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Incorporation of connected vehicle (CV) data into real-time traffic management systems presents a host of new challenges resulting from the current lack of data integrity and data privacy in traffic networks. Over the past few years, blockchain technologies have been inspiring extensive innovations in the transportation field. However, due to the transparency property, sensitive data stored on the blockchain would be accessible to anyone, resulting in a lack of privacy. In this paper, we propose a decentralized and location-aware architecture to address the data integrity along with the privacy-preserving issues in blockchain-based traffic management systems. Our proposed architecture integrates with permissioned and modular blockchain network and non-interactive zero-knowledge range proof (ZKRP) protocol. We develop the prototype system on the Hyperledger Fabric platform and Hyperledger Ursa cryptographic library. The performance results show that our approach is effective and feasible for real-time traffic management while preserving the data privacy requirements.

Autonomous vehicles are capable of sensing their environment and navigating without any human inputs. However, when autonomous vehicles are involved in accidents between themselves or with human subjects, liability must be indubitably decided based on accident forensics. This paper proposes a blockchain-inspired event recording system for autonomous vehicles. Specifically, we design the mechanism of “Proof-of-Event” with a dynamic federation consensus to achieve indisputable accident forensics by providing trustable and verifiable event information. We propose a dynamic federation consensus scheme to verify and confirm the new block of event data in an efficient way without any central authority. We conduct numerical analyses and prototyped experiments based on the proposed fast leader election algorithm and the Hyperledger Fabric blockchain network. The results show that our system is effective and feasible in generating and storing accident records in blockchain-based vehicular networks. The security capability of the proposed scheme is also discussed against multiple threats and attack scenarios.

Existing work on placing additional relay nodes in wireless sensor networks to improve network connectivity typically assumes homogeneous wireless sensor nodes with an identical transmission radius. In contrast, this paper addresses the problem of deploying relay nodes to provide fault tolerance with higher network connectivity in heterogeneous wireless sensor networks, where sensor nodes possess different transmission radii. Depending on the level of desired fault tolerance, such problems can be categorized as: 1) full fault-tolerant relay node placement, which aims to deploy a minimum number of relay nodes to establish κ(κ≥1) vertex-disjoint paths between every pair of sensor and/or relay nodes and 2) partial fault-tolerant relay node placement, which aims to deploy a minimum number of relay nodes to establish κ(κ≥1) vertex-disjoint paths only between every pair of sensor nodes. Due to the different transmission radii of sensor nodes, these problems are further complicated by the existence of two different kinds of communication paths in heterogeneous wireless sensor networks, namely, two-way paths, along which wireless communications exist in both directions; and one-way paths, along which wireless communications exist in only one direction. Assuming that sensor nodes have different transmission radii, while relay nodes use the same transmission radius, this paper comprehensively analyzes the range of problems introduced by the different levels of fault tolerance (full or partial) coupled with the different types of path (one-way or two-way). Since each of these problems is NP-hard, we develop O(σκ2-approximation algorithms for both one-way and two-way partial fault-tolerant relay node placement, as well as O(σκ3-approximation algorithms for both one-way and two-way full fault-tolerant relay node placement (σ is the best performance ratio of existing approximation algorithms for finding a minimum κ-vertex connected spanning graph). To facilitate the applications in higher dimensions, we also extend these algorithms and derive their performance ratios in d-dimensional heterogeneous wireless sensor networks (d ≥3). Finally, heuristic implementations of these algorithms are evaluated via QualNet simulations. [ABSTRACT FROM AUTHOR]

An introduction to the paper is presented in which the editor discusses the cross-layer energy-efficient design and power control mechanisms, cross-layer routing protocols, and cross-layer multimedia schemes.

