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Today, the network design process remains ad hoc and largely complexity agnostic, often resulting in suboptimal networks characterized by excessive amounts of dependence and commands in device configurations. The unnecessary high configuration complexity can lead to a huge increase in both the amount of manual intervention required for managing the network and the likelihood of configuration errors, and thus must be avoided. In this paper, we present an integrated top–down design approach and show how it can minimize the unnecessary configuration complexity in realizing reachability-based access control, a key network design objective that involves designing three distinct network elements: virtual local-area network (VLAN), IP address, and packet filter. Capitalizing on newly developed abstractions, our approach integrates the design of these three elements into a unified framework by systematically modeling how the design of one element may impact the complexity of other elements. Our approach goes substantially beyond the current divide-and-conquer approach that designs each element in complete isolation, and enables minimizing the combined complexity of all elements. Specifically, two new optimization problems are formulated, and novel algorithms and heuristics are developed to solve the formulated problems. Evaluation on a large campus network shows that our approach can effectively reduce the packet filter complexity and VLAN trunking complexity by more than 85% and 70%, respectively, when compared with the ad hoc approach currently used by the operators. [ABSTRACT FROM PUBLISHER]

In this paper, we focus on a particular type of opportunistic ad-hoc networks, namely Pedestrian Ad-hoc NETworks (PANETs). In PANETs, nodes are densely distributed and each node may transmit information to all other nodes in the network via multi-hop broadcasting. Even though flooding is the simplest technique to broadcast information with multi-hop communications, it can be very inefficient because of redundant transmissions which may induce collisions. This problem is known, in the literature, as the “broadcast storm problem.” In this work, we present a novel probabilistic forwarding technique, denoted as Distance-based Silencing IF (DiSIF), which is derived from the probabilistic broadcasting protocol Irresponsible Forwarding (IF) and one of its extensions, denotes Silencing IF (SIF). The performance of the DiSIF protocol is analyzed and compared with those of other existing protocols, investigating the impact of fundamental network parameters. Lower bounds (exact and approximate) on the average number of hops, expedient to evaluate the propagation efficiency of DiSIF, are also derived. Finally, under the assumption that each node (e.g., a smartphone) relies on Global Positioning System (GPS) to estimate its position, the robustness of DiSIF against a GPS positioning error is investigated. [ABSTRACT FROM AUTHOR]

Sensing and networking have been regarded as key enabling technologies of future smart vehicles. Sensing allows vehicles to be context awareness, while networking empowers context sharing among ambients. Existing vehicular communication solutions mainly rely on homogeneous network, or heterogeneous network via data offloading. However, today’s vehicular network implementations are highly heterogeneous. Therefore, conventional homogeneous communication and data offloading may not be able to satisfy the requirement of the emerging vehicular networking applications. In this paper, we apply the software-defined network (SDN) to the heterogeneous vehicular networks to bridge the gaps. With SDN, heterogeneous network resources can be managed with a unified abstraction. Moreover, we propose an SDN-based wireless communication solution, which can schedule different network resources to minimize communication cost. We investigate the problems in both single and multiple hop cases. We also evaluate the proposed approaches using traffic traces. The effectiveness and the efficiency are validated by the results. [ABSTRACT FROM PUBLISHER]

This paper explores direct phone-to-phone communication (via WiFi interface) among vehicles to support participatory sensing applications. Sensing data usually contains location, speed, and fuel consumption of the car, and has a long time delay between collected and transferred to the server. Direct communication among phones aboard is important in reducing data transfer delay time and sharing participatory sensing information in an inexpensive manner. We design a practical and optimized communication mechanism for direct phone-to-phone data transfer among phones aboard that strategically enables phone-to-phone and/or phone-to-WiFiAP communications by optimally toggling the phones between the normal client and the hotspot modes. We take advantage of the WiFi hotspot functionality on smartphones, and hence require neither involvement of participants nor changes to existing wireless infrastructure and protocols. An analytical model is established to optimize toggling between client and hotspot modes for optimal system efficiency. We fully implement this system on off-the-shelf Google Galaxy Nexus and Nexus S phones. Through a 35-vehicle two-month deployment study, as well as simulation experiments using the real-world T-drive 9,211-taxicab dataset, we show that our solution significantly reduces data transfer delay time and maintains over 80 percent system efficiency under varying system parameters. [ABSTRACT FROM PUBLISHER]

There are few equations for underwater communications in the related literature. They show that the speed propagation and absorption coefficient in freshwater are independent of the working frequency of the transmitted signals. However, some studies demonstrate that electromagnetic waves present lower losses when they are working at certain frequencies. In this paper, we perform a set of measurements of electromagnetic (EM) waves at 2.4 GHz in the underwater environment. In our study case, we fix the water conditions and we measure the behavior of EM as a function of several network parameters such as the working frequency, data transfer rates and modulations. Our results will show that higher frequencies do not mean worse network performance. We will also compare our conclusion with some statements extracted from other works. [ABSTRACT FROM PUBLISHER]

This paper proposes FlashLinQ—a synchronous peer-to-peer wireless PHY/MAC network architecture. FlashLinQ leverages the fine-grained parallel channel access offered by OFDM and incorporates an analog energy-level-based signaling scheme that enables signal-to-interference ratio (SIR)-based distributed scheduling. This new signaling mechanism, and the concomitant scheduling algorithm, enables efficient channel-aware spatial resource allocation, leading to significant gains over a CSMA/CA system using RTS/CTS. FlashLinQ is a complete system architecture including: 1) timing and frequency synchronization derived from cellular spectrum; 2) peer discovery; 3) link management; and 4) channel-aware distributed power, data rate, and link scheduling. FlashLinQ has been implemented for operation over licensed spectrum on a digital signal processor/field-programmable gate array (DSP/FPGA) platform. In this paper, we present FlashLinQ performance results derived from both measurements and simulations. [ABSTRACT FROM AUTHOR]

