Resource management and interference mitigation for dense heterogeneous small-cell networks

Abstract

Facing an unprecedented challenge of capacity increase, the wireless communications community is exploring many solutions. Among these solutions, the ones that brought the most attention in recent years are: the deployment of more network nodes leading to the densification of the existing traditional networks, the increase of spectrum resources with mmWave frequencies, and the increase of the number of antennas at the receiver and transmitter through massive MIMO. These three trendy solutions are the core of the fifth generation of wireless communications systems (5G) in which dense small-cells networks approach stands out because of its high scalability. Ultra dense networks will be demanded in certain geographical areas by means of a contiguous layer of small coverage. These will deliver significant area capacity density through spatial reuse of spectrum resources along with tight scheduling coordination between adjacent cells and the macro base station layer. However, guaranteeing the efficient coexistence of a large number of small-cells with traditional macrocells as well as the interference from the overlapping small-cells from the perspective of resource management is a fundamental issue. In the first part of this thesis, we propose a Fractional Frequency Reuse (FFR) scheme for sector-based two-tier macrocell-femtocell networks joint with a Quality-of-Service (QoS)- aware admission control strategy. The optimal parameters for cell channel partitioning in the proposed FFR scheme and an analytical model for performance evaluation of the proposed system are developed. Numerical results are presented to demonstrate the performance enhancement in term of blocking probabilities of the proposed framework. In the second part, we investigate a cooperative approach for self-organizing small-cells networks. We propose a novel game theoretic approach for joint co-tier and cross-tier cooperation in heterogeneous networks that offers a significant improvement in performance for users from both tiers. First, we propose a coalition structure game with a weighted Owen value as imputation, where the Small-cell Base Stations (SBSs) and their connecting Macrocell User Equipments (MUEs) form a priori union. Second, we propose a canonical game with a weighted solidarity value as imputation to allow cooperation among SBSs and MUEs when they fail to connect to nearby SBSs. We compare through extensive simulations the proposed frameworks with state-of-the-art resource allocation solutions, access modes and legacy game-theoretic approaches. We show that the proposed framework obtains the best performances for the MUEs and SUEs in terms of throughput and fairness. In the third part, we investigate the combination of dense small-cells deployment and spatial frequency reuse in millimeter-wave (mmWave) systems and show its great potential for achieving the 1 Gbps median throughput target in 5G networks. We propose a spatial frequency reuse model for two-tier ultra-dense networks in the mmWave frequency bands opened to mobile communications networks in 5G. We demonstrate in this work that an adequate frequency allocation and reuse in 5GmmWave networks with the support of a dense small-cells deployment enables very high throughputs and Signal-to-Interference-plus-Noise (SINR) ratio coverage in ultra-dense systems. The performances of this scheme are evaluated both analytically in terms of coverage probability, and through system-simulation in terms of achieved throughput, and compared to traditional microwave systems and mmWave models with no spatial reuse.

Date	13 Jun 2017
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	François Gagnon (Supervisor)