Han-wen Luo

Shanghai Jiao Tong University, Shanghai, Shanghai Shi, China

Are you Han-wen Luo?

Claim your profile

Publications (18)3.16 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper deals with the design and performance analysis of transmit precoder optimization for multiple input multiple output (MIMO) systems with limited feedback of channel state information. A capacity criterion based optimal codebook construction algorithm for MIMO precoded spatial multiplexing systems is presented. The optimal precoder structure combining precoding and power allocation is employed. Simulation results show that the capacity criteria based codebook can achieve higher capacity than that of equally power allocation based codebook of previous research.
    Journal of Shanghai Jiaotong University (Science) 01/2009; 14(2):215-218.
  • Source
    Feng She, Han-wen Luo, Lei Chen, Hua Xia
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper deals with design and analysis of user scheduling and power allocation for multi-antenna OFDM systems with DPC, ZF-DPC, ZF-BF and TDMA transmit strategies. We consider the general multi-user downlink scheduling problem and power minimization with multi-user rate constraints. According to the channel state, it is shown that there is a power optimal policy which selects a subset of users in each scheduling interval. We present user selection algorithms for DPC, ZF-DPC, ZF-BF and TDMA for multi-antenna OFDM system in broadcast channels, and we also present the practical water-filling solution in this paper. By the selected users with the consideration of fairness, we derive the power optimization algorithm with multi-user rate constraints. We also analyze the power duality of uplink-downlink for the transmit strategies of DPC, ZF-DPC and ZF-BF. Simulation results show that the present user-scheduling algorithm and power minimization algorithm can achieve good power performance, and that the scheduling algorithm can guarantee fairness.
    Journal of Zhejiang University - Science A: Applied Physics & Engineering 01/2008; 9(2):215-224. · 0.53 Impact Factor
  • Source
    Feng She, Han-wen Luo, Xin Wang
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper deals with the design and performance analysis of the transmission precoder optimization for multiple-input multiple-output (MIMO) systems with limited feedback of channel state information (CSI). We assume that the receiver can get perfect channel knowledge by channel estimation while the transmitter only has partial channel knowledge from limited feedback. We present a minimum mean square error (MMSE) criterion based codebook construction algorithm for MIMO precoded spatial multiplexing systems under a specific average power constraint. The optimal transmitter structure is employed in this paper. Simulation results show that the MMSE criteria based codebook construction algorithm with hybrid design of power allocation and precoding can achieve better performance than that of equal power allocation based codebook of previous research.
    Journal of Zhejiang University - Science A: Applied Physics & Engineering 10/2007; 8(12):1894-1900. · 0.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A channel estimation approach for orthogonal frequency division multiplexing with multiple-input and multiple-output (MIMO-OFDM) in rapid fading channels is proposed. This approach combines the advantages of an optimal training sequence based least-square (OLS) algorithm and an expectation-maximization (EM) algorithm. The channels at the training blocks are estimated using an estimator based on the OLS algorithm. To compensate for the fast Rayleigh fading at the data blocks, a time domain based Gaussian interpolation filter is presented. Furthermore, an EM algorithm is introduced to improve the performance of channel estimation by a few iterations. Simulations show that this channel estimation approach can effectively track rapid channel variation.
    Journal of Shanghai University (English Edition) 05/2007; 11(3):278-282.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A space-time coded multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system is considered as a solution to the future wideband wireless communication system. This paper proposes an extended Kalman filtering-based (EKF-based) channel estimation method for space-time coded MIMO-OFDM systems. The proposed method can exploit pilot symbols and an extended Kalman filter to estimate channel without any prior knowledge of channel statistics. In comparison with the least square (LS) and the least mean square (LMS) methods, the EKF-based approach has a better performance in theory. Computer simulations demonstrate the proposed method outperforms the LS and LMS methods. Therefore it can offer dramatic system performance improvement at a modest cost of computational complexity.
