A virtual delay queue-based backpressure scheduling for multi-cell cellular edge computing systems

To further improve delay performance in multi-cell cellular edge computing systems,a new delay-driven joint communication and computing resource BP(backpressure)scheduling algorithm is proposed.Firstly,the mathematical models of the communication delay and computing delay in multi-cell cellular edge computing systems are established and expressed as virtual delay queues.Then,based on the virtual delay models,a novel joint wireless subcarrier and virtual machine resource scheduling algorithm is proposed to stabilize the virtual delay queues in the framework of the BP scheduling principle.Finally,the delay performance of the proposed virtual queue-based BP scheduling algorithm is evaluated via simulation experiments and compared with the traditional queue length-based BP scheduling algorithm.Results show that under the considered simulation parameters,the total delay of the proposed BP scheduling algorithm is always lower than that of the traditional queue length-based BP scheduling algorithm.The percentage of the reduced total delay can be as high as 51.29%when the computing resources are heterogeneously configured.Therefore,compared with the traditional queue length-based BP scheduling algorithms,the proposed virtual delay queue-based BP scheduling algorithm can further reduce delay in multi-cell cellular edge computing systems.

Cross-Layer Adaptive Resource Allocation Algorithm with Diverse QoS Requirements for Single-Cell OFDMA Systems

The orthogonal frequency division multiple access( OFDMA) based communication system has been considered as the main trend of next-Generation communication system. But the existing resource allocation algorithm designed for such system is always with high complexity thus hard to be realized. To solve such problem with the constraints of spectrum efficiency and buffer state,a novel cross-layer resource allocation algorithm( RAA) is proposed in this paper. The goal of our RAA is to maximize the system throughput while satisfying several practical constraints,such as fairness among services,head of line( Ho L) delay and diverse quality of service( Qo S) requirements. Due to these constraints,finding the optimal solution becomes a NPhard problem. Therefore in this paper a novel method to solve such problem with acceptable complexity is proposed within following steps: firstly,based on the link state we formulate the ideal subchannel allocation strategy as a convex optimization problem,which can be efficiently solved by our proposed lagrange multiplier technique subchannel allocation( LMTSA) algorithm; secondly,according to the obtained channel allocation matrix,a power allocation algorithm based on the water-filling power allocation( WPA) idea is deployed to get the optimal power allocation matrix combining with adaptive modulation and coding( AMC); finally,through a greedy algorithm,the ultimate subchannel and power allocation matrix can be obtained based on iterative method. The simulation results illustrate that we can achieve the higher throughput and better Qo S performance than the widely-used maximum throughput( MT) algorithm and round robin( RR) algorithm.

ICI Management for Efficient Radio Resource Allocation in Multi-Cell OFDMA Networks

Two Inter-cell Interference (ICI) management algorithms: Primary Interference Balancing (PIB) algorithm and Interfering Bits Loading Avoidance (IBLA) algorithm are proposed for canceling the ICI effects which the existing efficient radio resource allocation algorithms do not consider. The efficient radio resource allocation algorithm, i.e., Pre-assignment and Reassignment (PR) algorithm, obtains the lowest complexity and achieves good throughput performance in single cell OFDMA system. However, in multi-cell multi-sector OFDMA networks, PR algorithm is not applicable because it does not take ICI into consideration. The proposed PIB algorithm balances the number of loading bits for the desired User Equipment (UE) and the major interfering UE, as well as optimizes the SINR performance; meanwhile, IBLA avoids loading certain number of interfering bits which would make SINR unqualified. Simulations confirm the ICI management effectiveness and feasibility of both the proposals.

Capacity Calculation and Sub-Optimal Power Allocation Scheme for OFDM-Based Systems

For emerging cellular wireless systems, the mitigation of inter-cell interference is the key to achieve a high capacity and good user experience. This paper is devoted to the performance analysis of interference mitigation techniques for the downlink in an orthogonal frequency division multiple access (OFDMA) network, with a focus on the Long Term Evolution-Advanced (LTE-A) standard. Here we have derived a general closed-form equation of system capacity taking multiple cells into consideration and then we have investigated a coordination technique for interference mitigation. For the given interference constraint, how power should be transmitted into each OFDM sub-carrier for prevailing channel condition such that the total transmission rate of the base station can be maximized.

Congestion Relief in Downlink OFDMA Cellular System Using Inter-Cell Relay

This paper proposes the concept of inter-cell relay for downlink orthogonal frequency division multiple access(OFDMA) cellular systems, which uses multi-hop to relay calls from overloaded cells to light-load neighboring cells. It is shown that when using inter-cell relay, the number of calls in the congestion cell can be significantly increased. The congestion cell is divided into two parts. One is called non-relay area(NRA), in which a call directly communicates with the base station(BS) of a congested cell. The other is called relay area(RA), in which a call communicates with the BS of a neighboring cell through a relay station(RS). The two parts have different user-call densities. By adjusting the densities of two parts, we will maximize the number of supported calls inside a congested cell. The results show the benefits gained from inter-cell relay in congestion relief, which can reduce cell congestion by fully utilizing the available resources in the neighboring cells.

