基于中继协作的多用户MIMO技术

介绍了多用户MIMO系统方案,给出了多中继协作的多用户MIMO系统的模型,对一种简单的中继协作的多用户MIMO系统的性能进行了仿真,并分析了仿真结果。     

基于网络MIMO协作增加下行蜂窝吞吐量

文章用站点的12根天线，功能分区化，预定的分组数据和固定的用户数估计下行蜂窝网中单用户MIMO，多用户MIMO和网络MIMO的性能。与每站点有3个扇区的单用户MIMO基准系统相比，当同一基站的天线之间在站内协作时，发现网络MIMO协作可以增加吞吐量。此时站内协作的系统几乎可以与高度分区化系统（每个站点有12个扇区）的表现一样好，并且增加协作簇的大小也可以增加吞吐量的增益。     

LTE-A下行单用户MIMO增强技术研究

无线通信系统中,基站可以针对信道空间特性采用不同的下行传输模式获得空间复用增益和波束成形增益以提升系统性能。LTE-A中的下行单用户MIMO增强技术,采用了基于码本以及非码本的预编码技术优化性能,有必要分析其技术特点和增益来源以指导产品设计。分析了LTE-A中单用户MIMO技术演进的新特点,着重研究了新的双码本结构,在对信道属性匹配、码本搜索运算复杂度和UE上报载荷方面的改进。针对LTE-A预编码技术性能问题,通过计算机链路级仿真比较了LTE—A中基于码本以及非码本预编码技术的吞吐量性能,仿真结果表明码本技术较非码本技术具有一定优势。     

下一代无线通信系统的多用户MIMO技术

多输入多输出（MIMO）技术已成为下一代无线通信系统的关键技术之一.目前,MIMO系统的研究已经从点对点的单用户系统扩展到点对多点的多用户MIMO系统.介绍了多用户MIMO系统的模型,特别是下行链路的基于空分多址方式消除用户间干扰的预处理方法,并讨论了多用户分集和调度等相关问题.多用户MIMO系统是下一代无线通信系统的一种典型应用系统,因此研究其具有非常重要的意义.     

基于码本的有限反馈非酉矩阵预编码多用户MIMO系统

该文提出了一种基于码本的有限反馈非酉矩阵预编码下行多用户MIMO系统。该方案根据用户反馈的信道信息SINR在发送端进行调度和预编码来提高系统容量。预编码的码本设计依据格拉斯曼空间装箱原理,并将码本中的向量按其相关性构成非酉矩阵来提高预编码增益和抑制多用户共道干扰。新方案反馈量少、复杂度低,在相同情况下比传统的单用户MIMO系统和基于码本的酉矩阵预编码多用户MIMO系统都具有更好的性能。     

多用户MIMO技术及其在LTE系统中的应用

MIMO技术已成为下一代无线通信系统的关键技术之一。目前,MIMO技术的研究已经从点对点的单用户MIMO技术扩展到点对多点的多用户MIMO技术。由于多用户MIMO技术能极大提高系统吞吐量,3GPPLTE也采纳了该技术。分析并比较了ZF和PU2RC这两种多用户MIMO方案,得出LTE中多用户MIMO技术趋向于采用ZF方案的结论。仿真结果也证明了这个结论。     

LTE系统中多用户MIMO容量分析

首先简单介绍了LTE通信技术,在此基础上分析单用户MIMO系统容量以及相应的功率分配问题,随后对多用户MIMO系统功率分配问题做了简单介绍,并给出上行链路和下行链路的容量区域表达式,最后给出4种信道情况下容量之间的关系。     

LTE-A中基于CoMP的预编码算法

在LTE-A系统中引入了多点协作（CoMP）技术,它能够有效降低小区间干扰,提升系统吞吐量,它可以看做是一个协作的多用户MIMO系统,但是每个用户会同时接收到有用信息和来自其他用户的干扰。而采用预编码方案可以有效消除MIMO用户之间的干扰。本文重点研究了基于CoMP技术所使用的经典预编码算法,并在此基础上,提出了结合SLNR和SVD两种算法优势的改进算法,该算法可以同时消除用户间以及用户内的多天线干扰,使系统容量进一步提升。     

无线通信中的编码协作分集技术

为了解决MIMO（多输入多输出）技术在移动终端的多天线制约问题,提出了协作分集技术。它使得在多用户环境中,具有单根天线的移动台可以共享彼此的天线而产生一个虚拟MIMO系统,从而获得分集增益。文中介绍了协作分集的基本概念、编码协作机制,分析指出在普通编码协作中,当信道不完全对称时,码字的帧传输性能将大大受到影响。并由此提出了一种新的协作方案——空时协作方法,并讨论了未来的研究方向。     

CoMP-MU-MIMO上行用户配对方案性能比较

协作多点传输（CoMP）是3GPP长期演进（LTE）的一个重要技术点,并将在上行采用多用户MIMO技术。分析了上行构成多用户MIMO的用户配对选择方法,并提出了一种在物理层进行用户传输速率公平性的调度方法,使系统在单个用户性能与整个系统的频率效率间取得较好的折衷。用系统仿真的方法对系统性能进行了仿真,证明了所提出算法的有效性。     

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.     

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。     

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.     

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.     

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.     

Affinity Propagation Based CoMP Clusters for Dense Small Cell Networks with Backhaul Constraints

Dense small cells have been considered as a promising solution for improving system throughput in 5G networks. When a large number of small cells are overlapped, serious inter-cell interference (ICI) becomes one of the major technical challenges. Coordinated multi-point (CoMP) is an effective technology to mitigate ICI. In this paper, we study affinity propagation based CoMP cluster for dense small cell networks with backhaul constrains. The graph based static clusters and affinity propagation based clusters are formed so as to achieve good performance and reduce complexity. By taking into account the hybrid CoMP mode, the optimal problem which maximizes the system throughput with the limit-capacity backhaul has been formulated. An effective hybrid CoMP cluster strategy is gained by solving the optimal problem. The simulation results demonstrate that the proposed scheme could enhance average throughput.     

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.     

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。     

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.     

LTE-Advanced系统多点协作传输技术研究

CoMP技术是LTE-A的关键技术之一,能够显著的提高小区吞吐量和边缘用户速率。文章首先阐述了CoMP的技术优势;随后介绍了CoMP的技术原理,系统模型以及传输方案等方面的内容;最后总结CoMP技术面临的机遇和挑战。