Optimal packet length scheduling for regulated media streaming

We present, for a prerecorded stream, an algorithm to determine a packet length schedule that is optimal with respect to appropriate measures of distortion and quality smoothness, when the traffic is required to adhere to specified token bucket regulation constraints.     

Optimal uplink packet scheduling for CDMA non-real-time data

The problem of optimal uplink packet scheduling for non-real-time data in CDMA systems is investigated and a load-based optimisation model is presented. In contrast to existing models, the proposed model takes the actual load of each mobile user into consideration and adopts an achievable throughput in the objective function. The proposed model also optimises the resource utilisation. Numerical results show that the proposed model can achieve a higher throughput and a higher resource utilisation.     

Optimal broadcast scheduling in packet radio networks using meanfield annealing

We present an efficient broadcast scheduling algorithm based on mean field annealing (MFA) neural networks. Packet radio (PR) is a technology that applies the packet switching technique to the broadcast radio environment. In a PR network, a single high-speed wideband channel is shared by all PR stations. When a time-division multi-access protocol is used, the access to the channel by the stations' transmissions must be properly scheduled in both the time and space domains in order to avoid collisions or interferences. It is proven that such a scheduling problem is NP-complete. Therefore, an efficient polynomial algorithm rarely exists, and a mean field annealing-based algorithm is proposed to schedule the stations' transmissions in a frame consisting of certain number of time slots. Numerical examples and comparisons with some existing scheduling algorithms have shown that the proposed scheme can find near-optimal solutions with reasonable computational complexity. Both time delay and channel utilization are calculated based on the found schedules     

Optimal and suboptimal packet scheduling over correlated time varying flat fading channels

We address the issue of optimal packet scheduling over correlated fading channels which trades off between minimization of three goals: average transmission power, average delay and average packet dropping probability. We show that the problem forms a weakly communicating Markov decision process and formulate the problem as both unconstrained and constrained problem. Relative value iteration (RVI) algorithm is used to find optimal deterministic policy for unconstrained problem, while optimal randomized policy for constrained problem is obtained using linear programming (LP) technique. Whereas with RVI only a finite number of scheduling policies can be obtained over the feasible delay region, LP can produce policies for all feasible delays with a fixed dropping probability and is computationally faster than the RVI. We show the structure of optimal deterministic policy in terms of the channel and buffer state and form a simple log functional suboptimal scheduler that approximately follows the optimal structure. Performance results are given for both constant and bursty Poisson arrivals, and the proposed suboptimal scheduler is compared with the optimal and channel threshold scheduler. Our suboptimal scheduler performs close to the optimal scheduler for every feasible delay and is robust to different channel parameters, number of actions and incoming traffic distributions.     

QoS-guaranteed packet scheduling in wireless networks

To guarantee the quality of service (QoS) of a wireless network, a new packet scheduling algorithm using cross-layer design technique is proposed in this article. First, the demand of packet scheduling for multimedia transmission in wireless networks and the deficiency of the existing packet scheduling algorithms are analyzed. Then the model of the QoS-guaranteed packet scheduling (QPS) algorithm of high speed downlink packet access (HSDPA) and the cost function of packet transmission are designed. The calculation method of packet delay time for wireless channels is expounded in detail, and complete steps to realize the QPS algorithm are also given. The simulation results show that the QPS algorithm that provides the scheduling sequence of packets with calculated values can effectively improve the performance of delay and throughput.     

Fair scheduling in wireless packet networks

Fair scheduling of delay and rate-sensitive packet flows over a wireless channel is not addressed effectively by most contemporary wireline fair-scheduling algorithms because of two unique characteristics of wireless media: (1) bursty channel errors and (2) location-dependent channel capacity and errors. Besides, in packet cellular networks, the base station typically performs the task of packet scheduling for both downlink and uplink flows in a cell; however, a base station has only a limited knowledge of the arrival processes of uplink flows. We propose a new model for wireless fair-scheduling based on an adaptation of fluid fair queueing (FFQ) to handle location-dependent error bursts. We describe an ideal wireless fair-scheduling algorithm which provides a packetized implementation of the fluid mode, while assuming full knowledge of the current channel conditions. For this algorithm, we derive the worst-case throughput and delay bounds. Finally, we describe a practical wireless scheduling algorithm which approximates the ideal algorithm. Through simulations, we show that the algorithm achieves the desirable properties identified in the wireless FFQ model     

