MC-NOMA增强型反向散射网络中的谱能效率均衡优化

环境信号的不确定性导致不可预测的谱能机会.传输机会和能源供应的缺乏给反向散射通信网络的多址接入设计带来了极大的挑战.本文针对多载波非正交多址接入(multicarrier non-orthogonal multiple ac-cess,MC-NOMA)增强型反向散射网络,提出了一种分阶段优化算法实现均衡调控下的谱能效率...     

基于公平度和惩罚函数的OFDMA自适应资源分配

针对基于速率自适应准则的正交频分多址自适应资源分配中系统容量和用户公平度的问题,提出了一种采用子载波分配和功率分配两步来解决该问题的新方案。该方案主要通过基于公平度的子载波分配算法和基于惩罚函数的功率分配算法来实现。在子载波分配算法中,当满足公平度约束时就提高系统的容量,否则就提升用户的公平度。而子载波分配后,并不能较好地兼顾系统容量和用户公平度。所以,在功率分配算法中,又基于惩罚函数提出了一种新的功率寻优策略,并且该策略利用基于模拟退火思想的改进人工蜂群算法来实现系统容量和用户公平度的折中。仿真结果表明所提出的方案不仅可以有效地提升系统容量,同时也可以实现给定的公平度约束,进而证明所提方案的有效性。     

Resource allocation with minimum transmit power in multicast OFDM systems

To minimize the total transmit power for multicast service in an orthogonal frequency division multiplexing (OFDM) downlink system, resource allocation algorithms that adaptively allocate subcarriers and bits are proposed. The proposed algorithms select users with good channel conditions for each subcarrier to reduce the transmit power, while guaranteeing each user’s instantaneous minimum rate requirement. The resource allocation problem is first formulated as an integer programming (IP) problem, and then, a full search algorithm that achieves an optimal solution is presented. To reduce the computation load, a suboptimal algorithm is proposed. This suboptimal algorithm decouples the joint resource allocation problem by separating subcarrier and bit allocation. Greedy-like algorithms are employed in both procedures. Simulation results illustrate that the proposed algorithms can significantly reduce the transmit power compared with the conventional multicast approach and the performance of the suboptimal algorithm is close to the optimum.     

改进的子载波比特功率分配算法

针对多用户多输入多输出-正交频分复用(multiple input multiple output-orthogonal frequency divi-sion multiplexing,MIMO-OFDM)系统的自适应资源分配问题,对子载波比特功率两步分配(Two-Steps)和联合分配方法进行了比较,分析了收发天线数目对系统性能的影响.提出了一种改进的子载波比特功率算法,该算法基于两个用户可以同时在一个子载波上发送数据的子载波复用方法,将子载波和比特功率联合分配,对比特重新调整的迭代过程进行了改进.仿真结果表明,该算法在不影响系统误码性能的前提下降低了复杂度.     

基于SC-FDMA的可调公平度动态子载波分配算法

高速无线数据传输利用自适应的资源分配方式以对抗无线传输环境的不利影响。基于单载波频分复用系统提出一种最大平均容量动态子载波分配算法,并在此算法基础上引入公平系数,提出一种公平度可调的动态子载波分配算法,以实现系统分配公平性与总容量性能之间的权衡。仿真结果表明,最大平均容量算法在显著降低算法复杂度的同时,能获得与贪婪算法相近的系统总容量及误码率性能。可调公平度算法通过调整公平系数,能在较大范围内调整信道资源分配的公平度,满足不同传输质量需求,且不增加算法复杂度。     

基于OFDMA的无线协作多播网络资源分配算法

在传统的无线多播传输中,多播组的系统性能受限于多播组内的最差用户的信道质量。为了克服多播组的系统性能受限的问题,将协作传输引入到基于正交频分多址(orthogonal frequency division multiple access,OFDMA)的无线多播网络中,并提出了在总传输速率受限的情况下,最小化总传输功率的动态资源分配算法。为了减少计算复杂度和保障公平性,提出了协作公平子载波分配算法(cooperative fair, CF)和迭代注水功率分配算法。仿真结果显示,在多播组的用户中进行协作传输的系统性能,要远高于采用传统多播直接传输的性能,并且所提算法也在保证系统性能的同时,实现了多播组间良好的公平性。     

基于用户QoS的MIMO/OFDM系统资源分配研究

在多用户、多天线环境下的正交频分复用(OFDM)系统中,提出一个低复杂度的自适应资源分配方案。包括自适应子载波分配、功率分配以及波束成型等。目的就是在保障各用户的服务质量要求(QoS)(即包括传输速率和比特误码率(BER)要求)的同时,最小化总的发射功率。利用随机矩阵和排序统计的理论知识,进行详细的性能分析。理论分析和仿真试验都表明,该方案可以有效地保障用户的QoS,并提高系统的整体性能。最后,仿真结果也验证了理论分析的正确性。     

