支持优先级与公平策略的队列规程

首先介绍了队列调度算法在流量控制中的关键地位,然后讨论了现有队列调度算法,如基于优先级的调度算法、轮询调度算法与公平队列调度算法,最后提出了一种新的队列规程,该队列规程融合了优先级调度算法与DRR调度算法。在网络正常情况下,不同业务流公平地共享网络带宽,在网络出现拥塞的情况下,高优先级业务流能够抢占带宽,保证其较低的丢包率,并能够实现两种调度算法的快速切换。     

基于区间二型模糊神经网络的垂直切换算法

在超密集异构无线网络中,针对传统垂直切换算法无法同时描述网络状态的模糊性和随机性,导致网络性能得不到有效提升的问题,提出一种基于区间二型模糊神经网络的垂直切换算法.重构了两阶段判决算法:在网络预筛选阶段,定义了历史接入率,结合当前候选网络集的数目设置阈值.根据接收信号强度和剩余可用带宽,对用户接收范围内的所有网络进行初步筛选;再在垂直切换判决阶段,将剩余候选网络的时延,丢包率以及误码率作为区间二型模糊神经网络的输入,利用前馈神经网络的结构完成模糊逻辑推理,经训练之后计算得到输出判决值,从而选择最佳接入网络.实验结果表明,该算法能在保证时间开销较低的同时,有效降低切换决策的错误概率,减少切换失败和切换次数,提升网络总吞吐量.     

基于EPON承载IPTV业务的加权调度算法研究

针对IPTV业务数据量较大,容易产生数据包丢失和延时,设计了一种调度算法.该算法根据IPTV节目订制用户数,采用加权轮询调度机制(WRR),合理地分配IPTV下行数据流的带宽,从而有效地减少了组播数据包的丢失和延时,提高了IPTV的服务质量.通过OPNET仿真得到结果,WRR机制比没有加权重的轮询调度机制(RR)丢包率降低了86.7％,平均队列时延减少了23.4％.     

IP语音包的自适应编码和封装算法的研究

IP电话与传统电话相比语音质量较差，其中最主要的原因是因特网的带宽变化较大，导致丢包率较大。该文根据因特网带宽变化的特点提出了1种应用在IP电话网关中的语音自适应编码与封装策略，采用该策略的编码器能根据网络的带宽变化动态调节语音编码速率和语音包封装大小。据此，本文提出了4种算法：一种基于RTP协议语音包丢失率的计算算法、变速率编码算法，不同长度IP语音包的封装算法和根据丢包率来调整编码速率和封装的自适应算法。     

认知无线网络动态权值调整的频谱切换策略

认知无线网络中,次用户的目标信道选择受次用户传输功率、信道衰落因子、信道带宽、信道可用率等因素影响。针对基于多属性判决的频谱切换没有充分考虑各因素的重要程度和动态变化问题,本文提出了基于动态权值调整的频谱切换策略。根据主观经验和网络环境变化动态调整权值,采用多属性简单加权法计算各信道目标函数值,根据目标函数值降序排列结果选择切换的目标信道。仿真结果表明,本文所提出的算法能够减少次用户的切换次数,提高有效数据传输速率。      

基于控制分组收集的数据信道调度算法

在OBS网络中,核心节点的调度算法是影响网络交换性能的重要因素.如何有效地对数据突发(Data Burst)分组进行合理调度,提高信道利用率,减少丢包率是关键问题所在.在讨论了两种数据信道调度算法的基础上提出了一种BHP收集调度算法,该算法在一个收集周期内对到达的多个BHP所对应的突发数据进行集中调度,从而达到合理调度.仿真结果表明BHP收集调度算法比其他两种算法的突发丢失率性能都要好.     

基于可靠次用户信息的协作频谱感知算法研究

对认知无线电系统最基本要求之一就是次用户必须有能力以高的精确率来确定主用户是否存在。而以前对认知无线电频谱感知的研究表明:在实际认知网络中次用户之间的相互协作可以提高其频谱检测性能。然而,对于协作频谱感知而言,随着协作次用户数目的增加,势必会增大用于传输本地检测结果到融合中心的专用控制信道带宽,从而增加系统开销。该文在控制信道带宽有限的约束条件下,提出一种通过考虑可靠次用户信息的协作频谱感知算法来进一步改善频谱检测的性能。该算法的基本思想:只有具有可靠的本地检测结果的次用户才发送自己的检测结果到融合中心,否则,该次用户不发送任何信息。同时,对提出的该算法在理论上进行了推导,通过仿真结果表明:在控制信道带宽受限的约束下,相比于传统的或门协作频谱感知算法,提出的算法能够大大改善对主用户的检测性能。     

基于粒子群优化算法的数据中心网络流量调度策略

为解决当前数据中心网络存在链路负载不均衡及带宽资源浪费问题,提出了一种基于粒子群优化算法的流量调度策略.该策略结合软件定义网络控制器可获取全局网络拓扑信息的特性,依据当前链路带宽资源状况及网络流量的带宽需求建立目标函数.首先,根据流的源地址和目的地址找出最短路径集,通过定义粒子聚合度判断算法是否有陷入局部最优的趋势;然后,结合约束条件与目标函数,利用优化的粒子群算法从最短路径集中找出网络流量的最佳调度路径.实验结果表明,相比于其他算法,该算法有效地提高了网络平均吞吐量,获取了较低的丢包率,从而减轻了带宽资源的浪费,更好地实现了网络的负载均衡.     

