Joint packet scheduling and resource allocation with quality fairness for wireless VoD system

This paper investigates the problem of multiuser packet scheduling and resource allocation for video transmission over downlink OFDMA networks. A cross-layer approach is proposed to maximize the received video quality under the video quality fairness constraint. Unlike the previous methods in which the objective index is estimated the video quality in the unit of bit, the proposed algorithm develops the objective index in unit of packet, which is more fit for video transmission. In order to solve the optimization problem, a suboptimal algorithm of joint packet scheduling and resource allocation is proposed. The algorithm is compatible with the emerging wireless standards, such as IEEE 802.16. The simulation results show that the proposed method outperforms the conventional resource allocation schemes in terms of received video qualities and quality fairness.     

基于QoS保证的多用户OFDM系统跨层资源分配

针对正交频分复用(OFDM)系统资源分配和调度问题,提出一种基于第三代移动通信长期演进(LTE)系统的分块跨层资源分配算法。此算法考虑物理层的信道状态信息、媒体接入层(MAC)的有限用户缓存队列长度、用户的丢失率和时延等QoS要求,以提高系统频谱效率为总体目标。通过从实时视频业务和混合业务两种业务类型下进行大量对比分析,得出提出的算法能有效提高系统的频谱效率和降低系统时延。     

Cross-Layer Design for OFDMA Wireless Systems With Heterogeneous Delay Requirements

This paper proposes a cross-layer scheduling scheme for OFDMA wireless systems with heterogeneous delay requirements. We shall focus on the cross-layer design which takes into account both queueing theory and information theory in modeling the system dynamics. We propose a delay-sensitive cross-layer design, which determines the optimal subcarrier allocation and power allocation policies to maximize the total system throughput, subject to the individual user's delay constraint and total base station transmit power constraint. The delay-sensitive power allocation was found to be multilevel water-filling in which urgent users have higher water-filling levels. The delay-sensitive subcarrier allocation strategy has linear complexity with respect to number of users and number of subcarriers. Simulation results show that substantial throughput gain is obtained while satisfying the delay constraints when the delay-sensitive jointly optimal power and subcarrier allocation policy is adopted.     

下行多业务OFDMA系统中基于有效容量的资源分配算法研究

该文对多业务OFDMA系统的下行链路资源分配进行了研究,侧重考虑了实时业务用户的QoS要求,建立2维马尔可夫无线信道模型,采用自适应调制技术、有效容量理论以及有效带宽理论,为实时用户分配资源;并实现了非实时业务用户、尽力而为业务用户的资源分配。仿真结果表明,所提算法保证了下行OFDMA系统吞吐量的同时,在实时业务的延时和丢包率等方面都有一定的优越性。     

Utility-based resource allocation and scheduling in OFDM-based wireless broadband networks

This article discusses downlink resource allocation and scheduling for OFDM-based broadband wireless networks. We present a cross-layer resource management framework leveraged by utility optimization. It includes utility-based resource management and QoS architecture, resource allocation algorithms, rate-based and delay-based multichannel scheduling that exploits wireless channel and queue information, and theoretical exploration of the fundamental mechanisms in wireless resource management, such as capacity, fairness, and stability. We also provide a solution that can efficiently allocate resources for heterogeneous traffic with diverse QoS requirements.     

正交频分多址系统中一种面向多业务应用的自适应资源分配算法

针对正交频分多址(OFDMA)系统下行链路多业务自适应调度的问题,该文首先以最大化系统吞吐量为优化目标、每种业务的服务质量(QoS)保证为约束条件,建立了一种通用的多业务自适应资源分配模型。为解决此优化问题,提出了一种具体的自适应资源调度算法。该算法对实时业务按照用户选择最好的信道的原则分配尽可能少的资源以保证其QoS,对非实时业务把尽可能多的剩余资源按照信道选择最好的用户的原则进行分配,充分利用信道资源,提升系统容量。仿真结果表明,该算法保证了下行OFDMA系统吞吐量的同时,在实时业务的延时和丢包率等方面有一定的优越性。     

