5 Typical Link Budget Parameters
Variable Unit
(a) Transmit power dB
(b) BS cabling loss dB
(c) BS antenna gain dB
(d) Rx antenna gain dB
(e) Receiver cabling loss dB
(f ) Thermal noise density dBm/Hz
(g) Interference density dBm/Hz
(h) Total I N density dBm/Hz
(i) Receiver NF dB
(j) System BW dB Hz
(k) Handoff gain dB
(l) Lognormal margin dB
(m) Path loss dB
(n) Building path loss dB
(o) Various implementations of losses dB
(p) Receive sensitivity a b c d e k l m n o
(q) Required Eb/(Io No) q h i j
A few very useful formulas should be presented; the first is the following very simple relationship.
(5.172)
Here the processing gain (PG) is the number of chips used to encode the QPSK symbol. The factor
of 2 was introduced to convert the symbol energy to bit energy. The second is given as follows, which
is essentially a substitution of the above formulas
(5.173) Srx kT # NF # Eb
No
# Rb
S
N
Eb
No
# 2 # 1
PG
These formulas can be used to derive the receiver sensitivity. For example, assume the BER
requirements are 1E-3, then we would obtain the required Eb/No to meet the requirements. This in turn
will be used in the above formula to provide us with the receiver sensitivity.
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