Robust MIMO Communications Against Antenna Blockage and Interference

Airborne platforms, either piloted or unmanned, are an integral part of most situational awareness systems. An imperative to the success of such situational awareness systems is the ability to reliably deliver high throughput low latency data from these airborne platforms. This paper presents a promising airborne multiple-input multiple-output (MIMO) communication system for the intended situation awareness applications. The proposed system addresses three major challenges in airborne MIMO communications: 1) antenna blockage due largely to the movement and orientation of the airborne platforms; 2) the presence of unknown interference inherent to the intended application; 3) the lack of channel state information (CSI) at the transmitter. Built on the Diagonal Bell-Labs Layered Space-Time (D-BLAST) MIMO architecture, the system integrates three key design approaches: spatial spreading to counter antenna blockage; temporal spreading to mitigate signal to interference and noise ratio degradation due to interference; and a simple low rate feedback scheme to enable adaptivity in the absence of full transmitter CSI. A fully functioning experimental 4 ⨯ 4 MIMO system is built using USRP software radio systems. Extensive studies using the developed system validate the performance advantage over the conventional D-BLAST system in the presence of channel impairment due to antenna blockage and interference.