Abstract
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.
Highlights
The deployment of femtocells is generating attention among mobile operators as a cost-effective and highbandwidth solution for generation wireless networks
Operating in the licensed spectrum owned by a mobile operator, femtocells provide mobile convergence services through the broadband backhaul in long-term evolution (LTE) networks
We investigate the effiect of beamforming on the SIR gain in a two-tier femtocell network
Summary
The deployment of femtocells is generating attention among mobile operators as a cost-effective and highbandwidth solution for generation wireless networks. Assigning diffierent spectrums to macrocell and femtocell networks, respectively, can be a solution to the cross-tier interference mitigation [14]. A centralized beamforming strategy that adaptively changes beam patterns and controls the total transmit power of cells is proposed in [17] These cochannel deployments are still exposed to the cross-tier interference problem. Femtocells in the inner region use a partitioned spectrum They do not use the optimal division ratio between shared and partitioned spectrum, though they require centralized coordinators which induce some cross-tier control overhead and delay. We assume that base stations (MeNB and HeNBs) are equipped with beamforming antennas, while user equipments (MUE and HUEs) are not due to their physical device limitations
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