超密集网络中基于聚类的资源分配方案

超密集网络(ultra-dense network, UDN)中,毫微微基站(femto-cell base station, FBS)的密集和随机部署会导致严重的小区间干扰。为了减轻干扰、保障用户服务质量(quality of service, QoS),提出了一种UDN中基于聚类的资源分配方案。首先,设计了一种基于加权密度的改进K-means聚类算法,将FBS动态划分为不同的簇。然后,以最大化UDN系统吞吐量为目标提出了一种两阶段时频资源分配方案:第一阶段,每个聚类内使用贪婪算法执行时频资源块的分配;第二阶段,利用资源补偿分配算法分配剩余的资源块,在考虑用户公平性的同时保证用户QoS。仿真结果表明,本文提出的资源分配方案能够有效提升系统吞吐量,同时保证用户QoS和公平性。     

AF-OFDM非对称通信双向中继系统能效优化

针对具有非对称通信需求的单中继协同放大转发正交频分复用(amplify forward orthogonal frequency division multiplexing,AF-OFDM)双向中继系统,提出一种中继能效优化策略。在AF-OFDM双向非对称中继通信系统中,子载波有两种工作模式:单向中继传输和双向中继传输。以系统能效为优化目标,构建联合中继传输模式选择、功率分配和比特加载组合优化模型;采用结构近似优化算法,首先固定子载波分配集合,优化单向中继传输和双向中继传输的功率分配,将原优化问题分解为两个子优化问题求解,然后优化子载波分配集合,利用子载波配对形成的线性结构搜索双向中继传输的最佳子载波数,避免穷举搜索造成的大运算量。仿真结果表明,该能效优化策略能有效提高AF-OFDM双向非对称中继通信系统的能量效率。     

Utility function based fair data scheduling algorithm for OFDM wireless network

A system model is formulated as the maximization of a total utility function to achieve fair downlink data scheduling in multiuser orthogonal frequency division multiplexing (OFDM) wireless networks. A dynamic subcarrier allocation algorithm (DSAA) is proposed, to optimize the system model. The subcarrier allocation decision is made by the proposed DSAA according to the maximum value of total utility function with respect to the queue mean waiting time. Simulation results demonstrate that compared to the conventional algorithms, the proposed algorithm has better delay performance and can provide fairness under different loads by using different utility functions.     

Joint power and spectrum allocation algorithm in cognitive radio networks

The spectrum sharing problem between primary and cognitive users is mainly investigated.Since the interference for primary users and the total power for cognitive users are constrained,based on the well-known water-filling theorem,a novel one-user water-filling algorithm is proposed,and then the corresponding simulation results are given to analyze the feasibility and validity.After that this algorithm is used to solve the communication utility optimization problem subject to the power constraints in cognitive radio network.First,through the gain to noise ratio for cognitive users,a subcarrier and power allocation algorithm based on the optimal frequency partition is proposed for two cognitive users.Then the spectrum sharing algorithm is extended to multiuser conditions such that the greedy and parallel algorithms are proposed for spectrum sharing.Theory and simulation analysis show that the subcarrier and power allocation algorithms can not only protect the primary users but also effectively solve the spectrum and power allocation problem for cognitive users.     

Heuristic based data scheduling algorithm for OFDMA wireless network

A system model based on joint layer mechanism is formulated for optimal data scheduling over fixed point-to-point links in OFDMA ad-hoc wireless networks. A distributed scheduling algorithm （DSA） for system model optimization is proposed that combines the randomly chosen subcarrier according to the channel condition of local subcarriers with link power control to limit interference caused by the reuse of subcarrier among links. For the global fairness improvement of algorithms, a global power control scheduling algorithm （GPCSA） based on the proposed DSA is presented and dynamically allocates global power according to difference between average carrier-noise-ratio of selected local links and system link protection ratio. Simulation results demonstrate that the proposed algorithms achieve better efficiency and fairness compared with other existing algorithms.     

一种低复杂度的MIMO-OFDMA下行链路资源分配方案

针对MIMO-OFDMA下行链路系统,考虑在总功率和BER 以及用户数据速率成比例的约束下,以获取整个系统吞吐量极大化为准则,提出一种基于成比例公平性约束的资源分配方案。该方案在子载波分配时,松弛成比例约束条件,使用户数据速率近似地成比例于每个用户分配的子载波数,在功率分配时,推导出一种线性的不需要迭代的低复杂度功率分配方案。仿真和分析表明,整个方案在保证系统吞吐量的前提下,取得了用户间良好的速率公平性,同时又具有较低的计算复杂度。     

Construction of time-frequency codes based on protograph LDPC codes in OFDM communication systems

This paper proposes a scheme to construct timefrequency codes based on protograph low density parity check (LDPC) codes in orthogonal frequency division multiplexing (OFDM) communication systems.This approach synthesizes two techniques:protograph LDPC codes and OFDM.One symbol of encoded information by protograph LDPC codes corresponds to one subcarrier,namely the length of encoded information equals to the number of subcarriers.The design of good protograph LDPC codes with short lengths is given,and the proposed protograph LDPC codes can be of fast encoding,which can reduce the encoding complexity and simplify encoder hardware implementation.The proposed approach provides a higher coding gain in the Rayleigh fading channel.The simulation results in the Rayleigh fading channel show that the bit error rate(BER) performance of the proposed time-frequency codes is as good as random LDPC-OFDM codes and is better than Tanner LDPC-OFDM codes under the condition of different fading coefficients.     

