Dissemination Delay Research Articles

Information Dissemination Delay in Vehicle-to-Vehicle Communication Networks in a Traffic Stream

Vehicle-to-vehicle (V2V) communication networks, as one of the core components of connected vehicle systems, have been granted many promising applications to address traffic mobility, safety, and sustainability. However, only a limited amount of work has been completed to understand the fundamental properties of information propagation in such systems, while comprehensively considering traffic and communication reality. Motivated by this view, this proposed research develops analytical formulations to estimate information propagation time delay via a V2V communication network formed on a one-way or two-way road segment with multiple lanes. Distinguished to previous efforts, the proposed study carefully involves several critical communication and traffic flow features in reality, such as wireless communication interference, intermittent information transmission, and dynamic traffic flow. Moreover, this study elaborately analyzes the interactions between information and traffic flow under sparse and congested traffic flow conditions. The numerical experiments based on Next-Generation Simulation field data illustrate that the proposed analytical formulations are able to provide very good estimation, with the relative error less than 5%, for the information propagation time delay on a one-way or two-way road segment under various traffic conditions. The proposed work can be further extended to characterize information propagation time delay and coverage over local transportation networks.

A multi-hop broadcast protocol design for emergency warning notification in highway VANETs

Multi-hop broadcast transmission is used in vehicular ad hoc networks (VANETs) to alert all vehicles within a geographical area of an emergency situation. However, the successful dissemination of multi-hop warning messages beyond the transmission range of a vehicle faces three major issues: (i) the broadcast storm, (ii) the severe interference with the existing periodic single-hop safety messages, and (iii) the hidden nodes. In this paper, we propose an efficient time-slotted multi-hop broadcast protocol that significantly reduces the number of required transmissions, while ensuring a timely and successful delivery of the warning messages. To alleviate the broadcast storm problem, we select only a subset of vehicles on the road to serve as the potential relay nodes. Each of these ‘segment leaders’ is responsible for forwarding the warning messages arrived in its own road segment. To avoid interfering with the safety messages transmitted periodically, we propose to allocate separate time slots for the warning messages. We also devise a signaling mechanism that ensures the reliable delivery of these multi-hop messages. Simulation results confirm that the developed protocol substantially outperforms existing schemes in terms of the number of required multi-hop transmissions and the dissemination delay. At the same time, the proposed solution maintains a high reception rate and low end-to-end delay for the single-hop safety messages.

Data Dissemination in VANETs: A Scheduling Approach

Data dissemination is a promising application for the vehicular network. Existing data dissemination schemes are generally built upon some random-access protocol, which results in the unavoidable collision problem. To address this problem, in this paper we design a novel data dissemination strategy from the scheduling perspective. A data dissemination scheduling framework is then proposed. In the proposed framework, the main challenge is how best to assign the transmission opportunity to nodes with maximum dissemination utility and to avoid the collision problem. We then propose a novel and practical relay selection strategy and adopt the space-time network coding (STNC) with low detection complexity and space-time diversity gain to improve the dissemination efficiency. Compared with the random-access dissemination such as CodeOn-Basic and the noncooperative transmission, our proposed data dissemination strategy performs better in terms of the dissemination delay. In addition, the proposed strategy works even better in the dense network than the sparse scenario, benefitting from the space-time diversity gain of STNC and no-collision transmissions. This is in sharp contrary to the CodeOn-Basic method.

The impact of digital dissemination for research and scholarship.

The impact of digital dissemination for research and scholarship.

A Yersinia pestis tat mutant is attenuated in bubonic and small-aerosol pneumonic challenge models of infection but not as attenuated by intranasal challenge.

Bacterial proteins destined for the Tat pathway are folded before crossing the inner membrane and are typically identified by an N-terminal signal peptide containing a twin arginine motif. Translocation by the Tat pathway is dependent on the products of genes which encode proteins possessing the binding site of the signal peptide and mediating the actual translocation event. In the fully virulent CO92 strain of Yersinia pestis, the tatA gene was deleted. The mutant was assayed for loss of virulence through various in vitro and in vivo assays. Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type. Cell morphology of the mutant bacteria was altered and demonstrated a more elongated form. In addition, while cultures of the mutant strain were able to produce a biofilm, we observed a loss of adhesion of the mutant biofilm structure compared to the biofilm produced by the wild-type strain. Immuno-electron microscopy revealed a partial disruption of the F1 antigen on the surface of the mutant. The virulence of the ΔtatA mutant was assessed in various murine models of plague. The mutant was severely attenuated in the bubonic model with full virulence restored by complementation with the native gene. After small-particle aerosol challenge in a pneumonic model of infection, the mutant was also shown to be attenuated. In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains. However, an increased time-to-death and delay in bacterial dissemination was observed in mice infected with the ΔtatA mutant as compared to the parent strain. Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

