LSAPSP: Load distribution‐based slot allocation and path establishment using optimized substance particle selection in sensor networks

Sensor node energy conservation is the primary design parameters in wireless sensor networks (WSNs). Energy efficiency in sensor networks directly prolongs the network lifetime. In the process of route discovery, each node cooperates to forward the data to the base station using multi‐hop routing. But, the nodes nearer to the base station are loaded more than the other nodes that lead to network portioning, packet loss and delay as a result nodes may completely loss its energy during the routing process. To rectify these issues, path establishment considers optimized substance particle selection, load distribution, and an efficient slot allocation scheme for data transmission between the sensor nodes in this paper. The selection of forwarders and conscious multi‐hop path is selected based on the route cost value that is derived directly by taking energy, node degree and distance as crucial metrics. Load distribution based slot allocation method ensures the balance of data traffic and residual energy of the node in areal‐time environment. The proposed LSAPSP simulation results show that our algorithm not only can balance the real‐time environment load and increase the network lifetime but also meet the needs of packet loss and delay.     

DynaChannAl: dynamic channel allocation with minimal end‐to‐end delay for two‐tier wireless sensor networks

With recent advances in wireless networking and in low‐power sensor technology, wireless sensor networks (WSNs) have taken significant roles in various applications. Whereas some WSNs only require minimal bandwidth, newer applications operate with a noticeably larger amount of data. One way to deal with these applications is to maximize the available capacity by utilizing multiple wireless channels. We propose DynaChannAl, a distributed dynamic wireless channel allocation algorithm that effectively distributes nodes to multiple wireless channels in WSNs. Specifically, DynaChannAl targets applications where mobile nodes connect to preexisting wireless backbones and takes the expected end‐to‐end queuing delay as its core metric. We used the link quality indicator values provided by 802.15.4 radios to whitelist high‐quality links and evaluate these links with the aggregated queuing latency, making it useful for applications that require minimal end‐to‐end delay (i.e., health care). DynaChannAl is a lightweight and adoptable scheme that can be incorporated easily with predeveloped systems. As the first study to consider end‐to‐end latency as the core metric for channel allocation in WSNs, we evaluate DynaChannAl on a 45 node test bed and show that DynaChannAl successfully distributes source nodes to different channels and enables them to select channels and links that minimizes the end‐to‐end latency. Copyright © 2012 John Wiley & Sons, Ltd.     

Delay constraint multipath routing for wireless multimedia ad hoc networks

According to the disadvantages of real time and continuity for multimedia services in ad hoc networks, a delay constraint multipath routing protocol for wireless multimedia ad hoc networks, which can satisfy quality of service (QoS) requirement (QoS multipath optimized link state routing [MOLSR]), is proposed. The protocol firstly detects and analyzes the link delay among the nodes and collects the delay information as the routing metric by HELLO message and topology control message. Then, through using the improved multipath Dijkstra algorithm for path selection, the protocol can gain the minimum delay path from the source node to the other nodes. Finally, when the route is launched, several node‐disjoint or link‐disjoint multipaths will be built through the route computation. The simulation and test results show that QoS‐MOLSR is suitable for large and dense networks with heavy traffic. It can improve the real time and reliability for multimedia transmission in wireless multimedia ad hoc networks. The average end‐to‐end delay of QoS‐MOLSR is four times less than the optimized link state routing. Copyright © 2014 John Wiley & Sons, Ltd.     

Tree‐based channel assignment schemes for multi‐channel wireless sensor networks

Many sensor node platforms used for establishing wireless sensor networks (WSNs) can support multiple radio channels for wireless communication. Therefore, rather than using a single radio channel for whole network, multiple channels can be utilized in a sensor network simultaneously to decrease overall network interference, which may help increase the aggregate network throughput and decrease packet collisions and delays. This method, however, requires appropriate schemes to be used for assigning channels to nodes for multi‐channel communication in the network. Because data generated by sensor nodes are usually delivered to the sink node using routing trees, a tree‐based channel assignment scheme is a natural approach for assigning channels in a WSN. We present two fast tree‐based channel assignment schemes (called bottom up channel assignment and neighbor count‐based channel assignment) for multi‐channel WSNs. We also propose a new interference metric that is used by our algorithms in making decisions. We validated and evaluated our proposed schemes via extensive simulation experiments. Our simulation results show that our algorithms can decrease interference in a network, thereby increasing performance, and that our algorithms are good alternatives for static channel assignment in WSNs. Copyright © 2015 John Wiley & Sons, Ltd.     

