A history-based energy-efficient routing protocol for opportunistic networks

In this thesis, a history-based energy-efficient routing protocol (called AEHBPR) for opportunistic networks (OppNets) is proposed, which saves the energy consumption by avoiding unnecessary packets transmission in the network and by clearing the buffer of nodes carrying the copies of the already delivered packets. The proposed AEHBPR protocol is evaluated using the Opportunistic NEtwork (ONE) simulator with both synthetic and real mobility traces, showing a superior performance compared to the History-Based Prediction for Routing (HBPR) protocol and AEProphet, in terms of average remaining energy, number of dead nodes, number of delivered messages, and overhead ratio, where AEProphet is the ProPHet routing protocol for OppNets on which the same energy-aware mechanism has been implemented.

A history-based energy-efficient routing protocol for opportunistic networks

In this thesis, a history-based energy-efficient routing protocol (called AEHBPR) for opportunistic networks (OppNets) is proposed, which saves the energy consumption by avoiding unnecessary packets transmission in the network and by clearing the buffer of nodes carrying the copies of the already delivered packets. The proposed AEHBPR protocol is evaluated using the Opportunistic NEtwork (ONE) simulator with both synthetic and real mobility traces, showing a superior performance compared to the History-Based Prediction for Routing (HBPR) protocol and AEProphet, in terms of average remaining energy, number of dead nodes, number of delivered messages, and overhead ratio, where AEProphet is the ProPHet routing protocol for OppNets on which the same energy-aware mechanism has been implemented.

Donations and the Overhead Ratio Are Related Even When Donors Do Not Bother About Efficiency

Empirical research on donor behavior infers from donations being negatively related to overhead ratios (or indicators based on these ratios) that donors give more to more “efficient” organizations. This relation is proved to be at least partly driven by a purely mechanical link between donations and overhead ratios, which therefore should be isolated when studying empirically the behavioral effect of overhead ratio–based indicators on donors’ giving decisions.

The Optimal Checkpoint Interval for the Long-Running Application

For the distributed computing system, excessive or deficient checkpointing operations would result in severe performance degradation. To minimize the expected computation execution of the long-running application with a general failure distribution, the optimal equidistant checkpoint interval for fault tolerant performance optimization is analyzed and derived in this paper. More precisely, the optimal checkpointing period to determine the proper checkpoint sequence is proposed, and the derivation of the expected effective rate of the defined computation cycle is introduced. Corresponding to the maximal expected effective rate, the constraint of the optimal checkpoint sequence can be obtained. From the constraint of optimality, the optimal equidistant checkpoint interval can be obtained according to the minimal fault tolerant overhead ratio. By the numerical results, the proposal is practical to determine a proper equidistant checkpoint interval for fault tolerant performance optimization.

If Someone Else Pays for Overhead, Do Donors Still Care?

To better evaluate the effectiveness of overhead-free donations on giving behavior, we seek to further investigate the robustness of the findings from Gneezy et al. using a nonstudent population. In an online experiment, we test whether (a) the level of overhead costs affects giving decisions and whether (b) overhead aversion disappears once donors are informed that an anonymous donor has already covered all overhead costs. Results show that donations decrease as overhead spending increases when donors have to pay for overhead. However, unlike the original article, we find mixed results when someone else covered overhead costs. Participants exposed to a nonprofit with a 33% overhead ratio where overhead was already covered still displayed overhead aversion. However, this aversion disappeared at a high overhead ratio of 67%. The overall results remain unchanged after controlling for demographics. Our results hold important implications for nonprofit organizations who must find a careful balance between appealing to donors for short-term financial gain and addressing the need to alter skewed donor expectations toward financial efficiency in the long run.

ANALYSIS OF EPIDEMIC, PROPHET AND SPRAY AND WAIT ROUTING PROTOCOLS IN THE MOBILE OPPORTUNISTIC NETWORKS

Background: The opportunistic mobile networks (OMNs) are a type of mobile adhoc networks (MANETs) with delay-tolerant network (DTN) features, where the sender to receiver connectivity never exists most of the time, due to dynamic nature of the nodes and the network partition. The real use of OMNs is to provide connectivity in challenged environments. Methods: The paper presents the detailed analysis of three routing protocols, namely Epidemic, PROPHET and Spray and Wait, against variable size of the messages and the time to live (TTL) in the networks. The key contribution of the paper is to explore routing protocols with mobility models for the dissemination of data to the destination. Routing uses the store-carryforward mechanism for message transfer and network has to keep compromise between message delivery ratio and delivery delay. Results: The results are generated from the experiments with Opportunistic Network Environment (ONE) simulator. The performance is evaluated based on three metrics, the delivery ratio, overhead ratio and the average latency. The results show that the minimum message size (256 KB) offers better performance in the delivery than the larger message size (1 MB). It has also been observed that with the epidemic routing, since there are more message replicas, which in turn increase the cost of delivery, so with a smaller message, the protocol can reduce the overhead ratio with a high proportion. Conclusion: The average latency observed increases with the increase of the TTL of the message in three protocols with variation of the message size from 256KB to 1 MB.

