中继协作无线网络中不完美反馈下基于网络编码的重传方案

无线广播网络传输过程中,目的节点反馈信息丢失或部分丢失导致发送节点不能了解目的节点的真实接收状态.为提高不完美反馈下无线网络的重传效率,本文提出中继协作无线网络中不完美反馈下基于网络编码的重传方案.本方案基于部分可观察马尔科夫决策过程对不完美反馈下的重传过程进行建模.发送节点根据系统观测状态和最大置信度更新系统估计状态,根据数据包发送顺序,优先选择最早丢失且能够恢复最多丢包的编码包重传.目的节点缓存不可解编码包以提升编解码机会.重传过程中源节点关注目的节点请求包需求,相同情况优先选择传输可靠性较高的中继节点,以提升传输有效性.仿真结果表明,在不完美反馈下相对于传统方案,本方案可有效提高重传效率.     

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。     

基于机会式网络编码的低时延广播传输算法

为了提高无线网络中数据包广播传输的效率,本文提出了一种基于机会式网络编码的广播传输算法.该算法在发送端按一定顺序选择不同终端的丢包,并采用异或运算编码重传包,在终端采用从重传包中解码数据包的方法恢复丢包.该算法优先恢复时间重要性较高的丢包,并使多个终端同时从单个重传包恢复其丢包,因此有效地提高了广播传输效率并降低了传输...     

D2D网络中基于立即可解网络编码的时延最小化重传方案

该文针对D2D无线网络中多终端并发协作重传冲突避免问题,提出一种基于立即可解网络编码的时延最小化重传方案。在重传阶段,充分利用D2D无线网络终端协作传输数据的优势,结合各终端数据包接收状态,综合考虑时延的影响因素,选取单次重传时延增量较小的数据包生成编码包,最小化重传时延。同时,构建终端冲突图,在图中搜索极大独立集,根据各终端的编码包权重值,选择最大加权独立集中的终端作为并发协作重传终端,从而降低重传次数。仿真结果表明,所提方案能够进一步改善D2D无线网络的重传效率。     

Weighted partial network coding and its applications in wireless mesh networks

Network coding (NC) has showed to be beneficial to improve transmission performance in wireless mesh networks. Random linear coding is usually applied as the default coding schema. However, random linear coding causes significant decoding delay and jitter at receiver. Further, current NC does not support weight assignment to original packets, which is however indispensable for popular applications such as quality of service control and multipath media streaming in wireless mesh networks. Partial network coding (PNC) can largely reduce decoding delay and receiving fluctuation while keeping the benefit of NC. However, PNC does not support weight‐based data replacement and weight assignment to original packets. In this work, we propose weighted partial network coding (WPNC), which is a generalized coding schema of PNC. WPNC inherits all merits of PNC and part of NC. With WPNC, both decoding delay and receiving fluctuation will be reduced as observed in PNC. Also, WPNC is quite suitable for those applications that require weight assignment to original packets. After providing the whole framework of WPNC and thorough theoretical analysis to its performance, we have demonstrated how WPNC can be integrated with quality of service control and multipath routing supported media streaming in wireless mesh networks. Performance of WPNC is inter‐validated by both theoretical analysis and numeric evaluations. Copyright © 2011 John; Wiley & Sons, Ltd.     

A framework of data caching for improving decoding efficiency of opportunistic network coding

Throughput performance of wireless networks can be enhanced by applying network coding (NC) technique based on opportunistic listening. The packets sent or overheard by a network node should be locally cached for the purpose of possible future decoding. How to manage the cache to reduce the overhead incurred in performing NC and, meanwhile, exploit performance gain is an interesting issue that has not been deeply investigated. In this paper, we present a framework for packet caching policy in multihop wireless networks, aiming at improving decoding efficiency, and thus throughput gain of NC. We formulate the caching policy design as an optimization problem for maximizing decoding utility and derive a set of optimization rules. We propose a distributed network coding caching policy (NCP), which can be readily incorporated into various existing NC architectures to improve NC performance gain. We theoretically analyze the performance improvement of NCP over completely opportunistic NC (COPE). In addition, we use simulation experiments based on ns‐2 to evaluate the performance of NCP. Numerical results validate our analytical model and show that NCP can effectively improve the performance gain of NC compared with COPE. Copyright © 2013 John Wiley & Sons, Ltd.     

