Wideband spectrum compressive sensing for frequency availability in LEO-based mobile satellite systems

摘要

Availability of L/S frequency band is a critical requirement for global communication provided by a constellation of low Earth orbit satellites. This paper investigates the issue of low Earth orbit mobile satellite system frequency availability, where wideband compressed signal detection approach is utilized to obtain active user subbands and their locations which should be avoided during frequency allocation. Compressed sensing can be achieved by exploiting the sparsity of wideband signal spectrum, whose useful frequency support occupies only a small portion of the entirely wide spectrum. An estimate of the signal spectrum can be obtained by using reconstruction algorithms. We define two novel wideband spectrum compressed sensing methods based on discrete cosine transform and Walsh-Hadamard transform, briefly named DCT-WSCS and WHT-WSCS, which significantly improve the performance of spectrum recovery and signal detection compared with conventional discrete Fourier transform-based compressed spectrum sensing method. Furthermore, with the help of inter-satellite links, the scheme of multiple satellites cooperatively sensing with a final decision according to OR and MAJ fusion rules is proposed, which can bring diversity gains. Finally, in-depth numerical simulations under a particular scenario demonstrate the performance of the proposed scheme in the aspect of signal reconstruction precision, detection probability, and processing time.