Abstract
Owing to the large amount of unlicensed bandwidth in its spectral vicinity, 60 GHz technology has attracted much attention as a means for meeting the growing requirements for high-rate indoor wireless communication. In this thesis, the multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) technique is considered for the IEEE 802.15.3c 60 GHz indoor channel model. In multi-user systems, inter-user interference (IUI) affects the system performance, and interference alignment (IA) is a promising technique for mitigating IUI. Therefore, iterative algorithms of IA are considered in the thesis. As currently used iterative algorithms of IA are shown to easily fall into local minima, we propose two algorithms for improving the performance by switching cost functions. Another problem with current iterative algorithms is that precoding and combining matrices must be calculated for each subcarrier, which increases the complexity for systems with a large number of subcarriers. We modify two iterative algorithms of IA into carrier grouping type, enabling the system complexity to be reduced through designing precoding and combining matrices for a group of subcarriers. As the initial value is known to be crucial for iterative algorithms, we also introduce a method to choose the initial value for carrier grouping algorithms. Finally, simulation results are shown to compare the performance of each scheme.