User's Manual

Designing a Fusion Wideband Solution
Page 96 InterReach Fusion Wideband Installation, Operation, and Reference Manual
© 2015 TE Connectivity D-620616-0-20 Rev K • TECP-77-044 Issue 9 • March 2015
Other CDMA Issues
Other CDMA issues are as follows:
• Never combine multiple sectors (more t
han one CDMA signal at the same frequency) into a
Fusion Wideband system. The combined CDMA signals will interfere with each other.
• Try to minim
ize overlap between in-building coverage areas that utilize different sectors, as
well as in-building coverage and outdoor coverage areas. This is important because any area
in which more than one dominant pilot signal (at the same frequency) is measured by the
mobile will result in soft-handoff. Soft-handoff decreases the overall network capacity by
allocating multiple channel resources to a single mobile phone.
CDMA Link Budget Analysis for a Microcell Application
Noise Rise On the uplink, the noise floor is determined not only by the Fusion Wideband system, but also by the number
of mobiles that are transmitting. This is because when the Base Station attempts to despread a particular
mobile’s signal, all other mobile signals appear to be noise. Because the noise floor rises as more mobiles
try to communicate with a Base Station, the more mobiles there are, the more power they have to transmit.
Hence, the noise floor rises rapidly:
noise rise = 10log
10
(1 / (1 – loading))
where loading is the number of users as a percentage of the theoretical maximum number of users.
Typically, a Base Station is set
to limit the loading to 75%. This noise ratio must be included in the link budget
as a worst-case condition for uplink sensitivity. If there are less users than 75% of the maximum, then the
uplink coverage will be better than predicted.
Hand-off Gain CDMA supports soft hand-off, a process by which the mobile communicates simultaneously with more than
one Base Station or more than one sector of a Base Station. Soft hand-off provides improved receive
sensitivity because there are two or more receivers or transmitters involved. A line for hand-off gain is
included in the CDMA link budgets worksheet although the gain is set to 0 dB because the in-building system
will probably be designed to limit soft-handoff.
Table 86. CDMA Link Budget Analysis: Downlink
Line Downlink
Transmitter
a. BTS transmit power per traffic channel (dBm) 30.0
b. Voice activity factor 50%
c. Composite power (dBm) 40.0
d. Attenuation between BTS and Fusion Wideband (dB) –24
e. Power per channel into Fusion Wideband (dBm) 9.0
f. Composite power into Fusion Wideband (dBm) 16.0
g. Fusion Wideband gain (dB) 0.0
h. Antenna gain (dBi) 3.0
i. Radiated power per channel (dBm) 12.0
j. Composite radiated power (dBm) 19.0
Table 85. Additional Link Budget Considerations for CDMA (Cont.)
Consideration Description