This study proposes a tractable approach to analyze the physical-layer security in the downlink of a multi-tier heterogeneous cellular network. This method is based on stochastic geometry, has low computational comple...This study proposes a tractable approach to analyze the physical-layer security in the downlink of a multi-tier heterogeneous cellular network. This method is based on stochastic geometry, has low computational complexity, and uses the two-dimensional Poisson point process to model the locations of K-tier base stations and receivers, including those of legitimate users and eavesdroppers. Then, the achievable secrecy rates for an arbitrary user are determined and the upper and lower bounds of secrecy coverage probability derived on the condition that cross-tier interference is the main contributor to aggregate interference. Finally, our analysis results reveal the innate connections between information-theoretic security and the spatial densities of legitimate and malicious nodes.展开更多
采用随机几何理论分析异构蜂窝网络性能时,通常假设用户均匀分布且独立于基站。但在实际的异构蜂窝网络中,小基站一般部署在热点地区或覆盖盲区,因此,小基站与用户的空间位置存在相关性。针对三维空间中蜂窝用户以小基站为父节点的Mater...采用随机几何理论分析异构蜂窝网络性能时,通常假设用户均匀分布且独立于基站。但在实际的异构蜂窝网络中,小基站一般部署在热点地区或覆盖盲区,因此,小基站与用户的空间位置存在相关性。针对三维空间中蜂窝用户以小基站为父节点的Matern簇过程和Thomas簇过程进行建模,再采用最大信号干扰比(signal to interference ratio,SIR)的小区接入准则,在瑞利衰落信道下推导出下行链路的覆盖概率;通过蒙特卡罗仿真验证理论结果,分析用户簇过程的半径或方差、SIR门限值、小基站密度和小基站功率对覆盖概率的影响,并比较三维用户簇分布模型、三维用户均匀分布模型和二维用户簇分布模型的网络性能。实验结果表明基于三维用户簇分布模型的异构蜂窝网络具有较好的覆盖概率。展开更多
In this paper, the joint resource allocation （RA） problem with quality of service （QoS） provisioning in downlink heterogeneous cellular networks （HCN） is studied. To fully exploit the network capacity, the HCN i...In this paper, the joint resource allocation （RA） problem with quality of service （QoS） provisioning in downlink heterogeneous cellular networks （HCN） is studied. To fully exploit the network capacity, the HCN is modeled as a K-tier cellular network where each tier＇s base stations （BSs） have different properties. However, deploying numbers of low power nodes （LPNs） which share the same frequency band with macrocell generates severe inter-cell interference. Enhancement of system capacity is restricted for inter-cell interference. Therefore, a feasible RA scheme has to be developed to fully exploit the resource efficiency. Under the constraint of inter-cell interference, we formulate the RA problem as a mixed integer programming problem. To solve the optimization problem we develop a two-stage solution. An integer subchannel assignment algorithm and Lagrangian-based power allocation algorithm are designed. In addition, the biasing factor is also considered and the caused influence on system capacity is evaluated. Simulation results show that the proposed algorithms achieve a good tradeoff between network capacity and interference. Moreover, the average network efficiency is highly improved and the outage probability is also decreased.展开更多
Heterogeneous cellular networks improve the spectrum efficiency and coverage of wireless communication networks by deploying low power base station （BS） overlapping the conventional macro cell. But due to the dispar...Heterogeneous cellular networks improve the spectrum efficiency and coverage of wireless communication networks by deploying low power base station （BS） overlapping the conventional macro cell. But due to the disparity between the transmit powers of the macro BS and the low power BS, cell association strategy developed for the conventional homogeneous networks may lead to a highly unbalanced traffic loading with most of the traffic concentrated on the macro BS. In this paper, we propose a load-balance cell association scheme for heterogeneous cellular network aiming to maximize the network capacity. By relaxing the association constraints, we can get the upper bound of optimal solution and convert the primal problem into a convex optimization problem. Furthermore we propose a Lagrange multipliers based distributed algorithm by using Lagrange dual theory to solve the convex optimization, which converges to an optimal solution with a theoretical performance guarantee. With the proposed algorithm, mobile terminals （MTs） need to jointly consider their traffic type, received signal-to-interference-noise-ratios （SINRs） from BSs, and the load of BSs when they choose server BS. Simulation results show that the load balance between macro and pico BS is achieved and network capacity is improved significantly by our proposed cell association algorithm.展开更多
研究了在有限反馈约束下的异构蜂窝网络下行链路中与宏蜂窝共存的小蜂窝能量效率最大化问题。其中,宏基站(Macro Base Station,MBS)和小基站(Small Base Station,SBS)通过共享频谱分别向宏用户(Macro User,MU)和小用户(Small User,SU)...研究了在有限反馈约束下的异构蜂窝网络下行链路中与宏蜂窝共存的小蜂窝能量效率最大化问题。其中,宏基站(Macro Base Station,MBS)和小基站(Small Base Station,SBS)通过共享频谱分别向宏用户(Macro User,MU)和小用户(Small User,SU)发送信号。提出了有限反馈和功率带宽联合优化方案来最大限度地提高小蜂窝中所有SU的平均能量效率。由于所构建的目标函数是分式形式并且具有非凸性,采用丁克尔巴赫方法将分式形式化为等价减法形式,并通过增广拉格朗日乘子法求解,提出两层迭代优化算法得到目标函数的最优解。仿真结果表明,相比于传统功率带宽等分配的反馈比特优化方案,所提方案明显地提升了小蜂窝所有SU的平均能量效率。展开更多
基金supported in part by National Natural Science Foundation of China under Grant No.61401510,61521003National High-tech R&D Program(863 Program)under Grant No.2015AA01A708
文摘This study proposes a tractable approach to analyze the physical-layer security in the downlink of a multi-tier heterogeneous cellular network. This method is based on stochastic geometry, has low computational complexity, and uses the two-dimensional Poisson point process to model the locations of K-tier base stations and receivers, including those of legitimate users and eavesdroppers. Then, the achievable secrecy rates for an arbitrary user are determined and the upper and lower bounds of secrecy coverage probability derived on the condition that cross-tier interference is the main contributor to aggregate interference. Finally, our analysis results reveal the innate connections between information-theoretic security and the spatial densities of legitimate and malicious nodes.
