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Search Results: 1 - 10 of 78229 matches for " CHEN Linglong "
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Compressive Sensing Based Multi-User Detector for the Large-Scale SM-MIMO Uplink
Zhen Gao,Linglong Dai,Zhaocheng Wang,Sheng Chen,Lajos Hanzo
Mathematics , 2015, DOI: 10.1109/TVT.2015.2501460
Abstract: Conventional spatial modulation (SM) is typically considered for transmission in the downlink of small-scale MIMO systems, where a single one of a set of antenna elements (AEs) is activated for implicitly conveying extra bits. By contrast, inspired by the compelling benefits of large-scale MIMO (LS- MIMO) systems, here we propose a LS-SM-MIMO scheme for the uplink (UL), where each user having multiple AEs but only a single radio frequency (RF) chain invokes SM for increasing the UL-throughput. At the same time, by relying on hundreds of AEs but a small number of RF chains, the base station (BS) can simultaneously serve multiple users whilst reducing the power consumption. Due to the large number of AEs of the UL-users and the comparably small number of RF chains at the BS, the UL multi-user signal detection becomes a challenging large-scale under-determined problem. To solve this problem, we propose a joint SM transmission scheme and a carefully designed structured compressive sensing (SCS)-based multi-user detector (MUD) to be used at the users and BS, respectively. Additionally, the cyclic- prefix single-carrier (CPSC) is used to combat the multipath channels, and a simple receive AE selection is used for the improved performance over correlated Rayleigh-fading MIMO channels. We demonstrate that the aggregate SM signal consisting of SM signals of multiple UL-users in one CPSC block appears the distributed sparsity. Moreover, due to the joint SM transmission scheme, aggregate SM signals in the same transmission group exhibit the group sparsity. By exploiting these intrinsically sparse features, the proposed SCS-based MUD can reliably detect the resultant SM signals with low complexity. Simulation results demonstrate that the proposed SCS-based MUD achieves a better signal detection performance than its counterparts even with higher UL-throughtput.
Smart Pilot Assignment for Massive MIMO
Xudong Zhu,Zhaocheng Wang,Linglong Dai,Chen Qian
Mathematics , 2015,
Abstract: A massive multiple-input multiple-output (MIMO) system, which utilizes a large number of antennas at the base station (BS) to serve multiple users, suffers from pilot contamination due to inter-cell interference. A smart pilot assignment (SPA) scheme is proposed in this letter to improve the performance of users with severe pilot contamination. Specifically, by exploiting the large-scale characteristics of fading channels, the BS firstly measures the inter-cell interference of each pilot sequence caused by the users with the same pilot sequence in other adjacent cells. Then, in contrast to the conventional schemes which assign the pilot sequences to the users randomly, the proposed SPA method assigns the pilot sequence with the smallest inter-cell interference to the user having the worst channel quality in a sequential way to improve its performance. Simulation results verify the performance gain of the proposed scheme in typical massive MIMO systems.
Soft Pilot Reuse and Multi-Cell Block Diagonalization Precoding for Massive MIMO Systems
Xudong Zhu,Zhaocheng Wang,Chen Qian,Linglong Dai,Jinhui Chen,Sheng Chen,Lajos Hanzo
Mathematics , 2015,
Abstract: The users at cell edge of a massive multiple-input multiple-output (MIMO) system suffer from severe pilot contamination, which leads to poor quality of service (QoS). In order to enhance the QoS for these edge users, soft pilot reuse (SPR) combined with multi-cell block diagonalization (MBD) precoding are proposed. Specifically, the users are divided into two groups according to their large-scale fading coefficients, referred to as the center users, who only suffer from modest pilot contamination and the edge users, who suffer from severe pilot contamination. Based on this distinction, the SPR scheme is proposed for improving the QoS for the edge users, whereby a cell-center pilot group is reused for all cell-center users in all cells, while a cell-edge pilot group is applied for the edge users in the adjacent cells. By extending the classical block diagonalization precoding to a multi-cell scenario, the MBD precoding scheme projects the downlink transmit signal onto the null space of the subspace spanned by the inter-cell channels of the edge users in adjacent cells. Thus, the inter-cell interference contaminating the edge users' signals in the adjacent cells can be efficiently mitigated and hence the QoS of these edge users can be further enhanced. Our theoretical analysis and simulation results demonstrate that both the uplink and downlink rates of the edge users are significantly improved, albeit at the cost of the slightly decreased rate of center users.
On the measure division construction of Λ-coalescents
Linglong Yuan
Mathematics , 2013,
Abstract: This paper provides a new construction of \Lambda-coalescents called "measure division construction". This construction is pathwise and consists of dividing the characteristic measure \Lambda into several parts and adding them one by one to have a whole process. Using this construction, a "universal" normalization factor \mu^{(n)} for the randomly chosen external branch length T^{(n)} has been discovered for a class of coalescents. This class of coalescents covers processes similar to Bolthausen-Sznitman coalescent, the coalescents without proper frequencies, and also others.
