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Delay Tolerant Network (DTN) provides communication in environments composed of nodes with heterogeneous characteristics such as frequent disconnections, limited transmission range, dynamic topology, and scarce resources. Data delivery is achieved via the mobility of nodes by employing multi-copy protocols in which each node is allowed to create and transmit multiple copies of each message. The data is delivered at a higher consumption of node energy, buffer space, and network bandwidth. Similarly, buffer space is a critical resource to store and carry messages. Effective management can reduce message drops and increase delivery rate. The existing techniques observe message transmissions to evaluate energy consumption and basic buffer management policies to overcome congestion. In this paper, we have proposed an Energy Estimation based Routing Protocol (EERP) in which instead of number of transmissions the energy quota has been assigned to each message. In addition, buffer management of DTN node has been considered more critical. Therefore, we have proposed a buffer management policy in which messages are dropped based on their level of energy consumption. The simulation results prove that the proposed EERP has performed better in terms of increasing delivery ratio, buffer time average, and reducing message transmission, drop, and hop count average. [ABSTRACT FROM AUTHOR]

Delay Tolerant Network offers communication architecture for scenarios where attaining uninterrupted connectivity between source and destination is challenging due to dynamic topology, short transmission range, and mobility of nodes. The messages are delivered by a store, carry, and forward mechanism in which the node store the messages in its buffer, and carries them while moving and forward to its opportunistically connected peers. The buffer space is limited, and the stored messages are dropped to overcome congestion. The existing buffer management policies have utilized the message header data fields to compute heuristic metrics, or probability measures and have not focused on incorporating community characteristics in designing algorithms. In this paper, we have proposed a Social Community Buffer Management Policy for Delay Tolerant Networks in which the community metric consisting of Global Rank Value (GRV) and Local Rank Value (LRV) has been introduced. The GRV is the ability of any individual node to encounter the community in which the message destination resides. Similarly, LRV is the ability of a node to directly connect to the message destination. The congested node does not drop messages for which it has higher GRV and LRV values than predefined thresholds. Furthermore, we have integrated a message-locking mechanism in which the combination of lock variables such as Source Drop Lock, Must Accommodate Lock, Local Rank Lock, and Global Rank Lock are introduced within the message header. We have performed the simulation of existing BMSS, DOA, LIFO, MOFO, Ndrop, SHLI, and DLA with SCBM under real-time mobility scenarios. The simulation result proves the proposed SCBM performs better in terms of increasing delivery rate, buffer time average, and reducing overhead, message transmissions, and message drop. [ABSTRACT FROM AUTHOR]

In Cooperative Vehicle Infrastructure System (CVIS), the roadside unit (RSU) obtains many kinds of monitoring data through observation equipment carried by the RSU. The monitoring data from RSUs are transmitted to an RSU that is connected to the backbone network using the "store–carry–forward" scheme through the mobile vehicle. The monitoring data obtained by RSUs are timely, and different types of monitoring data have corresponding timelines. Reducing end-to-end delays to ensure more packets can be transmitted before deadlines is challenging. In this paper, we propose a Distributed Packet Scheduling Scheme for Delay-Packets Queue Length Tradeoff System (DDPS) in CVIS to solve the multi-RSU-distributed packet transmission problem. We also establish the vehicle speed state, vehicle communication quantity prediction, data arrival, and end-to-end delay minimization models. After Lyapunov's optimization theory transformed the optimization model, a knapsack problem was described. The simulation results verified that DDPS reduced the end-to-end average delay and ensured the data queue's stability under packet deadline conditions. [ABSTRACT FROM AUTHOR]

Vehicular Ad Hoc Networks (VANETs) are increasingly playing a fundamental role in improving driving safety. However, VANETs in a sparse environment may add risk to driving safety. The probability of a low density of vehicles in a rural area at midnight is very high. Consequently, the packet will be lost due to the lack of other vehicles, and the arrival of the following vehicles in the accident area is unavoidable. To overcome this problem, VANET is integrated with Wireless Sensor Network (WSN). The most challenging features of VANETs are their high mobility. This high mobility causes sensor nodes to consume most of their energy during communication with other nodes, leading to frequent network disconnectivity. With the evolution of VANET and WSN, the Store/Carry-Forward (SCF) paradigm has emerged as an exciting research area in the Delay Tolerant Networks (DTNs) to solve network disconnectivity. This paper proposes the Energy-Mobility-Connectivity aware routing protocol (EMCR) for a hybrid network of VANET-WSN. A comprehensive performance analysis that considers realistic propagation models and real city scenario traffic is performed in NS3. The simulation results show that the SCF mechanism is essential in the EMCR protocol to maximize the delivery ratio and minimize energy consumption and overhead. [ABSTRACT FROM AUTHOR]

