异构网中的高能效混合协作传输方法

该文提出一种异构网中高能量效率的协作传输方法。协作联合处理(CoMP-JP)和协作波束成型(CoMP- CB)是异构网中两种常用的协作传输方法。通过研究CoMP-JP和CoMP-CB发现：CoMP-JP利用较大的阵列增益能够降低基站的发射功耗,但是需要消耗很高的信号处理功耗、骨干网功耗和电路功耗;CoMP-CB虽然消耗较少的信号处理和骨干网功耗,但是会导致较大的发射功耗。为了充分利用CoMP-JP和CoMP-CB在降低能耗方面的优点,并且有效地降低电路功耗,该文提出一种基于CoMP-JP和CoMP-CB传输的混合协作预编码方法。仿真结果表明,与CoMP-JP和CoMP-CB模式下的迫零预编码相比,所提出的混合协作预编码能够支持更高的系统频谱效率,并且大大提高系统的能量效率。     

基于CoMP传输的分布式异构网络资源分配

摘要：提高无线资源利用效率是缓解日益增长的无线通信需求和有限的可用传输资源之间矛盾的主要途径。基于多点协调（coordinated multipoint,CoMP）传输技术的异构网络在提高频谱效率和能量效率方面具有巨大的潜力,近年来受到学术界和工业界的广泛关注。在研究基于CoMP技术的异构网络资源分配问题的基础上,提出了一种基于交叉熵方法的分布式频谱资源调度算法。仿真实验验证了本文提出方法在系统吞吐量、能量效率以及用户公平性等方面的有效性。     

LTE异构网技术分析

随着社会和通信技术的发展,人们对移动数据业务的需求爆发性增长,而频率和站址的资源缺失有限的,已经无法满足其如此迅速的增长。在此背景下,应用新技术来疏导热点数据业务,分类数据流量势在必行,异构网应运而生。它将成为移动网络的长期发展趋势,但是异构网的引入又带来复杂的同频干扰、移动性管理等问题。本文将对LTE异构网的组网方案、关键技术进行研究,并提出组网及技术应用建议。     

LTE异构网技术分析

随着社会和通信技术的发展,人们对移动数据业务的需求爆发性增长,而频率和站址的资源缺失有限的,已经无法满足其如此迅速的增长。在此背景下,应用新技术来疏导热点数据业务,分类数据流量势在必行,异构网应运而生。它将成为移动网络的长期发展趋势,但是异构网的引入又带来复杂的同频干扰、移动性管理等问题。本文将对LTE异构网的组网方案、关键技术进行研究,并提出组网及技术应用建议。     

HetNet场景下基于时延的多基站协作传输方法

小基站的部署有效提高了无线网络的覆盖范围和系统容量,多点协作传输(CoMP)技术被认为是一种减少基站间干扰的有效策略。提出了一种用于HetNet场景下基于时延的多基站协作传输方法。首先,利用各协作基站传输信号到用户之间的时延差,据此计算时延补偿因子,在基站端发送信号时进行频域上的相位旋转,实现时延补偿;其次,依据基站间回程时延,选择合适的协作基站,实现基站协作同步,并减少回程时延,降低时延对协作传输的影响。最后,在matlab平台下对该方案进行仿真验证,相比传统方案该方案可降低干扰,提升边缘用户吞吐量和系统整体的吞吐量。     

基站间频偏对TD-LTE-A CoMP技术影响的评估

针对协作多点传输技术(CoMP)在实际系统中运用时,基站间频率偏移可能带来的问题,建立合适的系统模型,在不同场景下对基站间频率偏移对于协作多点传输的影响进行了深入的研究。仿真分析表示,基站间频率偏移对协作多点传输技术的性能不会带来太大的影响,引入频偏后系统性能仍较SU/MU-MIMO有较大的增益。这一研究工作为协作多点传输的可行性和有效性提供了有力的支持。     

