Social‐based reputation‐aware data forwarding for improved multicast delivery in the presence of selfish nodes in DTNs

Delay/disruption tolerant networks (DTNs) are potentially applicable in the challenged scenarios like post‐disaster environments. In such networks, data forwarding generally relies on the mutual cooperation of the nodes. However, in reality, despite the availability of necessary resources for data forwarding, a node could misbehave by dropping messages received from other nodes with whom it has no strong social ties. Such a node is called a socially selfish node, which would cause a poor delivery ratio in the network. In this paper, we aim to address the problem of multicast data forwarding in the presence of such selfish nodes, by means of efficient relay selection in DTNs. First, we define a realistic reputation model, in contrast to existing models, to define the socially selfish/misbehaving nodes in the network. Further, a game‐theoretic analysis is carried out that implies data forwarding cost is also an influential parameter in handling selfishness/misbehavior. Subsequently, the problem is formulated as a constrained optimization problem, which is NP hard. Therefore, a heuristic is proposed by combining the reputation of a node and the cost of message forwarding to appropriately identify relay nodes, thus improve the performance of the multicast message delivery in the network. We utilize a social metric, centrality to minimize the message forwarding cost in terms of the number of relay nodes. Finally, the comparative performance evaluation in ONE simulator with practical scenarios shows the superiority of the proposed scheme over the other prominent schemes.     

An Improved Routing Algorithm Based on Social Link Awareness in Delay Tolerant Networks

The routing efficiency in delay tolerant networks is degraded due to intermittent connection and high latency. Additionally, socially selfish nodes in social networks refuse to provide message forwarding service since there are limited resources. To solve these problems, an improved routing algorithm based on the social link awareness is proposed. In this algorithm, multiple social features of the nodes’ behaviors are utilized to quantify the nodes pairs’ social links. The social links of the nodes pairs are computed based on their encounter history. These social links can be used to construct the friendship communities of the nodes. The intra-community and inter-community forwarding mechanisms are implemented to raise the successful delivery ratio with low overhead and decrease the transmission delay. Simulation results show that the proposed algorithm shortens the routing delay and increases the successful delivery ratio, thereby improving the routing efficiency.     

Performance Modeling for Relay Cooperation in Delay Tolerant Networks

Delay tolerant networks (DTNs) rely on the mobility of nodes and sequences of their contacts to compensate for lack of continuous connectivity and thus enable messages to be delivered from end to end in a “store-carry-forward” way, where multiple relay nodes are usually employed in the message delivery process. In this paper, we focus on such relay cooperation and analytically explore its impact on the delivery performance in DTNs. Specifically, we first develop a continuous time Markov chain-based theoretical framework to model the complicated message delivery process in delay tolerant networks adopting the two-hop relay algorithm. We then derive closed-form expressions for both the expected delivery delay and the corresponding expected delivery cost, where the important relay behaviors of forwarding traffic for itself or for other nodes are carefully incorporated into the analysis.     

基于信誉的延迟容忍网络激励方案

由于长延迟、频繁中断等特性,延迟容忍网络采用“存储-携带-转发”的路由方式实现报文的传递.这种传输方式建立在网络节点互相信任,诚实合作的假设之上.然而,由于受到自身资源的限制,网络中存在自私节点拒绝参与网络合作的行为,导致网络传输性能下降,甚至无法正常运行.针对此类问题,本文提出一种基于信誉的延迟容忍网络激励方案,鼓励节点共享资源,并约束自私行为.设计了一种观测协议,以解决延迟容忍网络环境下对网络节点行为的观测问题;提出了一种信誉模型,通过信任值评价节点的可信程度,从而优化路由决策,惩罚自私节点.仿真结果表明了本文提出的激励方案的有效性和可行性.     

机会网络中自私行为影响的分析与调节

以往针对机会网络中节点自私性影响评估的研究,建立了多种分析模型,然而并未考虑如何应用这些理论模型.本文分别在网络无TTL限制和有TTL限制两种情况下,利用评估模型对自私节点的影响进行分析,并提出一种基于消息分类的自私模型,评估了自私节点对延迟和消息投递率的影响.分析表明,机会网络受自私节点的影响不仅与自私节点的数目有关,而且与节点的移动速度,消息传输范围有关.因此,可以通过调节这些参数提高网络的性能,减少自私节点的影响.首先,通过理论推导分别得出了2-hop路由和传染病路由在延迟保证下的合作节点数目和消息传输范围以及传染病路由在消息投递率保证下消息的TTL.随后,通过ONE仿真平台对自私节点影响的评估,证明自私行为影响下网络性能的理论值与实验值近似,并且证明了通过理论分析获得的参数值也与实验值近似.     