Delay Tolerant Network (DTN) establishes the communication framework in environments where source and destination cannot establish the end-to-end path due to the limited transmission range, frequent disconnections, and network partitioning. The messages are delivered to their destinations by adopting a store, carry and forward paradigm in which the node stores the arriving message in its buffer, carries it while moving, and forwards on connecting to other nodes. The DTN multi-copy protocols diffuse the several message copies on all connected nodes and deplete the network resources such as buffer space, bandwidth, and energy. This resource consumption is controlled by incorporating a social community message forwarding technique. The node employs the global rank forwarding metric while moving outside the community and shifts to the local rank forwarding metric while moving within the community. This method produces congestion in scenarios where the node continues message replications on higher global and local rank peers. As a result, more messages are dropped, and message delivery is reduced. This paper presented the Message Locking Routing Protocol for Delay Tolerant Network (CTML). The CTML controls the message forwarding process by employing the Local Rank Lock (LRL) and Global Rank Lock (GRL). The Local Rank Lock (LRL) controls the message transmission during node mobility within the community whereas Global Rank Lock (GRL) refrains the message forwarding during node mobility outside the community. Thus, the small number of transmissions reduces congestion. Similarly, CTML control message drop by using Message Drop Lock (MDL) where a node cannot drop a message with higher global rank or local rank values. Finally, the delivery ratio has been increased by using Deliver to Destine Lock (DDL) lock where a node with higher threshold values to meet the destination is enforced to forward the message directly to its destination. The simulation results prove that the proposed CTML has performed better in terms of reducing message transmissions , message drop, hop-count average, overhead, and raising delivery ratio. [ABSTRACT FROM AUTHOR]

In Cooperative Vehicle Infrastructure System (CVIS), the roadside unit (RSU) obtains many kinds of monitoring data through observation equipment carried by the RSU. The monitoring data from RSUs are transmitted to an RSU that is connected to the backbone network using the “store–carry–forward” scheme through the mobile vehicle. The monitoring data obtained by RSUs are timely, and different types of monitoring data have corresponding timelines. Reducing end-to-end delays to ensure more packets can be transmitted before deadlines is challenging. In this paper, we propose a Distributed Packet Scheduling Scheme for Delay-Packets Queue Length Tradeoff System (DDPS) in CVIS to solve the multi-RSU-distributed packet transmission problem. We also establish the vehicle speed state, vehicle communication quantity prediction, data arrival, and end-to-end delay minimization models. After Lyapunov’s optimization theory transformed the optimization model, a knapsack problem was described. The simulation results verified that DDPS reduced the end-to-end average delay and ensured the data queue’s stability under packet deadline conditions.

Vehicular Ad Hoc Networks (VANETs) are increasingly playing a fundamental role in improving driving safety. However, VANETs in a sparse environment may add risk to driving safety. The probability of a low density of vehicles in a rural area at midnight is very high. Consequently, the packet will be lost due to the lack of other vehicles, and the arrival of the following vehicles in the accident area is unavoidable. To overcome this problem, VANET is integrated with Wireless Sensor Network (WSN). The most challenging features of VANETs are their high mobility. This high mobility causes sensor nodes to consume most of their energy during communication with other nodes, leading to frequent network disconnectivity. With the evolution of VANET and WSN, the Store/Carry-Forward (SCF) paradigm has emerged as an exciting research area in the Delay Tolerant Networks (DTNs) to solve network disconnectivity. This paper proposes the Energy-Mobility-Connectivity aware routing protocol (EMCR) for a hybrid network of VANET-WSN. A comprehensive performance analysis that considers realistic propagation models and real city scenario traffic is performed in NS3. The simulation results show that the SCF mechanism is essential in the EMCR protocol to maximize the delivery ratio and minimize energy consumption and overhead.

We consider intermittently connected vehicular networks (ICVNs) in which base stations (BSs) are installed along a highway to connect moving vehicles with internet. Due to the deployment cost, it is hard to cover the entire highway with BSs. To minimize the outage time in the uncovered area (UA), several store-carry-forward (SCF) schemes have been proposed in which a vehicle is selected to act as a relay by buffering data to be relayed to a target vehicle in the UA. In this paper, we propose a full-duplex (FD) SCF scheme that exploits the relay's ability to simultaneously receive and transmit in order to improve the effective communication time (ECT) with the target vehicle and accordingly deliver more data to it in the UA. The optimal power allocation (PA) that maximizes the ergodic capacities of the links is determined and the amount of data that can be buffered inside the BS coverage and can be delivered by each relay candidate to the target vehicle in the UA is found. Since the relay cannot deliver more data in the UA than what can be buffered inside the coverage, the performance of each relay candidate is limited by the minimum of the two amounts and hence is used as a relay selection (RS) criteria. To reduce the computational complexity, an alternative RS scheme that selects the relay candidate that offers the highest ECT is proposed. As compared to half-duplex SCF schemes, simulation results show that the proposed FD schemes are capable of delivering significantly higher amount of data to the target vehicle in the UA.

