Min Gong

Tsinghua University, Peping, Beijing, China

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Publications (8)1.55 Total impact

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    ABSTRACT: A novel two dimensional differential demodulation (2D DD) is investigated, which exploits both the time and the frequency dimensions using the orthogonal frequency division multiplexing (OFDM) frame structure. Without changing the transmitter, the proposed 2D DD based on graph attempts to search for a more confident bypass, probably containing multiple DD operations. Simplified soft decision metrics of the amplitude ratio and phase difference are derived by making use of a Gaussian approximation. Two optimal path searching algorithms, based on depth-first search (DFS) and breadth-first search (BFS) respectively, are brought up and analyzed in details. Moreover, a random access memory (RAM) method is combined with DFS and BFS to further simplify the optimal path searching algorithms for a small maximum path length. Taking the 64-differential amplitude and phase shift keying (64-DAPSK) modulation scheme for example, simulation results show that the proposed 2D DD can obtain substantial performance gains with reasonable computational complexity. Among the four optimal path searching algorithms, BFS-RAM algorithm is the most potential one for practical applications with its ability of parallel computation. In addition, 2D DD is advantageous to withstand the Doppler effect, which is hence suitable for high mobile broadband wireless access systems.
    Aeu-international Journal of Electronics and Communications - AEU-INT J ELECTRON COMMUN. 01/2011; 65(11):893-900.
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    ABSTRACT: A novel two-dimensional differential demodulation (2-D DD) algorithm, which exploits both the time and frequency dimensions by using the orthogonal frequency division multiplexing (OFDM) frame structure, was investigated for 64-differential amplitude and phase shift keying (DAPSK) modulated OFDM signals. Without changing the transmitter, the proposed algorithm based on graph attempts to search for a more confident bypass, probably containing multiple DD operations, to demodulate one 64-DAPSK symbol rather than conventional direct DD. In order to carry out the optimal path searching process, the soft decision metrics of the amplitude ratio and phase difference were derived by making use of a Gaussian approximation. Simulation results show that the proposed algorithm can obtain substantial performance gains with reasonable computational complexity for uncoded AWGN and frequency selective fading channels. In addition, it is advantageous to withstand the Doppler effect, which is hence suitable for high mobile (e.g., in a car or train) broadband wireless access (BWA) systems.
    Consumer Communications and Networking Conference (CCNC), 2010 7th IEEE; 02/2010
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    ABSTRACT: Distributed antenna systems (DAS) reduce the access distance for users in areas away from the cell center, thereby, enhancing the transmission capability for those users. Recent studies have shown that antenna selection transmission (AST) is preferable to maximum ratio transmission (MRT) in a multicell DAS environment, owing to its interference reduction. However, it is obvious that users still suffer from strong interference at the cell edge when applying universal frequency reuse in DAS. We propose an efficient cooperative beamforming transmission (CBT) algorithm, whose basic idea is taking the distributed transmitting antennas within a cell and receiving antennas including desired users and adjacent cells' interfered users, as a distributed multiple-input multiple-output (D-MIMO) channel, by which CBT mitigates the interference through joint precoding. We analyze the proposed algorithm mathematically and compare it with other existing algorithms. A Monte-Carlo simulation is also carried out to verify the derivation. Both the analysis and simulation results show that the CBT algorithm outperforms both AST and MRT especially near the cell edge.
    Proceedings of the 6th International Wireless Communications and Mobile Computing Conference, IWCMC 2010, Caen, France, June 28 - July 2, 2010; 01/2010
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    ABSTRACT: Single-crystalline antimony trisulfide (Sb2S3) nanomaterials with flower-like and rod-like morphologies were successfully synthesized under refluxing conditions by the reaction of antimony trichloride (SbCl3) and thiourea with PEG400 and OP-10 as the surfactants. X-ray diffraction (XRD) indicates that the obtained sample is orthorhombic-phase Sb2S3 with calculated lattice parameters a=1.124nm, b=1.134nm and c=0.382nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show that the flower-like Sb2S3 is 9–10μm in size, which is composed of thin leaves with thickness of 0.05–0.2μm, width of 0.8–2.2μm and length of 2.5–3μm, and the rod-like Sb2S3 is 45–360nm in diameter and 0.7–4μm in length, respectively. UV–Vis analysis indicates that the band gap of Sb2S3 nanorods is 1.52eV, suitable for photovoltaic conversion. A possible mechanism of formation was proposed. The effects of reaction time and surfactants on the growth of nanomaterials with different morphologies were also investigated.
    Journal of Crystal Growth 01/2009; 311(14):3651-3655. · 1.55 Impact Factor
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    ABSTRACT: This paper undertakes the performance evaluation and comparison of different phase shift keying (PSK) modulation schemes in aeronautical channels. Specifically, bit error rate (BER) curves and outage probabilities of various modulation schemes in high dynamic environments are investigated by means of numerical analysis and computer simulation. Simulation results show that the performance of all modulation schemes degrades with the increase of the power ratio or dynamic factor, and that differential quadrature phase shift keying (DQPSK), differential 8 phase shift keying (D8PSK), 16 and 64 differential amplitude and phase shift keying (DAPSK) perform better than other same order modulation schemes, respectively. As the conclusion, the differential modulation schemes are more suitable for the aeronautical channels in order to withstand the Doppler shift and the changing rate of the Doppler.
    Tsinghua Science & Technology 01/2009; 14:1-6.
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    ABSTRACT: Amplitude phase-shift keying (APSK), especially 16APSK and 32APSK modulations, have been efficiently applied into satellite broadcasting and communications, such as DVB-S2, which endows the system with high spectrum efficiency and transmission rate. However, fewer design about the trellis coding and modulation based on APSK has been reported so far. In this paper, the symmetric and asymmetric TCM for 16APSK and 32APSK have been proposed and investigated. The proposed symmetric scheme has been proved more than 2dB gain in AWGN channel compared with the relatively low modulation schemes, e.g. 8PSK vs. 16APSK and 16APSK vs. 32APSK, which can be considered as a good alternative if the system works beneath the demodulation threshold of the relatively low modulation schemes. Moreover, the asymmetric TCM scheme is proposed in fading channel to achieve additional more than 1dB gain.
    Telecommunications, 2008. ICT 2008. International Conference on; 07/2008
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    ABSTRACT: A novel dynamic resource allocation algorithm is proposed for matching the OFDMA system in high speed mobile environment, which suffers from high inter-carrier interference and large dynamic range of mobile speed for versatile users. With the non-linear optimization, the objective function of the transmission power can be directly mapped with the variables, such as the mobile speed of users, channel state information, modulation and coding schemes etc. Compared with the hitherto resource allocation algorithms in IEEE 802.16e, the proposed scheme has even more comprehensive capability depicting the features for high speed mobile and better performance in BER and QoS guarantee, especially in case the speed is more than 300 km/h.
    Proceedings of IEEE International Conference on Communications, ICC 2008, Beijing, China, 19-23 May 2008; 01/2008
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    ABSTRACT: Low Rate Orthogonal Convolutional Codes (LROCC) have been confirmed an outstanding performance in AWGN channel with multiple users, such as the en-route situation in the aeronautical communications with several aircrafts. However, the orthogonal sequences in LROCC still suffer from multipath interference in fading channel, which degrades the performance in practical scenarios. In this paper, extended CCK sequences have been applied instead of orthogonal sequences to form the low rate convolutional codes, which enable the aeronautical communications system a strong capability in the multipath interference cancellation(e.g., low elevation flight).
    01/2008;