联合处理中自适应调度算法研究

在新一代移动通信中,协作多点传输技术因其可以有效提高边缘用户性能而被广泛研究.对于协作多点传输来说,其核心思想是通过不同小区间协作来改变边缘用户的性能,从而提升系统性能.针对单用户多输入多输出的特点,本文是在经典调度算法的基础上改进了的自适应调度算法,此算法在每个时频资源块上灵活的选择较优的传输模式,从而增强系统性能.通过仿真表明了这种调度算法在保持较好公平性的同时,又可以很好的提升平均小区吞吐量和边缘用户频谱效率.     

LTE-Advanced中协作多点传输技术研究

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）。CoMP技术是一种干扰消除技术,通过小区间的联合调度和协作传输,使小区边缘的CoMP用户的干扰信号变为有用信号,或降低来自邻小区的干扰水平,从而提高小区边缘吞吐量,并且增强系统性能。文章主要介绍了协作多点传输技术及其原理,对CoMP技术中的协作簇选择、CoMP用户划分、用户传输方案及预编码做出了介绍,通过仿真对比得到采用CoMP技术的系统性能增益,最后对协作多点传输技术作出了展望。     

一种交互式中继选择策略

提出了一种协作中继网络的交互式中继节点选择(IRS)策略。用户首先分布式构造基于信道状况及中继节点负载情况的中继选择函数,选择最优的中继节点;中继节点再根据资源分配情况、业务优先级以及加权信道调度算法进行反向用户选择。仿真结果表明,相比于已研究的算法,所提出的IRS算法结合了信道状况、MAC层资源与用户业务状况等因素,利用用户和中继之间的两步式交互中继选择来调节小区内的用户负载分布,获得了小区吞吐量与用户公平性之间的折衷。     

CoMP系统低复杂度集中式调度算法研究

在3GPPLTE—A网络中,可以使用CoMP（多点协作）技术来提高边缘用户的性能。为了最大化全网边缘用户的总吞吐量,关键是要确定在每个PRB（物理资源块）中同时被服务的用户集合、每个被调度用户所对应的协作基站、以及各基站的传输功率。基于每个边缘用户的RSRP（参考信号接收功率）,提出一种低复杂度的集中式传输调度算法,针对每个PRB中被服务的边缘用户和相应的协作基站进行动态选择,并通过仿真实验验证算法的性能增益。     

多点传输系统的联合调度方案

在下行蜂窝网络中,多点传输计划因可以大幅度提高扇区平均吞吐量和小区边缘用户速率而越来越受到关注。传统的独立调度算法中参与多点传输的扇区分别调度各自的用户,这种独立调度算法限制了系统性能的进一步提高。文章提出了一种针对SF-DCHSDPA系统新的联合调度方案,基站间通过交换信息选择适合的传输方案。可更好地调度用户。通过系统级仿真结果可以看出,新提出的联合调度算法可以获得更好的扇区平均吞吐量和边缘用户体验。     

协作多点通信系统中的切换机制

协作多点技术能有效改善小区边缘用户性能,提高系统吞吐量。协作多点技术需要设计全新的切换机制,否则将会限制其实际性能。文章基于协作多点通信系统架构下的切换场景提出了一种支持协作多点通信的切换机制,包括协作小区集合切换和协作传输点选择／更新的信息交互以及信令传输流程。该切换机制可有效支持协作多点通信,同时降低信息交互及信令开销。     

基于PMI反馈的联合处理

为了提高LTE-Adwanced系统边缘用户的吞吐量和性能,本文在协作多点传输的基础上提出了两种联合处理的算法,这两种算法分别采用全局预编码和间接预编码的方式,把来自不同小区的干扰信号联合处理使其成为有用信号,仿真结果表明两种算法都能很好的提高边缘用户的性能。     

LTE-A系统中比例公平调度算法的改进

在非连续载波聚合(高频+低频)场景下,载波衰减特性不同,聚合的载波有不同的覆盖范围,使得不同用户可调度的载波数量不同,若使用传统比例公平( PF)算法会导致小区不同位置用户资源配置的不公平性。本文提出了一种分组权重PF调度算法( GWPF ),根据用户可调度的载波数量,将用户和载波分组,并引入加权因子对原比例公平算法进行加权处理,从而提高用户公平性。仿真结果表明GWPF较PF算法有着更好的用户公平性和边缘小区吞吐量。     