In a Vehicular Adhoc Network (VANET), Road Side Units (RSUs) deployed along the highways are generally dispossessed from a permanent connection to grid-power and mostly the RSU operations are sustainable on alternative sources such as solar power, wind power, etc. The power consumption of RSU is dominated by the downlink (RSU-to-vehicle) communication cost and it is a function of RSU to vehicle distance. Moreover, the RSUs cannot cover entire highway segment due to high deployment cost and they leave an outage area in between neighboring RSUs. In this case, a target vehicle entering into an outage area with unserved requests can be served by selecting relay (store-carry-forward) vehicles. This paper proposes RSU assisted relay scheduling algorithm for faster data retrieval to the target vehicle while minimizing the RSU energy consumption. Firstly, a time slot based relay scheduling problem is formulated and then the NP-hardness of the problem is proved. Secondly, a greedy algorithm (GA) and a forward relay scheduler (FRS) are proposed to schedule the relay vehicles in forward direction (i.e. target moving direction). The GA selects the relay vehicles which are near to RSU and takes less time to reach the target vehicle. The FRS apply the concepts of Auction Theory to optimally assign the relay vehicles to time slots, that can jointly minimize RSU energy consumption and end-to-end delay to the target vehicle. Here, the Auction process allows the relay vehicles to bid for time slots by using their local information such as speed, location, cooperative cache size, direction, etc. Furthermore, the proposed Auction based RSU assisted relay scheduling (RRS) triggers the neighboring RSUs which can cooperate by sharing unserved data and schedule the relay vehicles driving in both forward and backward (i.e. opposite to target) directions in a bidirectional highway. Simulation results show that the efficacy of the proposed algorithms over other relay scheduling algorithms with respect to energy consumption, end-to-end delay and residual data delivery. [ABSTRACT FROM AUTHOR]

As energy supply on Unmanned Aerial Vehicle (UAV) is limited, energy efficient data transmission in UAV networks would be of great concern to the researchers. Nevertheless, UAV networks exhibit strong dynamic nature compared to ordinary Mobile Ad hoc Network (MANET), it is not rare that some nodes will be disjoint from other nodes from time to time. Under such circumstance, ordinary hop-by-hop routing schemes can not be used anymore, for there is no route existed from source to destination. Some solutions use store-carry-forward (SCF) routing to facilitate end to end data transmission. However, when should we use SCF routing, when we should use hop-by-hop routing if we taking energy into consideration? Is hop-by-hop routing always better than SCF? If it is good or not when the hop-by-hop routing is combined with the SCF routing? All these questions need to be answered. In this paper, we answered above questions by proposing three types of minimum energy consumption models of hop-by-hop routing, and two SCF routing models. We compared all these models and considered four tactics of combination modes for the transmissions in a rotary-wing UAV network. The researches show that two tactics have better performance than other modes in energy saving capabilities by reducing 70% at most with the hop-by-hop routing, and the transmission time of combination modes are in same scale compared with hop-by-hop routing. The two tactics are appropriate for different UAV networks respectively, in which the source UAV can or cannot get the GPS information of relay UAVs in the route. The research conclusion can also be used for the transmissions in a fixed-wing UAV network by modifying the energy consumption models of fixed wing UAV, which is different from rotary wing UAVs.

The delay tolerant network multi-copy protocols create and transmit multiple copies of each message that overload the buffer size, energy and bandwidth. The resource consumption is controlled by transmitting the messages to nodes having high encountering ability to meet their destinations. Hence, nodes loss energy only in transmitting and receiving messages and went to dead state. However, message transmission continues even though the destination is dead. This wastes the network resources because messages destining to dead node will not be able to find their destinations. The existing routing protocols focus on message transmissions and do not have any mechanism to detect inactive nodes or to stop massage replications destining to inactive nodes. In this paper we have proposed a routing protocol called as Energy Efficient Inactive Node Detecting Based Routing Protocol for Delay Tolerant Network (InD). The proposed protocol has employed the node mobility to detect inactive nodes. Moreover, an intelligent buffer management policy has been designed that detect and drop those messages which are destining to dead nodes. The real time mobility scenarios have been used to evaluate the performance of existing and proposed routing protocols under the metrics of message transmissions, message drop, and message delivery and hop count average. [ABSTRACT FROM AUTHOR]

