WiMAX拓展实时轮询调度机制分析

为了提高无线资源的利用率,使WiMAX系统更好地支持语音业务,基于IEEE 802.16e协议的QoS调度体系,提出了针对带有静默压缩语音业务的拓展实时轮询调度机制的具体实现方案.而且通过对方案中关键参数的分析,给出了一种QoS保证方法.方法根据用户时延对数据带宽分配进行补偿,并按照用户负载情况动态地调整轮询请求带宽的分配周期.使用OPNET软件进行了系统级性能评估,结果表明所提出的方法可有效地降低用户上行接入时延和上行丢包率,从而提高了通信质量.     

一种用于升空平台MAC层的调度架构

为满足升空平台的协议和不同业务流的属性需求,提出了一种完整的可以满足介质访问控制层服务质量和动态带宽分配的有效的调度方案,该调度方案不仅包括移动中心站对移动站的带宽分配,还包括移动站内上行业务的二级带宽分配架构。在仿真中通过对时隙发送特性、不同业务的延时特性,以及同种业务下不同算法的时延比较,验证了该调度方案的可行性。     

无线城域网带宽调度算法的设计与仿真

无线城域网空中接口规范IEEE802.16标准将刚络中的业务流分为UGS、rtPS、nrtPS和BE四种类型,虽然协议中提出了对不同类型业务的QoS保证机制,但并没有给出具体的能保障不同业务服务质量的调度算法.通过研究不同类型业务各自特点及其适用的调度方法,提出了一种基于802.16的上行带宽调度算法--分类联合调度算法,使系统中不同类型的业务流具有可比拟的调度因子,从而进行业务流的自动分类和联合调度.理论分析和仿真结果表明,算法有效提高网络资源利用率,同时能满足不同业务流的QoS需求.     

平流层通信平台MAC层的调度方案建模及仿真

平流层升空平台能够满足可提供战时服务、能快速部署,适用于区域性覆盖.为满足平台支持的多用户、多优先权、综合业务的接入策略并解决资源动态分配问题.提出了一种可以满足平台MAC层的服务质量(QoS)和动态带宽分配的调度架构,架构包括移动中心站(MCS)对移动站(MS)的带宽分配和移动站内上行业务的二级带宽调度架构,并根据不同业务需求采用不同的调度算法.仿真结果表明:调度方案能很好的满足所有类型业务的服务质量需求.并提供了较好的公平性,保证了架构的可行性.     

LTE系统上行半静态调度资源碰撞问题的改进

调度是LTE(长期演进)系统中基站为每个用户分配资源的重要环节和关键技术。针对LTE系统中的网络电话(VoIP)、视频流等业务,LTE提出了一种新型的调度方式——半静态调度。在资源调度中上行资源更为宝贵,针对上行半静态混合重传(HARQ)过程中可能存在的资源碰撞问题,通过对半静态调度周期以及半静态授权起始位置的研究,得出了不同配置下具有针对性的上行周期,并提出了一种延迟发送碰撞进程的解决方案,减少了资源碰撞,有效提高了系统的资源利用率和稳定性。     

WiMAX上行链路实时业务改进调度算法

针对WiMAX建议的rtPS和ertPS调度机制处理变速率实时业务时MAC层开销大,导致时延增大的缺点,提出了一种能够有效调度多用户变速率实时业务的上行链路调度算法。该算法在SS端实时监控数据率,减少发送带宽请求的次数,从而提高整体的上行链路资源利用率,并在BS上行调度器中优化调度策略,使得最急迫的用户优先得到服务。仿真结果表明该算法与ertPS相比,在不影响系统吞吐量的情况下上行时延减少了约15%。     

基于队列长度的上行资源调度性能分析及策略

对无线通信网络上行队列调度进行了分析和设计.提出一种基于队列长度的上行资源调度策略,建立了数学模型,采用双随机泊松过程模型,对上行资源调度进行了理论分析,推导提出了衡量调度性能的参数:延时和带宽利用率.将该策略应用于基于IEEE 802.16d的无线网络,数值分析和仿真结果表明,所提算法能对上行资源进行优化配置,实现系统所需的QoS服务.     