用于多信道无线网络的综合链路速率分配算法

This paper presents a link allocation and rate assignment algorithm for multi-channel wireless networks. The objective is to reduce network conflicts and guarantee the fairness among links. We first design a new network model. With this network model, the multi-channel wireless network is divided into several subnets according to the number of channels. Based on this, we present a link allocation algorithm with time complexity O(l2 ) to allocate all links to subnets. This link allocation algorithm adopts conflict matrix to minimize the network contention factor. After all links are allocated to subnets, the rate assignment algorithm to maximize a fairness utility in each subnet is presented. The rate assignment algorithm adopts a near-optimal algorithm based on dual decomposition and realizes in a distributed way. Simulation results demonstrate that, compared with IEEE 802. 11b and slotted seeded channel hopping algorithm, our algorithm decreases network conflicts and improves the network throughput significantly.     

太赫兹无线局域网MAC协议优化设计

针对现有太赫兹无线网络MAC(Medium Access Control)协议中存在的无线局域网场景下原有波束赋形方案不适用、关联请求时段在新入网节点数量受限情况下时隙利用率低,以及网络流量较大时扇区号靠后的节点一直无法获得时隙导致时延陡增的情况,提出了一种适用于无线局域网的高效低时延太赫兹MAC协议(High Efficiency and Low Latency Terahertz MAC,HELL-MAC)。该协议利用中心控制节点与普通节点间的信息交互减少了不必要的波束赋形过程,采用机会性复用关联S-CAP(Sub-channel Access Period)机制提高了时隙利用率,采用公平时隙分配机制提高了时隙分配的公平性,从而减少了波束赋形时间,降低了平均端到端时延,提高了信道利用率。     

无线Mesh网络集中式信道分配算法设计

以集中式无线Mesh网络(WMN)为基础,分析和研究了传统多信道分配算法,并在此基础上提出了以节点优先级和分组为特点的多接口多信道分配算法(Channel Assignment based on Rank of Node and Link group,CAR-NL),该算法结合节点分级和链路负载预期评估机制,通过节点链路分组按级分配信道。通过仿真实验表明,该算法能有效提高无线Mesh网络多业务流并发执行时系统整体吞吐量,并实现较低的丢包率。     

Simulation‐based real‐time routing protocol with load distribution in wireless sensor networks

In wireless sensor networks (WSNs), sensors gather information about the physical world and the base station makes decision and then performs appropriate actions upon the environment. This technology enables a user to effectively sense and monitor from a distance in real‐time. WSNs demand real‐time forwarding which means messages in the network are delivered according to their end‐to‐end deadlines (packet lifetime). This paper proposes a novel real‐time routing protocol with load distribution (RTLD) that ensures high packet throughput with minimized packet overhead and prolongs the lifetime of WSN. The routing depends on optimal forwarding (OF) decision that takes into account of the link quality (LQ), packet delay time and the remaining power of next hop sensor nodes. The proposed mechanism has been successfully studied through simulation work. Copyright © 2009 John Wiley & Sons, Ltd.     

Low‐jitter slot assignment algorithm for deadline‐aware packet transmission in wireless video surveillance sensor networks

This work presents a distributed time‐slot assignment algorithm which adopts TDMA as Medium Access Control, specially suited to support applications with strict delay, jitter, and throughput requirements characterized by convergecast traffic pattern in sensor networks. (e.g. wireless video surveillance sensor networks). The proposed algorithm has three characteristics: (1) every node is guaranteed a path to the base station for its data delivery. In the path, sufficient resource is reserved and weighted fairness can be achieved. (2) It uses cascading time‐slot assignment and jitter minimization algorithm in each node to minimize jitter and end‐to‐end delay. (3) Nodes are only active during their scheduled slots and sleep otherwise. This offers energy saving by reducing idle listening and avoiding overhearing. The performance of the proposed algorithm is evaluated over simulations and analyzed theoretically in comparison with existing slot assignment algorithm. The results show that our algorithm provides lower end‐to‐end delay, jitter, and higher throughput. Copyright © 2010 John Wiley & Sons, Ltd.     

FPGA implementation of dynamic channel assignment algorithm for cognitive wireless sensor networks

The reliability of wireless sensor networks (WSNs) in industrial applications can be thwarted due to multipath fading, noise generated by industrial equipment or heavy machinery and particularly by the interference generated from other wireless devices operating in the same spectrum band. Recently, cognitive WSNs (CWSNs) were proposed to improve the performance and reliability of WSNs in highly interfered and noisy environments. In this class of WSN, the nodes are spectrum aware, that is, they monitor the radio spectrum to find channels available for data transmission and dynamically assign and reassign nodes to low-interference condition channels. In this work, we present the implementation of a channel assignment algorithm in a field-programmable gate array, which dynamically assigns channels to sensor nodes based on the interference and noise levels experimented in the network. From the results obtained from the performance evaluation of the CWSN when the channel assignment algorithm is considered, it is possible to identify how many channels should be available in the network in order to achieve a desired percentage of successful transmissions, subject to constraints on the signal-to-interference plus noise ratio on each active link.     

