Scheduling Algorithm with Quality of Service Support in IEEE 802.16 Networks

The MAC layer in IEEE802.16 is designed to differentiate service among traffic categories with different multimedia requirements.In this paper,a scheduling algorithm at MAC layer for multiple connections with diverse QoS requirements is proposed.As for this algorithm,each connection is assigned a priority,which is updated dynamically based on its service status concluding queue characteristic and channel state.A connection with the highest priority is scheduled each time.Analytical model is developed by assuming a Finite State Markov Chain(FSMC)channel model.Simulation results show that the proposed scheduling algorithm can improve the performance of mean waiting time and throughput in broadband wireless networks.

A New Fairness-Oriented Packet Scheduling Scheme with Reduced Channel Feedback for OFDMA Packet Radio Systems

In this paper, we propose a flexible and fairness-oriented packet scheduling approach for 3GPP UTRAN long term evolution (LTE) type packet radio systems, building on the ordinary proportional fair (PF) scheduling principle and channel quality indicator (CQI) feedback. Special emphasis is also put on practical feedback reporting mechanisms, including the effects of mobile measurement and estimation errors, reporting delays, and CQI quantization and compression. The performance of the overall scheduling and feedback re-porting process is investigated in details, in terms of cell throughput, coverage and resource allocation fairness, by using extensive quasistatic cellular system simulations in practical OFDMA system environment with frequency reuse of 1. The performance simulations show that by using the proposed modified PF ap-proach, significant coverage improvements in the order of 50% can be obtained at the expense of only 10-15% throughput loss, for all reduced feedback reporting schemes. This reflects highly improved fairness in the radio resource management (RRM) compared to other existing schedulers, without essentially com-promising the cell capacity. Furthermore, we demonstrate the improved functionality increase in radio re-source management for UE’s utilizing multi-antenna diversity receivers.

Packet Scheduling Algorithm for Real-Time Services in Broadband WMAN

Packet scheduling algorithm is the key technology to guarantee Quality of Service (QoS) and balance the fairness between users in broadband Wireless Metropolitan Area Network (WMAN). Based on the research of Proportional Fairness (PF) algorithm and Modified Largest Weighted Delay First (M-LWDF) algorithm, a new packet scheduling algorithm for real-time services in broadband WMAN, called Enhanced M-LWDF (EM-LWDF), was proposed. The algorithm phases in new information to measure the load of service queues and updates the state parameters in real-time way, which remarkably improves system performance.Simulation results show that comparing with M-LWDF algorithm, the proposed algorithm is advantageous in performances of queuing delay and fairness while guaranteeing system throughput.

Modeling and performance evaluation of QoS-aware job scheduling of computational grids

To achieve high quality of service （QoS） on computational grids, the QoS-aware job scheduling is investigated for a hierarchical decentralized grid architecture that consists of multilevel schedulers. An integrated QoS-aware job dispatching policy is proposed, which correlates priorities of incoming jobs used for job selecting at the local scheduler of the grid node with the job dispatching policies at the global scheduler for computational grids. The stochastic high-level Petri net （SHLPN） model of a two-level hierarchy computational grid architecture is presented, and a model refinement is made to reduce the complexity of the model solution. A performance analysis technique based on the SHLPN is proposed to investigate the QoS-aware job scheduling policy. Numerical results show that the QoS-aware job dispatching policy outperforms the QoS-unaware job dispatching policy in balancing the high-priority jobs, and thus enables priority-based QoS.

Improved Delay Priority Resource Scheduling with Low Packet Loss Rate for MBMS in LTE Systems

An improved delay priority resource scheduling algorithm with low packet loss rate for multimedia broadcast multicast service(MBMS)in long term evolution(LTE)systems is proposed in this paper.Real-time services in LTE systems require lower delay and packet loss rate.However,it is difficult to meet the QoS requirements of real-time services using the current MBMS resource scheduling algorithm.The proposed algorithm in this paper jointly considers user delay information and real-time channel conditions.By introducing the user delay information,the lower delay and fairness of users are guaranteed.Meanwhile,by considering the channel conditions of users,the packet loss rate can be effectively reduced,improving the system throughput.Simulation results show that under the premise of ensuring the delay requirements of real-time services,the proposed algorithm achieves a lower packet loss rate compared to other existing algorithms.Furthermore,it can achieve a good balance between system throughput and user fairness.

A QoS-Aware Packet Scheduling Mechanism in Cognitive Radio Networks for Smart Grid Applications

Cognitive radio sensor network is applied to facilitate network monitoring and management, and achieves high spectrum efficiencies in smart grid. However, the conventional traffic scheduling mechanisms are hard to provide guaranteed quality of service for the secondary users. It is because that they ignore the influence of diverse transition requirements in heterogeneous traffi c. Therefore, a novel Qo S-aware packet scheduling mechanism is proposed to improve transmission quality for secondary users. In this mechanism, a Qo S-based prioritization model is established to address data classification firstly. And then, channel quality and the effect of channel switch are integrated into priority-based packet scheduling mechanism. At last, the simulation is implemented with MATLAB and OPNET. The results show that the proposed scheduling mechanism improves the transmission quality of high-priority secondary users and increase the whole system utilization by 10%.

