Lancom AirLancer MC-54, Manual

Page: 10 / 47

Introduction
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AirLancer
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10
EN
An infrastructure-network is excellently suitable as an extension to existing
wired LANs. For extension of a LAN in areas, where a wiring is not possible
or uneconomical, the infrastructure-network represents an ideal alternative.
1.4 Standardized radio transmission by IEEE
IEEE 802.11
AirLancer client adapters work with the IEEE 802.11 standard. This standard
family represents an extension of the already existing IEEE standards for
LANs, of which IEEE 802.3 for Ethernet is the most popular one. Within the
IEEE 802.11 family there exist different standards for the radio transmission
in different frequency ranges and with different speeds.
AirLancer client
adapters support according to their respective type the IEEE 802.11b standard
with up to 11Mbps transfer rate into 2,4 GHz frequency band, the IEEE
802.11g standard with up to 54 Mbps transfer rate in the 2,4 GHz frequency
band, and the 802.11a standard with up to 54 Mbps transfer rate in the 5 GHz
frequency band.
IEEE 802.11a
54 Mbps
IEEE 802.11a describes the operation of Wireless LANs in the 5 GHz fre-
quency band (5,15 GHz to 5,75 GHz) with up to 54 Mbps maximum transfer
rate. The real throughput depends however on the distance and/or on the
quality of the connection. With increasing distance and diminishing connect-
ing quality, the transmission rate lowers to 48 Mbps, afterwards to 36 Mbps
etc., up to a minimum of 6 Mbps. The distance of transmission ranges from
up to 125 m in open expanses, in buildings typically up to 25 m. The IEEE
802.11a standard uses OFDM (
O rthogonal F requency D ivision M ultiplexing)
as modulation scheme.
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.
OFDM
In the 5 GHz frequency band, the OFDM modulation scheme is used for IEEE
802.11a. OFDM is a modulation scheme, which utilizes multiple independent
carrier frequencies for the signal transmission, and which modulates these
multiple carriers each with a reduced data transfer rate. Thus the OFDM mod-
ulation scheme is very insensitive in particular to echoes and other impair-
ments and enables high data transfer rates.
IEEE 802.11b
11 Mbps
IEEE 802.11b describes the operation of local Wireless LANs in the ISM fre-
quency band (
I ndustrial, S cientific, M edical: 2.4 up to 2.483 GHz). The maxi-
mum transfer rate is up to 11 Mbps. The real throughput depends however on