User's Manual

Help Hot Line (U.S. only): 1-800-530-9960 6-3
D-620616-0-20 Rev A CONFIDENTIAL
Downlink RSSI Design Goal
brated tone for a fixed antenna and making measurements with a mobile antenna
throughout the area surrounding the transmitter.
6. Determine the items required to connect to the base station: Refer to
Section 6.8, “Connecting a Main Hub to a Base Station,” on page 6-27.
Once you know the quantities of Fusion Wideband equipment to be used, you can
determine the accessories (combiners/dividers, surge suppressors, repeaters,
attenuators, circulators, and so on.) required to connect the system to the base sta-
tion.
The individual elements that must be considered in designing a Fusion Wideband
solution are explained in the following sections.
NOTE: Access the LGC Wireless Customer Portal at LGCWireless.com
for on-line dimensioning and design tools.
6.2 Downlink RSSI Design Goal
Wireless service providers typically provide a minimum downlink signal level and an
associated confidence factor when specifying coverage requirements. These two fig-
ures of merit are a function of wireless handset sensitivity and margins for fading and
body loss. Wireless handset sensitivity is the weakest signal that the handset can pro-
cess reliably and is a combination of the thermal noise in the channel, noise figure of
the handset receiver front end and minimum required SNR. Fade margins for multi-
path fading (fast or small-scale) and log-normal shadow fading (slow or large-scale)
are determined by the desired confidence factor, and other factors. Downlink RSSI
design goal calculations for the GSM protocol are shown below for a 95% area cover-
age confidence factor.
Noise Power
10 Log (KT)+10 Log (200 KHz); K=1.38X10
–23
, T=300 degrees Kelvin
–121 dBm
Wireless Handset Noise Figure 8 dB
Required SNR 9 dB
Multipath Fade Margin
95% Reliability for Rician K=6 dB
6dB
Log-normal Fade Margin
95% Area/87% Edge Reliability for 35 dB PLS and 9 dB Sigma
10 dB
Body Attenuation + 3 dB
Downlink RSSI Design Goal (P
DesignGoal
)
Signal level received by wireless handset at edge of coverage area
–85 dBm