    Journal of Shanghai University (English Edition) 01/2007; 11(5):469-473.
  • Source
    Ming Ding, Han-wen Luo, Yun Wu
    [Show abstract] [Hide abstract]
    ABSTRACT: A novel cell search scheme for OFDM cellular systems is proposed. It is based on one OFDM symbol with several identical slots as preamble, the time domain repetition structure of which can be utilized to accomplish OFDM timing/frequency synchronization. The cell ID is comprised of two parts: a sub-carrier mask index g and a sequence index x. Each sub-carrier mask activates or deactivates some of the sub-carriers, after which a differentially coded sequence is loaded on pairs of the adjacent active sub-carriers. The user equipment (UE) recognizes the mask with index g via power detection of the received frequency domain signal. Then it estimates the index x from differential demodulation followed by detection of the frequency domain sequence. In order to improve the performance, a method of jointly estimating g and x is devised. Simulation results showed that the proposed scheme is able to support a very large number of cell IDs while maintaining a good performance even in bad multi-cell environment.
    Journal of Zhejiang University - Science A: Applied Physics & Engineering 12/2006; 8(1):10-17. · 0.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper proposes a simple method to enlarge the estimation range of conventional carrier frequency offset (CFO) estimation methods based on correlations among the identical parts of the preamble. A novel preamble is designed, which is composed of one regular OFDM training block with even numbers of identical parts and one irregular OFDM training block with odd numbers of identical parts. The initial estimates obtained over the two training blocks are next exploited to jointly estimate the CFO. By elaborately selecting the numbers of identical parts for the two training blocks, the proposed CFO estimator can estimate frequency offset over tens of the subcarrier spacing. Simulation results showed that the proposed CFO estimator satisfies the estimate range requirement for the practical OFDM systems, while achieving a very good estimate performance.
    Journal of Zhejiang University - Science A: Applied Physics & Engineering 11/2006; 7(12):2104-2109. · 0.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Considering that channel estimation plays a crucial role in coherent detection, this paper addresses a method of Recursive-least-squares (RLS) channel estimation with adaptive forgetting factor in wireless space-time coded multiple-input and multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. Because there are three different forgetting factor scenarios including adaptive, two-step and conventional ones applied to RLS channel estimation, this paper describes the principle of RLS channel estimation and analyzes the impact of different forgetting factor scenarios on the performances of RLS channel estimation. Simulation results proved that the RLS algorithm with adaptive forgetting factor (RLS-A) outperformed that with two-step forgetting factor (RLS-T) or with conventional forgetting factor (RLS-C) in both estimation accuracy and robustness over the multiple-input multiple-output (MIMO) channel, i.e., a wide-sense stationary uncorrelated scattering (WSSUS) and frequency-selective slowly fading channel. Hence, we can employ the RLS-A method by adjusting forgetting factor adaptively to track and estimate channel state parameters successfully in space-time coded MIMO-OFDM systems.
    Journal of Zhejiang University - Science A: Applied Physics & Engineering 03/2006; 7(4):507-515. · 0.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Differential space-time coding was proposed recently in the literature for multi-antenna systems, where neither the transmitter nor the receiver knows the fading coefficients. Among existing schemes, double differential space-time (DDST) coding is of special interest because it is applicable to continuous fast time-varying channels. However, it is less effective in frequency-selective fading channels. This paper’ls authors derived a novel time-frequency double differential space-time (TF-DDST) coding scheme for multi-antenna orthogonal frequency division multiplexing (OFDM) systems in a time-varying frequency-selective fading environment, where double differential space-time coding is introduced into both time domain and frequency domain. Our proposed TF-DDST-OFDM system has a low-complexity non-coherent decoding scheme and is robust for time-and frequency-selective Rayleigh fading. In this paper, we also propose the use of state-of-the-art low-density parity-check (LDPC) code in serial concatenation with our TF-DDST scheme as a channel code. Simulations revealed that the LDPC based TF-DDST OFDM system has low decoding complexity and relatively better performance.
