基于网络编码的无线网络分布式协作通信机制

 本文提出了一种基于无线网络编码的协作通信机制NCCC.无线网络编码能够在取得合作分集的性能增益的同时,降低网络中断概率.分布式中继节点选择算法是NCCC机制的核心,该算法根据即时信道状态,选择执行网络编码操作的最优中继节点.理论和仿真结果证明, NCCC机制可以提高无线网络双向多信源多信宿传输的性能和鲁棒性.     

无线网络中基于网络编码的路由算法

网络编码为无线网络带来了更高的可靠性,二者的结合已经引起了很多研究学者的关注,无线网络中基于网络编码的路由算法更是值得探讨和研究的问题,本文在网络编码的基础上分别对网络编码的多路径路由算法和编码感知的路由算法进行了分析和研究,以期实现提高无线传输效率的目标。     

一种基于网络编码的重传算法研究

无线网络中,节点发送的数据分组传输失败后,执行重传机制。传统的重传机制ARQ由于在一次重传中只能发送一个丢失的数据分组,因此传输效率比较低。利用网络编码技术和AQR重传机制,我们可以在重传中使用网络编码,广播发送由多个丢失数据分组编码得到的编码分组,从而提高重传效率。本文中我们提出一种将网络编码应用于多个发送方多个接收方(MSMR)无线网络中的算法RMBNC。理论推导和仿真分析验证了我们提出的算法的有效性。     

无线网络中的物理层网络编码技术

文章介绍了无线网络中的物理层网络编码技术。首先介绍了一种在物理层实现的结合网络编码和纠错编码的方法。然后介绍了一种模拟网络编码方法,该方法可以充分利用无线介质的广播特性,挖掘无线广播信道和无线多址接入信道的容量,从而提高数据吞吐量。最后介绍了物理层网络编码的研究热点。     

Nakagami-m信道协作网络编码中断性能分析

无线网络编码是一项能极大提高无线网络流量的有用技术,而协作分集可以有效地克服无线衰落的影响。研究了Nakagami-m信道下协作网络编码系统中断性能,分析了不同协作策略下的互信息表达式,推导了协作网络编码中断概率闭式表达式,并对分析的结果进行了仿真。仿真结果显示,在高SNR和谱效率R〈4条件下,协作网络编码中断概率较分布式空时编码性能SNR增益有接近2 dB的提高,并且随分布参数m值的增大,协作网络编码中断概率性能逐步改善。     

一种改进的网络编码广播重传算法

在无线网络广播传输中,为了提升效率提出改进的基于冗余避免的网络编码广播重传算法（INCBRRA）。对接收状态矩阵进行重排列后,再主动避免重传不可解码的编码组合,从而优先编码有助于接收节点解码的丢失数据包组合。分析结果表明,INCBRRA算法相比于现有算法能有效减少重传次数,提升了传输效率。     

无线通信中网络编码技术应用研究

围绕网络编码这一热点,详细分析讨论网络编码的原理、应用在有线和无线中的网络编码方案以及在无线通信中的物理层网络编码,并且分析了其性能。得出物理层网络编码技术是可以逼近无线网络传输容量极限的有效方法。对比传统的中继方式,由于物理层网络编码的应用信源节点可以同时发送信息到中继节点,使得传递信息的时隙从原来的4时隙减为2时隙,从而将系统的吞吐量提高了一倍。     

无线网络编码机会路由综述

作为无线网络协议中两个重要的研究方向,网络编码和机会路由广泛应用于社会各个方面,为提高无线网络的总体性能,融合网络编码和机会路由已成为当今研究热点。文章系统地总结了网络编码与机会路由的方法和研究现状,对网络吞吐量、可靠性、转发效率、延时等性能进行介绍和分析。最后,对融合网络编码和机会路由提高网络性能方面的工作进行了展望。     

无线通信中的网络编码技术

网络编码是一种提高网络吞吐量和性能的新技术,预计将成为未来网络的一项关键技术.本文概述了无线网络中的网络编码技术,无线网络被认为是网络编码最可能得到应用的领域之一,网络编码技术使无线媒质的广播属性可以得到充分利用,无线网络和传感器网络为网络编码的应用提供了巨大的机会.本文结合不同无线场景介绍了网络编码的各种编码方法,包括传统的网络编码、物理层网络编码、模拟网络编码以及复数域网络编码,并对未来发展给出了展望.     