Dynamic spectrum access (DSA) is an important design aspect for the cognitive radio networks (CRNs). Most of the existing DSA schemes are to govern the secondary user traffic in a licensed spectrum without considering the transmissions also in the unlicensed bands. In this paper, we propose two DSA schemes (i.e., without and with buffer) for cognitive radios access in both licensed and unlicensed bands in a distributed CRN. A Markov chain analysis for each of the proposed DSA schemes is presented and forced termination probability, blocking probability and traffic throughput are derived. In addition, we discuss a number of errors in the Markov model and analysis of the blocking and forced termination probabilities in a CRN, given in Al-Mahdi et al. (IEEE Commun Lett 13(9):676-678, ). This paper shows the corresponding correct derivations and results, and simulation results are given to support our analyses. [ABSTRACT FROM AUTHOR]

In cellular consumer devices, one of the limiting factors for efficiency is that of overhead on the network layer that effects on the performance of the network. A substantial design issue is that, with cellular consumer devices, the discovery phase of the routing process, when attempting to establish a mobile ad hoc network, a high demand is placed on the network layer. Hence, a challenge for the designer is to reduce this demand, thus increasing overall device availability. Routing algorithms, and hence the performance of the networks are adversely affected by inefficient carrier sensing methods which can lead to increasing packet loss within the network environment. In this paper, the effect of physical and virtual carrier sensing on the route discovery mechanism has been identified and this paper suggests that choosing a suitable carrier sensing threshold in a high density and noisy mobile ad hoc network yields a better performance than if the default value is used. [ABSTRACT FROM PUBLISHER]

This paper introduces cooperative caching policies for minimizing electronic content provisioning cost in Social Wireless Networks (SWNET). SWNETs are formed by mobile devices, such as data enabled phones, electronic book readers etc., sharing common interests in electronic content, and physically gathering together in public places. Electronic object caching in such SWNETs are shown to be able to reduce the content provisioning cost which depends heavily on the service and pricing dependences among various stakeholders including content providers (CP), network service providers, and End Consumers (EC). Drawing motivation from Amazon's Kindle electronic book delivery business, this paper develops practical network, service, and pricing models which are then used for creating two object caching strategies for minimizing content provisioning costs in networks with homogenous and heterogeneous object demands. The paper constructs analytical and simulation models for analyzing the proposed caching strategies in the presence of selfish users that deviate from network-wide cost-optimal policies. It also reports results from an Android phone-based prototype SWNET, validating the presented analytical and simulation results. [ABSTRACT FROM AUTHOR]

This paper focuses on the delivery probability performance in a two-hop relay mobile ad hoc network (MANET) with erasure coding. Available works in this line either considered a simple extreme case of achieving the delivery probability 1, or assumed a simple traffic pattern with only one source-destination pair, or studied a very special MANET scenario (i.e., the sparsely distributed MANET) by assuming that whenever two nodes meet together they can transmit to each other. Obviously, such models cannot be applied for an accurate delivery probability analysis in the general MANETs where the interference, medium contention and traffic contention issues are of significant importance. In this paper, a general finite-state absorbing Markov chain theoretical framework is first developed to model the complicated message spreading process in the challenging MANETs. Based on the theoretical framework, closed-form expressions are further derived for the corresponding message delivery probability under any given message lifetime and message size, where all the above important issues in MANETs are carefully incorporated into analysis. As verified through extensive simulation studies, the new framework can be used to accurately predict the message delivery probability behavior and characterize its relationship with the message size, replication factor and node density there. [ABSTRACT FROM AUTHOR]

Graph theory is a traditional mathematical method to analyze computer networks, including intelligent wireless networks, such as ad hoc networks, sensor networks, and wireless mesh networks. Because of the variety of the network nodes and wireless links, conventional graph theory and set theory used to describe the element of the network (node and link) are not suitable to model the modern complex wireless networks. Recent research in weighted graph and random graph theories that place a weight on the links and a probability to decide the existence of the link or not is a further step to model the wireless network in a near real-life scenario. However, it lacks the ability to describe the properties of the network node. In this paper, a new mathematical tool, polychromatic sets (PS-sets), is introduced in modeling the complex wireless networks. PS-sets have the ability to describe the property of each element, which we believe will be a perfect tool to describe the network nodes and links of wireless networks. This paper demonstrates a scalable network modeling using PS-sets theory and a routing scheme based on this model. Evaluation results show that it is simple and scalable, and its performance is superior to other conventional routing schemes. The PS-sets theory could become a new tool in studying modern complex wireless networks. [ABSTRACT FROM PUBLISHER]

This paper presents an Omnidirectional mobile target-node (TN) localization technique in nonline-of-sight (NLOS) scenarios. Here, a TN cooperates with base-nodes (BNs) with antenna-arrays to allow them to find its position via time-of-arrival (TOA) and direction-of-arrival (DOA) measurements. When line-of-sight (LOS) channel is available, each BN localizes TNs in its coverage area with reasonable accuracy. However, when LOS channel is obstructed, considerable localization error is generated. To avoid NLOS error, a technique is proposed to identify if a TN is in the LOS of multiple BNs or not. The technique enables BNs to determine and localize their shared reflection points, and to localize NLOS TNs. The paper assumes single-bounce-reflection NLOS channel between BNs and TNs. In NLOS scenarios, when three or more reflection points are shared by a TN and multiple sets of BNs, the shared reflection points are localized via DOA fusion, and then the TN is localized via TOA fusion. The equations for NLOS identification, shared reflection points determination and localization and NLOS TN localization are theoretically derived. Simulations are conducted to evaluate the proposed technique in terms of the probability of false alarm and misdetection of NLOS identification and shared reflection points determination, and NLOS TN localization accuracy. [ABSTRACT FROM AUTHOR]

This paper proposes Trajectory-based Statistical Forwarding (TSF) scheme, tailored for the multihop data delivery from infrastructure nodes (e.g., Internet access points) to moving vehicles in vehicular ad hoc networks. To our knowledge, this paper presents the first attempt to investigate how to effectively utilize the packet destination vehicle's trajectory for such an infrastructure-to-vehicle data delivery. This data delivery is performed through the computation of a target point based on the destination vehicle's trajectory that is an optimal rendezvous point of the packet and the destination vehicle. TSF forwards packets over multihop to a selected target point where the vehicle is expected to pass by. Such a target point is selected optimally to minimize the packet delivery delay while satisfying the required packet delivery probability. The optimality is achieved analytically by utilizing the packet's delivery delay distribution and the destination vehicle's travel delay distribution. Through theoretical analysis and extensive simulation, it is shown that our design provides an efficient data forwarding under a variety of vehicular traffic conditions. [ABSTRACT FROM PUBLISHER]