Position-based routing has proven to be well suited for highly dynamic environment such as Vehicular Ad Hoc Networks (VANET) due to its simplicity. Greedy Perimeter Stateless Routing (GPSR) and Greedy Perimeter Coordinator Routing (GPCR) both use greedy algorithms to forward packets by selecting relays with the best progress towards the destination or use a recovery mode in case such solutions fail. These protocols could forward packets efficiently given that the underlying network is fully connected. However, the dynamic nature of vehicular network, such as vehicle density, traffic pattern, and radio obstacles could create unconnected networks partitions. To this end, we propose GeoDTN+Nav, a hybrid geographic routing solution enhancing the standard greedy and recovery modes exploiting the vehicular mobility and on-board vehicular navigation systems to efficiently deliver packets even in partitioned networks. GeoDTN+Nav outperforms standard geographic routing protocols such as GPSR and GPCR because it is able to estimate network partitions and then improves partitions reachability by using a store-carry-forward procedure when necessary. We propose a virtual navigation interface (VNI) to provide generalized route information to optimize such forwarding procedure. We finally evaluate the benefit of our approach first analytically and then with simulations. By using delay tolerant forwarding in sparse networks, GeoDTN+Nav greatly increases the packet delivery ratio of geographic routing protocols and provides comparable routing delay to benchmark DTN algorithms.

Wireless communication is essential for search and rescue operations in the aftermath of natural disasters. In post-disaster scenarios, unmanned aerial vehicles (UAVs) can be used to capture image and video data from the disaster area and transfer the data to a ground station, owing to their rapid mobility. However, packet forwarding is a challenge because of unstable links and intermittent connectivity in highly dynamic UAV networks. In this paper, we propose a location-aided delay tolerant routing (LADTR) protocol for UAV networks for use in post-disaster operations, which exploits location-aided forwarding combined with a store-carry-forward (SCF) technique. Ferrying UAVs are introduced to enable an efficient SCF, and this is the first attempt at introducing and using ferrying UAVs for routing in UAV networks, to the best of our knowledge. Ferrying UAVs improve the availability of connection paths between searching UAVs and the ground station, thus reducing end-to-end delays and increasing the packet delivery ratio. Future UAV locations are estimated based on the location and speed of UAVs equipped with a global positioning system. The forwarding UAV node predicts the position of the destination UAV node and then decides where to forward. The proposed LADTR ensures that the contact rate between UAV nodes remains high, which enables a high packet delivery ratio, and ensures single-copy data forwarding to avoid replication of each message. Our performance study shows that the proposed LADTR outperforms the four typical routing protocols reported in the literature in terms of packet delivery ratio, average delay, and routing overhead.

In search and rescue mission, micro aerial vehicles (MAVs) are typically used to capture image and video from an aerial perspective and transfer the data to the ground station. Because of the power limitation, a cluster of MAVs are required for a large search area, hence an ad-hoc wireless network must be maintained to transfer data more conveniently and fast. However, the unstable link and the intermittent connectivity between the MAVs caused by MAVs’ movement may challenge the packet forwarding. This paper proposes a delay tolerant packet forwarding algorithm based on location estimation for MAV networks, called DTNest algorithm. In the algorithm, ferrying MAVs are used to transmit data between MAVs and the ground station, and the locations of both searching MAVs and ferrying MAVs are estimated to compute the distances between the MAVs and destination. The MAV that is closest to the destination is selected greedy to forward packet. If a MAV cannot find the next hop MAV using the greedy strategy, the packets will be stored and re-forwarded once again in the next time slot. The experiment results show that the proposed DTNest algorithm outperforms the typical DTNgeo algorithm in terms of packet delivery ratio and average routing hops. [ABSTRACT FROM AUTHOR]

Mobile social network is a kind of social networks through which the nodes have some social features such as: gender, job, friendship relations, centrality, and so on. The nodes mobility, leads to avoid forming connected routes between the source and the destination all the times. Therefore, routing is one of the main challenges in these networks. In such networks for routing store–carry–forward pattern is used. In this method each node produces a packet or receives it from another node, carries it until it finds an appropriate opportunity, and delivers it to the encountered node when an opportunity occurs. During the time interval through which the node tries to find a good opportunity and carries the packet is called carry time. Most proposed routing methods have had some suggestions on store step or forward step. It seems that we can improve routing in these networks through considering carry time by the nodes. This means that the longer carry time of a node shows that it is not an appropriate candidate to redistribute the packet. In this paper a routing algorithm based on carry time (CTR) is proposed. In this method carry time by the nodes is saved for each packet. The proposed method was presented considering three states of single-copy and only based on carry time, single copy and based on carry time and the probability of encountering the nodes, and multi copy and quota based on carry time and encountering the nodes. The simulation results show that proposed method optimized regarding delivery ratio and the average delay compared to the related works. [ABSTRACT FROM AUTHOR]

The delay tolerant network Spray and Wait routing protocol minimizes resource consumption by defining the 'n' number of message transmission quota. However, with same transmission quota, a large-size message consumes more buffer space, bandwidth and energy. Similarly, existing buffer management policies consider message-size, arrival-time, hop-count and do not notice the congestion a message has produce in the network. In order to address the aforementioned issues, we have proposed a routing protocol called as resource refrain quota based routing protocol for delay tolerant network. The proposed protocol assigns the transmission energy quota to 'n' number of message copies. Moreover, message was transmitted just to those nodes having high probability value to meet message destination. We have also devised a mechanism to drop those messages which are responsible to produce the congestion. [ABSTRACT FROM AUTHOR]