A Novel Distributed Scheduling Algorithm for Downlink Relay Networks

To extend network coverage and to possibly increase data packet throughput, the future wireless cellular networks could adopt relay nodes for multi-hop data transmission. This letter proposes a novel distributed scheduling algorithm for downlink relay networks. Soft-information indicating the probability of activating each network link is exchanged iteratively among neighboring network nodes to determine an efficient schedule. To ensure collision-free simultaneous data transmissions, collision-avoiding local constraint rules are enforced at each network node. To increase resource utility, the soft-information is weighted according to the urgency of data transmission across each link, which also helps maintain throughput fairness among network users.     

Joint load balanced stable routing and communication segment assignment in mobile cognitive radio ad‐hoc networks

The fundamental issues in mobile cognitive radio ad‐hoc networks are the selection of the optimal stable paths between nodes and proper assignment of the frequency channels/time slots (communication segments) to the links. In this paper, a joint load balanced stable routing and communication segment assignment algorithm is proposed that considers jointly the mobility prediction, mitigating the co‐channel interference and energy consumption. The novelty of the proposed algorithm lies in the increasing of the path stability, which benefits from the maximum link lifetime parameter and introduced weighting function to keep routes away from the PU's region. This avoids the negative impacts on the PUs' operations and decreases the conflict of the cognitive nodes. In the proposed algorithm, the concept of load balancing is considered that yields in the balancing energy consumption in the network, improving the network performance and distributing traffic loads on all available channels. The effectiveness of the proposed algorithm is verified by evaluating the aggregate interference energy, average end‐to‐end delay, goodput, and the energy usage per packet under 6 scenarios. The results show that the performance of the proposed algorithm is significantly better than the recently proposed joint stable routing and channel assignment protocol.     

Lifetime optimization for reliable broadcast and multicast in wireless ad hoc networks

In this paper, we consider the reliable broadcast and multicast lifetime maximization problems in energy‐constrained wireless ad hoc networks, such as wireless sensor networks for environment monitoring and wireless ad hoc networks consisting of laptops or PDAs with limited battery capacities. In packet loss‐free networks, the optimal solution of lifetime maximization problem can be easily obtained by tree‐based algorithms. In unreliable networks, we formulate them as min–max tree problems and prove them NP‐complete by a reduction from a well‐known minimum degree spanning tree problem. A link quality‐aware heuristic algorithm called Maximum Lifetime Reliable Broadcast Tree (MLRBT) is proposed to build a broadcast tree that maximizes the network lifetime. The reliable multicast lifetime maximization problem can be solved as well by pruning the broadcast tree produced by the MLRBT algorithm. The time complexity analysis of both algorithms is also provided. Simulation results show that the proposed algorithms can significantly increase the network lifetime compared with the traditional algorithms under various distributions of error probability on lossy wireless links. Copyright © 2012 John Wiley & Sons, Ltd.     

DRAND: Distributed Randomized TDMA Scheduling for Wireless Ad Hoc Networks

This paper presents a distributed implementation of RAND, a randomized time slot scheduling algorithm, called DRAND. DRAND runs in O(delta ) time and message complexity where delta is the maximum size of a two-hop neighborhood in a wireless network while message complexity remains O(delta ), assuming that message delays can be bounded by an unknown constant. DRAND is the first fully distributed version of RAND. The algorithm is suitable for a wireless network where most nodes do not move, such as wireless mesh networks and wireless sensor networks. We implement the algorithm in TinyOS and demonstrate its performance in a real testbed of Mica2 nodes. The algorithm does not require any time synchronization and is shown to be effective in adapting to local topology changes without incurring global overhead in the scheduling. Because of these features, it can also be used even for other scheduling problems such as frequency or code scheduling (for FDMA or CDMA) or local identifier assignment for wireless networks where time synchronization is not enforced. We further evaluate the effect of the time-varying nature of wireless links on the conflict-free property of DRAND-assigned time slots. This experiment is conducted on a 55-node testbed consisting of the more recent MicaZ sensor nodes.     