A Generalization of Kingman's Model of Selection and Mutation
Linglong Yuan
Mathematics , 2015,
Abstract: This paper generalizes Kingman's model of selection and mutation which studies the limit distribution of type values (or fitness values) in an asexual population of discrete generations and infinite size undergoing selection and mutation. A small set of assumptions for selection effects are proposed and for the mutation, as in Kingman's model, we assume that the type value of a mutant is independent of that of parent's. General macroscopic epistasis (or individual interactions) are designable through selection effect functions. Convergence to the unique limit type distribution is obtained for the general model. This setting covers the specific case studied in Kingman's model and also partially generalizes the framework of B\"urger's. The generalized model is then applied to Lenski experiment which investigates in the laboratory the long-term evolution of 12 initially identical populations of Escherichia coli in identical environments.
Development of a genome-wide multiple duplex-SSR protocol and its applications for the identification of selfed progeny in switchgrass
Liu Linglong,Wu Yanqi
BMC Genomics , 2012, DOI: 10.1186/1471-2164-13-522
Abstract: Background Switchgrass (Panicum virgatum) is a herbaceous crop for the cellulosic biofuel feedstock development in the USA and Europe. As switchgrass is a naturally outcrossing species, accurate identification of selfed progeny is important to producing inbreds, which can be used in the production of heterotic hybrids. Development of a technically reliable, time-saving and easily used marker system is needed to quantify and characterize breeding origin of progeny plants of targeted parents. Results Genome-wide screening of 915 mapped microsatellite (simple sequence repeat, SSR) markers was conducted, and 842 (92.0%) produced clear and scorable bands on a pooled DNA sample of eight switchgrass varieties. A total of 166 primer pairs were selected on the basis of their relatively even distribution in switchgrass genome and PCR amplification quality on 16 tetraploid genotypes. Mean polymorphic information content value for the 166 markers was 0.810 ranging from 0.116 to 0.959. From them, a core set of 48 loci, which had been mapped on 17 linkage groups, was further tested and optimized to develop 24 sets of duplex markers. Most of (up to 87.5%) targeted, but non-allelic amplicons within each duplex were separated by more than 10-bp. Using the established duplex PCR protocol, selfing ratio (i.e., selfed/all progeny x100%) was identified as 0% for a randomly selected open-pollinated ‘Kanlow’ genotype grown in the field, 15.4% for 22 field-grown plants of bagged inflorescences, and 77.3% for a selected plant grown in a growth chamber. Conclusions The study developed a duplex SSR-based PCR protocol consisting of 48 markers, providing ample choices of non-tightly-linked loci in switchgrass whole genome, and representing a powerful, time-saving and easily used method for the identification of selfed progeny in switchgrass. The protocol should be a valuable tool in switchgrass breeding efforts.
On the extendibility of finitely exchangeable probability measures
Takis Konstantopoulos,Linglong Yuan
Mathematics , 2015,
Abstract: We give necessary and sufficient conditions in order that a finite sequence $(X_1, \ldots, X_n)$ of exchangeable random elements in a fairly general space $S$ be extendible to a longer finite or to an infinite exchangeable sequence. This is done by formulating the extendibility problem as the extension problem for certain bounded linear functionals on suitable normed spaces and by using the Hahn-Banach theorem and other functional and measure-theoretic techniques. We examine when such a finitely exchangeable random sequence is a mixture (with respect to a probability measure) of product measures and also study the preservation of the extendibility property under suitable limiting operations.
A direct proof of the finite exchangeability representation theorem
Takis Konstantopoulos,Linglong Yuan
Mathematics , 2014,
Abstract: We give a direct proof of the theorem that says that every exchangeable probability measure on the $n$-fold Cartesian product of a measurable space $(S, \mathscr S)$ is a mixture of product measures with respect to a signed measure (referred to as "mixing measure") on the space of probability measures on $S$. The mixing measure is not necessarily unique. The contribution of this note is the streamlining of the proof by Kerns and Sz\'ekely, discussing measurability issues and some properties of a "canonical mixing measure".
Discussion of "Multivariate quantiles and multiple-output regression quantiles: From $L_1$ optimization to halfspace depth"
Linglong Kong,Ivan Mizera
Statistics , 2010, DOI: 10.1214/09-AOS723C
Abstract: Discussion of "Multivariate quantiles and multiple-output regression quantiles: From $L_1$ optimization to halfspace depth" by M. Hallin, D. Paindaveine and M. Siman [arXiv:1002.4486]
Quantile tomography: using quantiles with multivariate data
Linglong Kong,Ivan Mizera
Statistics , 2008, DOI: 10.5705/ss.2010.224
Abstract: The use of quantiles to obtain insights about multivariate data is addressed. It is argued that incisive insights can be obtained by considering directional quantiles, the quantiles of projections. Directional quantile envelopes are proposed as a way to condense this kind of information; it is demonstrated that they are essentially halfspace (Tukey) depth levels sets, coinciding for elliptic distributions (in particular multivariate normal) with density contours. Relevant questions concerning their indexing, the possibility of the reverse retrieval of directional quantile information, invariance with respect to affine transformations, and approximation/asymptotic properties are studied. It is argued that the analysis in terms of directional quantiles and their envelopes offers a straightforward probabilistic interpretation and thus conveys a concrete quantitative meaning; the directional definition can be adapted to elaborate frameworks, like estimation of extreme quantiles and directional quantile regression, the regression of depth contours on covariates. The latter facilitates the construction of multivariate growth charts---the question that motivated all the development.
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