A Resource Allocation Algorithm of Physical-Layer Security for OFDMA System under Non-ideal Condition

In this paper, a resource allocation scheme based on physical layer security under non-ideal condition for OFDMA system is introduced. Firstly, the program uses the information security constructing an OFDMA system Wiretap Channel Model under non-ideal condition. Based on this model, arti?cial noise is generated for secure communications combatting passive multiple eavesdroppers. In order to maximize the average secrecy outage capacity without channel state information of eavesdroppers, we use dual decomposition method to implement subcarriers and power allocation in joint optimization. Simulation results show that the average secrecy outage capacity can achieve 7.81 bit/s/Hz while secrecy outage probability is 0.05 with 50 dB mtransmitpower and 64 sub-carrier for 8 authorized users.

大规模MIMO OFDMA下行系统能效资源分配算法

针对大规模多输入多输出(MIMO)正交频分多址(OFDMA)下行移动通信系统,提出了一种基于能效最优的资源分配算法。所提算法在采用迫零(ZF)预编码的情况下,以最大化系统能效的下界为准则,同时考虑每个用户的最低速率要求,通过调整带宽分配、功率分配和基站天线数分配来优化能效函数。首先根据优化条件提出了一种迭代算法确定每个用户的带宽分配,然后利用分数规划的性质并采用凸优化方法,通过联合调整基站端的发射天线数和用户的发射功率来优化能效函数。仿真结果表明,所提算法在较少迭代次数的同时能够取得较好的系统能效性能和吞吐量性能。

基于非合作博弈论的多小区OFDMA系统动态资源分配算法研究

该文采用非合作博弈论的方法研究了多小区OFDMA系统中的动态资源分配问题,首先将各基站的发射功率平均分配给各子载波,然后由所有小区在每个子载波上独立地进行资源分配博弈,给出了用户调度与功率分配联合博弈框架。为了进一步简化,将用户调度和资源分配分开完成,通过将信道增益引入到定价函数中,提出了一种新的定价机制,建立了用户确定时的非合作功率分配博弈模型,分析了其纳什均衡的存在性和唯一性,并设计了具体的博弈算法。仿真结果表明,所提算法在保证吞吐量性能的同时,进一步提升了系统的公平性。

比例速率约束下OFDMA系统近似最优的资源分配算法

中继协作OFDMA系统以及非中继OFDMA系统,在比例速率公平性约束下的无线资源分配问题,是含非线性等式约束的混合离散型优化问题,很难得到满足实时性要求的近似最优算法。该文分别基于这两种系统在速率公平性约束下的等价优化模型,提出拉格朗日松弛的联合优化算法。算法的关键在于OFDMA系统的渐进强对偶性,这个性质使得多项式时间算法的设计成为可能。该文算法的复杂度与系统载波数目成线性关系;仿真结果表明,算法的性能极好地逼近最优分配方案性能。

下行多用户MIMO-OFDMA/SDMA系统动态资源分配

该文对下行多用户MIMO-OFDMA/SDMA系统动态资源分配算法进行了研究,在满足各种约束条件的前提下,以最大化系统吞吐量为目标建立了相应的优化模型。由于最优解难以获得,将整个优化过程分两步完成,第1步定义了一个用于度量配置多根天线的用户空间兼容性的指标,并根据该指标提出了相应的调度算法;第2步提出了两种次优的资源分配算法。仿真结果表明,所提算法优于传统的随机调度算法,与"功率复用"策略结合时,所提算法的性能接近于基于用户选择的最优分配算法的性能。

下行SDM/OFDMA系统中基于效用函数的多用户调度算法

该文研究了空分复用/正交频分多址(SDM/OFDMA)无线通信系统中的多用户调度问题,针对该系统的空时频三维调度特点,提出一种基于效用函数的多用户调度算法。该算法利用空间多用户分集获得增益,同时兼顾系统的整体效率和用户的个体效用。通过计算机仿真验证了算法具有和穷举搜索算法相近的性能,但算法复杂度大大降低。

多小区OFDMA解码转发中继通信系统的分布式资源分配算法

现有的多小区OFDMA中继通信系统资源分配的研究主要集中在单个小区的场景下,而不考虑由相邻小区引起的共信道干扰的影响。然而,实际系统中更高的频率复用因子和较小的小区半径,会导致严重的小区间干扰。该文考虑了多小区OFDMA解码转发中继通信系统的资源分配,它是一个混合离散型优化问题,即使在单小区场景下也是NP-hard难解的。由于全局最优求解的复杂性,该文提出一种分布式的次优的资源分配算法。算法分成两步:首先基于较低的信道反馈系统开销,分配子载波以满足用户的QoS要求;然后,将功率控制问题进一步简化并分解为多个凸优化的子问题,由椭球算法不断收敛的对偶变量迭代调整各个子问题的最优求解。仿真结果表明,与参考算法相比,所提算法的系统容量和边缘用户的吞吐量性能都有很大的提升。

放大-转发OFDMA中继系统多业务资源分配方案

针对独立功率限制、放大-转发OFDMA中继系统的多业务资源分配问题,提出一种在满足实时用户要求前提下,非实时用户数据速率最大化的资源分配方案.根据业务的不同将问题分解为实时和非实时用户的资源分配两个子问题.对于实时用户的资源分配,利用Lagrange方法计算.对于非实时用户的资源分配,每个子载波分配给信道条件最好的用广,针对功率分配提出两步功率分配方法.首先按照总功率约束进行初始功率分配,然后对各子载波的功率进行调整以满足独立功率约束.对于子载波分配提出一种低复杂度的子载波集合分配算法.仿真结果表明,该方案在满足多业务用户要求的同时使系统性能得到优化,且计算复杂度低.

