Cisco Catalyst IR1800 Series Installation Manual page 48

Antenna Installation Best Practices
When you use cellular antennas such as 3G UMTS, 4G/LTE, 4G/LTEA (LTE Advanced) with a modular
router and a pluggable module, try to mount the antennas a certain distance away from the router. For
example, in indoor deployments, an appropriate extension cable and antenna stand can be utilized. For
outdoor installations, choose a suitable outdoor antenna, and mount it away from obstructions such that
the antennas have a direct view of the cellular tower. The antenna's performance, and therefore that of
the router, will not be optimal if mounted directly on a pluggable module. Primary reasons for possible
degradation of performance include:
Keep antennas away from electrical and signal cable clutter. Metal conductors inside cables may block
an antenna's view of the base station. Additionally, unshielded (and even shielded cables in some cases)
may radiate signals that interfere with RF signal reception.
We recommend that all the cellular antennas for the IR1800 are oriented vertically to ensure polarization
match. While polarization of the signal may change because it is reflected from obstructions, when the
view is unobstructed, vertical polarization is optimal.
Note When cellular FDD Band 5 is deployed with 3G WCDMA, 4G/LTE, or 4G/LTEA C/A, such as with P-LTE-US or
P-LTEA-EA pluggable modules on certain carriers, ensure that both the Main and Aux cellular antennas are
physically separated from the IR1800 chassis by a minimum of 5 feet (1.5 meters). This is applicable only to the
P-LTE-xx receiver operation in Band 5 in a narrow 875-MHz frequency range. No significant effect has been
observed on the P-LTE-xx cellular Band 5 receiver when antennas are separated from the chassis by more
than 5 feet (1.5 meters). This information does not apply when the receive signal does not overlap 875 MHz,
such as when operating on other bands, or other frequencies within FDD Band 5.
For optimal MIMO performance, set the cellular Main and Aux antennas apart by at least 17 inches (43
cm). At the lowest LTE frequency of 700 MHz, 17 inches represents 1 wavelength. Spacing of half (or 0.5)
wavelength or 8.5 inch (22.5 cm) results in good MIMO performance.
Setting the Main and Aux LTE antennas less than 8.5 inches apart may result in significantly reduced
MIMO performance.
Placing the antennas too close to each other, for example 3 inches, results in the antennas significantly
detuning from their original designed performance because of antenna coupling.
Wherever possible, mount the IR1800 router with the pluggable LTE module and the antenna where the
cellular base station or tower are within sight and without physical obstructions. Barriers along the line
of sight between the router and the local base station degrades the wireless radio signals. Install the
IR1800, pluggable modules, and antennas above floor level in office environments, or near the ceiling, for
better performance because most obstructions tend to be near the floor level.
The density of the materials used in a building's construction determines the number of walls the signal
must pass through while still maintaining adequate coverage. Consider the following before choosing
the location for installing the antenna:
Cisco Catalyst IR1800 Rugged Series Router Hardware Installation Guide
40
The router antenna's view of the cellular base station tower being obstructed by Ethernet cables,
power cables, USB cables, and walls.
Possible coupling of digital noise from inside the router to the antenna when unshielded Ethernet
cables are used.
Paper and vinyl walls have very little effect on signal penetration.
Solid and precast concrete walls limit signal penetration to one or two walls without degradation of
coverage.
Concrete and wood block walls limit signal penetration to three or four walls.
A signal can penetrate five or six walls constructed of drywall or wood.
Antenna Selection and Installation