Regression based critical information aggregation and dissemination in VANETs: A cognitive agent approach

Data aggregation in Vehicular Ad hoc NETworks (VANETs) is an efficient technique for effective usage of communication resources. In dense VANET traffic scenarios, data aggregation is needed to represent several numbers of almost similar critical information into one refined critical information to reduce bandwidth requirements. This paper proposes a cognitive agent based critical information aggregation and dissemination in VANETs by using regression mechanism. Regression based cognitive agent approach efficiently aggregates the collected critical information and minimizes redundant data dissemination. The proposed scheme works over clustered vehicles by using a set of static and mobile agents. The scheme operates in the following steps: (1) validation and filtering of collected critical information; (2) generation of beliefs based on valid and filtered critical information; (3) aggregating the beliefs to develop desire using a regression technique; (4) revision of desire for better quality of aggregation; (5) finalizing the intention based on revised desire; (6) disseminating aggregated information to neighboring clusters. We validate the proposed scheme by simulation. The scheme performs better as compared to ESSMD (Event Suppression for Safety Message Dissemination) scheme in terms of critical information acquisition delay, aggregation delay, end-to-end delay, dissemination delay and bandwidth utilization.

Deploying Roadside Units in Sparse Vehicular Networks: What Really Works and What Does Not

The 802.11p/WAVE standard relies on the presence of onboard units (OBUs) and roadside units (RSUs) for communications in vehicular networks. In this paper, we study the benefits of deploying RSUs to improve communications in highway scenarios. We develop an analytical model to analyze communication delay in a highway scenario with bidirectional traffic, considering both connected and disconnected RSUs, and validate our model via simulations and experimental measurements with 802.11p equipment. Contrary to conventional wisdom, our results show that significant benefits of RSUs in terms of connectivity and message dissemination can only be achieved when the deployed RSUs are interconnected. Conversely, deploying a large number of disconnected RSUs will lead to little or no benefit in message dissemination delay.

Optimal selection of aggregation locations for participatory sensing by mobile cyber-physical systems

Mobile cyber-physical systems entail large volumes of data collected by various sensors and cameras embedded in vehicles and mobile devices. Participatory sensing is a model widely encouraged by cyber-physical systems (CPS) to provide a smart knowledge base to consumers using various sensed data contributed by voluntary participants. Aggregation is a viable approach to convert the sensed data into a usable form. An efficient way to perform aggregation is to divide the network into a number of geographical regions, called aggregation regions. In this paper, we propose a novel mechanism to determine aggregation regions based on the location of Access Points (APs). Besides, we propose a strategy to determine the optimal location of aggregation that minimizes the delay of dissemination of sensed data.

DOVE: Data Dissemination to a Desired Number of Receivers in VANET

Efficient data dissemination to a desired number of receivers in a vehicular ad hoc network (VANET) is a new issue and a challenging one considering the dynamic nature of VANETs. We aim to accurately control the number of receivers in a particular area of interest, achieve low dissemination delay, and incur only small communication overhead. To achieve these goals, we designed the data dissemination to a desired number of receivers in VANET (DOVE) scheme. DOVE is inspired by processor scheduling treating roads as processors to optimize the workload assignment and improve the efficiency of on-road dissemination. DOVE reaches the desired number of receivers with little inaccuracy and minimizes the dissemination delay with low communication overhead. We enhance our protocol with workload backup to deal with vehicles that are quitting the network. We utilize the unique characteristics of VANET and propose heuristics accordingly to significantly reduce the dissemination delay and overhead. Simulation results show that our scheme can disseminate data to almost all the pregiven number of receivers with a light overhead and low delay.

