Analytical Model of Cooperation in Ad Hoc Networks

The problem of cooperation among selfish nodes in ad hoc networks has gained recently a considerable attention. In this paper we propose a dynamic game theoretical model of cooperation in ad hoc networks, based on evolutionary game theory. Our model enables us to make predictions about possible equilibrium points of the network composed of the selfish and learning nodes, which can dynamically adjust their strategy in order to maximize their own payoff. In particular, we show that if an ad hoc network implements a reputation mechanism, all long term equilibrium points of the system will include cooperating nodes. In fact, in most of the equilibrium points, the cooperators will constitute a majority of the nodes. We believe that this new approach, borrowing from biological research, can have broader applications for studying dynamics of distributed communication systems.     

Localization systems for wireless sensor networks

Monitoring applications define an important class of applications used in wireless sensor networks. In these applications the network perceives the environment and searches for event occurrences (phenomena) by sensing different physical properties, such as temperature, humidity, pressure, ambient light, movement, and presence (for target tracking). In such cases the location information of both phenomena and nodes is usually required for tracking and correlation purposes. In this work we summarize most of the concepts related to localization systems for WSNs as well as how to localize the nodes in these networks (which allows the localization of phenomena). By dividing the localization systems into three distinct components -distance/angle estimation, position computation, and localization algorithm - besides providing a didactic viewpoint, we show that these components can be seen as subareas of the localization problem that need to be analyzed and studied separately.     

An Energy-Efficient Method for Nodes Assignment in Cluster-Based Ad Hoc Networks

One of the most critical issues in wireless ad hoc networks is represented by the limited availability of energy within network nodes. Thus, making good use of energy is a must in ad hoc networks. In this paper, we define as network lifetime the time period from the instant when the network starts functioning to the instant when the first network node runs out of energy. Our objective is to devise techniques to maximize the network lifetime in the case of cluster-based systems, which represent a significant sub-set of ad hoc networks. Cluster-based ad hoc networks comprise two types of nodes: cluster-heads and ordinary nodes. Cluster-heads coordinate all transmissions from/to ordinary nodes and forward all traffic in a cluster, either to other nodes in the cluster or to other cluster-heads. In this case, to prolong the network lifetime we must maximize the lifetime of the cluster-heads because they are the critical network element from the energy viewpoint. We propose an original approach to maximize the network lifetime by determining the optimal assignment of nodes to cluster-heads. Given the number of cluster-heads, the complexity of the proposed solution grows linearly with the number of network nodes. The network topology is assumed to be either static or slowly changing. Two working scenarios are considered. In the former, the optimal network configuration from the energy viewpoint is computed only once; in the latter, the network configuration can be periodically updated to adapt to the evolution of the cluster-heads energy status. In both scenarios, the presented solution greatly outperforms the standard assignment of nodes to cluster-heads, based on the minimum transmission power criterion.     

Optimization of energy-constrained wireless powered communication networks with heterogeneous nodes

In this paper, we generalize conventional time division multiple access (TDMA) wireless networks to a new type of wireless networks coined generalized wireless powered communication networks (g-WPCNs). Our prime objective is to optimize the design of g-WPCNs where nodes are equipped with radio frequency (RF) energy harvesting circuitries along with constant energy supplies. This constitutes an important step towards a generalized optimization framework for more realistic systems, beyond prior studies where nodes are solely powered by the inherently limited RF energy harvesting. Towards this objective, we formulate two optimization problems with different objective functions, namely, maximizing the sum throughput and maximizing the minimum throughput (maxmin) to address fairness. First, we study the sum throughput maximization problem, investigate its complexity and solve it efficiently using an algorithm based on alternating optimization approach. Afterwards, we shift our attention to the maxmin optimization problem to improve the fairness limitations associated with the sum throughput maximization problem. The proposed problem is generalized, compared to prior work, as it seemlessly lends itself to prior formulations in the literature as special cases representing extreme scenarios, namely, conventional TDMA wireless networks (no RF energy harvesting) and standard WPCNs, with only RF energy harvesting nodes. In addition, the generalized formulation encompasses a scenario of practical interest we introduce, namely, WPCNs with two types of nodes (with and without RF energy harvesting capability) where legacy nodes without RF energy harvesting can be utilized to enhance the system sum throughput, even beyond WPCNs with all RF energy harvesting nodes studied earlier in the literature. We establish the convexity of all formulated problems which opens room for efficient solution using standard techniques. Our numerical results show that conventional TDMA wireless networks and WPCNs with only RF energy harvesting nodes are considered as lower bounds on the performance of the generalized problem setting in terms of the maximum sum throughput and maxmin throughput. Moreover, the results reveal valuable insights and throughput-fairness trade-offs unique to our new problem setting.