OBS网络中的主动拥塞控制策略研究及性能分析

根据光突发交换(Optical Burst Switching--OBS)网络的结构和特点,分析了其核心节点在数据信道调度发生拥塞时拥塞控制策略的缺陷,提出了OBS网络中一种主动拥塞控制策略(ACC),详细讨论了该策略的具体实现过程.通过仿真验证,在OBS网络中采用该算法能减少突发数据包的丢包率,从而达到改善整个OBS网络性能的目的.     

一种新的语音流队列管理调度机制

本文提出一种新的语音流队列管理调度机制,结合随机早期探测(RED)和主动丢包调度算法实现因特网语音流的队列管理和调度.采用仿真方法分析了新机制的性能特征,并与RED做了性能对比.当网络拥塞时,该算法可有效改善包转发的性能.语音质量测试表明新机制是可行的和有效的.     

PSHO-HF-PM: An Efficient Proactive Spectrum Handover Mechanism in Cognitive Radio Networks

In the paper, we develop an efficient proactive spectrum handover mechanism by using packet scheduling algorithm, called PSHO-HF-PM, to reduce unusable channel. It effectively integrates several mechanisms (hole filling and packet migration) to reduce the bandwidth fragment and support QoS. Its basic idea is in that a new packet is scheduled by migrating some packets to other channels if none of holes in any channels can accommodate it; otherwise repeating the above processes after random waiting time. Meanwhile under an effective data structure, such as the balanced binary search tree, its computational complexity will be \(O(2n\log n)\) at most. In the proposed packet scheduling algorithm, packet migration plays a key role in the improvement of bandwidth efficiency and QoS. We also evaluate the performance of total service time for proactive spectrum handover mechanism based on a Preemptive Resume Priority M/G/1 queuing network model. The performance analysis and simulation results show that it performs much better than other proactive and reactive handover mechanism in collision rate, total service time, packet loss probability and bandwidth fragment ratio.     

TD-LTE集群通信系统中基于小区筛选和AHP的切换算法研究

为了提高TD-LTE集群通信系统中用户的切换成功率以及降低阻塞率,文章根据TD-LTE及集群通信的特点,提出一种基于小区筛选(Filtration)机制结合层次分析法(Analytic Hierarchy Process)的切换算法(FAHP)。该算法在利用筛选机制保证目标小区满足通信需求的情况下,结合层次分析法选择出合理的目标小区。仿真分析结果表明,与传统的切换算法相比,该算法能有效提高用户的切换成功率,降低系统的阻塞率。     

基于业务请求数据包长度的机会频谱接入算法

针对非时隙主用户网络,研究了单个次用户在周期性感知框架下的机会频谱接入问题。通过建立次用户信道感知和接入模型,提出了一种基于次用户请求业务数据包长度的机会频谱接入算法。该算法根据每个时隙分配给次用户业务数据包长度,自适应调整机会频谱接入策略。仿真结果表明,所提算法能够在干扰水平要求较高情况下,提高次用户平均有效传输吞吐量的同时,实现有效吞吐量与碰撞概率的折中;同时当外部环境发生变化时算法具有较强的鲁棒性。     

Analysis and performance evaluation of an efficient handover algorithm for cognitive HetNets

Cognitive heterogeneous network is a promising technology to meet the requirements of future wireless networks in cost and energy efficiency. By using vertical handover (VHO) between different network tiers, such as macro and femto, the traffic congestion can be potentially alleviated, and the spectral efficiency is significantly increased. However, performing VHO for a cognitive handover user (CHU) and simultaneously guaranteeing the quality of service of the primary user (PU) is the most challenging issue in such a network. This paper proposes an efficient VHO strategy in a cognitive heterogeneous network, which considers both adaptive average received signal and spectrum availability, namely, average received signal and spectrum availability. To analyse the performance of the proposed average received signal and spectrum availability algorithm, several metrics are investigated. First, the assignment probability of a CHU from a macro base station to a femto base station is evaluated and simplified in a closed‐form expression. Then, the outage probability of a CHU and collision probability of the PU are theoretically investigated for the proposed algorithm and are compared with 2 well‐known algorithms, the modified received signal strength–α and the received signal strength and wireless transmission loss. We also introduce a new performance metric, referred to as figure of merit, which jointly considers the assignment and outage probability of a CHU, collision probability of a PU, and the number of unnecessary handovers of a CHU. Figure of merit effectively shows the superiority of the proposed handover algorithm to conventional ones.     