DEEP: Density-Aware Emergency Message Extension Protocol for VANETs

With the rapid developments in vehicular communication technology, academics and industry researchers are paying increasing attention to vehicular ad hoc networks (VANETs). In VANETs, dissemination delay and reliability are important criteria for many applications, especially for emergency messages. Existing approaches have difficulty satisfying both requirements simultaneously because they conflict with one another. In this paper, we propose a novel mechanism, called the Density-aware Emergency message Extension Protocol (DEEP) to disseminate emergency messages in VANETs. DEEP resolves the broadcast storm problem, achieves low dissemination delay, and provides high reliability over a realistic multi-lane freeway scenario. The mechanism delivers emergency messages to a specific area (e.g., the area before the exit) in a timely manner and guarantees that all relevant vehicles in that area will receive the messages. Drivers can then change their routes and avoid getting caught in a traffic jam. Performance evaluations via NS-2 simulations demonstrate that DEEP achieves both lower dissemination delay and higher reliability than existing approaches.

Analysis of Message Dissemination in Vehicular Networks

Safety-critical applications form the main motivation for intelligent transportation systems (ITSs). Studying the major concerns in such applications, i.e., delay and reliability, through mathematical analysis is extremely beneficial because it enables us to design optimized schemes. Such analysis is, however, challenging due to the dynamics of such a network. In this paper, we present a mathematical model to study delay and reliability of emergency message dissemination in vehicular networks. First, a basic model is presented using simplified assumptions about the channel. Then, we enhance the model using Rician distribution as a realistic fading model for vehicular environment. We make some interesting observations from the presented model. First, the end-to-end reliability has a fairly fast transition over time, which we formally prove in this observation. The second observation from the analytical model confirms the fact that using the vehicle density on the road is a good metric for setting the right forwarding probability in vehicles. We exploit this conclusion and propose a completely distributed forwarding strategy. Simulation studies indicate that our model does capture the delay characteristics of vehicular networks. It also affirms the effectiveness of our warning dissemination scheme in terms of delay and single-hop reliability in comparison with other well-known routing methods. We believe that this is a promising step toward accurate characterization of communication delay and reliability in vehicular networks.

Howell Pritchard Jones

Inflammation constitutes an important component of host defense against pathogenic bacteria. This innate immune response is crucial for clearance of pathogens and survival of the host. However, unrestrained inflammatory reaction...

Mobile social networking aided content dissemination in heterogeneous networks

Since more and more mobile applications are based on the proliferation of social information, the study of Mobile Social Networks (MSNs) combines social sciences and wireless communications. Operating wireless networks more efficiently by exploiting social relationships between MSN users is an appealing but challenging option for network operators. An MSN-aided content dissemination technique is presented as a potential extension of conventional cellular wireless networks in order to satisfy growing data traffic. By allowing the MSN users to create a self-organized ad hoc network for spontaneously disseminating contents, the network operator may be able to reduce the operational costs and simultaneously achieve an improved network performance. In this paper, we first summarize the basic features of the MSN architecture, followed by a survey of the factors which may affect MSN-aided content dissemination. Using a case study, we demonstrate that one can save resources of the Base Station (BS) while substantially lowering content dissemination delay. Finally, other potential applications of MSN-aided content dissemination are introduced, and a range of future challenges are summarized.

Point-of-Care Testing as an Influenza Surveillance Tool: Methodology and Lessons Learned from Implementation

Objectives. Disease surveillance combines data collection and analysis with dissemination of findings to decision makers. The timeliness of these activities affects the ability to implement preventive measures. Influenza surveillance has traditionally been hampered by delays in both data collection and dissemination. Methods. We used statistical process control (SPC) to evaluate the daily percentage of outpatient visits with a positive point-of-care (POC) influenza test in the University of Utah Primary Care Research Network. Results. Retrospectively, POC testing generated an alert in each of 4 seasons (2004–2008, median 16 days before epidemic onset), suggesting that email notification of clinicians would be 9 days earlier than surveillance alerts posted to the Utah Department of Health website. In the 2008-09 season, the algorithm generated a real-time alert 19 days before epidemic onset. Clinicians in 4 intervention clinics received email notification of the alert within 4 days. Compared with clinicians in 6 control clinics, intervention clinicians were 40% more likely to perform rapid testing (P = 0.105) and twice as likely to vaccinate for seasonal influenza (P = 0.104) after notification. Conclusions. Email notification of SPC-generated alerts provided significantly earlier notification of the epidemic onset than traditional surveillance. Clinician preventive behavior was not significantly different in intervention clinics.

