无线传感器网络中机会协作传输及其性能研究

该文基于Nakagami信道且考虑节点电路处理能耗,研究无线传感器网络中机会协作传输及其性能,解决怎么协作何时协作协作的性能3个问题,并从理论上分析机会协作的可能性。仿真结果表明:机会协作传输能有效地提高系统性能;节点的电路处理能耗会影响系统性能,当节点电路处理能耗大到一定程度,机会协作传输不能带来任何性能增益。     

一种在物理层实现协作分集的无线传感器网络

无线传感器网络通常具有存在大量冗余节点、共同的传送目标和能量资源极其有限等特性,因此可以在不同的协议层面上实现协作传输以提高能量有效性,从而延长网络的生命周期.本文研究了一种在物理层进行协作分集完成无线传感器网络中远距传输的方法,提出了可实现的信令和远程接收算法,分析了等效网络多径信道特性和远程接收机能够获得的最大分集增益以及影响分集增益的因素,提出了在分布式网络中提高空间分集增益的方法.     

无线网络中机会协作传输及其性能研究

研究无线网络中如何利用信道的实时信息(信道幅度)进行机会协作传输及其性能.首先讨论机会协作传输策略;接着从理论上分析不同衰落下机会协作传输的可能性,并给出闭式表达式;然后,分析机会协作传输的功率分配方案以最优化系统性能;最后通过仿真验证性能.仿真结果表明:1)机会协作传输能明显提高性能,而节点间最优功率分配方案则能进一步提高协作传输性能;2)即使协作节点到目的节点的信道统计特性次于源节点到目的节点的信道统计特性,机会协作传输仍能带来明显的性能增益.     

一种基于IEEE802.15.4的单信道全双工MAC协议

针对半双工IEEE802.15.4无线传感网络中有效数据速率不高和隐藏节点问题,提出了一种新的基于IEEE802.15.4的单信道全双工MAC协议,设计了单信道全双工帧结构和通信机制.根据负载数据包存储情况动态决定单信道全双工通信时长,获得平均129%网络吞吐量增益,大大提高了有效数据传输速率.全双工的工作机制可以抑制隐藏节点问题,本协议提出动态共享同步随机回退机制,减少了握手请求并增加了单信道全双工通信机会,进一步抑制了隐藏节点导致的碰撞问题,降低了系统误比特率,提高了网络可靠性.     

基于潜在博弈的多源多跳无线传感器网络流量分配算法

无线传感器网络中存在大量数据,数据融合及网络优化可以有效降低网络能耗,提升网络吞吐量。由于无线传感器网络自身的广播特性,在无线网络中应用网络编码可以带来吞吐量提升等性能增益。考虑将N个源节点的K个数据发送到D个不同目的节点的情况,源节点在自身可用路径上分配流量,利用博弈论研究无线传感器网络流量分配问题,提出了一种动态控制方案,源节点根据效用函数调整路径流量分配,以增加网络编码机会,从而降低网络能耗。理论分析和仿真结果表明,该方案是稳定、有效的。     

中继协作传输的吞吐量分析

在无线自组织网络中,通过中继节点协作传输,可在接收端形成分集增益,使得在信道条件较差时也能进行高速、可靠地无线通信。本文提出了一个新的协议,围绕以下三个问题作了分析：何时进行协作,如何选择协作节点,协作节点怎样转发数据包。本文最大的不同是,根据目的节点正确解调需要的信噪比,来调节中继节点向目的节点转发数据时的发送功率,从而减小协作传输的能耗,并在一定程度减小了协作传输干扰范围,增加了网络中可激活的的链路条数,提高了网络吞吐量。     

业务流预测在网络编码平台的实现及验证

网络编码由于可以利用无线信道的广播特性带来的空间冗余条件,在无线自组织网络中的应用显示了巨大的潜力。但TCP业务的机会网络编码在无线自组织网络中获得的增益却很小。基于这一问题,提出对TCP业务流具有的自相似性进行FARIMA模型建模,进行数据包到达时间的预测,从而为路由节点根据网络状态进行正确的编码等待决定提供依据,仿真结果验证了TCP业务流的自相似性,预测算法具有良好的预测结果。文中详细介绍了预测算法在COPE网络编码的NS2平台中的具体实现流程。     

认知无线电网络基于D-OFDM的中继选择算法

认知无线电技术能有效提高频谱利用率,而协作中继是解决信号在无线媒介中消失问题的关键技术。文章基于认知无线电网络,通过创建协作表,提出了一种利用协作中继提高频谱利用率和数据传输速率的中继选择算法。其中的协作表包括信道增益、信道可用率和认知节点的不同频谱。该算法通过选择合适的中继节点以最大化源节点的传输速率。仿真结果表明了该中继选择算法的有效性。     

