HetNet中基于上行CoMP的动态多小区接入算法

提出了HetNet中基于上行CoMP的动态多小区接入算法(UCDS),动态选择协作基站,利用CoMP机制,改善小区边缘用户的上行传输性能。进一步地,提出了基于二次判决的协作小区选择算法(DJCS),以减少参与协作的基站数,降低协作复杂度并节省基站端资源。仿真结果表明,UCDS算法能显著提高边缘用户的平均吞吐率和传输能效,而DJCS算法在保证用户性能的情况下,降低了基站端的能耗。     

Research on uplink coordinated transmission schemes in LTE-advanced systems

The investigation of inter-cell interference mitigation techniques is a key area in wireless communications.Coordinated multiple points(CoMP) transmission/reception is a candidate technique for interference cancellation in 3GPP LTE-Advanced system.However,the coordination scheme in CoMP remains a key research problem to be solved,which will have a strong influence on the performance of CoMP.In this paper,a novel coordinated transmission scheme is proposed for the uplink LTE-Advanced system.In our scheme,several base transceiver stations(BTS) and users are selected as coordination partners which form a CoMP cluster.Joint processing is used at the receiver to mitigate interference.From the perspective of coordinated partner selection,our scheme can be divided into static and dynamic coordination which are both considered to fully exploit the throughput gain of CoMP.The proposed schemes are evaluated by system level simulation and compared with the conventional LTE system based upon single cell processing.Our simulation results demonstrate that the proposed schemes attain superior performance as opposed to the conventional system in terms of cell average and cell edge throughput.     

Effective resource scheduling scheme considering scheduling relevancy for downlink joint transmission system

Coordinated multi-point(CoMP) transmission is a promising technique to improve both cell average and cell edge throughput for long term evolution-advanced(LTE-A).For CoMP joint transmission(CoMP-JT) in heterogeneous scenario,if joint transmission(JT) users are firstly scheduled,other non-JT users will not be allocated sufficient resources,i.e.,scheduling relevancy exists in the users under different cells in the same coordination cluster.However,the CoMP system throughput will decline remarkably,if the impact of scheduling relevancy is not considered.To address this issue,this paper proposes a novel scheduling scheme for CoMP in heterogeneous scenario.The principles of the proposed scheme include two aspects.Firstly,this scheme gives priority to user fairness,based on an extended proportional fairness(PF) scheduling algorithm.Secondly,the throughput of the coordination cluster should be maintained at a high level.By taking the non-CoMP system as a baseline,the proposed scheme is evaluated by comparing to random PF(RPF) and orthogonal PF(OPF) scheme.System-level simulation results indicate that,the proposed scheme can achieve considerable performance gain in both cell average and cell edge throughput.     

阵列处理器中改进几乎空白子帧算法的并行化实现

两层异构网络中出现的小区间干扰协调是当前异构网络干扰问题研究的热点。针对软件实现增强小区调度几乎空白子帧(ABS)的干扰方案存在处理数据量大、速度慢的缺点,基于可重构阵列结构提出了一种动态ABS干扰协调的并行化硬件实现方案。该算法在增强小区内根据用户数动态分配ABS比例,以改善小区边缘用户的信道容量,通过流水线的方式使用多个轻核处理元(PE)实现并行计算以提高运算效率。测试结果表明,使用12个PE同时调度实现算法的映射,运行1983个周期,其性能比单个PE提升77.03%,该算法的并行计算能力得到显著提升,宏基站用户的吞吐量可以达到4.76 Mbit/s.     

LTE—AdvancedCoMP中自适应动态小区选择方案

为了提高小区边缘用户的性能,满足小区边缘频谱效率的要求,LTE—Advanced系统中引入了协作多点传输技术（ CoMP, Coordinated Multi- Point transmission）。提出一种新的下行协作方案,该算法首先判定网络中的用户类型,其次为小区边缘用户选择协作集合。此方案利用信干噪比（SINR, Signal- to- Interference plus Noise Ratio）阈值自适应的确定协作小区的数量,能有效避免不必要的协作,能降低系统的信息传输负担。仿真结果表明,提出的算法相比已经存在的算法能够明显改善协作效率同时能够降低基站间的信息传输负担。     

Autonomous Schemes for Inter-cell Interference Coordination in the Downlink of LTE Systems

