In this paper the scheduling problem in downlink multiuser MIMO system is described as an optimization problem and particle swarm optimization （PSO） algorithm is introduced to address such problem. Two PSO schedulin...In this paper the scheduling problem in downlink multiuser MIMO system is described as an optimization problem and particle swarm optimization （PSO） algorithm is introduced to address such problem. Two PSO scheduling methods with different objective functions applicable to different requirements on capacity and complexity are investigated. One is the capacity based PSO（C-PSO） scheduling method aiming at achieving the near optimal capacity; and the other is the lower bound of eigenvalue based PSO （LBE-PSO） scheduling method with the purpose of reducing computational complexity and at the same time achieving as large as possible capacity gain. Furthermore, convergence analysis of PSO from both the particle and the velocity aspects is also presented to derive the convergent condition, which is validated by several examples of different parameter values. Simulation results reveal that the C-PSO can obtain nearly the same capacity as the exhaustive search method with lower complexity, while the LBE-PSO provides a viable approach by striking a better tradeoff between capacity and computational complexity.展开更多
Due to the limited uplink capability in heterogeneousnetworks (HetNets), the decoupled uplinkand downlink access (DUDA) mode has recently beenproposed to improve the uplink performance. In thispaper, the random discon...Due to the limited uplink capability in heterogeneousnetworks (HetNets), the decoupled uplinkand downlink access (DUDA) mode has recently beenproposed to improve the uplink performance. In thispaper, the random discontinuous transmission (DTX)at user equipment (UE) is adopted to reduce the interferencecorrelation across different time slots. By utilizingstochastic geometry, we analytically derive themean local delay and energy efficiency (EE) of an uplinkHetNet with UE random DTX scheme under theDUDA mode. These expressions are further approximatedas closed forms under reasonable assumptions.Our results reveal that under the DUDA mode, there isan optimal EE with respect to mute probability underthe finite local delay constraint. In addition, with thesame finite mean local delay as under the coupled uplinkand downlink access (CUDA) mode, the HetNetsunder the DUDA mode can achieve a higher EE witha lower mute probability.展开更多
UAV-aided cellular networks,millimeter wave(mm-wave) communications and multi-antenna techniques are viewed as promising components of the solution for beyond-5G(B5G) and even 6G communications.By leveraging the power...UAV-aided cellular networks,millimeter wave(mm-wave) communications and multi-antenna techniques are viewed as promising components of the solution for beyond-5G(B5G) and even 6G communications.By leveraging the power of stochastic geometry,this paper aims at providing an effective framework for modeling and analyzing a UAV-aided heterogeneous cellular network,where the terrestrial base stations(TBSs) and the UAV base stations(UBSs) coexist,and the UBSs are provided with mm-wave and multi-antenna techniques.By modeling the TBSs as a PPP and the UBSs as a Matern hard-core point process of type Ⅱ(MPH-Ⅱ),approximated but accurate analytical results for the average rate of the typical user of both tiers are derived through an approximation method based on the mean interference-to-signal ratio(MISR) gain.The influence of some relevant parameters is discussed in detail,and some insights into the network deployment and optimization are revealed.Numerical results show that some trade-offs are worthy of being considered,such as the antenna array size,the altitude of the UAVs and the power control factor of the UBSs.展开更多
Large-scale MIMO （multiple-input multiple-output） systems with numerous low-power antennas can provide better performance in terms of spectrum efficiency, power saving and link reliability than conventional MIMO. Fo...Large-scale MIMO （multiple-input multiple-output） systems with numerous low-power antennas can provide better performance in terms of spectrum efficiency, power saving and link reliability than conventional MIMO. For large-scale MIMO, there are several technical issues that need to be practically addressed （e.g., pilot pattern design and low-power transmission design） and theoretically addressed （e.g., capacity bound, channel estimation, and power allocation strategies）. In this paper, we analyze the sum rate upper bound of large-scale MIMO, investigate its key technologies including channel estimation, downlink precoding, and uplink detection. We also present some perspectives concerning new channel modeling approaches, advanced user scheduling algorithms, etc.展开更多
In multi-user distributed antenna systems （DAS）, the scenario where each distributed antenna port is a multi-antenna array has not been comprehensively studied. In this article, four simple extended methods for down...In multi-user distributed antenna systems （DAS）, the scenario where each distributed antenna port is a multi-antenna array has not been comprehensively studied. In this article, four simple extended methods for downlink transmission are analyzed and compared in this scenario, two of which are based on the block diagonalization （BD） algorithm, namely joint BD and intra BD method. The other two methods are joint time division multiplexing （TDM） method and central antenna system （CAS） method. These four methods are evaluated through both theoretic analysis and insightful simulations. The theoretic analysis includes the receiving signal combination, post-processing signal to interference plus noise ratio （SINR） calculation. It shows that the intra BD method requires less channel state information at the transmitter （CSIT） and has lower computational complexity and process latency. Simulation results show that the joint BD method provides the best performance, and the intra BD method suffers little performance loss. Overall, the intra BD method is proved to be an optimal tradeoff which achieves high capacity, especially for the cell edge users, with relatively low complexity when power constraints are considered.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 60572148, 60702060)the "111 Project" (Grant No. B08038)+1 种基金the Special Project of ISN (Grant No. ISN03080005)the National Key Project of New Generation Broad Band Wireless Mobile Communication Network (Grant No. 2009ZX03003-005)
文摘In this paper the scheduling problem in downlink multiuser MIMO system is described as an optimization problem and particle swarm optimization （PSO） algorithm is introduced to address such problem. Two PSO scheduling methods with different objective functions applicable to different requirements on capacity and complexity are investigated. One is the capacity based PSO（C-PSO） scheduling method aiming at achieving the near optimal capacity; and the other is the lower bound of eigenvalue based PSO （LBE-PSO） scheduling method with the purpose of reducing computational complexity and at the same time achieving as large as possible capacity gain. Furthermore, convergence analysis of PSO from both the particle and the velocity aspects is also presented to derive the convergent condition, which is validated by several examples of different parameter values. Simulation results reveal that the C-PSO can obtain nearly the same capacity as the exhaustive search method with lower complexity, while the LBE-PSO provides a viable approach by striking a better tradeoff between capacity and computational complexity.
