Connected Dominating Sets in Wireless Networks with Different Transmission Ranges

Since there is no fixed infrastructure or centralized management in wireless ad hoc networks, a Connected Dominating Set (CDS) has been proposed to serve as a virtual backbone. The CDS of a graph representing a network has a significant impact on the efficient design of routing protocols in wireless networks. This problem has been studied extensively in Unit Disk Graphs (UDG), in which all nodes have the same transmission ranges. However, in practice, the transmission ranges of all nodes are not necessarily equal. In this paper, we model a network as a disk graph and introduce the CDS problem in disk graphs. We present two efficient approximation algorithms to obtain a minimum CDS. The performance ratio of these algorithms is constant if the ratio of the maximum transmission range over the minimum transmission range in the network is bounded. These algorithms can be implemented as distributed algorithms. Furthermore, we show a size relationship between a maximal independent set and a CDS as well as a bound of the maximum number of independent neighbors of a node in disk graphs. The theoretical analysis and simulation results are also presented to verify our approaches.     

On Construction of Virtual Backbone in Wireless Ad Hoc Networks with Unidirectional Links

Since there is no fixed infrastructure in wireless ad hoc networks , virtual backbone has been proposed as the routing infrastructure to alleviate the broadcasting storm problem. The virtual backbone construction has been studied extensively in {em undirected} graphs, especially in unit disk graphs, in which each node has the same transmission range. In practice, however, transmission ranges of all nodes are not necessarily equal. In this paper, we model such a network as a disk graph, where unidirectional links are considered. To study the virtual backbone construction in disk graphs, we consider two problems: Strongly Connected Dominating Set (SCDS) and Strongly Connected Dominating and Absorbing Set (SCDAS). We propose a constant approximation algorithm and discuss its improvements for the SCDS problem . We also propose a heuristic for the SCDAS problem. Through extensive simulations, we verify our theoretical analysis and also demonstrate that the SCDS can be extended to form an SCDAS with marginal extra overhead.     

Approximation Algorithms for the Connected Dominating Set Problem in Unit Disk Graphs

The connected dominating set （CDS） problem, which consists of finding a smallest connected dominating set for graphs is an NP-hard problem in the unit disk graphs （UDGs）. This paper focuses on the CDS problem in wireless networks. Investigation of some properties of independent set （IS） in UDGs shows that geometric features of nodes distribution like angle and area can be used to design efficient heuristics for the approximation algorithms. Several constant factor approximation algorithms are presented for the CDS problem in UDGs. Simulation results show that the proposed algorithms perform better than some known ones.     

The first constant factor approximation for minimum partial connected dominating set problem in growth-bounded graphs

The idea of virtual backbone has emerged to improve the efficiency of flooding based routing algorithms for wireless networks. The effectiveness of virtual backbone can be improved as its size decreases. The minimum connected dominating set (CDS) problem was used to compute minimum size virtual backbone. However, as this formulation requires the virtual backbone nodes to connect all other nodes, even the size of minimum virtual backbone can be large. This observation leads to consider the minimum partial CDS problem, whose goal is to compute a CDS serving only more than a certain portion of the nodes in a given network. So far, the performance ratio of the best approximation algorithm for the problem is \(O(\ln \varDelta ),\) where \(\varDelta\) is the maximum degree of the input general graph. In this paper, we first assume the input graph is a growth-bounded graph and introduce the first constant factor approximation for the problem. Later, we show that our algorithm is an approximation for the problem in unit disk graph with a much smaller performance ratio, which is of practical interest since unit disk graph is popular to abstract homogeneous wireless networks. Finally, we conduct simulations to evaluate the average performance of our algorithm.     

Zone-based virtual backbone formation in wireless ad hoc networks

Efficient protocol for clustering and backbone formation is one of the most important issues in wireless ad hoc networks. Connected dominating set (CDS) formation is a promising approach for constructing virtual backbone. However, finding the minimum CDS in an arbitrary graph is a NP-Hard problem. In this paper, we present a novel zone-based distributed algorithm for CDS formation in wireless ad hoc networks. In this Zone algorithm, we combine the zone and level concepts to sparsify the CDS constructed by previous well-known approaches. Therefore, this proposed algorithm can significantly reduce the CDS size. Particularly, we partition the wireless network into different zones, construct a dominating tree for each zone and connect adjacent zones by inserting additional connectors into the final CDS (at the zone borders). Our comprehensive simulation study using a custom simulator shows that this zone-based algorithm is more effective than previous approaches. The number of nodes in the CDS formed by this Zone algorithm is up to around 66% less than that constructed by others. Moreover, we also compare the performance of Zone algorithm with some recently proposed CDS formation protocols in ns2 simulator.     

