The mode switching between spatial multiplexing （SM） and space-time block code （STBC） diversity is investigated for the multiple-input multiple-output （MIMO） automatic repeat request （ARQ） system. Five importa...The mode switching between spatial multiplexing （SM） and space-time block code （STBC） diversity is investigated for the multiple-input multiple-output （MIMO） automatic repeat request （ARQ） system. Five important practical factors are considered in the proposed switching scheme： transmit correlation, ARQ technique, packet loss probability （PLP） constraint, discrete rate transmission （DRT） and channel coding. Under the spatially correlated channel, the distributions of the post signal-to-interference-plus- noise ratio （SiNR） for the SM mode and the STBC mode are obtained by using Gamma approximations. Then this paper derives the closed-form expressions of the PLP and the throughput for different modes when the ARQ technique is employed, based on which the mode switching algorithm is proposed to improve the spectral efficency. In the simulation, the correction of the expressions is first verified. Then, the significant gain observed by the proposed algorithm is presented. Since the switching point is the key parameter to implement the mode switching, this paper also shows how the switching point is affected by the practical factors considered.展开更多
The feedback delay can severely affect the quality of the channel state information at the transmitter(CSIT)which is fed back from the receiver.The outdated CSIT will cause large performance loss in the transmit beamf...The feedback delay can severely affect the quality of the channel state information at the transmitter(CSIT)which is fed back from the receiver.The outdated CSIT will cause large performance loss in the transmit beamforming systems.The effect of variable feedback delay on the capacity of transmit beamforming systems over Rayleigh fading channels is studied.First,the case of fixed feedback delay is considered and a closed-form expression of system capacity is derived.Based on the results of fixed delay,the delay following certain distributions in variable delay case is assumed and the closed-form expressions of capacities are derived.The closed-form expressions show that the capacity is significantly affected by the statistical characteristics of the feedback delay.The obtained results provide an analytical insight into the effects caused by variable delay on the system capacity.展开更多
针对发射波形正交性退化影响机载多输入多输出(multiple-input multiple-output,MIMO)雷达的杂波特性,基于信号空间和子阵空间的变换原理,建立了波形正交性退化下的机载MIMO雷达杂波通用模型和标准模型。基于带限信号的最优逼近特性,分...针对发射波形正交性退化影响机载多输入多输出(multiple-input multiple-output,MIMO)雷达的杂波特性,基于信号空间和子阵空间的变换原理,建立了波形正交性退化下的机载MIMO雷达杂波通用模型和标准模型。基于带限信号的最优逼近特性,分析了波形正交性退化下的空时等效阵列孔径变化规律,提出了杂波自由度(degree of freedom,DOF)的估计准则。最后,仿真验证了杂波模型及杂波自由度估计准则的有效性。展开更多
基金supported by the Chinese Important National Science and Technology Specific Project(2010ZX03002-003-01)
文摘The mode switching between spatial multiplexing （SM） and space-time block code （STBC） diversity is investigated for the multiple-input multiple-output （MIMO） automatic repeat request （ARQ） system. Five important practical factors are considered in the proposed switching scheme： transmit correlation, ARQ technique, packet loss probability （PLP） constraint, discrete rate transmission （DRT） and channel coding. Under the spatially correlated channel, the distributions of the post signal-to-interference-plus- noise ratio （SiNR） for the SM mode and the STBC mode are obtained by using Gamma approximations. Then this paper derives the closed-form expressions of the PLP and the throughput for different modes when the ARQ technique is employed, based on which the mode switching algorithm is proposed to improve the spectral efficency. In the simulation, the correction of the expressions is first verified. Then, the significant gain observed by the proposed algorithm is presented. Since the switching point is the key parameter to implement the mode switching, this paper also shows how the switching point is affected by the practical factors considered.
基金supported by the Natural Science Foundation of Shanghai(09ZR1430500)the Chinese National Science and Technology Major Project(2011ZX03003-001-01,2009ZX03002-003-004)
文摘The feedback delay can severely affect the quality of the channel state information at the transmitter(CSIT)which is fed back from the receiver.The outdated CSIT will cause large performance loss in the transmit beamforming systems.The effect of variable feedback delay on the capacity of transmit beamforming systems over Rayleigh fading channels is studied.First,the case of fixed feedback delay is considered and a closed-form expression of system capacity is derived.Based on the results of fixed delay,the delay following certain distributions in variable delay case is assumed and the closed-form expressions of capacities are derived.The closed-form expressions show that the capacity is significantly affected by the statistical characteristics of the feedback delay.The obtained results provide an analytical insight into the effects caused by variable delay on the system capacity.
文摘针对发射波形正交性退化影响机载多输入多输出(multiple-input multiple-output,MIMO)雷达的杂波特性,基于信号空间和子阵空间的变换原理,建立了波形正交性退化下的机载MIMO雷达杂波通用模型和标准模型。基于带限信号的最优逼近特性,分析了波形正交性退化下的空时等效阵列孔径变化规律,提出了杂波自由度(degree of freedom,DOF)的估计准则。最后,仿真验证了杂波模型及杂波自由度估计准则的有效性。
