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.     

Priority-based rate control for service differentiation and congestion control in wireless multimedia sensor networks

In wireless multimedia sensor networks (WMSNs) a sensor node may have different types of sensor which gather different kinds of data. To support quality of service (QoS) requirements for multimedia applications having a reliable and fair transport protocol is necessary. One of the main objectives of the transport layer in WMSNs is congestion control. We observe that the information provided may have different levels of importance and argue that sensor networks should be willing to spend more resources in disseminating packets carrying more important information. Some applications of WMSNs may need to send real time traffic toward the sink node. This real time traffic requires low latency and high reliability so that immediate remedial and defensive actions can be taken when needed. Therefore, similar to wired networks, service differentiation in wireless sensor networks is also an important issue. We present a priority-based rate control mechanism for congestion control and service differentiation in WMSNs. We distinguish high priority real time traffic from low priority non-real time traffic, and service the input traffic based on its priority. Simulation results confirm the superior performance of the proposed model with respect to delays, delay variation and loss probability.     

AdHoc网络中考虑事件紧急度的跨层QoS保障机制

考虑Ad Hoc网络中事件紧急度,提出一种可以有效改善整体高优先级业务流时延和时延抖动性能的跨层QoS服务质量保障算法.根据时延要求及业务分组距离目的点的跳数信息,评估此业务的紧急度,并在调度传输时充分考虑各个事件的紧急度.在有实时要求的业务发生超时的情况下,通过合适的路由置换方法,改善业务流时延及网络吞吐量.本文重点讨论如何在IEEE802.11e协议基础上实现对指定优先级业务流的服务质量保障.GloMoSim仿真环境下的仿真结果显示该算法与原有IEEE802.11e协议相比,对于高优先级业务,在分组端到端时延、时延抖动以及网络吞吐量方面有较大的改善.     

A multi-layer experimental study of multimedia and QoS communication in wireless mesh networks

A significant issue in Mesh networks is to support multimedia transmissions while providing Quality of Service (QoS) guarantees to mobile users. For real-time multimedia streaming, unstable throughput or insufficient bandwidth will incur unexpected delay or jitter, and it remains difficult to provide comprehensive service guarantees for a wireless mesh environment. In this paper, we target the problem of providing multimedia QoS in wireless mesh networks. We design and implement a campus test-bed for supporting multimedia traffic in mobile wireless mesh networks, and investigate in detail some possible improvements on a number of layers to enable multimedia transmission over wireless networks with QoS support. We first study a number of improvements of some existing routing protocols to support multimedia transmissions. Some new admission control and rate control mechanisms are studied and their performance gains are verified in our experiments. In our new cross-layer adaptive rate control (CLARC) mechanism, we adaptively change the video encoder’s output bit rate based on the available network bandwidth to improve the quality of the received video. We also design a mobile gateway protocol to connect the MANET to Internet and a wireless LAN management protocol to automatically manage WLAN to provide some QoS.     

基于北斗系统的QoS保障地理位置路由算法

基于北斗定位/导航系统,研究无线多媒体传感器网络(WMSNs)定位技术在地理位置信息路由算法中的应用,根据贪婪策略和地理位置信息设计一个无线多媒体传感器网络QoS支持路由算法。该算法与SPEED算法一样,提供软时延保障。同时,优化的代价函数平衡了能耗、网络生存期和无线带宽等参数。在理论上分析该算法的软、硬时延保障及其他QoS性能,结果表明,该算法能为WMSNs的多媒体通信提供较多的QoS控制保障。     

基于QoS机制的宽带接入路由器

高速化和多媒体化成为未来网络发展的主要方向，适时灵活的网络增值应用需要在网络的接入端就要提供QoS保证，该文详细分析了接入路由器的QoS策略服务机制和QOS保障机制，提出了新一代基于QoS机制的宽带接入路由器的系统设计。     

