Dual priority SDMA in aeronautical communications

In order to achieve an efficient usage of limited aeronautical spectrum for broadband air to ground (A/G) communications, in this paper, an underlay mode space division multiple access (SDMA) is developed to support dual priority levels of services simultaneously for the future A/G communication system. Using orthogonal beamforming over the antenna array, the proposed underlay mode SDMA is able to provide interference free communications for the high priority service (e.g., air traffic control, ATC) of the m-th airborne station (AS-m), while its spectrum resource can be multiplexed in underlay mode for another low priority service (e.g., airline passenger communications, APC) of AS-n. We further propose an orthogonal deficiency based AS pairing criterion to minimize the performance degradation of low priority services. The signal-to-interference-plus-noise ratio (SINR) outage probability and achievable rate of underlay services are analyzed, while the simulation results confirm that the throughput could be approximately doubled when the number of pairing candidates is sufficiently large.