一种多属性决策的异构网络选择算法

针对异构网络融合环境下的网络选择不能仅依靠物理信号强度的特点,利用多属性决策理论提出了一种异构网络选择算法。该算法考虑业务要求、用户喜好以及网络差异,通过层次分析法和熵值法确定网络属性的权重,并由此计算可得网络性能,选出最优网络。仿真结果表明,此算法可以准确选择接入网络,并当用户在网络边缘做兵乓运动时有效减小切换次数,降低丢包率。     

Self‐organising cluster‐based cooperative load balancing in OFDMA cellular networks

Mobility load balancing (MLB) redistributes the traffic load across the networks to improve the spectrum utilisation. This paper proposes a self‐organising cluster‐based cooperative load balancing scheme to overcome the problems faced by MLB. The proposed scheme is composed of a cell clustering stage and a cooperative traffic shifting stage. In the cell clustering stage, a user‐vote model is proposed to address the virtual partner problem. In the cooperative traffic shifting stage, both inter‐cluster and intra‐cluster cooperations are developed. A relative load response model is designed as the inter‐cluster cooperation mechanism to mitigate the aggravating load problem. Within each cluster, a traffic offloading optimisation algorithm is designed to reduce the hot‐spot cell's load and also to minimise its partners’ average call blocking probability. Simulation results show that the user‐vote‐assisted clustering algorithm can select two suitable partners to effectively reduce call blocking probability and decrease the number of handover offset adjustments. The relative load response model can address public partner being heavily loaded through cooperation between clusters. The effectiveness of the traffic offloading optimisation algorithm is both mathematically proven and validated by simulation. Results show that the performance of the proposed cluster‐based cooperative load balancing scheme outperforms the conventional MLB. Copyright © 2013 John Wiley & Sons, Ltd.     

高效公平的EPON TCP性能调节机制

 提出了一个基于效用的EPON公平性指标算法.通过建立一个基于ACK特征包的ACK压缩和解压缩机制,消除了上游ONU的ACK对下游ONU下行数据流的影响,在保证ONU之间的公平性的同时,提高了带宽的使用效率.通过建立一个效用分类器,在维护了优先级机制扩展性的前提下,提高了并发的同业务类业务流之间的公平性.通过建立一个时延公平调度机制,在保证带宽的使用率前提下,保证了ONU的业务类之间的时延公平性.仿真结果很好验证了本机制的优点.     

Interference and Resource management strategy for handover in femtocells

Interference in femtocells due to neighboring femtocells and macrocells is a major issue of two-tier networks. Handover should be made to reduce interference, if and only if, when resources are available. Otherwise, it will further degrade network performance. Resource management should be made in an efficient manner that will not cause interference between macrocells and neighboring femtocells. Since distance between macro base station (MBS) and femto access point (FAP) is short, therefore, it is very hard to sustain low handover probability when macro user moves from MBS to FAP. We proposed handover algorithm for uplink co-channel interference mitigation that will make handover decision on the basis of time-to-stay and signal to interference plus noise ratio thresholds along with efficient resource management mechanism to reduce number of handovers and also resolve interference problem.

     

P2P流媒体中的多发送端选择算法

 在多对单P2P流模式下,如何选择多个发送端,并为其最优地分配发送速率和数据是一个难题.为此,提出了一种新的多发送端选择和最优速率及数据分配算法(MSRDA).首先把待解决的问题模型化为线性最优化问题,然后给出了求解最优化问题的算法.不同于已有的算法只按链路的丢包率来选择发送端,MSRDA根据到各发送端链路的丢包率与链路的可用带宽比升序排序来选择多发送端,并最优地分配发送速率和数据.理论分析和仿真实验结果表明:在不同的网络条件下MSRDA能有效地减少聚合带宽的丢包率,并具有自适应性,优于现有同类算法.     

An efficient handover decision in heterogeneous LTE-A networks under the assistance of users’ profile

The increasing demand for wireless networks calls for the use of heterogeneous networks in order to fulfil user requirements. Mobility management is considered one of the important entities for such networks. The handover is one of the main features of mobility management in regard to the long term evolution advanced (LTE-A) system, which depends purely on the hard handover. The vertical handover decision is a significant component of heterogeneous networks; it authorizes the user equipment (UE) to migrate between the two-tier LTE-A wireless networks. Femtocell, or also known as the home-evolved nodeB (HeNB), has turned out to be a promising arrangement, as it enhances the coverage and the quality of service for users on one hand, and offloads the eNB on the other hand. In this paper, an advanced handover technique is presented, in terms of adding new and critical parameters, as well as combining between the present UE trajectory and the HeNB cell location. A polynomial function is used to predict the future UE position while the cosine function along with distance are used for the selection of an appropriate target cell. The proposed algorithm is evaluated and then compared to the present work based on the handover number, number of signaling measurements, packet delay ratio, packet loss ratio, and system throughput. Simulation of the LTE-Sim demonstrates that the proposed algorithm significantly reduces the number of handovers, the transmission measurement number, the packet delay ratio, and the packet loss ratio and increases system throughput.