时延和能耗均衡的强连通支配集构造算法

针对无线传感器网络中链路的非对称性,提出时延约束的强连通支配树(SDTT,strongly connected dominating tree with bounded transmission delay)问题,给出在有向图上构建传输时延和能量消耗均衡的强连通支配集的强连通支配树(SCDT,distributed strongly connected dominating tree)算法。首先在单位圆图(UDG)模型的基础上构建极大独立集(MIS),然后在具有双向权值的有向图上基于最小支撑树和最短路径树实现分布式SCDT算法,同时满足时延和能耗均衡的约束条件要求。理论算例分析和仿真结果表明提出的算法能有效地解决SDTT问题,构造联合约束的强连通支配集,形成时延和能耗均衡的虚拟骨干。     

Sharp thresholds for relative neighborhood graphs in wireless Ad Hoc networks

In wireless ad hoc networks, relative neighborhood graphs (RNGs) are widely used for topology control. If every node has the same transmission radius, then an RNG can be locally constructed by using only one hop information if the transmission radius is set no less than the largest edge length of the RNG. The largest RNG edge length is called the critical transmission radius for the RNG. In this paper, we consider the RNG over a Poisson point process with mean density η in a unit-area disk.     

Greedy construction of load‐balanced virtual backbones in wireless sensor networks

Inspired by the backbone concept in wired networks, a virtual backbone is expected to bring substantial benefits to routing in wireless sensor networks (WSNs). A connected dominating set (CDS) is used as a virtual backbone for efficient routing and broadcasting in WSNs. Most existing works focus on constructing a minimum CDS, a k‐connect m‐dominating CDS, a minimum routing cost CDS, or a bounded‐diameter CDS. However, the load‐balance factor is not considered for CDSs in WSNs. In this paper, a greedy‐based approximation algorithm is proposed to construct load‐balanced CDS in a WSN. More importantly, we propose a new problem: the Load‐balanced Allocate Dominatee problem. Consequently, we propose an optimal centralized algorithm and an efficient probability‐based distributed algorithm to solve the Load‐balanced Allocate Dominatee problem. For a given CDS, the upper and lower bounds of the performance ratio of the distributed algorithm are analyzed in the paper. Through extensive simulations, we demonstrate that our proposed methods extend network lifetime by up to 80% compared with the most recently published CDS construction algorithm. Copyright © 2012 John Wiley & Sons, Ltd.     

物联网感知层多路径传输策略研究

多路径数据传输是无线传感器网络亟需解决的一个关键问题.本文针对节点故障、链路失效和外界干扰影响网络稳定性和可靠性,提出一种基于混合蛙跳算法的无线传感器网络多路径传输策略.首先我们详细介绍了蛙跳算法及其原理,之后我们将其应用到无线传感器网络多路径传输策略之中,接着运用混合蛙跳算法对传感网络节点其进行更新、划分、重组以便选择出最优节点建立传输最优路径,提高网络的稳定性和可靠性.通过算法仿真与结果对比提出的算法与AODV、粒子群PSO算法相比,在网络能耗、传输时延、丢包率、连通率和可靠度等方面都具有较好的性能.其中网络能耗比AODV、PSO算法降低了62.5％和35.8％.     

Polynomial time solution to minimum forwarding set problem in wireless networks under disk coverage model

In this paper, we consider a practical problem, called Minimum Forwarding Set Problem (MFSP), that emerges within the context of implementing (energy efficient) communication protocols for wireless ad hoc or sensor networks. For a given node v, MFSP asks for a minimum cardinality subset of 1-hop neighbors of v to cover v’s 2-hop neighbors. MFSP problem is also known as multi-point relay (MPR) problem. It is shown to be an NP-complete problem for its general case that does not consider the coverage characteristics of wireless transmissions. In this paper, we present two polynomial time algorithms to solve the MFSP problem under disk coverage model for wireless transmissions. In our earlier work, we presented a polynomial time algorithm for this problem under unit disk coverage model. In the current work, we present several observations on the geometric characteristics of wireless transmissions under disk coverage model and build two alternative dynamic programming based solutions with different run time and space complexities to the problem. Disk coverage model is a more general model because it allows nodes to use arbitrary power levels for transmissions. As a result, the presented algorithms provide a more practical solution that can be used as a building block for energy efficient communication protocols designed for wireless ad hoc and sensor networks.     

