摘要
异构网络是先进长期演进(long term evolution advanced, LTE-A)系统中的一个重要研究项目。它是由一些具有不同覆盖范围的relay和pico节点基站采用相同频率重叠布施在宏蜂窝网中混合而成的新型架构的网络。基于LTE-A技术的异构网络在干扰管理方面面临巨大挑战。为了解决该问题,我们给出了三个有效的干扰管理方案。
1.提出了一种基于各子网节点基站感知的小区间下行同频信道干扰管理技术。首先给出了典型异构场景下的干扰区域的认知干扰模型。其次对该模型中宏基站和子网节点基站间的相互作用进行了研究。为了实现干扰管理,建立了认知临界比和功率补偿因子的策略框架来获得宏基站和子网节点基站的最大节约功率的效用函数。这样我们把对干扰管理的研究转化为关于宏基站和子网节点基站的最大节约功率的多目标非线性规划问题。为了获得两者均满意得折中解,我们将多目标非线性规划转换成了单目标规划问题并结合遗传算法来获得全局近似最优解。然后我们针对基于LTE-A技术的异构网络,给出了的设计方案的具体实现过程。最后,通过量化评估验证了文中提出的交互式多目标非线性规划遗传算法的可行性,系统级仿真结果说明了感知干扰管理方案的有效性。
2.为了保持相同的网络性能,负载平衡和干扰管理是异构网络在设计重叠布施时必须要考虑的问题。我们提出一种多域协作负载平衡方案,主要目标是降低系统负载资源利用率和抑制同频信道干扰。首先,我们把同频信道干扰引入到负载平衡方案中,然后又将负载平衡的问题转化为域间和域内的最小化有效负载资源利用率的优化问题。在量化评估中,我们采用了遗传算法给出了域间方案的最小负载资源利用率的仿真结果,结果显示了域间负载平衡方案可以使系统的总有效负载资源利用率降低很多。在系统级仿真中,信号与干扰加噪声比和吞吐量的性能指标得到了很大的改善,公平性和负载均衡性也得到很好的验证。所有结果显示了推荐方案是一种有效的负载平衡和干扰管理方案。
3.新型架构下的异构网络由于重叠布施低功率基站不但引入严重的同频干扰,并且造成成本资源置配不均衡,这些都是异构网络性能提升需要解决的关键问题。针对该问题,我们提出了一种异构网络的多域协作成本资源管理方案。该方案考虑同频信道干扰,并将负载资源利用率转化为成本资源函数的优化问题,通过遗传算法实现最小成本资源对应的最优负载资源和合理的功率资源分配。量化评估显示了推荐方案优于传统的域内成本优化方案,节约了43%的成本资源。在系统级仿真中,通过和传统的域内方案比较分析,信号与干扰加噪声比和小区平均吞吐量参数值均证明推荐方案消除了大量的同频信道干扰,有效配置功率和负载成本资源,使得系统性能有很大的改善。
Heterogeneous network (Het-Net) is part of the long-term evolution advanced (LTE-A) study item and represents cellular deployments with a mixture of cells of different overlapping coverage areas, e.g., a number of relay and pico cells overlaid by a macro cell in the same frequency. Het-Net for LTE-A creates severe interference. It is an urgent task to overcome the interference for improving the system performance. In our study, we have proposed the three schemes for interference management.
1. The cognitive interference model in interference zone (IZ) of the prac-tical heterogeneous scenario is proposed. Based on investigation of interaction between the macro base station (BS) and subnet nodes in this model, the strategy framework of the cognitive critical ratio and power reward factor is set up for interference management aim-ing to get the maximum net saving power. The study of interference management is transformed into a multiple objective non-linear pro-gramming (MONLP) of the maximum saving power for the macro BS and subnet nodes. To facilitate the best compromise solution for both, the MONLP is changed into single objective programming and genetic algorithm (GA) is employed to obtain the global optimum so-lution. In addition, the practical implementation using the proposed algorithm in Het-Net for LTE-A is designed. Finally, numerical eval-uation is used to test the applicability of the proposed algorithm, and svstem level simulation results demonstrate the effectiveness of the proposed interference management scheme.
2. Load balancing and interference management are required in Het-Net design for LTE-A to maintain system performance. In this article, an inter-domain cooperative load balancing scheme focusing on reducing the effective resource utilization and mitigating the co-channel inter-ference is proposed in multi-domain Het-Net. First, the conception of multi-domain in Het-Net is set up and the co-channel interference is incorporated into the proposed load balancing scheme. Then the load balancing issue is modeled as a multi-domain load resource op-timization problem for minimizing the effective resource utilization. The detailed implementation for the proposed load balancing scheme is designed. In the numerical evaluation, the genetic algorithm (GA) as an optimization method is used to demonstrate that the total ef-fective load resource utilization is significantly reduced through our proposed inter-domain load balancing scheme. In the system level simulation, the performance results of SINR and throughput demon-strate that the proposed scheme has great advantages in interference management. At the same time, the performance for fairness and load balancing obtains the attractive gain.
3. In Het-Net deployment, when multiple low-power nodes are deployed across macro coverage, the geographical coverage overlap can cause se-vere co-channel interference and unbalanced cost resource allocation. A scheme of multi-domain cooperative cost resource management in Het-Net is proposed, which can effectively allocate the power and load cost resource. The co-channel interference is incorporated in this scheme. The load resource utilization is changed into the optimization issue for the cost resource function. By the genetic algorithms, the optimal solution can be obtained. In numerical evaluation, compar-ing with the traditional intra-domain scheme, the utilization of cost in proposed scheme is better. And the43%of cost resource, using the inter-domain cost resource optimization scheme, can be saved. In system-level simulation, the results of SINR and cell average through- put demonstrate the attractive performance gain, due to mitigating more co-channel interference.
引文
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