Social-aware routing for cognitive radio–based vehicular ad hoc networks

Cognitive radio–based vehicular ad hoc networks can solve the problem of limited spectrum resource and growing vehicular communication service demands in intelligent transportation systems, and thus, it receives much concern recently. In cognitive radio–based vehicular ad hoc networks, the high mobility of vehicles and the dynamic spectrum activity of cognitive radio make routing in such networks a great challenge. Some routing researches have been proposed in cognitive radio–based vehicular ad hoc networks with single-objective optimization and neglecting the nodes’ social behaviors which can improve the network performance. From this perspective, we propose a social-aware routing scheme for cognitive radio–based vehicular ad hoc networks, with the purpose of increasing the packet delivery ratio and decreasing the overhead ratio. First, we analyze the social centrality of primary users to offer an accuracy spectrum hole measurement. Moreover, we develop a social community partition algorithm to divide secondary users into intra-community and inter-community groups. Furthermore, considering the tradeoff between the packet delivery ratio and the overhead ratio, we adopt different replication policies and forwarding ranks in different community communication processes. In the intra-community communication process, we employ the single-copy policy and the contact duration rank. In the inter-community communication process, we utilize the optimized-binary-tree replication policy and the bridge coefficient rank. Simulation results show that our social-aware routing scheme achieves the higher package delivery ratio and the lower overhead ratio when compared with the existing cognitive radio–based vehicular ad hoc networks routing schemes and other standard routing schemes.

An Improved Opportunistic Routing Protocol for Intermittently Connected Delay Tolerant Wireless Sensor Networks

In intermittently connected delay tolerant wireless sensor networks, sensor data generated at sensor nodes should be delivered to a sink node using opportunistic contacts between intermittently connected nodes. Since there is no stable end-to-end routing path from a source node to a sink node in intermittently connected network, an opportunistic routing protocol to deliver sensor data efficiently is needed. In this paper, an improved opportunistic routing protocol is proposed, where both current delivery predictability and maximum delivery predictability are used together to decide whether sensor data should be forwarded or not to a contact node. The proposed protocol can reduce buffer overflow and thus increase the delivery ratio, which is one of the most important performance measures in delay tolerant wireless sensor networks. The performance of the proposed routing protocol is compared with that of PRoPHET protocol and FREAK protocol, by varying buffer sizes and the number of nodes, in terms of delivery ratio, overhead ratio, and delivery latency. Performance analysis results show that the proposed protocol has better delivery ratio, overhead ratio, and delivery latency than the PRoPHET protocol and FREAK protocol have, in most considered parameter values, with appropriate selection of message dissemination thresholds.

Analisis Performansi Protokol Routing Proaktif pada Jaringan Mobile Adhoc

Intelligent Transportation Systems (ITS) menawarkan paradigma pemodelan baru yang mendukung komunikasi antar kendaraan secara real time menggunakan routing protocol yang disebut Vehicular Ad Hoc Network (VANET). Pada dasarnya kinerja routing protocol dipengaruhi oleh arus dan aturan lalu lintas yang bersifat dinamis sehingga perubahan tersebut akan menyebabkan perubahan pada kinerja routing protocol juga. Untuk itu, penelitian ini mengusulkan rancangan mobilitas realistis berdasarkan data makroskopis dan mikroskopis jalan perkotaan. Rancangan mobilitas dibagi menjadi 2 skenario berdasarkan kepadatan kendaraan, yaitu 125 dan 200 node. Penelitian ini bersifat simulasi dan dibagi menjadi 2 tahap. Tahap pertama yaitu simulasi mobilitas yang menunjukkan pergerakan kendaraan serta aturan lalu lintas yang disesuaikan dengan kondisi realistis. Tahap kedua adalah simulasi jaringan yang bertujuan untuk mengevaluasi kinerja routing protocol DSDV dan OLSR terhadap rancangan model mobilitas. Untuk menguji kinerja kedua routing protocol, maka digunakan 3 metrik pengujian yaitu Packet Delivery Ratio (PDR), Overhead Ratio (OR) dan End to End Delay (E2ED). Hasil simulasi menunjukkan OLSR unggul pada metrik PDR dan OR, yaitu masing-masing 88.62% dan 57.11%. Sedangkan E2ED terbaik ditunjukkan oleh DSDV dengan nilai 0.523 detik. Kinerja terbaik kedua routing protocol ditunjukkan pada skenario 125 node. Hal ini menunjukkan kedua routing protocol belum mampu mengatasi kondisi lalu lintas perkotaan yang sangat padat.