Network capacity investigation has been intensive in the past few years. A large body of work on wireless network capacity has appeared in the literature. However, so far most of the effort has been made on two-dimensional (2-D) wireless networks only. With the great development of wireless technologies, wireless networks are envisioned to extend from 2-D space to three-dimensional (3-D) space. In this paper, we investigate the throughput capacity of 3-D regular ad hoc networks (RANETs) and of 3-D nonhomogeneous ad hoc networks (NANETs), respectively, by employing a generalized physical model. In 3-D RANETs, we assume that the nodes are regularly placed, while in 3-D NANETs, we consider that the nodes are distributed according to a general Nonhomogeneous Poisson Process (NPP). We find both lower and upper bounds in both types of networks in a broad power propagation regime, i.e., when the path loss exponent is no less than 2. [ABSTRACT FROM AUTHOR]

Applying directional antennas in wireless ad hoc networks can theoretically achieve higher spatial multiplexing gain and, thus, higher network throughput. However, in practice, deafness, hidden-terminal, and exposed terminal problems are exaggerated with directional antennas, and they cause the degradation of the overall network performance. Although there are several random-access-based medium-access control (MAC) protocols being proposed in the literature for networks with directional antennas, the deafness, hidden-terminal, and exposed terminal problems have yet to be fully solved. In this paper, we present a new MAC protocol called the dual-sensing directional MAC (DSDMAC) protocol for wireless ad hoc networks with directional antennas. Different from existing protocols, the DSDMAC protocol relies on the dual-sensing strategy to identify deafness, resolve the hidden-terminal problem, and avoid unnecessary blocking. The integrity of the DSDMAC protocol is verified and validated using Spin, which is a formal protocol verification and validation tool. We further develop an analytical framework to quantify the performance of the DSDMAC protocol and conduct extensive simulations, which verify the accuracy of the analysis. The protocol verification, analysis, and simulation results show the robustness and superior performance of the DSDMAC protocol, which can achieve a much higher network throughput and lower delay utilizing the spatial multiplexing gain of the directional antennas. The results presented in this paper show that the proposed DSDMAC protocol can substantially outperform the state-of-the-art protocols. [ABSTRACT FROM PUBLISHER]

IEEE- and ASTM-adopted dedicated short-range communications (DSRC) standards are key enabling technologies for the next generation of vehicular safety communications. Vehicle-safety-related communication services, which require reliable and fast message delivery, usually demand broadcast communications in vehicular ad hoc networks (VANETs). In this paper, we propose and justify a distributive cross-layer scheme for the design of the control channel in DSRC with three levels of broadcast services that are critical to most potential vehicle-safety-related applications. The new scheme for enhancing broadcast reliability includes preemptive priority in safety services, dynamic receiver-oriented packet repetitions for one-hop emergency warning message dissemination, a multifrequency busy tone and minislot within the distributed interframe space (DIFS) in IEEE 802.11, and robust distance-based relay selection for multihop broadcast of emergency notification messages. Compared with a current draft of IEEE 802.11p and other schemes for DSRC safety-related services, the scheme proposed in this paper is more robust and scalable and easy to implement. Additionally, we investigate the reliability and performance of the proposed broadcast scheme for DSRC VANET safety-related services on the highway analytically and by simulations. The analytic model accounts for the impact of the hidden terminal problem, the fading channel conditions, varied message arrival intervals, and the backoff counter process on reliability and performance. [ABSTRACT FROM PUBLISHER]

Road congestion results in a huge waste of time and productivity for millions of people. A possible way to deal with this problem is to have transportation authorities distribute traffic information to drivers, which, in turn, can decide (or be aided by a navigator) to route around congested areas. Such traffic information can be gathered by relying on static sensors placed at specific road locations (e.g., induction loops and video cameras) or by having single vehicles report their location, speed, and travel time. While the former approach has been widely exploited, the latter has come about only more recently; consequently, its potential is less understood. For this reason, in this paper, we study a realistic test case that allows the evaluation of the effectiveness of such a solution. As part of this process, (a) we designed a system that allows vehicles to crowd-source traffic information in an ad hoc manner, allowing them to dynamically reroute based on individually collected traffic information; (b) we implemented a realistic network-mobility simulator that allowed us to evaluate such a model; and (c) we performed a case study that evaluates whether such a decentralized system can help drivers to minimize trip times, which is the main focus of this paper. This study is based on traffic survey data from Portland, OR, and our results indicate that such navigation systems can indeed greatly improve traffic flow. Finally, to test the feasibility of our approach, we implemented our system and ran some real experiments at UCLA's C-Vet test bed. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to study the contribution of intervehicle communication (IVC) to reduce the number of secondary collisions caused by an accident. We assess the impact of broadcast protocols used to disseminate warning messages and the impact of IVC penetration ratio on the number of collisions. There are two main contributions in this paper. First, it addresses the analytical evaluation of broadcast protocols in Vehicular Ad hoc NETworks (VANETs). We propose a general framework based on point processes to evaluate the performance of this protocol. Our approach is based on the theory of point processes and Palm calculus. We derive, for a generic frame error rate (FER) function, simple formulas for computing the delay required to propagate messages. These formulas hold for any FER function, enabling the comparison of broadcast performance under different radio propagation environments. In the second part of this paper, we propose an analytical evaluation of the number of vehicles involved in a collision. This analysis allows us to study the impact of radio technology penetration ratio and the impact of safety message delivery delays on the number of collisions. [ABSTRACT FROM PUBLISHER]

In vehicular ad hoc network (VANET) safety applications, the source vehicle that detects an accident can generate a warning message and propagate it to the following vehicles to notify other drivers before they reach the potential danger zone on the road. Recent studies have shown that sparse vehicle traffic leads to network fragmentation, which poses a crucial research challenge for safety applications. In this paper, we analyze and quantify the improvement in VANET connectivity when a limited number of roadside units (RSUs) are deployed and to investigate the routing performance for broadcast-based safety applications in this enhanced VANET environment. Our results show that, even with a small number of RSUs, the performance in terms of the probability of network connectivity, the rehealing delay, the number of rehealing hops, and the message penetration time can be significantly improved in highway VANET scenarios. [ABSTRACT FROM PUBLISHER]