下行多用户CoMP系统资源分配算法

针对下行多用户多点协作传输系统(MU-CoMP)边值自适应(MA)的问题,提出了一种快速资源分配算法。该算法首先根据用户的速率要求及平均信道增益估计出每个用户需要的子载波数目,在此基础上设计合理的子载波分配算法进行子载波分配,通过预判并且剔除不适合传输数据的较差空间子信道实现快速比特加载。仿真结果表明,所提算法在满足用户最低速率和误码率要求的前提下有效地降低了总发射功率,以较低的复杂度获得了接近最优算法的性能。     

LTE—A异构网络中CoMP—JP在不同功率分配方案下的性能对比

为解决异构网络中的干扰问题,研究了存在LTE-A异构网络中进行相干协作多天线传输,并使用迫零预编码时不同功率分配片案对系统性能的影响。包括按最大数据率分配、按公平性分配和等功率分配,并进行了相应的仿真分析。结果表明,三种功率分配方案对宏用户的影响差别并不大,主要差别体现存微用户上;宏用户的数据率主要受到微小区与宏用户位置关系的影响,而这种彰响本质上是由微基站的单机站功率约束造成的。     

基于NOMA的全双工多层异构网下行链路覆盖分析

针对异构网（Heterogeneous Network,HetNet）无线回程,现有研究主要集中于提升网络吞吐量,而对回程覆盖性能研究较少.由此,本文构造了一种在小小区基站（Small cell Base Station,SBS）上结合全双工（Full-Duplex,FD）和非正交多址接入（Non-Orthogonal Multiple Access,NOMA）技术的大规模多输入多输出（Multiple Input Multiple Output,MIMO）辅助多层HetNet模型.利用信干比（Signal-to-Interference Ratio,SIR）来模拟有源SBS的分布,得出不同类型接收端的干扰;然后推导了移动用户（Mobile User,MU）下行链路覆盖概率闭合表达式.仿真和数值结果表明,SBS下行链路覆盖概率会随着小小区下行链路功率共享系数的增加而减小;此外,通过对比NOMA和正交多址接入（Orthogonal Multiple Access,OMA）以及FD和半双工（Half-Duplex,HD）对下行链路覆盖性能的影响,本文提出的方案能显著提升网络性能.     

面向LTE-Advanced的CoMP试验系统及外场试验网

介绍了面向下一代移动通信系统的发展与演进,分析了3GPP LTE-Advanced系统需求指标及关键技术,针对LTE-Advanced系统协作多点(CoMP)技术,研发了试验系统,并基于试验系统搭建了外场试验网。测试结果表明了CoMP技术的优势。     

A green radio resource allocation scheme for LTE-A downlink systems with CoMP transmission

In this paper, we propose a green radio resource allocation (GRRA) scheme for LTE-advanced downlink systems with coordinated multi-point (CoMP) transmission to support multimedia traffic. The GRRA scheme defines a green radio utility function, which is composed of the required transmission power, assigned modulation order, and the number of coordinated transmission nodes. By maximizing this utility function, the GRRA scheme can effectively save transmission power, enhance spectrum efficiency, and guarantee quality-of-service requirements. The simulation results show that when the traffic load intensity is greater than 0.7, the GRRA scheme can save transmission power by more than 33.9 and 40.1 %, as compared with the conventional adaptive radio resource allocation (ARRA) scheme (Tsai et al. in IEEE Trans Wireless Commun 7(5):1734–1743, 2008) with CoMP and the utility-based radio resource allocation (URRA) scheme (Katoozian et al. in IEEE Trans Wireless Commun 8(1):66–71, 2009) with CoMP, respectively. Besides, it enhances the system throughput by approximately 5.5 % and improves Jain’s fairness index for best effort users by more than 155 % over these two ARRA and URRA schemes.     