    Journal of Zhejiang University - Science A: Applied Physics & Engineering 01/2006; 7(2):141-148. · 0.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A fast frequency offset estimation scheme for OFDM is proposed. This scheme is low-overhead oriented, which uses only one OFDM symbol with L identical slots as preamble. By extracting the phase from correlation between two identical halves of the preamble, the fractional frequency offset is estimated and then compensated. After reshaping the compensated preamble into many L-point sub-symbols, which are processed by FFT algorithm, the estimate of integer frequency offset is accomplished by finding the maximum magnitude of the combined frequency domain signals. To further reduce the computational load of the algorithm, the scheme is carried out in a multistage manner. Simulation results show that the proposed scheme exhibits good performance, while maintaining a low complexity
    Wireless Communications, Networking and Mobile Computing, 2006. WiCOM 2006.International Conference on; 01/2006
  • Ming Ding, Han-wen Luo, Yun Wu, Ren-mao Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: A cell identification scheme for OFDM cellular systems is proposed, which uses only one OFDM symbol with several identical slots as preamble. After performing OFDM timing/frequency synchronization, the UE identifies its cell ID by a novel scheme composed of cell group identification and cell index identification. Each cell group is distinguished from others by a unique subcarrier mask, which is an m-sequence. It activates or deactivates a subset of the subcarriers. Furthermore, cells with different indices in the same cell group load different differentially coded sequences on the adjacent active subcarriers. The UE recognizes the cell-group-specific mask via power detection of the received frequency domain signal. Then it identifies the cell index from differential demodulation and detection of the cell-index-specific sequence. Simulation results show that the proposed scheme is able to support a very large number of cell IDs and it works well even in bad multi-cell environment
    01/2006;
  • Ling-yun Cai, Wen-tao Song, Han-wen Luo
    [Show abstract] [Hide abstract]
    ABSTRACT: The downlink frame structure for beyond 3G mobile communication systems is presented. Beyond 3G systems utilize the OFDM technique. However, a problem encountered in OFDM is that channel dispersion destroys orthogonality between carriers, causing inter-symbol interference. It is also sensitive to high peak to mean power ratio (PAPR). Therefore it spends much time on obtaining frequency, time, and frame synchronization. This paper proposes to add a frame synchronization channel in the time domain to overcome the shortcoming of OFDM. As transmitter diversity improves the system performance, beyond 3G systems employ space-time block coded (STBC). Fast cell search algorithm including slot synchronization, frame synchronization and cell ID identification is then discussed, which is based on the frame synchronization channel in transmitter diversity systems. Detection and false alarm probabilities in AWGN and Rayleigh channels are analyzed, and the mean acquisition time is obtained. Computer simulations are conducted to evaluate the performance of the cell search algorithm under different channel conditions.
    Journal of Shanghai University (English Edition) 01/2005; 9(5):419-424.
  • Shu-wei Shan, Han-wen Luo, Wen-tao Song
    [Show abstract] [Hide abstract]
    ABSTRACT: A simple channel estimator for space-time coded orthogonal frequency division multiplexing (OFDM) systems in rapid fading channels is proposed. The channels at the training bauds are estimated using the EM (expectation-maximization) algorithm, while the channels at the data bauds are estimated based on the method for modelling the time-varying channel as the linear combination of several time-invariant "Doppler channels". Computer simulations showed that this estimator outperforms the decision-directed tracking in rapid fading channels and that the performance of this method can be improved by iteration.
    Journal of Zhejiang University SCIENCE 02/2004; 5(1):45-9.
  • Xuan Li, Wen-tao Song, Han-wen Luo