This paper presents new design formulations that aim at optimizing the performance of an orthogonal frequency-division multiple-access (OFDMA) ad hoc cognitive radio network through joint subcarrier assignment and power allocation. Aside from an important constraint on the tolerable interference induced to primary networks, to efficiently implement spectrum-sharing control within the unlicensed network, the optimization problems considered here strictly enforce upper and lower bounds on the total amount of temporarily available bandwidth that is granted to individual secondary users. These new requirements are of particular relevance in cognitive radio settings, where the spectral activities of primary users are highly dynamic, leaving little opportunity for secondary access. A dual decomposition framework is then developed for two criteria (throughput maximization and power minimization), which gives rise to the realization of distributed solutions. Because the proposed distributed protocols require very limited cooperation among the participating network elements, they are particularly applicable to ad hoc cognitive networks, where centralized processing and control are certainly inaccessible. In this paper, we recommend that the network collaboration is made possible through the implementation of virtual timers at individual secondary users and through the exchange of pertinent information over a common reserved channel. It is shown that not only is the computational complexity of the devised algorithms affordable but that the performance of these algorithms in practical scenarios attains the actual global optimum as well. The potential of the proposed approaches is thoroughly verified by asymptotic complexity analysis and numerical results. [ABSTRACT FROM PUBLISHER]

This paper focuses on intelligent transportation systems and, more precisely, on intervehicle ad hoc networks. A vehicular ad hoc network (VANET) is a highly dynamic network as the vehicles communicate using short-range wireless communications and can move very quickly. Thus, for example, we can only rely on short interactions between vehicles to exchange information about relevant events. In this paper, we describe in detail a dissemination protocol that vehicles can use to share information by using vehicle-to-vehicle communications. The dissemination approach considers the relevance of the data, represented by what we call encounter probability, to decide when a rediffusion is needed. The protocol is able to disseminate data about any type of event in the network (e.g., available parking spaces, accidents or obstacles in the road, information about moving objects such as emergency vehicles that should get the right of way, etc.) by setting appropriate weights for the different factors that affect the computation of the encounter probability. An extensive experimental evaluation with different types of events shows the interest of the proposal: The vehicles receive the relevant messages in time, and the network overload is limited. [ABSTRACT FROM PUBLISHER]

Developing applications, particularly real-time applications, for wireless vehicular ad hoc networks (VANETs) requires a reasonable assurance of the likely performance of the network, at the least in terms of packet loss ratios and end-to-end delay. Because wireless propagation strongly influences performance, particularly in an urban environment, this paper improves on simpler propagation models for simulations by augmenting ray-tracing-derived models of propagation. In the non-line-of-sight (NLOS) component, the propagation distance is more closely calculated according to the reflection distance, the effect of roadside obstacles is included, and for the modeling of fast fading, a phase factor is introduced, all without necessarily overly increasing the computational load. In the line-of-sight (LOS) component, as well as the roadside obstacle modeling, single and double reflections from roadside buildings are added to the standard two-ray ground-propagation model, the distribution of vehicles within a street segment is used to more closely model the ground reflection ray, and the reflection coefficient is also accordingly adjusted to account for reflections from vehicles. The results have been compared with widely used measurement studies of city streets in the literature, which have confirmed the overall advantage of the improvements, particularly in the case of the NLOS component. A simulation case study shows that, in general, optimistic performance predictions of packet loss occur with the two-ray ground-propagation model when indiscriminately applied. This paper therefore represents a way forward for VANET wireless channel modeling in simulations. [ABSTRACT FROM PUBLISHER]

This paper studies the problem of congestion control and scheduling in ad hoc wireless networks that have to support a mixture of best-effort and real-time traffic. Optimization and stochastic network theory have been successful in designing architectures for fair resource allocation to meet long-term throughput demands. However, to the best of our knowledge, strict packet delay deadlines were not considered in this framework previously. In this paper, we propose a model for incorporating the quality-of-service (QoS) requirements of packets with deadlines in the optimization framework. The solution to the problem results in a joint congestion control and scheduling algorithm that fairly allocates resources to meet the fairness objectives of both elastic and inelastic flows and per-packet delay requirements of inelastic flows. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to give a big survey in enhancing the balance of the routing load and the consumption of resources using network layer metrics for the path discovery in the MAODV protocol. A ad hoc network (AD HOC NETWORKS) consists of a collection of wireless mobile nodes, which form a temporary network without relying on any existing infrastructure or centralized administration. The bandwidth of the ad hoc networks architecture is limited and shared between the participating nodes in the network, therefore an efficient utilization of the network bandwidth is very important. Multicasting technology can minimize the consumption of the link bandwidth and reduce the communication cost too. As multimedia and group-oriented computing gains more popularity for users of ad hoc networks, the effective Quality of Service (QoS) of the multicasting protocol plays a significant role in ad hoc networks. In this paper we propose a reconstruction of the MAODV protocol by extending some featuring QoS in MAODV. All simulations are prepared with the NS2 simulator and compare the performance of this algorithm with the MAODV algorithm. The achieved results illustrate faster path discovery and more performing routing balance in the use of MAODV-Extension. This paper would give relatively a modest support in Mobile Technology according to QoS communication. [ABSTRACT FROM AUTHOR]

Recently, cooperative communications, in the form of having each node equipped with a single antenna and exploit spatial diversity via some relay node's antenna, is shown to be a promising approach to increase data rates in wireless networks. Under this communication paradigm, the choice of a relay node (among a set of available relay nodes) is critical in the overall network performance. In this paper, we study the relay node assignment problem in a cooperative ad hoc network environment, where multiple source–destination pairs compete for the same pool of relay nodes in the network. Our objective is to assign the available relay nodes to different source–destination pairs so as to maximize the minimum data rate among all pairs. The main contribution of this paper is the development of an optimal polynomial time algorithm, called ORA, that achieves this objective. A novel idea in this algorithm is a “linear marking” mechanism, which maintains linear complexity of each iteration. We give a formal proof of optimality for ORA and use numerical results to demonstrate its capability. [ABSTRACT FROM PUBLISHER]

