Аннотация
This thesis is devoted to presenting the application
of the Genetic Programming (GP) paradigm to a class of
Digital Signal Processing (DSP) problems. Its main
contributions are
a new methodology for representing Discrete-Time
Dynamic Systems (DDS) as expression trees. The
objective is the state space specification of DDSs: the
behaviour of a system for a time instant t_0 is
completely accounted for given the inputs to the system
and also a set of quantities which specify the state of
the system. This means that the proposed method must
incorporate a form of memory that will handle this
information.
For this purpose a number of node types and associated
data structures are defined. These will allow for the
implementation of local and time recursion and also
other specific functions, such as the sigmoid commonly
encountered in neural networks. An example is given by
representing a recurrent NN as an expression tree.
a new approach to the channel equalisation problem. A
survey of existing methods for channel equalisation
reveals that the main shortcoming of these techniques
is that they rely on the assumption of a particular
structure or model for the system addressed. This
implies that knowledge about the system is available;
otherwise the solution obtained will have a poor
performance because it was not well matched to the
problem.
This gives a main motivation for applying GP to channel
equalisation, which is done in this work for the first
time. Firstly, to provide a unified technique for a
wide class of problems, including those which are
poorly understood; and secondly, to find alternative
solutions to those problems which have been
successfully addressed by existing techniques.
In particular, in the equalisation of nonlinear
channels, which have been mainly addressed with Neural
Networks and various adaptation algorithms, the
proposed GP approach presents itself as an interesting
alternative.
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