A fully connected vehicular ad hoc network (VANET) establishes a strong foundation for the development of smart cities, where one of the main objectives is the improvement of the welfare of commuting passengers. The availability of a multi-hop path across a VANET system, through vehicle-to-vehicle communication, depends mainly on the vehicular density and the willingness of vehicles to cooperate with one another. This paper proposes to minimize the path availability's dependence on vehicular density and cooperation, by utilizing unmanned aerial vehicles (UAVs). Particularly, this paper explores, both mathematically as well as through an extensive simulation study, the advantages of exploiting UAVs as store-carry-forward nodes so as to enhance the availability of a connectivity path as well as to reduce the end-to-end packet delivery delay. The obtained results shed clear light on the benefits emanating from the coupling of UAVs with vehicles in the context of a highly promising, innovative, and hybrid vehicular networking architecture.

Data delivery in opportunistic networks requires robustness and resiliency due to the mobility and probabilistic propagation channels caused by fading. Besides the 100% data delivery, delivery with minimum delay, overhead, buffer consumption, and controlling unnecessary transmissions/replications are equally important. In this paper, we propose a data delivery solution for opportunistic networks. The solution comprises two main algorithms: store-carry-cooperative forward routing and information epidemic control. In the data forwarding, nodes proactively monitor and exploit the direct/two-hop cooperative forwarding opportunities and adaptively switch between the cooperative forwarding and reactive store-carry-forward routing. An information epidemics control algorithm, which provides earlier control signal distribution time and faster recovery rate, is also proposed. The susceptible-infected-recovered model is used to study the effectiveness of the proposed mechanism. Extensive network performance evaluation is conducted under a wide range of scenarios, which include fading environments, obstacle-constrained environments, and mobile social network environments. We show that: 1) the information epidemics control mechanism provides higher vaccination rate and recovery rate; 2) proactive replication incurs a number of unnecessary transmissions; 3) monitoring the vicinity and exploiting the opportunity shorten the data delivery delay; and 4) with the integrated solution, a robust data delivery is achieved and a substantial amount of unnecessary transmissions are well deterred.

Delay tolerant network is a type of network where the end-to-end path is not available from source to destination due to the node mobility, dynamic topology and network partitioning or such a path is highly unstable and may split almost immediately after it has been explored. In this background, existing ad hoc routing protocols would be unsuccessful. Therefore, the concept of store-carry-forward mechanism is utilized by introducing a new layer on the top of transport layer called as bundle layer. The bundle layer store message(s) in a finite size buffer for the long duration of time. As a result, node buffer runs out of space and drop messages to overcome congestion. In this paper, we aim to schedule the node buffer by using local knowledge-based buffer management policies called as best message-size selections buffer management policy. We have utilized the local information available in message header such as message-size to control the drop of messages. The evaluation of proposed policy with the existing DOA, DLA, LIFO, MOFO, N-drop and SHLI have been analyzed in ONE simulator in terms of reducing message drop, overhead, latency and raising the delivery ratio. [ABSTRACT FROM AUTHOR]

The Internet of Drones (IoD) aims to organize and control airspace to allow multiple drones to fly at the same time in a fair and organized way. Thus, applications such as drone delivery of goods are expected to work in urban environments safely. As a result, the airspace will have constant drone traffic, and the IoD will have its density linked to factors such as the day of the week and the time of day. Hence, the IoD is expected to present dense and sparse scenarios. In the case of sparse scenarios, drones may have difficulty communicating with each other and with the control station. Therefore, this work proposes a store–carry–forward protocol for Delay-Tolerant IoD, called IoDMix. Specifically, we use a multi-vehicle scenario to fill the communication gaps in IoD and integrate it into Intelligent Transportation Systems (ITS). In the urban scenario, it is expected the collaboration of distinct networks to improve their metrics. In this work, we consider a partnership between IoD, vehicular networks, public transport networks, and bicycle networks to form a heterogeneous network in situations where the IoD needs to be Delay-Tolerant (DTIoD). Our results show that the IoDMix protocol has a higher delivery rate when compared to a baseline protocol. To the best of our knowledge, this is the first work considering a routing protocol that uses multi-vehicle to fill IoD communication gaps. [ABSTRACT FROM AUTHOR]

