User's Manual

Estimating RF Coverage
InterReach Fusion Wideband Installation, Operation, and Reference Manual Page 83
D-620616-0-20 Rev K • TECP-77-044 Issue 9 • March 2015 © 2015 TE Connectivity
ESTIMATING RF COVERAGE
The maximum output Power Per Carrier (based on the number and type of RF carriers being
transmitted) and the minimum acceptable received power at the wireless device (that is, the RSSI
design goal) essentially establish the RF downlink budget and, consequently, the maximum
Allowable Path Loss (APL) between the RAU’s antenna and the wireless device. Since in-building
systems, such as the Fusion Wideband, are generally downlink-limited, this approach is
applicable in the majority of deployments.
Figure 15.
Determining APL between the Antenna and the Wireless Device
Equation 1
Equation 1 is as follows:
APL = (P – L
coax
+ G) – RSSI
where:
• APL = the maximum allowable path loss in dB
• P = the Power Per Carrier tran
smitted by the RAU in dBm
• L
coax
= the coaxial cable loss between the RAU and passive antenna in dB
• G = the gain of the passive antenna in dBi
Coaxial
cable is used to connect the RAU to an antenna. Table 70 lists coaxial cable loss for various
cable lengths.
You can calculate the distance (d), corresponding to the maximum allowable pat
h
loss using
equations introduced in the following sections.
Table 70.
Coaxial Cable Losses (L
coax
)
Length of Cable
(.195 in. diameter)
Loss at 850 MHz (dB) Loss at 1900 MHz (dB)
0.9 m (3 ft) 0.6 0.8
1.8 m (6 ft) 1.0 1.5
3.0 m (10 ft) 1.5 2.3
RAU
RSSI =
power at the
wireless device
Distance = d
G = Antenna Gain
P =
power per carrier
from the RAU
L
coax
= Coaxial cable loss