User's Manual Part 1

Link Budget Analysis
InterReach Fusion Wideband Installation, Operation, and Reference Manual Page 95
D-620616-0-20 Rev H • TECP-77-044 Issue 7 • May 2013 © 2013 TE Connectivity Ltd.
OtherCDMAIssues
OtherCDMAissuesareasfollows:
• Neve
rcombinemultiplesectors(morethanoneCDMAsignalatthesamefrequency)intoa
FusionWidebandsystem.ThecombinedCDMAsignalswillinterferewitheachother.
• Trytomini
mize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.
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 de-spread 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80. AdditionalLinkBudgetConsiderationsforCDMA(Cont.)
Consideration Description