Macro-femtocell Networks Research Articles

Location-based spectrum allocation and partitioning scheme for cross-tier interference mitigation in macro-femtocell networks

In this paper, we address the cross-tier interference problem in a two-tier network which consists of overlaid femtocells within a macrocell range. In the considered network, macro and femto base stations are assumed with the capabilities of power control and beamforming, differently from user terminals. Under such environments, we devise a decentralized solution where each femtocell determines whether to use shared spectrum or partitioned spectrum, considering users’ location information. Introducing two simple distance thresholds, we can optimally partition the spectrum and allocate them without detailed channel information. Simulation results demonstrate that our decentralized scheme achieves comparable performance to the centralized one with low overhead and feedback delay.

Mobile Network Offloading

The mobile data traffic growth and the high fraction of indoor-generated traffic push mobile operators to devise new deployment strategies such as mobile network offloading. The purpose of this paper is to evaluate the energy consumption and the deployment cost, based on the demanded traffic level, for a joint macro-femtocell network which enables mobile network offloading in Helsinki Metropolitan Area by 2015. This deployment is compared to an optimized only macro cellular network. The study tries to resolve under what conditions, in terms of demanded traffic, deployment cost and energy consumption, a mobile operator should deploy femtocells. Assuming that only the new network infrastructure is installed by 2015, the results show that wide-to-local area offloading is beneficial for a mobile operator to handle the mobile data traffic growth, reduce the deployment costs and the energy consumption of the radio access network.

A decentralized spectrum allocation and partitioning scheme for a two-tier macro-femtocell network with downlink beamforming

Abstract This article examines spectrum allocation and partitioning schemes to mitigate cross-tier interference under downlink beamforming environments. The enhanced SIR owing to beamforming allows more femtocells to share their spectrum with the macrocell and accordingly improves overall spectrum efficiency. We first design a simplified centralized scheme as the optimum and then propose a practical decentralized algorithm that determines which femtocells to use the full or partitioned spectrum with acceptable control overhead. To exploit limited information of the received signal strength efficiently, we consider two types of probabilistic femtocell base station (HeNB) selection policies. They are equal selection and interference weighted selection policies, and we drive their outage probabilities for a macrocell user. Through performance evaluation, we demonstrate that the outage probability and the cell capacity in our decentralized scheme are significantly better than those in a conventional cochannel deployment scheme. Furthermore, we show that the cell utility in our proposed scheme is close to that in the centralized scheme and better than that in the spectrum partitioning scheme with a fixed ratio.

A green handover protocol in two-tier OFDMA macrocell–femtocell networks

Femtocells are a promising technology to improve network performance with the short-range, low-power, and cost-beneficial small base stations. A femtocell is a low-power wireless access point that operates in licensed spectrum to connect a standard device to an operator’s network using a digital subscriber line (DSL) connection. Most of the energy consumption of the telecommunication networks is caused by the base stations. It is important to reduce the energy consumption of the base stations for green ICT (information and communication technology). A two-tier orthogonal frequency-division multiple access (OFDMA) macro-femtocell network is a key issue to significantly reduce the total power consumption of the base stations. In this paper, we develop a green handover protocol in two-tier OFDMA macrocell–femtocell networks. The green handover protocol allows the femtocell base station to completely switch off its radio communication and associated processing when not involved in an active call. To improve the energy efficiency of femtocell base station, the proposed green handover protocol intelligently switches on its radio communication and associated processing, or called a “wake up” from the idle mode, if the remaining data of a mobile host can be completely uploaded through the wake-up femtocell base station. Finally, the mathematical analysis and the performance simulation illustrate that the proposed protocol provides a more power-saving result compared with existing energy-saving handover protocols.

Energy and cost impacts of relay and femtocell deployments in long-term-evolution advanced

In long-term-evolution-advanced (LTE-advanced), heterogeneous deployments of relays, femtocells and conventional macrocells are expected to provide coverage extension and throughput enhancement, while significantly lowering the energy consumption and total-cost-of-ownership (TCO) in cellular networks. This study presents a methodology for estimating the total energy consumption, taking into account the total operational power and embodied energy, and TCO of wireless cellular networks, and in particular provides a means to compare homogeneous and heterogeneous network (HetNets) deployments. The authors introduce realistic energy models and energy metrics based on information available from mobile-network operators (MNOs) and base stations manufacturers. Additionally, up-to-date operational and capital expenditure (OPEX and CAPEX) models are used to calculate TCO of candidate networks. The authors evaluate two scenarios for HetNets, namely a joint macro-relay network and a joint macro–femtocell network, with different relay and femtocell deployments densities. The results obtained show that compared to macro-centric networks, joint macro-relay networks are both energy and cost efficient, whereas joint macro–femtocell networks reduce the networks TCO at the expense of increased energy-consumption. Finally, it is observed that energy and cost gains are highly sensitive to the OPEX model adopted.