Cooperative communications fundamentally changes the abstraction of a wireless link and offers significant potential advantages for wireless networks. However, such technologies are evaluated with idealized scenarios where many control costs are assumed to be negligible. Moreover, even if these costs appear small in simple network scenarios, they increase significantly with the size and traffic level of the network, requiring careful evaluation, or even innovative design, of cooperative protocols to ensure their usefulness in realistic networks. This article describes a realistic evaluation of cooperative communications in a networking context. Insights obtained from this evaluation help guide work on cooperative communications toward practical and potentially beneficial protocols. [ABSTRACT FROM AUTHOR]

Abstract  Today’s static spectrum allocation policy results in a situation where the available spectrum is being exhausted while many licensed spectrum bands are under-utilized. To resolve the spectrum exhaustion problem, the cognitive radio wireless network, termed CogNet in this paper, has recently been proposed to enable unlicensed users to dynamically access the licensed spectrum bands that are unused in either temporal or spatial domain, through spectrum-agile cognitive radios. The CogNet plays the role of secondary user in this shared spectrum access framework, and the spectrum bands accessible by CogNets are inherently heterogeneous and dynamic. To establish the communication infrastructure for a CogNet, the cognitive radio of each CogNet node detects the accessible spectrum bands and chooses one as its operating frequency, a process termed channel assignment. In this paper we propose a graph-based path-centric channel assignment framework to model multi-hop ad hoc CogNets and perform channel assignment from a network perspective. Simulation results show that the path-centric channel assignment framework outperforms traditional link-centric approach. [ABSTRACT FROM AUTHOR]

The minimum-energy multicast tree problem aims to construct a multicast tree rooted at the source node and spanning all the destination nodes such that the sum of transmission power at non-leaf nodes is minimized. However, aggressive power assignment at non-leaf nodes, although conserving more energy, results in multicast trees that suffer from higher hop count and jeopardizes delay-sensitive applications, signifying a clear tradeoff between energy efficiency and delay. This article formulates these issues as a constrained Steiner tree problem, and describes a distributed constrained Steiner tree algorithm, which jointly conserves energy and bounds delay for multicast routing in ad hoc networks. In particular, the proposed algorithm concurrently constructs a constrained Steiner tree, performs transmission power assignment at non-leaf nodes, and strives to minimize the sum of transmission power of non-leaf nodes, subject to the given maximum hop count constraint. Simulation results validate the effectiveness and reveal the characteristics of the proposed algorithm. [ABSTRACT FROM AUTHOR]

This paper proposes a new approach that applies multibeam directional antennas to controlling topology by reducing the power intensity directionally instead of omnidirectionally. In contrast to omnidirectional topology control, which reduces transmission power (and, thus, the resulting transmission range) in all directions, the proposed approach maintains the original power range in certain directions while clearing the power intensity in other directions. This paper shows that the proposed approach and the omnidirectional topology control approach are equivalent in terms of the probability distribution of the number of symmetric neighbors in their resulting topologies. Major benefits of this approach include reduced and steady hop count, power saving independent of the number of neighbors within the original power range, and symmetric link in terms of SNR quality, as compared to omnidirectional topology control approaches. Simulation studies have demonstrated these benefits and highlighted its trade-offs. [ABSTRACT FROM AUTHOR]

For mobile ad hoc networks, network-wide broadcast is a critical network layer function supporting route discovery and maintenance in many unicast and multicast protocols. A number of broadcast schemes have been proposed; however, almost all of them assume the usage of omnidirectional antennas and focus on broadcast overhead in terms of the number of forwarding nodes. Directional antennas have narrow beams and can potentially reduce broadcast overhead in terms of the ratio of the number of received duplicate packets to the number of nodes that receive broadcast packets. In this paper, we propose to map probability-based directional and omnidirectional broadcast to bond and site percolation, respectively, and describe a collection of directional antenna-based broadcast schemes for mobile ad hoc networks. A thorough and comparative simulation study is conducted to demonstrate the efficiency of the proposed schemes. [ABSTRACT FROM AUTHOR]

