PhD Theses

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Browsing PhD Theses by Subject "Algorithms"

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    Development of efficient algorithms for minimizing synchronization errors and analogue distortions in multicarrier systems
    (University of Dar es Salaam, 2014) Ibwe, Kwame Salum
    Orthogonal Frequency Division Multiplexing (OFDM) technology promises to be a key technique for achieving high data rate capacity for current and future wireless communication systems. The increase in data rate makes OFDM very sensitive to synchronization errors and analogue distortions. This thesis used the structure and statistics of received OFDM signal at the receiver to estimate and compensate for synchronization errors, analogue distortions and the channel. The effects of synchronization errors and analogue distortions on OFDM systems were first analyzed quantitatively under variant wireless channels. Then virtual subcarriers and maximum likelihood principles were used for frequency offset estimation and symbol timing respectively. The minimum variance techniques were used for channel estimation. Finally algorithms for mitigation of peak-to-average power ratio (PAPR) and In-phase Quadrature (IQ) imbalances using statistics of received signal were developed. Results show that the developed synchronization algorithms have low complexity of order of number of subcarriers (N), are communication standards independent, have Mean Square Error (MSE) of 0.43 dB and long acquisition range of order of {-N/2, N/2}. Channel estimation algorithms developed showed a 5dB improvement in MSE over existing methods in low Signal to Noise Power Ratio (SNR) of 5.8 dB. Finally the blind algorithms for minimization of IQ imbalance and PAPR were communication standards independent, low complexity (< N) and guaranteed 0dB PAPR transmission.