一种新的基于GPON的动态带宽分配算法

为了实现吉比特无源光网络(GPON)带宽分配的公平性,降低网络的丢包率及传输延时,文章研究了GPON系统传输汇聚层的帧结构及动态带宽分配的实现方法,提出了一种新的动态带宽分配(DBA)算法--基于QoS的二层动态带宽分配算法.基本思路是根据不同等级业务的带宽需求,在PON层和ONU层分别进行带宽的合理分配.理论分析和仿真试验证明,这种算法可以提高带宽的利用率,保证不同业务的不同时延要求,并且对不同用户和不同等级的业务都具有很好的公平性.     

基于时延和速率效用函数的LTE无线资源调度算法研究

为了提高LTE实时业务调度的公平性,在M-LWDF资源调度算法的优先级判断机制中引入了平均传输速率和保证比特速率,将经济学中的效用思想和效用函数引入M-LWDF调度算法,提出了一种基于时延效用函数和速率效用函数的M-LWDF改进算法,更好地体现了调度算法的时延特性和速率特性。仿真结果表明基于时延和速率效用函数的M-LWDF调度算法具有更高的公平性,能够更好地满足对实时业务的调度要求。     

EPON支持QoS的动态带宽算法研究

本文给出了一种支持多优先级业务的带宽分配算法。其中高优先级业务固定带宽分配和低优先级业务动态带宽分配,将上行帧分为第一时隙和第二时隙两部分,各ONU高优先级业务在上行第一时隙发送,第二时隙用于低优先级业务,同时采用固定周期的带宽分配方案,因此降低了高优先级业务的时延和时延抖动。通过ONU实行内部调度并且参与上行接入计算,避免了上行复杂的同步问题,提高了链路利用率。     

TWDM-PON中用户行为感知的动态资源分配策略

TWDM-PON是下一代光接入网的主流方案,具有带宽高、距离长、用户多等特点.针对用户行为差异性增大的问题,为有效降低网络时延及提升资源分配的公平性,提出一种用户行为感知的动态资源分配策略.根据用户行为带来的业务动态变化状况,动态调整ONU的轮询机制以满足用户服务水平变化要求,并划分子周期交替发送不同等级的业务,设计高效的数据块加载方法来实现负载均衡的多波长传输.仿真结果表明,与传统策略相比,所提策略在保证资源利用率高达95%的同时,既使业务平均时延改善50%以上,也使资源分配具有更好的公平性.     

以太无源光网络动态带宽分配算法研究

动态带宽分配是以太无源光网络的重点研究领域之一,其中光网络单元(ONU)内的带宽分配影响到用户的服务质量.文中在分析已有算法的基础上,提出了一种用于ONU内带宽分配的改进令牌桶算法,即每个分配周期中累积的令牌数取决于ONU分配的带宽,而不是ONU的基本带宽.给出了该算法详细的代码描述,并通过在模拟流量下的仿真,证明了该算法能保证不同类型数据的优先顺序,并能保证各种负载条件下带宽分配的公平性,因此相对于已有算法有更好的适用性.     

新型的EPON结构及其保护倒换策略

本文提出一种新型的EPON结构,可以实现ONU间直接对等通信。ONU之间的通信不再需要OLT的转发,提高了系统带宽利用率,降低包传输时延。同时提出了该网络结构下的保护倒换方案,实现快速故障检测和倒换.保证网络的高可靠性。     

基于公平性的自相似业务接纳控制研究

文中研究了基于分形稳定运动有效带宽的计算方法,利用迭代过程推导出了聚合流有效带宽的计算公式,提出了一种基于有效带宽的公平性的自相似业务接纳控制算法,在接纳判断过程中引入了公平性机制,保证了业务接纳的公平性,通过MATLAB和OPNET相结合的仿真方法证明了该算法的有效性.结果证明了文中提出的算法保障了网络的服务质量,保证了各业务接纳的公平性,同时保持了网络高的利用率.     

支持多业务的EPON动态带宽分配算法

EPON的关键技术之一是动态带宽分配(DBA)问题。为了支持语音、视频、数据等多业务和保证不同的服务质量(Qo S)和有效克服轻载惩罚问题,本文提出了一种支持多业务的EPON动态带宽分配算法。通过对ONU侧的业务按照优先级进行区分,对到来的业务按照严格的优先级排队,以此保证高优先级业务的时延要求;引入预测避免出现了轻载惩罚,在OLT侧预测高优先级业务的到来情况,为ONU多分配预测的带宽大小。实验表明,本文算法提高了网络的服务质量。     