适合TCP的网络编码重传机制

通过理论分析,看出基于反馈的重传方法比定量重传的方法有更低的解码延迟。提出了一种新型的基于反馈的网络编码(FNC)重传机制,利用seen机制中的隐含信息来获取接收方解码所需的重传分组个数,并改变了编码规则使部分分组可以提前解码。该机制不仅可以处理有固定误码率的随机分组丢失,还可以有效地应对大量突发性分组丢失。仿真结果显示,该机制在高误码率下也能保持较高的吞吐量,且极大地减少了解码延迟,传输过程基本不受分组丢失的影响,有效地对拥塞控制协议隐藏了链路错误。算法简单有效,更适于在实际系统中应用。     

WiNoC中EF-ACK容错无线接口设计

无线片上网络中的无线信道面临着严重的可靠性挑战,无线路由器的容错设计对整个片上网络的传输效率有着较大的影响.本文提出一种EF-ACK容错无线接口设计,将多条确认信息配置在一个数据包内,通过无线信道传递确认信息数据包;在无线接口处设立重传数据缓冲区,以更高效的方式确认数据以及控制错误数据包的重传;另外,提出了基于网络状态的编解码控制,在网络情况较差时用BCH编码的方式提高数据的鲁棒性.实验表明,本文方案使用了较小的额外面积和功耗开销,高效地完成了对于数据的无线确认反馈,且在错误率较高时,可以保证网络中较低的网络延迟和较高的饱和吞吐量,大大提高了网络的性能.     

一种基于流内与流间网络编码的无线路由算法

 网络编码能极大提高网络吞吐量和可靠性.该文提出了一种基于流内网络编码与流间网络编码的无线路由算法,首先用改进的流间网络编码策略寻找一条固定路由,发现尽可能多的编码机会以减少传输次数;再用流内网络编码与局部机会路由结合的方法实施每跳的数据包传输,减少数据包的重传次数.理论分析和仿真实验表明,此算法比传统的编码感知路由算法具有更高的吞吐量和可靠性.     

D2D网络中基于牺牲节点的网络编码协作重传策略

针对D2D无线网络中多终端并发协作重传过程中平均解码时延较高的问题,提出了一种牺牲节点的协作重传策略.在重传阶段,发送终端在立即可解网络编码(Instantly Decodable Network Coding,IDNC)图上根据接收终端与发送终端的链路质量、终端数据包权重和接收终端的连通度选择出发送终端的最优编码包,...     

无线Mesh网络中跨层协作的路由策略

网络编码可以提高无线Mesh网络的吞吐量,但是网络编码在无线Mesh网络中实际应用获得最大网络利用率是需要解决的问题。提出一种多路径策略,能够通过将网络编码和TCP进行最大化融合提高网络的利用率。网络编码被加入到现有的网络系统,通过解决速率控制问题和分组调度问题,调整源节点的数据编码分块,降低数据包重传的次数,提高网络的吞吐量。     

中继协作多播网络中基于最小集合覆盖的编码重传方案

为提高单中继协作多播传输效率,本文提出一种基于最小集合覆盖的分类网络编码重传方案.该方案充分利用中继节点协作传输的优势,将接收端的丢包按中继节点的接收状态分为两类,并按类先后进行编码重传.在各类丢包内部,根据对应的状态反馈矩阵寻找编码机会生成编码包,并将编码包的选择过程抽象为集合覆盖问题,通过求最小集合覆盖使重传次数逼近最小值.此外,在不增加所得前类编码包数的前提下,利用两类丢包之间的编码机会进一步生成新编码包,以减少重传编码包数,从而提高重传效率.分析与仿真结果表明了该方案的有效性.     

无线网络中基于网络编码的可靠广播传输

Recently, network coding has been applied to the loss recovery of reliable broadcast transmission in wireless networks. Since it was proved that fi nding the optimal set of lost packets for XOR-ing is a complex NP-complete problem, the available time-based retransmission scheme and its enhanced retransmission scheme have exponential computational complexity and thus are not scalable to large networks. In this paper, we present an efficient heuristic scheme based on hypergraph coloring and also its enhanced ...     

无线物联网中基于网络编码的能量受限数据传输机制

本文针对无线物联网能量有限的应用场景,提出一种基于网络编码的能量受限数据传输机制NCDT.NCDT引入传染病路由的思想,对网络编码数据包的传输方式进行建模.通过限制编码数据包在网络中的复制次数,以及参与数据包交换的移动终端数量,控制网络的整体能量消耗.NCDT机制在限制网络编码资源消耗的同时,保证了在传输过程中取得较高的传输可靠性.     