大尺度信干比共享下的基站协作干扰协调

在基于正交频分多址接入(OFDMA)技术的蜂窝移动小区中,小区间的干扰是影响系统性能的主要因素。多点协调(CoMP)技术被视为能够协调小区间干扰的主要手段。在下行多点协作传输系统中,小区基站采用三向天线来对小区划分扇区,从而消除了相邻小区边缘处的干扰。各扇区分别计算扇区内用户的大尺度信干比(SIR),小区之间通过共享大尺度信干比信息,对各自服务的用户按照一定的规则进行匹配,对小区中心用户的SIR和边缘用户的SIR进行了折中,从而有效解决小区边缘用户由于小区间干扰带来的低信干噪比(SINR)问题。仿真结果表明,本文提出的用户匹配算法以较小的反馈开销,较大的提高了小区边缘用户的信干噪比和系统吞吐量。      

一种基于多点协作的上行资源调度方式

介绍了基于多点协作的上行资源调度方式。从边缘用户与中心用户判定、无线资源分配模式选择、天线设置与接收数据处理和系统仿真结果四个方面进行了论述。重点分析了中心用户与边缘用户区分标准的设定和资源分配、频选模式的频选度量值设定以及多点协作方式的联合接收数据处理等问题。仿真结果表明,通过合理设置和调整系统的控制参数,多点协作可以有效地降低系统误码率、提升系统吞吐量。     

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.     

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。     

支持协作多点技术的网络架构的研究

协作多点(coordinated multi-point,CoMP)技术因能有效改善小区边缘用户性能,提高系统吞吐量,引起了业界的广泛关注和研究。CoMP的研究要基于一定的网络架构,目前已有的中心式和分布式网络架构存在回程容量大、CoMP时延高、复杂度高等问题。本文提出了改进型分布式网络架构,在传统分布式网络架构的基础上增加了集中控制的逻辑实体,能有效简化CoMP流程,减少CoMP时延以及实现复杂度。     

Spectrum efficiency sub-carrier and energy efficiency power allocation for downlink multi-user CoMP in multi-cell system

Coordinated multi-point transmission/reception （CoMP） was proposed currently as an effective technology to improve cell-edge throughput in next-generation wireless systems. Most of the existing work discussed clustering methods mostly to maximize the edge user throughput while neglecting the problem of energy efficiency, such as those algorithm clustering base stations （BSs） of better channel condition and BSs of worse channel condition together. In addition, BSs usually increase the transmit power to achieve higher throughput without any considering of interference caused to other users, that may result in energy waste. The authors focus on the throughput maximizing problem while fully considering energy saving problem in CoMP systems. A coefficient is defined to describe the fitness of clusters. Then a sub-carrier allocation algorithm with clustering method is put forward for CoMP downlink, which can save the transmit power of BS and increase the throughput. Furthermore a power allocation scheme is proposed based on non-cooperation game; in which the transmit power is decreased by BSs generally to reach the Nash equation （NE）. Simulation shows that the proposed sub-carrier allocation scheme and power allocation algorithm are better than the existing ones on users＇ throughput while consumes much less energy.     

Clustering and scheduling methods based on SLNR in downlink CoMP system简

In downlink coordinated multi-point（CoMP） system, full cooperation is always not applicable in real world because of its high request in the backhaul. To deal with this problem, clustering decision is made to process transmission. In this paper clustering methods based on the metric signal-to-leakage-plus-noise（SLNR） is proposed. In addition, user scheduling schemes based on SLNR is also put up to make the scheduling set as large as possible. Simulation results show that the proposed clustering methods not only reduce the data sharing among the cooperating base stations（BSs）, but also improve the system throughput compared with the traditional clustering methods based on channel strength.     

Cell Clustering and Resource Allocation Scheme for CoMP SU-MIMO

In view of the problem of high implementation complexity and system performance degradation in existing schemes, a novel downlink coordination scheme consisting of two steps was proposed for CoMP single-user multi-input multi-output (CoMP SU-MIMO). Firstly, through a combination of the conventional network-defined method and UE-specific method, we proposed a CoMP Cooperation Set (CCS) selection method which could provide most of the achievable throughput gain with lower complexity. Secondly, a resource allocation scheme was provided for the coordination among overlapping CCSs, by inheriting the idea of fair treatment for cell-center users and cell-edge users and conquering the limitation of the conventional schemes which could be only used for non-overlapping CCS method. Simulation results show that the proposed scheme could increase the cell average throughput significantly as well as improve the fairness between cell-center users and cell-edge users compared with the existing schemes.     

