LTE网络中具备QoS保障的动态负载均衡算法

研究了3GPPLTE网络中考虑不同服务质量(quality-of-service,QoS)要求的动态负载均衡算法.小区间的负载不均衡对于不同QoS要求用户有不同负面影响.对于有保障速率要求的用户,负载不均衡会导致较高的新呼叫阻塞率;而对于那些没有速率要求的用户,负载不均衡会导致繁忙小区中边缘用户过于恶化的吞吐量.全网中这两类用户的负载均衡问题紧密耦合,难以用一个统一的目标函数来分析研究.因此提出一个相应的多目标优化问题,其目标函数分别是针对全网内有QoS要求用户的负载均衡指示函数和针对全网内没有QoS要求用户的总效用函数,限制条件为实际小区物理资源和用户QoS要求.对该问题的复杂度进行了分析后,提出了一个实时的低复杂度低开销的分布式负载均衡算法结构,包括QoS保障的混合调度,QoS感知的负载均衡切换和呼叫准入控制.最后,系统级仿真结果显示提出的全新的负载均衡算法结构达到了较好的负载均衡效果,可以显著降低有QoS要求用户的新呼叫阻塞率,同时以略微损失全网无QoS要求用户总吞吐量的代价大幅提升繁忙小区中边缘用户的实际吞吐量.

QoS guaranteed dynamic load balancing algorithm in 3GPP LTE networks

In this paper, dynamic load balancing with different quality-of-service (QoS) requirements is investigated in 3GPP long-term evolution (LTE) networks. Load unbalancing among neighboring cells often has different negative impacts on users with different QoS demands. For users with minimum rate requirements, the load unbalancing results in high new call blocking rate, while for users with no rate guarantees, the throughput of boundary users in an overloaded cell often significantly decreases. Furthermore, the different load unbalancing problems are coupled with each other so that it is difficult to analyze the problem in a uniform manner. To deal with this issue, a multi-objective optimization problem is proposed. The objectives in the problem are load balancing index of users with QoS requirements and the total utility function of users without QoS requirements, and the constraints are physical resource limits and QoS demands. Then the complexity of the problem is analyzed, and a real-time distributed algorithm framework with low complexity/overhead is proposed, which includes a QoS guaranteed hybrid scheduling scheme, handover of users with and without QoS requirements, and a call admission control algorithm. Extensive simulations are conducted and the results show that the proposed algorithm framework leads to significantly better load balancing so as to yield the decrement of new call blocking rate of users with QoS requirements, and the increment of throughput of boundary users with only a bit degradation of total throughput of users without QoS requirements.