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|Title: ||Transmitter based techniques for ISI and MAI mitigation in CDMA-TDD downlink|
|Authors: ||Georgoulis, Stamatis L|
|Supervisor(s): ||Cruickshank, David|
|Issue Date: ||Jun-2003|
|Publisher: ||University of Edinburgh. College of Science and Engineering. School of Engineering and Electronics|
|Abstract: ||The third-generation (3G) of mobile communications systems aim to provide enhanced voice,
text and data services to the user. These demands give rise to the complexity and power consumption
of the user equipment (UE) while the objective is smaller, lighter and power efficient
mobiles. This thesis aims to examine ways of reducing the UE receiver’s computational cost
while maintaining a good performance.
One prominent multiple access scheme selected for 3G is code division multiple access. Receiver
based multiuser detection techniques that utilise the knowledge of the downlink channel
by the mobile have been extensively studied in the literature, in order to deal with multiple
access and intersymbol interference. However, these techniques result in high mobile receiver
Recently, work has been done on algorithms that transfer the complexity from the UE to the
base station by exploiting the fact that in time division duplex mode the downlink channel can
be known to the transmitter. By linear precoding of the transmitted signal the user equipment
can be simplified to a filter matched to the user’s spreading code. In this thesis the problem
of generic linear precoding is analysed theoretically and a method for analytical calculation
of BER is developed. The most representative of the developed precoding techniques are described
under a common framework, compared and classified as bitwise or blockwise. Bitwise
demonstrate particular advantages in terms of complexity and implementation but lack in performance.
Two novel bitwise algorithms are presented and analysed. They outperform significantly
the existing ones, while maintain a reduced computational cost and realisation simplicity.
The first, named inverse filters, is the Wiener solution of the problem after applying a minimum
mean squared error criterion with power constraints. The second recruits multichannel adaptive
algorithms to achieve the same goal. The base station emulates the actual system in a cell
to converge iteratively to the pre-filters that precode the transmitted signals before transmission.
The advantages and the performance of the proposed techniques, along with a variety of
characteristics are demonstrated by means of Monte Carlo simulations.|
|Appears in Collections:||Engineering thesis and dissertation collection|
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