A DTN node under multi copy protocols forwards a message to all connected nodes and improves message delivery at higher consumption of network resources. The probabilistic protocols control resource expenditure by transmitting a message only to nodes having high probability value to encounter its destination. The probability value is increased in terms of number of encounters and reduced by time interval since nodes last saw each other. The probability value computation does not consider impact of speed and number of hops a node has moved away from message destination. Similarly, node with low probability value to deliver a message continue its replication on high probable nodes. This replication produce congestion and messages are dropped before reaching their destinations. In this paper, we have proposed a routing protocol known as Probabilistic and Replication Based Locking Routing protocol for Delay Tolerant Network (RBL). The RBL defines a replication based locking method in which message transmissions and drop have been reduced via novel concept of locking. Moreover, probability value of a node has been computed by dynamic parameters such as the number of hops a node is away from message destination, speed and time elapsed since nodes last saw each other. The RBL has been compared with state-of-art routing protocols under renowned real time mobility traces. The proposed RBL has reduced message transmissions, message drop, hop count, end-to-end delay and increases message delivery. [ABSTRACT FROM AUTHOR]

In opportunistic networks due to the inconsistency of the nodes link, routing is carried out dynamically and we cannot use proactive routes. In these networks, nodes use opportunities gained based on store-carry-forward patterns to forward messages. Every node that receives a message when it encounters another node makes decision regarding the forwarding or not forwarding the node encountered. In some previous methods, the recognition of whether encounter with current node is considered as an appropriate opportunity or not has been carried out based on the comparison of the probability of carrier node and the node encountered. In these methods, if the message is delivered to the encountered node, a better opportunity would be lost. To fight with this challenge we have posed CPTR method by using conditional probability tree method through which in addition to the probability of the delivery of carrier and encountered nodes' message delivery, the opportunities for after encounter will be involved in messages' forwarding. Results of simulation showed that the proposed method can improve the ratio of delivery and delay of message delivery compared to other similar methods in networks with limited buffer. [ABSTRACT FROM AUTHOR]

Thanks to the research on Vehicular Ad Hoc Networks (VANETs), we will be able to deploy applications on roadways that will contribute to energy efficiency through a better planning of long trips. With this goal in mind, we have designed a gas/charging station advertising system, which takes advantage of the broadcast nature of the network. We have found that reducing the number of total sent packets is important, as it allows for a better use of the available bandwidth. We have designed improvements for a distance-based flooding scheme, so that it can support the advertising application with good results in sparse to dense roadway scenarios.

The recent release of standards for vehicular communications will hasten the development of smart cities in the following years. Many applications for vehicular networks, such as blocked road warnings or advertising, will require multi-hop dissemination of information to all vehicles in a region of interest. However, these networks present special features and difficulties that may require special measures. The dissemination of information may cause broadcast storms. Urban scenarios are especially sensitive to broadcast storms because of the high density of vehicles in downtown areas. They also present numerous crossroads and signal blocking due to buildings, which make dissemination more difficult than in open, almost straight interurban roadways. In this article, we discuss several options to avoid the broadcast storm problem while trying to achieve the maximum coverage of the region of interest. Specifically, we evaluate through simulations different ways to detect and take advantage of intersections and a strategy based on store-carry-forward to overcome short disconnections between groups of vehicles. Our conclusions are varied, and we propose two different solutions, depending on the requirements of the application. [ABSTRACT FROM AUTHOR]

Delay Tolerant Network (DTN) is a kind of network in which the source may not be able to establish the stable and uninterrupted path to destination due to network partitioning, dynamic topology change and frequent disconnections. In order to dealt disruption and disconnections a store, carry and forward paradigm is used in which node stores the incoming messages in its buffer, carries it while moving and forward when comes within the transmission range of other nodes. Message forwarding contributes and important role in increasing its delivery. For instance, probabilistic routing protocol forwards message to a node having high probability value to meet message destination. These protocols cannot handle a situation in which the node continually transmits messages even the probability difference is very small. In this paper, we have proposed a routing protocol known as Threshold Based best custodian Routing Protocol (TBbcRP) for delay tolerant network. We have proposed a threshold-based method to compute the quality value which is the ability of node to carry message. A self-learning mechanism has been used to remove the delivered messages from the network. Moreover, a buffer aware mechanism has been used that make sure availability of buffer space at receiver before message transmission. We have compared the performance of TBbcRP with Epidemic, PRoPHET and Delegated Forwarding. The proposed TBbcRP outperforms in terms of maximizing the delivery probability, reducing number of transmissions and message drop. [ABSTRACT FROM AUTHOR]