跨层资源调度算法综述

跨层资源调度对实现资源的有效利用,保证业务的QoS起着重要作用.本文对跨层资源调度的研究状况进行了概述:根据所采用的技术体制和约束类型,介绍了单载波系统和OFDM系统的多用户机会调度问题和相应算法,分析了单一类型和多种类型资源共享约束下的机会调度算法:分别从队列调度、子载波分配和功率控制3个方面,对基于队列和信道状态信息的资源调度算法进行了分析和比较:对提高反馈信息的准确性、减少反馈信息量的方法和机制进行了简要介绍.最后指出了需要进一步研究的问题.     

OFDMA系统跨层资源分配算法

OFDM具有高频谱利用率和抗多径衰落的优点,已被公认为第三代移动通信系统长期演进标准以及第四代移动通信系统的核心技术。OFDMA是基于OFDM的一种多用户接入技术,在OFDMA系统中,各用户在不同的子载波上同时传输数据。主要研究了OFDMA系统中的跨层资源分配算法。详细分析了保证速率比例公平的非实时业务跨层资源分配算法,仿真结果说明该算法能够较好地保证用户之间的公平性,并能够获得较大的系统吞吐量和较小的业务延时。     

3GPP LTE系统中无线视频传输调度算法研究

摘要：针对3GPP LTE系统,本文提出了适用于下行链路视频业务的一种新的分组调度算法,即时延优先比例公平调度（Delay First-Proportional Fair Scheduling,DF-PFS）。当需要做出调度决策时,该算法利用每个用户的数据包时延信息和瞬时下行信道条件,在满足用户QoS前提下最大限度地提高系统吞吐量。同时,当用户选择资源块（RB）进行传输后,即从用户集合中将该用户删除,避免接近eNodeB的用户一直占用无线资源,确保了资源分配的公平性。实验仿真结果表明,该算法在丢包率和PSNR性能上优于最大权重时延优先（M-LWDF）算法,在保证用户间公平性前提下,满足了视频业务的QoS要求。     

Cross-layer resource allocation over wireless relay networks for quality of service provisioning

The authors propose a physical-datalink cross-layer resource allocation scheme over wireless relay networks for quality-of-service (QoS) guarantees. By integrating information theory with the concept of effective capacity, the proposed scheme aims at maximizing the relay network throughput subject to a given delay QoS constraint. This delay constraint is characterized by the so-called QoS exponent thetas, which is the only requested information exchanged between the physical layer and the datalink layer in our cross-layer design based scheme. Over both amplify-and-forwards (AF) and decode-and-forward (DF) relay networks; the authors develop the associated dynamic resource allocation algorithms for wireless multimedia communications. Over DF relay network, the authors also study a fixed power allocation scheme to provide QoS guarantees. The simulations and numerical results verify that our proposed cross-layer resource allocation can efficiently support diverse QoS requirements over wireless relay networks. Both AF and DF relays show significant superiorities over direct transmissions when the delay QoS constraints are stringent. On the other hand, the results demonstrate the importance of deploying the dynamic resource allocation for stringent delay QoS guarantees.     

Green Resource Allocation for Multiple OFDMA Based Networks: A Survey

Orthogonal frequency division multiple access (OFDMA) is a popular and widely accepted multiple access technique to provide high data rate services in a mobile environment in the area of wireless communications. OFDMA can provide better flexibility in allocating the radio spectra by utilizing subcarrier allocations, scheduling, and energy control to obtain multi-dimension diversity gains. Due to its resource allocation flexibility, OFDMA has been widely used as a green air interface technology for the emerging broadband wireless access networks. This paper extensively addresses the integration of green OFDMA to the future air interface technologies, for instance:two-tier cellular, multi radio access technologies (RATs), FemtoCell, and relay networks. The main focus of the paper is to review and analyze the current OFDMA techniques to address the green resource allocation in multiuser diversity, where the critical constraints are the computational complexity, energy efficiency, and the sub-channel assignment. The future trend of OFDMA based networks will aim to maximize the energy efficiency of the exclusive channel assignment through a joint sub-channel and power allocation to accommodate high data traffic networks specially the relay based 5G cellular networks.     

