This paper discusses the use of multiple-antenna techniques in mobile WiMAX systems. We first
present antenna array techniques, which primarily reduce interference and enhance the useful signal
power. Next, we give a general description of multi-input multi-output (MIMO) systems, which can be
used for different purposes including diversity, spatial multiplexing and interference reduction. Then,
we focus on the multi-antenna profiles adopted for WiMAX systems, discuss their relative merits, and
address the implementation issues. Finally, we outline the design options taken by SEQUANS
Communications and highlight their performance.