WSN中利用蚁群路径优化的时隙选择重排算法

针对无线传感器网络(WSN)汇聚传输中的数据传输时间和功耗问题,提出了考虑时间同步和唤醒延迟的汇聚传输时隙选择重排算法。将时分多址接入(TDMA)用作介质访问协议,并允许每个节点在传输时隙期间可以发送或接收数据;设计新的WSN数据收集树模型,将传感器节点生成的数据通过无线链路形成的多跳网络发送到汇聚节点,在数据收集树的每条链路上分析时隙顺序,优化时隙选择,并基于蚁群算法优化路径选择,减少传输能量消耗和均衡簇头能量。实验结果表明,提出的算法可以实现显著的数据传输性能提高和功耗节约。     

Ad hoc网络中TDMA分布式动态时隙分配算法

基于时分多址(TDMA)的时隙分配算法能够提供很好的无线资源利用率,特别是在高负载的环境下.提出了一种适于Ad hoc基于TDMA的无冲突动态分布式时隙分配算法,通过动态改变帧长来控制未用时隙的过量增长,提高了系统吞吐量.该算法通过设置帧长为时隙2的次方,使其在不同帧长的节点中无冲突地包传输.节点间的同步采用本地同步方式.仿真结果表明该算法与IEEE 802.11相比提高了系统吞吐量并降低了端-端延迟.     

无线传感器网络节点实时流量负载的时隙调度算法

目前无线传感器网络基于TDMA的MAC协议基本考虑节点处于连续工作而忽略事件驱动状态,没有考虑到复杂多变的网络环境,造成节点能量过度的浪费.提出了一种根据节点实时流量负载的时隙调度算法(TART),TART算法基于簇结构, 采用分布式与集中式相结合的方式,成员节点实时向簇首发送自己数据流量信息,由簇头动态调节簇内节点时隙更新频率和顺序,降低时隙划分的能量和时间代价,减少节点的空闲侦听时间.仿真表明,算法有效地提高了网络能量有效性,延长了网络生存周期,降低数据包的延时.     

工业无线多跳多信道通信链路优化研究

工业无线技术推广应用的主要瓶颈是通信可靠性难以满足要求。多跳无线通信中,各子链路通信质量都直接影响端到端可靠性,可靠通信面临更多挑战。针对这种情况,研究了多跳多信道通信链路,通过优化时隙和信道资源提高端到端可靠性。建立了工业无线通信多跳多信道链路模型,研究了实时性约束下链路端到端可靠性最大化问题,提出了优化模型;将优化问题转化为资源调度问题,进而用贪婪算法进行了求解,从而提供了一种易于现场应用的轻量级优化算法。开发了相应的半实物仿真平台,验证了算法的有效性。     

基于最低开销模型的传感网络通信优化仿真

当传感网络中某条链路发生变化时,需要重新计算最短路径树,一旦传感网络规模较大,传统的算法采用抑制链路改变的方法提高传感网络通信容量,但这大幅抑制通信节点周期内路径选择灵活性,通信延迟明显.提出一种改进的A-OSPF算法并应用到传感网络通信优化中,该算法在原始的OSPF基础上融人了最低开销节点机制,增强了传感网络中节点构建的概率,考虑了节点移动性,将更加平稳的链路当成节点,按照链路代价原理得到源节点到目标节点的最佳路径,确保数据包可在链路质量最高的路径上进行传递,降低传感网络数据传送的平均端到端延时.仿真结果表明改进算法在传感网络生存周期以及平均端到端延时方法优于原始的OSPF算法,实现了延长传感网络生存周期以及能量均衡的目标.     

基于优先级分类的工业无线网络确定性调度算法

确定性调度技术对于工业无线网络数据的实时性和确定性传输有着重要意义.本文针对工业无线网络数据流本身存在优先级分类属性的情况,基于多信道时分多址接入(TDMA)技术,在分析高优先级数据流对低优先级数据流造成的链路冲突延时和信道竞争延时基础上,对网络进行调度预处理,进而排除参数不合理的网络,并向网络管理者反馈.对于通过预处理的网络,调度算法优先为高优先级数据流的链路分配时隙和信道资源,而对属于同一类优先级的数据流,提出一种基于比例冲突空余时间的调度方案,在满足可调度性条件的前提下,根据各链路的比例冲突空余时间值从小到大依次分配时隙和信道资源.实验结果表明,所提出的调度算法可以取得较高的网络调度成功率.     

基于时延优化的移动Ad Hoc网络路由算法

TDMA协议基于时隙预留的机制能够用于在移动Ad Hoc网络中提供QoS保证,然而在大规模网络中,该时分通信会带来较大的端到端时延.提出了一种基于时延优化的启发式算法,该算法将时延作为路由代价函数,并充分考虑了阻塞控制.仿真结果表明,相对于传统的基于最短跳数的路由算法,该算法能够大大减小端到端时延,可以为移动网络中实现多媒体应用提供一种有效途径.     

