基于网络编码的多跳无线网络可靠组播

多跳无线网络中实现可靠组播面临许多挑战,数据丢失恢复是其中的核心问题之一。该文提出一种基于8GF(2)域的随机线性网络编码的多跳无线网络中高效可靠组播(Network Coding Reliable Multicast,NCRM)算法,克服了XOR编码方式的局限性,将原始数据包划分成不同"代"(generation)进行发送,恢复节点采用随机线性网络编码方式发送编码包,发生丢包的组播组成员发送携带丢包比特向量的NACK(Negative ACKnowledgement),经过邻居恢复、多跳恢复或源端恢复,完成可靠组播过程。该文建立了节点丢失恢复过程的齐次马尔科夫链数学模型,给出理论平均时延和重传跳数。NS2仿真结果验证了理论分析模型的准确性。数值结果表明,与PGM(PragmaticGeneral Multicast)和CoreRM可靠组播协议相比,NCRM算法显著改善了网络吞吐量和丢失恢复延时等性能。     

大型无线网络中的多跳网络编码

基于网络编码的协作分集技术是目前的无线网络的研究热点.许多研究从理论上证明了它的有效性,但是对于大型网络中网络编码技术的应用的研究涉及较少.采用LDPC码的结构研究了协作分集网络中的网络编码构造,并把它拓展到多跳网络中.这种方法可以根据瞬时的网络拓扑结构形成网络编码,从而适应移动环境下多节点的随机接入,通过获得的网络编码增益提高网络可靠性.     

大型无线网络中的多跳网络编码

基于网络编码的协作分集技术是目前的无线网络的研究热点。许多研究从理论上证明了它的有效性,但是对于大型网络中网络编码技术的应用的研究涉及较少。采用LDPC码的结构研究了协作分集网络中的网络编码构造,并把它拓展到多跳网络中。这种方法可以根据瞬时的网络拓扑结构形成网络编码,从而适应移动环境下多节点的随机接入,通过获得的网络编码增益提高网络可靠性。     

无线网络编码技术的探讨

文章介绍了网络编码这一新技术在不同类型无线网络中的潜在应用,分析了网络编码在不同应用中所能带来的性能提升以及存在的问题,并对这些问题提出了可能的解决思路,为网络编码技术在无线网络中的实用提供了参考。     

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.     

基于网络编码的无线网络路由协议

基于机会的网络编码方法(COPE)研究网络编码在无线环境中的协议层面上具体实现的问题,但COPE被动地等待编码机会的出现.为了更大限度的提高网络编码的性能,需要将网络编码与无线路由协议相结合来在无线节点上创造出更多的编码机会以减少总的传输次数,以有效的提升网络的吞吐量.当前的编码感知路由算法主要包括基于Markovian路由度量的路由协议、编码感知机会路由协议(CORE)、分布式编码感知路由协议(DCAR)、速率匹配的编码感知多路径路由协议(RCR)、编码感知多路径路由协议(CAMP)等.无线网络内的编码感知路由领域中新型路由度量和跨层设计等问题还需要进一步研究.     

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。     

无线多跳通信网络中的网络编码技术

网络编码允许中间节点对接收信息进行编码并转发出去,提高了网络吞吐量和链路的健壮性,采用网络编码技术能显著提高无线多跳通信网络的传输性能。文章在综合论述了网络编码的原理和研究现状后,介绍了线性网络编码及其代数实现,总结了无线通信网络中应用网络编码技术的研究方法,给出了相关网络编码算法的性能仿真结果。     

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。     

基于网络编码的无线网络广播重传方法

提出了一种适用于无线广播的基于网络编码的重传方法--NCWBR,通过网络编码组合不同的丢失包进行重传.理论分析表明,该方法能保证接收节点的编码可解性,同时重传次数较原方法更优;模拟测试结果表明,与逐个重传的方法相比,NCWBR有效地减少了信息包的平均传输次数,提高了传输效率.     

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.     

基于网络编码的无线体域网多中继协作节能策略

针对无线体域网中传输链路存在中断情况从而消耗额外能量的问题,在多源多中继系统模型中引入网络编码,提出一种基于网络编码多中继协作算法,并分析了该算法下系统的网络能耗,推导出系统的每比特网络整体能耗公式。仿真结果表明:该算法与传统的多路径多中继转发算法相比,可以较大程度的减少网络的整体能耗,适当地增加信源节点或者减少中继节点的数目对降低网络的整体能耗也有一定的作用。该算法能减少多源多中继网络的整体能耗,延长网络的生命周期。     

A network coding based interference cancelation scheme for wireless ad hoc networks

The performance of wireless networks is limited by multiple access interference (MAI) in the traditional communication approach where the interfered signals of the concurrent transmissions are treated as noise. In this paper, we treat the interfered signals from a new perspective on the basis of additive electromagnetic (EM) waves and propose a network coding based interference cancelation (NCIC) scheme. In the proposed scheme, adjacent nodes can transmit simultaneously with careful scheduling; therefore, network performance will not be limited by the MAI. Additionally we design a space segmentation method for general wireless ad hoc networks, which organizes network into clusters with regular shapes (e.g., square and hexagon) to reduce the number of relay nodes. The segmentation method works with the scheduling scheme and can help achieve better scalability and reduced complexity. We derive accurate analytic models for the probability of connectivity between two adjacent cluster heads which is important for successful information relay. We proved that with the proposed NCIC scheme, the transmission efficiency can be improved by at least 50% for general wireless networks as compared to the traditional interference avoidance schemes. Numeric results also show the space segmentation is feasible and effective. Finally we propose and discuss a method to implement the NCIC scheme in a practical orthogonal frequency division multiplexing (OFDM) communications networks. Copyright © 2009 John Wiley & Sons, Ltd.     

