PN code tracking plays a very important role in CDMA communication systems.
In literature, the influences of multipath fading and of multiuser interference
on PN code tracking are studied separately. The multipath fading influence is
mitigated by combining a rake receiver and a channel estimator in
the Delay-Locked Loop (DLL). The multiuser interference is overcome by
incorporating a data estimator into the DLL. In the downlink, PN code tracking
may suffer from the multipath fading influence. However, the multipath fading
and the multiuser interference influences exist in the uplink. Unfortunately,
sole use of the aforementioned methods cannot solve out both influences simultaneously.
In this thesis, two new Coherent Decision-Directed Delay-Locked Loop (CDD-DLL)
PN-Code tracking schemes are developed and either can overcome both influences.
First, a channel and a data estimators are incorporated into the DLL inherent
with a rake receiver. This new scheme works properly in an environment with
multipath fading and multiuser interference. Second, the original CDD-DLL is
combined with a multipath interference canceller (MPI) to reduce both influences.
Analytical results are derived for the two schemes proposed and are validated
with numerical simulations. Simulation results show that the conventional DLLs
working in a multipath fading and multiuser interference environment can be
significantly improved using the new schemes. Moreover, the latter outperforms
the former because the multipath interference is cancelled completely.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0621101-035721 |
| Date | 21 June 2001 |
| Creators | Yu, Hao-Chih |
| Contributors | Ching-Tai Chiang, Chao-Hung Chen, Jin-Nan Li, Shiunn-Jang Chern |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0621101-035721 |
| Rights | unrestricted, Copyright information available at source archive |
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