Search Results

Journal Papers

1. P. Osti, S. Aalto and P. Lassila, Performance and optimization of dynamic-TDD intercell coordination with elastic traffic, Telecommunication Systems, vol. 63, no. 4, pp. 655-679, 2016 (bib)

   Abstract: We study the intercell coordination problem between two interfering cells combined with dynamic TDD serving elastic data traffic. We model the system at the so-called flow level, where the number of flows varies dynamically and each flow has a random service requirement. Due to the interference between the stations the system is modeled as a set of four interacting processor sharing queues. Our objective is to consider, by using several approaches, the gains from dynamic policies that utilize instantaneous state information to minimize the total mean number of flows. Assuming that the capacity is shared dynamically according to the notion of balanced fairness yields a general policy that is also Pareto optimal, and we are able to explicitly analyze its performance. For exponential service times, we also apply the theory of Markov Decision Processes and the policy iteration algorithm to minimize the number of flows in the system. Finally, we define priority policies for certain special cases and show that they are even stochastically optimal. Our numerical results show that the gains from the dynamic policies compared with a statically optimized policy can be significant. Surprisingly, the gains can be achieved largely by our novel robust heuristic policy that only relies on instantaneous information about the number of flows.

Conference Papers

1. P. Osti, P. Lassila and S. Aalto, Performance of D2D underlay and overlay for elastic traffic, in Proceedings of The 19th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM 2016), 2016 (bib)

   Abstract: We explore the performance of different resource allocation schemes for transferring elastic traffic in a cellular network that is either overlaid or underlaid with D2D traffic. To this end, we model a single cell during uplink transmissions and jointly consider the presence of a randomly varying number of D2D and cellular users in the system. We use different processor sharing queueing models to characterize the performance of the overlaying and underlaying schemes and measure the performance as the mean ow level delay. In the overlaying approach, depending on the load a certain fraction of the radio resources is reserved for the D2D traffic and the cellular traffic, and hence there is no interference between the D2D and cellular users. In the underlaying approach, the D2D users are allowed to opportunistically transmit unless being interfered by a cellular user nearby. Our numerical studies reveal that the underlaying D2D traffic scheme provides a good performance compared to other methods, especially if the interference range of a cellular user is small compared with the cell dimensions. Moreover, the so-called dynamic overlay method we propose appears to perform better than the static overlay scheme.