Interference Coordination In Hierarchical Heterogeneous Networks:Game Theoretic Models And Approaches

The unrelenting bandwidth demand from wireless mobile users is driv-ing the present wireless technologies toward their limits. As a matter of fact, the most optimistic hope from latest 3GPP standards, such as LTE-A is unable to meet the bandwidth demand of the future users of fifth generation mobile wireless (5G) networks. In such settings to meet the unprecedented transmis-sion capacity demands economically, operators are opting network densifica-tion i.e., aggressively deploying small-cells in a co-channel mode within the hierarchical heterogeneous networks (HetNets). The resulting hierarchical Het-Nets comprise of more smaller and denser heterogeneous small-cells, which will confront serious technical challenges. Among others, the inter-cell inter-ference (ICI) comes forth as a former acquaintance but with new significance. Consequently, ICI becomes the most dominating channel impairment and de-teriorates the overall network performance significantly. Inspired by the game theory, this dissertation mainly deals with the management of ICI problem in hi-erarchical HetNets through advance inter-cell interference coordination (ICIC) techniques.In the first contribution, the inter-tier interference problem between femto-cell base stations (FBSs) and macrocell user equipments (MUEs) in the down-link scenario under co-channel mode with frequency reuse of 1 is examined. Where MUEs are severely affected by FBSs interference that are working in closed subscriber group (CSG) mode. In such situation, Stackelberg game is used to model the power control problem. In this propose game, the leader’s goal (Macrocell base stion (MBS)) is to protect its users from excessive interfer-ence of FBSs (followers) by imposing price on each FBS causing interference to its MUEs, and finally maximizes its utility function (i.e., revenue). While FBSs have to maximize their utility functions in respect of their sum-rates. The solution of the game lies in determining the Stackelberg equilibrium (SE). We derive the closed form solutions for the game, hence avoiding exhaustive search for resource allocation, which is normally the case with conventional solutions.In the second contribution, the intra-tier interference in the downlink of an underlay small-cell tier is investigated, which are densely deployed. In this work, we consider the constraint that the non-cooperative MBS users are shar-ing the same spectrum with the small-cell access points(SAPs), establishing that mutual interference among small-cells is a limiting factor. In the consid-ered scenario, we show how SAPs’ individual performance is network depen-dent, owing to the same spectrum sharing and the network infrastructure. To tackle the intra-tier interference issue, the coalitional game in partition form is utilized, which takes into account the external effects and optimize the strate-gic decisions. Considering the fact that SAPs are selfish and rational, a simple distributed algorithm based on merge-only rule is proposed to form coalitions adaptively according to the interference conditions within the network, and mit-igate the mutual interference through coordination among coalition members.In the third contribution, we extend the afore mentioned problem by con-sidering hyper dense deployment of SAPs coupled with full load assumption that all the active users are running multimedia service. In such situation, en-suring distinct quality of service (QoS) requirements for multimedia applica-tions become even more challenging. Keeping in view the dimension of such a problem, self-organization capabilities is leveraged for coalition formation ap-proach while mitigating intra-tier interference dynamically. Here, we utilize merge and split with partial reversibility rule to propose a simple and efficient coalition formation algorithm. Furthermore, this work is extended by utilizing 3.5 GHz band for cellular transmission and compared their results to get better insight in hyper dense settings.Altogether, this dissertation leveraged game theoretic tools and proposed not only stable and fast converging semi-distributed power control scheme for inter-tier interference, but also proposed adaptive, distributed algorithms for intra-tier interference, which shows high performance improvement for a wide range of network sizes. Though notable solutions exist for certain problems, but attributes of the proposed algorithms such as its low complexity, fast con-vergence and high efficiency with low overhead make it suitable for implemen-tation in practical, scalable way.