基于时延和速率效用函数的LTE无线资源调度算法研究

为了提高LTE实时业务调度的公平性,首先在M-LWDF资源调度算法的优先级判断机制中引入了平均传输速率和保证比特速率,然后将经济学中的效用思想和效用函数引入到M-LWDF调度算法中,提出了一种基于时延效用函数和速率效用函数的M-LWDF改进算法,以便更好地体现调度算法的时延特性和速率特性。     

一种新的基于认购速率和QoS等级的动态带宽分配算法

为了实现吉比特无源光网络带宽分配的公平性,降低网络的传输延时,设计了一种新的媒质访问控制协议,提出了一种新的动态带宽分配算法.其基本思想是:在保证拥有不同QoS业务的用户得到认购速率的基础上,根据网络负载的大小,动态地将某些用户未使用的带宽分配给其他带宽需求大的用户,以提高网络的带宽利用率.仿真结果表明,这种新的算法在严格控制数据传输延时的前提下,能够保证多用户之间带宽分配的公平性.     

A Cross-layer Dual Queue Approach for Improving TCP Fairness in Infrastructure WLANs

Fairness is one of the most important performance measures in IEEE 802.11 Wireless Local Area Networks (WLANs), where channel is accessed through competition. In this paper, we focus on the fairness problem between TCP uplink and downlink flows in infrastructure WLANs from the cross-layer perspective. First, we show that there exists a notable discrepancy between throughput of uplink flow and that of downlink flow, and discuss its root cause from the standpoint of different responses to TCP data packet drop and TCP ACK packet drop at the access point (AP) buffer. In order to mitigate this unfairness, we propose a dual queue scheme, which works in a cross-layer manner. It employs two separate queues at the AP, one for the data packets of downlink TCP flows and another for the ACK packets of uplink TCP flows, and selects these queues with appropriate probabilities so that TCP per-flow fairness is improved. Moreover, we analyze the behavior of the dual queue scheme and derive throughputs of uplink and downlink flows. Based on this analysis, we obtain the optimal queue selection probabilities for fairness. Extensive simulation results confirm that the proposed scheme is effective and useful in resolving the TCP unfairness problem without deteriorating overall utilization.     

A buffer management algorithm for improving up/down transmission congestion protocol fairness in IEEE 802.11 wireless local area networks

The fair allocation of the resources is an important issue in wireless local area network (WLAN) because all wireless nodes compete for the same wireless radio channel. When uplink and downlink transmission congestion protocol (TCP) flows coexist in WLAN, the network service is biased toward the uplink TCP flows, and the downlink TCP flows tend to starve. In this article, we investigate the special up/down TCP unfairness problem and point out that the direct cause is the uplink acknowledgement (ACK) packets occupy most buffer space of access point. We thus propose a buffer management algorithm to ensure the fairness among uplink and downlink TCP flows. In order to limit the greedy behavior of ACK packets, the proposed algorithm adjusts the maximum size of buffer allocated for the ACK packets. Analysis and simulation results show that the proposed solution not only provides the fairness but also achieves 10–20% lower queue delay and higher network goodput than the other solutions. Copyright © 2012 John Wiley & Sons, Ltd.     

A Channel Adaptive ACK Mechanism in High Rate Wireless Personal Area Networks

In IEEE 802.15.3 wireless personal area networks, the acknowledgement (ACK) mechanism has significant impact on the overall throughput. In this paper, we propose a channel adaptive ACK (CA-ACK) mechanism where an ACK is selectively transmitted depending on wireless channel conditions to maximize the data throughput. Specifically, an ACK is transmitted only when the frame error rate is greater than a pre-defined threshold; this threshold is derived for a given payload size and data rate using developed analytical models. Simulation results demonstrate that CA-ACK improves the throughput adaptively to varying channel conditions.     

认知无线电系统中基于多标拍卖的信道分配机制

为在认知无线电系统中实现对频谱的有效管理,文中提出了一种基于多标拍卖的信道分配机制,并给出了三种分配规则:吞吐量最大规则、效用公平规则以及时间公平规则.最后通过仿真验证了三种分配规则下的系统性能,仿真结果说明,进行信道分配时利用吞吐量最大规则能使系统吞吐量达到最大,采用效用公平规则能达到最佳效用公平性.使用时间公平规则可保证用户在为传输文件而竞争频谱资源过程中的时间公平,且文件的平均传输时间最少、时延最小.     