Delay-tolerant networks (DTNs) are distinguished by low connectivity and/or unreliable links, dynamic topology change and network partitioning. Therefore, each node transmits the multiple copies of the message to increase its delivery likelihood. This phenomenon produces congestion that results in the dropping of earlier stored messages. The objective of buffer management policy is to determine which message should be eliminated when the buffer overflow happens. The existing buffer management policies can be divided into two categories: (i) local knowledge-based and (ii) global knowledge based. In a DTN environment, getting global knowledge is impossible and local knowledge-based policies are more practical. This study focuses on the local knowledge-based policies in order to reduce the drop ratio and maximize the delivery. In this paper, we presented a buffer scheduling policy called as weight based drop policy. In this proposed scheme, we dynamically adjust message weight criteria assuming message's properties, which are message size, remaining time-to-live, message stay time in queue, hop count, and replication count. In order to utilize the buffer efficiently we use weight criteria for finding the most appropriate message for drop and rank the forward messages to its neighboring nodes. The simulation performed in ONE simulator. The simulation results of weight based drop policy by using map based mobility movement outperformed the existing DLA, FIFO, MOFO, SHIL and LIFO in terms of reducing a number of transmission, dropped messages, overhead and enhanced delivery and buffer time average. [ABSTRACT FROM AUTHOR]

The delegated forwarding (DF) curb transmissions by forwarding the message to a node that holds high quality value seen by the message. However, DF assumes infinite buffer space that is not possible in real time applications. In addition, quality value computation considers the encountering history and does not account for additional network parameters such as aging and transitive connectivity. In this paper, we have proposed a routing protocol called as DF++ that compute quality value based on probabilistic model used in PRoPHET protocol and forwards the message to current node by adaptive computation of available buffer space. We have compared performance of DF++ with DF, Epidemic and PRoPHET routing protocols. The proposed DF++ has higher delivery probability and fewer message drop and transmissions. [ABSTRACT FROM AUTHOR]

The recent release of standards for vehicular communications will hasten the development of smart cities in the following years. Many applications for vehicular networks, such as blocked road warnings or advertising, will require multi-hop dissemination of information to all vehicles in a region of interest. However, these networks present special features and difficulties that may require special measures. The dissemination of information may cause broadcast storms. Urban scenarios are especially sensitive to broadcast storms because of the high density of vehicles in downtown areas. They also present numerous crossroads and signal blocking due to buildings, which make dissemination more difficult than in open, almost straight interurban roadways. In this article, we discuss several options to avoid the broadcast storm problem while trying to achieve the maximum coverage of the region of interest. Specifically, we evaluate through simulations different ways to detect and take advantage of intersections and a strategy based on store-carry-forward to overcome short disconnections between groups of vehicles. Our conclusions are varied, and we propose two different solutions, depending on the requirements of the application.

With the extension of wireless technology, vehicular ad hoc networks provide important services for the dissemination of general data and emergency warnings. However, since, the vehicle topology frequently changes from a dense to a sparse network depending on the speed of the moving vehicles and the time of day, vehicular ad hoc networks require a protocol that can facilitate the efficient and reliable dissemination of emergency messages in a highly mobile environment under dense or intermittent vehicular connectivity. Therefore, this paper proposes a new vehicular broadcast protocol, called BL-CAST, that can operate effectively in both dense and sparse network scenarios. As a low overhead multi-hop broadcast protocol, BL-CAST does not rely on the periodic exchange of beacons for updating location information. Instead, the location information of a vehicle is included in a broadcast message to identify the last rebroadcasting vehicle in an intermittently connected network. Simulation results show that BL-CAST outperforms the DV-CAST protocol in terms of the end-to-end delay, message delivery ratio and network overhead. [ABSTRACT FROM AUTHOR]

Delay tolerance network probabilistic routing protocols forward message to a node by observing its predictability value to meet the message destination. However, it is vital to predict the ability of node to carry the transmitted message. For instance, the traffic confluence on the high probable nodes can produce congestion that results in the drop of previously stored messages. These drops diminish the delivery ratio because the dropped message lost its opportunity to be delivered. Since, there exist multiple copies of each message; therefore, the same node invariably receives the dropped messages from other parts of the network and causes the highest number of transmissions. Additionally, the replication from source node continues on the high probable peers even the previous copies were transmitted on the better predictable neighbors than the current. In this paper, we have proposed a novel routing method called as the adaptive threshold based locking method that maintains the contemporary status of the node based on its activity in the network. We have used the adaptive status measuring metrics such as transmit factor, drop factor and hop away count. Moreover, a threshold based locking method has been introduced to control the diffusion of messages. We have performed the comparison of existing and proposed routing methods with real time mobility traces. The proposed strategy has bolstered the delivery ratio and minimizes hop count, end-to-end delay and number of transmission. [ABSTRACT FROM AUTHOR]