On the tradeoff between altruism and selfishness in MANET trust management

Mobile ad hoc and sensor networks may consist of a mixture of nodes, some of which may be considered selfish due to a lack of cooperativeness in providing network services such as forwarding packets. In the literature, existing trust management protocols for mobile ad hoc networks advocate isolating selfish nodes as soon as they are detected. Further, altruistic behaviors are encouraged with incentive mechanisms. In this paper, we propose and analyze a trust management protocol for group communication systems where selfish nodes exist and system survivability is highly critical to mission execution. Rather than always encouraging altruistic behaviors, we consider the tradeoff between a node’s individual welfare (e.g., saving energy to prolong the node lifetime) vs. global welfare (e.g., achieving a given mission with sufficient service availability) and identify the best design condition of this behavior model to balance selfish vs. altruistic behaviors. With the system lifetime and the mission success probability as our trust-based reliability metric, we show that our behavior model that exploits the tradeoff between selfishness vs. altruism outperforms one that only encourages altruistic behaviors.     

Information Propagation through Opportunistic Communication in Mobile Social Networks

At present, people can communicate with each other through short range communication technologies (Bluetooth, WiFi, etc.) installed in their smart terminals. Due to limited communication range, communication is opportunistic, and mobile social networks formed by such technologies can be seen as delay tolerant networks (DTN). This paper presents a theoretical framework to evaluate the performance of information propagation in such network based on ODE equations. This framework can evaluate the impact of peoples?? many behaviors. For example, people may not want to help others because of their selfish nature. In addition, peoples who are not interested in the message may not receive the message at all, but they become to be interested in the message later. On the other hand, people may discard the message after they used it. We check the accuracy of our model through simulations based on both synthetic and real motion traces (the average deviation is not bigger than 5.09?%). Numerical results show that peoples?? behaviors really have certain impact on the performance of information propagation. For example, if the selfish level is bigger, some persons cannot obtain message at all. If peoples discard message with bigger probability, above result may also appear.     

A cooperative forwarding scheme for social preference-based selfishness in mobile social networks

Most schemes in mobile social networks (MSNs) assume that nodes simply forward messages without considering selfishness. We therefore first devise social preference-based selfishness for MSNs by which nodes decide to drop or keep (forward) and replace messages to save buffer space according to the message preference and the communities of nodes. We then propose a novel cooperative forwarding scheme for social preference-based selfishness in MSNs, the social preference-aware forwarding scheme (SPF) incorporates the proposed message forwarding scheme and a buffer replacement policy for the message preference. It takes advantage of social information with the home-cell community-based mobility model. Considering the contact probability and buffer replacement policy for the message preferences, SPF, therefore, efficiently delivers messages to the destination by reflecting the degree of selfishness to which nodes cooperatively manage their buffer spaces and how frequently and how recently they meet. Consequently, all nodes can cooperatively drop or keep (forward) and replace the messages in the buffer spaces for the message preferences in SPF. SPF outperforms Epidemic, PRoPHET, and SimBet in terms of delivery ratio, network traffic, buffer space, hop count, and replacement frequency.     

Analysis and Design of Warning Delivery Service in Intervehicular Networks

This paper focuses on inter-vehicular networks providing warning delivery service. As soon as a danger is detected, the propagation of a warning message is triggered, with the aim of guaranteeing a safety area around the point in which the danger is located. Multiple broadcast cycles can be generated so that a given lifetime of the safety area is guaranteed. The service is based on multi-hop ad hoc inter-vehicular communications with a probabilistic choice of the relay nodes. The scenario we consider consists of high speed streets, such as highways, in which vehicles exhibit one-dimensional movements along the direction of the road. We propose an analytical model for the study of this service and derive performance indices such as the probability that a vehicle is informed, the average number of duplicate messages received by a vehicle and the average delay. Moreover, we use the model to discuss system design issues, which include the proper setting of the forwarding probability at each vehicle, so that a given probability to receive the warning can be guaranteed to all vehicles in the safety area. The model is validated against simulation results. Since it is very accurate, the model can be instrumental to the performance evaluation and design of broadcasting techniques in inter-vehicular networks.     

Road traffic and geography topology based opportunistic routing for VANETs

The message delivery .ratio and transmission delay is affected deeply by road traffic flow in vehicular ad hoc networks （VANETs）. An opportunistic routing based on geography and road traffic flow for VANETs （ORRIS） was proposed. ORRIS leverages the knowledge of geography positions, motion vectors and road traffic flows. In order to estimate the traffic flow density, the history of encounter number of the vehicles in the opposite direction is considered in ORRIS. The forwarding decisions are made by distributed vehicles based on the geography topology and the road traffic flow. The real map based simulation results show that ORRIS has a better performance than other algorithms, especially when the road traffic is busy or the traffic flow rates have great differences between roads.     

