Method for encoding data in bursts

The invention relates to a method for encoding data in a sequence of bursts (..., Bi-2, Bi-1, Bi, Bi+1,...), wherein each burst includes a block of data symbols and a block of redundancy symbols. The block of redundancy symbols (Ri) of the current burst (Bi) of the sequence is generated by the calculating the sum of a series of encoding values relating to a series of bursts (Bi-2, Bi-1), each encoding value from the series of encoding values being obtained by a respective encoding function applied to the block of data symbols of the burst corresponding to the series of bursts

Enabling Realistic Cross-Layer Analysis based on Satellite Physical Layer Traces

We present a solution to evaluate the performance of transport protocols as a function of link layer reliability schemes (i.e. ARQ, FEC and Hybrid ARQ) applied to satellite physical layer traces. As modelling such traces is complex and may require approximations, the use of real traces will minimise the potential for erroneous performance evaluations resulting from imperfect models. Our Trace Manager Tool (TMT) produces the corresponding link layer output, which is then used within the ns-2 network simulator via the additionally developed ns-2 interface module. We first present the analytical models for the link layer with bursty erasure packets and for the link layer reliability mechanisms with bursty erasures. Then, we present details of the TMT tool and our validation methodology, demonstrating that the selected performance metrics (recovery delay and throughput efficiency) exhibit a good match between the theoretical results and those obtained with TMT. Finally, we present results showing the impact of different link layer reliability mechanisms on the performance of TCP Cubic transport layer protocol

Enabling Realistic Cross-Layer Analysis based on Satellite Physical Layer Traces

We present a solution to evaluate the performance of transport protocols as a function of link layer reliability schemes (i.e. ARQ, FEC and Hybrid ARQ) applied to satellite physical layer traces. As modelling such traces is complex and may require approximations, the use of real traces will minimise the potential for erroneous performance evaluations resulting from imperfect models. Our Trace Manager Tool (TMT) produces the corresponding link layer output, which is then used within the ns-2 network simulator via the additionally developed ns-2 interface module. We first present the analytical models for the link layer with bursty erasure packets and for the link layer reliability mechanisms with bursty erasures. Then, we present details of the TMT tool and our validation methodology, demonstrating that the selected performance metrics (recovery delay and throughput efficiency) exhibit a good match between the theoretical results and those obtained with TMT. Finally, we present results showing the impact of different link layer reliability mechanisms on the performance of TCP Cubic transport layer protocol.Comment: 6 pages, 5 figures and 1 table. Submitted at PIMRC 201

Enhanced HARQ for Delay Tolerant Services in Mobile Satellite Communications

The objective of our paper is to improve efficiency (in terms of throughput or system capacity) for mobile satellite communications. In this context, we propose an enhanced Hybrid Automatic Repeat reQuest (HARQ) for delay tolerant services. Our proposal uses the estimation of the mutual information. We evaluate the performance of the proposed method for a land mobile satellite channel by means of simulations. Results are compared with those obtained with a classical incremental redundancy (IR) HARQ scheme. The technique we propose, shows a better performance in terms of efficiency while maintaining an acceptable delay for services

Enhancing satellite system throughput using adaptive HARQ for delay tolerant services in mobile communications

In this paper we propose the introduction of adaptive hybrid automatic repeat request (HARQ) in the context of mobile satellite communications. HARQ schemes which are commonly used in terrestrial links, can be adapted to improve the throughput for delay tolerant services. The proposed method uses the estimation of the mutual information between the received and the sent symbols, in order to estimate the number of bits necessary to decode the message at next transmission. We evaluate the performance of our method by simulating a land mobile satellite (LMS) channel. We compare our results with the static HARQ scheme, showing that our adaptive retransmission technique has better efficiency while keeping an acceptable delay for services

Making H-ARQ suitable for a mobile TCP receiver over LEO satellite constellations

This paper investigates strategies to carry out delay tolerant services over LEO satellite constellations for mobile receiver. In this context, LEO constellations are characterized by important delay variations where propagation impairments are mostly localized on the Land Mobile Satellite (LMS) channel (i.e. on the last hop). To cope with this issue, distinct reliability schemes can be introduced at the physical or link layers. Although their capacity to cope with transmission errors has been demonstrated, these recovery schemes may induce a high jitter that could severely damage TCP's internal timers and reliability schemes. As a matter of fact, transport and link layers’ reliability schemes exhibit a clear discrepancy. Following temporal traces representing the delay between a mobile terminal and the last hop satellite from a LEO constellation, we assess how HARQ mechanisms impact on the RTO based retransmission and the duplicate acknowledgments of TCP. Based on ns-2 simulations, we propose a layer-2 buffer that let both link and transport layers to conjointly perform. Our evaluations show an end-to-end data rate increase and more generally illustrate the benefit of re-ordering packets at the link layer when link-layer erasure coding recovery mechanisms are used conjointly with TCP

Transporter, conserver en mer au XVIIIe siècle, de la diversité vers la standardisation

International audienceCet article propose de décrire différents modes de conditionnement des denrées transitant par bateau au cours du XVIIIe siècle. Pour cela, la distinction est faite entre cargaison et produits destinés à la vie des hommes embarqués. La diversité des terres cuites, de la production verrière, des contenants en bois et en matières organiques seront abordés à l’aune de la Jeanne Élisabeth, brick de commerce suédois armé au cabotage international et naufragé en 1755 devant Villeneuve-lès-Maguelone (Hérault). Enfin, le navire sera présenté comme contenant lui-même tant dans ses aménagements spécifiques que dans le plan de chargement

L’épave de la Jeanne-Élisabeth, 1755 (Villeneuve-lès-Maguelone, Hérault). 2008-2016, bilan de huit campagnes de fouilles

International audienceThe wreck of the Jeanne-Elisabeth, 1755 (Villeneuve-lès-Maguelone, Hérault). 2008-2016, an overview of eight excavation campaigns.The Jeanne-Elisabeth is a Swedish merchantman that was lost during a storm on 14 November 1755, very close to the Languedoc-Roussillon coast in the French Mediterranean. On board the ship were ten Swedish sailors and eleven passengers of different nationalities, including two Frenchmen, whose bodies were found the next morning on the shore. This vessel of 200 tons and 25-metres length, probably snow-rigged, sailing from Cadiz to Marseille, carried 24,360 silver Spanish piasters minted in Mexico and Peru. A secondary cargo consisted of high added-value goods such as dyestuffs. The looting of this site in 2007 led to a Customs investigation and, the following year, to an archaeological evaluation by the DRASSM. The exceptional nature of the preserved remains and archaeological material has made the Jeanne-Elisabeth a reference site in terms of 18th century naval architecture and material culture.La Jeanne-Élisabeth est un navire de commerce suédois perdu lors d’une tempête le 14 novembre 1755 sur les côtes du Languedoc-Roussillon (Méditerranée française) à quelques encablures de la plage. À son bord, le navire compte dix marins suédois et onze passagers de différentes nationalités dont deux Français dont les corps seront retrouvés le lendemain sur le rivage. Ce brick de 200 tonneaux et 25 m de long, probablement gréé en senau, transporte entre Cadix et Marseille 24 360 piastres d’argent espagnoles frappées au Mexique et au Pérou. Une cargaison secondaire se compose de marchandises à forte valeur ajoutée comme des produits tinctoriaux. Le pillage de ce site en 2007 conduit à une enquête douanière et l’année suivante à son expertise archéologique par le Drassm. Le caractère exceptionnel des vestiges et des mobiliers conservés font de la Jeanne-Élisabeth un site de référence en matière d’architecture navale et de culture matérielle du XVIIIe siècle