网络编码在无线通信网络中的应用

网络编码是一种可以逼近网络容量传输理论极限的有效方法,在无线网络环境。中有着广泛的应用前景。在无线中继网络中采用网络编码技术,可以使中继节点同时为多个用户转发数据,从而获得较高的转发效率。网络编码在无线中继网络中的典型应用方案包括噪声中继采用置信传播算法实现网络编码,复数域网络编码算法以及信道编码和网络编码联合设计方法,它们均可在获得较高网络吞吐量的同时实现完全分集。在多用户协作通信网络中采用网络编码技术,可获得更高的分集增益以及更低的符号错误概率。     

带有编码冗余控制的机会网络数据转发机制

网络编码方法能有效提高数据传输效率,但采用该方法的机会网络数据转发机制均未考虑传输中的编码数据迭代冗余副本控制问题。为了充分降低译码复杂度并减少迭代冗余副本,提出了相遇持续时间估计及编码机会感知方法,进而设计了带有传输容量估计的编码冗余控制数据转发机制。节点以分布式的方式感知数据编码机会,为不同扩散程度的数据确定相应的优先级,并根据传输容量估计结果完成转发控制,以充分利用节点间的相遇持续时间。结果表明,所提出机制有效地减少了网络中的冗余副本,使译码所需的数据量趋于理论上的最小值,改善了网络资源利用率。     

无线网络面向视频传输优化的机会网络编码机制

现有的无线网络编码机制大多没有考虑无线链路质量对于视频传输的影响,导致视频质量降低。该文针对这一问题,提出面向视频传输优化的机会网络编码(O2NC)机制。该机制结合网络编码和机会路由技术,根据传输路径收益和视频数据的重要程度计算候选节点集合;同时,考虑视频数据包编码比重和重要程度等参数,评估编码包综合效用,选取转发效用值最大的视频编码组合。仿真结果表明,与典型的网络编码协议相比,O2NC机制能够显著提高视频序列的可解码帧率和峰值信噪比(PSNR)。     

基于反馈重传的网络信道编码多播研究

在无线网络中,采用现用机制(ARQ)带宽利用率并不是很高。针对这种情况,提出了一种将网络编码思想融入到重传机制中的方式———NC-ARQ,来提高单跳无线网络(例如WiMAX、WLAN等)的带宽利用率。此外,高误比特率下,在NC-ARQ基础上将网络编码与信道编码结合,即NC-HARQ,可以进一步改善无线网络的带宽利用率。分析了在传统反馈重传机制和信道编码中加入网络编码后,多播网络带宽利用率的增益。理论和仿真都证明了加入网络编码后,反馈重传机制的带宽利用率能得到较大改善。     

基于网络编码与空时编码的协作MAC协议

针对无线ad hoc网络中协作造成的中继效率低以及不同QoS需求难以满足等问题,提出了一种联合网络编码和空时编码的协作MAC协议(NSTCMAC)。NSTCMAC将网络编码与空时编码技术相结合,设计出区分业务类型的协作MAC协议传输机制,以满足不同业务类型的QoS需求;进一步通过马尔科夫链模型分析了区分业务类型的协作机制及性能。仿真结果表明,相比传统的DCF、COOPMAC以及CD-MAC协议,NSTCMAC协议能更好地保证不同的QoS需求,并能有效地解决协作造成的中继效率低的问题。     

Joint Transmission Rate Control and Opportunistic Network Coding Over Wireless Networks