面向OFDM无线中继系统的功率分配算法

针对正交频分复用无线中继系统的绿色通信问题,提出一种低复杂度功率分配算法.首先,采用"放大-转发"中继策略,源节点在中继传输的两阶段都发送相同信息.然后,通过联合优化源节点和中继节点在各子载波上的传输功率,使系统以最小功耗代价满足用户通信服务质量要求.由于该问题是一个复杂的多变量耦合非凸问题,直接求解难度高.对此,综合...     

一种提供QoS保证的公平跨层资源分配方案

提出了一种基于正交频分多址接入（orthogonal frequency division multiple access, OFDMA）系统的跨层资源分配方案。在保证各种业务服务质量（quality of service, QoS）要求的基础上,以获取系统最大吞吐量为目标,兼顾用户之间资源分配的比例公平性。该方案充分考虑了媒体接入控制（media access control, MAC）层各种业务的QoS要求和无线信道的大尺度衰落特性,将MAC层的分组调度与物理层的资源分配进行联合设计,MAC层根据物理层分配给每个用户的时变信道容量进行分组调度,物理层根据MAC层中各用户的队列状态信息为每个用户分配信道资源。仿真结果表明,该方案可以满足多用户各种业务的QoS要求,与采用等功率分配的依赖信道状态的分组调度（channel state dependent packet scheduling, CSDPS）算法相比可以提高系统下行总吞吐量,且较好地改善具有不同路径损耗的用户之间的公平性。     

大规模MIMO系统的智能天线选择与功率分配方法研究

为了满足大规模多输入多输出(multiple input multiple output, MIMO)系统的数据传输需求并降低系统能耗,提出一种基于量子化学反应优化的智能天线选择与功率分配方法。根据大规模MIMO系统不同时段的用户传输需求建立智能天线选择与功率分配模型,推导出其最大能效方程。为有效求解该非线性、多约束的混合优化难题,结合量子计算和化学反应优化机制的优势设计了量子化学反应优化算法,可得到最佳的天线选择与功率分配方案。仿真结果表明,所提的智能天线选择与功率分配方法能实时满足用户的信息传输需求,显著提高系统能效。针对不同的仿真场景,所提方法与现有的智能算法与分配策略相比均可得到最高的系统能效。     

大规模MIMO系统的智能天线选择与功率分配方法研究

为了满足大规模多输入多输出(multiple input multiple output, MIMO)系统的数据传输需求并降低系统能耗,提出一种基于量子化学反应优化的智能天线选择与功率分配方法。根据大规模MIMO系统不同时段的用户传输需求建立智能天线选择与功率分配模型,推导出其最大能效方程。为有效求解该非线性、多约束的混合优化难题,结合量子计算和化学反应优化机制的优势设计了量子化学反应优化算法,可得到最佳的天线选择与功率分配方案。仿真结果表明,所提的智能天线选择与功率分配方法能实时满足用户的信息传输需求,显著提高系统能效。针对不同的仿真场景,所提方法与现有的智能算法与分配策略相比均可得到最高的系统能效。     

毫米波大规模MIMO-NOMA系统中基于动态子连接混合结构的预编码设计

针对毫米波大规模多输入多输出-非正交多址接入(massive multiple input multiple output non-orthogonal multiple access, mMIMO-NOMA)系统硬件成本和功耗过大问题, 基于动态子连接混合结构(dynamically sub-connected hybrid architecture, DSC-HA), 提出一种高效预编码方案。首先,在用户分组的基础上, 基于等效信道增益最大化原则, 利用Kuhn-Munkras算法匹配各NOMA簇用户的信道状态信息, 以实现动态天线分组, 进而完成模拟预编码设计。接着, 利用NOMA簇内强用户的等效信道来实现数字预编码设计, 以减小簇间干扰。最后, 通过优化簇内用户间功率分配来减小簇内用户间干扰。仿真结果表明, 基于DSC-HA的预编码方案不但系统和速率优于基于子连接混合结构的预编码方案, 而且能效明显优于基于全连接混合结构和基于全数字结构的预编码方案。     

Improvement and performance of parallel multilevel fast multipole algorithm

The method of establishing data structures plays an important role in the efficiency of parallel multilevel fast multipole algorithm(PMLFMA).Considering the main complements of multilevel fast multipole algorithm(MLFMA) memory,a new parallelization strategy and a modified data octree construction scheme are proposed to further reduce communication in order to improve parallel efficiency.For far interaction,a new scheme called dynamic memory allocation is developed.To analyze the workload balancing performance of a parallel implementation,the original concept of workload balancing factor is introduced and verified by numerical examples.Numerical results show that the above measures improve the parallel efficiency and are suitable for the analysis of electrical large-scale scattering objects.