异构蜂窝网络中用户关联与基站功率的协同优化

为实现异构蜂窝网络中宏基站和小基站之间的负载均衡，提出了一种基于效用函数最大化模型的用户关联机制和基站功率控制的协同优化方案。通过迭代算法求解该协同优化问题，首先在基站功率固定的情况下求得最佳用户关联策略，然后在所得的用户关联策略基础上通过Zoutendijk可行方向法求得基站最佳功率。通过协同优化获得的用户关联策略和基站功率控制实现了基站之间的负载均衡，通过降低宏基站功率和关闭闲置小基站降低了基站的能耗。仿真实验表明，所提方案和不实施功率控制的用户关联策略相比，实现了宏基站与小基站之间的负载均衡，降低了宏基站对小基站用户的干扰，提升了小基站用户的信号干扰噪声比，用户速率中位值提高了20%。

Joint optimization of cell association and power control in heterogeneous cellular networks

This paper proposes a joint optimization framework over cell association and base station(BS) power control to achieve load balancing among different tiers of BSs in heterogeneous cellular networks. The solution is obtained by iteratively updating cell association and power control schemes.A power control algorithm based on the Zoutendijk feasible direction method is proposed to solve the power control subproblem. The obtained cell association and power control schemes lead to load balancing among base stations and reduce power consumption by reducing the transmission power of macro BSs and closing idle BSs. Simulation results show that compared with cell association schemes without power control,the proposed approach encourages offloading users to small cell BSs,reduces the interference experienced by the offloaded users and achieves 20% increase in mean user rates.