Ka-band return link for UAVs using adaptive spreading factor for DSSS in a DVB-RCS2 context

Robin Draye (1) , José Radzik (1)

1 DEOS - Département Electronique, Optronique et Signal

This paper evaluates the potential performances of a Direct Sequence Spread Spectrum (DSSS) satellite communication for Unmanned Aerial Vehicles (UAVs) in Ka-band using low directional antenna. The need to comply with the interference templates established by ITU enforces a bound to the signal power emitted toward adjacent satellites and greatly limits the accessible data rate. That prevents the UAVs communications to use a dedicated repeater for the return link. Instead, simultaneous transmission with return link communications in accordance to DVB-RCS2 standard is investigated. The proposed system is thus based on simultaneous transmission of narrow-band carriers (DVB-RCS2 primary system) and spread spectrum carriers (secondary system dedicated to UAVs). Mutual interferences are evaluated, it is shown that secondary transmissions do not affect primary systems availability, but conversely DVB-RCS2 carriers forces the secondary systems to use a high spreading factor, typically between 28 and 214 which can be updated as the number of primary active carriers changes within the beam. A compromise between secondary burst length and speed of adaptation for spreading factor is also discussed. Typically, if the targeted Packet Error Rate (PER) of the secondary link is 10e-5 and modulation is QPSK with a code rate 1/3, SNIR has to be held over 0 dB. This objective is reached with a spreading factor switching from 2e10 to 2e14 as the number of active primary carriers changes with a maximum bandwidth occupation of 90%, resulting in a data rate varying between 8 kbps and 34 kbps for the secondary system and a SNIR maintained between 1.5 dB and 4.5 dB.

Mots clés: Ka-band UAV DVB-RCS2

Domaines: Traitement du signal et de l'image [eess.SP]

Robin Draye, José Radzik. Ka-band return link for UAVs using adaptive spreading factor for DSSS in a DVB-RCS2 context. 23th Ka and Broadband Communications Conference, Oct 2017, Trieste, Italy. pp. 1-12. ⟨hal-01738689⟩