Joint subcarrier and power allocation with fairness in uplink OFDMA systems based on ant colony optimization

One of the key problems in uplink orthogonal frequency division multiple access systems is to efficiently and fairly allocate subcarriers and powers. However, most existing work has not sufficiently taken into account fairness when allocating these resources so that subcarriers cannot be fairly allocated among users with different channel conditions. To overcome this shortcoming, we first present an optimization framework with fairness, which aims to fairly allocate subcarriers among different users and to distribute the transmission power of each user over the assigned subcarriers. Here, the fairness is guaranteed by associating each user with a utility function and placing a lower limit on the number of subcarriers assigned. In particular, different from previous work, utility functions are allowed to be nonconcave and nondifferentiable so that our framework can be suitable for resource allocation for real‐time applications. Furthermore, an iterative algorithm based on the ant colony optimization is proposed, according to which subcarriers can be efficiently and fairly allocated among different users. Simulation results verify the convergence of our algorithm. In addition, our algorithm outperforms several other algorithms in terms of the fairness of resource allocation. Copyright © 2012 John Wiley & Sons, Ltd.     

W-CDMA/UMTS下一种解决TCP有效性和公平性的跨层方案

在UMTS系统中,由于MAC层的包调度引入了用户间的竞争,带来了传输层TCP有效性和公平性问题,为了解决这个问题,该文提出了一种主动ACK包转发控制策略(AAFC),它的基本思想是在基站处嵌入AAFC模块,通过MAC层和传输层之间的消息传递来控制基站处ACK包的转发,以此来保证用户间TCP流的公平性以及链路层无线资源的最充分利用。仿真结果证明了AAFC方案的有效性。     

移动WiMAX网络下行链路TCP吞吐量公平性的跨层优化

该文提出了一种移动WiMAX网络中的TCP公平性跨层优化模型,设计了基于此模型的cross-layer TCP改进协议。利用端节点链路层的速率信息和在基站BS(Base Station)处预分配ACK分组所需带宽的策略改善了下行终端的QoS (Quality of Service)指标,保证了下行终端和上行终端的吞吐量公平性。仿真结果表明cross- layer-TCP改进协议能够在保持原有系统吞吐量的前提下改善下行终端的公平性。     

Cooperative bargaining solution for efficient and fair spectrum management in cognitive wireless networks

This paper studies the fairness among the primary users (PUs) and the secondary users (SUs) for resource allocation in cognitive radio systems. We propose a novel co‐opetition strategy based on the Kalai–Smorodinsky bargaining solution to balance the system efficiency and the fairness among users. The strategy formulates the spectrum sharing problem as a nonlinear and integral sum utility maximization subject to a set of constraints describing the co‐opetition among the PUs and the SUs. Then, we solve the maximization problem by proposing a heuristical method that consists of four steps: multi‐PU competition, PU's subcarrier contribution, multi‐SU competition, and SU's subcarrier contribution. Extensive simulation results are presented by comparing the co‐opetition strategy with several conventional ones, including the Kalai–Smorodinsky bargaining solution, sum rate maximization as well as the Max–Min. Results indicate that the co‐opetition strategy can jointly balance the system efficiency and fairness in multiuser resource allocation, as it is able to support more satisfied users and in the meanwhile improve the utility of those unsatisfied. Moreover, the co‐opetition can help enable the coexistence of the PUs and the SUs in cognitive radio systems. Copyright © 2013 John Wiley & Sons, Ltd.     

信道公平分配的局部拥塞控制算法

提出基于信道公平分配的局部拥塞控制算法FCA(fair channel allocation),在缓解局部拥塞的同时增强信道分配的公平性。为减少获取邻居节点实时缓存信息的通信开销和提高以单一节点缓存是否溢出为检测模型的准确性,FCA采用以节点实时缓存长度预测为基础的邻居节点缓存总长度和分组平均传输延迟作为检测指标的拥塞检测模型。为避免使用独立拥塞通告消息增加信道负载,FCA采用在ACK控制帧中增加一个节点地址位携带拥塞信息。在去拥塞阶段,FCA采用基于实时缓存长度和队列优先权值的信道分配机制保证公平传输和防止部分节点因缓存增速过快导致溢出分组丢失。实验结果表明,FCA在碰撞次数、分组传递率、吞吐量和公平性等方面相比802.11、CODA和PCCP具有显著优势。     

Dynamic Resource Adjustment for Coexistence of LAA and Wi‐Fi in 5 GHz Unlicensed Bands

To enable the coexistence of Licensed Assisted Access (LAA) and Wi‐Fi in 5 GHz unlicensed bands, a new channel access mechanism is proposed. Accounting for the fairness between LAA and Wi‐Fi, the proposed mechanism finds the optimal transmission time ratio by adaptively adjusting the transmission durations for LAA and Wi‐Fi. In addition, we propose a new analytical model for the distributed coordination function of IEEE 802.11 through some modifications of conventional analytical models for saturation and non‐saturation loads. By computing the activity ratio of Wi‐Fi, the proposed analytical model is able to control the time ratio between LAA and Wi‐Fi, which is required for practical implementation of the proposed access mechanism. Through numerical simulations, the proposed channel access mechanism is compared with conventional methods in terms of throughput and utility.