User's Manual

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D-620616-0-20 Rev E CONFIDENTIAL
Link Budget Analysis
Table 6-25 Link Budget Considerations for Narrowband Systems
Consideration Description
BTS Transmit Power The power per carrier transmitted from the base station output
Attenuation between
BTS and Fusion
Wideband
This includes all losses: cable, attenuator, splitter/combiner, and so forth.
On the downlink, attenuation must be chosen so that the maximum power per carrier going into the
Main Hub does not exceed the levels given in Section 6.3.
On the uplink, attenuation is chosen to keep the maximum uplink signal and noise level low enough
to prevent base station alarms but small enough not to cause degradation in the system sensitivity.
If the Fusion Wideband noise figure minus the attenuation is at least 10 dB higher than the BTS
noise figure, the system noise figure is approximately that of Fusion Wideband alone. Refer to Sec-
tion 6.8 for ways to independently set the uplink and downlink attenuations between the base station
and Fusion Wideband.
Antenna Gain The radiated output power includes antenna gain. For example, if you use a 3 dBi antenna at the
RAU that is transmitting 0 dBm per carrier, the effective radiated power (relative to an isotropic radi-
ator) is 3 dBm per carrier.
BTS Noise Figure This is the effective noise floor of the base station input (usually base station sensitivity is this effec-
tive noise floor plus a certain C/I ratio).
Fusion Wideband
Noise Figure
This is Fusion Wideband’s uplink noise figure, which varies depending on the number of Expansion
Hubs and RAUs, and the frequency band. Fusion Wideband’s uplink noise figure is specified for a
1-1-8 configuration. Thus, the noise figure for a Fusion Wideband system (or multiple systems
whose uplink ports are power combined) is NF(1-1-8) + 10*log(# of Expansion Hubs). This repre-
sents an upper-bound because the noise figure is lower if any of the Expansion Hub’s RAU ports are
not used.
Thermal Noise This is the noise level in the signal bandwidth (BW).
Thermal noise power = –174 dBm/Hz + 10Log(BW).
Required C/I ratio For each wireless standard, a certain C/I (carrier to interference) ratio is needed to obtain acceptable
demodulation performance. For narrowband systems, (TDMA, GSM, EDGE, iDEN, AMPS) this
level varies from about 9 dB to 20 dB.
Mobile Transmit
Power
The maximum power the mobile can transmit (power transmitted at highest power level setting).
Multipath Fade
Margin
This margin allows for a certain level of fading due to multipath interference. Inside buildings there
is often one or more fairly strong signals and many weaker signals arriving from reflections and dif-
fraction. Signals arriving from multiple paths add constructively or destructively. This margin
accounts for the possibility of destructive multipath interference. In RF site surveys the effects of
multipath fading are typically not accounted for because such fading is averaged out over power
level samples taken over many locations.
Protocol
Signal
Bandwidth
Thermal
Noise
TDMA 30 kHz –129 dBm
GSM 200 kHz –121 dBm
iDEN 25 kHz –130 dBm