无线网络中可靠的链路调度算法设计与分析

无线信号在传输过程中存在许多不确定性的干扰，导致信号到达接收端时其质量严重下降，接收端不能正确解码接收到的信号，使无线通信出现差错。目前，基于SINR（Signal to Interference plus Noise Ratio）干扰模型的低延迟链路调度算法是提高无线网络可靠性和通信容量的有效方法。基于此本文提出一种近似比为O(log Δ)的最短链路调度算法（Δ是最长链路长度与最短链路长度的比值），所有链路采用一致功率分配，根据链路长度把链路集划分为不同的子集，运用TDMA运行机制，为每个子集中相互干扰的链路分配不同的传输时隙，使每个时隙中的链路同时通信。通过理论证明了本文算法的正确性和有效性。     

基于DRAND算法的漏斗-MAC协议

针对漏斗-MAC协议的不足,给出一种分布式时隙分配（DRAND）算法改进方案。在基于集中式时分多址（TDMA）调度算法的漏斗-MAC协议基础上引入分布式时隙分配方案,保证节点两跳范围内的时隙没有重叠,从而能最大限度地避免数据干扰和冲突。NS-2仿真表明,改进的协议能进一步减少系统能量消耗,维持较高的信道利用率。     

基于TDMA方式WMN中一种链路调度机制研究

基于TDMA方式的无线网状网中,链路调度对网络性能起着重要作用.针对固定顺序的待调度链路集,提出求解最优调度周期的启发式算法;基于链路顺序对算法性能的影响,从全局优化的角度对全网链路进行排序,提出基于遗传算法的最优链路调度机制.仿真结果表明,该算法能快速收敛于全网链路的最小调度周期,具有比现有算法更高的传输效率和更低的实施复杂度.     

基于EDF调度算法的端到端延迟保证方法

EDF(EarliestDeadlineFirst)是一种高效的调度算法。为了将其应用于提供端到端延迟保证,提出了一种新的算法JT-EDF(JitterTunableEDF),并证明了所有的端到端EDF调度算法都可以在相同的条件下保证相同的端到端延迟界。     

基于多跳间时延协作的最久分组优先算法

提出了一种基于多跳间时延协作的Crossbar调度算法。该算法以分组头中记录的时延为权重对分组进行调度，通过控制分组在各跳上的时延来达到调节端到端时延的目的。算法还使路由器避免了维护每个流的状态信息以及对单个流进行的复杂的队列管理和调度。计算机仿真表明，算法具有较高的资源利用率、较低的端到端时延抖动和较低的分组丢弃率等特点。     

基于TDMA的空中自组网MAC层资源调度算法研究

空中移动无线自组织网络是一种拓扑结构快速变化,有自组织性的多跳无中心网络;针对传统时隙分配算法资源利用率低、吞吐量不足、通信距离近等问题,采用引入分配系数的混合时隙分配模式,通过节点业务优先级和流量预测相结合,设计了一种基于TDMA定向分布式资源动态调度算法（M-TDMA）;对比分析了节点数量、传输速率、分配系数以及不同拓扑等多个维度对算法传输时延、吞吐量以及丢包率的影响;最后通过仿真实验对资源调度算法进行验证;仿真结果表明,在20个网络节点时,网络的最大传输时延小于600 ms,网络吞吐量可以达到4.5 Mbps以上, M-TDMA算法通过高效的资源调度,有效降低了网络传输时延并提高了网络吞吐量;     

Optimal replicator factor control in wireless sensor networks

For TDMA MAC protocols in wireless sensor networks (WSNs), redundancy and retransmission are two important methods to provide high end-to-end transmission reliability. Since reliable transmissions will lead to more energy consumption, there exists an intrinsic tradeoff between transmission reliability and energy efficiency. For each link, we name the number of its reserved time slots in each MAC superframe as a replicator factor. In the following paper, we propose a reliability-lifetime tradeoff framework (RLTF) for WSNs to study replicator factor control problem. First, for the redundancy TDMA MAC, we formulate replicator factor control problem as convex programming. By the gradient projection method, we develop a fully distributed algorithm to solve the convex programming. Second, for the retransmission TDMA MAC, we set the retransmission upper bound for each link according to the optimal replicator factors under the redundancy MAC and compute the total communication overhead for the retransmission MAC. Finally, we compare the communication overhead of these two MAC protocols under different channel conditions.     

