Evaluation of mobile networks with multihop extension

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Dr. Fazekas Péter
Department of Networked Systems and Services

In traditional cellular networks user equipment has direct radio connection with the base station. As the volume of data traffic in mobile networks increase rapidly, provided service quality and capacity near the edge of cells becomes insufficient. Moreover, the growing penetration of mobile data communications rise the need for providing service over areas that had not been covered so far. The basic solution to these problems is the deployment of more base stations, that is the densification of cellular networks. Scientific literature and network standards consider other solutions as well, like cooperative base stations, distributed antenna systems, multiantenna transmission, etc.

A further improvement possibility is the application of wireless relays. 3GPP (3rd Generation Partnership Project) defines several types of relays (e.g. simple „amplify and forward” repeater, or „decode and forward relay”, etc.). These devices have the advantage of being simpler and their lower price, along with the faster and cheaper deployment. Relays do not require backhaul links to be installed, hence within their coverage area the signal to noise ratio can be increased easily, hence better service quality can be achieved. Applying these devices means that in this case user terminals do not communicate directly with the base station, rather through the relay station.

In this study I evaluate the efficiency of cellular networks extended by mobile relays. Throughout this work I assume that the mobile devices being present int he network are capable of relaying other users’ data towards/from the base station. I use static computer simulations to analyse the possible coverage extension with mobile relaying in a single base station system. For this I considered three possible spatial distributions of miobile devices: uniform distribution to model urban traffic, two dimensional Gaussian distribution to model hotspot scenarios and uniform distribution over a line, to model cells around high traffic roads. I evaluate the increase in coverage area through multihop relaying, considering the effect of maximum number of relaying hops allowed, user density and the ratio of the distances of mobile – mobile and base station – mobile links.

After that I investigate the other benefits of these networks. With usage of mobile relays the average cell capacity can increase as well beside the cell area extension, so it can be an effective solution to the growth of traffic demand.


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