E-BEB: Enhanced Binary Exponential Backoff Algorithm for Multi-hop Wireless Ad-hoc Networks

Binary exponential backoff algorithm is the de-facto medium access control protocol for wireless local area networks, and it has been employed as the standard contention resolution algorithm in multi-hop wireless ad-hoc networks. However, this algorithm does not function well in multi-hop wireless environments due to its several performance issues and technical limitations. In this paper, we propose a simple, efficient, priority provision, and well performed contention resolution algorithm called enhanced binary exponential backoff (E-BEB) algorithm for impartial channel access in multi-hop wireless ad-hoc networks. We also provide a simple and accurate analytical model to study the system saturation throughput of the proposed scheme. Simulations are conducted to evaluate the performance of E-BEB algorithm. The results show that the E-BEB algorithm can alleviate the fairness problem and support multimedia transmission in multi-hop wireless environments.     

A distributed battery recovery aware topology control algorithm for wireless sensor networks

Battery recovery effect is a phenomenon that the available capacity of a battery could increase if the battery can sleep for a certain period of time since its last discharging. Accordingly, the battery can work for a longer time when it takes some rests between consecutive discharging processes than when it works all the time. However, this effect has not been considered in the design of energy‐efficient topology control algorithms for wireless sensor networks. In this paper, we propose a distributed battery recovery effect aware connected dominating set constructing algorithm (BRE‐CDS) for wireless sensor networks. In BRE‐CDS, each network node periodically decides to join the connected dominating set or not. Nodes that have slept in the preceding round have priority to join the connected dominating set in the current round while nodes that have worked in the preceding round are encouraged to take sleep in the current round for battery recovery. Detailed algorithm design is presented. The computational complexity of BRE‐CDS is deduced to be O(D²), where D is node degree. Simulation results show that BRE‐CDS can significantly prolong the network lifetime as compared with existing work. Copyright © 2016 John Wiley & Sons, Ltd.     

无线传感器网络中一种能量均衡的基于连通支配集的数据收集算法

采用连通支配集来构建虚拟骨干可以减轻无线传感器网络的广播风暴问题.目前已有大量工作通过构造最小连通支配集形成网络虚拟骨干来进行高效数据收集.然而,最小连通支配集并不能有效均衡节点的能量耗费,导致网络生命周期较短.提出了一种能量均衡的基于连通支配集的分布式算法EBCDS来进行数据收集,通过选择能量水平和度均比较大的节点组成连通支配集,支配集中的节点组成一个规模不大但具有较高能量水平的网络骨干.网络中的所有数据沿骨干在较小的寻路空间中转发,能够节省节点能量,使骨干节点不会因为能量不足而过早死亡.理论分析表明,EBCDS能以O(nlogn)的消息复杂度构造连通支配集,仿真实验表明,EBCDS能有效节省节点能耗并延长网络生命周期.     

Construction and maintenance of virtual backbone in wireless networks

In ad hoc wireless networks, there is no predefined infrastructure and nodes communicate with each other via peer communications. In order to make routing efficient in such networks the connected dominating set (CDS) can act as virtual backbone for the network. A smaller virtual backbone suffers less from the interference problem and incurs less maintenance overhead. Computing minimum CDS backbone is proven to be NP-Hard, it is therefore desirable to use efficient heuristic algorithms to find a virtual backbone of small size. Diameter and average backbone path length (ABPL) are other major criteria for evaluation of the backbone produced by an algorithm. In this paper, after giving a brief survey of classical CDS algorithms, two new centralized algorithms are described for the construction of the virtual backbone and their performance has been compared with five recent algorithms (two centralized and three distributed) along the parameters: size, diameter, and ABPL. The new algorithms perform better on most of the criteria. The re-construction of entire CDS upon movement or failure of a few nodes is very costly in terms of processing power, battery utilization, bandwidth utilization etc., as compared to maintaining the CDS for the affected nodes, since the re-construction of the CDS is to be performed for the whole network while maintenance involves the affected nodes and their neighbours only. A new distributed algorithm is described that maintains the virtual backbone on movement or failure of a single node. The overhead of CDS maintenance with this algorithm compares very favourably against that of re-construction.     

A new distributed approximation algorithm for constructing minimum connected dominating set in wireless ad hoc networks

In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub‐graph. However, finding the minimum connected dominating set (MCDS) is a well‐known NP‐hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one‐hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd.     