Particle Swarm Optimization Based Approach for Resource Allocation and Scheduling in OFDMA Systems

Orthogonal Frequency-Division Multiple Access (OFDMA) systems have attracted considerable attention through technologies such as 3GPP Long Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX). OFDMA is a flexible multiple-access technique that can accommodate many users with widely varying applications, data rates, and Quality of Service (QoS) requirements. OFDMA has the advantages of handling lower data rates and bursty traffic at a reduced power compared to single-user OFDM or its Time Division Multiple Access (TDMA) or Carrier Sense Multiple Access (CSMA) counterparts. In our work, we propose a Particle Swarm Optimization based resource allocation and scheduling scheme (PSORAS) with improved quality of service for OFDMA Systems. Simulation results indicate a clear reduction in delay compared to the Frequency Division Multiple Access (FDMA) scheme for resource allocation, at almost the same throughput and fairness. This makes our scheme absolutely suitable for handling real time traffic such real time video-on demand.

Class of Service Support Layer for Wireless Mesh Networks

This paper presents an add-on Class of Service (CoS) layer for wireless mesh networks. The proposed protocol is applicable for contention-based MACs and is therefore compatible with most of the Wireless Local Area Network (WLAN) and Wireless Sensor Network (WSN) protocols. The protocol has a locally centralized control for managing data flows, which either reserve a fixed bandwidth or are weighted by fair scheduling. The protocol reduces transmission collisions, thus improving the overall throughput. IEEE 802.11 adhoc WLAN has been taken as a platform for simulations and prototyping for evaluating the protocol performance. Network Simulator Version 2 (NS2) simulations show that the CoS protocol efficiently differentiates bandwidth, supports bandwidth reservations, and reaches less than 10 ms transfer delay on IEEE 802.11b WLAN. Testing with a full prototype implementation verified the performance of the protocol.

A Service Ratio-Based Dynamic Fair Queueing Algorithm for Packet-Switching Networks

A new weighted fair queueing algorithm is proposed, which uses the novel flow-based service ratio parameters to schedule flows. This solves the main drawback of traditional weighted fair queneing algorithms- the packet-based calculation of the weight parameters. In addition, this paper proposes a novel service ratio calculation method and a queue mangement technology. The former adjusts the service ratio parameters adaptively based on the dynamics of the packet lengths and thee solves the unfairness problem induced by the variable packet length. The latter improves the utilization of the server＇s queue buffer and reduces the delay jitter through restricting the buffer length for each flow.

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.

一种多用户MIMO/OFDMA系统的资源分配和调度方案

针对下行多用户多入多出/正交频分复用系统,提出了一种适合多业务类型的资源分配和调度算法.综合考虑了不同业务类型的服务质量需求,根据用户的信道条件、吞吐量和队列状态确定调度优先级;结合用户信道的空间相关性进行用户选择、功率分配和比特加载.通过充分利用空、时、频多用户分集增益。在保证实时业务最小时延要求和非实时业务最小速率要求的同时,最大化系统的吞吐量.仿真结果说明,所提算法在系统吞吐量、丢包率及最小速率满足率方面得到了改善.

宽带OFDMA系统有效支持QoS的分组调度算法

提出了2种适用于多用户正交频分复用多址接入(OFDMA)系统的分组数据调度算法,分别是多载波正比公平(MPF)算法和增强容量的MPF算法.理论分析和数值结果表明,2种算法都能保证用户的不同业务质量(QoS)要求,并且实现用户数据的公平发送,但是与MPF相比,增强容量的MPF算法具有更大的灵活性和更高的系统吞吐量.

OFDM下行链路的跨层自适应传输算法

提出了一种适用于正交频分复用(OFDM)下行(前向)链路的跨层自适应传输算法.算法考虑了物理层的信道状态信息、功率约束以及数据链路层(DLL)的业务和用户的调度公平.基于比例公平原则和注水原理,给出了算法的6个具体步骤.仿真结果表明该跨层传输方案优于单纯在物理层采用子载波和功率分配自适应算法的方案,相对于后者能够提高用户数据包的传输成功率和降低包的传输时延,并能支持更多的用户.