基于负载自适应的无线自组网视频传输队列调度算法

移动终端多媒体业务的发展目前已经成为终端发展的必然趋势.如何在移动终端构成Ad hoc网络时有效地进行视频传输是无线网络研究的热点之一.提出了一种基于负载状况的跨层优化方案,其基本思想是结合应用层视频编码的特点和接入层的网络负载和资源的情况联合进行优化.在特定的资源下通过概率接入的方法对重要性更高的数据包进行更优先的接入.仿真结果显示,在网络处于高负载、多跳传输等场景下,提出的方案视频传输质量PSNR值提升3 dB以上.相对于传统调度算法,系统时延也可以大幅度降低.     

Guest Editorial Cross-layer Optimized Wireless Multimedia Communications

The 19 papers in this special issue focus on cross-layer optimized wireless multimedia communications. The papers are organized into four sections: quality of service support for wireless networks; system architecture for multimedia over wireless networks; resource allocation in wireless multimedia communications, and multimedia coding and scheduling issues in wireless networks.     

基于能效优化的用户调度与资源分配算法

该文针对多用户OFDMA移动通信下行系统,提出了基于能效优化的用户调度和资源分配方法。所提方法在满足用户服务质量(QoS)要求的前提下,以最大化系统能效为准则建立优化模型,假设在发射端完全已知信道状态信息(CSI)的情况下,充分利用系统内在的分集,给出了用户调度与速率分配的策略,有效地提高了系统的能量使用效率。仿真结果表明,所提算法的性能在较低复杂度前提下能够取得接近最优算法的性能。     

一种适用于多用户OFDM系统下行链路的跨层设计调度算法

该文提出了一种适用于多用户正交频分复用(OFDM)系统下行链路的调度算法,基于跨层结构设计,并分别考虑了媒体接入控制(MAC)层的用户服务质量(QoS)要求、用户公平性、数据包队列状态信息以及物理层的信道状态信息(CSI)和功率约束等。多用户OFDM系统可以通过该调度算法充分利用MAC层和物理层的不同参数特性,在保证用户QoS的同时最大化频谱的利用效率。仿真结果表明,在小区内各个移动用户具有不同的接收SNR的情况下,该算法具有服务质量随信噪比波动平缓、丢包率低、实现复杂度低等特点。     

A Dynamic Resource Allocation Scheme for the Downlink Heterogeneous Traffic of Internet Protocol (IP) Based OFDM networks

Radio Resource management mechanisms such as physical-centric radio resource allocation and medium access control (MAC)—centric packet scheduling are expected to play a substantial role in the performance of orthogonal frequency division multiplexing (OFDM) based wireless networks. OFDM provide fine granularity for resource allocation since they are capable of dynamically assigning sub-carriers to multiple users and adaptively allocating transmit power. The current layered networking architecture, in which each layer is designed and operated independently, results in inefficient resource use in wireless networks due to the nature of the wireless medium, such as time-varying channel fading. Thus, we need an integrated adaptive design across different layers, allowing for a cross-layer design. In this paper, a scheduling scheme is proposed to dynamically allocate resources for the downlink data transmission of internet protocol based OFDM networks. Generally to maximize the capacity and user satisfaction improvements in packet data admission, scheduling and policing are necessary. Of the three, efficient scheduling has the greatest impact on increased system capacity or effective spectrum usage. In addition, proper scheduling can greatly improve user satisfaction. The contribution of this work is twofold: first we evaluate current allocation schemes by exploiting the knowledge of channel sate information (CSI) and traffic characteristics in terms of queue state information (QSI) to acquire the system performance on a real time network. Second, the resource allocation scheme is extended by incorporating MAC layer information as well as opportunistic packet scheduling in the time-domain-based on minimum weight cost function. The key factors that affect the overall system performance in terms of system average throughput and delay are identified, evaluated and discussed.     