A green scheduling with adaptive spatial division multiple access grouping for multi‐user coordinated multi‐point networks

Multi‐User Coordinated Multi‐Point (MU‐CoMP), which couples CoMP with Multi User‐Multiple Input Multiple Output (MU‐MIMO), appears as a promising solution to enhance the Long Term Evolution‐Advanced (LTE‐A) system performance. However, some challenging issues in MU‐CoMP networks require more investigation. First, the set of users transmitting under CoMP mode should be properly identified. Secondly, time‐frequency resource should be efficiently partitioned between CoMP and non‐CoMP users in order to improve the system radio capacity. Thirdly, a fair and green scheduler is much needed for a more energy efficient system. This paper deals with these three issues. We propose an adaptive transmission mode selection according to the total load in the cluster and to users' quality of service. The adequate size of the Spatial Division Multiple Access users' groups is also analyzed. We finally propose a new scheduling algorithm to further enhance the radio capacity and the energy consumption in the cluster. Simulations results showed that significant improvements are obtained in terms of total system throughput and outage probability in the cluster with our proposed scheme. Moreover, energy efficiency has increased by four times with our proposed scheduling algorithm as compared to commonly used schedulers. Copyright © 2015 John Wiley & Sons, Ltd.     

CoMP中联合传输技术的研究

协作多点传输与接收(Coordinated Multiple Point transmission and reception,CoMP)技术作为提高小区吞吐量尤其是小区边缘用户吞吐量的关键技术,目前已经成为LTE-Advanced的研究热点之一。就其中基于SU-MIMO的下行联合传输(CoMP-SU-MIMO)技术进行了研究,分析了系统模型,提出了用户信干噪比(SINR)的计算方法。最后对系统进行了系统级仿真,并通过与传统的SU-MIMO性能比较,得出了联合传输技术在提高边缘用户性能和小区吞吐量方面的优势。     

Low-complexity SAGE-based MMSE channel estimation for CoMP multi-user systems

Coordinated multiple point(CoMP) transmission/reception has been investigated recently as a promising technology to increase the cell-edge user performance of long term evolution-advanced(LTE-A),and channel estimation is a crucial technology for CoMP systems.In this paper,we consider a reduced-complexity minimum mean square error(MMSE) channel estimator for CoMP systems.The estimator uses space alternating generalized expectation maximization(EM)(SAGE) algorithm to avoid the inverse operation of the joint MMSE estimator.In the proposed scheme,the base stations(BSs) in the CoMP system estimate the channels of all the coordinated users serially and iteratively.We derive the SAGE-based estimators and analyze complexity.Simulation results verify that the performance of the proposed algorithm is close to the joint MMSE estimation algorithm while reducing the complexity greatly.     

Selective interference alignment and neutralization in coordinated multipoint using multiuser MIMO

In wireless communication, the concept of coordinated multipoint (CoMP) transmission is more attractive, and it transpired the notion based on interference management techniques. Interference alignment (IA) and interference neutralization (IN) methods can substantially align and neutralize the interference signals. The existing work in the CoMP transmission using multiuser multi-input and multi-output (MU-MIMO) had long-held problems such as specific limit of intercell (ICI) and cochannel interference (CCI) cancelation that contain low performance in cell-edge users. The proposed framework of the transmission signal in selective interference alignment and neutralization (SIAN) CoMP MU-MIMO system transmits multiple data streams in multipath by using downlink coordination between base stations and receiver side. This work contributes the individual perspectives to implement the IA and IN to align and cancel the interfered signals at the receiver side. Once the perspectives mentioned above are executed, zero-forcing (ZF) and rechanneling filter are applied on the receiver side to eliminate residual ICI. In addition, spectral efficiency significantly improves the achievable data rate and enhances the performance of cell-edge users and reduces the CCI at the receiver side. Furthermore, the antenna configuration signals are decoded to get the exact version of interference-free signals with null path loss of signal transmission. The effectiveness of the proposed framework analyzes and verifies the numerical evaluation of the achievable degree of freedom. Finally, the simulation demonstrates the comparison of the proposed CoMP scheme with MIMO ZF and non-CoMP schemes, which significantly improve the performance of spectral efficiency for cell-edge users.