In delay tolerant network interruptions will occur continuously because there is no end-to-end path exists for the longer period of time from source to destination. In this context, delays can be immensely large due to its environment contrails e.g. wildlife tracking, sensor network, deep space and ocean networks. Furthermore, larger replication of messages put into the network is to increase delivery probability. Due to this high buffer occupancy storage space and replication result in a huge overhead on the network. Consequently, well-ordered intelligent message control buffer drop policies are necessary to operate on buffer that allows control on messages drop when the node buffers are near to overflow. In this paper, we propose an efficient buffer management policy which is called message drop control source relay (MDC-SR) for delay tolerant routing protocols. We also illustrate that conventional buffer management policy like Drop oldest, LIFO and MOFO be ineffective to consider all appropriate information in this framework. The proposed MDC-SR buffer policy controls the message drop while at the same time maximizes the delivery probability and buffer time average and reduces the message relay, drop and hop count in the reasonable amount. Using simulations support on an imitation mobility models Shortest Path Map Based Movement and Map Route Movements, we show that our drop buffer management MDC-SR with random message sizes performs better as compared to existing MOFO, LIFO and DOA. [ABSTRACT FROM AUTHOR]

Thanks to the research on Vehicular Ad Hoc Networks (VANETs), we will be able to deploy applications on roadways that will contribute to energy efficiency through a better planning of long trips. With this goal in mind, we have designed a gas/charging station advertising system, which takes advantage of the broadcast nature of the network. We have found that reducing the number of total sent packets is important, as it allows for a better use of the available bandwidth. We have designed improvements for a distance-based flooding scheme, so that it can support the advertising application with good results in sparse to dense roadway scenarios. [ABSTRACT FROM AUTHOR]

Routing in delay/disruption-tolerant networks (DTNs) is without the assumption of contemporaneous end-to-end connectivity to relay messages. Geographic routing is an alternative approach using real-time geographic information instead of network topology information. However, if considering the mobility of destination, its real-time geographic information is often unavailable due to sparse network density in DTNs. Using historical geographic information to overcome this problem, we propose the converge-and-diverge (CaD) by combining two routing phases that depend on the proximity to the movement range estimated for destination. The key insight is to promote message replication converging to the edge of this range and diverging to the entire area of this range to achieve fast delivery, given limited message lifetime. Furthermore, the concept of delegation replication (DR) is explored to overcome the limitation of routing decisions and the local maximum problem. Evaluation results under the Helsinki city scenario show an improvement of CaD in terms of delivery ratio, average delivery latency, and overhead ratio. Since geographic routing in DTNs has not received much attention, apart from the design of CaD, our novelty also focuses on exploring DR to overcome the limitation of routing decision and the local maximum problem, in addition to enhancing efficiency, as DR originally intended. [ABSTRACT FROM PUBLISHER]

Position-based routing has proven to be well suited for highly dynamic environment such as Vehicular Ad Hoc Networks (VANET) due to its simplicity. Greedy Perimeter Stateless Routing (GPSR) and Greedy Perimeter Coordinator Routing (GPCR) both use greedy algorithms to forward packets by selecting relays with the best progress towards the destination or use a recovery mode in case such solutions fail. These protocols could forward packets efficiently given that the underlying network is fully connected. However, the dynamic nature of vehicular network, such as vehicle density, traffic pattern, and radio obstacles could create unconnected networks partitions. To this end, we propose GeoDTN+Nav, a hybrid geographic routing solution enhancing the standard greedy and recovery modes exploiting the vehicular mobility and on-board vehicular navigation systems to efficiently deliver packets even in partitioned networks. GeoDTN+Nav outperforms standard geographic routing protocols such as GPSR and GPCR because it is able to estimate network partitions and then improves partitions reachability by using a store-carry-forward procedure when necessary. We propose a virtual navigation interface (VNI) to provide generalized route information to optimize such forwarding procedure. We finally evaluate the benefit of our approach first analytically and then with simulations. By using delay tolerant forwarding in sparse networks, GeoDTN+Nav greatly increases the packet delivery ratio of geographic routing protocols and provides comparable routing delay to benchmark DTN algorithms. [ABSTRACT FROM AUTHOR]

Two schools of thought exist in terms of handling mobility in mobile ad hoc networks (MANETs). One is the traditional connection-based model, which views node mobility as undesirable and tries to either remove (through recovery schemes) or mask (through tolerant schemes) the effect of mobility. The other is the mobility-assisted model, which considers mobility as a desirable feature, where routing is based on the store-carry-forward paradigm with random or controlled movement of mobile nodes (called ferries). It is well known that mobility increases the capacity of MANETs by reducing the number of relays in routing. Surprisingly, only two models, diameter hop count in the connection-based model and constant hop count in the mobility-assisted model, which correspond to two extremes of the spectrum, have been systematically studied. In this paper, we propose a new routing model that deals with message routing, as well as trajectory planning, of the ferries that carry the message. A logarithmic number of relays are enforced to achieve a good balance among several contradictory goals, including increasing network capacity, increasing ferry sharing, and reducing moving distance. The model considers the dynamic control of ferries in terms of the number of ferries, trajectory planning of ferries, and node communication and synchronization. The effectiveness of the proposed model is evaluated analytically, as well as through simulation. [ABSTRACT FROM AUTHOR]