Exploiting Concurrency for Efficient Dissemination in Wireless Sensor Networks

Wireless sensor networks (WSNs) can be successfully applied in a wide range of applications. Efficient data dissemination is a fundamental service which enables many useful high-level functions such as parameter reconfiguration, network reprogramming, etc. Many current data dissemination protocols employ network coding techniques to deal with packet losses. The coding overhead, however, becomes a bottleneck in terms of dissemination delay. We exploit the concurrency potential of sensor nodes and propose MT-Deluge, a multithreaded design of a coding-based data dissemination protocol. By separating the coding and radio operations into two threads and carefully scheduling their executions, MT-Deluge shortens the dissemination delay effectively. An incremental decoding algorithm is employed to further improve MT-Deluge's performance. Experiments with 24 TelosB motes on four representative topologies show that MT-Deluge shortens the dissemination delay by 25.5-48.6 percent compared to a typical data dissemination protocol while keeping the merits of loss resilience.

Contact duration aware evaluation for content dissemination delay in mobile social network

Groups of people with mobile phones using short-range connections such as WiFi and Bluetooth to propagate messages can be modeled as, with regard to regular absence of end-to-end connection, mobile social networks MSNs, which can be exploited to offload a significant amount of mobile content from the overloaded infrastructure networks such as 3G. The study of content transmission delay for the applications of mobile content dissemination in MSNs is an important problem, because to enhance the network capacity, the traffic is offloaded at the cost of inducing longer delay. In contrast to existing works, which ignore the factors of contact duration limits and large content size, we present a contact duration aware framework to model the content dissemination process in MSNs, give an explicit expression for the average content dissemination delay, and reveals its relationship with various system parameters of content size, users' selfishness, number of involved subscribers, infecting ratio, and so on. We apply our proposed model to real-life traces to assess its reliability by comparing the theoretical results with measured statistics and present extensive upshots to evaluate the influence of various parameters on system performance. The results demonstrate the accuracy of our proposed framework and reveal that system parameters of content size, system infecting ratio and intragroup transmission are the most important factors to influence the content dissemination delay. Copyright © 2013 John Wiley & Sons, Ltd.

Performance Modeling of Safety Messages Broadcast in Vehicular Ad Hoc Networks

In vehicular ad hoc networks (VANETs), because all vehicles in range are shown as destination nodes and less time is spent for the medium access process, broadcast communication is considered a highly appropriate technique for the dissemination of safety messages in such networks. However, the lack of request-to-send/clear-to-send handshaking and packet acknowledgment makes the communication more vulnerable to interferences, thus resulting in lower communication reliability. In this paper, we present an analytical model for the performance evaluation of safety message dissemination in vehicular ad hoc networks with two priority classes. In particular, considering the IEEE 802.11 broadcast protocol and using 2-D Markov modeling, we derive the joint distribution of the numbers of low-priority periodic messages, which are in transmission mode and in a backoff process in a highway. Then, the result is used to derive the average dissemination delay of high-priority event-driven messages in the presence of the low-priority traffic in the network. The results are helpful in determining a good tradeoff between network parameters such as vehicles' transmission range, safety traffic generation rate, and medium access control (MAC) parameters to satisfy the required delay bounds for the critical high-priority traffic.

Lightweight, efficient, robust epidemic dissemination

Today’s intensive demand for data such as live broadcast or news feeds requires efficient and robust dissemination systems. Traditionally, designs focus on extremes of the efficiency/robustness spectrum by either using structures, such as trees for efficiency or by using loosely-coupled epidemic protocols for robustness.We present Brisa, a hybrid approach combining the robustness of epidemics with the efficiency of structured approaches. Brisa implicitly emerges embedded dissemination structures from an underlying epidemic substrate. The structures’ links are chosen with local knowledge only, but still ensuring connectivity. Failures can be promptly compensated and repaired thanks to the epidemic substrate, and their impact on dissemination delays masked by the use of multiple independent structures.Besides presenting the protocol design, we conduct an extensive evaluation in real environments, analyzing the effectiveness of the structure creation mechanism and its robustness under dynamic conditions. Results confirm Brisa as an efficient and robust approach to data dissemination in large dynamic environments.