Joint routing, scheduling, and power control for multichannel wireless sensor networks with physical interference

Reliability and real-time requirements bring new challenges to the energy-constrained wireless sensor networks, especially to the industrial wireless sensor networks. Meanwhile, the capacity of wireless sensor networks can be substantially increased by operating on multiple nonoverlapping channels. In this context, new routing, scheduling, and power control algorithms are required to achieve reliable and real-time communications and to fully utilize the increased bandwidth in multichannel wireless sensor networks. In this paper, we develop a distributed and online algorithm that jointly solves multipath routing, link scheduling, and power control problem, which can adapt automatically to the changes in the network topology and offered load. We particularly focus on finding the resource allocation that realizes trade-off among energy consumption, end-to-end delay, and network throughput for multichannel networks with physical interference model. Our algorithm jointly considers 1) delay and energy-aware power control for optimal transmission radius and rate with physical interference model, 2) throughput efficient multipath routing based on the given optimal transmission rate between the given source-destination pairs, and 3) reliable-aware and throughput efficient multichannel maximal link scheduling for time slots and channels based on the designated paths, and the new physical interference model that is updated by the optimal transmission radius. By proving and simulation, we show that our algorithm is provably efficient compared with the optimal centralized and offline algorithm and other comparable algorithms.     

低占空比WSN中一种节点休眠调度算法

低占空比无线传感器网络（low-duty-cycle wireless sensor networks,简称LDC-WSN）可以有效地延长网络生命周期.但是,现有的LDC-WSN中端到端的延迟非常大,并且现在很多关于LDC-WSN的算法没有充分考虑传输链路质量的问题.为了解决这两个问题,提出了一种基于链路质量和能量感知的节点休眠调度算法（link-quality and energy-aware based scheduling scheme,简称LES）.仿真实验结果表明,相比现在的典型算法,LES算法能够在满足同样延迟要求的情况下很明显地节省能量,从而延长网络的工作寿命.     

Local heuristic for the refinement of multi-path routing in wireless mesh networks

We consider wireless mesh networks and the problem of routing end-to-end traffic over multiple paths for the same origin–destination pair with minimal interference. We introduce a heuristic for path determination with two distinguishing characteristics. First, it works by refining an extant set of paths, determined previously by a single- or multi-path routing algorithm. Second, it is totally local, in the sense that it can be run by each of the origins on information that is available no farther than the node’s immediate neighborhood. We have conducted extensive computational experiments with the new heuristic, using AODV and OLSR, as well as their multi-path variants, as underlying routing methods. For two different CSMA settings (as implemented by 802.11) and one TDMA setting running a path-oriented link scheduling algorithm, we have demonstrated that the new heuristic is capable of improving the average throughput network-wide. When working from the paths generated by the multi-path routing algorithms, the heuristic is also capable to provide a more evenly distributed traffic pattern.     

OLSR-aware channel access scheduling in wireless mesh networks

Wireless mesh networks (WMNs) have emerged as a key technology having various advantages, especially in providing cost-effective coverage and connectivity solutions in both rural and urban areas. WMNs are typically deployed as backbone networks, usually employing spatial TDMA (STDMA)-based access schemes which are suitable for the high traffic demands of WMNs. This paper aims to achieve higher utilization of the network capacity and thereby aims to increase the application layer throughput of STDMA-based WMNs. The central idea is to use optimized link state routing (OLSR)-specific routing layer information in link layer channel access schedule formation. This paper proposes two STDMA-based channel access scheduling schemes (one distributed, one centralized) that exploit OLSR-specific information to improve the application layer throughput without introducing any additional messaging overhead. To justify the contribution of using OLSR-specific information to the throughput, the proposed schemes are compared against one another and against their non-OLSR-aware versions via extensive ns-2 simulations. Our simulation results verify that utilizing OLSR-specific information significantly improves the overall network performance both in distributed and in centralized schemes. The simulation results further show that OLSR-aware scheduling algorithms attain higher end-to-end throughput although their non-OLSR-aware counterparts achieve higher concurrency in slot allocations.     

A cyclic MAC scheduler for collecting data from heterogeneous sensors

Many wireless sensor networks applications, e.g., structural health monitoring (SHM), require the sensors to construct a multihop network to collect the environmental data in real-time. These sensors generally generate sensing data in fixed rates, so their transmission schedules can be deterministically listed. Time division multiple access (TDMA) is especially appropriate for these applications because it can prevent radio interference, thereby reducing the transmission power and maximizing wireless spectrum reuse. However, to reserve sufficient bandwidths on distinct links of a heterogeneous WSN, a complex TDMA schedule is necessary, and a sensor node might need to keep a large TDMA schedule table in its tiny memory. To prevent a large size TDMA schedule table, this paper proposes a CyclicMAC scheduler that assigns each node a temporal transmission pattern which is merely parameterized by period and phase. The CyclicMAC scheduler determines the period to satisfy the bandwidth requirement of the node, and adjusts the phase to achieve collision-freeness and reduce the end-to-end latency as well. The end-to-end latency of the resulting schedule is proven to be optimal if the wireless links only interfere with their parent link and sibling links. As far as we know, CyclicMAC is the first that simultaneously addresses the three design issues of TDMA scheduling, which satisfies heterogeneous bandwidth requirements, minimizing schedule table size, and reducing end-to-end latency, for multihop wireless sensor networks.