Multiple Antenna Techniques in WiMAX Systems

Multiple antenna systems can offer significant improvements in system performance due to their ability to exploit multipath signal propagation and take advantage of its random nature in order to achieve diversity or spatial multiplexing gain. As such, they are very suitable for implementation in WiMAX (Worldwide Interoperability for Microwave Access) systems to improve its performance in harsh urban and indoor environments. WiMAX physical layer is based on Orthogonal Frequency Division Multiplexing (OFDM), which is very robust to multipath propagation and enables straightforward usage of MIMO techniques. In this paper multiple antenna techniques and their use in Fixed and Mobile WiMAX systems are discussed. We present test results, collected with field measurements during a Fixed WiMAX system deployment, and describe results obtained by applying a channel simulator whose parameters are tuned according to field measurement data. A performance comparison between STC (Space-Time Coding) and non-STC operation mode is analyzed for different coding and modulation schemes specified in the standard.