双服务器分组调度算法

分组调度算法对于确保分组交换系统的QoS具有重要意义。时延,公平性,计算复杂度是微量分组度算法的主要指标。本文提出了一种双服务器分组调度算法,该算法在两种不同的工作状态下分别采用两种服务规则决定分组的服务次序。其中一种服务规则用来确保分组的时延,另一种服务规则在时延得到保障的情况下对系统的公平性进行改善,这两种规则计算都不复杂。因此本文提出的算法具有时延低,公平性较好,计算复杂度低的特点。     

输入排队结构交换机分组调度研究

以决定分组调度算法的交换结构为基础,从协调,减少和隔离输入排队交换结构中输入输出竞争裁决冲突的角度,分别讨论了VOQ,CIOQ,CICQ结构中的分组调度问题,并以当前最新的调度算法为例加以说明,进行了定性分析和定量对比,指出了具体有待研究的问题。随后讨论了最近才开始研究的光电混合结构中的分组调度问题。最后从交换结构和算法两个方面探讨了今后的研究方向和发展趋势。     

TD-HSUPA的自适应调度算法

提出了自适应分组调度的策略,使TD-HSUPA(high speed uplink packet access,高速上行分组接入)可以更加灵活地进行分组调度。在自适应调度算法中,系统进行调度算法的同时,在后台运用遗传算法找出更适合当前无线网络环境的权值。系统仿真表明,该算法可以灵活地处理各种网络环境。     

GPRS中分组调度算法

主要讨论通用无线分组业务（GPRS）调度算法。首先介绍了一些常用分组调度算法，给出了GPRS中服务质量（QoS)定义和GPRS中选择分组调度算法原则，并根据对GPRS特性和三种算法性能的分析与比较，提出了一种新的基于延迟约束分组调度算法。通过仿真发现，新算法可在满足延迟要求基础上以较小复杂度获得比其余算法更高的资源利用率。     

一种无时间标记的包调度策略

本文提出一种多队列的包调度算法，该方法在调度的公平性、延时和所需的缓冲空间等性能方面与PGPS，PRPS等调度算法有相同的性能，同时无需对各个到达的数据包记上时间标记，使调度操作更为简单有效。     

Split-channel pipelined packet scheduling for wireless networks

To reduce medium access control (MAC) overhead and improve channel utilization, there has been extensive research on dynamically adjusting the channel access behavior of a contending station based on channel feedback information. This paper explores an alternative approach, named pipelined packet scheduling, to reduce the MAC overhead. MAC overheads can be divided into bandwidth-dependent and bandwidth-independent components and these overheads can both be reduced by using split-channel pipelining mechanisms, as demonstrated in this paper. In the past, pipelining mechanisms have not been well studied. This paper introduces two total pipelining schemes that attempt to fully pipeline contention resolution with data transmission. Further, the paper identifies shortcomings of total pipelining in the wireless environment and proposes a partial pipelining approach to overcome these shortcomings. Simulation results show that substantial performance improvement in channel utilization, average packet access delay, and access energy cost can be achieved with a properly designed scheme.     

