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Abstract-We propose a cooperation and accounting scheme for multi-hop cellular networks, which stimulates cooperation among nodes by making it a rewarding alternative to selfishness. The paper describes an architecture with highly decentralized security and accounting mechanisms. Our scheme charges senders and rewards forwarders, supports both sender-and receiverbased payments and coexists with ad hoc only traffic. We use of service stations deployed throughout the network to offer nodes a possibility to refill their money accounts. We present the results of simulation runs, where we investigated the liveliness of the proposed scheme. We find that the number of service stations and their distribution correlate in different ways.

Abstract. Today's public Wireless LANs are restricted to hotspots. With the current technology, providers can only target a small audience and in turn charge high prices for their service to generate revenue. Also, providers can not react appropriate to dynamic changes of the demand. With multi-hop cellular networks the coverage area can be increased and the installation costs and investment risks for the provider can be reduced. However, the individual customers play an important role in such networks and their participation must be encouraged. Therefore, we propose a cooperation and accounting scheme which introduces monetary rewards. We compare our scheme called CASHnet with the Nuglet scheme using simulations under the criteria of network liveliness as well as goodput, overhead and packet error rate.

Virtual routers are software entities, i.e. user space processes, emulating IP routers on one or several (Linux) computers. Virtual routers can be used for both networking research and education. In contrast to simulation, virtual routers process packets in real-time and the virtual router code is similar to code in real routers. In the case of research, larger network test-beds can be built using a relatively small number of computers. New functionalities such as new queuing mechanisms are supported by a modular software architecture and can be tested in a rather safe environment compared to kernel space implementations. Virtual routers can also be used as a tool aiming to allow students to perform virtual experiments within a computer networks course. Students can create and experiment with arbitrary virtual IP network topologies. The web-based user interface allows students to interact remotely with the emulated routers, but simultaneously it is very similar to commonly available configuration interfaces of network devices in reality. This enables students to configure routers like in the real world but also to experiment in a much more robust and safe environment.