无线Ad hoc网络中的协同路由

近几年,协同分集技术得到了广泛的关注。在无线Ad hoc网络中采用协同技术可以为网络带来分集增益,减轻信道衰落的影响。研究了无线Ad hoc网络在网络层采用协同技术的方法和形式——协同路由算法,通过节点在传输数据时主动寻找协同节点为其转发数据,可以有效地提高网络性能。对现有的几种协同路由算法和协同节点选择机制进行了详细的研究,分析了其各自技术优势及存在的问题。最后探讨了协同路由有待解决的问题及未来的研究发展方向。     

一种基于自适应网络卷积编码的协作中继方法

在无线衰落信道环境中,协作中继是一种增加额外分集增益的有效方法,而网络编码可以用来提高网络吞吐量。网络编码采用XOR(异或)来混合两个源端的信息包,其稳健性差并且每个中继只能服务两个源端。该文提出一种自适应网络卷积编码协作中继方法,在中继端采用卷积编码方法代替XOR来混合两个或多个源端的信息包,混合后的信息可以看作是卷积编码器的一路输出,然后将其转发给目的端。当信道处于深度衰落时,该文提出了一种宽松自适应网络卷积编码协作中继方法,放松了中继参与转发的条件。该文提出的中继方法稳健性好,可以自适应匹配变化的无线网络拓扑结构,并且减少了网络编码协作中继方法所需要的中继个数。理论分析和仿真结果表明所提出的中继方法相比网络编码协作中继方法在性能上有大幅提高,尤其是随着协作节点数目增加,可保证系统获得稳定的额外满分集增益。     

WSNs中基于转发区域调整的能效地理路由

针对无线传感网络(WSNs)的数据传输问题,提出基于转发区域调整的能效地理位置路由(FAEG)。FAEG限定了数据包的转发区域,构建候选转发节点集,并从节点集中选择权重大的节点传递数据包;通过节点剩余能量和离目的节点距离信息计算节点权重,使剩余能量大和离目的节点近的节点具有优先传递数据包的资格,提高了路由稳定性。节点遭遇路由空洞时,则调整转发区域,在更广范围内选择传输数据包的节点。仿真结果表明,提出的FAEG降低了能耗,并提高了数据包传递率。     

Opportunistic routing with in-network aggregation for asynchronous duty-cycled wireless sensor networks

We propose an opportunistic routing protocol for wireless sensor networks designed to work on top of an asynchronous duty-cycled MAC. Opportunistic routing can be very effective when used with asynchronous duty-cycled MAC because expected waiting time of senders—when they stay on active mode and transmit packet streams—is significantly reduced. If there are multiple sources, energy consumption can be reduced further through in-network aggregation. The idea proposed in this paper is to temporarily increase duty cycle ratio of nodes holding packets, in order to increase chance of in-network aggregation and thus reduce energy consumption and extend network lifetime. In the proposed protocol called opportunistic routing with in-network aggregation (ORIA), whenever a node generates a packet or receives a packet to forward, it waits for a certain amount of time before transmitting the packet. Meanwhile, the node increases its duty cycle ratio, hoping that it receives packets from other nodes and aggregate them into a single packet. Simulation results show that ORIA saves considerable amount of energy compared to general opportunistic routing protocols, as well as tree-based protocols.     

无线传感网络中基于探测包的多径路由

多径路由是应对无线传感网络(WSNs)的链路质量差的重要技术.现存的构建多径路由依赖集中运算或迭代的分布式运算,消耗大量的运行时间.为此,提出基于探测包的多径路由(EPMR).EPMR路由先利用探测包的传输,收集局部拓扑信息.依据接收探测包的到达时间,设置端口优先级,优先考虑端口优先级的节点参与路由.一旦参与了一条路径...     

车联网中基于动态传输距离的多跳稳定路由

数据传输是车联网(VANETs)实现交通安全的基础。然而,车辆的移动、信号传输的衰减以及彼此间的干扰对链路的可靠性均有影响。为此,提出基于动态传输距离的多跳稳定(DTMS)路由。DTMS路由在选择下一跳转发节点时,考虑到因衰减而导致的传输距离的变小,先估计车辆动态传输距离,再依据动态传输距离估计链路的连通时间以及距离因素,然后,计算邻居节点的权重,最后,基于节点权重值设置定时器,进而竞争产生下一跳转发节点。仿真结果表明,提出的DTMS路由有效地提高了数据包传输成功率。     

水下传感网络中基于链路质量和位置的协作路由

水下传感网络是开发水域环境的有效技术手段。但在水下环境传输数据,信号衰减快,通信链路质量差,降低了数据包传递率。提出基于链路质量和位置的协作(LQLC)路由。LQLC路由引用协作路由思想,利用链路质量和节点能量信息,构建候选转发节点集;再从候选转发节点集中选择具有最优链路质量的节点作为转发节点;最后在候选转发节点集中选择离转发节点最近的节点作为协作节点。仿真结果表明,提出的LQLC路由提高了数据包传递率。     