无线多媒体传感器网络并发传输性能建模及实验评估

针对无线多媒体传感器网络（wireless multimedia sensor network,WMSN）在多路视频并发传输性能方面缺乏定量化评估的问题,对WMSN的并发性能进行了建模分析与实验验证．首先利用排队论和概率论原理构造了一个基于IEEE 802.11的WMSN数据链路层延迟模型,为实验提供理论依据．而后实验测量了基于IEEE 802.11的WMSN在不同网络拓扑下,不同因素（如距离、跳数、并发视频数）对视频评价指标（延迟、抖动、信道利用率）的影响．理论及实验结果表明,IEEE 802.11协议仅能支持四路以下视频并发传输,不适合高并发视频传输,亟待开展WMSN专属协议及算法的研究．     

可靠多媒体多播传输协议

对于大规模多媒体多播应用来说,一个有效发现和修正传输错误的可靠多媒体多播协议是必要的。该文研讨了多媒体多播应用中的允许延迟和分组丢失率问题,提出了一种基于协议转接概念的可靠多播传输协议(RMTP)。RMTP协议聚焦在允许延迟上提供多媒体服务质量保证,转接节点放置在多播树上,数据恢复在两个转接节点之间进行。RMTP协议转接能立即满足重传需求和减少分组的复制数量。最后,给出了RMTP协议的性能分析及与SRM协议的比较。研究表明RMTP协议为多媒体多播传输提供了一种新的有效途径。     

Optimized H.264 Video Encoding and Packetization for Video Transmission Over Pipeline Forwarding Networks

Previous works showed that the quality-of-service (QoS) requirements of multimedia applications can be optimally satisfied by pipeline forwarding (PF) by providing end-to-end delay guarantees as well as high network resource utilization. However, the unavoidable mismatch between reserved resources and the unpredictable traffic profile of a video stream has an impact on the resulting application layer quality. Therefore, a new low-complexity H.264 video encoding and packetization scheme based on a distortion-optimized macroblock grouping technique is designed here to maximize the performance of video transmission on PF networks. The scheme considers the perceptual importance of the different parts of the video data to group the most important information in few packets that are the natural candidates to receive the deterministic service provided by PF. Results show peak signal-to-noise ratio (PSNR) gains up to 2.5 dB over traditional video encoding and packetization schemes, as well as more graceful degradation in case of high network load.     

LEO卫星网QoS遗传算法路由协议

为了满足多媒体应用的QoS要求,卫星路由协议应该更有效地利用网络资源,提供更好的QoS保障。为此提出了一个基于遗传算法的LEO卫星网络QoS路由协议,称为遗传卫星路由协议（GSRP）。改进了新的操作函数,如适应度函数、终止函数,以及变异率和路由表。仿真结果表明,GSRP能够实现较少CBP和HBP的可靠的点对点时延约束,以及比传统的算法更有效的负载平衡。     

A game theoretic approach for power allocation with QoS constraints in wireless multimedia sensor networks

The distinctive features of wireless multimedia sensor networks (WMSNs) include application-specific quality-of-service (QoS) requirements and limited energy supply, with which each node makes its own decisions selfishly. Therefore this paper presents a power control game theoretic approach for WMSNs by studying the effect of transmission power on QoS and energy efficiency. The game approach determines the transmission strategy using utility optimization according to the fluctuation of channel states. Here, the utility function is defined by effective throughput per unit power while satisfying the user’s delay QoS constraints. The existence and uniqueness of Nash equilibrium for the proposed game are proved. Finally, the simulation results show that each user chooses the optimal transmission power to maximize its utility based on other constant parameters and the effects of delay constraints on the user’s utility are quantified as well.     

无线多媒体传感器网络多路径路由协议综述

在无线多媒体传感器网络路由协议中,多路径路由协议（MRP）有利于提高数据传输的可靠性和实现网络负载平衡,为多媒体数据流提供服务质量（QoS）保障。介绍了MRP的分类方法,并根据路由建立时机和数据传输技术,将其分为主动式、响应式和编码式三大类,对每一类涉及的MRP进行了详细的阐述和分析。最后归纳比较这些协议的特点,并指出MRP未来的研究重点。     

An efficient joint channel assignment and QoS routing protocol for IEEE 802.11 multi-radio multi-channel wireless mesh networks

