A directional data dissemination protocol for vehicular environments

Vehicular networks have become a promising platform for large-scale urban sensing. On-demand data retrieval is a crucial operation for many applications of vehicular networks. It is particularly challenging, however, to achieve high performance of on-demand data retrieval in sparse vehicular networks. Data replication based on random linear network coding can solve the coupon collection problem but suffers the problem of unnecessary data replications which waste the precious communication opportunities of sparse vehicular networks. With real traces we reveal the existence of community structures in vehicular networks, which causes excessive linearly correlated blocks. Motivated by the important observation, we propose a community-aware data replication scheme based on random linear network coding. To reduce the excessive correlated coded blocks because of community structures, we make probabilistic control on the data replication phase, taking the community structures into account. It is demonstrated through extensive simulations that the community-aware scheme can effectively save up to 50% communication opportunities whiling achieving high performance of on-demand data retrieval.

Data dissemination from multiple sources to mobile sinks is fundamental and challenging in WSN applications due to limited energy supply of sensor nodes and sink mobility. Previous data dissemination protocols either rely on an energy-consuming coordinate system or build an inefficient backbone. In this paper, we propose a hierarchical role-based data dissemination (HRDD) protocol in wireless sensor networks. In HRDD, a small number of sensor nodes are assigned to serve as cluster heads and agents to form the data dissemination backbone and mitigate unnecessary query forwarding. In addition, HRDD designs an efficient data delivery mechanism that provides shorter paths to accelerate data delivery as well as reduce the number of data transmissions. An adaptive backbone maintenance mechanism is also introduced for low-energy cluster heads and agents to reduce their load, thereby prolonging the network lifetime. The experimental results show that HRDD achieves the longer network lifetime, the shorter delay, and the high success ratio compared to the prior work.

HashQuery, a Hash-area-based data dissemination protocol, was designed in wireless sensor networks. Using a Hash function which uses time as the key, both mobile sinks and sensors can determine the same Hash area. The sensors can send the information about the events that they monitor to the Hash area and the mobile sinks need only to query that area instead of flooding among the whole network, and thus much energy can be saved. In addition, the location of the Hash area changes over time so as to balance the energy consumption in the whole network. Theoretical analysis shows that the proposed protocol can be energy-efficient and simulation studies further show that when there are 5 sources and 5 sinks in the network, it can save at least 50% energy compared with the existing two-tier data dissemination(TTDD) protocol, especially in large-scale wireless sensor networks.

Data dissemination in VANETs has recently attracted much attention. The important problem is the proper protocol performance in different network density. The most of existing protocol are struggling to perform well in sparse networks. In this paper, a new protocol was purposed for data dissemination in VANETs. This protocol is simple and does not struggle with problem in sparse network. A proper handshaking algorithm is also designed for congestion avoiding during vehicle's communication. The results show that purposed algorithm success depends on vehicle's speed. If the vehicle's speed is increased, the vehicle should travel more distance for message decoding. The vehicle's speed increasing also causes less delay in message decoding. The vehicle's speed should be set for balance between delay and decoding distance.

Wireless sensor network-based (WSN-based) applications need an efficient and reliable data dissemination service to facilitate maintenance, management and data distribution tasks. As WSNs nowadays are becoming pervasive and data intensive, bulk data dissemination protocols have been extensively studied recently. This paper provides a comprehensive survey of the state-of-the-art bulk data dissemination protocols. The large number of papers available in the literature propose various techniques to optimize the dissemination protocols. Different from the existing survey works which separately explores the building blocks of dissemination, our work categorizes the literature according to the optimization purposes: Reliability, Scalability and Transmission/Energy efficiency. By summarizing and reviewing the key insights and techniques, we further discuss on the future directions for each category. Our survey helps unveil three key findings for future direction: (1) The recent advances in wireless communications (e.g., study on cross-technology interference, error estimating codes, constructive interference, capture effect) can be potentially exploited to support further optimization on the reliability and energy efficiency of dissemination protocols; (2) Dissemination in multi-channel, multi-task and opportunistic networks requires more efforts to fully exploit the spatial-temporal network resources to enhance the data propagation; (3) Since many designs incur changes on MAC layer protocols, the co-existence of dissemination with other network protocols is another problem left to be addressed.

One of the major challenges in facing the design of disseminating protocol for Wireless Sensor Networks (WSNs) is to find an energy efficiency way. Recently, several researches have been studied for this issue, and SPMS, that outperforms the well-known protocol SPIN, specially is a representative protocol. Also one of many characters of SPMS is the using of the shortest path to minimize the energy consumption. However, since it repeatedly uses the same path as the shortest path, the maximizing of the network lifetime is impossible, though it reduces the energy consumption. In this paper, we propose a novel data dissemination protocol, called Energy and Distance Aware protocol based on SPIN (EDAS), that guarantees energy-efficient data transmission and maximizes network lifetime. EDAS solves the network lifetime problem by using the residual energy and the efficient distance between nodes to determine a path for data dissemination. The simulation results show that EDAS guarantees energy-efficient transmission and moreover increases the network lifetime by approximately 69% than that of SPMS.KeywordsWireless Sensor NetworksData Dissemination ProtocolEnergy EfficiencyLifetimeSPMS