一种改进的DRR调度算法

为了简单有效地分配链路带宽,该文分析了 DRR(Deficit Round Robin)算法在数据交换实现上的局限性,提出了一种基于令牌扣除并平滑输出突发性的调度算法。该算法能够减小调度开销,平滑输出突发性,硬件实现简单。证明了在多数情况下改进算法的公平性优于 DRR算法。仿真结果表明改进算法能够有效地分配输出链路的带宽,缓解令牌数选取对输出突发性和抖动性的影响。     

QoS-oriented packet scheduling scheme for opportunistic networks

The unique characteristics of opportunistic networks (ONs), such as intermittent connectivity and limited network resources, makes it difficult to support quality of service (QoS) provisioning, particularly to guarantee delivery ratio and delivery delay. In this paper, we propose a QoS-oriented packet scheduling scheme (QPSS) to make decisions for bundle transmissions to satisfy the needs for the delivery ratio and delivery delay constraints of bundles. Different from prior works, a novel bundle classification method based on the reliability and latency requirements is utilized to decide the traffic class of bundles. A scheduling algorithm of traffic class and bundle redundancy is used to maintain a forwarding and dropping priority queue and allocate network resources in QPSS. Simulation results indicate that our scheme not only achieves a higher overall delivery ratio but also obtains an approximate 14% increase in terms of the amount of eligible bundles.     

Jointly optimal routing and scheduling in packet ratio networks

A multihop packet radio network is considered with a single traffic class and given end-to-end transmission requirements. A transmission schedule specifies at each time instant the set of links which are allowed to transmit. The purpose of a schedule is to prevent interference among transmissions from neighboring links. Given amounts of information are residing initially at a subset of the network nodes and must be delivered to a prespecified set of destination nodes. The transmission schedule that evacuates the network in minimum time is specified. The decomposition of the problem into a pure routing and a pure scheduling problem is crucial for the characterization of the optimal transmission schedule     

Minimising the size of voids in optical packet switching using a novel packet scheduling algorithm

In this paper, we propose a new packet scheduling algorithm to minimise the size of voids in optical packet switching. The effects of excess load, output utilisation, and packet loss probability are closely studied. Other contributing factors to the packet loss probability, which include the buffer depth and the numbers of wavelength channels, are also investigated. The proposed algorithm is of importance to next generation networks where broadband capabilities with end-to-end quality of service over all-IP optical networks is envisaged.     

最佳小波包多载波调制解调技术

本文利用离散小波包变换（ＤＷＰＴ）导出信号窨的诱导小波包基。在此基础上建立起基于ＤＷＰＴ的小波包多载波传输系统的概念,提出了最佳小波包多载波市制解调技术。技术根据给定的信道特性,采用类似于最佳基搜索城众多的小波包多载波市制解调方案中快速寻求出最佳方案,使得系统解调出的信号中所要信号与符号间干扰的信干比在不增强噪声的前提下达了最大。     

A distributed scheduling architecture for scalable packet switches

The continuous growth in the demand for diversified quality-of-service (QoS) guarantees in broadband networks introduces new challenges in the design of packet switches that scale to large switching capacities. Packet scheduling is the most critical function involved in the provision of individual bandwidth and delay guarantees to the switched flows. Most of the scheduling techniques proposed so far assume the presence in the switch of a single contention point, residing in front of the outgoing links. Such an assumption is not consistent with the highly distributed nature of many popular architectures for scalable switches, which typically have multiple contention points, located in both ingress and egress port cards, as well as in the switching fabric. We define a distributed multilayered scheduler (DMS) to provide differentiated QoS guarantees to individual end-to-end flows in packet switches with multiple contention points. Our scheduling architecture is simple to implement, since it keeps per-flow scheduling confined within the port cards, and is suitable to support guaranteed and best-effort traffic in a wide range of QoS frameworks in both IP and ATM networks     

A new model for scheduling packet radio networks

Packet radio networks are modeled as arbitrary graphs by most researchers. In this paper we show that an arbitrary graph is an inaccurate model of the radio networks. This is true because there exists a large class of graphs which will not model the radio networks. Radio networks can be modeled accurately by a restricted class of graphs called the planar point graphs. Since the radio networks can accurately be modeled only by a restricted class of graphs, the NP-completeness results for scheduling using an arbitrary graph as the model, do not correctly reflect the complexity of the problem. In this paper we study the broadcast scheduling problem using the restricted class as the model. We show that the problem remains NP-complete even in this restricted domain. We give an O(n log n) algorithm when all the transceivers are located on a line. This revised version was published online in July 2006 with corrections to the Cover Date.