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1.
针对无线认知传感器网络的资源有限性和频谱动态分配,提出了基于首要信道半双工的无线认知传感器网络广播协议。在没有公共信道和时钟同步的情况下,该协议通过单个收发机的收发状态转换和信道表的交换进行网络的初始化。经过网络初始化,节点由首要信道形成拓扑,节点通过首要信道以半双工数据传送方式进行广播。仿真实验表明,与完全广播相比,该协议降低了广播延迟和开销,更利于应用于无线认知传感器网络。  相似文献   

2.
灵活高效的频谱共享技术能够实现频谱资源的最大化利用,有效地缓解了无线频谱紧缺的现状。在一个与TDMA/FDMA蜂窝网络共存的多跳认知无线Mesh网络环境下,基于覆盖式(Underlay)与机会式(Overlay)相结合的频谱共享机制,提出了一种有效的链路层频谱决策与网络层路由的跨层设计方案。仿真结果表明,该方案比基于最小跳数的随机信道选择算法在网络端到端传输性能上有显著的优势。  相似文献   

3.
肖博  习勇  韩君妹 《电讯技术》2016,56(10):1159-1164
在瑞利衰落信道中,为改善采用Chase合并混合自动重传请求( CC-HARQ)协议的多跳中继网络的频谱效率性能,考虑发送帧长和发送功率的跨层优化,研究了提升其频谱效率的跨层优化策略。不同于传统的中断概率分析,通过利用对数域线性阈值的平均误帧率估计方法,给出了多跳CC-HARQ协议频谱效率的精确表达式,在发送功率固定时设计了最优发送帧长策略,在发送帧长固定时设计了最优发送功率分配方案,进一步提出了跨层的联合优化方案。仿真结果验证了所设计优化方案在理论上的正确性和有效性,同时在仿真中可以观察到采用跨层的优化策略后,多跳 CC-HARQ中继网络的频谱效率获得了显著的提升,其中跨层的联合优化方案比传统的固定帧长等功率策略在频谱效率上提升了0.014 b/s·Hz-1。  相似文献   

4.
传统的无线通信系统空中接口的高层协议采用简单的分层结构,每层进行独立的设计和操作,各层间的接口是静态的。这种设计方法简化了网络设计,具有很好的通用性,但是无线通信系统的信道是随着时间、空间和频率而随机变化的,同时用户的多媒体业务和整个网络状态也是动态的、变化的,而传统的分层协议结构不能很好的适应无线通信的特点,不能保证用户多媒体业务的QoS(服务质量),传输的可靠性和提高无线资源的利用率,本文针对此问题阐述了跨层无线资源管理的思想,跨层设计能够根据用户多媒体业务的QoS和信道的随机变化特性等,跨过层间功能进行优化,更好的保证了不同多媒体业务的QoS,利用各个用户间信道的独立随机变化的特性,最大化系统的传输效率。  相似文献   

5.
基于节点接入能力的ad hoc网络按需路由协议   总被引:3,自引:0,他引:3  
官骏鸣  陆阳  盛锋  王俊伟 《通信学报》2007,28(10):32-37
基于802.11协议MAC层重传策略,提出一个衡量节点接入能力的参数CAM(capacity of access to medium),以体现节点周围信道的繁忙程度及其抢占信道能力。在此基础上,联合MAC层和网络层进行跨层设计,提出了一个拥塞感知路由CAOR(congestion aware on-demand routing)协议。仿真表明:该协议能够在降低开销的前提下,显著增加网络吞吐量,并降低平均端到端的时延。  相似文献   

6.
摘 要:为满足认知无线网络中宽带业务实时传输的需求,提出低延迟的MAC层频谱接入方案,包括频谱感知调度与信道接入竞争两部分。在频谱感知阶段,认知用户选取最佳可用信道数实现感知与传输的延迟最小化;在信道接入竞争阶段,协议考虑频谱资源动态变化的特点,通过设计数据帧格式以及邻居节点协同侦听机制,减小信道冲突与“聋终端”的影响。理论与实验结果表明,与传统的认知无线网络MAC层协议相比,提出的接入方案数据传输延迟更短,同时在授权信道空闲率较大时吞吐量性能略优。  相似文献   

7.
提出一种基于时分多址接入(TDMA)的多跳时隙预留的协议(TMSR)以支持Ad Hoc网络中的实时应用,协议中节点为实时数据包的多跳转发预留信道时隙,通过超帧把数据包从源节点传输到远端的目的节点。通过NS2对提出的协议性能进行评估,重点分析了静态和移动环境下该协议的平均端到端时延和平均吞吐量,同时,在单跳仿真场景中,对TMSR协议与ETDMA进行对比,仿真结果表明随着数据流量的增加,TMSR提供了比E-TDMA更好的数据包吞吐量和时延性能。在多跳仿真场景中,采用TMSR协议的节点间的平均端到端的时延满足了实时应用的端到端多跳时延要求。  相似文献   