In this paper, we study distributed channel assignment in wireless networks with applications to peer discovery in ad hoc wireless networks. We model channel assignment as a coloring problem for spatial point processes in which n nodes are located in a unit cube uniformly at random and each node is assigned one of K colors, where each color represents a channel. The objective is to maximize the spatial separation between nodes of the same color. In general, it is hard to derive the optimal coloring algorithm, and we therefore consider a natural online greedy coloring algorithm first proposed by Ko and Rubenstein in 2005. We prove two key results: 1) with just \log n/\log \log n colors, the distance separation achieved by the greedy coloring algorithm asymptotically matches the optimal distance separation that can be achieved by an algorithm which is allowed to optimally place the nodes but is allowed to use only one color; and 2) when K=\Omega (\log n), the greedy coloring algorithm asymptotically achieves the best distance separation that can be achieved by an algorithm which is allowed to both optimally color and place nodes. The greedy coloring algorithm is also shown to dramatically outperform a simple random coloring algorithm. Moreover, the results continue to hold under node mobility . [ABSTRACT FROM PUBLISHER]

“Pairing” is the establishment of authenticated key agreement between two devices over a wireless channel. Such devices are ad hoc in nature as they lack any common preshared secrets or trusted authority. Fortunately, these devices can be connected via auxiliary physical (audio, visual, tactile) channels which can be authenticated by human users. They can, therefore, be used to form the basis of a pairing operation. Recently proposed pairing protocols and methods are based upon bidirectional physical channels. However, various pairing scenarios are asymmetric in nature, i.e., only a unidirectional physical channel exists between two devices (such as between a cell phone and an access point). In this paper, we show how strong mutual authentication can be achieved even with a unidirectional visual channel, where prior methods could provide only a weaker property termed as presence. This could help reduce the execution time and improve usability of prior pairing methods. In addition, by adopting recently proposed improved pairing protocols, we propose how visual channel authentication can be used even on devices that have very limited displaying capabilities, all the way down to a device whose display consists of a cheap single light-source, such as a light-emitting diode. We present the results of a preliminary usability study evaluating our proposed method. [ABSTRACT FROM PUBLISHER]

Combining mobile platforms such as manned or unmanned vehicles and peer-assisted wireless communication is an enabler for a vast number of applications. A key enabler for the applications is the routing protocol that directs the packets in the network. Routing packets in fully connected mobile ad hoc networks (MANETs) has been studied to a great extent, but the assumption on full connectivity is generally not valid in a real system. This case means that a practical routing protocol must handle intermittent connectivity and the absence of end-to-end connections. In this paper, we propose a geographical routing algorithm called location-aware routing for delay-tolerant networks (LAROD), enhanced with a location service, location dissemination service (LoDiS), which together are shown to suit an intermittently connected MANET (IC-MANET). Because location dissemination takes time in IC-MANETs, LAROD is designed to route packets with only partial knowledge of geographic position. To achieve low overhead, LAROD uses a beaconless strategy combined with a position-based resolution of bids when forwarding packets. LoDiS maintains a local database of node locations, which is updated using broadcast gossip combined with routing overhearing. The algorithms are evaluated under a realistic application, i.e., unmanned aerial vehicles deployed in a reconnaissance scenario, using the low-level packet simulator ns-2. The novelty of this paper is the illustration of sound design choices in a realistic application, with holistic choices in routing, location management, and the mobility model. This holistic approach justifies that the choice of maintaining a local database of node locations is both essential and feasible. The LAROD–LoDiS scheme is compared with a leading delay-tolerant routing algorithm (spray and wait) and is shown to have a competitive edge, both in terms of delivery ratio and overhead. For spray and wait, this case involved a new packet-level implementation in ns-2 as opposed to the original connection-level custom simulator. [ABSTRACT FROM PUBLISHER]

The space and time dynamics of moving vehicles regulated by traffic signals governs the node connectivity and communication capability of vehicular ad hoc networks (VANETs) in urban environments. However, none of the previous studies on node connectivity has considered such dynamics with the presence of traffic lights and vehicle interactions. In fact, most of them assume that vehicles are distributed homogeneously throughout the geographic area, which is unrealistic. We introduce in this paper a stochastic traffic model for VANETs in signalized urban road systems. The proposed model is a composite of the fluid model and stochastic model. The former characterizes the general flow and evolution of the traffic stream so that the average density of vehicles is readily computable, while the latter takes into account the random behavior of individual vehicles. As the key contribution of this paper, we attempt to approximate vehicle interactions and capture platoon formations and dissipations at traffic signals through a density-dependent velocity profile. The stochastic traffic model with approximation of vehicle interactions is evaluated with extensive simulations, and the distributional result of the model is validated against real-world empirical data in London. In general, we show that the fluid model can adequately describe the mean behavior of the traffic stream, while the stochastic model can approximate the probability distribution well even when vehicles interact with each other as their movement is controlled by traffic lights. With the knowledge of the mean vehicular density dynamics and its probability distribution from the stochastic traffic model, we determine the degree of connectivity in the communication network and illustrate that system engineering and planning for optimizing both the transport (in terms of congestion) and communication networks (in terms of connectivity) can be carried out with the proposed model. [ABSTRACT FROM PUBLISHER]

The performance of backoff scheme plays an important role in designing efficient Medium Access Protocols for ad hoc networks. In this paper, we propose an adaptive backoff scheme and evaluate the performance of the proposed scheme for ad hoc networks. The backoff mechanism devised by us grants a node access to the channel based on its probability of collision for a transmitted frame in comparison to the nodes in the two-hop contention area. We use both an analytical model and simulation experiments to evaluate the performance of our adaptive backoff mechanism in an ad hoc network. The results show that our protocol exhibits a significant improvement in power saving, end-to-end goodput, packet delivery ratio, and hop-put, compared with the existing IEEE 802.11 DCF. Copyright © 2010 John Wiley & Sons, Ltd. In this paper, we propose an adaptive backoff scheme and evaluate the performance of the proposed scheme for ad hoc networks. The backoff mechanism devised by us grants a node access to the channel based on its probability of collision for a transmitted frame in comparison to those of nodes in the two-hop contention area. We use both an analytical model and simulation experiments to evaluate the performance of our adaptive backoff mechanism in an ad hoc network. The results show that our protocol exhibits a significant improvement in power saving, end-to-end goodput, packet delivery ratio, and hop put, compared to the existing IEEE 802.11 DCF. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

