3 research outputs found
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
Combining Adaptive Coding and Modulation With Hierarchical Modulation in Satcom Systems
We investigate the design of a broadcast system in order to maximize throughput. This task is usually challenging due to channel variability. Forty years ago, Cover introduced and compared two schemes: time sharing and superposition coding. Even if the second scheme was proved to be optimal for some channels, modern satellite communications systems such as DVB-SH and DVB-S2 rely mainly on a time sharing strategy to optimize the throughput. They consider hierarchical modulation, a practical implementation of superposition coding, but only for unequal error protection or backward compatibility purposes. In this article, we propose to combine time sharing and hierarchical modulation together and show how this scheme can improve the performance in terms of available rate. We introduce a hierarchical 16-APSK to boost the performance of the DVB-S2 standard. We also evaluate various strategies to group the receivers in pairs when using hierarchical modulation. Finally, we show in a realistic case, based on DVB-S2, that the combined scheme can provide throughput gains greater than 10% compared to the best time sharing strategy
Rate adaptive resource allocation with fairness control for OFDMA networks
The use of opportunistic radio resource allocation techniques in order to efficiently manage the resources generates
a low fairness among the users in a cellular system due to uneven Quality of Service (QoS) distribution. Some classic rate adaptive policies tried to tackle this problem for OFDMA systems by
proposing solutions to maximize capacity, maximize fairness, or find a static trade-off between these two objectives. This
work generalizes these classic policies and propose a dynamic fairness/rate adaptive technique based on dynamic sub-carrier
assignment and equal power allocation that considers a new fairness constraint in the optimization problem. By means of
extensive system-level simulations, it is demonstrated that the
proposed technique is able to provide an instantaneous (short-term) fairness control, which provides to the network operator
the flexibility to operate on any desired trade-off point.Peer ReviewedPostprint (published version