3,822 research outputs found
Fast-SSC-Flip Decoding of Polar Codes
Polar codes are widely considered as one of the most exciting recent
discoveries in channel coding. For short to moderate block lengths, their
error-correction performance under list decoding can outperform that of other
modern error-correcting codes. However, high-speed list-based decoders with
moderate complexity are challenging to implement. Successive-cancellation
(SC)-flip decoding was shown to be capable of a competitive error-correction
performance compared to that of list decoding with a small list size, at a
fraction of the complexity, but suffers from a variable execution time and a
higher worst-case latency. In this work, we show how to modify the
state-of-the-art high-speed SC decoding algorithm to incorporate the SC-flip
ideas. The algorithmic improvements are presented as well as average
execution-time results tailored to a hardware implementation. The results show
that the proposed fast-SSC-flip algorithm has a decoding speed close to an
order of magnitude better than the previous works while retaining a comparable
error-correction performance.Comment: 5 pages, 3 figures, appeared at IEEE Wireless Commun. and Netw. Conf.
(WCNC) 201
Analog Network Coding for Multi-User Spread-Spectrum Communication Systems
This work presents another look at an analog network coding scheme for
multi-user spread-spectrum communication systems. Our proposed system combines
coding and cooperation between a relay and users to boost the throughput and to
exploit interference. To this end, each pair of users, and
, that communicate with each other via a relay
shares the same spreading code. The relay has two roles, it synchronizes
network transmissions and it broadcasts the combined signals received from
users. From user 's point of view, the signal is decoded, and
then, the data transmitted by user is recovered by subtracting
user 's own data. We derive the analytical performance of this
system for an additive white Gaussian noise channel with the presence of
multi-user interference, and we confirm its accuracy by simulation.Comment: 6 pages, 2 figures, to appear at IEEE WCNC'1
A new need for safety stocks in a supply chain dedicated to customized mass production.
In a supply chain designed for the production of goods of wide variety, the production schedule creates an ordered list of all the alternate components that will be mounted on a same post of the chain. The supply of these components by the supplier may induce transportation-related constraints. There from systematically follows a time-gap between orders and deliveries. This mechanism, commonly called “rank-change”, may be analyzed with the help of the multinomial distribution associated to these alternate components; only a simulation approach has relevance as of that matter, for an analytic approach is not possible. Such an analysis allows assessing the importance of the need to form safety stocks because of the lot sizing, even though requirements are certain.stock de sécurité; lotissement dans transport; chaîne logistique;
Synchronization and decoupling of plants piloting in a supply chain dedicated to customized mass production.
The synchronization of the production of a manufacturing supplier, who makes alternate components assembled on his industrial customer’s work station with this client’s production specialized in mass production of highly diversified products, must take into account the improvement of their knowledge of the final demand (displacement of the Order Penetration Point) and the distance of some of the suppliers. The customer periodically forwards firm orders to his supplier calculated so as to preclude any production line stoppage. It is necessary that the supplier honor them to ensure the decoupling of the control of these two entities in the supply chain and define the efficiency of synchronization. In the considered context, the supplier also receives all available projected information from the industrial customer (final orders, firm on the short term, and structural characteristics of the final demand beyond). The efficiency of the supplier depends on the proper use of all information, notably when the production cycle of alternate components is longer than the demand cycle. In the study of the customer’s requirements, it is necessary to take into account the batch constraints linked to transportation, which compels the customer to hold safety stocks even though the set up organization guarantees that orders will be duly honored. The determinants of these stocks will be put in evidence. Similarly at the supplier, safety stocks will be necessary if the production process involves grouping in batches.synchronisation de la production dans une chaîne logistique; stock de sécurité; chaîne logistique;
A process oriented approach to service concepts.