基金supported in part by the National Key R&D Program of China under Grant 2021YFB 2900304the Shenzhen Science and Technology Program under Grants KQTD20190929172545139 and ZDSYS20210623091808025.
文摘Due to the limited uplink capability in heterogeneousnetworks (HetNets), the decoupled uplinkand downlink access (DUDA) mode has recently beenproposed to improve the uplink performance. In thispaper, the random discontinuous transmission (DTX)at user equipment (UE) is adopted to reduce the interferencecorrelation across different time slots. By utilizingstochastic geometry, we analytically derive themean local delay and energy efficiency (EE) of an uplinkHetNet with UE random DTX scheme under theDUDA mode. These expressions are further approximatedas closed forms under reasonable assumptions.Our results reveal that under the DUDA mode, there isan optimal EE with respect to mute probability underthe finite local delay constraint. In addition, with thesame finite mean local delay as under the coupled uplinkand downlink access (CUDA) mode, the HetNetsunder the DUDA mode can achieve a higher EE witha lower mute probability.
基金supported by National Natural Science Foundation of China (No.62001135)the Joint funds for Regional Innovation and Development of the National Natural Science Foundation of China(No.U21A20449)the Beijing Natural Science Foundation Haidian Original Innovation Joint Fund (No.L232002)
文摘UAV-aided cellular networks,millimeter wave(mm-wave) communications and multi-antenna techniques are viewed as promising components of the solution for beyond-5G(B5G) and even 6G communications.By leveraging the power of stochastic geometry,this paper aims at providing an effective framework for modeling and analyzing a UAV-aided heterogeneous cellular network,where the terrestrial base stations(TBSs) and the UAV base stations(UBSs) coexist,and the UBSs are provided with mm-wave and multi-antenna techniques.By modeling the TBSs as a PPP and the UBSs as a Matern hard-core point process of type Ⅱ(MPH-Ⅱ),approximated but accurate analytical results for the average rate of the typical user of both tiers are derived through an approximation method based on the mean interference-to-signal ratio(MISR) gain.The influence of some relevant parameters is discussed in detail,and some insights into the network deployment and optimization are revealed.Numerical results show that some trade-offs are worthy of being considered,such as the antenna array size,the altitude of the UAVs and the power control factor of the UBSs.
基金supported by the National Basic Research 973 Program of China under Grant No. 2012CB31600the Beijing Natural Science Foundation under Grant No. 4110001+1 种基金the National Science and Technology Major Project of China under Grant No.2013ZX03003003Samsung Funded Project (The Research of Large-Scale MIMO)
文摘Large-scale MIMO （multiple-input multiple-output） systems with numerous low-power antennas can provide better performance in terms of spectrum efficiency, power saving and link reliability than conventional MIMO. For large-scale MIMO, there are several technical issues that need to be practically addressed （e.g., pilot pattern design and low-power transmission design） and theoretically addressed （e.g., capacity bound, channel estimation, and power allocation strategies）. In this paper, we analyze the sum rate upper bound of large-scale MIMO, investigate its key technologies including channel estimation, downlink precoding, and uplink detection. We also present some perspectives concerning new channel modeling approaches, advanced user scheduling algorithms, etc.
基金supported by Qualcomm and Projects (NSF60772112,2009ZX03003-008-01)
文摘In multi-user distributed antenna systems （DAS）, the scenario where each distributed antenna port is a multi-antenna array has not been comprehensively studied. In this article, four simple extended methods for downlink transmission are analyzed and compared in this scenario, two of which are based on the block diagonalization （BD） algorithm, namely joint BD and intra BD method. The other two methods are joint time division multiplexing （TDM） method and central antenna system （CAS） method. These four methods are evaluated through both theoretic analysis and insightful simulations. The theoretic analysis includes the receiving signal combination, post-processing signal to interference plus noise ratio （SINR） calculation. It shows that the intra BD method requires less channel state information at the transmitter （CSIT） and has lower computational complexity and process latency. Simulation results show that the joint BD method provides the best performance, and the intra BD method suffers little performance loss. Overall, the intra BD method is proved to be an optimal tradeoff which achieves high capacity, especially for the cell edge users, with relatively low complexity when power constraints are considered.
