Feng Li

Qinghai Normal University, China

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Publications (14)9.51 Total impact

  • Dong Liang · Feng Li · ZongBen Xu ·
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    ABSTRACT: The problem of counting the number of spanning trees is an old topic in graph theory with important applications to reliable network design. Usually, it is desirable to put forward a formula of the number of spanning trees for various graphs, which is not only interesting in its own right but also in practice. Since some large graphs can be composed of some existing smaller graphs by using the product of graphs, the number of spanning trees of such large graph is also closely related to that of the corresponding smaller ones. In this article, we establish a formula for the number of spanning trees in the lexicographic product of two graphs, in which one graph is an arbitrary graph G and the other is a complete multipartite graph. The results extend some of the previous work, which is closely related to the number of vertices and Lapalacian eigenvalues of smaller graphs only.
    Sciece China. Information Sciences 11/2014; 57(11). DOI:10.1007/s11432-014-5110-z · 0.85 Impact Factor
  • Feng Li · Zongben Xu ·
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    ABSTRACT: This letter proposes a new method for cooperative spectrum sensing by exploiting sparsity. The novel scheme uses the theory of Bayesian hierarchical prior modeling in the framework of sparse Bayesian learning. This model has sparsity-inducing penalization terms leading to sparser solutions compared with typically ${l_1}$ norm based ones. Based on the factor graph that represents the signal model of the hierarchical prior models, the variational message passing (VMP) algorithm is implemented to estimate the power spectral density (PSD) map.
    IEEE Signal Processing Letters 05/2014; 21(5):586-590. DOI:10.1109/LSP.2014.2311902 · 1.75 Impact Factor
  • Source
    Zongben Xu · Feng Li · Haixing Zhao ·

    01/2014; 44(4):482. DOI:10.1360/112013-22
  • Feng Li · Zongben Xu · Shihua Zhu ·
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    ABSTRACT: This paper studies the problem of joint estimation of data and channels for orthogonal frequency-division multiplexing (OFDM) systems using variational inference. The proposed methods are used to combat imperfect channel estimation at the receiver since it can degrade system performance seriously. The proposed methods simplify the maximum a posteriori (MAP) scheme based on the theory of variational inference and formulate an optimization problem using variational free energy. The channel state information (CSI) and data are dealt with jointly and iteratively. The proposed schemes offer a variety of solutions for getting soft information when turbo equalization is implemented for coded systems. The effectiveness of the new approach is demonstrated by Monte Carlo simulations.
    IEEE Transactions on Vehicular Technology 03/2013; 62(3):1394-1399. DOI:10.1109/TVT.2012.2231972 · 1.98 Impact Factor
  • Ying Liu · Feng Li · Shihua Zhu · Lina Geng ·
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    ABSTRACT: In this paper, we propose an improved utility-based radio resource allocation algorithm in orthogonal frequency division multiple access (OFDMA) wireless networks. The queue state information (QSI), channel state information (CSI), QoS requirements and transmitted packets are synthetically considered in the utility function, thus it can meet the needs of networks with multi-service better. Based on the proposed utility function, the problem is designed as the sum utility maximization subject to both base station (BS) power and each subcarrier power. A heuristic algorithm based on Lagrange Multipliers method is used to solve the formulated optimization problem. Numeric simulation results show that compared with traditional approaches which do not take the QSI and transmitted packets into account, our proposed approach achieves better performance in terms of balancing throughput, delay and fairness.
    Wireless Communications and Mobile Computing Conference (IWCMC), 2013 9th International; 01/2013
  • Feng Li · Zongben Xu · Haixing Zhao · Wei Wang ·

    01/2012; 42(8):949. DOI:10.1360/112010-1050
  • Feng Li · Zongben Xu · Haixing Zhao ·

