  Cooperative communication using unmanned aerial vehicles (UAVs) is a
promising technology for infrastructureless wireless networks. One of the key
challenges in UAV based communications is the backhaul throughput. In this
paper, we propose optimization of the UAV swarm positions to achieve a high
mulitplexing gain in line-of-sight (LoS) MIMO backhaul. We develop two
distributed algorithms to position the UAVs such that each UAV moves a minimal
distance to realize the highest capacity LoS MIMO channel. The first approach
uses iterative gradient descent (GD) and the second uses iterative brute force
(BF). Simulations show that both algorithms can achieve up to 6 times higher
capacity compared to the approach relying on random UAV placement, earlier
proposed in the literature. BF has the advantage of not requiring any location
information, while GD is less sensitive to errors in motion.
