This paper is concerned with the joint linear precoder design problem for the multiuser multiple-input multiple-output (MIMO) heterogeneous networks (HetNets) in which multiple femto base stations (FBSs) coexist with a macro base station (MBS). | SCIENCE & TECHNOLOGY DEVELOPMENT, , - 2015 Optimal precoder designs for sum rate maximization in MIMO multiuser multicells Ha Hoang Kha Nguyen Dinh Long Tuan Do-Hong Ho Chi Minh city University of Technology, VNU-HCM, Vietnam (Manuscript Received on July 15, 2015, Manuscript Revised August 30, 2015) ABSTRACT This paper is concerned with the joint linear precoder design problem for the multiuser multiple-input multiple-output (MIMO) heterogeneous networks (HetNets) in which multiple femto base stations (FBSs) coexist with a macro base station (MBS). To tackle the inter-user interference in the macrocell, we exploit the blockdiagonalization scheme and then use the convex optimization to maximize the sum rate of the macrocell. The FBS transmission strategy is to maximize the sum-rate of femtocells subject to the transmitted power constraints per FBS and restrictions on the cross-tier interference to macro-users (MUs). Such a design problem is typically nonconvex, and, thus, challenging to find the FBS precoders. We reformulate the design problem of the FBS precoders as a . (difference of convex functions) programming, and develop an efficient iterative algorithm to obtain the optimal precoders. Numerical simulation results show that the proposed algorithm outperforms the other methods in terms of the total sum-rate of the HetNet. Keywords: Linear precoders, MIMO interference channels, multicells, HetNets, . programming. 1. INTRODUCTION Heterogeneous networks (HetNets) have recently become a major research topic in wireless communications due to its great potential to improve the coverage and capacity of wireless networks [1], [2]. In Long Term Evolution (LTE) Advanced HetNets, micro, pico, and femto cells with low power base stations and short range of coverage can be placed in different locations to improve the spectral efficiency since these cells operate in the licensed spectrum of the macrocell and provide the high quality of .
