Lancom AirLancer MC-54, Руководство пользователя

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Introduction
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AirLancer
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EN
the distance and/or on the quality of the connection. With increasing dis-
tance and diminishing connecting quality the transmission rate lowers to 5,5
Mbps, afterwards to 2 and finally to 1 Mbps. The range of the transmission
distances is between up to 150 m in open expanses and in buildings typically
up to 30 m. Due to different frequency bands in use, IEEE 802.11b is not com-
patible to IEEE 802.11a.
Please notice that not all frequencies are permitted in each country! You will
find a table with the allotted frequencies and the permission regulations in
the appendix.
DSSS
For shielding against interferences by other transmitters, which have possibly
the same frequency band, the DSSS procedure (
D irect S equence S pread
S pectrum) is used for IEEE 802.11b in the 2,4 GHz frequency band. A trans-
mitter normally uses only a very narrow range of the available frequency band
for transmission. If exactly this range is used by another transmitter, interfer-
ences in transmission would be the result. With the DSSS procedure the
transmitter uses a broader spread of the possible frequencies and becomes
more insensitive to narrow-band disturbances then. This procedure is also
used in military range for increasing tap-proof security.
IEEE 802.11g
54 Mbps
The IEEE 802.11g standard works likewise with up to 54 Mbps data transmis-
sion rate in the 2,4 GHz frequency band. Contrary to IEEE 802.11b, the OFDM
modulation is used for IEEE 802.11g like already introduced for IEEE 802.11a.
IEEE 802.11g contains a special compatibility mode that ensures a downward
compatibility to the popular IEEE 802.11b standard . However, in this compat-
ibility mode you encounter reduced transmission speeds. Due to the different
frequency bands, IEEE 802.11g can not be compatible to IEEE 802.11a. The
transmission distances of IEEE 802.11g products are comparable with those
of IEEE 802.11b products.
Transfer rates
The indicated transfer rates are always to interpret as gross data rates, i.e.
that the entire protocol overhead - as for example the complex protocols to
secure the radio transmission - are included in the indicated transfer rates.
The net data transfer rate can be thus lower than the indicated gross data
rates, typically over up to the half for all IEEE 802.11 standards mentioned
above.
Ranges
The actually obtained distances for radio transfers depend strongly on the
individual spatial environment. In particular influences of noise and obstacles