Enhanced Cell Range Expansion and Radio Resource Allocation for a Better Traffic Offloading in HetNets

Abstract

Cell range expansion (CRE) is a promising solution to offload macrocells' traffic and improve the radio capacity in heterogeneous network (HetNet). On the other hand, enhanced inter-cell interference coordination (eICIC) techniques are introduced in HetNets to mitigate the severe interference caused between the small cells and the macrocell. In this paper, we present a novel application of the CRE coupled with a new time and frequency domain based eICIC technique. Our approach offers a dynamic radio resource allocation scheme which takes into account the number of femtocells inside the macrocell, the femtocells' loads and the macrocell load. First, we propose a so called FT-CRE scheme which alternates the transmission of the macrocell and the femtocells offering high traffic offloading. Then, a more elaborated scheme called enhanced FT-CRE (eFT-CRE) is presented. In this scheme, the need in traffic offloading is estimated so that time and frequency resources are allocated between the macrocell and the femtocells accordingly. The performance of both proposed FT-CRE and eFT-CRE schemes is evaluated through simulations. The results showed that when FT-CRE scheme is applied, the achieved throughput of the victim macro-users served by femtocells which apply the CRE is increased by 6 times as compared to a common application of CRE technique based on time domain multiplexing eICIC only. The outage probability of these victim macro-users is also significantly decreased. More importantly, the eFT-CRE scheme reveals more effective in terms of total achieved throughput in the system, the outage probability and energy efficiency at the macrocell.