Power-saving scheduling with a QoS guarantee in a mobile WiMAX system

This paper presents a power-saving scheduling scheme to improve energy efficiency and guarantee Quality of Service (QoS) in Mobile Worldwide Interoperability for Microwave Access (WiMAX), i.e. IEEE 802.16e. Due to the popularization of multimedia services such as Voice over IP (VoIP) and MPEG video, different types of QoS coexist in one mobile subscriber station (MSS). Many previous studies have considered the QoS issue. Unfortunately, they only considered the delay in QoS. In this work, we consider that delay and jitter types of QoS should be scheduled at the same time and integrate the sleep duration in one MSS. The packets would be scheduled successively to reduce the number of status transitions under the QoS requirements of delay and jitter. The proposed approach not only minimizes power consumption of the MSS, but also guarantees both the delay and jitter QoS of real-time connections.     

基于IEEE802.16d PMP网络的业务调度研究

研究无线城域网PMP网络结构TDD模式下媒质接入机制和MAC层调度机制.通过对截断二进制指数算法的研究给出上行调度碰撞解决机制的一种实现方案,在保证QoS要求的同时最优地利用了动态分配的带宽.最后使用NS网络仿真软件对此进行了仿真,给出了UGS和rtPS调度业务数据仿真的结果.     

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.     

A cross-layer elastic CAC and holistic opportunistic scheduling for QoS support in WiMAX

QoS provisioning is an important issue in the deployment of broadband wireless access networks with real-time and non-real-time traffic integration. An opportunistic MAC (OMAC) combines cross-layer design features with opportunistic scheduling scheme to achieve high system utilization while providing QoS support to various applications. A single scheduling algorithm cannot guarantee all the QoS requirements of traffics without the support of a suitable CAC and vice versa. In this paper, we propose a cross-layer MAC scheduling framework and a corresponding opportunistic scheduling algorithm in tandem with the CAC algorithm to support QoS in WiMAX point-to-multipoint (PMP) networks. Extensive experimental simulations have been carried out to evaluate the performance of our proposal. The simulation results show that our proposed solution can improve the performance of WiMAX networks in terms of packet delay, packet loss rate and throughput. The proposed CAC scheme can guarantee the admitted connections to meet their QoS requirements.     

Power-aware opportunistic downlink scheduling in IEEE 802.16 wireless networks

The IEEE 802.16 is a standard for fixed and mobile Broadband Wireless Access (BWA). In this paper, we deal with two key challenges of 802.16-based networks. First, terminals close to cell edge experience poor channel quality, due to severe path-loss and high interference from concurrent transmissions in nearby cells. To address this issue, we propose a framework based on a static partitioning of bandwidth into chunks with different transmission power levels. Terminals with impaired channel conditions can then benefit from being allocated a higher amount of transmission power than the others. Secondly, transmissions should be scheduled according to Quality of Service (QoS) requirements to keep users with real-time video or voice calls satisfied, while best-effort connections should fairly share the remaining capacity. To this aim, we propose a scheduling algorithm, called Power-aware Opportunistic Downlink Scheduling (PODS), that aims at meeting both the QoS and fairness requirements, while taking into account the different power levels of the bandwidth chunks. The performance of the proposed scheduler is assessed through detailed packet-level simulation in realistic scenarios and compared with well-known scheduling algorithms. Results confirm that PODS is able to exploit power boosting to provide real-time connections with the desired level of QoS, irrespectively of their MSs’ channel quality.     

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.     

Scheduling solution for the IEEE 802.16 base station

The IEEE 802.16 standard defines a wireless broadband access network technology called WiMAX. It introduces several advantages, one of which is the support for QoS at the MAC level. To ensure meeting the QoS requirements, the 802.16 base station must run some algorithm to allocate slots between connections. This algorithm is not defined in the 802.16 specification but rather is open for alternative implementations. We propose a simple, yet efficient, solution that is capable of allocating slots based on the QoS requirements, bandwidth request sizes, and the 802.16 network parameters. To test the proposed solution, we have implemented the 802.16 MAC and PHY layers in the NS-2 simulator. Several simulation scenarios are presented that demonstrate how the scheduling solution allocates resources in various cases. According to the simulation results, the proposed scheduling solution ensures the QoS requirements of all 802.16 service classes. The solution shares free resources fairly and demonstrates work-conserving behaviour.     

