7.6.4 Searching Operation
In this section, we will describe two searching operations, namely, the cell search procedure and the
multipath searcher. Since this is a spread spectrum system, the receiver is anticipating various echos
aEb
Nob2
4.08 dB
aEb
Nob2
12 dB 5 dB 10 log(256) 3 dB
aEb
Nob1
19.08 dB
aEb
Nob1
12 dB 10 dB 10 log(256) 3 dB
Eb
No
Ec
Ior
# Ior
Ioc
# SF # 1
2
3G WIDEBAND CDMA 387
FIGURE 7.57 Geometry values from downtown London.
Central London Geometry CDF
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
??“10 ??“5 0 5 10 15 20 25 30
Geometry (dB)
CDF
Central
London
Microcell
of the transmitted chip sequence, also called delay spread. Hence the UE will need to not only find
(or search for) the nearest neighbor cell, but also find as many ???good??? multipaths as possible, in order
to keep the RAKE receiver satisfied. A ???satisfied??? RAKE is a term used to describe a scenario where
the RAKE is actively demodulating at least one valid multipath signal.
The first searching operation is cell search, where the UE needs to find the nearest NodeB. This is
accomplished by the use of the following physical channels: P-SCH, S-SCH, P-CPICH, and P-CCPCH.
Pages:
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638