  • Feng Li · Wei Wang · Zongben Xu · Haixing Zhao ·
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    ABSTRACT: Many large graphs can be constructed from existing smaller graphs by using graph operations, for example, the Cartesian product and the lexicographic product. Many properties of such large graphs are closely related to those of the corresponding smaller ones. In this short note, we give some properties of the lexicographic products of vertex-transitive and of edge-transitive graphs. In particular, we show that the lexicographic product of Cayley graphs is a Cayley graph.
    Applied Mathematics Letters 11/2011; 24(11):1924-1926. DOI:10.1016/j.aml.2011.05.021 · 1.34 Impact Factor
  • Source
    Wei Wang · Feng Li · Hongliang Lu · Zongben Xu ·
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    ABSTRACT: For a given graph G with (0, 1)-adjacency matrix AG, the generalized characteristic polynomial of G is defined to be ϕG=ϕG(λ,t)=det(λI-(AG-tDG)), where I is the identity matrix and DG is the diagonal degree matrix of G. In this paper, we are mainly concerned with the problem of characterizing a given graph G by its generalized characteristic polynomial ϕG. We show that graphs with the same generalized characteristic polynomials have the same degree sequence, based on which, a unified approach is proposed to show that some families of graphs are characterized by ϕG. We also provide a method for constructing graphs with the same generalized characteristic polynomial, by using GM-switching.
    Linear Algebra and its Applications 03/2011; 434(5):1378-1387. DOI:10.1016/j.laa.2010.11.024 · 0.94 Impact Factor
  • Guomei Zhang · Shihua Zhu · Feng Li · Pinyi Ren ·
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    ABSTRACT: An improved soft-input soft-output (SISO) minimum mean-squared error (MMSE) detection method is proposed for joint coding and precoding OFDM systems under imperfect channel estimation. Compared with the traditional mismatched detection which uses the channel estimate as its exact value, the signal model of the proposed detector is more accurate and the influence of channel estimation error (CEE) can be effectively mitigated. Simulations indicate that the proposed scheme can improve the bit error rate (BER) performance with fewer pilot symbols.
    IEICE Transactions on Communications 03/2010; 93-B(3):757-761. DOI:10.1587/transcom.E93.B.757 · 0.23 Impact Factor
  • Guomei Zhang · Shihua Zhu · Shaopeng Wang · Feng Li ·
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    ABSTRACT: An improved iterative minimum, mean-squared error (MMSE) channel estimation method is proposed for joint coding and precoding OFDM systems. Compared with the traditional simplified estimator, the proposed scheme provides higher estimation quality with slight complexity increment at low signal-to-noise ratio (SNR) values. The performance of the iterative receiver including the proposed estimator approaches that of the perfect MMSE estimator without any simplification. Copyright © 2009 The Institute of Electronics, Information and Communication Engineers.
    IEICE Transactions on Communications 07/2009; 92-B(7):2520-2524. DOI:10.1587/transcom.E92.B.2520 · 0.23 Impact Factor
  • Feng Li · Shihua Zhu · Mei Rong ·
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    ABSTRACT: This letter presents an iterative detection scheme for orthogonal frequency division multiplexing (OFDM) systems with imperfect channel state information (CSI). In deriving the proposed scheme, channel estimation error is combated by using the theory of variational inference. The proposed scheme deals with the channel impulse response parameters and detects the information symbols iteratively and jointly. The effectiveness of the new approach is demonstrated by Monte-Carlo simulations.
    IEEE Signal Processing Letters 06/2009; 16(5-16):434 - 437. DOI:10.1109/LSP.2009.2016460 · 1.75 Impact Factor
  • Feng Li · Shihua Zhu · Mei Rong ·
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    ABSTRACT: Time variations of wireless multipath channels can lead to severe intercarrier interference (ICI) in orthogonal frequency division multiplex (OFDM) systems, whereas large Doppler frequency spread can provide us with time diversity gain. In order to take advantage of the time diversity and to suppress the interference and noise enhancement at the same time, the receiver normally detects the data successively. In this letter, we propose an improved detection ordering based on the log-likelihood ratio (LLR) rather than the signal-to-noise ratio (SNR) for the successive detector. Using both theoretical analysis and computer simulation, it is shown that this scheme outperforms the traditional successive detection methods.
    IEICE Transactions on Communications 05/2009; 92-B(5):1892-1896. DOI:10.1587/transcom.E92.B.1892 · 0.23 Impact Factor
  • Feng Li · Shihua Zhu · Lei Wang ·
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    ABSTRACT: A simplified equalization method based on the band structure of the frequency domain channel matrix is proposed for the single carrier systems employing cyclic prefix (SC-CP) over time-varying wireless channels. Using both theoretical analysis and computer simulation, it is shown that the complexity of this method is proportional to the number of symbols in one SC-CP block and is less than that of traditional block equalization methods. We also show that they have similar performance.
    IEICE Transactions on Communications 12/2007; E90B(12). DOI:10.1093/ietcom/e90-b.12.3733 · 0.23 Impact Factor