With the emerging of video, voice over IP (VoIP) and other real-time multimedia services, more and more people pay attention to quality of service (QoS) issues in terms of the bandwidth, delay and jitter, etc. As one effective way of broadband wireless access, it has become imperative for wireless mesh networks (WMNs) to provide QoS guarantee. Existing works mostly modify QoS architecture dedicated for ad hoc or sensor networks, and focus on single radio and single channel case. Meanwhile, they study the QoS routing or MAC protocol from view of isolated layer. In this paper, we propose a novel cross-layer QoS-aware routing protocol on OLSR (CLQ-OLSR) to support real-time multimedia communication by efficiently exploiting multi-radio and multi-channel method. By constructing multi-layer virtual logical mapping over physical topology, we implement two sets of routing mechanisms, physical modified OLSR protocol (M-OLSR) and logical routing, to accommodate network traffic. The proposed CLQ-OLSR is based on a distributed bandwidth estimation scheme, implemented at each node for estimating the available bandwidth on each associated channel. By piggybacking the bandwidth information in HELLO and topology control (TC) messages, each node disseminates information of topology and available bandwidth to other nodes in the whole network in an efficient way. From topology and bandwidth information, the optimized path can be identified. Finally, we conduct extensive simulation to verify the performance of CLQ-OLSR in different scenarios on QualNet platform. The results demonstrate that our proposed CLQ-OLSR outperforms single radio OLSR, multi-radio OLSR and OLSR with differentiated services (DiffServ) in terms of network aggregate throughput, end-to-end packet delivery ratio, delay and delay jitter with reasonable message overheads and hardware costs. In particular, the network aggregate throughput for CLQ-OLSR can almost be improved by 300% compared with the single radio case.     

基于转接节点的可靠多媒体多播协议

研讨了多媒体多播应用中的允许延迟和分组丢失率问题,提出了一种基于转接节点概念的可靠多播协议（RMPRM）。RMPRM协议聚焦在允许延迟上提供多媒体服务质量保证,转接节点放置在多播树上,数据恢复在两个转接节点之间进行。RMPRM协议转接能满足重传需求和减少分组的复制数量。给出了RMPRM协议与不可靠多播协议的比较。仿真实验表明,该协议具有较高的传输率和较低的端到端的传输延迟。     

MANET中基于遗传算法的QoS多播路由协议

随着多媒体业务的普及,如何为MANET多播路由提供QoS保障成为研究热点。提出了一种带宽和时延受限的QoS多播路由协议,它利用遗传算法搜索满足QoS要求的最优多播树。仿真结果表明该协议收敛速度快,寻径成功率高,它为移动网络中具有QoS保障的多播通信提供了一种有效途径。     

支持多媒体业务的新型无线多跳网络MAC协议*

提出了一种单信道无线多跳网络同步媒体接入控制协议—M-TDMA。基于信道预约,协议采用分类调度机制以满足多媒体业务中各类业务的服务质量需求。协议采用信道使用列表（CUL）、预约控制时隙、划分竞争期和非竞争期等措施维护预约信道,降低分组冲突率,提高信道使用率。分析结果表明,协议在保证分组传输可靠性的同时,传输时延较低,能够较好地支持多媒体业务的服务质量需求。     

Delay-jitter control in multimedia applications

The growing needs of multimedia communications are leading to new developments in providing real-time communication with guarantees. Several extensions have been proposed for different layers of the Open Systems Interconnection Reference Model to accomodate these needs. In this paper, we study methods for guaranteeing delay jitter bounds for high-speed networks in the network and application layers of this model. The method proposed for the network layer provides distributed jitter control. The method proposed for the application layer allows the destination application to control delay jitter. We use a simulation to compare the effects on delay jitter in each method for various scenarios, such as constant bit rate, cross traffic, and bursty data. In addition, the buffer space requirements for accommodating real-time channels are monitored at each node in the network.     