Application-aware scheduling for VoIP in Wireless Mesh Networks

Wireless Mesh Networks (WMNs) are seen as a means to provide last mile connections in Next Generation Networks (NGNs). Because of their auto-configuration capabilities and the low deployment cost WMNs are considered to be an efficient solution for the support of multiple voice, video and data services in NGNs. This paper looks at the optimal provision of resources in WMNs for Voice over IP (VoIP) traffic, which has strict performance requirements in terms of delay, jitter and packet loss. In WMNs, because of the challenges introduced by wireless multi-hop transmissions and limited resources, providing performance quality for VoIP comparable to the voice quality in the traditional circuit-switched networks is a major challenge.This paper analyses different scheduling mechanisms for TDMA-based access control in mesh networks as specified in the IEEE 802.16-2004 WiMAX standard. The performance of the VoIP applications when different scheduling mechanisms are deployed is analysed on a variety of topologies using ns-2 simulation and mathematical analysis. The paper concludes that on-demand scheduling of VoIP traffic – typically deployed in 802.11-based WMNs – is not able to provide the required VoIP quality in realistic mesh WiMAX network scenarios and is therefore not optimal from a network operator’s point of view. Instead, it is shown, that continuous scheduling is much better suited to serve VoIP traffic. The paper then proposes a new VoIP-aware resource coordination scheme and shows, through simulation, that the new scheme is scalable and provides good quality for VoIP service in a wide range of network scenarios. The results shown in the paper prove that the new scheme is resilient to increasing hop count, increasing number of simultaneous VoIP sessions and the background traffic load in the network. Compared to other resource coordination schemes the VoIP-aware scheduler significantly increases the number of supported calls.     

GAME based dynamic resource scheduling in QoS aware radio access networks

Radio resource management and QoS are finally inseparable in wideband CDMA networks. In this paper, we propose a novel wireless resource scheduler, called GAME-C, that integrates our genetic algorithm for mobiles equilibrium (GAME) with the standard CDMA transmitter closed loop power control (CLPC). GAME assigns optimally both transmitting power and bit rate to every mobile station. Optimal allocation is in the sense that every user gets only enough resources necessary for meeting or exceeding its QoS requirements while minimizing interference to other users. Having done that, we gain further benefits as well. In addition to QoS provisioning, lower transmitting power extends a mobile station battery life. Moreover, the base station coverage efficiency is improved by decreasing the probability of blocking new connections or dropping current ones. In short, GAME-C expands the number of QoS-satisfied mobile stations in a cell. Various simulations show improvements achieved over the established (CLPC) basic scheme.     

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。     

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.     

片上网络带宽资源QoS调度算法

提出一种片上网络带宽资源QoS调度算法。通过分布式地动态调整有保障服务(GS)连接在每个路由器中的优先级,解决共享同一物理链路的不同GS连接之间的传输冲突问题,从而保障时延、带宽和时延抖动等QoS。通过给尽力而为服务(BE)通道分配动态优先级和监控GS流量2种方法的应用,有效提高了BE数据流的服务质量及链路利用率。     

一种基于区分服务的嵌套队列调度算法

现有队列调度算法只能满足某一种特定类型业务流量的服务质量(QoS)需求,无法广泛支持多种类型业务流量。为此,提出一种基于区分服务的嵌套队列调度算法。将现有队列调度算法通过嵌套模型进行组合,并根据该嵌套模型进行队列调度,从而为多种类型业务流量提供均衡的QoS保障。仿真结果表明,该算法能够满足不同类型业务流量的QoS需求,其各项性能指标所达效果与最优效果的差距较小,并且在多种类型业务流量的支持方面比现有队列调度算法表现更好。     

基于效用函数的OFDM混合业务资源调度算法*

主要研究了QoS和BE两种混合业务场景下OFDM无线网络下行链路的资源调度问题,提出了一个基于效用函数的跨层资源调度模型,其能够自适应地对两种业务进行资源的联合优化分配。该模型被抽象为一个非线性整数规划问题,优化目标是系统总效用最大化,同时满足同信道干扰（CCI）约束以及QoS业务的质量要求。将该非线性整数规划问题转换为连续松弛凸规划问题进行求解,并结合最优松弛解,提出了一种简单的动态子载波分配算法,即MMU(mix-max-utility) 算法。仿真结果验证了该调度算法能使系统较好地支持混合业务,系统     

An opportunistic resource allocation approach for mixed QoS and non-QoS connections in OFDMA wireless networks

An opportunistic resource allocation approach is proposed to guarantee both fair resource allocation and high system throughput under combinations of QoS and non-QoS connections in OFDMA networks. This approach features dynamic connection classification and packet prioritization based on real-time network conditions and QoS constraints. A classifier is first employed to prioritize QoS connections by observing the channel state of each subscriber station and the utilization of network resources. It performs a finite-horizon Markov decision process with dynamic rules affected by system load. The transmission order of packets is then determined by an opportunistic multiservice scheduler according to the QoS requirements of connections and the output of the classifier. Having the scheduling result, an allocator assigns slots to the scheduled packets, and its output is linked back to the connection classifier through a resource usage observer for all subscriber stations. The sub-channel allocation problem is also solved by cooperation between the slot allocator and the packet scheduler. Results of numerical analysis and NS2 simulation confirm the advantages claimed above. The same conclusion can also be drawn from the comparison with several existing approaches in terms of system throughput, service successful ratio, average spectral efficiency, and system revenue.     