一种为地面节点充电的多UAV任务分配与路线规划方法

以多个无人机（UAV）为大面积分布的传感器节点无线充电为应用场景，提出了一种分布式快速拍卖算法（DFAMTA）用于为多个UAV分配任务及规划航线。利用该算法，不需集中控制器，每个UAV根据自己的续航能力和获知的节点位置及剩余电量信息，建立包含多个节点的任务集进行投标；中标者的确定在单个任务层面上独立并行进行，大大节省了任务分配的收敛时间。理论证明，DFAMTA算法在最差情况下也能获得最优分配算法50%的性能。仿真验证了算法在收敛时间上的优势以及在改善无线传感器网络系统平均覆盖率方面的优越性。     

The Impact of Deployment Pattern and Routing Scheme on the Lifetime in Multi-Sink Wireless Sensor Network

Extensive use of sensor and actuator networks in many real-life applications introduced several new performance metrics at the node and network level. Since wireless sensor nodes have significant battery constraints, therefore, energy efficiency, as well as network lifetime, are among the most significant performance metrics to measure the effectiveness of given network architecture. This work investigates the performance of an event-based data delivery model using a multipath routing scheme for a wireless sensor network with multiple sink nodes. This routing algorithm follows a sink initiated route discovery process with the location information of the source nodes already known to the sink nodes. It also considers communication link costs before making decisions for packet forwarding. Carried out simulation compares the network performance of a wireless sensor network with a single sink, dual sink, and multi sink networking approaches. Based on a series of simulation experiments, the lifetime aware multipath routing approach is found appropriate for increasing the lifetime of sensor nodes significantly when compared to other similar routing schemes. However, energy-efficient packet forwarding is a major concern of this work; other network performance metrics like delay, average packet latency, and packet delivery ratio are also taken into the account.

     

An Efficient Cross-Layer Optimization Algorithm for Data Transmission in Wireless Sensor Networks

In this paper, we propose a cross layer congestion optimization scheme for allocating the resources of wireless sensor networks to achieve maximization of network performance. The congestion control, routing selection, link capacity allocation, and power consumption are all taken account to yield an optimal scheme based on the Lagrangian optimization. The Lagrangian multiplier is adopted to adjust power consumption, congestion rate, routing selection and link capacity allocation, so that the network performance can be satisfied between the trade-off of efficiency and fairness of resource allocation. The proposed algorithm can significantly achieve the maximization of network performance in relieving the network congestion with less power consumption. Excellent simulation results are obtained to demonstrate our innovative idea, and show the efficiency of our proposed algorithm.     

动态TDMA时隙分配算法在数据链中的仿真

固定TDMA分配算法能够保证节点数据发送的公平性,但不可能针对当前业务和网络状态进行时隙预留分配,很难实现差别服务和提供支持QoS（服务质量）的机制。因此提出一种适用于TTNT（战术瞄准网络技术）数据链通信系统的动态TDMA时隙分配算法,在高负载的网络环境下,这种算法加入了优先级机制并根据业务量轻重对各节点采取不同的发送策略,对时隙有较高利用率,提高了Ad Hoc（自组织网）网络系统吞吐量。在OPNET网络仿真平台上进行了仿真验证,仿真结果表明该算法在吞吐量和时延方面都优于固定TDMA算法。     

Bounded‐delay and loss‐free guarantees for real‐time video in integrated services packet networks

In this paper, we analyse upper bounds on the end‐to‐end delay and the required buffer size at the leaky bucket and packet switches within the network in the context of the deterministic bandwidth allocation method in integrated services packet networks. Based on that formulation, we then propose a CAC method suitable to ISPN to guarantee the bounded end‐to‐end delay and loss‐free packet transmissions. As an example application, the GOP–CBR MPEG‐2 is considered. In that case, we also show tighter bounds by slightly modifying the coding method of GOP–CBR MPEG‐2. Using the actual traced data of GOP–CBR MPEG‐2, we discuss the applicabilities of our analytical results and proposed CAC by comparing with simulation. Numerical results show that the loose upper bounds can also achieve more utilization even in the context of deterministic bandwidth allocation compared with the peak bandwidth allocation strategy. Copyright © 2000 John Wiley & Sons, Ltd.     

Web browsing optimization over 2.5G and 3G: end‐to‐end mechanisms vs. usage of performance enhancing proxies

2.5 Generation (2.5G) and Third Generation (3G) cellular wireless networks allow mobile Internet access with bearers specifically designed for data communications. However, Internet protocols under‐utilize wireless wide area network (WWAN) link resources, mainly due to large round trip times (RTTs) and request‐‐reply protocol patterns. Web browsing is a popular service that suffers significant performance degradation over 2.5G and 3G. In this paper, we review and compare the two main approaches for improving web browsing performance over wireless links: (i) using adequate end‐to‐end parameters and mechanisms and (ii) interposing a performance enhancing proxy (PEP) between the wireless and wired parts. We conclude that PEPs are currently the only feasible way for significantly optimizing web browsing behavior over 2.5G and 3G. In addition, we evaluate the two main current commercial PEPs over live general packet radio service (GPRS) and universal mobile telecommunications system (UMTS) networks. The results show that PEPs can lead to near‐ideal web browsing performance in certain scenarios. Copyright © 2006 John Wiley & Sons, Ltd.