Oscar Dario Ramos-Cantor

Optimal resource block allocation and muting in heterogeneous networks

In this paper, we investigate user association and resource block (RB) allocation in downlink heterogeneous cellular networks. Our goal is to jointly optimize user association and RB allocation to maximize network throughput while taking into account fairness among users. To effectively control interference, RB muting is employed. The problem is addressed in an integer linear programming (ILP) framework. Due to the combinatorial nature of the problem, the computational complexity of solving it becomes prohibitively high even for medium size networks. Therefore, we propose to decouple user association from the original problem, and formulate a low-complexity ILP problem for the optimal RB allocation and muting. Simulation results show that the proposed RB allocation and muting scheme achieves significantly higher throughput and better fairness compared with conventional schemes.

Centralized coordinated scheduling in LTE-Advanced networks

This work addresses the problem associated with coordinating scheduling decisions among multiple base stations in an LTE-Advanced downlink network in order to manage inter-cell interference with a centralized controller. To solve the coordinated scheduling problem, an integer non-linear program is formulated that, unlike most existing approaches, does not rely on exact channel state information but only makes use of the specific measurement reports defined in the 3GPP standard. An equivalent integer linear reformulation of the coordinated scheduling problem is proposed, which can be efficiently solved by commercial solvers. Extensive simulations of medium to large-size networks are carried out to analyze the performance of the proposed coordinated scheduling approaches, confirming available analytical results reporting fundamental limitations in the cooperation due to out-of-cluster interference. Nevertheless, the schemes proposed in this paper show important gains in average user throughput of the cell-edge users, especially in the case of heterogeneous networks.

Budget constrained small cell deployment planning for heterogeneous LTE networks

We address the problem of small cell deployment planning in LTE networks. The wireless network is modeled with multiple heterogeneities such as hotspots in the mobile user distribution, site-specific acquisition costs and different types of small cell base stations with different cost and transmit power. The objective is to lower the maximum load of any macro cell in the network, by deploying the optimal types of small cells in the optimal locations. We introduce a problem formulation that accounts for the mentioned heterogeneities and an approximated linear formulation, which achieves better performance than existing iterative methods.

Improved link adaptation with coordinated scheduling in non-fully loaded wireless networks

In mobile communication networks under bursty traffic conditions the interference experienced by the users varies constantly. Therefore, the periodic reporting of channel state information becomes inaccurate and the link adaptation performance deteriorates. In this work, a coordinated scheduling scheme is proposed to improve the link adaptation performance of a non-fully loaded network in the downlink. For that purpose an integer linear program is formulated which, at the time of scheduling a user, targets to reproduce the interference scenario as observed during the generation of the channel state information report. Although combinatorial in nature, the proposed optimization framework is suitable for even middle to large scale networks. Extensive system level simulation results show a reduction of the block error rate, i.e., the improvement of the link adaptation performance, achieved by the proposed coordinated scheduling scheme compared with a scheduler that does not benefit from cooperation.

A cooperative power control scheme for interference management in LTE-Advanced based cognitive radio networks

A cooperative power control scheme is proposed for heterogeneous cellular networks to improve the throughput of the users connected to low transmission power cells, e.g., femto-or pico cells. The proposed scheme dynamically reduces the transmission power of the dominating interfering macro base station, to effectively increase the SINR conditions of the users connected to the low power cells. The cooperative scheme is entirely based on available measurement reports, e.g., in the LTE-Advanced systems and enjoys low computational complexity. Thus, the proposed cooperative power control scheme can be applied in scenarios with limited back-haul and computation capabilities. Extensive system level simulation results show significant throughput improvement of cell edge users with a limited impact on the performance of the cooperative macro base station.