基于SINR的动态无线网络分布式链路调度

无线信号之间的干扰阻碍了信号的并发传输,降低了无线网络的吞吐量.链路调度是提高无线网络吞吐量、减少信号传输延迟的一种有效方法.因为SINR (signal to interference plus noise ratio)模型准确地描述了无线信号传播的固有特性,能够真实反映无线信号之间的干扰,提出一种在动态无线网络中基于SINR模型的常数近似因子的在线分布式链路调度算法(OLD＿LS).在线的意思是指,在算法执行的过程中任意节点可以随时加入网络,也可以随时离开网络.节点任意加入网络或者从网络中离开体现了无线网络的动态变化的特性. OLD＿LS算法把网络区域划分为多个正六边形,局部化SINR模型的全局干扰.设计动态网络下的领导者选举算法(LE),只要网络节点的动态变化速率小于1/ε, LE就可以在O(log n+log R)ε≤5(1-2^1-α/2)/6,α表示路径损耗指数, n是网络节点的规模, R是最长链路的长度.根据文献调研,所提算法是第1个用于动态无线网络的在线分布式链路调度算法.     

一种无线多媒体传感器网络分区链路调度算法

链路干扰是无线多媒体传感器网络实现大容量、实时、可靠传输的主要困难。为提高多跳传输模式下无线网络性能,基于MAC层的调度算法得到了广泛关注。调度算法为每条链路分配合理的传输时槽,降低了冲突和重传次数,能显著提高网络传输性能。但随着网络规模的增大,无论是集中式还是分布式调度算法,都存在调度开销增大和性能降低的问题。针对这一问题,根据节点分布密度和承载网络流量大小,将网络划分为密集区域和稀疏区域。稀疏区域的节点传输冲突较小,直接采用CSMA的协议。密集区域的节点传输冲突大,采用基于队列长度的分布式调度。分区调度能够有效降低网络规模扩大导致的调度算法复杂性增大的问题。仿真实验表明,分区调度算法无论是在队列长度,还是在延时性能上,较传统算法有明显改善。     

无线传感器和执行器网络控制系统设计与仿真

无线传感器和执行器网络通过无线网络(ZigBee)将传感器和执行器与控制器相连,完成分布式传感和执行任务。针对无线网络传输和被控对象延时的不良影响,首先详细介绍了基于TrueTime 2.0的无线网络控制系统在Windows 7和Matlab R2010b环境下的搭建,给出了系统的仿真模型。对控制器节点分别采用常规PID控制和模糊PID控制算法进行仿真研究。仿真结果表明,对于存在延时环节的无线网络控制系统,模糊PID控制可以取得较好的控制效果,系统鲁棒性较强。该研究对物联网智能家居系统的设计具有一定参考价值。     

Dk-hop: 一个有向k跳无线干扰模型

无线链路调度算法的性能直接受无线干扰模型准确性的影响. 尽管由于其简单性而被广泛采用, k跳干扰模型并不能准确建模真实的无线干扰特性, 从而导致链路调度算法的理论性能与实际性能之间存在很大差异. 本文考虑无线传输方向性因素对干扰的影响, 提出了Dk-hop无线干扰模型. 该模型有效排除了k跳隐藏链路, 从而更准确地对无线干扰进行了建模.理论分析表明, 当k值不超过IR+1时(IR为载波感知距离和传输距离之比), Dk-hop比k跳干扰模型更为准确, 且仍然保持了k跳干扰模型的简单性. 为与真实的无线干扰保持接近, k的合理取值范围应为[IR-2, IR+1].     

可变频宽无线网络中信道频谱分配与链路调度

考虑信道频宽对链路传输距离和链路间干扰的影响,对可变频宽无线网络现有的累积干扰模型进行了改进,并基于改进的干扰模型对可变频宽无线网络的信道频谱分配和链路调度问题进行了建模分析。设计了一种两层优化算法对信道频谱分配和链路调度问题进行解耦,提出了一种考虑链路负载需求满足程度的链路优先级指标,启发式地构建并发传输信道分配矩阵的方法。仿真结果表明,两层优化算法能够在合理时间内收敛,启发式方法能够高效地构建并发传输信道分配矩阵。     

基于混合干扰模型的多信道Mesh网络调度算法

研究了多信道无线Mesh网络中的调度及信道分配问题,设计了一种综合协议干扰模型与物理干扰模型的混合干扰模型,并在此干扰模型下提出了一种集中式调度算法。该算法在目前普遍使用的协议干扰模型的基础上,考虑了无线链路的物理传输特性：即使存在一定的干扰,也可以成功接收发射端发送的数据。模拟实验表明该算法可以提高Mesh网络中链路的并行性,有效减少总传输时间。     