For reducing the loss of data packet due to network congestion and mobility, rate control algorithm is effective means for ensuring the fair allocation of network resource among communication flows and alleviating network congestion. The Transport Control Protocol (TCP) was originally designed for wire-line networks, where the links are assumed to be reliable and with fixed capacities. However, the performance of TCP becomes very poor when it is directly used in ad hoc networks. Some optimization-based congestion control schemes have been proposed to improve TCP performance in ad hoc networks, but the mobility of hosts and route change frequently are not considered for designing rate control algorithm. In this paper, we propose rate control algorithms in a more practical way by taking into account link congestion and node movement. Numerical results show that the rate control algorithms can approach the globally optimal value and show the effect of the node mobility on the algorithms. [ABSTRACT FROM AUTHOR]

The open literature contains numerous studies of capacity bounds for an N-node wireless ad-hoc network but the number of cooperating nodes has generally been limited to two. In this paper, we present a simple time-share lower bound for such a network, but with two or more cooperating nodes. These results are then compared against our previous information theoretic upper bounds with hop-by-hop routing, frequency reuse, and no cooperation. While simulations show that our simple time-share lower bound with cooperation does not outperform our previous upper bound without cooperation, we do note a significant increase in achievable capacity relative to time-share results without cooperation. Also, our results indicate that there is no significant improvement when more than two nodes cooperate. [ABSTRACT FROM AUTHOR]

Relay nodes in an ad hoc network can be modelled as fluid queues, in which the available service capacity is shared by the input and output. In this paper such a relay node is considered; jobs arrive according to a Poisson process and bring along a random amount of work. The total transmission capacity is fairly shared, meaning that, when n jobs are present, each job transmits traffic into the queue at rate 1/( n + 1) while the queue is drained at the same rate of 1/( n + 1). Where previous studies mainly concentrated on the case of exponentially distributed job sizes, the present paper addresses regularly varying jobs. The focus lies on the tail asymptotics of the sojourn time S. Using sample-path arguments, it is proven that $${\mathbb{P}\left\{ S > x \right\}}$$ behaves roughly as the residual job size, i.e., if the job sizes are regularly varying of index − ν, the tail of S is regularly varying of index 1 − ν In addition, we address the tail asymptotics of other performance metrics, such as the workload in the queue, the flow transfer time and the queueing delay. [ABSTRACT FROM AUTHOR]

Most publications on the capacity and performance of wireless ad hoc networks share the underlying assumption of a uniform random distribution of nodes. In this paper, we study the effects of different node distributions on the local throughput of the slotted ALOHA MAC protocol. The throughput achieved in a network where the nodes are distributed according to a Poisson point process is used as a baseline performance measure for the comparison with other point distributions. We show that non-uniform random node distributions have a strong impact on the local throughput. This has also effects on the network capacity and performance. The results show that the node topology should be taken into account in more detailed analyses and simulations of ad hoc, sensor, and mesh networks. [ABSTRACT FROM AUTHOR]

This paper presents a decentralized mobility control algorithm for the formation and maintenance of an optimal cascaded communication chain between a lead sensor-equipped robot and a control station, using a team of robotic vehicles acting as communication relays in an unknown and dynamic RF environment. The gradient-based controller presented uses measurements of the signal-to-noise ratio (SNR) field of neighbor communication links, as opposed to relative position between nodes, as input into a localized performance function. By using the SNR field as input into the control system, the controller is reactive to unexpected and unpredictable changes in the RF environment that is not possible with range-based controllers. Since the operating environment is not known a priori to deployment of a robotic sensor network, an adaptive model-free extremum seeking (ES) algorithm, that uses the motion of the relays to estimate the performance function gradient, is presented to control the motion of 2D nonholonomic vehicles acting as communication relays using the gradient-based controller. Even without specific knowledge of the SNR field, simulations show that the ES decentralized chaining controller using measurements of the SNR field, will drive a team of robotic vehicles to locations that achieve the global objective of maximizing capacity of a cascaded communication chain, even in the presence of an active jamming source. [ABSTRACT FROM AUTHOR]

The mobile ad hoc wireless network (MAWN) promises to become an ever-present technology with application to a myriad of areas. This networking scheme has its roots in DoD technology, yet, the ability to measure and calculate its reliability is largely absent. This paper describes the unique attributes of the MAWN and how the classical methods for analysis of network reliability must be adjusted. The methods developed acknowledge the dynamic and scalable nature of the new networking scheme along with its absence of infrastructure and remove the need to a priori define a network configuration. The methods rely on a novel modeling approach that recognizes the effects of mobility on the formation of the network's configurations. Hence, this paper proposes a Monte Carlo simulation method that accounts for node mobility, node reliability and node performance in the network's connectivity and resultant network reliability. [ABSTRACT FROM AUTHOR]

In recent years, the need for high security with reliability in the wireless network has tremendously been increased. To provide high security in reliable networks, mobile ad hoc networks (MANETs) play a top role, like open network boundary, distributed network, and fast and quick implementation. By expanding the technology, the MANET faces a number of security challenges due to self-configuration and maintenance capabilities. Besides, traditional security solutions for wired networks are ineffective and inefficient because of the nature of highly dynamic and resource-constrained MANETs. In this paper, the researchers focus on improving reliable data transmission with high security in the MANET using an optimization technique. In the proposed MANET system, the nodes are clustered by utilizing an energy-efficient routing protocol. Then, the modified discrete particle swarm optimization is used to select the optimal cluster head. A secured routing protocol and a signcryption model can be used to improve the transmission security of the reliable MANET. The signcryption algorithm encrypts the digital signature, which can enhance the overall efficiency and confidentiality. The security-based analysis is performed on the basis of packet delivery ratio, energy consumption, network lifetime, and throughput. Finally, the result demonstrates that the MANET with optimization techniques achieves a high transmission rate and improves the reliable data security. [ABSTRACT FROM AUTHOR]