Content-Aware Resource Allocation and Packet Scheduling for Video Transmission over Wireless Networks

A cross-layer packet scheduling scheme that streams pre-encoded video over wireless downlink packet access networks to multiple users is presented. The scheme can be used with the emerging wireless standards such as HSDPA and IEEE 802.16. A gradient based scheduling scheme is used in which user data rates are dynamically adjusted based on channel quality as well as the gradients of a utility function. The user utilities are designed as a function of the distortion of the received video. This enables distortion-aware packet scheduling both within and across multiple users. The utility takes into account decoder error concealment, an important component in deciding the received quality of the video. We consider both simple and complex error concealment techniques. Simulation results show that the gradient based scheduling framework combined with the content-aware utility functions provides a viable method for downlink packet scheduling as it can significantly outperform current content-independent techniques. Further tests determine the sensitivity of the system to the initial video encoding schemes, as well as to non-real-time packet ordering techniques.     

Cross-Layer Radio Resource Allocation for Multicarrier Air Interfaces in Multicell Multiuser Environments

Packet scheduling over shared channels is one of the most attractive issues for researchers dealing with radio resource allocation in wireless networks as modern systems' different traffic types, with different application requirements, need to coexist over the air interface. Recently, attention has been attracted to multicarrier techniques and the application of cross-layer approaches to the design of wireless systems. In this paper, a radio access network using a multicarrier air interface is considered in a multicell multiuser context. We propose a new cross-layer scheduling algorithm that manages channel, physical layer, and application-related information; we compare its performance with a previously published cross-layer strategy and with simpler well-known channel-aware or channel-unaware techniques and then discuss its optimization. We investigate the performance in terms of perceived user quality and fairness in the presence of mixed realistic traffic composed of H.264 video streaming with tight bounds on the delay jitter and file transfer protocol (FTP) data. To support video traffic, application-suited buffer-management techniques are also considered in conjunction with scheduling, and link adaptation is implemented at the physical layer to better exploit channel fluctuations. The role of scheduling and resource-allocation functionalities are discussed. It is shown that the cross-layer strategy proposed guarantees the same performance obtained by the previously published algorithm while reducing complexity. Moreover, under heavily loaded conditions, the cross-layer scheduling strategy provides a significant gain with respect to simple channel-aware or channel-unaware techniques.     

LTE-A异构网络下的高效资源分配算法

分析了OFDMA上行系统中,由宏基站(macrocell)和家庭式基站(femtocell)组成的双层网络,并提出了高效的资源分配算法。为避免严重的跨层干扰导致双层网络中的资源分配不协调,提出了一个跨层干扰控制算法。在基于干扰控制算法的结果上,提出包括功率分配和频谱分配的资源分配算法,以满足UE的目标速率,并获得较好的吞吐量性能。通过仿真,结果显示所提的资源分配算法相比较传统的算法,尤其在UE QoS保证和吞吐量性能的体现上,能获得明显的性能增益。     

Adaptive envelope process and minimum service curve applied to resource block allocation in the LTE downlink

In this work, we propose a resource allocation algorithm for the LTE downlink that makes use of an adaptive multifractal envelope process and a minimum service curve. The proposed scheduling algorithm aims to improve some network parameters while guaranteeing a maximum delay to the user by considering the following information: backlog, channel condition and user traffic behavior. In order to estimate the maximum network delay, we propose an adaptive minimum service curve for the LTE network that can be used for admission control purposes in the resource allocation algorithm. The performance of the proposed scheduling algorithm is compared to those of several scheduling schemes known in the literature through computational simulations of the LTE downlink. In order to develop a new adaptive envelope process and to precisely describe network flows, we propose an adaptive algorithm to estimate the parameters of the Multifractal Wavelet Model (MWM). The proposed envelope process is compared to the main traffic model based envelope processes known in the literature. Simulations of the LTE downlink considering AMC (Adaptive Modulation and Coding) are carried out showing the efficiency of the proposed resource allocation approach that considers adaptive estimation of network traffic parameters.