Existing opportunistic network coding architectures (e.g., COPE) rely on pseudobroadcast to deliver a coded packet to multiple receivers in a single transmission. Only the primary receiver acknowledges the reception by MAC-layer acknowledgements (synchronous ACKs) and the other receivers receive the coded packet by overhearing and acknowledge the reception by asynchronous ACKs, which are usually piggybacked in outgoing data packets. In realistic wireless networks, this mechanism may cause unnecessary retransmissions if asynchronous ACKs are dropped due to packet losses or arrive late and thus compromise the throughput gain brought by network coding. In this paper, we propose a framework of joint rate control and code selection (ORC) to address this issue, aiming at improving the performance gain of opportunistic network coding in wireless networks. The framework of ORC consists of two mechanisms: (1) Rate control: the optimal transmission rate for coded packets is selected by formulating the rate control process as a Finite Horizon Markov Decision Process. (2) Code selection: based on the results of rate selection, the packet combination for forming the coded packet is determined. Numerical results show that ORC can substantially improve the performance gain of opportunistic network coding compared with COPE.     

Fair coding for inter‐session network coding in wireless mesh networks

Because of the broadcast and overhearing capability of wireless networks, network coding can greatly improve throughput in wireless networks. However, our investigation of existing inter‐session network coding protocols found that the short‐term unfairness that existed in 802.11‐based medium access control (MAC) protocols actually decreases the coding opportunity, which in turn compromises the throughput gain of network coding. To alleviate the negative impact of this unfairness, we propose a coding‐aware cross‐layer heuristic approach to optimize the coordination of network coding and MAC layer protocol, named FairCoding, which can significantly increase coding opportunities for inter‐session network coding through a fair short‐term traffic allocation for different coding flows. Experiment evaluation shows that the proposed mechanism can bring more coding opportunities and improve the total throughput of wireless mesh networks by up to 20%, compared with the coding mechanism, without considering the negative impact of the short‐term unfairness. Copyright © 2015 John Wiley & Sons, Ltd.     

无线局域网IEEE 802.11的一种高效调度方案

深入分析了无线局域网IEEE 802.11系列标准的现有调度方案,提出了一种基于IEEE 802.11e标准中HCF接入模式的高效调度方案SA-Multipoll.设计了调度帧结构和调度时序,推导了满足时延和带宽要求的准入协商和调度效率公式.通过数值计算和仿真结果证实了SA-Multipoll的调度效率高于singlepoll,也高于现有multipoll方案中效率较高的CP-Multipoll方案.     

Research on pedestrian trajectory prediction method based on social attention mechanism

In order to improve the speed,accuracy and model interpretability of trajectory prediction in pedestrian interaction,a GAN model based on social attention mechanism was proposed.Firstly,a new type of social relationship on pedestrians was defined to model social relationships and a network model based on the attention mechanism was designed to improve the speed and interpretability of network prediction.Secondly,the influence of different pooling mechanisms on the prediction results was explored to determine the pooling model with excellent performance.Finally,a trajectory prediction network was built on this basis and trained on the UCY and ETH data sets.The experimental results show that the model not only has better prediction accuracy than the existing methods,but also improves the real-time performance by 18.3% compared with the existing methods.     

QoS-aware energy-saving mechanism for hybrid optical-wireless broadband access networks

Hybrid optical-wireless broadband access network (HOWBAN) takes full advantage of the high capacity and reliability of the passive optical network and the flexibility, ubiquity of the wireless network. Similar to other access networks, the issue of high energy consumption is a great challenge for HOWBAN. In HOWBAN, optical network units (ONUs) consume a great amount of energy. The sleep of ONUs can greatly improve the energy efficiency of HOWBAN. However, the quality of service (QoS) will be decreased while the packets are waiting in ONUs and optical line terminal. In this paper, we propose a QoS-aware energy-saving mechanism. A dynamic bandwidth allocation mechanism is designed to guarantee the QoS, where different priorities are considered. Meanwhile, we employ different sleep strategies by taking different priorities’ tolerant delays into account to prolong the sleep time of ONUs. Then, based on the evaluation of packet delay, the optimal sleep parameter is derived to maximum the energy efficiency. In addition, a load balancing and resource allocation mechanism is adopted in the wireless domain to reduce the delay and congestion caused by ONUs’ sleep. Results show that the proposed mechanism can effectively improve the energy efficiency and meet the QoS requirements of packets.