TY - JOUR AU - Linneweber, Gerit A. AU - Jacobson, Jake AU - Busch, Karl Emanuel AU - Hudry, Bruno AU - Christov, Christo P. AU - Dormann, Dirk AU - Yuan, Michaela AU - Otani, Tomoki AU - Knust, Elisabeth AU - de Bono, Mario AU - Miguel-Aliaga, Irene ID - 6122 IS - 1-2 JF - Cell SN - 0092-8674 TI - Neuronal control of metabolism through nutrient-dependent modulation of tracheal branching VL - 156 ER - TY - JOUR AB - Nous étudions le comportement asymptotique du nombre de variétés dans une certaine classe ne satisfaisant pas le principe de Hasse. Cette étude repose sur des résultats récemmentobtenus par Colliot-Thélène. AU - Bretèche, Régis de la AU - Browning, Timothy D ID - 6319 IS - 1 JF - Journal de Théorie des Nombres de Bordeaux SN - 1246-7405 TI - Contre-exemples au principe de Hasse pour certains tores coflasques VL - 26 ER - TY - CONF AB - We describe coding techniques that achieve the capacity of a discrete memoryless asymmetric channel. To do so, we discuss how recent advances in coding for symmetric channels yield more efficient solutions also for the asymmetric case. In more detail, we consider three basic approaches. The first one is Gallager's scheme that concatenates a linear code with a non-linear mapper, in order to bias the input distribution. We explicitly show that both polar codes and spatially coupled codes can be employed in this scenario. Further, we derive a scaling law between the gap to capacity, the cardinality of channel input and output alphabets, and the required size of the mapper. The second one is an integrated approach in which the coding scheme is used both for source coding, in order to create codewords with the capacity-achieving distribution, and for channel coding, in order to provide error protection. Such a technique has been recently introduced by Honda and Yamamoto in the context of polar codes, and we show how to apply it also to the design of sparse graph codes. The third approach is based on an idea due to Böcherer and Mathar and separates completely the two tasks of source coding and channel coding by “chaining” together several codewords. We prove that we can combine any suitable source code with any suitable channel code in order to provide optimal schemes for asymmetric channels. In particular, polar codes and spatially coupled codes fulfill the required conditions. AU - Mondelli, Marco AU - Urbanke, Rudiger AU - Hassani, Hamed ID - 6740 T2 - 52nd Annual Allerton Conference on Communication, Control, and Computing TI - How to achieve the capacity of asymmetric channels ER - TY - JOUR AB - We explore the relationship between polar and RM codes and we describe a coding scheme which improves upon the performance of the standard polar code at practical block lengths. Our starting point is the experimental observation that RM codes have a smaller error probability than polar codes under MAP decoding. This motivates us to introduce a family of codes that “interpolates” between RM and polar codes, call this family C inter = {C α : α ∈ [0, 1j}, where C α|α=1 is the original polar code, and C α|α=0 is an RM code. Based on numerical observations, we remark that the error probability under MAP decoding is an increasing function of α. MAP decoding has in general exponential complexity, but empirically the performance of polar codes at finite block lengths is boosted by moving along the family Cinter even under low-complexity decoding schemes such as, for instance, belief propagation or successive cancellation list decoder. We demonstrate the performance gain via numerical simulations for transmission over the erasure channel as well as the Gaussian channel. AU - Mondelli, Marco AU - Hassani, Hamed AU - Urbanke, Rudiger ID - 6739 IS - 9 JF - IEEE Transactions on Communications SN - 0090-6778 TI - From polar to Reed-Muller codes: A technique to improve the finite-length performance VL - 62 ER - TY - JOUR AB - With the aim of extending the coverage and improving the performance of impulse radio ultra-wideband (UWB) systems, this paper focuses on developing a novel single differential encoded decode and forward (DF) non-cooperative relaying scheme (NCR). To favor simple receiver structures, differential noncoherent detection is employed which enables effective energy capture without any channel estimation. Putting emphasis on the general case of multi-hop relaying, we illustrate an original algorithm for the joint power allocation and path selection (JPAPS), minimizing an approximate expression of the overall bit error rate (BER). In particular, after deriving a closed-form power allocation strategy, the optimal path selection is reduced to a shortest path problem on a connected graph, which can be solved without any topology information with complexity O(N 3 ), N being the number of available relays of the network. An approximate scheme is also presented, which reduces the complexity to O(N 2 ) while showing a negligible performance loss, and for benchmarking purposes, an exhaustive-search based multi-hop DF cooperative strategy is derived. Simulation results for various network setups corroborate the effectiveness of the proposed low-complexity JPAPS algorithm, which favorably compares to existing AF and DF relaying methods. AU - Mondelli, Marco AU - Zhou, Qi AU - Lottici, Vincenzo AU - Ma, Xiaoli ID - 6744 IS - 3 JF - IEEE Transactions on Wireless Communications TI - Joint power allocation and path selection for multi-hop noncoherent decode and forward UWB communications VL - 13 ER -