8.
针对无人机编队在进行远距离实时视频传输时频谱资源不足且利用效率低、吞吐量要求较高、传输任务难以完成等问题,提出了多智能体强化学习驱动的动态信道分配算法,使得无人机编队可以根据传输任务和信道环境动态地选择使用的信道,实现了频谱资源的高效利用。该算法使用了集中式训练分布式执行的架构,通过联合探索和联合学习的方式保证了无人机间的探索和合作能力,使得每架无人机均可以依据局部观测信息同时独立分配自身使用信道,提高了算法的灵活性和可行性,并减少了频谱分配用时。仿真结果表明,该算法训练过程性能更好,执行时相比于现有算法可以提高编队整体的平均任务传输成功率。  相似文献   

9.
该文在双向多中继选择系统中,分析了采用自适应调制的基于三时隙时分广播(TDBC)中继传输协议的系统性能,给出了存在信道估计误差时,系统的端到端信干噪比表达式,然后通过不等式缩放将表达式转化为多个服从指数分布变量和的形式,求出了其上界的分布,并利用该分布推导出了系统平均频谱效率的上界闭式表达式.通过仿真可以看出,理论分析结果与蒙特卡洛仿真结果相吻合,随着信道估计误差的增加,系统的平均频谱效率降低,并会由于自干扰不能完全被消除而出现平台.为了降低信道估计误差对系统性能的影响,该文进一步提出了一种中继端最优的功率分配策略.  相似文献   

10.
提出了一种基于半静态干扰协调的支持多业务QoS的OFDMA资源分配算法PQSIC。算法按信道质量将用户分为中心和边缘用户,综合考虑业务的QoS要求和边缘用户的信道质量,在特定的频率资源规划方案基础上确定小区中心、边缘用户的可用频率资源,然后将其可用频率资源分别在小区中心和边缘用户中进行分配。仿真结果表明:PQSIC算法能合理分配频率资源,较好地保证多业务系统中用户的QoS。  相似文献   

11.
We investigate the problem of how to minimize the energy consumption in multi-hop Wireless Sensor Network (WSN), under the constraint of end-to-end reliability Quality of Seervice (QoS) requirement. Based on the investigation, we jointly consider the routing, relay selection and power allocation algorithm, and present a novel distributed cross-layer strategy using opportunistic relaying scheme for cooperative communication. The results show that under the same QoS requirement, the proposed cross-layer strategy performs better than other cross-layer cooperative communication algorithms in energy efficiency. We also investigated the impact of several parameters on the energy efficiency of the cooperative communication in WSNs, thus can be used to provide guidelines to decide when and how to apply cooperation for a given setup.  相似文献   

12.
We propose a cross-layer framework for efficient multi-layer-video multicast with rate adaptation and quality-of-service (QoS) requirements in multirate wireless networks. We employ time division multiple access at the physical layer to transmit different video layers' data. The multicast sender then dynamically regulates the transmission rate and time-slot allocation based on the channel state information (CSI) and loss QoS requirements imposed by upper protocol layers. Under our proposed cross-layer framework, we first design a rate adaptation algorithm to fulfill the diverse loss QoS requirements for all video layers while achieving high multicast throughput. We then develop a time-slot allocation scheme which synchronizes data transmission across different video layers. Also conducted are simulation results to validate and evaluate our designed adaptive multicasting schemes under the proposed cross-layer framework.  相似文献   

13.
In this paper, we present a new quality of service (QoS) routing protocol for mobile ad hoc networks (MANETs). Most of the existing routing protocols assume homogeneous nodes in MANETs, i.e., all nodes have the same communication capabilities and characteristics. However, in many ad hoc networks, nodes are not the same. Some nodes have longer transmission range, larger transmission bandwidth, and are more reliable and robust than other nodes. We take advantage of the non-homogeneous property to design more efficient QoS routing protocol. And node location information is used to aid routing. We also develop a new algorithm to calculate end-to-end bandwidth for a given path. Our QoS routing protocol contains end-to-end bandwidth calculation and bandwidth reservation. QoS route is discovered and setup only when it is needed. Extensive simulation studies demonstrate the good performance of the QoS routing protocol.  相似文献   

14.
Based on cross-layer design, a modified 2-dimensional queuing model (2DQM) is proposed in this paper to tackle the problem of end-to-end quality of service (QoS) metric calculation. This model exploits the traffic arrival process, multi-rate transmission in the physical layer and error recovery technology with the protocol of truncated automatic repeat request in the data link layer. Based on this model, QoS metrics of wireless links can be evaluated hop by hop. The model can be used in more realistic scenarios of multi-hop wireless networks, although the computational complexity of 2DQM is slightly higher compared with existing 1-dimensional queuing model. Simulation results indicate that the proposed model can estimate the end-to-end packet loss-rate and average delay more accurately than existing models, and a model based QoS routing algorithm can find routes with better QoS performance (with lower end-to-end packet loss-rate and delay).  相似文献   

