Information transmission schemes based on adaptive coded modulation for UAV surveillance systems with satellite relays

Abstract

To expand their search range, unmanned aerial vehicles (UAVs) used for surveillance employ satellites as relays to forward monitoring data to the UAV’s command and control centers. With updated sensors, the amount of UAV detection data increases sharply, and the demand for bandwidth and transmission rates increase continuously. In this paper, the Ka-band is introduced to the satellite system as a solution instead of the Ku, C and other bands. Highly robust constant coded modulations (CCMs), such as the binary low-density parity-check (LDPC) and the coded quadrature phase shift keying (QPSK) are adopted to handle poor channel conditions caused by rain attenuation, which lead to a waste of spectral efficiency, especially in poor weather conditions; Adaptive Coded Modulation (ACM) can relieve the problems detailed above. Aiming at the problem mentioned above, we have proposed two different transmission schemes for two typical scenarios, including high quality of service (QoS) and high throughput service. The first is the so called automatic repeat request (ARQ)+ACM (target bit error rate (BER) algorithm) for high QoS, which means ARQ and ACM are employed by UAV-satellite links and satellite-center links, respectively. The second, denoted as coded cooperation (CC)+ACM (the maximum throughput algorithm) for high throughput services, designates that CC is employed for UAV-satellite links and ACM is employed for satellite-center links. Simulation results show that the ARQ+ACM scheme achieves higher spectral efficiency than CCM in cases that keep the BER below 10−5, and the CC+ACM scheme attains 3 to 7.5 times the spectral efficiency of CCM.