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Compensating temporary overload or site outage in cellular mobile networks is still an unsolved problem in order to avoid situations where services are unavailable. For this objective, we propose to use a swarm of Unmanned Aerial Vehicles (UAVs) equipped with cellular technology to temporarily offload traffic into neighbouring cells in LTE/4G networks. We discuss relay placement, amount of relays and relay transmit power for overload and outage compensation and provide an analytical model for evaluating system performance in the downlink. We assume that the spatial separation between the aerial service provider, users, and offload eNodeB is beneficial for temporarily increasing spectral efficiency. Our results give evidence, that aerial network provisioning can be used for optimizing mobile networks in overload and outage scenarios.

Abstract. Digital signatures are one of the most important applications of microprocessor smart cards. The most widely used algorithms for digital signatures, RSA and ECDSA, depend on finite field engines. On 8-bit microprocessors these engines either require costly coprocessors, or the implementations become very large and very slow. Hence the need for better methods is highly visible. One alternative to RSA and ECDSA is the Merkle signature scheme which provides digital signatures using hash functions only, without relying on any number theoretic assumptions. In this paper, we present an implementation of the Merkle signature scheme on an 8-bit smart card microprocessor. Our results show that the Merkle signature scheme provides comparable timings compared to state of the art implementations of RSA and ECDSA, while maintaining a smaller code size.

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