Cet article s’intéresse à l’amélioration de la qualité des services et à leur conception en discutant des concepts classiquement mobilisés dans l’analyse des services, au travers d’une approche orientée processus. Il commence par passer en revue les définitions proposées par quelques chercheurs bien connus, spécialistes des services. Il propose une nouvelle typologie des service basée sur une approche orientée processus, permettant de discuter la portée de certaines caractéristiques généralement associées aux services. Il pointe ensuite les similitudes existant entre la production de biens et celle de services et traite du continuum biens-services. Il s’intéresse enfin au clivage des opérations réalisées en front office et en back office, l’explicitation de la ligne de partage permettant de discuter de la qualité de service du double point de vue du consommateur et du producteur, dans une perspective de conception d’un service.The authors aim to contribute to the research on improvement of service quality and on service design by discussing service concepts through a process oriented approach. They begin by reviewing the service definitions given by some well known researchers working on service. They propose a new process oriented service classification which helps to challenge the validity of some service characteristics. They point out similarities between manufacturing and service production and discuss good-service continuum. They focus on separation of back-office operations from the front-office operations by the line of visibility which may help to discuss service quality from both producer's and customer's perspective in a service design context.Management de la production de services; Définition d'un service; Continuum produits-services; Classification des services; Coproduction;
Blind Detection of Polar Codes
Polar codes were recently chosen to protect the control channel information
in the next-generation mobile communication standard (5G) defined by the 3GPP.
As a result, receivers will have to implement blind detection of polar coded
frames in order to keep complexity, latency, and power consumption tractable.
As a newly proposed class of block codes, the problem of polar-code blind
detection has received very little attention. In this work, we propose a
low-complexity blind-detection algorithm for polar-encoded frames. We base this
algorithm on a novel detection metric with update rules that leverage the a
priori knowledge of the frozen-bit locations, exploiting the inherent
structures that these locations impose on a polar-encoded block of data. We
show that the proposed detection metric allows to clearly distinguish
polar-encoded frames from other types of data by considering the cumulative
distribution functions of the detection metric, and the receiver operating
characteristic. The presented results are tailored to the 5G standardization
effort discussions, i.e., we consider a short low-rate polar code concatenated
with a CRC.Comment: 6 pages, 8 figures, to appear at the IEEE Int. Workshop on Signal
Process. Syst. (SiPS) 201
Scheduling Coordination in a Supply Chain Using Advance Demand Information.
In an environment of mass customization where demand information can be placed in advance with sequencing orders, the question of the best use of this information arises in a supply chain. This situation led the authors to analyze the efficiency of current mechanisms of scheduling coordination when suppliers' processes are not completely reliable. Policies such as periodic replenishment or the kanban system, characterized by a replacement of the items to consume, cannot be exploited effectively with the current rules. This paper presents and justifies new scheduling coordination rules allowing synchronous production in an unreliable environment. This new approach has been benchmarked in the automotive industry as an appropriate method to avoid stockouts and decrease the safety stock.Chaîne logistique; Synchronisation de la production dans une chaîne logistique; kanban; Production synchrone; Point de Pénétration de commande;
Comparison of Polar Decoders with Existing Low-Density Parity-Check and Turbo Decoders
Polar codes are a recently proposed family of provably capacity-achieving
error-correction codes that received a lot of attention. While their
theoretical properties render them interesting, their practicality compared to
other types of codes has not been thoroughly studied. Towards this end, in this
paper, we perform a comparison of polar decoders against LDPC and Turbo
decoders that are used in existing communications standards. More specifically,
we compare both the error-correction performance and the hardware efficiency of
the corresponding hardware implementations. This comparison enables us to
identify applications where polar codes are superior to existing
error-correction coding solutions as well as to determine the most promising
research direction in terms of the hardware implementation of polar decoders.Comment: Fixes small mistakes from the paper to appear in the proceedings of
IEEE WCNC 2017. Results were presented in the "Polar Coding in Wireless
Communications: Theory and Implementation" Worksho
Exploitation of the knowledge of the final demand in the piloting of a logistics chain.
The transition from synchronous supplies to synchronous production represent a possible alternative to the neighbourhood logistics configurations, especially in the automotive industry. It allows to gain, on certain conditions, efficiency and more manoeuvrability faced with a strong variability of the demand on the supply chain. The utilization of the Order Penetration Point (OPP) will introduce problems in piloting production between clients and suppliers processes. This article is based on several working assumptions which form an algorithm for the resolution of this problem resulting from an analysis of two industrial cases with stochastic models.synchronous production; supply chain; anticipation; piloting of flows; order penetration point; kanban;
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