MIMO adaptivity for tactical communications in dynamic multipath and mobility environments

In this paper we investigate practical adaptivity methods for tactical multiple-input multiple-output (MIMO) applications that need to operate on-the-move in variable multipath environments. The key features of these methods include the ability to estimate in real-time the MIMO channel between the transmitter and receiver in a dynamic multipath environment, select the highest performance spatial operating mode, and adapt the transmit waveform and receive/transmit processing. As channel dynamics vary, the proposed adaptive MIMO system determines whether to operate in Uninformed Transmitter (without feedback) or Informed Transmitter mode based on both spatial and temporal metrics that characterize the channel conditions. The adaptivity methods investigated in this study will be used in a real-time testbed designed to demonstrate the key features of an adaptive MIMO link and assess performance in a real-world environment. In this paper we also describe the adaptive MIMO testbed, the frame transmission structure, and channel sounding waveform used for the spatial adaptivity tests.