • IMPROVES INTERFERENCE RESISTANCE
         • FREQUENCY-HOPPING SPREAD SPECTRUM (FHSS)
           • TRANSMITS BY RAPIDLY SWITCHING CARRIER FREQUENCIES
             • USES MULTIPLE FREQUENCY CHANNELS
           • REQUIRES SENDER/RECEIVER SYNCHRONIZATION
           • USED IN ORIGINAL 802.11 STANDARD
           • USED BY BLUETOOTH
           • IMPROVES SPECTRAL EFFICIENCY
           • CHANNEL HOPPING
             • REDUCES EFFECTS OF INTERFERENCE & CONGESTION
         • ORTHOGONAL FREQUENCY-DIVISION MULTIPLEXING (OFDM)
           • SUBSET OF FREQUENCY DIVISION MULTIPLEXING (FDM)
           • SINGLE CHANNEL USES
             • MULTIPLE SUB-CHANNELS ( ORTHOGONAL)ON ADJACENT FREQUENCIES
               • THIS ALLOW SUBCARRIERS OVERLAP WITHOUT INTERFERENCE
           • HIGH SPECTRAL EFFICIENCY
           • RESISTANT TO MULTIPATH EFFECTS
           • USED IN 802.11A/G/N/AC
             • OFDM
           • 802.11AX
             • OFDM VARIANT CALLED OFDMA