无线自组织网络MAC调度技术研究*

从提高无线自组织网络服务质量的角度出发,介绍了无线自组织网络MAC调度技术的研究动机和技术本质。从无线干扰模型的建立、集中式与分布式调度算法的设计、调度复杂性理论、集中式和分布式调度算法的性能比较、拓扑透明MAC调度技术这五个相关研究方向入手,全面介绍了无线自组织网络MAC调度技术的研究进展和当前面临的挑战,并讨论了未来可能的发展方向。     

DLSOMAC:一个面向分布式无线链路调度技术的MAC协议

无线网络分布式链路调度技术通过发掘无线传输间的复用达到提高吞吐量的目的. 链路调度策略的形成需要节点间公平地交互含有如节点ID、队列长度等信息的短报文,并且这些短报文同步传输,导致信道拥挤.由于存在信道空闲侦听开销,在拥挤信道中频繁后退,以及隐藏终端和暴露终端的问题,传统的CSMA/CA (Carrier sense multiple access with collision avoidance)协议传输性能低下,难以为分布式无线链路调度技术服务. 针对链路调度策略形成期间报文短、信道拥挤以及公平性要求的挑战.提出了一个简单的随机MAC (Media access control)协议DLSOMAC (Distributed link scheduling oriented MAC). DLSOMAC协议没有信道侦听过程,以降低短报文的传输延迟开销;基于分布式息票收集算法,均匀分散传输时刻来降低冲撞概率和提高公平性,以满足分布式链路调度技术对MAC层的需求.用排队论分析了DLSOMAC的报文传输延迟性能.仿真实验表明, 在短报文情况下,无论网络负载轻重与否, DLSOMAC协议的报文传输延迟明显优于CSMA/CA,并且报文越短,性能相对越好.即使在长报文的情况下,当网络负载很重时, DLOSMAC协议也稍优于CSMA/CA协议,适合于为自组织网络的分布式链路调度技术服务.     

无线网状网多源多径组播P2P流媒体分发

由于无线网络相邻链路间信号相互干扰,无线网状网中P2P流媒体分发不能直接利用现有有线网络P2P流媒体分发的调度算法.为提高无线网状网P2P流媒体分发质量,通过引入流媒体传输率失真模型和组播无线信号干扰模型,提出一种跨层多源多径组播调度策略,并采用改进的遗传算法对该策略进行实现.与多源多径单播调度算法相比,由于多源多径组播调度算法利用了无线网络实质采用广播方式传输数据的特点,能有效的减少流媒体数据传输冲突概率.仿真实验表明,多源多径组播调度算法更能有效的提高无线网状网P2P流媒体分发质量.     

全双工无线供能物联网的物理层安全性能分析

面对干扰和窃听,传统的安全信息传输大都基于密钥加密的方法,在面向动态变化无线网络环境时会产生对称性密码系统的密钥分配、非对称性密码系统的高计算复杂度等问题。而快速增长的无线业务流量和物联网类型的海量设备接入,会引起计算复杂度的进一步提升和能量开销的激增。针对此问题,提出一种基于物理层安全技术的全双工无线供能物联网的安全通信方法,利用噪声和无线信道随机性来限制窃听者接收信息量。该方法首先基于信息论对全双工无线供能物联网安全容量进行分析,然后根据安全容量的分析模型推导得到了安全中断概率（SOP）的闭合表达式。最后,考虑到噪声、干扰机干扰、空间互干扰,以及残余自干扰等因素对安全容量的影响,提出一种全双工无线供能物联网安全波束成形方法,该方法通过降低联合干扰来增加发送和接收端的互信息量,提高全双工无线功能物联网的安全容量。通过蒙特卡罗仿真验证了推导结果的准确性,仿真结果表明,在安全容量和SOP指标上,全双工无线供能物联网比传统半双工无线功能物联网有较大性能增益。     

Interference-Aware Joint Routing and TDMA Link Scheduling for Static Wireless Networks

We study efficient interference-aware joint routing and TDMA link scheduling for a multihop wireless network to maximize its throughput. Efficient link scheduling can greatly reduce the interference effect of close-by transmissions. Unlike the previous studies that often assume a unit disk graph model, we assume that different terminals could have different transmission ranges and interference ranges. In our model, a communication link may not exist due to barriers or is not used by a predetermined routing protocol. Using a mathematical formulation, we develop interference aware joint routing and TDMA link schedulings that optimize the networking throughput subject to various constraints. Our linear programming formulation will find a flow routing whose achieved throughput (or fairness) is at least a constant fraction of the optimum. Then, by assuming known link capacities and link traffic loads, we study link scheduling under the RTS/CTS interference model and the protocol interference model with fixed transmission power. For both models, we present both efficient centralized and distributed algorithms that use time slots within a constant factor of the optimum. We also present efficient distributed algorithms whose performances are still comparable with optimum, but with much less communications. Our theoretical results are corroborated by extensive simulation studies.     

