LANCOM L
-
300 Access Point series
Chapter 5: Advanced wireless LAN configuration
57
EN
Double bandwidth (40 MHz channels)
A wireless LAN module normally uses a frequency range of 20 MHz in
which data to be transmitted is modulated to the carrier signals. 802.11a/
b/g use 48 carrier signals in a 20 MHz channel. The use of double the fre-
quency range of 40 MHz means that 96 carrier signals can be used, resul-
ting in a doubling of the data throughput.
802.11n can use 52 carrier signals in one 20 MHz channel for modulation
and up to 108 in a 40 MHz channel. The use of the 40 MHz option for
802.11n therefore means a performance gain of more than double.
Antenna grouping
LANCOM Access Points with 802.11n support can use up to three anten-
nas for transmitting and receiving data. Using several antennas with
802.11n can have different purposes:
Improved data throughput: Using "spatial multiplexing" allows par-
allel data streams to be implemented to transmit double the amount
of data.
Improving wireless coverage: Cyclic shift diversity (CSD) can be used
to transmit a radio signal in different phases. This reduces the risk of
the signal being erased at certain points in the radio cell.
Depending on the application the use of the antennas can be set:
When using the device in Access Point mode to connect wireless LAN
clients it is generally recommended to use all three antennas in par-
allel in order to achieve good network coverage.
Antenna ports 1 and 3 are used for 2 parallel data streams for
ex ample in point to point connections with an appropriate dual slant
antenna. The third antenna port is deactivated.
For applications with only one antenna (for example an outdoor
application with just one antenna) the antenna is connected to port 1
and ports 2 and 3 are deactivated
The ''Auto' setting means that all available antennas are used.
5.2.3
Performance settings for wireless LAN networks
Some performance settings can be configured separately for each logical
wireless LAN network (i.e. for each SSID).
Number of spatial streams