A Cross-Layer Routing Scheme Using Adaptive Retransmission Strategy for Wireless Mesh Networks

In this paper, we develop a link quality-based adaptive adjustment mechanism of the MAC maximum retransmission count to reduce collision probability of wireless Mesh networks. Based on statistics acquired in the link layer and the retransmission strategy, a multi-metric cross-layer on-demand routing scheme is proposed for wireless Mesh networks. The proposed scheme uses information such as available link bandwidth, node residual load rate and transmission efficiency of a path adequately to cross-layer routing. The network layer can adaptively select an optimal path to deliver packets based on the acquired statistics of the MAC layer. Extensive simulation results demonstrate that the proposed scheme can reduce link failure probability, improve network throughput, and decrease the end-to-end delay effectively.     

A Cooperative Peer-to-Peer Repair Scheme Based on Hybrid Network Coding

Cooperative peer-to-peer (P2P) repair (CPR) is an efficient way to recover the lost packets in wireless multicast system. Using network coding in CPR can further improve the transmission efficiency. However, there will be high computational overhead for random linear network coding and high optimization complexity for XOR-based network coding when the number of multicast data packet is relatively large. With regard to this problem, we propose a hybrid network coding based cooperative P2P repair scheme (HNC-CPR) with two efficient and light-weight scheduling algorithms. The HNC-CPR scheme can reduce the computational complexity while ensuring high transmission efficiency. Finally, example analyses and simulations demonstrate the efficiency and low-complexity of HNC-CPR.     

基于机会式网络编码的高效广播传输算法

为了提高无线网络广播传输的效率,针对单跳无线网络提出了采用编码方法的广播传输算法。在传统的无线广播传输模型的基础上,分别实现了基于机会式网络编码的单组合分组广播传输算法和多组合分组广播传输算法。它们采用不同的策略选择多个丢失分组编码组合成重传分组,并通过从编码组合数据分组中恢复丢失分组的方式来提高广播传输的吞吐量。仿真结果表明,新算法在不同无线信道传输模型下相比已有的算法有效地降低了广播传输所需的传输带宽。     

基于网络编码的机会网络高效路由算法

针对采用Epidemic机制的机会网络路由算法在数据分组传送阶段存在通信冗余的问题,提出了一种基于网络编码的高效路由算法--NCBER(network-coding-based epidemic routing）。NCBER在传送数据分组的过程中使用主动异或网络编码和多播,并取消了 Request（请求）控制分组,从而减少数据分组的转发次数和控制分组数量,降低网络开销,缩短分组传输时延。理论分析和仿真结果表明,NCBER 算法在网络开销和数据分组端到端时延性能方面优于经典的Epidemic路由算法及其改进算法MRRMR（message redundancy removal of multi-copy routing）,并且使数据传送成功率保持在100%。     

基于网络编码的无线单跳传输框架的研究与实现

为了解决无线链路易出错从而降低传输效率以及由于重传导致数据流间传输不公平,基于网络编码的思想,在无线单跳传输结构下,提出了基于编码组的传输模型,并根据中心站点的传输数据不同,分为内部数据传输模型和外部数据传输模型.基于上述传输模型,提出了一种基于编码组的数据传输框架.最后通过仿真实验,分析了ARQ单播策略、FEC单播策略和编码组传输框架的传输延迟,同时还对它们的传输吞吐量进行分析比较,并且在节点突发出错情景下分析ARQ单播策略、FEC单播策略和基于重传的编码组传输框架的吞叶量变化.实验表明:FTCG能够提高传输效率,并且在节点突发出错情景下能有效解决由于节点突发出错而造成的系统吞吐量急剧下降问题,保证了数据传输的公平性.     

改进无线网络TCP性能的研究

对采用TCP协议传输数据的实现过程及其在无线网络中可能遇到的问题进行了描述。对因无线信道误码率较高和频繁切换而导致网络性能下降的问题,提出了无线链路层快速重传技术改善网络性能的有效措施,并研究了在无线网络中链路层快速重传技术对无线TCP数据传输的影响。仿真表明链路层快速重传可以有效地改善无线TCP的性能,进一步提高了网络利用率和吞吐量。