Abstract By adjusting the transmission power of mobile nodes, topology control aims to reduce wireless interference, reduce energy consumption, and increase effective network capacity, subject to connectivity constraints. In this paper, we introduce the Ant-Based Topology Control (ABTC) algorithm that adapts the biological metaphor of Swarm Intelligence to control topology of mobile ad hoc networks. ABTC is a distributed algorithm where each node asynchronously collects local information from nearby nodes, via sending and receiving ant packets, to determine its appropriate transmission power. The operations of ABTC do not require any geographical location, angle-of-arrival, topology, or routing information, and are scalable. In particular, ABTC attempts to minimize the maximum power used by any node in the network, or minimize the total power used by all of the nodes in the network. By adapting swarm intelligence as an adaptive search mechanism, ABTC converges quickly to a good power assignment with respect to minimization objectives, and adapts well to mobility. In addition, ABTC may achieve common power, or properly assign power to nodes with non-uniform distribution. Results from a thorough comparative simulation study demonstrate the effectiveness of ABTC for different mobility speed, various density, and diverse node distributions. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates the benefits and impacts of using directional antennas for multicast communications in ad hoc networks. In terms of signal reception, directional antennas have shown considerable improvement in the performance of all aspects over omni-directional antennas, especially over dense networks with heavy traffic load. In addition, we have found that transmitting multicast packets directionally to known neighboring group members or forwarders can help reduce the average end-to-end packet delay and increase the overall throughput. However, directional transmission of unacknowledged data transfers may result in lower performance in terms of packet delivery ratio than omni-directional transmission in any carrier sensing MAC protocols under moderate load due to the effect from the hidden terminal problem. Both analytical results and simulation results, as well as an acknowledgment mechanism to improve the successful delivery rate of multicast data packets, are presented. [ABSTRACT FROM AUTHOR]

The topology of an ad hoc network has a significant impact on its performance in that a dense topology may induce high interference and low capacity, while a sparse topology is vulnerable to link failure and network partitioning. Topology control aims to maintain a topology that optimizes network performance while minimizing energy consumption. Existing topology control algorithms utilize either a purely centralized or a purely distributed approach. A centralized approach, although able to achieve strong connectivity (k-connectivity for k ≥ 2), suffers from scalability problems. In contrast, a distributed approach, although scalable, lacks strong connectivity guarantees. We propose a hybrid topology control framework, Cluster-based Topology Control (CLTC), that achieves both scalability and strong connectivity. By varying the algorithms utilized in each of the three phases of the framework, a variety of optimization objectives and topological properties can be achieved. In this paper, we present the CLTC framework; describe topology control algorithms based on CLTC and prove that k-connectivity is achieved using those algorithms; analyze the message complexity of an implementation of CLTC, namely, CLTC-A, and present simulation studies that evaluate the effectiveness of CLTC-A for a range of networks. Index Terms—Topology control; clustering; ad hoc networks; transmission power assignment; strong connectivity. [ABSTRACT FROM AUTHOR]

Focuses on the use of guerilla management architecture in facilitating adaptive and autonomous management of ad hoc networks. Importance of multihop wireless kinks in mobile nodes communication; Accounts on the intrinsic attributes of ad hoc networks; Details on the deployment of ad hoc networks.

This article introduces a sensor information networking architecture, called SINA, that facilitates querying, monitoring, and tasking of sensor networks. SINA serves the role of middleware that abstracts a network of sensor nodes as a collection of massively distributed objects. SINA's execution environment provides a set of configuration and communication primitives that enable scalable and energy-efficient organization of and interactions among sensor objects. On top the execution environment is a programmable substrate that provides mechanisms to create associations and coordinate activities among sensor nodes. Users then access information within a sensor network using declarative queries, or perform tasks using programming script [ABSTRACT FROM PUBLISHER]

Iterative transformation of performance models into operational systems is a desirable approach for designing performance-critical systems. This paper describes an approach called MIDAS that supports the design of distributed systems via iterative refinement of hybrid models. A hybrid model is a partially implemented design where some components exist as simulation models and others as operational subsystems. It is an executable model and may be used to determine the stochastic performance characteristics of a partially elaborated design. MIDAS enhances the applicability of hybrid models in system design with its support for interrupts and its inclusion of distributed components in the partially implemented design. The paper describes how an existing simulation language may be extended to program hybrid models, and shows how simulation algorithms may be adapted to execute hybrid models. A prototype MIDAS implementation is operational and was used to develop a set of applications. The experimental results of the exercise are also described. [ABSTRACT FROM AUTHOR]

This letter extends and improves prior unicast transport capacity results for the general multi-channel, multi- radio, multi-hop wireless networks, where channels may have different data rates, and the number of interfaces per node may differ from the number of channels available in the network. Both the upper bound and the lower bound are rigorously derived for the Arbitrary Networks with interference modeled by the protocol model. Also presented is a minor but important improved use of the protocol model in the derivation of the transport capacity upper bound. [ABSTRACT FROM PUBLISHER]