Protecting the location privacy is one of the main challenges in vehicular ad-hoc networks (VANETs). Although, standardization bodies, such as IEEE and ETSI, have adopted a pseudonym-based scheme as a solution for this problem, an efficient pseudonym changing and management is still an open issue. In this paper, we propose PRIVANET, a complete and efficient pseudonym changing and management framework. The PRIVANET has a hierarchical structure and considers the vehicular geographic area as a grid. Each cell of this grid contains one or many logical zones, called vehicular location privacy zones (VLPZs). These zones can easily be deployed over the widespread roadside infrastructures (RIs), such as gas stations, to provide a secure changing and management of pseudonyms. The proposed framework consists of different building blocks: 1) an effective VLPZ-based pseudonym changing strategy; 2) a reputation-based mechanism to motivate selfish vehicles to enter VLPZs; 3) an adapted user-centric privacy model; 4) a secure hybrid mechanism for the distribution of pseudonyms sets and CRLs; 5) a method to generate the IP and MAC addresses from the pseudonym; 6) a stochastic model to estimate the number of VLPZs required at a given cell; and 7) a mathematical model for an optimal placement of the VLPZs over RIs to reduce the transportation cost of vehicles in terms of time. An extensive simulation study using a realistic map and with real traffic mobility measurements is carried out to evaluate and validate the performance of the PRIVANET. The simulation results demonstrate the effectiveness of the proposed framework. [ABSTRACT FROM AUTHOR]

Routing selection and supporting Quality of Service (QoS) are fundamental problems in Mobile Ad Hoc Network (MANET). Many different protocols have been proposed in the literature and some performance simulations are made to address this challenging task. This paper discusses the performance evaluation and comparison of two typical routing protocols; Ad Hoc On-Demand Distance Vector (AODV) and Destination-Sequenced Distance- Vector (DSDV) based on measuring the power consumption in network with varing of the QoS parameters. In this paper, we have studied and analyzed the impact of variations in QoS parameter combined with the choice of routing protocol, on network performance. The network performance is measured in terms of average throughput, packet delivery ratio (PDR), average jitter and energy consumption. The simulations are carried out in NS-3. The simulation results show that DSDV and AODV routing protocols are less energy efficient. The main aim of this paper is to highlight the directions for the future design of routing protocol which would be better than the existing ones in terms of energy utilization and delivery ratio. [ABSTRACT FROM AUTHOR]

The performance of existing coded caching schemes is sensitive to the worst channel quality, a problem which is exacerbated when communicating over fading channels. In this paper, we address this limitation in the following manner: in short-term, we allow transmissions to subsets of users with good channel quality, avoiding users with fades, while in long-term we ensure fairness among users. Our online scheme combines (i) the classical decentralized coded caching scheme with (ii) joint scheduling and power control for the fading broadcast channel, as well as (iii) congestion control for ensuring the optimal long-term average performance. We prove that our online delivery scheme maximizes the alpha-fair utility among all schemes restricted to decentralized placement. By tuning the value of alpha, the proposed scheme can achieve different operating points on the average delivery rate region and tune performance according to an operator’s choice. We demonstrate via simulations that our scheme outperforms two baseline schemes: (a) standard coded caching with multicast transmission, limited by the worst channel user yet exploiting the global caching gain; (b) opportunistic scheduling with unicast transmissions exploiting the fading diversity but limited to local caching gain. [ABSTRACT FROM AUTHOR]

Due to the requirement of real time controlling on the vehicular ad-hoc networks (VANETs), the security measure should be fast, lightweight, and strong. In this paper, we investigate the secure communication between the on-board unit and the roadside unit which has strong computing ability to remedy the insufficient computing power of on-board unit. The novel schemes are developed to guarantee both security and energy harvest. Specifically, a muti-antenna roadside unit (PT) conveys a secret message to a muti-antenna primary on-board unit (PR) intercepted by multiple muti-antenna adversaries (Eves). Simultaneously, a secondary roadside unit (ST) adopts simultaneous wireless information and power transfer (SWIPT) strategy to send secret-free data embeded with energy-carrying artificial noise (AN) to its service subscriber (SR), by which secrecy guarantee is provided for the primary on-board unit and the quality of service (QoS) is satisfied, i.e., data traffic and harvested energy. Technically, considering the secondary link's data transmission rate, harvested energy, and transmit power, we propose joint power allocation designs for the nonconvex secrecy rate maximization (SRM) problems under either perfect channel state information (CSI) or norm-bounded channel uncertainty model. Simulation results show that the proposed secondary link-aided secrecy designs can achieve better performance in terms of secrecy rate and energy efficiency. [ABSTRACT FROM AUTHOR]

The ad hoc network is an emerging wireless communication technology. Recently, the reliability of ad hoc networks has attracted increasing attention in the literature. In this paper, the reliability of such networks is analyzed by incorporating the impacts of node failures and interference, because node failures usually obstruct the achievement of the intended function of a network, and interference is a key factor that degenerates the communication quality. We consider a general case that an ad hoc network is functional if at least k arbitrary nodes are operational and connected. Accordingly, two novel reliability indices, the generalized k-terminal reliability and the average generalized k-terminal reliability, are proposed, and their calculation methods are provided based on the Laplace transformation technique and the graph theory. For optimizing the design of an ad hoc network, a multiobjective optimization problem is investigated to maximize the reliability level and minimize the cost. The optimization problem is handled by the weighted sum method, and the most suitable solution is selected by the fuzzy satisfying approach. Finally, a numerical example is given to demonstrate the application of the proposed methods. [ABSTRACT FROM AUTHOR]

Hybrid Mobile ad hoc network (H-MANET) is a network in which MANET is connected to the Internet using some special nodes called Internet Gateways (IGs). Previous work in this field considered the infinite buffer scenario and therefore buffer overflow would never occur. But in realistic MANET, the buffer size of each node is strictly bounded that incurs packet loss and intensifies delay. In this paper, a mathematical model has been proposed for modeling of multipath delay analysis for IG selection in H-MANET. The proposed work is used to estimate end to end delay of each individual path amongst Source Node (SN) and IGs. The M/M/m/R network model has been employed for modeling the network in which packets arrive in Poisson distribution in a bounded queue with finite buffer capacity. Burke theorem has been used to calculate queuing delay of each individual path as well as the complete path from the SN to an IG. Furthermore, best IG is selected for data transmission based on delay analysis of multiple paths. The Opnet modeler 18.0 has been used to perform the simulation work. The numerical results represent the effectiveness of proposed model. [ABSTRACT FROM AUTHOR]

