| Orthogonal Frequency Division Multiplexing (OFDM) has attracted considerable attention in recent years due to its desirable properties such as its high data rate transmission capability, as well as its robustness to multipath delay spread. Which is the most popular techniques recently introduced in IEEE 802.11 and IEEE 802.16. OFDM is considered as the candidate for the 4th generation digital communication systems. The first part of my Ph.D research focuses on OFDM, in which we establish a constraint optimization problem to find the optimal transmission pulse that minimize the signal-to-average inter-carrier-interference (ICI) ratio, which is my first contribution for OFDM systems. Secondly, we propose a time domain interpolation method to do the channel estimation of OFDM systems, in which we fully explore the sparsity of the wireless channel by using non-orthogonal basis functions.; My second part of Ph.D research focuses on the mismatch errors calibration of the multiple time-interleaved analog-to-digital converters (ADCs), in which we apply non-linear least square technique to calibrate the time errors and gain mismatches for multiple time-interleaved ADCs. The proposed approach is applicable to any number of time-interleaved ADCs and requires only modest oversampling. While the algorithm is mainly designed for blind calibration, it can as well be operated in non-blind mode. Theoretical analysis and numerical simulations show fast convergence and good estimation performance of the proposed algorithm. For instance, for an 8-ADC system, numerical experiments demonstrate that the resulting signal to noise ratio (SNR) of the output signal after mismatch detection and interpolation, is higher than the SNR of the input signal. |