一种基于OFDM的具有QoS保证的无线IP分组调度算法

根据无线正交频分复用(OFDM)系统的多载波并行传输特性及多用户无线通信系统的特点,利用跨层交互算法,提出了1种适用于IP分组业务的无线多业务分组调度算法(AS-OFDM).该算法通过在系统的网络层、链路层及物理层之间传递系统信息,实现了无线资源的自适应分配和IP分组的自适应调度.仿真试验表明,同传统的IP调度算法相比,该调度算法在保证不同业务的服务质量(QoS)的条件下,能够实现对无线资源更为有效的利用和保证并具有相同业务需求的不同用户之间的公平性.

OFDMA系统实时业务分组调度算法

在移动通信系统中,常见的调度算法在处理实时业务时一般为信道状况好的用户分配过多的资源,而信道状况差的用户获得的调度机会相对较少。为保证实时业务的延迟要求,并兼顾不同用户间的公平性,基于正交频分多址接入系统,提出一种实时业务分组调度算法。在调度过程中,采用丢弃过期数据包的策略节省了系统资源。对信道状况好的用户采用较大的调度间隔,并采用高阶的调制编码方案将累积的数据包在一个调度间隔内发送,从而给予信道状况差的用户更多的调度机会。仿真结果证明,提出的算法能较好的满足实时业务的延迟要求,相对于改进的最大权重延迟优先算法和正比公平算法提高了用户间的公平性。

OFDMA系统中基于多业务QoS保证的机会调度算法

针对正交频分多址接入(Orthogonal frequency division multiple access,OFDMA)系统中多业务资源调度问题,提出了一种基于服务质量(Quality of service,QoS)的最小性能保证的资源机会调度算法。以系统总吞吐量优化为目标,根据业务的QoS参量设计子载波调度参数,并利用图论中最大加权双向匹配问题的求解算法,在各业务间公平分配子载波资源,保证了各业务的QoS要求。仿真结果表明,所提算法在保证各业务的最低速率要求的前提下有效地提高了系统总吞吐量性能。

宽带OFDM系统支持实时分组业务的接纳控制策略

针对基于分组交换的宽带正交频分复用(OFDM)无线通信系统,提出了新的动态呼叫接纳控制策略.采用马尔可夫队列模型和维纳过程预测理论,分析了实时业务的分组等待时延与其接纳概率的关系.并利用此关系,得到了以分组等待时延和切换中断概率为约束条件的最大接纳概率.该策略满足系统实时业务用户连接层面和分组层面服务质量的同时达到系统带宽资源的最大化利用.仿真结果验证了所提策略的性能.

中继OFDMA系统混合业务的分步跨层调度算法

由于实时和非实时两类业务具有不同的QoS要求,因此需要设计一种混合分组调度算法为两类业务用户提供QoS保证。在分析传统的PF与M-LWDF算法的基础上,根据已有的信道条件和不同的业务需求,使用MATLAB搭建系统仿真平台,设计了分步的跨层调度策略。仿真结果表明,该算法在满足公平性要求的情况下,不但能保证实时业务的时延需要,而且能够获得很好的吞吐量。

基于OFDMA面向QoS保障的新型多址接入协议

下一代无线局域网(wireless local area network,WLAN)IEEE 802.11ax标准委员会将高服务质量(quality of service,QoS)保障作为下一代WLAN的重要技术目标之一。由于无线业务种类繁多,因此对QoS的要求必然也是多种多样,然而现有的基于正交频分多址(orthogonal frequency division multiple access,OFDMA)的介质访问控制(media access control,MAC)协议均不能很好地支持QoS多样化且要求高的特点。针对这一问题,提出了一种面向QoS的下一代WLAN OFDMA多址接入协议。在该协议中,一方面考虑后向兼容性,沿用IEEE 802.11e的4种优先级业务;另一方面引入面向QoS的优先级调度算法以支持未来无线业务QoS多样化且要求高的特点。最后,通过仿真验证所提协议QoS-OFDMA MAC的系统有效吞吐量比顺序调度算法的OFDMA MAC和比例公平调度算法的OFDMA MAC分别提高了57.8%和59%。

Performance Analysis of Uplink Distributed Massive MIMO System with Cross-Layer Design over Rayleigh Fading Channel

The performance of uplink distributed massive multiple-input multiple-output(MIMO)systems with crosslayer design(CLD) is investigated over Rayleigh fading channel, which combines the discrete rate adaptive modulation with truncated automatic repeat request. By means of the performance analysis, the closed-form expressions of average packet error rate(APER)and overall average spectral efficiency(ASE)of distributed massive MIMO systems with CLD are derived based on the conditional probability density function of each user’s approximate effective signal-to-noise ratio(SNR)and the switching thresholds under the target packet loss rate(PLR)constraint.With these results,using the approximation of complementary error functions,the approximate APER and overall ASE are also deduced. Simulation results illustrate that the obtained theoretical ASE and APER can match the corresponding simulations well. Besides,the target PLR requirement is satisfied,and the distributed massive MIMO systems offer an obvious performance gain over the co-located massive MIMO systems.