3 research outputs found
Smart antennas: state of the art
Aim of this contribution is to illustrate the state of the art of smart antenna research from several perspectives. The bow is drawn from transmitter issues via channel measurements and modeling, receiver signal processing, network aspects, technological challenges towards first smart antenna applications and current status of standardization. Moreover, some future prospects of different disciplines in smart antenna research are given.Peer Reviewe
Enhanced multi-user DMT spectrum management using polynomial matrix decomposition techniques
This thesis researches the increasingly critical roles played by intelligent resource management
and interference mitigation algorithms in present-day input multiple output (MIMO)
communication systems. This thesis considers the application of polynomial matrix decomposition
(PMD) algorithms, an emerging broadband factorisation technology for broadband
MIMO access networks. Present DSL systems’ performance is constrained by the presence
of interference (crosstalk) between multiple users sharing a common physical cable bundle.
Compared to the traditional static spectrum management methods that define their survival
to the worst-case scenarios, DSM methods provides some degree of flexibility to both direct
channel and noise parameters to improve evolvability and robustness significantly. A novel
crosstalk-aware DSM algorithm is proposed for the efficient management of multi-user DSL
systems. Joint power allocation procedures are considered for the proposed single-channel
equalisation method in DSL access networks.
This thesis then shows that DSM can also benefit overdetermined precoding-equalisation
systems, when the channel state information (CSI) parameters call for a specific decision
feedback criterion to achieve a perfect reconstruction. A reasonable redundancy is introduced
to reformulate the original multi-user MIMO problem into the simplest case of power
management problem. DSM algorithms are primarily applied to solve the power allocation
problem in DSM networks with the aim of maximising the system attribute rather than
meeting specific requirements. Also, a powerful PMD algorithm known as sequential
matrix diagonalisation (SMD) is used for analysing the eigenvalue decomposition problem
by quantifying the available system resource including the effects of the crosstalk and its
parameters. This analysis is carried out through joint precoding and equalisation structures.
The thesis also investigates dynamic interference mitigation strategies for improving
the performance of DSL networks. Two different mitigation strategies through a decision
feedback equalisation (DFE) criterion are considered, including zero-forcing (ZF) and
minimum mean square error (MMSE) equalisers. The difference between ZF and MMSE
equalisations is analysed. Some experimental simulation results demonstrate the performance
of both ZF and MMSE equalisation under the DFE equalisation constraint settings. Model reduction on the MMSE equalisation is thus applied to balance the crosstalk interference and
enhance the data-rate throughput.
Finally, the thesis studies a multi-user MIMO problem under the utility maximisation
framework. Simulation results illustrate that the power allocation of multi-user DSL transmission
can be jointly controlled and the interference can often be mitigated optimally on
a single user basis. Driven by imperfect CSI information in current DSL networks, the
research presents a novel DSM method that allows not only crosstalk mitigation, but also the
exploitation of crosstalk environments through the fielding of versatile, flexible and evolvable
systems. The proposed DSM tool is presented to achieve a robust mitigating system in any
arbitrary overdetermined multi-user MIMO environment. Numerical optimisation results show that the mitigation of crosstalk impairment using the proposed DSM strategy. The design and implementation of the proposed DSM are carried out in the environment of
MATLAB