无线自组织网络中流间网络编码机会发现方法的研究

编码机会对流间网络编码协议的性能具有重要影响,包括AODV在内的大多数距离向量路由协议仅知道针对某个目的节点的一跳邻居信息,无法有效地发现编码机会。针对该问题,从节点需要掌握的网络拓扑信息这一角度,提出了编码机会有效发现的条件并从充分性与必要性两方面进行了分析,然后基于AODV路由协议进行了实现,同时利用真实的网络实验与网络仿真对所提条件进行了验证。实验与仿真结果表明,所提条件是正确的,可以有效地提高无线自组织网络的性能。     

无线mesh网络中编码感知且负载均衡的组播路由

提出一种新的基于网络编码的负载均衡路由量度CRM-LB(coding-aware routing metric with load balancing),CRM-LB在CRM(coding-aware routing metric)的基础上增加了对路径p上所有节点通信密集程度与网络拥塞程度的考虑。进一步提出了基于CRM-LB的无线mesh网络多播路由CLR(coding and load-balancing routing)。该协议可以增加网络编码机会,同时考虑到网络中的负载均衡。通过性能分析和仿真实验表明,该协议在提高多播吞吐量的前提下,不仅能更好地支持网络编码,而且网络负载基本均衡。     

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.     

High efficient multipacket decoding approach for network coding in wireless networks

To improve the performance of transmission by reducing the number of transmission and network overhead of wireless single-hop networks, this paper presents a high efficient multipacket decoding approach for network coding (EMDNC) in wireless networks according to the idea of encoding packets which cannot be decoded and are stored in buffer by receiving nodes, the lost packets can be recovered from these encoded packets. Compared with the network coding wireless broadcasting retransmission (NCWBR), EMDNC can improve the efficiency of decoding and reduce the number of retransmission and transmission delay. Simulation results reveal that EMDNC can effectively reduce the number of retransmission and network overhead.     

Relay algorithm based on network coding in wireless local network

The network coding is a new technology in the field of information in 21st century. It could enhance the network throughput and save the energy consumption, and is mainly based on the single transmission rate. However, with the development of wireless network and equipment, wireless local network MAC protocols have already supported the multi-rate transmission. This paper investigates the optimal relay selection problem based on network coding. Firstly, the problem is formulated as an optimization problem. Moreover, a relay algorithm based on network coding is proposed and the transmission time gain of our algorithm over the traditional relay algorithm is analyzed. Lastly, we compare total transmission time and the energy consumption of our proposed algorithm, Network Coding with Relay Assistance (NCRA), Transmission Request (TR), and the Direct Transmission (DT) without relay algorithm by adopting IEEE 802.11b. The simulation results demonstrate that our algorithm that improves the coding opportunity by the cooperation of the relay nodes leads to the transmission time decrease of up to 17% over the traditional relay algorithms.     

一种新的基于网络编码的碰撞解决算法

文中提出一种叫做网络编码树算法的新的碰撞解决算法,该算法在树算法的基础上结合了网络编码技术.树算法没有充分利用碰撞的数据包,对于碰撞数据包的处理往往采用丢弃的方式.通过引入网络编码技术,可以利用碰撞的数据包带来的信息,从而提高树算法的效率和性能.通过仿真,将网络编码分裂树算法与现有的其他碰撞解决算法进行了性能比较,证实网络编码树算法大幅度地提高网络的吞吐量并降低了平均延时.     

Applications of network coding to improve TCP performance over wireless mesh networks: a survey

There is growing interest in the use of wireless mesh network (WMN) as a last‐mile option for Internet access. Despite the many benefits of WMNs, the performance of Internet access may not be ideal. One of the main issues is the interaction of transmission control protocol (TCP) with the underlying network. The poor performance of TCP over multi‐hop networks is well‐documented, and extensive research exists, which addresses TCPs foible and enhance TCP performance for multi‐hop environments. This paper provides a thorough survey of TCP performance issues over WMNs and the available solutions to address these issues. Among the existing methods, we focused on network coding (NC) and the ways that TCP interacts with network coded systems. NC is a technique that encodes the received packets in each node before forwarding them towards the destination. The use of NC in the transport layer to address performance issues raised by wireless access is a recent research topic. This paper presents a detailed study of TCP interaction with NC. Some open research areas in this field are suggested. Copyright © 2012 John Wiley & Sons, Ltd.