Featured Application: Privacy ensuring emergency vehicle approaching warning system. With the deployment of Vehicular Ad hoc Networks (VANETs), new transport safety and efficiency applications are emerging. One of the fields where the adoption of information and communication technologies (ICT) is expected to bring great benefits, is emergency systems. A properly designed emergency vehicle warning system should provide car drivers with adequate reaction times and additional information, complementing the currently used lights and sirens. The objective is to increase road safety and to create conditions for a fast and reliable movement of emergency vehicles (EVs). The available literature addressing privacy issues in VANET-based emergency vehicle warning systems is strongly limited. In this paper, the privacy ensuring emergency vehicle approaching warning system (PEEV-WS) is proposed based on a requirements analysis. Privacy is ensured by avoiding transmissions of sensitive information (e.g., expected EV route) over the wireless channel. This is achieved by assigning the decision-making responsibility to an EV and determining which vehicles can potentially interfere with the EV in the near future, and to notify those vehicles only by unicasting vehicle-customized information. The performance of the system is evaluated by federated telco-traffic simulations in terms of end-to-end delay and message delivery probability for three commonly used ad hoc routing protocols—Ad hoc On-Demand Distance Vector (AODV), Greedy Perimeter Stateless Routing (GPSR), and Dynamic MANET On-demand (DYMO), as well as in terms of reaction time, which the system provides to the drivers. Despite low applicability of the ad hoc routing protocols for vehicular communication, especially for low-latency and high-frequency applications, the simulations of the communication network demonstrate that the AODV protocol, with the modified configuration, can support the emergency vehicle warning system. The traffic simulations confirm that the system has the potential to provide drivers with sufficient reaction time. [ABSTRACT FROM AUTHOR]

Wireless ad hoc networks are expected to provide broadband services parallel to their wired counterparts in near future. To address this need, MIMO (multiple-input-multiple-output) antenna techniques hold significant promise. Most previous work on capacity analysis of ad hoc networks is based on an implicit assumption that each link exclusively occupies a geometric area, referred to as exclusion region that characterizes the amount of spatial resource occupied by a link. When multiple antennas are deployed at each node, however, multiple links can transmit in the vicinity of each other simultaneously, as interference can now be suppressed by spatial signal processing. As such, the concept of "exclusion region" no longer applies. In this paper, we investigate link-layer throughput capacity of MIMO ad-hoc networks. In contrast to previous work, the amount of spatial resource occupied by each link is characterized by the actual interference it imposes on other links. To calculate the link-layer capacity, we first derive the probability distribution of post-detection SINR (signal to interference and noise ratio) at a receiver. The result is then used to calculate the number of active links and the corresponding data rates that can be sustained within an area. Our analysis shows that there exists an optimal active-link density that maximizes the link-layer throughput capacity. This will serve as a guideline for the design of medium access protocols for MIMO ad-hoc networks. To the best of knowledge, this paper is the first attempt to characterize the capacity of MIMO ad-hoc networks by considering the actual PHY-layer signal and interference model. The results in this paper pave the way for further study on network-layer transport capacity of ad-hoc networks with MIMO. [ABSTRACT FROM PUBLISHER]

Single-constrained QoS routing protocols have inherent defects when applied into wireless ad hoc networks. Due to a single constraint parameter is only considered, they can't always cope with the problems caused by the uncertainty of ad hoc networks well. They are not robust enough. In order to overcome the drawbacks of single-constrained QoS routing protocols and improve the Quality of Service (QoS) of ad hoc networks, this paper proposed a multi-constrained QoS routing protocol based on fuzzy logic. It is developed from Dynamic Source Routing (DSR). The proposed protocol is service-aware in the sense that it considers the QoS required by different types of services and takes different network state parameters as the constraint conditions for fuzzy based routing system. New route discovery procedure and novel route maintenance mechanism are designed to support corresponding QoS requirements. Speed of packets sending is also adjusted adaptively referring to the outputs of the proposed fuzzy system. Performance of the fuzzy based DSR protocol is measured and evaluated under different conditions. Simulation results show that the improved protocol has better QoS guarantee capabilities compared to single-constrained QoS routing protocols for large-scale networks in terms of lower delay, smoother delay variation and lower packet loss rate. [ABSTRACT FROM AUTHOR]

This paper revisits the topology control problem for multi-hop wireless ad hoc networks. It accounts for the maximum number of links interfering with each node in the network, which is referred to as the interference load in the paper. Finding a topology with minimum interference load is an NP-complete problem. In this paper, we develop the essential theorems and lemmas for constructing low interference load topologies for wireless ad hoc networks. Based on the theoretical results, we provide the design guidelines for topology construction with low interference load, and propose a polynomial-time solution accordingly. The performance of the proposed mechanism is evaluated via simulations. The results show that the proposed mechanism outperforms existing work in terms of lower interference load even using the maximum transmission power in the generated topology. [ABSTRACT FROM PUBLISHER]

In this paper, we deal with an amplify-and-forward (AF) cooperative strategy in slot-based, block-fading environments. In contrast with previous schemes, which assume a constant channel during the cooperative frame (several slots), here, we relax this constraint and assume a classical quasi-static block-fading channel (constant for one slot). This additional degree of freedom modifies the behavior of the conventional nonorthogonal AF (NAF) schemes and generates a new block-fading NAF (BFNAF) protocol, where the source can usefully retransmit the same data during the cooperative slot. This new protocol is interesting at low spectral efficiencies, where diversity against fading is more important. To overcome performance degradation, which characterizes cooperative schemes at low signal-to-noise ratios (SNR5), an adaptive version of the considered schemes is also proposed, where cooperation is activated according to the outage behavior of the direct link. Moreover, an optimal hybrid protocol that allows intelligent switching between noncooperation, NAF, and BFNAF protocols is also proposed. Another issue that is discussed throughout this paper is the optimal power allocation of the investigated schemes. The proposed power-allocation strategy uses as an optimization criterion the well-defined asymptotic expressions of the outage probabilities, which are averaged over the fading statistics. The minimization (and avoidance for the nonhybrid protocols) of the required data feedback makes it suitable for practical ad hoc networks with crucial power constraints. The enhancement of the proposed schemes and the efficiency of the power allocation policy are shown by theoretical analysis and simulation results. [ABSTRACT FROM AUTHOR]