Achieving Efficient Flooding by Utilizing Link Correlation in Wireless Sensor Networks

Although existing flooding protocols can provide efficient and reliable communication in wireless sensor networks on some level, further performance improvement has been hampered by the assumption of link independence, which requires costly acknowledgments (ACKs) from every receiver. In this paper, we present collective flooding (CF), which exploits the link correlation to achieve flooding reliability using the concept of collective ACKs. CF requires only 1-hop information at each node, making the design highly distributed and scalable with low complexity. We evaluate CF extensively in real-world settings, using three different types of testbeds: a single-hop network with 20 MICAz nodes, a multihop network with 37 nodes, and a linear outdoor network with 48 nodes along a 326-m-long bridge. System evaluation and extensive simulation show that CF achieves the same reliability as state-of-the-art solutions while reducing the total number of packet transmission and the dissemination delay by 30%-50% and 35%-50%, respectively.

The Small Molecule Inhibitor of VLA4 TBC3486 Sensitizes Resistant ALL to Chemotherapy

AbstractAbstract 1500Significant progress notwithstanding, drug resistant acute lymphoblastic leukemia (ALL) remains a therapeutic challenge, as well as acute and long-term off-target toxicity of anti-ALL therapies can be dose-limiting or debilitating. Therefore, the development of more targeted therapies is desirable. We recently provided evidence that chemotherapy resistance of ALL cells can be partly overcome by interfering with the function of VLA4, the alpha4beta1 integrin, in vivo. In those studies, we used the anti-functional antibody Natalizumab. We extended our studies to an alternative VLA4 inhibitor, the novel non-peptidic small molecule TBC3486. Previous in vitro assays and molecular modeling studies indicate that TBC3486 behaves as a ligand mimetic, competing with VCAM-1 for the MIDAS site of VLA-4. As such, the compound has been shown to be efficacious in VLA-4 dependent models of inflammatory and autoimmune disease. The potential usefulness of this novel inhibitor in leukemia treatment was tested in our established in vitro and in vivo assays. LAX7R cells, primary pre-B-ALL with a normal karyotype from a patient with an early relapse, were used throughout for the studies reported here. LAX7R cells were treated with 25μM TBC3486 or THI0012 control, the inactive enantiomer of TBC3486, and seeded onto plates coated with human VCAM-1. Adhesion, scored after 2 days, was significantly inhibited by TBC3486 compared to control treated cells (7.9%±4.0 vs 95.4%±8.0; p=0.003). Proliferation rate and cell viability were unaffected by the treatments. In a co-culture system of LAX7R cells with OP9 stroma cells, which we use as an in vitro model of stroma-mediated chemotherapy resistance, we assessed differential effects of VDL (Vincristine, Dexamethasone, L-Asparaginase) on leukemia cell survival in the presence or absence of TBC3486. Stromal adhesion significantly protected LAX7R cells against VDL chemotherapy; this effect was significantly attenuated by TBC3486 compared to the control as determined by Trypan blue exclusion of dead cells (Cell viability of 39.9%±5.1 vs. 57.2±1.8; p=0.02). After these encouraging observations, we next evaluated the benefit of TBC3486 on leukemia progression in a xenotransplant assay. LAX7R cells were lentivirally labelled with luciferase for in vivo tracking and injected into NOD/SCID hosts. Three days after leukemia cell transfer, mice received either TBC3486 or THI0012 (control) (10mg/kg/d) daily for 2 weeks (intraperitoneally), with or without VDL chemotherapy. This experiment is in progress, but already survival of leukemia-bearing mice was significantly prolonged, from a median survival time (MST) for control mice of 33 days post-leukemia injection to a MST of 47 days post-leukemia injection for TBC3486 treated mice (p=0.02). Similarly, bioluminescence imaging revealed a marked delay of leukemia cell dissemination (p<0.0001). Taken together, our data demonstrate that small molecule inhibition of VLA4 using the novel TBC3486 is a suitable approach for targeting of chemotherapy-resistant leukemia. Further studies are warranted to understand and evaluate preclinically adjuvant small molecule inhibition of integrins to overcome relapse of ALL. Disclosures:No relevant conflicts of interest to declare.