云计算中一种多DAG工作流可抢占式调度策略

为解决多用户工作流调度过程中的公平性问题,提高资源利用率,满足不同用户DAG工作流的不同QoS需求,提出了抢占式多DAG工作流动态调度模型。该算法将DAG工作流按照QoS需求进行优先级划分,采用高优先级作业优先占有资源的原则调度作业。相同优先级DAG工作流的任务依据带有启发性信息的slowdown进行资源抢占,进一步提高了作业调度的公平性;对于不同优先级的作业调度,提出了基于阈值的回填算法,该算法在保证作业调度公平的同时提高了资源利用率。     

一种适用于宽带无线多媒体网络的上行带宽分配方案

提出了一种适用于宽带无线多媒体网络的上行无线带宽分配方案。该方案将业务数据分为3种类型,即实时恒定速率业务、恒定变速率业务、非实时业务,针对不同业务对时延和带宽的不同需求,采取不同的方法获取上行带宽,较好地解决了多业务并发时的上行带宽分配问题,较传统技术提高了带宽利用率,减少了协议开销和传输时延。在详细描述算法的基础上,建立了对应的仿真系统对算法进行了验证。     

LTE系统中上行资源调度算法研究

3GPP LTE采用了多种新技术来提升系统的性能的同时,也增加了LTE系统无线资源管理的复杂度.主要研究了LTE系统中上行无线资源管理算法,针对上行BSR汇报机制误差带来的问题,提出一种更精确的基于happy bits补充汇报BSR的方案来改进其上行资源调度的性能.该机制利用BSR控制单元对应的MAC子头中的两个保留比特(happy bits),通过一定的映射规则,不需要额外的开销,更加精细的反映UE上行缓存状态信息,提高了用户和无线资源调度的效率.仿真结果表明,本文所提出的改进方案比原方案在资源利用率,吞吐量和用户公平性方面都有较为理想的提升,有效地改善了系统资源利用率.     

An efficient bandwidth allocation algorithm for real-time VBR stream transmission under IEEE 802.16 wireless networks

This paper investigates variable rate control strategies for real-time multimedia variable bit rate (VBR) services over IEEE 802.16 broadband wireless networks. A data rate control mechanism is derived for the case where the uplink channel provides real-time services and the traffic rate parameter remains constant. This paper shows that the common queuing scheduling algorithms have some bandwidth allocation fairness problems for the real-time polling service (rtPS) in the MAC layer. In other words, the use of a VBR for the rtPS by a WiMAX system results in additional access latency jitter and bandwidth allocation disorder in the transmitted multimedia streams during the regular time interval polling of subscribe stations (SSs) for the contention bandwidth request period. However, the proposed scheduling algorithm solves these SSs contending with bandwidth resource allocation problems based on an extended rtPS (ertPS) of quality-of-service (QoS) pre-programming for a ranging response non-contention polling period. The adopted bandwidth allocation of max–min fairness queue scheduling uses a time constraint condition to transmit real-time multimedia VBR streaming in an IEEE 802.16 broadband wireless environment. In addition, we use the ns-2 simulation tool to compare the capacity of multimedia VBR stream and show that the proposed ertPS scheduling algorithm outperforms other rtPS scheduling algorithms.     

Above packet level admission control and bandwidth allocation for IEEE 802.16 wireless MAN

IEEE 802.16 wireless Metropolitan Area Network (MAN) is expected to revolutionize the broadband wireless access technology. Efficient resource management is essential in providing scalability in such large IEEE 802.16-based wireless network and Quality of Service (QoS) for multimedia applications (VoIP, MPEG, FTP, WWW) is usually achieved by appropriate classification of scheduling services and grant/request mechanism. In this paper, we firstly discuss the QoS issue in IEEE 802.16 wireless MANs and propose a dynamic admission control scheme for scheduling services defined in the 802.16 specification. The proposed scheme provides the highest priority for Unsolicited Grant Service (UGS) connections and maximizes the bandwidth utilization by employing bandwidth borrowing and degradation. We develop an approximate analytical model to evaluate the system performance by assuming that the traffic processes of all scheduling services are Poisson processes. In fact, the self-similarity of non-voice traffic makes its traffic process far from Poisson process and should be modeled by Poisson Pareto Burst Process (PPBP). Therefore, in the later part of the paper, we analyze upper bound blocking probabilities of all scheduling services above the packet level using PPBP model for fractal traffic and Gaussian model for aggregated traffic in large wireless network as well as using the Chernoff bound method. Based on the analytical results, we give another admission control and bandwidth allocation mechanism above the packet level so as to minimize the blocking probability of each type of service in IEEE 802.16 wireless MAN. Analytical and simulation results are obtained and compared to demonstrate the effectiveness of proposed schemes and validate our analytical models.     

An intelligent scheduling system using fuzzy logic controller for management of services in WiMAX networks

The appearance of media applications with high bandwidth and quality of service requirements has made a significant impact in telecommunications technology. In this direction, the IEEE802.16 has defined wireless access systems called WiMAX. These systems provide high-speed communications over a long distance. For this purpose some service classes with QoS requirements are defined; but the QoS scheduler is not standardized in IEEE802.16. The scheduling mechanism has a significant effect on the performance of WiMAX systems for use of bandwidth and radio resources. Some scheduling algorithms have been introduced by researchers; but they only provide some limited aspects of QoS. An intelligent decision support system is therefore necessary for scheduling. In this paper a fuzzy based scheduling system is proposed for compounds of real-time and non-real-time polling services which provide QoS requirements and fairness in dynamic conditions. A series of simulation experiments have been carried out to evaluate the performance of the proposed scheduling algorithm in terms of latency and throughput QoS parameters. The results show that the proposed method performs effectively regarding both of these criteria and achieves proportional system performance and fairness among different types of traffic.     

