Reliable transmissions in AWSNs by using O-BESPAR hybrid antenna

An AWSN composed of bird-sized Unmanned Aerial Vehicles (UAVs) equipped with sensors and wireless radio, enables low cost high granularity three-dimensional sensing of the physical world. The sensed data is relayed in real-time over a multi-hop wireless communication network to ground stations. In this paper, we investigate the use of a hybrid antenna to accomplish efficient neighbor discovery and reliable communication in AWSNs. We propose the design of a hybrid Omni Bidirectional ESPAR (O-BESPAR) antenna, which combines the complimentary features of an isotropic omni radio (360° coverage) and directional ESPAR antennas (beamforming and reduced interference). Control and data messages are transmitted separately over the omni and directional modules of the antenna, respectively. Moreover, a communication protocol is presented to perform neighbor UAVs discovery and beam steering. We present results from an extensive set of simulations. We consider three different real-world AWSN application scenarios and employ empirical aerial link characterization to demonstrate that the proposed antenna design and protocol reduces the packet loss rate and end to end delay by up to 54% and 49% respectively, and increases the goodput by up to 33%, as compared to a single omni or ESPAR antenna.