Inter-cell interference (ICI) is one of the key challenges that limit the performance of Long Term Evolution and Long Term Evolution Advanced cellular systems. One approach to deal with ICI is through interference avoidance. Unlike static avoidance techniques where a-priori frequency planning and/or explicit inter-cell coordination is used, dynamic avoidance techniques rely on adapting its frequency planning and allocation based on the current state of the network. However, this improvement in performance comes with the cost of an increased complexity due to the coordination and alignments needed among the base stations (eNB) to manage and allocate channels among the users. Accordingly, autonomous ICI coordination techniques are receiving much interest among the various interference avoidance techniques. In this paper, we propose an autonomous self-adaptive scheme (SA, for short) for radio resource management and interference coordination. We then extend the proposed scheme to become self-adaptive power-aware (SAPA) in order to optimize and reduce the transmission power of the eNBs. A key feature in the proposed schemes is that all computations are independent of the number of users and cells in the network. This allows the proposed schemes to adapt to networks of any size and with an arbitrary number of users. Extensive simulation confirms that the proposed SA scheme ensures efficient frequency reuse patterns that lead to significant performance improvements in the throughput of the edge users without affecting other users. Moreover, the SAPA scheme achieves significant improvement in the power efficiency, while maintaining the throughput enhancements achieved by the SA scheme for both center and edge users.     

Dynamic spectrum allocation for cell range extension in tiered Macro-Pico heterogeneous networks

Heterogeneous networks are employed in the next generation communication systems to enhance the area spectral efficiency (ASE), where cell range extension (CRE) is a promising technique to improve the cell edge performance and utilize the low power node (LPN) resources more effectively. In this paper we propose a dynamic spectrum allocation scheme for Macro-Pico scenario to mitigate both the co-tier and cross-tier interferences. The available system spectrum is divided into different parts by four steps, i.e. user set partition, service request collection, cross-tier occupation and CRE occupation decision, while the service request of each user is taken into consideration. During the process implementation, the reference signal receiving power (RSRP) threshold is derived by mathematical means to judge cell edge macro users when a predefined ratio is given. Simulation results show that the proposed scheme reaches almost the same cell edge performance with the best existing option, meanwhile provides higher overall system throughput and better spectral efficiency. Therefore, much better balance is achieved.     

Dynamic Cooperative Base Station Selection Scheme for Downlink CoMP in LTE-Advanced Networks

Coordinated Multi-Point (CoMP) transmission is a technique proposed to enhance the spectral efficiency and system throughput in an interference limited cellular networks. In CoMP joint processing (JP) scheme multiple base stations (BSs) are coordinately transmit data streams to each user. As more than two base stations are involved, abundant spatial resources are exploited and more backhaul spectrum for JP cooperation is required. The backhaul architecture for CoMP JP is crucial to provide low latency, unlimited capacity, less power consumption, and perfect synchronization among the BSs. However, satisfying all these constraints is impossible as the number of cooperative BSs increases for each user. In this paper, a dynamic cooperative base station selection scheme is proposed to reduce the backhaul load for CoMP user by selecting the appropriate number of coordinated BSs from the CoMP cluster to ensure the certain quality of service (QoS). In particular, for cell edge user the number of cooperative BSs per user has been selected in order to achieve reduced overhead and the allocation of backhaul capacity is performed under the max–min fairness criterion. Simulation results show that the proposed selection scheme achieves significant performance improvement than other transmission modes in terms of the average sum rate per backhaul use and minimal total power consumption.     

异构网中基于BD的协作波束赋形算法研究

波束赋形是下一代无线蜂窝网中提高频谱效率的一项重要技术,文中在多用户波束赋形技术的研究基础上,研究了CoMP中的CB技术。针对LTE系统中的小区间干扰严重,且已有的干扰协调技术无法有效解决边缘用户频谱效率低的问题,LTE-A系统引入了多点协作传输/接收技术。该技术通过相邻小区间的联合处理或协作波束赋形,可抑制小区间干扰,提高用户的接收信号质量,使系统容量和小区边缘用户的频谱效率得到有效提高。     

一种超密集异构网中联合干扰协调方法研究

针对5G超密集异构网中严重的跨层干扰问题,该文提出一种基于现有的增强型小区间干扰协调技术和协同多点传输技术的联合干扰协调方法。运用随机几何理论工具推导了两层超密集异构网下用户的中断概率,频谱效率和网络平均遍历容量表达式。仿真结果表明:该文提出的联合的干扰协调方案,相比于传统协同多点传输技术,不仅降低了协作用户数目,同时使得用户在信干比阈值为0 dB时的中断概率降低了15%;相比较于增强型小区间干扰协调技术,在偏置值为10 dB时,扩展区域的用户频谱效率改善为35%,整个网络平均遍历容量提升了3.4%。     

Joint interference coordination approach in femtocell networks for QoS performance optimization

