基于最小均方误差的多用户MIMO下行预编码

在多输入多输出(MIMO)多用户下行链路中,可联合收发处理和功率分配,从而获得更好的通信性能。提出的多用户MIMO预编码方法分解成两步实现:首先消除用户间的干扰使之等效为多个单用户系统,在此基础上以最小均方误差(MMSE)为准则,进行收发的联合优化和功率分配,从而改善系统的误码率(BER)性能。仿真表明,所提出的方法与现有的一些方法相比,可以获得较大的信噪比(SNR)增益。     

两类多用户MIMO线性预编码的功率分配*

将多用户MIMO线性预编码分为干扰消除和干扰抑制两类,针对干扰消除中的块对角化（block diagonalization,BD）迫零算法,讨论了经典注水功率分配,提出一种信噪比控制功率分配方案。该方案可使系统各子流接收信噪比相同,各个用户的误码性能一致,也可控制用户之间的任意信噪比比例;研究了干扰抑制类预编码的统一功率分配方案,提出一种针对存在干扰系统的适用于相关信道的迭代注水算法。该算法引入经典注水的思想,将干扰和噪声一并考虑。仿真结果表明,该算法在相关信道下使系统和容量获得了明显提高。     

5G超密集异构网络带内无线回传资源分配方案

为实现5G超密集异构网络中无线回传链路和接入链路之间的最优资源分配,研究多用户场景下双层异构网络的联合用户调度和功率分配问题,在队列稳定和无线回传资源有限的情况下,综合考虑用户调度、功率分配和干扰控制等因素,对带内无线回传的最优资源分配问题进行数学建模并求解,基于李雅普诺夫优化理论提出联合用户调度和功率分配的优化算法。将优化问题解耦为网络内各个用户的调度以及宏基站和小基站的功率分配过程,采用MOSEK求解器和二分类方法获得用户调度向量,利用拉格朗日乘子法求解功率分配问题,并通过队列的时刻更新过程实现最优资源分配。仿真结果表明,在多用户场景下,该方案能够有效提升网络总吞吐量以及网络效用,并且毫米波频段的通信性能优于传统蜂窝网络频段。     

多载波系统中自适应比特功率分配算法研究

本文提出了一种多载波系统中自适应功率和比特分配算法。该算法在低信噪比时基于最大化信道容量分配比特,基于最小化误码率分配功率;在高信噪比时采用Fischer算法进行比特功率分配。仿真结果表明,低信噪比时所提算法比Fisher算法性能好,高信噪比时和Fisher算法的性能一样好。因此,文中所提算法比Fisher算法更具有实际应用价值。仿真结果也表明了子载波数对系统性能的影响。     

基于模代数预编码的MIMO室内可见光通信系统

针对基于模代数预编码(THP)的多用户多输入多输出(MIMO)室内可见光通信系统存在误码率高、功率利用率低的问题,提出一种基于格基规约THP的多用户MIMO(MU-MIMO)通信系统。通过改进的格基规约THP对信道矩阵进行优化使其满秩,在此基础上,设计多用户接收信号均衡分配方案。仿真结果表明,在信噪比较高且信道不稳定的情况下,MU-MIMO通信系统具有较强的鲁棒性以及较低的误码率,多用户接收信号均衡分配方案有效解决了THP算法中用户接收信息的公平分配问题。     

基于协作通信技术的无线非再生中继组播网络中的功率最优分配

针对无线非再生中继网络中多播协作通信系统的节点功率最优分配问题,提出了一种新的基于多用户协作分集协议(multi-user diversity-cooperative protocol)的MDPTS(multi-user diversity-cooperative protocol transmission scheme)传输方案.在总功率一定时,利用分集复用增益的权衡对系统的性能进行了分析.在此基础上以系统误帧率最小为目标,提出了发射端和中继器间的功率优化分配方案,在信噪比足够大的条件下,以误帧率下界为目标函数,通过拉格朗日法求得系统的功率分配最优解.仿真结果表明,与采用传统传输方案的网络相比,采用MDPTS传输方案的网络具有更高的分集增益和复用增益上限,因此系统性能也更好.     

一种非理想反馈MIMO-OFDM系统资源分配算法

针对多用户MIMO-OFDM系统资源分配问题,给出了一种基于非理想反馈的自适应子载波分配算法。由于实际系统中往往存在反馈时延和反馈误差,利用置信系数和等价方差模型来表征反馈信道状态信息的质量,以最大化系统和容量为目标,在发射总功率一定并满足误码率约束条件下,将子载波分配给信道增益最好的用户,然后对所有子载波进行注水功率分配。理论分析和仿真结果表明,该算法能够充分利用多用户的分集增益,有效地提高了系统和容量性能。     