     

A comparison of CCS tandem overload controls

In this paper we analyse issues associated with overloads in tandem switching systems in Common Channel Signalling (CCS) networks. In particular, we examine the need for, and effectiveness of, Automatic Congestion Control (ACC), a CCS mechanism which allows a congested switching system to inform adjacent CCS nodes of its level of overload, and subsequently controls the rate at which traffic is sent to the congested node. We demonstrate the critical need for end-offices and tandem switching systems to implement some form of ACC if network performance is to be maintained during congestion, especially in tandem exchanges. In addition, we find that the presently defined ACC should be expanded to allow more levels of congestion to be reported to adjacent nodes, so that a more effective, finer grained control is produced.     

Performance analysis of relative location estimation for multihop wireless sensor networks

In this paper, we present new analytical, simulated, and experimental results on the performance of relative location estimation in multihop wireless sensor networks. With relative location, node locations are estimated based on the collection of peer-to-peer ranges between nodes and their neighbors using a priori knowledge of the location of a small subset of nodes, called reference nodes. This paper establishes that when applying relative location to multihop networks the resulting location accuracy has a fundamental upper bound that is determined by such system parameters as the number of hops and the number of links to the reference nodes. This is in contrast to the case of single-hop or fully connected systems where increasing the node density results in continuously increasing location accuracy. More specifically, in multihop networks for a fixed number of hops, as sensor nodes are added to the network the overall location accuracy improves converging toward a fixed asymptotic value that is determined by the total number of links to the reference nodes, whereas for a fixed number of links to the reference nodes, the location accuracy of a node decreases the greater the number of hops from the reference nodes. Analytical expressions are derived from one-dimensional networks for these fundamental relationships that are also validated in two-dimensional and three-dimensional networks with simulation and UWB measurement results.     

应用于Ad Hoc网络中的密度自适应泛洪广播策略

针对Ad Hoc网络中泛洪广播机制可能带来的大量资源浪费问题,本文提出了一种新型的泛洪广播机制——密度自适应的泛洪广播策略.该策略根据发送节点的邻节点密度,以最密集节点的一次发送将覆盖较多节点为出发点,选取尽可能少的邻节点作为转发节点,减少了分组在网络中的重复传输,大大改善了网络的性能.仿真结果表明,密度自适应泛洪广播策略的性能明显优于普通的泛洪广播策略.     

On the design of self-organized cellular wireless networks

It has been observed that complex networks such as the Internet, World Wide Web, social networks, and biological systems are self-organizing in nature and exhibit some common properties such as the power law degree distribution. Recently, two models (i.e., small world and scale-free network models) have been proposed and successfully used to describe the nature of such networks. In this article we investigate whether these concepts can also be applied to cellular wireless networks, which typically do not exhibit self-organizing or scalability properties due to the limited range of the wireless nodes. Our ultimate goal is to design robust, reliable, scalable, and efficiently utilized wireless networks via self-organizing mechanisms.     

VLC Turbulence Effects on the Performance of the Fish School Behavior Modeling Mobile Diffusion Adaptive Networks in Underwater Environments

Implementation of different telecommunication systems based on wireless optical technologies requires careful awareness of the link conditions in order to predict the performance of each system and its expectations. Wireless optical communication channels, like telecommunication channels, have a fading phenomenon, which is called optical turbulence. A particular class of adaptive networks has the ability to move nodes and can move and converge to moving or static targets. The applications of these networks include dynamic and regional observation and pursuit of underwater military objects. The best type of communication technologies proposed for such networks is Visible Light Communication, or VLC, through which sensors, like the fish schools, with the optical communication between each other, move toward the targets. Investigating the impact of channel conditions and optical noise on these networks are other innovations of this research. In this paper, we model the behavior of a fish school in underwater VLC conditions using a mobile diffusion network. Our simulation results show the effects of water properties on the convergence of the mobile network nodes to a certain target. It is shown that as the water temperature, salinity level and the distance between the nodes increase, the convergence error rises and the nodes become departed from the target position.

