Interference management for self-organized femtocells towards green networks
ABSTRACT The femtocell concept is an emerging technology for deploying the next generation of the wireless networks, aiming at indoor coverage enhancement, increasing capacity and offloading the overlay macrocell traffic. One of the main challenges in short range femtocell networks is how to (re)configure the Home Node Bs (HNBs) in an autonomous manner so as to manage interference and diminish the energy consumption among nearby femtocells efficiently. In this paper, we investigate the indoor femtocell deployment making use of both the Frequency Division Duplexing (FDD) and the Time Division Duplexing (TDD) methods. In the FDD case, the HNBs share both the Uplink (UL) and Downlink (DL) channels with the macrocell without any cooperation to coordinate their access to the air interface. Conversely, in the TDD underlay case, femtocells only reuse the macrocell UL spectrum and cooperate with each other in order to minimize the interference among themselves, either with or without further coordination with the Macro User Equipment (MUE). The proposed solution is evaluated by means of system-level simulations using the Monte Carlo approach. Investigations have shown that the TDD underlay approach not only reduces the perceived interference levels, but also diminishes the outage probability.
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ABSTRACT: Worldwide mobile broadband communications networks are increasingly contributing to global energy consumption. In this paper we tackle the im-portant issue of enhancing the energy efficiency of cellular networks without compromising coverage and users perceived Quality of Service (QoS). The motivation is twofold. First, operators need to reduce their operational energy bill. Second, there is a request of environmental protection from governments and customers to reduce CO 2 emissions due to information and communica-tions technology. To this end, in this paper we first present the holistic system view design adopted in EARTH (Energy Aware Radio and neTworking tecH-nologies) project. The goal is to ensure that any proposed solution to improve energy efficiency does not degrade the energy efficiency or performance on any other part of the system. Then, we focus on technical solutions related to resource allocation strategies designed for increasing diversity order, robust-ness and effectiveness of a wireless multi-user communication system. We investigate both standalone and heterogeneous cells deployment scenarios. In standalone cells deployment scenarios, the challenge is to reduce the overall downlink energy consumption while adapting the target of spectral efficiency to the actual load of the system and meeting the QoS. Then, with hetero-geneous deployment scenarios, different cell scales that ranges from macro to Journal of Green Engineering, 267–301. c 2011 River Publishers. All rights reserved. 268 E. Calvanese Strinati et al. micro, pico and even femto cells, potentially may share the same spectrum in a given geographical area. In such scenarios interference is the most limiting problem to achieve the desired performance. Our analysis reveals how pro-posed methodologies permit to achieve notable energy gain over traditional resource allocation techniques especially in not saturated scenarios.
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ABSTRACT: Full-duplex (FD) radio has been introduced for bidirectional communications on the same temporal and spectral resources so as to maximize spectral efficiency. In this paper, motivated by the recent advances in FD radios, we provide a foundation for hybrid-duplex heterogeneous networks (HDHNs), composed of multi-tier networks with a mixture of access points (APs), operating either in bidirectional FD mode or downlink half-duplex (HD) mode. Specifically, we characterize the net- work interference from FD-mode cells, and derive the HDHN throughput by accounting for AP spatial density, self-interference cancellation (IC) capability, and transmission power of APs and users. By quantifying the HDHN throughput, we present the effect of network parameters and the self-IC capability on the HDHN throughput, and show the superiority of FD mode for larger AP densities (i.e., larger network interference and shorter communication distance) or higher self-IC capability. Furthermore, our results show operating all APs in FD or HD achieves higher throughput compared to the mixture of two mode APs in each tier network, and introducing hybrid-duplex for different tier networks improves the heterogenous network throughput.IEEE Transactions on Wireless Communications 11/2014; DOI:10.1109/TWC.2015.2396066 · 2.76 Impact Factor
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ABSTRACT: The deployment of femtocells comes as a solution to increase indoor coverage although it may also increase the interference level in the network. In this paper we evaluate the use of multiple co-channel femtocells as relays to the outdoor user in a cognitive radio context, where the outdoor user can be seen as a primary user and the indoor users are seen as secondary users. We show that multiple co-channel femtocells, besides allowing several secondary users to access the spectrum, may considerably increase the performance of the primary user if the femtocells act as relays to the primary signal. Moreover, results show that with the increase of the number of cooperative co-channel femtocells the capacity constraints on the backhaul can be relaxed.Telecommunications and Signal Processing (TSP), 2013 36th International Conference on; 01/2013