Spectrum efficiency improvement techniques for wireless communications
Zhao, Bo (2011) Spectrum efficiency improvement techniques for wireless communications. PhD thesis, University of Warwick.Full text not available from this repository.
Official URL: http://webcat.warwick.ac.uk/record=b2521751~S15
Ultra-wideband (UWB) and cognitive radio have been proposed as two
important approaches to improve the spectrum efficiency of wireless communications.
The aim of this thesis is to study these two techniques
considering different practical conditions.
The study of the UWB technique begins with the analysis of the statistical
properties of the sum of path gains using maximum ratio combining
technique based on the IEEE UWB channel models. This analysis helps
to justify the equivalent tapped-delay-line discrete UWB channel models.
Following the study of the UWB channel models, signal-to-interferenceplus-
noise ratio is analyzed for direct sequence binary phase shift keying
UWB Rake receivers. Closed-form expressions for the signal-to-interferenceplus-
noise ratio are derived by taking inter-path interference, inter-chip
interference and inter-symbol interference as well as multiple-access interference
into account. The analysis framework is further used to optimize
the integration interval for UWB transmitted reference receivers.
In addition to the signal-to-interference-plus-noise ratio, channel capacity
of UWB systems with timing errors is also analyzed in this work.
Both additive white Gaussian noise and multipath fading channels are
studied. All the necessary interferences are considered. Moreover, transmitted reference systems are also considered as an example of non-coherent
UWB systems for the capacity analysis.
Novel adaptive receivers are also proposed for multi-user UWB systems
in this thesis, as conventional matched-filter detection is not optimal in
multi-user environments due to the non-Gaussian multiple-access interference.
The new receivers adopt modified correlation operations without designing
new decision rules. Numerical results show that the new receivers
outperform the conventional receivers in both additive white Gaussian
noise and multipath fading channels.
For cognitive radio, spectrum sensing based on energy detection is
studied. In order to make the analysis closer to practical applications,
traffic load of the multiple primary users is taken into account. Expressions
for the probability of detection, probability of false alarm and error
probability are derived for both standalone spectrum sensing and collaborative
spectrum sensing. In addition, the effect of the primary user traffic
on the signal-to-noise ratio wall of energy detection is evaluated when
noise uncertainty is present.
Collaborative user number selection is also investigated in this work.
The number of collaborative users is selected to maximize the effective
throughput considering both the sensing performance in the physical layer
and the throughput performance in the upper layer. Different channel
conditions and decision rules are considered. Expressions for the optimum
number of collaborative users are derived and verified.
|Item Type:||Thesis or Dissertation (PhD)|
|Subjects:||Q Science > QA Mathematics
T Technology > TK Electrical engineering. Electronics Nuclear engineering
|Library of Congress Subject Headings (LCSH):||Ultra-wideband devices, Cognitive radio networks, Wireless communication systems, Radio frequency|
|Official Date:||March 2011|
|Institution:||University of Warwick|
|Theses Department:||School of Engineering|
|Supervisor(s)/Advisor:||Chen, Yunfei ; Green, Roger J.|
|Extent:||xxvii, 250 leaves : ill., charts|
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