Optimal Joint Transmission Beamforming for Small-Cell Networks with QoS Guarantee

Abstract

In the multicell networks inter-cell interference (ICI) is a critical problem to solve especially for the cell-edge User Equipments (UEs) Coordinated Multipoint-Joint Transmission (CoMP-JT) technique has been proposed where by neighboring the Base Stations (BSs) cooperate to reduce ICI Conventionally CoMP-JT is applied to the macro-cell networks where only single BS is deployed at each macro cell As the notion of the small-cell networks becomes emerging it is of importance to investigate CoMP-JT in the context of small-cell networks where more than one low-power BS are deployed at each macro cell In this thesis we consider a combination of small cell deployment and CoMP-JT technique To guarantee the quality-of-service (QoS) the optimal JT beamforming aims to minimize transmitted power with individual signal-to-interference-plus-noise-ratio (SINR) constraints We first consider the non-robust JT beamforming where perfect channel-state-information (CSI) is assumed at the BS side We then consider the robust JT beamforming which takes the CSI errors into account Since both the formulated problems are non-convex in nature we obtain the optimal solutions by applying Lagrangian duality to the non-robust JT beamforming problem and Semidefinite Relaxation (SDR) and Bernstein-type inequality to the robust JT beamforming problem respectively in order to reduce the high computational complexity Numerical results are provided to evaluate the performance of the proposed methods in comparison with existing methods

Date of Award	2020
Original language	English
Supervisor	Kuang-Hao Liu (Supervisor)