Wireless LAN – WLAN
120
3.10
WLAN according to 802.11h
BAT54-Rail/F..
Release
7.54
06/08
With the 802.11h enhancement in September 2003, the private use of the
5 GHz band was finally possible even outside closed spaces. To protect mil-
itary applications in the 5 GHz band, the DFS (Dynamic Frequency Selec-
tion) and TPC (Transmission Power Control) procedures were prescribed.
Moreover, the use of DFS and TPC can achieve significantly higher transmis-
sion powers (maximum 1000 mW) than the other standards that were previ-
ously valid.
U ETSI standards
ETSI adopted the first standard for controlling remote data transfers back in
1996 under the name of Hiperlan (High Performance Radio Local Area Net-
works). The first version (Hiperlan Type 1) was intended for use in the fre-
quency range of 5.15 to 5.30 GHz with a transmission rate of 20 MBit/s. As
no manufacturers took up this standard, Hiperlan initially had no practical sig-
nificance.
With the new version, Hiperlan Type 2, in 2000, ETSI introduced a WLAN so-
lution that operates in the 5 GHz band similarly to IEEE 802.11a, and also
provides a gross data rate of 54 MBps. However, as the frequencies and the
OFMD modulation method that was also used for 802.11a overlapped, it was
necessary to adapt the standards between IEEE and ETSI to avoid disrup-
tions to the systems.
U European harmonization
To standardize the use of the 5 GHz band in Europe, the European Commis-
sion issued the ETSI 301 893 standard on July 11, 2005. The member states
of the EU are obliged to implement this by October 31, 2005.
Instead of the three sub-bands described in the 802.11a/h standards (5150 -
5350 MHz, 5470 - 5725 MHz and 5725 - 5875 MHz for the UK), the
ETSI 301 893 standard regulates the three following areas with different
specifications:
D 5150 -5250 MHz
D 5250 -5350 MHz
D 5470 - 5725 MHz
The guidelines focus on preventive measures for avoiding disruptions to oth-
er systems that use the same frequency band. This includes radar equipment
that counts as "primary applications". The "secondary applications" such as
WLAN have to change the frequency as soon as a conflict is detected.
D Dynamic Frequency Selection – DFS
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