     

A group-based security scheme for wireless sensor networks

In recent years, wireless sensor networks have been a very popular research topic, offering a treasure trove of systems, networking, hardware, security, and application-related problems. Distributed nature and their deployment in remote areas, these networks are vulnerable to numerous security threats that can adversely affect their proper functioning. The problem is more critical if its purpose is for some mission-critical applications such as in a tactical battlefield. This paper presents a security scheme for group-based distributed wireless sensor networks. Our first goal is to devise a group-based secure wireless sensor network. We exploit the multi-line version of matrix key distribution technique and Gaussian distribution to achieve this goal. Secondly, security mechanisms are proposed for such a group-based network architecture in which sensed data collected at numerous, inexpensive sensor nodes are filtered by local processing on its way through more capable and compromise-tolerant reporting nodes. We address the upstream requirement that reporting nodes authenticate data produced by sensors before aggregating and the downstream requirement that sensors authenticates commands disseminated from reporting nodes. Security analysis is presented to quantify the strength of the proposed scheme against security threats. Through simulations, we validate the analytical results.     

Bounds on the reliability of distributed systems with unreliable nodes & links

The reliability of distributed systems & computer networks in which computing nodes and/or communication links may fail with certain probabilities have been modeled by a probabilistic network. Computing the residual connectedness reliability (RCR) of probabilistic networks under the fault model with both node & link faults is very useful, but is an NP-hard problem. Up to now, there has been little research done under this fault model. There are neither accurate solutions nor heuristic algorithms for computing the RCR. In our recent research, we challenged the problem, and found efficient algorithms for the upper & lower bounds on RCR. We also demonstrated that the difference between our upper & lower bounds gradually tends to zero for large networks, and are very close to zero for small networks. These results were used in our dependable distributed system project to find a near-optimal subset of nodes to host the replicas of a critical task.     

Relative degree adaptive flooding broadcast algorithm for ad hoc networks

Broadcasting has been widely used in mobile Ad hoc networks as a communication means to disseminate information to all reachable nodes. Because radio signals are likely to overlap with others in a geographical area, straightforward broadcasting by flooding becomes very costly and results in serious redundancy, contention and collision, to which we refer as the broadcast storm problem. In this paper we propose the Relative Degree Adaptive flooding Broadcast (RDAB) algorithm for Ad hoc networks to efficiently reduce the broadcast overhead in the network. Based on the current situation of the network and the degree of the nodes, RDAB calculates the relative degree of the nodes, decides which nodes need to re-transmit and which nodes only need to receive. The higher the neighbor node's relative degree, the more uncovered nodes it can cover, hence these nodes can be selected to re-transmit broadcasting packets in the networks. We analyze the reliability and the validity of the RDAB algorithm to prove that the RDAB algorithm is a valid flooding broadcast algorithm. Simulation results show that the RDAB strategy outperforms the Ordinary Flooding Broadcast Method (OBM) and the Multipoint Relaying (MPR) protocol for Ad hoc networks.     

基于节点控制的空间信息网拓扑重构算法

空间信息网是一种融合陆海空天信息系统的新型自组织网络,成为研究热点.针对网络特点和应用需求,提出一种预防和恢复相结合的拓扑重构策略,通过检测拓扑关键点触发预防性重构,通过拓扑故障触发恢复性重构,重构时在一定范围内选择冗余节点,该节点在虚拟力的导向下自主地移动剑待维护区域,并以修复区域的局部拓扑通信代价最小为目标,进行拓...     

Secure Multi-copy Routing in Compromised Delay Tolerant Networks

Routing in delay tolerant networks (DTNs) is challenging due to their unique characteristics of intermittent node connectivity. Different protocols (single-, multi-copy, erasure-coding-based etc.) utilizing store-carry-and-forward paradigm have been proposed to achieve routing of messages in such environments by opportunistic message exchanges between nodes that are in the communication range of each other. The sparsity and distributed nature of these networks together with the lack of stable connectivity between source destination pairs make these networks vulnerable to malicious nodes which might attempt to learn the content of the messages being routed between the nodes. In this paper, we study DTNs in which malicious nodes are present, to which we refer to as compromised DTNs. We discuss and analyze the effects of presence of malicious nodes on routing of messages in compromised DTNs. We propose a two period routing approach which aims at achieving the desired delivery ratio by a given delivery deadline in presence of malicious nodes. Our simulation results with both random networks and real DTN traces show that, with proper parameter setting, the proposed method can achieve delivery ratios which surpass those reached by other algorithms by a given delivery deadline.     