Future heterogeneous networks with dense cell deployment may cause high intercell interference. A number of interference coordination (IC) approaches have been proposed to reduce intercell interference. For dense small‐cell deployment with high intercell interference between cells, traditional forward link IC approaches intended to improve edge user throughput for best effort traffic (ie, file transfer protocol download), may not necessarily improve quality of service performance for delay‐sensitive traffic such as voice over long‐term evolution traffic. This study proposes a dynamic, centralized joint IC approach to improve forward link performance for delay‐sensitive traffic on densely deployed enterprise‐wide long‐term evolution femtocell networks. This approach uses a 2‐level scheme: central and femtocell. At the central level, the algorithm aims to maximize network utility (the utility‐based approach) and minimize network outage (the graphic‐based approach) by partitioning the network into clusters and conducting an exhaustive search for optimized resource allocation solutions among femtocells (femto access points) within each cluster. At the femtocell level, in contrast, the algorithm uses existing static approaches, such as conventional frequency reuse (ReUse3) or soft frequency reuse (SFR) to further improve user equipment quality of service performance. This combined approach uses utility‐ and graphic‐based SFR and ReUse3 (USFR/GSFR and UReUse3/GReUse3, respectively). The cell and edge user throughput of best effort traffic and the packet loss rate of voice over long‐term evolution traffic have been characterized and compared using both the proposed and traditional IC approaches.     

Sequential frequency reuse with power control for OFDMA systems

Orthogonal frequency division multiple access (OFDMA) is a promising technique for high data rate communications in future cellular systems. Since frequency resources are universally reused in every cell in a system, a typical OFDMA system tries to maximize the spectral efficiency. Users located near the cell‐edge tend to have the weakest signal strength. So they might experience severe inter‐cell interferences (ICIs). In this paper, we propose a sequential frequency reuse (SqFR) that reduces ICIs by a sequential sub‐channel allocation. By giving more power to sub‐carriers allocated to cell‐edge users, our SqFR significantly enhances the performance of cell‐edge users. The performance of the proposed SqFR is investigated via the analysis and simulations. Simulation results show that proposed SqFR improves the performance of cell‐edge users in an OFDMA system under both homogeneous and heterogeneous traffic conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Load-adaptive frequency reuse scheme for inter-cell interference coordination in relay networks

Cellular relay networks adopting orthogonal frequency division multiple(OFDM)technology has been widely accepted for next generation wireless communication due to its advantage in enlarging coverage scale as well as improving data rate.In order to improve the performance of user equipments(UEs)near the cell edge,especially to avoid the interference from inter-cell and intra cell,an enhanced soft frequency reuse scheme is adopted in this paper to assure inter-cell interference coordination(ICIC).Compared with traditional frequency allocation work,the proposed scheme is interference-aware and load-adaptive,which dynamically assigns available frequency among UES under certain schedule method in variable traffic load condition and mitigates interference using information provided by interference indicator.It can improve signal-to-interference plus noise ratio(SINR)of the UE in each sub channel thus enable the system achieve better throughput and blocking probability performance.Simulation results prove that the proposed scheme may achieve desirable performance on throughput,blocking probability and spectral utilization in the sector under different traffic load compared with other schemes.     

基于信漏噪比的异构网络载波干扰协调技术

针对异构网络存在小区间干扰的问题,提出了一种基于频域载波聚合的干扰协调管理机制。该机制将所有小区的用户分为中心用户和边缘用户,采用可降低干扰的信漏噪比(SLNR)准则,动态调度用户和选择小区载波,并将每种小区载波选择方案对应一种调度用户分组的机制,即对小区的中心用户和边缘用户采用不同优先级,以此有效避免小区间的干扰,其中优先级采用比例公平和SLNR准则。仿真结果表明,由于在系统目标最大化时实现了频率复用增益和干扰消除增益间实现最佳的平衡,可有效取得系统流量的分流和总吞吐量的提升。     

Systematic energy-balanced cooperative transmission scheme in wireless sensor networks

Energy efficiency is a critical issue in wireless sensor networks(WSNs).In order to minimize energy consumption and balance energy dissipation throughout the whole network,a systematic energy-balanced cooperative transmission scheme in WSNs is proposed in this paper.This scheme studies energy efficiency in systematic view.For three main steps,namely nodes clustering,data aggregation and cooperative transmission,corresponding measures are put forward to save energy.These measures are well designed and tightly coupled to achieve optimal performance.A half-controlled dynamic clustering method is proposed to avoid concentrated distribution of cluster heads caused by selecting cluster heads randomly and to get high spatial correlation between cluster nodes.Based on clusters built,data aggregation,with the adoption of dynamic data compression,is performed by cluster heads to get better use of data correlation.Cooperative multiple input multiple output(CMIMO) with an energy-balanced cooperative cluster heads selection method is proposed to transmit data to sink node.System model of this scheme is also given in this paper.And simulation results show that,compared with other traditional schemes,the proposed scheme can efficiently distribute the energy dissipation evenly throughout the network and achieve higher energy efficiency,which leads to longer network lifetime span.By adopting orthogonal space time block code(STBC),the optimal number of the cooperative transmission nodes varying with the percentage of cluster heads is also concluded,which can help to improve energy efficiency by choosing the optimal number of cooperative nodes and making the most use of CMIMO.     