Low density of vehicles in rural areas and during the periods when the vehicle traffic is low in cities (such as at night) makes the classical ad-hoc network algorithms impractical for Vehicular Ad Hoc Networks. End-to-end connectivity requirement of these algorithms causes this deflection. Connections get broken when a suitable network element isn't available for data transfer. This problem which occurs in the low dense Vehicular Networks can be solved by using delay tolerant approaches in routing algorithms. By using the store-carry-forward method, data is carried by network elements until a suitable network element has been found. By this way, network connectivity is provided in a delayed manner between the vehicles which are momentarily not connected. In this paper, the impact of delayed transfer of data to an end-to-end transfer and the impact of data lifetime to the network performance are examined. Considering the speed of the vehicles and the desired throughput, lifetime of data is determined according to the network connectivity. Results contributes to the fulfilment of the Quality of Service (QoS) requirements in Vehicular Network applications.

Classical ad-hoc network algorithms become impractical for Vehicular Ad Hoc Networks when density of vehicles is low in rural areas and during the periods when the vehicle traffic is low in cities (such as at night). End-to-end connectivity requirement of these algorithms causes deflection. Connections get broken when a suitable network element isn't available for data transfer. This problem which occurs in low dense partially connected Vehicular Ad hoc Networks can be solved by using delay tolerant approaches in routing algorithms. By using the store-carry-forward method, data is carried by network elements until a suitable network element is found. By this way, network connectivity is provided in a delayed manner between momentarily disconnected vehicles. In this paper, the impact of delayed transfer of data to an end-to-end transfer and the impact of data lifetime to the network performance are examined. Considering the speed of vehicles and the desired throughput, lifetime of data is determined according to the network connectivity. The results of this study contribute to the fulfilment of the Quality of Service (QoS) requirements in Vehicular Ad Hoc Network applications.

Vehicle-to-vehicle networks have gained significant interest in recent times from researchers all around the world. V2V/V2I are emerging as an efficient solution for achieving road safety and securely transmitting data from one vehicle to other. However, in such opportunistic environments such as a sparse vehicular network where disruption, dynamic network topology, fast vehicle movement, and environmental conditions are the major concerns, data forwarding is extremely challenging. Traditional ad-hoc routing protocols like Ad hoc On-Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) fail to deliver in such laborious conditions. Routing protocols of Delay/Disruption Tolerant Networks(DTN) exploit the Store-Carry-Forward Mechanism (SCF) strategy in these cases. Taking advantage of temporary connections to disseminate information is the focus of DTN. DTN helps to increase information propagation coverage in sparse areas where there are very few devices. In this paper, we first compare the performance of AllJoyn framework and Direct Delivery protocol in a single-hop scenario and then draw the attention towards a multi-hop scenario by comparing other three routing protocols that use DTN as the underlying paradigm. These protocols are Flooding, Epidemic, and PRoPHET. The performances are evaluated by transmitting the files of size 1, 4, and 10 MB from a static sender to a mobile receiver in the multi-hop scenario. We also develop an Android application that contains the implementation of these routing protocols along with file sharing functionality. From the outcomes of this experiment, it can be said that Epidemic routing protocol performs the best in our considered multi-hop scenario in terms of transfer delay, coverage, and throughput whereas, Direct Delivery routing protocol performs better than AllJoyn in single-hop communication.

Integrating vehicular ad hoc network and 3G networks helps to use suitable characteristics of networks in exchanging information. In the proposed integrated network, mobile gateways are used as gateways between two networks. Selecting optimum network and gateway is the key point in the phase of vertical handover decision-making process. The multi-criteria algorithms provide simultaneous attention to several important aspects of vertical handover process which improves system efficiency in accordance with the objectives of the defined heterogeneous network. In the proposed method, analytic hierarchy process method is used to determine the weights of the criteria and the modified VIKOR (from Serbian: VIseKriterijumska Optimizacija i Kompromisno Resenje that means: Multi-criteria Optimization and Compromise Solution, with pronunciation: VIKOR) method is used for decision making in heterogeneous networks. The simulation results show that the proposed algorithm is suitable for selecting the optimum gateway in a heterogeneous wireless networks and it improves the average number of vertical handovers, average delay, and throughput in sparse vehicular networks.

With the growth of large urban centers, some problems arise and solutions must be sought to contain them. In this context, traffic congestion is one such problem, where road infrastructure does not follow the high growth in the number of vehicles. Traffic Management Systems (TMS) arise to mitigate traffic-related problems, with automatic detection of slow roadways and vehicle rerouting to avoid such routes. Such applications are supported by the Vehicular Ad hoc NETworks (VANETs), where traffic information are disseminated between the vehicles or central server, and thus the better decisions about traffic management can be made. However, the data dissemination in VANETs is a challenging task, due to the short-range communication and high node mobility. Thus, this paper introduces a protocol for Data Dissemination based on Metrics of Complex Networks, called CRONOS. It provides data dissemination of traffic data with low overhead and high coverage. Simulation results show that CRONOS reduced the number of transmissions by 95%, the congestion time by 48.95%, and travel time by 18.11% for a TMS application.

