Secure cooperation stimulation under noise and imperfect monitoring in Java Creation QR in Java Secure cooperation stimulation under noise and imperfect monitoring

Secure cooperation stimulation under noise and imperfect monitoring using barcode creation for none control to generate, create none image in none applications. Code 128 Code Set C (i.e., a false al none for none arm).

On the other hand, when a packet has been dropped by a certain relay, with probability no more than pm this can be observed as a forwarding event (i.e., missed detection).

Here pf and pm characterize the capability of the underlying monitoring mechanism. It is easy to understand that pf and pm may vary according to the underlying monitoring mechanism and the monitoring environment. Before devising cooperation-stimulation strategies for autonomous mobile ad hoc networks, we rst summarize some challenges that we may meet.

Existence of noise. In many cooperation-enforcement schemes, such as in [396] [121], each node decides its next-step action solely on the basis of the quality of service it has received in the current and/or previous stages, such as the normalized throughput. However, if there exists noise, some packets may be dropped unintentionally during the delivery.

This can reduce the quality of service experienced by some nodes. As a consequence, these nodes will also lower the service quality provided by them. Such an avalanche effect may quickly propagate throughout the network and after some time no nodes will forward packets for the others.

When designing cooperation-stimulation strategies in realistic scenarios, the effect of noise has to be thoroughly considered. Imperfect monitoring. Since nodes usually base their decisions solely on what they have observed, imperfect monitoring can always be taken advantage of by greedy or malicious nodes to increase their performance.

For example, when the misseddetection ratio is high, a node can always drop other nodes packets but still claim that it has forwarded them. None of the existing approaches have been designed with consideration of noise and imperfect monitoring, which greatly limits their potential applications in realistic scenarios. Presence of malicious users.

If no malicious nodes exist and all nodes want to enjoy a high-quality network service, such as high throughput, stimulating cooperation may be less challenging according to the following logic: misbehavior by some nodes can lead to a decrease of service quality experienced by some other nodes, which may consequently reduce the service quality they provide. After some while, such quality degradation will propagate back to those nodes which initially misbehaved. Therefore, nodes have no incentive to intentionally behave maliciously.

However, since the attackers goal is usually to decrease the network service quality, they would like to cause propagation of such misbehavior. This makes cooperation stimulation extremely challenging. Further, it has been recognized that malicious behavior in autonomous ad hoc networks will not be uncommon due to the loose access control, and security issues have been overlooked in the past when designing cooperation-stimulation strategies.

Topology dependence. It has been pointed out in [121] that network topology plays an important role when designing cooperation-enforcement strategies, and usually it is impossible to nd a strategy to force all nodes to play fully cooperatively in static ad hoc networks. For example, if a user is in a bad location such that no user relies on him to forward packets, it is usually impossible for him to nd other users to help him.

. 22.2 Design challenges and game description Changing topolo none for none gy and opponent. In ad hoc networks, at each time instant each node may request different nodes to forward packets for it due to topology change or other reasons, and/or be requested by different nodes. This also poses a big challenge to cooperation stimulation: since nodes are sel sh, unless a relay node is sure with high con dence that requesters will return the favor later, it has no incentive to forward packets for them.

Varying service-request rate. Similarly to changing opponents, we have identi ed that a variable request rate also plays an important role. For example, if a node has too many packets to send, it is usually impossible to let the other nodes forward all the packets for it, unless it can return enough favors to the others.

Further, due to the topology change, a node that is being requested might not need the requester s help immediately, though it may later. Non-repeated model. Most of the existing literature addresses cooperation enforcement under a repeated-game model, such as in [396] [427] [5] [121], which assume either random connection or a xed setup.

However, the repeated-game model rarely holds in reality. This leads to a new challenge, namely that favors cannot be returned immediately, which is a major hurdle for effective cooperation stimulation. In [98], Dawkins demonstrated that reciprocal altruism is bene cial for every ecological system when favors are granted simultaneously.

However, when favors cannot be granted simultaneously, altruism might not guarantee satisfactory future payback, especially when the future is unpredictable. The situation will deteriorate further when the observation is imperfect with high false-alarm and missed-detection ratios. In this chapter, one critical goal is to design attack-resistant cooperation-stimulation strategies for autonomous mobile ad hoc networks that can work well even in a noisy and hostile environment with imperfect monitoring.

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