Semi‐distributed dynamic inter‐cell interference coordination scheme for interference avoidance in heterogeneous networks

Inter‐cell interference (ICI) is a major problem in heterogeneous networks, such as two‐tier femtocell (FC) networks, because it leads to poor cell‐edge throughput and system capacity. Dynamic ICI coordination (ICIC) schemes, which do not require prior frequency planning, must be employed for interference avoidance in such networks. In contrast to existing dynamic ICIC schemes that focus on homogeneous network scenarios, we propose a novel semi‐distributed dynamic ICIC scheme to mitigate interference in heterogeneous network scenarios. With the goal of maximizing the utility of individual users, two separate algorithms, namely the FC base station (FBS)‐level algorithm and FC management system (FMS)‐level algorithm, are employed to restrict resource usage by dominant interference‐creating cells. The distributed functionality of the FBS‐level algorithm and low computational complexity of the FMS‐level algorithm are the main advantages of the proposed scheme. Simulation results demonstrate improvement in cell‐edge performance with no impact on system capacity or user fairness, which confirms the effectiveness of the proposed scheme compared to static and semi‐static ICIC schemes.     

基于认知的LTE系统动态频谱分配

传统的软频率复用(SFR)无法适应长期演进(LTE)系统中业务的动态分布,可能导致小区中心和边缘区域频谱利用率不均。针对此问题,该文提出一种基于认知的LTE系统动态频谱分配方法(Cog-DSA)。该方法利用基站间的相互协作获得频谱使用状态信息,从而确定可用频谱集合,并评估来自邻小区的同频干扰,最终根据可用资源块的通信质量,对重负荷小区边缘进行频谱的动态借用和服务基站的灵活选择。仿真结果表明,所提方法能够有效改善频谱利用率,减少小区间干扰,显著提升边缘用户的传输速率。     

超密集网络中干扰协调方法及性能分析

在超密集网络中,全频重用能够提升网络的平均吞吐量,但严重的小区间干扰限制了边缘用户数据率的提升。如何有效地管理超密集网络中的干扰、提升边缘用户数据率是重要的研究问题。本文研究了超密集网络中两种有代表性的干扰协调方法,随机干扰协调和基于拓扑干扰协调,分析了这两种方法的平均数据率和边缘用户数据率、以及系统参数对其性能的影响。理论分析和仿真的结果表明,采用随机干扰协调能够提升边缘用户的信干噪比,但不能提升边缘用户数据率。这使得当系统增加频率重用因子时,会牺牲平均用户数据率同时也不能提高边缘用户数据率。采用基于拓扑的干扰协调能够同时提升边缘用户的信干噪比和数据率;当频率重用因子较低时,提高重用因子可以通过以较少牺牲平均用户数据率为代价有效提高边缘用户数据率,从而实现平均数据率和边缘用户数据率的折中。      

多小区大规模MIMO系统中基于部分导频交替复用的导频污染减轻方法

在多小区大规模多输入多输出(Multiple Input Multiple Output,MIMO)系统中,导频污染(Pilot Co- ntamination,PC)已成为制约整个系统性能的瓶颈。本文从系统级角度出发,提出了一种基于部分导频交替复用(Alternately Fractional Pilot Reuse,AFPR)的导频配置方案,即相邻小区的边缘用户配置相互正交的导频序列,而小区中心用户复用相邻小区边缘用户所配置的导频序列。同时从理论上推导出基于AFPR的导频配置方案上行可达频谱效率(Spectral Efficiency,SE)的关系式。数值仿真结果表明,相比于传统的导频配置方案,无论采用最大比合并(Maximum Ratio Combining,MRC)还是迫零(Zero Forcing,ZF)接收,该方案可显著地提升系统性能增益。      

Dynamic bias setting for range extension in LTE-advanced macro-pico heterogeneous networks

In co-channel deployment of macro cell and pico cells, cell range extension （RE）, a simple and typical cell association scheme, is introduced to achieve better load balancing and improve cell edge performance. In this article, a novel dynamic and distributed bias setting scheme is proposed for RE technique in macro-pico heterogeneous networks. In this strategy, the worst user throughput of each cell during an adjusting time interval T is obtained to change the bias values according to certain procedures, where an introduced indicator is used to freeze the possibility of increasing bias value if needed. Furthermore, silent state and coarse control process are employed to achieve low overheads and computational complexity. Simulation results show that the proposed scheme can greatly improve the cell-edge performance compared with the static bias setting strategies, while maintaining the overall cell performance at the same time.