Channel order estimation is an important problem in many fields including signal processing,
communications, acoustics, and more. In this thesis, blind channel order estimation problem
is considered for single-input, multi-output (SIMO) FIR systems. The problem is to estimate
the effective channel order for the SIMO system given only the output samples corrupted by
noise. Two new methods for channel order estimation are presented. These methods have
several useful features compared to the currently known techniques. They are guaranteed to
find the true channel order for noise free case and they perform significantly better for noisy
observations. These algorithms show a consistent performance when the number of observations,
channels and channel order are changed. The proposed algorithms are integrated with
the least squares smoothing (LSS) algorithm for blind identification of the channel coefficients. LSS algorithm is selected since it is a deterministic algorithm and has some additional
features suitable for order estimation. The proposed algorithms are compared with a variety
of dierent algorithms including linear prediction (LP) based methods. LP approaches are
known to be robust to channel order overestimation. In this thesis, it is shown that significant
gain can be obtained compared to LP based approaches when the proposed techniques are
used. The proposed algorithms are also compared with the oversampled single-input, single-output (SISO) system with a generic decision feedback equalizer, and better mean-square
error performance is observed for the blind setting.
Channel order estimation problem is also investigated for semi-blind systems where a pilot
signal is used which is known at the receiver. In this case, two new methods are proposed
which exploit the pilot signal in dierent ways. When both unknown and pilot symbols are
used, a better estimation performance can be achieved compared to the proposed blind methods.
The semi-blind approach is especially effective in terms of bit error rate (BER) evaluation
thanks to the use of pilot symbols in better estimation of channel coecients. This approach
is also more robust to ill-conditioned channels. The constraints for these approaches, such
as synchronization, and the decrease in throughput still make the blind approaches a good
alternative for channel order estimation. True and effective channel order estimation topics
are discussed in detail and several simulations are done in order to show the significant performance
gain achieved by the proposed methods.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12611107/index.pdf |
| Date | 01 September 2009 |
| Creators | Karakutuk, Serkan |
| Contributors | Tuncer, Temel Engin |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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