MIMO (Multiple Input Multiple Output) is a technology that improves the capacity of a radio link by using multiple antennas for both transmission and receiving. MIMO technology exploits multipath propagation, which occurs when radio waves travel from the source emitter to the receiving antenna via multiple routes. MIMO can be used for a variety of drone and unmanned vehicle communication methods, including Wi-Fi and LTE networks such as 3G, 4G and 5G.
Radio channels can be affected by fading, which changes the signal-to-noise ratio and in turn increases the error rate. Fading can be caused by a number of variables including weather conditions and geographical location, and may occur in many environments that UAVs and robotic vehicles operate in. MIMO combats this by providing diversity – multiple versions of the same signal that are extremely unlikely to be affected the same way at the same time. MIMO systems may use time, frequency or space-based techniques to provide diversity and hence improve the stability of the radio link.
Advantages for Unmanned Vehicles
MIMO radios provide excellent performance for unmanned systems in harsh and noisy environments where other radio systems may fail, such as urban areas, maritime and mountainous regions. Radios utilizing multiple input and output technology can be used to stream data and video from the vehicle’s payloads back to the ground control station, handling the high-capacity requirements for applications such as surveillance and monitoring.
Drone Radio Networks
MIMO can be combined with MANET (mobile ad hoc networking) technologies in order to create flexible, self-configuring, self-organizing radio networks that can link together large numbers of drones and unmanned vehicles in areas with no existing communications infrastructure.
MIMO antennas can be mounted on different parts of a drone in order to cover the different orientations that the vehicle may go through during flight, thus minimising drop-out when the vehicle is moving. MIMO antenna placement can take advantage of polarisation diversity, which allows the use of compact, efficient antennas that have minimal impact on the SWaP (size, weight and power) budget of an unmanned vehicle.