Traffic scheduling solutions with QoS support for an input-buffered multimedia router

Quality of service (QoS) support in local and cluster area environments has become an issue of great interest in recent years. Most current high-performance interconnection solutions for these environments have been designed to enhance conventional best-effort traffic performance, but are not well-suited to the special requirements of the new multimedia applications. The multimedia router (MMR) aims at offering hardware-based QoS support within a compact interconnection component. One of the key elements in the MMR architecture is the algorithms used in traffic scheduling. These algorithms are responsible for the order in which information is forwarded through the internal switch. Thus, they are closely related to the QoS-provisioning mechanisms. In this paper, several traffic scheduling algorithms developed for the MMR architecture are described. Their general organization is motivated by chances for parallelization and pipelining, while providing the necessary support both to multimedia flows and to best-effort traffic. Performance evaluation results show that the QoS requirements of different connections are met, in spite of the presence of best-effort traffic, while achieving high link utilizations.     

Structuring communication software for quality-of-serviceguarantees

We propose architectural mechanisms for structuring host communication software to provide QoS guarantees. We present and evaluate a QoS sensitive communication subsystem architecture for end hosts that provides real time communication support for generic network hardware. This architecture provides services for managing communication resources for guaranteed QoS (real time) connections, such as admission control, traffic enforcement, buffer management, and CPU and link scheduling. The architecture design is based on three key goals: maintenance of QoS guarantees on a per connection basis, overload protection between established connections, and fairness in delivered performance to best effort traffic. Using this architecture we implement real time channels, a paradigm for real time communication services in packet switched networks. The proposed architecture features a process per channel model that associates a channel handler with each established channel. The model employed for handler execution is one of “cooperative” preemption, where an executing handler yields the CPU to a waiting higher priority handler at well defined preemption points. The architecture provides several configurable policies for protocol processing and overload protection. We present extensions to the admission control procedure for real time channels to account for cooperative preemption and overlap between protocol processing and link transmission at a sending host. We evaluate the implementation to demonstrate the efficacy with which the architecture maintains QoS guarantees on outgoing traffic while adhering to the stated design goals     

M-WiMAX中马尔可夫预测的PF调度算法研究

在M-WiMAX系统中为了获得多用户分集增益,更好地发挥自适应调制编码（AMC）的作用,在改进比例公平算法（PF）基础上设计出一个预测的PF分组调度算法（Pre-PF）来调度系统中的非实时业务。PF调度算法在调度判决表达式中用调度时刻瞬时速率作为参数,这样影响调度的稳定性和整体性能,尤其在移动无线通信中更加明显。提出用马尔可夫预测模型来计算下一个调度时刻的瞬时速率,用它来平滑当前瞬时速率,减小移动无线信道瞬时速率对调度性能的影响。平滑后的瞬时速率能更好地代表移动信道传输速率的变化趋势。仿真结果表明,该调度算法保证了非实时业务流的服务质量,提高了系统的平均吞吐量、稳定性和公平性。     

Providing traffic smoothness and service guarantees within ATM networks through a rate-controlled service discipline

With the introduction of diverse rate requirements under a variety of statistical multiplexing schemes, traffic burstiness behavior of a source stream and its quality-of-service (QoS) performances within the ATM networks become difficult to model and analyze. In this paper, we address this issue and propose a rate-controlled service discipline that provides control of the traffic burstiness while maintaining QoS guarantees for traffic flows with various rate requirements. According to our analysis, traffic streams from different connections can be well regulated at the output of each network node based on their rate requirements. Traffic envelope and the associated burstiness behavior inside the network can thus be effectively characterized. In addition, by assuming a leaky-bucket constrained input source, we prove that the proposed scheme can provide end-to-end delay and jitter bounds for each connection passing through a multi-hop network. Further, due to the low traffic burstiness, only a small buffer space is required at the internal switches for guaranteeing QoS requirements.     

Dynamic rerouting of guaranteed Quality-of-Service connections

To support the widespread demands for integrated services various solutions have been proposed to provide guaranteed Quality-of-Service (QoS) services in packetswitched networks. These solutions usually require fixed route selection and resource reservation on a per connection basis. The routing and reservation decisions, combined with load fluctuations, introduce the problems of network unavailability and loss of network management flexibility. We believe that these problems can be alleviated by transparently rerouting connections to properly balance the network load. In this paper, we present a solution that supportstransparent route modification ofguaranteed QoS connections during the life time of the connections. As the emphasis of this work is to support transparency we must ensure that during and after the rerouting, the QoS guarantees made to the client are preserved, and the interface instances at both the sender and receiver are unaltered. Our solution includes the mechanisms that support the transparent rerouting of connections, and a routing algorithm that is based on the traffic characteristics, the delay, and the jitter requirements of a connection. This routing algorithm can also use various administrative constraints and facilitate the reuse of resources currently reserved by the connection. To optimize the solution, additional mechanisms have been introduced to reduce the time needed to reroute a connection and to support rerouting of segments of a connection. The solution has been implemented in the context of the Tenet scheme and route changes can be observed and controlled by using the Simple Network Management Protocol (SNMPv 1). Simulation experiments and some initial measurements of the implementation demonstrate that such a scheme is useful, practical, and can be achieved with load overhead.