ADC InterReach Fusion Installation, Operation And Reference Manual page 94

Link Budget Analysis
Consideration
BTS Transmit Power
Attenuation between
BTS and Fusion
Antenna Gain
BTS Noise Figure
Fusion Noise Figure
Thermal Noise
Required C/I ratio
Mobile Transmit
Power
Multipath Fade
Margin
6-26
CONFIDENTIAL
Link Budget Considerations for Narrowband Systems
Table 6-20
Description
The power per carrier transmitted from the base station output
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 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 alone. Refer to Section 6.8 for ways to inde-
pendently set the uplink and downlink attenuations between the base station and Fusion.
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.
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).
This is Fusion's uplink noise figure, which varies depending on the number of Expansion Hubs and
RAUs, and the frequency band. Fusion's uplink noise figure is specified for a 1-1-8 configuration.
Thus, the noise figure for a Fusion system (or multiple systems whose uplink ports are power com-
bined) is NF(1-1-8) + 10*log(# of Expansion Hubs). This represents an upper-bound because the
noise figure is lower if any of the Expansion Hub's RAU ports are not used.
This is the noise level in the signal bandwidth (BW).
Thermal noise power = –174 dBm/Hz + 10Log(BW).
Signal
Protocol Bandwidth
TDMA 30 kHz
GSM 200 kHz
iDEN 25 kHz
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.
The maximum power the mobile can transmit (power transmitted at highest power level setting).
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.
InterReach Fusion Installation, Operation, and Reference Manual
Thermal
Noise
–129 dBm
–121 dBm
–130 dBm
D-620610-0-20 Rev D