C-RAN网络中CoMP性能分析与优化

针对无线通信中的能耗巨大和移动用户潮汐现象带来的基站利用率低下问题,C-RAN作为一种基于集中化处理、协作式无线电和实时云计算架构的无线接入网架构,是一种低成本、高性能的解决方案。针对C-RAN网络中的CoMP性能,通过计算无线链路损耗分析了JT下的CoMP的理论增益。针对C-RAN网络规划设计问题,定性分析了CoMP增益与C-RAN网络Cell数的比例关系,最后结合仿真结果给出了合理的网络规划设计建议,且理论证明其能够很好地解决移动运营商所面临的上述挑战。     

Joint power and bandwidth allocation in downlink transmission

We formulate and analyze the problem of optimal downlink scheduling with instantaneous channel and queue size information when both power and bandwidth may be adaptively split among multiple users. We derive optimal solutions of low computational complexity, as well as faster and simpler approximations, to various versions of this problem when the power, rate, and bandwidth allocations to the users can all take continuous values. For this case, we show that the optimal scheme requires transmission to no more than two users during each time slot when users can receive at arbitrary rates, even when the user rate per unit of bandwidth is upper bounded by the best available modulation scheme. Our methods also extend easily to incorporate other intuitive constraints such as upper limits on user rates to improve frame fill efficiency. Simulation results suggest that the simple approximations work nearly as well as the throughput optimal schemes when continuous bandwidth and power partitions are allowed. In practice, the rate and bandwidth assignments to users take discrete values, and we present heuristic methods motivated by the continuous optimum to this discrete case.     

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.     

Adaptive resource allocation for downlink grouped MC-CDMA systems with power and BER constraints

This paper proposes a complete solution to adaptively allocate resource for downlink Multi-Carrier Code Division Multiple Access (MC-CDMA) systems with the power and bit error rate (BER) constraints. Under frequency-selective fading channels, the whole spectrum is divided into several groups and each user is allocated to a group based on its channel state information (CSI). After grouping, the adaptive modulation algorithm assigns the bit loading and allocates the transmission power for each user according to its effective channel response. Simulation results show that the proposed solution can achieve high throughput, guarantee the required BER, and reduce the blocking probability.     

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.     

Uplink–downlink duality with regard to constraints imposed in practice

The uplink–downlink duality is reviewed with regard to constraints imposed on the transmission schemes in practice. In particular, the effects of non-Gaussian signaling, the use of implementable precoding schemes, and the availability of only imperfect channel state information at the central base-station are analyzed and discussed. The sources for violating the uplink–downlink duality in practical schemes are identified, and it is shown under which setting still the same (but not optimum) performance of both transmission directions can be achieved. Besides treating signal-to-interference plus noise ratios, as usually done, the duality is studied with respect to bit error rate, a parameter more relevant in practical applications.     

UL CoMP在LTE智能立体网络中的应用及外场测试结果

文章分析UL CoMP(上行多小区协作)原理及其在智能立体网络中的应用,在此基础上介绍了UL CoMP在爱立信北京LTE试验网中的测试结果。结果表明通过UL CoMP移动终端可实现从低功率RRU上获得最好的上行接收,同时从高功率RRU上获得最好的下行传输,从而解决智能立体网络中上下行功率不均衡的问题,显著改善小区边缘用户体验。     

Solution of the multiuser downlink beamforming problem with individual SINR constraints

We address the problem of joint downlink beamforming in a power-controlled network, where independent data streams are to be transmitted from a multiantenna base station to several decentralized single-antenna terminals. The total transmit power is limited and channel information (possibly statistical) is available at the transmitter. The design goal: jointly adjust the beamformers and transmission powers according to individual SINR requirements. In this context, there are two closely related optimization problems. P1: maximize the jointly achievable SINR margin under a total power constraint. P2: minimize the total transmission power while satisfying a set of SINR constraints. In this paper, both problems are solved within a unified analytical framework. Problem P1 is solved by minimizing the maximal eigenvalue of an extended crosstalk matrix. The solution provides a necessary and sufficient condition for the feasibility of the SINR requirements. Problem P2 is a variation of problem P1. An important step in our analysis is to show that the global optimum of the downlink beamforming problem is equivalently obtained from solving a dual uplink problem, which has an easier-to-handle analytical structure. Then, we make use of the special structure of the extended crosstalk matrix to develop a rapidly converging iterative algorithm. The optimality and global convergence of the algorithm is proven and stopping criteria are given.