认知多中继网络中断性能优化研究

研究了认知多中继网络的中断性能优化方法,提出了认知节点发射功率最大值受限和主用户干扰功率受限条件下的最优功率分配(OPA)方法,优化设计感知时间使认知中继网络的中断性能最优。仿真结果表明,最佳功率分配方案的中断性能优于等功率分配(EPA)方案,且存在最佳的感知时间使认知多中继网络的中断性能最优,在高信噪比区域采用多个认知中继协作传输可有效提高认知无线电网络的中断性能。     

基于部分信道信息反馈的多用户MIMO传输机制研究

在宽带无线通信系统中,多天线技术的实现依赖于多用户MIMO传输机制及信道信息反馈的有效解决.提出一种发送端进行干扰消除的TIE算法及相应的用户选择算法和功率分配算法,并提出一种基于向量量化的部分信道信息反馈机制,可以在多用户环境中提高系统性能并能有效降低信道信息反馈开销.分析了采用部分信道反馈机制的TIE算法的性能,论证了其性能特征.实验结果表明,与其他算法相比TIE算法可以有效地提高系统数据速率,而部分信道反馈机制可以在保持系统数据速率的前提下极大地降低信道反馈信令的开销.     

基于比例公平的多用户MIMO-OFDM系统自适应资源分配算法*

针对传统多用户MIMO-OFDM系统中自适应资源分配算法计算复杂度较高、实时性不强、无法保证用户间公平性等问题,提出了一种低复杂度的自适应子载波、比特及功率分配算法。在子载波分配上,该算法能够在兼顾比例速率约束的前提下使系统发射功率达到最小化;在比特及功率分配上,该算法将非线性优化问题转换为线性优化问题,在保证系统性能的同时显著降低计算量。仿真结果表明,该算法具有良好的性能,能够有效降低计算量,并使系统容量在用户间分配得更加公平和合理。     

Robust multiuser MIMO scheduling algorithms with imperfect CSI

Robust multiuser multiple-input-multiple-output (MIMO) scheduling algorithms are proposed in this paper.With imperfect channel state information (CSI),traditional scheduling algorithms for the multiuser MIMO system based on the zero forcing precoding scheme will lose some performance due to the multi-user interference (MUI).In order to improve the system average throughput,we study the robust multiuser MIMO scheduling problem with imperfect CSI.From the average capacity formula,we derive a robust factor which can transform the robust multiuser MIMO scheduling problem into the traditional one,thus most existing non-robust scheduling algorithms can be robust if this factor is adopted.Simulation results show that compared with the traditional algorithms,the proposed robust algorithms can improve the system average throughput significantly under the CSI error environment.     

Downlink data transmission scheduling algorithms in wireless networks

The problem of downlink data transmission scheduling in wireless networks is studied. It is pointed out that every downlink data transmission scheduling algorithm must have two components to solve the two subproblems of power assignment and transmission scheduling. Two types of downlink data transmission scheduling algorithms are proposed. In the first type, power assignment is performed before transmission scheduling. In the second type, power assignment is performed after transmission scheduling. The performance of two algorithms of the first type which use the equal power allocation method are analyzed. It is shown that both algorithms exhibit excellent worst-case performance and asymptotically optimal average-case performance under the condition that the total transmission power is equally allocated to the channels. In general, both algorithms exhibit excellent average-case performance. It is demonstrated that two algorithms of the second type perform better than the two algorithms of the first type due to the equal time power allocation method. Furthermore, the performance of our algorithms are very close to the optimal and the room for further performance improvement is very limited. It is shown that all the above algorithms can be extended to schedule downlink data transmissions with parallel channels. It is also shown that the simple sequential scheduling algorithm is optimal if the total transmission power is equally allocated to the channels. As an extra contribution, an M/G/1 queueing model for the FCFS queueing discipline is established, and it is observed that increasing the number of channels has more impact on the reduction of the average response time than increasing the total transmission power.     

无线网络信道队列状态感知资源调度算法

资源调度时实现资源的有效利用、保证业务的QoS发挥着重要作用.对跨层资源调度问题的研究状况进行了概述.(1)根据所采用的技术体制和约束类型,介绍了单载波系统和OFDM系统的多用户机会调度问题和算法,分析了单一类型和多种类型资源共享约束下的机会调度算法;(2)分别从队列调度、子栽波分配和功率控制3个方面,对基于队列和信道状态信息的资源调度算法进行了分析和比较;最后指出了需要进一步研究的问题.     