Ant based Pareto optimal solution for QoS aware energy efficient multicast in wireless networks

Most of the group communication technologies support real-time multimedia applications such as video conferencing and distributed gaming. These applications require quality-of-service (QoS) aware multicast routing protocol to deliver the same data stream to a predefined group of receivers. Since nodes in wireless networks are severely energy constrained due to finite battery source, hence it is of paramount importance that QoS aware multicast routing protocol be energy efficient. Transmission power control is one of the methods used to save energy. In this method, the nodes dynamically adjust the transmission power so that energy consumption in the tree is minimized. However, reduction in the transmission power increases the number of forwarding nodes in the multicast tree. This negatively impacts the QoS in terms of propagation delay, delay jitter, and packet loss etc. In wireless networks, there is a trade-off between the energy consumption and the QoS guarantees provided by the network. We unify these requirements into a multiobjective framework referred to as Energy Efficient QoS Multicast Routing (E²QoSMR). The goal is to simultaneously optimize the total power consumption and the QoS parameters in the multicast tree. We extend two algorithms based on metaphor of swarm intelligence for finding an energy efficient multicast tree satisfying the QoS guarantees. Extensive simulations have been conducted to validate the correctness and efficiency of the algorithms. The simulation result of the algorithms is compared with the nondominated sorting genetic algorithm, NSGA-III. The experimental results are consolidated by statistical analyses that demonstrate the ability of the algorithms to generate the Pareto optimal solution set.     

Providing MAC QoS for multimedia traffic in 802.11e based multi-hop ad hoc wireless networks

Ad hoc wireless networks with their widespread deployment, now need to support applications that generate multimedia and real-time traffic. Video, audio, real-time voice over IP, and other multimedia applications require the network to provide guarantees on the Quality of Service (QoS) of the connection. The 802.11e Medium Access Control (MAC) protocol was proposed with the aim of providing QoS support at the MAC layer. The 802.11e performs well in wireless LANs due to the presence of Access Points (APs), but in ad hoc networks, especially multi-hop ones, it is still incapable of supporting multimedia traffic.One of the most important QoS parameters for multimedia and real-time traffic is delay. Our primary goal is to reduce the end-to-end delay, thereby improving the Packet Delivery Ratio of multimedia traffic, that is, the proportion of packets that reach the destination within the deadline, in 802.11e based multi-hop ad hoc wireless networks.Our contribution is threefold: first we propose dynamic ReAllocative Priority (ReAP) scheme, wherein the priorities of packets in the MAC queues are not fixed, but keep changing dynamically. We use the laxity and the hop length information to decide the priority of the packet. ReAP improves the PDR by over 28% in comparison with 802.11e, especially under heavy loads. Second, we introduce Adaptive-TXOP (A-TXOP), where transmission opportunity (TXOP) is the time interval during which a node has the right to initiate transmissions. This scheme reduces the delay of video traffic by reducing the number of channel accesses required to transmit large video frames. It involves modifying the TXOP interval dynamically based on the packets in the queue, so that fragments of the same packet are sent in the same TXOP interval. A-TXOP is implemented over ReAP to further improve the performance of video traffic. ReAP with A-TXOP helps in reducing the delay of video traffic by over 27% and further improves the quality of video in comparison with ReAP without A-TXOP. Finally, we have TXOP-sharing, which is aimed at reducing the delay of voice traffic. It involves using the TXOP to transmit to multiple receivers, in order to utilize the TXOP interval fully. It reduces the number of contentions to the channel and thereby reduces the delay of voice traffic by over 14%. A-TXOP is implemented over ReAP to further improve the performance of voice traffic. The three schemes (ReAP, A-TXOP, and TXOP-sharing) work together to improve the performance of multimedia traffic in 802.11e based multi-hop ad hoc wireless networks.     

一种QoS保证的WMSNs实时路由协议

为了满足无线多媒体传感器网络(WMSNs)对数据的实时性要求,本文提出了一种QoS保证的WMSNs实时路由协议(WMSNRR).该协议在路由选择时,充分考虑两跳节点的转播速率及剩余能量等信息.同时,还采用了一种基于缓存队列长度和节点收发数据率的控制方法,区分业务进行拥塞控制.仿真结果表明,在节点非均匀分布的情况下,该协...