In this paper, we propose a data dissemination protocol for asynchronous duty-cycling wireless sensor networks. In an asynchronous duty-cycling network, each node independently selects its wake-up time. In this environment, data dissemination becomes energy consuming, because broadcasting a packet does reach all neighbors but only the neighbors that are awake at the time. A node can forward its packet to all neighbors by continuously transmitting the packet for a whole wake-up interval, but it leads to high energy consumption and high dissemination delay. The idea proposed in this paper is to use opportunistic forwarding, where each node forwards the packet to a neighbor that wakes up early and receives the packet. Each node forwards the packet, as long as there is a neighboring node that has not received the packet yet. The main benefit of this opportunistic forwarding-based dissemination is that every time a packet is disseminated, it may take a different path to reach the nodes. At the beginning of dissemination, a sender needs to transmit for a very short duration of time because there are plenty of neighboring nodes to receive the packet. As more nodes receive the packet, the transmit duration of the sender becomes longer, thus consuming more energy. Since the order of dissemination is different every time, energy consumption is naturally balanced among the nodes, without explicit measures. Through extensive simulations, we show that the proposed protocol achieves longer network lifetime and shorter dissemination delay compared to other dissemination protocols in various network environments.

The popularity of concurrent transmissions (CT) has soared after recent studies have shown their feasibility on the four physical layers specified by BLE 5, hence providing an alternative to the use of IEEE 802.15.4 for the design of reliable and efficient low-power wireless protocols. However, to date, the extent to which physical layer properties affect the performance of CT has not yet been investigated in detail. This article fills this gap and provides an extensive study on the impact of the physical layer on CT-based solutions using IEEE 802.15.4 and BLE 5. We first highlight through simulation how the impact of errors induced by relative carrier frequency offsets on the performance of CT highly depends on the choice of the underlying physical layer. We then confirm these observations experimentally on real hardware and with varying environmental conditions through an analysis of the bit error distribution across received packets, unveiling possible techniques to effectively handle these errors. We further study the performance of CT-based data collection and dissemination protocols in the presence of RF interference on a large-scale testbed, deriving insights on how the employed physical layer affects their dependability.

A Vehicular Ad Hoc Network (VANET) is a subclass of Mobile Ad Hoc Networks, which provides wireless communication among vehicles as well as between vehicles and roadside units. Providing safety, traffic efficiency and user comfort for drivers and passengers are promising goals of these networks. To reach these goals many envisaged applications for VANETs will rely on data dissemination, turning this task into an essential service. However, due to some inherent characteristics of VANETs, such as intermittent connectivity, highly dynamic topology, and diverse network densities, data dissemination is a challenging activity in this kind of network. Although data dissemination has been extensively studied in the literature, existing solutions do not effectively address the broadcast storm and network partition problems when considered together. To deal with both problems, we propose a network partition-aware geographical data dissemination protocol, which eliminates the broadcast storm and maximizes the data dissemination capability across network partitions with short delays and low overhead. The proposed algorithm is able to autonomically adjust message transmissions in the network. Simulation results show that our proposed approach provides good efficiency with respect to the coverage of event processing, delay and overhead.

This paper considers the basic $\mathcal{PULL}$ model of communication, in which in each round, each agent extracts information from few randomly chosen agents. We seek to identify the smallest amount of information revealed in each interaction (message size) that nevertheless allows for efficient and robust computations of fundamental information dissemination tasks. We focus on the Majority Bit Dissemination problem that considers a population of $n$ agents, with a designated subset of source agents. Each source agent holds an input bit and each agent holds an output bit. The goal is to let all agents converge their output bits on the most frequent input bit of the sources (the majority bit). Note that the particular case of a single source agent corresponds to the classical problem of Broadcast. We concentrate on the severe fault-tolerant context of self-stabilization, in which a correct configuration must be reached eventually, despite all agents starting the execution with arbitrary initial states. We first design a general compiler which can essentially transform any self-stabilizing algorithm with a certain property that uses $\ell$-bits messages to one that uses only $\log \ell$-bits messages, while paying only a small penalty in the running time. By applying this compiler recursively we then obtain a self-stabilizing Clock Synchronization protocol, in which agents synchronize their clocks modulo some given integer $T$, within $\tilde O(\log n\log T)$ rounds w.h.p., and using messages that contain $3$ bits only. We then employ the new Clock Synchronization tool to obtain a self-stabilizing Majority Bit Dissemination protocol which converges in $\tilde O(\log n)$ time, w.h.p., on every initial configuration, provided that the ratio of sources supporting the minority opinion is bounded away from half. Moreover, this protocol also uses only 3 bits per interaction.