15.
Virtual MIMO-based cross-layer design for wireless sensor networks   总被引:10,自引:0,他引:10  
In this paper, a novel multihop virtual multiple-input-multiple-output (MIMO) communication protocol is proposed by the cross-layer design to jointly improve the energy efficiency, reliability, and end-to-end (ETE) QoS provisioning in wireless sensor network (WSN). In the protocol, the traditional low-energy adaptive clustering hierarchy protocol is extended by incorporating the cooperative MIMO communication, multihop routing, and hop-by-hop recovery schemes. Based on the protocol, the overall energy consumption per packet transmission is modeled and the optimal set of transmission parameters is found. Then, the issues of ETE QoS provisioning of the protocol are considered. The ETE latency and throughput of the protocol are modeled in terms of the bit-error-rate (BER) performance of each link. Then, a nonlinear constrained programming model is developed to find the optimal BER performance of each link to meet the ETE QoS requirements with a minimum energy consumption. The particle swarm optimization (PSO) algorithm is employed to solve the problem. Simulation results show the effectiveness of the proposed protocol in energy saving and QoS provisioning.  相似文献   

16.
End-to-End QoS for Video Delivery Over Wireless Internet   总被引:6,自引:0,他引:6  
Providing end-to-end quality of service (QoS) support is essential for video delivery over the next-generation wireless Internet. We address several key elements in the end-to-end QoS support, including scalable video representation, network-aware end system, and network QoS provisioning. There are generally two approaches in QoS support: the network-centric and the end-system centric solutions. The fundamental problem in a network-centric solution is how to map QoS criterion at different layers respectively, and optimize total quality across these layers. We first present the general framework of a cross-layer network-centric solution, and then describe the recent advances in network modeling, QoS mapping, and QoS adaptation. The key targets in end-system centric approach are network adaptation and media adaptation. We present a general framework of the end-system centric solution and investigate the recent developments. Specifically, for network adaptation, we review the available bandwidth estimation and efficient video transport protocol; for media adaptation , we describe the advances in error control, power control, and corresponding bit allocation. Finally, we highlight several advanced research directions.  相似文献   

17.
As the rapid growth of smart hand-held devices, multihop wireless access networks have a lot of potential applications in a variety of fields in civilian and military environments. Many of these applications, such as realtime audio/video streaming, will require some form of end-to-end QoS assurance. In this paper, we present an adaptive per hop differentiation (APHD) scheme towards achieving end-to-end delay assurance in multihop wireless networks. Our scheme is based on EDCA technique which is proposed in 802.11e draft. In EDCA, data packets of different priorities will use different MAC contention parameter set, which translate into different delays. Our APHD scheme extends the capability of EDCA into multihop environment by taking end-to-end delay requirement into consideration at each intermediate hop. Following a cross-layer design approach, APHD is aimed to be a distributed and localized technique. Individual nodes keep track of the channel state independently without any intercommunication overhead. Data packets carry end-to-end delay requirement along with other important information in the packet header. At an intermediate node, based on data packet’s end-to-end requirement, its accumulative delay so far, and the current node’s channel status, APHD smartly adjusts data packet’s priority level in order to satisfy its end-to-end delay requirement. Simulation results show that APHD scheme can provide excellent end-to-end delay assurance while achieving much higher network utilization, compared to a pure EDCA scheme.  相似文献   

18.
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.  相似文献   

19.
The FCC and ETSI have allocated spectrum in the 5.9 GHz band for intelligent transportation systems. However, this spectrum supports short-range transmissions (up to 1000 m) and limited bandwidth (up to 75 MHz), which are not enough to meet the increasing demand for in-car infotainment services. In this paper, we propose a distributed routing protocol for vehicular ad hoc networks, where cognitive radio enabled vehicles (CRVs) dynamically share the TV-band channels. In the proposed protocol, CRVs jointly select relay nodes, channels, transmission powers, and transmission rates so that their total transmission rates are maximized while meeting their rate demands and power constraints. This selection process is carefully executed so that ongoing communications between primary radios (PRs) and between other CRVs are not disrupted. Once the relay nodes are selected, they continue to relay more messages as long as they stay in a predefined forwarding area. By doing so, the overhead for selecting relay nodes can be substantially reduced. Channels, powers, and rates are changed on a per-packet and per-hop basis so that the proposed protocol can efficiently adapt to spectrum dynamics. Simulation results show that our protocol increases the end-to-end network throughput by up to 250 % and decreases the end-to-end delay by up to 400 % compared with other geographical routing protocols.  相似文献   

20.
Cross-layer design approaches are critical for efficient utilization of the scarce radio resources with QoS provisioning in the third-generation wireless networks and beyond. Better system performance can be obtained from information exchanges across protocol layers, which may not be available in the traditional layering architecture. This article provides an overview of cross-layer design approaches for resource allocation in 3G CDMA networks, summarizes state-of-the-art research results, and suggests further research issues. In addition, a cross-layer design approach for real-time video over time-varying CDMA channels is proposed, where link layer resource allocation benefits from information in both the application and physical layers. Simulations results are given to demonstrate the effectiveness of the proposed approach.  相似文献   

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