Table 6-24 Additional Link Budget Considerations For Cdma - ADC InterReach Fusion Installation, Operation And Reference Manual

Consideration Description
Power This depends on how many channels are active. For example, the signal is about 7 dB lower if only the
per carrier, pilot, sync, and paging channels are active compared to a fully-loaded CDMA signal. Furthermore, in the
downlink CDMA forward link, voice channels are turned off when the user is not speaking. On average this is
assumed to be about 50% of the time. So, in the spreadsheet, both the power per Walsh code channel (rep-
resenting how much signal a mobile will receive on the Walsh code that it is de-spreading) and the total
power are used.
The channel power is needed to determine the maximum path loss, and the total power is needed to deter-
mine how hard the Fusion system is being driven.
The total power for a fully-loaded CDMA signal is given by (approximately):
Information Rate This is simply
Process Gain The process of de-spreading the desired signal boosts that signal relative to the noise and interference.
This gain needs to be included in the link budget. In the following formulas, P
Note that the process gain can also be expressed as 10log
rate.
Eb/No This is the energy-per-bit divided by the received noise and interference. It's the CDMA equivalent of sig-
nal-to-noise ratio (SNR). This figure depends on the mobile's receiver and the multipath environment.
If the receiver noise figure is NF (dB), then the receive sensitivity (dBm) is given by:
D-620610-0-20 Rev D
P + P = –76 dBm (for PCS, J-STD-008)
TX RX
where P is the mobile's transmitted power and P
TX
mobile.
The power level transmitted under closed-loop power control is adjusted by the base
station to achieve a certain E
ence between these power levels, '
ated from the RAU, P
'
= P
P downink
'
= P
P downink
It's a good idea to keep –12 dB < '
Table 6-24 provides link budget considerations for CDMA systems.
Additional Link Budget Considerations for CDMA
Table 6-24
voice channel power
total power =
= voice channel power + 10 dB
10log (9.6 Kbps) = 40 dB for rate set 1
10
10log (14.4 Kbps) = 42 dB for rate set 2
10
P = 10log (1.25 MHz / 9.6 Kbps) = 21 dB rate set 1
G 10
P = 10log (1.25 MHz / 14.4 Kbps) = 19 dB rate set 2
G 10
=
P NF + E /N + thermal noise in a 1.25 MHz band – P
sensitivity b o
= NF +
E /N – 113 (dBm/1.25 MHz) – P
b o
Help Hot Line (U.S. only): 1-800-530-9960
/N (explained in Table 6-24 on page 6-31). The differ-
b 0
, can be estimated by comparing the power radi-
P
, to the minimum received signal, P
downink
+ P + 73 dBm (for Cellular)
uplink
+ P + 76 dBm (for PCS)
uplink
< 12 dB.
P
+ 13 dB + 10log
10
(CDMA bandwidth) minus the information
10
G
Link Budget Analysis
is the power received by the
RX
uplink
(50%)
= process gain:
G
G
, at the RAU:
6-31
CONFIDENTIAL