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Publications (10)0 Total impact

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    ABSTRACT: In order to improve system performance and reduce receiver hardware complexity and cost, we investigate a new multiple-input multiple-output (MIMO) scheme combining maximal-ratio transmit and receiver antenna selection combining (the MRT/RAS scheme). In this scheme, a single receive antenna, which maximizes the received signal-to-noise (SNR) at the receiver, is selected for demodulation. The closed-form outage probability and the bit error rate (BER) of the MRT/RAS system are presented. The simulation demonstrates that the MRT/RAS scheme can achieve a full diversity order, as if all the receive antennas were used. It is shown that the TAS/MRC scheme outperforms some more complex space-time codes of the same spectral efficiency. The analytical results are verified by simulation
    Wireless Communications, Networking and Mobile Computing, 2006. WiCOM 2006.International Conference on; 10/2006
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    ABSTRACT: In this paper, we investigate adaptive resource allocation strategy for downlink multi-input-multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) system. We design a transmit scheme as a concatenation of dynamic sub-carriers and bit assignment, adaptive modulation and beam-forming. Our adaptive goal is margin adaptive optimization, which minimize the total transmission power subject to a target BER performance constraint on each sub-carrier, while meeting a constant bit rate. By use of Rayleigh fading model assumption, we introduce a new concept: the channel feedback coefficient, so as to compensate the error inducted by feedback channel. Simulation results show that the proposed resource allocation scheme outperforms the multi-user MIMO-OFDM with static allocation technique, and can lessen the performance loss caused by channel state information feedback error.
    Proc SPIE 11/2005;
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    ABSTRACT: First Page of the Article
    Vehicular Technology Conference, 2005. VTC-2005-Fall. 2005 IEEE 62nd; 10/2005
  • Lee Li, Guangxi Zhu, Xiao Xiao, Jian Liu
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    ABSTRACT: Cross-layer design is becoming a popular design methodology for the next-generation mobile systems. In this paper, we try to exploit a cross-layer adaptive transmission algorithm for downlink OFDM system. This algorithm takes into consideration not only the channel state information and power limitation in the physical layer, but also traffic scheduling and user fairness constraint at the data link layer. Based on proportional fairness principle and water-pouring theorem, we present a complete description of this cross-Layer adaptive downlink transmission five-step algorithm. Simulation results show that the proposed cross-layer scheme outperforms the mere physical layer adaptive markedly. The novel algorithm is able to improve performance of the packet success rate (PSR) per TC and average packet delay, support added active users.
    Wireless Communications, Networking and Mobile Computing, 2005. Proceedings. 2005 International Conference on; 10/2005
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    ABSTRACT: In this paper, the impact of multiuser diversity for V-BLAST based OFDM systems in frequency selective fading channel is considered, and a multiuser subcarrier allocation criterion is developed aimed to optimizing the system-level performance. Mathematical analyses and numeric simulations demonstrate that the proposed subcarrier assignment strategy outperforms the static assignment scheme significantly, even with little amount of feedback. In order to guarantee the users' quality of service (QoS), a reallocation algorithm is given, and it behaves well in our experiments.
    Wireless Communications, Networking and Mobile Computing, 2005. Proceedings. 2005 International Conference on; 10/2005
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    ABSTRACT: This paper investigates the problem of adaptive resource allocation in the downlink of multiuser OFDM systems with V_BLAST architecture. In order to get a high spectral efficiency even in low SNR, we propose a novel low-complexity adaptive subchannel-bit allocation and power reallocation algorithm. The algorithm considers the users' quality of service (QoS) requirements. Simulation results show that the proposed algorithm performs almost as well as the optimal solution. Moreover, higher spectral efficiency is achieved for larger number of users due to the multiuser diversity and the power reallocation is used in low SNR field.
    Wireless Communications, Networking and Mobile Computing, 2005. Proceedings. 2005 International Conference on; 10/2005
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    ABSTRACT: In this paper, we apply quasi-orthogonal space-time block code through constellation rotation (QOSTBC_CR) in OFDM system, construct the QOSTBC_CR-OFDM code and propose the decoder. Since OFDM can combat frequency-selective channels and the QOSTBC_CR have both full rate and full diversity, the QOSTBC_CR-OFDM performs effectively in frequency-selective channels. Simulation results show that QOSTBC_OR-OFDM achieves better tradeoff between transmission rate and diversity gain. This approves the theoretical analysis.
    Computer and Information Technology, 2005. CIT 2005. The Fifth International Conference on; 10/2005
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    ABSTRACT: In this paper, the subcarrier allocation problems for downlink transmission of spatial multiplexing based OFDM systems are investigated. With the goal of maximizing the instantaneous capacity, two categories of subcarrier assignment criteria are derived, that is, exclusive manner based criteria which allocate each subcarrier to a single user, and shared manner based criteria which allow multiple users to share a subcarrier. Simulation results demonstrate that both the presented criteria are capable of utilizing the multiuser diversity to enhance the capacity of spatial multiplexing based OFDM systems significantly. Furthermore, via experiments we find that compared with shared criteria, allocating each subcarrier to a single user is a feasible choice to achieve tradeoff among complexity, overhead, and capacity enhancement
    Personal, Indoor and Mobile Radio Communications, 2005. PIMRC 2005. IEEE 16th International Symposium on; 10/2005
  • Lee Li, Guangxi Zhu, Xiao Xiao, Jian Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: Cross-layer design is becoming a popular design methodology for the next-generation mobile systems. In this paper, we try to exploit a cross-layer adaptive transmission algorithm for downlink OFDM system. This algorithm takes into consideration not only the channel state information and power limitation in the physical layer, but also traffic scheduling and user fairness constraint at the data link layer. Based on proportional fairness principle and water-pouring theorem, we present a complete description of this cross-layer adaptive downlink transmission six-step algorithm. Simulation results show that the proposed cross-layer scheme outperforms the mere physical layer adaptive markedly. The novel algorithm is able to improve performance of the packet success rate (PSR) per TC and average packet delay, support added active users.
    Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications, 2005. MAPE 2005. IEEE International Symposium on; 09/2005
  • [Show abstract] [Hide abstract]
    ABSTRACT: To improve system performance and reduce the complexity and cost of receiver hardware, we investigated a new multiple-input multiple-output (MIMO) scheme combining maximal-ratio transmitting and receiver antenna selection (MRT/RAS). In this scheme, a single receiving antenna, which maximizes the signalto-noise ratio (SNR) at the receiver, is selected for demodulation. The closed-form outage probability and the bit error rate (BER) of the MRT/RAS system are both presented. The simulation demonstrates that the MRT/RAS scheme can achieve a full diversity order as if all the receiving antennas were used. It is shown that the MRT/RAS scheme outperforms some more complex space-time codes of the same spectral efficiency. The analytical results are verified by simulation. In the end, we also analyze the MRT/RAS system based on partial channel information.
    Frontiers of Electrical and Electronic Engineering in China 3(4):411-417.