In this paper, we present an approach to provide Quality of Service (QoS) for networked mobile gaming. In order to examine the QoS requirements of mobile games, we ported a simple real-time game called GAV (GPL Arcade Volleyball) to a PDA and performed several traffic measurements over both GPRS and UMTS networks. We show that due to high end-to-end delay and delay jitter, realtime games are not supported by GPRS. While UMTS improves both delay and jitter, it still does not match the requirements of real-time games. The key reason for this problem is that overprovisioning, as it is used to allow real-time games in the Internet, is very expensive in mobile networks. At the same time, QoS classes for mobile networks are not tailored to real-time games. In order to reduce delay and jitter for this application class, while still accounting for the very bursty nature of real-time game flows, we propose to use a combination of statistical multiplexing and QoS guarantees. The general idea is to aggregate multiple game flows and perform reservation for that aggregate. As a theoretical background, we use a queuing system based model. Through simulation of a sample network with the traffic data generated by GAV, we validate our assumptions and demonstrate the performance and characteristics of our approach.
SUMMARYCryptographic primitives need to be carefully evaluated when being applied in components ensuring enhanced protection aims. This work analyses the performance of RSA-and ECDSA-based digital signature schemes in the context of multi-hop ad hoc networks. Our work shows that contrary to a single wireless hop scenario with restricted clients in the wireless network and a powerful server in the fixed network, the choice of an appropriate signature candidate is not as obvious as for the aforementioned architecture. Our performance analysis considers three partially interdependent axes (a) the required security level, (b) the device restriction and (c) the protocol specification with the required security relationships, and the assumed traffic flow. We take (c) into account by analysing two charging protocols for wireless multi-hop scenarios. By generalising our observations, we carefully derive some recommendations to strengthen the security engineering process for dependable distributed systems over the wireless network.
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