异构网络下基于混合保护子帧的干扰协调方案

增强型小区间干扰协调（enhanced inter cell interference coordination,eICIC)引入几乎空白子帧(almost black subframes,ABS)来降低异构网络中小区间的干扰,然而过多的ABS会损失宏蜂窝用户性能。为了提高异构网络的性能,联合考虑ABS和低功率几乎空白子帧(low power-ABS,LP-ABS),提出了一种基于混合保护子帧(Hybrid Protected Subframes,HPS)的干扰协调方案。该方案综合考虑用户资源分配、HPS密度、HPS混合比例以及用户接入策略,以最大化系统比例公平效用为目标。仿真结果显示,所提方案在系统负载均衡、用户吞吐量以及用户公平性等指标上都优于传统增强型小区间干扰协调方案。     

基于多智能体Actor-Critic算法的异构网络能效优化

为了最大限度地提高异构网络（Heterogeneous Hetworks,HetNets）的能量利用率,本文将能效优化问题设计为一个多级决策问题,根据优化目标的资源分配,首先将初始问题分解为对参数ABS（几乎空白子帧,Almost Blank Subframe）比例和CRE（小区间范围扩展,Cell Range Expansion）进行优化的两个子问题,采用多智能体Actor-Critic（Multi-Agent Actor-Critic,MAAC）算法对子问题进行求解,然后通过迭代各优化子问题的解,解决初始优化问题。在参数优化过程中,将单个小基站作为一个智能体,采用MAAC算法对各自CRE寻找最优解,实现小区间异步CRE优化。实验结果表明,该方法在保持能效稳定提高的前提下,相比较于表格式Q学习的循环Q学习算法,其收敛速度提高了40％,并且通过异步优化CRE的方式取得了基站间更均衡的负载。     

Spectrum‐efficiency enhancement in small cell networks with biasing cell association and eICIC: An analytical framework

Load balancing and interference management play crucial roles in small cell network (SCN) capacity and spectrum efficiency (SE) enhancement. By performing load balancing between macrocell and small cells, biasing cell association has attracted great attentions since it is proposed. Additionally, enhanced intercell interference coordination (eICIC) technology is also developed as an efficient interference mitigation method for the biasing cell association‐based SCNs. In this paper, we develop an SE enhancement framework with joint consideration of the eICIC factor and biasing factor. Using the stochastic geometry theory, the network is modeled by spatial Poisson point process. We firstly derive the downlink average rate, which is performed at a typical user. Secondly, the eICIC factor‐related network SE is analyzed by proving the existence of optimal eICIC factor, which maximizes the network SE. For the intractability of the closed‐form expression of optimal eICIC factor, a bisection search‐based algorithm is developed then. At last, numerical results confirm our analysis and show the proposed algorithm performance. Copyright © 2014 John Wiley & Sons, Ltd.     

异构网关键技术与组网策略研究

简要介绍了异构网的基本概念和构成,深入研究了各种异构网的关键技术,并通过不同场景的应用策略分析,给出了异构网络的部署发展建议。     

LTE-A异构网中空白子帧的动态配置

为了解决LTE-A异构网中负载均衡和干扰问题,3GPP提出了增强型干扰协调技术。这项技术提出用空白子帧减少微基站边缘用户的干扰。从公平性角度讨论了动态的空白子帧设定,并提出了两种空白子帧配置算法。仿真表明,提出的两种动态空白子帧设定方法有效提升了系统的公平性。此外,仿真还对比了这两种动态的配置方法,表明最大化公平性的配置方法能够有效缓解微基站边缘用户随着覆盖区域增大吞吐量不断减小的趋势。     

A measurement‐based study of handover improvement through range expansion and interference coordination

Although the range expansion and inter‐cell interference coordination (ICIC) have been shown to successfully enhance the capacity and load balancing in the Heterogeneous Network, their impacts on the handover (HO) performance are not fully understood in existing studies. In this paper, a novel measurement‐based approach is adopted to investigate these issues, where the real measured data of the reference signal received power in a macro–pico co‐channel deployment are collected. Then the mobility performance in terms of the HO failure rate and ping‐pong rate is simulated with various ICIC schemes in the same reality environment. This has been made possible by modeling the possible HO failure events based on evaluating the downlink received signal‐to‐interference‐plus‐noise ratio from reference signal received power. The simulation results indicate that range expansion together with ICIC can have positive or negative influences on macro‐to‐pico, pico‐to‐macro, pico‐to‐pico and macro‐to‐macro HOs in the Heterogeneous Network. The existing static ICIC or mobility‐based ICIC cannot handle the intra‐layer (pico‐to‐pico and macro‐to‐macro) interference, thus limiting their abilities to improve the mobility performance. Motivated by this, a dynamic‐ICIC‐aided HO procedure is proposed. The proposed HO enhancement method is more flexible and effective in mitigating both the inter‐layer and intra‐layer interference, outperforming the existing methods significantly. Copyright © 2014 John Wiley & Sons, Ltd.     

TD-LTE中家庭基站的干扰管理

据预测在LTE网络中将有超过80%的数据业务发生在室内,因此室内覆盖对LTE通信网来说很重要。家庭基站是近年来新兴的室内覆盖技术。针对引入家庭基站的TD-LTE系统,文中分析了其存在的干扰场景,之后针对各种干扰场景给出相应的干扰管理策略,并详细介绍了3GPP R10中开发的毫微微小区（femtocell）增强型小区间干扰协调（eICIC,enhanced Inter-Cell Interference Coordination）技术,最后给出今后的研究方向。     

Distributed optimization of enhanced intercell interference coordination and resource allocation in heterogeneous networks

In two‐tier heterogeneous networks (HetNets), the cross‐tier interference caused by spectrum sharing between macrocell and small cells poses obstacle to ideal overall network performance. Both enhanced intercell interference coordination (eICIC) at the macrocell base station (MBS) and resource allocation (RA) at small cell base station (SBS) have been considered as efficient approaches to mitigate the cross‐tier interference. In this paper, we propose a distributed optimization framework to jointly optimize the eICIC and RA schemes at different tiers. In specific, an enhanced almost blank subframe (ABS) scheme is performed by the MBS to encourage SBSs to adopt hybrid access policy and admit the offloaded macrocell users (MUs) so as to guarantee their QoS requirements. To model the intricate interaction between two tiers, we formulate the joint optimization problem as a one‐leader multiple‐follower Stackelberg game. We prove the existence of Stackelberg equilibrium (SE) and obtain the optimal strategies for both tiers. Numerical results are presented to show that the proposed framework with hybrid access policy converges to a unique SE and utilities for both tiers is maximized, which creates a win‐win situation.     

LTE空口性能测试中信号干扰源的模拟实现

为了能在实验室内模拟信号干扰源进行基站与终端之间的空口无线性能的互操作性测试,本文分析传统的室内信号发生仪加扰法和室外邻区业务干扰法的优缺点,提出了模拟室外信号干扰源的室内加扰方法。该信号干扰源的模拟实现不仅成本较低,能够代替昂贵的信号放生器,且其具有频率,强度可控可调,业务模型随机可变的特点。通过实验室内预测,为后期外厂测试提供了更多的保障。目前该实现已在终端实验室互操作性测试服务中使用。