A comparative study of sound localization algorithms for energy aware sensor network nodes

Sound localization using energy-aware hardware for sensor networks nodes is a problem with many applications in surveillance and security. In this paper, we evaluate four algorithms for sound localization using signals recorded in a natural environment with an array of commercial off-the-shelf microelectromechanical systems microphones and a specially designed compact acoustic enclosure. We evaluate performance of the algorithms and their hardware complexity which relates directly to energy consumption.     

物联网中适用于野外战场的基于口令的安全通信方案

Mobile Ad hoc NETwork (MANET) is a part of the Internet of Things (IoT). In battlefield communication systems, ground soldiers, tanks, and unmanned aerial vehicles comprise a heterogeneous MANET. In 2006, Byun et al. proposed the first constant-round password-based group key exchange with different passwords for such networks. In 2008, Nam et al. discovered the shortcomings of the scheme, and modified it. But the works only provide the group key. In this paper, we propose a password-based secure communication scheme for the IoT, which could be applied in the battlefield communication systems and support dynamic group, in which the nodes join or leave. By performing the scheme, the nodes in the heterogeneous MANET can realize secure broadcast, secure unicast, and secure direct communication across realms. After the analyses, we demonstrate that the scheme is secure and efficient.     

Distributed topology construction of Bluetooth wireless personal area networks

Bluetooth, a wireless technology based on a frequency-hopping physical layer, enables portable devices to form short-range wireless ad hoc networks. Bluetooth hosts are not able to communicate unless they have previously discovered each other through synchronization of their timing and frequency-hopping patterns. Thus, even if all nodes are within proximity of each other, only those nodes which are synchronized with the transmitter can hear the transmission. To support any-to-any communication, nodes must be synchronized so that the pairs of nodes, which can communicate with each other, form a connected graph. Using Bluetooth as an example, we first provide deeper insights into the issue of link establishment in frequency-hopping wireless systems. We then introduce an asynchronous distributed protocol that begins with nodes having no knowledge of their surroundings and terminates with the formation of a connected network topology satisfying all constraints posed by Bluetooth. An attractive protocol feature is its ease in implementation using the communication primitives offered by the Bluetooth Specification.     

ARDEN: Anonymous networking in delay tolerant networks

Delay Tolerant Networks (DTNs) provide a communications infrastructure for environments lacking continuous connectivity. Such networks rely on the mobility of nodes and the resulting opportunistic connections to carry messages from source to destination. Unfortunately, exchanging packets with an arbitrary intermediary node makes privacy difficult to achieve in these systems as any adversary can easily act as an intermediary and determine the sender and receiver of a message. In this paper, we present ARDEN, an anonymous communication mechanism for DTNs based on a modified onion routing architecture. Instead of selecting specific nodes through which messages must pass as is traditionally done in onion routing, ARDEN uses Attribute-Based Encryption (ABE) to specify and manage groups that may decrypt and forward messages. Through simulation, we show that this approach not only increases throughput and reduces end-to-end latency over traditional onion routing techniques, but also adds minimal overhead when compared to DTN routing protocols that do not provide anonymity guarantees. Through this, we show that ARDEN is an effective solution for anonymous communication in intermittently connected networks such as DTNs.     

A distributed energy-efficient clustering scheme for deploying IDS in MANETs

Cluster-based intrusion detection systems, where cluster heads (CHs) detect misbehavior of their member nodes, have been proposed in mobile ad-hoc networks (MANETs) in order to protect the network and save the energy. However, long-term survival of all nodes is more important so as not to partition the network. The extension of the network lifetime in the cluster-based IDS depends on which nodes are selected as CHs, which consume much more energy than cluster members due to monitoring them and detecting intrusions. In this paper, we propose a Distributed Energy Efficient Cluster Formation (DEECF) scheme, which exploits the expected residual energy of mobile nodes to select CHs and starts the cluster formation from leaf nodes to reduce the number of clusters. The scheme consists of the cluster construction algorithm and the cluster maintenance algorithm, both of which can be performed at each node in a distributed way without any global knowledge. We prove the correctness of the algorithms, and show that the DEECF scheme is more energy efficient than other clustering schemes by extensive simulation.