Energy Attentive and Pre-fault Recognize Mechanism for Distributed Wireless Sensor Network Using Fuzzy Logic Approach

Wireless sensor networks (WSNs) have been transforming over recent years with development in the design of smart real-time applications. However, it presents numerous challenges in terms of fault-tolerant communication, low latency, scalability, and transmission efficiency. It is extremely difficult for WSNs to detect runtime faults since they're unaware of the internal processes at work within the sensor node. As a result, valuable sensed information cannot reach its destination and performance starts degrading. Towards this objective, the proposed mechanism applies a novel pre-fault detection mechanism based on a fuzzy rule-based method for multilevel transmission in distributed sensor networks. The proposed mechanism uses a fuzzy rule set to make routing decisions. A fuzzy decision rule set is proposed to perform routing based on the fuzzy fault count status of a node. The proposed mechanism assists in identifying the fault in advance and determining the optimal routing path to save energy and improve network performance. In accordance with the node fault status, the data transmission rate is finalized to prevent further energy consumption. The results demonstrated that the proposed mechanism performed well on judgment evaluation metrics like the energy dissipation ratio, throughput, packet loss rate and communication delay.

     

Opportunistic media access control and routing for delay-tolerant mobile ad hoc networks

In delay-tolerant mobile ad hoc networks, motion of network nodes, network sparsity and sporadic density can cause a lack of guaranteed connectivity. These networks experience significant link delay and their routing protocols must take a store-and-forward approach. In this paper, an opportunistic routing protocol is proposed, along with its compatible media access control, for non-real-time services in delay-tolerant networks. The scheme is mobility-aware such that each network node needs to know its own position and velocity. The media access control employs a four-fold handshake procedure to probe the wireless channel and cooperatively prioritize candidate nodes for packet replication. It exploits the broadcast characteristic of the wireless medium to utilize long-range but unreliable links. The routing process seizes opportunities of node contacts for data delivery. It takes a multiple-copy approach that is adaptive with node movements. Numerical results in mobile ad hoc networks and vehicular ad hoc networks show superior performance of the proposed protocol compared with other routing protocols. The mobility-aware media access control and routing scheme exhibits relatively small packet delivery delay and requires a modest amount of total packet replications/transmissions.     

一种适用于异步无线传感器网络的机会路由机制

无线传感器网络通常使用低占空比的异步睡眠调度来降低节点能耗。由于发送节点在接收节点醒来后才能向其发送数据,这将引入额外的等待时延。在最近的一些任播路由机制中,发送节点动态地选择最先醒来的候选节点转发数据,以最小化等待时延。但是,由于从最先醒来的候选节点到基站的时延可能并不低,任播路由机制并不一定能最小化端到端总时延。为此,提出了一种适用于异步无线传感器网络的机会路由机制,将路由决策建模为强马尔科夫过程,并根据最优停止理论推导出该过程一种简化的停止规则。仿真结果表明,节点到基站的最大端到端时延仅为基于地理位置的机会路由的68.5%。     

An efficient and intelligent routing strategy for vehicular delay tolerant networks

The vehicular delay-tolerant network is the real-life application based area of Delay tolerant network where communication takes place using vehicular nodes and roadside units. The topology used in vehicular networks is highly dynamic by architecture due to the use of moving vehicular nodes. It operates in such a scenario where a direct path between source and destination remains absent on the most piece of the time. In case of non-existence of connected path vehicular delay-tolerant network works opportunistically and uses the same store, carry, and forward paradigm as Delay Tolerant Network. However, the routing protocols designed for vehicular delay-tolerant network faces crucial challenges like inadequate relay node, incomplete data transfer, a large number of packet drop, and uncertain delivery time. In this research paper, we propose a novel routing strategy for the vehicular delay-tolerant network. The proposed routing strategy selects efficient vehicular relay node for complete packet transfer and intelligently reduces the packet drop for timely packet delivery. We implement the proposed routing strategy in the ONE simulator; the ONE simulator provides an opportunistic environment for nodes. We analyze the performance of the proposed strategy under various simulations results using different parameters. The results show that the proposed strategy outperforms standard routing protocols in terms of considered parameters and provide an efficient solution for the problem of disconnection.

     

机会网络中一种低缓存占用的Epidemic 路由算法

由于机会网络中节点的缓存空间有限,容易导致数据分组丢失和时延增加。针对部分数据分组已经到达目的节点,但是该类分组仍在网络中其它节点存储、传输问题,提出一种低缓存占用的Epidemic路由算法(RBER)。该算法通过SV运算进行节点缓存清理,从而避免这类冗余数据分组对缓存的占用。理论分析和仿真结果表明,该机制能够降低网络开销、数据分组的发送和缓存占用。