Cisco AIR-BR1410A-A-K9 - Aironet 1410 Wireless Bridge Deployment Manual page 3

The 5GHz Band is actually a conglomerate of three Bands in USA: 5.150-5.250(UNII 1), 5.250-
5.350(UNII 2), and 5.725-5.875(UNII 3) GHz. UNII-1 and the UNII-2 bands are contiguous
and are indeed treated by 802.11a as being a continuous swath of spectrum 200MHz wide, more
than twice the size of the 2.4GHz ISM band. This results in a key benefit for 802.11a—the
200MHz wide UNII-1 and UNII-2 bands are divided up into eight non-overlapping channels,
each 25MHz wide.
1.2 Regulations
Outdoor Bridging utilizes UNII 3 band and there are regulatory limitations that apply in this band.
1.2.1 Federal Communications Commission (FCC) Regulations with respect to the
UNII 3 Band
Devices that operate in Unlicensed Bands do not require any formal licensing process, but
operations in these bands still obligate the user to follow regulations. The geographical bodies in
different parts of the world regulate these Bands. WLAN devices must comply with the local
geographical regulatory domains. The regulatory agencies set the radio emission requirements for
WLAN to minimize the amount of interference a radio can generate or receive from another in the
same proximity. The Federal Communications Commission (FCC) is responsible for framing rules
and regulations for WLAN operations in a particular band in United States. The set of FCC
regulations that apply to WLAN operation in the 5 GHz band is a subset of FCC Part 15
regulations. In addition to US, Australia, New Zealand and various parts of Asia and Oceania also
fall in the FCC regulatory domain.
For latest information please refer to the following URL:
www.cisco.com/go/aironet/compliance
http://www.cisco.com/warp/public/779/smbiz/wireless/approvals.html
1.2.2 Effective Isotropic Radiated Power (EIRP)
The radio energy radiated from an antenna is called the Effective Isotropic Radiated Power (EIRP).
The EIRP is usually expressed in Watts or dBm. To enable fair and equitable sharing of the
unlicensed band, regulatory domains impose maximum EIRP levels.
Directional antennas, such as Yagi and Parabolic dishes have the capability of shaping the signal
from the transmitter so it appears stronger in a particular direction (much the same as the reflector
on a flashlight strengthens a light beam). This is known as antenna gain.
Antenna cables can add loss attenuating the transmitted signal. The longer the cable, the more
attenuation, and the more signal loss in the cable affecting both receive and transmit. Cable
attenuation is dependent upon the grade and manufacturer. Low-loss cable is typically around 6.7
dB per 100 ft (30m) at 2.4GHz.
As the EIRP is a measure of the power out of the antenna, the EIRP must include the antenna gain
and the cable loss together with the power out of the transmitter.
Copyright © 2004 Cisco Systems, Inc. All rights reserved.
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