An efficient algorithm for the link allocation problem on ATM-basedpersonal communication networks

The personal communication network (PCN) is an emerging wireless network that promises many new services for the telecommunication industry. The proliferation of demands for extending wireless services to integrated services which supports the transmission of data and multimedia information has resulted in the need for broadband wireless systems that are able to provide service capabilities similar to those of wireline networks. The ATM cell-relay paradigm is one possible approach to provide broadband wireless transmission with PCNs using the ATM switching networks for interconnection of PCN cells. In an ATM-based PCN, the communication path between a pair of mobile terminals might be elongated due to the mobility of the terminals. The link allocation problem is that of allocating backbone links among ATM switches to reduce the effects of terminal mobility on the performance of ATM-based PCNs. Huang and Wang (1997) have shown that this problem is NP-complete. In this paper, we propose a new efficient heuristic algorithm for the link allocation problem. One novel feature of our algorithm is that we are able to derive sufficient conditions under which our algorithm is able to guarantee optimal solutions. Our empirical study shows that the average lengths of communication paths obtained by our algorithm are shorter than those obtained by Huang and Wang's algorithm. In addition, the number of successfully established paths obtained by our algorithm is significantly more than that obtained by the aforementioned     

Adding the Reliability on Tree Based Topology Construction Algorithms for Wireless Sensor Networks

Topology control is a technique used in wireless sensor networks to maximize energy efficiency and network lifetime. In previous literature, many tree based techniques have been proposed to save energy and increase the network lifetime. In tree based algorithms, the most promising solution is the formation of a network backbone, which serves on behalf of rest of the nodes in the network and therefore leading towards Connected Dominating Set (CDS) formulation. However, one imminent problem with all tree based solution is a compromise on network reliability. Therefore, to address reliability issues in tree based solutions, in this paper, we propose Poly3 which maintains cliques of size three in order to achieve network reliability on top of the CDS algorithm. This makes the network more robust to link removal. Our empirical and mathematical analysis reveals that Poly3 provides better reliability than algorithms of the same kind.     

Distributed Approximation Algorithms for Spectrum Allocation in Wireless ad Hoc Networks

Spectrum allocation is a difficult and hot issue in wireless ad hoc networks. An efficient method of spectrum allocation is a key factor to improve quality of service and performance of wireless networks. In this paper, we consider the spectrum allocation problem which asks how to allocate the least number of spectrum blocks in a field to ensure the service on any random k locations simultaneously. Our solution to the spectrum allocation problem is the minimum k-Roman dominating set. We propose two distributed algorithms for the issue of spectrum allocation in wireless ad hoc networks. One is a distributed 6k-approximation algorithm for the spectrum allocation of satisfying any random k (k ≥ 2) locations in the class of unit ball graphs. The other one is a better distributed algorithm for finding a (1 + ε)-approximation for the spectrum allocation problem of serving any random two locations, in the class of growth-bounded graphs. We also describe the simulation results and analyze them.     

A new model for scheduling packet radio networks

Packet radio networks are modeled as arbitrary graphs by most researchers. In this paper we show that an arbitrary graph is an inaccurate model of the radio networks. This is true because there exists a large class of graphs which will not model the radio networks. Radio networks can be modeled accurately by a restricted class of graphs called the planar point graphs. Since the radio networks can accurately be modeled only by a restricted class of graphs, the NP-completeness results for scheduling using an arbitrary graph as the model, do not correctly reflect the complexity of the problem. In this paper we study the broadcast scheduling problem using the restricted class as the model. We show that the problem remains NP-complete even in this restricted domain. We give an O(n log n) algorithm when all the transceivers are located on a line. This revised version was published online in July 2006 with corrections to the Cover Date.     

Graph coloring based channel assignment framework for rural wireless mesh networks

IEEE 802.11 based wireless mesh networks with directional antennas are expected to be a new promising technology and an economic approach for providing wireless broadband services in rural areas. In this paper, we discuss interference models and address how they can affect the design of channel assignment in rural mesh networks. We present a new channel assignment framework based on graph coloring for rural wireless mesh networks. The goal of the framework is to allow synchronously transmitting or receiving data from multiple neighbor links at the same time, and continuously doing full-duplex data transfer on every link, creating an efficient rural mesh network without interference. Channel assignment is shown to be NP-hard. We frame this channel allocation problem in terms of Adjacent Vertex Distinguishing Edge Coloring （AVDEC）. Detailed assignment results on grid topology are presented and discussed. Furthermore, we design an algorithm. Finally, we evaluate the perform- ance of the proposed algorithm through extensive simulations and show the algorithm is effective to the regular grid topologies, and the number of colors used by the algorithm is upper bounded by A ~ 1. Hence the algorithm guarantees that the number of channels available in standards such as IEEE 802.11a is sufficient to have a valid AVDEC for many grid topologies. We also evaluate the proposed algorithm for arbitrary graphs. The algorithm provides a lower upper bound on the minimum number of channels to the AVDEC index channel assignment problem.