Airborne Networks with Multi-beam Smart Antennas: Towards a QOS-Supported, Mobility-Predictive MAC

Airborne networks require throughput-efficient MAC for mission-oriented communications. The use of multi-beam smart antennas (MBSAs) could provide the network with better throughput performance since all beams can send out data concurrently. In this paper, we propose a two-layer MAC design for MBSA-based airborne network. In the upper layer, we use TDMA-like schedule control to separate the packet collision domains in multi-beam data transmissions. In the lower layer, we use the CSMA/CA based scheme that is compatible with conventional 802.11 protocols. Such a two-layer scheme significantly reduces the packet contentions and thus improves the throughput. In addition, in order to support mission priorities in the network, we introduce the QoS-oriented MAC control in both upper and lower layers. Furthermore, a mesh network time synchronization method is proposed to guarantee the beam synchronization. A Hierarchical Dirichlet Process (HDP) enhanced Hidden Markov Model (HMM) is used for mobility prediction in each beam (direction) of a node. These approaches could better exploit the benefits of MBSAs. The simulation results show that our proposed MAC protocol outperforms the standard 802.11 DCF and general MBSA-based MAC designs. The validation of the QoS control, synchronization and prediction schemes are also evaluated. It turns out that these schemes could greatly improve the overall performance of the airborne networks.