Channel Division Multiple Access

Ultra-WideBand (UWB) has been recently presented as a promising radio technology due to the large bandwidth available. This feature enables point to point high data rates at short range as well as high temporal resolution with long channel impulse reponses (CIR). In this paper, we present an original multiple access scheme called Channel Division Multiple Access (ChDMA), where we use the CIR as a user signature. The signature code is given by the channel and the users are separated by their position: this signature is uniquely determined by the user's position, which changes from one position to another. This signature location-dependent property provides decentralized flexible multiple access as the codes are naturally generated by the radio channel. The results derived can be straightforwardly applied to UWB ad-hoc networks. To analyze the multiple access scheme performance, we evaluate the channel capacity in a wideband power limited regime by the tradeoff of the spectral efficiency (b/s/hz) versus the ratio between the number of users and the system resolution. The framework is analyzed and validated by capacity assessments using UWB measurements performed at Eurecom and compared with classical CDMA schemes with random spreading. The following receivers are considered: optimal joint processing, single-user matched filter and MMSE receiver...

Genetic Control of a Central Pattern Generator: Rhythmic Oromotor Movement in Mice Is Controlled by a Major Locus near Atp1a2

Fluid licking in mice is a rhythmic behavior that is controlled by a central pattern generator (CPG) located in a complex of brainstem nuclei. C57BL/6J (B6) and DBA/2J (D2) strains differ significantly in water-restricted licking, with a highly heritable difference in rates (h2≥0.62) and a corresponding 20% difference in interlick interval (mean ± SEM = 116.3±1 vs 95.4±1.1 ms). We systematically quantified motor output in these strains, their F1 hybrids, and a set of 64 BXD progeny strains. The mean primary interlick interval (MPI) varied continuously among progeny strains. We detected a significant quantitative trait locus (QTL) for a CPG controlling lick rate on Chr 1 (Lick1), and a suggestive locus on Chr 10 (Lick10). Linkage was verified by testing of B6.D2-1D congenic stock in which a segment of Chr 1 of the D2 strain was introgressed onto the B6 parent. The Lick1 interval on distal Chr 1 contains several strong candidate genes. One of these is a sodium/potassium pump subunit (Atp1a2) with widespread expression in astrocytes, as well as in a restricted population of neurons. Both this subunit and the entire Na+/K+-ATPase molecule have been implicated in rhythmogenesis for respiration and locomotion. Sequence variants in or near Apt1a2 strongly modulate expression of the cognate mRNA in multiple brain regions. This gene region has recently been sequenced exhaustively and we have cataloged over 300 non-coding and synonymous mutations segregating among BXD strains, one or more of which is likely to contribute to differences in central pattern generator tempo