多小区OFDMA系统基于罚函数-SA的资源分配算法

在多小区OFDMA系统中,基于集中式资源管理,考虑本小区对其它小区的干扰情况,对各个小区的子载波和功率分配进行调整,从而达到最小化总功率的目的。基于离散功率取值,提出了一个资源分配组合优化问题模型。为了进一步降低模型复杂度,采用罚函数的方法简化问题模型,用改进的模拟退火算法进行求解。理论分析和仿真结果表明,与A.Abrardo提出的多分配算法相比,所提出的算法能够有效降低算法复杂度,且能够获得更好的吞吐量。

基于FDD-OFDMA系统的多用户下行传输跨层优化

该文针对FDD-OFDMA移动通信下行系统受限干扰的问题,提出了一种资源调度跨层设计方法。所提方法在满足目标误包率的前提下,以最大化系统goodput(发射端成功发射的比特率)为准则建立优化模型,能在发射端完全不知道信道状态信息(CSI)的情况下,利用反馈的确认/否定确认(ACK/NAK)信息实现用户调度以及速率分配的优化。仿真结果表明,所提算法在较低复杂度前提下获得很接近发射端完全已知信道状态信息的系统goodput。

组播/单播OFDMA系统中资源分配算法研究

本文研究了组播/单播OFDMA系统中的无线资源分配,为了在满足组播速率需求的条件下最大化单播用户的总速率的优化目标,提出两种资源分配算法。分别采用代价函数和适度度量作为依据为组播用户选择子载波,剩余资源按照最大吞吐量准则分配给单播用户。仿真表明,两种算法均能够满足组播速率需求,且获得的单播用户的总速率接近理论最大值。

低复杂度的OFDMA系统调度与资源分配算法

针对多用户多业务OFDMA系统存在的缺陷与不足,提出了一种低复杂度的分组调度与资源分配算法.该算法考虑队列状态、QoS要求、信道情况和业务优先级等信息,分别定义了实时轮询服务、非实时轮询服务和尽力而为服务的效用函数,算法在满足各种业务延时、传输速率和丢包率约束条件下,通过最大化非实时业务总吞吐量实现调度和资源分配.仿真结果表明,与已有算法相比,该算法在非实时业务总吞吐量下降不大的情况下,在性能和复杂度之间取得了较好的折中.

OFDMA上行系统中基于随机集理论的多用户信道估计

针对正交频分多址(OFDMA)上行系统,提出一种基于随机集理论的导频辅助多用户信道估计算法。该算法利用有限随机集合来建模和表示OFDMA上行系统中的用户状态、各用户对应的多径信道状态以及信道冲激响应等未知量,采用贝叶斯滤波理论来描述多用户信道估计问题,通过使用Rao-Blackwellized粒子滤波算法,实现了活动用户数和信道多径数动态变化情况下的多用户时变信道估计。计算机仿真结果证明了该算法的有效性。

中继OFDMA系统用户公平性的资源分配算法的研究

在OFDMA解码—转发中继系统中,为了公平地进行资源分配,提出了在两个用户模型下,在保证每个用户最小速率需求的前提下,先按照用户预定速率比进行子载波分配,再根据实际速率比对用户的子载波进行调整的分配算法,最后使整个系统的吞吐量达到最大。提出了三种方案。方案一通过对Lagrange对偶函数问题的求解,根据所得代价函数值的大小对用户的子载波做重新调整。这样不仅考虑到了公平性,也减少了用户的速率损失。方案二、方案三分别从子载波端和用户端出发考虑子载波的分配问题,且从不同的分配角度分析了公平性问题。研究结果表明,三种方案获得的公平性均有所提高。

多小区OFDMA系统中分数频率复用方法的优化分析

在以OFDMA为基本多址方式的第四代移动通信系统中,频率复用作为提高系统性能的有效方法受到了广泛的关注,特别是分数频率复用和软频率复用。然而,如何进一步优化基于这些频率复用方法的OFDMA系统还有待研究。本文分析了多小区OFDMA系统负载和频率集合分配比例对小区总吞吐量和小区边缘用户数据速率的影响。同时,给出了在保证小区边缘用户服务质量的条件下,使小区总吞吐量最优的小区中心频率分配比例,并用仿真进行验证。仿真结果还表明了,随着分配比例的增大,小区总吞吐量先增大后减小。