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper deals with a new receiver scheme that combines turbo equalization and turbo trellis coded modulation (turbo TCM). This receiver serially concatenates a soft input soft output (SISO) equalizer and a soft-out symbol-by-symbol MAP turbo TCM decoder through an iterative process. In certain cases, the joint turbo equalization and turbo TCM scheme can totally overcome the channel frequency selectivity and obtain high bandwidth efficiency and greater coding gain. This scheme has modest complexity since a sub-optimal reduced-state MAP equalization algorithm and simple turbo TCM component codes are employed. Simulation results show that this receiver can achieve comparable performance with the turbo TCM receiver on a non-selective Gaussian channel with coding
    Personal, Indoor and Mobile Radio Communications, 2001 12th IEEE International Symposium on; 10/2001
  • Xuan Li, Wen-tao Song, Han-wen Luo
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper deals with a new receiver scheme that combines turbo equalization and turbo trellis coded modulation (TTCM). This receiver serially concatenates a soft-input soft-output (SISO) equalizer and a soft-out symbol-by-symbol MAP (maximum a posteriori) TTCM decoder through an iterative process. In certain cases, the joint turbo equalization and TTCM scheme can totally overcome the channel frequency selectivity and obtain high bandwidth efficiency and more coding gains. This scheme has modest complexity since a suboptimal reduced-state MAP equalization algorithm and simple TTCM component codes are employed. Simulation results show that this receiver can achieve comparable performance with TTCM receiver on a non-selective Gaussian channel with coding
    Vehicular Technology Conference, 2001. VTC 2001 Spring. IEEE VTS 53rd; 02/2001
  • [Show abstract] [Hide abstract]
    ABSTRACT: This extended abstract presents a new class of codes, chaotic turbo codes, which can be used in chaotic secure communication for mobile systems. In our research, the conventional turbo codes and chaotic digital encoder are implemented together in an effective way. After a lot of simulation, we found that chaotic turbo codes bring some important properties to both turbo codes and chaotic secure communication. We have also made great efforts into developing and evaluating some practical chaotic iterative decoding algorithms for efficient exploitation
    EUROCON'2001, Trends in Communications, International Conference on.; 02/2001
  • Xuan Li, Wen-tao Song, Han-wen Luo
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a short-latency Turbo-codes decoder for the third generation mobile communication system. In the decoder, we employed a modified sliding window log-BCJR (SW-log-BCJR) algorithm in which two sliding windows work in parallel. With this algorithm the decoding latency of Turbo-codes decoder is half reduced and the complexity and memory increment is reasonable. Simulation shows that if we properly choose the size of the sliding window length, the performance degradation of the proposed algorithm is within 0.2 dB at BER=10<sup>-5</sup> relative to BCJR algorithm. Turbo decoder using the proposed algorithms is implemented on single-chip Xilinx FPGA and up to 2 Mbps throughput is reached
    Electronics, Circuits and Systems, 2000. ICECS 2000. The 7th IEEE International Conference on; 02/2000
  • Source
    You-Yun Xu, Wen-Tao Song, Han-Wen Luo
    [Show abstract] [Hide abstract]
    ABSTRACT: Asia Cellular Satellite System (ACeS) is a $900 million fully financed project that uses two A2100AX geo satellites manufactured by Lockheed Martin. The services of the original design are voice, data, fax and paging throughout Southeast Asia, China and India. In this paper, we present a supplementary design, which called ACeS Multi-media System (AMS), for the original ACeS to offer some more narrow-band multi-media services such as Internet, Intranet and ISDN services to mobile or fixed users thus to make it more competitive in the market. The paper discusses the system description, frame/burst formats of satellite transmission links, design of the combining scheme of turbo codes and QAM modulation etc. This system can also be modified for military communications
    Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE; 02/1999

Publication Stats

17 Citations
3.16 Total Impact Points

Institutions

  • 1999–2009
    • Shanghai Jiao Tong University
      • Department of Electronic Engineering
      Shanghai, Shanghai Shi, China
  • 2004
    • Shanghai University
      • Department of Electronic Engineering
      Shanghai, Shanghai Shi, China