Channel Probes for OFDM Equalizer Compensation of Channel Frequency Response and of Frequency Dependent Transmitter and Receiver Gain and Phase Imbalances
The growing number of users in the world of mobile communications and the ever increasing demand for higher data rates calls for inexpensive and flexible transmitter/ receiver architectures in wireless communication systems. Achieving such data rates imposes serious challenges on underlying hardware and RF circuitry causing non idealities and impairments more so than current systems. This can lead to significant performance degradation at the transmitter and receiver. In this thesis, we consider the problem of imbalances between the I- and Q- branches of the modulator/demodulator, in particular for OFDM systems. A novel compensation approach is proposed to solve this problem using baseband processing techniques, allowing for flexible RF design for high speed wireless systems. In particular, the proposed solution models transmit and receive side impairments such as receiver mixers, filters, phase and frequency errors and even channel distortions. The solution is obtained by joint estimation and compensation of the I/Q imbalance caused by the above impairments. The problem is studied for a OFDM wireless system and an analytical solution is presented in this thesis. Performance evaluations using MATLAB simulations are presented to confirm the effectiveness of the proposed method under various scenarios.
