Quasi-optimal grouping for broadcast systems with hierarchical modulation

Recently, we proposed to combine time sharing with hierarchical modulation to increase the transmission rate of broadcast systems. Our proposal involves to group the receivers in pairs in order to transmit with hierarchical modulation. We introduced several grouping strategies but the optimal matching remained an open question. In this letter, we show that the optimal grouping is the solution of an assignment problem, for which efficient algorithms exist such as the Hungarian method. Based on this algorithm, we study the performance of the optimal grouping in terms of spectrum efficiency for a DVB-S2 system.Comment: Submitte

Improving broadcast channel rate using hierarchical modulation

We investigate the design of a broadcast system where the aim is to maximise the throughput. This task is usually challenging due to the channel variability. Modern satellite communications systems such as DVB-SH and DVB-S2 mainly rely on time sharing strategy to optimize throughput. They consider hierarchical modulation but only for unequal error protection or backward compatibility purposes. We propose in this article to combine time sharing and hierarchical modulation together and show how this scheme can improve the performance in terms of available rate. We present the gain on a simple channel modeling the broadcasting area of a satellite. Our work is applied to the DVB-SH standard, which considers hierarchical modulation as an optional feature.Comment: 5 pages, submitte

Frame format and DSP receiver design for a 56-GBaud GEO DP-QPSK coherent optical feeder link

International audienceThis paper addresses the design of a custom digital signal processing receiver and companion frame format for a 56 GBaud coherent optical Dual-Polarization Quadrature Phase- Shift Keying GEO feeder link. The selected algorithms combine standard practice from both coherent optical fiber and RF satellite communications. Robust blind algorithms are used in the first stages, followed by data-aided algorithms for subsequent fine carrier and phase recovery. A simplified blind equalizer architecture is proposed for fast and robust polarization demul- tiplexing, based on a modified constant-modulus algorithm. Our simulations demonstrate the possibility to establish links at an electrical SNR as low as -6 dB, in the presence of realistic values of system impairments, using less than 5% signaling overhead