Kiran Kumar Somasundaram

Proportional Fairness in LTE-Advanced Heterogeneous Networks with eICIC

The enhanced Inter-Cell Interference Coordination (eICIC) techniques introduced for LTE-Advanced HetNets yield significant gains by offloading macro cell users to small cells. Interference management is enabled via Almost Blank Subframes (ABS) on which the high power macro cells mute. This creates two different interference patterns corresponding to non-ABS and ABS subframes, which makes analyzing resource allocation and throughput performance non-trivial. We introduce a utility model for the eICIC framework that enables us to study resource allocation with different interference patterns. We use a semi-analytical method using this model to study resource allocation of pico cell-center users on both non-ABS and ABS subframes. We show for proportional fairness, the pico cell-center users may need to be scheduled on ABS subframes. We also demonstrate that this model can be used to determine the optimal ABS configuration for a given deployment.

Joint user association and resource allocation in UE-Relay assisted heterogeneous networks

We propose a novel approach that aims at extending femtocell coverage by enabling nearby idle User Equipments (UEs) in the proximity of femtocells to serve as relays, called UE-Relays. The users that would nominally connect to macrocells are offloaded to femtocells via the coverage extension provided by the UE-Relays. The problem of determining the optimal subset of idle UEs to be enabled as UE-Relays and the user association to these relays is a non-trivial problem because it depends on the projected capacity of the relay access and backhaul.We formulate the user association as an optimization problem that maximizes the network-wide log utility of the user rates. Our simulation results corroborate our expectations: overlaying a femtocelltier with UE-Relays will increase the user throughput and the network throughput. In addition, we compare our approach with a MAX-SINR based user association, and evaluate the performance profiles at varying scenario settings. The proposed rate-based scheme outperforms the SINR-based cell selection, thus validating the idea that, in heterogeneous cellular networks, user association should be performed based on the load rather than relying merely on link quality indicators.