An effective scheduling scheme for multi-hop multicast in wireless mesh networks

With the utilization of concurrent transmission strategy, a throughput-enhanced scheduling scheme is devised for multicast service in wireless multi-hop mesh networks. Since the performance of a multicast mechanism is constrained in a wireless setting due to the interference among local wireless transmissions, the interference relationships are first characterized by introducing a graph transformation method. Based on the graph transformation, the multicast scheduling problem is converted to the graph coloring problem, and then a capacity greedy algorithm is designed to provide concurrent transmission scheduling so that the demanded multicast transmission rate can be achieved. Moreover, the necessary and sufficient conditions of multicast schedulable feasibility are derived. Through corresponding simulations, it is shown that the proposed strategy can enhance the throughput of wireless multi-hop multicast systems significantly.     

An effective scheduling scheme for multi-hop multicast in wireless mesh networks

With the utilization of concurrent transmission strategy, a throughput-enhanced scheduling scheme is devised for multicast service in wireless multi-hop mesh networks. Since the performance of a multicast mechanism is constrained in a wireless setting due to the interference among local wireless transmissions, the interference relationships are first characterized by introducing a graph transformation method. Based on the graph transformation, the multicast scheduling problem is converted to the graph coloring problem, and then a capacity greedy algorithm is designed to provide concurrent transmission scheduling so that the demanded multicast transmission rate can be achieved. Moreover, the necessary and sufficient conditions of multicast schedulable feasibility are derived. Through corresponding simulations, it is shown that the proposed strategy can enhance the throughput of wireless multi-hop multicast systems significantly.     

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.     

物联网中移动代理的应用研究

通过对物联网网络管理技术的研究,分析了物联网网络管理中存在的问题。针对物联网无线化、移动化的发展趋势,给出了基于分布式网络代理管理模型,该模型通过引入移动代理技术,能够使之更好地适应物联网的管理需求。     

Gray physical interference model based link scheduling algorithms

To improve the concurrent data transmission capability of wireless multi-hop networks,this paper proposes adopting a gray physical interference model instead of using the threshold physical interference model.The model allows non-ideal links to be involved in scheduling,under the premise of not affecting the quality of existing transmission links.In addition,we design two greedy algorithms to schedule more links with SINR values located in the transition region.The results show that a gray physical interference model is more accurate than a threshold physical interference one,the concurrent transmission capability of a network based on the gray physical interference model is significantly increased,and network throughput is increased by 20%.     

无线接入网中一类联合调度算法的鲁棒稳定性分析

针对无线通讯中的随机时延抖动和外界干扰等会引发数据包传输的不稳定问题,研究不稳定传输下无线接入网中一类联合调度算法的鲁棒稳定性.首先,通过将基站中的队列尺寸定义为系统状态,并将不稳定传输建模为分布函数未知的随机扰动,利用具有一个弹性壁的Markov随机游走模型描述系统状态的变化;其次,根据在联合调度算法下系统状态的期望逗留时间等信息,得到该Markov模型的状态转移概率矩阵;再次,给出模型中状态正常返的充分条件,即队列尺寸的鲁棒稳定性判据,并对该判据进行验证;最后,通过数值仿真结果表明了所提方法的有效性.     

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;     

相继干扰消除的无线网络中的调度性能分析

研究了支持相继干扰消除(successive interference cancellation,简称SIC)的无线网络中链路调度算法的设计与分析,首先,为刻画SIC的顺序检测特性,提出M-level非累积干扰模型与有序累积干扰模型.然后,由于两种模型下的调度均为NP-hard问题,研究了近似调度的性能:(1)给出了一种工作于有序累积干扰模型的调度机制,其近似比为O(g),其中,g为网络的链路多样性指数;(2)给出了一种工作于M-level非累积干扰模型的调度机制,其近似比为常数.最后,通过仿真实验考察了SIC对调度性能的影响.