一种基于WiMAX mesh网络的区分服务调度方案

IEEE 802.16支持多种不同类型的调度服务,并将服务质量支持机制引入媒体接入控制层,却没有规定相应的调度算法。在IEEE 802.16定义的mesh模式下,针对不同类型服务,提出了一种区分服务的调度方案,该方案采用集中式和分布式混合调度。仿真结果表明:该方案下系统平均时延和用户满意度均有所改善。     

一种面向公平保证QoS的WiMAX二级调度方案

IEEE 802.16作为全球微波接入互操作系统技术标准,虽然定义了5类信流(分别是UGS,rtPS,ertPS,nrtPS和BE),并将服务质量支持机制引入媒体接入控制层,却没有规定相应的调度算法.为有效保证各种多媒体通信的服务质量,提出了一种基于正交频分多址接入技术和自适应调制编码机制的二级调度方案.该调度方案采用跨层设计思想,适用于PMP WiMAX网络下行链路中.一级调度器按照QoS优先级顺序调度位于不同类型缓存器的队头分组,从而满足rtPS业务的最大时延限定和nrtPS业务的最小速率要求;完成一级调度后,为满足用户速率公平性.二级调度器根据自适应调制编码信息及用户状态信息调度位于不同用户缓存器的队头分组.仿真结果表明该方案能够有效保证各种多媒体通信服务满足QoS要求并兼顾用户速率公平,同时也可获得较高的WiMAX系统吞吐量.     

An efficient scheduling algorithm for radio resource reuse in IEEE 802.16j multi-hop relay networks

The IEEE 802.16j standard for WiMAX introduced the concept of relay station in order to increase the service area and decrease the deployment cost of the network. In this paper, we have proposed an efficient scheduling scheme for IEEE 802.16j networks, which maximizes the number of connections that are scheduled in a particular time slot. The proposed scheme schedules the connections based on their priority, which is decided by the quality of service (QoS) requirement of the connections. A selected connection can be scheduled in the current timeslot only if it is not having interference with any of the already scheduled connections. Our algorithm considers scheduling of lower priority connections even if any higher priority connection is not scheduled due to interference. Thus, the delay for lower priority connections is reduced without increasing the delay for higher priority connections. In addition, our algorithm achieves higher frame utilization and higher system throughput by reducing the length of the schedule.     

IEEE 802.16中支持QoS的有效带宽分配机制

基于IEEE 802.16协议,研究宽带无线接入网中保障QoS的有效带宽资源分配和调度问题。首先,在PMP模式下设计一个有效率的QoS调度算法,利用参数的调整提供更具有弹性的服务质量,以利于rtPS服务支持多媒体传输;然后利用标准中所提供的QoS参数调度各种不同类型的服务业务,分配上传带宽,进而达到有效地使用网络资源。仿真实验结果表明,本方案能够在保证QoS需求的同时,有效地分配带宽资源。     

IEEE802.16e的实时上行链路调度服务优化算法

深入分析了IEEE802.16e建议的三种实时调度服务算法：UGS、rtPS、ertPS，并在此基础上提出了一种优化的实时调度服务算法：irtPS。该优化的调度服务算法在保证变化数据率实时上行链路的延时性能基础上，最大限度地提高了实时上行链路的资源利用率。数学建模分析结果显示，在保证延时性能的前提下，该优化的调度服务算法的系统容量较IEEE802.16e建议算法的系统容量有显著增加。     

Relay technologies and technical issues in IEEE 802.16j Mobile Multi-hop Relay (MMR) networks

An amendment to the 802.16e standard namely IEEE 802.16j specifying relay station (RS) and multi-hop relay base station (MR-BS) was approved in year 2006 supports Mobile Multi-hop Relay networks. (MMR). It provides coverage extension to isolated area and throughput enhancement by specifying relay stations. The physical (PHY) layer of WiMAX IEEE 802.16j standard is based on the IEEE 802.16-2004 and IEEE 802.16e-2005 standards and was designed from IEEE 802.11a. This paper reviews the Relay technologies and technical issues in the physical and MAC layer of IEEE 802.16j such as Data forwarding schemes frame structure, Link adaptation, modulation and coding, these issues belongs to physical layer, QoS scheduling services, Bandwidth allocation and request, Network planning, MAC handover procedures, connection management, path management, interference management, all these issues belongs to MAC layer.