Performance analysis of hop‐limited epidemic routing in DTN with limited forwarding times

Because of the uncertainty of transmission opportunity in delay tolerant networks (DTN), routing algorithms in DTN often need nodes to serve as relays for others to carry and forward messages. One classic policy is the Epidemic routing (ER) algorithm. To reduce the overhead, the hop‐limited ER protocol is proposed. This method can get better performance through controlling the message hop count. However, because of the energy constraint or other factors, each node may forward only limited times, that is, both the message hop count and the forwarding times may be limited. This paper proposes a unifying framework to evaluate the performance of ER with the aforementioned constraints. Simulations based on both synthetic and real motion traces show the accuracy of the framework. In addition, we explore the impact of many parameters (e.g., message hop count) through extensive numerical results. For example, numerical results show that both the message hop count and the forwarding times can have certain impact on the routing performance, but their impact is related with many other factors (e.g., the number of nodes). Copyright © 2014 John Wiley & Sons, Ltd.     

基于信誉值维护的机会网络自私节点检测机制

机会网络中自私节点的存在严重影响路由转发的性能。为在路由时避开此类节点、消除其对网络性能的影响,提出了一种基于信誉值维护的自私节点检测机制,通过两跳ACK消息来监测节点行为,利用监测信息计算节点的信誉值,并将其作为判断节点是否自私的依据。在多种路由算法上加载该检测机制进行仿真实验,结果表明该检测机制可准确识别机会网络中的自私节点,提高消息投递的成功率,并能有效控制消息副本数和网络开销。     

Reputation based selfishness prevention techniques for mobile ad-hoc networks

Mobile ad-hoc networks require nodes to cooperate in the relaying of data from source to destination. However, due to their limited resources, selfish nodes may be unwilling to forward packets, which can deteriorate the multi-hop connectivity. Different reputation-based protocols have been proposed to cope with selfishness in mobile ad-hoc networks. These protocols utilize the watchdog detection mechanism to observe the correct relaying of packets, and to compile information about potential selfish nodes. This information is used to prevent the participation of selfish nodes in the establishment of multi-hop routes. Despite its wide use, watchdog tends to overestimate the selfish behavior of nodes due to the effects of radio transmission errors or packet collisions that can be mistaken for intentional packet drops. As a result, the availability of valid multi-hop routes is reduced, and the overall performance deteriorates. This paper proposes and evaluates three detection techniques that improve the ability of selfishness prevention protocols to detect selfish nodes and to increase the number of valid routes.     

Routing in Delay-Tolerant Networks Comprising Heterogeneous Node Populations

Communication networks are traditionally assumed to be connected. However, emerging wireless applications such as vehicular networks, pocket-switched networks, etc., coupled with volatile links, node mobility, and power outages, will require the network to operate despite frequent disconnections. To this end, opportunistic routing techniques have been proposed, where a node may store-and-carry a message for some time, until a new forwarding opportunity arises. Although a number of such algorithms exist, most focus on relatively homogeneous settings of nodes. However, in many envisioned applications, participating nodes might include handhelds, vehicles, sensors, etc. These various "classes” have diverse characteristics and mobility patterns, and will contribute quite differently to the routing process. In this paper, we address the problem of routing in intermittently connected wireless networks comprising multiple classes of nodes. We show that proposed solutions, which perform well in homogeneous scenarios, are not as competent in this setting. To this end, we propose a class of routing schemes that can identify the nodes of "highest utility” for routing, improving the delay and delivery ratio by four to five times. Additionally, we propose an analytical framework based on fluid models that can be used to analyze the performance of various opportunistic routing strategies, in heterogeneous settings.     

On minimizing the system information age in vehicular ad-hoc networks via efficient scheduling and piggybacking

Recent advances in vehicular networks have enforced researchers to focus on various information dissemination techniques. Exchanging information among the vehicles is imperative due to the ever-changing network topology in vehicular networks. However, random transmitter selection in traditional CSMA based channel access mechanism limits the delay performance. Data, such as state information, is often time critical, and hence, efficient information dissemination techniques to improve delay performance are essential. In this work, we aim to minimize the average system age which is the mean number of time slots old a vehicle’s information is at all other vehicles in the network. To achieve this, we explore the benefits of simultaneous transmission along with piggybacking of information for multi-hop communication. While allowing simultaneous transmission guarantees faster dissemination of information, piggybacking facilitates dissemination of more information per transmission, thereby keeping the network more updated. We have also analysed the relationship between piggybacked information and number of vehicles in the network. Simulation results show improvement in network performance. Our analytical results are in good agreement with the simulation results.     

