Capacity Versus Bit Error Rate Trade-Off in the DVB-S2 Forward Link

Matteo Berioli,Christian Kissling,Rémi Lapeyre

doi:10.1155/2007/14798

Matteo Berioli, Christian Kissling + Show 1 more

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https://doi.org/10.1155/2007/14798

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Abstract

The paper presents an approach to optimize the use of satellite capacity in DVB-S2 forward links. By reducing the so-called safety margins, in the adaptive coding and modulation technique, it is possible to increase the spectral efficiency at expenses of an increased BER on the transmission. The work shows how a system can be tuned to operate at different degrees of this trade-off, and also the performance which can be achieved in terms of BER/PER, spectral efficiency, and interarrival, duration, strength of the error bursts. The paper also describes how a Markov chain can be used to model the ModCod transitions in a DVB-S2 system, and it presents results for the calculation of the transition probabilities in two cases.

Highlights

The original DVB-S standard dates back to 1995 and was intended for delivery of broadcasting services, the underlying transport stream of DVB-S was defined to be MPEG-2
DVBS2 can achieve a capacity increase of up to 30% under the same transmission conditions compared to the older DVB-S standard what is achieved by applying higher order modulation schemes and by the use of low density parity check codes (LDPC) and Bose-Chaudhuri-Hochquenghem (BCH) codes
Once the modulation and coding combination (ModCod) switching criterion has been specified the software simulates the evolution over time of the system; from these simulations we can derive statistics about the permanence in the different ModCods for each ModCod switching criterion, this was done by computing transition matrices and solving them

Summary

Introduction

The original DVB-S standard dates back to 1995 and was intended for delivery of broadcasting services, the underlying transport stream of DVB-S was defined to be MPEG-2. The second generation of DVB-S provides a new way of fade mitigation by means of adaptation of the coding and modulation (ACM) to the different channel states This implies the need for every terminal to signal its perceived channel state back to the gateway which can make a frame-by-frame decision of the modulation and coding combination (ModCod) to be applied based on these measurements. The possibility to select the modulation and coding for an individual destination allows to make a more efficient use of the system capacity since transmission in a higher-order modulation in combination with a low coding rate (e.g., for clear sky conditions) allows to transmit more bits per symbol than a low-order modulation with high coding rate (e.g., for rainy channels) In this way it is possible to use individually for every ground terminal (or for every group of terminals in the same spot beam) the highest possible modulation scheme and the lowest coding rate which still allows to cope with the channel impairments to provide low BER. The adaptive selection of the best suited ModCod results in an increased net data throughput while terminals in bad channel conditions are still able to receive their data since they can use ModCods with lower-order modulation and higher coding (but at the cost of lower spectral efficiency and lower throughput)

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