文摘采用随机几何理论分析异构蜂窝网络性能时,通常假设用户均匀分布且独立于基站。但在实际的异构蜂窝网络中,小基站一般部署在热点地区或覆盖盲区,因此,小基站与用户的空间位置存在相关性。针对三维空间中蜂窝用户以小基站为父节点的Matern簇过程和Thomas簇过程进行建模,再采用最大信号干扰比(signal to interference ratio,SIR)的小区接入准则,在瑞利衰落信道下推导出下行链路的覆盖概率;通过蒙特卡罗仿真验证理论结果,分析用户簇过程的半径或方差、SIR门限值、小基站密度和小基站功率对覆盖概率的影响,并比较三维用户簇分布模型、三维用户均匀分布模型和二维用户簇分布模型的网络性能。实验结果表明基于三维用户簇分布模型的异构蜂窝网络具有较好的覆盖概率。
基金supported by the National Science and Technology Major Project (2011ZX03001-007-03)the National Natural Science Foundation of China (61271182)the Research Fund for the Doctoral Program of Higher Education of China (20120005120010)
文摘In this paper, the joint resource allocation （RA） problem with quality of service （QoS） provisioning in downlink heterogeneous cellular networks （HCN） is studied. To fully exploit the network capacity, the HCN is modeled as a K-tier cellular network where each tier＇s base stations （BSs） have different properties. However, deploying numbers of low power nodes （LPNs） which share the same frequency band with macrocell generates severe inter-cell interference. Enhancement of system capacity is restricted for inter-cell interference. Therefore, a feasible RA scheme has to be developed to fully exploit the resource efficiency. Under the constraint of inter-cell interference, we formulate the RA problem as a mixed integer programming problem. To solve the optimization problem we develop a two-stage solution. An integer subchannel assignment algorithm and Lagrangian-based power allocation algorithm are designed. In addition, the biasing factor is also considered and the caused influence on system capacity is evaluated. Simulation results show that the proposed algorithms achieve a good tradeoff between network capacity and interference. Moreover, the average network efficiency is highly improved and the outage probability is also decreased.
基金supported by the Beijing Higher Education Young Elite Teacher Project(YETP0432)
文摘Heterogeneous cellular networks improve the spectrum efficiency and coverage of wireless communication networks by deploying low power base station （BS） overlapping the conventional macro cell. But due to the disparity between the transmit powers of the macro BS and the low power BS, cell association strategy developed for the conventional homogeneous networks may lead to a highly unbalanced traffic loading with most of the traffic concentrated on the macro BS. In this paper, we propose a load-balance cell association scheme for heterogeneous cellular network aiming to maximize the network capacity. By relaxing the association constraints, we can get the upper bound of optimal solution and convert the primal problem into a convex optimization problem. Furthermore we propose a Lagrange multipliers based distributed algorithm by using Lagrange dual theory to solve the convex optimization, which converges to an optimal solution with a theoretical performance guarantee. With the proposed algorithm, mobile terminals （MTs） need to jointly consider their traffic type, received signal-to-interference-noise-ratios （SINRs） from BSs, and the load of BSs when they choose server BS. Simulation results show that the load balance between macro and pico BS is achieved and network capacity is improved significantly by our proposed cell association algorithm.
文摘研究了在有限反馈约束下的异构蜂窝网络下行链路中与宏蜂窝共存的小蜂窝能量效率最大化问题。其中,宏基站(Macro Base Station,MBS)和小基站(Small Base Station,SBS)通过共享频谱分别向宏用户(Macro User,MU)和小用户(Small User,SU)发送信号。提出了有限反馈和功率带宽联合优化方案来最大限度地提高小蜂窝中所有SU的平均能量效率。由于所构建的目标函数是分式形式并且具有非凸性,采用丁克尔巴赫方法将分式形式化为等价减法形式,并通过增广拉格朗日乘子法求解,提出两层迭代优化算法得到目标函数的最优解。仿真结果表明,相比于传统功率带宽等分配的反馈比特优化方案,所提方案明显地提升了小蜂窝所有SU的平均能量效率。
文摘鉴于异构蜂窝网络(Heterogeneous cellular network,HCN)的自身特性,传统最强信号接入(小区选择)方式已不再适合,新型小区选择方案急需引入。不同于传统接入方案,新型方案应具备平衡各类基站负载的能力。为反映用户资源消耗水平与实现平衡网络负载的目的,设计了一个服务质量(Quality of service,QoS)感知的负载平衡方案。该方案以资源消耗量作为基站负载,且同时拟合了用户服务质量需求。最终,该方案被规划为网络加权效益最大化问题。从规划问题的形式来看,该问题为非线性、混合整数优化问题,因此求解其最优解富于挑战性(尤其针对大规模问题)。为解决该问题,尝试利用对偶分解法设计了一个分布式算法。仿真结果表明,相比于最强信号接入和区域拓展接入,提出的接入方案具有更高的负载平衡水平与更低的呼叫阻塞概率。