Cooperative and Opportunistic Channel Access for Vehicle to Roadside (V2R) Communications

This paper focuses on vehicle to roadside (V2R) communications in vehicular networks based on the IEEE 802.11 DCF MAC protocol. In vehicular networks, roadside units (RSUs) are typically spaced apart along the road and each vehicle can be connected to an RSU only when the vehicle is within its transmission range. Due to the high relative speed between a moving vehicle and a stationary RSU, the residence time of the vehicle within the coverage of each RSU is very short. Thus it is hard for the system to reach a steady state. With multi-hop forwarding, in which a vehicle may be connected to an RSU through relaying over other vehicles, the connection time of each V2R access may be extended. But this is at the expense of introducing wireless interference among vehicles, which may dramatically degrade the system performance. To tackle these challenges, we propose a new mechanism called Proxy-based Vehicle to RSU access (PVR) for V2R communications. This protocol is designed to exploit cooperative and opportunistic forwarding between any two distant RSUs and to emulate back-to-back transmissions within the coverage of an RSU. As a result, it can shorten the access delay by taking advantage of opportunistic forwarding and mitigate the interference problem during the short residence time within the coverage of an RSU. The simulation results show that PVR achieves excellent performance and outperforms all existing solutions for V2R communications in vehicular networks.     

Incentive based scheme for improving data availability in vehicular ad-hoc networks

Vehicular networks are popular in recent years to provide low cost communication medium during mobility. Vehicular Delay Tolerant Networks (DTNs) are one of the major categories of emerging technology. DTNs work on carry and forward mechanism to deliver data to the destination. The network performance gets severely affected due to reluctance shown by selfish nodes where few nodes show no interest in forwarding others data due to lack of any personal profit. The proposed mechanism is based on coalition game theory and discusses about incentive based mechanism which provides incentive to nodes which are forwarding data to forward to destination and motivates other vehicles in the network to participate in coalition to forward data. This scheme not only encourages other selfish nodes to forward their private data and other nodes’ public data as early as possible to destination but also increases reliability in the network as more nodes show their interest in selected routing protocol. The proposed scheme outperforms in overall benefit earned by individual node and whole coalition, and increases mutual cooperation which improves availability of data in the network.     

CPTR: conditional probability tree based routing in opportunistic networks

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.     

An evolutionary bargaining‐based approach for incentivized cooperation in opportunistic networks

Opportunistic networking enables users to communicate in an environment where connectivity is intermittent or unstable. However, such networking scheme assumes that mobile nodes voluntary cooperate, which cannot be guaranteed. Some nodes can simply exhibit selfish behavior and thus diminish the effectiveness of the approach. In this paper, a game scenario is formulated in which the nodes try to convince each other to participate in packets forwarding. Each node is considered as a player in this game. When a node comes in the communication range of another, a bargaining game starts between them as part of the message forwarding process. Both players try to have a mutual agreement on a price for message forwarding. We present a new incentive mechanism called evolutionary bargaining‐based incentive scheme (EBIS) to motivate selfish nodes to cooperate in data forwarding. In EBIS, a node negotiates with other nodes to obtain an agreeable amount of credit for its forwarding service. Nodes apply a sequential bargaining game and then adapt their strategies using an evolutionary model to maximize the probability of reaching an agreement. Unlike classical bargaining games, nodes in our model are boundedly rational. In addition, we use the evolutionary stable strategy (ESS) concept to determine the adaptive strategies for the nodes. The comparison of EBIS with a benchmarked model demonstrates that EBIS performs better in terms of packet delivery ratio and average latency.     

Integrated Social and QoS Trust-Based Routing in Delay Tolerant Networks

We propose and analyze a class of integrated social and quality of service (QoS) trust-based routing protocols in mobile ad-hoc delay tolerant networks. The underlying idea is to incorporate trust evaluation in the routing protocol, considering not only QoS trust properties but also social trust properties to evaluate other nodes encountered. We prove that our protocol is resilient against bad-mouthing, good-mouthing and whitewashing attacks performed by malicious nodes. By utilizing a stochastic Petri net model describing a delay tolerant network consisting of heterogeneous mobile nodes with vastly different social and networking behaviors, we analyze the performance characteristics of trust-based routing protocols in terms of message delivery ratio, message delay, and message overhead against connectivity-based, epidemic and PROPHET routing protocols. The results indicate that our trust-based routing protocols outperform PROPHET and can approach the ideal performance obtainable by epidemic routing in delivery ratio and message delay, without incurring high message overhead. Further, integrated social and QoS trust-based protocols can effectively trade off message delay for a significant gain in message delivery ratio and message overhead over traditional connectivity-based routing protocols.