Pewss: A platform of extensible workflow simulation service for workflow scheduling research

This paper presents a Platform of Extensible Workflow Simulation Service (Pewss), which we have developed to provide a cloud service for aiding research work in workflow scheduling. The simulation has been a major tool for performance evaluation and comparison in workflow scheduling research. However, researchers usually have to develop their own simulation programs with limited functionality, simply outputting summarized performance results. Pewss has been developed for easing and improving current practices in conducting performance simulations during studying of existing workflow scheduling algorithms or designing of new scheduling algorithms. Pewss has been designed based on the Software as a Service (SaaS) model, adopting a multiuser Web‐based client/server architecture. Conducting simulation experiments on Pewss, researchers simply have to implement the scheduling algorithm under study instead of a whole simulation environment, allowing them to focus on their research work without spending unnecessary efforts on the simulation implementation details. Pewss provides the visualization of a workflow execution schedule based on simulation results, offering a convenient way for researchers to gain an insight into the effectiveness, characteristics, and performance bottleneck of scheduling algorithms. As a multiuser environment, Pewss also provides functionality for researchers to facilitate comparative performance analysis and collaborative research works effectively. Pewss has been used in our research work on task‐parallel workflow scheduling and has been planned to be extended to support other types of workflow scheduling research problems, eg, mixed‐parallel workflows.     

Power and performance management for parallel computations in clouds and data centers

We address scheduling independent and precedence constrained parallel tasks on multiple homogeneous processors in a data center with dynamically variable voltage and speed as combinatorial optimization problems. We consider the problem of minimizing schedule length with energy consumption constraint and the problem of minimizing energy consumption with schedule length constraint on multiple processors. Our approach is to use level-by-level scheduling algorithms to deal with precedence constraints. We use a simple system partitioning and processor allocation scheme, which always schedules as many parallel tasks as possible for simultaneous execution. We use two heuristic algorithms for scheduling independent parallel tasks in the same level, i.e., SIMPLE and GREEDY. We adopt a two-level energy/time/power allocation scheme, namely, optimal energy/time allocation among levels of tasks and equal power supply to tasks in the same level. Our approach results in significant performance improvement compared with previous algorithms in scheduling independent and precedence constrained parallel tasks.     

Multiuser detection algorithm based on belief propagation in multiple-input multiple-output systems

In MIMO (multiple-input, multiple-output) systems, signals from differenttransmitting antennas interfere at each receiving antenna and multiuser detection (MUD)algorithms may be adopted to improve the system performance. This paper proposes anovel multiuser detection algorithm in MIMO systems based on the idea of "beliefpropagation" which has achieved great accomplishment in decoding of low-densityparity-check codes. The proposed algorithm has a low computation complexityproportional to the square of transmitting/receiving antenna number. Simulation resultsshow that under low signal-to-noise ratio (SNR) circumstances, the proposed algorithmoutperforms the traditional linear minimum mean square error (MMSE) detector while itencounters a "floor' of bit error rate under high SNR circumstances. So the proposedalgorithm is applicable to MIMO systems with channel coding and decoding. Although inthis paper the proposed algorithm is derived in MIMO systems, obviously it can be appliedto ordinary code-division m     

并行任务图的优化调度算法

科学与工程计算中的很多复杂应用问题需要使用科学工作流技术,超算领域中的科学工作流常以并行任务图建模,并行任务图的有效调度对应用的高效执行有重要意义。给出了资源限制条件下并行任务图的调度模型;针对Fork-Join类并行任务图给出了若干最优化调度结论;针对一般并行任务图提出了一种新的调度算法,该算法考虑了数据通信开销对资源分配和调度性能的影响,并对已有的CPA算法在特定情况下进行了改进。通过实验与常用的CPR和CPA算法做比较,验证了提出的新算法能够获得很好的调度效果。本文提出的调度算法和得到的最优调度结论对工作流应用系统的高性能调度功能开发具有借鉴意义。     

基于任务分配与调度的GSAT算法求解3-SAT问题

基于不同分配策略的云计算任务调度以及任务分配与调度的主要目的,提出了一种新的算法—求解3-SAT问题的基于任务分配与调度的GSAT算法。该算法将3-SAT问题中的每一个变量形成一个任务,在GSAT算法的基础上,引入任务分配与调度指导贪心搜索;同时,在保留原有贪心搜索的前提下,根据任务分配与调度的思想和3-SAT问题的特点,设计了两种新的策略—分配策略和调度策略共同完成整个贪心搜索过程。以标准的SATLAB库中变量个数从 20～250的3 700个不同规模的标准Uniform Random 3-SAT 问题对新的算法的性能进行了合理的测试,并与高效和普通性能改进的GSAT算法的结果作了比较,结果表明,该算法具有更高的成功率和更少的翻转次数。     

A study of power allocation in multi-MRN aided multiuser networks

It is promising that mobile relay nodes (MRNs), i.e., relays mounted on top of transportation vehicles, are deployed in future mobile communication systems in order to improve system performance. In this paper a multi-MRN aided multiuser system is studied. The system performance under direct transmission mode and MRN assisted transmission mode are compared with variable parameter of vehicle penetration loss (VPL). The mobile users are separated into two categories in which the direct transmission mode and the MRN assisted transmission mode are selected to transmit in downlink, respectively. A novel power allocation algorithm is proposed to increase the average system capacity under the constraint of total transmit power. The different power allocation schemes are applied for users in two categories to improve the system performance. It is demonstrated by simulation results that the proposed algorithm outperforms the average power allocation algorithm.