Networked airborne communications using adaptive multi-beam directional links

Advances in digital arrays provide new techniques for increasing throughput in airborne adaptive directional networks. By adaptive directional linking, we mean systems that can dynamically change both the transmit and receive spatial patterns used for a link on a packet-by-packet basis. Using several arrays at each node, and several beams per array, these systems are able to both focus transmit energy in favorable directions, and reject interference at reception. Our problem space overlaps considerably with Multiple Input Multiple Output (MIMO) systems and distributed MIMO, but differs in several important ways. First and foremost, our links are largely line of sight, and as such, typically have a maximum rank of one and little time variation; hence, point-to-point multi-stream and diversity techniques have little benefit. We do however consider multiple transmissions at each transmitting array face, not to a common receiver, but to several distributed receiving nodes. As we will show, the primary driver of network performance becomes geometry and array technology rather than channel phenomenology. We explore the utility of various spatial processing strategies both on the receive and transmit side of the networked links, and the gains associated with multiple simultaneous transmissions.